Photovoltaic energy storage system

Abstract

Provided in the present application is a photovoltaic energy storage system, comprising: an inverter, an energy storage device and a voltage compensation assembly. The inverter comprises a direct-current conversion circuit, a direct-current bus, an inverter circuit and a first switch, wherein a positive input end of the direct-current conversion circuit is used for connecting to a positive electrode of a photovoltaic assembly, and a negative input end of the direct-current conversion circuit is used for connecting to a negative electrode of the photovoltaic assembly; and the first switch is disposed between a connection point of the voltage compensation assembly and the negative input end of the direct-current conversion circuit and a negative electrode of the direct-current bus, and is used for controlling connection and disconnection between the voltage compensation assembly and the negative electrode of the direct-current bus. The photovoltaic energy storage system further comprises a controller, which is used for, when an output voltage and / or an output current of the photovoltaic assembly is less than or equal to a threshold value, controlling the first switch to be disconnected and controlling the voltage compensation assembly to operate, so that the voltage of the negative electrode of the photovoltaic assembly relative to the ground is raised to a zero voltage or a positive voltage. According to the solution, PID compensation can be carried out on a photovoltaic assembly at night, so as to solve the PID problem of the photovoltaic assembly.

Description

A photoelectric storage system

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on December 20, 2023, with application number 202311766580.0 and invention name “A Photovoltaic Storage System”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of power electronics technology, and more specifically, to a photovoltaic storage system and a control method applied to the photovoltaic storage system. Background Art

[0003] As countries around the world continue to promote energy conservation, emission reduction and energy transformation, renewable energy power generation technology has received increasing attention. Among them, photovoltaic power generation systems have been widely used in power systems and microgrids due to their technological maturity and economic efficiency.

[0004] However, photovoltaic power generation systems have long been plagued by inefficiencies. After a period of use, photovoltaic modules experience performance degradation, leading to a drop in the overall system's output power. Research has found that the cause of this phenomenon is the high voltage between the circuitry within the crystalline silicon photovoltaic module and its grounded metal frame, which causes a continuous degradation in the module's power generation performance. This phenomenon is known as potential induced degradation (PID).

[0005] Generally, for a pure solar inverter, it generates electricity by connecting to the grid during the day, and at night, the voltage compensation module can be used to raise the voltage between the negative pole (PV-) of the photovoltaic module and the earth (PE), thereby performing PID compensation on the photovoltaic module.

[0006] However, for solar-storage systems, even at night when the PV panels are not outputting energy, the energy storage device still provides energy to the PV-storage inverter, allowing the PV-storage inverter to continue grid-connected operation. During this time, the voltage between the PV-pole (PV-) and the earth (PE) remains negative, making it impossible to perform PID compensation on the PV panels using the voltage compensation module. Furthermore, since the PV panels are all voltage-free at night, the negative voltage between the PV-pole (PV-) and the earth (PE) of all PV panels in all PV strings remains the same, causing PID issues that are more severe than during the day.

[0007] Based on this, the present application aims to provide a photovoltaic storage system that can perform PID compensation on photovoltaic modules at night to solve the PID problem of photovoltaic modules in the photovoltaic storage system. Summary of the Invention

[0008] The present application provides a solar storage system that can perform PID compensation on photovoltaic modules at night to solve the PID problem of photovoltaic modules.

[0009] In a first aspect, a photovoltaic storage system is provided, characterized in that it includes: an inverter, an energy storage device and a voltage compensation component, the inverter includes a DC conversion circuit, a DC bus, an inverter circuit and a first switch, the positive input end of the DC conversion circuit is used to connect the positive pole of the photovoltaic component, the negative input end of the DC conversion circuit is used to connect the negative pole of the photovoltaic component, the positive output end of the DC conversion circuit is connected to the positive pole of the DC bus, the negative output end of the DC conversion circuit is connected to the negative pole of the DC bus, the positive pole of the DC bus is connected to the positive input end of the inverter circuit and the positive pole of the energy storage device, and the negative pole of the DC bus is connected to the negative input end of the inverter circuit and The negative pole of the energy storage device is connected, the positive pole of the voltage compensation component is used to connect the negative pole of the photovoltaic component, and the negative pole of the voltage compensation component is connected to the ground. The first switch is arranged between the connection point of the voltage compensation component and the negative input terminal of the DC conversion circuit and the negative pole of the DC bus, and is used to control the on and off between the voltage compensation component and the negative pole of the DC bus; the photovoltaic storage system also includes a controller, which is used to: when the output voltage and / or output current of the photovoltaic component is less than or equal to the threshold, control the first switch to be disconnected, and control the voltage compensation component to operate, so that the voltage of the negative pole of the photovoltaic component to the ground is raised to zero voltage or positive voltage.

[0010] According to the above technical solution, when the output voltage and / or output current of the photovoltaic module is less than or equal to a threshold, the controller controls the first switch to open, thereby disconnecting the negative pole of the photovoltaic module from the negative pole of the DC bus. Furthermore, the controller controls the voltage compensation component to operate, thereby raising the voltage between the negative pole (PV-) of the photovoltaic module and the earth (PE) to a zero voltage or positive voltage, thereby implementing PID compensation for the photovoltaic module at night. Furthermore, in the embodiments of the present application, an isolation transformer is not required, which greatly reduces costs, the number of components, and the size, while further improving the power generation efficiency of the photovoltaic storage system.

[0011] In conjunction with the first aspect, in certain implementations of the first aspect, the voltage compensation component includes a voltage compensation module and a second switch, the voltage compensation module and the second switch being connected in series, the voltage compensation module outputting a positive voltage, and the controller being specifically configured to control the second switch to close to enable the voltage compensation component to operate. According to the above technical solution, PID compensation can be performed on photovoltaic modules at night, thereby resolving PID issues in photovoltaic modules in a solar-storage system.

[0012] In combination with the first aspect, in certain implementations of the first aspect, the controller is further used to: when the voltage of the DC bus is less than or equal to a first preset value, control the switching tube of the DC conversion circuit to an open-loop switching mode; wherein, when the switching tube is in the open-loop switching mode, the voltage across the first switch decreases.

[0013] According to the above technical solution, when the energy storage device in the solar-storage system experiences a low-limit shutdown (e.g., a battery SOC low-limit shutdown, a device failure, a low battery charge, or manual shutdown of the energy storage switch), the first switch can be safely closed before the solar-storage system shuts down. This prevents contact damage, increased contact impedance, and even damage to the first switch, thereby improving overall system reliability.

[0014] In combination with the first aspect, in certain implementations of the first aspect, the controller is further used to: control the first switch to close when the voltage value across the first switch is less than or equal to a second preset value, and the second preset value is a safe shutdown voltage value across the first switch.

[0015] According to the above technical solution, when the energy storage device in the solar-storage system experiences a low-limit shutdown (e.g., a battery SOC low-limit shutdown, a device failure, a low battery charge, or manual shutdown of the energy storage switch), the first switch can be safely closed before the solar-storage system shuts down. This prevents contact damage, increased contact impedance, and even damage to the first switch, thereby improving overall system reliability.

[0016] In combination with the first aspect, in certain implementations of the first aspect, the controller is further configured to: control the first switch to close when the duration of the switch tube being in the open-loop ripple mode is greater than or equal to a preset duration.

[0017] According to the above technical solution, when the energy storage device in the solar-storage system experiences a low-limit shutdown (e.g., a battery SOC low-limit shutdown, a device failure, a low battery charge, or manual shutdown of the energy storage switch), the first switch can be safely closed before the solar-storage system shuts down. This prevents contact damage, increased contact impedance, and even damage to the first switch, thereby improving overall system reliability.

[0018] In conjunction with the first aspect, in certain implementations of the first aspect, the controller is further configured to: when the output voltage and / or output current of the photovoltaic module exceeds the threshold, control the first switch to close and control the voltage compensation component to stop operating. According to the above technical solution, PID compensation can be performed on the photovoltaic module at night, thereby resolving the PID problem of the photovoltaic module in the solar-storage system.

[0019] In combination with the first aspect, in certain implementations of the first aspect, when the switching tube is in the open-loop wave transmission mode, the voltage across the first switch decreases as the duration of the switching tube in the open-loop wave transmission mode increases, wherein the relationship between the voltage and the duration satisfies a linear function.

[0020] According to the above technical solution, when the energy storage device in the solar-storage system experiences a low-limit shutdown (e.g., a battery SOC low-limit shutdown, a device failure, a low battery charge, or manual shutdown of the energy storage switch), the first switch can be safely closed before the solar-storage system reaches the low-limit shutdown state. This prevents contact damage, increased contact impedance, and even damage to the first switch, thereby improving overall system reliability.

[0021] In conjunction with the first aspect, in certain implementations of the first aspect, the solar energy storage system further includes a first diode connected in parallel across the first switch, wherein a forward current of the first diode is in a direction opposite to a current flowing through the first switch when the first switch is closed. According to the above technical solution, the first diode is provided in anti-parallel connection across the first switch to eliminate the effects of overvoltage in the circuit.

[0022] In combination with the first aspect, in some implementations of the first aspect, the first switch includes any one of the following: a relay, a metal oxide semiconductor field effect transistor (MOSFIT), and an insulated gate bipolar transistor (IGBT).

