A structure and control method for an energy storage system for AC grid interconnection

Abstract

This invention discloses an energy storage system structure for AC grid interconnection, comprising: an energy storage battery unit; a first DC / AC converter device, the AC side of which is connected to a first AC grid, and the positive and negative terminals of its DC side are respectively connected to the positive and negative terminals of the energy storage battery unit; and a second DC / AC converter device, the AC side of which is connected to a second AC grid, and the positive and negative terminals of its DC side are respectively connected to the positive and negative terminals of the energy storage battery unit. This technical solution enables asynchronous interconnection of different AC grids through energy storage, increasing the flexibility of AC current power exchange between the two sides.

Description

Technical Field

[0001] This invention belongs to the field of energy storage DC / AC converter technology, specifically relating to the structure and control method of an energy storage system for AC grid interconnection. Background Technology

[0002] Existing connection methods between AC power grids are divided into AC connections and DC connections. AC connections directly link two power grids via AC transmission lines. However, AC connections present several problems, such as synchronization instability, and typically require unified dispatching, resulting in poor control flexibility on both sides. DC connections, usually referring to flexible or conventional DC connections, can decouple the operation and control of the two AC power grids, but currently have higher costs, increasing investment and requiring a larger footprint, thus increasing control complexity.

[0003] Therefore, it is urgent to study new AC power grid connection methods to achieve friendly interconnection between different AC power grids and increase the flexibility of AC current power exchange between the two sides. Summary of the Invention

[0004] To address the issue of friendly interconnection of AC power grids, this application proposes an energy storage system structure and control method for AC power grid interconnection, which can realize asynchronous interconnection of different AC power grids through energy storage, increasing the flexibility of AC current power exchange between the two sides.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] As a first aspect of this application, a storage system architecture for AC grid interconnection is proposed, comprising:

[0007] Energy storage battery unit;

[0008] The first DC / AC converter device has its AC side connected to the first AC power grid, and its DC side positive and negative terminals are respectively connected to the positive and negative terminals of the energy storage battery unit.

[0009] The second DC / AC converter device has its AC side connected to the second AC power grid, and its DC side positive and negative terminals connected to the positive and negative terminals of the energy storage battery unit, respectively.

[0010] Preferably, 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; the number of DC / AC converters in the first DC / AC converter device and the second DC / AC converter device is equal to the number of energy storage battery packs included in the energy storage battery unit.

[0011] Preferably, the energy storage system structure for AC grid interconnection includes at least two sets of energy storage battery units, at least two sets of second DC / AC converter devices, and at least two sets of first switches. The first DC / AC converter devices are connected to at least two sets of energy storage battery units through at least two sets of first switches, and the at least two sets of second DC / AC converter devices are correspondingly connected to at least two sets of energy storage battery units. The number of switches in each set of first switches is equal to the number of energy storage battery groups included in the energy storage battery units.

[0012] Preferably, the energy storage system structure for AC grid interconnection includes at least two sets of energy storage battery units, at least two sets of second DC / AC converter devices, and at least two sets of second switches. The first DC / AC converter devices are directly connected to the at least two sets of energy storage battery units, and the at least two sets of second DC / AC converter devices are respectively connected to the at least two sets of energy storage battery units through the at least two sets of second switches. The number of switches in each set of second switches is equal to the number of energy storage battery groups included in the energy storage battery units.

[0013] Preferably, the energy storage system structure for AC grid interconnection includes at least two sets of energy storage battery units, at least two sets of second DC / AC converter devices, at least two sets of first switches, and at least two sets of second switches. The first DC / AC converter devices are connected to the two sets of energy storage battery units respectively through the at least two sets of first switches, and the at least two sets of second DC / AC converter devices are correspondingly connected to the at least two sets of energy storage battery units respectively through the at least two sets of second switches. The number of switches in each set of first switches and the number of switches in each set of second switches are equal to the number of energy storage battery groups included in the energy storage battery units.

[0014] Preferably, the energy storage system structure for AC grid interconnection includes at least two sets of energy storage battery units, at least two sets of first switches, and at least two sets of second switches; the first DC / AC converter device is connected to the two sets of energy storage battery units respectively through at least two sets of first switches, and the second DC / AC converter device is connected to the two sets of energy storage battery units respectively through at least two sets of second switches; the number of switches in each set of first switches and the number of switches in each set of second switches are equal to the number of energy storage battery groups included in the energy storage battery unit.

[0015] Preferably, the first DC / AC converter device is connected to the first AC power grid via a transformer, and / or the second DC / AC converter device is connected to the second AC power grid via a transformer.

[0016] Preferably, the first DC / AC converter device and the energy storage battery unit are connected to the energy storage battery unit via a DC / DC converter and / or the second DC / AC converter device and the energy storage battery unit are connected to the energy storage battery via a DC / DC converter.

[0017] Preferably, the energy storage battery unit is a chemical battery, a supercapacitor, or a fuel cell.

[0018] As a second aspect of this application, a control method for an energy storage system structure for AC grid interconnection is proposed, which adopts independent control considering current over-limit. That is, the DC / AC converters in the first DC / AC converter equipment and the second DC / AC converter equipment are independently charged and discharged according to their respective AC side requirements. When the AC side current of the DC / AC converter exceeds the limit, the AC side current is limited.

[0019] Preferably, when the AC side current of the DC / AC converter exceeds the limit, the AC side current is limited. The limit control setting is determined based on the maximum allowable charge / discharge current setting of the DC / AC converter in the first DC / AC converter device and the second DC / AC converter device, the real-time current, the control mode of the DC / AC converter, and the maximum allowable charge / discharge current of the energy storage battery pack in the energy storage battery unit.

