Discharge control method for direct current converter, power conversion device and energy storage device

Abstract

The application provides a discharge control method of a direct current converter, a power conversion device and an energy storage device. The method comprises the following steps: acquiring actual photovoltaic voltages and photovoltaic power generation powers of photovoltaic modules corresponding to each direct current conversion circuit; when at least two direct current conversion circuits are connected to the same MPPT circuit, determining a reference photovoltaic voltage based on the actual photovoltaic voltages and determining a reference power generation power based on the photovoltaic power generation powers; acquiring target discharge powers of the at least two direct current conversion circuits; determining a discharge mode of the direct current conversion circuit based on the reference photovoltaic voltage and the reference power generation power; when the discharge mode is an analog discharge mode, constructing a first analog discharge curve based on the target discharge powers of the at least two direct current conversion circuits; and controlling the at least two direct current conversion circuits to discharge based on the first analog discharge curve.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of clean energy, in particular to a discharge control method of a direct current converter, a power conversion device and an energy storage device. BACKGROUND

[0002] In a light storage system coupled with an energy storage device at a direct current side, when the energy storage device discharges, the discharge power of the energy storage device and the power generation power of a photovoltaic assembly are output to a direct current end of an inverter as total discharge power. Therefore, the discharge curve of the energy storage device will affect the maximum power tracking of the inverter, and then affect whether the photovoltaic assembly can work at a maximum power point. In order to make the photovoltaic assembly work at the maximum power point, one of the discharge modes of the energy storage device is to construct a simulated power-voltage (PV) curve to discharge in the form of simulating the PV curve of the photovoltaic assembly. The simulated PV curve needs to be matched with the actual PV curve of the photovoltaic assembly, so that the energy utilization rate of the photovoltaic assembly can be maximized under various working conditions. Ideally, the maximum power point voltage of the simulated PV curve should overlap with the maximum power point voltage of the photovoltaic assembly.

[0003] In some scenarios, there are multiple direct current buses in the light storage system, and corresponding photovoltaic assemblies and energy storage devices are connected to the multiple direct current buses respectively. The energy storage device can include a direct current conversion circuit and a battery pack, and the discharge power of the energy storage device can be controlled by controlling the direct current conversion circuit. In the related art, a corresponding simulated PV curve can be constructed for the direct current conversion circuit on the direct current bus, and based on the simulated PV curve and the discharge voltage controlled by the MPPT circuit corresponding to the direct current bus, the direct current conversion circuit on the direct current bus is controlled to output a corresponding discharge power.

[0004] However, when two or more direct current buses are connected to the same MPPT circuit, if the maximum power point voltages of the simulated PV curves corresponding to the direct current conversion circuits on the corresponding direct current buses are inconsistent, the MPPT circuit cannot make each direct current conversion circuit work at the maximum power point of the corresponding simulated PV curve, which will result in low discharge efficiency of the energy storage device, i.e., the actual discharge power of each energy storage device cannot simultaneously reach the corresponding target discharge power, thereby affecting the working efficiency of the light storage system. SUMMARY

[0005] Therefore, the present application provides a discharge control method of a direct current converter, a power conversion device and an energy storage device, which can ensure the discharge efficiency of at least two direct current conversion circuits.

[0006] The first aspect of the present application provides a discharge control method of a direct current converter, the direct current converter comprising at least two direct current conversion circuits, a first end of each direct current conversion circuit being configured to be connected to a same direct current bus with a corresponding photovoltaic module and a direct current end of an inverter, a second end of each direct current conversion circuit being configured to be connected to a corresponding battery pack, and the direct current end of the inverter being configured to be connected to an MPPT circuit. The method comprises: obtaining an actual photovoltaic voltage and a photovoltaic power generation power of the corresponding photovoltaic module of each direct current conversion circuit; when the at least two direct current conversion circuits are connected to the same MPPT circuit, determining a reference photovoltaic voltage based on the actual photovoltaic voltages, and determining a reference power generation power based on the photovoltaic power generation powers; obtaining a target discharge power of the at least two direct current conversion circuits; determining a discharge mode of the direct current conversion circuit based on the reference photovoltaic voltage and the reference power generation power; when the discharge mode is a simulation discharge mode, constructing a first simulation discharge curve based on the target discharge power of the at least two direct current conversion circuits; and controlling the at least two direct current conversion circuits to discharge based on the first simulation discharge curve.

[0007] The second aspect of the present application provides a power conversion device, the power conversion device comprising a controller and a direct current converter, the direct current converter comprising at least two direct current conversion circuits, a first end of each direct current conversion circuit being configured to be connected to a same direct current bus with a corresponding photovoltaic module and a direct current end of an inverter, a second end of each direct current conversion circuit being configured to be connected to a battery pack, and the direct current end of the inverter being configured to be connected to an MPPT circuit; and the controller being configured to perform the discharge control method of the direct current converter according to any one of the above.

[0008] The third aspect of the present application provides an energy storage device, the energy storage device comprising a battery pack, a controller and a direct current converter, the direct current converter comprising at least two direct current conversion circuits, a first end of each direct current conversion circuit being configured to be connected to a same direct current bus with a corresponding photovoltaic module and a direct current end of an inverter, a second end of each direct current conversion circuit being configured to be connected to the battery pack, and the direct current end of the inverter being configured to be connected to an MPPT circuit; and the controller being configured to perform the discharge control method of the direct current converter according to any one of the above.

[0009] The discharge control method of the direct current converter provided in the application first acquires the actual photovoltaic voltage and the photovoltaic power generation power of the photovoltaic module corresponding to each direct current conversion circuit. When at least two direct current conversion circuits are connected to the same MPPT circuit, the reference photovoltaic voltage is determined based on the actual photovoltaic voltage, the reference power generation power is determined based on the photovoltaic power generation power, and the target discharge power of the at least two direct current conversion circuits is acquired, so as to determine the discharge mode of the direct current conversion circuit based on the reference photovoltaic voltage and the reference power generation power. In this way, the method preliminarily determines the same discharge mode for the at least two direct current conversion circuits connected to the same MPPT circuit. Further, when the discharge mode is the simulation discharge mode, the method constructs the corresponding first simulation discharge curve based on the target discharge power of the at least two direct current conversion circuits, and controls the discharge of the corresponding at least two direct current conversion circuits based on the first simulation discharge curve, so as to control the discharge of the corresponding direct current conversion circuit according to the first simulation discharge curve. In this way, the at least two direct current conversion circuits can discharge based on the same first simulation discharge curve.

[0010] Compared with the scheme in the related art that the MPPT circuit cannot make the direct current conversion circuits of each energy storage device work at the maximum power point of the corresponding simulation PV curve at the same time, the discharge control method provided in the application can make the at least two direct current conversion circuits work at the maximum power point of the first simulation discharge curve when the MPPT circuit controls the discharge voltage of the at least two direct current conversion circuits to be the maximum power point voltage of the first simulation discharge curve, so as to ensure the discharge efficiency of the at least two direct current conversion circuits. BRIEF DESCRIPTION OF DRAWINGS

[0011] In order to more clearly illustrate the technical solutions of the application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some of the embodiments of the application, and therefore should not be regarded as a limitation on the protection scope of the application. In the various drawings, similar components are denoted by similar reference numerals.

[0012] Figure 1 The application scenario diagram of the discharge control method of the direct current converter provided in an embodiment of the application.

[0013] Figure 2 The flowchart of the discharge control method of the direct current converter provided in an embodiment of the application.

[0014] Figure 3 The sub-step flowchart of step S206 provided in an embodiment of the application.

[0015] Figure 4 The sub-step flowchart of step S204 provided in an embodiment of the application.

[0016] Figure 5 A sub-step flowchart of step S205 provided by an embodiment of the present application is shown in the following.

[0017] Figure 6 A sub-step flowchart of determining the connection relationship between the at least two DC converters and the MPPT circuit provided by an embodiment of the present application is shown in the following.

[0018] Figure 7 For Figure 6 A sub-step flowchart of step S605 is shown in the following.

[0019] Figure 8 A sub-step flowchart of step S202 provided by an embodiment of the present application is shown in the following.

[0020] Figure 9 Another application scenario of the discharge control method of the DC converter provided by an embodiment of the present application is shown in the following.

[0021] Figure 10 Another application scenario of the discharge control method of the DC converter provided by an embodiment of the present application is shown in the following.

[0022] Figure 11 A functional block diagram of the power conversion device provided by an embodiment of the present application is shown in the following.

[0023] Figure 12 A functional block diagram of the energy storage device provided by an embodiment of the present application is shown in the following.

[0024] Figure 13 A functional block diagram of the electronic device provided by an embodiment of the present application is shown in the following.

[0025] Figure 14 A functional block diagram of the control device provided by an embodiment of the present application is shown in the following. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present application will be described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments of the present application.

[0027] It should be noted that when one component is considered to be “connected” to another component, it can be directly connected to the other component or can exist a middle component at the same time. When one component is considered to be “provided on” another component, it can be directly provided on the other component or can exist a middle component at the same time. The terms “top”, “bottom”, “upper”, “lower”, “left”, “right”, “front”, “back”, and the like used herein are only for the purpose of illustration.

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description herein is for describing particular embodiments only and is not intended to be limiting of the application.

[0029] Some embodiments will be described in the following detailed description and in relation to the drawings. The embodiments and features described below can be combined with each other, insofar as they do not contradict each other.

[0030] Please refer to Figure 1 , Figure 1 The application scenario of the discharge control method of the direct current converter provided by an embodiment of the application is shown in the figure. The scenario includes a photovoltaic module (corresponding to the first photovoltaic module 10A and the second photovoltaic module 10B in Figure 1 ), an inverter 20, a load 30, a power grid 40, a direct current converter (Direct Current to Direct Current, DC-DC) 50, and a battery pack 60.

[0031] Specifically, the inverter 20 includes a first maximum power point tracking (Maximum Power Point Tracking, MPPT) circuit 21A and an inverter circuit 22. For the convenience of wiring, the inverter 20 is also provided with a direct current input port (for example, a first direct current input port a and a second direct current input port b) and an alternating current output port (corresponding to the alternating current output port c in Figure 1 ). The specific topology of the first MPPT circuit 21A and the inverter circuit 22 is not limited in the embodiments of the application. For example, the first MPPT circuit 21A can be a boost circuit, and the inverter circuit 22 can be a full-bridge inverter circuit or a half-bridge inverter circuit, etc. It can be understood that in another embodiment, the first MPPT circuit 21A can also be independent of the inverter 20.

[0032] The direct current converter 50 includes at least two direct current conversion circuits, for example, corresponding to the first direct current conversion circuit 51A and the second direct current conversion circuit 51B in Figure 1 ). Wherein, the circuit structure of the direct current conversion circuit is not limited in the embodiments of the application, and the direct current conversion circuit can include any one of a boost circuit, a buck circuit, and / or a buck-boost circuit, etc. Further, the direct current conversion circuit can adopt a dual active bridge (Dual Active Bridge, DAB) conversion circuit.

