CN110086421B - Intelligent photovoltaic module and photovoltaic power generation system - Google Patents
Intelligent photovoltaic module and photovoltaic power generation system Download PDFInfo
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- 230000001276 controlling effect Effects 0.000 description 7
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- 230000005611 electricity Effects 0.000 description 3
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02S—GENERATION OF ELECTRIC POWER BY CONVERSION OF INFRARED RADIATION, VISIBLE LIGHT OR ULTRAVIOLET LIGHT, e.g. USING PHOTOVOLTAIC [PV] MODULES
- H02S40/00—Components or accessories in combination with PV modules, not provided for in groups H02S10/00 - H02S30/00
- H02S40/30—Electrical components
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02S—GENERATION OF ELECTRIC POWER BY CONVERSION OF INFRARED RADIATION, VISIBLE LIGHT OR ULTRAVIOLET LIGHT, e.g. USING PHOTOVOLTAIC [PV] MODULES
- H02S40/00—Components or accessories in combination with PV modules, not provided for in groups H02S10/00 - H02S30/00
- H02S40/30—Electrical components
- H02S40/34—Electrical components comprising specially adapted electrical connection means to be structurally associated with the PV module, e.g. junction boxes
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/50—Photovoltaic [PV] energy
Abstract
According to the intelligent photovoltaic module and the photovoltaic power generation system, the parameters of the intelligent photovoltaic module and the photovoltaic power generation system are detected through the detection control unit, and when the parameters meet the preset switching conditions, the on-off of the switch in the switch unit is controlled, so that the voltage limiting circuits arranged at two ends of the corresponding battery substrings or two ends of the battery modules are switched in or out, and the power optimizer is replaced to realize the adjustment of the voltage of the intelligent photovoltaic module and the photovoltaic power generation system; the problem of high cost caused by adopting a power optimizer is solved while the maximum serial number of the components of the string is increased.
Description
Technical Field
The invention relates to the technical field of power electronics, in particular to an intelligent photovoltaic module and a photovoltaic power generation system.
Background
As photovoltaic power generation in new energy industries, it is a trend to reduce costs and improve efficiency to realize flat-price internet surfing. The method comprises the following steps of (1) increasing the maximum serial number of components of a system string, wherein the method is a common mode; for example, for a conventional 1000V system voltage component, the open circuit voltage Voc of the component is calculated according to the historical lowest air temperature of the installation site, and then the maximum component series number N of the system string is obtained by dividing 1000V by the open circuit voltage Voc; in order to increase the serial number of the assemblies, the voltage grade of a system can be increased from 1000V to 1500V by increasing the insulation voltage-resistant grade of the assemblies, and further, the serial number of the maximum assemblies can be increased by 50% under the same condition, so that the system cost is obviously reduced.
However, due to the requirements of the packaging material, the insulation and voltage rating of the junction box and the cable, the level of difficulty in attempting to further increase the voltage of the component system is high, and the investment cost may be greater than the profit. On the basis, in the prior art, a power optimizer is generally adopted to regulate the voltage of the components under 1500V system voltage, so that the maximum component series quantity of the string is further increased; however, the cost of the power optimizer is too high and the general applicability is low.
Disclosure of Invention
The invention provides an intelligent photovoltaic module and a photovoltaic power generation system, and aims to solve the problem of high cost caused by the adoption of a power optimizer in the prior art.
In order to achieve the purpose, the technical scheme provided by the application is as follows:
one aspect of the present invention provides an intelligent photovoltaic module, comprising: the device comprises a detection control unit, a switch unit, a power supply module, a battery module and at least one voltage limiting circuit; wherein:
the battery module comprises at least two battery sub-strings connected in series, each battery sub-string comprising at least one minimum battery unit;
the voltage limiting circuits are arranged at two ends of the corresponding battery substrings or two ends of the battery modules;
the switch unit comprises at least one switch;
the detection control unit is used for detecting parameters of the intelligent photovoltaic assembly and controlling the on-off of a switch in the switch unit when the parameters meet preset switching conditions, so that the voltage limiting circuit is switched on or off to adjust the voltage of the intelligent photovoltaic assembly;
the power module is used for supplying power to the detection control unit.
