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

Abstract

The application provides a method for activating an energy storage battery, an inverter and an energy storage system. The method comprises the following steps: when a power grid voltage exists in a power grid and the energy storage battery is in a dormant state, controlling a pre-charging switch unit and a first inverter switch unit to be in a closed state to pre-charge a capacitor unit; then, controlling the pre-charging switch unit to be in an open state; then, controlling a second inverter switch unit to be in a closed state to enable the power grid to charge the capacitor unit; then, lifting the voltage of a direct-current bus through an inverter circuit; then, stabilizing the voltage of the capacitor unit through a direct-current conversion circuit and charging the energy storage battery; and receiving a battery activation success instruction sent by the energy storage battery when the energy storage battery is charged to a preset battery voltage, so that the energy storage battery is in an activated state when the voltage of the energy storage battery is not less than the preset battery voltage. The application can automatically activate the energy storage battery to reduce the labor, material and time costs and improve the user experience.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power energy storage, and in particular to a method for activating an energy storage battery, an inverter and an energy storage system. BACKGROUND

[0002] An energy storage system in the field of power usually includes a power source, an inverter and an energy storage battery. In the energy storage system in the field of power, if the power source does not output for a long time, the energy storage battery is likely to run out of power and enter a "power deficit" dormant state when supplying power to a load for a long time. For example, in the energy storage system in the field of photovoltaic, when the photovoltaic array does not output voltage, the energy storage battery will be in a "power deficit" dormant state after running out of power.

[0003] The energy storage battery in the "power deficit" dormant state cannot be used normally, and the energy storage battery needs to be activated at this time. The traditional method is to manually charge the energy storage battery using a direct current power source until the energy storage battery has a basic stable power, that is, to activate the energy storage battery to a state capable of being integrated into the energy storage system for use. However, this method wastes manpower, material resources and time, and the user experience is poor. SUMMARY

[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 the cost of manpower, material resources and time, and improve the user experience.

[0005] The application provides a method for activating an energy storage battery, which is applied to an energy storage system. The energy storage system comprises an inverter and an energy storage battery. 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. 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 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 comprises a pre-charging switch unit. The method comprises the following steps: when the power grid voltage exists 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 pre-charging the capacitor unit, controlling the pre-charging switch unit to be in an open state; after the pre-charging switch unit is opened, controlling the second inverter switch unit to be in a closed state to enable the power grid to charge the capacitor unit; after charging the capacitor unit, lifting the voltage of the DC bus through the inverter circuit; after the voltage of the DC bus is lifted, stabilizing the voltage of the capacitor unit through the DC conversion circuit and charging the energy storage battery; and when the battery voltage of the energy storage battery reaches a preset battery voltage, receiving a battery activation success instruction sent by the energy storage battery. 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.

[0006] In some embodiments, after pre-charging the capacitor unit, the pre-charging switch unit is controlled to be in an open state, comprising: after pre-charging the capacitor unit to a first preset voltage of the DC bus, the pre-charging switch unit is controlled to be in an open state. 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 power grid.

[0008] In some embodiments, after the voltage of the DC bus is lifted, the voltage of the capacitor unit is stabilized through the DC conversion circuit, comprising: after the voltage of the DC bus is lifted to a third preset voltage, the voltage of the DC bus is maintained at the third preset voltage through the DC conversion circuit. The third preset voltage is greater than the voltage of the power grid.

[0009] In some embodiments, after the pre-charging switch unit is opened, the second inverter switch unit is controlled to be in a closed state to enable the power grid to charge the capacitor unit, comprising: after the pre-charging switch unit is opened for a first preset time, the second inverter switch unit is controlled to be in a closed state to enable the power grid to charge the capacitor unit.

[0010] In some embodiments, the method further comprises: after the voltage of the DC bus is lifted, stabilizing the voltage of the capacitor unit and charging the energy storage battery by the DC conversion circuit, including: after the voltage of the DC bus is lifted for a third preset time, stabilizing the voltage of the capacitor unit and charging the energy storage battery by the DC conversion circuit.

[0011] In some embodiments, the method further comprises: after the voltage of the DC bus is lifted, stabilizing the voltage of the capacitor unit and charging the energy storage battery by the DC conversion circuit, including: after the voltage of the DC bus is lifted for a third preset time, stabilizing the voltage of the capacitor unit and charging the energy storage battery by the DC conversion circuit.