[0033] Each photovoltaic assembly includes one photovoltaic panel, or includes multiple photovoltaic panels connected in series, in parallel, or in series-parallel, which is not limited here. In the case of certain environmental factors such as temperature and light intensity, the photovoltaic assembly can realize photovoltaic power generation and generate power. The power grid 40 may, for example, be a municipal power grid, other local power grid, or micro power grid. The load 30 may, for example, be various alternating current loads in a home. The battery pack 60 includes battery cells (not shown in the figure) for storing and releasing electric energy, and a battery management system (BMS, not shown in the figure) for managing the charging and discharging states of the battery cells.

[0034] Specifically, in the scenario shown, Figure 1 In the scenario shown, the first end of the first direct current conversion circuit 51A and the corresponding first photovoltaic assembly 10A and the first direct current input port a of the inverter 20 are connected to the same direct current bus (DC_BUS1+, DC_BUS1-). The first end of the second direct current conversion circuit 51B and the corresponding second photovoltaic assembly 10B and the second direct current input port b of the inverter 20 are connected to another direct current bus (DC_BUS2+, DC_BUS2-). The first direct current input port a and the second direct current input port b are both connected to the input end of the first MPPT circuit 21A. That is, the first end of each direct current conversion circuit is used to be connected to the same direct current bus with the corresponding photovoltaic assembly and the direct current end of the inverter, the second end of each direct current conversion circuit is used to connect the corresponding battery pack, and the direct current end of the inverter is used to connect the MPPT circuit.

[0035] Based on such a design, each photovoltaic assembly can output photovoltaic power to the corresponding direct current bus. Among them, the first MPPT circuit 21A on the direct current bus can be used to track the maximum power point of the photovoltaic assembly, so that the photovoltaic assembly outputs the maximum power to the direct current bus. When the photovoltaic power of the photovoltaic assembly is greater than the required power of the load 30, the power of the direct current bus can be partially transmitted to the inverter circuit 22, and the inverter circuit 22 supplies power to the load 30 after inverting the power, and another part of the power of the direct current bus can be converted by the first direct current conversion circuit 51A or the second direct current conversion circuit 51B to charge the battery pack 60. Conversely, when the power generated by the photovoltaic assembly is less than the required power of the load 30, the battery pack 60 can be discharged, and the power released by the battery pack 60 is converted by the first direct current conversion circuit 51A or the second direct current conversion circuit 51B to be transmitted to the direct current bus to make up for the required power of the load 30.

[0036] In this way, the photovoltaic assembly, the inverter 20, the direct current converter 50, and the battery pack 60 can jointly constitute a photovoltaic energy storage system (which can be referred to as a light storage system), and the entire system can realize self-generation and self-use, and the load 30 does not need to take power from the power grid 40.

[0037] It can be understood that when the battery pack 60 cannot make up the required power of the load 30, the power grid 40 can also supply power to the load 30. In addition, in addition to supplying power to the load 30 and the battery pack 60, the photovoltaic assembly can also feed excess power into the power grid 40.

[0038] In addition, the scene also includes a controller (not shown in the figure). The controller can be a microcontroller unit (MCU) or other control circuit. The controller can be separately arranged, or integrated with other parts of the scene such as the inverter 20 or any one of the direct current converters 50, which is not limited here. The controller can serve as an energy management system (EMS) of the entire scene. The controller is connected to each direct current converter 50 and is used to control the power conversion of each direct current converter 50, thereby controlling the charging and discharging power of the battery pack 60. The controller can also be connected to the BMS of the battery pack 60, so as to obtain the parameters of each battery pack 60 detected by the BMS and control the charging and discharging state of the battery pack 60 through the BMS. The controller can also be connected to the inverter 20, so as to control the inversion process of the inverter 20.

[0039] In related technologies, in a photovoltaic storage system coupled with a battery pack on the direct current side, when the battery pack is discharged through a direct current converter, the discharging power of the direct current converter and the power generation power of the photovoltaic assembly are output as total discharging power to the direct current end of the inverter. Therefore, the discharging curve of the direct current converter will affect the maximum power tracking of the inverter, and then affect whether the photovoltaic assembly can work at the maximum power point. In order to make the photovoltaic assembly work at the maximum power point, one of the discharging control modes of the direct current converter is to construct a simulated power-voltage (PV) curve to discharge in the form of simulating the PV curve of the photovoltaic assembly. The simulated PV curve needs to be matched with the actual PV curve of the photovoltaic assembly, so as to maximize the energy utilization rate of the photovoltaic assembly under various working conditions. Ideally, the maximum power point voltage of the simulated PV curve should overlap with the maximum power point voltage of the photovoltaic assembly.

[0040] In some scenes, there are multiple direct current buses in the photovoltaic storage system, and corresponding photovoltaic assemblies, direct current converters and battery packs are connected to the multiple direct current buses respectively. At this time, the simulated PV curve of the direct current converter on the corresponding direct current bus can be constructed according to the power generation parameters of the photovoltaic assembly on the corresponding direct current bus. However, in similar Figure 1In a photovoltaic-storage system, when two or more DC buses are connected to the same MPPT circuit, if the maximum power point voltage of the simulated PV curve of the DC converter on the corresponding DC bus is inconsistent, the MPPT circuit cannot make each DC converter work at the maximum power point of the corresponding simulated PV curve at the same time. This will result in low discharge efficiency of the DC converter, that is, the actual discharge power of each DC converter cannot reach the corresponding target discharge power at the same time, thus affecting the working efficiency of the photovoltaic-storage system.

[0041] Specifically, with Figure 1 Taking the photovoltaic-storage system shown as an example, when both the first DC-DC converter circuit 51A and the second DC-DC converter circuit 51B are connected to the first MPPT circuit 21A, the first photovoltaic module 10A and the second photovoltaic module 10B, which are correspondingly connected to the first DC-DC converter circuit 51A and the second DC-DC converter circuit 51B, both perform maximum power point tracking through the first MPPT circuit 21A. This is because the first MPPT circuit 21A has a built-in anti-reverse diode (…). Figure 1 (Not shown, or the anti-reverse diode may also be located on the photovoltaic module). Thus, normally, when the first MPPT circuit 21A is operating, the actual photovoltaic voltage of the first photovoltaic module 10A, i.e., the first actual photovoltaic voltage, is equal to the actual photovoltaic voltage of the second photovoltaic module 10B, i.e., the second actual photovoltaic voltage. However, in practice, due to potential errors in the sampling process of the actual photovoltaic voltage, the first actual photovoltaic voltage and the second actual photovoltaic voltage may not be equal. In another scenario, when the maximum power point voltage of the first photovoltaic module 10A is greater than the open-circuit voltage of the second photovoltaic module 10B, the first actual photovoltaic voltage and the second actual photovoltaic voltage may also be different, and the second photovoltaic module 10B may be unable to output photovoltaic power at this time.

[0042] In the case where the first actual photovoltaic voltage is not equal to the second actual photovoltaic voltage, if the first DC conversion circuit 51A discharges based on the first actual photovoltaic voltage and the corresponding simulated discharge curve, and the second DC conversion circuit 51B discharges based on the second actual photovoltaic voltage and the corresponding simulated discharge curve, the maximum power point voltage when the first DC conversion circuit 51A discharges can be different from the maximum power point voltage when the second DC conversion circuit 51B discharges. Since the first DC conversion circuit 51A and the second DC conversion circuit 51B are both connected to the first MPPT circuit 21A, compared to the case where the maximum power point voltage when the first DC conversion circuit 51A and the second DC conversion circuit 51B discharge is the same, in the case where the maximum power point voltage when the first DC conversion circuit 51A and the second DC conversion circuit 51B discharge is different, the discharge voltage controlled by the MPPT circuit 21A cannot simultaneously satisfy the maximum power point voltage when the first DC conversion circuit 51A and the second DC conversion circuit 51B discharge, and at least the actual discharge power of the first DC conversion circuit 51A or the second DC conversion circuit 51B cannot simultaneously reach the target discharge power corresponding to the maximum power point voltage, i.e., the discharge efficiency of the DC conversion circuit in the light storage system is reduced.

[0043] Based on this, the present application provides a discharge control method of a DC converter, which improves the discharge efficiency of the battery pack and the energy utilization rate of the photovoltaic module. Understandably, the control method can be performed by the controller of the DC converter 50.

[0044] Please refer to Figure 2 The discharge control method of the DC converter comprises the following steps:

[0045] Step S201: Obtain the actual photovoltaic voltage and the photovoltaic power generation power of the photovoltaic module corresponding to each DC conversion circuit.

[0046] The actual photovoltaic voltage refers to the actual output voltage of the photovoltaic module. In some embodiments, a voltage sensor or other circuit or electronic device capable of sampling voltage can be arranged at the output end of the photovoltaic module to periodically obtain the actual photovoltaic voltage.

[0047] The photovoltaic power generation power refers to the actual output power of the photovoltaic module. In some embodiments, a power sensor or other circuit or electronic device capable of sampling power can be arranged at the output end of the photovoltaic module to periodically obtain the actual power generation power of the photovoltaic module. In other embodiments, a current sensor (such as a Hall sensor) or other circuit or electronic device capable of sampling current can also be arranged at the output end of the photovoltaic module to periodically obtain the output current of the photovoltaic module. In this way, the power generation power of the photovoltaic module can be calculated based on the obtained photovoltaic voltage and output current of the photovoltaic module.

[0048] corresponding to Figure 1 That is, step S201 needs to acquire the actual photovoltaic voltage and photovoltaic power generation power of the first photovoltaic module 10A, and acquire the actual photovoltaic voltage and photovoltaic power generation power of the second photovoltaic module 10B.

[0049] Step S202: When at least two direct current conversion circuits are connected to the same MPPT circuit, a reference photovoltaic voltage is determined based on the actual photovoltaic voltage of each, and a reference power generation power is determined based on the photovoltaic power generation power of each.

[0050] The reference photovoltaic voltage is used to represent the photovoltaic voltage of the photovoltaic module connected to the same MPPT circuit. The reference power generation power is used to represent the photovoltaic power generation power of the photovoltaic module connected to the same MPPT circuit. And the reference photovoltaic voltage and the reference power generation power are used to jointly represent the illumination state of the environment in which the at least two photovoltaic modules connected to the same MPPT circuit are located.

[0051] When the direct current end of the inverter is connected to one MPPT circuit and at least two direct current buses, and the corresponding photovoltaic module and direct current conversion circuit are connected to each of the at least two direct current buses, the photovoltaic panel with a low voltage value cannot participate in the discharging operation, because once it participates in the discharging operation, the voltages of the two photovoltaic panels will be consistent, and the voltage values are all the maximum value of the actual photovoltaic voltage of all photovoltaic modules connected to the same MPPT circuit.

[0052] For example, in some embodiments, the maximum value of the actual photovoltaic voltage can be taken as the reference photovoltaic voltage, and the average value of all photovoltaic power generation powers can be taken as the reference power generation power.

[0053] It should be noted that taking the maximum value of the actual photovoltaic voltage can exclude the low-voltage photovoltaic panel that does not participate in the discharging from the outside, so as to prevent the misjudgment of the discharging mode of the corresponding direct current conversion circuit. That is, when the maximum value of the actual photovoltaic voltage is taken, the actual photovoltaic voltage with other low voltage values can be actively ignored, so that the discharging mode judged according to this can be consistent when the at least two direct current conversion circuits are controlled to discharge subsequently, that is, when the discharging mode is the simulation discharging mode, the parameters used to construct the first simulation discharging curve are consistent. Understandably, the present application does not limit the specific calculation method of determining the reference photovoltaic voltage based on the actual photovoltaic voltage of each, and the specific calculation method of determining the reference power generation power based on the photovoltaic power generation power of each. For example, in other embodiments, the average value of all actual photovoltaic voltages can be taken as the reference photovoltaic voltage, and the average value of all photovoltaic power generation powers can be taken as the reference power generation power.

