Method for activating energy storage battery, inverter and energy storage system

Abstract

The invention provides a method for activating an energy storage battery, an inverter and an energy storage system, and the method comprises the steps: controlling a pre-charging switch unit and a first inverter switch unit to be in a closed state, so as to carry out the pre-charging of a capacitor unit when a power grid has a power grid voltage and the energy storage battery is in a dormant state; then, the pre-charging switch unit is controlled to be in an off state; then, the second inverter switch unit is controlled to be in a closed state, so that the power grid charges the capacitor unit; then, the voltage of the direct-current bus is boosted through an inverter circuit; then, the direct current conversion circuit stabilizes the voltage of the capacitor unit and charges the energy storage battery; when the energy storage battery is charged to the preset battery voltage, a battery activation success instruction sent by the energy storage battery is received, and when the voltage of the energy storage battery is not smaller than the preset battery voltage, the energy storage battery is in an activated state. The energy storage battery can be automatically activated to reduce manpower, material resources and time cost, and the user experience is improved.

Description

Technical Field

[0001] The present application relates to the field of electric energy storage technology, and in particular to a method for activating an energy storage battery, an inverter, and an energy storage system. Background Art

[0002] Energy storage systems in the power sector usually include power supplies, inverters, and energy storage batteries. In energy storage systems in the power sector, if the power supply does not output for a long time, the energy storage battery is prone to run out of power and enter a "power-deficient" dormant state when it supplies power to the load for a long time. For example, in energy storage systems in the photovoltaic field, when the photovoltaic array has no voltage output, the energy storage battery will be in a "power-deficient" dormant state after it runs out of power.

[0003] The energy storage battery cannot be used normally when it is in a dormant state due to power loss. At this time, the energy storage battery needs to be activated. The traditional method is to use a DC power supply to manually charge the energy storage battery until the energy storage battery has a basic stable power, that is, to activate it to a state where it can be incorporated into the energy storage system. However, this method wastes manpower, material resources, and time, and the user experience is poor. Summary of the invention

[0004] In view of the above, it is necessary to provide a method for activating an energy storage battery, an inverter, and an energy storage system, which can automatically activate the energy storage battery to reduce manpower, material and time costs and improve user experience.

[0005] The present application provides a method for activating an energy storage battery, which is applied to an energy storage system. The energy storage system includes: an inverter and an energy storage battery. The inverter includes a DC bus, a DC conversion circuit, a capacitor unit, an inverter circuit, a first inverter switch unit, a second inverter switch unit, and a pre-charging circuit. The energy storage battery is connected to the DC conversion circuit. The DC conversion circuit is connected to the DC end of the inverter circuit through the DC bus. The AC end of the inverter circuit is connected to the power grid. The capacitor unit is arranged on the DC bus. The first inverter switch unit and the second inverter switch unit are connected in series between the inverter circuit and the power grid. The input end of the pre-charging circuit is connected between the first inverter switch unit and the second inverter switch unit. The output end of the pre-charging circuit is connected to the DC bus. The pre-charging circuit includes the pre-charging switch unit. The method includes: when there is a grid voltage in the power grid and the energy storage battery is in a dormant state, When the capacitor unit is in the pre-charging state, the pre-charging switch unit and the first inverter switch unit are controlled to be in the closed state to pre-charge the capacitor unit through the pre-charging circuit; after the capacitor unit is pre-charged, the pre-charging switch unit is controlled to be in the disconnected state; after the pre-charging switch unit is disconnected, the second inverter switch unit is controlled to be in the closed state so that the power grid can charge the capacitor unit; after the capacitor unit is charged, the voltage of the DC bus is raised through the inverter circuit; after the voltage of the DC bus is raised, the voltage of the capacitor unit is stabilized through the DC conversion circuit and the energy storage battery is charged; when the battery voltage of the energy storage battery reaches the preset battery voltage, a battery activation success instruction sent by the energy storage battery is received, and the energy storage battery is in the activated state when the battery voltage is not less than the preset battery voltage, and the battery activation success instruction is used to indicate that the energy storage battery is in the activated state.

[0006] In some embodiments, controlling the pre-charging switch unit to be in an off state after pre-charging the capacitor unit includes: controlling the pre-charging switch unit to be in an off state after pre-charging the capacitor unit to a voltage of the DC bus to be a first preset voltage, and the first preset voltage is less than the voltage of the power grid.

[0007] In some embodiments, after the second inverter switch unit is closed, the voltage of the DC bus is charged to a second preset voltage, and the second preset voltage is equal to the voltage of the grid.

[0008] In some embodiments, after the voltage of the DC bus is raised, the voltage of the capacitor unit is stabilized by a DC conversion circuit, including: after the voltage of the DC bus is raised to a third preset voltage, the DC conversion circuit is used to maintain the voltage of the DC bus at a third preset voltage, and the third preset voltage is greater than the voltage of the power grid.

[0009] In some embodiments, after the pre-charging switch unit is disconnected, the second inverter switch unit is controlled to be in a closed state so that the power grid charges the capacitor unit, including: after the pre-charging switch unit is disconnected for a first preset time, the second inverter switch unit is controlled to be in a closed state so that the power grid charges the capacitor unit.

[0010] In some embodiments, after charging the capacitor unit, raising the voltage of the DC bus through the inverter circuit includes: after charging the capacitor unit for a second preset time, raising the voltage of the DC bus through the inverter circuit.

[0011] In some embodiments, after the voltage of the DC bus is raised, the voltage of the capacitor unit is stabilized and the energy storage battery is charged by a DC conversion circuit, including: after the voltage of the DC bus is raised for a third preset time, the voltage of the capacitor unit is stabilized and the energy storage battery is charged by a DC conversion circuit.

[0012] In some embodiments, it also includes: after receiving the battery activation success instruction, sending a charging instruction to the inverter circuit and the DC conversion circuit to control the inverter circuit to charge the energy storage battery through the DC conversion circuit.