[0012] In some embodiments, the method further comprises: 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 further comprises: a rectifier unit, an input end of the rectifier unit being connected between the first inverter switch unit and the second inverter switch unit, and an output end of the rectifier unit being connected to the DC bus through the pre-charge switch unit; the method further comprises: when the grid voltage exists, controlling the pre-charge 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 further comprises a grid switch unit, the grid switch being connected between the second inverter switch unit and the grid; the method further comprises: before controlling the pre-charge 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 further comprises an auxiliary power supply, the auxiliary power supply being connected to the grid and being used to provide power for a control circuit of the inverter; before controlling the pre-charge switch unit and the first inverter switch unit to be in a closed state, the method further comprises: starting the control circuit by the auxiliary power supply to make the control circuit execute any of the foregoing methods for activating the energy storage battery.

[0016] The application also provides an inverter applied to an energy storage system, comprising: 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-charge circuit and a control circuit, 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 the DC bus, 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, an input end of the pre-charge circuit is connected between the first inverter switch unit and the second inverter switch unit, an output end of the pre-charge circuit is connected to the DC bus, the pre-charge circuit comprises a pre-charge switch unit, and the control circuit is used for: when the power grid exists a power grid voltage and the energy storage battery is in a dormant state, controlling the pre-charge switch unit and the first inverter switch unit to be in a closed state to make the power grid pre-charge the capacitor unit through the pre-charge circuit; and after pre-charging the capacitor unit, controlling the pre-charge switch unit to be in an open state; and after the pre-charge switch unit is opened, controlling the second inverter switch unit to be in a closed state to make the power grid charge the capacitor unit; and after charging the capacitor unit, raising a voltage of the DC bus through the inverter circuit; and after the voltage of the DC bus is raised, stabilizing the voltage of the capacitor unit through the DC conversion circuit and charging the energy storage battery; and when the energy storage battery is charged to a preset battery voltage, receiving a battery activation success instruction sent by the energy storage battery; and after receiving the battery activation success instruction, sending a charging instruction to the inverter circuit and the DC conversion circuit to control a photovoltaic array of the energy storage system to charge the energy storage battery.

[0017] In some embodiments, the pre-charge circuit further comprises: 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-charge switch unit.

[0018] In some embodiments, the pre-charge circuit further comprises: a current limiting unit, the current limiting unit is arranged between the output end of the rectifier unit and the pre-charge switch unit.

[0019] The application also provides an energy storage system, comprising: a photovoltaic array, an inverter and an energy storage battery; 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, a pre-charge circuit and a control circuit, the energy storage battery is connected to the DC conversion circuit, the DC conversion circuit is connected to a DC end of the inverter circuit through the DC bus, 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, an input end of the pre-charge circuit is connected between the first inverter switch unit and the second inverter switch unit, an output end of the pre-charge circuit is connected to the DC bus, the pre-charge circuit comprises a pre-charge switch unit, and the control circuit is used for: when the power grid has a power grid voltage and the energy storage battery is in a dormant state, controlling the pre-charge switch unit and the first inverter switch unit to be in a closed state to make the power grid pre-charge the capacitor unit through the pre-charge circuit; and after pre-charging the capacitor unit, controlling the pre-charge switch unit to be in an open state; and after the pre-charge switch unit is opened, controlling the second inverter switch unit to be in a closed state to make the power grid charge the capacitor unit; and after charging the capacitor unit, raising a voltage of the DC bus through the inverter circuit; and after the voltage of the DC bus is raised, stabilizing the voltage of the capacitor unit through the DC conversion circuit and charging the energy storage battery; and when the energy storage battery is charged to a preset battery voltage, receiving a battery activation success instruction sent by the energy storage battery; and after receiving the battery activation success instruction, sending a charging instruction 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 electric energy and transmits the electric energy to the power grid or the energy storage battery through the inverter; the energy storage battery is used for storing the electric energy generated by the photovoltaic array, and sends the 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, the application has at least the following advantages:

[0021] 1、In the application, when the energy storage battery is in a dormant state, the energy storage battery can be automatically activated in reverse by 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-charge circuit to reduce the voltage difference between the DC bus of the inverter and the power grid, thereby reducing the damage of the inverter caused by the surge current. Compared with the prior art, by automatically activating the energy storage battery, the labor, material and time costs can be reduced, and the user experience can be improved.