[0054] Step S203: Acquire the target discharging power of the at least two direct current conversion circuits.

[0055] The target discharging power is used to represent an ideal value of the discharging power of the at least two DC conversion circuits, i.e., an ideal value of the discharging power of the DC converter 50. In some embodiments, the target discharging power can be calculated according to a power control loop between the optical storage system and the power grid 40. The present application does not limit the specific method of obtaining the target discharging power. For example, in other embodiments, the target discharging power can also be a preset value preset in the memory.

[0056] Step S204: determining the discharging mode of the DC conversion circuit based on the reference photovoltaic voltage and the reference power generation power.

[0057] As described above, the reference photovoltaic voltage and the reference power generation power are used to represent the illumination state of the photovoltaic assembly as a whole connected to the same MPPT circuit. Then, in order to maximize the discharging efficiency of the DC conversion circuit, the DC conversion circuit can be switched to different discharging modes corresponding to different illumination states.

[0058] Moreover, when one MPPT circuit connected to the DC end of the inverter is connected to at least two DC buses, and the at least two DC buses are each connected to a corresponding photovoltaic assembly and DC conversion circuit, the photovoltaic assembly with a low voltage value on the at least two DC buses connected to the same MPPT circuit cannot participate in the discharging operation, because the voltages of the two photovoltaic assemblies connected to the same MPPT circuit will remain the same once they participate in the discharging operation. Then, at this time, the discharging modes of the at least two DC conversion circuits connected to the same MPPT circuit should also be the same, so that the two DC conversion circuits both discharge according to the actual photovoltaic voltage of the photovoltaic assembly actually participating in the discharging operation (i.e., the discharging voltage of the first end of the DC conversion circuit).

[0059] Therefore, in step S204, the discharging mode of the at least two DC conversion circuits can be determined based on the reference photovoltaic voltage and the reference power generation power. For example, when the illumination state is divided into weak light and strong light, the discharging mode can also be divided into two discharging modes. In other embodiments, the illumination state can also be subdivided into three or more illumination states, for example, when the illumination state is divided into no light, weak light, and strong light, the discharging mode can also be divided into three discharging modes, and the corresponding discharging mode is determined according to the illumination state. The present application does not limit the type of discharging mode.

[0060] In this way, after step S204 is performed, the discharging modes of the at least two DC conversion circuits connected to the same MPPT circuit are the same.

[0061] Step S205: when the discharging mode is the simulated discharging mode, constructing a first simulated discharging curve based on the target discharging power of the at least two DC conversion circuits.

[0062] Please refer again to Figure 1 Since at least two DC conversion circuits (for example, the first DC conversion circuit 51A and the second DC conversion circuit 51B) are connected to the same MPPT circuit (for example, the first MPPT circuit 21A), that is, the first ends of the at least two DC conversion circuits are connected to the input end of the same MPPT circuit, so the discharge voltage of the first end of each DC conversion circuit is actually equal. In this way, if the at least two DC conversion circuits are still based on different analog discharge curves at this time, and discharge according to the discharge voltage on the DC bus corresponding to each DC conversion circuit, the at least two DC conversion circuits cannot work at the maximum power point of the respective analog discharge curves at the same time, which will lead to low battery pack discharge efficiency, that is, the actual discharge power does not reach the target discharge power, thereby affecting the working efficiency of the light storage system.

[0063] Therefore, in step S205, an analog discharge curve, that is, a first analog discharge curve, can be constructed with the discharge voltage of the DC conversion circuit as the independent variable and the discharge power of the at least two DC conversion circuits as the dependent variable, which is used to represent the relationship between the discharge voltage and the discharge power of the at least two DC conversion circuits.

[0064] Understandably, the first analog discharge curve can be a discharge curve simulating the PV curve of the photovoltaic module. That is, similar to the PV curve, the first analog discharge curve also has a maximum power point power and a corresponding maximum power point voltage. And the maximum power point power is the target discharge power of the at least two DC conversion circuits.

[0065] Step S206: Control the discharge of the at least two DC conversion circuits based on the first analog discharge curve.

[0066] Wherein, controlling the discharge of the at least two DC conversion circuits based on the first analog discharge curve can be understood as controlling the discharge of each DC conversion circuit according to the first analog discharge curve; or it can also be understood that each DC conversion circuit corresponds to a same form of analog discharge curve, that is, the first analog discharge curve.

[0067] Understandably, when the at least two DC conversion circuits are connected to the same MPPT circuit, if the at least two DC conversion circuits discharge, the actual discharge voltages of the at least two DC conversion circuits are the same, and the actual discharge power of the at least two DC conversion circuits and the photovoltaic power of the at least two photovoltaic modules are output to the input end of the same MPPT circuit as the total discharge power.

[0068] The MPPT circuit actually performs maximum power tracking on a synthesized curve obtained by superimposing the first analog discharge curve and the PV curve of the at least two photovoltaic modules as a whole when performing maximum power tracking. In this way, when different DC conversion circuits correspond to different analog discharge curves and the maximum power point voltages of the different analog discharge curves are different, since the actual discharge voltages controlled by the MPPT circuit cannot be two voltages at the same time, different DC conversion circuits cannot work at the maximum power point at the same discharge voltage, resulting in low discharge efficiency of the battery pack, i.e., the actual discharge power does not reach the target discharge power, thereby affecting the working efficiency of the light storage system.

[0069] Therefore, the method provided in the embodiments of the present application can construct a first analog discharge curve and control different DC conversion circuits based on the first analog discharge curve and the actual discharge voltage. Since each DC conversion circuit is controlled based on the first analog discharge curve, when the actual discharge voltage controlled by the MPPT circuit is at the maximum power point voltage of the first analog discharge curve, each DC conversion circuit can work at the maximum working point at the same time, i.e., output according to the target discharge power, thereby ensuring the working efficiency of the light storage system.

[0070] In some embodiments, after the first analog discharge curve is constructed, the first analog discharge curve can be moved following the actual photovoltaic voltage of the photovoltaic module participating in the discharge operation (i.e., the maximum value in the actual photovoltaic voltages of all photovoltaic modules connected to the same MPPT circuit) and the actual discharge voltage, and the corresponding DC conversion circuit is controlled to discharge according to the moved first analog discharge curve.

[0071] In this way, the first analog discharge curve is moved following the reference photovoltaic voltage and the actual discharge voltage, and the corresponding DC conversion circuit is controlled to discharge according to the first analog discharge curve, so that when the maximum power point tracking of the MPPT circuit reaches a steady state, the maximum power point voltage of the first analog discharge curve is close to or even overlaps with the maximum power point voltage of the PV curve of the at least two photovoltaic modules as a whole. In this way, not only can the energy utilization efficiency of the at least two photovoltaic modules be improved, but also when the discharge voltages of the at least two DC conversion circuits are both the maximum power point voltage, the actual discharge power of the at least two DC conversion circuits is the target discharge power, thereby ensuring the discharge efficiency of the at least two DC conversion circuits.

[0072] Understandably, in some embodiments, when the target discharge power corresponding to each DC conversion circuit is equal, step S203 can be to obtain the target discharge power corresponding to any DC conversion circuit of the at least two DC conversion circuits.

[0073] In some embodiments, step S203 can be obtaining a target discharge power corresponding to each of the at least two DC conversion circuits. Accordingly, step S205 can be that each of the at least two DC conversion circuits connected to the same MPPT circuit respectively constructs a first analog discharge curve based on the corresponding target discharge power, and the maximum power point voltage of the first analog discharge curve constructed by each DC conversion circuit is the same (the maximum power point power on the first analog discharge curve corresponding to different DC conversion circuits can be the target discharge power of the corresponding DC conversion circuit). At this time, the first analog discharge curve can be understood as a set of a series of analog discharge curves with the same maximum power point voltage. Accordingly, the control of the discharge of the at least two DC conversion circuits based on the first analog discharge curve in step S206 can be the control of the discharge of the corresponding DC conversion circuit based on the first analog discharge curve with the same maximum power point voltage constructed by each DC conversion circuit respectively.

[0074] Please refer to Figure 3 In some embodiments, step S206 includes the following sub-steps:

[0075] Step S301: obtaining an actual discharge voltage of the at least two DC conversion circuits.

[0076] The actual discharge voltage refers to the discharge voltage of the first end of each DC conversion circuit. When the discharge of the at least two DC conversion circuits connected to the same MPPT circuit is controlled based on the same first analog discharge curve, the discharge voltage of the at least two DC conversion circuits connected to the same MPPT circuit when working normally can be controlled to be equal, at this time, the discharge voltage of the first end of any one of the at least two DC conversion circuits connected to the same MPPT circuit can be directly obtained as the actual discharge voltage.

[0077] It can be understood that the discharge voltage of the first end of the DC conversion circuit can be periodically obtained by setting a voltage sensor or other circuit or electronic device capable of sampling voltage at the first end of the DC conversion circuit.

[0078] Step S302: determining a given discharge power based on the actual discharge voltage and the first analog discharge curve.

[0079] The given discharge power represents a given value of the discharge power of the at least two DC conversion circuits. In step S302, the given discharge power can be the discharge power on the first analog discharge curve corresponding to the actual discharge voltage.

[0080] Specifically, for each DC conversion circuit, the discharge power on the first analog discharge curve corresponding to the actual discharge voltage can be periodically determined according to the obtained actual discharge voltage, so as to take the discharge power as the given discharge power.

[0081] Step S303: controlling discharging of the at least two DC conversion circuits according to the given discharging power.

[0082] In some embodiments, when discharging of the at least two DC conversion circuits is controlled based on the same first simulated discharging curve, step S303 can include: controlling discharging of the at least two DC conversion circuits according to the given discharging power and each DC conversion circuit. For example, the given discharging power can be substituted into a control loop of each DC conversion circuit respectively to obtain a driving signal of each DC conversion circuit, and discharging of the corresponding DC conversion circuit is controlled based on the driving signal.

[0083] In some other embodiments, when discharging of the corresponding DC conversion circuit is controlled based on the first simulated discharging curve with the same maximum power point voltage constructed for each DC conversion circuit respectively, it can be that, after each DC conversion circuit determines the corresponding given discharging power according to the corresponding actual discharging voltage, discharging is performed according to the corresponding given discharging power.

[0084] It can be understood that, in step S303, according to the given discharging power of each DC conversion circuit, the second end of the corresponding DC conversion circuit obtains DC power from the battery pack 60 for conversion, and outputs an actual discharging power through the first end, and the value of the actual discharging power reaches the given discharging power.

[0085] In this way, by performing steps S301 to S303, discharging of the at least two DC conversion circuits can be controlled based on the first simulated discharging curve, and discharging can be performed considering the specific circuit conditions of each DC conversion circuit, which is conducive to improving the safety of the optical storage system.