Preferably, the voltage limiting circuit is a voltage dividing circuit;
the switching unit includes: a first switch, a second switch and a third switch;
the first switch is connected in series between the negative electrode of the corresponding battery sub-string and the positive electrode of the adjacent battery sub-string, or between the negative electrode of the battery module and the negative electrode of the intelligent photovoltaic module;
the second switch is connected in series in the voltage division circuit;
one end of the third switch is connected with the voltage division output end of the voltage division circuit, and the other end of the third switch is connected with the anode of the adjacent battery sub-string or the cathode of the intelligent photovoltaic assembly.
Preferably, the voltage dividing circuit includes a first resistor and a second resistor connected in series;
the middle point of the first resistor and the second resistor is a voltage division output end of the voltage division circuit.
Preferably, the voltage limiting circuit is a load circuit;
the switching unit includes: a fourth switch;
the fourth switch is connected in series in the load circuit.
Preferably, the load circuit includes a third resistor.
Preferably, the parameters are: any one of current, voltage, temperature and irradiance;
the preset switching conditions include: a voltage limiting condition and a recovery condition;
the voltage limiting condition is a condition representing that an inverter connected with the intelligent photovoltaic module is in an open circuit state;
the recovery condition is a condition representing that an inverter connected with the intelligent photovoltaic module is in a normal working state.
Preferably, the parameter is voltage;
the voltage limiting condition is that the voltage is greater than a voltage limiting threshold;
the recovery condition is that the voltage is less than a reset threshold.
Preferably, the detection control unit is configured to control on/off of a switch in the switch unit when the parameter meets a preset switching condition, so that the voltage limiting circuit is switched on or off to adjust the voltage of the intelligent photovoltaic module, and specifically configured to:
when the parameters meet the voltage limiting condition, controlling the on-off of a switch in the switch unit to enable the voltage limiting circuit to be put into use so as to reduce the voltage of the intelligent photovoltaic module;
and when the parameters meet the recovery conditions, controlling the on-off of a switch in the switch unit to switch out the voltage limiting circuit so as to improve the voltage of the intelligent photovoltaic module.
Preferably, when the voltage limiting circuit is arranged at two ends of the corresponding battery sub-string, the intelligent photovoltaic module further comprises: at least one bypass diode;
and each bypass diode is connected with each corresponding battery sub-string in one-to-one reverse parallel connection mode.
Preferably, the voltage limiting circuit is arranged in the junction box, or is packaged inside the intelligent photovoltaic module, or is independently arranged outside the intelligent photovoltaic module.
In another aspect, the present invention further provides a photovoltaic power generation system, including: the photovoltaic power generation system comprises an inverter and at least one photovoltaic string connected with the direct current side of the inverter; wherein:
the photovoltaic string comprises at least one intelligent photovoltaic module as described in any one of the above.
According to the intelligent photovoltaic module provided by the invention, the detection control unit detects the parameters of the intelligent photovoltaic module, and when the parameters meet the preset switching conditions, the on-off of the switch in the switch unit is controlled, so that the voltage limiting circuits arranged at two ends of the corresponding battery substrings or two ends of the battery modules are switched on or off, and the power optimizer is further replaced to realize the adjustment of the voltage of the intelligent photovoltaic module; the problem of high cost caused by adopting a power optimizer is solved while the maximum serial number of the components of the string is increased.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
Fig. 1a to fig. 2 are schematic diagrams of three structures of an intelligent photovoltaic module provided in an embodiment of the present invention;
fig. 3 to 5 are graphs of three output characteristics of the intelligent photovoltaic module provided by the embodiment of the present invention;
fig. 6 is a schematic structural diagram of a photovoltaic power generation system according to another embodiment of the present application.
Detailed Description
The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
The invention provides an intelligent photovoltaic module, which aims to solve the problem of high cost caused by the adoption of a power optimizer in the prior art.
Specifically, this intelligence photovoltaic module includes: the device comprises a detection control unit, a switch unit, a power supply module, a battery module and at least one voltage limiting circuit; wherein:
the battery module comprises at least two battery substrings connected in series; each battery sub-string comprises at least one minimum battery unit (battery piece), that is, the number of battery pieces contained in each battery sub-string can be selected arbitrarily, for example, the number of battery pieces contained in each battery sub-string is 1, 2, 3, 4 … … n, etc.