[0022] 2、In the application, when the grid has voltage, by sequentially controlling the DC conversion circuit, inverter circuit, first inverter switch unit, second inverter switch unit and pre-charge switch unit, the voltage of the DC bus of the inverter can be lifted 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 application, when the grid has voltage, by sequentially controlling the DC conversion circuit, inverter circuit, first inverter switch unit, second inverter switch unit and pre-charge switch unit, the voltage of the DC bus of the inverter can be lifted 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. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 is the structure of the inverter of the embodiment of the application and its circuit connection schematic diagram.

[0025] Figure 2 is the structure of the pre-charge circuit of the embodiment of the application and its circuit connection schematic diagram.

[0026] Figure 3 is the flowchart of the method for activating the energy storage battery of the embodiment of the application.

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

[0028] Figure 5 is the flowchart of the method for activating the energy storage battery of another embodiment of the application.

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

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

[0031] MAIN ELEMENT SYMBOL EXPLANATION

[0032] Energy storage system 1

[0033] Inverter 11

[0034] Photovoltaic array 12

[0035] Energy storage battery 13

[0036] Power grid 2

[0037] Power grid switch unit 21

[0038] DC conversion circuit 110

[0039] Capacitance unit 111

[0040] Inverter circuit 112

[0041] First inverter switch unit 113

[0042] Second inverter switch unit 114

[0043] Precharge circuit 115

[0044] Control circuit 116

[0045] Precharge switch unit 1151

[0046] Current limiting unit 1152

[0047] Rectification unit 1153

[0048] The following detailed description will further describe the present application in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0049] In the description of the embodiments of the present application, the words "exemplary", "or", "for example" are used to mean as an example, instance, or illustration. Any embodiment or design described as "exemplary" or "for example" in the present application should not be construed as being more preferred or advantageous than other embodiments or designs. In fact, the use of the words "exemplary", "or", "for example" is intended to present concepts in a concrete manner.

[0050] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. It is understood that the use of "a", "an" or "the" herein does not exclude a plurality, and "a" or "an" means "one or more". It is further understood that the use of "multiple" or "plurality" herein does not exclude a single instance. It is understood that the use of "or" in the present application refers to a non-exclusive "or", unless otherwise stated. For example, "A or B" means "A or B or both". It is further understood that the use of "and" in the present application refers to a non-exclusive "and", unless otherwise stated. For example, "A and B" means "A or B or both". It is understood that the use of "and / or" in the present application refers to a non-exclusive "and / or", unless otherwise stated. For example, "A and / or B" means "A or B or both". It is understood that the use of "at least one" in the present application refers to one or more, unless otherwise stated. For example, "at least one of a, b or c" means "a or b or c or any combination of these". It is understood that the use of "one or more" in the present application refers to one or more, unless otherwise stated. For example, "one or more of a, b or c" means "a or b or c or any combination of these". It is understood that the use of "one or more of a, b or c" in the present application refers to one or more of a, b or c, unless otherwise stated. For example, "one or more of a, b or c" means "a or b or c or any combination of these".

[0051] In addition, it should be noted that the terms "first", "second" in the description and claims of the present application and the drawings are used to distinguish similar objects, and are not used to describe a specific order or sequence.

[0052] With the increasing demand for renewable energy worldwide, energy storage technology is an important part of renewable energy utilization, and the requirements for energy storage technology are also increasing. The energy storage system in the field of electric power usually includes power supply, inverter and energy storage battery. In the energy storage system in the field of electric power, if the power supply does not output for a long time, the energy storage battery supplies power to the load for a long time, and the energy storage battery is easy to run out of power and enter a "power deficit" sleep state.

[0053] Photovoltaic power generation as a clean and renewable energy source is increasingly widely used. The energy storage system in the photovoltaic field usually includes photovoltaic array, inverter, energy storage battery (also known as "storage battery") and other devices, among which the inverter is one of the key devices, which is responsible for converting the direct current generated by the photovoltaic array into alternating current and entering the power grid or supplying the home. 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, which can be used when there is no solar energy to provide energy. However, the energy storage system in the photovoltaic field has many special working conditions. For example, at night, the photovoltaic array has no energy output, and the energy storage battery will run out of power and enter a "power deficit" sleep state. Before the arrival of the day, 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 in the daytime, the energy storage battery is still in a "power deficit" sleep state and cannot be used normally.

