Discharge control method of direct current converter, power conversion equipment and energy storage equipment

Abstract

The invention provides a discharge control method of a direct current converter, power conversion equipment and energy storage equipment. The method comprises the following steps: acquiring actual photovoltaic voltage and photovoltaic power generation power of a photovoltaic module corresponding to each DC conversion circuit; when the at least two DC conversion circuits are connected to the same MPPT circuit, determining a reference photovoltaic voltage based on each actual photovoltaic voltage, and determining a reference generated power based on each photovoltaic generated power; obtaining target discharge power of the at least two DC conversion circuits; determining a discharge mode of the DC conversion circuit based on the reference photovoltaic voltage and the reference generated power; when the discharge mode is a simulated discharge mode, constructing a first simulated discharge curve based on the target discharge power of the at least two DC conversion circuits; and controlling the at least two DC conversion circuits to discharge based on the first simulated discharge curve.

Description

Technical Field

[0001] The present application relates to the field of clean energy technology, and in particular to a discharge control method of a DC converter, a power conversion device, and an energy storage device. Background Art

[0002] In a photovoltaic storage system coupled with an energy storage device on the DC side, when the energy storage device is discharged, the discharge power of the energy storage device and the power generation power of the photovoltaic module are output to the DC end of the inverter as the 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 module can operate at the maximum power point. In order to make the photovoltaic module operate at the maximum power point, one of the discharge methods of the energy storage device is to construct a simulated power-voltage (PV) curve to discharge in the form of a PV curve that simulates the photovoltaic module. The simulated PV curve needs to be matched with the actual PV curve of the photovoltaic module so that the energy utilization of the photovoltaic module 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 module.

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

[0004] However, when two or more DC busbars are connected to the same MPPT circuit, if the maximum power point voltages of the simulated PV curves corresponding to the DC conversion circuits on the corresponding DC busbars are inconsistent, the MPPT circuit cannot enable each DC conversion circuit to operate at the maximum power point of the corresponding simulated PV curve at the same time, which will result in low discharge efficiency of the energy storage device, that is, the actual discharge power of each energy storage device cannot reach the corresponding target discharge power at the same time, thereby affecting the working efficiency of the photovoltaic storage system. Summary of the invention

[0005] In view of this, the present application provides a discharge control method of a DC converter, a power conversion device and an energy storage device to ensure the discharge efficiency of at least two DC conversion circuits.

[0006] The first aspect of the present application provides a discharge control method for a DC converter, wherein the DC converter includes at least two DC conversion circuits, wherein the first end of each DC conversion circuit is used to connect to the same DC bus with the corresponding photovoltaic component and the DC end of the inverter, the second end of each DC conversion circuit is used to connect to the corresponding battery pack, and the DC end of the inverter is used to connect to the MPPT circuit. The method includes: obtaining the actual photovoltaic voltage and photovoltaic power generation power of the photovoltaic component corresponding to each DC conversion circuit; when at least two DC conversion circuits are connected to the same MPPT circuit, determining the reference photovoltaic voltage based on each actual photovoltaic voltage, and determining the reference power generation power based on each photovoltaic power generation power; obtaining the target discharge power of at least two DC conversion circuits; determining the discharge mode of the DC conversion circuit based on the reference photovoltaic voltage and the reference power generation power; when the discharge mode is a simulated discharge mode, constructing a first simulated discharge curve based on the target discharge power of at least two DC conversion circuits; and controlling the discharge of at least two DC conversion circuits based on the first simulated discharge curve.

[0007] A second aspect of the present application provides a power conversion device, which includes a controller and a DC converter. The DC converter includes at least two DC conversion circuits. The first end of each DC conversion circuit is used to connect to the same DC bus with the DC end of the corresponding photovoltaic component and inverter, and the second end of each DC conversion circuit is used to connect to a battery pack, and the DC end of the inverter is used to connect to the MPPT circuit; the controller is used to execute the discharge control method of the DC converter as described in any one of the above items.

[0008] The third aspect of the present application provides an energy storage device, characterized in that the energy storage device includes a battery pack, a controller and a DC converter, the DC converter includes at least two DC conversion circuits, the first end of each DC conversion circuit is used to connect to the same DC bus with the corresponding photovoltaic component and the DC end of the inverter, the second end of each DC conversion circuit is used to connect the battery pack, and the DC end of the inverter is used to connect the MPPT circuit; the controller is used to execute the discharge control method of the DC converter as described in any one of the above items.

[0009] The discharge control method of the DC converter provided in the present application first obtains the actual photovoltaic voltage and photovoltaic power generation of the photovoltaic assembly corresponding to each DC conversion circuit. When at least two DC conversion circuits are connected to the same MPPT circuit, the reference photovoltaic voltage is determined based on each actual photovoltaic voltage, and the reference power generation is determined based on each photovoltaic power generation. The target discharge power of at least two DC conversion circuits is obtained, thereby determining the discharge mode of the DC conversion circuit based on the reference photovoltaic voltage and the reference power generation. In this way, the method preliminarily determines the same discharge mode for at least two DC conversion circuits connected to the same MPPT circuit. Furthermore, when the discharge mode is a simulated discharge mode, the method constructs a corresponding first simulated discharge curve based on the target discharge power of at least two DC conversion circuits, and controls the discharge of the corresponding at least two DC conversion circuits based on the first simulated discharge curve, so as to control the discharge of the corresponding DC conversion circuit according to the first simulated discharge curve. In this way, at least two DC conversion circuits can be discharged based on the same first simulated discharge curve.

[0010] Compared with the solution in the related art in which the MPPT circuit cannot make the DC conversion circuits of each energy storage device work at the maximum power point of the corresponding simulated PV curve at the same time, the discharge control method provided in the present application can make the at least two DC conversion circuits work at the maximum power point of the first simulated discharge curve at the same time when the MPPT circuit controls the discharge voltage of the at least two DC conversion circuits to be the maximum power point voltage of the first simulated discharge curve, thereby ensuring the discharge efficiency of the at least two DC conversion circuits. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] In order to more clearly illustrate the technical solution of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present application and should not be regarded as limiting the scope of protection of the present application. In each of the drawings, similar components are numbered similarly.

[0012] Figure 1 A schematic diagram of an application scenario of a discharge control method for a DC converter provided in an embodiment of the present application.

[0013] Figure 2 A schematic flow chart of a discharge control method for a DC converter provided in one embodiment of the present application.

[0014] Figure 3 A schematic diagram of the sub-step flow chart of step S206 provided in an embodiment of the present application.

[0015] Figure 4 A schematic diagram of the sub-step flow of step S204 provided in an embodiment of the present application.

[0016] Figure 5 A schematic diagram of the sub-step flow chart of step S205 provided in an embodiment of the present application.

[0017] Figure 6 A schematic diagram of a sub-step flow chart for determining a connection relationship between at least two DC converters and an MPPT circuit provided in an embodiment of the present application.

[0018] Figure 7 for Figure 6 Schematic diagram of the sub-step flow chart of step S605.

[0019] Figure 8 A schematic diagram of the sub-step flow of step S202 provided in an embodiment of the present application.

[0020] Fig. 9 A schematic diagram of another application scenario of the discharge control method of a DC converter provided in an embodiment of the present application.

[0021] Fig.10 A schematic diagram of another application scenario of the discharge control method of a DC converter provided in an embodiment of the present application.

[0022] Fig.11 A functional block diagram of a power conversion device provided in one embodiment of the present application.

[0023] Fig.12 A functional block diagram of an energy storage device provided in one embodiment of the present application.

[0024] Fig.13 A functional block diagram of an electronic device provided in one embodiment of the present application.

[0025] Fig.14 A functional block diagram of a control device provided in one embodiment of the present application. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present application will be described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments.

[0027] It should be noted that when a component is considered to be "connected" to another component, it may be directly connected to the other component or there may be a central component at the same time. When a component is considered to be "located on" another component, it may be directly located on the other component or there may be a central component at the same time. The terms "top", "bottom", "upper", "lower", "left", "right", "front", "back", and similar expressions used herein are for illustrative purposes only.

