Matrix type expandable modular multi-level battery energy storage system and control method

Abstract

The invention provides a matrix type expandable modular multi-level battery energy storage system. The matrix type expandable modular multi-level battery energy storage system comprises a direct-current power grid and a three-phase power grid, the energy storage bridge arm comprises an energy storage upper bridge arm and an energy storage lower bridge arm, a first port of the energy storage upper bridge arm is connected with the positive end of the direct-current power grid, a second port of the energy storage lower bridge arm is connected with the negative end of the direct-current power grid, and the second port of the energy storage upper bridge arm and the first port of the energy storage lower bridge arm are connected with a three-phase power grid; the energy storage bridge arm is of a matrix type net structure formed by energy storage units in a matrix arrangement mode, and an independent controller is arranged in each energy storage unit and used for executing a control instruction. The energy storage bridge arm comprises 1-X energy storage units which are arranged in the transverse direction and connected in parallel and 1-N energy storage units which are arranged in the longitudinal direction and connected in series. Through matrix arrangement of the energy storage units, high expansibility and flexibility of the system are achieved, the independent controller in each energy storage unit can accurately execute the control instruction, and the overall performance and reliability of the system are improved.

Description

Technical Field

[0001] The present application relates to the technical field of battery energy storage and system control, and in particular to a matrix-type scalable modular multi-level battery energy storage system and a control method. Background Art

[0002] Efficient, stable and large-capacity energy storage systems have become a core component of power systems. However, how to further improve the capacity and fault tolerance of energy storage systems while ensuring efficient operation of the system has become a key research direction. The existing large-capacity energy storage system topologies mainly include three-level, CHB structure and conventional MMC structure. The above traditional battery energy storage system topologies have the following technical problems:

[0003] 1. Poor expansion capability

[0004] For the three-level topology, the expansion of the system is mainly achieved by increasing the battery voltage or connecting energy storage converters of the same topology in parallel to increase the current. However, this method has the following disadvantages: the battery voltage level needs to be increased; an industrial frequency transformer must be used for voltage boosting; multiple energy storage converters connected in parallel will affect the overall output of the system, which brings difficulties to the design aspects such as efficiency, volume, and cost of the system. For the CHB structure, the synchronization of control signals is particularly important. As the number of modules increases, the delay and phase difference of the control signals between modules may lead to a decrease in system performance, or even resonance, affecting the stability and reliability of the system. For the traditional MMC structure, adding sub-modules during the expansion process will make it more difficult to balance the voltage and power between sub-modules.

[0005] 2. The system’s fault tolerance is insufficient

[0006] The shortcoming of the three-level structure lies in the battery system. Once a battery failure occurs, the system energy balance management is complex and the fault recovery time is longer, which poses a challenge to the continuous operation and fault tolerance of the system. There is a technology that uses a matrix-type reconfigurable battery system to flexibly connect the batteries in a matrix, which can solve the battery energy control problem to a certain extent, but direct connection of the battery (without relying on devices such as inductors) will cause circulation problems. For the CHB structure, since multiple modules are connected in series, the failure of a single module may affect the stability of the entire system, so the fault tolerance in large-scale applications is limited. For the traditional MMC structure, the increase in sub-modules in the energy storage unit may cause the system response time to become longer, and it cannot respond in time under fault conditions. Summary of the invention

[0007] In view of the defects in the prior art, the purpose of this application is to provide a matrix-type expandable modular multi-level battery energy storage system and a control method. By combining energy storage units, the voltage level and the rated current that can pass through the battery energy storage system can be increased. While ensuring that the energy storage set does not need to be redesigned for different voltage levels and power levels, the battery energy storage system can adapt to different power scales and capacity requirements.

[0008] In one aspect of the present application, there is provided a matrix-type scalable modular multi-level battery energy storage system, comprising: a DC power grid and a three-phase power grid;

[0009] An energy storage bridge arm, wherein the energy storage bridge arm comprises an energy storage upper bridge arm and an energy storage lower bridge arm, wherein a first port of the energy storage upper bridge arm is connected to a positive end of the DC grid, a second port of the energy storage lower bridge arm is connected to a negative end of the DC grid, and a second port of the energy storage upper bridge arm and a first port of the energy storage lower bridge arm are connected to the three-phase grid;

[0010] The energy storage bridge arm is an energy storage unit arranged in a matrix to form a matrix network structure, and an independent controller is provided in the energy storage unit for executing control instructions;

[0011] The energy storage bridge arm includes 1 to X energy storage units connected in parallel in the transverse direction and 1 to N energy storage units connected in series in the longitudinal direction.

[0012] Further, one end of the 1 to X parallel energy storage units arranged in the transverse direction is connected to each other, and the other end is connected to each other and connected in series with one end of the energy storage unit below the 1 to N series energy storage units arranged in the longitudinal direction, forming NxX energy storage units, constituting the matrix network structure;

[0013] The energy storage upper bridge arm has the same structure as the energy storage bridge arm, and both are composed of energy storage units arranged in a matrix.

[0014] Further, the energy storage upper bridge arm includes a first energy storage upper bridge arm, a second energy storage upper bridge arm and a third energy storage upper bridge arm; the energy storage lower bridge arm includes a first energy storage lower bridge arm, a second energy storage lower bridge arm and a third energy storage lower bridge arm;

[0015] The first energy storage upper bridge arm and the first energy storage lower bridge arm form a first phase cluster, the first port of the first energy storage upper bridge arm is connected to the positive end of the DC grid, the second port of the second energy storage lower bridge arm is connected to the negative end of the DC grid, and the second port of the first energy storage upper bridge arm and the first port of the second energy storage lower bridge arm are connected to the first phase of the three-phase grid;

[0016] The second energy storage upper bridge arm and the second energy storage lower bridge arm form a second phase cluster, the first port of the second energy storage upper bridge arm is connected to the positive end of the DC grid, the second port of the second energy storage lower bridge arm is connected to the negative end of the DC grid, and the second port of the second energy storage upper bridge arm and the first port of the second energy storage lower bridge arm are connected to the second phase of the three-phase grid;

[0017] The third energy storage upper bridge arm and the third energy storage lower bridge arm form a third phase cluster, the first port of the third energy storage upper bridge arm is connected to the positive end of the DC power grid, the second port of the third energy storage lower bridge arm is connected to the negative end of the DC power grid, and the second port of the third energy storage upper bridge arm and the first port of the third energy storage lower bridge arm are connected to the third phase of the three-phase power grid.

