Energy storage system and battery active equalization method and device thereof, and computer program product

Abstract

The invention relates to the technical field of energy storage, in particular to an energy storage system, a battery active equalization method and device thereof and a computer program product. The system comprises a battery module, a bridge circuit topology and a control loop; wherein the battery modules are electrically connected through the bridge circuit topology to form a battery cluster; the control loop is configured to control the working state of the battery module connected to the battery cluster by controlling the on-off of a switching device in the bridge circuit topology; the working state comprises a power-on state and a bypass state, and the power-on state comprises a charging state and a discharging state; and when the working state of the battery module is controlled, feedforward control is performed on a direct current bus of the energy storage system through a grid-connected inverter of the energy storage system. According to the scheme provided by the invention, online hundred-ampere-level battery active equalization management can be provided, the equalization duration is effectively shortened, and the full-capacity network-hanging standby time of the energy storage device is prolonged.

Description

Technical Field

[0001] This disclosure relates to the field of energy storage technology, and in particular to an energy storage system and its battery active balancing method, device and computer program product. Background Technology

[0002] New energy generator sets exhibit volatility and randomness, making high-power, long-duration energy storage an important supplement and a key component of power stations operating in weak grid conditions. Energy storage batteries, with their large number of individual cells, are prone to degradation over long periods, necessitating online monitoring of their health and active state-of-charge balancing. Currently, normal battery charging and discharging (100 amperes, 120~200A) is managed by grid-connected inverters (DC / AC conversion), while active balancing largely relies on inter-module switching power supplies (DC / DC conversion). These power supplies are auxiliary equipment, not involved in normal charging and discharging, and operate offline. They require high-frequency switching matrices and energy storage components, making the technology complex and costing 3 to 5 times more than passive balancing. Although they support bidirectional energy transfer from multiple batteries, their current carrying capacity is limited (only 1~10A), resulting in long balancing times and shortening the full-capacity grid-connected standby time of the energy storage device. Summary of the Invention

[0003] This disclosure aims to at least partially solve one of the technical problems in the aforementioned technologies, and to this end proposes an energy storage system comprising: Battery module, bridge circuit topology, and control loop; among which... The battery modules are electrically connected through the bridge circuit topology to form a battery cluster; The control loop is configured as follows: By controlling the on / off state of the switching devices in the bridge circuit topology, the working state of the battery module connected to the battery cluster is controlled; the working state includes: power-on state and bypass state, and the power-on state includes: charging state and discharging state. When controlling the working state of the battery module, the DC bus of the energy storage system is fed forward controlled through the grid-connected inverter of the energy storage system.

[0004] Furthermore, the battery module is composed of several battery cells electrically connected together.

[0005] Furthermore, the bridge circuit topology includes: a half-bridge circuit topology and a full-bridge circuit topology; the bridge circuit topology is a two-level circuit topology or a three-level circuit topology.

[0006] Furthermore, the switching devices in the bridge circuit topology are power semiconductor switching devices.

[0007] Furthermore, the power semiconductor switching device is a bidirectional switch.

[0008] Furthermore, the control loop is configured to suppress DC voltage fluctuations and converter grid-connected power output fluctuations of the energy storage system by performing feedforward control on the DC bus of the energy storage system.

[0009] Furthermore, the feedforward control uses the square of the DC bus voltage of the battery cluster as a reference input, which is provided by the battery management system; the negative feedback input of the control loop is provided by the energy storage system based on the detection data of the DC bus voltage sensor of the battery cluster.

[0010] Furthermore, the control loop includes: square calculation, addition and subtraction, compensator, saturator, dynamic model of energy storage inverter, dynamic model of DC capacitor, square root calculation and unity feedback.

[0011] Furthermore, the control loop is configured to control the upper and lower limits of the transfer function output through the saturator; the upper and lower limits depend on the fluctuation range of the DC bus voltage of the energy storage system and the port voltage fluctuations of the battery cells constituting the battery module during charging and discharging.

[0012] Furthermore, the control loop is configured to: when controlling the working state of the battery module connected to the battery cluster by controlling the on / off state of the switching devices in the bridge circuit topology, perform a tiered switching of the battery modules to be moved into or out of the battery cluster, that is, at the same time, only a single battery module is moved into the battery cluster or only a single battery module is moved out of the battery cluster.

[0013] Furthermore, the control loop is configured to: when controlling the working state of the battery module connected to the battery cluster by controlling the on / off state of the switching devices in the bridge circuit topology, synchronously switch the battery modules to be moved into or out of the battery cluster, that is, perform the operation of moving all battery modules to be processed into or out of the battery cluster at the same time.

[0014] Furthermore, the control loop is configured to: when controlling the working state of the battery module connected to the battery cluster by controlling the on / off state of the switching devices in the bridge circuit topology, perform a combination of tiered switching and synchronous switching on the battery module to be moved into or out of the battery cluster.

