CN113258773A - Power conversion system, power conversion device and control method thereof - Google Patents
Power conversion system, power conversion device and control method thereof Download PDFInfo
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- CN113258773A CN113258773A CN202110540628.0A CN202110540628A CN113258773A CN 113258773 A CN113258773 A CN 113258773A CN 202110540628 A CN202110540628 A CN 202110540628A CN 113258773 A CN113258773 A CN 113258773A
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M3/00—Conversion of dc power input into dc power output
- H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
- H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
- H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M3/145—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M3/155—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M3/156—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators
- H02M3/158—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators including plural semiconductor devices as final control devices for a single load
- H02M3/1584—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators including plural semiconductor devices as final control devices for a single load with a plurality of power processing stages connected in parallel
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/42—Circuits or arrangements for compensating for or adjusting power factor in converters or inverters
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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
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
- Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes
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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
- Y02E10/56—Power conversion systems, e.g. maximum power point trackers
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Dc-Dc Converters (AREA)
Abstract
The invention provides a power conversion system, a power conversion device and a control method thereof, wherein in the power conversion device, the input ends of all DCDC conversion circuits in the power conversion device are respectively connected with corresponding input power supplies, and the output ends are connected in parallel; wherein, at least one DCDC conversion circuit is in an input-output common positive pole structure, and the other at least one DCDC conversion circuit is in an input-output common negative pole structure; the negative electrode of the input end of the DCDC conversion circuit with the input-output common-positive electrode structure is connected with the positive electrode of the input end of the DCDC conversion circuit with the input-output common-negative electrode structure through a corresponding switch unit; therefore, when the voltage of the input power supply is lower, the switch unit can be switched on, so that the input power supplies on two sides of the switch unit are connected in series, and simultaneously, because of the structural arrangement of the DCDC conversion circuits on two sides of the switch unit, the DCDC conversion circuits on two sides of the switch unit are bypassed, so that the conversion efficiency of the device is improved, and the heat generation of the circuit is reduced.
Description
Technical Field
The present invention relates to the field of power conversion technologies, and in particular, to a power conversion system, a power conversion apparatus, and a control method thereof.
Background
A photovoltaic inverter generally has multiple MPPT (Maximum Power Point Tracking) units therein, and a DCDC conversion circuit as an MPPT unit is generally implemented by using a boost circuit. In order to facilitate the internal design, in the prior art, the multiple paths of boost in the photovoltaic inverter mostly adopt an input-output common-negative structure shown in fig. 1 or an input-output common-positive structure shown in fig. 2.
When the photovoltaic input voltage is higher, the corresponding boost circuit can be bypassed by the bypass unit, so that the conversion efficiency of the circuit is improved. When the photovoltaic input voltage is lower, the boost circuit works to provide energy meeting the voltage requirement for the later stage; however, when the voltage is low, the ripple of the inductor in the boost circuit is large, and the conversion efficiency of the circuit is not high.
Disclosure of Invention
In view of the above, the present invention provides a power conversion system, a power conversion apparatus and a control method thereof to improve conversion efficiency.
In order to achieve the above purpose, the embodiments of the present invention provide the following technical solutions:
a first aspect of an embodiment of the present invention provides a power conversion apparatus, including: the device comprises a control unit, at least two DCDC conversion circuits controlled by the control unit and at least one switching unit; wherein:
the input end of each DCDC conversion circuit is connected with a corresponding input power supply, and the output end of each DCDC conversion circuit is connected in parallel;
at least one DCDC conversion circuit is of an input-output common positive structure, and at least one DCDC conversion circuit is of an input-output common negative structure;
and the input end cathode of the DCDC conversion circuit with at least one input/output common anode structure is connected with the input end anode of the DCDC conversion circuit with at least one input/output common cathode structure through the corresponding switch unit.
Preferably, each of the DCDC conversion circuits is connected to another DCDC conversion circuit through the corresponding switch unit.