[0013] In some embodiments, the pre-charging circuit also includes: a rectifier unit, the input end of the rectifier unit is connected between the first inverter switch unit and the second inverter switch unit, and the output end of the rectifier unit is connected to the DC bus through the pre-charging switch unit; the method also includes: when there is a grid voltage in the power grid, controlling the pre-charging switch unit and the first inverter switch unit to be in a closed state to charge the capacitor unit through the rectifier unit.

[0014] In some embodiments, the energy storage system also includes a grid switch unit, and the grid switch is connected between the second inverter switch unit and the grid; the method also includes: before controlling the pre-charging switch unit and the first inverter switch unit to be in a closed state, controlling the grid switch unit to be in a closed state.

[0015] In some embodiments, the inverter also includes an auxiliary power supply, which is connected to the power grid and is used to provide power to the control circuit of the inverter; before controlling the pre-charging switch unit and the first inverter switch unit to be in a closed state, the method also includes: starting the control circuit through the auxiliary power supply so that the control circuit executes any of the aforementioned methods for activating the energy storage battery.

[0016] The present application also provides an inverter, which is applied to an energy storage system, and includes: a DC bus, a DC conversion circuit, a capacitor unit, an inverter circuit, a first inverter switch unit, a second inverter switch unit, a pre-charging circuit and a control circuit, wherein the DC conversion circuit is connected to an energy storage battery in the energy storage system, the DC conversion circuit is connected to a DC end of the inverter circuit through a DC bus, and an AC end of the inverter circuit is connected to a power grid, the capacitor unit is arranged on the DC bus, the first inverter switch unit and the second inverter switch unit are connected in series between the inverter circuit and the power grid, the input end of the pre-charging circuit is connected between the first inverter switch unit and the second inverter switch unit, the output end of the pre-charging circuit is connected to the DC bus, the pre-charging circuit includes a pre-charging switch unit, and the control circuit is used to: when there is a grid voltage in the power grid and the energy storage battery is in a dormant state, control the pre-charging switch unit and the first inverter switch unit to switch the power grid to the power grid. The switch unit is in a closed state so that the power grid pre-charges the capacitor unit through the pre-charging circuit; and, after the capacitor unit is pre-charged, the pre-charging switch unit is controlled to be in an open state; and, after the pre-charging switch unit is disconnected, the second inverter switch unit is controlled to be in a closed state so that the power grid charges the capacitor unit; and, after the capacitor unit is charged, the voltage of the DC bus is raised through the inverter circuit; and, after the voltage of the DC bus is raised, the voltage of the capacitor unit is stabilized through the DC conversion circuit and the energy storage battery is charged; and, when the energy storage battery is charged to a preset battery voltage, a battery activation success instruction issued by the energy storage battery is received; and, after receiving the battery activation success instruction, a charging instruction is sent to the inverter circuit and the DC conversion circuit to control the photovoltaic array of the energy storage system to charge the energy storage battery.

[0017] In some embodiments, the pre-charging circuit further includes: a rectifier unit, an input end of the rectifier unit is connected between the first inverter switch unit and the second inverter switch unit, and an output end of the rectifier unit is connected to the DC bus through the pre-charging switch unit.

[0018] In some embodiments, the pre-charging circuit further includes: a current limiting unit, which is arranged between the output end of the rectifying unit and the pre-charging switch unit.

[0019] The present application also provides an energy storage system, including: a photovoltaic array, an inverter and an energy storage battery; the inverter includes: a DC bus, a DC conversion circuit, a capacitor unit, an inverter circuit, a first inverter switch unit, a second inverter switch unit, a pre-charging circuit and a control circuit; the energy storage battery is connected to the DC conversion circuit, the DC conversion circuit is connected to the DC end of the inverter circuit through the DC bus, the AC end of the inverter circuit is connected to the power grid, the capacitor unit is arranged on the DC bus, the first inverter switch unit and the second inverter switch unit are connected in series between the inverter circuit and the power grid, the input end of the pre-charging circuit is connected between the first inverter switch unit and the second inverter switch unit, the output end of the pre-charging circuit is connected to the DC bus, the pre-charging circuit includes a pre-charging switch unit, and the control circuit is used to: when there is a grid voltage in the grid and the energy storage battery is in a dormant state, control the pre-charging switch unit and the first inverter switch unit to be in a closed state so that the grid pre-charges the capacitor unit through the pre-charging circuit; and, when the capacitor unit is pre-charged After the pre-charging of the capacitor, the pre-charging switch unit is controlled to be in an open state; and, after the pre-charging switch unit is disconnected, the second inverter switch unit is controlled to be in a closed state so that the power grid charges the capacitor unit; and, after the capacitor unit is charged, the voltage of the DC bus is raised through the inverter circuit; and, after the voltage of the DC bus is raised, the voltage of the capacitor unit is stabilized and the energy storage battery is charged through the DC conversion circuit; and, when the energy storage battery is charged to a preset battery voltage, a battery activation success instruction issued by the energy storage battery is received; and, after receiving the battery activation success instruction, a charging instruction is sent to the inverter circuit and the DC conversion circuit to control the photovoltaic array of the energy storage system to charge the energy storage battery; the photovoltaic array converts solar energy into electrical energy and transmits the electrical energy to the power grid or the energy storage battery through the inverter; the energy storage battery is used to store the electrical energy generated by the photovoltaic array, and sends a battery activation success instruction to the control circuit when the battery voltage is not less than the preset battery voltage.

[0020] Compared with the prior art, this application has at least the following advantages:

[0021] 1. In this application, when the energy storage battery is in a dormant state, the energy storage battery can be automatically reverse activated by the electric energy provided by the power grid, and during the activation process, the capacitor unit of the inverter is precharged through the precharging circuit to reduce the voltage difference between the DC bus of the inverter and the power grid, thereby reducing the situation where surge current is generated and damages the inverter. Compared with the existing technology, by automatically activating the energy storage battery, the manpower, material and time costs can be reduced, and the user experience can be improved.