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0029] Some embodiments will be described below in conjunction with the accompanying drawings. In the absence of conflict, the following embodiments and features in the embodiments may be combined with each other.

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

[0031] Specifically, the inverter 20 includes a first maximum power point tracking (MPPT) circuit 21A and an inverter circuit 22. For easy wiring, the inverter 20 is also provided with a DC input port (such as a first DC input port a and a second DC input port b) and an AC output port (corresponding to Figure 1 The AC output port c in the embodiment of the present application does not limit the specific topology of the first MPPT circuit 21A and the inverter circuit 22. The first MPPT circuit 21A may be, for example, a boost circuit, and the inverter circuit 22 may be, for example, a full-bridge inverter circuit or a half-bridge inverter circuit. It is understandable that in another embodiment, the first MPPT circuit 21A may also be independent of the inverter 20.

[0032] The DC converter 50 includes at least two DC conversion circuits, for example, corresponding to Figure 1 The first DC conversion circuit 51A and the second DC conversion circuit 51B in the embodiment of the present application do not impose any limitation on the circuit structure of the DC conversion circuit, and the DC conversion circuit may include any boost circuit, buck circuit and / or buck-boost circuit. As a further example, the DC conversion circuit may adopt a dual active full bridge (DAB) conversion circuit.

[0033] Each photovoltaic assembly includes a photovoltaic panel, or includes multiple photovoltaic panels connected in series, in parallel, or in series-parallel, which is not limited here. Under certain environmental factors such as temperature and light intensity, the photovoltaic assembly can realize photovoltaic power generation and generate power. The power grid 40 can be, for example, a municipal power grid, other local power grids or a microgrid. The load 30 can be, for example, various types of AC loads in a home. The battery pack 60 includes a battery cell (not shown in the figure) for storing and releasing electrical energy, and a power management system (Battery Management System, BMS, not shown in the figure) for managing the charge and discharge status of the battery cell.

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

[0035] Based on such a design, each photovoltaic module can output photovoltaic power to the corresponding DC bus. Among them, the first MPPT circuit 21A on the DC bus can be used to track the maximum power point of the photovoltaic module, so that the photovoltaic module outputs the maximum power to the DC bus. When the photovoltaic power of the photovoltaic module is greater than the required power of the load 30, the power of the DC bus can be partially transmitted to the inverter circuit 22, and the inverter circuit 22 inverts the power and supplies power to the load 30. Another part of the power of the DC bus can be converted by the first DC conversion circuit 51A or the second DC conversion circuit 51B to charge the battery pack 60. On the contrary, when the power generation power of the photovoltaic module 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 DC conversion circuit 51A or the second DC conversion circuit 51B and then transmitted to the DC bus to supplement the needs of the load 30.

[0036] In this way, the photovoltaic components, inverter 20, DC converter 50 and battery pack 60 can together constitute a photovoltaic energy storage system (also referred to as a photovoltaic storage system). The entire system can generate electricity for its own use, and the load 30 does not need to draw electricity from the power grid 40.

[0037] It is understandable that when the battery pack 60 cannot supplement the power required by the load 30, the 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 module can also feed excess power into the grid 40.

[0038] In addition, the scene also includes a controller (not shown in the figure). Among them, the controller can adopt a microcontroller unit (MCU) or other control circuit. The controller can be set separately or integrated with other parts in the scene such as the inverter 20 or any DC converter 50, which is not limited here. The controller can serve as an energy management system (EMS) for the entire scene. The controller is connected to each DC converter 50 and is used to control the power conversion of each DC converter 50, thereby controlling the charge and discharge power of the battery pack 60. The controller can also be connected to the BMS of the battery pack 60, so that the parameters of each battery pack 60 detected by the BMS can be obtained and the charge and discharge state of the battery pack 60 can be controlled by the BMS. The controller can also be connected to the inverter 20, so that the inversion process of the inverter 20 can be controlled.

[0039] In the related art, in a photovoltaic storage system with a battery pack coupled to the DC side, when the battery pack is discharged through a DC converter, the discharge power of the DC converter and the power generation power of the photovoltaic module are output to the DC end of the inverter as the total discharge power. Therefore, the discharge curve of the DC converter will affect the maximum power tracking of the inverter, and then affect whether the photovoltaic module can operate at the maximum power point. In order to make the photovoltaic module operate at the maximum power point, one of the discharge control methods of the DC converter is to construct a simulated power-voltage (PV) curve to discharge in the form of a PV curve that simulates the photovoltaic module. The simulated PV curve needs to be coordinated with the actual PV curve of the photovoltaic module so that the energy utilization of the photovoltaic module 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 module.

[0040] In some scenarios, there are multiple DC buses in the photovoltaic storage system, and corresponding PV modules, DC converters and battery packs are connected to the multiple DC buses. In this case, the simulated PV curve of the DC converter on the corresponding DC bus can be constructed according to the power generation parameters of the PV modules on the corresponding DC bus. Figure 1In a photovoltaic storage system, when two or more DC busses are connected to the same MPPT circuit, if the maximum power point voltages of the simulated PV curves of the DC converters on the corresponding DC busses are 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, which will cause the discharge efficiency of the DC converter to be low, that is, the actual discharge power of each DC converter cannot reach the corresponding target discharge power at the same time, thereby affecting the working efficiency of the photovoltaic storage system.

[0041] Specifically, Figure 1 Taking the photovoltaic storage system shown in the figure as an example, when the first DC conversion circuit 51A and the second DC conversion circuit 51B are both connected to the first MPPT circuit 21A, the first photovoltaic assembly 10A and the second photovoltaic assembly 10B correspondingly connected to the first DC conversion circuit 51A and the second DC conversion circuit 51B are both subjected to maximum power tracking through the first MPPT circuit 21A. Figure 1 (Not shown, or, the anti-reverse diode may also be set on the photovoltaic component), so, under normal circumstances, when the first MPPT circuit 21A is working, the actual photovoltaic voltage of the first photovoltaic component 10A, that is, the first actual photovoltaic voltage, is equal to the actual photovoltaic voltage of the second photovoltaic component 10B, that is, the second actual photovoltaic voltage. However, in actual situations, due to errors that may exist in the sampling process of the actual photovoltaic voltage, the first actual photovoltaic voltage may not be equal to the second actual photovoltaic voltage. In another scenario, when the maximum power point voltage of the first photovoltaic component 10A is greater than the open circuit voltage of the second photovoltaic component 10B, the first actual photovoltaic voltage may also be different from the second actual photovoltaic voltage, and the second photovoltaic component 10B cannot output photovoltaic power generation power at this time.

[0042] When 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, it may happen that the maximum power point voltage of the first DC conversion circuit 51A when discharging is different from the maximum power point voltage of the second DC conversion circuit 51B when discharging. Since the first DC conversion circuit 51A and the second DC conversion circuit 51B are both connected to the first MPPT circuit 21A, compared with the case where the maximum power point voltages of the first DC conversion circuit 51A and the second DC conversion circuit 51B are the same when they are discharged, when the maximum power point voltages of the first DC conversion circuit 51A and the second DC conversion circuit 51B are different when they are discharged, the discharge voltage controlled by the MPPT circuit 21A cannot simultaneously meet the maximum power point voltages of the first DC conversion circuit 51A and the second DC conversion circuit 51B when they are discharged, which will at least make the actual discharge power of the first DC conversion circuit 51A or the second DC conversion circuit 51B unable to simultaneously reach the target discharge power corresponding to the maximum power point voltage, thereby reducing the discharge efficiency of the DC conversion circuit in the photovoltaic storage system.

[0043] Based on this, the present application provides a discharge control method of a DC converter to improve the discharge efficiency of a battery pack and the energy utilization rate of a photovoltaic module. It is understandable that the control method can be executed by a controller of the DC converter 50 .

[0044] See also Figure 2 , the discharge control method of the DC converter comprises the following steps:

[0045] Step S201: obtaining the actual photovoltaic voltage and 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 voltage sampling, may be provided at the output end of the photovoltaic module to periodically obtain the actual photovoltaic voltage.