[0020] Preferably, the step of limiting the AC side current when the AC side current of the DC / AC converter exceeds the limit specifically includes:

[0021] The maximum allowable charging and discharging current settings for the DC / AC converters in the first and second DC / AC converter devices are set to I, respectively. set1 and I set2 ;

[0022] Measure the AC side current of the DC / AC converter in the first DC / AC converter equipment and the second DC / AC converter equipment, and calculate their effective values ​​I1 and I2 respectively;

[0023] Set the control modes of the DC / AC converters in the first and second DC / AC converter devices, setting one side as the main operation mode and the other side as the auxiliary operation mode; the main operation mode prioritizes autonomous current control, and the auxiliary operation mode calculates the required current based on the current tracking of the main operation mode.

[0024] Set the maximum allowable charge / discharge current I of the energy storage battery pack in the energy storage battery unit. setb , where I setb >I set1 I setb >I set2 ;

[0025] When the first DC / AC converter is in main operating mode, the upper limit of its AC side current limiting control is equal to I. set1In the second DC / AC converter equipment, the DC / AC converter operates in auxiliary mode, and its AC side current limiting control upper limit value is equal to min{I set2 ,|I setb -I1|};When the second DC / AC converter equipment side DC / AC converter is in main operation mode, its AC side current limiting control upper limit value is equal to I set2 In the first DC / AC converter equipment, the DC / AC converter operates in auxiliary mode, and its AC side current limiting control upper limit value is equal to min{I set1 ,|I setb -I2|}.

[0026] As a third aspect of this application, a control method for an energy storage system structure for AC grid interconnection is proposed, which adopts active power ride-through control, that is, the DC / AC converter devices on both sides of the energy storage battery unit track the power of the other side under the premise that the AC current on both sides does not exceed the current limit on their own side.

[0027] Preferably, the tracking of the other party's power operation specifically includes:

[0028] Set the control modes of the DC / AC converters in the first and second DC / AC converter devices, setting one side as the main operation mode and the other side as the auxiliary operation mode; the main operation mode prioritizes autonomous current control, and the auxiliary operation mode calculates the required current based on the current tracking of the main operation mode.

[0029] Measure the AC side current of the DC / AC converter in the first DC / AC converter equipment and the second DC / AC converter equipment, and compare the AC side current of the DC / AC converter with the corresponding current limit value;

[0030] In response to the fact that the AC side current of both DC / AC converters does not exceed the current limit of their respective sides, the DC / AC converter in auxiliary mode obtains the real-time power of the DC / AC converter in main mode from the DC / AC converter in main mode, and uses the real-time power as the reference power of the DC / AC converter in auxiliary mode.

[0031] As a fourth aspect of this application, a control method for an energy storage system structure for AC grid interconnection is proposed. The method is characterized by using AGC command tracking superimposed with local frequency regulation control, that is, the DC / AC converter superimposes the received AGC power reference value with the local frequency regulation power as the operating power reference value of the DC / AC converter.

[0032] As the fifth aspect of this application, a control method for an energy storage system structure for AC grid interconnection is proposed. The method adopts AVC command tracking superimposed local reactive power compensation control. That is, the DC / AC converter responds to the AVC command within the voltage control dead zone, and after exceeding the dead zone, it adjusts the reactive power locally in a closed loop according to the voltage magnitude based on the previous AVC command.

[0033] Preferably, the local self-closed-loop adjustment of reactive power according to voltage magnitude specifically refers to increasing reactive power output when voltage decreases and decreasing reactive power output when voltage increases.

[0034] The beneficial effects of this invention are:

[0035] 1. This invention connects the DC side of two DC / AC converters to the positive and negative terminals of the energy storage battery respectively, and connects the AC side to different AC power grids respectively, realizing asynchronous interconnection of different AC power grids through energy storage. This avoids problems such as synchronization stability that exist when two AC power grids are connected through a weak interconnection channel, and is more economical than the DC connection scheme.

[0036] 2. Energy storage can store electricity on both sides of the AC power grid, thereby improving the efficiency of energy storage utilization.

[0037] 3. The present invention can increase the flexibility of AC current power exchange between the two sides, and the AC power grids on both sides can exchange power according to demand, so as to realize flexible power mutual assistance. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of an energy storage system for AC power grid interconnection provided in Embodiment 1 of the present invention;

[0039] Figure 2 This is a schematic diagram of an energy storage system for AC power grid interconnection provided in Embodiment 2 of the present invention;

[0040] Figure 3 This is a schematic diagram of an energy storage system for AC power grid interconnection provided in Embodiment 3 of the present invention;

[0041] Figure 4 This is a schematic diagram of a two-level topology of a DC / AC converter provided in an embodiment of the present invention;

[0042] Figure 5 This is a schematic diagram of a three-level topology of a DC / AC converter provided in an embodiment of the present invention;

[0043] Figure 6 This is a schematic diagram of an energy storage system for AC power grid interconnection provided in Embodiment 4 of the present invention;

[0044] Figure 7 This is a schematic diagram of an energy storage system for AC power grid interconnection provided in Embodiment 5 of the present invention;

[0045] Figure 8 This is a schematic diagram of an energy storage system for AC power grid interconnection provided in Embodiment 6 of the present invention;

[0046] Figure 9 This is a schematic diagram of an energy storage system for AC power grid interconnection provided in Embodiment 7 of the present invention;

[0047] Figure 10 This is a schematic diagram of an energy storage system for AC power grid interconnection provided in Embodiment 8 of the present invention;

[0048] Figure 11 This is a schematic diagram of an energy storage system for AC power grid interconnection provided in Embodiment 9 of the present invention;

[0049] Figure 12 This is a schematic diagram of an energy storage system for AC power grid interconnection provided in Embodiment 10 of the present invention;

[0050] Figure 13 This is a schematic diagram of an energy storage system for AC power grid interconnection provided in Embodiment 11 of the present invention;

[0051] Figure 14 This is a schematic diagram of an energy storage system for AC power grid interconnection provided in Embodiment 12 of the present invention;

[0052] Figure 15 This is a schematic diagram of an energy storage system for AC power grid interconnection provided in Embodiment 13 of the present invention;

[0053] Figure 16 The triple-interleaved cascaded buck / boost bidirectional DC-DC converter topology provided in this embodiment of the invention;

[0054] Figure 17 This is a cascaded Buck-boost bidirectional DC-DC converter topology provided in an embodiment of the present invention;

[0055] Figure 18 This is the full-bridge bidirectional DC-DC converter topology provided in the embodiments of the present invention;

[0056] Figure 19 A schematic flowchart of a structural control method for an energy storage system used in AC power grid interconnection is provided for the implementation of this invention.