[0022] 2. In the present application, when there is voltage in the power grid, by sequentially controlling the operation of the DC conversion circuit, the inverter circuit, the first inverter switch unit, the second inverter switch unit and the pre-charging switch unit, the voltage of the DC bus of the inverter can be gradually raised and stabilized at a threshold value that can activate the energy storage battery, thereby improving the reliability, safety and stability of the energy storage battery activation.

[0023] 3. In the present application, when there is voltage in the power grid, the DC conversion circuit, the inverter circuit, the first inverter switch unit, the second inverter switch unit and the pre-charging switch unit are controlled to work in sequence at multiple time intervals, so that the voltage of the DC bus of the inverter can be gradually raised and stabilized at a threshold value that can activate the energy storage battery. On the one hand, it reduces the situation in which the circuit is prone to form a loop due to the possibility of too short a time during control, affecting the control accuracy. On the other hand, it reduces the problem of power failure of the DC bus of the inverter and improves the stability of the DC bus voltage. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of the structure and circuit connection of the inverter of an embodiment of the present application.

[0025] Figure 2 It is a schematic diagram of the structure of the pre-charging circuit and its circuit connection according to an embodiment of the present application.

[0026] Figure 3 It is a flow chart of a method for activating an energy storage battery according to an embodiment of the present application.

[0027] Figure 4 It is a schematic diagram of the control logic and voltage relationship of each circuit unit in the method for activating an energy storage battery in an embodiment of the present application.

[0028] Figure 5 It is a flow chart of a method for activating an energy storage battery according to another embodiment of the present application.

[0029] Figure 6 It is a schematic diagram of the structure and circuit connection of the energy storage system of an embodiment of the present application.

[0030] Figure 7 It is a schematic diagram of the structure and circuit connection of the energy storage system of an embodiment of the present application.

[0031] Main component symbols

[0032] Energy storage system 1

[0033] Inverter 11

[0034] Photovoltaic array 12

[0035] Energy storage battery 13

[0036] Grid 2

[0037] Grid switch unit 21

[0038] DC conversion circuit 110

[0039] Capacitor unit 111

[0040] Inverter circuit 112

[0041] The first inverter switch unit 113

[0042] The second inverter switch unit 114

[0043] Precharge circuit 115

[0044] Control circuit 116

[0045] Pre-charge switch unit 1151

[0046] Current limiting unit 1152

[0047] Rectification unit 1153

[0048] The following specific implementation methods will further illustrate the present application in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0049] In the description of the embodiments of the present application, words such as "exemplary", "or", "for example" and the like are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary" or "for example" in the embodiments of the present application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary", "or", "for example" and the like is intended to present related concepts in a concrete manner.

[0050] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by technicians in the technical field in this application. The terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. It should be understood that, unless otherwise specified in this application, " / " means or. For example, A / B can represent A or B. "And / or" in this application is only a description of the association relationship of associated objects, indicating that three relationships can exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. "At least one" means one or more. "Multiple" means two or more than two. For example, at least one of a, b or c can represent: a, b, c, a and b, a and c, b and c, a, b and c seven situations.

[0051] It should also be noted that the terms "first" and "second" in the specification, claims and drawings of the present application are used to distinguish similar objects, rather than to describe a specific order or sequence.

[0052] As the global demand for renewable energy grows, energy storage technology is one of the important links in the utilization of renewable energy, so the requirements for energy storage technology are getting higher and higher. Energy storage systems in the power sector usually include power supplies, inverters and energy storage batteries. In energy storage systems in the power sector, if the power supply does not output for a long time, the energy storage battery is prone to exhaustion and enter a "power-deficient" dormant state when supplying power to the load for a long time.

[0053] Photovoltaic power generation is a clean and renewable energy source, and its application is becoming more and more extensive. The energy storage system in the photovoltaic field usually includes photovoltaic arrays, inverters, energy storage batteries (also called "batteries") and other equipment. Among them, the inverter is one of the key equipment. It is responsible for converting the direct current generated by the photovoltaic array into alternating current and feeding it into the power grid or supplying it to households. When the energy of the photovoltaic array can normally meet the needs, the excess energy will be stored in the energy storage battery through the inverter, and can be used when there is no solar energy to provide energy. However, there are many special working conditions in the energy storage system in the photovoltaic field. For example, at night, the photovoltaic array has no energy output, and the energy storage battery will be exhausted to a "power-deficient" dormant state. Before the day comes, if the energy storage battery can be activated in advance, the energy storage battery can be charged by the photovoltaic array during the day. Otherwise, during the day, the energy storage battery is still in a "power-deficient" dormant state and cannot be used normally.

[0054] In the related art, in order to keep the energy storage battery powered on for a long time to meet the energy storage function of the inverter, the energy management function of the energy storage system is used to control the SOC (State of Charge) of the energy storage battery. If the SOC is lower than a certain threshold, the inverter detects that the energy storage battery is low in power and will actively charge the energy storage battery through the photovoltaic array or the power grid to ensure the normal state of the energy storage battery. However, when the energy storage system has problems with the energy management function of the energy storage battery, the energy storage battery will be on standby for a long time and the internal energy will be exhausted until it enters a "power-deficient" dormant state. When the photovoltaic array and the power grid have output voltage, the energy storage battery is still in a "power-deficient" dormant state, and the inverter cannot replenish the power of the photovoltaic array and the power grid to the energy storage battery. At this time, it is necessary to manually use a DC power supply to charge the energy storage battery until the energy storage battery has a basic stable power, that is, the energy storage battery needs to be activated until it can be incorporated into the energy storage system for use.

[0055] However, this method of manually using a DC power supply to charge and activate the energy storage battery lacks automation, wastes manpower, material resources, and time, and has a poor user experience. In addition, if the energy storage battery enters a "power-deficient" dormant state multiple times, it will also have a certain impact on the life of the energy storage battery.

[0056] To this end, the embodiments of the present application provide a method for activating an energy storage battery, an inverter, and an energy storage system, which can automatically activate the energy storage battery to reduce manpower, material and time costs and improve user experience.

