CN109412197B - Voltage conversion circuit capable of generating carrier signal and used for photovoltaic module power optimization - Google Patents
Voltage conversion circuit capable of generating carrier signal and used for photovoltaic module power optimization Download PDFInfo
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- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
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- H02J7/35—Parallel operation in networks using both storage and other dc sources, e.g. providing buffering with light sensitive cells
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- Y02E10/00—Energy generation through renewable energy sources
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- Y02E10/56—Power conversion systems, e.g. maximum power point trackers
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Abstract
The invention relates to a voltage conversion circuit for power optimization of photovoltaic modules, which can generate a carrier signal, wherein a first inductor is arranged on a voltage output path of the voltage conversion circuit used as a switch mode power supply, and a first switch and a first capacitor which are connected together in series are connected in parallel at two ends of the first inductor. Identifying a pattern of the carrier signal during a communication phase in which the voltage conversion circuit transmits the carrier signal includes: driving the first switch to be turned off, wherein the condition that the direct current transmission line is lack of a pulse which is transiently loaded on the direct current transmission line by a potential difference and is regarded as a carrier signal is defined as that the carrier signal has a first logic state; the first switch is driven to be switched on, and the carrier signal is defined to have a second logic state when the DC transmission line is mixed with a pulse which is induced by the transient loading of the potential difference on the DC transmission line and is regarded as the carrier signal. The first logic state and the second logic state of the carrier signal represent opposite logic states.
Description
Technical Field
The invention mainly relates to the field of photovoltaic power generation, in particular to a voltage converter capable of realizing voltage reduction, voltage boosting or voltage boosting in an application occasion containing a photovoltaic cell, which can determine to carry out carrier mode communication and receiving on target working data of a photovoltaic module matched with the voltage converter according to actual conditions.
Background
With the rapid development and growth of the global photovoltaic power generation industry scale and the high penetration of the internet, intellectualization has become the development trend of photovoltaic power stations, and intelligent power generation, efficient operation and maintenance and safety management have become common industry insights. The intelligent solution of the photovoltaic power station is provided by applying professional technologies in the field of information and communication, the Internet of things of the photovoltaic energy industry is created, the intellectualization of the photovoltaic power generation system is facilitated, the power generation efficiency of the photovoltaic power station is improved, the intelligent operation and maintenance are realized, remote real-time monitoring and highly intelligent management are carried out on each core device of a centralized or distributed photovoltaic power generation system on an intelligent service platform, and the core problem is that target working parameters of photovoltaic modules are collected. The function of the parameter data of the photovoltaic module is represented by: the substantial sources of faults, problems and defects of the photovoltaic module can be analyzed in time according to a big data algorithm; analyzing an optimal energy storage grid-connected mode, aiming at maximizing profits to realize the opportunity of photovoltaic energy storage and electric power release to a power grid, and planning a real-time grid-connected scheme for a power station to play a role in peak clipping and valley filling of the power grid; monitoring the operation condition and historical operation data of each photovoltaic module in real time, and early warning various potential safety hazards of some photovoltaic modules in the future according to big data; and screening the performances of the components provided by different photovoltaic component suppliers in the power generation historical data, and informing the power station of the real performances of the components provided by the different component suppliers.
The most important link in the field of photovoltaic power generation, except for an inverter, is voltage conversion, and the main purpose is to convert the voltage of a battery from an original value which is easy to fluctuate into a stable voltage value, and the voltage converter is one of core circuits for voltage conversion from direct current to direct current. The method comprises the steps of boosting or reducing the voltage of a battery, boosting or reducing the original light conversion voltage of the battery according to actual requirements, and then inverting and grid-connecting the obtained expected direct-current voltage. In a photovoltaic power generation system, in order to ensure safe and reliable operation of the power generation system, various potential threats need to be discovered in time: for example, the hot spot effect caused by shadow shielding is a negative threat, which may cause some batteries to be converted from a power supply into a load to cause the battery panel to be heated to be burnt, and the real-time accurate monitoring of the working parameters such as the voltage, the current, the power, the temperature and the power generation amount of the photovoltaic battery is an important link in the photovoltaic power generation system. The monitoring of the working parameters of the photovoltaic cell in practical application occasions adopts power line carrier communication as a communication means, the parameters of the photovoltaic cell are easily transmitted to a power line which provides photovoltaic voltage by the photovoltaic cell as communication data by means of power line carriers, the real-time parameters of the photovoltaic cell can be acquired by decoding carrier signals from the power line, and wireless communication is also a means for receiving and transmitting data besides the carriers. Wireless communication is very limited to the application site of the components: most of centralized large power stations are distributed in suburbs or even open water areas, distributed roof-type small power stations are distributed on the top of buildings for receiving solar radiation, and the non-near-field communication scale causes great defects to the application range of wireless communication.
In consideration of the fact that the working parameter monitoring of the photovoltaic cell is carried out in practical application occasions, more power line carriers are adopted as communication means, the parameters of the photovoltaic cell are easily transmitted to a power line, which provides photovoltaic voltage, of the photovoltaic cell as communication data by means of the power line carriers, and then the real-time parameters of the photovoltaic cell can be acquired by decoding carrier signals from the power line. Unlike a common data communication line, which is originally intended for transmission of electric power rather than data, a power line is not ideal for data communication, but is a very unstable transmission channel, which is characterized by significant noise and severe signal attenuation. In order to overcome the problem of instability, the power line broadband carrier technology adopts modulation technologies such as spread spectrum and orthogonal frequency division multiplexing, and the fact proves that multi-carrier orthogonal frequency division multiplexing is an effective method for solving the problem of transmission interference on a power line so far, and the power line broadband communication adopts the orthogonal frequency division multiplexing technology to effectively resist multipath interference so that interfered signals can still be reliably received. The method for improving the reliability of the signal by sampling the similar means is only one aspect, but in the case of simultaneous application of the photovoltaic cell and the carrier, since the voltage level of the photovoltaic cell itself is greatly changed by the ambient temperature and the light radiation intensity, the distortion of the carrier signal itself propagation on the power line and the characteristic of the cell that the output characteristic is easy to fluctuate are mixed together, so that the actual carrier signal expected to be captured by the receiving end is not accurate, the error rate is high, and the voltage superposed on the photovoltaic cell string group is also interfered by the carrier, so that the actual voltage on the whole string group may not be within the expected range. According to the method and the device, the voltage, the current, the power, the temperature and other target working parameters of the photovoltaic cell are transmitted by utilizing the carrier signal, a reasonable communication mechanism is established, parameter data are sent from the cell panel through the communication mechanism, the pressure of data acquisition is reduced, and negative influence on the power generation of the cell panel is avoided in the communication process of data acquisition.
Disclosure of Invention
In an optional non-limiting embodiment, the present application discloses a voltage conversion circuit applied to photovoltaic modules and integrated with a carrier transmission function, wherein each battery string group for providing a string level voltage is connected with a plurality of photovoltaic modules in series, each photovoltaic module is configured with the voltage conversion circuit for performing maximum power point tracking and an output voltage output by the voltage conversion circuit after dc voltage conversion is performed on the paired photovoltaic module, and further comprising:
a first inductance arranged on a voltage output path of the voltage conversion circuit functioning as a switched mode power supply;
the first switch and the first capacitor are connected in parallel at two ends of the first inductor and are connected together in series;
identifying a pattern of a carrier signal during a communication phase in which the voltage conversion circuit transmits the carrier signal includes:
the first switch is in a switch-on state, a high-frequency switch ripple which is generated by mixing a switch control signal in the process of driving the voltage conversion circuit and is mixed into the output voltage is filtered from the output voltage, and the condition that the high-frequency switch ripple which is regarded as a carrier signal is filtered on a direct current transmission line for transmitting the output voltage is defined as a first logic state of the carrier signal;
the first switch is in a turn-off state, a switch control signal is superposed in the output voltage, the output voltage is mixed to a high-frequency switch ripple in the output voltage in the process of driving the voltage conversion circuit, and a second logic state of the carrier signal is defined on a direct current transmission line for conveying the output voltage due to the fact that the high-frequency switch ripple which is regarded as the carrier signal is mixed on the direct current transmission line.
The voltage conversion circuit integrated with the carrier sending function and applied to the photovoltaic modules is characterized in that any one of the voltage conversion circuits is driven by a switch control signal to convert a voltage source generated by a corresponding one of the photovoltaic modules into a direct-current voltage for boosting or reducing or boosting.
The voltage conversion circuit integrated with the carrier transmission function and applied to the photovoltaic module, wherein each voltage conversion circuit comprises a first input end and a second input end coupled to the positive electrode and the negative electrode of one photovoltaic module, a first output end and a second output end for providing output voltage, and an output capacitor of the voltage conversion circuit is connected between the first output end and the second output end; and
there is also a first node coupled to the first output terminal and a second node coupled to the second output terminal, the first inductor being connected between the first output terminal and the first node or between the second output terminal and the second node.
The voltage conversion circuit integrated with the carrier transmission function and applied to the photovoltaic module is characterized in that multiple stages of voltage conversion circuits are connected in series, and a second node of any previous-stage voltage conversion circuit is coupled to a first node of an adjacent next-stage voltage conversion circuit through the direct current transmission line; thereby to obtain
When the voltage conversion circuits of the multiple stages are connected in series, their respective output capacitors are connected in series with each other, and the total cascade voltage provided by the voltage conversion circuits of the multiple stages is equal to the sum of the voltages on their respective output capacitors.
The voltage conversion circuit integrated with the carrier sending function and applied to the photovoltaic module is characterized in that a second switch and a second capacitor are connected in series between a first node and a second node of each voltage conversion circuit;
the first and second switches are complementary switches at a stage when the carrier signal has a second logic state, and the second switch is in an on state when the first switch is in an off state to increase a ripple amplitude of the high frequency switching ripple.
The voltage conversion circuit applied to the photovoltaic module and integrating the carrier sending function comprises:
the first power switch and the second power switch are connected in series between the first input end and the second input end;
the third power switch and the fourth power switch are connected in series between the first output end and the second output end;
a main inductance element is provided between a first interconnection node to which both the first and second power switches are connected and a second interconnection node to which both the third and fourth power switches are connected.
The voltage conversion circuit integrated with the carrier sending function and applied to the photovoltaic module is in a non-communication stage where no carrier signal is emitted, and the first switch is in a continuous off state.
The voltage conversion circuit integrating the carrier sending function and applied to the photovoltaic module is characterized in that the switching operation frequency of the switch control signal in the process of driving the voltage conversion circuit is higher than the switching frequency of the first switch in the communication stage.
The voltage conversion circuit applied to the photovoltaic module and integrating the carrier transmission function is described above, wherein one of the first logic state and the second logic state is used for characterizing 1 or 0 of the binary symbols, and the other is used for characterizing the rest of the binary symbols.
In an optional non-limiting embodiment, the present application discloses a method for generating a carrier signal by a voltage conversion circuit applied to a photovoltaic module, wherein each battery string for providing a string voltage has a plurality of photovoltaic modules connected in series, and each photovoltaic module is configured with the voltage conversion circuit for performing maximum power point tracking and outputs an output voltage after dc voltage conversion by a photovoltaic module paired with the voltage conversion circuit; and
a first inductance arranged on a voltage output path of the voltage conversion circuit serving as a switched mode power supply;
the first switch and the first capacitor are connected in parallel at two ends of the first inductor and are connected together in series;
the method comprises the following steps:
driving a first switch to be continuously turned off in a non-communication stage when the voltage conversion circuit does not transmit the carrier signal;
driving a first switch to switch between on and off in a communication phase in which the voltage conversion circuit transmits a carrier signal;
driving a first switch to be switched on in a communication stage, filtering out a high-frequency switch ripple which is regarded as a carrier signal and is generated by mixing a switch control signal in the output voltage in the process of driving the voltage conversion circuit from the output voltage, and defining the carrier signal as having a first logic state on a direct current transmission line for transmitting the output voltage because the high-frequency switch ripple is filtered out;
and driving the first switch to be switched off in a communication stage, superposing a switch control signal in the output voltage, mixing the switch control signal to a high-frequency switch ripple which is regarded as a carrier signal in the output voltage in the process of driving the voltage conversion circuit, and defining that the carrier signal has a second logic state on a direct current transmission line for transmitting the output voltage because the high-frequency switch ripple is mixed on the direct current transmission line.