[0015] Furthermore, the control loop is also configured to: after a battery module is moved in or out, wait until the DC voltage fluctuation of the DC bus of the energy storage system has attenuated to a stable level before moving the next battery module to be processed in or out.

[0016] Furthermore, the expression for the transfer function of the dynamic model of the energy storage inverter includes:

[0017] in, The transfer function represents the dynamic model of the energy storage inverter; This represents the time constant of the dynamic model of the energy storage inverter; It is a complex frequency variable.

[0018] Furthermore, the expression for the transfer function of the DC capacitor dynamic model includes:

[0019] in, The transfer function representing the dynamic model of a DC capacitor; This indicates the DC support capacitor value of the grid-connected inverter in the energy storage system; This represents the time constant of the dynamic model of a DC capacitor. It is a complex frequency variable.

[0020] Furthermore, the time constant The expressions include:

[0021] in, This represents the peak value of the AC phase voltage of the power grid to which the energy storage system is connected; This represents the grid-connected reactance value of the grid-connected inverter of the energy storage system; This represents the active power flowing between the grid-connected inverter of the energy storage system and the power grid.

[0022] Furthermore, the expression for the compensator corresponding to the compensator model includes:

[0023] in, The transfer function representing the compensator model; This indicates the DC support capacitor value of the grid-connected inverter in the energy storage system; It is a complex frequency variable; Indicates that there is no compensator The transfer function at the zero point.

[0024] Furthermore, the compensator has no Transfer function at zero point The corresponding expressions include:

[0025] in, express Gain coefficient; It is a constant; express The pole parameters.

[0026] Furthermore, the expression for the loop gain of the control loop includes:

[0027] in, This represents the loop gain of the control loop; The transfer function representing the compensator model; The transfer function represents the dynamic model of the energy storage inverter; The transfer function representing the dynamic model of a DC capacitor; Indicates that there is no compensator The transfer function at the zero point; This represents the time constant.

[0028] This disclosure also proposes an active battery balancing method for energy storage systems, including: The working state of the battery module connected to the battery cluster is controlled by controlling the switching devices in the bridge circuit topology; the working state includes: power-on state and bypass state, and the power-on state includes: charging state and discharging state. When controlling the working state of the battery module, the DC bus of the energy storage system is fed forward controlled through the grid-connected inverter of the energy storage system.

[0029] Furthermore, by implementing feedforward control on the DC bus of the energy storage system, the DC voltage fluctuations of the energy storage system and the grid-connected power output fluctuations of the converter are suppressed.

[0030] Furthermore, the feedforward control uses the square of the DC bus voltage of the battery cluster as a reference input, which is provided by the battery management system; the negative feedback input of the control loop is provided by the energy storage system based on the detection data of the DC bus voltage sensor of the battery cluster.

[0031] Furthermore, when controlling the working state of the battery module connected to the battery cluster by controlling the switching devices in the bridge circuit topology, the battery module to be moved into or out of the battery cluster is switched by a combination of tiered switching and synchronous switching.

[0032] This disclosure also proposes an electronic device, including a memory and a processor, wherein the memory stores a computer program or instructions, which, when executed by the processor, are at least used to implement the methods described above.

[0033] This disclosure also proposes a computer-readable storage medium storing a computer program or instructions that, when executed by a processor, are at least used to implement the methods described above.

[0034] This disclosure also proposes a computer program product stored in a computer-readable storage medium, which, when executed by a processor, is used to implement at least the above-described method.

[0035] Compared with the prior art, the beneficial effects of this disclosure are: This disclosure proposes an energy storage system and its active battery balancing method, which can provide an online, 100-ampere-level active battery balancing management technology. It is suitable for online management of the power-on status of battery modules after they are connected in series and clustered together. It is especially suitable for energy storage cells and modules with a capacity of 100 ampere-hours and converter systems, effectively reducing the balancing time and improving the full-capacity grid-connected standby time of energy storage devices.