Preferably, one or more DCDC conversion circuits are connected to both sides of each of the switching units.
Preferably, the switching unit includes:
at least one of a relay, a contactor, a semiconductor switching tube, and a diode.
Preferably, the DCDC conversion circuit includes: an input capacitor, an output capacitor and a main circuit;
the input capacitor is arranged on the input side of the main circuit, and the output capacitor is arranged on the output side of the main circuit.
Preferably, the DCDC conversion circuit includes: buck circuitry, boost circuitry, or buck-boost circuitry.
Preferably, each of the DCDC conversion circuits is further provided with a bypass unit.
Preferably, the method further comprises the following steps: a DCAC conversion circuit;
and the direct current side of the DCAC conversion circuit is connected with the output end of each DCDC conversion circuit through a direct current bus.
Preferably, the control unit includes: a master controller and a slave controller of each of the DCDC conversion circuits;
and each slave controller is in communication connection with the master controller.
Preferably, the main controller is: a system controller; alternatively, the first and second electrodes may be,
when the power conversion device includes a DCAC conversion circuit, the main controller is: a controller of the DCAC conversion circuit.
Another aspect of the present invention further provides a control method of a power conversion apparatus, applied to a control unit of the power conversion apparatus described in any one of the above paragraphs, the control method including:
detecting an input voltage of each DCDC conversion circuit in the power conversion device;
judging whether each DCDC conversion circuit on two sides of the same switch unit in the power conversion device meets a preset low input condition or not;
and if the judgment result is yes, controlling the corresponding switch unit to be conducted.
Preferably, the determining whether each of the DCDC conversion circuits on both sides of the same switching unit in the power conversion apparatus satisfies a preset low input condition includes:
judging whether at least one input voltage of each DCDC conversion circuit on two sides of the same switch unit meets a preset low voltage condition; alternatively, the first and second electrodes may be,
and judging whether the input voltage of each DCDC conversion circuit at two sides of the same switch unit meets the preset low voltage condition or not.
Preferably, after determining whether each of the DCDC conversion circuits on both sides of the same switching unit in the power conversion apparatus satisfies a preset low input condition, the method further includes:
if the judgment result is negative, the corresponding switch unit is controlled to be switched off, and the DCDC conversion circuit connected with the corresponding switch unit performs chopping operation.
Preferably, the preset low voltage condition includes:
does not rise above the first threshold or has fallen below a second threshold; the second threshold is less than the first threshold.
Preferably, the normal operating condition includes:
has risen above the first threshold or, has not fallen below the second threshold; the second threshold is less than the first threshold.
The third aspect of the present invention also provides a power conversion system including: at least two input power sources, and a power conversion device as described in any of the preceding paragraphs.
Preferably, the power conversion device is: a dc combiner box without a DCAC conversion circuit, or a string inverter with a DCAC conversion circuit.
Preferably, the input power supply is: photovoltaic modules, photovoltaic strings, or energy storage cells.
The input end of each DCDC conversion circuit in the power conversion device is connected with a corresponding input power supply, and the output end of each DCDC conversion circuit is connected in parallel; wherein, at least one DCDC conversion circuit is in an input-output common positive pole structure, and the other at least one DCDC conversion circuit is in an input-output common negative pole structure; the negative electrode of the input end of the DCDC conversion circuit with the input-output common-positive electrode structure is connected with the positive electrode of the input end of the DCDC conversion circuit with the input-output common-negative electrode structure through a corresponding switch unit; therefore, when the voltage of the input power supply is lower, the switch unit can be switched on, so that the input power supplies on two sides of the switch unit are connected in series, and simultaneously, because of the structural arrangement of the DCDC conversion circuits on two sides of the switch unit, the DCDC conversion circuits on two sides of the switch unit are bypassed, so that the conversion efficiency of the device is improved, and the heat generation of the circuit is reduced.
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 embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.