[0057] Figure 1 It is a schematic diagram of the structure and circuit connection of the inverter 11 according to an embodiment of the present application.

[0058] The embodiment of the present application first provides an inverter 11, which can be applied to an energy storage system. The energy storage system may refer to an energy storage system in the electric power field, including but not limited to: a photovoltaic energy storage system, a wind energy storage system, a hydraulic energy storage system, and a thermal energy storage system. The inverter 11 involved in the embodiment of the present application particularly refers to an inverter 11 applied to a photovoltaic energy storage system.

[0059] like Figure 1 As shown, the inverter 11 involved in the embodiment of the present application may include: a DC bus BUS, a DC conversion circuit 110, a capacitor unit 111, an inverter circuit 112, a first inverter switch unit 113, a second inverter switch unit 114, a pre-charging circuit 115 and a control circuit 116.

[0060] The DC conversion circuit 110 can be connected to the energy storage battery 13 in the energy storage system, and can be used to convert the DC power into power and then input it into the energy storage battery 13. The DC conversion circuit 110 can be a BUCK step-down circuit.

[0061] The DC end of the inverter circuit 112 is connected to the DC conversion circuit 110 via the DC bus BUS, and the AC end of the inverter circuit 112 is connected to the power grid 2. The inverter circuit 112 can be used to convert the AC power of the power grid 2 into DC power and input it into the DC conversion circuit 110 to activate or charge the energy storage battery 13, or can be used to convert the DC power generated by the power generation module in the energy storage system, such as the DC power generated by the photovoltaic array, into AC power and input it into the power grid 2. The inverter circuit 112 involved in the embodiment of the present application has a similar or identical function to the existing known inverter circuit, so the existing known inverter circuit can be one of the existing known inverter circuits, and its internal structure can refer to the circuit structure of the known inverter circuit, which will not be repeated here.

[0062] The capacitor unit 111 is arranged on the DC bus BUS, and can be used to store electrical energy to provide the voltage of the DC bus BUS. Specifically, the capacitor unit 111 may include at least one capacitor, such as 1, 2, 3 or more. In some embodiments, a plurality of capacitors may be arranged in series and parallel on the positive DC bus and the positive DC bus of the DC bus BUS. The capacitor on the DC bus is also called a DC bus capacitor, which may be an electrolytic capacitor.

[0063] The first inverter switch unit 113 and the second inverter switch unit 114 may be connected in series between the inverter circuit 112 and the power grid 2. The first inverter switch unit 113 may include a plurality of switches, and the switches may be any type of electronically controlled switches, such as relays, contactors, and the like. A plurality of switches may be provided in a line connected to the power grid 2. For example, if the line of the power grid 2 includes three live wires and one neutral wire, the number of switches of the first inverter switch unit 113 may be four, and one switch may be provided on each of the live wire and the neutral wire connected to the power grid 2.

[0064] The structure of the second inverter switch unit 114 is the same as or similar to that of the first inverter switch unit 113, except that: a plurality of switches can be arranged in the line connected to the power grid 2 and are farther away from the power grid 2 than the switch of the first inverter switch unit 113. For example, if the line of the power grid 2 includes 3 live wires and 1 neutral wire, the number of switches of the second inverter switch unit 114 can be 4, and one switch is respectively arranged on the live wire and the neutral wire connected to the power grid 2, and the four switches are farther away from the power grid 2 than the switch of the first inverter switch unit 113.

[0065] Figure 2 Schematic diagram of the structure and circuit connection of the pre-charging circuit 115 according to an embodiment of the present application.

[0066] like Figure 1 As shown, the input end of the pre-charging circuit 115 is connected between the first inverter switch unit 113 and the second inverter switch unit 114, wherein the positive input end of the pre-charging circuit 115 is connected to one of the live wires of the power grid 2 between the first inverter switch unit 113 and the second inverter switch unit 114, and the negative input end of the pre-charging circuit 115 is connected to the neutral wire in the line of the power grid 2 between the first inverter switch unit 113 and the second inverter switch unit 114.

[0067] The output end of the pre-charging circuit 115 is connected to the DC bus BUS, wherein the positive output end of the pre-charging circuit 115 is connected to the positive DC bus of the DC bus BUS, and the negative output end of the pre-charging circuit 115 is connected to the positive DC bus of the DC bus BUS.

[0068] In some embodiments, Figure 2As shown, the pre-charging circuit 115 may include a pre-charging switch unit 1151, and the pre-charging switch unit 1151 may include multiple switches, and the switch may be a relay. Multiple switches may be arranged between the DC bus BUS and the pre-charging circuit 115. The pre-charging switch unit 1151 may include 4 switches. Among them, 2 switches are connected in series and arranged at the positive output end of the pre-charging circuit 115, and 2 switches are connected in series and arranged at the negative output end of the pre-charging circuit 115.

[0069] In the embodiments of the present application, Figure 2 As shown, the pre-charging circuit 115 further includes a rectifier unit 1153, which is used to rectify the AC power of the power grid 2 into DC power and to charge the capacitor unit 111. The input end of the rectifier unit 1153 is connected between the first inverter switch unit 113 and the second inverter switch unit 114, and the output end of the rectifier unit 1153 is connected to the DC bus BUS through the pre-charging switch unit 1151.

[0070] In some embodiments, Figure 2 As shown, the pre-charging circuit 115 further includes a current limiting unit 1152, which is disposed between the output end of the rectifying unit 1153 and the pre-charging switch unit 1151. The current limiting unit 1152 may include a plurality of current limiting resistors, for example, both the positive and negative output ends of the rectifying unit 1153 may be provided with current limiting resistors.

[0071] In some embodiments, the inverter 11 may further include an auxiliary power supply, which is connected to the grid 2 and used to provide power to the control circuit 116 of the inverter 11. Before the control circuit 116 controls the pre-charging switch unit 1151 and the first inverter switch unit 113 to be in a closed state, or it can be considered that the control circuit 116 has not yet worked, the control circuit 116 can be started by the auxiliary power supply so that the control circuit 116 controls the grid 2 switch unit, the first inverter switch unit 113, the second inverter switch unit 114, the pre-charging switch unit 1151, the DC conversion circuit 110 and the inverter circuit 112 to activate the energy storage battery 13.