[0086] In some embodiments, step S204 includes:

[0087] When the reference photovoltaic voltage is less than a preset voltage threshold, or the reference power generation power is less than a preset power threshold, it is determined that the discharging mode is the simulated discharging mode.

[0088] The preset voltage threshold can be understood as a critical voltage threshold between the light state and the no-light state of the photovoltaic module, and the preset power threshold can be understood as a critical power threshold between the strong-light state and the weak-light state of the photovoltaic module. Specifically, the preset voltage threshold and the preset power threshold can be set according to actual needs. For example, the preset voltage threshold can be set to 130V, and the preset power threshold can be set to 150W. When the reference photovoltaic voltage is less than the preset voltage threshold, or the reference power generation power is less than the preset power threshold, it indicates that the current light condition causes the photovoltaic voltage generated by the at least two photovoltaic modules as a whole to be low or the power generation power to be low, and at this time, it can be considered that the at least two photovoltaic modules as a whole are in the first state, for example, the weak-light state. Understandably, the weak-light state may, for example, be the state of the at least two photovoltaic modules in a time period with weak light such as early morning, evening, or overcast day, or even the state in a no-light time period such as night.

[0089] Understandably, the current-voltage characteristics of the photovoltaic module will be different under different light. Specifically, under no-light conditions, the photovoltaic module has no output current and photovoltaic voltage. Under weak-light conditions, the photovoltaic module has output voltage, but due to weak light, the output power is small, and at this time, almost no current is output. As the light increases, when the output power increases, the output current of the photovoltaic module also increases. When the light further increases, the output current of the photovoltaic module continues to increase. When the light reaches a certain degree, the characteristic curve of the photovoltaic module tends to be stable, and at this time, under the tracking of the MPPT circuit, the output current and photovoltaic voltage of the photovoltaic module are stable at the maximum power point. Therefore, it can be considered that under weak-light conditions, the photovoltaic voltage of the photovoltaic module is low and the PV curve is unstable; under strong-light conditions, the PV curve of the photovoltaic module is stable. Again, since the output end of the photovoltaic module and the DC conversion circuit are connected to the DC bus, when the actual discharge voltage of the DC conversion circuit is greater than the photovoltaic voltage, the photovoltaic module cannot output power generation power due to the influence of the reverse diode (not shown in the figure) on the DC bus.

[0090] Therefore, when the reference photovoltaic voltage is less than the preset voltage threshold, or the reference power generation power is less than the preset power threshold, it is determined that the discharge mode is the simulation discharge mode, so as to control the at least two DC conversion circuits to discharge based on the first simulation discharge curve. It should be understood that under weak-light conditions, since the PV curve of the photovoltaic module is unstable, it is difficult to perform maximum power tracking, and the power generation power output by the photovoltaic module is extremely small. Therefore, under weak-light conditions, it can be determined that the discharge mode is the simulation discharge mode, and the simulation discharge curve is constructed for the DC converter, which is conducive to the maximum power tracking of the MPPT circuit based on the simulation discharge curve.

[0091] In some embodiments, in the simulation discharging mode, the first simulation discharging curve can also be moved following the actual discharging voltage, so that after the light recovery / enhancement, the MPPT circuit can track to the maximum power point of the PV curve of the at least two photovoltaic components as soon as possible, so that the at least two photovoltaic components output power as soon as possible, and the energy utilization rate of the at least two photovoltaic components is improved.

[0092] The moving of the first simulation discharging curve can be understood as moving the maximum power point voltage and / or the open circuit voltage of the first simulation discharging curve.

[0093] Specifically, when it is determined according to the reference photovoltaic voltage and the reference power generation power that the at least two photovoltaic components are in a weak light state, the principle of moving the first simulation discharging curve is to continuously move the first simulation discharging curve to the left, so that the maximum power point voltage of the first simulation discharging curve approaches the maximum power point voltage of the photovoltaic component, until the maximum power point voltage of the first simulation discharging curve reaches the minimum discharging voltage value of the corresponding DC conversion circuit. It can be understood that in the weak light state, the power generation power of the at least two photovoltaic components is small, and therefore the maximum power point of the PV curve of the at least two photovoltaic components is likely to be on the left side of the maximum power point of the first simulation discharging curve (i.e., the maximum power point voltage and the power generation power of the PV curve are small). At this time, moving the first simulation discharging curve to the left can make the maximum power point voltage of the first simulation discharging curve approach the maximum power point voltage of the PV curve of the at least two photovoltaic components. For the MPPT circuit, in the process of moving the first simulation discharging curve to the left to approach the PV curve, the MPPT tracking range is continuously moved to the left, until the actual discharging voltage of each DC conversion circuit is adjusted to the minimum discharging voltage value of the corresponding DC conversion circuit. In this way, the at least two photovoltaic components can output power as soon as possible.

[0094] In addition, the maximum power point voltage of the photovoltaic module can also be on the right side of the first simulated discharge curve. Therefore, when the MPPT circuit performs maximum power point tracking, if the first simulated discharge curve only moves to the left, it is possible that the first simulated discharge curve affects the tracking result of the maximum power point of the photovoltaic module by the MPPT circuit. Therefore, when the MPPT circuit continues to track to the right beyond the maximum power point voltage of the first simulated discharge curve, the first simulated discharge curve can move to the right along with the discharge voltage. Specifically, a voltage difference between the discharge voltage and the maximum power point voltage of the first simulated discharge curve can be calculated, and when the voltage difference is greater than a preset difference value, the maximum power point voltage of the first simulated discharge curve is set to a value obtained by subtracting the preset difference value from the discharge voltage, so that the difference between the discharge voltage and the maximum power point voltage of the first simulated discharge curve is kept at the preset difference value, that is, the maximum power point voltage of the first simulated discharge curve moves to the right along with the discharge voltage. In this way, when the DC conversion circuit discharges based on the first simulated discharge curve, the discharge power close to the target discharge power can be maintained during the right tracking of the MPPT circuit, and the influence on the maximum power tracking result of the MPPT circuit is reduced. In this way, under the maximum power tracking of the MPPT circuit, the maximum power point voltage of the first simulated discharge curve will eventually approach or even overlap with the maximum power point voltage of the PV curve of the at least two photovoltaic modules as a whole, so that the at least two DC conversion circuits are controlled according to the moved first simulated discharge curve to discharge, which can reduce the influence on the photovoltaic module and improve the energy utilization rate of the photovoltaic module.

[0095] Please refer to Figure 4 In some embodiments, step S204 further includes:

[0096] When the reference photovoltaic voltage is greater than or equal to the preset voltage threshold value and the reference power generation power is greater than or equal to the preset power threshold value, it is determined that the discharge mode is the constant power discharge mode.

[0097] Understandably, when the reference photovoltaic voltage is greater than or equal to the preset voltage threshold value and the reference power generation power is greater than or equal to the preset power threshold value, it indicates that the current light condition causes the at least two photovoltaic modules as a whole to generate a relatively high photovoltaic voltage and power generation power, and therefore it can be considered that the at least two photovoltaic modules as a whole are in a strong light state. The strong light state may, for example, be a state of the photovoltaic module in a time period with sufficient light in the daytime.

[0098] As described above, when the photovoltaic module is in the strong light state, the PV curve of the at least two photovoltaic modules as a whole is relatively stable, that is, the maximum power point on the PV curve is relatively stable, and the MPPT circuit can accurately track the maximum power point on the PV curve. At this time, the simulated discharge curve does not need to be constructed for the DC conversion circuit, and the MPPT circuit only needs to track the maximum power point on the PV curve of the at least two photovoltaic modules as a whole.

[0099] Correspondingly, the method further comprises:

[0100] Step S401: When the discharge mode is the constant power discharge mode, determining that the target discharge power is the given discharge power.

[0101] Step S402: Discharging the at least two DC conversion circuits according to the given discharge power.

[0102] Thus, when the discharge mode is the constant power discharge mode, the given discharge power of the DC conversion circuit does not need to be determined based on the first simulation discharge curve, and the calculation complexity can be effectively reduced.

[0103] It can be understood that step S402 is substantially the same as step S303, and will not be described here.

[0104] In the above embodiment, when the discharge mode is the constant power discharge mode, the given discharge power of the DC conversion circuit is always the target discharge power, and is irrelevant to the discharge voltage controlled by the MPPT circuit, that is, regardless of how the discharge voltage controlled by the MPTT circuit changes, the actual discharge power of the DC conversion circuit will be maintained at the target discharge power as much as possible. In this way, the discharge power of the DC conversion circuit can be avoided to adversely affect the maximum power tracking of the MPPT circuit.

[0105] Please refer to Figure 5 In some embodiments, step S205 comprises the following sub-steps:

[0106] Step S501: When the discharge mode is the simulation discharge mode, obtaining a working voltage range of the MPPT circuit.

[0107] In some embodiments, the MPPT circuit mentioned in the present embodiment is an MPPT circuit connected with the at least two DC conversion circuits. The working range of the MPPT circuit includes a maximum scanning voltage and a minimum scanning voltage. In some embodiments, the maximum scanning voltage and the minimum scanning voltage can be obtained by the controller of the DC converter 50 communicating with the inverter 20. In other embodiments, the maximum scanning voltage and the minimum scanning voltage can also be pre-stored data. The present application does not limit the method of obtaining the maximum scanning voltage and the minimum scanning voltage.

[0108] Step S502: Determining a reference open circuit voltage and a reference maximum power point voltage based on the working voltage range.

[0109] In some embodiments, determining the reference open circuit voltage based on the working voltage range comprises: when the maximum scanning voltage is greater than or equal to the first scanning voltage, determining that the first voltage value is the reference open circuit voltage.

[0110] The first scanning voltage is a preset maximum scanning voltage reference value. The first voltage value is a preset open-circuit voltage value. The first voltage value is less than the first scanning voltage.

[0111] It can be understood that, since the MPPT circuit performs maximum power point tracking within a limited voltage scanning range, in order to ensure that the MPPT circuit can normally perform maximum power tracking, it is necessary to limit the reference open-circuit voltage of the first analog discharge curve within the working voltage range of the MPPT circuit.

[0112] When the maximum scanning voltage of the MPPT circuit is greater than the first scanning voltage, it indicates that the working voltage range of the MPPT circuit is wide enough, and the preset first voltage value can be directly determined as the reference open-circuit voltage of the initial first analog discharge curve. The first scanning voltage and the first voltage value can be set according to actual needs. For example, the first scanning voltage can be 550V, and the first voltage value can be 500V.

[0113] In some other embodiments, determining the reference open-circuit voltage based on the working voltage range further includes: when the maximum scanning voltage is less than the first scanning voltage, determining the reference open-circuit voltage according to the maximum scanning voltage and a first voltage parameter.

[0114] The first voltage parameter is a preset difference value between the reference open-circuit voltage and the maximum scanning voltage.

[0115] It can be understood that, when the maximum scanning voltage of the MPPT circuit is less than the first scanning voltage, it indicates that the working voltage range of the MPPT circuit is small, and the reference open-circuit voltage of the initial first analog discharge curve needs to be determined according to the maximum scanning voltage of the MPPT circuit and the first voltage parameter, so that the discharge voltage of the initial first analog discharge curve is within the voltage scanning range of the MPPT circuit. In some embodiments, a value obtained by subtracting the first voltage parameter from the maximum scanning voltage can be used as the reference open-circuit voltage. The first voltage parameter can be set according to actual needs. For example, the first voltage parameter can be 50V.