Fig. 1 and 2 are schematic structural diagrams of two photovoltaic inverters provided in the prior art;
fig. 3 and 4 are schematic partial structural diagrams of a power conversion device according to an embodiment of the present invention;
fig. 5 is a schematic structural diagram of a power conversion device according to an embodiment of the present invention;
fig. 6 is a specific structural diagram of a power conversion device according to an embodiment of the present invention;
fig. 7 is a schematic structural diagram of another power conversion device according to an embodiment of the present invention;
fig. 8 is a flowchart of a control method of a power conversion apparatus according to an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, 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 invention.
In this application, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.
The present invention provides a power conversion device, as shown in fig. 5, comprising: a control unit (not shown) and at least two DCDC conversion circuits 101 and at least one switching unit K1 controlled by the control unit; wherein:
the input terminals of the respective DCDC conversion circuits 101 are respectively connected to corresponding input power supplies (an input power supply 1 and an input power supply 2 as shown in fig. 5), and the output terminals of the respective DCDC conversion circuits 101 are connected in parallel to both ends of the output circuit as shown in fig. 1.
At least one DCDC conversion circuit 101 has an input/output common positive structure (as shown in fig. 3), and at least one DCDC conversion circuit 101 has an input/output common negative structure (as shown in fig. 4). The input-output common-anode structure refers to that the anode of the input side and the anode of the output side of the circuit are connected together or are equipotential; the input-output common-negative structure means that the input side negative electrode and the output side negative electrode of the circuit are connected together or are equipotential.
The negative terminal of the input terminal of the at least one input/output common-positive electrode DCDC conversion circuit 101 is connected to the positive terminal of the input terminal of the at least one input/output common-negative electrode DCDC conversion circuit 101 via the corresponding switch unit K1. That is, two sides of each switch unit K1 are respectively connected with at least one DCDC conversion circuit 101, and fig. 5 shows that only two sides of each switch unit K1 are respectively connected with one DCDC conversion circuit 101, and in practical application, any one side of each switch unit K1 can be connected with two or more DCDC conversion circuits 101; when two or more DCDC conversion circuits 101 are connected to one side thereof, the respective DCDC conversion circuits 101 are connected in parallel. For each switching cell K1, only one DCDC converter circuit 101 of corresponding configuration may be provided on one side, or at least two DCDC converter circuits 101 connected in parallel may be provided on the other side.
Since the input terminal of each DCDC conversion circuit 101 is connected to the corresponding input power source, that is, both sides of each switch unit K1 are connected to at least one input power source, respectively, as shown in fig. 5, both sides of each switch unit K1 are connected to one input power source (e.g., input power source 1 and input power source 2 shown in fig. 5); when at least two input power supplies are connected to a certain side thereof, the respective input power supplies are connected in parallel.
In this embodiment, the number of the input power supplies and the DCDC conversion circuits 101 on both sides of each switch unit K1 is not specifically limited, and it is within the protection scope of the present application as long as the structure of the DCDC conversion circuit 101 connected on both sides of each switch unit K1 meets the above limitation.
Each of the switch cells K1 and all the input power supplies connected to both sides thereof constitute a series configuration, and all the DCDC conversion circuits 101 in the power conversion device may constitute at least one such series configuration by being connected to the switch cell K1. Furthermore, all the DCDC conversion circuits 101 in the power conversion device may be connected to the corresponding switch unit K1, so that all the DCDC conversion circuits 101 are paired according to different types of structures; one or a few of the remaining DCDC conversion circuits 101 may not be connected to the corresponding switch unit K1; it is not specifically limited herein, and may be within the scope of the present application depending on the application environment.