[0057] Figure 20 A schematic diagram of the structure control method for an energy storage system for AC power grid interconnection provided for the implementation of this invention.

[0058] Among them, 1-first AC power grid, 2-second AC power grid, 3-first DC / AC converter equipment, 4-second DC / AC converter equipment, 5-energy storage battery unit, 6-first switch, 7-second switch, 8-transformer on the side of the first DC / AC converter equipment, 9-transformer on the side of the second DC / AC converter equipment, 10-DC / DC converter on the side of the first DC / AC converter equipment, and 11-DC / DC converter on the side of the second DC / AC converter equipment. Detailed Implementation

[0059] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0060] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0061] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can also refer to the internal connection of two components; and they can refer to a wireless connection or a wired connection. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0062] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0063] This invention discloses an energy storage system structure for AC power grid interconnection. In one embodiment, such as... Figure 1As shown, the energy storage system structure for AC grid interconnection includes: a first DC / AC converter device 3, a second DC / AC converter device 4, and an energy storage battery unit 5. The AC side of the first DC / AC converter device 3 is connected to the first AC grid 1, and its DC side positive and negative terminals are connected to the positive and negative terminals of the energy storage battery unit 5, respectively. The AC side of the second DC / AC converter device 4 is connected to the second AC grid 2, and its DC side positive and negative terminals are connected to the positive and negative terminals of the energy storage battery unit 5, respectively. The frequencies of the first AC grid 1 and the second AC grid 2 can be the same or different. In this embodiment, the DC sides of the two DC / AC converter devices are connected to the positive and negative terminals of the energy storage battery, and their AC sides are connected to different AC grids. This allows the two AC grids to be interconnected through the energy storage battery, enabling flexible power exchange through the energy storage system according to the control needs of the two AC grids, thus achieving asynchronous interconnection of the AC grids.

[0064] 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; the number of DC / AC converters in the first DC / AC converter device and the second DC / AC converter device is equal to the number of energy storage battery packs in the energy storage battery unit.

[0065] In this embodiment, the DC sides of two DC / AC converters are connected to the positive and negative terminals of the energy storage battery, respectively, while the AC sides are connected to different AC power grids. This achieves asynchronous interconnection of different AC power grids through energy storage, avoiding synchronization stability issues that exist when connecting two AC power grids through weak interconnection channels. This approach is more economical than DC connection schemes. Furthermore, the energy storage can utilize the stored electricity in both AC power grids, improving energy storage utilization efficiency. This also increases the flexibility of AC current power exchange between the two sides, allowing them to exchange power as needed, achieving flexible power mutual support.

[0066] like Figure 2 In the illustrated energy storage system structure for AC grid interconnection, 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. The AC side of the DC / AC converter PCS3-1 is connected to AC grid 1, and the positive and negative terminals of the DC side of PCS3-1 are connected to the positive and negative terminals of the energy storage battery pack BAT5-1, respectively. The AC side of the DC / AC converter PCS4-1 is connected to AC grid 2, and the positive and negative terminals of the DC side of PCS4-1 are connected to the positive and negative terminals of the energy storage battery pack BAT5-1, respectively.

[0067] like Figure 3In the illustrated energy storage system structure for AC grid interconnection, 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. The AC terminals of both DC / AC converters PCS3-1 and PCS3-2 are connected to the AC grid 1. The positive and negative terminals of the DC side of PCS3-1 are connected to the positive and negative terminals of energy storage battery pack BAT5-1, respectively, and the positive and negative terminals of the DC side of PCS3-2 are connected to the positive and negative terminals of energy storage battery pack BAT5-2, respectively. The AC terminals of DC / AC converters PCS4-1 and PCS4-2 are both connected to AC power grid 2. The positive and negative terminals of the DC side of PCS4-1 are connected to the positive and negative terminals of the energy storage battery pack BAT5-1, respectively, and the positive and negative terminals of the DC side of PCS4-2 are connected to the positive and negative terminals of the energy storage battery pack BAT5-2, respectively.

[0068] In energy storage systems, DC / AC converters employ IGBT-based voltage source converter topologies to achieve bidirectional energy flow between AC and DC systems. Commonly used topologies include... Figure 4 The two-level topology shown and as follows Figure 5 The three-level topology shown.

[0069] In some embodiments, the energy storage system structure for AC grid interconnection includes two sets of energy storage battery units and two sets of second DC / AC converter devices. A switching switch can be provided between the first DC / AC converter device and the energy storage battery unit, or between the second DC / AC converter device and the energy storage battery unit, or both the first DC / AC converter device and the energy storage battery unit can be provided. During normal operation, only one set of energy storage battery units is connected to the AC grid. When an operating energy storage battery unit becomes unavailable due to a fault or out-of-range SOC, the DC / AC converter can switch to the other set of energy storage battery units via the switching switch.