[0072] The control circuit 116 can be used to execute the method involved in the embodiment of the present application. For this purpose, the embodiment of the present application also provides a method for activating an energy storage battery, which is applied to any of the above inverters, and is particularly applied to a photovoltaic energy storage inverter. In order to facilitate the description of the method for activating an energy storage battery, the method is referred to as the "method". Figure 3 It is a flow chart of a method for activating an energy storage battery according to an embodiment of the present application. Figure 4 It is a schematic diagram of the control logic and voltage relationship of each circuit unit in the method for activating an energy storage battery in an embodiment of the present application.

[0073] See also Figure 3 As shown, in an embodiment of the present application, the method may include:

[0074] Step S100: when there is grid voltage in the grid and the energy storage battery is in a dormant state, the pre-charging switch unit and the first inverter switch unit are controlled to be in a closed state to pre-charge the capacitor unit through the pre-charging circuit.

[0075] Among them, when the grid voltage exists in the grid, it can mean that the energy storage system is connected to the grid and the grid has electricity, and the grid voltage can be obtained by manual detection or by detection of the detection circuit in the energy storage system. In this application, after the energy storage system is connected to the grid and the detection result of the grid voltage is obtained, the energy storage battery in the dormant state can be automatically reverse activated by the grid.

[0076] In addition, as mentioned above, under normal circumstances, when the SOC of the energy storage battery is lower than a certain threshold, for example, the normal operating voltage of a low-voltage energy storage battery is 40 to 56V (volts), when it is lower than 40V (volts), the inverter detects that the energy storage battery is low in power and will actively charge the energy storage battery through the photovoltaic array or the power grid to ensure that the energy storage battery can work normally. When the energy storage battery is in a dormant state, it means that the SOC of the energy storage battery is lower than the normal operating threshold and enters dormancy. For example, when it is lower than 24V, the key functions of the energy storage battery are incomplete, so it cannot be charged or discharged, and the energy storage battery needs to be activated.

[0077] The peak value of the grid voltage is 230*√2V, and the voltage of the DC bus of the inverter is 0V. If the inverter is directly connected to the grid, a path will be formed between the DC bus and the grid instantly. The voltage difference between the DC bus and the grid is too large, and surges will occur, which may damage the components in the inverter. Therefore, by precharging the capacitor unit through the precharging circuit, the voltage difference between the DC bus of the inverter and the grid can be reduced, thereby reducing the generation of surge current and damage to the inverter.

[0078] In some embodiments, the pre-charging circuit further includes a rectifier unit. The input end of the rectifier unit is connected between the first inverter switch unit and the second inverter switch unit, and the output end of the rectifier unit is connected to the DC bus through the pre-charging switch unit. The rectifier unit can be used to convert the AC power of the power grid into DC power to pre-charge the inverter. Therefore, in step S100, when there is a grid voltage in the power grid, the pre-charging switch unit and the first inverter switch unit can be controlled to be in a closed state to charge the capacitor unit through the rectifier unit. Thus, the situation where the surge current is generated and damages the inverter is reduced.

[0079] Step S200: After pre-charging the capacitor unit, control the pre-charging switch unit to be in an off state.

[0080] Among them, Figure 4As shown, the pre-charging switch unit can be controlled to be in an off state after the capacitor unit is pre-charged to the voltage of the DC bus to be the first preset voltage U1, and the first preset voltage U1 is less than the voltage of the grid. For example, if the grid voltage is about 230V, the first preset voltage U1 can be 210V.

[0081] Step S300: after the pre-charging switch unit is disconnected, the second inverter switch unit is controlled to be in a closed state so that the grid charges the capacitor unit.

[0082] When the second inverter switch unit is in a closed state, the grid is connected to the inverter circuit, and the power of the grid can charge the capacitor unit through the switch tube in the inverter circuit. Since the switch tube of the inverter circuit is mainly used to convert direct current into alternating current and input it into the grid, when the power of the grid charges the capacitor unit through the switch tube in the inverter circuit, the body diode of the switch tube is mainly used to achieve reverse connection.

[0083] In some embodiments, Figure 4 As shown, after the second inverter switch unit is closed, the voltage of the DC bus is charged to the second preset voltage U2, which is equal to the voltage of the grid. For example, if the grid voltage is about 230V, the second preset voltage U2 is also about 230V.

[0084] In some embodiments, Figure 4 As shown, in step S300, after the pre-charging switch unit is disconnected for the first preset time t1, the second inverter switch unit can be controlled to be in a closed state so that the power grid charges the capacitor unit. The first preset time t1 may be no greater than a threshold value, such as 10ms (milliseconds), 20ms (milliseconds) or 30ms (milliseconds), etc. In this case, the problem of the inverter circuit and the pre-charging circuit forming a loop affecting the control accuracy due to the instantaneous connection when the pre-charging switch unit is disconnected and the second inverter unit is controlled to be closed can be reduced. At the same time, the situation where the DC bus of the inverter is powered off due to the long interval time when the pre-charging switch unit is disconnected and the second inverter unit is controlled to be closed can also be reduced, thereby improving stability.

[0085] Step S400: after charging the capacitor unit, raising the voltage of the DC bus through the inverter circuit.

[0086] When the voltage of the DC bus is raised by the inverter circuit, the AC power of the power grid passes through the IGBT (Insulated Gate Bipolar Transistor) and the boost inductor in the inverter circuit, and the voltage reaching the DC bus will be raised, that is, the inverter circuit at this time is regarded as a boost circuit.

[0087] In some embodiments, Figure 4As shown, in step S400, after charging the capacitor unit for a second preset time t2, the voltage of the DC bus can be raised by the inverter circuit. The second preset time t2 may be not less than a threshold value, such as 3s (seconds), 4s (seconds), 5s (seconds) or 6s (seconds). In this case, the capacitor unit can be charged for a sufficient time so that the voltage of the DC bus can be charged to be equal to the grid voltage.