The voltage limiting circuits are arranged at two ends of the corresponding battery substrings (as shown in fig. 1a and fig. 2) or two ends of the battery module (as shown in fig. 1 b);
the switch unit comprises at least one switch, and the number of the switches can be any number, such as 1, 2, 3, 4 … … x and the like, according to the specific application environment; the switch is preferably a controllable electronic switch, such as a Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET), an Insulated Gate Bipolar Transistor (IGBT), a triode, a relay, and the like, and is within the protection range of the present application depending on the application environment.
The detection control unit is used for detecting parameters of the intelligent photovoltaic module and controlling the on-off of a switch in the switch unit when the parameters meet preset switching conditions, so that the voltage limiting circuit is switched on or off to adjust the voltage of the intelligent photovoltaic module. In practical applications, the parameters may be: any one of current, voltage, temperature and irradiance; the preset switching condition comprises: a voltage limiting condition and a recovery condition; the voltage limiting condition is a condition representing that an inverter connected with the intelligent photovoltaic module is in an open circuit state; the recovery condition is a condition indicating that an inverter connected to the intelligent photovoltaic module is in a normal working state, such as a grid-connected state, and/or a load-connected state. Preferably, the parameter is voltage; the voltage limiting condition is that the voltage is greater than a voltage limiting threshold; and the recovery condition is a voltage less than a reset threshold. In practical application, when the parameter is current, the voltage limiting condition is that the current is smaller than a voltage limiting current value; and the recovery condition is that the current is greater than the recovery current value. The setting of each threshold value and the setting of conditions under the selection of other parameters may be determined according to the specific application environment, and are not limited herein and are within the scope of the present application.
The power module is used for supplying power for the detection control unit, and can get electricity (as shown in fig. 1a to fig. 2) from intelligent photovoltaic module itself, also can supply power by external power source, and it does not do specifically to do here and does not restrict, and it is decided according to its application environment, all in the protection scope of this application.
Fig. 1a and 1b show an alternative design in which the battery module comprises two battery sub-strings and the switching unit comprises: a first switch K1, a second switch K2, and a third switch K3; the detection control unit can realize detection and judgment of corresponding parameters of the intelligent photovoltaic module and control the on-off of three switches K1, K2 and K3; the voltage limiting circuit is a voltage dividing circuit, and the voltage dividing circuit includes: a first resistor R1 and a second resistor R2; the first switch K1 is connected in series between the negative pole of the corresponding battery sub-string and the positive pole of the adjacent battery sub-string (as shown in FIG. 1 a), or between the negative pole of the battery module and the negative pole of the intelligent photovoltaic module (as shown in FIG. 1 b); the second switch K2 is connected in series in the voltage division circuit; one end of the third switch K3 is connected to the voltage dividing output end of the voltage dividing circuit, i.e., the middle point between the first resistor R1 and the second resistor R2 (when the second switch K2 is connected therebetween, either end of the second switch K2 may be connected); the other end of the third switch K3 is connected to the positive pole of the adjacent cell sub-string (as shown in fig. 1 a) or to the negative pole of the intelligent photovoltaic module (as shown in fig. 1 b).
Fig. 2 shows another alternative structure, in which the battery module includes two battery sub-strings, and the switch unit includes: a fourth switch K4; the detection control unit can detect and judge the corresponding parameters of the intelligent photovoltaic module and control the on-off of the fourth switch K4; the voltage limiting circuit is a load circuit, and the load circuit includes: a third resistor R3; the fourth switch K4 is connected in series in the load circuit.
When the voltage limiting circuits are arranged at two ends of corresponding battery substrings, that is, as shown in fig. 1a and fig. 2, the intelligent photovoltaic module preferably further includes at least one bypass diode D1, each bypass diode is connected in one-to-one correspondence with each corresponding battery substring in an inverse parallel manner, and is used for performing bypass shunting on the limited battery substrings, and when the output current of the limited battery substrings or the whole battery module has a mismatch problem with the working current of the system, the bypass diode D1 can implement conduction shunting.
The description is given by way of example in FIG. 1 b:
when the inverter connected to the intelligent photovoltaic module is in an open circuit state, such as when the inverter is not started in the morning and evening, the voltage of the intelligent photovoltaic module is an open circuit voltage V in fig. 3ocExceeding a voltage limiting threshold VY(ii) a At the moment, the detection control unit judges that the voltage limiting condition is met, and then sends a control command, controls the switch K1 to be opened, controls the switch K2 and the switch K3 to be closed, and enables a voltage limiting circuit (a voltage division circuit consisting of a first resistor R1 and a second resistor R2) to be accessed into a system; at the moment, the output voltage of the intelligent photovoltaic module is Voc1，Voc1Satisfy NxVoc1< 1500, and Voc1≤VYN is the maximum series number of photovoltaic modules in the system, and 1500 is the system voltage of the photovoltaic modules; the corresponding working path is the process (r) shown in fig. 3.