[0018] Furthermore, the first energy storage upper bridge arm, the second energy storage upper bridge arm, the third energy storage upper bridge arm, the first energy storage lower bridge arm, the second energy storage lower bridge arm and the third energy storage lower bridge arm have the same number of energy storage units in the same phase cluster, and all of them are NxX energy storage units forming a matrix network structure.

[0019] Further, the energy storage unit includes 1 to n energy storage submodules and a bridge arm energy storage inductor, the energy storage submodule has a first end and a second end; the second end of the previous energy storage submodule of the 1 to n energy storage submodules is connected to the first end of the next energy storage submodule;

[0020] The second end of the nth energy storage submodule is connected to the first end of the bridge arm energy storage inductor;

[0021] The first end of the first energy storage submodule serves as the first end of the energy storage unit, and the second end of the bridge arm energy storage inductor serves as the second end of the energy storage unit.

[0022] Further, the energy storage submodule includes: a first switch device, a second switch device, a third switch device, a fourth switch device, a first freewheeling diode, a second freewheeling diode, a third freewheeling diode, a fourth freewheeling diode, a filter capacitor and an energy storage device;

[0023] The control ends of the first switch device, the second switch device, the third switch device, and the fourth switch device are respectively connected to the external modulation function port; the first end of the first switch device is connected to the cathode of the first freewheeling diode, the first end of the filter capacitor, and the first end of the energy storage device, and the second end of the first switch device is connected to the anode of the first freewheeling diode and the first end of the third switch device; the first end of the second switch device is connected to the cathode of the second freewheeling diode, the first end of the filter capacitor, and the first end of the energy storage device, and the second end of the second switch device is connected to the anode of the second freewheeling diode and the first end of the fourth switch device; the first end of the third switch device is connected to the cathode of the third freewheeling diode, and the second end of the third switch device is connected to the anode of the third freewheeling diode, the second end of the filter capacitor, and the second end of the energy storage device; the first end of the fourth switch device is connected to the cathode of the fourth freewheeling diode, and the second end of the fourth switch device is connected to the anode of the fourth freewheeling diode, the second end of the filter capacitor, and the second end of the energy storage device;

[0024] The connection point between the second end of the first switch device and the third switch device serves as the first end of the energy storage unit, and the connection point between the second end of the second switch device and the fourth switch device serves as the second end of the energy storage unit.

[0025] A second aspect of the present application provides a control method for a matrix-type scalable modular multi-level battery energy storage system, comprising:

[0026] Receive the system expansion demand signal, determine the target capacity after expansion according to the capacity of the original battery energy storage circuit, the voltage level of the AC and DC sides, and the U characteristics of the energy storage device of the energy storage unit, define the rated power of the energy storage unit, and determine the number of energy storage units to be added;

[0027] Determine whether an energy storage unit in the energy storage system fails. If so, execute the reallocation process; if not, execute the allocation process.

[0028] Furthermore, the receiving system expansion demand signal determines the target capacity after expansion according to the capacity of the original battery energy storage circuit, the AC and DC side voltage levels, and the U characteristics of the energy storage device of the energy storage unit, defines the rated power of the energy storage unit, and determines the number of added energy storage units, including:

[0029] Receive the system expansion demand signal and target capacity. According to the capacity of the original battery energy storage circuit, the AC and DC voltage levels, and the energy storage device U characteristics of the energy storage unit, the capacity of the system before expansion is P origin , determine the target capacity after expansion as P target ;

[0030] Select an energy storage device U with a voltage level consistent with the original energy storage device U as the energy storage device U of the energy storage unit in the added energy storage bridge arm, and define a rated power of the energy storage unit;

[0031] The rated capacity of the energy storage device U of the original energy storage unit is calculated according to the capacity before expansion, and the number of added energy storage units is determined.

[0032] Furthermore, the determining whether an energy storage unit in the energy storage system fails, and if so, executing a reallocation process, includes:

[0033] Obtain the number of energy storage units N and the rated discharge current I of the energy storage device U in the energy storage unit N ;

[0034] Other energy storage units will be allocated to the current I D Satisfaction relationship: And the rated current value of the switching device in the energy storage unit should also satisfy the relationship I mosN ≥I D ;

[0035] In the formula, I D The current allocated to other energy storage units; N is the number of energy storage units; I N is the rated discharge current of the energy storage device U in the energy storage unit;

[0036] I mosN is the rated current value of the switching device in the energy storage unit.

[0037] Further, the execution allocation process includes: the main controller outputs voltage and current to the outside through closed-loop control based on the voltage and current of each bridge arm of the three phases, and sends the voltage and current control signals allocated to each SET to the SET controller;

[0038] The SET controller receives the voltage and current control signals allocated by the main controller, performs voltage modulation on the voltage of each SET, outputs the voltage and current allocation results, and sends a switch control signal to the energy storage submodule controller;

[0039] The energy storage submodule executes the switch control signal, and samples the temperature of the energy storage submodule and battery energy information, and sends them to the SET controller for energy balancing and power distribution.

[0040] Compared with the prior art, the present invention has at least one of the following beneficial effects:

[0041] 1. This application can increase the voltage level and rated current of the battery energy storage system by combining energy storage units. The battery energy storage system can adapt to different power scales and capacity requirements while ensuring that the energy storage set does not need to be redesigned for different voltage levels and power levels.