[0116] Further, determining the reference maximum power point voltage based on the working voltage range includes: determining the reference maximum power point voltage of the initial first analog discharge curve according to the reference open-circuit voltage and a second voltage parameter.

[0117] The second voltage parameter is a preset difference value between the reference open-circuit voltage and the reference maximum power point voltage.

[0118] In some embodiments, a value obtained by subtracting the second voltage parameter from the reference open-circuit voltage can be used as the reference maximum power point voltage. The second voltage parameter can be 100V.

[0119] Step S503: constructing a first simulated discharge curve based on the reference open circuit voltage, the reference maximum power point voltage and the target discharge power.

[0120] It can be understood that because the real PV curve formula is complex, the software is not easy to implement and the implementation is not meaningful. Therefore, the shape of the PV curve of the photovoltaic module can be simulated, and a simplified function with similar shape is used to construct the first simulated discharge curve.

[0121] Similarly, in the case where the reference open circuit voltage and the reference maximum power point voltage have been determined in step S502, the shape of the two curves from the voltage zero point to the maximum power point and from the maximum power point to the point where the open circuit voltage is located in the PV curve can be fitted in step S503. to form the initial first simulated discharge curve.

[0122] It can be understood that the function used to form the first simulated discharge curve includes but is not limited to an exponential function, a quadratic function or a composite function formed by a combination of multiple function types. The present application does not limit the specific function for forming the first simulated discharge curve, as long as the shape of the first simulated discharge curve is similar to the PV curve (e.g. approximately inverted V-shaped), and the first simulated discharge curve has the target discharge power, the reference maximum power point voltage and the reference open circuit voltage determined in steps S501 to S503.

[0123] Exemplarily, in some scenarios, the function of the first simulated discharge curve can be:

[0124]

[0125] In this function, P is the given discharge power of the at least two DC conversion circuits; U is the actual discharge voltage of the at least two DC conversion circuits; pwr_tag is the maximum power point power (i.e. the target discharge power of the at least two DC conversion circuits); mid_vol is the reference maximum power point voltage; open_vol is the reference open circuit voltage, and the reserved power is 20W.

[0126] Wherein, the reserved power is used to maintain the function of the MPPT circuit while maintaining the working state of the DC conversion circuit. It can be understood that since the first end of the at least two DC conversion circuits and the input end of the MPPT circuit are connected to the DC bus, if the given discharge power is configured to be 0 when the actual discharge voltage is greater than the reference open circuit voltage, then when the photovoltaic module is in a state of no light, and the actual discharge voltage is greater than the reference open circuit voltage, the given discharge power is 0, and the at least two DC conversion circuits stop outputting the discharge power. In this way, the MPPT circuit cannot continue to perform maximum power tracking or even cannot work normally. Therefore, in the first simulated discharge curve, when the actual discharge voltage is greater than the reference open circuit voltage, the given discharge power is determined as the reserved power to maintain the normal working of the MPPT circuit.

[0127] In some embodiments, the reserved power is 20W. Understandably, the reserved power can be adjusted according to the specific circuit parameters of the DC conversion circuit and the MPPT circuit, and the application does not limit the value of the reserved power.

[0128] Understandably, the function of the first simulated discharge curve is not limited to the above function, and the application does not limit the function of the first simulated discharge curve.

[0129] In summary, in steps S501 to S503, the reference open circuit voltage and the reference maximum power point voltage of the first simulated discharge curve are determined according to the scanning parameters of the MPPT circuit, and then the curve between the zero point and the maximum power point and the curve between the maximum power point and the point where the reference open circuit voltage is located are fitted by function to form the first simulated discharge curve. In this way, the first simulated discharge curve formed by the application does not need to consider the real PV curve parameters of the photovoltaic module, and does not need to worry about the problem of distortion of the initial discharge curve caused by the external environment.

[0130] Understandably, in other embodiments, when each DC conversion circuit calculates a different reference open circuit voltage or pre-stores a corresponding reference open circuit voltage, in order to ensure that the maximum power point voltage of the first simulated discharge curve constructed by each DC conversion circuit connected to the same MPPT circuit is the same, the first simulated discharge curve can be constructed based on a selected value in the reference open circuit voltage of each DC conversion circuit connected to the same MPPT circuit and the target discharge power. The selected value can be the maximum value, the minimum value, the mode, the median, the average or other types of values in all reference open circuit voltages, and the application does not limit this. For example, when controlling the discharge of at least two DC conversion circuits based on the same first simulated discharge curve, the first simulated discharge curve can be constructed based on the maximum value in all reference open circuit voltages and the target discharge power of at least two conversion circuits; when controlling the discharge of the corresponding DC conversion circuit based on the first simulated discharge curve with the same maximum power point voltage constructed by each DC conversion circuit, the corresponding first simulated discharge curve can be established based on the maximum value in all reference open circuit voltages and the corresponding target discharge power of each DC conversion circuit. Further, when there is a DC conversion circuit that does not participate in the discharge among all DC conversion circuits connected to the same MPPT circuit, then based on the above principle, the maximum value in the reference open circuit voltage of all DC conversion circuits participating in the discharge is selected to construct the first simulated discharge curve.

[0131] Since the reference open circuit voltage and the reference maximum power point voltage have a fixed relationship in the first simulated discharge curve, in other embodiments, the first simulated discharge curve can also be constructed based on the corresponding reference maximum power point voltage pre-stored by each DC conversion circuit.

[0132] Thus, when the first analog discharge curve is constructed based on the pre-stored reference open circuit voltage or reference maximum power point voltage of each direct current conversion circuit, the maximum power point voltage of the first analog discharge curve corresponding to each direct current conversion circuit connected to the same MPPT circuit is the same, so as to ensure the discharge efficiency of the direct current conversion circuit.

[0133] In some embodiments, after step S206 is performed, the method further comprises:

[0134] adjusting the reference open circuit voltage and the reference maximum power point voltage of the first analog discharge curve according to a preset adjustment rule.

[0135] The preset adjustment rule comprises: when the reference photovoltaic voltage is greater than a preset voltage threshold and the reference power generation power is less than a preset power threshold, lowering the reference open circuit voltage of the first analog discharge curve according to a first preset step size to left shift the first analog discharge curve, until the reference open circuit voltage reaches a minimum open circuit voltage of the direct current conversion circuit, or the reference open circuit voltage is less than a dynamic voltage value, and stopping left shifting the first analog discharge curve, wherein the dynamic voltage value is dynamically set according to the actual discharge voltage.

[0136] Understandably, the controller of the direct current converter 50 can only obtain the actual photovoltaic voltage and cannot determine whether the maximum power point of the photovoltaic assembly is on the left side or the right side of the current actual discharge voltage, so the controller of the direct current converter 50 cannot actually determine whether the analog discharge curve should be left shifted or right shifted to approach the maximum power point of the PV curve of the at least two photovoltaic assemblies as a whole. However, since the at least two photovoltaic assemblies as a whole are currently in a weak light state, the maximum power point of the photovoltaic assembly in the weak light state is more likely to be on the left side than the maximum power point of the photovoltaic assembly in the strong light state, so in this embodiment, the reference open circuit voltage (and the reference maximum power point voltage) of the first analog discharge curve is actively controlled to be left shifted to increase the opportunity for the reference maximum power point voltage of the first analog discharge curve to overlap with the maximum power point voltage of the PV curve of the at least two photovoltaic assemblies as a whole.

[0137] The first preset step size represents the change amount of the reference open circuit voltage each time the reference open circuit voltage is left shifted. For example, the first preset step size can be 0.5V / S. Lowering the reference open circuit voltage of the first analog discharge curve according to the first preset step size to left shift the first analog discharge curve means that the position of the reference open circuit voltage of the first analog discharge curve is moved 0.5V to the left to obtain a new first analog discharge curve.

[0138] It is appreciated that, since the reference maximum power point voltage is related to the reference open circuit voltage, the reference maximum power point voltage of the first analog discharge curve is also decreased according to the first preset step length while the reference open circuit voltage of the first analog discharge curve is decreased according to the first preset step length, so as to left shift the first analog discharge curve. The present application does not limit the specific value of the first preset step length.

[0139] The minimum open circuit voltage represents the lower limit of the reference open circuit voltage caused by the circuit parameters of the DC conversion circuit. It is appreciated that the DC conversion circuit has a minimum discharge voltage when discharging, that is, the left shift range of the first analog discharge curve is limited from the circuit performance parameters of the DC conversion circuit itself. Therefore, by setting the minimum open circuit voltage, the left shift is stopped when the actual discharge voltage approaches the lower limit of the discharge voltage of the DC conversion circuit. In some embodiments, the minimum open circuit voltage can be determined according to the minimum discharge voltage of the DC conversion circuit in the full power state. For example, the minimum open circuit voltage can be 210V. In this way, by comparing the size relationship between the left shifted reference open circuit voltage and the minimum open circuit voltage, the left shift range of the reference open circuit voltage can be conveniently controlled.

[0140] In other embodiments, the minimum open circuit voltage can be the sum of the minimum discharge voltage of the DC conversion circuit and the second voltage parameter. It is appreciated that, since the difference between the reference maximum power point voltage and the reference open circuit voltage on the first analog discharge curve is the second voltage parameter, setting the minimum open circuit voltage as the sum of the minimum discharge voltage and the second voltage parameter can make the DC conversion circuit work at the maximum power point even at the minimum discharge voltage. In other embodiments, the minimum open circuit voltage can also be set according to different circuit parameters of the DC conversion circuit, and the present application does not limit the specific value of the minimum open circuit voltage.

[0141] The dynamic voltage value is used to represent the dynamic open circuit voltage range obtained according to the actual discharge voltage. It is appreciated that, since the reference maximum power point voltage and the reference open circuit voltage on the first analog discharge curve have a preset distance (for example, the second voltage parameter), if the MPPT circuit performs maximum power tracking, in order to make the DC conversion circuit work at the maximum power point as much as possible, the actual discharge voltage should be closer to the reference maximum power point voltage, that is, the reference maximum power point voltage should be close to the actual discharge voltage and move with the movement of the actual discharge voltage. In this way, according to the relationship between the reference maximum power point voltage and the actual discharge voltage, and the relationship between the reference maximum power point voltage and the reference open circuit voltage, a dynamic open circuit voltage range can be calculated. In this way, when the moved reference open circuit voltage is less than the dynamic voltage value, it means that the current left shift is too much and should be stopped.

[0142] In summary, the embodiment controls the first analog discharge curve to move left by reducing the reference open circuit voltage on the first analog discharge curve, and thereby increases the opportunity for the reference maximum power point voltage of the first analog discharge curve to overlap with the maximum power point voltage of the PV curve when at least two photovoltaic components are in a weak light state, so as to improve the energy utilization rate of the photovoltaic components.

[0143] In some embodiments, the dynamic voltage value is a sum of the actual discharge voltage and the first preset voltage value, and the first analog discharge curve is moved following the actual discharge voltage when the reference photovoltaic voltage is greater than the preset voltage threshold and the reference power generation power is less than the preset power threshold, and the method further comprises:

[0144] When the reduced reference open circuit voltage is less than the dynamic voltage value, the moving left of the first analog discharge curve is stopped.

