Energy storage system structure for Alternating-Current power grid interconnection and control method

Abstract

The present application discloses an energy storage system structure for an AC power grid interconnection and a control method. The energy storage system structure for an AC power grid interconnection

Description

This application belongs to the field of energy storage DC / AC converter technologies, and specifically, to an energy storage system structure for alternating-current power grid interconnection and a control method. BACKGROUND Existing connections between alternating-current power grids are divided into alternating-current connections and direct-current connections. The alternating-current connection is to directly connect two power grids by an alternating-current power transmission line. Power grids in an alternating-current connection have many problems such as a synchronization stability problem, and usually require use of unified scheduling, resulting in poor flexibility of control on two sides. The direct-current connection usually refers to a flexible direct-current connection or a conventional direct-current connection. Although alternating-current power grids on two sides can be decoupled, run, and controlled, currently, due to problems of higher construction costs, higher investment, and a larger occupied area, there is control complexity. Therefore, there is an urgent need to study a novel alternating-current power grid connection, to achieve friendly interconnection between different alternating-current power grids and improve the flexibility of alternating-current power exchanges between the two sides. SUMMARY 08 10 24 To resolve the problems in friendly interconnection between alternating-current power grids, this application provides an energy storage system structure for alternating-current power grid interconnection and a control method, to implement asynchronous interconnection between different alternating-current power grids through energy storage, and improve the flexibility of alternating-current power exchanges between two sides. To achieve the foregoing objectives, the following technical solutions are used in this application. According to an aspect of this application, an energy storage system structure for alternating-current power grid interconnection is provided, including: an energy storage battery unit; a first DC / AC converter device, where an alternating-current side thereof is connected to a first alternating-current power grid, and positive and negative poles on a direct-current side thereof are respectively connected to positive and negative poles of the energy storage battery unit; and a second DC / AC converter device, where an alternating-current side thereof is connected to a second alternating-current power grid, and positive and negative poles on a direct-current side thereof are respectively connected to the positive and negative poles of the energy storage battery unit. In an embodiment, the first DC / AC converter device includes at least one DC / AC converter, the second DC / AC converter device includes at least one DC / AC converter, and the energy storage battery unit includes at least one energy storage battery pack, where a quantity of DC / AC converters in the first DC / AC converter device and a quantity of DC / AC converters in the second DC / AC converter device are equal to a quantity of energy storage battery packs in the energy storage battery unit. In an embodiment, the energy storage system structure for alternating-current power grid interconnection includes at least two energy storage battery units, at least two second DC / AC converter devices, and at least two first switches, where the first DC / AC converter device is respectively connected to the at least two energy storage battery units by the at least two first switches, and the at least two second DC / AC converter devices are respectively connected to the at least two energy storage battery units correspondingly, where a quantity of switches in each first switch is equal to a quantity of energy storage battery packs in the energy storage battery unit. 08 10 24 In an embodiment, the energy storage system structure for alternating-current power grid interconnection includes at least two energy storage battery units, at least two second DC / AC converter devices, and at least two second switches, where the first DC / AC converter device is directly connected to the at least two energy storage battery units, and the at least two second DC / AC converter devices are respectively connected to the at least two energy storage battery units correspondingly by the at least two second switches, where a quantity of switches in each second switch is equal to a quantity of energy storage battery packs in the energy storage battery unit. In an embodiment, the energy storage system structure for alternating-current power grid interconnection includes at least two energy storage battery units, at least two second DC / AC converter devices, at least two first switches, and at least two second switches, where the first DC / AC converter device is respectively connected to the at least two energy storage battery units by the at least two first switches, and the at least two second DC / AC converter devices are respectively connected to the at least two energy storage battery units correspondingly by the at least two second switches, where a quantity of switches in each first switch and a quantity of switches in each second switch are both equal to a quantity of energy storage battery packs in the energy storage battery unit. In an embodiment, the energy storage system structure for alternating-current power grid interconnection includes at least two energy storage battery units, at least two first switches, and at least two second switches, where the first DC / AC converter device is respectively connected to the at least two energy storage battery units by the at least two first switches, and the second DC / AC converter device is respectively connected to the at least two energy storage battery units by the at least two second switches, where a quantity of switches in each first switch and a quantity of switches in each second switch are both equal to a quantity of energy storage battery packs in the energy storage battery unit. In an embodiment, the first DC / AC converter device is connected to the first alternating-current power grid by a transformer, and / or the second DC / AC converter device is connected to the second alternating-current power grid by a transformer. In an embodiment, the first DC / AC converter device is connected to the energy storage battery unit by a DC-DC converter, and / or the second DC / AC converter device is connected to the energy storage battery unit by a DC-DC converter. In an embodiment, the first DC / AC converter device is connected to the energy storage battery unit by a DC-AC converter, and / or the second DC / AC converter device is connected to the energy storage battery unit by a DC-AC converter. 08 10 24 In an embodiment, the energy storage battery unit is a chemical battery, a supercapacitor, or a fuel cell. According to another aspect of this application, independent control taking current limit exceeding into account is adopted, that is, independent charge and discharge control is performed on both the DC / AC converters in the first DC / AC converter device and the second DC / AC converter device according to requirements on respective alternating-current sides thereof, and when an alternating-current side current of a DC / AC converter exceeds a limit, amplitude-limited control is performed on the alternating-current side current. In an embodiment, in the step of when the alternating-current side current of the DC / AC converter exceeds the limit, the amplitude-limited control is performed on the alternating-current side current, setting of the amplitude-limited control is determined according to maximum allowable charge and discharge current set values of the DC / AC converters in the first DC / AC converter device and the second DC / AC converter device, a real-time current, control modes of the DC / AC converters, and a maximum allowable charge and discharge current of the energy storage battery pack in the energy storage battery unit. In an embodiment, the step of when the alternating-current side current of the DC / AC converter exceeds the limit, the amplitude-limited control is performed on the alternating-current side current specifically includes: setting the maximum allowable charge and discharge current set values of the DC / AC converters in the first DC / AC converter device and the second DC / AC converter device to IsM and Iset2 respectively; measuring alternating-current side currents of the DC / AC converters in the first DC / AC converter device and the second DC / AC converter device, and calculating effective values thereof as and / 2 respectively; setting the control modes of the DC / AC converters in the first DC / AC converter device and the second DC / AC converter device, and setting one of the first DC / AC converter device and the second DC / AC converter device into a primary operation mode and the other into an auxiliary operation mode, where the primary operation mode is to preferentially autonomously control a current, and the auxiliary operation mode is to track and calculate a required current according to a current current of the primary operation mode; and setting the maximum allowable charge and discharge current of the energy storage battery pack in the energy storage battery unit, where Isetb >Isetl and Isetb >Iset2, where 08 10 24 when the DC / AC converter of the first DC / AC converter device is in the primary operation mode, an upper limit of amplitude-limited control on the alternating-current side current of the DC / AC converter in the first DC / AC converter device is equal to Isetl, the DC / AC converter in the second DC / AC converter device is in the auxiliary operation mode, an upper limit of amplitude-limited control on the alternating-current side current of the DC / AC converter in the second DC / AC converter device is equal to min{ Iset2, 1|}; when the DC / AC converter of the second DC / AC converter device is in the primary operation mode, the upper limit of the amplitude-limited control on the alternating-current side current of the DC / AC converter in the second DC / AC converter device is equal to Isea, the DC / AC converter in the first DC / AC converter device is in the auxiliary operation mode, the upper limit of the amplitude-limited control on the alternating-current