An energy storage system

Abstract

The application provides an energy storage system, comprising: an energy storage converter, a plurality of battery clusters, a high-voltage box corresponding to each battery cluster, and a controller; the high-voltage box comprises a switching module and a conversion module; each battery cluster is connected with the first end of the corresponding switching module and the first end of the conversion module, the second end of each switching module is connected with the energy storage converter through a DC bus, the second end of each conversion module is connected with a three-phase power distribution end of the energy storage system; and the controller is used for controlling the switching module corresponding to each battery cluster to be balanced to disconnect the corresponding battery cluster to be balanced from the DC bus and starting the conversion module corresponding to the battery cluster to be balanced, so that the three-phase power distribution end balances the electric quantity of each battery cluster to be balanced when performing an electric quantity balancing task. The energy storage system can use the conversion module to balance the battery clusters with a large power when the battery clusters are unbalanced, thereby accelerating the balancing speed of the battery clusters.

Description

Technical Field

[0001] This invention relates to the field of energy storage technology, and more particularly to an energy storage system. Background Technology

[0002] A battery cluster consists of multiple batteries connected in series or in parallel. Series connection increases the battery terminal voltage, while parallel connection increases battery capacity. Each battery cluster is connected to an energy storage converter, which in turn connects to the power grid, forming an energy storage system. The battery cluster, as the component for storing and releasing electrical energy, is a key piece of equipment in the energy storage system and directly affects its safe and stable operation.

[0003] In the later stages of operation, traditional energy storage systems experience widening inconsistencies between individual cells. Premature overvoltage (triggering charge inactivity) or undervoltage (triggering discharge inactivity) in a single cell can lead to a system-wide shutdown, reducing the usable capacity of the entire battery pack. While existing cell control units employ both active and passive balancing methods to address these differences, active balancing, where each battery cluster is connected to the energy storage converter via a DC-DC converter and its charging / discharging and balancing management, requires a high-power DC-DC converter for each cluster, placing stringent demands on device specifications. Passive balancing, primarily addressing cell-to-cell inconsistencies, suffers from insufficient balancing power. Over long-term operation, the passive balancing capability fails to compensate for cell degradation, leading to a gradual widening of inconsistencies between cells. Summary of the Invention

[0004] This invention provides an energy storage system to address the problem of widening differences between battery clusters in the prior art.

[0005] In a first aspect, embodiments of the present invention provide an energy storage system, comprising:

[0006] The system includes a controller, an energy storage converter, multiple battery clusters, and a high-voltage box corresponding to each battery cluster; the high-voltage box includes a switching module and a converter module.

[0007] Each battery cluster is connected to the first terminal of the corresponding switch module and the first terminal of the converter module. The second terminal of each switch module is connected to the energy storage converter via a DC bus. The second terminal of each converter module is connected to the three-phase power distribution terminal of the energy storage system.

[0008] When performing a power balancing task, the controller controls the switching module corresponding to each battery cluster to be balanced to disconnect the connection between the corresponding battery cluster to be balanced and the DC bus, and starts the converter module corresponding to the battery cluster to be balanced, so that the three-phase power distribution terminal performs power balancing for each battery cluster to be balanced.

[0009] In one possible implementation, the controller is specifically configured to perform a power balancing task when it detects the presence of battery clusters with uneven power levels, and to designate the battery clusters with uneven power levels as battery clusters to be balanced.

[0010] In one possible implementation, the controller is specifically configured to perform a power balancing task when it detects the presence of battery clusters with uneven power levels, and to treat all battery clusters in the energy storage system as battery clusters to be balanced.

[0011] In one possible implementation, the converter module includes a rectifier unit and a DC-DC converter unit;

[0012] The AC terminal of the rectifier unit is connected to the three-phase power distribution terminal, the DC terminal of the rectifier unit is connected to the first terminal of the DC-DC unit, and the second terminal of the DC-DC unit is connected to the corresponding battery cluster.

[0013] In one possible implementation, the rectifier unit includes a first diode, a second diode, a third diode, a fourth diode, a fifth diode, and a sixth diode;

[0014] The cathodes of the first diode, the second diode, and the third diode are connected to the positive DC terminal of the rectifier unit. The anode of the first diode is connected to phase A of the three-phase distribution terminal and the cathode of the fourth diode. The anode of the second diode is connected to phase B of the three-phase distribution terminal and the cathode of the fifth diode. The anode of the third diode is connected to phase C of the three-phase distribution terminal and the cathode of the sixth diode. The anodes of the fourth diode, the fifth diode, and the sixth diode are connected to the negative DC terminal of the rectifier unit.