[0145] The first preset voltage value is used to represent a voltage gap between the actual discharge voltage and the reference open circuit voltage after the moving. In some embodiments, the first preset voltage value is, for example, 95V, and the sum of the actual discharge voltage and the first preset voltage value is calculated as the dynamic voltage value.

[0146] Since the value obtained by subtracting the second voltage parameter from the reference open circuit voltage is used as the reference maximum power point voltage, and assuming that the second voltage parameter is 100V and the first preset voltage value is 95V, the reduced reference open circuit voltage is less than the dynamic voltage value, that is, the difference obtained by subtracting the reference maximum power point voltage of the first analog discharge curve after the moving left from the actual discharge voltage is greater than 5V. Understandably, the value obtained by subtracting the reference maximum power point voltage after the moving left from the actual discharge voltage is greater than 5V, which indicates that the MPPT circuit is tracking to the right. Therefore, at this time, the moving left of the first analog discharge curve should be stopped, and the first analog discharge curve should be moved right according to the actual discharge voltage, so that the direct current conversion circuit can maintain the discharge power more smoothly, so as to reduce the influence of the discharge power of the direct current conversion circuit on the maximum power tracking of the photovoltaic power generation power of the at least two photovoltaic components. The present application does not limit the specific value of the first preset voltage value. In other embodiments, the first preset voltage value can also be other values.

[0147] When the reference photovoltaic voltage is greater than the preset voltage threshold and the reference power generation power is less than the preset power threshold, the first analog discharge curve is moved following the reference photovoltaic voltage and the actual discharge voltage, and the method further comprises: updating the reference open circuit voltage of the first analog discharge curve according to the dynamic voltage value to move the first analog discharge curve to the right.

[0148] In some embodiments, the dynamic voltage value can be used as the updated reference open circuit voltage. In this way, when it is determined that the left-shifted reference open circuit voltage is less than the dynamic voltage value, the dynamic voltage value is directly used as the updated open circuit voltage to increase the reference open circuit voltage of the first simulated discharge curve to right-shift the first simulated discharge curve. In this way, when the photovoltaic power of the at least two photovoltaic components causes the MPPT circuit to right-shift, the first simulated discharge curve can be right-shifted in time, and the maximum power tracking of the MPPT circuit eventually reaches a steady state, thereby maximizing the utilization of the energy of the photovoltaic components.

[0149] In some embodiments, the preset adjustment rule can include: when the reference photovoltaic voltage changes from being greater than the preset voltage threshold to being less than or equal to the preset voltage threshold, updating the reference open circuit voltage of the first simulated discharge curve according to a second preset step to move the first simulated discharge curve until the moved first simulated discharge curve returns to the initial first simulated discharge curve.

[0150] It can be understood that when the reference photovoltaic voltage changes from being greater than the preset voltage threshold to being less than or equal to the preset voltage threshold, the photovoltaic component switches from a weak light state to a no-light state, or the photovoltaic component switches from a strong light state to a no-light state.

[0151] The second preset step represents the amount of change in the reference open circuit voltage each time the first simulated discharge curve is updated. In some embodiments, the second preset step can be 0.1V / S.

[0152] In this embodiment, the moved first simulated discharge curve returns to the initial first simulated discharge curve, that is, the reference open circuit voltage of the moved first simulated discharge curve is equal to the reference open circuit voltage in the initial first simulated discharge curve.

[0153] In this way, updating the reference open circuit voltage of the first simulated discharge curve according to the second preset step to move the first simulated discharge curve until the moved first simulated discharge curve returns to the initial first simulated discharge curve includes:

[0154] When the reference open circuit voltage of the first simulated discharge curve is less than the reference open circuit voltage in the initial first simulated discharge curve, the reference open circuit voltage is increased according to the second preset step to right-shift the first simulated discharge curve until the moved first simulated discharge curve returns to the initial first simulated discharge curve.

[0155] When the reference open circuit voltage of the first simulated discharge curve is greater than the reference open circuit voltage in the initial first simulated discharge curve, the reference open circuit voltage is decreased according to the second preset step to left-shift the first simulated discharge curve until the moved first simulated discharge curve returns to the initial first simulated discharge curve.

[0156] Understandably, in other embodiments, the second preset step size can also be other numerical values, and the application does not limit the specific numerical value of the second preset step size.

[0157] Understandably, the first preset step size and the second preset step size mentioned in the application can be fixed preset values, or can be dynamic values; or one of the first preset step size and the second preset step size can be a preset value, and the other of the first preset step size and the second preset step size can be a dynamic value. In this way, when the first preset step size and / or the second preset step size is a dynamic value, the movement of the reference open-circuit voltage and the reference maximum power point voltage on the first simulated discharge curve can be more accurate and faster.

[0158] In some embodiments, before step S202 is performed, the method further comprises:

[0159] According to the actual photovoltaic voltage of the photovoltaic module corresponding to each direct current conversion circuit and / or the discharge voltage of each direct current conversion circuit, determine the connection relationship between the at least two direct current converters and the MPPT circuit.

[0160] Further, when the embodiment control method of the application is applied Figure 1 , please refer to Figure 6 , according to the actual photovoltaic voltage of the photovoltaic module corresponding to each direct current conversion circuit and / or the discharge voltage of each direct current conversion circuit, determine the connection relationship between the at least two direct current converters and the MPPT circuit, which can include:

[0161] Step S601: Determine whether the first photovoltaic voltage and the second photovoltaic voltage are greater than a preset voltage.

[0162] The first photovoltaic voltage is the photovoltaic voltage of the photovoltaic module (i.e. the first photovoltaic module 10A) corresponding to the first direct current conversion circuit 51A, and the second photovoltaic voltage is the photovoltaic voltage of the photovoltaic module (i.e. the second photovoltaic module 10B) corresponding to the second direct current conversion circuit 51B. The size of the preset voltage can be set according to the actual situation, for example, set to 50V.

[0163] Understandably, when the first photovoltaic voltage and the second photovoltaic voltage are both greater than the preset voltage, it means that the first photovoltaic module 10A and the second photovoltaic module 10B are both under certain light conditions (for example, during the day), and the power generation is large. In this case, the photovoltaic module is usually in a stable operating state, the photovoltaic voltage is stable, and the probability of causing a connection relationship misjudgment is low. Therefore, the first photovoltaic voltage and the second photovoltaic voltage at this time can be used to confirm the connection relationship between the direct current converter and the MPPT circuit.

[0164] When both the first photovoltaic voltage and the second photovoltaic voltage are greater than 0 and less than or equal to the preset voltage, it indicates that both the first photovoltaic component 10A and the second photovoltaic component 10B are in the light condition, but the power generation is small. In this case, the photovoltaic component can not be in a stable operation state, and the photovoltaic voltage is not stable, which can cause misjudgment of the connection relationship. Therefore, the power generation power at this time cannot be used to confirm the connection relationship between the direct-current converter 50 and the MPPT circuit.

[0165] Step S602: If both the first photovoltaic voltage and the second photovoltaic voltage are greater than the preset voltage, calculate the first voltage difference between the first photovoltaic voltage and the second photovoltaic voltage.

[0166] The first voltage difference is the absolute value of the difference between the first photovoltaic voltage and the second photovoltaic voltage.

[0167] Step S603: If the first voltage difference is greater than the first preset voltage difference, it is determined that the first direct-current conversion circuit and the second direct-current conversion circuit are respectively connected to different maximum power point tracking circuits one by one.

[0168] The size of the first preset voltage difference can be set according to the actual situation, for example, the first preset voltage difference can be an empirical value of 50V obtained by experimental test.

[0169] Understandably, when the first voltage difference is greater than the first preset voltage difference, it indicates that the first photovoltaic voltage of the first photovoltaic component 10A and the second photovoltaic voltage of the second photovoltaic component 10B are quite different, and do not have the characteristic that the voltages of the parallel branches are equal. Therefore, at this time, it can be determined that the first photovoltaic component 10A and the second photovoltaic component 10B are respectively connected to different maximum power point tracking circuits one by one. Since the first photovoltaic component 10A and the first direct-current conversion circuit 51A are connected to the same direct-current bus, and the second photovoltaic component 10B and the second direct-current conversion circuit 51B are also connected to the same direct-current bus, at this time, it can be determined that the first direct-current conversion circuit 51A and the second direct-current conversion circuit 51B are respectively connected to different maximum power point tracking circuits one by one.

[0170] As can be seen, in the case where both the first photovoltaic voltage and the second photovoltaic voltage are greater than the preset voltage, the first photovoltaic voltage and the second photovoltaic voltage can be used to self-check the connection relationship that the first direct-current conversion circuit 51A and the second direct-current conversion circuit 51B are respectively connected to different MPPT circuits.

[0171] Of course, in the above process, it is also possible that both the first photovoltaic voltage and the second photovoltaic voltage are 0, that is, neither the first photovoltaic module 10A nor the second photovoltaic module 10B generates electricity, in which case, the connection relationship between the DC converter and the MPPT circuit cannot be determined. Alternatively, it is also possible that the first voltage difference is less than or equal to the first preset voltage difference, that is, the voltage difference between the first photovoltaic module 10A and the second photovoltaic module 10B is small, but this is likely to be caused by different light intensities, shielding degrees, temperatures, and other factors of different photovoltaic modules. Therefore, in this case, it is also difficult to determine the connection relationship between the DC converter and the MPPT circuit.

[0172] Therefore, for these two cases, please continue to refer to Figure 3 , according to the actual photovoltaic voltage of the photovoltaic module corresponding to each DC conversion circuit and / or the discharge voltage of each DC conversion circuit, the connection relationship between the at least two DC converters and the MPPT circuit can also include:

[0173] Step S604: If any photovoltaic voltage is less than or equal to the preset voltage, or the first voltage difference is less than or equal to the first preset voltage difference, then when all photovoltaic voltages are 0, control one of the DC conversion circuits to discharge.

[0174] That is, when the first photovoltaic voltage is less than or equal to the preset voltage, or the second photovoltaic voltage is less than or equal to the preset voltage, or the first voltage difference between the first photovoltaic voltage and the second photovoltaic voltage is less than or equal to the first preset voltage difference, wait for the first photovoltaic module 10A and the second photovoltaic module 10B to stop generating electricity, and then control the first DC conversion circuit 51A to output the voltage to the corresponding first DC input port a, or control the second DC conversion circuit 51B to output the voltage to the corresponding second DC input port b.

[0175] Step S605: Determine the connection relationship between the DC converter and the maximum power point tracking circuit according to the output voltage corresponding to all DC conversion circuits.

[0176] As can be seen, in the case where the first photovoltaic voltage is less than or equal to the preset voltage, or the second photovoltaic voltage is less than or equal to the preset voltage, or the first voltage difference between the first photovoltaic voltage and the second photovoltaic voltage is less than or equal to the first preset voltage difference, in order to avoid misjudgment of the connection relationship caused by the first photovoltaic voltage and the second photovoltaic voltage, another self-checking method will be used to realize self-checking of the connection relationship between the first DC conversion circuit 51A and the second DC conversion circuit 51B and the MPPT circuit by using the output voltage corresponding to the DC conversion circuit, to ensure the accuracy of the self-checking.