[0054] In the related art, in order to keep the energy storage battery in the on state for a long time to meet the energy storage function of the inverter, the SOC (State of Charge) of the energy storage battery is controlled by the energy management function of the energy storage system. If the SOC is lower than a certain threshold, the inverter detects that the energy storage battery has low power, and actively charges 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 management function of the energy storage system for the energy storage battery fails, the energy storage battery will be on standby for a long time and the internal energy will be depleted until the "power deficit" sleep state. When the photovoltaic array and the power grid have output voltage, the energy storage battery is still in the "power deficit" sleep state, and the inverter cannot supplement the energy of the photovoltaic array and the power grid to the energy storage battery. At this time, it is necessary to manually charge the energy storage battery with a direct current source to have a basic stable power, that is, to activate the energy storage battery to be able to be used in the energy storage system.

[0055] However, this artificial method of charging the energy storage battery with a direct current power supply lacks automation, wastes manpower, material resources and time, and the user experience is poor. Moreover, if the energy storage battery enters the "low power" dormant state multiple times, it will also have a certain impact on the service life of the energy storage battery.

[0056] Therefore, 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 the cost of manpower, material resources and time, and improve the user experience.

[0057] Figure 1 is a schematic diagram of the structure and circuit connection of the inverter 11 of the embodiments of the present application.

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

[0059] As shown in Figure 1 , the inverter 11 involved in the embodiments of the present application can include: a direct current bus BUS, a direct current 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-charge circuit 115 and a control circuit 116.

[0060] The direct current conversion circuit 110 can be connected to the energy storage battery 13 in the energy storage system, and can be used to input the power converted from direct current into the energy storage battery 13. The direct current conversion circuit 110 can be a BUCK step-down circuit.

[0061] The direct current end of the inverter circuit 112 is connected to the direct current conversion circuit 110 through the direct current bus BUS, and the alternating current end of the inverter circuit 112 is connected to the power grid 2. The inverter circuit 112 can be used to convert the alternating current of the power grid 2 into direct current and input it into the direct current conversion circuit 110 to activate or charge the energy storage battery 13, or can be used to convert the direct current generated by the power generation module in the energy storage system, such as the direct current generated by the photovoltaic array, into alternating current and input it into the power grid 2. The inverter circuit 112 involved in the embodiments of the present application has similar or the same effect as the known inverter circuit, so the known inverter circuit can be one of the known inverter circuits, and the internal structure thereof can refer to the circuit structure of the known inverter circuit, which will not be described here.

[0062] The capacitor unit 111 is arranged on the DC bus BUS and can be used to store electric energy to provide the voltage of the DC bus BUS. Specifically, the capacitor unit 111 can include at least one capacitor, for example, 1, 2, 3 or more. In some embodiments, a plurality of capacitors can 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, also known as the DC bus capacitor, can be an electrolytic capacitor.

[0063] The first inverter switch unit 113 and the second inverter switch unit 114 can be connected in series between the inverter circuit 112 and the power grid 2. The first inverter switch unit 113 can include a plurality of switches, which can be any kind of electrically controlled switch, such as a relay, a contactor, etc. The plurality of switches can be arranged in the line connected to the power grid 2, for example, the line of the power grid 2 includes 3 live wires and 1 neutral wire, then the number of switches of the first inverter switch unit 113 can be 4 and each of the live wires and the neutral wire connected to the power grid 2 is arranged with a switch.

[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, and the difference is that the plurality of switches can be arranged in the line connected to the power grid 2 and farther away from the power grid 2 than the switches of the first inverter switch unit 113. For example, the line of the power grid 2 includes 3 live wires and 1 neutral wire, then the number of switches of the second inverter switch unit 114 can be 4 and each of the live wires and the neutral wire connected to the power grid 2 is arranged with a switch, and the 4 switches are farther away from the power grid 2 than the switches of the first inverter switch unit 113.

[0065] Figure 2 is a structure of a pre-charge circuit 115 of an embodiment of the present application and a schematic diagram of a circuit connection thereof.

[0066] As shown in Figure 1 , the input end of the pre-charge 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-charge 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-charge 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-charge circuit 115 is connected to the DC bus BUS, wherein the positive output end of the pre-charge circuit 115 is connected to the positive DC bus of the DC bus BUS, and the negative output end of the pre-charge circuit 115 is connected to the positive DC bus of the DC bus BUS.