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

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

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

[0050] The reference photovoltaic voltage is used to characterize the photovoltaic voltage of the photovoltaic components connected to the same MPPT circuit. The reference power generation is used to characterize the photovoltaic power generation of the photovoltaic components connected to the same MPPT circuit. The reference photovoltaic voltage and the reference power generation are used to jointly characterize the lighting state of the environment in which at least two photovoltaic components connected to the same MPPT circuit are located.

[0051] When an MPPT circuit connected to the DC end of the inverter is connected to at least two DC bus bars, and the at least two DC bus bars are connected to corresponding photovoltaic modules and DC conversion circuits, the photovoltaic panels with low voltage values ​​cannot participate in the discharge operation, because once they participate in the discharge operation, the voltages of the two photovoltaic panels will remain consistent, and their voltage values ​​will be the maximum value of the actual photovoltaic voltages of all photovoltaic modules connected to the same MPPT circuit.

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

[0053] It should be noted that the maximum value calculation processing of the actual photovoltaic voltage can exclude the low-voltage photovoltaic panels that do not participate in the discharge, so as to prevent the misjudgment of the discharge mode of the corresponding DC conversion circuit. In other words, when the maximum value of the actual photovoltaic voltage is taken, the actual photovoltaic voltage of other low-voltage values ​​can be actively ignored, so that the discharge mode that can be judged accordingly when the subsequent control of at least two DC conversion circuits to discharge is consistent, that is, when the discharge mode is a simulated discharge mode, the parameters used to construct the first simulated discharge curve are consistent. It is understandable that the present application does not limit the specific calculation method for determining the reference photovoltaic voltage based on each actual photovoltaic voltage, and the specific calculation method for determining the reference power generation power based on each photovoltaic power generation power. For example, in other embodiments, the average value of all actual photovoltaic voltages can be used as the reference photovoltaic voltage, and the average value of all photovoltaic power generation powers can be used as the reference power generation power.

[0054] Step S203: obtaining target discharge powers of at least two DC conversion circuits.

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

[0056] Step S204: determining a discharge 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 are used to jointly represent the overall illumination state of the photovoltaic components connected to the same MPPT circuit. Then, in order to maximize the discharge efficiency of the DC conversion circuit, the DC conversion circuit can switch to different discharge 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 corresponding photovoltaic modules and DC conversion circuits are connected to the at least two DC buses, the photovoltaic modules with low voltage values ​​on the at least two DC buses connected to the same MPPT circuit cannot participate in the discharge operation, because once participating in the discharge operation, the voltages of the two photovoltaic modules connected to the same MPPT circuit will remain consistent. Then at this time, the discharge 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 are discharged according to the actual photovoltaic voltage of the photovoltaic module actually participating in the discharge operation (i.e., the discharge voltage of the first end of the DC conversion circuit).

[0059] Therefore, in step S204, the discharge 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 a weak illumination state and a strong illumination state, the discharge mode can also be correspondingly divided into two discharge modes. In other embodiments, the illumination state can be further subdivided into three or more illumination states. For example, when the illumination state is divided into a no illumination state, a weak illumination state, and a strong illumination state, the discharge mode can also be correspondingly divided into three discharge modes, and the corresponding discharge mode is determined according to the illumination state. The present application does not limit the types of discharge modes.

[0060] In this way, after executing step S204, the discharge modes of at least two DC conversion circuits connected to the same MPPT circuit can be made the same.

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

[0062] Please refer again Figure 1 , since at least two DC conversion circuits (e.g., the first DC conversion circuit 51A and the second DC conversion circuit 51B) are connected to the same MPPT circuit (e.g., the first MPPT circuit 21A), that is, the first ends of at least two DC conversion circuits are connected to the input end of the same MPPT circuit, the discharge voltage at the first end of each DC conversion circuit is actually equal. In this way, if at least two DC conversion circuits are still based on different simulated discharge curves at this time, and discharge according to the discharge voltage on their respective corresponding DC buses, then the at least two DC conversion circuits cannot simultaneously operate at the maximum power points of their respective simulated discharge curves, which will result in low discharge efficiency of the battery pack, that is, the actual discharge power does not reach the target discharge power, thereby affecting the working efficiency of the photovoltaic storage system.

[0063] Therefore, in step S205, a simulated discharge curve can be constructed with the discharge voltage of the DC conversion circuit as the independent variable and the discharge power of at least two DC conversion circuits as the dependent variable, i.e., the first simulated discharge curve, 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 simulated discharge curve may be a discharge curve simulating a PV curve of a photovoltaic module. That is, similar to the PV curve, the first simulated 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: controlling at least two DC conversion circuits to discharge based on the first simulated discharge curve.

[0066] Among them, controlling the discharge of at least two DC conversion circuits based on the first simulated discharge curve can be understood as controlling the discharge of each DC conversion circuit respectively according to the first simulated discharge curve; or, it can also be understood as each DC conversion circuit correspondingly constructs a simulated discharge curve of the same form, namely the first simulated discharge curve.

[0067] It can be understood that when 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 generation power of at least two photovoltaic modules are output to the input end of the same MPPT circuit as the total discharge power.

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

[0069] To this end, the method provided in the embodiment of the present application can construct a first simulated discharge curve, and control different DC conversion circuits based on the first simulated discharge curve and the actual discharge voltage. Since each DC conversion circuit is controlled based on the first simulated discharge curve, when the actual discharge voltage controlled by the MPPT circuit is at the maximum power point voltage of the first simulated discharge curve, each DC conversion circuit can simultaneously operate at the maximum operating point, that is, according to the target discharge power output, thereby ensuring the working efficiency of the photovoltaic storage system.

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

[0071] In this way, the first simulated 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 simulated 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 simulated discharge curve is close to or even overlaps with the maximum power point voltage of the PV curve of at least two photovoltaic components as a whole. In this way, not only the energy utilization efficiency of at least two photovoltaic components can be improved, but also when the discharge voltages of at least two DC conversion circuits are both the maximum power point voltages, the actual discharge power of the at least two conversion circuits is the target discharge power, thereby ensuring the discharge efficiency of at least two DC conversion circuits.

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

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

[0074] See also Figure 3 In some embodiments, step S206 includes the following sub-steps:

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

[0076] The actual discharge voltage refers to the discharge voltage at the first end of each DC conversion circuit. When at least two DC conversion circuits are controlled to discharge based on the same first simulated discharge curve, the discharge voltages of at least two DC conversion circuits connected to the same MPPT circuit can be controlled to be equal when they are working normally. At this time, the discharge voltage at 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] Understandably, a voltage sensor, or other circuits or electronic devices capable of voltage sampling, may be provided at the first end of the DC conversion circuit to periodically acquire the discharge 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 simulated discharge curve.

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

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

[0081] Step S303: controlling at least two DC conversion circuits to discharge according to a given discharge power.

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

[0083] In other embodiments, when the corresponding DC conversion circuit is controlled to discharge based on the first simulated discharge curve with the same maximum power point voltage constructed for each DC conversion circuit, each DC conversion circuit can discharge according to the corresponding given discharge power after determining the corresponding given discharge power according to the corresponding actual discharge voltage.

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

[0085] In this way, by executing steps S301 to S303, at least two DC conversion circuits can be controlled to discharge based on the first simulated discharge curve, and the discharge can be performed taking into account the specific circuit conditions of each DC conversion circuit, which is beneficial to improving the safety of the photovoltaic 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, the discharge mode is determined to be a simulated discharge mode.

[0088] Among them, the preset voltage threshold can be understood as the critical voltage threshold of the photovoltaic module in the illuminated state and the unilluminated state, and the preset power threshold can be understood as the critical power threshold of the photovoltaic module in the strong illumination state and the weak illumination state. 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 means that the current lighting conditions make the photovoltaic voltage or power generation of at least two photovoltaic modules as a whole lower. At this time, it can be considered that at least two photovoltaic modules are in the first state as a whole, such as a weak illumination state. Understandably, the weak illumination state can be, for example, the state of at least two photovoltaic modules in a period of weak illumination such as early morning, evening or cloudy days, or even in a period of no illumination such as night.