[0015] In one possible implementation, the DC-DC unit includes a first capacitor, a second capacitor, a first inductor, a first switching unit, a second switching unit, a third switching unit, and a fourth switching unit;

[0016] The first terminal of the first inductor is connected to the positive terminal of the first terminal of the DC-DC unit. The second terminal of the first inductor is connected to the first terminal of the first switching unit, the first terminal of the third switching unit, and the first terminal of the first capacitor. The second terminal of the first switching unit is connected to the first terminal of the second switching unit. The second terminal of the second switching unit and the second terminal of the first capacitor are connected to the negative terminal of the DC-DC unit. The second terminal of the third switching unit is connected to the first terminal of the fourth switching unit. The second terminal of the fourth switching unit is connected to the positive terminal of the second terminal of the DC-DC unit. The first terminal of the second capacitor is connected to the first terminal of the second switching unit. The second terminal of the second capacitor is connected to the second terminal of the third switching unit.

[0017] In one possible implementation, the converter module further includes a buffer unit;

[0018] The buffer unit includes a first switch, a seventh diode, a second resistor, a buffer switch, and a fuse;

[0019] The first terminal of the first switch is connected to the positive DC terminal of the rectifier unit and the anode of the seventh diode, respectively. The cathode of the seventh diode is connected to the first terminal of the buffer switch. The second terminal of the buffer switch is connected to the first terminal of the second resistor. The second terminal of the second resistor is connected to the first terminal of the fuse. The second terminal of the first switch is connected to the second terminal of the fuse and the positive terminal of the first terminal of the DC-DC unit, respectively.

[0020] In one possible implementation, the switching module includes a main contactor; a first end of the main contactor is connected to the battery cluster, and a second end of the main contactor is connected to the DC bus.

[0021] Specifically, the controller is used to disconnect the main contactor of the switching module corresponding to the battery cluster when an uneven charge level is detected.

[0022] In one possible implementation, the controller includes a main control unit, a cluster-level control unit corresponding to each battery cluster, and a battery control unit corresponding to each battery in the battery cluster;

[0023] The main control unit is communicatively connected to the energy storage converter and each cluster-level control unit. The cluster-level control unit is communicatively connected to the switching module, converter module and battery control unit of each battery in the corresponding battery cluster. The battery control unit is communicatively connected to the corresponding battery.

[0024] The battery control unit is used to acquire the electrical parameters of each battery and send the electrical parameters of each battery to the cluster-level control unit;

[0025] The cluster-level control unit determines the electrical parameters of the corresponding battery cluster based on the electrical parameters of each battery, and sends the electrical parameters of the corresponding battery cluster to the main control unit;

[0026] The main control unit determines whether there are battery clusters with uneven power based on the electrical parameters of each battery cluster and each battery. When there are battery clusters with uneven power, it sends a switch module shutdown command and a converter module start command to the cluster-level control unit of the target battery cluster. The target battery cluster is any battery cluster with uneven power.

[0027] The cluster-level control unit of the target battery cluster is used to control the corresponding switch module to disconnect the battery cluster from the DC bus according to the switch module shutdown command, and to start the corresponding converter module according to the converter module start command.

[0028] In one possible implementation, the main control unit is further configured to control the energy storage converter to prohibit charging and discharging before sending the switch module shutdown command and the converter module start command to the cluster-level control unit of the target battery cluster; and to release the prohibition of charging and discharging of the energy storage converter when the cluster-level control unit corresponding to the target battery cluster sends the converter module start information.