[0036] Other features and advantages of this disclosure will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the disclosure. The objects and other advantages of this disclosure may be realized and obtained by means of the structures particularly pointed out in the written description and the accompanying drawings. The technical solutions of this disclosure will be further described below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0037] The accompanying drawings are provided to further illustrate the present disclosure and form part of the specification. They are used together with the embodiments of the present disclosure to explain the disclosure and do not constitute a limitation thereof. In the drawings: Figure 1 A topology diagram showing how battery modules are connected to clusters via a half-bridge circuit; Figure 2 A topology diagram showing the battery modules connected to the cluster via a full-bridge circuit; Figure 3 This is a topology diagram of an insulated-gate bipolar transistor and a freewheeling diode connected in parallel internally as a bidirectional switch. Figure 4 The topology diagram for a back-to-back MOSFET module (two N-type MOSFETs connected in series) as a bidirectional switch; Figure 5 This is a schematic diagram showing how a battery module enters the energized state within a cluster via a half-bridge circuit. Figure 6 This is a schematic diagram showing how a battery module enters a bypass state within a cluster via a half-bridge circuit. Figure 7 This is a schematic diagram showing how a battery module enters a charging state within a cluster via a full-bridge circuit. Figure 8 This is a schematic diagram showing how a battery module enters a discharge state within a cluster via a full-bridge circuit. Figure 9 This is a schematic diagram showing how a battery module enters a bypass state within a cluster via a full-bridge circuit. Figure 10This is a schematic diagram showing how a battery module enters another bypass state within a cluster via a full-bridge circuit. Figure 11 A schematic diagram of feedforward control of DC bus voltage for an energy storage inverter system; Figure 12 A graph showing the DC bus voltage curve in response to a sudden change in DC voltage. Figure 13 This is a schematic diagram of an active battery balancing method for an energy storage system. Figure 14 A schematic diagram of an electronic device; Figure 15 This is a schematic diagram of a computer-readable storage medium. Detailed Implementation

[0038] The present disclosure will be described below with reference to the accompanying drawings. The preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present disclosure.

[0039] This disclosure proposes an energy storage system comprising: Battery module, bridge circuit topology, and control loop; among which... The battery modules are electrically connected through the bridge circuit topology to form a battery cluster; The control loop is configured as follows: By controlling the on / off state of the switching devices in the bridge circuit topology, the working state of the battery module connected to the battery cluster is controlled; the working state includes: power-on state and bypass state, and the power-on state includes: charging state and discharging state. When controlling the working state of the battery module, the DC bus of the energy storage system is fed forward controlled through the grid-connected inverter of the energy storage system.

[0040] According to some embodiments of this disclosure, in the energy storage system proposed in this disclosure, battery modules are connected in a bridge circuit topology to form a battery cluster. The control loop controls the operating state of the battery modules connected to the battery cluster by controlling the on / off state of the switching devices in the bridge circuit topology, thereby achieving active battery balancing. Simultaneously, while controlling the operating state of the battery modules, the control loop performs feedforward control of the DC bus of the energy storage system through a grid-connected inverter.

[0041] Furthermore, the battery module is composed of several battery cells electrically connected together.

[0042] According to some embodiments of this disclosure, a battery cluster can include either a group of battery modules connected in series or multiple groups of battery modules connected in parallel. A battery module can include either a group of individual battery cells connected in series or multiple groups of individual battery cells connected in series in parallel. For example, 16 individual battery cells connected in series form one group, and three groups connected in parallel form one battery module. 14 of these battery modules connected in series form one battery cluster, comprising a total of 672 cells. Alternatively, 16 individual battery cells connected in series form one battery module, and 14 battery modules connected in series are combined. Within one battery cluster, three such series-connected battery modules are connected in parallel, comprising a total of 672 cells.

[0043] According to some embodiments of this disclosure, the cells of all battery cells may be the same or different, and the cells may have various electrochemical forms, including lithium batteries, lead-acid batteries, fuel cells, and flow batteries. For example, lithium batteries include lithium iron phosphate and ternary lithium batteries.

[0044] According to some embodiments of this disclosure, the battery cells constituting the battery module of the energy storage system are lithium iron phosphate cells with typical capacities ranging from 314Ah to 486Ah, or vanadium redox flow cells with typical power ranges of 125kW and 625kW.

[0045] Furthermore, the bridge circuit topology includes: a half-bridge circuit topology and a full-bridge circuit topology; the bridge circuit topology is a two-level circuit topology or a three-level circuit topology.

[0046] According to some embodiments of this disclosure, the bridge circuit topology connecting the battery modules in the energy storage system proposed in this disclosure can be adopted as follows: Figure 1 The half-bridge circuit topology shown can also be adopted as follows: Figure 2 The full-bridge circuit topology shown is as follows; the bridge circuit topology can be a two-level bridge circuit topology or a three-level bridge circuit topology.

[0047] Furthermore, the bridge circuit topology types include: a two-level half-bridge circuit, a two-level full-bridge circuit, a half-bridge circuit using diode neutral point clamping of three levels, a full-bridge circuit using diode neutral point clamping of three levels, a half-bridge circuit using active neutral point clamping of three levels, and a full-bridge circuit using active neutral point clamping of three levels.

[0048] Furthermore, the switching devices in the bridge circuit topology are power semiconductor switching devices.

[0049] Furthermore, the power semiconductor switching device is a bidirectional switch.

[0050] According to some embodiments of this disclosure, the bridge circuit topology uses a bidirectional switch. The bidirectional switch can be composed of a fully controlled power semiconductor switch and an uncontrolled diode connected in parallel, or it can be composed of fully controlled power semiconductors connected back to back in series, or it can be a combination of the above devices in parallel and series, thereby improving the current and voltage withstand capability of the bidirectional switch.