In the power conversion device provided by this embodiment, through the above structure, when the voltage of the input power is lower than a threshold, the corresponding DCDC conversion circuit 101 operates independently, which may result in a large inductance ripple inside the DCDC conversion circuit, and low conversion efficiency, the corresponding switch unit K1 may be turned on, and then the input power on both sides of the DCDC conversion circuit may be connected in series, so that the input voltage on both sides of the DCDC conversion circuit may be connected in series to obtain a higher voltage value, that is, the input voltage may be equivalently increased, and the DCDC conversion circuit 101 may supply power to the output circuit without operating. Specifically, after the input power supply 1 and the input power supply 2 are connected in series, current flows into the output circuit from a common positive electrode line, and then flows back to the input power supply from a common negative electrode line; meanwhile, because the structure of the DCDC conversion circuits 101 on the two sides is arranged, the DCDC conversion circuits 101 on the two sides of the switch unit K1 are all in a bypass mode, compared with the situation that the switch unit K1 is not arranged in the prior art, the working efficiency of the circuit can be improved, and the heat of the circuit is reduced.
In practical applications, since output parameters of each input power supply are generally close to each other, on-off control of each switch unit K1 can be achieved substantially simultaneously, that is, when each DCDC conversion circuit 101 is connected to a corresponding switch unit K1, each DCDC conversion circuit 101 can be switched to a bypass state when the switch unit K1 is turned on or an independent operation state when the switch unit K1 is turned off at the same time. However, in consideration of special situations such as occlusion, there may be a large difference in output parameters of the input power sources connected to both sides of the same switch unit K1, and if the voltage of the input power source on one side is high and the voltage of the input power source on the other side is lower than the threshold value, then: the MPPT can be guaranteed as a priority, that is, the independent operation state of the DCDC conversion circuits 101 on both sides thereof is maintained; only when the voltage of the input power supplies on the two sides is lower than the threshold value, the input power supplies are controlled to be conducted, so that the DCDC conversion circuits 101 on the two sides are bypassed, the conversion efficiency is improved, and the heating of the circuits is reduced; alternatively, it is preferable to improve the conversion efficiency, that is, to control the switching unit K1 to be turned on when one of the voltages of the input power supplies connected to the same switching unit K1 is lower than the threshold value; depending on the specific application environment, are all within the scope of the present application.
In practical applications, on the basis of the above embodiment, preferably, the switch unit K1 may be: one or any combination of types and numbers of semiconductor switch tubes such as relays, contactors, diodes, IGBTs or MOSFETs, etc., are not specifically limited herein, and are all within the scope of the present application as long as the on/off function of the series connection between the corresponding input power sources can be realized.
Preferably, referring to fig. 3 to 5, the DCDC conversion circuit 101 includes an input capacitance (Cin as illustrated in fig. 3 and 4 and Cin1 and Cin2 as illustrated in fig. 5), an output capacitance (Co as illustrated in fig. 3 and 4 and Co1 and Co2 as illustrated in fig. 5), and a main circuit (main circuit as illustrated in fig. 3 and 4 and main circuit 1 and main circuit 2 as illustrated in fig. 5); the main circuit may be: the buck circuit, the boost circuit (including Q1, L1, and D1 shown in fig. 6, or Q2, L2, and D2), the buck-boost circuit, or other similar transformation circuits are not limited herein, and are within the scope of the present application depending on the application environment.
In practical applications, each of the DCDC conversion circuits 101 should be provided with a bypass unit (not shown) to bypass the main circuit of the DCDC conversion circuit 101 when the voltage of the input power is high, thereby improving the conversion efficiency. The specific implementation manner of the bypass unit can be referred to in the prior art, and is not described in detail.
In addition, when the power conversion apparatus includes the DCDC conversion circuit 101 in which at least two output terminals are connected in parallel, the power conversion apparatus can be used as a junction box, such as a photovoltaic string junction box, an energy storage battery junction box, or the like. In practical applications, the power conversion apparatus may further include, as shown in fig. 7 (which is illustrated on the basis of fig. 5), that is: a DCAC conversion circuit 102; the dc side of the DCAC conversion circuit 102 is connected to the output terminals of the DCDC conversion circuits 101 via a dc bus; in this case, the power conversion device may be used as a photovoltaic inverter or an energy storage converter.