[0029] This invention provides an energy storage system, including an energy storage converter, multiple battery clusters, a high-voltage box corresponding to each battery cluster, and a controller. The high-voltage box includes a switch module and a converter module. Each battery cluster is connected to the first terminal of the corresponding switch module and the first terminal of the converter module. The second terminal of each switch module is connected to the energy storage converter via a DC bus. The second terminal of each converter module is connected to the three-phase power distribution terminal of the energy storage system. The controller is used to control the switch module corresponding to each battery cluster to be balanced to disconnect the corresponding battery cluster from the DC bus and start the converter module corresponding to the battery cluster to be balanced when performing a power balancing task, so that the three-phase power distribution terminal performs power balancing for each battery cluster to be balanced. The aforementioned energy storage system can perform high-power equalization management of battery clusters using a converter module when there is an imbalance between battery clusters, thereby accelerating the equalization management speed of battery clusters and preventing the continuous increase of differences between battery clusters. Moreover, the converter module provided in this application only needs to equalize the difference in charge between battery clusters and does not need to perform full-range charge and discharge management of battery clusters. Therefore, the requirements for the power and voltage withstand capability of the current module are not high, thereby saving device costs and heat dissipation costs. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 A schematic diagram of the energy storage system provided in this embodiment of the invention;

[0032] Figure 2 This is a circuit diagram of the converter module provided in an embodiment of the present invention;

[0033] Figure 3 This is a flowchart illustrating the implementation of the battery cluster-level equalization management method provided in this embodiment of the invention. Detailed Implementation

[0034] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of the invention. However, those skilled in the art will understand that the invention can be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods are omitted so as not to obscure the description of the invention with unnecessary detail.

[0035] To make the objectives, technical solutions, and advantages of the present invention clearer, specific embodiments will be described below in conjunction with the accompanying drawings.

[0036] Figure 1 This is a schematic diagram of the energy storage system provided in an embodiment of the present invention. Figure 1 As shown, the energy storage system includes: a controller, a power conversion system (PCS), multiple battery clusters, and a high-voltage box corresponding to each battery cluster; the high-voltage box includes a switching module and a converter module (ACDC).

[0037] Each battery cluster is connected to the first terminal of the corresponding switch module and the first terminal of the converter module ACDC. The second terminal of each switch module is connected to the energy storage converter PCS via a DC bus. The second terminal of each converter module ACDC is connected to the three-phase power distribution terminal of the energy storage system.

[0038] The controller is used to control the switching module corresponding to each battery cluster to be balanced to disconnect the connection between the corresponding battery cluster to be balanced and the DC bus when performing the power balancing task, and to start the converter module ACDC corresponding to the battery cluster to be balanced, so that the three-phase power distribution terminal can perform power balancing for each battery cluster to be balanced.

[0039] Specifically, when the battery cluster is performing normal charging and discharging tasks, the switching module controls the on and off of the battery cluster. When the battery cluster is undergoing equalization management, the switching module is turned off and the converter module is turned on, thereby balancing the power of the battery cluster through the converter module.

[0040] Specifically, the converter module is used to rectify the AC power from the three-phase distribution terminal into DC power and supply it to the battery pack, or to invert the DC power from the battery pack into AC power and supply it to the three-phase distribution terminal. The three-phase distribution terminal can be a station service distribution terminal, which is connected to the power grid via a transformer. In addition, the three-phase distribution terminal can also be a three-phase power supply terminal for other external applications.

[0041] The aforementioned energy storage system can perform high-power equalization management of battery clusters using a converter module when there is an imbalance between battery clusters. Compared to passive equalization targeting differences between cells, the method provided in this application can reduce the differences between battery clusters more quickly, thereby improving equalization management efficiency. Moreover, the converter module provided in this application only needs to equalize the difference in charge between battery clusters and does not need to perform full-range charge and discharge management of the battery clusters. Therefore, the requirements for the maximum power, withstand voltage, and withstand capability of the current module are not high, so it is not necessary to select a high-power converter module, thereby saving device costs and heat dissipation costs.

[0042] In one possible implementation, the controller is specifically configured to perform a power balancing task when it detects the presence of battery clusters with uneven power levels, and to designate the battery clusters with uneven power levels as battery clusters to be balanced.

[0043] Specifically, the above method only requires disconnecting the battery clusters with unbalanced power levels from the energy storage converter PCS, and charging / discharging the unbalanced battery clusters through the three-phase power distribution terminal, while keeping the normal battery clusters connected to the DC bus for charging and discharging scheduling. This reduces the interference of the balancing process on the energy storage charging and discharging process and makes it suitable for a wider range of scenarios.