[0070] like Figure 6The illustrated embodiment of the energy storage system for AC grid interconnection includes a first DC / AC converter device 3, two sets of energy storage battery units 5, two sets of second DC / AC converter devices 4, and two sets of first switches 6. The first DC / AC converter devices 3 are connected to the two sets of energy storage battery units 5 respectively through the two sets of first switches 6, and the two sets of second DC / AC converter devices 4 are respectively connected to the two sets of energy storage battery units 5. In this embodiment, the first DC / AC converter device 3 includes two DC / AC converters, PCS3-1 and PCS3-2; each group of energy storage battery units 5 includes two energy storage battery packs, the first group of energy storage battery units 5 includes BAT5-1 and BAT5-2, and the second group of energy storage battery units 5 includes BAT5-3 and BAT5-4; the first group of second DC / AC converter devices 4 includes two DC / AC converters, PCS4-1 and PCS4-2, and the second group of second DC / AC converter devices 4 includes two DC / AC converters, PCS4-3 and PCS4-4; the first group of first switches 6 includes switches 6-1 and 6-2, and the second group of first switches 6 includes switches 6-3 and 6-4. The AC sides of DC / AC converters PCS3-1 and PCS3-2 are both connected to AC power grid 1. The DC side of PCS3-1 is connected to energy storage battery pack BAT5-1 via switch 6-1 and to energy storage battery pack BAT5-3 via switch 6-3. The DC side of PCS3-2 is connected to energy storage battery pack BAT5-2 via switch 6-2 and to energy storage battery pack BAT5-4 via switch 6-4. The AC sides of DC / AC converters PCS4-1, PCS4-2, PCS4-3, and PCS4-4 are all connected to AC power grid 2. The direct sides of the two converters PCS4-1 and PCS4-2 in the first group of second DC / AC converter equipment 4 are connected to energy storage battery packs BAT5-1 and BAT5-2, respectively. The direct sides of the two converters PCS4-3 and PCS4-4 in the second group of second DC / AC converter equipment 4 are connected to energy storage battery packs BAT5-3 and BAT5-4, respectively. Under normal operating conditions, one set of the two sets of first switches 6 is closed to form a circuit connecting to the corresponding energy storage battery unit, while the other set is open. When an operating energy storage battery unit becomes unavailable due to a fault or exceeding the SOC range, the open / closed states of the two sets of switches are switched, thereby switching the system operation to the other set of energy storage battery units. In some embodiments, more sets of energy storage battery units 5, the second DC / AC converter device 4, and the first switches 6 can be provided, with the number of sets of all three being equal, as described in the reference. Figure 6 The connection methods correspond to the connection.

[0071] like Figure 7 The illustrated embodiment of the AC grid interconnection energy storage system also includes a first DC / AC converter device 3, two sets of energy storage battery units 5, and two sets of second DC / AC converter devices 4. (The last sentence appears to be incomplete and possibly refers to a different embodiment.) Figure 6The difference between the illustrated embodiments is that the first DC / AC converter device 3 is directly connected to the two groups of energy storage battery units 5. Instead of providing two groups of first switches 6, two groups of second switches 7 are provided between the two groups of energy storage battery units 5 and the two groups of second DC / AC converter devices 4. The first group of second switches 7 includes switch 1-1 and switch 1-2, and the second group of second switches 7 includes switch 7-3 and switch 7-4. The DC side of the PCS4-1 in the first group of second DC / AC converter devices 4 is connected to the energy storage battery bank BAT5-1 via switch 7-1, and the DC side of the PCS4-2 is connected to the energy storage battery bank BAT5-2 via switch 7-2. The DC side of the PCS4-3 in the second group of second DC / AC converter devices 4 is connected to the energy storage battery bank BAT5-3 via switch 7-3, and the DC side of the PCS4-4 is connected to the energy storage battery bank BAT5-4 via switch 7-4. The other parts are the same as Figure 6 the embodiments described above and will not be elaborated here. Under normal operation, one of the two groups of second switches 7 is closed to form a path to connect to the corresponding energy storage battery unit, and the other is open. When the operating energy storage battery unit becomes unavailable due to faults or the SOC exceeding the range, etc., the opening and closing states of the two switches are switched, so as to switch the system operation to the other group of energy storage battery units. In some embodiments, more groups of energy storage battery units 5, second DC / AC converter devices 4 and second switches 7 can also be provided, and the number of groups of the three is equal, and they are connected correspondingly according to the Figure 7 connection method shown.

[0072] For example, Figure 8 the structure of the energy storage system for AC grid interconnection in the illustrated embodiment also includes a group of first DC / AC converter devices 3, two groups of energy storage battery units 5, two groups of second DC / AC converter devices 4 and two groups of first switches 6. The difference from the Figure 6 embodiment shown is that in addition to the first DC / AC converter device 3 being connected to the two groups of energy storage battery units 5 through two groups of first switches 6, two groups of second switches 7 are also provided between the two groups of energy storage battery units 5 and the two groups of second DC / AC converter devices 4. The first group of second switches 7 includes switch 1-1 and switch 1-2, and the second group of second switches 7 includes switch 7-3 and switch 7-4. The DC side of the PCS4-1 in the first group of second DC / AC converter devices 4 is connected to the energy storage battery bank BAT5-1 via switch at 7-1, and the DC side of the PCS4-2 is connected to the energy storage battery bank BAT5-2 via switch 7-2. The DC side of the PCS4-3 in the second group of second DC / AC converter devices 4 is connected to the energy storage battery bank BAT5-3 via switch 7-3, and the DC side of the PCS4-4 is connected to the energy storage battery bank BAT5-4 via switch 7-4. The other parts are the same as Figure 6The implementation details are similar and will not be repeated here. Under normal operating conditions, one set of the two sets of first switches 6 is closed, and one set of the corresponding two sets of second switches 7 is closed, forming a circuit to connect to the corresponding energy storage battery unit. The other set of first switches 6 and the corresponding second switches 7 are open. When the operating energy storage battery unit becomes unavailable due to fault or SOC exceeding the range, the opening and closing states of the two sets of first switches 6 and 7 are switched, thereby switching the system operation to the other set of energy storage battery units. In some embodiments, more sets of energy storage battery units 5, second DC / AC converter devices 4, first switches 6, and second switches 7 may be provided, with the number of sets of all four being equal. Refer to [reference needed]. Figure 8 The connection methods correspond to the connection.