[0089] Understandably, the current and voltage characteristics of photovoltaic modules will be different under different illumination conditions. Specifically, under no illumination conditions, the photovoltaic module has no output current and photovoltaic voltage. Under weak illumination conditions, the photovoltaic module has an output voltage, but due to the weak illumination, the output power is small, and there is almost no current output at this time. As the illumination increases, when the output power increases, the output current of the photovoltaic module will also increase. When the illumination increases further, the output current of the photovoltaic module continues to increase. When the illumination reaches a certain level, the characteristic curve of the photovoltaic module will tend to be stable. 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 illumination conditions, the photovoltaic voltage of the photovoltaic module is low and the PV curve is relatively unstable; under strong illumination conditions, the PV curve of the photovoltaic module is relatively stable. In addition, since the output end and the DC conversion circuit of the photovoltaic module 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 the power generation power due to the influence of the reverse diode (not shown in the figure) on the DC bus.

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

[0091] In some embodiments, in the simulated discharge mode, the first simulated discharge curve can also be moved following the actual discharge voltage, so that after the light is restored / enhanced, the MPPT circuit can track to the maximum power point of the PV curve of the at least two photovoltaic components as a whole as soon as possible, so that the at least two photovoltaic components can output the generated power as soon as possible, thereby improving the energy utilization rate of the at least two photovoltaic components.

[0092] The moving of the first simulated discharge curve may be understood as moving the maximum power point voltage and / or the open circuit voltage of the first simulated discharge curve.

[0093] Specifically, when it is determined that at least two photovoltaic components are in a weak illumination state as a whole according to the reference photovoltaic voltage and the reference power generation, the principle of moving the first simulated discharge curve is: continuously move the first simulated discharge curve to the left so that the maximum power point voltage of the first simulated discharge curve is close to the maximum power point voltage of the photovoltaic component until the maximum power point voltage of the first simulated discharge curve reaches the minimum discharge voltage value of the corresponding DC conversion circuit. It can be understood that in a weak illumination state, the power generation power of at least two photovoltaic components as a whole is small, then the maximum power point of the PV curve of at least two photovoltaic components as a whole is likely to be located on the left side of the maximum power point of the first simulated discharge curve (that is, the maximum power point voltage and power generation power of the PV curve are both small). At this time, moving the first simulated discharge curve to the left can make the maximum power point voltage of the first simulated discharge curve close to the maximum power point voltage of the PV curve of at least two photovoltaic components as a whole. For the MPPT circuit, in the process of the first simulated discharge curve moving leftward close to the PV curve, its MPPT tracking range continues to move leftward until the actual discharge voltage of each DC conversion circuit is adjusted to the minimum discharge voltage value of the corresponding DC conversion circuit. In this way, at least two photovoltaic components can output power generation as soon as possible.

[0094] In addition, the maximum power point voltage of the photovoltaic module may 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 will affect the MPPT circuit's tracking result of the maximum power point of the photovoltaic module. Therefore, when the MPPT circuit continues to track the maximum power point voltage of the first simulated discharge curve to the right beyond the maximum power point voltage of the first simulated discharge curve, the first simulated discharge curve can follow the discharge voltage to move to the right. Specifically, the voltage difference between the discharge voltage and the maximum power point voltage of the first simulated discharge curve can be calculated. When the voltage difference is greater than the preset difference, the maximum power point voltage of the first simulated discharge curve is set to the value obtained by subtracting the preset difference 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 maintained at the preset difference, that is, the maximum power point voltage of the first simulated discharge curve moves to the right following the discharge voltage. In this way, when the DC conversion circuit discharges based on the first simulated discharge curve, the discharge power can be kept close to the target discharge power during the MPPT circuit tracking to the right, thereby reducing the impact on the maximum power tracking result of the MPPT circuit. 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 be close to or even overlap with the maximum power point voltage of the PV curve of at least two photovoltaic modules as a whole. In this way, the discharge of at least two DC conversion circuits is controlled according to the moved first simulated discharge curve, which can reduce the impact on the photovoltaic modules and thus improve the energy utilization rate of the photovoltaic modules.

[0095] See also Figure 4 In some embodiments, step S204 further includes:

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

[0097] Understandably, when the reference photovoltaic voltage is greater than or equal to the preset voltage threshold, and the reference power generation is greater than or equal to the preset power threshold, it means that the current light conditions cause at least two photovoltaic modules to generate a relatively high photovoltaic voltage and power generation as a whole, so it can be considered that at least two photovoltaic modules are in a strong light state as a whole. The strong light state can be, for example, the state of the photovoltaic module in a period of sufficient light during the day.

[0098] As described above, when the photovoltaic modules are under strong light, the PV curve of 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 track the maximum power point on the PV curve more accurately. At this time, it is not necessary to construct a simulated discharge curve for the DC conversion circuit, and the MPPT circuit only needs to track the maximum power point on the PV curve of at least two photovoltaic modules as a whole.

[0099] Accordingly, the method further includes:

[0100] Step S401: when the discharge mode is the constant power discharge mode, determining the target discharge power to be a given discharge power.

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

[0102] In this way, when the discharge mode is the constant power discharge mode, it is not necessary to determine the given discharge power of the DC conversion circuit based on the first simulated discharge curve, which can effectively reduce the calculation complexity.

[0103] It is understandable that step S402 is substantially the same as step S303 and will not be described in detail herein.

[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, which is irrelevant to the discharge voltage controlled by the MPPT circuit, that is, no matter how the discharge voltage controlled by the MPPT 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 prevented from adversely affecting the maximum power tracking of the MPPT circuit.

[0105] See also Figure 5 In some embodiments, step S205 includes the following sub-steps:

[0106] Step S501: when the discharge mode is the simulated discharge mode, obtaining the operating voltage range of the MPPT circuit.

[0107] Among them, the MPPT circuit mentioned in this embodiment is an MPPT circuit connected to at least two DC conversion circuits. The operating range of the MPPT circuit includes a maximum scanning voltage and a minimum scanning voltage. In some embodiments, the controller of the DC converter 50 can communicate with the inverter 20 to obtain the maximum scanning voltage and the minimum scanning voltage. In other embodiments, the maximum scanning voltage and the minimum scanning voltage can also be pre-stored data. This application does not limit the method for 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 operating voltage range.

[0109] In some embodiments, determining the reference open-circuit voltage based on the operating voltage range includes: when the maximum scan voltage is greater than or equal to the first scan voltage, determining the first voltage value as the reference open-circuit voltage.

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

[0111] Understandably, since the MPPT circuit has a limited voltage scanning range when performing maximum power point tracking, in order to ensure that the MPPT circuit can perform maximum power point tracking normally, it is necessary to limit the reference open circuit voltage of the first simulated discharge curve to within the operating 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 operating voltage range of the MPPT circuit is wide enough, and the preset first voltage value can be directly used to determine the reference open circuit voltage of the initial first simulated 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, for example.

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

[0114] The first voltage parameter is a preset difference between a reference open circuit voltage and a maximum scan voltage.

[0115] Understandably, when the maximum scanning voltage of the MPPT circuit is less than the first scanning voltage, it means that the operating voltage range of the MPPT circuit is small, and it is necessary to determine the reference open-circuit voltage of the initial first simulated discharge curve according to the maximum scanning voltage of the MPPT circuit and the first voltage parameter, so that the discharge voltage of the initial first simulated discharge curve is within the voltage scanning range of the MPPT circuit. In some embodiments, the 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. Exemplarily, the first voltage parameter can be 50V, for example.

[0116] Furthermore, determining the reference maximum power point voltage based on the operating voltage range includes: determining the reference maximum power point voltage of the initial first simulated discharge curve according to the reference open circuit voltage and the second voltage parameter.

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

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

[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] Understandably, because the real PV curve formula is complex, it is not easy to implement in software and the implementation is not meaningful. Therefore, the shape of the PV curve of the photovoltaic module can be imitated to construct the first simulated discharge curve using a simplified function with a similar shape.

[0121] Similarly, when the reference open circuit voltage and the reference maximum power point voltage have been determined in step S502, a function can be used to fit the shapes of the two curves from the voltage zero point to the maximum power point and from the maximum power point to the open circuit voltage in the PV curve in step S503 to form an initial first simulated discharge curve.