In the above embodiment, the control unit for controlling the operations of each switch unit K1 and each DCDC conversion circuit 101 may be an integrated controller, and may include: a master controller and a slave controller of each DCDC conversion circuit 101; each slave controller is in communication connection with the master controller; each slave controller respectively controls the corresponding DCDC conversion circuit 101 to act, and each slave controller respectively forms a DCDC converter together with the corresponding DCDC conversion circuit 101 and the required voltage/current detection module thereof; the main controller is mainly used for controlling the operation of each switch unit K1.
In practical applications, the main controller may be: a system controller; if the power conversion apparatus does not include the DCAC conversion circuit 102, each slave controller is directly connected in communication with the system controller; if the power converter includes the DCAC conversion circuit 102, each slave controller may be connected to the system controller and the controller of the DCAC conversion circuit 102 in a communication manner, or may be connected to the system controller in a communication manner through the controller of the DCAC conversion circuit 102.
Alternatively, when the power conversion apparatus includes the DCAC conversion circuit 102, the main controller is: the controller of the DCAC conversion circuit 102 is responsible for controlling the operation of the DCAC conversion circuit 102 and controlling the operation of each switch cell K1.
In practical applications, the specific configuration of the control unit may be determined according to the application environment, and is within the protection scope of the present application.
Another embodiment of the present invention further provides a control method for a power conversion device, which is applied to the control unit of the power conversion device according to any of the above embodiments, and the structural configuration and the operation principle of the power conversion device may be referred to the above embodiments, and are not described again.
Referring to fig. 8, the control method includes:
s101, the input voltage of each DCDC conversion circuit in the power conversion device is detected.
In practical applications, the control unit, such as an integrated controller, or each slave controller inside the control unit may implement detection of the input voltage of the corresponding DCDC conversion circuit through the voltage detection module at the input side of each DCDC conversion circuit; the input voltage thereof, i.e. the voltage of the input power supply to which its input side is connected. Each slave controller obtains a detection value of each input voltage and transmits the detection value to the master controller.
And S102, judging whether each DCDC conversion circuit on two sides of the same switch unit in the power conversion device meets a preset low input condition or not.
The control unit, such as an integrated controller, or a main controller within the control unit, determines the specifics of each input power source. The preset low input condition may specifically mean that at least one input voltage among input voltages of all DCDC conversion circuits meets the preset low voltage condition, that is, MPPT is guaranteed to be a priority when the voltage difference between input power supplies on both sides is large; or, the input voltages of all the DCDC conversion circuits all satisfy the preset low voltage condition, that is, when the voltage difference between the input power supplies on the two sides is large, the conversion efficiency is preferentially improved; it is not specifically limited herein, and is within the scope of the present application, depending on the application environment.
When the DCDC conversion circuits on both sides of the same switching unit satisfy the preset low input condition, step S103 is performed.
And S103, controlling the corresponding switch unit to be conducted.
After the switch unit is conducted, input power supplies on two sides of the switch unit are connected in series, and DCDC conversion circuits on two sides of the switch unit are bypassed, so that the conversion efficiency is reduced, and the heat productivity of devices is reduced.
Preferably, as shown in fig. 8, after determining whether each of the DCDC conversion circuits on both sides of the same switching unit in the power conversion apparatus satisfies the preset low input condition in step S102, if the determination result is no, the control method further includes:
and S104, controlling the corresponding switch unit to be turned off, and controlling the DCDC conversion circuit connected with the corresponding switch unit to perform chopping operation.
This integrated control ware or main control unit after obtaining the detected value of each input voltage, when judging its size, still can consider whether it can make corresponding DCDC converting circuit carry out the chopping operation under the conversion efficiency who satisfies the requirement, for example MPPT work, judges promptly whether it can normal operating, if can, then need not to switch on the switch unit, each DCDC converting circuit directly carry out the chopping operation can.
It should be noted that, when the switch unit K1 is a diode, as shown in fig. 6, due to the existence of the diode D2, after the circuit is chopped, the diode as the switch unit K1 is turned off, so that the corresponding DCDC conversion circuit can also operate normally.