[0177] It can be understood that if multiple DC conversion circuits are connected with the same MPPT circuit, as long as any DC conversion circuit outputs a certain voltage to the DC input port, the same voltage can be detected on the DC input port corresponding to the other DC conversion circuit. Conversely, if each DC conversion circuit is connected with a different MPPT circuit one by one, the output voltage of each DC conversion circuit when discharging will not affect each other.

[0178] In the above step S604, in order to avoid waste of battery pack electric energy due to excessive discharge of the DC conversion circuit, after discharging one of the DC conversion circuits, the control method further comprises:

[0179] When the output voltage corresponding to the discharging DC conversion circuit reaches the preset discharging voltage, the output voltage corresponding to the non-discharging DC conversion circuit is obtained.

[0180] That is, if the controller controls the first DC conversion circuit 51A to discharge, when the output voltage of the first DC conversion circuit 51A output to the first DC input port a reaches the preset discharging voltage, the output voltage of the second DC conversion circuit 51B output to the second DC input port b is obtained. Further, the controller determines the connection relationship between the DC converter and the maximum power point tracking circuit according to the output voltage corresponding to the first DC conversion circuit 51A (i.e. the preset discharging voltage) and the output voltage corresponding to the second DC conversion circuit 51B.

[0181] If the controller controls the second DC conversion circuit 51B to discharge, when the output voltage of the second DC conversion circuit 51B output to the second DC input port b reaches the preset discharging voltage, the output voltage of the first DC conversion circuit 51A output to the first DC input port a is obtained. Further, the controller determines the connection relationship between the DC converter and the maximum power point tracking circuit according to the output voltage corresponding to the first DC conversion circuit 51A and the output voltage corresponding to the second DC conversion circuit 51B (i.e. the preset discharging voltage). The preset discharging voltage can be set according to the actual situation (such as the working voltage range of the MPPT circuit), which is not limited here.

[0182] Specifically, please continue to refer to Figure 7 The process of determining the connection relationship between the DC converter and the maximum power point tracking circuit according to the output voltages corresponding to all DC converters in step S605 can include:

[0183] Step S701: calculating a second voltage difference between the first output voltage and the second output voltage.

[0184] The first output voltage is an output voltage corresponding to the first DC conversion circuit 51A, and the second output voltage is an output voltage corresponding to the second DC conversion circuit 51B. The second voltage difference is an absolute value of a result of subtraction of the first output voltage from the second output voltage.

[0185] Step S702: Determine whether the second voltage difference is less than a second preset voltage difference.

[0186] The second preset voltage difference can be set according to actual conditions, for example, 10V.

[0187] Step S703: If the second voltage difference is greater than or equal to the second preset voltage difference, determine that the first DC conversion circuit and the second DC conversion circuit are respectively connected in one-to-one correspondence with different maximum power point tracking circuits.

[0188] It can be understood that when the second voltage difference is greater than or equal to the second preset voltage difference, it indicates that the first output voltage corresponding to the first DC conversion circuit 51A and the second output voltage corresponding to the second DC conversion circuit 51B are quite different, and do not have the characteristic that the voltages of the parallel branches are equal. Therefore, at this time, it can be determined that the first DC conversion circuit and the second DC conversion circuit are respectively connected in one-to-one correspondence with different maximum power point tracking circuits.

[0189] Step S704: If the second voltage difference is less than the second preset voltage difference, determine that the first DC conversion circuit and the second DC conversion circuit are connected in parallel to the same maximum power point tracking circuit.

[0190] It can be understood that when the second voltage difference is less than the second preset voltage difference, it indicates that the first output voltage corresponding to the first DC conversion circuit 51A and the second output voltage corresponding to the second DC conversion circuit 51B are quite small, and can be considered as equal, that is, having the characteristic that the voltages of the parallel branches are equal. Therefore, at this time, it can be determined that the first DC conversion circuit 51A and the second DC conversion circuit 51B are connected in parallel to the same maximum power point tracking circuit.

[0191] As can be seen, in the case that the first photovoltaic voltage is less than or equal to the preset voltage, or the second photovoltaic voltage is less than or equal to the preset voltage, or the first voltage difference between the first photovoltaic voltage and the second photovoltaic voltage is less than or equal to the first preset voltage difference, the output voltage corresponding to the DC conversion circuit can be used to self-check the connection relationship that the first DC conversion circuit 51A and the second DC conversion circuit 51B are respectively connected with different MPPT circuits, and also can be used to self-check the connection relationship that the first DC conversion circuit 51A and the second DC conversion circuit 51B are connected in parallel to the same MPPT circuit. Therefore, the connection relationship obtained by the self-checking method can be more accurate.

[0192] Moreover, in general, the control method of the embodiments of the present application can realize self-checking of the connection relationship between the DC converter 50 and the MPPT circuit, regardless of whether the photovoltaic assembly outputs or not, and regardless of how much the photovoltaic assembly outputs.

[0193] It can be understood that, in an embodiment, the steps of judging the sizes of the first photovoltaic voltage and the second photovoltaic voltage can be omitted, and the first output voltage and the second output voltage can be directly obtained, and the connection relationship between the DC converter and the MPPT circuit can be determined according to the first output voltage and the second output voltage.

[0194] Please refer to Figure 8 In some embodiments, the step S202 comprises the following sub-steps:

[0195] Step S801: Taking the maximum value of the actual photovoltaic voltages as the reference photovoltaic voltage.

[0196] Please refer to Figure 1 As described above, based on Figure 1 The circuit connection relationship shown in the figure, when the first actual photovoltaic voltage of the first photovoltaic assembly 10A and the second actual photovoltaic voltage of the second photovoltaic assembly 10B are not equal, the photovoltaic assembly corresponding to the lower voltage of the first actual photovoltaic voltage and the second actual photovoltaic voltage cannot be discharged. At this time, taking the maximum value of the actual photovoltaic voltages as the reference photovoltaic voltage can ensure that the photovoltaic assembly with higher actual photovoltaic voltage participates in the discharge operation, which is more conducive to improving the energy utilization efficiency of the photovoltaic assembly in the photovoltaic storage system, and can also exclude the photovoltaic assembly with lower actual photovoltaic voltage, preventing misjudgment of the discharge mode.

[0197] Step S802: Calculate the average value of each photovoltaic power generation power to obtain the reference power generation power.

[0198] It can be understood that, since the photovoltaic power generation power of at least two photovoltaic assemblies ultimately flows to the inverter 20, and the discharge mode of at least two DC conversion circuits is related to the photovoltaic power generation power of at least two photovoltaic assemblies, when at least two DC conversion circuits are connected to the same MPPT circuit, the reference power generation power obtained by calculating the average value of each photovoltaic power generation power is more conducive to keeping the discharge mode of at least two DC conversion circuits consistent.

[0199] For example, when the actual photovoltaic voltage V1 of the first photovoltaic component is 400 V, the corresponding photovoltaic power P1 is 1000 W, when the actual photovoltaic voltage V2 of the second photovoltaic component is 400 V, the corresponding photovoltaic power P2 is 50 W, and the discharge mode of the DC / DC converter DCDC1 corresponding to the first photovoltaic component is in the constant power discharge mode and the discharge mode of the DC / DC converter DCDC2 corresponding to the second photovoltaic component is in the analog discharge mode according to the conventional discharge mode, at this time, the analog discharge curve of the DC / DC converter DCDC2 will move to the leftmost end. Once the analog discharge curve of the DC / DC converter DCDC2 starts to move, the maximum power point voltage of the DC / DC converter DCDC2 will deviate from 400 V, at this time, the maximum power point of the first analog discharge curve obtained after superimposing the first analog discharge curve and the PV curve of the two photovoltaic components will also deviate from 400 V, causing the first photovoltaic component to be unable to discharge at full power, and the DC / DC converter DCDC2 will not discharge completely, and the influence is the greatest when the analog discharge curve of the DC / DC converter DCDC2 moves to the leftmost end. Therefore, after improvement according to the scheme of the present application, the reference photovoltaic voltage V = max (V1, V2) = 400 V and the reference power P = (P1+P2) / 2 = 525 W can be obtained, and the DC / DC converter DCDC1 and the DC / DC converter DCDC2 can be in the constant power mode, that is, the maximum power point voltage of the superimposed first analog discharge curve is still 400 V, which does not affect the discharge power of the two photovoltaic components.

[0200] Please refer to Figure 9 , Figure 9 Another scenario of the discharge control method of the DC / DC converter provided by the present application is shown. Figure 9 The scenario shown is basically the same as the scenario shown in Figure 1 The difference between the scenario shown and the scenario shown in Figure 9 The scenario shown includes a third photovoltaic component 10C, the inverter 20 further includes a second MPPT circuit 21B and a third DC input port d, and the DC / DC converter 50 further includes a third DC / DC converter 51C. The first end of the third DC / DC converter 51C is connected to the same DC bus (DC_BUS3+, DC_BUS3-) as the corresponding third photovoltaic component 10C and the third DC input port d of the inverter 20. Based on Figure 9 Based on the scenario shown, the discharge control method of the DC / DC converter provided by the present application further includes:

[0201] When the MPPT circuit is connected to only a DC / DC converter and a photovoltaic component, the actual photovoltaic voltage of the connected photovoltaic component and the actual discharge voltage of the DC / DC converter are obtained, the second analog discharge curve is moved according to the actual discharge voltage, and the connected DC / DC converter is discharged according to the moved second analog discharge curve.

[0202] The second simulation discharge curve is constructed based on the maximum scanning voltage and the minimum scanning voltage of the MPPT circuit connected to only the DC conversion circuit and the photovoltaic module, and the maximum power point power of the second simulation discharge curve is the target discharge power of the MPPT circuit connected to only the DC conversion circuit and the photovoltaic module.

[0203] It can be understood that the second simulation discharge curve is moved according to the actual discharge voltage, and the process of controlling the connected DC conversion circuit to discharge according to the moved second simulation discharge curve is substantially the same as the process of moving the first simulation discharge curve according to the reference photovoltaic voltage in the embodiment of the present application, and controlling at least two DC conversion circuits to discharge according to the moved first simulation discharge curve, which will not be described here.

[0204] Please refer to Figure 10 , Figure 10 Another scenario diagram of the discharge control method of the DC converter provided in the present application is shown. Figure 10 The scenario shown is substantially the same as the scenario shown in Figure 1 The difference between the two scenarios is that Figure 10 The first DC conversion circuit 51A in is connected to the first battery pack 60A, and the second DC conversion circuit 51B is connected to the second battery pack 60B. Wherein, the use state of each battery pack includes a disabled state and an enabled state. The disabled state is used to indicate that the battery pack is currently malfunctioning or in any other state that is not suitable for operation. The enabled state is used to indicate that the battery pack is currently in a usable state.

[0205] In some embodiments, based on Figure 10 The scenario shown, step S202 further includes:

[0206] Controlling the photovoltaic module corresponding to the battery pack in the disabled state to stop working.

[0207] Taking the maximum value of the actual photovoltaic voltage of the photovoltaic module corresponding to the battery pack in the enabled state as the reference photovoltaic voltage, and calculating the average value of the photovoltaic power of each photovoltaic module corresponding to the battery pack in the enabled state to obtain the reference power generation power.