[0051] Furthermore, the configuration of power semiconductor switching devices includes: a fully controlled power semiconductor switch connected in parallel with an uncontrolled diode; a back-to-back series connection of MOSFET power semiconductors (including two N-type MOSFETs connected back-to-back and two P-type MOSFETs connected back-to-back); a bistable relay or dual relay; or a parallel connection of an insulated-gate bipolar transistor (IGBT) and an uncontrolled diode. The uncontrolled diode includes a freewheeling diode, and the IGBT and freewheeling diode are internally connected in parallel as a bidirectional switch structure. Figure 3 As shown; a back-to-back MOSFET module (two N-type MOSFETs connected in series) is used as a bidirectional switch. Figure 4 As shown.

[0052] According to some embodiments of this disclosure, for Figure 1 The battery module shown is connected to the cluster topology via a half-bridge circuit. The operating state of the battery module can be controlled by controlling bidirectional switches 1 and 2. Figure 5 As shown, when bidirectional switch 1 is closed and bidirectional switch 2 is opened, the battery module enters a powered-on state (charging or discharging) within the cluster through the half-bridge circuit; as... Figure 6 As shown, when bidirectional switch 2 is closed and bidirectional switch 1 is opened, the battery module enters a bypass state within the cluster via the half-bridge circuit. (This is for...) Figure 2 The battery module shown is connected to the cluster topology via a full-bridge circuit, as follows: Figure 7 As shown, when bidirectional switches 1 and 4 are closed and bidirectional switches 2 and 3 are opened, the battery module enters the charging state within the cluster through the full-bridge circuit; as... Figure 8 As shown, when bidirectional switches 2 and 3 are closed and bidirectional switches 1 and 4 are opened, the battery module enters a discharge state within the cluster through the full-bridge circuit; as... Figure 9 As shown, when bidirectional switches 1 and 3 are closed and bidirectional switches 2 and 4 are opened, the battery module enters a bypass state within the cluster via the full-bridge circuit; as... Figure 10 As shown, when bidirectional switches 2 and 4 are closed and bidirectional switches 1 and 3 are opened, the battery module can also enter the bypass state within the cluster through the full-bridge circuit.

[0053] Furthermore, the control loop is configured to suppress DC voltage fluctuations and converter grid-connected power output fluctuations of the energy storage system by performing feedforward control on the DC bus of the energy storage system.

[0054] According to some embodiments of this disclosure, the number of battery modules connected in series within the battery cluster can be changed online. This change will cause fluctuations in the DC voltage across the battery cluster. Feedforward control of the DC bus voltage can effectively suppress DC voltage fluctuations and effectively suppress fluctuations in the grid-connected power output of the converter.

[0055] Furthermore, the feedforward control uses the square of the DC bus voltage of the battery cluster as a reference input, which is provided by the battery management system; the negative feedback input of the control loop is provided by the energy storage system based on the detection data of the DC bus voltage sensor of the battery cluster.

[0056] According to some embodiments of this disclosure, in the energy storage system proposed in this disclosure, the control loop notifies the grid-connected inverter of the energy storage system in advance to perform feedforward control on the DC bus voltage of the energy storage system before controlling the working state of the battery modules in the battery cluster.

[0057] Furthermore, the control loop includes: square calculation, addition and subtraction, compensator, saturator, dynamic model of energy storage inverter, dynamic model of DC capacitor, square root calculation and unity feedback.

[0058] Furthermore, the control loop is configured to control the upper and lower limits of the transfer function output through the saturator; the upper and lower limits depend on the fluctuation range of the DC bus voltage of the energy storage system and the port voltage fluctuations of the battery cells constituting the battery module during charging and discharging.

[0059] According to some embodiments of this disclosure, the control loop is as follows: Figure 10 As shown, it includes a quadratic calculation, addition and subtraction, compensator, saturator, dynamic model of energy storage inverter, dynamic model of DC capacitor, square root calculation and unity feedback connected in sequence. The feedforward control of the DC bus of the energy storage system uses the square of the DC bus voltage of the battery cluster as the reference input, which is provided by the battery management system. The negative feedback input of the feedforward control is provided by the energy storage system based on the detection data of the DC bus voltage sensor of the battery cluster.

[0060] Furthermore, the control loop is configured to: when controlling the working state of the battery module connected to the battery cluster by controlling the on / off state of the switching devices in the bridge circuit topology, perform a tiered switching of the battery modules to be moved into or out of the battery cluster, that is, at the same time, only a single battery module is moved into the battery cluster or only a single battery module is moved out of the battery cluster.