[0044] In one possible implementation, the controller is specifically configured to perform a power balancing task when it detects the presence of battery clusters with uneven power levels, and to treat all battery clusters in the energy storage system as battery clusters to be balanced.

[0045] The above solution can achieve offline balancing of cluster-level batteries in energy storage systems and is suitable for scenarios with strict scheduling requirements, such as those where energy storage systems are not allowed to charge or discharge to the grid.

[0046] In one possible implementation, such as Figure 2 As shown, the converter module includes a rectifier unit 101 and a DC-DC unit 103;

[0047] The AC terminal of the rectifier unit 101 is connected to the three-phase power distribution terminal, the DC terminal of the rectifier unit 101 is connected to the first terminal of the DC-DC unit 103, and the second terminal of the DC-DC unit 103 is connected to the corresponding battery cluster.

[0048] In one possible implementation, the rectifier unit 101 includes a first diode D1, a second diode D2, a third diode D3, a fourth diode D4, a fifth diode D5, and a sixth diode D6;

[0049] The cathodes of the first diode D1, the second diode D2, and the third diode D3 are connected to the positive terminal of the DC rectifier unit. The positive terminal of the first diode D1 is connected to phase A of the three-phase distribution terminal and the cathode of the fourth diode D4. The positive terminal of the second diode D2 is connected to phase B of the three-phase distribution terminal and the cathode of the fifth diode D5. The positive terminal of the third diode D3 is connected to phase C of the three-phase distribution terminal and the cathode of the sixth diode D6. The positive terminals of the fourth diode D4, the fifth diode D5, and the sixth diode D6 are connected to the negative terminal of the DC rectifier unit.

[0050] In one possible implementation, such as Figure 2 As shown, the DC-DC unit 103 includes a first capacitor C2, a second capacitor C4, a first inductor L1, a first switching unit Q1, a second switching unit Q2, a third switching unit Q3, and a fourth switching unit Q4.

[0051] The first terminal of the first inductor L1 is connected to the positive terminal of the first terminal of the DC-DC unit. The second terminal of the first inductor L1 is connected to the first terminal of the first switching unit Q1, the first terminal of the third switching unit Q3, and the first terminal of the first capacitor C2. The second terminal of the first switching unit Q1 is connected to the first terminal of the second switching unit Q2. The second terminal of the second switching unit Q2 and the second terminal of the first capacitor C2 are connected to the negative terminal of the DC-DC unit. The second terminal of the third switching unit Q3 is connected to the first terminal of the fourth switching unit Q4. The second terminal of the fourth switching unit Q4 is connected to the positive terminal of the second terminal of the DC-DC unit. The first terminal of the second capacitor C4 is connected to the first terminal of the second switching unit Q2. The second terminal of the second capacitor C4 is connected to the second terminal of the third switching unit Q3.

[0052] Specifically, Figure 2 The converter module shown can charge the battery cluster from the three-phase power distribution terminal, enabling the battery cluster to achieve cluster-level power balance through charging.

[0053] In one possible implementation, the converter module further includes a buffer unit 102;

[0054] The buffer unit 102 includes a first switch, a seventh diode D7, a second resistor R2, a buffer switch K_f, and a fuse fu;

[0055] The first terminal of the first switch is connected to the positive DC terminal of the rectifier unit and the anode of the seventh diode D7, respectively. The cathode of the seventh diode D7 is connected to the first terminal of the buffer switch K_f. The second terminal of the buffer switch K_f is connected to the first terminal of the second resistor R2. The second terminal of the second resistor R2 is connected to the first terminal of the fuse fu. The second terminal of the first switch is connected to the second terminal of the fuse fu and the positive terminal of the first terminal of the DC-DC unit, respectively.

[0056] In one possible implementation, the rectifier unit is a bidirectional synchronous rectifier circuit, and correspondingly, the DC-DC unit is a bidirectional DC-DC circuit. By setting the bidirectional synchronous rectifier circuit and the bidirectional DC-DC circuit, the power balance of unbalanced battery clusters can be achieved by charging the battery clusters from the three-phase power distribution terminal or discharging them from the battery clusters to the three-phase power distribution terminal.

[0057] In one possible implementation, the converter module further includes a first filtering unit;

[0058] The first end of the first filter unit is connected to the DC end of the rectifier unit, and the second end of the first filter module is connected to the first end of the DC-DC unit.