[0208] Correspondingly, at least two DC conversion circuits in step S205 and step S206 are DC conversion circuits corresponding to the battery pack in the enabled state.

[0209] In this way, by performing the steps provided in the embodiment, the battery pack in the disabled state can be prevented from interfering with the work of other battery packs.

[0210] In some embodiments, when the at least two DC conversion circuits include a first DC conversion circuit and a second DC conversion circuit, the method further includes:

[0211] When the first photovoltaic voltage is greater than the second photovoltaic voltage, and the first battery pack and the second battery pack are both in the disabled state, the MPPT circuit is controlled to perform maximum power tracking according to the first photovoltaic voltage, wherein the first photovoltaic voltage is a photovoltaic voltage of a photovoltaic module corresponding to the first direct-current conversion circuit, the second photovoltaic voltage is a photovoltaic voltage of a photovoltaic module corresponding to the second direct-current conversion circuit, the first battery pack is a battery pack corresponding to the first direct-current conversion circuit, and the second battery pack is a battery pack corresponding to the second direct-current conversion circuit.

[0212] In this way, by performing the method provided in the embodiment, the energy utilization efficiency of the photovoltaic module can be improved.

[0213] Referring to Figure 11 The application further provides a power conversion device 100, comprising a controller 70 and a direct-current converter 50. The direct-current converter 50 comprises at least two direct-current conversion circuits, a first end of each direct-current conversion circuit is used to be connected to the same direct-current bus with a corresponding photovoltaic module and a direct-current end of an inverter, a second end of each direct-current conversion circuit is used to be connected to a battery pack 60, and the direct-current end of the inverter 20 is used to be connected to an MPPT circuit. The controller 70 is used to perform the discharge control method of the direct-current converter according to any one of the above.

[0214] Referring to Figure 12 The application further provides an energy storage device 200, comprising a battery pack 60, a controller 70 and a direct-current converter 50. The direct-current converter 50 comprises at least two direct-current conversion circuits, a first end of each direct-current conversion circuit is used to be connected to the same direct-current bus with a corresponding photovoltaic module and a direct-current end of an inverter 20, a second end of each direct-current conversion circuit is used to be connected to the battery pack 60, and the direct-current end of the inverter 20 is used to be connected to an MPPT circuit. The controller 70 is used to perform the discharge control method of the direct-current converter according to any one of the above.

[0215] Referring to Figure 13 The application further provides an electronic device 300, comprising a processor 310 and a memory 320. The memory 320 is used to store programs, instructions or codes for performing the discharge control method of the direct-current converter. The processor 310 is used to execute the programs, instructions or codes stored in the memory 320. The programs, instructions or codes stored in the memory 320 can execute part or all of the steps of the discharge control method of the direct-current converter in any one of the above embodiments.

[0216] The application further provides a control device 400 applied to the direct-current converter 50 or an electronic device integrated with the direct-current converter 50. Figure 14 The structural block diagram of the control device 400 provided in the embodiment of the application is schematically shown. As Figure 14 shown, the control device 400 comprises:

[0217] The first obtaining module 410 is configured to obtain an actual photovoltaic voltage and a photovoltaic power generation power of the photovoltaic module corresponding to each direct-current conversion circuit.

[0218] The first determining module 420 is configured to determine a reference photovoltaic voltage based on the actual photovoltaic voltages when the at least two direct-current conversion circuits are connected to the same MPPT circuit, and determine a reference power generation power based on the photovoltaic power generation powers.

[0219] The second obtaining module 430 is configured to obtain a target discharge power of the at least two direct-current conversion circuits.

[0220] The second determining module 440 is configured to determine a discharge mode of the direct-current conversion circuit based on the reference photovoltaic voltage and the reference power generation power.

[0221] The constructing module 450 is configured to construct a first simulation discharge curve based on the target discharge power of the at least two direct-current conversion circuits when the discharge mode is a simulation discharge mode.

[0222] The control module 460 is configured to control the at least two direct-current conversion circuits to discharge based on the first simulation discharge curve.

[0223] The specific details of the control device 400 provided in the embodiments of the present application for implementing the discharge control method of the direct-current converter have been described in detail in the embodiments of the discharge control method of the direct-current converter, and will not be described here again.

[0224] The present application also provides a computer readable medium having a computer program stored thereon, which, when executed by a processor, implements the discharge control method of the direct-current converter in the above technical solutions. The computer readable medium can adopt a portable compact disc read-only memory (CD-ROM) and include program codes, and can run on a terminal device, such as a personal computer. However, the program product of the present application is not limited to this, and in this document, the readable storage medium can be any tangible medium containing or storing a program, which can be used by or in conjunction with an instruction execution system, device or apparatus.

[0225] The program product described above can adopt any combination of one or more readable media. The readable medium can be a readable signal medium or a readable storage medium. The readable storage medium may, for example, but is not limited to, an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, device or apparatus, or any combination thereof. More specific examples (non-exhaustive list) of readable storage media include an electrical connection having one or more wires, a portable disc, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination thereof.

[0226] The computer readable signal medium can include a data signal propagated in baseband or propagated as a carrier wave in a propagated data signal, in which the readable program code is embodied. Such propagated data signal can take various forms, including but not limited to electro-magnetic, optical or any suitable combination thereof. The readable signal medium can also be any readable medium other than the readable storage medium that can send, propagate or transfer the program for use by or in connection with an instruction execution system, apparatus or device.

[0227] The program code contained on the readable medium can be transmitted using any suitable medium, including but not limited to wireless, wired, optical fiber, RF, etc., or any suitable combination thereof.

[0228] The program code for carrying out operations of the present application can be written in any combination of one or more programming languages, including an object oriented programming language such as Java, C++, etc., and conventional procedural programming languages, such as the "C" programming language or similar programming languages. The program code can execute entirely on the user's computing device, partly on the user's device, as a stand-alone software package, partly on the user's computing device and partly on a remote computing device or entirely on the remote computing device or server. In the latter scenario, the remote computing device can be connected to the user's computing device through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection can be made to an external computing device, such as through the Internet using an Internet Service Provider.

[0229] In addition, the above-described flowcharts are merely schematic illustrations of the processes included in the method according to the exemplary embodiments of the present application, and are not intended to be limiting. It is readily understood that the processes shown in the above-described flowcharts do not indicate or limit the time sequence of the processes. In addition, it is readily understood that the processes can be executed synchronously or asynchronously, for example, in a plurality of modules.

[0230] The above merely provides the specific implementation of the present application, but the protection scope of the present application is not limited to this. Any person skilled in the art can easily think of various equivalent modifications or replacements within the technical scope disclosed by the present application, and these modifications or replacements should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A discharge control method of a DC converter, characterized by, The direct current converter comprises at least two direct current conversion circuits, a first end of each of the direct current conversion circuits is used to be connected to a same direct current bus with a corresponding photovoltaic module and a direct current end of an inverter, a second end of each of the direct current conversion circuits is used to be connected to a corresponding battery pack, and the direct current end of the inverter is used to be connected to an MPPT circuit; the method comprises: acquiring actual photovoltaic voltages and photovoltaic power generation powers of the corresponding photovoltaic modules of each of the direct current conversion circuits; when the at least two direct current conversion circuits are connected to the same MPPT circuit, determining a reference photovoltaic voltage based on the actual photovoltaic voltages and determining a reference power generation power based on the photovoltaic power generation powers; acquiring target discharge powers of the at least two direct current conversion circuits; determining a discharge mode of the direct current conversion circuit based on the reference photovoltaic voltage and the reference power generation power; when the discharge mode is an analog discharge mode, constructing a first analog discharge curve based on the target discharge powers of the at least two direct current conversion circuits; controlling the at least two direct current conversion circuits to discharge based on the first analog discharge curve.

2. The method of claim 1, wherein, The controlling the at least two direct current conversion circuits to discharge based on the first analog discharge curve comprises: acquiring actual discharge voltages of the at least two direct current conversion circuits; determining a given discharge power based on the actual discharge voltages and the first analog discharge curve; controlling the at least two direct current conversion circuits to discharge according to the given discharge power.

3. The method of claim 1, wherein, The determining the discharge mode of the direct current conversion circuit based on the reference photovoltaic voltage and the reference power generation power comprises: when the reference photovoltaic voltage is less than a preset voltage threshold or the reference power generation power is less than a preset power threshold, determining that the discharge mode is the analog discharge mode.

4. The method of claim 3, wherein, The determining the discharge mode of the direct current conversion circuit based on the reference photovoltaic voltage and the reference power generation power further comprises: when the reference photovoltaic voltage is greater than or equal to the preset voltage threshold and the reference power generation power is greater than or equal to a preset power threshold, determining that the discharge mode is a constant-power discharge mode; correspondingly, the method further comprises: when the discharge mode is the constant-power discharge mode, determining that the target discharge power is a given discharge power; controlling the at least two direct current conversion circuits to discharge according to the given discharge power.

5. The method of claim 1, wherein, The constructing the first analog discharge curve based on the target discharge powers of the at least two direct current conversion circuits when the discharge mode is the analog discharge mode comprises: when the discharge mode is the analog discharge mode, acquiring a working voltage range of the MPPT circuit; determining a reference open-circuit voltage and a reference maximum power point voltage based on the working voltage range; constructing the first analog discharge curve based on the reference open-circuit voltage, the reference maximum power point voltage and the target discharge power.

6. The method of claim 1, wherein, The method further comprises: adjusting the reference open-circuit voltage and the reference maximum power point voltage of the first analog discharge curve according to a preset adjustment rule.

7. The method according to any one of claims 1 to 5, characterized in that, The method further comprises: According to the actual photovoltaic voltage of each photovoltaic module corresponding to the direct current conversion circuit and / or the discharge voltage of each direct current conversion circuit, a connection relationship between the at least two direct current converters and the MPPT circuit is determined.

8. The method of claim 1, wherein, Based on the actual photovoltaic voltages, a reference photovoltaic voltage is determined, and based on the photovoltaic power, a reference power generation power is determined, including: Taking the maximum value in the actual photovoltaic voltages as the reference photovoltaic voltage; Calculating the average value of the photovoltaic power generation powers to obtain the reference power generation power.

9. A power conversion device, characterized by, The power conversion device includes a controller and a direct current converter, the direct current converter includes at least two direct current conversion circuits, a first end of each direct current conversion circuit is used to be connected to the same direct current bus with a corresponding photovoltaic module and a direct current end of an inverter, a second end of each direct current conversion circuit is used to connect a battery pack, and the direct current end of the inverter is used to connect an MPPT circuit; the controller is used to execute the discharge control method of the direct current converter according to any one of claims 1 to 8.

10. An energy storage device, characterized by, The energy storage device includes a battery pack, a controller and a direct current converter, the direct current converter includes at least two direct current conversion circuits, a first end of each direct current conversion circuit is used to be connected to the same direct current bus with a corresponding photovoltaic module and a direct current end of an inverter, a second end of each direct current conversion circuit is used to connect a battery pack, and the direct current end of the inverter is used to connect an MPPT circuit; the controller is used to execute the discharge control method of the direct current converter according to any one of claims 1 to 8.

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