[0068] In some embodiments, as shown in Figure 2As shown in FIG. 1, the pre-charge circuit 115 can include a pre-charge switch unit 1151, which can include a plurality of switches, which can be relays. The plurality of switches can be arranged between the DC bus BUS and the pre-charge circuit 115. The pre-charge switch unit 1151 can include four switches. Two of the switches are arranged in series at the positive output of the pre-charge circuit 115, and the other two switches are arranged in series at the negative output of the pre-charge circuit 115.

[0069] As shown in FIG. 1, the pre-charge circuit 115 can include a pre-charge switch unit 1151, which can include a plurality of switches, which can be relays. The plurality of switches can be arranged between the DC bus BUS and the pre-charge circuit 115. The pre-charge switch unit 1151 can include four switches. Two of the switches are arranged in series at the positive output of the pre-charge circuit 115, and the other two switches are arranged in series at the negative output of the pre-charge circuit 115. Figure 2 As shown in FIG. 1, the pre-charge circuit 115 further includes a rectifier unit 1153 for rectifying the AC power from the power grid 2 into DC power and for charging the capacitor unit 111. The input of the rectifier unit 1153 is connected between the first inverter switch unit 113 and the second inverter switch unit 114, and the output of the rectifier unit 1153 is connected to the DC bus BUS through the pre-charge switch unit 1151.

[0070] As shown in FIG. 1, the pre-charge circuit 115 further includes a pre-charge switch unit 1151, which can include a plurality of switches, which can be relays. The plurality of switches can be arranged between the DC bus BUS and the pre-charge circuit 115. The pre-charge switch unit 1151 can include four switches. Two of the switches are arranged in series at the positive output of the pre-charge circuit 115, and the other two switches are arranged in series at the negative output of the pre-charge circuit 115. Figure 2 As shown in FIG. 1, the pre-charge circuit 115 further includes a pre-charge switch unit 1151, which can include a plurality of switches, which can be relays. The plurality of switches can be arranged between the DC bus BUS and the pre-charge circuit 115. The pre-charge switch unit 1151 can include four switches. Two of the switches are arranged in series at the positive output of the pre-charge circuit 115, and the other two switches are arranged in series at the negative output of the pre-charge circuit 115.

[0071] In some embodiments, the inverter 11 can further include an auxiliary power supply, which is connected to the power grid 2 and used to provide power for the control circuit 116 of the inverter 11. Before the control circuit 116 controls the pre-charge switch unit 1151 and the first inverter switch unit 113 to be in the 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 to activate the energy storage battery 13 by controlling the power grid switch unit, the first inverter switch unit 113, the second inverter switch unit 114, the pre-charge switch unit 1151, the DC conversion circuit 110, and the inverter circuit 112.

[0072] The control circuit 116 can be used to execute the method related to the embodiments of the present application. For this purpose, the embodiments of the present application further provide a method for activating an energy storage battery, which can be applied to any of the inverters described above, and 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 "method" hereinafter. Figure 3 is a flowchart of the method for activating an energy storage battery according to an embodiment of the present application. Figure 4 is a schematic diagram of the control logic and voltage relationship of each circuit unit in the method for activating an energy storage battery according to an embodiment of the present application.

[0073] Please refer to Figure 3 As shown in FIG. 1, the method according to an embodiment of the present application can include:

[0074] Step S100: When the grid voltage exists and the energy storage battery is in the dormant state, control the pre-charge switch unit and the first inverter switch unit to be in the closed state to pre-charge the capacitor unit through the pre-charge circuit.

[0075] Wherein, when the grid voltage exists can mean that the energy storage system is connected to the grid and the grid has power, 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 obtains the detection result of the grid voltage, the energy storage battery in the dormant state can be automatically activated in reverse through the grid.

[0076] In addition, as described above, generally, when the SOC of the energy storage battery is lower than a certain threshold value, for example, the normal working voltage of the low-voltage energy storage battery is 40-56V (volts), and when it is lower than 40V (volts), the inverter detects that the energy storage battery has low power and actively charges the energy storage battery through the photovoltaic array or the grid to ensure that the energy storage battery can work normally. When the energy storage battery is in the dormant state, it can mean that the SOC of the energy storage battery is lower than the threshold value of normal working and enters the dormant state, for example, lower than 24V, the key function of the energy storage battery is 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*sqrt(2)V, and the voltage of the DC bus of the inverter is 0V. If the inverter is directly connected to the grid, a path is formed between the DC bus and the grid instantaneously, and the voltage difference between the DC bus and the grid is too large, which can cause a surge phenomenon and damage the devices in the inverter. Therefore, by pre-charging the capacitor unit through the pre-charge circuit, the voltage difference between the DC bus of the inverter and the grid can be reduced, thereby reducing the damage of the inverter caused by the generation of surge current.