In addition, when a certain input voltage is higher than the voltage of the output circuit, the bypass unit of the corresponding DCDC conversion circuit can be automatically conducted, and therefore conversion efficiency is improved.
It should be noted that, in practical application, the control unit controls the action process of each switch unit, and may be a control with hysteresis; that is, it is preferable that:
the preset low voltage condition includes: does not rise above the first threshold or has fallen below a second threshold; the second threshold is less than the first threshold.
And the normal operating conditions include: has risen above the first threshold, or, has not fallen below the second threshold; the second threshold is less than the first threshold.
Taking a photovoltaic group series-parallel box or a photovoltaic inverter as an example, when light is weak every morning, the voltage of each input power supply, namely the input voltage of each DCDC conversion circuit, gradually rises from zero, and when the voltage of each input power supply does not rise to be larger than a first threshold value, the switch unit is controlled to be conducted; when the voltage rises to be larger than the first threshold value, the switching unit is controlled to be switched off, and the DCDC conversion circuit enters the MPPT operation. When the illumination gradually weakens every evening, each input voltage gradually decreases from a normal value, the switch unit is not controlled to be conducted when the illumination decreases to be smaller than the first threshold value, but the switch unit is controlled to be conducted when the illumination continuously decreases to be smaller than the second threshold value, the DCDC conversion circuit is bypassed, and the reduction of the conversion efficiency is avoided. In the case of weak light, if the input voltage fluctuates between two thresholds, the switching unit does not operate frequently, but maintains the previous state, thereby avoiding the loss of the lifetime of the devices in the switching unit.
Another embodiment of the present invention also provides a power conversion system, as shown in fig. 5, 6 or 7, including: at least two input power sources (input power source 1 and input power source 2 as shown in the figure), and a power conversion device as described in any of the above embodiments. The structural arrangement and the working principle of the power conversion device can be seen from the above embodiments, and are not described again. The control unit of the power conversion apparatus may perform the control method described in the above embodiments, and is not described herein again.
In practical applications, the power conversion device may be: a dc combiner box without a DCAC conversion circuit, or a string inverter with a DCAC conversion circuit. And the input power can be: photovoltaic modules, photovoltaic strings, or energy storage cells. It is not specifically limited herein, and is within the scope of the present application, depending on the application environment.
The rest of the principle is the same as the above embodiments, and is not described in detail here.
The same and similar parts among the various embodiments in the present specification are referred to each other, and each embodiment focuses on differences from other embodiments. In particular, the system or system embodiments are substantially similar to the method embodiments and therefore are described in a relatively simple manner, and reference may be made to some of the descriptions of the method embodiments for related points. The above-described system and system embodiments are only illustrative, wherein the units described as separate parts may or may not be physically separate, and the parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of the present embodiment. One of ordinary skill in the art can understand and implement it without inventive effort.
Those of skill would further appreciate that the various illustrative elements and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both, and that the various illustrative components and steps have been described above generally in terms of their functionality in order to clearly illustrate this interchangeability of hardware and software. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the implementation. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.
In the above description of the disclosed embodiments, the features described in the embodiments in this specification may be replaced or combined with each other to enable those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (17)
1. A power conversion device, comprising: the device comprises a control unit, at least two DCDC conversion circuits controlled by the control unit and at least one switching unit; wherein:
the input end of each DCDC conversion circuit is connected with a corresponding input power supply, and the output end of each DCDC conversion circuit is connected in parallel;
at least one DCDC conversion circuit is of an input-output common positive structure, and at least one DCDC conversion circuit is of an input-output common negative structure;
and the input end cathode of the DCDC conversion circuit with at least one input/output common anode structure is connected with the input end anode of the DCDC conversion circuit with at least one input/output common cathode structure through the corresponding switch unit.
2. The power converter according to claim 1, wherein each of the DCDC conversion circuits is connected to another of the DCDC conversion circuits through the corresponding switching unit.