[0061] According to some embodiments of this disclosure, the change in the number of battery modules in the battery cluster can be planned or it can be caused suddenly by alarm protection. Generally, it is mainly planned in advance. The planning is based on the power control command received by the energy storage system, which allows only a portion of the battery modules to participate in the power-on state during a certain period of time. The planned switching is generally based on tiered switching, that is, while moving the battery module in, the DC bus voltage of the battery cluster is increased, and while moving the replaced battery module out, the DC bus voltage of the battery cluster is reduced to the level before the switching.

[0062] Furthermore, the control loop is configured to: when controlling the working state of the battery module connected to the battery cluster by controlling the on / off state of the switching devices in the bridge circuit topology, synchronously switch the battery modules to be moved into or out of the battery cluster, that is, perform the operation of moving all battery modules to be processed into or out of the battery cluster at the same time.

[0063] According to some embodiments of this disclosure, when an alarm protection is suddenly triggered, the energy storage system requires a certain battery module to exit the working state. The energy storage system then switches on a healthy battery module to replace the battery module that triggered the aforementioned alarm protection, maintaining the DC voltage of the battery cluster within a normal operating range. For sudden switching, synchronous switching is generally preferred; that is, while removing the battery module to be replaced, the DC bus voltage of the battery cluster is reduced, and then while moving the battery module in, the DC bus voltage of the battery cluster is increased to the level before the switching.

[0064] According to some embodiments of this disclosure, when an alarm protection is suddenly triggered, the state of the battery modules in the powered-on state needs to be changed immediately. Synchronous switching is generally used. For example, two bypass battery modules with the highest port voltage can be selected and switched synchronously with one designated faulty battery module. The bypass battery module moves into the battery cluster, and the faulty battery module moves out of the battery cluster. This reduces the impact of the DC voltage drop in the battery cluster during the switching process. Alternatively, (n+1) bypass battery modules with the highest port voltage can be selected and switched synchronously with n designated faulty battery modules. The bypass battery modules move into the battery cluster, and the faulty battery modules move out of the battery cluster. This also reduces the impact of the DC voltage drop in the battery cluster during the switching process. Alternatively, the bypass battery module closest to the battery module's port voltage can be selected and switched synchronously with the designated faulty battery module. The faulty battery module moves out of the battery cluster, and the bypass battery module moves into the battery cluster.

[0065] According to some embodiments of this disclosure, the number of battery modules within a battery cluster may change, either by increasing or decreasing; or the total number may remain constant, but battery modules constituting the total number may be moved in or out.

[0066] Furthermore, the control loop is configured to: when controlling the working state of the battery module connected to the battery cluster by controlling the on / off state of the switching devices in the bridge circuit topology, perform a combination of tiered switching and synchronous switching on the battery module to be moved into or out of the battery cluster.

[0067] According to some embodiments of this disclosure, the change in the number of battery modules connected in series within a battery cluster can also be a synchronous switching, i.e., simultaneously moving two or more battery modules in and out. The operation can be either tiered switching or synchronous switching, or a combination of both. For example, if an alarm protection is suddenly triggered, synchronous switching is performed first to maintain the normal operation of the energy storage system until the DC voltage of the battery cluster stabilizes. Then, based on the health status and state of charge of each battery module within the battery cluster, one battery module can be selected to replace the battery module that was just moved into the battery cluster during synchronous switching, based on tiered switching. Based on tiered switching, the power-on state of the battery module moved into the battery cluster may not meet expectations, resulting in rapid degradation. In such cases, synchronous switching is immediately performed to remove the battery module from the battery cluster.

[0068] Furthermore, the control loop is also configured to: after a battery module is moved in or out, wait until the DC voltage fluctuation of the DC bus of the energy storage system has attenuated to a stable level before moving the next battery module to be processed in or out.

[0069] According to some embodiments of this disclosure, in order to maintain the DC voltage of the battery cluster within a normal operating range, a single selected battery module can be put into operation first. After the DC voltage of the battery cluster increases and stabilizes, the battery module that needs to be bypassed can be switched out. Alternatively, in a full-bridge circuit topology, to maintain the DC voltage of the battery cluster within a normal operating range, a selected battery module can be put into operation first. After the DC voltage of the battery cluster increases and stabilizes, another selected battery module can be put into operation. After the DC voltage of the battery cluster increases and stabilizes again, the battery module that needs to reverse its power-on state can be switched to a bypass state first. After the DC voltage of the battery cluster decreases and stabilizes, the battery module can be put back into the battery cluster to reverse its operating state. For example, it can switch from charging to bypass first, and then to discharging; or from discharging to bypass first, and then to charging.

[0070] According to some embodiments of this disclosure, the energy storage system can adopt the following control schemes during the discharge operation: 1. As the battery module voltage decreases, increase the number of battery modules connected in series within the battery cluster; 2. As the battery module voltage decreases, maintain the number of battery modules connected in series within the battery cluster, and replace the battery module in the working state but with a lower port voltage with a battery module in the bypass state. 3. During the charging process of the energy storage system, as the voltage of the battery module increases, the number of battery modules connected in series within the battery cluster is maintained, and a battery module in bypass state replaces a battery module in operation but with a higher port voltage.