[0023] In combination with the first aspect, in certain implementations of the first aspect, the switch tube includes any one of the following: a metal oxide semiconductor field effect transistor (MOSFIT) and an insulated gate bipolar transistor (IGBT).

[0024] In a second aspect, an inverter is provided, comprising: a DC conversion circuit, a DC bus, an inverter circuit and a first switch, wherein the positive input terminal of the DC conversion circuit is used to connect to the positive pole of the photovoltaic module, the negative input terminal of the DC conversion circuit is used to connect to the negative pole of the photovoltaic module, the positive output terminal of the DC conversion circuit is connected to the positive pole of the DC bus, the negative output terminal of the DC conversion circuit is connected to the negative pole of the DC bus, the positive pole of the DC bus is connected to the positive input terminal of the inverter circuit, the negative pole of the DC bus is connected to the negative input terminal of the inverter circuit, and the positive pole of the DC bus is used to connect to the positive pole of the energy storage device, and the negative pole of the DC bus is used to connect to the positive pole of the energy storage device. The first switch is used to connect the negative pole of the energy storage device, the negative input end of the DC conversion circuit is used to connect the positive pole of the voltage compensation component, and the negative pole of the voltage compensation component is connected to the ground. The first switch is arranged between the negative input end of the DC conversion circuit and the negative pole of the DC bus, and is used to control the on-off between the negative input end of the DC conversion circuit and the negative pole of the DC bus; the inverter also includes a controller, which is used to: when the output voltage and / or output current of the photovoltaic component is less than or equal to the threshold, control the first switch to be disconnected, and control the voltage compensation component to operate, so that the voltage of the negative pole of the photovoltaic component to the ground is raised to zero voltage or positive voltage.

[0025] According to the above technical solution, when the output voltage and / or output current of the photovoltaic module is less than or equal to a threshold, the controller controls the first switch to open, thereby disconnecting the negative pole of the photovoltaic module from the negative pole of the DC bus. Furthermore, the controller controls the voltage compensation component to operate, thereby raising the voltage between the negative pole (PV-) of the photovoltaic module and the earth (PE) to a zero voltage or positive voltage, thereby implementing PID compensation for the photovoltaic module at night. Furthermore, in the embodiments of the present application, an isolation transformer is not required, which greatly reduces costs, the number of components, and the size, while further improving the power generation efficiency of the photovoltaic storage system.

[0026] In conjunction with the second aspect, in certain implementations of the second aspect, the voltage compensation component includes a voltage compensation module and a second switch, the voltage compensation module and the second switch being connected in series, the voltage compensation module outputting a positive voltage, and the controller being specifically configured to control the second switch to close to operate the voltage compensation component. According to the above technical solution, PID compensation can be performed on photovoltaic modules at night, thereby resolving PID issues in photovoltaic modules in a solar-storage system.

[0027] In combination with the second aspect, in certain implementations of the second aspect, the controller is further used to: when the voltage of the DC bus is less than or equal to a first preset value, control the switching tube of the DC conversion circuit to an open-loop switching mode; wherein, when the switching tube is in the open-loop switching mode, the voltage across the first switch decreases.

[0028] According to the above technical solution, when the energy storage device in the solar-storage system experiences a low-limit shutdown (e.g., a battery SOC low-limit shutdown, a device failure, a low battery charge, or manual shutdown of the energy storage switch), the first switch can be safely closed before the solar-storage system shuts down. This prevents contact damage, increased contact impedance, and even damage to the first switch, thereby improving overall system reliability.

[0029] In combination with the second aspect, in certain implementations of the second aspect, the controller is also used to: control the first switch to close when the voltage value across the first switch is less than or equal to a second preset value, and the second preset value is a safe shutdown voltage value across the first switch.

[0030] According to the above technical solution, when the energy storage device in the solar-storage system experiences a low-limit shutdown (e.g., a battery SOC low-limit shutdown, a device failure, a low battery charge, or manual shutdown of the energy storage switch), the first switch can be safely closed before the solar-storage system shuts down. This prevents contact damage, increased contact impedance, and even damage to the first switch, thereby improving overall system reliability.

[0031] In combination with the second aspect, in certain implementations of the second aspect, the controller is further configured to: control the first switch to close when the duration of the switch tube being in the open-loop ripple mode is greater than or equal to a preset duration.

[0032] According to the above technical solution, when the energy storage device in the solar-storage system experiences a low-limit shutdown (e.g., a battery SOC low-limit shutdown, a device failure, a low battery charge, or manual shutdown of the energy storage switch), the first switch can be safely closed before the solar-storage system shuts down. This prevents contact damage, increased contact impedance, and even damage to the first switch, thereby improving overall system reliability.

[0033] In conjunction with the second aspect, in certain implementations of the second aspect, the controller is further configured to: when the output voltage and / or output current of the photovoltaic module exceeds the threshold, control the first switch to close and control the voltage compensation component to stop operating. According to the above technical solution, PID compensation can be performed on the photovoltaic module at night to resolve the PID problem of the photovoltaic module in the solar energy storage system.

[0034] In combination with the second aspect, in certain implementations of the second aspect, when the switching tube is in the open-loop wave transmission mode, the voltage across the first switch decreases as the duration of the switching tube in the open-loop wave transmission mode increases, wherein the relationship between the voltage and the duration satisfies a linear function.

[0035] According to the above technical solution, when the energy storage device in the solar-storage system experiences a low-limit shutdown (e.g., a battery SOC low-limit shutdown, a device failure, a low battery charge, or manual shutdown of the energy storage switch), the first switch can be safely closed before the solar-storage system reaches the low-limit shutdown state. This prevents contact damage, increased contact impedance, and even damage to the first switch, thereby improving overall system reliability.

[0036] In conjunction with the second aspect, in certain implementations of the second aspect, the inverter further includes a first diode connected in parallel across the first switch, wherein a forward current of the first diode is in a direction opposite to a current flowing through the first switch when the first switch is closed. According to the above technical solution, providing the first diode in anti-parallel connection across the first switch can eliminate the effects of overvoltage in the circuit.

[0037] In combination with the second aspect, in some implementations of the second aspect, the first switch includes any one of the following: a relay, a metal oxide semiconductor field effect transistor (MOSFIT), and an insulated gate bipolar transistor (IGBT).

[0038] In combination with the second aspect, in certain implementations of the second aspect, the switch tube includes any one of the following: a metal oxide semiconductor field effect transistor (MOSFIT) and an insulated gate bipolar transistor (IGBT).

[0039] In a third aspect, a control method is provided, which includes: obtaining the output voltage and / or output current of a photovoltaic component; when the output voltage and / or output current of the photovoltaic component is less than or equal to a threshold value, controlling the first switch to disconnect, and controlling the voltage compensation component to operate, so that the voltage of the negative pole of the photovoltaic component to the ground is raised to zero voltage or positive voltage, wherein the positive pole of the voltage compensation component is used to connect the negative pole of the photovoltaic component, and the negative pole of the voltage compensation component is connected to the ground, wherein the first switch is arranged between the connection point of the voltage compensation component and the negative input end of the DC conversion circuit and the negative pole of the DC bus, and is used to control the on and off between the voltage compensation component and the negative pole of the DC bus, the negative pole of the DC bus is connected to the negative pole of the energy storage device, and the positive pole of the DC bus is connected to the positive pole of the energy storage device.

[0040] According to the above technical solution, when the output voltage and / or output current of the photovoltaic module is less than or equal to a threshold, the controller controls the first switch to open, thereby disconnecting the negative pole of the photovoltaic module from the negative pole of the DC bus. Furthermore, the controller controls the voltage compensation component to operate, thereby raising the voltage between the negative pole (PV-) of the photovoltaic module and the earth (PE) to a zero voltage or positive voltage, thereby implementing PID compensation for the photovoltaic module at night. Furthermore, in the embodiments of the present application, an isolation transformer is not required, which greatly reduces costs, the number of components, and the size, while further improving the power generation efficiency of the photovoltaic storage system.

[0041] In combination with the third aspect, in certain implementations of the third aspect, the method further includes: obtaining the voltage of the DC bus; when the voltage of the DC bus is less than or equal to a first preset value, controlling the switching tube of the DC conversion circuit to operate in an open-loop switching mode; wherein, when the switching tube is in the open-loop switching mode, the voltage across the first switch decreases.

[0042] According to the above technical solution, when the energy storage device in the solar-storage system experiences a low-limit shutdown (e.g., a battery SOC low-limit shutdown, a device failure, a low battery charge, or manual shutdown of the energy storage switch), the first switch can be safely closed before the solar-storage system reaches the low-limit shutdown state. This prevents contact damage, increased contact impedance, and even damage to the first switch, thereby improving overall system reliability.

[0043] In combination with the third aspect, in certain implementations of the third aspect, the method further includes: obtaining a voltage value across the first switch; when the voltage value across the first switch is less than or equal to a second preset value, controlling the first switch to close, and the second preset value is a safe shutdown voltage value across the first switch.

[0044] According to the above technical solution, when the energy storage device in the solar-storage system experiences a low-limit shutdown (e.g., a battery SOC low-limit shutdown, a device failure, a low battery charge, or manual shutdown of the energy storage switch), the first switch can be safely closed before the solar-storage system reaches the low-limit shutdown state. This prevents contact damage, increased contact impedance, and even damage to the first switch, thereby improving overall system reliability.