The method described above, wherein:
each voltage conversion circuit comprises a first input end and a second input end which are coupled to the positive electrode and the negative electrode of one photovoltaic assembly, a first output end and a second output end which provide output voltage, and an output capacitor of each voltage conversion circuit is connected between the first output end and the second output end; and
there is also a first node coupled to the first output terminal and a second node coupled to the second output terminal, the first inductor being connected between the first output terminal and the first node or between the second output terminal and the second node.
The method described above, wherein:
the voltage conversion circuits are connected in series, and the second node of any previous-stage voltage conversion circuit is coupled to the first node of the adjacent next-stage voltage conversion circuit through the direct current transmission line; thereby, the device
When the voltage conversion circuits of the multiple stages are connected in series, their respective output capacitors are connected in series with each other, and the total cascade voltage provided by the voltage conversion circuits of the multiple stages is equal to the sum of the voltages on their respective output capacitors.
The method described above, wherein:
a second switch and a second capacitor are connected in series between the first node and the second node of each voltage conversion circuit;
in a phase in which the carrier signal has a second logic state:
and driving the second switch to be switched on so as to improve the fluctuation amplitude of the high-frequency switch ripple.
In an optional non-limiting embodiment, the present application discloses a voltage conversion circuit for photovoltaic module power optimization, which can generate a carrier signal, wherein each cell string for providing a string level voltage has a plurality of photovoltaic modules connected in series, each photovoltaic module is configured with the voltage conversion circuit for performing maximum power point tracking and an output voltage output by the voltage conversion circuit after dc voltage conversion performed by the photovoltaic module paired with the voltage conversion circuit, and further includes:
a first inductance arranged on a voltage output path of the voltage conversion circuit functioning as a switched mode power supply;
the first switch and the first capacitor are connected in parallel at two ends of the first inductor and are connected together in series;
identifying a pattern of the carrier signal during a communication phase in which the voltage conversion circuit transmits the carrier signal includes:
the first switch is in an off state, the potential difference between two ends of the charged first capacitor is not superposed on a direct current transmission line for transmitting the output voltage, and the condition that the direct current transmission line is lack of the potential difference and is transiently loaded on the direct current transmission line to induce a pulse which is regarded as a carrier signal is defined that the carrier signal has a first logic state;
the first switch is in an on state, the potential difference between the two ends of the charged first capacitor is directly superposed on a direct current transmission line for transmitting the output voltage, and the carrier signal is defined to have a second logic state under the condition that the direct current transmission line is mixed with pulses which are induced by the transient loading of the potential difference on the direct current transmission line and are regarded as the carrier signal.
The voltage conversion circuit for photovoltaic module power optimization, which can generate a carrier signal, is described above, wherein:
each voltage conversion circuit comprises a first input end and a second input end which are coupled to the positive electrode and the negative electrode of one photovoltaic assembly, a first output end and a second output end which provide output voltage, and an output capacitor of each voltage conversion circuit is connected between the first output end and the second output end; and
there is also a first node coupled to the first output terminal and a second node coupled to the second output terminal, the first inductor being connected between the first output terminal and the first node or between the second output terminal and the second node.
The voltage conversion circuit for photovoltaic module power optimization capable of generating carrier signals is described above, wherein:
the voltage conversion circuits are connected in series, and the second node of any previous-stage voltage conversion circuit is coupled to the first node of the adjacent next-stage voltage conversion circuit through the direct current transmission line; thereby to obtain
When the voltage conversion circuits of the plurality of stages are connected in series, their respective output capacitances are connected in series with each other, and the total string voltage provided by the voltage conversion circuits of the plurality of stages is equal to the sum of the voltages across their respective output capacitances.
The voltage conversion circuit for photovoltaic module power optimization capable of generating carrier signals is described above, wherein:
the first inductor is connected between the first output end and a first node;
a first end of the first capacitor is coupled to a reference voltage source;
a second terminal of the first capacitor is coupled to the first output terminal;
the first switch is connected between a first terminal of the first capacitor and the first node.
The voltage conversion circuit for photovoltaic module power optimization, which can generate a carrier signal, is described above, wherein:
the first inductor is connected between the second output end and a second node;
the first end of the first capacitor is coupled to a reference voltage source;
a second terminal of said first capacitor is coupled to said second node;
the first switch is connected between the first end of the first capacitor and the second output end.
The voltage conversion circuit for photovoltaic module power optimization, which can generate a carrier signal, is described above, wherein:
a first terminal of the first capacitor is coupled to the reference voltage source through a second switch;
after the first capacitor is discharged when the first switch is in the on state, the second switch is switched to the on state to charge the first capacitor, and after the charging is finished, the second switch is switched to the off state.
The voltage conversion circuit for photovoltaic module power optimization capable of generating carrier signals is described above, wherein:
the voltage conversion circuit includes:
the first power switch and the second power switch are connected in series between the first input end and the second input end;
the third power switch and the fourth power switch are connected in series between the first output end and the second output end;
a main inductance element is provided between a first interconnection node to which both the first and second power switches are connected and a second interconnection node to which both the third and fourth power switches are connected.
The voltage conversion circuit for photovoltaic module power optimization capable of generating carrier signals is described above, wherein:
the voltage conversion circuit is in a non-communication stage where the carrier signal is not transmitted, and the first switch is in a continuous off state.
The voltage conversion circuit for photovoltaic module power optimization capable of generating carrier signals is described above, wherein:
one of the first and second logic states is used to characterize a 1 or 0 in the binary symbol and the other is used to characterize the remaining other of the binary symbols.
In an optional non-limiting embodiment, the present application discloses a method for generating a carrier signal by a voltage conversion circuit for photovoltaic module power optimization, wherein each battery string group for providing a string level voltage is connected with a plurality of photovoltaic modules in series, each photovoltaic module is configured with the voltage conversion circuit for performing maximum power point tracking and outputs a dc voltage converted output voltage by the photovoltaic module matched with the voltage conversion circuit; and
a first inductance arranged on a voltage output path of the voltage conversion circuit serving as a switched mode power supply;
the first switch and the first capacitor are connected in parallel at two ends of the first inductor and are connected together in series;
the method comprises the following steps:
driving a first switch to be continuously turned off in a non-communication stage in which the voltage conversion circuit does not transmit the carrier signal;
driving a first switch to switch between on and off in a communication phase in which the voltage conversion circuit transmits a carrier signal;
driving the first switch to turn off in the communication phase, wherein the potential difference across the charged first capacitor is not superimposed on the dc transmission line carrying the output voltage, and the pulse condition of the carrier signal induced on the dc transmission line due to lack of the potential difference transient loading on the dc transmission line is defined as the carrier signal having a first logic state;
and in the communication stage, the first switch is driven to be switched on, the potential difference between the two ends of the charged first capacitor is directly superposed on a direct current transmission line for transmitting the output voltage, and the condition that the direct current transmission line is mixed with pulses which are induced by transient loading of the potential difference on the direct current transmission line and are regarded as carrier signals is defined as that the carrier signals have a second logic state.
The method described above, wherein:
each voltage conversion circuit comprises a first input end and a second input end which are coupled to the positive electrode and the negative electrode of one photovoltaic module, a first output end and a second output end which provide output voltage, and an output capacitor of each voltage conversion circuit is connected between the first output end and the second output end; and
there is also a first node coupled to the first output terminal and a second node coupled to the second output terminal, the first inductor being connected between the first output terminal and the first node or between the second output terminal and the second node.
The method described above, wherein:
the voltage conversion circuits are connected in series, and the second node of any previous voltage conversion circuit is coupled to the first node of the adjacent next voltage conversion circuit through the direct current transmission line; thereby to obtain
When the voltage conversion circuits of the plurality of stages are connected in series, their respective output capacitances are connected in series with each other, and the total string voltage provided by the voltage conversion circuits of the plurality of stages is equal to the sum of the voltages across their respective output capacitances.
The method described above, wherein:
the first inductor is connected between the first output end and a first node;
a first end of the first capacitor is coupled to a reference voltage source;
a second terminal of the first capacitor is coupled to the first output terminal;
the first switch is connected between a first terminal of the first capacitor and the first node.
The method described above, wherein:
the first inductor is connected between the second output end and a second node;
a first end of the first capacitor is coupled to a reference voltage source;
a second terminal of said first capacitor is coupled to said second node;
the first switch is connected between the first end of the first capacitor and the second output end.
The method described above, wherein:
a first end of the first capacitor is coupled to the reference voltage source through a second switch;
and in the communication stage, the first switch is driven to be switched from off to on, so that the first capacitor is discharged, the second switch is also driven to be switched on to charge the first capacitor, and the second switch is driven to be switched off after the charging is finished.
The core thought of the application is to make full use of the characteristics of the switch type power supply, high-frequency ripples naturally existing in the switching action process of the voltage converter are used as communication carriers, stable switch ripple signals on a main inductance element inherent in the voltage converter are coupled to the output end of a circuit to a direct current bus, the core thought is not limited by a specific voltage conversion topological form, such as BOOST and BUCK-BOOST except typical BUCK are applicable, because the topologies can not open an energy storage inductor, and the switch ripples are coupled to the energy storage inductor mostly, so that the application can send the stable high-frequency ripples to the direct current bus in a coupling mode on the premise of not additionally increasing a communication module and a carrier circuit, thereby realizing the composite transmission of power signals and enabling target parameters of a battery to carry out data communication through the carriers.
Drawings
To make the above objects, features and advantages more comprehensible, embodiments accompanied with figures are described in detail below, and features and advantages of the present invention will become apparent upon reading the following detailed description and upon reference to the following figures.
Fig. 1 is a schematic diagram of photovoltaic modules connected in series to form a battery string and then connected in parallel by the battery string to power an inverter.
Fig. 2 is a schematic diagram of an example of a plurality of photovoltaic modules connected in series with each other in the same cell string.
Fig. 3 is an exemplary diagram of a photovoltaic module corresponding to power optimization by a voltage conversion circuit.
Fig. 4 is a schematic diagram of a carrier module configured by the voltage conversion circuit based on the requirements of the data of the transmit component.
Fig. 5 is a schematic diagram of a carrier module employed by the voltage conversion circuit utilizing the inherent high frequency switching ripple.
Fig. 6 is a schematic diagram of logic states in which the switching ripple, which is regarded as a carrier, appears after being filtered out in a part of the time period.
Fig. 7 is a schematic diagram of a carrier module employed by the voltage conversion circuit to enhance the amplitude of the high frequency switching ripple.
Fig. 8 is a schematic diagram of a general waveform in which a high-frequency switching ripple, which is regarded as a carrier signal, can improve the amplitude intensity.
Fig. 9 is a schematic diagram of a carrier module employed by the voltage conversion circuit with a separate additional capacitor voltage.
Fig. 10 is a schematic diagram of an improved carrier module employed by the voltage conversion circuit with additional capacitor voltage.
Fig. 11 is a schematic diagram of the logic states exhibited by pulses caused by the capacitor voltage viewed as a carrier.
Detailed Description
The present invention will be described more fully hereinafter with reference to the accompanying examples, which are intended to illustrate and not to limit the invention, but to cover all those embodiments, which may be learned by those skilled in the art without undue experimentation.