side current of the DC / AC converter in the first DC / AC converter device is equal to min{ Isetl, | Isetb and when the alternating-current side currents of the DC / AC converters in the first DC / AC converter device and the second DC / AC converter device exceed the upper limits of the amplitude-limited control on the corresponding alternating-current side currents, the amplitude-limited control is performed on the alternating-current side currents. According still another aspect of this application, a control method for the energy storage system structure for alternating-current power grid interconnection is provided, where active power ride-through control is adopted, that is, DC / AC converter devices on two sides of the energy storage battery unit track power operation of the other side on a premise that neither of alternating-current side currents on the two sides exceeds a current limit on the local side. In an embodiment, the step of tracking the power operation of the other side includes: setting control modes of the DC / AC converters in the first DC / AC converter device and the second DC / AC converter device, and setting one of the first DC / AC converter device and the second DC / AC converter device into a primary operation mode and the other into an auxiliary operation mode, where the primary operation mode is to preferentially autonomously control a current, and the auxiliary operation mode is to track and calculate a required current according to a current current of the primary operation mode; measuring alternating-current side currents of the DC / AC converters in the first DC / AC converter device and the second DC / AC converter device, and comparing the alternating-current side currents of the DC / AC converters with current limits on corresponding sides; and obtaining, by the DC / AC converter in the auxiliary operation mode in response to that neither of the alternating-current side currents of the DC / AC converters on the two sides 08 10 24 exceeds a current limit on the local side, a real-time power of the DC / AC converter in the primary operation mode from the DC / AC converter in the primary operation mode, and using the real-time power as a reference power of the DC / AC converter in the auxiliary operation mode. According still another aspect of this application, a control method for the energy storage system structure for alternating-current power grid interconnection is provided, where local frequency regulation-superimposed automatic generation control (AGC) command tracking control is adopted, that is, the DC / AC converter superimposes a received AGC power reference value with a local frequency regulation power as an operation power reference value of the DC / AC converter. According still another aspect of this application, a control method for the energy storage system structure for alternating-current power grid interconnection is provided, where local reactive compensation-superimposed automatic voltage control (AVC) command tracking control is adopted, that is, the DC / AC converter makes a response according to an AVC command in a voltage control dead zone, and locally autonomously regulates a reactive power based on a value of a voltage according to the AVC command outside the voltage control dead zone. In an embodiment, the step of locally autonomously regulating the reactive power based on the value of the voltage specifically refers to increasing a reactive output when the voltage drops and reducing the reactive output when the voltage rises. According to an aspect of this application, an electronic device is provided, including: one or more processors; and a storage apparatus, configured to store one or more programs. When executed by the one or more processors, the one or more programs cause the one or more processors to implement the foregoing method. According to an aspect of this application, a computer-readable storage medium is provided, having a computer program stored therein. When executed by a processor, the program implements the foregoing method. Beneficial effects of this application are as follows: 1. In this application, direct-current sides of two DC / AC converter devices are respectively connected to positive and negative poles of an energy storage battery, and alternating-current sides of the two DC / AC converter devices are respectively connected to different alternating-current power grids, to implement asynchronous interconnection between the different alternating-current power grids, which can avoid problems, such as a synchronization stability problem, when the two alternating-current power grids are 08 10 24 connected by a weak communication channel, and is more economical than a direct-current connection solution. 2. Through energy storage, electricity of the alternating-current power grids on two sides can be stored, which improves the utilization efficiency of stored energy. 3. Solutions of this application can improve the flexibility of alternating-current power exchanges between the two sides, and the alternating-current power grids on the two sides can perform power exchanges according to requirements, to achieve flexible regulation of power. BRIEF DESCRIPTION OF THE DRAWINGS FIG. lisa schematic diagram of an energy storage system structure for alternating-current power grid interconnection according to an embodiment of this application; FIG. 2 is a schematic diagram of an energy storage system structure for alternating-current power grid interconnection according to an embodiment of this application; FIG. 3 is a schematic diagram of an energy storage system structure for alternating-current power grid interconnection according to an embodiment of this application; FIG. 4 is a schematic diagram of a two-level topology of a DC / AC converter according to an embodiment of this application; FIG. 5 is a schematic diagram of a three-level topology of a DC / AC converter according to an embodiment of this application; FIG. 6 is a schematic diagram of an energy storage system structure for alternating-current power grid interconnection according to an embodiment of this application; FIG. 7 is a schematic diagram of an energy storage system structure for alternating-current power grid interconnection according to an embodiment of this application; FIG. 8 is a schematic diagram of an energy storage system structure for alternating-current power grid interconnection according to an embodiment of this application; FIG. 9 is a schematic diagram of an energy storage system structure for alternating-current power grid interconnection according to an embodiment of this application; FIG. 10 is a schematic diagram of an energy storage system structure for alternating-current power grid interconnection according to an embodiment of this application; FIG. 11 is a schematic diagram of an energy storage system structure for alternating-current power grid interconnection according to an embodiment of this application; 08 10 24 FIG. 12 is a schematic diagram of an energy storage system structure for alternating-current power grid interconnection according to an embodiment of this application; FIG. 13 is a schematic diagram of an energy storage system structure for alternating-current power grid interconnection according to an embodiment of this application; FIG. 14 is a schematic diagram of an energy storage system structure for alternating-current power grid interconnection according to an embodiment of this application; FIG. 15 is a schematic diagram of an energy storage system structure for alternating-current power grid interconnection according to an embodiment of this application; FIG. 16 shows a topology of a triple interleaved cascade buck / boost bidirectional DC-DC converter according to an embodiment of this application; FIG. 17 shows a topology of a cascade buck-boost bidirectional DC-DC converter according to an embodiment of this application; FIG. 18 shows a topology of a full-bridge bidirectional DC-DC converter according to an embodiment of this application; FIG. 19 is a schematic flowchart of a control method for an energy storage system structure for alternating-current power grid interconnection according to an embodiment of this application; FIG. 20 is a schematic flowchart of another control method for an energy storage system structure for alternating-current power grid interconnection according to an embodiment of this application; and FIG. 21 is a block diagram of an electronic device according to an embodiment of this application. 1-first alternating-current power grid, 2-second alternating-current power grid, 3-first DC7AC converter device, 4-second DC / AC converter device, 5-energy storage battery unit, 6-first switch, 7-second switch, 8-transformer on a side of the first DC / AC converter device, 9-transformer on a side of the second DC / AC converter device, 10-DC-DC converter on a side of the first DC / AC converter device 3, 11-DC-DC converter on a side of the second DC / AC converter device. DETAILED DESCRIPTION The technical solutions of this application are clearly and completely described below with reference to the accompanying drawings. Apparently, the described embodiments are merely some of rather than all of the embodiments of this application. All other embodiments 08 10 24 obtained by a person of ordinary skill in the art based on embodiments of this application without creative efforts shall fall within the protection scope of this application. In the description of this application, it should be noted that, a direction or location relationship indicated by a term "center", "on", "under", "left", "right", "vertical", "horizontal", "inner", "outer", or the like is a direction or location relationship shown based on the accompanying drawings, and is used only for ease and brevity of description of this application, but is not intended to indicate or imply that a mentioned apparatus or element needs to have a particular direction and is constructed and operated in the particular direction. Therefore, the direction or location relationship cannot be understood as a limitation on this application. In addition, terms "first", "second", and "third" are merely intended for a descriptive purpose, and cannot be understood as indicating or implying relative importance. In the description of this application, it should be noted that, unless otherwise explicitly specified or defined, the terms such as "install", "connect", and "connection" should be understood in a broad sense. For example, the connection may be a fixed connection, a detachable connection, or an integral connection; or may be a mechanical connection or