[0045] In combination with the third aspect, in certain implementations of the third aspect, the method further includes: when the duration of the switch tube being in the open-loop wave transmission mode is greater than or equal to a preset duration, controlling the first switch to close.

[0046] According to the above technical solution, when the energy storage device in the solar-storage system experiences a low-limit shutdown (e.g., a battery SOC low-limit shutdown, a device failure, a low battery charge, or manual shutdown of the energy storage switch), the first switch can be safely closed before the solar-storage system reaches the low-limit shutdown state. This prevents contact damage, increased contact impedance, and even damage to the first switch, thereby improving overall system reliability.

[0047] In conjunction with the third aspect, in certain implementations of the third aspect, the method further includes: controlling the first switch to close and the voltage compensation component to stop operating when the output voltage and / or output current of the photovoltaic module exceeds the threshold. According to the above technical solution, PID compensation can be performed on the photovoltaic module at night to resolve the PID problem of the photovoltaic module in the solar-storage system.

[0048] In combination with the third aspect, in certain implementations of the third aspect, the voltage across the first switch decreases, including: the voltage across the first switch decreases as the duration that the switch tube is in the open-loop wave transmission mode increases, wherein the relationship between the voltage and the duration satisfies a linear function.

[0049] According to the above technical solution, when the energy storage device in the solar-storage system experiences a low-limit shutdown (e.g., a battery SOC low-limit shutdown, a device failure, a low battery charge, or manual shutdown of the energy storage switch), the first switch can be safely closed before the solar-storage system reaches the low-limit shutdown state. This prevents contact damage, increased contact impedance, and even damage to the first switch, thereby improving overall system reliability.

[0050] In combination with the third aspect, in certain implementations of the third aspect, the first switch includes any one of the following: a relay, a metal oxide semiconductor field effect transistor (MOSFIT), and an insulated gate bipolar transistor (IGBT).

[0051] In combination with the third aspect, in certain implementations of the third aspect, the switch tube includes any one of the following: a metal oxide semiconductor field effect transistor (MOSFIT) and an insulated gate bipolar transistor (IGBT). BRIEF DESCRIPTION OF THE DRAWINGS

[0052] FIG1 is a schematic diagram of an application scenario of a photovoltaic storage system 100 provided in an embodiment of the present application.

[0053] FIG2 is a schematic structural diagram of a solar storage system 100 provided in yet another embodiment of the present application.

[0054] FIG3 is a schematic structural diagram of a solar storage system 100 provided in another embodiment of the present application.

[0055] FIG4 is a schematic structural diagram of a solar storage system 100 provided in yet another embodiment of the present application.

[0056] FIG5 is a schematic structural diagram of a DC conversion circuit 121 provided in an embodiment of the present application.

[0057] FIG6 is a schematic diagram of a current path of a switch tube Q1 in a DC conversion circuit 121 provided in an embodiment of the present application when in an open-loop wave generation mode.

[0058] FIG7 is a schematic diagram showing how the voltage across the first switch S1 changes with time when the switch tube Q1 is in the open-loop wave generating mode.

[0059] FIG8 is a schematic flow chart of a control method 800 provided in an embodiment of the present application.

[0060] FIG9 is a schematic flow chart of a control method 800 provided in yet another embodiment of the present application.

[0061] FIG10 is a schematic flow chart of a control method 800 provided in yet another embodiment of the present application. DETAILED DESCRIPTION

[0062] The technical solution in this application will be described below with reference to the accompanying drawings.

[0063] In the description of the embodiments of the present application, unless otherwise specified, “ / ” means or, for example, A / B can mean A or B; “and / or” in this article is merely a way to describe the association relationship of associated objects, indicating that three relationships can exist, for example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone.

[0064] In the embodiments of the present application, prefixes such as "first" and "second" are used only to distinguish different description objects and have no limiting effect on the position, order, priority, quantity or content of the described objects. The use of prefixes such as ordinal numbers to distinguish description objects in the embodiments of the present application does not constitute a restriction on the described objects. For the statement of the described objects, please refer to the description in the context of the claims or embodiments, and the use of such prefixes should not constitute an unnecessary restriction. In addition, in the description of this embodiment, unless otherwise specified, the meaning of "plurality" is two or more.

[0065] References to "in some embodiments" and the like in this specification mean that a particular feature, structure, or characteristic described in connection with that embodiment is included in one or more embodiments of the present application. Thus, phrases such as "in some embodiments" and the like appearing in different places in this specification do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized. The terms "including," "comprising," "having," and variations thereof all mean "including but not limited to," unless otherwise specifically emphasized.

[0066] The application scenario of the photovoltaic storage system provided in the embodiment of the present application is described in detail below with reference to FIG1 .

[0067] Figure 1 is a schematic diagram of an application scenario for a photovoltaic storage system 100 provided in an embodiment of the present application. As shown in Figure 1 , the devices in the application scenario of photovoltaic storage system 100 include: photovoltaic modules 110, photovoltaic inverters 120, and energy storage devices 130. Optionally, photovoltaic storage system 100 may also include: a power grid 140 and a load 150.

[0068] Specifically, photovoltaic assembly 110, also known as a photovoltaic array, includes multiple photovoltaic strings. Photovoltaic is also called photovoltaic, or simply PV. A string is also called a string. Each photovoltaic string includes multiple photovoltaic panels connected in series. Photovoltaic panels are used to convert light energy into electrical energy. The electrical energy generated by photovoltaic panels is direct current (DC). The voltage across a photovoltaic string is equal to the sum of the voltages generated by the multiple photovoltaic panels. The output power of photovoltaic assembly 110 can represent the electrical energy output per unit time by the photovoltaic assembly.

[0069] PV inverter 120 can convert direct current (DC) from PV panels 110 into alternating current (AC) and transmit the AC power to grid 140 or load 150. Alternatively, PV inverter 120 can transmit the DC power from PV panels 110 to energy storage device 130 for charging. It should be noted that direct current (DC) is also called direct current, and alternating current (AC) is also called alternating current. PV inverter 120 can also be referred to as a DC-AC converter or inverter circuit (DC-AC).

[0070] Optionally, the photovoltaic inverter 120 may further include a voltage stabilizing module (not shown in the figure), which can realize the voltage stabilization function of the voltage output by the power generation module. Exemplarily, the voltage stabilizing module can be a DC-DC converter, or a DC-DC converter, or a DC conversion circuit (DC-DC). As an example, the DC conversion circuit (DC-DC) can be set in the maximum power point tracking (MPPT) module in the photovoltaic inverter. It should be noted that the DC conversion circuit (DC-DC) is usually set before the inverter circuit (DC-AC) in the photovoltaic inverter 120, and is used to stabilize the DC power output by the photovoltaic module 110 and output it to the inverter circuit.

[0071] Continuing with Figure 1 , energy storage device 130 in solar-storage system 100 can store and release electrical energy. For example, energy storage device 130 can store DC power from photovoltaic modules 110. Energy storage device 130 can also power grid 140 or load 150 via photovoltaic inverter 120. Therefore, energy storage device 130 has a wide range of applications, including but not limited to household applications, industrial green power applications, and smart photovoltaic power plant scenarios.

[0072] As can be seen from the above description, photovoltaic inverter 120 is a converter that can convert direct current (DC) into alternating current (AC). Specifically, photovoltaic inverter 120 can include two DC ports (e.g., DC port 1 and DC port 2) and an AC port. The two DC ports are used to connect photovoltaic module 110 and energy storage device 130, respectively. For example, DC port 1 is used to connect photovoltaic module 110, and DC port 2 is used to connect energy storage device 130. The AC port can be used to output AC power, which can be distributed through a distribution box (not shown), such as to grid 140 and load 150.

[0073] PV panels 110 can feed power to grid 140 and supply power to load 150 via the DC port. Energy storage device 130 can supply power to load 150 via the DC port. Grid 140 can supply power to load 150 via the AC port. In other words, PV inverter 130 serves as the connection hub between load 150 and the energy module (which may include PV panels 110, energy storage device 130, and grid 140).

[0074] In the practical application of solar-storage systems, during daytime grid-connected power generation, the high voltage between the circuits in the PV modules and their grounded metal frames causes a continuous degradation in the PV module's power generation performance, a phenomenon known as potential-induced degradation (PID). However, due to the presence of energy storage devices in solar-storage systems, the inverter (or inverter circuit) in the solar-storage system continues to operate connected to the grid at night. At this time, the negative pole (PV-) of the PV module maintains a negative voltage relative to the earth (PE). Therefore, existing solar-storage systems are unable to perform PID compensation on the PV modules at night.

[0075] Currently, the industry uses isolated inverters, such as high-frequency transformer isolation solutions and power-frequency transformer isolation solutions, to achieve PID compensation for photovoltaic modules in solar-storage systems at night. However, the isolated inverters used in these solutions have a large number of components, are larger in size, and are more expensive. Furthermore, the presence of the transformer can reduce the power generation efficiency of the photovoltaic system.