When the inverter is in the initial stage of the loaded state or the grid-connected state, the output IV curve of the intelligent photovoltaic module enters the voltage limiting state shown in the figure 3, and the short-circuit current I of the intelligent photovoltaic moduleSCShort-circuit current I with IV curve in normal stateSCThe same is true. Through inverter control, reduce group string both ends voltage, namely reduce intelligent photovoltaic module's output voltage to V promptlyX，VXIs a reset threshold, namely a reset threshold; the corresponding working path is the process shown in fig. 3.
Then, the detection control unit issues a control command, the control switch K1 is closed, the control switches K2 and K3 are opened, and the voltage limiting circuit (a voltage dividing circuit consisting of a first resistor R1 and a second resistor R2) is switched out of the system. The output IV curve of the intelligent photovoltaic module becomes asThe normal state shown in fig. 3; the corresponding working path is the process shown in fig. 3, and the intelligent photovoltaic module works in (V)a，IX) Dot, Va<VY。
MPP search is carried out on the IV curve of the inverter in a normal state, so that the intelligent photovoltaic module works in (V)m，Im) Point; the corresponding working path is the procedure (r) shown in fig. 3.
When the output voltage of the intelligent photovoltaic module is influenced by the environment, the detection control unit in the intelligent photovoltaic module detects that the output voltage V exceeds the threshold voltage VYIn time, the intelligent photovoltaic module works in (V)Y，IY) Dot, VY＞VmThe detection control unit issues a control command, the switch K1 is controlled to be disconnected, the switches K2 and K3 are controlled to be closed, the resistors R1 and R2 are connected to the system again, and the working state of the intelligent photovoltaic module is switched to the IV curve in the voltage limiting state from the normal state IV curve; the corresponding working path is shown in fig. 3 for process (c).
After entering the voltage limiting state, when the output voltage of the intelligent photovoltaic module is smaller than the reset threshold value V againXWhen the voltage limiting circuit is switched out, the process (c) is executed again. The subsequent processes can be analogized, and the description is not continued.
The difference between the scheme shown in fig. 2 and the scheme shown in fig. 1a and 1b is that when the output voltage of the module needs to be reduced, the detection control unit controls the fourth switch K4 to be closed, and the output voltage of the intelligent photovoltaic module is reduced by introducing the load resistor R3; when the component voltage needs to be recovered, the detection control unit controls the fourth switch K4 to be switched off, and the voltage of the intelligent photovoltaic component is recovered by switching out the load resistor R3.
As shown in fig. 4, the series resistance of the original photovoltaic module can be represented by K3, and the parallel resistance can be represented by K1, by analyzing the IV curve of the voltage limiting state in fig. 3, where the IV curve of the voltage limiting state is affected by the IV characteristics of the original photovoltaic module and the resistances R1 and R2 in the voltage limiting circuit. In a voltage limiting state, the series resistance of the whole assembly can be represented by K4, and the parallel resistance can be represented by K2. When the second resistor R2 in the voltage limiting circuit is largerThe smaller the absolute value of the corresponding K4. When the first resistor R1 in the voltage limiting circuit is smaller, the absolute value of the corresponding K2 is larger. When K2 is equal to Isc/Voc1The IV curve for the limited state becomes the result shown in fig. 5, i.e. the IV curve is a straight line feature. Based on the accurate calculation of the reset threshold, the condition that the IV curve of the voltage limiting state is a straight line characteristic can be selected; based on the voltage range control consideration of the inverter, the distance between the reset threshold VX and the voltage limiting threshold VY can be shortened by adjusting the IV curve of the voltage limiting state through the resistance values of the resistors R1 and R2. The selection of the resistance values of R1 and R2 is not limited, the IV curve of the voltage limiting state is not limited, and the setting can be flexibly selected according to specific conditions. That is to say, in practical application, the adjustment control of the output voltage of the component in a wider range can be realized through the flexible selection and setting of the divider resistor, so that not only is the circuit realized more simply and conveniently, but also the voltage adjustment control range is wider. In addition, in practical application, voltage limiting circuits can be arranged at two ends of different sub-strings in the photovoltaic module, and the problem of series or parallel mismatch among the sub-strings is reduced through adjustment and control of the voltage dividing resistors.