an electrical connection; or may be a direct connection, an indirect connection through an intermediary, or internal communication between two components; or may be a wireless connection or a wired connection. A person of ordinary skill in the art may understand the specific meanings of the foregoing terms in this application according to specific situations. In addition, technical features involved in different implementations of this application described below may be combined with each other provided that there is no conflict between them. This application discloses an energy storage system structure for alternating-current power grid interconnection. In an embodiment, as shown in FIG. 1, the energy storage system structure for alternating-current power grid interconnection includes a first DC / AC converter device 3, a second DC / AC converter device 4, and an energy storage battery unit 5. An alternating-current side of the first DC / AC converter device 3 is connected to a first alternating-current power grid 1, and positive and negative poles on a direct-current side of the first DC / AC converter device 3 are respectively connected to positive and negative poles of the energy storage battery unit 5. An alternating-current side of the second DC / AC converter device 4 is connected to a second alternating-current power grid 2, and positive and negative poles on a direct-current side of the second DC / AC converter device 4 are respectively connected to the positive and negative poles of the energy storage battery unit 5. The first alternating-current power grid 1 and the second alternating-current power grid 2 08 10 24 may have a same frequency or different frequencies. In this embodiment, direct-current sides of two DC / AC converter devices are respectively connected to positive and negative poles of an energy storage battery, and alternating-current sides thereof are respectively connected to different alternating-current power grids. In this way, two alternating-current power grids can be interconnected to each other by the energy storage battery, power is exchanged flexibly through an energy storage system according to control requirements of the alternating-current power grids on the two sides, to implement asynchronous interconnection between the alternating-current power grids. The first DC / AC converter device includes at least one DC / AC converter, the second DC / AC converter device includes at least one DC / AC converter, and the energy storage battery unit includes at least one energy storage battery pack. A quantity of DC / AC converters in the first DC / AC converter device and a quantity of DC / AC converters in the second DC / AC converter device are equal to a quantity of energy storage battery packs in the energy storage battery unit. In this embodiment, direct-current sides of two DC / AC converter devices are respectively connected to positive and negative poles of an energy storage battery, and alternating-current sides thereof are respectively connected to different alternating-current power grids, to implement asynchronous interconnection between the different alternating-current power grids, which can avoid problems, such as a synchronization stability problem, when the two alternating-current power grids are connected by a weak communication channel, and is more economical than a direct-current connection solution. In addition, through energy storage, electricity of the alternating-current power grids on two sides can be stored, which improves the utilization efficiency of stored energy. This application can improve the flexibility of alternating-current power exchanges between the two sides, and the alternating-current power grids on the two sides can perform power exchanges according to requirements, to achieve flexible power exchanges. In an energy storage system structure for alternating-current power grid interconnection shown in FIG. 2, the first DC / AC converter device 3 includes a DC / AC converter PCS3-1, the second DC / AC converter device 4 includes a DC / AC converter PCS4-1, and the energy storage battery unit includes an energy storage battery pack BAT5-1. An alternating-current side of the DC / AC converter PCS3-1 is connected to the first alternating-current power grid 1, and positive and negative poles on a direct-current side of PCS3-1 are respectively connected to positive and negative poles of the energy storage battery pack BAT5-1. An alternating-current side of the DC / AC converter PCS4-1 is connected to the first alternating- 08 10 24 current power grid 2, and positive and negative poles on a direct-current side of PCS4-1 are respectively connected to the positive and negative poles of the energy storage battery pack BAT5-1. In an energy storage system structure for alternating-current power grid interconnection shown in FIG. 3, the first DC / AC converter device 3 includes two DC / AC converters PCS3-1 and PCS3-2, the second DC / AC converter device 4 includes two DC / AC converters PCS4-1 and PCS4-2, and the energy storage battery unit includes two energy storage battery packs BAT5-1 and BAT5-2. Both alternating-current sides of the DC / AC converters PCS3-1 and PC S3-2 are connected to the alternating-current power grid 1, positive and negative poles of a direct-current side of PCS3-1 are respectively connected to positive and negative poles of the energy storage battery pack BAT5-1, and positive and negative poles of a direct-current side of PC S3-2 are respectively connected to positive and negative poles of the energy storage battery pack BAT5-2. Both alternating-current sides of the DC / AC converters PCS4-1 and PCS4-2 are connected to the alternating-current power grid 2, positive and negative poles of a direct-current side of PCS4-1 are respectively connected to the positive and negative poles of the energy storage battery pack BAT5-1, and positive and negative poles of a direct-current side of PCS4-2 are respectively connected to the positive and negative poles of the energy storage battery pack BAT5-2. The DC / AC converter in the energy storage system uses an IGBT-based voltage source converter topology to implement bidirectional flowing of energy between an alternating-current system and a direct-current system. Common topologies include a two-level topology shown in FIG. 4 and a three-level topology shown in FIG. 5. In an embodiment, the energy storage system structure for alternating-current power grid interconnection includes two energy storage battery units and two second DC / AC converter devices. Switches may be arranged between the first DC / AC converter device and the energy storage battery units, or switches may be arranged between the second DC / AC converter device and the energy storage battery units, or switches may be arranged between the first DC / AC converter device and the energy storage battery units and between the second DC / AC converter devices and the energy storage battery units. During normal operation, only one energy storage battery unit is connected to an alternating-current power grid. When the running energy storage battery unit is unavailable due to a reason such as a failure or SOC over-range, a DC / AC converter can switch to another energy storage battery unit. In an embodiment, as shown in FIG. 6, the energy storage system structure for alternating-current power grid interconnection includes one first DC / AC converter device 3, 08 10 24 two energy storage battery units 5, two second DC / AC converter devices 4, and two first switches 6. The first DC / AC converter device 3 is respectively connected to the two energy storage battery units 5 by the two first switches 6. The two second DC / AC converter devices 4 are respectively connected to the two energy storage battery units 5 correspondingly. In this embodiment, the first DC / AC converter device 3 includes two DC / AC converters PCS3-1 and PCS3-2. Each energy storage battery unit 5 includes two energy storage battery packs. The first energy storage battery unit 5 includes BAT5-1 and BAT5-2, and the second energy storage battery unit 5 includes BAT5-3 and BAT5-4. The first second DC / AC converter device 4 includes two DC / AC converters PCS4-1 and PCS4-2, and the second second DC / AC converter device 4 includes two DC / AC converters PCS4-3 and PCS4-4. The first first switch 6 includes a switch 6-1 and a switch 6-2, the second first switch 6 includes a switch 6-3 and a switch 6-4. Both the alternating-current sides of the DC / AC converters PCS3-1 and PCS3-2 are connected to the alternating-current power grid 1. The direct-current side of PCS3-1 is connected to the energy storage battery pack BAT5-1 by the switch 6-1 and connected to the energy storage battery pack BAT5-3 by the switch 6-3. The direct-current side of PCS3-2 is connected to the energy storage battery pack BAT5-2 by the switch 6-2 and connected to the energy storage battery pack BAT5-4 by the switch 6-4. Alternating-current sides of the DC / AC converters PCS4-1, PCS4-2, PCS4-3, and PCS4-4 are all connected to the alternating-current power grid 2. Direct-current sides of the two DC / AC converters PCS4-1 and PCS4-2 of the first second DC / AC converter device 4 are respectively connected to the energy storage battery packs BAT5-1 and BAT5-2, direct-current sides of the two DC / AC converters PCS4-3 and PCS4-4 of the second second DC / AC converter device 4 are respectively connected to the energy storage battery packs BAT5-3 and BAT5-4. In normal operation, one of the two first switches 6 is closed to form a circuit to connect to the corresponding energy storage battery unit, and the other first switch 6 is open. When the running energy storage battery unit is unavailable due to a reason such as a failure or SOC over-range, closed and open states of the two switches are switched, to switch the operation of the system to the other energy storage battery unit. In an embodiment, more energy storage battery units 5, second DC / AC converter devices 4, and first switches 6 may alternatively be arranged, quantities of the three are equal, and they are correspondingly connected to each other referring to the connection manners in FIG. 6. In an embodiment, as shown in FIG. 7, the energy storage system structure for alternating-current power grid interconnection also includes one first DC / AC converter device 3, two energy storage battery units 5, and two second DC / AC converter devices 4, and 08 10 24 differs from the embodiment shown in FIG. 6 in that the first DC / AC converter device 3 is directly correspondingly connected to the two energy storage battery units 5, the two first switches 