[0076] Based on this, the present application aims to provide a photovoltaic storage system that can perform PID compensation on photovoltaic modules at night to solve the PID problem of photovoltaic modules in the photovoltaic storage system, and can reduce costs and further improve the power generation efficiency of the photovoltaic storage system.

[0077] FIG2 is a schematic structural diagram of a solar storage system 100 provided in yet another embodiment of the present application.

[0078] As shown in FIG2 , the photovoltaic storage system 100 includes an inverter 120 , an energy storage device 130 and a voltage compensation component 160 , wherein the inverter further includes a DC conversion circuit 121 , an inverter circuit 122 and a DC bus.

[0079] Specifically, the positive input terminal of the DC conversion circuit 121 is used to connect to the positive electrode of the photovoltaic module 110, and the negative input terminal of the DC conversion circuit 121 is used to connect to the negative electrode of the photovoltaic module 110. The photovoltaic module 110 is used to convert light energy into direct current. It should be noted that the input terminals (positive input terminal and negative input terminal) of the DC conversion circuit 121 can be used to connect to one or more photovoltaic modules 110. It should be understood that this embodiment of the present application does not limit this. In addition, the specific description of the photovoltaic module 110 can be referred to the above, and will not be repeated here.

[0080] The positive output terminal of the DC conversion circuit 121 is connected to the positive pole of the DC bus, and the negative output terminal of the DC conversion circuit 121 is connected to the negative pole of the DC bus. The positive pole of the DC bus is connected to the positive input terminal of the inverter circuit 122 and the positive pole of the energy storage device 130, and the negative pole of the DC bus is connected to the negative input terminal of the inverter circuit 122 and the negative pole of the energy storage device 130. The DC conversion circuit 121 is used to convert the voltage of the input DC power and output it, while the inverter circuit 122 is used to convert the input DC power into AC power for output.

[0081] Optionally, the DC conversion circuit 121 may be a Boost circuit. Exemplarily, the DC conversion circuit 121 may be an MPPT circuit, or may be a circuit capable of implementing an MPPT function. It should be understood that this application does not impose any limitation on this.

[0082] It should be noted that the DC conversion circuit 121 is equivalent to the voltage stabilizing module described above, and the inverter circuit 122 is equivalent to the DC-AC converter described above. The relevant descriptions of the DC conversion circuit 121, the inverter circuit 122 and the energy storage device 130 can also be referred to the above and will not be repeated here.

[0083] Optionally, the energy storage device 130 may include a battery module. For example, the battery module may also be referred to as a battery pack.

[0084] Optionally, the energy storage device 130 may further include a direct current (DC)-DC conversion circuit, which is electrically connected to the battery module.

[0085] Continuing with FIG2 , the positive pole of the voltage compensation component 160 is used to connect to the negative pole (PV-) of the photovoltaic component 110, and the negative pole of the voltage compensation component 160 is connected to the ground (PE). The voltage compensation component 160 is used to perform PID compensation on the photovoltaic component when the output voltage and / or output current of the photovoltaic component 110 is less than or equal to a threshold value, so that the voltage of the negative pole of the photovoltaic component 110 relative to the ground is raised to zero voltage or positive voltage.

[0086] In an embodiment of the present application, the photovoltaic storage system 100 also includes a first switch 170, wherein the first switch 170 is arranged between the connection point of the voltage compensation component 160 and the negative input end of the DC conversion circuit 121 and the negative pole of the DC bus, and is used to control the on and off between the voltage compensation component 160 and the negative pole of the DC bus.

[0087] It should be noted that the first switch 170 is disposed at the connection point between the voltage compensation component 160 and the negative input terminal of the DC conversion circuit 121 and the negative pole of the DC bus, and there are several possible examples. Specifically, FIG3 is a schematic structural diagram of a photovoltaic storage system 100 provided in another embodiment of the present application. As shown in FIG3 , the location of the first switch 170 in the photovoltaic storage system 100 is as follows.

[0088] Exemplarily, the first switch 170 may be provided between a connection point between the voltage compensation component 160 and the negative input terminal of the DC conversion circuit 121 and the negative input terminal of the DC conversion circuit 121 , as shown in FIG2 .

[0089] Exemplarily, the first switch 170 may be provided between the negative input terminal of the DC conversion circuit 121 and the negative output terminal of the DC conversion circuit 121 , as shown in FIG3( a ).

[0090] Exemplarily, the first switch 170 may be provided between the negative output terminal of the DC conversion circuit 121 and the negative electrode of the DC bus, as shown in FIG3( b ).

[0091] It should be understood that the position of the first switch 170 is merely an example and is not limited to this embodiment of the present application.

[0092] Furthermore, the photovoltaic storage system 100 may further include a controller (not shown). The controller is configured to, when the output voltage and / or output current of the photovoltaic module 110 is less than or equal to a threshold, control the first switch 170 to be disconnected and control the voltage compensation component 160 to operate, so that the voltage between the negative electrode of the photovoltaic module 110 and the ground is raised to zero voltage or a positive voltage.

[0093] Specifically, the output voltage and / or output current of the photovoltaic assembly 110 being less than or equal to the threshold value can be understood as indicating that, at night, the photovoltaic assembly 110 no longer converts light energy into direct current, and the current or voltage output by the photovoltaic assembly 110 is less than or equal to the threshold value. Specifically, for the photovoltaic storage system 100, at night, the energy storage device 130 provides energy to the inverter circuit 122, and the inverter circuit 122 continues to operate in grid-connected mode. When the output voltage and / or output current of the photovoltaic assembly 110 is less than or equal to the threshold value, the controller controls the first switch 170 to disconnect and controls the voltage compensation assembly 160 to operate. Among them, controlling the operation of the voltage compensation component 160 can be understood as controlling the voltage compensation component 160 to output a positive voltage, so that when the connection between the negative pole (PV-) of the photovoltaic component 110 and the negative input terminal of the inverter circuit 122 is disconnected, the voltage compensation component 160 can output a positive voltage to the negative pole (PV-) of the photovoltaic component 110, so that the voltage of the negative pole (PV-) of the photovoltaic component 110 to the earth (PE) is raised to zero voltage or positive voltage, thereby realizing PID compensation of the photovoltaic component 110 at night.

[0094] For example, in one possible implementation, the controller is configured to: when the output voltage of the photovoltaic assembly 110 is less than or equal to a threshold, control the first switch 170 to be disconnected. It should be understood that the threshold in this case is a voltage threshold.

[0095] For example, in one possible implementation, the controller is configured to: when the output current of the photovoltaic assembly 110 is less than or equal to a threshold, control the first switch 170 to be disconnected. It should be understood that the threshold in this case is a current threshold.

[0096] For example, in one possible implementation, the controller is configured to control first switch 170 to open when both the output voltage and output current of photovoltaic assembly 110 are less than or equal to threshold values. It should be understood that the threshold values ​​in this case are a current threshold and a voltage threshold, respectively. That is, when both the output voltage and output current are less than or equal to the threshold values, it can be understood that the output voltage is less than or equal to the voltage threshold, and the output current is also less than or equal to the current threshold.

[0097] FIG4 is a schematic structural diagram of a solar storage system 100 provided in yet another embodiment of the present application.

[0098] Optionally, in one possible implementation, the voltage compensation component 160 is a voltage compensation module 161. Specifically, as shown in (a) of Figure 4, when the output voltage and / or output current of the photovoltaic component 110 is less than or equal to a threshold, the controller controls the first switch 170 to disconnect and controls the voltage compensation module 161 to operate so that the voltage of the negative pole of the photovoltaic component 110 to the ground is raised to zero voltage or positive voltage.

[0099] Here, controlling the voltage compensation module 161 to work can be understood as controlling the voltage compensation module 161 to output a positive voltage.

[0100] Optionally, in one possible implementation, the voltage compensation component 160 includes a voltage compensation module 161 and a second switch 162, as shown in FIG4(b) or FIG4(c). The voltage compensation module 161 and the second switch 162 are connected in series, that is, the positive or negative electrode of the voltage compensation module 161 is connected to the second switch 162, and the voltage compensation module 161 continuously outputs a positive voltage.

[0101] Specifically, when the output voltage and / or output current of the photovoltaic component 110 is less than or equal to the threshold, the controller controls the first switch 170 to be disconnected and controls the second switch 162 to be closed, so that the voltage compensation component 160 works, thereby raising the voltage of the negative pole of the photovoltaic component 110 to the ground to zero voltage or positive voltage.

[0102] Here, controlling the voltage compensation component 160 to work can be understood as controlling the voltage compensation component 160 to output a positive voltage.

[0103] Optionally, in another possible implementation, the controller is further configured to: when the output voltage and / or output current of the photovoltaic assembly 110 is greater than a threshold, control the first switch 170 to be closed (turned on).

[0104] Among them, the output voltage and / or output current of the photovoltaic component 110 is greater than the threshold value. It can be understood that during the day, the photovoltaic component 110 converts solar energy into direct current output. At this time, the controller controls the first switch 170 to be turned on, and the photovoltaic component 110, the inverter circuit 122, etc. in the solar storage system 100 operate normally. At this time, the voltage compensation component 160 does not perform PID compensation to the negative pole (PV-) of the photovoltaic component 110.