[0071] Furthermore, the expression for the transfer function of the dynamic model of the energy storage inverter includes:

[0072] in, The transfer function represents the dynamic model of the energy storage inverter; This represents the time constant of the dynamic model of the energy storage inverter; It is a complex frequency variable.

[0073] According to some embodiments of this disclosure, the energy storage converter dynamic characteristic model proposed in this disclosure for Set time constant The time is 0.5ms to 5ms. It should be noted that... This indicates the inverter, as opposed to a conventional serial number. This transfer function is suitable for voltage source inverters in energy storage systems. It is a current-controlled transfer function that can perform active and reactive power control, making it suitable for grid integration and grid construction.

[0074] Furthermore, the expression for the transfer function of the DC capacitor dynamic model includes:

[0075] in, The transfer function representing the dynamic model of a DC capacitor; This indicates the DC support capacitor value of the grid-connected inverter in the energy storage system; This represents the time constant of the dynamic model of a DC capacitor. It is a complex frequency variable.

[0076] Furthermore, the time constant The expressions include:

[0077] in, This represents the peak value of the AC phase voltage of the power grid to which the energy storage system is connected; This represents the grid-connected reactance value of the grid-connected inverter of the energy storage system; This represents the active power flowing between the grid-connected inverter of the energy storage system and the power grid.

[0078] According to some embodiments of this disclosure, the transfer function of the capacitor dynamic characteristic model proposed in this disclosure for C represents the DC support capacitor value of the grid-connected inverter. Time constant. The settings are shown in the following formula:

[0079] This refers to the active power flowing between the grid-connected inverter and the power grid. When the grid-connected inverter outputs active power to the power grid... When the value is positive, it means that when absorbing active power, It is a negative value; L is the grid-connected reactance of the inverter; This refers to the peak value of the AC phase voltage of the grid to which the energy storage system is connected. The value range is generally between -0.5ms and 0.5ms.

[0080] Furthermore, the expression for the compensator corresponding to the compensator model includes:

[0081] in, The transfer function representing the compensator model; This indicates the DC support capacitor value of the grid-connected inverter in the energy storage system; It is a complex frequency variable; Indicates that there is no compensator The transfer function at the zero point.

[0082] Furthermore, the compensator has no Transfer function at zero point The corresponding expressions include:

[0083] in, express Gain coefficient; It is a constant; express The pole parameters.

[0084] According to some embodiments of this disclosure, the compensator model transfer function proposed in this disclosure for , This refers to the DC support capacitor value of the grid-connected inverter mentioned earlier. This indicates that the compensator does not have The partial transfer function expression at the zero point is usually designed to be free of zeros. Zero-point lead compensator. It can be appropriately configured using root locus or frequency response methods. The parameters. The general form is , As the extreme point, is a constant greater than 1, and k is the gain value.

[0085] Furthermore, the expression for the loop gain of the control loop includes:

[0086] in, This represents the loop gain of the control loop; The transfer function representing the compensator model; The transfer function represents the dynamic model of the energy storage inverter; The transfer function representing the dynamic model of a DC capacitor; Indicates that there is no compensator The transfer function at the zero point; This represents the time constant.

[0087] The above solution will be further explained below with reference to the embodiments: Example 1: This example proposes a tiered replacement of the operating state of two battery modules, a and b, within a battery cluster. Based on the health and state of charge of battery modules a and b, the battery management system instructs the energy storage converter to first switch module b from a bypass state to an on-state, while simultaneously increasing the cluster DC bus voltage to 850V. After the DC bus voltage passes the transient and stabilizes, module a is then switched from an on-state to a bypass state. After the DC bus voltage passes the transient and stabilizes, the cluster DC bus voltage, which was 850V before and after the tiered replacement, undergoes a brief transition to 900V. In this tiered switching, module b is first put into operation, followed by bypassing the target module a, ensuring that the cluster DC voltage remains higher than the system requirements before and after the switch. This improves the reliability of online module switching.

[0088] Example 2: This example proposes a synchronous replacement method for the operating state of two battery modules, a and b, within a cluster. Module a suddenly detects a fault and exits the cluster first. During the exit process, module a synchronously notifies the cluster and the system. The system determines that among the modules in the bypass state within the cluster, module b's health and state of charge are most suitable for replacing module a. The battery management system notifies the energy storage converter to switch module b from the bypass state to the energized state. Considering the worst-case scenario, module a exits first, followed by module b. There is a 1ms delay between synchronous switching. The cluster DC bus voltage experiences a brief drop of 1ms, from 850V to XV. It then rises from XV back to 850V. In the event of a sudden battery module fault, the synchronous switching method ensures that the cluster DC voltage remains above 800V.