[0059] Specifically, the first filtering unit is an EMI filter.

[0060] In one possible implementation, the converter module further includes a second filtering unit;

[0061] The first end of the second filter unit is connected to the second end of the DCDC unit, and the second end of the second filter module is connected to the corresponding battery cluster.

[0062] Specifically, the second filtering unit is an EMI filter.

[0063] In one possible implementation, the converter module includes a fully controlled rectifier circuit for converting between the AC power from the three-phase distribution terminal and the DC power output from the battery cluster.

[0064] In one possible implementation, the switching module includes a main contactor; a first end of the main contactor is connected to the battery cluster, and a second end of the main contactor is connected to the DC bus.

[0065] Specifically, the controller is used to disconnect the main contactor of the switching module corresponding to the battery cluster when an uneven charge level is detected.

[0066] Specifically, such as Figure 1 As shown, the high-voltage box A11 includes a main contactor KM1-1, a secondary contactor KM1-3, a disconnecting switch QS1, a first resistor R1, and a converter module ACCDC1. The first terminals of the main contactor KM1-1, the secondary contactor KM1-3, and the converter module ACCDC1 are all connected to the corresponding battery clusters. The second terminal of the secondary contactor KM1-3 is connected to the first terminal of the first resistor R1. The second terminals of the first resistor R1 and the main contactor KM1-1 are all connected to one terminal of the disconnecting switch QS1. The other terminal of the disconnecting switch QS1 is connected to the DC bus. The second terminal of the converter module ACCDC1 is connected to the three-phase power distribution terminal.

[0067] In one possible implementation, the controller includes a main control unit, a cluster-level control unit corresponding to each battery cluster, and a battery control unit corresponding to each battery in the battery cluster;

[0068] The main control unit is communicatively connected to the energy storage converter and each cluster-level control unit. The cluster-level control unit is communicatively connected to the switching module, converter module and battery control unit of each battery in the corresponding battery cluster. The battery control unit is communicatively connected to the corresponding battery.

[0069] The battery control unit is used to acquire the electrical parameters of each battery and send the electrical parameters of each battery to the cluster-level control unit;

[0070] The cluster-level control unit determines the electrical parameters of the corresponding battery cluster based on the electrical parameters of each battery, and sends the electrical parameters of the corresponding battery cluster to the main control unit;

[0071] The main control unit determines whether there are battery clusters with uneven power based on the electrical parameters of each battery cluster and each battery. When there are battery clusters with uneven power, it sends a switch module shutdown command and a converter module start command to the cluster-level control unit of the target battery cluster. The target battery cluster is any battery cluster with uneven power.

[0072] The cluster-level control unit of the target battery cluster is used to control the corresponding switch module to disconnect the battery cluster from the DC bus according to the switch module shutdown command, and to start the corresponding converter module according to the converter module start command.

[0073] In one possible implementation, the main control unit and each cluster-level control unit are connected via a CAN bus. The main control unit is connected to the energy storage converter via both the CAN bus and dry contacts. Each cluster-level control unit is connected to its corresponding converter module via dry contacts.

[0074] In one possible implementation, the cluster-level control unit and each battery control unit are connected via a CAN bus. Each battery control unit is connected to its corresponding battery via a dry contact.

[0075] In one possible implementation, the main control unit is also connected to the dehumidifier, liquid chiller and air conditioner of the energy storage system via RS485 bus, and is connected to the operation light, fault light, fire alarm, fire action, UPS, emergency stop feedback, water immersion feedback and door status via dry contacts.

[0076] In one possible implementation, the main control unit is further configured to control the energy storage converter to prohibit charging and discharging before sending the switch module shutdown command and the converter module start command to the cluster-level control unit of the target battery cluster; and to release the prohibition of charging and discharging of the energy storage converter when the cluster-level control unit corresponding to the target battery cluster sends the converter module start information.

[0077] To achieve online equalization management of battery clusters, this embodiment adds a converter module to each battery cluster. The first end of the converter module is connected to the battery cluster, and the second end of the converter module is connected to the three-phase power distribution terminal. Since the converter module requires a certain voltage difference between the DC bus and the battery to operate, online equalization is adopted. Due to the voltage difference problem, power cannot be directly drawn from the DC bus of the energy storage converter. Therefore, this application draws power from the three-phase power distribution terminal, which can not only achieve equalization between battery clusters, but also avoid interference of the equalization process on the energy storage charging and discharging process, and is more adaptable to a wider range of scenarios.