It should be noted that fig. 1a to fig. 2 are only one example, and in practical applications, the setting positions of the switches are not limited to those shown in the drawings, as long as the switching of the voltage limiting circuit can be realized; the voltage limiting circuit is not limited to the voltage dividing circuit and the load circuit shown in the figure, and the voltage dividing circuit and the load circuit are not limited to the voltage dividing circuit and the load circuit shown in the figure as long as the voltage regulating function can be realized. The voltage limiting circuit can also only comprise one short circuit connecting wire, namely when an inverter connected with the intelligent photovoltaic module is in an open circuit state, the corresponding battery sub-string (or battery module) is short-circuited by controlling the corresponding switch through the detection control unit, and the purpose of reducing the voltage of the string can also be achieved. However, after the battery substring is short-circuited, the battery substring does not generate electricity, and the battery substring is in a short-circuit working mode, so that the heat spot battery piece generates heat seriously, the system power generation amount is reduced, and the service life of the assembly is also shortened. Therefore, the voltage limiting circuit is preferably a voltage dividing circuit or a load circuit.
It is worth mentioning that in the prior art, though byThe maximum serial number of the components in the string can be increased by using the components with 1500V system voltage, but the maximum serial number of the components in the string is calculated by the formula N1500/VocIn which V isocIs the open circuit voltage of the component at the local historical lowest air temperature. The working scene of the actual inverter output is mainly an open circuit state and a load or grid-connected state, and the voltage at two ends of the input side of the inverter in the open circuit state is an open circuit voltage V of a stringoc(ii) a The voltage at two ends of the input side of the inverter is the voltage V corresponding to the maximum power point tracking state in the load or grid-connected statem. And when the system is in an open circuit state, the system does not generate electricity outwards, and no benefit is generated. And when the system is in a load or grid-connected state, the system generates power outwards, so that benefits are generated. That is, V is useful for power generationmPoint voltage, VocThe point is based only on safety considerations (the string maximum voltage does not exceed the component maximum system voltage requirement when the inverter is unloaded or grid tied). Therefore, at VmAnd VocThe voltage between the two is regarded as an invalid voltage interval which is not beneficial to power generation, if the system can be designed, the maximum system voltage requirement of the components of the system in an open circuit state and a load or grid-connected state can be met, and the maximum power point voltage V can be obviously reducedmAnd open circuit voltage VocThe maximum series number of the components of the system string can be further increased by the invalid voltage interval in between. At present, the above purpose is mainly achieved by a power optimizer, but the cost of the power optimizer is too high, and the general applicability is low.
When the output of the inverter is in an open circuit state, the intelligent photovoltaic module provided by the embodiment reduces the output voltage of the intelligent photovoltaic module by the input of the voltage limiting circuit, improves the output current, further reduces the string voltage of the system in the state, and meets the maximum system voltage requirement of the module; when the output of the inverter is in a loaded state or a grid-connected state, the output voltage of the inverter is recovered through the cutting of the voltage limiting circuit, the output current is reduced, and the string voltage of the system in the state is further improved but does not exceed the maximum system voltage requirement of the component; namely, the switching setting of the voltage limiting circuit is realized through the on-off control of x switches, thereby realizing the groupingThe variation of output voltage and current of the component can meet the maximum system voltage requirement of the component when the system is in different states, and can obviously reduce VmAnd VocThe maximum series components of the system are increased in number in the invalid voltage interval, and the initial installation cost of the system is further reduced. In addition, a DCDC conversion circuit is not needed, so that the problem of high cost caused by the adoption of a power optimizer is solved, and the method has a remarkable cost advantage.
In practical application, the voltage limiting circuit can be arranged in the junction box, or can be packaged in the intelligent photovoltaic module, or can be independently arranged outside the intelligent photovoltaic module. The specific arrangement mode of each device in the intelligent photovoltaic module can be determined according to the application environment, and is not limited herein, and is within the protection scope of the present application.
In addition, a plurality of voltage limiting circuits can be contained in the intelligent photovoltaic module, each voltage limiting circuit can be switched simultaneously, and independent switching can be realized by independently controlling different switches through the detection control unit so as to realize more flexible control of output voltage values. The method can be determined according to the specific application environment, and is not limited herein, and is within the protection scope of the present application.