3. The power conversion apparatus according to claim 1, wherein one or more of the DCDC conversion circuits are connected to both sides of each of the switching units.
4. The power conversion apparatus according to claim 1, wherein the switch unit includes:
at least one of a relay, a contactor, a semiconductor switching tube, and a diode.
5. The power conversion apparatus according to claim 1, wherein the DCDC conversion circuit includes: an input capacitor, an output capacitor and a main circuit;
the input capacitor is arranged on the input side of the main circuit, and the output capacitor is arranged on the output side of the main circuit.
6. The power conversion apparatus according to claim 5, wherein the DCDC conversion circuit includes: buck circuitry, boost circuitry, or buck-boost circuitry.
7. The power conversion apparatus according to claim 5, wherein each of the DCDC conversion circuits is further provided with a bypass unit.
8. The power conversion device according to claim 1, further comprising: a DCAC conversion circuit;
and the direct current side of the DCAC conversion circuit is connected with the output end of each DCDC conversion circuit through a direct current bus.
9. The power conversion apparatus according to any one of claims 1 to 8, wherein the control unit includes: a master controller and a slave controller of each of the DCDC conversion circuits;
and each slave controller is in communication connection with the master controller.
10. The power conversion apparatus according to claim 9, wherein the main controller is: a system controller; alternatively, the first and second electrodes may be,
when the power conversion device includes a DCAC conversion circuit, the main controller is: a controller of the DCAC conversion circuit.
11. A control method of a power conversion apparatus, applied to a control unit of the power conversion apparatus according to any one of claims 1 to 10, the control method comprising:
detecting an input voltage of each DCDC conversion circuit in the power conversion device;
judging whether each DCDC conversion circuit on two sides of the same switch unit in the power conversion device meets a preset low input condition or not;
and if the judgment result is yes, controlling the corresponding switch unit to be conducted.
12. The method according to claim 11, wherein determining whether each of the DCDC conversion circuits on both sides of the same switching unit in the power conversion apparatus satisfies a preset low input condition includes:
judging whether at least one input voltage of each DCDC conversion circuit on two sides of the same switch unit meets a preset low voltage condition; alternatively, the first and second electrodes may be,
and judging whether the input voltage of each DCDC conversion circuit at two sides of the same switch unit meets the preset low voltage condition or not.
13. The method according to claim 12, further comprising, after determining whether each of the DCDC conversion circuits on both sides of the same switching unit in the power conversion apparatus satisfies a preset low input condition:
if the judgment result is negative, the corresponding switch unit is controlled to be switched off, and the DCDC conversion circuit connected with the corresponding switch unit performs chopping operation.
14. The method according to any one of claims 11 to 13, wherein the preset low voltage condition includes:
does not rise above the first threshold or has fallen below a second threshold; the second threshold is less than the first threshold.
15. A power conversion system, comprising: at least two input power sources, and a power conversion device as claimed in any one of claims 1 to 10.
16. The power conversion system according to claim 15, wherein the power conversion device is: a dc combiner box without a DCAC conversion circuit, or a string inverter with a DCAC conversion circuit.
17. The power conversion system according to claim 15 or 16, wherein the input power source is: photovoltaic modules, photovoltaic strings, or energy storage cells.
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| CN202110540628.0A CN113258773A (en) | 2021-05-18 | 2021-05-18 | Power conversion system, power conversion device and control method thereof |
| PCT/CN2021/138257 WO2022242135A1 (en) | 2021-05-18 | 2021-12-15 | Power conversion system, power conversion apparatus, and control method therefor |
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| WO2022242135A1 (en) * | 2021-05-18 | 2022-11-24 | 阳光电源股份有限公司 | Power conversion system, power conversion apparatus, and control method therefor |
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| CN115864814B (en) * | 2023-02-27 | 2023-05-30 | 阳光电源股份有限公司 | Soft start circuit and power conversion equipment |
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