[0122] Understandably, 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 combining multiple function types. The present application does not limit the specific function that forms the first simulated discharge curve, as long as the shape of the first simulated discharge curve is similar to the PV curve (e.g., roughly inverted V shape), and the first simulated discharge curve has a target discharge power, a reference maximum power point voltage determined in steps S501 to S503, and a reference open circuit voltage.

[0123] For example, in some scenarios, the function of the first simulated discharge curve may be:

[0124]

[0125] In this function, P is the given discharge power of at least two DC conversion circuits; U is the actual discharge voltage of at least two DC conversion circuits; pwr_tag is the maximum power point power (i.e., the target discharge power of 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] Among them, the reserved power is used to maintain the function of the MPPT circuit while maintaining the DC conversion circuit in a working state. It can be understood that since the first ends of 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 component is in a no-light state and the actual discharge voltage is greater than the reference open-circuit voltage, the given discharge power is 0, then at least two DC conversion circuits stop outputting discharge power, so that the MPPT circuit cannot continue to perform maximum power tracking and may even fail to 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 to be the reserved power to maintain the normal operation of the MPPT circuit.

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

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

[0129] In summary, in step S501 to step S503, the reference open circuit voltage and the reference maximum power point voltage of the first simulated discharge curve are first determined according to the scanning parameters of the MPPT circuit, and then the curve between the zero point to the maximum power point and the maximum power point to the reference open circuit voltage is fitted by function to form the first simulated discharge curve. In this way, the first simulated discharge curve formed by the present application does not need to consider the actual PV curve parameters of the photovoltaic module, nor does it need to worry about the distortion of the initial discharge curve caused by the external environment.

[0130] It is understandable that 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 the selected value of 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, minimum value, mode, median, average or other type of value among all reference open circuit voltages, and the present application is not limited to this. For example, when at least two DC conversion circuits are controlled to discharge based on the same first simulated discharge curve, the first simulated discharge curve can be constructed based on the maximum value of all reference open circuit voltages and the target discharge power of at least two conversion circuits; when the corresponding DC conversion circuit is controlled to discharge 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 of all reference open circuit voltages and the target discharge power corresponding to each DC conversion circuit. Furthermore, when there is a DC conversion circuit that does not participate in discharge among all the DC conversion circuits connected to the same MPPT circuit, based on the above principle, the maximum value of the reference open-circuit voltages of all the DC conversion circuits participating in 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 may also be constructed based on the corresponding reference maximum power point voltage pre-stored in each DC conversion circuit.

[0132] In this way, when the first simulated discharge curve is constructed based on the reference open-circuit voltage or reference maximum power point voltage pre-stored in each DC conversion circuit, the maximum power point voltage of the first simulated discharge curve corresponding to each DC conversion circuit connected to the same MPPT circuit is the same, so as to ensure the discharge efficiency of the DC conversion circuit.

[0133] In some embodiments, after executing step S206, the method further includes:

[0134] The reference open circuit voltage and the reference maximum power point voltage of the first simulated discharge curve are adjusted according to a preset adjustment rule.

[0135] Among them, the preset adjustment rules include: 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 reference open circuit voltage of the first simulated discharge curve is reduced according to the first preset step size to shift the first simulated discharge curve to the left until the reference open circuit voltage reaches the minimum open circuit voltage of the DC conversion circuit, or the reference open circuit voltage is less than the dynamic voltage value, and the left shift of the first simulated discharge curve is stopped, wherein the dynamic voltage value is dynamically set according to the actual discharge voltage.

[0136] Understandably, the controller of the DC converter 50 can only obtain the actual photovoltaic voltage but cannot determine whether the maximum power point of the photovoltaic module is on the left or right side of the current actual discharge voltage. Therefore, the controller of the DC converter 50 cannot actually determine whether the simulated discharge curve should be shifted left or right to approach the maximum power point of the PV curve of at least two photovoltaic modules as a whole. However, since at present at least two photovoltaic modules as a whole are in a weak light state, and the maximum power point of the photovoltaic module in the weak light state may be further to the left than the maximum power point of the photovoltaic module in the strong light state, the reference open-circuit voltage (and reference maximum power point voltage) of the first simulated discharge curve is actively controlled to shift left in this embodiment to increase the chance of overlapping the reference maximum power point voltage of the first simulated discharge curve and the maximum power point voltage of the PV curve of at least two photovoltaic modules as a whole.

[0137] The first preset step size represents the amount of change of the reference open circuit voltage each time it is shifted to the left. For example, the first preset step size may be 0.5 V / S. The reference open circuit voltage of the first simulated discharge curve is reduced according to the first preset step size to shift the first simulated discharge curve to the left, that is, the reference open circuit voltage of the first simulated discharge curve is shifted to the left by 0.5 V to obtain a new first simulated discharge curve.

[0138] Understandably, since the reference maximum power point voltage is related to the reference open circuit voltage, when the reference open circuit voltage of the first simulated discharge curve is reduced according to the first preset step size, the reference maximum power point voltage of the first simulated discharge curve is also reduced according to the first preset step size, thereby shifting the first simulated discharge curve to the left. The present application does not limit the specific value of the first preset step size.

[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. Understandably, the DC conversion circuit has the lowest discharge voltage when discharging, that is, from the circuit performance parameters of the DC conversion circuit itself, the left shift amplitude of the first simulated discharge curve is limited. 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 lowest discharge voltage of the DC conversion circuit at full power. Exemplarily, the minimum open circuit voltage can be 210V, for example. In this way, by comparing the magnitude relationship between the reference open circuit voltage after the left shift and the minimum open circuit voltage, the left shift amplitude of the reference open circuit voltage can be conveniently controlled.

[0140] In other embodiments, the minimum open circuit voltage may be the sum of the minimum discharge voltage of the DC conversion circuit and the second voltage parameter. It is understood that since the difference between the reference open circuit voltage of the first simulated discharge curve and the reference maximum power point voltage is the second voltage parameter, setting the minimum open circuit voltage to the sum of the minimum discharge voltage and the second voltage parameter allows the DC conversion circuit to operate at the maximum power point even at the minimum discharge voltage. In other embodiments, the minimum open circuit voltage may 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 characterize the dynamic open circuit voltage range obtained according to the actual discharge voltage. It is understandable that, since there is a preset distance (such as a second voltage parameter) between the reference maximum power point voltage and the reference open circuit voltage on the first simulated discharge curve, 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, based on 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 reference open circuit voltage after the move is less than the dynamic voltage value, it means that the current left shift is too much and the left shift should be stopped.

[0142] In summary, this embodiment controls the first simulated discharge curve to shift left by lowering the reference open-circuit voltage on the first simulated discharge curve, thereby increasing the chance of overlapping between the reference maximum power point voltage of the first simulated discharge curve and the maximum power point voltage of the PV curve when at least two photovoltaic modules are in a weak light state as a whole, so as to improve the energy utilization rate of the photovoltaic modules.

[0143] In some embodiments, the dynamic voltage value is the sum of the actual discharge voltage and the first preset voltage value, and 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 simulated discharge curve is moved following the actual discharge voltage, further comprising:

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

[0145] The first preset voltage value is used to represent the voltage difference between the actual discharge voltage and the reference open circuit voltage after the shift. 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 can be 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, assuming that the second voltage parameter is 100V, the first preset voltage value is 95V. In this way, the reduced reference open circuit voltage is less than the dynamic voltage value, and the difference obtained when the actual discharge voltage is subtracted from the reference maximum power point voltage of the first simulated discharge curve after the left shift is greater than 5V. Understandably, the value of the actual discharge voltage minus the reference maximum power point voltage after the left shift is greater than 5V, indicating that the MPPT circuit is tracking to the right. Therefore, at this time, the left shift of the first simulated discharge curve should be stopped, and the first simulated discharge curve should be right-shifted according to the actual discharge voltage, so that the DC conversion circuit can maintain the discharge power more smoothly, so as to reduce the impact of the discharge power of the DC conversion circuit on the maximum power tracking of the photovoltaic power generation power of at least two photovoltaic modules. The present application does not limit the specific numerical value of the first preset voltage value. In other embodiments, the first preset voltage value can also be other numerical values.