On the basis of the above embodiments, the other embodiment of the present invention provides two specific implementation forms, such as:
taking the scheme shown in fig. 1b as an example, the voltage limiting circuits are disposed at two ends of the battery module, and for a conventional photovoltaic module formed by connecting 60 battery pieces in series, that is, the voltage limiting circuits are disposed at two ends of the 60 battery pieces after being connected in series; the voltage limiting circuit is arranged in the component junction box, and the photovoltaic component selects the output power P under the STC conditionm280W photovoltaic module, corresponding open circuit voltage Voc36V, short-circuit current Isc9A, series resistance Rs0.3 Ω, parallel resistance Rsh1K Ω. When the voltage limiting circuit is selected to have R1 ═ 1.2 Ω and R2 ═ 0.3 Ω, the corresponding open-circuit voltage V is obtained when the intelligent photovoltaic module is in the voltage limiting stateoc124V. Taking a voltage limiting threshold VYReset threshold V at 30VXThe maximum serial number N of the components in the 1500V system is 18V1500/VY50. The following describes the voltage-limiting reset operation path specifically:
1. when the output of the inverter is in an open-circuit state, the detection control unit detects the output voltage V of the intelligent photovoltaic moduleoc36V, greater than a voltage limiting threshold VY30V, the detection control unit issues a voltage limiting command, namely K1 is opened, K2 and K3 are closed, the voltage limiting circuit is connected into the system, at the moment, the intelligent photovoltaic module starts to work on a voltage limiting state IV curve, and the corresponding open-circuit voltage becomes Voc1＝24V。
2. The inverter carries out MPP search on the IV curve of the string, when the controlled bus current acts on the voltage limiting component (the limited intelligent photovoltaic component), the corresponding working voltage is equal to the reset threshold value VXWhen becoming 18V, the detection control unit gives the instruction that resets, namely K1 is closed, K2 and K3 open, and the voltage limiting circuit cuts out the system, and this intelligence photovoltaic module begins to work on normal IV curve this moment, and corresponding voltage is VaSatisfy Va＜VY。
3. When the bus current controlled by the inverter acts on the voltage limiting component, the corresponding working voltage V is equal to VYWhen 24V, the detection control unit issues a voltage limiting command, namely K1 is opened, K2 and K3 are closed, the voltage limiting circuit is connected into the system, at the moment, the intelligent photovoltaic module starts to work on a voltage limiting state IV curve, and the corresponding voltage V isbSatisfy Vb＞VX。
4. When V isb＝VXWhen the voltage is 18V, the detection control unit issues a reset instruction as in the above process 2.
Similar to the scheme shown in fig. 1a, the voltage limiting circuits are disposed at two ends of 1/3 cell substrings in the photovoltaic module, for the conventional photovoltaic module formed by connecting 60 cells in series, that is, disposed at two ends of a substring formed by connecting 20 cells in series, and at the same time, 1 bypass diode is connected in parallel at two ends of the voltage limiting substring (the limited cell substring), the voltage limiting circuits are disposed in the module junction box, and the photovoltaic module outputs power P under the STC conditionm280W photovoltaic module, corresponding open circuit voltage Voc36V, short-circuit current Isc9A, series resistance Rs0.3 Ω, parallel resistance Rsh1K Ω. When the 1/3 cell sub-string of the photovoltaic module is in the voltage limiting state, the corresponding open-circuit voltage V at the two ends of the photovoltaic module is selected to be 1K Ω R1 and 1K Ω R2 in the voltage limiting circuitoc130V. Taking a voltage limiting threshold VYReset threshold V at 30VX24V, the maximum serial number N of the components in the 1500V system is 1500/VY50. The following describes the voltage-limiting reset operation path specifically:
1. when the output of the inverter is in an open-circuit state, the detection control unit detects the output voltage V of the intelligent photovoltaic moduleoc36V, greater than a voltage limiting threshold VY30V, the detection control unit issues a voltage limiting command, namely K1 is opened, K2 and K3 are closed, the voltage limiting circuit is connected into the system, at the moment, the intelligent photovoltaic module starts to work on a voltage limiting state IV curve, and the corresponding open-circuit voltage becomes Voc130V. Because the current of the voltage-limiting substrings is obviously lower than that of other non-voltage-limiting substrings, the bypass diodes connected in parallel with the voltage-limiting substrings are conducted due to current mismatch, the effect of bypass shunting is achieved, and the current output of the assembly is not influenced.