[0042] 2. This application does not need to adjust the control system structure (including the system's control resources and control strategies) when expanding or reducing the system capacity. The expansion method is simple and easy to implement, avoiding the problem of repeated design when the energy storage system copes with different power levels, reducing the difficulty of energy storage system design. At the same time, the matrix structure helps to balance energy within the system. In addition, when a few modules fail, the system can achieve fault-free operation through reasonable power allocation, so it has strong scalability and reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Other features, objects and advantages of the present application will become more apparent by reading the detailed description of non-limiting embodiments with reference to the following drawings:

[0044] Figure 1 This is a structural diagram of a matrix-type expandable modular multi-level battery energy storage system in one embodiment of the present application.

[0045] Figure 2 This is a structural diagram of a solution in which the energy storage bridge arm has only a single energy storage unit in one embodiment of the present application.

[0046] Figure 3 This is a structural diagram of the connection method of the energy storage unit in one embodiment of the present application.

[0047] Figure 4 This is a basic structural diagram of an energy storage unit in one embodiment of the present application.

[0048] Figure 5 This is a structural diagram of a full-bridge structure in which the energy storage unit is a bipolar topology in one embodiment of the present application.

[0049] Figure 6 This is a framework diagram of a matrix-type expandable modular multi-level battery energy storage system in one embodiment of the present application.

[0050] Figure 7 This is a flow chart of a matrix-type expandable modular multi-level battery energy storage system control method in one embodiment of the present application.

[0051] Figure 8 This is a structural diagram of a battery energy storage circuit connected to form a specific embodiment in one embodiment of the present application. DETAILED DESCRIPTION

[0052] The present application is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present application, but do not limit the present application in any form. It should be noted that, for those of ordinary skill in the art, several variations and improvements can also be made without departing from the concept of the present application. These all belong to the protection scope of the present application.

[0053] Reference Figure 1 As shown, a matrix-type expandable modular multi-level battery energy storage system according to an embodiment of the present application includes: a DC power grid and a three-phase power grid; an energy storage bridge arm, the energy storage bridge arm includes an energy storage upper bridge arm and an energy storage lower bridge arm, the first port of the energy storage upper bridge arm is connected to the positive end of the DC power grid, the second port of the energy storage lower bridge arm is connected to the negative end of the DC power grid, the second port of the energy storage upper bridge arm and the first port of the energy storage lower bridge arm are connected to the three-phase power grid; the energy storage bridge arm is an energy storage unit arranged in a matrix to form a matrix mesh structure, and an independent controller is provided in the energy storage unit for executing control instructions.

[0054] The energy storage bridge arm includes 1 to X parallel energy storage units arranged in the transverse direction and 1 to N series energy storage units arranged in the longitudinal direction.

[0055] This application realizes the high scalability and flexibility of the system through the matrix arrangement of energy storage units. By combining energy storage units, the voltage level and rated current that can pass through the battery energy storage system can be increased. While ensuring that the energy storage set does not need to be redesigned for different voltage levels and power levels, the battery energy storage system can adapt to different power scales and capacity requirements. At the same time, the independent controller in each energy storage unit can accurately execute control instructions, which improves the overall performance and reliability of the system and is suitable for large-scale battery energy storage applications; at the same time, the matrix structure helps to balance energy within the system. In addition, when a few modules fail, the system can achieve fault-free operation through reasonable power allocation, so it has strong scalability and reliability.

[0056] The electric energy is received through the DC grid and distributed to the energy storage bridge arm. The energy storage bridge arm consists of an upper energy storage bridge arm and a lower energy storage bridge arm, which are respectively connected to the positive and negative ends of the DC grid and connected to the three-phase grid through their respective ports. Inside the energy storage bridge arm, the energy storage units are arranged in a matrix to form a mesh structure. The energy storage units are arranged in parallel from 1 to X in the horizontal direction and in series from 1 to N in the vertical direction to meet different energy storage needs. Each energy storage unit is equipped with an independent controller, which is responsible for receiving and executing control instructions, thereby realizing precise control and management of the energy storage system.

[0057] In some specific embodiments, one ends of 1 to X parallel energy storage units arranged in the horizontal direction are connected to each other, and the other ends are connected to each other and connected in series with one end of the energy storage unit below 1 to N series energy storage units arranged in the vertical direction, forming NxX energy storage units, forming a matrix network structure.

[0058] Specifically, the system includes NxX energy storage units arranged in a matrix. The energy storage units are X units in parallel horizontally (the first ends of the X energy storage units are connected together, and the second ends are connected together), and N units in series vertically (the second end of the upper energy storage unit is connected to the first end of the lower energy storage unit), and the NxX units form a matrix network structure. The first port of the first row of energy storage units is connected to the first port of the energy storage structure, and the second port of the Nth row of energy storage units is connected to the second port of the energy storage structure.

[0059] Among them, the structure of the energy storage upper bridge arm is the same as that of the energy storage bridge arm, and both are composed of energy storage units arranged in a matrix.

[0060] In some specific embodiments, the energy storage upper bridge arm includes a first energy storage upper bridge arm, a second energy storage upper bridge arm and a third energy storage upper bridge arm; the energy storage lower bridge arm includes a first energy storage lower bridge arm, a second energy storage lower bridge arm and a third energy storage lower bridge arm.

[0061] The first energy storage upper bridge arm and the first energy storage lower bridge arm form a first phase cluster, the first port of the first energy storage upper bridge arm is connected to the positive end of the DC grid, the second port of the second energy storage lower bridge arm is connected to the negative end of the DC grid, and the second port of the first energy storage upper bridge arm and the first port of the second energy storage lower bridge arm are connected to the first phase of the three-phase grid.

[0062] The second energy storage upper bridge arm and the second energy storage lower bridge arm form a second phase cluster, the first port of the second energy storage upper bridge arm is connected to the positive end of the DC grid, the second port of the second energy storage lower bridge arm is connected to the negative end of the DC grid, and the second port of the second energy storage upper bridge arm and the first port of the second energy storage lower bridge arm are connected to the second phase of the three-phase grid.