[0105] Optionally, in a possible implementation, the controller is further configured to: when the output voltage and / or output current of the photovoltaic component 110 is greater than a threshold, control the first switch 170 to close (turn on) and control the voltage compensation component 160 to stop working.

[0106] It should be noted that the voltage compensation component 160 stopping working can be understood as the voltage compensation component 160 stopping outputting a positive voltage. Specifically, the controller can control the voltage compensation component 160 to stop working while controlling the first switch 170 to be turned on.

[0107] Exemplarily, when the voltage compensation component 160 is the voltage compensation module 161 , while controlling the first switch 170 to be turned on, the voltage compensation module 161 is controlled to stop working, that is, the voltage compensation module 161 no longer outputs a positive voltage.

[0108] For example, when voltage compensation assembly 160 includes voltage compensation module 161 and second switch 162, controlling first switch 170 to be turned on while simultaneously controlling voltage compensation assembly 160 to stop operating can be considered as controlling second switch 162 in voltage compensation assembly 160 to be turned off. That is, when second switch 162 is turned off, the electrical connection between the negative electrode (PV-) of photovoltaic assembly 110 and voltage compensation assembly 160 is severed, and voltage compensation assembly 160 no longer outputs a positive voltage, i.e., voltage compensation assembly 160 stops operating.

[0109] It should also be noted that in the embodiment of the present application, the controller can also manually control the voltage compensation component 160 to stop working while controlling the first switch 170 to be turned on. It should be understood that the embodiment of the present application is not limited to this.

[0110] It should also be noted that the execution order of the controller controlling the conduction of the first switch 170 and the controller controlling the voltage compensation component 160 to stop working is not prioritized. It should be understood that the above content is only an example and this application does not limit this.

[0111] It should be noted that the first switch 170 mentioned above can be a relay, or a metal oxide semiconductor field effect transistor (MOSFIT), or an insulated gate bipolar transistor (IGBT). It should be understood that the embodiment of the present application is not limited to this.

[0112] Optionally, in one possible implementation, the photovoltaic storage system 100 further includes a first diode D1, which is connected in parallel to both ends of the first switch 170, wherein the direction of the forward current of the first diode D1 is opposite to the direction of the current flowing when the first switch 170 is closed.

[0113] Specifically, as shown in Figure 3(b), the direction of the forward current of the first diode D1 is opposite to the direction of the current flowing through the first switch 170 when it is closed. This means that the first diode D1 is connected in antiparallel across the first switch 170. It should be understood that the purpose of providing the first diode D1 is to eliminate the effects of overvoltage. For example, when the photovoltaic module 110 outputs a voltage, the voltage difference across the first switch 170 is first eliminated by the first diode D1 before the first switch 170 is closed.

[0114] It should be noted that the position of the first switch 170 shown in FIG3(b) is for illustration only. Since the first diode D1 can be provided in antiparallel connection at both ends of the first switch 170, the position of the first diode D1 is not limited to that shown in FIG3(b). It should be understood that the present application does not impose any limitation on this.

[0115] In summary, according to the above technical solution, when the output voltage and / or output current of the photovoltaic module is less than or equal to the threshold, the controller controls the first switch to open, thereby disconnecting the negative pole of the photovoltaic module from the negative pole of the DC bus. Furthermore, the controller controls the voltage compensation component to operate so that the voltage between the negative pole (PV-) of the photovoltaic module and the earth (PE) is raised to zero voltage or a positive voltage, thereby achieving PID compensation for the photovoltaic module at night. Furthermore, in the embodiments of the present application, an isolation transformer is not required, which greatly reduces costs, the number of components, and the size, while further improving the power generation efficiency of the photovoltaic storage system.

[0116] However, if the energy storage device in the solar-storage system reaches a lower limit and shuts down (for example, due to a battery SOC lower limit shutdown, a storage device failure, a lower power limit, or manual shutdown of the energy storage switch), the solar-storage system loses power. To ensure that the solar-storage system can operate normally when the photovoltaic panels have output voltage or output current during the day, it is necessary to control the first switch to close before the energy storage device reaches a lower limit and shuts down.

[0117] However, because the PV-storage system continues to operate in grid-connected mode at night, when the first switch is controlled to be open, the voltage compensation component raises the voltage between the negative pole (PV-) of the PV module and the earth (PE) to zero or positive voltage. Meanwhile, the negative pole (BUS-) of the DC bus in the PV-storage system is at a negative voltage relative to the earth. Consequently, a large voltage difference exists across the first switch. In this situation, closing the first switch by the controller could damage the first switch contacts, increase contact impedance, and affect overall system reliability. In severe cases, it could even damage the first switch.

[0118] To avoid the aforementioned problem with the first switch, in the embodiment of the present application, the controller is further configured to control the switching transistor Q1 in the DC converter circuit 121 to operate in an open-loop mode when the voltage of the DC bus is less than or equal to a first preset value. The first preset value is a pre-set voltage value.

[0119] It should be understood that the DC bus voltage can be considered as the input bus voltage of the inverter circuit 122 in the inverter, or the input bus voltage of the auxiliary power source in the inverter 120. When the DC bus voltage is less than or equal to the first preset value, it can be understood that the energy storage device 130 in the solar-storage system 100 has reached a lower limit shutdown state, and in this case, the energy storage device 130 does not provide energy to the inverter 120.

[0120] It should be noted that when the controller controls the switch tube Q1 in the DC conversion circuit 121 to be in the open-loop wave generating mode, the voltage across the first switch 170 decreases.

[0121] The structure of the DC converter circuit 121 and the current path of the switch tube in the DC converter circuit in the open-loop wave-generating mode are described in detail below with reference to Figures 5 and 6. Figure 5 is a schematic structural diagram of a DC converter circuit 121 according to an embodiment of the present application, and Figure 6 is a schematic diagram of the current path of the switch tube Q1 in the DC converter circuit 121 according to an embodiment of the present application in the open-loop wave-generating mode.

[0122] As shown in Figure 5, the DC conversion circuit 121 includes: a positive input terminal, a negative input terminal, an inductor L1, a first switch S1, a second diode D2, a switch tube Q1 and a bus capacitor C1, a positive output terminal (BUS+), and a negative output terminal (BUS-). The positive input terminal and the negative input terminal are used to connect to one or more photovoltaic modules (not shown in the figure), and the positive output terminal (BUS+) and the negative output terminal (BUS-) are used to connect to the DC bus. One end of the bus capacitor C1 is connected to the positive output terminal (BUS+), and the other end of the bus capacitor C1 is connected to the negative output terminal (BUS-).

[0123] It should be understood that the first switch S1 is equivalent to the first switch 170 described above. For ease of understanding, the first switch S1 will be uniformly used for detailed description below.

[0124] It should be noted that the switch tube Q1 can be a metal oxide semiconductor field effect transistor (MOSFIT) or an insulated gate bipolar transistor (IGBT). It should be understood that the embodiment of the present application does not limit this.

[0125] Specifically, one end of the inductor L1 is connected to the positive input terminal, the other end of the inductor L1 is connected to the anode of the second diode D2, the anode of the second diode D2 is also connected to the first end of the switch tube Q1, the cathode of the second diode D2 is connected to the positive output terminal (BUS+), the second end of the switch tube Q1 is connected to the negative output terminal (BUS-), and the second end of the switch tube Q1 is also connected to one end of the first switch S1, and the other end of the first switch S1 is connected to the negative input terminal.

[0126] Optionally, when the switch tube Q1 is a MOS tube, the first end is the drain and the second end is the source. That is, the anode of the second diode D2 is also connected to the drain of the switch tube Q1, the source of the switch tube Q1 is connected to the negative output terminal (BUS-), and the source of the switch tube Q1 is also connected to one end of the first switch S1.

[0127] Optionally, when the switch tube Q1 is an IGBT, the first end is the emitter and the second end is the collector. That is, the anode of the second diode D2 is also connected to the emitter of the switch tube Q1, the collector of the switch tube Q1 is connected to the negative output terminal (BUS-), and the collector of the switch tube Q1 is also connected to one end of the first switch S1.

[0128] Optionally, the DC conversion circuit 121 may further include a filter capacitor C2 , wherein one end of the filter capacitor C2 is connected to the positive input end, and the other end of the filter capacitor C2 is connected to the negative input end.

[0129] Optionally, the DC conversion circuit 121 may further include a common-mode inductor, wherein the input ports (positive input and negative input) of the DC conversion circuit 121 are connected to the input port of the common-mode inductor, and the output ports of the common-mode inductor are connected to the output ports (positive output and negative output) of the DC conversion circuit 121. The common-mode inductor is used to filter common-mode noise in the AC power.

[0130] Optionally, the DC conversion circuit 121 may further include a filter capacitor C3 , wherein one end of the filter capacitor C3 is connected to the positive input end, and the other end of the filter capacitor C3 is connected to the negative input end.

[0131] It should be noted that the specific structure of the DC converter circuit 121 shown in FIG5 is only for illustration, and it should be understood that the present invention is not limited thereto. For example, the position of the first switch S1 is not limited to the position shown in FIG5 .

[0132] Furthermore, when the controller controls the switch tube Q1 to be in the open-loop ripple generation mode, the current path in the DC conversion circuit 121 is as shown in FIG6 .