[0078] In some embodiments, the pre-charge circuit further comprises 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-charge switch unit. The rectifier unit can be used to convert the AC power of the grid into DC power to pre-charge the inverter. Therefore, in step S100, when the grid voltage exists, the pre-charge switch unit and the first inverter switch unit can be controlled to be in the closed state to charge the capacitor unit through the rectifier unit. Thus, the damage of the inverter caused by the generation of surge current is reduced.

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

[0080] Wherein, as Figure 4As shown, the pre-charge switch unit can be controlled to be in an open state after the capacitor unit is pre-charged to a voltage of the DC bus being a first preset voltage U1, and the first preset voltage U1 is less than the voltage of the power grid. For example, the voltage of the power grid is about 230V, and the first preset voltage U1 can be 210V.

[0081] Step S300: After the pre-charge switch unit is opened, the second inverter switch unit is controlled to be in a closed state to enable the power grid to charge the capacitor unit.

[0082] As shown, the second inverter switch unit is in a closed state, the power grid is connected to the inverter circuit, and at this time, the power of the power grid can charge the capacitor unit through the switch tube in the inverter circuit. Since the switch tube in the inverter circuit is mainly used to convert DC into AC and input into the power grid, when the power of the power grid charges the capacitor unit through the switch tube in the inverter circuit, the body diode of the switch tube is mainly used to realize reverse connection.

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

[0084] In some embodiments, as shown, Figure 4 As shown, in step S300, the second inverter switch unit can be controlled to be in a closed state to enable the power grid to charge the capacitor unit after the pre-charge switch unit is opened for a first preset time t1. The first preset time t1 can be not greater than a threshold value, for example, 10ms, 20ms or 30ms, etc. In this case, the problem of affecting control accuracy caused by instantaneous connection of the inverter circuit and the pre-charge circuit when the second inverter unit is controlled to be closed after the pre-charge switch unit is opened can be reduced, and at the same time, the situation that the DC bus of the inverter is powered off due to too long interval time when the second inverter unit is controlled to be closed after the pre-charge switch unit is opened can also be reduced, thereby improving stability.

[0085] Step S400: After charging the capacitor unit, the voltage of the DC bus is lifted through the inverter circuit.

[0086] As shown, when the voltage of the DC bus is lifted through the inverter circuit, the AC power of the power grid reaches the DC bus after the action of the IGBT (Insulated Gate Bipolar Transistor) and the boost inductor in the inverter circuit, and the voltage of the DC bus will be lifted, that is, the inverter circuit at this time is regarded as a boost circuit.

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

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

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

[0090] In some embodiments, as shown in Figure 4 As shown, in step S500, the voltage of the DC bus is maintained by the DC conversion circuit to a third preset voltage U3 after the voltage of the DC bus is lifted to the third preset voltage U3, and the third preset voltage U3 is greater than the voltage of the grid. For example, the voltage of the grid is about 230V, and the third preset voltage U3 is greater than 230V. Thus, it can be used to activate the energy storage battery.

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

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

[0093] In which, the energy storage battery voltage U4 is not less than the preset battery voltage in the activated state, for example, the low-voltage energy storage battery voltage U4 is not less than 24V. And, at this time, the key functions of the energy storage battery are complete, which can be used for charging and discharging, that is, the activated state, so the energy storage battery can send the battery activation success instruction to the inverter through the communication line, so that the inverter executes the normal work content, for example, the electrical energy generated by the photovoltaic array or the electrical energy of the grid is input into the energy storage battery for storage. The battery activation success instruction can be used to indicate that the energy storage battery is in the activated state.

[0094] In some other embodiments, the energy storage system can further comprise a grid switch unit, the grid switch unit being connected between the second inverter switch unit and the grid. By the grid switch unit, the safety of the energy storage system when connecting to the grid can be improved. Accordingly, the flowchart of the method of activating the energy storage battery of the present embodiments can refer to Figure 5 .