In a switching power supply system, a power supply generally employs a power semiconductor device as a switching element, and the duty ratio of the switching element is controlled by periodically turning on and off the switch to adjust an output voltage. The switch power supply mainly comprises an input circuit, a conversion circuit, an output circuit, a control unit and the like. The power conversion is a core part and mainly comprises a switching circuit, and a transformer is applied to some occasions. In order to meet the requirement of high power density, the converter needs to work in a high-frequency state, the switching transistor needs to adopt a crystal arm with high switching speed and short conduction and turn-off time, and a power thyristor, a power field effect transistor, an insulated bipolar transistor and the like are typically used as a power switch. The control mode is divided into various modes such as pulse width modulation, mixed modulation of pulse width modulation and frequency modulation, pulse frequency modulation and the like, and the pulse width modulation mode is commonly used. The switching mode power supply SMPS is classified into an alternating current to alternating current (AC/AC) converter such as a frequency converter, a transformer, according to the form of input and output voltages; also classified as alternating current to direct current (AC/DC) converters such as rectifiers; and into direct current to alternating current (DC/AC) converters such as inverters and the like; and into direct current to direct current (DC/DC) converters such as voltage converters, current converters. The switched mode power supply applied in this application is primarily a dc-to-dc voltage converter. Switching noise generated by switching operations when operating a switched mode power supply may cause electromagnetic interference to be generated in an electronic device including the switched mode power supply. Switching noise represents noise components occurring due to the switching operating frequency of the power switches configuring the switched mode power supply, as well as certain harmonic components. When electromagnetic interference occurs, the operation of peripheral electronic devices of the power device including the switch mode power supply is disturbed. A conventional method for suppressing the occurrence of electromagnetic interference is a method of changing the operating frequency of a modulation switch. The frequency modulation method generates an output voltage ripple that is frequency-modulated according to the switching operation, which is superimposed on an output voltage ripple component caused by the ripple of the input voltage, thereby generating a larger output voltage ripple.
In a switching power supply system, the characteristic of a switching power supply, namely a direct current-to-direct current voltage converter which is regarded as a power optimizer is fully utilized, inherent high-frequency switching ripples which naturally exist in a voltage conversion circuit in the switching action process of a power switch are used as communication carriers, inductance/capacitance elements are added into the voltage conversion circuit, and non-removable stable high-frequency switching ripple signals which are inherent in the voltage conversion circuit are coupled to the input end or the output end of the circuit and further transmitted to a common direct current transmission line for providing total cascade voltage. The logic state of the carrier signal can be discriminated by acquiring whether the ripple signal on the main transmission line exists through various high-frequency ripple sampling circuits on the main transmission line. According to the method and the device, on the premise that the coupling high-frequency ripple signal is transmitted to the transmission line, the naturally-existing switch ripple is used as a communication carrier wave, extra communication lines and signal modulation equipment do not need to be added, data communication can be achieved without extra injection signals, the size, the power consumption and the cost of a system are reduced, and the intelligent level of communication is improved.
The power optimizer is a direct current to direct current voltage reduction and boost type voltage converter, and is also a single-component-level battery maximum power tracking power device. And after the single component is subjected to maximum power optimization by the power optimizer, the single component is transmitted to a terminal inverter to be subjected to direct current-to-alternating current processing, and then the single component is supplied for local use or power generation internet surfing. The terminal inverter can be generally a pure inverter device without maximum power tracking or an inverter device equipped with two-stage maximum power tracking. The mainstream power optimizers are mainly classified into series type and parallel type, and topologies are slightly different, such as BUCK or BOOST or BUCK-BOOST circuits.
The design concept of fixed voltage is adopted by the series type power optimizer. In brief, the inverter control board determines a stable voltage of a direct current bus according to the alternating-current voltage, summarizes the maximum power collected by each serially-connected optimizer, and further calculates the bus current and transmits the bus current to the optimizer through wireless or power carrier. The voltage at the output of each optimizer is then equal to the power of the maximum power of the module collected divided by the bus current. When the assembly is blocked, the optimizer can re-determine the maximum output power value according to the volt-ampere curve and transmit the maximum output power value to the inverter control panel through wireless or power carrier waves. On the premise of maintaining the voltage of the direct current bus unchanged, the control board recalculates the bus current (becomes smaller) and feeds the bus current back to each optimizer. At this point, the power of the shielded components is reduced, and the optimizer also steps down to confirm that the output current is up to standard. The optimizers for other non-occluded components are boosted to meet the output current. If a component is too heavily shaded, the power optimizer bypasses the heavily shaded component until it returns to a workable state, and this regulation is essentially a voltage-balancing process, thereby providing the most stable and optimized dc-side bus voltage to the inverter.
The parallel type power optimizer also adopts a fixed voltage mode. The inverter determines the bus voltage according to the closed loop of the direct current and the alternating current, each optimizer boosts the voltage of the respective output end to a designated value, and the current input into the inverter is equal to the sum of the maximum power collected by each optimizer and the current obtained by dividing the maximum power by the rated voltage. Because the shielding of the thick cloud layer has little influence on the voltage of the component and mainly influences the output current, the parallel optimizer generally does not have frequent voltage mismatching regulation, and because of the parallel relationship, the output currents do not influence each other, so that the parallel optimizer can be indeed regarded as the advantage of the parallel optimizer compared with the serial optimizer. Meanwhile, if the individual components are seriously shielded and cannot start the boosting equipment, the optimizer automatically disconnects and sends a fault reporting signal, and restarts until the shielding problem is removed. However, compared with the series topology, the parallel topology also has the same defects as the micro-inverter, and the boost span is larger. At present, the open-circuit voltage of the popular components is about 38V, the working voltage is about 30V, the voltage boosting and reducing range of the series topology is controlled between 10% and 30% under the normal condition, and the variation range is increased to between 10% and 90% under the condition of insufficient voltage. However, both the parallel topology and the micro-inverter require boosting the component input voltage to a relatively high value, around 400V, which obviously corresponds to a 10-fold higher boost. This is a relatively challenging duty cycle for boost devices that do not use a transformer, but rather are only switch controlled.
One of the biggest topological features of the power optimizer is to separate the components and the inverter functionality, which is different from the traditional photovoltaic system. It appears that the components are connected to the inverter through the optimizer, and in fact the components are only used to start the optimizer, and the optimizer collects the maximum power of the components and then cooperates with each other to give the inverter function. Due to the technology of fixing the voltage, the problem of partial shielding of the photovoltaic power generation system is solved, the number of the components in each group of strings does not need to be equal for a system with a plurality of groups of strings, and even the orientation of the components in the same group of strings does not need to be the same. The open circuit voltage after the circuit breaking is only a tiny voltage such as 1V for the series type optimizer, and the open circuit voltage after the circuit breaking is the open circuit voltage of the assembly at most for the parallel type optimizer, so the safety performance and the reliability of the power generation system are also improved in a spanning mode.
Besides the advantages of the circuit topology on the structure, the power optimizer has inherent advantages on the maximum power point tracking algorithm. The traditional tracking algorithm of the maximum power point is basically based on two types: hill climbing method and logic measurement algorithm. Tracking of points of advance these also use a combination of: for example, a hill climbing method is combined with a constant range method, and a full scanning method with a fixed time interval is matched to find a maximum power point; the maximum power point is also found by combining a slope polarity method and a conductance increment method and matching with a detection step control method. Under ideal test conditions, the accuracy of the algorithms can reach over 99 percent, and actually, the biggest current challenge is the situation of multiple peaks and steep illumination increase. By multi-peaked is meant that multiple power peaks appear in the power-current or power-voltage graph of an array. The formation reasons of the array are various, one of the reasons is that a bypass diode is deflected in the forward direction due to shielding of part of the assemblies, so that one third of the batteries are bypassed, the working voltage of the string is reduced, and further, the voltage of the array is mismatched, so that the multi-wave peak condition is generated. Or a multi-peak condition caused by current mismatch in the same string due to blocking and the bypass diode is still in a reverse deflected inactive state. Multiple peaks and steep increases in illumination have a huge impact on many maximum power point algorithms, which can confuse the tracker's decision on the direction of detection and on which peak is the maximum power point due to its uncontrollable and variable nature. In fact, the root cause of the problem is that too many components are accessed. It is tried to connect only one component to each optimizer, each component has only two to three bypass diodes, and the components do not influence each other, which greatly reduces the difficulty of analyzing and tracking the maximum power point, and is also very concise and accurate for logic editing of the controller. Because only one IV curve of 38 volts and 8.9 amps is used, the maximum power point tracking of the optimizer does not require the traditional algorithm to track the maximum power point, and two methods are currently used, namely, a tangent point tracking method, and a method combining a resistance control method and a voltage control method with two-stage tracking. Based on the advantages, the capacity of the optimizer can be improved by about 30% compared with the traditional inverter. In addition to the limited ac power of the microinverter, the power optimizer may fully transfer the collected power to the inverter.
The power optimizer is compatible with all the crystalline silicon battery boards and can be matched with part of thin film battery systems, and the industry is also trying to make the optimizer have a wider compatibility range. However, most micro-inverters are incompatible or self-functionally grounded, which makes them incompatible with some mainstream components currently on the market. At the same time, the input voltage range of the power optimizer is between about 5 volts and 50 volts, which ensures that the optimization circuit can still be started and continue to operate even if the components are severely covered. The power optimizer can be matched with a third-party inverter, and communication with the third-party inverter and regulation and control of a system are carried out through an additional control box. The power optimizer or voltage conversion circuit is essentially a dc-to-dc converter such as BUCK, BOOST and BUCK-BOOST circuits. It should be emphasized that any scheme for tracking the maximum power of the photovoltaic cell in the prior art is also applicable to the voltage conversion circuit of the present application, and the common maximum power tracking methods include a constant voltage method, a conductance increment method, a disturbance observation method, and the like, and the present application does not describe any scheme how the voltage conversion circuit performs maximum power tracking MPPT.
In the field of photovoltaic power generation, a photovoltaic module or a photovoltaic cell PV is one of the core components of power generation, and a solar cell panel is divided into a monocrystalline silicon solar cell, a polycrystalline silicon solar cell, an amorphous silicon solar cell and the like in the direction of mainstream technology, so that the number of the battery modules adopted by a large-scale centralized photovoltaic power station is large, and the number of the battery modules adopted by a small-scale distributed household small-scale power station is relatively small. Long-term and durable monitoring of the panels is essential since silicon cells typically require a service life in the field of up to twenty or more years. Many internal and external factors cause the reduction of the power generation efficiency of the photovoltaic module, and factors such as manufacturing difference or installation difference between the photovoltaic modules themselves or shading or maximum power tracking adaptation cause low efficiency. Taking a typical shadow shielding as an example, if a part of photovoltaic modules is shielded by clouds, buildings, tree shadows, dirt and the like, the part of the photovoltaic modules can be changed into a load by a power supply and does not generate electric energy any more, the local temperature of the photovoltaic modules in places with serious hot spot effect may be higher, and some of the photovoltaic modules even exceed 150 ℃, so that the local area of the photovoltaic modules is burnt or forms a dark spot, welding spots are melted, packaging materials are aged, glass is cracked, corrosion and other permanent damages are caused, and the long-term safety and reliability of the photovoltaic modules are caused to be extremely hidden. The problems to be solved by photovoltaic power stations/systems are as follows: the working state of each installed photovoltaic cell panel can be observed in real time, the over-temperature, over-voltage, over-current, output end short circuit and other abnormal conditions of the battery can be pre-warned, and the emergency measures similar to active safety shutdown or other emergency measures are taken for the abnormal battery. Whether centralized photovoltaic power stations or distributed small power stations, it is essential to determine and identify those components that have potential problems based on the operating parameter data collected for the photovoltaic components.
In the field of photovoltaic power generation, photovoltaic modules or photovoltaic cells need to be connected in series to form a cell string, and then the cell string is connected in parallel to supply power to power equipment such as a combiner box or an inverter, so that the installation of the modules or the cells is required to be absolutely safe. If the photovoltaic modules have abnormal conditions such as over-temperature, over-voltage or over-current, the abnormal photovoltaic modules are required to be actively triggered to be turned off, and when the abnormal photovoltaic modules exit from the abnormal state and return to the normal state, the abnormal photovoltaic modules are required to be connected again, so that absolute safety is also required. In addition, in some occasions, the generated energy of the component needs to be detected or the output power condition needs to be monitored, which is the basis for judging the quality of the component, for example, if the generated energy of the component is obviously reduced, an abnormal event of power generation is likely to occur and is shielded by bird droppings, dust, buildings, tree shadows, clouds and the like, and measures such as cleaning batteries or changing the installation direction are needed. As known to those skilled in the art, a monocrystalline silicon solar cell, a polycrystalline silicon solar cell, an amorphous silicon solar cell, and the like are materials whose characteristics are easily degraded, and it is essential to monitor the degradation degree of a module, which is very important for determining the quality of a battery. The problems are that: we do not know how to discriminate those components in a large array of components as anomalous and those components as normal, and the following will address this problem. In many cases, the cells or assemblies with poor quality are directly judged in the installation stage, the problem cells with quality defects are never allowed to be assembled/installed in the photovoltaic cell array, otherwise, the generation efficiency of the whole array is low when the cells with quality problems enter the photovoltaic cell array, and worse, the abnormal voltage value or current value of one or more problem cells can cause the whole cell string group to be damaged at the same time, so that great loss is caused.