6 are not arranged, and two second switches 7 are arranged between the two energy storage battery units 5 and the two second DC / AC converter devices 4. The first second switch 7 includes a switch 1-1 and a switch 1-2. The second second switch 7 includes a switch 7-3 and a switch 7-4. The direct-current side of PCS4-1 in the first second DC / AC converter device 4 is connected to the energy storage battery pack BAT5-1 by the switch 7-1, the direct-current side of PCS4-2 is connected to the energy storage battery pack BAT5-2 by the switch 7-2, the direct-current side of PCS4-3 in the second second DC / AC converter device 4 is connected to the energy storage battery pack BAT5-3 by the switch 7-3, and the direct-current side of PCS4-4 is connected to the energy storage battery pack BAT5-4 by the switch 7-4. The remaining parts are similar to those in the embodiment of FIG. 6, and details are not described again. In normal operation, one of the two second switches 7 is closed to form a circuit to connect to the corresponding energy storage battery unit, and the other first switch 6 is open. When the running energy storage battery unit is unavailable due to a reason such as a failure or SOC over-range, closed and open states of the two switches are switched, to switch the operation of the system to the other energy storage battery unit. In an embodiment, more energy storage battery units 5, second DC / AC converter devices 4, and second switches 7 may alternatively be arranged, quantities of the three are equal, and they are correspondingly connected to each other referring to the connection manners in FIG. 7. In an embodiment, as shown in FIG. 8, the energy storage system structure for alternating-current power grid interconnection also includes one first DC / AC converter device 3, two energy storage battery units 5, two second DC / AC converter devices 4, and two first switches 6, and differs from the embodiment shown in FIG. 6 in that in addition to that the first DC / AC converter device 3 is correspondingly connected to the two energy storage battery units 5 by two first switches 6, two second switches 7 are further arranged between the two energy storage battery units 5 and the two second DC / AC converter devices 4. The first second switch 7 includes a switch 1-1 and a switch 1-2. The second second switch 7 includes a switch 7-3 and a switch 7-4. The direct-current side of PCS4-1 in the first second DC / AC converter device 4 is connected to the energy storage battery pack BAT5-1 by the switch 7-1, the direct-current side of PCS4-2 is connected to the energy storage battery pack BAT5-2 by the switch 7-2, the direct-current side of PCS4-3 in the second second DC / AC converter device 4 is connected to the energy storage battery pack BAT5-3 by the switch 7-3, and the direct-current side of PCS4-4 is connected to the energy storage battery pack BAT5-4 08 10 24 by the switch 7-4. The remaining parts are similar to those in the embodiment of FIG. 6, and details are not described again. In normal operation, one of the two first switches 6 is closed, and the corresponding second switch 7 is closed, to form a circuit to connect to the corresponding energy storage battery unit, and the other first switch 6 and the corresponding second switch 7 are open. When the running energy storage battery unit is unavailable due to a reason such as a failure or SOC over-range, closed and open states of the two first switches 6 and the two second switches 7 are switched, to switch the operation of the system to the other energy storage battery unit. In an embodiment, more energy storage battery units 5, second DC / AC converter devices 4, first switches 6, and second switches 7 may alternatively be arranged, quantities of the four are equal, and they are correspondingly connected to each other referring to the connection manners in FIG. 8. In an embodiment, the energy storage system structure for alternating-current power grid interconnection includes at least two energy storage battery units, at least two first switches, and at least two second switches. The first DC / AC converter device is respectively connected to the at least two energy storage battery units by the at least two first switches, and the second DC / AC converter device is respectively connected to the at least two energy storage battery units by the at least two second switches. A quantity of switches in each first switch and a quantity of switches in each second switch are both equal to a quantity of energy storage battery packs in the energy storage battery unit. The energy storage system structure for alternating-current power grid interconnection shown in FIG. 9 includes one first DC / AC converter device 3, one second DC / AC converter device 4, two energy storage battery units 5, two first switches 6, and two second switches 7. The first DC / AC converter device 3 is connected to the two energy storage battery units 5 by the two first switches 6 correspondingly, and the second DC / AC converter device 4 is connected to the two energy storage battery units 5 by the two second switches 7 correspondingly. Specifically, the direct-current side of PCS3-1 is connected to the energy storage battery pack BAT5-1 by the switch 6-1 and connected to the energy storage battery pack BAT5-3 by the switch 6-3. The direct-current side of PCS3-2 is connected to the energy storage battery pack BAT5-2 by the switch 6-2 and connected to the energy storage battery pack BAT5-4 by the switch 6-4. The direct-current side of PCS4-1 is connected to the energy storage battery pack BAT5-1 by the switch 7-1 and connected to the energy storage battery pack BAT5-3 by the switch 7-3. The direct-current side of PCS4-2 is connected to the energy storage battery pack BAT5-2 by the switch 7-2 and connected to the energy storage battery pack BAT5-4 by the switch 7-4. In normal operation, one of the two first switches 6 is closed, and the corresponding second switch 7 is 08 10 24 closed, to form a circuit to connect to the corresponding energy storage battery unit, and the other first switch 6 and the corresponding second switch 7 are open. When the running energy storage battery unit is unavailable due to a reason such as a failure or SOC over-range, closed and open states of the two first switches 6 and the two second switches 7 are switched, to switch the operation of the system to the other energy storage battery unit. In an embodiment, more energy storage battery units 5, first switches 6, and second switches 7 may alternatively be arranged, quantities of the three are equal, and they are correspondingly connected to each other referring to the connection manners in FIG. 9. In an embodiment, the first DC / AC converter device is connected to the first alternating-current power grid by a transformer, and / or the second DC / AC converter device is connected to the second alternating-current power grid by a transformer. In the embodiment shown in FIG. 10, based on the schematic diagram of FIG. 1, the alternating-current side of the first DC / AC converter device 3 is connected to the first alternating-current power grid 1 by the transformer 8. In the embodiment shown in FIG. 11, based on the schematic diagram of FIG. 1, the alternating-current side of the second DC / AC converter device 4 is connected to the second alternating-current power grid 2 by the transformer 9. In the embodiment shown in FIG. 12, based on the schematic diagram of FIG. 1, the alternating-current side of the first DC / AC converter device 3 is connected to the first alternating-current power grid 1 by the transformer 8, and in addition, the alternating-current side of the second DC / AC converter device 4 is connected to the second alternating-current power grid 2 by the transformer 9. Similarly, in all the embodiments of FIG. 2, FIG. 3, and FIG. 6 to FIG. 9, it is acceptable that only the alternating-current side of the first DC / AC converter device 3 is connected to the first alternating-current power grid 1 by the transformer 8, or only the alternating-current side of the second DC / AC converter device 4 is connected to the second alternating-current power grid 2 by the transformer 9, or the alternating-current side of the first DC / AC converter device 3 is connected to the first alternating-current power grid 1 by the transformer 8, and in addition, the alternating-current side of the second DC / AC converter device 4 is connected to the second alternating-current power grid 2 by the transformer 9. In an embodiment, the first DC / AC converter device is connected to the energy storage battery unit by a DC-DC converter and an energy storage battery, and / or the second DC / AC converter device is connected to the energy storage battery unit by a DC-DC converter and an energy storage battery. In the embodiment shown in FIG. 13, based on the schematic diagram of FIG. 1, the direct-current side of the first DC / AC converter device 3 is connected to the energy storage battery unit 5 by the DC-DC converter 10. In the embodiment shown in FIG. 08 10 24 14, based on the schematic diagram of FIG. 1, the direct-current side of the second DC / AC converter device 4 is connected to the energy storage battery unit 5 by the DC-DC converter 11. In the embodiment shown in FIG. 15, based on the schematic diagram of FIG. 1, the direct-current side of the first DC / AC converter device 3 is connected to the energy storage battery unit 5 by the DC-DC converter 10, and in addition, the direct-current side of the second DC / AC converter device 4 is connected to the energy storage battery unit 5 by the DC-DC converter 11. Similarly, in all the embodiments of FIG. 2, FIG. 3, and FIG. 6 to FIG. 12, it is acceptable that only the direct-current side of the first DC / AC converter device 3 is connected to the energy storage battery unit 5 by the DC-DC converter 10, or only the direct-current side of the second DC / AC converter device 4 is connected to the energy storage battery unit 5 by the DC-DC converter 11, or the direct-current side of the first DC / AC converter device 3 is connected to the energy storage battery unit 5 by the DC-DC converter 10, and in addition, the direct-current side of the second DC / AC converter device 4 is connected to the energy storage battery unit 5 nu the DC-DC converter 11. The DC-DC converter includes an isolated type and a non-isolated type. The former includes, but is not limited to, a flyback bidirectional DC-DC converter, a forward bidirectional DC-DC converter, a push-pull bidirectional DC-DC converter, a full-bridge bidirectional DC-DC converters, and the like. The latter includes, but not limited to, a buck / boost DC-DC converter, a boost / buck DC-DC converter, a buck-boost DC-DC converter, a Cuk DC-DC converter, a Sepic / Zeta DC-DC converter, a Zeta / Sepic DC-DC converter, and the like. FIG. 16 shows a topology of a triple interleaved cascade buck / boost bidirectional DC-DC converter. FIG. 17 shows a topology of a cascade buck-boost bidirectional DC-DC converter. FIG. 18 shows a topology of a full-bridge bidirectional DC-DC converter. In an embodiment, the energy storage battery unit may be a chemical battery, a supercapacitor, or a fuel cell. The embodiments of this application further provides a control method for the energy storage system structure for alternating-current power grid interconnection. In the control method, independent control taking current limit exceeding into account is adopted, that is, independent charge and discharge control is performed on both the DC / AC converters in the first DC / AC converter device and the second DC / AC converter device according to requirements on respective alternating-current sides thereof, and when an alternating-current side current of a DC / AC converter exceeds a limit, amplitude-limited control is performed on the alternating-current side current. The requirements on the alternating-current side include a system voltage, a frequency, and power angle stability. 