[0133] Referring to Figure 6(a), when switch Q1 turns on, current flows from Y-capacitor C4 through the PV module (or its equivalent diode), inductor L1, switch Q1, Y-capacitor C5, and ultimately to the chassis, forming a loop. At this point, the energy in Y-capacitors C1 and C5 is transferred to inductor L1 through the current flow shown in Figure 6(a).

[0134] However, when the switch tube Q1 is turned off, the current on the inductor L1 continues to flow, and the current path is shown in FIG6( b ). The second diode D2 is turned on, and the current flows through the bus capacitor C1 .

[0135] In this way, as the switch tube Q1 is continuously turned on and off in the open-loop wave generation mode, the energy on the Y capacitor C4 and the Y capacitor C5 can be released, thereby causing the voltage across the first switch S1 to continuously decrease.

[0136] Figure 7 is a schematic diagram illustrating how the voltage across the first switch S1 varies over time (or duration) when the switch Q1 is in open-loop ripple mode. It should be noted that the waveforms shown in Figure 7 specifically include: waveforms of the voltage across the first switch S1 (e.g., waveforms 1, 2, and 3) and the drive waveform of the switch Q1 in open-loop ripple mode (e.g., waveform 4).

[0137] As can be seen from Figure 7, when switch Q1 is not in open-loop ripple mode, that is, before time t0, the controller does not control switch Q1 to be in open-loop ripple mode. It can be seen that the voltage across first switch S1 drops slowly (waveform 1). When switch Q1 is in open-loop ripple mode, that is, after time t0, the controller controls switch Q1 to be in open-loop ripple mode. It can be seen that in open-loop ripple mode, due to the continuous on and off of switch Q1, the voltage across first switch S1 drops rapidly (waveform 2).

[0138] For example, it can be seen that the voltage across the first switch decreases as the duration (or time) that the switch is in the open-loop ripple mode increases, where the relationship between voltage and duration satisfies a linear function. In other words, the voltage across the first switch satisfies a monotonically decreasing linear function as the duration that the switch is in the open-loop ripple mode increases.

[0139] Optionally, in an embodiment of the present application, the controller is further configured to control the first switch S1 to conduct when the voltage across the first switch S1 is less than or equal to a second preset value. The second preset value is a safe shutoff voltage across the first switch S1, which can be understood as a critical voltage at which the first switch S1 can safely conduct. In other words, when the voltage across the first switch S1 is less than or equal to the second preset value, the first switch S1 conducts without causing contact damage, increased contact impedance, or damage to the first switch S1.

[0140] It should be noted that the second preset value is a threshold value set in advance.

[0141] Exemplarily, as shown in FIG7 , the second preset value is taken as a voltage value V2 for illustration.

[0142] Optionally, in a possible implementation, when the voltage value across the first switch S1 is less than or equal to the voltage value V2, the controller controls the first switch S1 to be turned on.

[0143] On the contrary, when the voltage across the first switch S1 is greater than the voltage value V2, the controller controls the first switch S1 to remain off until the detection device detects that the voltage across the first switch S1 is less than or equal to the voltage value V2, and then the controller controls the first switch S1 to be on.

[0144] Optionally, in a possible implementation, the controller is further configured to control the first switch S1 to be turned on when the duration of the switch tube being in the open-loop ripple mode is greater than or equal to a preset duration.

[0145] It should be understood that the preset time is the time required for the voltage across the first switch S1 to drop to the second preset value when the switch tube is in the open-loop wave transmission mode. It should be understood that the description of the second preset value can be referred to above and will not be repeated here.

[0146] Specifically, the controller starts timing when the switch tube Q1 is in the open-loop wave transmission mode. For example, as shown in Figure 7, the moment when the switch tube Q1 starts to be in the open-loop wave transmission mode is time t0. At this time, the controller starts timing, and when the duration of the switch tube Q1 in the open-loop wave transmission mode is greater than or equal to the preset duration, the first switch S1 is controlled to be turned on.

[0147] As shown in FIG7 , illustratively, taking the second preset value as the voltage value V2 as an example, it can be seen from the figure that the critical moment corresponding to the voltage value V2 is moment t1, that is, the moment corresponding to when the voltage across the first switch S1 drops to V2 is moment t1. At this time, it is assumed that the preset time length is the time period (t1-t0).

[0148] For example, in one possible implementation, the controller begins timing when the switch tube Q1 begins to operate in the open-loop ripple generation mode. Subsequently, when the duration of the switch tube Q1 operating in the open-loop ripple generation mode equals a preset duration, the controller controls the first switch S1 to turn on. For example, the controller may control the first switch S1 to turn on when the timing reaches a preset duration (e.g., a time period (t1-t0)).

[0149] For example, in one possible implementation, the controller begins timing when the switch Q1 begins to operate in the open-loop ripple mode. Subsequently, when the duration of the switch Q1 operating in the open-loop ripple mode exceeds a preset duration, the controller controls the first switch S1 to turn on. In other words, the controller can control the first switch S1 to turn on at any time after the timing reaches a preset duration (e.g., time period (t1-t0)). For example, as shown in FIG7 , the controller can control the first switch S1 to turn on at time t2. The time period (t2-t0) is greater than the time period (t1-t0).

[0150] It should be noted that the open-loop wave transmission mode described above is only an example, and the present application can also be applied to other wave transmission modes. For example, as long as the voltage across the first switch of the switch tube Q1 can be reduced to a certain threshold value (such as a second preset value) in this wave transmission mode, it can be sufficient.

[0151] According to the above technical solution, when the energy storage device in the solar-storage system experiences a shutdown (e.g., due to a battery SOC limit shutdown, a device failure, a battery charge limit, or manual shutdown of the energy storage switch), the first switch S1 can be safely turned on before the solar-storage system shuts down. This prevents contact damage, increased contact impedance, and even damage to the first switch S1, thereby improving overall system reliability.

[0152] FIG8 is a schematic flow chart of a control method 800 provided in an embodiment of the present application. As shown in FIG8 , the control method 800 specifically includes steps S810 and S820, which are described in detail below. It should be noted that the control method can be applied to the aforementioned photovoltaic storage system or to other photovoltaic power generation scenarios, and it should be understood that the present embodiment does not limit this.

[0153] It should be noted in advance that the relevant steps in the embodiments of the present application described below can be executed by the optical storage system, or the corresponding steps can be specifically executed by the controller.

[0154] S810: Obtain the output voltage and / or output current of the photovoltaic module.

[0155] S820, when the output voltage and / or output current of the photovoltaic component is less than or equal to the threshold, control the first switch to be disconnected, and control the voltage compensation component to operate so that the voltage of the negative electrode of the photovoltaic component to the ground is raised to zero voltage or positive voltage.

[0156] Specifically, when the output voltage and / or output current of the photovoltaic module is less than or equal to the threshold, it can be understood that at night, the photovoltaic module no longer converts light energy into direct current, and the output current or voltage of the photovoltaic module is less than or equal to the threshold. Specifically, for a photovoltaic storage system, at night, the energy storage device provides energy to the inverter circuit, and the inverter circuit continues to operate in grid-connected mode. When the output voltage and / or output current of the photovoltaic module is less than or equal to the threshold, the controller controls the first switch to disconnect and controls the voltage compensation component to operate.

[0157] Among them, controlling the operation of the voltage compensation component can be understood as controlling the voltage compensation component 160 to output a positive voltage, so that when the connection between the negative pole (PV-) of the photovoltaic component and the negative input terminal of the inverter circuit is disconnected, the voltage compensation component can output a positive voltage to the negative pole (PV-) of the photovoltaic component, so that the voltage of the negative pole (PV-) of the photovoltaic component to the earth (PE) is raised to zero voltage or positive voltage, thereby realizing PID compensation of the photovoltaic component at night.

[0158] For example, in one possible implementation, the controller obtains the output voltage of the photovoltaic module, and controls the first switch to be disconnected when the output voltage of the photovoltaic module is less than or equal to a threshold value. It should be understood that the threshold value in this case is a voltage threshold value.

[0159] For example, in one possible implementation, the controller obtains the output current of the photovoltaic module, and controls the first switch to be disconnected when the output current of the photovoltaic module is less than or equal to a threshold value. It should be understood that the threshold value in this case is a current threshold value.

[0160] For example, in a possible implementation, the controller obtains the output current and output voltage of the photovoltaic assembly, and controls the first switch to be disconnected when the output voltage and output current of the photovoltaic assembly are both less than or equal to a threshold value.

[0161] It should be understood that the thresholds at this time are the current threshold and the voltage threshold, that is, the output voltage and the output current are both less than or equal to the threshold, which can be understood as the output voltage being less than or equal to the voltage threshold, and the output current being less than or equal to the current threshold.

[0162] Optionally, in one possible implementation, the voltage compensation component is a voltage compensation module. Specifically, as shown in (a) of Figure 4, when the output voltage and / or output current of the photovoltaic component is less than or equal to a threshold, the controller controls the first switch to disconnect and controls the voltage compensation module to operate so that the voltage of the negative pole of the photovoltaic component to the ground is raised to zero voltage or positive voltage.

[0163] Here, controlling the voltage compensation module to work can be understood as controlling the voltage compensation module to output a positive voltage.