2. The inverter carries out MPP search on the IV curve of the string, and when the controlled bus current acts on the voltage limiting component, the corresponding working voltage is equal to the reset threshold value VXWhen 24V, the detection control unit gives a reset instruction, namely K1 is closed, K2 and K3 are opened, the voltage limiting circuit is switched into the system, the intelligent photovoltaic module starts to work on a normal IV curve at the moment, and the corresponding voltage is VaSatisfy Va＜VY。
3. When the bus current controlled by the inverter acts on the voltage limiting component, the corresponding working voltage V is equal to VYWhen 30V, the detection control unit issues a voltage limiting command, namely K1 is opened, K2 and K3 are closed, the voltage limiting circuit is connected into the system, at the moment, the intelligent photovoltaic module starts to work on a voltage limiting state IV curve, and the corresponding voltage V isbSatisfy Vb＞VX。
4. When V isb＝VXWhen the voltage is 24V, the detection control unit issues a reset instruction as in the above process 2.
The embodiment provides a specific embodiment of adjusting and controlling the output voltage of the assembly by arranging voltage limiting circuits at two ends of a battery sub-string or a battery module in the assembly, the specific embodiment can reduce the output voltage of the assembly when the output of an inverter is in an open circuit state, increase the output voltage of the assembly when the output of the inverter is in a load or grid-connected state, and meet the maximum system voltage requirement of the photovoltaic assembly under the two conditions. The maximum power point voltage V of the photovoltaic system is reduced through the access and cut-out control of the voltage limiting circuitmAnd open circuit voltage VocThe maximum series components of the system are increased in number in the invalid voltage interval, and the initial installation cost of the system is further reduced.
The rest of the structure and the principle are the same as those of the above embodiments, and are not described in detail here.
Another embodiment of the present invention further provides a photovoltaic power generation system, as shown in fig. 6, including: the photovoltaic power generation system comprises an inverter and at least one photovoltaic string connected with the direct current side of the inverter; wherein:
the photovoltaic string comprises at least one intelligent photovoltaic module as described in any one of the above embodiments.
Fig. 6 illustrates a photovoltaic power generation system formed by the above intelligent photovoltaic modules, and a plurality of intelligent photovoltaic modules with voltage limiting circuits are connected in series or in parallel and then connected to an inverter. When the output of the inverter is in an open circuit state, and the detection control unit in each intelligent photovoltaic module detects that the parameters meet the voltage limiting condition, the input of a voltage limiting circuit in the intelligent photovoltaic module is realized through switch control, and the voltage of the module is reduced, so that the open circuit voltage of the whole system is reduced; when the output of the inverter is in a load or grid-connected state, when the detection control unit in each intelligent photovoltaic assembly detects that the parameters meet the recovery conditions, the switching-out of the voltage limiting circuit in the intelligent photovoltaic assembly is realized through switch control, the assembly voltage is improved, the inverter works in the optimal voltage range, and the MPP voltage of the system string does not exceed the maximum system voltage of the assembly.
The number of intelligent photovoltaic modules with the voltage limiting function in one photovoltaic system string can be selected at will, and the other intelligent photovoltaic modules are ordinary photovoltaic modules without the voltage limiting function. The number of intelligent photovoltaic modules with the voltage limiting function is 1, 2, 3, 4 … … N and the like, and N is smaller than the maximum serial number of the modules.
It should be noted that the module related to the present application may be a whole cell module, a sliced cell module, an MWT (Metal Wrap Through) cell module, and other photovoltaic power generation products, and the module is not limited herein, and the cell is the smallest indivisible minimum power generation unit inside the module.
The structure and the working principle of the intelligent photovoltaic module can be seen from the above embodiment, and are not repeated here.
The embodiments of the invention are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments can be referred to each other. The device disclosed by the embodiment corresponds to the method disclosed by the embodiment, so that the description is simple, and the relevant points can be referred to the method part for description.
The foregoing is merely a preferred embodiment of the invention and is not intended to limit the invention in any manner. Although the present invention has been described with reference to the preferred embodiments, it is not intended to be limited thereto. Those skilled in the art can make numerous possible variations and modifications to the present teachings, or modify equivalent embodiments to equivalent variations, without departing from the scope of the present teachings, using the methods and techniques disclosed above. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention are still within the scope of the protection of the technical solution of the present invention, unless the contents of the technical solution of the present invention are departed.