See fig. 1, the zones directly in series with a conventional photovoltaic moduleThe difference lies in that: firstly, any photovoltaic module is provided with a power optimizer, the power optimizer completes voltage matching and electrical isolation between a battery and an inverter, and then the inverter completes inversion conversion from direct current to alternating current and supplies power to a terminal load. Similar to the conventional scheme, the photovoltaic power generation system is provided with a plurality of photovoltaic modules PV1, PV2 \8230, 8230and PVN which are connected in series to form a battery string, and the battery string is formed by connecting photovoltaic modules PV1 to PVN which are connected in series in N levels. The photovoltaic modules or photovoltaic cells PV are each provided with a power optimization circuit PO that performs maximum power tracking MPPT: for example, the photovoltaic voltage generated by the first photovoltaic module PV1 in the cell string is converted from dc to dc by the first power optimization circuit PO1 to perform power optimization, the photovoltaic voltage generated by the second photovoltaic module PV2 is converted from dc by the second power optimization circuit PO2, and the photovoltaic voltage generated by the photovoltaic module PVN to the nth stage is converted from dc by the power optimization circuit PON to perform power optimization. In essence, the voltage output by the power optimization circuit PO corresponding to each photovoltaic cell PV can be indicative of the actual voltage that the photovoltaic cell PV provides across the string of photovoltaic cells. The photovoltaic cell string set of any string is set to be connected with a first-stage photovoltaic module PV1, a second-stage photovoltaic module PV2 \8230inseries, and the photovoltaic modules from the Nth stage to the Nth stage are connected in series: the first-stage power optimization circuit PO1 performs maximum power tracking on the photovoltaic voltage source of the first-stage photovoltaic cell PV1 to perform voltage conversion and output V 1 The second stage power optimization circuit PO2 outputs V 2 The power optimization circuit PON of the nth stage performs maximum power tracking on the voltage of the photovoltaic cell PVN of the nth stage to perform dc voltage conversion and output V N 。
Referring to fig. 1, it can be calculated that the total string level voltage on any string of pv cell strings is roughly equal to: voltage V output by first stage power optimization circuit PO1 1 Plus the voltage V output by the PO2 circuit of the second stage 2 And the voltage V output by the third-stage power optimization circuit PO3 3 823080, 8230and accumulating the DC voltage V output by the PON to the Nth level power optimization circuit N The operation result of the cascade voltage is equal to V 1 + V 2 +……V N . The topology of the power optimization circuit/optimizer or the voltage conversion circuit PO referred to in this context is essentially a DC-to-DC/DC converter, and typical BUCK converters BUCK, BOOST converters BOOST, BUCK-BOOST converters BUCK-BOOST, etc. are all applicable to the power optimization circuit. It should be emphasized that any solution for maximum power tracking of a photovoltaic cell disclosed in the prior art is also applicable to the voltage conversion circuit of the present application, and common maximum power tracking methods include a constant voltage method, a conductance increment method, a disturbance observation method, and the like, and the detailed description of the solution for performing maximum power tracking on the voltage conversion circuit is not repeated herein. The voltage output by the power optimization circuit corresponding to each photovoltaic cell is explained before to characterize the actual voltage that the photovoltaic cell provides across the string of photovoltaic cells: the first-stage power optimization circuit PO1, the second-stage power optimization circuit PO2 to the Nth-stage power optimization circuit PON and the like are connected in series through a series connection transmission line LAN, N is a natural number, and the cascade voltage superposed by the optimizer on the transmission line is transmitted to power equipment INVT such as a combiner box/an inverter through a direct current bus for combination/inversion. A bus capacitor CD for stabilizing voltage is also connected in series between the positive and negative poles of the transmission line LAN as a dc bus.
Referring to fig. 2, in order to achieve these predetermined objectives, the power optimization system integrated with a communication function according to the present application, which is subsequently referred to herein, may reflect all operating parameters of the photovoltaic cells onto the power line by using power carriers, and provides a suitable solution for the photovoltaic power station to perform fault alarm, fault fast positioning, etc. on the cells, and is suitable for grid-connected or off-grid photovoltaic power generation systems of different scales. Especially, many battery anomalies can be found in the working stage of the battery to avoid the fault battery existing in the photovoltaic battery array for a long time, and the improvement of the battery safety level in the working stage is also one of the measures of the application. The carrier sending module CSG is used in cooperation with the processor 200, the processor 200 uses an unillustrated collecting module to collect a series of specified working parameters such as voltage, current, power, temperature and power generation amount of the photovoltaic cell PV, it is noted that the collecting module for collecting the working parameters belongs to the prior art, and the target working parameters may also include peripheral environmental factors where the photovoltaic module is located, which are detected by an environmental monitor: the collection module of each parameter such as ambient temperature, humidity, wind speed, illumination and atmospheric pressure, voltage acquisition module and current acquisition module and power acquisition module and temperature acquisition module and generated energy acquisition module belongs to prior art, and any scheme that can gather these operating parameter of battery all is applicable to this application, and this application is no longer explained current or the concrete collection module alone of voltage and temperature alone.
Referring to fig. 2, in an alternative embodiment: the first input end of the first stage voltage conversion circuit PO1 is connected to the positive electrode of the paired photovoltaic cell PV1, and the second input end of the first stage voltage conversion circuit PO1 is connected to the negative electrode of the photovoltaic cell PV1, the voltage conversion circuit PO1 outputs a stable voltage between the first output end or the first node N1 and the second output end or the second node N2, namely the first stage voltage conversion circuit PO1 captures a voltage source generated by the photovoltaic cell PV1 through the photovoltaic effect between the first input end and the second input end to perform power optimization to provide an output voltage. In an alternative embodiment presented in the present application, a leg called the carrier sending module CSG is directly connected between the first node N1 and the second node N2. In a non-illustrated embodiment, if the carrier transmission module of another type uses a carrier transmission circuit with a coupling transformer, the carrier transmission module of another coupling transformer type does not need to be connected between the first node and the second node, but instead only needs to connect the secondary winding of the coupling transformer between the serial connection line LAN and the first output terminal of the voltage conversion circuit or between the serial connection line LAN and the second output terminal of the voltage conversion circuit, and then a carrier pulse is input from the primary winding of the coupling transformer, and a carrier signal can be coupled or injected onto the bus from the first node or the second node. The above embodiment is to directly connect the carrier transmitting module CSG between the first node N1 and the second node N2 according to the scheme of fig. 2, so as to directly inject the carrier signal into the first node and the second node at the same time. The above is considered in terms of the station transmitting the carrier signal, and the station receiving the carrier signal can then decode/decode the carrier signal on those connected lines LAN connected to the first node and/or the second node using any currently known carrier decoding module. After the processor 200 associated with the photovoltaic cell transmits the data of the photovoltaic cell PV (e.g. the target operating parameter data of the cell) to the connection line LAN through any type of carrier sending module, other electronic devices can decode the carrier on the connection line LAN by using the DECODER. As a side for sensing and decoding the Carrier Signal, the DECODER is usually provided with a Carrier capture sensor module and a band pass filter module, and a processing unit similar to MCU/DSP, etc., wherein the power line passes through the Carrier capture sensor module (for example, using a rogowski air coil sensor, etc.) to detect the Carrier Signal on the transmission line by the sensor module, and in order to accurately capture real Carrier data and shield noise, the band pass filter module further filters the Carrier Signal sensed by the sensor module to remove noise not in a specific frequency range, and on the contrary, only those Carrier signals in the specific frequency range can represent the expected real Carrier Signal, and the processing unit receives the real Carrier Signal and decodes its Carrier data. Therefore, the carrier sending module CSG is used to transmit the power carrier signal to the serial connection line, the carrier signal can be converted into a binary symbol according to various currently specified communication protocols to perform data information interaction, and the decoding device can learn the meaning of data or instructions carried by the carrier signal sent by the carrier sending module CSG on the power line as long as it detects the power carrier on the connection line and then performs decoding. Note that the carrier wave form adopted by the processor 200 to broadcast/transmit the target working data is only an example in this application, and wireless communication forms such as wireless module WIFI or GPS or infrared-bluetooth (Blue-Tooth) can also be selected as an alternative in the industry to achieve the same function. And a DECODER DECODER is integrated at the data acquisition end for acquiring the battery data.
Referring to fig. 2, in practical applications, a large number of photovoltaic cells or photovoltaic modules are connected in series to form a desired string of cells, assuming a total of N levels of photovoltaic cells PV1, PV2\8230; \8230andPVN series connection, where N is usually a natural number greater than 1, the string voltage of the battery string is roughly equal to: voltage V output by first stage photovoltaic cell PV1 1 Plus the voltage V output by the second stage photovoltaic cell PV2 2 The voltage V output by the third-stage PV3 is added to the voltage 823030that is output by the Nth-stage PV cell N Is equal to V 1 + V 2 +……V N . The string voltage of the battery string is sent to the power equipment ESY such as the combiner box or the inverter. The total N-level photovoltaic cells PV1 and PV2 8230, wherein 8230is connected with PVN in series, wherein certain photovoltaic modules have no reason, the generated energy is reduced, or the voltage is reduced or the temperature of the modules suddenly rises too high, and the like, and belong to abnormal events of power generation, particularly, the battery hot spot effect caused by shadow shielding is a negative threat, and the battery hot spot effect can cause certain cells to be converted from a power supply to a load to cause the heat of a battery panel to be burnt out.
Referring to fig. 2, each photovoltaic module or photovoltaic cell is configured with a voltage conversion circuit that performs voltage boosting or voltage dropping or voltage boosting and voltage dropping: for example, a photovoltaic voltage generated by a first photovoltaic module PV1 in a cell string is subjected to DC/DC voltage conversion by a first voltage conversion circuit PO1 to perform voltage up-down, a photovoltaic voltage generated by a second photovoltaic module PV2 is subjected to voltage conversion by a second voltage conversion circuit PO2, \8230, and a photovoltaic voltage generated by a photovoltaic module PON up to an nth level is subjected to voltage conversion by a nth level voltage conversion circuit PON to perform a voltage up-down function. It is only the voltage output by the voltage conversion circuit PO corresponding to each photovoltaic cell PV that can represent the actual voltage that the photovoltaic cell PV provides on the photovoltaic cell string. The voltage conversion circuit PO or voltage converter is essentially a dc-to-dc voltage converter topology. In addition to collecting data for the photovoltaic module, the processor 200 described above also outputs a switching control signal for driving the voltage converter: the on or off state of the power switches in the voltage converter is substantially controlled by a switch control signal or modulation signal output by the microprocessor 200, such as a logic device, a plurality of processors, a control device, a state machine or controller or chip, a software-driven controller, a gate array and/or other equivalent controllers, wherein a pulse width modulation signal is particularly typical as the switch control signal. Fig. 2 shows that the first-stage voltage conversion circuit PO1, the second-stage voltage conversion circuit PO2, up to the so-called nth-stage voltage conversion circuit PON, and the like are connected in series via a serial line LAN, and a serial voltage obtained by superimposing voltages output from the voltage conversion circuits PO1 to PON on a transmission serial line is supplied to an electric power device ESY similar to a combiner box or an inverter for combining and re-inverting, and the like.
Referring to fig. 3, the basic principle of implementing the maximum power point tracking algorithm is explained by taking an optional two photovoltaic modules PV _ M and PV _ N as an example: the adjacent or non-adjacent photovoltaic modules PV _ M and PV _ N supply power to a voltage conversion circuit or voltage converters PO _ M and PO _ N, respectively, which performs maximum power tracking on the photovoltaic cells. The conversion efficiency of a photovoltaic module or cell is mainly affected by two aspects: the first is the internal cell characteristics of the photovoltaic cell; the second is the surrounding use environment of the battery, such as the solar radiation intensity, load condition, temperature condition, and the like. Under different external conditions, the photovoltaic cell can operate at different and unique maximum power points, and the real-time optimal working state of the photovoltaic cell under any illumination condition should be searched to convert the light energy into electric energy to the maximum extent.