[0073] In some embodiments, the energy storage system structure for AC grid interconnection includes at least two sets of energy storage battery units, at least two sets of first switches, and at least two sets of second switches; the first DC / AC converter device is connected to the two sets of energy storage battery units respectively through the at least two sets of first switches, and the second DC / AC converter device is connected to the two sets of energy storage battery units respectively through the at least two sets of second switches; the number of switches in each set of first switches and the number of switches in each set of second switches are equal to the number of energy storage battery packs included in the energy storage battery units. Figure 9The energy storage system structure for AC grid interconnection shown includes a first DC / AC converter device 3, a second DC / AC converter device 4, two sets of energy storage battery units 5, two sets of first switches 6, and two sets of second switches 7. The first DC / AC converter device 3 and the two sets of energy storage battery units 5 are connected to each other through the two sets of first switches 6, and the second DC / AC converter device 4 and the two sets of energy storage battery units 5 are connected to each other through the two sets of second switches 7. Specifically, the DC side of PCS3-1 is connected to the energy storage battery pack BAT5-1 via switch 6-1 and to the energy storage battery pack BAT5-3 via switch 6-3; the DC side of PCS3-2 is connected to the energy storage battery pack BAT5-2 via switch 6-2 and to the energy storage battery pack BAT5-4 via switch 6-4; the DC side of PCS4-1 is connected to the energy storage battery pack BAT5-1 via switch 7-1 and to the energy storage battery pack BAT5-3 via switch 7-3; the DC side of PCS4-2 is connected to the energy storage battery pack BAT5-2 via switch 7-2 and to the energy storage battery pack BAT5-4 via switch 7-4. Under normal operating conditions, one set of the two sets of first switches 6 is closed, and one set of the corresponding two sets of second switches 7 is closed, forming a circuit to connect to the corresponding energy storage battery unit. The other set of first switches 6 and the corresponding second switches 7 are open. When the operating energy storage battery unit becomes unusable due to fault or out-of-range SOC, the opening and closing states of the two sets of first switches 6 and 7 are switched, thereby switching the system operation to the other set of energy storage battery units. In some embodiments, more sets of energy storage battery units 5, first switches 6, and second switches 7 may be provided, with the number of sets equal for all three. Figure 9 The connection methods correspond to the connection.

[0074] In some embodiments, the first DC / AC converter device is connected to a first AC power grid via a transformer, and / or the second DC / AC converter device is connected to a second AC power grid via a transformer. For example... Figure 10 The illustrated embodiment is in Figure 1 Based on the schematic diagram, the AC side of the first DC / AC converter device 3 is connected to the first AC power grid 1 via transformer 8. For example... Figure 11 The illustrated embodiment is in Figure 1 Based on the schematic diagram, the AC side of the second DC / AC converter device 4 is connected to the second AC power grid 2 via transformer 9. For example... Figure 12 The illustrated embodiment shows that in Figure 1 Based on the schematic diagram, the AC side of the first DC / AC converter device 3 is connected to the first AC power grid 1 via transformer 8, while the AC side of the second DC / AC converter device 4 is connected to the second AC power grid 2 via transformer 9. Similarly, for... Figure 2 , Figure 3 , Figures 6-9In each embodiment, the AC side of the first DC / AC converter device 3 can be connected to the first AC power grid 1 via transformer 8, or the AC side of the second DC / AC converter device 4 can be connected to the second AC power grid 2 via transformer 9, or the AC side of the first DC / AC converter device 3 can be connected to the first AC power grid 1 via transformer 8 while the AC side of the second DC / AC converter device 4 can be connected to the second AC power grid 2 via transformer 9.

[0075] In some embodiments, the first DC / AC converter device and the energy storage battery unit are connected to the energy storage battery via a DC / DC converter, and / or the second DC / AC converter device and the energy storage battery unit are connected to the energy storage battery via a DC / DC converter. For example... Figure 13 The illustrated embodiment is in Figure 1 Based on the schematic diagram, the DC side of the first DC / AC converter device 3 is connected to the energy storage battery unit 5 via a DC / DC converter 10. For example... Figure 14 The illustrated embodiment is in Figure 1 Based on the schematic diagram, the DC side of the second DC / AC converter device 4 is connected to the energy storage battery unit 5 via a DC / DC converter 11. For example... Figure 15 The illustrated embodiment shows that in Figure 1 Based on the schematic diagram, the DC side of the first DC / AC converter device 3 is connected to the energy storage battery unit 5 via a DC / DC converter 10, while the DC side of the second DC / AC converter device 4 is connected to the energy storage battery unit 5 via a DC / DC converter 11. Similarly, for... Figure 2 , Figure 3 , Figures 6-12 In all embodiments, the DC side of the first DC / AC converter device 3 can be connected to the energy storage battery unit 5 only through the DC / DC converter 10, or the DC side of the second DC / AC converter device 4 can be connected to the energy storage battery unit 5 only through the DC / DC converter 11, or the DC side of the first DC / AC converter device 3 can be connected to the energy storage battery unit 5 through the DC / DC converter 10 while the DC side of the second DC / AC converter device 4 can be connected to the energy storage battery unit 5 through the DC / DC converter 11. The DC-DC converter includes isolated and non-isolated types. The former includes, but is not limited to, flyback bidirectional DC-DC converters, forward bidirectional DC-DC converters, push-pull bidirectional DC-DC converters, and full-bridge bidirectional DC-DC converters, while the latter includes, but is not limited to, Buck / Boost, Boost / Buck, Buck-Boost, Cuk, Sepic / Zeta, and Zeta / Sepic, etc. Figure 16 The diagram shows a triple-interleaved cascaded buck / boost bidirectional DC-DC converter topology. Figure 17The diagram shows the topology of a cascaded Buck-boost bidirectional DC-DC converter. Figure 18 It is a full-bridge bidirectional DC-DC converter topology.

[0076] In some embodiments, the energy storage battery unit can be a chemical battery, a supercapacitor, or a fuel cell.

[0077] This invention also proposes a control method for an energy storage system structure used in AC grid interconnection. The control method employs independent control considering current over-limit, meaning that the DC / AC converters in the first and second DC / AC converter devices each perform independent charging and discharging control based on their respective AC-side requirements. When the AC-side current of a DC / AC converter exceeds its limit, the AC-side current is limited. AC-side requirements include system voltage, frequency, and power angle stability.