08 10 24 In an embodiment, in the step of when the alternating-current side current of the DC / AC converter exceeds the limit, the amplitude-limited control is performed on the alternating-current side current, setting of the amplitude-limited control is determined according to maximum allowable charge and discharge current set values of the DC / AC converters in the first DC / AC converter device and the second DC / AC converter device, a real-time current, control modes of the DC / AC converters, and a maximum allowable charge and discharge current of the energy storage battery pack in the energy storage battery unit. In an embodiment, the step of when the alternating-current side current of the DC / AC converter exceeds the limit, the amplitude-limited control is performed on the alternating-current side current, as shown in FIG. 19, specifically includes: SI 10: Set the maximum allowable charge and discharge current set values of the DC / AC converters in the first DC / AC converter device and the second DC / AC converter device to IsM and 1^2 respectively. For example, in FIG. 2, a maximum allowable charge and discharge current set value of the DC / AC converter PCS3-1 is set to Isetl, and a maximum allowable charge and discharge current set value of the DC / AC converter PCS4-1 is set to I set! ■ SI 20: Measure alternating-current side currents of the DC / AC converters in the first DC / AC converter device and the second DC / AC converter device, and calculate effective values thereof as and / 2 respectively. For example, in FIG. 2, an alternating-current side current of the DC / AC converter PCS3-1 is measured, and an effective value thereof is calculated as / ,, and an alternating-current side current of the DC / AC converter PCS4-1 is measured, and an effective value thereof is calculated as / 2 • SI 30: Set the control modes of the DC / AC converters in the first DC / AC converter device and the second DC / AC converter device, and set one of the first DC / AC converter device and the second DC / AC converter device into a primary operation mode and the other into an auxiliary operation mode. The primary operation mode is to preferentially autonomously control a current, and the auxiliary operation mode is to track and calculate a required current according to a current current of the primary operation mode. For example, in FIG. 2, the DC / AC converter PCS3-1 is set to be in the primary operation mode, and the DC / AC converter PCS4-1 is set to be in the auxiliary operation mode, or the DC / AC converter PCS3-1 is set to be in the auxiliary operation mode, and the DC / AC converter PCS4-1 is set to be in the primary operation mode. In consideration of supporting 08 10 24 performance thereof, usually, a converter connected to a weak alternating-current power grid side is selected to be in the primary operation mode. S140: Set the maximum allowable charge and discharge current Isetb of the energy storage battery pack in the energy storage battery unit, where Jsetb >IsM and IseA >Iset2. For example, in FIG. 2, a maximum allowable charge and discharge current of the energy storage battery pack BAT5-1 is set to Isetb, where Isetb needs to be greater than IsM and Iset2. SI 50: When the DC / AC converter of the first DC / AC converter device is in the primary operation mode, an upper limit of amplitude-limited control on the alternating-current side current of the DC / AC converter in the first DC / AC converter device is equal to 1 , the DC / AC converter in the second DC / AC converter device is in the auxiliary operation mode, an upper limit of amplitude-limited control on the alternating-current side current of the DC / AC converter in the second DC / AC converter device is equal to min{ Iset2, 11^-1^ |}. When the DC / AC converter of the second DC / AC converter device is in the primary operation mode, the upper limit of the amplitude-limited control on the alternating-current side current of the DC / AC converter in the second DC / AC converter device is equal to the DC / AC converter in the first DC / AC converter device is in the auxiliary operation mode, the upper limit of the amplitude-limited control on the alternating-current side current of the DC / AC converter in the first DC / AC converter device is equal to min{ IsM, | Isetb For example, in FIG. 2, when PCS3-1 is in the primary operation mode, an upper limit of amplitude-limited control on an alternating-current side current of PCS3-1 is equal to Isetl, and an upper limit of amplitude-limited control on an alternating-current side current of PCS4-1 is equal to min{ | Isetb-Ii |}, where min means to obtain the smallest one in compared elements. When PCS4-1 is in the primary operation mode, the upper limit of the amplitude-limited control on the alternating-current side current of PCS4-1 is equal to and the upper limit of the amplitude-limited control on the alternating-current side current of PCS3-1 is equal to min{ IsM, |Isetb-I21}. SI 60: Perform, when an alternating-current side current of a DC / AC converter exceeds the upper limit of the amplitude-limited control on the corresponding alternating-current side current, amplitude-limited control on the alternating-current side current. In this embodiment, independent control taking current limit exceeding into account is adopted. The calculated upper limits of the amplitude-limited control on the alternating- 08 10 24 current side currents are used as amplitude limit inputs of the amplitude-limited control on the currents of the DC / AC converters, to implement current limiting, which can effectively deal with a scenario in which an alternating-current side current of a DC / AC converter or a current of an energy storage battery pack exceeds a limit. In a control method for the energy storage system structure for alternating-current power grid interconnection provided in an embodiment of this application, active power ride-through control is adopted, that is, DC / AC converter devices on the two sides of the energy storage battery unit track power operation of the other side on a premise that neither of alternating-current side currents on the two sides exceeds a current limit on the local side. In an embodiment, as shown in FIG. 20, the tracking power operation of the other side specifically includes: S210: Set the control modes of the DC / AC converters in the first DC / AC converter device and the second DC / AC converter device, and set one of the first DC / AC converter device and the second DC / AC converter device into a primary operation mode and the other into an auxiliary operation mode. The primary operation mode is to preferentially autonomously control a current, and the auxiliary operation mode is to track and calculate a required current according to a current current of the primary operation mode. For example, in FIG. 2, the DC / AC converter PCS3-1 is set to be in the primary operation mode, and the DC / AC converter PCS4-1 is set to be in the auxiliary operation mode, or the DC / AC converter PCS3-1 is set to be in the auxiliary operation mode, and the DC / AC converter PCS4-1 is set to be in the primary operation mode. In consideration of supporting performance thereof, usually, a converter connected to a weak alternating-current power grid side is selected to be in the primary operation mode. S220: Measure alternating-current side currents of the DC / AC converters in the first DC / AC converter device and the second DC / AC converter device, and compare the alternating-current side currents of the DC / AC converters with current limits on corresponding sides. For example, in FIG. 2, an alternating-current side current of the DC / AC converter PCS3-1 is measured, to obtain an effective value Ir thereof, and an alternating-current side current of the DC / AC converter PCS4-1 is measured, to obtain an effective value / 2 thereof. In addition, values of and a current limit 1^^ of PCS3-1 are compared, and values of A and a current limit / max2 of PCS4-1 are compared. S230: The DC / AC converter in the auxiliary operation mode obtains, in response to that neither of the alternating-current side currents of the DC / AC converters on the two sides 08 10 24 exceeds a current limit on the local side, a real-time power of the DC / AC converter in the primary operation mode from the DC / AC converter in the primary operation mode, and uses the real-time power as a reference power of the DC / AC converter in the auxiliary operation mode. For example, in FIG. 2, when is less than or equal to and / 2 is less than or equal to ^2, if PCS3-1 is in the primary operation mode, and PCS4-1 is in the auxiliary operation mode, PCS4-1 obtains a real-time power Pl of the converter PCS3-1 from PCS3-1 and uses Pl as a reference power of PCS4-1. If PCS4-1 is in the primary operation mode, and PCS3-1 is in the auxiliary operation mode, PCS3-1 obtains a real-time power P2 of the converter PCS4-1 from PCS4-1 and uses P2 as a reference power of PCS3-1. By adopting the active power ride-through control, power exchanges between two alternating-current systems can be implemented completely through energy storage, and impact on the energy storage battery can be reduced to the lowest. It should be understood that, steps in flowcharts of FIG. 19 and FIG. 20 are