[0088] Step S500: After the voltage of the DC bus is raised, the voltage of the capacitor unit is stabilized by the DC conversion circuit and the energy storage battery is charged.

[0089] The voltage of the capacitor unit is stabilized by the DC conversion circuit, that is, the DC bus voltage is maintained stable. If the DC bus voltage is constant, the port voltage of the DC conversion circuit connected to the DC bus is also constant. When the port voltage of the DC conversion circuit is constant, when the DC conversion circuit is started, the other end of the DC conversion circuit connected to the energy storage battery can activate the energy storage battery.

[0090] In some embodiments, Figure 4 As shown, in step S500, after the voltage of the DC bus is raised to the third preset voltage U3, the DC conversion circuit is used to maintain the voltage of the DC bus at the third preset voltage U3, and the third preset voltage U3 is greater than the voltage of the grid. For example, if the grid voltage is about 230V, the third preset voltage U3 is greater than 230V. This can be used to activate the energy storage battery.

[0091] In some embodiments, Figure 4 As shown, in step S500, after the voltage of the DC bus is raised for a third preset time t3, the voltage of the capacitor unit is stabilized by the DC conversion circuit and the energy storage battery is charged. Thus, the voltage of the DC bus is raised for a sufficient time so that the voltage of the DC bus can be raised to a level greater than the grid voltage.

[0092] Step S600: receiving a battery activation success instruction sent by the energy storage battery when the energy storage battery is charged to a preset battery voltage.

[0093] Among them, the energy storage battery voltage U4 is in an activated state when it is not less than the preset battery voltage, for example, the low-voltage energy storage battery voltage U4 is not less than 24V. Moreover, at this time, the key functions of the energy storage battery are complete and can be used for charging and discharging, that is, the activated state, so the energy storage battery can send a battery activation success instruction to the inverter through the communication line, so that the inverter can perform normal working content, such as inputting the electric energy generated by the photovoltaic array or the electric energy of the power grid into the energy storage battery for storage. The battery activation success instruction can be used to indicate that the energy storage battery is in an activated state.

[0094] In some other embodiments, the energy storage system may further include a grid switch unit, and the grid switch is connected between the second inverter switch unit and the grid. The grid switch unit can improve the safety of the energy storage system when it is connected to the grid. Figure 5 .

[0095] Figure 5 The embodiment shown and Figure 3 The difference of the illustrated embodiment is that it further comprises:

[0096] Step S001: before controlling the pre-charging switch unit and the first inverter switch unit to be in a closed state, controlling the grid switch unit to be in a closed state.

[0097] It can be understood that before controlling the pre-charging switch unit and the first inverter switch unit to be in a closed state, that is, before step S100, the grid switch unit can be optionally controlled to be in a closed state. In addition, there can be multiple grid switch units, for example, two or more. This improves the safety of the energy storage system being connected to the grid.

[0098] In some other embodiments, the inverter may further include an auxiliary power supply, which is connected to the power grid and is used to provide electrical energy to the control circuit of the inverter.

[0099] Before controlling the pre-charging switch unit and the first inverter switch unit to be in a closed state, that is, before step S100, the method may also include: starting the control circuit through an auxiliary power supply so that the control circuit executes any of the aforementioned methods for activating the energy storage battery.

[0100] As mentioned above, after the energy storage battery is activated, the inverter can input the power generated by the photovoltaic array or the power grid into the energy storage battery for storage. Figure 5 As shown, the method may further include:

[0101] Step S700: after receiving the battery activation success instruction, sending a charging instruction to the inverter circuit and the DC conversion circuit to charge the energy storage battery.

[0102] Among them, the inverter circuit and the DC conversion circuit can input the electric energy generated by the photovoltaic array or the electric energy of the power grid into the energy storage battery for storage based on the charging instruction.

[0103] When the energy storage battery is in a dormant state, the auxiliary power supply can be started, and then the control circuit of the inverter can be started to execute the above steps S100 to S600 to activate the energy storage battery. It can be understood that for safety requirements, the control circuit can also execute the above steps S001 to S600. In addition, the control circuit can also execute the above steps S001 to S700 or the above steps S001 to S700 to activate the energy storage battery and charge it normally.

[0104] In other embodiments, if the auxiliary power supply is connected to the power grid and the auxiliary power supply can continuously draw power from the power grid, the control circuit of the inverter also continues to work. When the energy storage battery is in a dormant state, the control circuit of the inverter can directly execute the above steps S100 to S600 to activate the energy storage battery. It can also be understood that for safety requirements, the control circuit can also execute the above steps S001 and steps S100 to S600. In addition, the control circuit can also execute the above steps S001 and steps S100 to S700 or the above steps S001 to S700 to activate the energy storage battery and charge it normally.

[0105] In summary, the present application automatically reversely activates the energy storage battery through the electric energy provided by the power grid, and during the activation process, the capacitor unit of the inverter is pre-charged through the pre-charging circuit to reduce the voltage difference between the DC bus of the inverter and the power grid, thereby reducing the situation where surge current is generated and damages the inverter. When there is voltage in the power grid, by sequentially controlling the operation of the DC conversion circuit, the inverter circuit, the first inverter switch unit, the second inverter switch unit and the pre-charging switch unit, the voltage of the DC bus of the inverter can be phased up and stabilized at a threshold value that can activate the energy storage battery, thereby improving the reliability, safety and stability of the activation of the energy storage battery.

[0106] Figure 6 It is a schematic diagram of the structure and circuit connection of the energy storage system 1 according to an embodiment of the present application.

[0107] The present application also provides an energy storage system 1. Figure 6 As shown, the energy storage system 1 may include: a photovoltaic array 12, an inverter 11 and an energy storage battery 13. The inverter 11 of the energy storage system 1 may be the inverter 11 involved in any of the above embodiments, so it will not be described in detail here.