[0078] In some embodiments, when the AC side current of the DC / AC converter exceeds the limit, the AC side current is limited. The limit control setting is determined based on the maximum allowable charge and discharge current setting of the DC / AC converter in the first DC / AC converter device and the second DC / AC converter device, the real-time current, the control mode of the DC / AC converter, and the maximum allowable charge and discharge current of the energy storage battery pack in the energy storage battery unit.

[0079] In some embodiments, when the AC side current of the DC / AC converter exceeds the limit, the AC side current is limited, such as... Figure 19 Specifically, it includes:

[0080] S110: Set the maximum allowable charging and discharging current settings for the DC / AC converters in the first and second DC / AC converter devices to I respectively. set1 and I set2 .For example Figure 2 The maximum allowable charging and discharging current setting of the DC / AC converter PCS3-1 is set to I. set1 Set the maximum allowable charging and discharging current setting of the DC / AC converter PCS4-1 to I. set2 .

[0081] S120: Measure the AC side current of the DC / AC converter in the first and second DC / AC converter devices, and calculate their effective values ​​I1 and I2, respectively. For example... Figure 2 Measure the AC side current of DC / AC converter PCS3-1 and calculate its effective value I1. Measure the AC side current of DC / AC converter PCS4-1 and calculate its effective value I2.

[0082] S130: Set the control mode of the DC / AC converter in the first and second DC / AC converter devices, setting one side to main operation mode and the other side to auxiliary operation mode; the main operation mode prioritizes autonomous current control, and the auxiliary operation mode calculates the required current based on the current tracking of the main operation mode. For example... Figure 2 The DC / AC converter PCS3-1 is set to primary operation mode, and the DC / AC converter PCS4-1 is set to secondary operation mode; alternatively, the DC / AC converter PCS3-1 is set to secondary operation mode, and the DC / AC converter PCS4-1 is set to primary operation mode. Considering its support performance, the converter connected to the weak AC power grid side is generally selected as the primary operation mode.

[0083] S140: Set the maximum allowable charge / discharge current I of the energy storage battery pack in the energy storage battery unit. setb , where I setb >I set1 I setb >I set2 ;For example Figure 2 The maximum allowable charge and discharge current of the BAT5-1 energy storage battery pack is set to I. setb I setb Needs to be greater than I set1 and I set2 .

[0084] S150: When the first DC / AC converter is in main operating mode, the upper limit of its AC side current limiting control is equal to I. set1 In the second DC / AC converter equipment, the DC / AC converter operates in auxiliary mode, and its AC side current limiting control upper limit value is equal to min{I set2 ,|I setb -I1|};When the second DC / AC converter equipment side DC / AC converter is in main operation mode, its AC side current limiting control upper limit value is equal to I set2 In the first DC / AC converter equipment, the DC / AC converter operates in auxiliary mode, and its AC side current limiting control upper limit value is equal to min{I set1 ,|I setb -I2|}. For example. Figure 2 When PCS3-1 is in master operation mode, the upper limit of the AC side current limiting control of PCS3-1 is equal to I. set1 The upper limit of the AC side current limiting control of PCS4-1 is equal to min{I set2 ,|I setb -I1|}, min means taking the smallest among the comparison elements. In PCS4-1 master mode, the upper limit of the AC side current limiting control of PCS4-1 is equal to I. set2The upper limit of the AC side current limiting control of PCS3-1 is equal to min{I set1 ,|I setb -I2|}.

[0085] S160: When the AC side current of the DC / AC converter exceeds the upper limit value of the corresponding AC side current limiting control, the AC side current is limited.

[0086] This embodiment adopts independent control that considers current over-limit. The calculated upper limit value of the AC side current limiting control is used as the amplitude limit input of the DC / AC converter current limiting control to achieve current limiting. This can effectively deal with scenarios where the AC current of the DC / AC converter or the current of the energy storage battery pack exceeds the limit.

[0087] The control method for the structure of an AC grid interconnection energy storage system proposed in one embodiment of the present invention adopts active power ride-through control, that is, the DC / AC converter devices on both sides of the energy storage battery unit track the power of the other side under the premise that the AC current on both sides does not exceed the current limit on their own side.

[0088] In some embodiments, such as Figure 20 As shown, the tracking of the other party's power operation specifically includes:

[0089] S210: Set the control mode of the DC / AC converter in the first and second DC / AC converter devices, setting one side to main operation mode and the other side to auxiliary operation mode; the main operation mode prioritizes autonomous current control, and the auxiliary operation mode calculates the required current based on the current tracking of the main operation mode. For example... Figure 2 The DC / AC converter PCS3-1 is set to primary operation mode, and the DC / AC converter PCS4-1 is set to secondary operation mode; alternatively, the DC / AC converter PCS3-1 is set to secondary operation mode, and the DC / AC converter PCS4-1 is set to primary operation mode. Considering its support performance, the converter connected to the weak AC power grid side is generally selected as the primary operation mode.

[0090] S220: Measure the AC side current of the DC / AC converter in the first and second DC / AC converter devices, and compare the AC side current of the DC / AC converter with the corresponding current limit value. For example... Figure 2 The AC side current of DC / AC converter PCS3-1 is measured to obtain its effective value I1. The AC side current of DC / AC converter PCS4-1 is measured to obtain its effective value I2. I1 is compared with the current limit value I of PCS3-1. max1 The magnitude of I2 and the current limit value I of PCS4-1 are compared. max2 Size;

[0091] S230: In response to the fact that the AC side current of both DC / AC converters does not exceed the current limit of its side, the DC / AC converter in auxiliary mode obtains the real-time power of the DC / AC converter in main mode from the DC / AC converter in main mode, and uses the real-time power as the reference power of the DC / AC converter in auxiliary mode. For example Figure 2 When I1 is less than or equal to I max1 And I2 is less than or equal to I max2 When PCS3-1 is in primary operation mode and PCS4-1 is in auxiliary operation mode, PCS4-1 obtains the real-time power P1 of the PCS3-1 converter from PCS3-1 and uses P1 as the reference power of PCS4-1; when PCS4-1 is in primary operation mode and PCS3-1 is in auxiliary operation mode, PCS3-1 obtains the real-time power P2 of the PCS4-1 converter from PCS4-1 and uses P2 as the reference power of PCS3-1.