Referring to fig. 3, the photovoltaic module PV _ M generates a desired output voltage using the voltage conversion circuit PO _ M while performing maximum power point tracking. The first input terminal NI1 of the voltage conversion circuit PO _ M is connected to the positive pole of the photovoltaic module PV _ M and the second input terminal NI2 of the voltage conversion circuit PO _ M is connected to the negative pole of the photovoltaic module PV _ M. Note that the first output terminal NO1 of the voltage conversion circuit PO _ M is coupled to the only first node ND1 of the voltage conversion circuit PO _ M, the second output terminal NO2 of the voltage conversion circuit PO _ M is connected to the second node ND2 of the voltage conversion circuit PO _ M, and further an output capacitor CO is connected between the first node ND1 and the second node ND 2. The voltage conversion circuit performs DC/DC voltage conversion on the voltage provided by the photovoltaic module and performs maximum power tracking calculation synchronously, so that the DC output voltage output by the voltage conversion circuit PO _ M is generated between the first output terminal and the second output terminal of the voltage conversion circuit PO _ M, and the output voltage is loaded on the output capacitor CO between the first node ND1 and the second node ND 2. That is, it corresponds to an output capacitor connected between the first node N1 and the second node N2 of the voltage conversion circuit itself of fig. 2. The power switch S1 and the power switch S2 of the BUCK conversion circuit BUCK in the voltage conversion circuit PO _ M are connected in series between the first input terminal NI1 and the second input terminal NI2, and the power switch S3 and the power switch S4 of the BOOST conversion circuit BOOST in the voltage conversion circuit PO _ M are connected in series between the first output terminal NO1 and the second output terminal NO 2. The power switch S1 and the power switch S2 in the Buck converter circuit are both connected to a first interconnection node NX1, and the power switch S3 and the power switch S4 in the Boost converter circuit are both connected to a second interconnection node NX2, so that a main inductance element L is disposed between the first interconnection node NX1 to which the front-side power switches S1 to S2 are connected and the second interconnection node NX2 to which the rear-side power switches S3 to S4 are connected in the Buck-Boost circuit topology, and the second output terminal NO2 and the second input terminal NI2 can be directly coupled together and set their potentials to a reference potential REF1. Corresponding to the output capacitance CO provided between the first output terminal and the second output terminal is an input capacitance CIN provided between the first input terminal NI1 and the second input terminal NI2 of the converter. The carrier transmitting module CSG configured by the voltage conversion circuit PO _ M may be connected between the first node N1 and the second node N2 on the output side of the voltage conversion circuit PO _ M. The direct driving capability of the processor 200 configured in the voltage conversion circuit PO _ M is weak, and it is not able to directly drive the switches such as MOSFET or IGBT, and the driver/buffer with stronger driving capability can be used to enhance the strength of the switch control signal to drive the power switches S1-S4.
Referring to fig. 3, the photovoltaic module PV _ N generates a desired output voltage while performing maximum power point tracking using the voltage conversion circuit PO _ N, the first input terminal NI1 of the voltage conversion circuit PO _ N is connected to the positive electrode of the photovoltaic module PV _ N and the second input terminal NI2 of the voltage conversion circuit PO _ N is connected to the negative electrode of the photovoltaic module PV _ N. Note that the first output terminal NO1 of the voltage conversion circuit PO _ N is connected to a first node ND1 uniquely corresponding to the voltage conversion circuit PO _ N itself, and the second output terminal NO2 of the voltage conversion circuit PO _ N is connected to a second node ND2 uniquely corresponding to the voltage conversion circuit PO _ N itself, and an output capacitor CO is further connected between the first node ND1 and the second node ND 2. The voltage conversion circuit PO _ N performs DC/DC voltage conversion on the voltage of the photovoltaic module PV _ N and performs maximum power tracking calculation synchronously, so that the DC output voltage output by the voltage conversion circuit PO _ N is generated between the first output terminal NO1 and the second output terminal NO2 of the voltage conversion circuit PO _ N, that is, the output voltage is applied to the output capacitor CO of the voltage conversion circuit PO _ N. The output capacitor CO is connected between the first node N1 and the second node N2 of the voltage conversion circuit itself in fig. 2. The power switch S1 and the power switch S2 of the BUCK conversion circuit BUCK in the voltage conversion circuit PO _ N are connected in series between the first input terminal NI1 and the second input terminal NI2, and the power switch S3 and the power switch S4 of the BOOST circuit BOOST in the voltage conversion circuit PO _ N are connected in series between the first output terminal NO1 and the second output terminal NO 2. Both the Buck power switch S1 and the Buck power switch S2 are connected to a first interconnection node NX1, both the Boost power switch S3 and the Boost power switch S4 are connected to a second interconnection node NX2, a main inductance element L is provided between the first interconnection node NX1 to which both the front side power switches S1 to S2 are connected and the second interconnection node NX2 to which both the rear side power switches S3 to S4 are connected in the Buck-Boost circuit, and the second output terminal NO2 and the second input terminal NI2 in the voltage conversion circuit PO _ N may be directly coupled together and set their potentials to a reference potential REF2. Also in the voltage conversion circuit PO _ N, corresponding to the output capacitor CO generally disposed between the first output terminal NO1 and the second output terminal NO2, is an input capacitor CIN disposed between the first input terminal NI1 and the second input terminal NI2 in the voltage conversion circuit PO _ N, and the carrier transmitting module CSG configured by the voltage conversion circuit PO _ N may be connected between the first node N1 and the second node N2 of the voltage conversion circuit PO _ N.
Referring to fig. 3, the voltage conversion circuit PO _ M and the voltage conversion circuit PO _ N are adjacent and connected in series, and in the series relationship of the voltage conversion circuits, for example: the second node ND2 of the previous stage voltage conversion circuit PO _ M is connected to the first node ND1 of the next stage voltage conversion circuit PO _ N. The multi-stage voltage conversion circuits PO1, PO2, \8230areconnected in series according to the rule, and any previous stage of voltage conversionThe second node ND2 of the circuit PO _ M is coupled to the first node ND1 of the adjacent succeeding stage voltage converting circuit PO _ N through the transmission line LAN, or the output capacitance CO of any preceding stage voltage converting circuit PO _ M is connected in series by the transmission line LAN and the output capacitance CO of the adjacent succeeding stage voltage converting circuit PO _ N. By analogy, the output capacitors C of the multi-stage voltage conversion circuit PO1 \ 8230and PON are connected in series O Are connected in series with each other: that is, the output capacitors CO and CO of the PO2 and CO \8230ofthe PO3 of the voltage converting circuit PO1 and the output capacitors CO of the PON and the like are connected in series by the transmission line LAN, the total cascade voltage provided by a series of the converting circuits PO1-PON and the like connected in series is equal to the sum of the voltages of their respective output capacitors CO of the voltage converting circuits PO 1-PON. In other words, the total string voltage of the entire series-connected plurality of converters may be provided between the first node of the voltage conversion circuit of the first stage and the second node of the voltage conversion circuit of the last final stage. In other words: the connection line LAN, which connects the voltage conversion circuits BS1 to BSN in series, provides a propagation path of the carrier signal in addition to the superposition path of the dc voltage.
Referring to fig. 3, taking the voltage conversion circuit PO _ M as an example, the carrier transmitting module configured by the voltage conversion circuit PO _ M includes a branch circuit having a first resistor R1, a bypass capacitor CBC and a switch element SW2, which is connected in series between a first node ND1 and a second node ND2 of the voltage conversion circuit PO _ M, and a second resistor R2 connected in parallel to two ends of the bypass capacitor CBC is further disposed in the branch circuit. As for the mechanism of the carrier sending module CSG sending the carrier, the voltage converting circuit PO _ M is taken as an example to be explained as follows: the driver signal DRI from the processor 200 configured by the voltage conversion circuit PO _ M drives the switching element SW2 in the carrier branch to switch rapidly between on and off, the switching element SW2 having a current flowing through it when switched on and the switching element SW2 having a current not flowing through it when switched off, so that the so-called carrier branch actively introduces a disturbing signal between the first node ND1 and the second node ND2 due to the driving signal DRI driving the switching element SW2 to switch rapidly off and on, the frequency of the disturbing signal being determined entirely by the driver signal DRI, the disturbing signal being injected directly onto the serial line LAN from the first node ND1 and/or the second node ND 2. The disturbance signal generated by the branch (carrier transmitting module CSG) due to the change of the current generated by the carrier branch off current being cut off and the carrier branch on is regarded as the power carrier signal. The above is primarily considered in view of the station transmitting the carrier signal, if the station is considered in view of receiving the carrier signal, decoding/decoding of the carrier signal can be achieved on those connected/series LANs shown in fig. 2 by means of currently any carrier decoding module belonging to the known art.
Referring to fig. 3, to explain the inventive spirit of the scheme for implementing current detection in the present application, a voltage converter for implementing power conversion is illustrated as an example, and the voltage converter is a BUCK circuit, i.e., the switch S1 and the switch S2 constitute a BUCK single arm. In the BUCK circuit, the illustrated switches S3-S4 can be directly eliminated from the circuit topology, and the main inductive element L of the BUCK circuit can be directly connected between the interconnection node NX1 and the first output NO 1. Or if the voltage converter is operated in the BUCK state, the switch S4 can be directly and continuously turned on, and the switch S3 can be continuously turned off, only the power switch S1 and the power switch S2 on the front side are driven to switch at high frequency, and the power conversion BUCK circuit can independently operate.
Referring to fig. 3, in order to explain the inventive spirit of the scheme for implementing current detection according to the present application, a voltage converter for implementing power conversion is illustrated as an example, and the voltage converter is a BOOST circuit, i.e., the switch S3 and the switch S4 constitute a BOOST single arm. In a BOOST circuit, the switches S1-S2 can be directly eliminated from the circuit topology, and the main inductive element L in the BOOST circuit can be connected directly between the interconnect node NX2 and the first input NI 1. Or if the voltage converter works in the BOOST state, the switch S1 can be directly and continuously turned on, and the switch S2 can be continuously turned off, only the power switch S3 and the power switch S4 on the rear side are driven to switch at high frequency, and the BOOST circuit of the power conversion can operate independently.
Referring to fig. 3, another alternative voltage converter for implementing power conversion is taken as an example: the power switches S1 and S2 are connected in series between the first input NI1 and the second input NI2, and the switches S3 and S4 using power transistors are connected in series between the first output NO1 and the second output NO2, note that the power switches S1 and S2 are connected to the interconnection node NX1 and the power switches S3 and S4 are connected to the interconnection node NX2, and the main inductance element L is additionally connected between the first interconnection node NX1 and the second interconnection node NX 2. Therefore, the single arms S1-S2 used as the BUCK of the front stage and the single arms S3-S4 used as the BOOST of the back stage form a BUCK-BOOST circuit, and the BUCK-BOOST circuit has the power conversion capability of BUCK and BOOST, and is in an H bridge type.
Referring to fig. 4, in addition to the carrier signals transmitted by the respective carrier modules of the voltage conversion circuit PO _ M and the voltage conversion circuit PO _ N being broadcast on the transmission serial line LAN as expected, the carrier waves may propagate backward to the voltage conversion circuit and even to the positive and negative electrodes of the battery in the direction of the battery, i.e., from the first output terminal NO1 coupled to the first node ND1 or from the second output terminal NO2 coupled to the second node ND 2. In order to avoid such negative effects of the carrier, it may be chosen to connect the first inductor LA between the second node ND2 and the second output terminal NO2, or connect the first inductor LA between the first node ND1 and the first output terminal NO1, where the first inductor LA may partially rectify the carrier to prevent backward flow, but this effect is very limited, and the carrier sending module CSG may be replaced by another carrier generation mode.