[0147] 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, the first simulated discharge curve is moved following the reference photovoltaic voltage and the actual discharge voltage, and also includes: updating the reference open-circuit voltage of the first simulated discharge curve according to the dynamic voltage value to right-shift the first simulated discharge curve.

[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 reference open-circuit voltage after the left shift 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, thereby shifting the first simulated discharge curve to the right. In this way, when the photovoltaic power generation power of at least two photovoltaic modules causes the MPPT circuit to track to the right, the first simulated discharge curve can be shifted to the right in time, and finally the maximum power tracking of the MPPT circuit reaches a steady state, thereby utilizing the energy of the photovoltaic module with maximum efficiency.

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

[0150] Understandably, the reference photovoltaic voltage changes from being greater than the preset voltage threshold to being less than or equal to the preset voltage threshold, which means that the photovoltaic component switches from a weak illumination state to a no illumination state, or the photovoltaic component switches from a strong illumination state to a no illumination state.

[0151] The second preset step size 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 size may be 0.1 V / S.

[0152] In this embodiment, the first simulated discharge curve after the shift is restored to the initial first simulated discharge curve, that is, the reference open circuit voltage of the first simulated discharge curve after the shift 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 length to move the first simulated discharge curve until the moved first simulated discharge curve is restored 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 a second preset step size to right-shift the first simulated discharge curve until the shifted 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 reduced according to a second preset step size to shift the first simulated discharge curve leftward until the shifted first simulated discharge curve returns to the initial first simulated discharge curve.

[0156] It is understandable that in other embodiments, the second preset step length may also be other values, and the present application does not limit the specific value of the second preset step length.

[0157] It is understandable that the first preset step length and the second preset step length mentioned in the present application can be fixed preset values ​​or dynamically changing values; or one of the first preset step length and the second preset step length can be a preset value, and the other of the first preset step length and the second preset step length can be a dynamically changing value. In this way, when the first preset step length and / or the second preset step length are dynamically changing values, the movement of the reference open circuit voltage and the reference maximum power point voltage on the first simulated discharge curve can be controlled more accurately and quickly.

[0158] In some embodiments, before executing step S202, the method further includes:

[0159] The connection relationship between at least two DC converters and the MPPT circuit is determined according to the actual photovoltaic voltage of the photovoltaic assembly corresponding to each DC conversion circuit and / or the discharge voltage of each DC conversion circuit.

[0160] Furthermore, when the control method of the embodiment of the present application is applied to Figure 1 Please refer to Figure 6 , determining the connection relationship between at least two DC converters and the MPPT circuit according to the actual photovoltaic voltage of the photovoltaic assembly corresponding to each DC conversion circuit and / or the discharge voltage of each DC conversion circuit, may include:

[0161] Step S601: confirm 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 assembly corresponding to the first DC conversion circuit 51A (i.e., the first photovoltaic assembly 10A), and the second photovoltaic voltage is the photovoltaic voltage of the photovoltaic assembly corresponding to the second DC conversion circuit 51B (i.e., the second photovoltaic assembly 10B). The size of the preset voltage can be set accordingly according to actual conditions, 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 assembly 10A and the second photovoltaic assembly 10B are both under certain lighting conditions (e.g., daytime) and have a large power generation capacity. In this case, the photovoltaic assembly is usually in a stable operating state, and the photovoltaic voltage is stable, so the probability of causing a misjudgment of the connection relationship 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 DC converter and the MPPT circuit.

[0164] When the first photovoltaic voltage and the second photovoltaic voltage are both greater than 0 and less than or equal to the preset voltage, it means that the first photovoltaic assembly 10A and the second photovoltaic assembly 10B are both under illumination conditions, but the power generation is small. In this case, the photovoltaic assembly may not be in a stable operating state, and the photovoltaic voltage is not stable, so it may cause a misjudgment of the connection relationship. Therefore, the power generation at this time cannot be used to confirm the connection relationship between the DC converter 50 and the MPPT circuit.

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

[0166] The first voltage difference is the absolute value of a subtraction result 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, determining that the first DC conversion circuit and the second DC conversion circuit are respectively connected to different maximum power point tracking circuits in a one-to-one correspondence.

[0168] The size of the first preset voltage difference may be set according to actual conditions. For example, the first preset voltage difference may be an empirical value of 50V obtained from experimental tests.

[0169] Understandably, when the first voltage difference is greater than the first preset voltage difference, it means that the first photovoltaic voltage of the first photovoltaic assembly 10A and the second photovoltaic voltage of the second photovoltaic assembly 10B differ greatly, and do not have the characteristic of equal voltage magnitude of the parallel branches. Therefore, at this time, it can be determined that the first photovoltaic assembly 10A and the second photovoltaic assembly 10B are respectively connected to different maximum power point tracking circuits in a one-to-one correspondence. Since the first photovoltaic assembly 10A and the first DC conversion circuit 51A are connected to the same DC bus, and the second photovoltaic assembly 10B and the second DC conversion circuit 51B are also connected to the same DC bus, therefore, at this time, it can be determined that the first DC conversion circuit 51A and the second DC conversion circuit 51B are respectively connected to different maximum power point tracking circuits in a one-to-one correspondence.

[0170] It can be seen that when the first photovoltaic voltage and the second photovoltaic voltage are both greater than the preset voltage, the first photovoltaic voltage and the second photovoltaic voltage can be used to self-detect the connection relationship between the first DC conversion circuit 51A and the second DC conversion circuit 51B and 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, the first photovoltaic assembly 10A and the second photovoltaic assembly 10B do not generate electricity. In this case, it is impossible to determine the connection relationship between the DC converter and the MPPT circuit. 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 assembly 10A and the second photovoltaic assembly 10B is small, but this is likely to be caused by the different light intensity, shading degree, temperature and other factors of different photovoltaic assemblies. Therefore, in this case, it is also difficult to determine the connection relationship between the DC converter and the MPPT circuit.

[0172] Therefore, for both cases, please continue to refer to Figure 3 , determining the connection relationship between at least two DC converters and the MPPT circuit according to the actual photovoltaic voltage of the photovoltaic assembly corresponding to each DC conversion circuit and / or the discharge voltage of each DC conversion circuit, may 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, one of the DC conversion circuits is controlled to discharge.

[0174] That is to say, 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 until the first photovoltaic component 10A and the second photovoltaic component 10B stop generating electricity, and then control the first DC conversion circuit 51A to output the voltage to its corresponding first DC input port a, or control the second DC conversion circuit 51B to output the voltage to its corresponding second DC input port b.

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

[0176] It can be seen from this that 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, in order to avoid misjudgment of the connection relationship caused by the first photovoltaic voltage and the second photovoltaic voltage, another self-check method will be adopted, using the output voltage corresponding to the DC conversion circuit to realize self-check of the connection relationship between the first DC conversion circuit 51A and the second DC conversion circuit 51B and the MPPT circuit, so as to ensure the accuracy of the self-check.

[0177] It can be understood that if multiple DC conversion circuits are connected to the same MPPT circuit, as long as any one of the DC conversion circuits outputs a certain voltage to the DC input port, the same voltage can be detected at the DC input ports corresponding to other DC conversion circuits. Conversely, if each DC conversion circuit is connected to a different MPPT circuit in a one-to-one correspondence, the output voltages of each DC conversion circuit during discharge will not affect each other.

[0178] In the above step S604, in order to avoid excessive discharge of the DC conversion circuit and waste of battery pack power, after controlling one of the DC conversion circuits to discharge, the control method further includes:

[0179] When the output voltage corresponding to the discharged DC conversion circuit reaches the preset discharge voltage, the output voltage corresponding to the undischarged DC conversion circuit is obtained.

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

[0181] If the controller controls the discharge of the second DC conversion circuit 51B, then when it is detected that the output voltage output by the second DC conversion circuit 51B to the second DC input port b reaches the preset discharge voltage, the output voltage output by the first DC conversion circuit 51A to the first DC input port a is obtained. Furthermore, 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 discharge voltage). Among them, the preset discharge voltage can be set accordingly according to the actual situation (such as the operating voltage range of the MPPT circuit, etc.), and is not specifically limited here.