[0092] By employing active power ride-through control, power exchange between the two AC systems can be achieved entirely through energy storage, minimizing the impact on the energy storage battery.

[0093] One embodiment of this invention proposes a control method for an energy storage system structure used in AC grid interconnection. This method employs AGC (Automatic Generation Control) command tracking superimposed with local frequency regulation control. Specifically, the DC / AC converter uses the received AGC power reference value superimposed with the local frequency regulation power as its operating power reference value. The AGC command responds to dispatch instructions, and the superimposed local frequency regulation allows for rapid response to faults or disturbances while maintaining normal dispatch instruction response, thus improving frequency stability.

[0094] The control method for the energy storage system structure for AC grid interconnection proposed in one embodiment of the present invention adopts AVC (Automatic Voltage Control) command tracking superimposed with local reactive power compensation control. That is, the DC / AC converter responds to the AVC command within the voltage control dead zone, and after exceeding the dead zone, it adjusts the reactive power locally in a closed loop according to the voltage magnitude based on the AVC command.

[0095] In some embodiments, reactive power is dynamically and continuously adjusted locally in a closed-loop manner according to voltage levels. Specifically, reactive power output is increased when voltage decreases and decreased when voltage increases. AVC reactive voltage control is a steady-state control method, while local control primarily responds to emergency voltage control. By employing AVC command tracking and superimposing local reactive power compensation control, system voltage stability under emergency fault conditions can be improved.

[0096] The present invention discloses a control method for an energy storage system structure for AC grid interconnection, which can employ one or more of the following: independent control considering current over-limit, active power ride-through control, AGC command tracking superimposed local frequency regulation control, and AVC command tracking superimposed local reactive power compensation control. The DC / AC converters on both sides can respectively perform primary frequency regulation and voltage regulation functions for the connected grid, contributing to the stable operation of the grid.

[0097] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. All modifications or changes made with reference to the above embodiments are within the protection scope of the present invention.

Claims

1. A control method for an energy storage system structure used in AC power grid interconnection, characterized in that, The structure of the energy storage system for AC grid interconnection includes: Energy storage battery unit; The first DC / AC converter device has its AC side connected to the first AC power grid, and its DC side positive and negative terminals are respectively connected to the positive and negative terminals of the energy storage battery unit. The second DC / AC converter equipment has its AC side connected to the second AC power grid, and its DC side positive and negative terminals are connected to the positive and negative terminals of the energy storage battery unit, respectively. Independent control considering current over-limit is adopted, that is, the DC / AC converters in the first DC / AC converter equipment and the second DC / AC converter equipment are independently charged and discharged according to their respective AC side requirements. When the AC side current of the DC / AC converter exceeds the limit, the AC side current is limited. The method of limiting the AC side current when the AC side current of the DC / AC converter exceeds the limit specifically includes: The maximum allowable charging and discharging current settings for the DC / AC converters in the first and second DC / AC converter devices are set to I, respectively. set1 and I set2 ; Measure the AC side current of the DC / AC converter in the first DC / AC converter equipment and the second DC / AC converter equipment, and calculate their effective values ​​I1 and I2 respectively; Set the control modes of the DC / AC converters in the first and second DC / AC converter devices, setting one side as the main operation mode and the other side as the auxiliary operation mode; the main operation mode prioritizes autonomous current control, and the auxiliary operation mode calculates the required current based on the current tracking of the main operation mode. Set the maximum allowable charge / discharge current I of the energy storage battery pack in the energy storage battery unit. setb , where I setb >I set1 I setb >I set2 ; When the first DC / AC converter is in main operating mode, the upper limit of its AC side current limiting control is equal to I. set1 In the second DC / AC converter equipment, the DC / AC converter operates in auxiliary mode, and its AC side current limiting control upper limit value is equal to min{I set2 ,|I setb -I1|};When the second DC / AC converter equipment side DC / AC converter is in main operation mode, its AC side current limiting control upper limit value is equal to I set2 In the first DC / AC converter equipment, the DC / AC converter operates in auxiliary mode, and its AC side current limiting control upper limit value is equal to min{I set1 ,|I setb -I2|}; When the AC side current of the DC / AC converter exceeds the upper limit value of the corresponding AC side current limiting control, the AC side current is limited.

2. The control method as described in claim 1, characterized in that, When the AC side current of the DC / AC converter exceeds the limit, the AC side current is limited. The limit control setting is determined based on the maximum allowable charge and discharge current setting of the DC / AC converter in the first DC / AC converter device and the second DC / AC converter device, the real-time current, the control mode of the DC / AC converter, and the maximum allowable charge and discharge current of the energy storage battery pack in the energy storage battery unit.

3. The control method as described in claim 1, characterized in that, 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; the number of DC / AC converters in the first DC / AC converter device and the second DC / AC converter device is equal to the number of energy storage battery packs included in the energy storage battery unit.

4. The control method as described in claim 1, characterized in that, It includes at least two sets of energy storage battery units, at least two sets of second DC / AC converter devices, and at least two sets of first switches. The first DC / AC converter devices are respectively connected to at least two sets of energy storage battery units through at least two sets of first switches. The at least two sets of second DC / AC converter devices are respectively connected to at least two sets of energy storage battery units. The number of switches in each set of first switches is equal to the number of energy storage battery groups included in the energy storage battery unit.

5. The control method as described in claim 1, characterized in that, It includes at least two sets of energy storage battery units, at least two sets of second DC / AC converter devices, and at least two sets of second switches. The first DC / AC converter devices are directly connected to the at least two sets of energy storage battery units, and the at least two sets of second DC / AC converter devices are respectively connected to the at least two sets of energy storage battery units through the at least two sets of second switches. The number of switches in each set of second switches is equal to the number of energy storage battery groups included in the energy storage battery unit.