displayed in sequence based on indication of arrows, but the steps are not necessarily performed in sequence based on a sequence indicated by the arrows. Unless otherwise clearly specified in this specification, the steps are performed without any strict sequence limit, and may be performed in other sequences. In addition, at least some steps in FIG. 19 and FIG. 20 may include a plurality of substeps or a plurality of stages. The substeps or the stages are not necessarily performed at the same moment, and instead may be performed at different moments. A performing sequence of the substeps or the stages is not necessarily performed in sequence, and instead may be performed in turn or alternately with another step or at least some of substeps or stages of the another step. In a control method for the energy storage system structure for alternating-current power grid interconnection provided in an embodiment of this application, local frequency regulation-superimposed AGC command tracking control is adopted, that is, the DC / AC converter superimposes a received AGC power reference value with a local frequency regulation power as an operation power reference value of the DC / AC converter. The AGC command is to respond to a scheduling instruction, and in addition, is superimposed with local frequency regulation, to make, after a failure or disturbance occurs, a quick response while normally responding to the scheduling instruction, which improves the frequency stability. In a control method for the energy storage system structure for alternating-current power grid interconnection provided in an embodiment of this application, local reactive 08 10 24 compensation-superimposed automatic voltage control command tracking control is adopted, that is, the DC / AC converter makes a response according to an AVC command in a voltage control dead zone, and locally autonomously regulates a reactive power based on a value of a voltage according to the AVC command outside the dead zone. In an embodiment, the step of locally autonomously regulating the reactive power based on the value of the voltage is dynamically continuously regulating a reactive output based on the value of the voltage, which specifically refers to increasing the reactive output when the voltage drops and reducing the reactive output when the voltage rises. The adopted AVC reactive voltage control is steady-state control, and the local control mainly responds to emergency voltage control. By adopting the local reactive compensation-superimposed AVC command tracking control, the voltage stability of the system in response to an emergency failure can be improved. In a control method for the energy storage system structure for alternating-current power grid interconnection in this application, one or more of independent control taking current limit exceeding into account, active power ride-through control, local frequency regulation-superimposed AGC command tracking control, and local reactive compensation-superimposed AVC command tracking control may be adopted. The DC / AC converters on the two sides may respectively implement functions, such as primary frequency regulation and voltage regulation, on the connected power grids, which helps stable operation of the power grids. FIG. 21 is a block diagram of an electronic device according to an exemplary embodiment of this application. It should be understood that the electronic device 600 shown in FIG. 21 is only an example, and does not impose any limitation on the functions and the scope of use of the embodiments of this application. As shown in FIG. 21, the electronic device 600 is represented in a form of a general-purpose computing device. Components of the electronic device 600 may include, but are not limited to: at least one processing unit 610, at least one storage unit 620, a bus 630 connecting different system components (including the storage unit 620 and the processing unit 610), a display unit 640, and the like. The storage unit has program code stored therein, and the program code may be executed by the processing unit 610, so that the processing unit 610 performs the methods according to the foregoing exemplary implementations of this application described in this specification. For example, the processing unit 610 may perform the methods shown in FIG. 19 and FIG. 20. 08 10 24 The storage unit 620 may include a readable medium in the form of a volatile storage unit, for example, a random access memory (RAM) 6201 and / or a cache storage unit 6202, and may further include a read-only memory (ROM) 6203. The storage unit 620 may further include a program / utility tool 6204 having a group of (at least one) program modules 6205. Such a program module 6205 includes, but is not limited to, an operating system, one or more application programs, other program modules, and program data. Each or a combination of these examples may include implementation of a network environment. The bus 630 may represent one or more of several types of bus structures, including a storage unit bus or a storage unit controller, a peripheral bus, an accelerated graphics port, a processing unit, or a local bus using any bus structure in a plurality of types of bus structures. The electronic device 600 may also communicate with one or more external devices 700 (for example, a keyboard, a pointing device, a Bluetooth device, and the like), and may also communicate with one or more devices that enable a user to interact with the electronic device 600, and / or communicate with any device (for example, a router, a modem, and the like) that enables the electronic device 600 to communicate with one or more other computing devices. Such communication may be performed by using an input / output (I / O) interface 650. In addition, the electronic device 600 may further communicate with one or more networks such as a local area network (LAN), a wide area network (WAN), and / or a public network (such as the Internet) through a network adapter 660. The network adapter 660 may communicate with another module of the electronic device 600 through the bus 630. It should be understood that although not shown in the figure, other hardware and / or software modules may be used in combination with the electronic device 600, including, but not limited to microcode, a device driver, a redundancy processing unit, an external disk drive array, a RAID system, a tape drive, a data backup storage system, or the like. Through the descriptions of the foregoing implementations, a person skilled in the art easily understands that the exemplary embodiments described herein may be implemented through software, or may be implemented through software located in combination with necessary hardware. The technical solutions according to the embodiments of this application may be implemented in a form of a software product. The software product may be stored in a non-volatile storage medium (which may be a CD-ROM, a USB flash drive, a removable hard disk, or the like) or on the network, including several instructions for instructing a computing device (which may be a personal computer, a server, a mobile terminal, a network 08 10 24 device, or the like) to perform the foregoing method according to the embodiments of this application. The software product may use any combination of one or more readable media. The readable medium may be a readable signal medium or a readable storage medium. The readable storage medium may be, for example, but not limited to, an electric, magnetic, optical, electromagnetic, infrared, or semi-conductive system, apparatus, or device, or any combination thereof. More specific examples (non-exhaustive list) of the readable storage medium may include: an electrical connection having one or more wires, a portable disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any appropriate combination thereof. The computer-readable storage medium may include a data signal propagated in a baseband or as part of a carrier, in which computer-readable program code is carried. A data signal propagated in such a way may assume a plurality of forms, including, but not limited to, an electromagnetic signal, an optical signal, or any appropriate combination thereof. The readable storage medium may also be any readable medium other than the readable storage medium, which readable medium may send, propagate, or transmit a program configured to be used by or in combination with an instruction execution system, apparatus, or device. The program code embodied on the readable storage medium may be transmitted by using any suitable medium, including, but not limited to, wireless, wired, cable, radio frequency (RF), and the like, or any appropriate combination thereof. The program code for executing the operations of this application may be written by using any combination of one or more programming languages. The programming languages include an object-oriented programming language such as Java and C++, and also include a conventional procedural programming language such as "C" or similar programming languages. The program code may be completely executed on a user computing device, partially executed on user equipment, executed as an independent software package, partially executed on a user computing device and partially executed on a remote computing device, or completely executed on a remote computing device or server. For the case involving a remote computing device, the remote computing device may be connected to a user computing device through any type of network including a local area network (LAN) or a wide area network (WAN), or may be connected to an external computing device (for example, through the Internet by using an Internet service provider). The computer-readable medium carries one or more programs. When the one or more programs are executed by a device, the computer-readable medium is enabled to implement the foregoing functions. A person skilled in the art may understand that the foregoing modules may be distributed in the apparatus according to the descriptions of the embodiments, or a corresponding change may be made, so that the modules are distributed in one or more apparatuses different from that in this embodiment. The modules in the foregoing embodiments may be combined into one module, or split into a plurality of submodules. The foregoing embodiments are merely intended for describing the technical solutions of this application, but are not intended to limit this application. Modifications or changes in various forms made by referring to the foregoing embodiments all fall within the protection scope of this application. 08 10 24