Claims (11)
1. An intelligent photovoltaic module, comprising: the device comprises a detection control unit, a switch unit, a power supply module, a battery module and at least one voltage limiting circuit; wherein:
the battery module comprises at least two battery sub-strings connected in series, each battery sub-string comprising at least one minimum battery unit;
the voltage limiting circuits are arranged at two ends of the corresponding battery substrings or two ends of the battery modules;
the switch unit comprises at least one switch;
the detection control unit is used for detecting parameters of the intelligent photovoltaic module and controlling the on-off of a switch in the switch unit when the parameters meet preset switching conditions, so that the voltage limiting circuit is switched on or off, and the voltage of the intelligent photovoltaic module is adjusted by changing the series resistance and the parallel resistance of the intelligent photovoltaic module;
the power module is used for supplying power to the detection control unit.
2. The intelligent photovoltaic module of claim 1, wherein the voltage limiting circuit is a voltage divider circuit;
the switching unit includes: a first switch, a second switch and a third switch;
the first switch is connected in series between the negative electrode of the corresponding battery sub-string and the positive electrode of the adjacent battery sub-string, or between the negative electrode of the battery module and the negative electrode of the intelligent photovoltaic module;
the second switch is connected in series in the voltage division circuit;
one end of the third switch is connected with the voltage division output end of the voltage division circuit, and the other end of the third switch is connected with the anode of the adjacent battery sub-string or the cathode of the intelligent photovoltaic assembly.
3. The intelligent photovoltaic module of claim 2, wherein the voltage divider circuit comprises a first resistor and a second resistor connected in series;
the middle point of the first resistor and the second resistor is a voltage division output end of the voltage division circuit.
4. The intelligent photovoltaic module of claim 1, wherein the voltage limiting circuit is a load circuit;
the switching unit includes: a fourth switch;
the fourth switch is connected in series in the load circuit.
5. The intelligent photovoltaic module of claim 4, wherein the load circuit comprises a third resistor.
6. The intelligent photovoltaic module of any of claims 1-5, wherein the parameters are: any one of current, voltage, temperature and irradiance;
the preset switching conditions include: a voltage limiting condition and a recovery condition;
the voltage limiting condition is a condition representing that an inverter connected with the intelligent photovoltaic module is in an open circuit state;
the recovery condition is a condition representing that an inverter connected with the intelligent photovoltaic module is in a normal working state.
7. The intelligent photovoltaic module of claim 6, wherein the parameter is voltage;
the voltage limiting condition is that the voltage is greater than a voltage limiting threshold;
the recovery condition is that the voltage is less than a reset threshold.
8. The intelligent photovoltaic module according to claim 6, wherein the detection control unit is configured to control on/off of a switch in the switch unit when the parameter satisfies a preset switching condition, so that the voltage limiting circuit is switched on or off to adjust the voltage of the intelligent photovoltaic module, and specifically configured to:
when the parameters meet the voltage limiting condition, controlling the on-off of a switch in the switch unit to enable the voltage limiting circuit to be put into use so as to reduce the voltage of the intelligent photovoltaic module;
and when the parameters meet the recovery conditions, controlling the on-off of a switch in the switch unit to switch out the voltage limiting circuit so as to improve the voltage of the intelligent photovoltaic module.
9. The intelligent photovoltaic module according to any one of claims 1 to 5, wherein when the voltage limiting circuits are disposed at two ends of the corresponding battery sub-strings, the intelligent photovoltaic module further comprises: at least one bypass diode;
and each bypass diode is connected with each corresponding battery sub-string in one-to-one reverse parallel connection mode.
10. The intelligent photovoltaic module of any of claims 1-5, wherein the voltage limiting circuit is disposed in a junction box, or is packaged inside the intelligent photovoltaic module, or is disposed outside the intelligent photovoltaic module independently.
11. A photovoltaic power generation system, comprising: the photovoltaic power generation system comprises an inverter and at least one photovoltaic string connected with the direct current side of the inverter; wherein:
the photovoltaic string comprises at least one intelligent photovoltaic module as claimed in any one of claims 1-10.
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| CN106026066A (en) * | 2016-07-29 | 2016-10-12 | 阳光电源股份有限公司 | Direct-current source protecting device and method |
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