[0063] The third energy storage upper bridge arm and the third energy storage lower bridge arm form a third phase cluster, the first port of the third energy storage upper bridge arm is connected to the positive end of the DC grid, the second port of the third energy storage lower bridge arm is connected to the negative end of the DC grid, and the second port of the third energy storage upper bridge arm and the first port of the third energy storage lower bridge arm are connected to the third phase of the three-phase grid.

[0064] This matrix-type scalable modular multi-level battery energy storage structure can be used not only in MMC, but also in other cascaded multi-level energy storage system structures, such as CHB.

[0065] In some specific embodiments, the first energy storage upper bridge arm, the second energy storage upper bridge arm, the third energy storage upper bridge arm, the first energy storage lower bridge arm, the second energy storage lower bridge arm and the third energy storage lower bridge arm in the same phase cluster have the same number of energy storage units, all of which are NxX energy storage units forming a matrix network structure.

[0066] Specifically, the first energy storage upper bridge arm and the first energy storage lower bridge arm have the same structure, and both include NxX energy storage units arranged in a matrix. In the first energy storage upper bridge arm and the first energy storage lower bridge arm, the energy storage units are X units in parallel horizontally (the first ends of the X energy storage units are connected together, and the second ends are connected together), and N units are connected in series vertically (the second end of the upper energy storage unit is connected to the first end of the lower energy storage unit), and the NxX units form a matrix mesh structure. In the first energy storage upper bridge arm, the first port of the energy storage unit in the first row is connected to the positive end of the DC power grid, and the second port of the energy storage unit in the Nth row is connected to the first phase of the AC power grid; in the first energy storage lower bridge arm, the first port of the energy storage unit in the first row is connected to the first phase of the AC power grid, and the second port of the energy storage unit in the Nth row is connected to the negative end of the DC power grid.

[0067] The second energy storage upper bridge arm has the same structure as the second energy storage lower bridge arm, and both include NxX energy storage units arranged in a matrix. In the second energy storage upper bridge arm and the second energy storage lower bridge arm, the energy storage units are X units in parallel horizontally (the first ends of the X energy storage units are connected together, and the second ends are connected together), and N units are connected in series vertically (the second end of the upper energy storage unit is connected to the first end of the lower energy storage unit), and NxX units form a matrix mesh structure. In the second energy storage upper bridge arm, the first port of the energy storage unit in the first row is connected to the positive end of the DC power grid, and the second port of the energy storage unit in the Nth row is connected to the second phase of the AC power grid; in the second energy storage lower bridge arm, the first port of the energy storage unit in the first row is connected to the second phase of the AC power grid, and the second port of the energy storage unit in the Nth row is connected to the negative end of the DC power grid.

[0068] The third energy storage upper bridge arm and the third energy storage lower bridge arm have the same structure, both of which include NxX energy storage units arranged in a matrix. In the third energy storage upper bridge arm and the third energy storage lower bridge arm, the energy storage units are X units in parallel horizontally (the first ends of the X energy storage units are connected together, and the second ends are connected together), and N units are connected in series vertically (the second end of the upper energy storage unit is connected to the first end of the lower energy storage unit), and NxX units form a matrix mesh structure. In the third energy storage upper bridge arm, the first port of the energy storage unit in the first row is connected to the positive end of the DC power grid, and the second port of the energy storage unit in the Nth row is connected to the third phase of the AC power grid; in the third energy storage lower bridge arm, the first port of the energy storage unit in the first row is connected to the third phase of the AC power grid, and the second port of the energy storage unit in the Nth row is connected to the negative end of the DC power grid.

[0069] By increasing the number of units connected in parallel horizontally, the rated current that the energy storage system can withstand can be increased, and by increasing the number of units connected in series vertically, the voltage level of the energy storage system can be increased. While ensuring that the internal structure, control system, and voltage resistance level of the energy storage unit remain unchanged, the energy storage circuit has a sufficiently large expansion range. The above expansion method is flexible and easy to implement. The method of connecting inductors in series with internal energy storage units avoids the direct series and parallel connection of a large number of energy storage devices. It can reduce the circulating current between devices while achieving redundancy and self-regulation in the event of system failure, so it has strong expansion capacity and fault tolerance.

[0070] In one embodiment, they all include a plurality of energy storage units with the same number of series connection, and the number of parallel connection energy storage units is not exactly the same.

[0071] Specifically, in the solution of this embodiment, NxX energy storage units in the first energy storage bridge arm form a matrix mesh structure, with X units in parallel horizontally and N units in series vertically, and the remaining energy storage bridge arms adopt a similar structure. By increasing the number of units in parallel horizontally, the rated current that the energy storage system can withstand can be increased, and by increasing the number of units in series vertically, the voltage level of the energy storage system can be increased. While ensuring that the internal structure, control system, and withstand voltage level of the energy storage unit remain unchanged, the energy storage circuit has a sufficiently large expansion range.

[0072] like Figure 4 As shown, in some specific embodiments, the energy storage unit includes 1 to n energy storage sub-modules and a bridge arm energy storage inductor, the energy storage sub-module has a first end and a second end; the second end of the previous energy storage sub-module of the 1 to n energy storage sub-modules is connected to the first end of the next energy storage sub-module; the second end of the nth energy storage sub-module is connected to the first end of the bridge arm energy storage inductor; the first end of the first energy storage sub-module serves as the first end of the energy storage unit, and the second end of the bridge arm energy storage inductor serves as the second end of the energy storage unit.

[0073] like Figure 2 As shown, in the above embodiment, it can be achieved by adding a new energy storage unit in the solution where the original energy storage bridge arm has only a single energy storage unit. Figure 2 In the energy storage system shown, the first energy storage upper bridge arm includes only one energy storage unit, the second energy storage upper bridge arm includes only one energy storage unit, and the third energy storage upper bridge arm includes only one energy storage unit; the first energy storage lower bridge arm includes only one energy storage unit, the second energy storage lower bridge arm includes only one energy storage unit, and the third energy storage lower bridge arm includes only one energy storage unit. At this time, in order to increase the capacity of the energy storage system, the number of parallel energy storage units or the number of series energy storage units in the first energy storage upper bridge arm, the first energy storage lower bridge arm, the second energy storage upper bridge arm, the second energy storage lower bridge arm, the third energy storage upper bridge arm, and the third energy storage lower bridge arm can be increased, or the number of series and parallel energy storage units can be increased at the same time, so as to achieve the expansion operation of the energy storage system.