[0164] Alternatively, in one possible implementation, the voltage compensation component includes a voltage compensation module and a second switch, as shown in FIG4( b). The voltage compensation module is connected in series with the second switch, that is, the positive electrode of the voltage compensation module is connected to the second switch, and the voltage compensation module continuously outputs a positive voltage.

[0165] Specifically, when the output voltage and / or output current of the photovoltaic component is less than or equal to the threshold, the controller controls the first switch to open and controls the second switch to close, so that the voltage compensation component works, thereby raising the voltage of the negative pole of the photovoltaic component to the ground to zero voltage or positive voltage.

[0166] Here, controlling the voltage compensation component to work can be understood as controlling the voltage compensation component to output a positive voltage.

[0167] Optionally, in another possible implementation, the controller controls the first switch to be turned on when the output voltage and / or output current of the photovoltaic assembly is greater than a threshold value.

[0168] Among them, the output voltage and / or output current of the photovoltaic component is greater than the threshold value, which can be understood as that during the day, the photovoltaic component converts solar energy into direct current output. At this time, the controller controls the first switch to be turned on, and the photovoltaic components, inverter circuits, etc. in the solar storage system operate normally. At this time, the voltage compensation component does not perform PID compensation to the negative pole (PV-) of the photovoltaic component.

[0169] It should be noted that the voltage compensation component stops working, which can be understood as the voltage compensation component stops outputting a positive voltage. Specifically, the controller can control the voltage compensation component to stop working while controlling the first switch to be turned on.

[0170] Exemplarily, when the voltage compensation component is a voltage compensation module, while controlling the first switch to be turned on, the voltage compensation module is controlled to stop working, that is, the voltage compensation module no longer outputs a positive voltage.

[0171] For example, when the voltage compensation assembly includes a voltage compensation module and a second switch, controlling the first switch to conduct while simultaneously controlling the voltage compensation assembly to cease operation can be considered as controlling the second switch in the voltage compensation assembly to be disconnected. That is, when the second switch is disconnected, the electrical connection between the negative electrode (PV-) of the photovoltaic module and the voltage compensation assembly is severed, and the voltage compensation assembly no longer outputs a positive voltage, i.e., the voltage compensation assembly ceases operation.

[0172] It should also be noted that the order in which the controller controls the conduction of the first switch and the controller controls the voltage compensation component to stop working is not specific. It should be understood that the above content is only an example and this application does not limit this.

[0173] It should be noted that the first switch mentioned above can be a relay, or a metal oxide semiconductor field effect transistor (MOSFIT), or an insulated gate bipolar transistor (IGBT). It should be understood that the embodiment of the present application is not limited to this.

[0174] In summary, according to the above technical solution, when the output voltage and / or output current of the photovoltaic module is less than a threshold value, the controller controls the first switch to open, thereby disconnecting the negative pole of the photovoltaic module from the negative pole of the DC bus. Furthermore, the controller controls the voltage compensation component to operate so that the voltage between the negative pole (PV-) of the photovoltaic module and the earth (PE) is raised to zero voltage or a positive voltage, thereby implementing PID compensation for the photovoltaic module at night. Furthermore, in the embodiments of the present application, an isolation transformer is not required, which greatly reduces costs, the number of components, and the size, while further improving the power generation efficiency of the photovoltaic storage system.

[0175] However, if the energy storage device in the solar-storage system reaches a lower limit and shuts down (for example, due to a battery SOC lower limit shutdown, a storage device failure, a lower power limit, or manual shutdown of the energy storage switch), the solar-storage system loses power. To ensure that the solar-storage system can operate normally when the photovoltaic panels have output voltage or output current during the day, it is necessary to control the first switch to close before the energy storage device reaches a lower limit and shuts down.

[0176] However, because the PV-storage system continues to operate in grid-connected mode at night, when the first switch is controlled to be open, the voltage compensation component raises the voltage between the negative pole (PV-) of the PV module and the earth (PE) to zero or positive voltage. Meanwhile, the negative pole (BUS-) of the DC bus in the PV-storage system is at a negative voltage relative to the earth. Consequently, a large voltage difference exists across the first switch. In this situation, closing the first switch by the controller could damage the first switch contacts, increase contact impedance, and affect overall system reliability. In severe cases, it could even damage the first switch.

[0177] Based on this, another embodiment of the present application provides a control method that can avoid the above-mentioned problem of the first switch. As shown in Figure 9, Figure 9 is a schematic flow chart of a control method 800 provided by another embodiment of the present application. The method may also include:

[0178] Step S831: Obtain the voltage of the DC bus.

[0179] Step S841: When the voltage of the DC bus is less than or equal to a first preset value, control the switching tube in the DC conversion circuit to operate in an open-loop mode, wherein the first preset value is a pre-set voltage value.

[0180] It should be understood that the DC bus voltage can be considered the input bus voltage of the inverter circuit in the inverter, or the input bus voltage of the auxiliary power source in the inverter. A DC bus voltage less than or equal to the first preset value can be understood as a lower limit shutdown of the energy storage device in the solar-storage system, in which case the energy storage device does not provide energy to the inverter.

[0181] It should be noted that when the controller controls the switch tube in the DC conversion circuit to be in the open-loop wave generation mode, the voltage across the first switch decreases.

[0182] It should be understood that for the description of the voltage across the first switch continuously decreasing when the switch tube Q1 is in the open-loop wave generating mode, reference can be made to the description of FIG. 6 to FIG. 7 , which will not be repeated here for the sake of simplicity.

[0183] Step S851: Obtain the voltage value across the first switch.

[0184] Step S861: When the voltage across the first switch is less than or equal to a second preset value, the first switch is controlled to close.

[0185] Among them, the second preset value is the safe shutdown voltage value across the first switch, which can be understood as: the critical voltage value at which the first switch can be safely turned on. That is, when the voltage across the first switch is less than or equal to the second preset value, the first switch will not be damaged when it is turned on, such as contact damage, increased contact impedance, and damage to the first switch.

[0186] It should be noted that the second preset value is a threshold value set in advance.

[0187] Exemplarily, as shown in FIG7 , the second preset value is taken as a voltage value V2 for illustration.

[0188] Optionally, in a possible implementation, when the voltage value across the first switch is less than or equal to the voltage value V2, the controller controls the first switch to be turned on.

[0189] On the contrary, when the voltage across the first switch is greater than the voltage value V2, the controller controls the first switch to remain off until the detection device detects that the voltage across the first switch is less than or equal to the voltage value V2, and then the controller controls the first switch to be on.

[0190] Alternatively, in a possible implementation, FIG10 is a schematic flow chart of a control method 800 provided in yet another embodiment of the present application. As shown in FIG10 , step S851 and step S861 may be replaced by step S852. That is, after executing step S841, step S852 is executed.

[0191] Step S852: When the duration of the switch tube being in the open-loop ripple mode is greater than or equal to the preset duration, the controller controls the first switch to be turned on.

[0192] It should be understood that the preset duration is a pre-set duration. It should be noted that the preset duration is the time required for the voltage across the first switch to drop to a second preset value when the switch tube is in open-loop ripple mode. It should be understood that the description of the second preset value can be found above and is not repeated here.

[0193] Specifically, the controller starts timing when the switch tube Q1 is in the open-loop wave transmission mode. For example, as shown in Figure 7, the moment when the switch tube Q1 starts to be in the open-loop wave transmission mode is time t0. At this time, the controller starts timing, and when the duration of the switch tube Q1 in the open-loop wave transmission mode is greater than or equal to the preset duration, the first switch is controlled to be turned on.

[0194] As shown in FIG7 , for example, taking the second preset value as the voltage value V2 as an example, it can be seen from FIG7 that the critical moment corresponding to the voltage value V2 is moment t1, that is, the moment corresponding to when the voltage across the first switch drops to V2 is moment t1. At this time, it is assumed that the preset time length is the time period (t1-t0).

[0195] For example, in one possible implementation, the controller begins timing when the switch tube Q1 begins to be in the open-loop wave-generating mode. Subsequently, when the duration of the switch tube Q1 in the open-loop wave-generating mode equals a preset duration, the controller controls the first switch to be turned on. For example, the controller may control the first switch to be turned on when the timing reaches a preset duration (e.g., time period (t1-t0)).

[0196] For example, in one possible implementation, the controller begins timing when the switch Q1 begins to operate in the open-loop wave-generating mode. Subsequently, when the duration of the switch Q1 operating in the open-loop wave-generating mode exceeds a preset duration, the controller controls the first switch to conduct. In other words, the controller can control the first switch to conduct at any time after the timing reaches a preset duration (e.g., time period (t1-t0)). For example, as shown in FIG7 , the controller can control the first switch to conduct at time t2. The time period (t2-t0) is greater than the time period (t1-t0).

[0197] According to the above technical solution, when the energy storage device in the solar-storage system experiences a shutdown (e.g., due to a battery SOC limit shutdown, a device failure, a low battery charge, or manual shutdown of the energy storage switch), the first switch can be safely turned on before the solar-storage system shuts down. This prevents contact damage, increased contact impedance, and even damage to the first switch, thereby improving overall system reliability.

[0198] Those skilled in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0199] Those skilled in the art will clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0200] In the several embodiments provided in this application, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. For example, the device embodiments described above are merely schematic. For example, the division of the units is merely a logical function division. In actual implementation, there may be other division methods, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0201] The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of these units may be selected to achieve the purpose of this embodiment according to actual needs.