6. The control method as described in claim 1, characterized in that, It includes at least two sets of energy storage battery units, at least two sets of second DC / AC converter devices, at least two sets of first switches, and at least two sets of second switches. The first DC / AC converter devices are connected to the two sets of energy storage battery units respectively through the at least two sets of first switches. The at least two sets of second DC / AC converter devices are connected to the at least two sets of energy storage battery units respectively through the at least two sets of second switches. The number of switches in each set of first switches and the number of switches in each set of second switches are equal to the number of energy storage battery groups included in the energy storage battery unit.

7. The control method as described in claim 1, characterized in that, It includes at least two sets of energy storage battery units, at least two sets of first switches, and at least two sets of second switches; the first DC / AC converter device is connected to the two sets of energy storage battery units respectively through at least two sets of first switches, and the second DC / AC converter device is connected to the two sets of energy storage battery units respectively through at least two sets of second switches; the number of switches in each set of first switches and the number of switches in each set of second switches are equal to the number of energy storage battery groups included in the energy storage battery unit.

8. The control method as described in claim 1, characterized in that, The first DC / AC converter device is connected to the first AC power grid via a transformer, and / or the second DC / AC converter device is connected to the second AC power grid via a transformer.

9. The control method according to any one of claims 1 to 8, characterized in that, The first DC / AC converter device is connected to the energy storage battery unit via a DC / DC converter and / or the second DC / AC converter device is connected to the energy storage battery unit via a DC / DC converter.

10. The control method as described in claim 1, characterized in that, The energy storage battery unit is a chemical battery, a supercapacitor, or a fuel cell.

11. A control method for an energy storage system structure used in AC power grid interconnection, characterized in that, The structure of the energy storage system for AC grid interconnection includes: Energy storage battery unit; The first DC / AC converter device has its AC side connected to the first AC power grid, and its DC side positive and negative terminals are respectively connected to the positive and negative terminals of the energy storage battery unit. The second DC / AC converter equipment has its AC side connected to the second AC power grid, and its DC side positive and negative terminals are connected to the positive and negative terminals of the energy storage battery unit, respectively. Active power ride-through control is adopted, which means that the DC / AC converter equipment on both sides of the energy storage battery unit tracks the power of the other side, provided that the AC current on both sides does not exceed the current limit on its own side. The operation of tracking the power of the target specifically includes: Set the control modes of the DC / AC converters in the first and second DC / AC converter devices, setting one side as the main operation mode and the other side as the auxiliary operation mode; the main operation mode prioritizes autonomous current control, and the auxiliary operation mode calculates the required current based on the current tracking of the main operation mode. Measure the AC side current of the DC / AC converter in the first DC / AC converter equipment and the second DC / AC converter equipment, and compare the AC side current of the DC / AC converter with the corresponding current limit value; In response to the fact that the AC side current of both DC / AC converters does not exceed the current limit of their respective sides, the DC / AC converter in auxiliary mode obtains the real-time power of the DC / AC converter in main mode from the DC / AC converter in main mode, and uses the real-time power as the reference power of the DC / AC converter in auxiliary mode.

12. The control method as described in claim 11, characterized in that, 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; the number of DC / AC converters in the first DC / AC converter device and the second DC / AC converter device is equal to the number of energy storage battery packs included in the energy storage battery unit.

13. The control method as described in claim 11, characterized in that, It includes at least two sets of energy storage battery units, at least two sets of second DC / AC converter devices, and at least two sets of first switches. The first DC / AC converter devices are respectively connected to at least two sets of energy storage battery units through at least two sets of first switches. The at least two sets of second DC / AC converter devices are respectively connected to at least two sets of energy storage battery units. The number of switches in each set of first switches is equal to the number of energy storage battery groups included in the energy storage battery unit.

14. The control method as described in claim 11, characterized in that, It includes at least two sets of energy storage battery units, at least two sets of second DC / AC converter devices, and at least two sets of second switches. The first DC / AC converter devices are directly connected to the at least two sets of energy storage battery units, and the at least two sets of second DC / AC converter devices are respectively connected to the at least two sets of energy storage battery units through the at least two sets of second switches. The number of switches in each set of second switches is equal to the number of energy storage battery groups included in the energy storage battery unit.

15. The control method as described in claim 11, characterized in that, It includes at least two sets of energy storage battery units, at least two sets of second DC / AC converter devices, at least two sets of first switches, and at least two sets of second switches. The first DC / AC converter devices are connected to the two sets of energy storage battery units respectively through the at least two sets of first switches. The at least two sets of second DC / AC converter devices are connected to the at least two sets of energy storage battery units respectively through the at least two sets of second switches. The number of switches in each set of first switches and the number of switches in each set of second switches are equal to the number of energy storage battery groups included in the energy storage battery unit.

16. The control method as described in claim 11, characterized in that, It includes at least two sets of energy storage battery units, at least two sets of first switches, and at least two sets of second switches; the first DC / AC converter device is connected to the two sets of energy storage battery units respectively through at least two sets of first switches, and the second DC / AC converter device is connected to the two sets of energy storage battery units respectively through at least two sets of second switches; the number of switches in each set of first switches and the number of switches in each set of second switches are equal to the number of energy storage battery groups included in the energy storage battery unit.

17. The control method as described in claim 11, characterized in that, The first DC / AC converter device is connected to the first AC power grid via a transformer, and / or the second DC / AC converter device is connected to the second AC power grid via a transformer.

18. The control method according to any one of claims 11 to 17, characterized in that, The first DC / AC converter device is connected to the energy storage battery unit via a DC / DC converter and / or the second DC / AC converter device is connected to the energy storage battery unit via a DC / DC converter.

19. The control method as described in claim 11, characterized in that, The energy storage battery unit is a chemical battery, a supercapacitor, or a fuel cell.

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