[0074] Specifically, the basic structure of the energy storage unit is consistent, and each energy storage unit includes n energy storage submodules and an energy storage bridge arm inductor. The n energy storage submodules and 1 energy storage bridge arm inductor are connected in series, the second end of the previous energy storage submodule is connected to the first end of the next energy storage submodule, and the second end of the nth energy storage submodule is connected to the first end of the bridge arm energy storage inductor. The first end of the first energy storage submodule serves as the first end of the energy storage unit, and the second end of the bridge arm energy storage inductor serves as the second end of the energy storage unit.

[0075] In the present application, it should be pointed out that, in one embodiment, the number of energy storage units can be further increased when there are already multiple energy storage units in the original energy storage bridge arm (the number of energy storage units in the energy storage bridge arm is NxX, N and X are greater than 1) to achieve further expansion of the energy storage system. That is, in the energy storage bridge arm, the number of energy storage units in parallel and in series increases. The more energy storage units are connected in parallel or in series, the larger the capacity of the corresponding battery energy storage system. When the number of energy storage units is increased to achieve the expansion of energy storage, each added energy storage unit corresponds to a new bridge arm energy storage inductor to ensure that each energy storage unit has a corresponding bridge arm energy storage inductor for filtering, and to suppress the circulating current between units, so as to ensure the working reliability of the battery energy storage circuit after the new energy storage unit is added.

[0076] like Figure 3 As shown, another implementation method of the present application is: the number of energy storage units connected in series in the longitudinal direction of all energy storage bridge arms is the same, that is, the energy storage units in the first energy storage upper bridge arm, the second energy storage upper bridge arm, the third energy storage upper bridge arm, the first energy storage lower bridge arm, the second energy storage lower bridge arm and the third energy storage lower bridge arm are all N rows. The number of energy storage units connected in parallel in the energy storage bridge arms is different, that is, the number of columns of energy storage units in the first energy storage upper bridge arm, the second energy storage upper bridge arm, the third energy storage upper bridge arm, the first energy storage lower bridge arm, the second energy storage lower bridge arm and the third energy storage lower bridge arm are inconsistent. Setting different numbers of parallel units can effectively improve the operational reliability of the energy storage circuit.

[0077] like Figure 5 As shown, specifically, the energy storage submodule includes: a first switch device, a second switch device, a third switch device, a fourth switch device, a first freewheeling diode, a second freewheeling diode, a third freewheeling diode, a fourth freewheeling diode, a filter capacitor and an energy storage device.

[0078] The control ends of the first switch device, the second switch device, the third switch device, and the fourth switch device are respectively connected to the external modulation function port; the first end of the first switch device is connected to the cathode of the first freewheeling diode, the first end of the filter capacitor and the first end of the energy storage device, and the second end of the first switch device is connected to the anode of the first freewheeling diode and the first end of the third switch device; the first end of the second switch device is connected to the cathode of the second freewheeling diode, the first end of the filter capacitor and the first end of the energy storage device, and the second end of the second switch device is connected to the anode of the second freewheeling diode and the first end of the fourth switch device; the first end of the third switch device is connected to the cathode of the third freewheeling diode, and the second end of the third switch device is connected to the anode of the third freewheeling diode, the second end of the filter capacitor and the second end of the energy storage device; the first end of the fourth switch device is connected to the cathode of the fourth freewheeling diode, and the second end of the fourth switch device is connected to the anode of the fourth freewheeling diode, the second end of the filter capacitor and the second end of the energy storage device.

[0079] The second end of the first switch device and the connection point of the third switch device serve as the first end of the energy storage unit, and the second end of the second switch device and the connection point of the fourth switch device serve as the second end of the energy storage unit.

[0080] In this application, the structure of the energy storage submodule is not unique, and can be a unipolar topology or a bipolar topology. When the energy storage unit is a full-bridge structure with a bipolar topology, please refer to Figure 5 , the positive output end is the midpoint of the left half bridge, and the negative output end is the midpoint of the right half bridge.

[0081] Specifically, the first end of the energy storage submodule is the positive output end of the energy storage submodule, and the second end of the energy storage submodule is the negative output end of the energy storage. In order to realize the series connection between the energy storage submodules, it is only necessary to connect the positive output end of the energy storage submodule with the negative output end of another energy storage submodule to realize the series connection of the two energy storage submodules.

[0082] The specific type of energy storage device U is not unique. In one embodiment, lithium batteries can be directly used. This solution avoids direct series and parallel connection of energy storage devices (i.e., batteries), isolates the differences of batteries in the form of modules, and even if different types of batteries are used in each energy storage unit, as long as a suitable and complete battery management system is used, even batteries with different capacities can be mixed and used in a multi-level structure energy storage system.

[0083] Among them, the device voltage levels of the energy storage submodules are consistent.

[0084] like Figure 6As shown, the above battery energy storage system adopts a distributed control structure, that is, each set is controlled by a controller, and each of the n submodules in the SET has a submodule controller for executing control instructions, which is responsible for opening the switch tube in the submodule issued by the SET.

[0085] A second aspect of the present application provides a control method for a matrix-type expandable modular multi-level battery energy storage system, comprising: receiving a system expansion demand signal, determining a target capacity after expansion according to the capacity of the original battery energy storage circuit, the AC and DC side voltage levels, and the U characteristics of the energy storage device of the energy storage unit, defining the rated power of the energy storage unit, and determining the number of energy storage units to be added;

[0086] Determine whether an energy storage unit in the energy storage system fails. If so, execute the reallocation process; if not, execute the allocation process.