[0108] The photovoltaic array 12 can convert solar energy into electrical energy and transmit the electrical energy to the power grid 2 or the energy storage battery 13 through the inverter 11 .

[0109] The energy storage battery 13 can be used to store the electric energy generated by the photovoltaic array 12, and send a battery activation success command to the control circuit 116 when the battery voltage is not less than the preset battery voltage. The energy storage battery 13 is on standby for a long time so that the internal energy is exhausted until it enters a "power-deficient" dormant state. For example, when the low-voltage energy storage battery 13 (48V type) is in a dormant state, when the voltage of the energy storage battery 13 is below 24V, the key functions of the energy storage battery 13 are incomplete. If normal charging and discharging (referring to energy storage and supplying energy to the load) continue, it will affect the life of the energy storage battery 13. Therefore, the energy storage battery 13 can be placed in a dormant state. At this time, if the energy storage battery 13 needs to be charged and discharged normally, the energy storage battery 13 needs to be activated, that is, by charging the voltage of the energy storage battery 13 to above 24V.

[0110] As described above, the method of using a DC power supply to charge and activate the energy storage battery 13 lacks automation, wastes manpower, material resources, and time, and has a poor user experience. To this end, the following method of reversely activating the energy storage battery 13 is provided, which automatically reversely activates the energy storage battery 13 through the electric energy provided by the power grid 2, and pre-charges the capacitor unit of the inverter 11 through the pre-charging circuit 115 during the activation process to reduce the voltage difference between the DC bus BUS of the inverter 11 and the power grid 2, thereby reducing the generation of surge current and damaging the inverter 11.

[0111] Figure 7 It is a schematic diagram of the structure and circuit connection of the energy storage system 1 according to an embodiment of the present application.

[0112] In some embodiments, Figure 7 As shown, the energy storage system 1 may further include a grid switch unit 21, and the grid 2 switch is connected between the second inverter switch unit 114 and the grid 2. The grid switch unit 21 can improve the safety of the energy storage system 1 when it is connected to the grid 2. In this embodiment, if the energy storage system 1 is provided with a grid switch unit 21, the control circuit 116 of the inverter 11 may also be used to control the grid switch unit 21 to be in a closed state before the pre-charging switch unit 1151 and the first inverter switch unit 113 are in a closed state.

[0113] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present application and are not intended to limit it. Although the present application has been described in detail with reference to the preferred embodiments, a person of ordinary skill in the art should understand that the technical solution of the present application may be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present application.

Claims

1. A method for activating an energy storage battery, applied to an energy storage system, characterized in that: The energy storage system comprises: an inverter and an energy storage battery, wherein the inverter comprises a DC bus, a DC conversion circuit, a capacitor unit, an inverter circuit, a first inverter switch unit, a second inverter switch unit and a pre-charging circuit, wherein the energy storage battery is connected to the DC conversion circuit, the DC conversion circuit is connected to the DC end of the inverter circuit through the DC bus, the AC end of the inverter circuit is connected to the power grid, the capacitor unit is arranged on the DC bus, the first inverter switch unit and the second inverter switch unit are connected in series between the inverter circuit and the power grid, the input end of the pre-charging circuit is connected between the first inverter switch unit and the second inverter switch unit, the output end of the pre-charging circuit is connected to the DC bus, and the pre-charging circuit comprises a pre-charging switch unit; The method comprises: When there is a grid voltage in the grid and the energy storage battery is in a dormant state, controlling the pre-charging switch unit and the first inverter switch unit to be in a closed state to pre-charge the capacitor unit through the pre-charging circuit; After precharging the capacitor unit, controlling the precharging switch unit to be in an off state; After the pre-charging switch unit is disconnected, controlling the second inverter switch unit to be in a closed state so that the power grid charges the capacitor unit; After charging the capacitor unit, raising the voltage of the DC bus through the inverter circuit; After the voltage of the DC bus is raised, the voltage of the capacitor unit is stabilized by the DC conversion circuit and the energy storage battery is charged; When the battery voltage of the energy storage battery reaches a preset battery voltage, a battery activation success instruction issued by the energy storage battery is received. The energy storage battery is in an activated state when the battery voltage is not less than the preset battery voltage. The battery activation success instruction is used to indicate that the energy storage battery is in the activated state.

2. The method for activating an energy storage battery according to claim 1, characterized in that: The step of controlling the pre-charging switch unit to be in an off state after pre-charging the capacitor unit comprises: After the capacitor unit is pre-charged until the voltage of the DC bus is a first preset voltage, the pre-charging switch unit is controlled to be in an off state, and the first preset voltage is less than the voltage of the power grid.

3. The method for activating an energy storage battery according to claim 1, characterized in that: After the second inverter switch unit is closed, the voltage of the DC bus is charged to a second preset voltage, and the second preset voltage is equal to the voltage of the power grid.

4. The method for activating an energy storage battery according to claim 1, characterized in that: After the voltage of the DC bus is raised, the voltage of the capacitor unit is stabilized by the DC conversion circuit, comprising: After the voltage of the DC bus is raised to a third preset voltage, the voltage of the DC bus is maintained at the third preset voltage through the DC conversion circuit, and the third preset voltage is greater than the voltage of the power grid.

5. The method for activating an energy storage battery according to claim 1, characterized in that: After the pre-charging switch unit is disconnected, controlling the second inverter switch unit to be in a closed state so that the power grid charges the capacitor unit includes: After the pre-charging switch unit is turned off for a first preset time, the second inverter switch unit is controlled to be in a closed state so that the power grid charges the capacitor unit.

6. The method for activating an energy storage battery according to claim 1, characterized in that: After charging the capacitor unit, raising the voltage of the DC bus by the inverter circuit includes: After the capacitor unit is charged for a second preset time, the voltage of the DC bus is raised by the inverter circuit.