Referring to fig. 5, in an alternative embodiment, an auxiliary inductor is arranged in a voltage output path of a voltage conversion circuit/optimizer for use as a switched mode power supply, the voltage path comprising a path coupled to a first output terminal or a second output terminal. For example, the first inductance LA is selected to be connected between the second node ND2 and the second output terminal NO2, or alternatively, the first inductance LA is selected to be connected between the first node ND1 and the first output terminal NO 1. A first switch SA and a first capacitor CA are connected in parallel at two ends of a first inductor LA: the first switch SA and the first capacitor CA which are connected in series with each other are connected in parallel at two ends of the first inductor LA, and the positions of the first switch SA and the first capacitor CA can be exchanged. The turning on or off of the first switch is controlled by a driving signal sent by the processor 200. The voltage conversion circuit PO _ M is taken as an example to explain how it cooperates with the first switch SA, the first capacitor CA and the first inductor LA to generate the carrier. The non-communication stage of the voltage conversion circuit PO _ M not transmitting the carrier signal drives the first switch SA to be continuously turned off, and the voltage conversion circuit is directly embodied as a power optimizer and cannot generate any carrier. However, during the communication phase in which the voltage conversion circuit PO _ M transmits the carrier signal, the first switch SA must be driven to switch at high frequency between ON and OFF: the first switch is not allowed to be continuously turned on or continuously turned off, the first switch SA is switched to the on state, the first switch SA and the first capacitor CA form a parallel resonant circuit at this stage, the frequency range of the high-frequency switching ripple on the main inductance element L falls within the range of the resonant frequency point of the resonant circuit and is filtered, the high-frequency switching ripple of the switching control signal (such as PWM) mixed into the output voltage of the voltage conversion circuit in the process of driving the voltage conversion circuit PO _ M is filtered from the output voltage VM generated by the voltage conversion circuit PO _ M, the high-frequency switching ripple on the dc transmission line LAN transmitting the output voltage of the voltage conversion circuit PO _ M is filtered because of the high-frequency switching ripple regarded as the carrier signal of the voltage conversion circuit PO _ M, the high-frequency switching ripple no longer exists, that is, the carrier signal is filtered, this case is defined as the first logic state of the carrier signal, and the carrier signal sensed on the dc transmission line by the decoder is low level, that is, for example, a symbol [0] is transmitted. Driving the first switch SA to switch on and off at high frequency: when the first switch SA is switched to an off state, the parallel resonant circuit formed by the first switch SA and the first capacitor CA at this stage is disabled, a high-frequency switch ripple in which a switch control signal is mixed to an output voltage in the process of driving the voltage conversion circuit PO _ M is undoubtedly superimposed on the output voltage VM generated by the voltage conversion circuit PO _ M, a high-frequency switch ripple regarded as a carrier signal is mixed on the dc transmission line LAN transmitting the output voltage, the high-frequency switch ripple is mixed again to the dc voltage, that is, the carrier signal is not filtered, this condition is defined as a second logic state of the carrier signal, and the carrier signal sensed by the decoder on the dc transmission line LAN is at a high level, for example, a symbol [1] is transmitted. In an alternative embodiment, the BUCK-BOOST of FIG. 5 may be replaced with a BUCK or BOOST topology. In an alternative embodiment, the carrier signal of the voltage converting circuit PO _ M should not be affected by other voltage converting circuits remaining in the series of voltage converting circuits PO1-PON, so the first switch SA of other voltage converting circuits should be turned off during the communication phase that the voltage converting circuit PO _ M transmits the carrier, for example, the first switch SA configured in the voltage converting circuit PO _ N is turned off during the communication phase that the voltage converting circuit PO _ M transmits the carrier in fig. 5.
Referring to fig. 6, in an alternative embodiment, processor 200 of voltage translation circuit PO _ M is configured to send data onto the transmission line in a manner that: the first switch SA of the control/drive voltage conversion circuit PO _ M configuration is turned off or on at a high frequency for a preset time period TPRE, which means that the symbol [0] or [1] is transmitted. A specific scheme is, for example, to require the first switch to be switched on or off at a high frequency in each byte cycle of the TPRE range (communication period during which data is transmitted). For example, it is required that the first switch SA is turned on at least once during the first data transmission period T1 of the time period TPRE, and a situation occurs where the switching ripple of the voltage conversion circuit PO _ M is filtered out, and the switching ripple curve has a filtered segment DER1 during the turn-on period, and the byte represented by this event is denoted as [0]. The first switch SA is required to switch off during the second data transmission period T2 of the time period TPRE, the segment of the switching ripple curve that is not filtered out, the byte represented by this event is denoted as [1]. It is required that the first switch SA is turned on one or more times during the third data transmission period T3 of the time period TPRE, for example, the switching ripple curve has filtered segments DER2 and DER3 during the period of time when the first switch SA is turned on twice, and the byte represented by this event is denoted as [0]. In the exemplary embodiment of the periods T1-T3, three consecutive bytes [010] or [101] are transmitted. According to the basic carrier transmission and detection principle and so on, there may be more data transmission cycles within the time period TPRE, which is not described in detail herein, and each cycle may implement transmission of one binary symbol 1 or 0. A 1 or 0 is considered to be written if a ripple signal occurs on the transmission line for three consecutive periods or more, and conversely, a 0 or 1 is considered to be written if there is no ripple signal on the transmission line. The voltage fluctuation of the high-frequency switching ripple has a certain jump range, and as shown in fig. 6, its positive amplitude is not higher than the upper limit value VHI and its negative amplitude is not lower than the lower limit value VLO, the high-frequency switching ripple is easily captured from the stable steady output voltage VM or the total cascade voltage on the transmission line LAN. In a preferred but not necessary embodiment, as the communication time period TPRE, the first switch SA is preferably turned on at least once when the first period T1 delivers the first start byte, thereby being characterized by the carrier filtering event, because the first switch SA is driven to be continuously turned off during the non-communication phase when the voltage conversion circuit PO _ M does not transmit the carrier signal, and how to distinguish the non-communication phase from the communication phase is one of the issues to be considered: the start byte of the communication time period TPRE may indicate that a carrier communication for performing a data transmission has started and that the voltage converter has started to go from said non-communication phase into said communication phase if it is characterized by the occurrence of an event filtering out the carrier. As an alternative, the first start byte may also be considered as a start bit only when defining the communication protocol, from which the data following the start bit is the real data. The switching control signal, e.g. PWM, has a switching frequency in driving the power switches S1-S4 of the voltage conversion circuit, which is preferably higher than the switching frequency at which the first switch SA is driven to switch on and off at a high frequency during said communication phase.
Referring to fig. 7, in an alternative embodiment, considering that the high-frequency switching ripple of the voltage conversion circuit PO _ M, which is reflected on the inductor L, is very weak, especially when the output voltage of the voltage conversion circuit PO _ M is relatively high or the total serial voltage of the entire battery string is relatively large, it is difficult to sense the switching ripple from the transmission line LAN. To overcome this problem, in the embodiment of fig. 7, an additional option is to connect a second switch SPM and a second capacitor CP in series between the first node ND1 and the second node ND2 of the voltage conversion circuit PO _ M, where it is permissible that the second switch SPM can be driven by the processor 200 to be turned on or off during the non-communication phase. However, in the communication phase, and more particularly in the phase in which the carrier signal has the second logic state, that is, when the first switch SAM of the voltage conversion circuit PO _ M is switched to the off state at a high frequency, the second switch SPM must be switched on, the first switch SAM and the second switch SPM correspond to complementary switches at that moment, when the first switch SAM is switched off, the second switch SPM is switched on to let the frequency range of the high-frequency switching ripple enter the resonant frequency point of the capacitor CP and the inductor LA of the converter, so that the fluctuation range of the high-frequency switching ripple is increased and is therefore easier to sense, and it is shown in fig. 6 that the positive amplitude of the switching ripple is not higher than the upper limit value VHI and the negative amplitude of the switching ripple is not lower than the lower limit value VLO. Referring to fig. 8, due to the introduction of the capacitor CP, the high-frequency switching ripple is more easily captured from the steady output voltage VM or the total cascade voltage on the transmission line after increasing the amplitude, and the positive amplitude of the high-frequency switching ripple exceeds the upper limit VHI and the negative amplitude thereof is lower than the lower limit VLO. In an alternative embodiment, the carrier of the voltage converting circuit PO _ M should not be affected by other voltage converting circuits remaining in the series of voltage converting circuits PO1-PON, and therefore the first switch of other voltage converting circuits should be turned off during the communication phase that the voltage converting circuit PO _ M transmits the carrier, for example, the first switch SAN in the voltage converting circuit PO _ N is turned off during the communication phase that the voltage converting circuit PO _ M transmits the carrier in fig. 7, and the first switch SAN and the first capacitor CAN are disconnected, at which time the second switch SPN connected in series between the first node ND1 and the second node ND2 of the voltage converting circuit PO _ N and the switch SPN in the second capacitor CP are allowed to be turned on or off. However, the first switch SAM and the first capacitor CAM in the voltage conversion circuit PO _ M that transmits the carrier signal are connected and disconnected at a high frequency.
Referring to fig. 9, another embodiment for implementing carrier transmission is shown, the topology is similar to that of fig. 1-7, except that a reference voltage source VRI is additionally introduced. Taking the voltage conversion circuit PO _ M as an example: the first inductor LA is connected between the second output terminal NO2 of the voltage converting circuit PO _ M and the second node ND2, the first terminal of the first capacitor CA is coupled to the reference voltage source VRI, the second terminal of the first capacitor CA is coupled to the second node ND2 of the converting circuit PO _ M, and the first switch SA is connected between the first terminal of the first capacitor CA and the second output terminal NO2 of the converting circuit PO _ M. The reference voltage source VRI coupled to the first end of the first capacitor CA of the voltage conversion circuit PO _ M may be an independent stable power source, or a voltage provided by the positive electrode of the photovoltaic module PV paired with the voltage conversion circuit PO _ M, i.e. an input voltage of the voltage conversion circuit PO _ M, or an output voltage of the voltage conversion circuit PO _ M itself, i.e. a potential at the first output terminal NO1 thereof.
Referring to fig. 9, another embodiment for implementing carrier transmission is shown, the topology is similar to that of fig. 1-7, and a reference voltage source VRI is also additionally introduced. Taking the voltage conversion circuit PO _ N as an example: the first inductor LA is connected between the second output terminal NO2 of the voltage converting circuit PO _ N and the second node ND2, the first terminal of the first capacitor CA is coupled to the reference voltage source VRI, the second terminal of the first capacitor CA is coupled to the second node ND2 of the converting circuit PO _ N, and the first switch SA is connected between the first terminal of the first capacitor CA and the second output terminal NO2 of the converting circuit PO _ N. The reference voltage source VRI coupled to the first end of the first capacitor CA of the voltage conversion circuit PO _ N may be an independent stable power source, or a voltage provided by the positive electrode of the photovoltaic module PV paired with the voltage conversion circuit PO _ N, i.e. an input voltage of the voltage conversion circuit PO _ N, or an output voltage of the voltage conversion circuit PO _ N itself, i.e. a potential at the first output terminal NO1 thereof.
Referring to fig. 9, in an alternative, but not required, embodiment, the turning on or off of the first switch SA is controlled by a driving signal sent by the processor 200 of the voltage conversion circuit pair. The voltage conversion circuit PO _ M is taken as an example to explain how it cooperates with the first switch SA, the first capacitor CA and the first inductor LA to generate the carrier. The non-communication stage of the voltage conversion circuit PO _ M not transmitting the carrier signal drives the first switch SA to be continuously turned off, and the voltage conversion circuit is directly embodied as a power optimizer and cannot generate any carrier. However, during the communication phase in which the voltage conversion circuit PO _ M transmits the carrier signal, the first switch SA must be driven to switch at high frequency between ON and OFF: the first switch SA and the first capacitor CA form a relatively closed loop at the stage when the first switch SA is switched to the on state, and a potential difference across the charged first capacitor CA is transiently superimposed directly on the dc link LAN carrying the output voltage VM, which potential difference induces a narrow pulse on the link each time the transient is applied to the dc link, resulting in: the condition of the pulse induced on the dc transmission line LAN due to the transient loading of the dc transmission line mixed with this potential difference, which is regarded as a carrier signal, is defined as the carrier signal having the second logic state, and the carrier signal sensed by the decoder on the dc transmission line being high, for example, representing that one symbol [1] is transmitted. The first switch SA is still driven in the communication phase to switch on and off at high frequency: the first switch SA is switched to the off state, at which stage the first switch SA and the first capacitor CA form a closed loop open, the potential difference across the charged first capacitor CA is not transiently superposed on the dc link LAN carrying said output voltage VM, the pulse induced on the dc link as a result of the absence of transient loading of this potential difference on the dc link LAN, which is considered as a carrier signal, is defined as the carrier signal having a first logic state, and the carrier signal sensed by the decoder on the dc link LAN is low, for example, characterized by the transmission of a symbol [0]. The BUCK-BOOST of fig. 9 may be replaced with a BUCK or BOOST topology as an alternative embodiment. In an alternative embodiment, the carrier signal of the voltage converting circuit PO _ M should not be affected by other voltage converting circuits remaining in the series of voltage converting circuits PO1-PON, the first switch SA of other voltage converting circuits should be turned off during the communication phase that the voltage converting circuit PO _ M transmits the carrier, for example, the first switch SA configured in the voltage converting circuit PO _ N is turned off during the communication phase that the voltage converting circuit PO _ M transmits the carrier. The narrow pulses are easily captured from the stable steady output voltage VM or the total cascade voltage on the transmission line.