[0087] In some specific embodiments, a system expansion demand signal is received, and a target capacity after expansion is determined according to the capacity of the original battery energy storage circuit, the voltage level of the AC and DC sides, and the U characteristics of the energy storage device of the energy storage unit, the rated power of the energy storage unit is defined, and the number of energy storage units to be added is determined, including: receiving a system expansion demand signal and a target capacity, and according to the capacity of the original battery energy storage circuit, the voltage level of the AC and DC sides, and the U characteristics of the energy storage device of the energy storage unit, the capacity of the system before expansion is P origin , determine the target capacity after expansion as P target ; Select an energy storage device U with a voltage level consistent with the original energy storage device U as the energy storage device U of the energy storage unit in the added energy storage bridge arm, and define the rated power of an energy storage unit; calculate the rated capacity of the energy storage device U of the original energy storage unit based on the capacity before expansion, and determine the number of added energy storage units.

[0088] In the above embodiment, the powers of the energy storage units are the same, so only the rated power of one energy storage unit needs to be defined.

[0089] Specifically, when there is a need to expand the battery energy storage circuit, first of all, according to the capacity of the original battery energy storage circuit, the voltage level of the AC and DC sides, and the U characteristics of the energy storage device of the energy storage unit, the capacity of the system before expansion is P origin , determine the target capacity after expansion as P t arg et Select an energy storage device U with the same voltage level as the original energy storage device U as the energy storage device U of the energy storage unit in the added energy storage bridge arm, and define the rated power of an energy storage unit as: P N =nU N I N Among them, I N is the rated discharge current of the energy storage device U in the energy storage unit, U NIt is the rated voltage level of the energy storage device U in the energy storage unit.

[0090] In some specific embodiments, after the expansion, it is determined whether the energy storage unit fails. If so, a redistribution process is performed, including: obtaining the number N of energy storage units and the rated discharge current I of the energy storage device U in the energy storage unit. N ; Other energy storage units will be allocated to the current I D Satisfaction relationship: And the rated current value of the switching device in the energy storage unit should also satisfy the relationship I mosN ≥I D .

[0091] In the formula, I D The current allocated to other energy storage units; N is the number of energy storage units; I N I is the rated discharge current of the energy storage device U in the energy storage unit; mosN is the rated current value of the switching device in the energy storage unit.

[0092] Specifically, the rated capacity of the energy storage device U of the original energy storage unit is calculated based on the capacity before expansion: Where k = N·X, which is the number of energy storage units in an energy storage bridge arm, and n is the number of energy storage submodules in an energy storage unit. The number of added energy storage units should satisfy: In addition, the rated current value I of the switching device in the energy storage unit mosN The relationship should be satisfied: When an energy storage unit in the energy storage system fails, the other energy storage units connected in parallel with the energy storage unit will additionally bear the power of the energy storage unit, and the system will operate with the fault. D Satisfaction relationship: In addition, the rated current value of the switching device in the energy storage unit should also satisfy the relationship: In this case, I mosN ≥I D .

[0093] like Figure 7 As shown, in some specific embodiments, the execution allocation process includes: the main controller outputs voltage and current to the outside through closed-loop control based on the voltage and current of each bridge arm of the three-phase, and sends the voltage and current control signals allocated to each SET to the SET controller; the SET controller receives the voltage and current control signals allocated by the main controller, performs voltage modulation on the voltage of each SET, outputs the voltage and current allocation results, and sends a switch control signal to the energy storage submodule controller; the energy storage submodule executes the switch control signal, and samples the energy storage submodule temperature and battery energy information, and sends them to the SET controller for energy balancing and power allocation.

[0094] Specifically, during the working process, the main controller first performs closed-loop control of the system's external output voltage and current based on the voltage and current information of each bridge arm of the three phases. Then, the main controller calculates and sends the voltage value that each SET should be allocated to the SET controller below. After the SET controller receives the voltage value, the SET controllers in the first column will modulate the voltage of each SET, while other SET controllers will allocate and control the current of their respective SET branches. At the same time, the SET controller will also sample the temperature and battery energy information of the submodule, and upload it to itself for energy balancing and power allocation decisions. Finally, the SET controller sends a control signal of the switch tube to the submodule based on the voltage and current distribution results and the energy and temperature status information of the submodule. The submodule controller executes these control signals, and continues to sample the temperature and battery energy information of the submodule, and uploads it to the SET controller for subsequent optimization.

[0095] Among them, SET controller is the controller of the energy storage unit; SET is the energy storage unit; the rated power of the energy storage unit is defined as the rated power of the newly added energy storage unit.

[0096] The present application realizes precise closed-loop control of the voltage and current of the three-phase bridge arm through the coordinated work of the main controller, SET controller and sub-module controller, improves the stability and accuracy of the external output voltage and current, and realizes the optimization of energy balance and power distribution by sampling the temperature and battery energy information of the sub-module.

[0097] In some specific embodiments, the SET controller receives the voltage and current control signals allocated by the main controller, performs voltage modulation on the voltage of each SET, outputs the voltage and current distribution results, and sends the switch control signal to the energy storage submodule controller, including: obtaining voltage and current control signals; sampling the voltage and current in each SET for voltage and current control; sampling the submodule temperature and battery energy information, and uploading them to the SET controller for energy balancing and power distribution; the SET controller sends the switch tube control signal to the submodule in the SET according to the above voltage and current distribution results and the energy and temperature status information of each submodule.

[0098] Finally, the control signal sent by the SET controller is executed to sample the submodule temperature and battery energy information, and uploaded to the SET controller for energy balancing and power allocation.

[0099] Among them, the submodule controller will sample the submodule temperature and battery energy information and upload it to the SET controller. The SET controller will upload it to the top-level controller after integration and processing for the overall scheduling control of the entire system; the system-level voltage and current control is completed at the top level, and after the information is sent to the SET controller, energy balancing will be added to further subdivide the control. The submodule temperature and energy information are related to its output power capability. Energy balancing means that more power is allocated to submodules with high energy status during discharge, and vice versa during charging.

[0100] Among them, the SET controller obtains and integrates the information sampled by the following n sub-module controllers.