[0089] Example 3: This example proposes a method for replacing the working state of three parallel battery modules a, b and c, and three parallel battery modules A, B and C within a cluster.

[0090] When the system detects that battery module A needs to be deactivated, it first switches battery modules A, B, and C from bypass to energized. Once these three modules are engaged, the cluster DC bus voltage will increase. Then, the system switches module A from energized to bypass, allowing modules B and C to fully absorb the current previously flowing through module A. Next, modules B and C are switched from energized to bypass. The cluster DC bus voltage will then drop. Once the DC bus voltage stabilizes, the entire replacement process is complete.

[0091] Example 4: This example presents a DC bus voltage control effect for sudden DC voltage changes. Switching in / out of a single PACK causes a sudden change in the DC voltage of the string PCS, varying by 50V. However, this change is predictable. The power controller of the PCS can be reliably notified in advance. The DC voltage controller principle is as described above, combining feedforward compensation and feedback control to simultaneously satisfy charging and discharging functions. Figure 11 As shown, after a brief drop to 790V, the DC voltage quickly and monotonically rose to 800V and stabilized at 800V. Table 1 was used to test various PACK online switching conditions, and the conclusion was that all of them could stabilize the DC bus voltage and the active and reactive power output of the grid-connected inverter.

[0092] Table 1

[0093] Based on the same technological concept, such as Figure 12 As shown, this disclosure also proposes an active battery balancing method for an energy storage system, including: The working state of the battery module connected to the battery cluster is controlled by controlling the switching devices in the bridge circuit topology; the working state includes: power-on state and bypass state, and the power-on state includes: charging state and discharging state. When controlling the working state of the battery module, the DC bus of the energy storage system is fed forward controlled through the grid-connected inverter of the energy storage system.

[0094] like Figure 13 As shown, this disclosure also proposes an electronic device, including a memory and a processor, wherein the memory stores a computer program or instructions, and when the computer program or instructions are executed by the processor, they are used to at least implement the above-described active battery balancing method for the energy storage system.

[0095] like Figure 14As shown, this disclosure also proposes a computer-readable storage medium storing a computer program or instructions, which, when executed by a processor, are used to at least implement the above-described active battery balancing method for energy storage systems.

[0096] like Figure 15 As shown, this disclosure also proposes a computer program product, which is stored in a computer-readable storage medium. When the computer program product is executed by a processor, it is used to at least implement the above-described active battery balancing method for energy storage systems.

[0097] It is obvious that those skilled in the art can make various modifications and variations to this disclosure without departing from its spirit and scope. Therefore, if such modifications and variations fall within the scope of the claims of this disclosure and their equivalents, this disclosure is also intended to include such modifications and variations.

Claims

1. An energy storage system, characterized in that, include: Battery module, bridge circuit topology, and control loop; among which... The battery modules are electrically connected through the bridge circuit topology to form a battery cluster; The control loop is configured as follows: By controlling the on / off state of the switching devices in the bridge circuit topology, the working state of the battery module connected to the battery cluster is controlled; the working state includes: power-on state and bypass state, and the power-on state includes: charging state and discharging state. When controlling the working state of the battery module, the DC bus of the energy storage system is fed forward controlled through the grid-connected inverter of the energy storage system.

2. The energy storage system as described in claim 1, characterized in that, The battery module is composed of several battery cells electrically connected together.

3. The energy storage system as described in claim 1, characterized in that, The bridge circuit topology includes: a half-bridge circuit topology and a full-bridge circuit topology; the bridge circuit topology is a two-level circuit topology or a three-level circuit topology.

4. The energy storage system as described in claim 1, characterized in that, The switching devices in the bridge circuit topology are power semiconductor switching devices.

5. The energy storage system as described in claim 4, characterized in that, The power semiconductor switching device is a bidirectional switch.

6. The energy storage system as described in claim 1, characterized in that, The control loop is configured to suppress DC voltage fluctuations and converter grid-connected power output fluctuations of the energy storage system by performing feedforward control on the DC bus of the energy storage system.

7. The energy storage system as described in claim 1, characterized in that, The feedforward control uses the square of the DC bus voltage of the battery cluster as a reference input, which is provided by the battery management system; the negative feedback input of the control loop is provided by the energy storage system based on the detection data of the DC bus voltage sensor of the battery cluster.

8. The energy storage system as described in claim 7, characterized in that, The control loop includes: square calculation, addition and subtraction, compensator, saturator, dynamic model of energy storage inverter, dynamic model of DC capacitor, square root calculation and unity feedback.

9. The energy storage system as described in claim 8, characterized in that, The control loop is configured to control the upper and lower limits of the transfer function output through the saturator; the upper and lower limits depend on the fluctuation range of the DC bus voltage of the energy storage system and the port voltage fluctuations of the battery cells constituting the battery module during charging and discharging.