Referring to fig. 10, another embodiment for implementing carrier transmission is shown, the topology is similar to that of fig. 1-7, except that a reference voltage source VRI is additionally introduced. Taking the voltage conversion circuit PO _ M as an example: the first inductor LA is connected between the second output terminal NO2 of the voltage converting circuit PO _ M and the second node ND2, the first terminal of the first capacitor CA is coupled to the reference voltage source VRI, the second terminal of the first capacitor CA is coupled to the second node ND2 of the converting circuit PO _ M, and the first switch SA is connected between the first terminal of the first capacitor CA and the second output terminal NO2 of the converting circuit PO _ M. The reference voltage source VRI coupled to the first end of the first capacitor CA of the voltage conversion circuit PO _ M may be an independent stable power source, or a voltage provided by the positive electrode of the photovoltaic module PV paired with the voltage conversion circuit PO _ M, i.e. an input voltage at the first input terminal NI1 of the voltage conversion circuit PO _ M, or an output voltage of the voltage conversion circuit PO _ M itself, i.e. a potential at the first output terminal NO1 thereof. What differs from the scheme of fig. 9 is that in this embodiment: the first terminal of the first capacitor CA needs to be indirectly coupled to the reference voltage source VRI via an additional switch SC, i.e. the additional auxiliary switch SC is connected between the reference voltage source VRI and the first terminal of the first capacitor CA. In this alternative embodiment the auxiliary switch SC prevents the first terminal of the first capacitor CA from being continuously charged, e.g. the first capacitor CA needs to be recharged after a so-called narrow pulse of discharge of the first switch SA in the on-state, said first capacitor CA being charged by the power supply VRI by switching the auxiliary switch SC to the on-state, and after the end of the charging the auxiliary switch SC is switched to the off-state. The processor 200 of the voltage conversion circuit PO _ M configuration may be used to drive the auxiliary switch SC. In a more specific embodiment, when the voltage converting circuit PO _ M enters the communication phase and the first switch SA is switched between on and off at a high speed, the auxiliary switch SC and the first switch SA are complementary switches, the auxiliary switch SC needs to be turned off when the first switch SA is turned on to generate a pulse, and the auxiliary switch SC is turned on to charge the capacitor when the first switch SA is turned off after the narrow pulse is generated.
Referring to fig. 10, another embodiment for implementing carrier transmission is shown, the topology is similar to that of fig. 1-7, and a reference voltage source VRI is also additionally introduced. Taking the voltage conversion circuit PO _ N as an example: the first inductor LA is connected between the first output terminal NO1 of the voltage converting circuit PO _ N and the first node ND1, the first terminal of the first capacitor CA is coupled to the reference voltage source VRI, the second terminal of the first capacitor CA is coupled to the first output terminal NO1 of the converting circuit PO _ N, and the first switch SA is connected between the first terminal of the first capacitor CA and the first node ND1 of the converting circuit PO _ N. The reference voltage source VRI coupled to the first end of the first capacitor CA of the voltage conversion circuit PO _ N can be a separate stable power source, or a voltage provided by the anode of the photovoltaic module PV of the PO _ N pair of the voltage conversion circuit PO _ N, i.e. the input voltage at the first input terminal NI1 of the voltage conversion circuit PO _ N. In the scheme of the embodiment: the first terminal of the first capacitor CA needs to be further indirectly coupled to the reference voltage source VRI through an auxiliary switch SC, i.e. the additional auxiliary switch SC is connected between the reference voltage source VRI and the first terminal of the first capacitor CA. In this alternative embodiment the auxiliary switch SC prevents the first terminal of the first capacitor CA from being continuously charged with charge, the first capacitor CA needs to be recharged after the discharge of the first switch SA in the on-state generates so-called narrow pulses, the auxiliary switch SC is switched to the on-state and charges said first capacitor CA via the reference voltage source VRI, and the auxiliary switch SC is switched to the off-state after the charging of the capacitor has ended. The processor 200 configured by the voltage conversion circuit PO _ N can be used to drive the auxiliary switch SC. In a special embodiment, when the voltage conversion circuit PO _ N enters the communication phase and the first switch SA switches between on and off at high frequency, the auxiliary switch SC and said first switch SA are complementary switches, the auxiliary switch SC needs to be turned off when the first switch SA is turned on to generate a pulse, and the auxiliary switch SC is turned on to charge the capacitor when the first switch SA is turned off after a narrow pulse is generated.
Referring to fig. 11, if no carrier wave, i.e., a narrow pulse, is added, the output voltage VM of the previous voltage conversion circuit PO _ M in the normal case shows a positive amplitude not higher than the maximum value VMH of the output voltage and a negative amplitude not lower than the minimum value VML of the output voltage. Referring to fig. 11, due to the introduction of the narrow pulse caused by the discharge of the capacitor CP, the narrow pulse is easier to identify and capture from the stable output voltage VM on the transmission line, or from the transmission line for providing the total cascade voltage, the output voltage VM of the voltage conversion circuit PO _ M is superimposed with the narrow pulse to cause the forward amplitude on the transmission line to exceed the maximum value VMH, in the figure, the voltage difference of the capacitor that can be provided due to the charging on the first capacitor CA is VCA, and it can be observed that after the output voltage VM is superimposed with the voltage difference VCA of the capacitor, the forward amplitude obviously causes the superimposed value to greatly exceed the maximum value VMH. The carrier of the voltage converting circuit PO _ M should not be affected by other voltage converting circuits remaining in the series of voltage converting circuits PO1-PON, so that when the voltage converting circuit PO _ M transmits the communication phase of the carrier represented by the narrow pulse, the first switch of the other voltage converting circuits should be turned off, and in an alternative embodiment, for example, the communication phase of the voltage converting circuit PO _ M transmitting the carrier in fig. 10 causes the first switch SA in the voltage converting circuit PO _ N to be turned off.
Referring to fig. 11, in an alternative embodiment, the processor 200 configured by the voltage conversion circuit PO _ M sends data to the transmission line by: the first switch SA of the control/drive voltage conversion circuit PO _ M configuration is turned off or on at a high frequency for a preset time period TPRE, which means that the symbol [0] or [1] is transmitted. A specific scheme is, for example, to require the first switch to be switched on or off at a high frequency in each byte cycle of the time period TPRE range (communication period during which data is transmitted). For example, if the first switch SA is required to be turned on at least once in the first data transmission period T1 of the time period TPRE, a narrow pulse is injected into the output path of the voltage conversion circuit PO _ M, the output voltage VM of the conversion circuit PO _ M has a curve having a segment DER1 superimposed by the narrow pulse in the on period of the first switch SA, and the byte represented by this event is denoted as [1]. The first switch SA is required to switch off during the second data transmission period T2 of the time period TPRE, the curve of the output voltage VM is free of any pulsed segments, and the byte represented by this event is denoted as [0]. In addition, it is required that the first switch SA is turned on one or more times during the third data transmission period T3 of the time period TPRE, for example, the curve of the output voltage VM has segments DER2 and DER3 of the narrow pulse respectively during the period of two times that the first switch SA is turned on, and the byte represented by this event is denoted as [1]. In the exemplary embodiment of the periods T1-T3, three consecutive bytes [101] or [010] are transmitted. According to the basic principle of carrier transmission and carrier sensing, there may be more data transmission cycles within the time period TPRE, which is not described in detail herein, and each cycle may implement transmission of one binary symbol 1 or 0. In three consecutive periods or more, a 1 or 0 is considered to be written if a narrow pulse, i.e., a carrier, occurs on the transmission line, and conversely, a 0 or 1 is considered to be written if no narrow pulse, i.e., a carrier, occurs on the transmission line. The voltage fluctuation of the output voltage VM originally has a certain fluctuation range, and if it is shown in the figure that its positive amplitude is not higher than the maximum value VMH and its negative amplitude is not lower than the minimum value VML, when the fluctuation range is no longer within the range due to the pulse, it is easy to capture a narrow pulse from the stable steady output voltage VM or the total cascade voltage on the transmission line. In an alternative embodiment, during the communication period TPRE, the first switch SA is preferably turned on at least once during the first period T1 to deliver the first starting byte, thereby being characterized by a narrow pulse event, because the first switch SA is driven to be continuously turned off during the non-communication period when the voltage conversion circuit PO _ M is not transmitting the carrier signal, and how to distinguish the non-communication period from the communication period is one of the issues to be considered: the start byte of the communication period TPRE may indicate that a carrier communication for performing a data transmission has started and that the voltage conversion circuit PO _ M has started to go from said non-communication phase into said communication phase if it is characterized by an event of occurrence of a narrow pulse. As an alternative, the first start byte may also be considered as a start bit only when defining the communication protocol, and only after the start bit, which marks that communication is initiated, is the real data. The switching control signal, such as PWM, has a switching frequency of operation in driving the power switches S1-S4 of the voltage conversion circuit. In an alternative embodiment it is preferably higher than the switching frequency at which the first switch SA is driven to switch on and off at high frequency during said communication phase.
Referring to fig. 10, in an alternative embodiment, the first switch SA is driven to be continuously turned off during a non-communication phase in which the voltage conversion circuit PO _ M does not transmit the carrier signal, and the first switch is driven to be switched on and off at a high frequency during a communication phase in which the voltage conversion circuit PO _ M transmits the carrier signal. The communication phase of the voltage conversion circuit PO _ M for transmitting the carrier signal generates and identifies the mode of the carrier wave, which comprises the following steps: driving the first switch SA to switch on, filtering out high-frequency switch ripples of a switch control signal from the output voltage VM of the voltage conversion circuit PO _ M, which are mixed to the output voltage VM in the process of driving the voltage conversion circuit PO _ M, simultaneously, transiently superimposing the potential difference across the charged first capacitor CA directly onto a dc transmission line that delivers the output voltage VM, and then, in case of a pulse that is considered as a carrier signal and induced by transient loading of the potential difference onto the dc transmission line due to mixing: when a first condition that a ripple component of the high-frequency switch in the carrier signal is removed from the dc link LAN transmitting the output voltage VM and a second condition that a pulse component of the carrier signal induced by the transient application of the potential difference to the dc link is mixed are satisfied, the first condition is defined as a first logic state of the carrier signal. In contrast, the driving of the first switch to switch on and off the high frequency in the communication phase in which the voltage conversion circuit transmits the carrier signal, the mode of generating and identifying the carrier signal in the communication phase in which the voltage conversion circuit PO _ M transmits the carrier signal includes: when the first switch SA is driven to switch off, the output voltage VM of the voltage conversion circuit PO _ M is superimposed with a high-frequency switch ripple in which the switch control signal is mixed into the output voltage VM in the process of driving the voltage conversion circuit PO _ M, so that a high-frequency switch ripple component regarded as a carrier signal is mixed on the dc transmission line that transmits the output voltage VM, and meanwhile, the potential difference across the charged first capacitor CA is not transiently superimposed on the dc transmission line that transmits the output voltage VM, and a pulse component regarded as a carrier signal is induced on the dc transmission line LAN due to lack of transient loading of the potential difference onto the dc transmission line, then: the second logic state of the carrier signal is defined when a third condition that a ripple component of the high-frequency switch considered as a carrier signal is mixed in a dc transmission line for transmitting the output voltage and a fourth condition that a pulse component of the carrier signal is induced in the dc transmission line due to the absence of transient loading of the potential difference on the dc transmission line are satisfied. One of the first logic state and the second logic state is used to characterize a 1 or 0 of the binary symbol and the other is used to characterize the remaining other of the binary symbols, such as the first logic state characterizing a carrier signal as high [1] and the second logic state characterizing a carrier signal as low [0], or the first logic state characterizing a carrier signal as low [0] and the second logic state characterizing a carrier signal as high [1], in general the binary symbols characterized by their logic states are opposite. That is, the schemes of fig. 9 and 5 are used in combination or the schemes of fig. 9 and 7 are used in combination, or the schemes of fig. 10 and 5 are used in combination or the schemes of fig. 10 and 7 are used in combination.