[0101] In order to facilitate understanding of the solution of expanding the capacity of the energy storage unit by increasing the number of energy storage units in the battery energy storage system of the present application, the following is an explanation in conjunction with the specific expansion operation. The voltage level of each energy storage device U is set to be the same. For example, in one embodiment, an energy storage device U with a rated voltage of 51.2V and a nominal capacity of 38Ah can be used in each energy storage unit.

[0102] Reference Figure 8 As shown, for example, in a more detailed embodiment, when it is necessary to expand the capacity of a 200kW energy storage system to 400kW, the DC side voltage is 800V, the AC side voltage is 380V, and each energy storage bridge arm of the energy storage system before the expansion includes 4 energy storage units (the energy storage units are connected in a 2X2 matrix), and each energy storage unit includes 6 energy storage sub-modules and 1 energy storage bridge arm inductor. In this embodiment, the target capacity is 400kW, and each energy storage bridge arm of the expanded system includes 9 energy storage units (the energy storage units are connected in a 3X3 matrix), and each energy storage unit includes 6 energy storage sub-modules and 1 energy storage bridge arm inductor. According to Figure 6 Assume that after the expansion, the energy storage unit Set1-1 fails, and after the energy storage unit is removed from the system, the system current is distributed by the energy storage units Set1-2 and Set1-3 connected in parallel with it.

[0103] The energy storage submodule in this embodiment includes a switch device, a capacitor, and an energy storage device U (i.e., a battery). Figure 5The structural connection shown constitutes an energy storage submodule. At the same time, the selected energy storage bridge arm inductance and AC side inductance in this embodiment are 1mH, the energy storage device U used is a lithium iron phosphate battery with a nominal voltage of 51.2V / 38AH, and the power MOSFET model used is SFG180N10PF. The main controller uses Beckoff's CX2020 controller, the set controller uses the xilinx K7 series FPGA, and the sub-module controller uses the pango PGL12G series FPGA. The voltage allocated to each SET in the original upper bridge arm is 200+311 / 2sinwt V, the voltage allocated to the lower bridge arm is 200-311 / 2sinwt V, and the current allocated to each SET is 27.13A.

[0104] In this embodiment, a power decoupling control method can be used to control the power on the AC side and the power on the DC side respectively, thereby indirectly controlling the charge and discharge state of the battery. A carrier phase shift modulation method is used to realize the switch control of the energy storage unit.

[0105] According to the above operations, the system capacity is expanded: the original capacity of the system is P origin = 200kW, the rated capacity of the energy storage device U of the original energy storage unit is calculated based on the capacity before expansion After the expansion, the number of added energy storage units should meet the following requirements: That is, the number of energy storage units added to each energy storage bridge arm In this case, 5 energy storage units will be added to each energy storage bridge arm to meet the above conditions for increasing the number of energy storage units. At this time, the current passing through the switch device in each energy storage unit is Satisfied at this time

[0106] After expansion, the system rated current is I N , assuming that SET1-1 fails and cannot operate, the current distribution from SET1-2 to SET1-3 is At this time, the switch devices in the energy storage unit satisfy the relationship: I mosN ≥I D . From the control level of the system, when the system adds 5 energy storage units, 5 SET controllers need to be added. After the energy storage system is expanded, the voltage and current allocated to each SET change. The voltage allocated to each SET in the upper bridge arm is 400 / 3+311 / 3sinwt V, and the voltage allocated to the lower bridge arm is 400 / 3-311 / 3sinwt V. The current allocated to each SET is 24.1A. In the above system, assuming that SET1-1 fails, the voltage allocated to the SET in parallel with SET1-1 remains unchanged, but the allocated current is modified to 36.2A.

[0107] The above describes the specific embodiments of the present application. It should be understood that the present application is not limited to the above specific embodiments, and those skilled in the art can make various modifications or variations within the scope of the claims, which does not affect the substantive content of the present application. The above preferred features can be used in any combination without conflicting with each other.

Claims

1. A matrix-type scalable modular multi-level battery energy storage system, characterized in that: include: DC grid and three-phase grid; An energy storage bridge arm, wherein the energy storage bridge arm comprises an energy storage upper bridge arm and an energy storage lower bridge arm, wherein a first port of the energy storage upper bridge arm is connected to a positive end of the DC grid, a second port of the energy storage lower bridge arm is connected to a negative end of the DC grid, and a second port of the energy storage upper bridge arm and a first port of the energy storage lower bridge arm are connected to the three-phase grid; The energy storage bridge arm is an energy storage unit arranged in a matrix to form a matrix network structure, and an independent controller is provided in the energy storage unit for executing control instructions; The energy storage bridge arm includes 1 to X energy storage units connected in parallel in the transverse direction and 1 to N energy storage units connected in series in the longitudinal direction.

2. The matrix-type scalable modular multi-level battery energy storage system according to claim 1, characterized in that: One ends of the 1 to X parallel energy storage units arranged in the transverse direction are connected to each other, and the other ends are connected to each other and connected in series with one end of the energy storage unit below the 1 to N series energy storage units arranged in the longitudinal direction, forming NxX energy storage units to form the matrix network structure; The energy storage upper bridge arm has the same structure as the energy storage bridge arm, and both are composed of energy storage units arranged in a matrix.

3. The matrix-type scalable modular multi-level battery energy storage system according to claim 2, characterized in that: The energy storage upper bridge arm includes a first energy storage upper bridge arm, a second energy storage upper bridge arm and a third energy storage upper bridge arm; the energy storage lower bridge arm includes a first energy storage lower bridge arm, a second energy storage lower bridge arm and a third energy storage lower bridge arm; The first energy storage upper bridge arm and the first energy storage lower bridge arm form a first phase cluster, the first port of the first energy storage upper bridge arm is connected to the positive end of the DC grid, the second port of the second energy storage lower bridge arm is connected to the negative end of the DC grid, and the second port of the first energy storage upper bridge arm and the first port of the second energy storage lower bridge arm are connected to the first phase of the three-phase grid; The second energy storage upper bridge arm and the second energy storage lower bridge arm form a second phase cluster, the first port of the second energy storage upper bridge arm is connected to the positive end of the DC grid, the second port of the second energy storage lower bridge arm is connected to the negative end of the DC grid, and the second port of the second energy storage upper bridge arm and the first port of the second energy storage lower bridge arm are connected to the second phase of the three-phase grid; The third energy storage upper bridge arm and the third energy storage lower bridge arm form a third phase cluster, the first port of the third energy storage upper bridge arm is connected to the positive end of the DC power grid, the second port of the third energy storage lower bridge arm is connected to the negative end of the DC power grid, and the second port of the third energy storage upper bridge arm and the first port of the third energy storage lower bridge arm are connected to the third phase of the three-phase power grid.