10. The energy storage system as described in claim 8, characterized in that, The control loop is configured to: when controlling the working state of the battery module connected to the battery cluster by controlling the on / off state of the switching devices in the bridge circuit topology, perform a tiered switching of the battery module to be moved into or out of the battery cluster, that is, at the same time, only a single battery module is moved into the battery cluster or only a single battery module is moved out of the battery cluster.

11. The energy storage system as described in claim 8, characterized in that, The control loop is configured to: when controlling the working state of the battery module connected to the battery cluster by controlling the on / off state of the switching devices in the bridge circuit topology, synchronously switch the battery modules to be moved into or out of the battery cluster, that is, perform the operation of moving all the battery modules to be processed into or out of the battery cluster at the same time.

12. The energy storage system as described in claim 8, characterized in that, The control loop is configured to: when controlling the working state of the battery module connected to the battery cluster by controlling the on / off state of the switching devices in the bridge circuit topology, perform a combination of tiered switching and synchronous switching on the battery module to be moved into or out of the battery cluster.

13. The energy storage system according to any one of claims 10-12, characterized in that, The control loop is further configured to: after moving a battery module in or out, wait until the DC voltage fluctuation of the DC bus of the energy storage system has attenuated to a stable level before moving the next battery module to be processed in or out.

14. The energy storage system as described in claim 8, characterized in that, The expression for the transfer function of the dynamic model of the energy storage inverter includes: in, The transfer function represents the dynamic model of the energy storage inverter; This represents the time constant of the dynamic model of the energy storage inverter; It is a complex frequency variable.

15. The energy storage system as described in claim 8, characterized in that, The expression for the transfer function of the DC capacitor dynamic model includes: in, The transfer function representing the dynamic model of a DC capacitor; This indicates the DC support capacitor value of the grid-connected inverter in the energy storage system; This represents the time constant of the dynamic model of a DC capacitor. It is a complex frequency variable.

16. The energy storage system as described in claim 15, characterized in that, The time constant The expressions include: in, This represents the peak value of the AC phase voltage of the power grid to which the energy storage system is connected; This represents the grid-connected reactance value of the grid-connected inverter of the energy storage system; This represents the active power flowing between the grid-connected inverter of the energy storage system and the power grid.

17. The energy storage system as described in claim 8, characterized in that, The expression for the compensator corresponding to the compensator model includes: in, The transfer function representing the compensator model; This indicates the DC support capacitor value of the grid-connected inverter in the energy storage system; It is a complex frequency variable; Indicates that there is no compensator The transfer function at the zero point.

18. The energy storage system as described in claim 17, characterized in that, The compensator has none Transfer function at zero point The corresponding expressions include: in, express Gain coefficient; It is a constant; express The pole parameters.

19. The energy storage system according to any one of claims 14-18, characterized in that, The loop gain of the control loop, and the corresponding expression, includes: in, This represents the loop gain of the control loop; The transfer function representing the compensator model; The transfer function represents the dynamic model of the energy storage inverter; The transfer function representing the dynamic model of a DC capacitor; Indicates that there is no compensator The transfer function at the zero point; This represents the time constant.

20. A method for active battery balancing in an energy storage system, characterized in that, include: The working state of the battery module connected to the battery cluster is controlled by controlling the on / off state of the switching devices in the bridge circuit topology. The operating states include: power-on state and bypass state; the power-on state includes: charging state and discharging state. When controlling the working state of the battery module, the DC bus of the energy storage system is fed forward controlled through the grid-connected inverter of the energy storage system.

21. The active battery balancing method for an energy storage system as described in claim 20, characterized in that, By implementing feedforward control on the DC bus of the energy storage system, the DC voltage fluctuations of the energy storage system and the grid-connected power output fluctuations of the converter are suppressed.

22. The active battery balancing method for an energy storage system as described in claim 20, characterized in that, The feedforward control uses the square of the DC bus voltage of the battery cluster as a reference input, which is provided by the battery management system; the negative feedback input of the control loop is provided by the energy storage system based on the detection data of the DC bus voltage sensor of the battery cluster.

23. The active battery balancing method for an energy storage system as described in claim 20, characterized in that, When controlling the working state of the battery module connected to the battery cluster by controlling the switching devices in the bridge circuit topology, the battery module to be moved into or out of the battery cluster is switched by a combination of tiered switching and synchronous switching.

24. An electronic device comprising a memory and a processor, characterized in that, The memory stores a computer program or instructions, which, when executed by the processor, are used to implement at least the method described in any one of claims 20-23.

25. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program or instructions, which, when executed by a processor, are used to implement at least the method described in any one of claims 20-23.

26. A computer program product, said computer program product being stored in a computer-readable storage medium, characterized in that, When the computer program product is executed by a processor, it is used to implement at least the method described in any one of claims 20-23.

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