Claims

08 10 24What is claimed is:

1. An energy storage system structure for alternating-current power grid interconnection, comprising:an energy storage battery unit;a first DC / AC converter device, wherein an alternating-current side thereof is connected to a first alternating-current power grid, and positive and negative poles on a direct-current side thereof are respectively connected to positive and negative poles of the energy storage battery unit; anda second DC / AC converter device, wherein an alternating-current side thereof is connected to a second alternating-current power grid, and positive and negative poles on a direct-current side thereof are respectively connected to the positive and negative poles of the energy storage battery unit wherein the direct-current sides of two DC / AC converter devices are respectively connected to positive and negative poles of the energy storage battery, and alternating-current sides thereof are respectively connected to different alternating-current power grids, to implement asynchronous interconnection between the different alternating-current power grids.

2. The energy storage system structure for alternating-current power grid interconnection according to claim 1, wherein the first DC / AC converter device comprises at least one DC / AC converter, the second DC / AC converter device comprises at least one DC / AC converter, and the energy storage battery unit comprises at least one energy storage battery pack, wherein a quantity of DC / AC converters in the first DC / AC converter device and a quantity of DC / AC converters in the second DC / AC converter device are equal to a quantity of energy storage battery packs in the energy storage battery unit.

3. The energy storage system structure for alternating-current power grid interconnection according to claim 1, comprising at least two energy storage battery units, at least two second DC / AC converter devices, and at least two first switches, wherein the first DC / AC converter device is respectively connected to the at least two energy storage battery units by the at least two first switches, and the at least two second DC / AC converter devices are respectively connected to the at least two energy storage battery units correspondingly, wherein a quantity of switches in each first switch is equal to a quantity of energy storage battery packs in the energy storage battery unit.08 10 244. The energy storage system structure for alternating-current power grid interconnection according to claim 1, comprising at least two energy storage battery units, at least two second DC / AC converter devices, and at least two second switches, wherein the first DC / AC converter device is directly connected to the at least two energy storage battery units, and the at least two second DC / AC converter devices are respectively connected to the at least two energy storage battery units correspondingly by the at least two second switches, wherein a quantity of switches in each second switch is equal to a quantity of energy storage battery packs in the energy storage battery unit.