[0182] For more information, please see 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 may 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 the output voltage corresponding to the first DC conversion circuit 51A, and the second output voltage is the output voltage corresponding to the second DC conversion circuit 51B. The second voltage difference is the absolute value of the subtraction result of the first output voltage and the second output voltage.

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

[0186] The second preset voltage difference may 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, determining that the first DC conversion circuit and the second DC conversion circuit are respectively connected to different maximum power point tracking circuits in a one-to-one correspondence.

[0188] It can be understood that when the second voltage difference is greater than or equal to the second preset voltage difference, it means 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 significantly different, and do not have the characteristic of equal voltage magnitudes of the parallel branches. Therefore, at this time, it can be determined that the first DC conversion circuit and the second DC conversion circuit are respectively connected one-to-one 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 means 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 slightly different and can be regarded as equal, that is, they have the characteristic of equal voltage magnitudes of the parallel branches. 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] It can be seen that 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, the output voltage corresponding to the DC conversion circuit can be used to self-check the connection relationship between the first DC conversion circuit 51A and the second DC conversion circuit 51B and different MPPT circuits, and the connection relationship between the first DC conversion circuit 51A and the second DC conversion circuit 51B connected in parallel to the same MPPT circuit. Therefore, the connection relationship obtained by this self-checking method can be more accurate.

[0192] Moreover, in general, no matter whether the photovoltaic module has output or not, and no matter how much the photovoltaic module outputs, the control method of the embodiment of the present application can realize self-checking of the connection relationship between the DC converter 50 and the MPPT circuit.

[0193] It is understandable that, in one embodiment, the step of determining the magnitude of the first photovoltaic voltage and the second photovoltaic voltage may be omitted, and the first output voltage and the second output voltage may be directly obtained, and the connection relationship between the DC converter and the maximum power point tracking circuit may be determined based on the first output voltage and the second output voltage.

[0194] See also Figure 8 In some embodiments, step S202 includes the following sub-steps:

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

[0196] Please also read Figure 1 , as mentioned above, based on Figure 1 In the circuit connection relationship shown, when the first actual photovoltaic voltage of the first photovoltaic component 10A is not equal to the second actual photovoltaic voltage of the second photovoltaic component 10B, the photovoltaic component corresponding to the lower voltage of the first actual photovoltaic voltage and the second actual photovoltaic voltage cannot discharge. At this time, taking the maximum value of each actual photovoltaic voltage as the reference photovoltaic voltage can ensure that the photovoltaic component based on the higher actual photovoltaic voltage participates in the discharge operation, which is more conducive to improving the energy utilization efficiency of the photovoltaic components in the photovoltaic storage system, and can also exclude the photovoltaic components with lower actual photovoltaic voltages to prevent misjudgment of the discharge mode.

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

[0198] It can be understood that since the photovoltaic power generation power of at least two photovoltaic components 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 components, 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] Exemplarily, when the actual photovoltaic voltage V1 of the first photovoltaic component is 400V, the corresponding photovoltaic power generation power P1 is 1000W, and when the second photovoltaic component V2 is 400V, the corresponding photovoltaic power generation power P2 is 50W. According to the conventional discharge mode, the discharge mode of the DC conversion circuit DCDC1 corresponding to the first photovoltaic component is in the constant power discharge mode, and the discharge mode of the DC conversion circuit DCDC2 corresponding to the second photovoltaic component is in the simulated discharge mode. At this time, the simulated discharge curve of the DC conversion circuit DCDC2 will move to the left to the leftmost end. Once the simulated discharge curve of the DC conversion circuit DCDC2 starts to move, the maximum power point voltage of the DC conversion circuit DCDC2 will deviate from 400V. At this time, the maximum power point of the first simulated discharge curve obtained by superimposing the first simulated discharge curve with the overall PV curve of the two photovoltaic components will also deviate from 400V, causing the first photovoltaic component to be unable to be discharged at full power, and the DC conversion circuit DCDC2 will also be incompletely discharged. When the simulated discharge curve of the DC conversion circuit DCDC2 moves to the left to the leftmost end, the impact is greatest. Therefore, after the improvement of the solution of the present application, the reference photovoltaic voltage V=max(V1, V2)=400V and the reference power generation power P=(P1+P2) / 2=525W can be obtained. The reference photovoltaic voltage and the reference power generation power can make the DC conversion circuit DCDC1 and the DC conversion circuit DCDC2 both in constant power mode, that is, at this time, the maximum power point voltage of the superimposed first simulated discharge curve is still maintained at 400V, which will not affect the discharge power of the two photovoltaic components.

[0200] See also Fig. 9 , Fig. 9 A schematic diagram of another scenario of the discharge control method of the DC converter provided in the present application. Fig. 9 The scene shown is similar to Figure 1 The scenes shown are roughly the same, except that Fig. 9 The illustrated scenario includes a third photovoltaic assembly 10C, the inverter 20 further includes a second MPPT circuit 21B and a third DC input port d, and the DC converter 50 further includes a third DC converter 51C. The first end of the third DC converter 51C is connected to the same DC bus (DC_BUS3+, DC_BUS3-) as the corresponding third photovoltaic assembly 10C and the third DC input port d of the inverter 20. Fig. 9 In the scenario shown, the discharge control method of the DC converter provided in the present application also includes:

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

[0202] Among them, the second simulated discharge curve is constructed based on the maximum scanning voltage and the minimum scanning voltage of the MPPT circuit that only connects a DC conversion circuit and a photovoltaic component, and the maximum power point power of the second simulated discharge curve is the target discharge power of the MPPT circuit that only connects a DC conversion circuit and a photovoltaic component.

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

[0204] See also Fig.10 , Fig.10 A schematic diagram of another scenario of the discharge control method of the DC converter provided in the present application. Fig.10 The scene shown is similar to Figure 1 The scenes shown are roughly the same, except that Fig.10 The first DC conversion circuit 51A is connected to the first battery pack 60A, and the second DC conversion circuit 51B is connected to the second battery pack 60B. 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 faulty or in any other state that is not suitable for work. The enabled state is used to indicate that the battery pack is currently in a usable state.

[0205] In some embodiments, based on Fig.10 In the illustrated scenario, step S202 further includes:

[0206] The PV panels corresponding to the disabled battery pack are controlled to stop working.

[0207] The maximum value of the actual photovoltaic voltages of the photovoltaic components corresponding to the battery pack in the enabled state is used as the reference photovoltaic voltage, and the average value of the photovoltaic power generation power of each photovoltaic component corresponding to the battery pack in the enabled state is calculated 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 executing the steps provided in this embodiment, it is possible to prevent a battery pack in a disabled state from interfering with the operation 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 a disabled state, the MPPT circuit is controlled to perform maximum power tracking according to the first photovoltaic voltage, wherein the first photovoltaic voltage is the photovoltaic voltage of the photovoltaic component corresponding to the first DC conversion circuit, the second photovoltaic voltage is the photovoltaic voltage of the photovoltaic component corresponding to the second DC conversion circuit, the first battery pack is the battery pack corresponding to the first DC conversion circuit, and the second battery pack is the battery pack corresponding to the second DC conversion circuit.

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

[0213] See also Fig.11 The present application also provides a power conversion device 100, including a controller 70 and a DC converter 50. The DC converter 50 includes at least two DC conversion circuits, the first end of each DC conversion circuit is used to connect to the same DC bus with the DC end of the corresponding photovoltaic module and inverter, the second end of each DC conversion circuit is used to connect to the battery pack 60, and the DC end of the inverter 20 is used to connect to the MPPT circuit. The controller 70 is used to execute the discharge control method of the DC converter as described in any one of the above items.

[0214] See also Fig.12 The present application also provides an energy storage device 200, including a battery pack 60, a controller 70 and a DC converter 50. The DC converter 50 includes at least two DC conversion circuits, the first end of each DC conversion circuit is used to connect to the same DC bus with the corresponding photovoltaic component and the DC end of the inverter 20, the second end of each DC conversion circuit is used to connect the battery pack 60, and the DC end of the inverter 20 is used to connect the MPPT circuit. The controller 70 is used to execute the discharge control method of the DC converter as described in any of the above items.