7. The method for activating an energy storage battery according to claim 1, characterized in that: After the voltage of the DC bus is raised, the voltage of the capacitor unit is stabilized by the DC conversion circuit and the energy storage battery is charged, including: After the voltage of the DC bus is raised for a third preset time, the voltage of the capacitor unit is stabilized by the DC conversion circuit and the energy storage battery is charged.

8. The method for activating an energy storage battery according to claim 1, characterized in that: Also includes: After receiving the battery activation success instruction, a charging instruction is sent to the inverter circuit and the DC conversion circuit to control the inverter circuit to charge the energy storage battery through the DC conversion circuit.

9. The method for activating an energy storage battery according to claim 1, characterized in that: The pre-charging circuit further includes: a rectifier unit, an input end of the rectifier unit is connected between the first inverter switch unit and the second inverter switch unit, and an output end of the rectifier unit is connected to the DC bus through the pre-charging switch unit; The method further comprises: When there is a grid voltage in the grid, the pre-charging switch unit and the first inverter switch unit are controlled to be in a closed state, so as to charge the capacitor unit through the rectifier unit.

10. The method for activating an energy storage battery according to claim 1, characterized in that: The energy storage system further comprises a grid switch unit, wherein the grid switch is connected between the second inverter switch unit and the grid; The method further comprises: Before controlling the pre-charging switch unit and the first inverter switch unit to be in a closed state, the grid switch unit is controlled to be in a closed state.

11. The method for activating an energy storage battery according to any one of claims 1 to 10, characterized in that: The inverter further includes an auxiliary power supply, which is connected to the power grid and is used to provide electric energy to the control circuit of the inverter; Before controlling the pre-charging switch unit and the first inverter switch unit to be in a closed state, the method further includes: The control circuit is started by the auxiliary power supply so that the control circuit executes the method for activating the energy storage battery according to any one of claims 1 to 10.

12. An inverter, applied to an energy storage system, characterized in that: include: A DC bus, a DC conversion circuit, a capacitor unit, an inverter circuit, a first inverter switch unit, a second inverter switch unit, a pre-charging circuit and a control circuit, wherein the DC conversion circuit is connected to the energy storage battery in the energy storage system, the DC conversion circuit is connected to the DC end of the inverter circuit through the DC bus, the AC end of the inverter circuit is connected to the power grid, the capacitor unit is arranged on the DC bus, the first inverter switch unit and the second inverter switch unit are connected in series between the inverter circuit and the power grid, the input end of the pre-charging circuit is connected between the first inverter switch unit and the second inverter switch unit, the output end of the pre-charging circuit is connected to the DC bus, the pre-charging circuit includes a pre-charging switch unit, and the control circuit is used for: When the grid voltage exists in the grid and the energy storage battery is in a dormant state, the pre-charging switch unit and the first inverter switch unit are controlled to be in a closed state so that the grid pre-charges the capacitor unit through the pre-charging circuit; and After precharging the capacitor unit, controlling the precharging switch unit to be in an off state; and, After the pre-charging switch unit is disconnected, the second inverter switch unit is controlled to be in a closed state so that the power grid charges the capacitor unit; and After charging the capacitor unit, raising the voltage of the DC bus through the inverter circuit; and After the voltage of the DC bus is raised, the voltage of the capacitor unit is stabilized and the energy storage battery is charged through the DC conversion circuit; and, When the energy storage battery is charged to a preset battery voltage, a battery activation success instruction sent by the energy storage battery is received; and, After receiving the battery activation success instruction, a charging instruction is sent to the inverter circuit and the DC conversion circuit to control the photovoltaic array of the energy storage system to charge the energy storage battery.

13. The inverter according to claim 12, characterized in that: The pre-charging circuit also includes: a rectifier unit, an input end of the rectifier unit is connected between the first inverter switch unit and the second inverter switch unit, and an output end of the rectifier unit is connected to the DC bus through the pre-charging switch unit.

14. The inverter according to claim 13, characterized in that: The pre-charging circuit further includes: a current limiting unit, which is arranged between the output end of the rectifying unit and the pre-charging switch unit.

15. An energy storage system, characterized in that: include: Photovoltaic arrays, inverters and storage batteries; The inverter includes: a DC bus, a DC conversion circuit, a capacitor unit, an inverter circuit, a first inverter switch unit, a second inverter switch unit, a pre-charging circuit and a control circuit. The energy storage battery is connected to the DC conversion circuit. The DC conversion circuit is connected to the DC end of the inverter circuit through the DC bus. The AC end of the inverter circuit is connected to the power grid. The capacitor unit is arranged on the DC bus. The first inverter switch unit and the second inverter switch unit are connected in series between the inverter circuit and the power grid. The input end of the pre-charging circuit is connected between the first inverter switch unit and the second inverter switch unit. The output end of the pre-charging circuit is connected to the DC bus. The pre-charging circuit includes a pre-charging switch unit. The control circuit is used for: When the grid voltage exists in the grid and the energy storage battery is in a dormant state, the pre-charging switch unit and the first inverter switch unit are controlled to be in a closed state so that the grid pre-charges the capacitor unit through the pre-charging circuit; and, after the capacitor unit is pre-charged, the pre-charging switch unit is controlled to be in an open state; and, after the pre-charging switch unit is disconnected, the second inverter switch unit is controlled to be in a closed state so that the grid charges the capacitor unit; and, after the capacitor unit is charged, the voltage of the DC bus is raised through the inverter circuit; and, after the voltage of the DC bus is raised, the voltage of the capacitor unit is stabilized through the DC conversion circuit and the energy storage battery is charged; and, when the energy storage battery is charged to a preset battery voltage, a battery activation success instruction issued by the energy storage battery is received; and, after receiving the battery activation success instruction, a charging instruction is sent to the inverter circuit and the DC conversion circuit to control the photovoltaic array of the energy storage system to charge the energy storage battery; The photovoltaic array converts solar energy into electrical energy and transmits the electrical energy to the power grid or the energy storage battery through the inverter; The energy storage battery is used to store the electric energy generated by the photovoltaic array, and sends a battery activation success instruction to the control circuit when the battery voltage is not less than the preset battery voltage.

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