[0202] In addition, each functional unit in each embodiment of the present application may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit.

[0203] If the functions are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present application, or the part that contributes to the prior art, or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes several instructions for enabling a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the method described in each embodiment of the present application. The aforementioned storage medium includes various media that can store program codes, such as a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk.

[0204] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of this application. Therefore, the scope of protection of this application should be based on the scope of protection of the claims.

Claims

1. A solar energy storage system, characterized in that: include: An inverter, an energy storage device and a voltage compensation component, wherein the inverter includes a DC conversion circuit, a DC bus, an inverter circuit and a first switch, The positive input terminal of the DC conversion circuit is used to connect the positive electrode of the photovoltaic module, and the negative input terminal of the DC conversion circuit is used to connect the negative electrode of the photovoltaic module. The positive output terminal of the DC conversion circuit is connected to the positive electrode of the DC bus, the negative output terminal of the DC conversion circuit is connected to the negative electrode of the DC bus, the positive electrode of the DC bus is connected to the positive input terminal of the inverter circuit and the positive electrode of the energy storage device, and the negative electrode of the DC bus is connected to the negative input terminal of the inverter circuit and the negative electrode of the energy storage device. The positive electrode of the voltage compensation component is used to connect to the negative electrode of the photovoltaic component, and the negative electrode of the voltage compensation component is connected to the ground. The first switch is arranged between the connection point between the voltage compensation component and the negative input terminal of the DC conversion circuit and the negative electrode of the DC bus, and is used to control the connection between the voltage compensation component and the negative electrode of the DC bus; The optical storage system further includes a controller, which is used for: When the output voltage and / or output current of the photovoltaic component is less than or equal to a threshold value, the first switch is controlled to be disconnected, and the voltage compensation component is controlled to operate so that the voltage of the negative electrode of the photovoltaic component to the ground is raised to zero voltage or positive voltage.

2. The photovoltaic storage system according to claim 1, characterized in that: The voltage compensation component includes a voltage compensation module and a second switch, the voltage compensation module is connected in series with the second switch, and the voltage compensation module outputs a positive voltage. The controller is specifically used for: The second switch is controlled to be closed so that the voltage compensation component works.

3. The photovoltaic storage system according to claim 1 or 2, characterized in that: The controller is also used for: When the voltage of the DC bus is less than or equal to a first preset value, controlling the switching tube of the DC conversion circuit to operate in an open-loop mode; Wherein, when the switch tube is in the open-loop wave generating mode, the voltage across the first switch decreases.

4. The solar storage system according to claim 3, characterized in that: The controller is also used for: When the voltage value across the first switch is less than or equal to a second preset value, the first switch is controlled to close, and the second preset value is a safe shutoff voltage value across the first switch.

5. The solar storage system according to claim 3, characterized in that: The controller is also used for: When the duration of the switch tube being in the open-loop wave-generating mode is greater than or equal to a preset duration, the first switch is controlled to be closed.

6. The photovoltaic storage system according to any one of claims 1 to 5, characterized in that: The controller is also used for: When the output voltage and / or output current of the photovoltaic component is greater than the threshold value, the first switch is controlled to be closed, and the voltage compensation component is controlled to stop working.

7. The solar energy storage system according to any one of claims 3 to 5, characterized in that: When the switch tube is in the open-loop wave generation mode, the voltage across the first switch decreases as the duration of the switch tube in the open-loop wave generation mode increases, wherein the relationship between the voltage and the duration satisfies a linear function.

8. The photovoltaic storage system according to any one of claims 1 to 7, characterized in that: The solar energy storage system further includes a first diode, The first diode is connected in parallel to two ends of the first switch, wherein a direction of a forward current of the first diode is opposite to a direction of a current flowing through the first switch when the first switch is closed.

9. An inverter, characterized in that: include: A DC conversion circuit, a DC bus, an inverter circuit and a first switch, The positive input terminal of the DC conversion circuit is used to connect the positive electrode of the photovoltaic module, and the negative input terminal of the DC conversion circuit is used to connect the negative electrode of the photovoltaic module. The positive output terminal of the DC conversion circuit is connected to the positive electrode of the DC bus, the negative output terminal of the DC conversion circuit is connected to the negative electrode of the DC bus, the positive electrode of the DC bus is connected to the positive input terminal of the inverter circuit, the negative electrode of the DC bus is connected to the negative input terminal of the inverter circuit, and the positive electrode of the DC bus is used to connect to the positive electrode of the energy storage device, and the negative electrode of the DC bus is used to connect to the negative electrode of the energy storage device. The negative input terminal of the DC conversion circuit is used to connect the positive electrode of the voltage compensation component, and the negative electrode of the voltage compensation component is connected to the ground. The first switch is arranged between the negative input terminal of the DC conversion circuit and the negative electrode of the DC bus, and is used to control the on-off between the negative input terminal of the DC conversion circuit and the negative electrode of the DC bus; The inverter further includes a controller, which is used for: When the output voltage and / or output current of the photovoltaic component is less than or equal to a threshold value, the first switch is controlled to be disconnected, and the voltage compensation component is controlled to operate so that the voltage of the negative electrode of the photovoltaic component to the ground is raised to zero voltage or positive voltage.

10. The inverter according to claim 9, characterized in that: The voltage compensation component includes a voltage compensation module and a second switch, the voltage compensation module is connected in series with the second switch, and the voltage compensation module outputs a positive voltage. The controller is specifically used for: The second switch is controlled to be closed so that the voltage compensation component works.

11. The inverter according to claim 9 or 10, characterized in that: The controller is also used for: When the voltage of the DC bus is less than or equal to a first preset value, controlling the switching tube of the DC conversion circuit to operate in an open-loop mode; Wherein, when the switch tube is in the open-loop wave generating mode, the voltage across the first switch decreases.

12. The inverter according to claim 11, characterized in that: The controller is also used for: When the voltage value across the first switch is less than or equal to a second preset value, the first switch is controlled to close, and the second preset value is a safe shutoff voltage value across the first switch.

13. The inverter according to claim 11, characterized in that: The controller is also used for: When the duration of the switch tube being in the open-loop wave-generating mode is greater than or equal to a preset duration, the first switch is controlled to be closed.

14. The inverter according to any one of claims 9 to 13, characterized in that: The controller is also used for: When the output voltage and / or output current of the photovoltaic component is greater than the threshold value, the first switch is controlled to be closed, and the voltage compensation component is controlled to stop working.

15. The inverter according to any one of claims 11 to 13, characterized in that: When the switch tube is in the open-loop wave generation mode, the voltage across the first switch decreases as the duration of the switch tube in the open-loop wave generation mode increases, wherein the relationship between the voltage and the duration satisfies a linear function.

16. The inverter according to any one of claims 9 to 15, characterized in that: The inverter further includes a first diode, The first diode is connected in parallel to two ends of the first switch, wherein a direction of a forward current of the first diode is opposite to a direction of a current flowing through the first switch when the first switch is closed.

17. A control method, characterized in that: The method comprises: Obtaining output voltage and / or output current of a photovoltaic module; When the output voltage and / or output current of the photovoltaic component is less than or equal to a threshold value, the first switch is controlled to be disconnected, and the voltage compensation component is controlled to work, so that the voltage of the negative electrode of the photovoltaic component to the ground is raised to zero voltage or positive voltage, wherein the positive electrode of the voltage compensation component is used to connect the negative electrode of the photovoltaic component, and the negative electrode of the voltage compensation component is connected to the ground, Among them, the first switch is arranged between the connection point of the voltage compensation component and the negative input end of the DC conversion circuit and the negative pole of the DC bus, and is used to control the on and off between the voltage compensation component and the negative pole of the DC bus, the negative pole of the DC bus is connected to the negative pole of the energy storage device, and the positive pole of the DC bus is connected to the positive pole of the energy storage device.

18. The control method according to claim 17, characterized in that: The method further comprises: Obtaining the voltage of the DC bus; When the voltage of the DC bus is less than or equal to a first preset value, controlling the switching tube of the DC conversion circuit to operate in an open-loop mode; Wherein, when the switch tube is in the open-loop wave generating mode, the voltage across the first switch decreases.

19. The control method according to claim 18, characterized in that: The method further comprises: Obtaining voltage values ​​across the first switch; When the voltage value across the first switch is less than or equal to a second preset value, the first switch is controlled to close, and the second preset value is a safe shutoff voltage value across the first switch.

20. The control method according to claim 18, characterized in that: The method further comprises: When the duration of the switch tube being in the open-loop wave-generating mode is greater than or equal to a preset duration, the first switch is controlled to be closed.

21. The control method according to any one of claims 17 to 20, characterized in that: The method further comprises: When the output voltage and / or output current of the photovoltaic component is greater than the threshold value, the first switch is controlled to be closed, and the voltage compensation component is controlled to stop working.

22. The control method according to any one of claims 18 to 20, characterized in that: The voltage across the first switch is reduced, comprising: The voltage across the first switch decreases as the duration that the switch tube is in the open-loop wave-generating mode increases, wherein the relationship between the voltage and the duration satisfies a linear function.

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