[0215] See also Fig.13 The present application also provides an electronic device 300, including a processor 310 and a memory 320. The memory 320 is used to store a program, instruction or code for executing the above discharge control method of the DC converter. The processor 310 is used to execute the program, instruction or code stored in the memory 320. The program, instruction or code stored in the memory 320 can execute some or all steps of the discharge control method of the DC converter in any of the above embodiments.

[0216] An embodiment of the present application further provides a control device 400 , which is applied to a DC converter 50 or an electronic device integrated with the DC converter 50 . Fig.14 The structure block diagram of the control device 400 provided in the embodiment of the present application is schematically shown. Fig.14 As shown, the control device 400 includes:

[0217] The first acquisition module 410 is used to acquire the actual photovoltaic voltage and photovoltaic power generation power of the photovoltaic assembly corresponding to each DC conversion circuit.

[0218] The first determination module 420 is used to determine the reference photovoltaic voltage based on each actual photovoltaic voltage and to determine the reference power generation power based on each photovoltaic power generation power when at least two DC conversion circuits are connected to the same MPPT circuit.

[0219] The second acquisition module 430 is used to acquire target discharge powers of at least two DC conversion circuits.

[0220] The second determination module 440 is used to determine the discharge mode of the DC conversion circuit based on the reference photovoltaic voltage and the reference power generation power.

[0221] The construction module 450 is used to construct a first simulated discharge curve based on the target discharge powers of at least two DC conversion circuits when the discharge mode is a simulated discharge mode.

[0222] The control module 460 is used to control the discharge of at least two DC conversion circuits based on the first simulated discharge curve.

[0223] The specific details of the discharge control method for the DC converter implemented by the control device 400 provided in the embodiment of the present application have been described in detail in the embodiment of the discharge control method for the corresponding DC converter, and will not be repeated here.

[0224] The present application also provides a computer readable medium having a computer program stored thereon, and when the computer program is executed by a processor, the discharge control method of the DC converter in the above technical solution is implemented. The computer readable medium can be a portable compact disk read-only memory (CD-ROM) and include program code, and can be run on a terminal device, such as a personal computer. However, the program product of the present invention is not limited thereto, 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 combination with an instruction execution system, an apparatus or a device.

[0225] The above program product 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 can be, for example, but not limited to, a system, device or device of electricity, magnetism, light, electromagnetic, infrared, or semiconductor, or any combination of the above. More specific examples (non-exhaustive list) of readable storage media include: an electrical connection with one or more wires, a portable disk, 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 disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the above.

[0226] Computer readable signal media may include data signals propagated in baseband or as part of a carrier wave, in which readable program code is carried. Such propagated data signals may take a variety of forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination of the above. Readable signal media may also be any readable medium other than a readable storage medium, which may send, propagate, or transmit a program for use by or in conjunction with an instruction execution system, apparatus, or device.

[0227] The program code embodied on the readable medium may be transmitted using any appropriate medium, including but not limited to wireless, wired, optical cable, RF, etc., or any suitable combination of the foregoing.

[0228] Program code for performing the operations of the present invention may be written in any combination of one or more programming languages, including object-oriented programming languages ​​such as Java, C++, etc., and conventional procedural programming languages ​​such as "C" or similar programming languages. The program code may be executed entirely on the user computing device, partially on the user device, as a separate software package, partially on the user computing device and partially on a remote computing device, or entirely on a remote computing device or server. In cases involving a remote computing device, the remote computing device may be connected to the user computing device through any type of network, including a local area network (LAN) or a wide area network (WAN), or may be connected to an external computing device (e.g., through the Internet using an Internet service provider).

[0229] In addition, the above-mentioned figures are only schematic illustrations of the processes included in the method according to an exemplary embodiment of the present invention, and are not intended to be limiting. It is easy to understand that the processes shown in the above-mentioned figures do not indicate or limit the time sequence of these processes. In addition, it is also easy to understand that these processes can be performed synchronously or asynchronously, for example, in multiple modules.

[0230] The above are only specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed in the present application, and these modifications or replacements should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A discharge control method for a DC converter, characterized in that: The DC converter includes at least two DC conversion circuits, the first end of each DC conversion circuit is used to connect to the same DC bus with the corresponding photovoltaic module and the DC end of the inverter, the second end of each DC conversion circuit is used to connect to the corresponding battery pack, and the DC end of the inverter is used to connect to the MPPT circuit; the method includes: Obtaining the actual photovoltaic voltage and photovoltaic power generation power of each photovoltaic module corresponding to the DC conversion circuit; When the at least two DC conversion circuits are connected to the same MPPT circuit, a reference photovoltaic voltage is determined based on each actual photovoltaic voltage, and a reference power generation power is determined based on each photovoltaic power generation power; Obtaining target discharge powers of the at least two DC conversion circuits; Determining a discharge mode of the DC conversion circuit based on the reference photovoltaic voltage and the reference generated power; When the discharge mode is a simulated discharge mode, constructing a first simulated discharge curve based on the target discharge powers of the at least two DC conversion circuits; The at least two DC conversion circuits are controlled to discharge based on the first simulated discharge curve.

2. The method according to claim 1, characterized in that The controlling the discharge of the at least two DC conversion circuits based on the first simulated discharge curve comprises: Obtaining actual discharge voltages of the at least two DC conversion circuits; Determining a given discharge power based on the actual discharge voltage and the first simulated discharge curve; The at least two DC conversion circuits are controlled to discharge according to the given discharge power.

3. The method according to claim 1, characterized in that: The step of determining the discharge mode of the DC conversion circuit based on the reference photovoltaic voltage and the reference power generation power includes: 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, the discharge mode is determined to be the simulated discharge mode.

4. The method according to claim 3, characterized in that The step of determining the discharge mode of the DC conversion circuit based on the reference photovoltaic voltage and the reference generated power further includes: When the reference photovoltaic voltage is greater than or equal to a 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; Accordingly, the method further includes: When the discharge mode is the constant power discharge mode, determining the target discharge power to be a given discharge power; The at least two DC conversion circuits are controlled to discharge according to the given discharge power.

5. The method according to claim 1, characterized in that When the discharge mode is a simulated discharge mode, constructing a first simulated discharge curve based on the target discharge powers of the at least two DC conversion circuits includes: When the discharge mode is a simulated discharge mode, obtaining an operating voltage range of the MPPT circuit; Determine a reference open circuit voltage and a reference maximum power point voltage based on the operating voltage range; The first simulated discharge curve is constructed based on the reference open circuit voltage, the reference maximum power point voltage, and the target discharge power.

6. The method according to claim 1, characterized in that The method further comprises: The reference open circuit voltage and the reference maximum power point voltage of the first simulated discharge curve are adjusted 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: The connection relationship between the at least two DC converters and the MPPT circuit is determined according to the actual photovoltaic voltage of the photovoltaic assembly corresponding to each DC conversion circuit and / or the discharge voltage of each DC conversion circuit.

8. The method according to claim 1, characterized in that Determining a reference photovoltaic voltage based on each of the actual photovoltaic voltages, and determining a reference power generation power based on each of the photovoltaic power generation powers, comprising: Taking the maximum value among the actual photovoltaic voltages as the reference photovoltaic voltage; The average value of each photovoltaic power generation power is calculated to obtain the reference power generation power.

9. A power conversion device, characterized in that: The power conversion device includes a controller and a DC converter, the DC converter includes at least two DC conversion circuits, the first end of each of the DC conversion circuits is used to connect to the same DC bus with the DC end of the corresponding photovoltaic component and inverter, the second end of each of the DC conversion circuits is used to connect to a battery pack, and the DC end of the inverter is used to connect to the MPPT circuit; the controller is used to execute the discharge control method of the DC converter as described in any one of claims 1 to 8.

10. An energy storage device, characterized in that: The energy storage device includes a battery pack, a controller and a DC converter, the DC converter includes at least two DC conversion circuits, the first end of each of the DC conversion circuits is used to connect to the same DC bus with the DC end of the corresponding photovoltaic component and inverter, the second end of each of the DC conversion circuits is used to connect to the battery pack, and the DC end of the inverter is used to connect to the MPPT circuit; the controller is used to execute the discharge control method of the DC converter as described in any one of claims 1 to 8.

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