Referring to fig. 9, in an improved embodiment, taking the voltage conversion circuit PO _ M as an example: the first inductor LA is connected between the second output terminal NO2 of the voltage converting circuit PO _ M and the second node ND2, the first terminal of the first capacitor CA is connected to the reference voltage source VRI, the second terminal of the first capacitor CA is connected to the second node ND2 of the converting circuit PO _ M, and the first switch SA is connected between the first terminal of the first capacitor CA and the second output terminal NO2 of the converting circuit PO _ M. The first terminal of the first capacitor CA of the voltage conversion circuit PO _ M may be directly coupled to the reference voltage source VRI or may also be coupled to the reference voltage source VRI with a pull-up resistor RP as shown. The embodiment of the voltage conversion circuit PO _ M of fig. 10 can be modified such that the auxiliary switch SC and the pull-up resistor RP are both connected in series between the first terminal of the first capacitor CA in the voltage conversion circuit PO _ M and the reference voltage source VRI. It should be appreciated that: the pull-up resistor RP that may be additionally added in the voltage conversion circuit PO _ M in fig. 9 and 10 is an option and may be omitted.
Referring to fig. 9, in an improved embodiment, taking the voltage conversion circuit PO _ N as an example: the first inductor LA is connected between the second output terminal NO2 of the voltage converting circuit PO _ N and the second node ND2, the first terminal of the first capacitor CA is coupled to the reference voltage source VRI, the second terminal of the first capacitor CA is coupled to the second node ND2 of the converting circuit PO _ N, and the first switch SA is connected between the first terminal of the first capacitor CA and the second output terminal NO2 of the converting circuit PO _ N. It can be observed that the first terminal of the first capacitor CA of the voltage conversion circuit PO _ N of fig. 9 is directly coupled to the reference voltage source VRI, whereas the first terminal of the first capacitor CA of the voltage conversion circuit PO _ M of fig. 9 can be coupled to the reference voltage source VRI by using the pull-up resistor RP. But as a modified example: the first terminal of the first capacitor CA of the voltage conversion circuit PO _ N in fig. 9 can also be indirectly coupled to the reference voltage source VRI by using a pull-up resistor not shown in the figure, i.e. a pull-up resistor is also connected between the first terminal of the first capacitor CA of the voltage conversion circuit PO _ N and the reference voltage source VRI. As an improvement: the embodiment of the voltage conversion circuit PO _ N of fig. 10 may be modified such that the auxiliary switch SC and the pull-up resistor are both connected in series between the first terminal of the first capacitor CA in the voltage conversion circuit PO _ N and the reference voltage source VRI. It should be appreciated that: the pull-up resistor that may be additionally added in the respective voltage conversion circuits PO _ N in fig. 9 and 10 is an option and may be omitted.
While the foregoing specification teaches, with reference to the specific embodiments provided above, and illustrated in the accompanying drawings, certain embodiments of the present invention as disclosed herein are considered exemplary and not restrictive. Various alterations and modifications will no doubt become apparent to those skilled in the art after having read the above description. Therefore, the appended claims should be construed to cover all such variations and modifications as fall within the true spirit and scope of the invention. Any and all equivalent ranges and contents within the scope of the claims should be considered to be within the intent and scope of the present invention.
Claims (14)
1. A voltage conversion circuit for photovoltaic module power optimization, capable of generating a carrier signal, wherein each cell string for providing a string voltage has a plurality of photovoltaic modules connected in series, each photovoltaic module is configured with the voltage conversion circuit for performing maximum power point tracking and an output voltage outputted by the voltage conversion circuit and subjected to dc voltage conversion by a photovoltaic module paired therewith, and further comprising:
a first inductance arranged on a voltage output path of the voltage conversion circuit functioning as a switched mode power supply;
the first switch and the first capacitor are connected in parallel at two ends of the first inductor and are connected together in series;
each voltage conversion circuit comprises a first input end and a second input end which are coupled to the positive electrode and the negative electrode of one photovoltaic module, a first output end and a second output end which provide output voltage, and an output capacitor of each voltage conversion circuit is connected between the first output end and the second output end; and
the first inductor is connected between the first output end and the first node or between the second output end and the second node;
identifying a pattern of a carrier signal during a communication phase in which the voltage conversion circuit transmits the carrier signal includes:
the first switch is in an off state, the potential difference between two ends of the charged first capacitor is not superposed on a direct current transmission line for transmitting the output voltage, and the condition that the direct current transmission line is lack of the pulse which is transiently loaded on the direct current transmission line and is taken as a carrier signal is defined as that the carrier signal has a first logic state;
the first switch is in the on state, the potential difference across the charged first capacitor is directly superimposed on the dc transmission line carrying the output voltage, and the carrier signal is defined as having a second logic state when the dc transmission line is mixed with pulses, induced by transient loading of the potential difference on the dc transmission line, which are regarded as carrier signals.
2. The voltage conversion circuit for photovoltaic module power optimization capable of generating a carrier signal as claimed in claim 1, wherein:
the voltage conversion circuits are connected in series, and the second node of any previous voltage conversion circuit is coupled to the first node of the adjacent next voltage conversion circuit through the direct current transmission line; thereby, the device
When the voltage conversion circuits of the plurality of stages are connected in series, their respective output capacitances are connected in series with each other, and the total string voltage provided by the voltage conversion circuits of the plurality of stages is equal to the sum of the voltages across their respective output capacitances.
3. The voltage conversion circuit for photovoltaic module power optimization capable of generating a carrier signal as claimed in claim 1, wherein:
the first inductor is connected between the first output end and a first node;
the first end of the first capacitor is coupled to a reference voltage source;
a second terminal of the first capacitor is coupled to the first output terminal;
the first switch is connected between a first terminal of the first capacitor and the first node.
4. The voltage conversion circuit for photovoltaic module power optimization capable of generating a carrier signal according to claim 1, wherein:
the first inductor is connected between the second output end and a second node;
the first end of the first capacitor is coupled to a reference voltage source;
a second terminal of said first capacitor is coupled to said second node;
the first switch is connected between the first end of the first capacitor and the second output end.
5. The voltage conversion circuit for photovoltaic module power optimization capable of generating a carrier signal according to claim 3 or 4, wherein:
a first terminal of the first capacitor is coupled to the reference voltage source through a second switch;
after the first capacitor is discharged when the first switch is in the on state, the second switch is switched to the on state to charge the first capacitor, and after the charging is finished, the second switch is switched to the off state.
6. The voltage conversion circuit for photovoltaic module power optimization capable of generating a carrier signal as claimed in claim 1, wherein:
the voltage conversion circuit includes:
the first power switch and the second power switch are connected in series between the first input end and the second input end;
the third power switch and the fourth power switch are connected in series between the first output end and the second output end;
a main inductance element is provided between a first interconnection node to which both the first and second power switches are connected and a second interconnection node to which both the third and fourth power switches are connected.
7. The voltage conversion circuit for photovoltaic module power optimization capable of generating a carrier signal as claimed in claim 1, wherein:
the voltage conversion circuit is in a non-communication stage where the carrier signal is not transmitted, and the first switch is in a continuous off state.
8. The voltage conversion circuit for photovoltaic module power optimization capable of generating a carrier signal as claimed in claim 1, wherein:
one of the first and second logic states is used to characterize a 1 or 0 in the binary symbol and the other is used to characterize the remaining other of the binary symbols.
9. A method for generating carrier signals by a voltage conversion circuit for photovoltaic module power optimization, characterized in that each battery string for providing string voltage is connected in series with a plurality of photovoltaic modules, each photovoltaic module is provided with the voltage conversion circuit for executing maximum power point tracking and an output voltage which is output by the voltage conversion circuit and is subjected to direct current voltage conversion by the photovoltaic module matched with the voltage conversion circuit; and
a first inductance arranged on a voltage output path of the voltage conversion circuit serving as a switched mode power supply;
the first switch and the first capacitor are connected in parallel at two ends of the first inductor and are connected together in series;
each voltage conversion circuit comprises a first input end and a second input end which are coupled to the positive electrode and the negative electrode of one photovoltaic assembly, a first output end and a second output end which provide output voltage, and an output capacitor of each voltage conversion circuit is connected between the first output end and the second output end; and
the first inductor is connected between the first output end and the first node or between the second output end and the second node;
the method comprises the following steps:
driving a first switch to be continuously turned off in a non-communication stage in which the voltage conversion circuit does not transmit the carrier signal;
driving a first switch to switch between on and off in a communication phase in which the voltage conversion circuit transmits a carrier signal;
driving the first switch to turn off in the communication phase, wherein the potential difference across the charged first capacitor is not superimposed on the dc transmission line carrying the output voltage, and the pulse condition of the carrier signal induced on the dc transmission line due to lack of the potential difference transient loading on the dc transmission line is defined as the carrier signal having a first logic state;
and in the communication stage, the first switch is driven to be switched on, the potential difference between the two ends of the charged first capacitor is directly superposed on a direct current transmission line for transmitting the output voltage, and the condition that the direct current transmission line is mixed with pulses which are induced by transient loading of the potential difference on the direct current transmission line and are regarded as carrier signals is defined as that the carrier signals have a second logic state.
10. The method of claim 9, wherein:
the voltage conversion circuits are connected in series, and the second node of any previous-stage voltage conversion circuit is coupled to the first node of the adjacent next-stage voltage conversion circuit through the direct current transmission line; thereby to obtain
When the voltage conversion circuits of the plurality of stages are connected in series, their respective output capacitances are connected in series with each other, and the total string voltage provided by the voltage conversion circuits of the plurality of stages is equal to the sum of the voltages across their respective output capacitances.
11. The method of claim 9, wherein:
the first inductor is connected between the first output end and a first node;
the first end of the first capacitor is coupled to a reference voltage source;
a second terminal of the first capacitor is coupled to the first output terminal;
the first switch is connected between a first terminal of the first capacitor and the first node.
12. The method of claim 9, wherein:
the first inductor is connected between the second output end and a second node;
a first end of the first capacitor is coupled to a reference voltage source;
a second terminal of said first capacitor is coupled to said second node;
the first switch is connected between the first end of the first capacitor and the second output end.
13. The method according to claim 11 or 12, characterized in that:
a first terminal of the first capacitor is coupled to the reference voltage source through a second switch;
after the first switch is driven to be switched from off to on in the communication stage to cause the first capacitor to discharge, the second switch is also driven to be switched on to charge the first capacitor, and the second switch is driven to be switched off after the charging is finished.
14. The method according to claim 11 or 12, characterized in that:
the reference voltage source supplied to each of the voltage converting circuits is an input voltage or an output voltage taken from each of the voltage converting circuits or an independent voltage stabilizing source.
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| CN110460093B (en) * | 2019-08-06 | 2023-03-24 | 丰郅(上海)新能源科技有限公司 | Photovoltaic split box |
| CN111953385B (en) * | 2020-09-18 | 2023-11-14 | 天津工业大学 | Power line communication circuit and method based on switch ripple modulation |
| CN112165343B (en) * | 2020-09-25 | 2021-10-22 | 合肥阳光新能源科技有限公司 | High-frequency communication device, high-frequency carrier transmission direction control method, device and medium |
| CN114389541B (en) * | 2022-02-10 | 2024-05-28 | 天津城建大学 | Photovoltaic power generation unit voltage regulation method and system integrating fault information transmission |
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