[0095] Figure 5 The difference between the embodiments shown in Figure 3 and the embodiments shown in

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

[0097] It can be understood that, before controlling the pre-charge switch unit and the first inverter switch unit to be in the closed state, i.e. before step S100, the grid switch unit can be controlled to be in the closed state, optionally. And the grid switch unit can be multiple, for example, two or more. Thus, the safety of the energy storage system when connecting to the grid can be improved.

[0098] In some other embodiments, the inverter can further comprise an auxiliary power supply, the auxiliary power supply being connected to the grid and used to provide power for the control circuit of the inverter.

[0099] Before controlling the pre-charge switch unit and the first inverter switch unit to be in the closed state, i.e. before step S100, the method can further comprise: starting the control circuit by the auxiliary power supply to make the control circuit execute any of the foregoing methods of activating the energy storage battery.

[0100] As described above, after the energy storage battery is activated, the inverter can input the power generated by the photovoltaic array or the power of the grid into the energy storage battery for storage. Therefore, as shown in Figure 5 , the method can further comprise:

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

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

[0104] In other embodiments, if the auxiliary power supply is connected to the power grid and the auxiliary power supply can continuously take power from the power grid, the control circuit of the inverter also continuously works. Then, when the energy storage battery is in the dormant state, the control circuit of the inverter can directly execute the 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 steps S001 and S100 to S600. In addition, the control circuit can also execute the steps S001 and S100 to S700 or the steps S001 to S700 to activate the energy storage battery and normally charge it.

[0105] In summary, the energy storage battery is automatically activated by the power provided by the power grid, and during the activation process, the capacitor unit of the inverter is pre-charged by the pre-charging circuit to reduce the voltage difference between the DC bus of the inverter and the power grid, thereby reducing the damage of the inverter caused by the surge current. 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 lifted 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 is a structure of an energy storage system 1 and a schematic diagram of a circuit connection thereof according to an embodiment of the present application.

[0107] The embodiment of the present application also provides an energy storage system 1. As shown in Figure 6 The energy storage system 1 can include a photovoltaic array 12, an inverter 11 and an energy storage battery 13. The inverter 11 of the energy storage system 1 can be the inverter 11 involved in any of the above embodiments, and therefore will not be described 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 instruction 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 provides a poor user experience. Therefore, the following method of reversely activating the energy storage battery 13 is provided. The energy storage battery 13 is automatically reverse activated using the power provided by the power grid 2. During the activation process, the capacitor unit of the inverter 11 is precharged via the precharge circuit 115 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 that could damage 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, as Figure 7 As shown, the energy storage system 1 may further include a grid switch unit 21, with the grid 2 switch 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 connected to the grid 2. In this embodiment, if the energy storage system 1 is provided with the 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 the closed state before the pre-charge switch unit 1151 and the first inverter switch unit 113 are in the closed state.

[0113] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application and are not intended to limit the present application. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions 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 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, and the pre-charging circuit includes a pre-charging switch unit; The method comprises: When the grid has a grid voltage 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 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 sent 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, wherein: The 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 reaches a first preset voltage, the pre-charging switch unit is controlled to be in an off state, where the first preset voltage is lower than the voltage of the power grid.

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

4. The method for activating an energy storage battery according to claim 1, wherein: The step of stabilizing the voltage of the capacitor unit by the DC conversion circuit after the voltage of the DC bus is raised includes: After the voltage of the DC bus is raised to a third preset voltage, the DC conversion circuit maintains the voltage of the DC bus at the third preset voltage, and the third preset voltage is greater than the voltage of the grid.

5. The method for activating an energy storage battery according to claim 1, wherein: After the pre-charging switch unit is disconnected, controlling the second inverter switch unit to be in a closed state so that the 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, wherein: 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, wherein: 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, wherein: 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, wherein: The pre-charging circuit further includes: a rectifier unit, wherein 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 a grid voltage exists 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, wherein: The energy storage system further includes 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 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 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, used in 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. 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. The control circuit is used to: When the grid has a grid voltage 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 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 grid charges the capacitor unit; and After charging the capacitor unit, the voltage of the DC bus is raised by the inverter circuit; and 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; and When the energy storage battery is charged to a preset battery voltage, a battery activation success instruction is received from the energy storage battery; 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 further includes: a rectifier unit, an input end of the rectifier unit being connected between the first inverter switch unit and the second inverter switch unit, and an output end of the rectifier unit being 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, and 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 the grid has a grid voltage 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 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; 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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