5. The energy storage system structure for alternating-current power grid interconnection according to claim 1, comprising at least two energy storage battery units, at least two second DC / AC converter devices, at least two first switches, and at least two second switches, wherein the first DC / AC converter device is respectively connected to the at least two energy storage battery units by the at least two first switches, and the at least two second DC / AC converter devices are respectively connected to the at least two energy storage battery units correspondingly by the at least two second switches, wherein a quantity of switches in each first switch and a quantity of switches in each second switch are both equal to a quantity of energy storage battery packs in the energy storage battery unit.

6. The energy storage system structure for alternating-current power grid interconnection according to claim 1, comprising at least two energy storage battery units, at least two first switches, and at least two second switches, wherein the first DC / AC converter device is respectively connected to the at least two energy storage battery units by the at least two first switches, and the second DC / AC converter device is respectively connected to the at least two energy storage battery units by the at least two second switches, wherein a quantity of switches in each first switch and a quantity of switches in each second switch are both equal to a quantity of energy storage battery packs in the energy storage battery unit.

7. The energy storage system structure for alternating-current power grid interconnection according to any one of claims 1 to 6, wherein the first DC / AC converter device is connected to the first alternating-current power grid by a transformer, and / or the second DC / AC converter device is connected to the second alternating-current power grid by a transformer.

8. The energy storage system structure for alternating-current power grid interconnection according to any one of claims 1 to 6, wherein the first DC / AC converter device is connected to the energy storage battery unit by a DC-DC converter, and / or the08 10 24second DC / AC converter device is connected to the energy storage battery unit by a DC-DC converter.

9. The energy storage system structure for alternating-current power grid interconnection according to claim 7, wherein the first DC / AC converter device is connected to the energy storage battery unit by a DC-AC converter, and / or the second DC / AC converter device is connected to the energy storage battery unit by a DC-AC converter.

10. The energy storage system structure for alternating-current power grid interconnection according to claim 1, wherein the energy storage battery unit is a chemical battery, a supercapacitor, or a fuel cell.

11. A control method for the energy storage system structure for alternating-current power grid interconnection according to any one of claims 1 to 10, wherein independent control taking current limit exceeding into account is adopted, that is, independent charge and discharge control is performed on both the DC / AC converters in the first DC / AC converter device and the second DC / AC converter device according to requirements on respective alternating-current sides thereof, and when an alternating-current side current of a DC / AC converter exceeds a limit, amplitude-limited control is performed on the alternating-current side current.

12. The control method according to claim 11, wherein in the step of when the alternating-current side current of the DC / AC converter exceeds the limit, the amplitudelimited control is performed on the alternating-current side current, setting of the amplitudelimited control is determined according to maximum allowable charge and discharge current set values of the DC / AC converters in the first DC / AC converter device and the second DC / AC converter device, a real-time current, control modes of the DC / AC converters, and a maximum allowable charge and discharge current of the energy storage battery pack in the energy storage battery unit.

13. The control method according to claim 12, wherein the step of when the alternating-current side current of the DC / AC converter exceeds the limit, the amplitude-limited control is performed on the alternating-current side current comprises:setting the maximum allowable charge and discharge current set values of the DC / AC converters in the first DC / AC converter device and the second DC / AC converter device toand 4z2 respectively;08 10 24measuring alternating-current side currents of the DC / AC converters in the first DC / AC converter device and the second DC / AC converter device, and calculating effective values thereof as and / 2 respectively;setting the control modes of the DC / AC converters in the first DC / AC converter device and the second DC / AC converter device, and setting one of the first DC / AC converter device and the second DC / AC converter device into a primary operation mode and the other into an auxiliary operation mode, wherein the primary operation mode is to preferentially autonomously control a current, and the auxiliary operation mode is to track and calculate a required current according to a current current of the primary operation mode; andsetting the maximum allowable charge and discharge current Isetb of the energy storage battery pack in the energy storage battery unit, wherein Isetb >Isetl and Isetb >IsM, whereinwhen the DC / AC converter of the first DC / AC converter device is in the primary operation mode, an upper limit of amplitude-limited control on the alternating-current side current of the DC / AC converter in the first DC / AC converter device is equal to Iseti, the DC / AC converter in the second DC / AC converter device is in the auxiliary operation mode, an upper limit of amplitude-limited control on the alternating-current side current of the DC / AC converter in the second DC / AC converter device is equal to min{ Iset2, | Isetb-Ii |};when the DC / AC converter of the second DC / AC converter device is in the primary operation mode, the upper limit of the amplitude-limited control on the alternating-current side current of the DC / AC converter in the second DC / AC converter device is equal to 1^, the DC / AC converter in the first DC / AC converter device is in the auxiliary operation mode, the upper limit of the amplitude-limited control on the alternating-current side current of the DC / AC converter in the first DC / AC converter device is equal to min{ Isetl, | Isetb-I21}; andwhen the alternating-current side currents of the DC / AC converters in the first DC / AC converter device and the second DC / AC converter device exceed the upper limits of the amplitude-limited control on the corresponding alternating-current side currents, the amplitude-limited control is performed on the alternating-current side currents.

14. A control method for the energy storage system structure for alternating-current power grid interconnection according to claim 1 to 10, wherein active power ride-through control is adopted, that is, DC / AC converter devices on two sides of the energy storage battery unit track power operation of the other side on a premise that neither of alternating-current side currents on the two sides exceeds a current limit on the local side.08 10 2415. The control method according to claim 14, wherein the step of tracking the power operation of the other side comprises:setting control modes of the DC / AC converters in the first DC / AC converter device and the second DC / AC converter device, and setting one of the first DC / AC converter device and the second DC / AC converter device into a primary operation mode and the other into an auxiliary operation mode, wherein the primary operation mode is to preferentially autonomously control a current, and the auxiliary operation mode is to track and calculate a required current according to a current current of the primary operation mode;measuring alternating-current side currents of the DC / AC converters in the first DC / AC converter device and the second DC / AC converter device, and comparing the alternating-current side currents of the DC / AC converters with current limits on corresponding sides; andobtaining, by the DC / AC converter in the auxiliary operation mode in response to that neither of the alternating-current side currents of the DC / AC converters on the two sides exceeds a current limit on the local side, a real-time power of the DC / AC converter in the primary operation mode from the DC / AC converter in the primary operation mode, and using the real-time power as a reference power of the DC / AC converter in the auxiliary operation mode.

16. A control method for the energy storage system structure for alternating-current power grid interconnection according to any one of claims 1 to 10, wherein local frequency regulation-superimposed automatic generation control (AGC) command tracking control is adopted, that is, the DC / AC converter superimposes a received AGC power reference value with a local frequency regulation power as an operation power reference value of the DC / AC converter.

17. A control method for the energy storage system structure for alternating-current power grid interconnection according to any one of claims 1 to 10, wherein local reactive compensation-superimposed automatic voltage control (AVC) command tracking control is adopted, that is, the DC / AC converter makes a response according to an AVC command in a voltage control dead zone, and locally autonomously regulates a reactive power based on a value of a voltage according to the AVC command outside the voltage control dead zone.

18. The control method according to claim 17, wherein the step of locally autonomously regulating the reactive power based on the value of the voltage specifically refers to increasing a reactive output when the voltage drops and reducing the reactive output when the voltage rises.

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