4. The matrix-type scalable modular multi-level battery energy storage system according to claim 3, characterized in that: The first energy storage upper bridge arm, the second energy storage upper bridge arm, the third energy storage upper bridge arm, the first energy storage lower bridge arm, the second energy storage lower bridge arm and the third energy storage lower bridge arm have the same number of energy storage units in the same phase cluster, all of which are NxX energy storage units forming a matrix network structure.

5. The matrix-type scalable modular multi-level battery energy storage system according to claim 1, characterized in that: The energy storage unit includes 1 to n energy storage submodules and a bridge arm energy storage inductor, wherein the energy storage submodule has a first end and a second end; the second end of the previous energy storage submodule of the 1 to n energy storage submodules is connected to the first end of the next energy storage submodule; The second end of the nth energy storage submodule is connected to the first end of the bridge arm energy storage inductor; The first end of the first energy storage submodule serves as the first end of the energy storage unit, and the second end of the bridge arm energy storage inductor serves as the second end of the energy storage unit.

6. The matrix-type scalable modular multi-level battery energy storage system according to claim 5, characterized in that: The energy storage submodule includes: a first switch device, a second switch device, a third switch device, a fourth switch device, a first freewheeling diode, a second freewheeling diode, a third freewheeling diode, a fourth freewheeling diode, a filter capacitor and an energy storage device; The control ends of the first switch device, the second switch device, the third switch device, and the fourth switch device are respectively connected to the external modulation function port; the first end of the first switch device is connected to the cathode of the first freewheeling diode, the first end of the filter capacitor, and the first end of the energy storage device, and the second end of the first switch device is connected to the anode of the first freewheeling diode and the first end of the third switch device; the first end of the second switch device is connected to the cathode of the second freewheeling diode, the first end of the filter capacitor, and the first end of the energy storage device, and the second end of the second switch device is connected to the anode of the second freewheeling diode and the first end of the fourth switch device; the first end of the third switch device is connected to the cathode of the third freewheeling diode, and the second end of the third switch device is connected to the anode of the third freewheeling diode, the second end of the filter capacitor, and the second end of the energy storage device; the first end of the fourth switch device is connected to the cathode of the fourth freewheeling diode, and the second end of the fourth switch device is connected to the anode of the fourth freewheeling diode, the second end of the filter capacitor, and the second end of the energy storage device; The connection point between the second end of the first switch device and the third switch device serves as the first end of the energy storage unit, and the connection point between the second end of the second switch device and the fourth switch device serves as the second end of the energy storage unit.

7. A control method for a matrix-type scalable modular multi-level battery energy storage system according to any one of claims 1 to 6, characterized in that: include: Receive the system expansion demand signal, determine the target capacity after expansion according to the capacity of the original battery energy storage circuit, the voltage level of the AC and DC sides, and the U characteristics of the energy storage device of the energy storage unit, define the rated power of the energy storage unit, and determine the number of energy storage units to be added; Determine whether an energy storage unit in the energy storage system fails. If so, execute the reallocation process; if not, execute the allocation process.

8. The control method of the matrix-type scalable modular multi-level battery energy storage system according to claim 7, characterized in that: The receiving system expansion demand signal determines the target capacity after expansion according to the capacity of the original battery energy storage circuit, the AC and DC side voltage levels, and the U characteristics of the energy storage device of the energy storage unit, defines the rated power of the energy storage unit, and determines the number of added energy storage units, including: Receive the system expansion demand signal and target capacity. According to the capacity of the original battery energy storage circuit, the AC and DC voltage levels, and the energy storage device U characteristics of the energy storage unit, the capacity of the system before expansion is P origin , determine the target capacity after expansion as P target ; Select an energy storage device U with a voltage level consistent with the original energy storage device U as the energy storage device U of the energy storage unit in the added energy storage bridge arm, and define a rated power of the energy storage unit; The rated capacity of the energy storage device U of the original energy storage unit is calculated according to the capacity before expansion, and the number of added energy storage units is determined.

9. The control method of the matrix-type scalable modular multi-level battery energy storage system according to claim 7, characterized in that: The determining whether an energy storage unit in the energy storage system fails, and if so, executing a reallocation process, includes: Obtain the number of energy storage units N and the rated discharge current I of the energy storage device U in the energy storage unit N ; Other energy storage units will be allocated to the current I D Satisfaction relationship: And the rated current value of the switching device in the energy storage unit should also satisfy the relationship I mosN ≥I D ; In the formula, I D The current allocated to other energy storage units; N is the number of energy storage units; I N is the rated discharge current of the energy storage device U in the energy storage unit; I mosN is the rated current value of the switching device in the energy storage unit.

10. The control method of the matrix-type scalable modular multi-level battery energy storage system according to claim 7, characterized in that: The execution allocation process includes: the main controller outputs voltage and current to the outside through closed-loop control based on the voltage and current of each bridge arm of the three phases, and sends the voltage and current control signals allocated to each SET to the SET controller; The SET controller receives the voltage and current control signals allocated by the main controller, performs voltage modulation on the voltage of each SET, outputs the voltage and current allocation results, and sends a switch control signal to the energy storage submodule controller; The energy storage submodule executes the switch control signal, and samples the temperature of the energy storage submodule and battery energy information, and sends them to the SET controller for energy balancing and power distribution.

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