[0078] See Figure 3 The diagram illustrates a flowchart of a battery cluster-level equalization management method provided by an embodiment of the present invention, applied to the aforementioned energy storage system. The process is described in detail below:

[0079] S101: Obtain the electrical parameters of each battery cluster, and determine whether there are battery clusters with uneven power based on the electrical parameters of each battery cluster.

[0080] In this embodiment, the executing entity can be the controller of the energy storage system. The controller can be the main control unit of the energy storage system or a separate cluster-level optimization controller. This embodiment will use the main control unit as an example for subsequent explanation.

[0081] Specifically, electrical parameters include, but are not limited to, total battery cluster voltage, battery voltage, and battery cluster SOC (State of Charge). The battery voltage is acquired by the battery control unit and sent to the cluster-level control unit. The cluster-level control unit acquires the total battery cluster voltage based on the battery voltage of each battery within the cluster and sends the total battery cluster voltage, the voltage of each battery within the corresponding cluster, and the SOC value of the battery cluster to the main control unit. The main control unit determines whether there are battery clusters with uneven charge levels based on the total battery cluster voltage and / or SOC value of each battery cluster.

[0082] In one possible implementation, the electrical parameters include battery voltage and SOC value; the specific implementation process of S101 includes:

[0083] The difference between the current SOC value and the SOC reference value of each battery cluster is calculated to obtain the corresponding power deviation value of each battery cluster. Among them, when the battery clusters are charged for power balancing, the SOC reference value is the maximum SOC value of all battery clusters in the energy storage system; when the battery clusters are discharged for power balancing, the SOC reference value is the minimum SOC value of all battery clusters in the energy storage system.

[0084] If the power deviation of a battery cluster is greater than a preset deviation threshold, and the voltage difference between batteries within the battery cluster exceeds a preset voltage threshold, then the power of the battery cluster is determined to be unbalanced.

[0085] In this embodiment, if the power deviation of a battery cluster is greater than a preset deviation threshold, the difference between the maximum and minimum battery voltages of all batteries in the battery cluster is calculated. If the difference between the maximum and minimum battery voltages of all batteries in the battery cluster exceeds a preset voltage threshold, the power of the battery cluster is determined to be unbalanced.

[0086] Specifically, using the method described above for determining unbalanced battery clusters based on the maximum SOC value, after identifying the unbalanced battery clusters, they need to be charged to achieve charge balance between these clusters and other battery clusters. During the charging process, when performing charge balance detection, the SOC value of each battery cluster is the maximum SOC value among the SOC values ​​of all cells within that cluster. Alternatively, using the method described above for determining unbalanced battery clusters based on the minimum SOC value, after identifying the unbalanced battery clusters, they need to be discharged to achieve charge balance between these clusters and other battery clusters. During the discharging process, when performing charge balance detection, the SOC value of each battery cluster is the minimum SOC value among the SOC values ​​of all cells within that cluster.

[0087] For example, the power deviation value can be 1% to 10%, preferably 5%. The preset voltage threshold can be 0.1V to 0.6V, preferably 0.35V.

[0088] S102: If there are battery clusters with unbalanced power, control the switch module corresponding to the battery cluster to disconnect the battery cluster from the DC bus and start the converter module corresponding to the battery cluster so that the battery cluster can be balanced through the external power distribution terminal.

[0089] In this embodiment, when an unevenly charged battery cluster is detected, the main control unit sends a switch module disconnect command and a converter module start command to the corresponding cluster-level control unit. After receiving the switch module disconnect command and the converter module start command, the cluster-level control unit first disconnects the main contactor in the switch module, and then controls the converter module corresponding to the battery cluster to start. The converter module enables the charging and discharging of the battery cluster to achieve the equalization of the battery cluster's charge.

[0090] In one possible implementation, the specific implementation process of controlling the switch module corresponding to the battery cluster to disconnect the battery cluster from the DC bus in S102 includes:

[0091] When the energy storage system is detected to have triggered a charging or discharging restriction condition, the energy storage converter is prohibited from charging and discharging.

[0092] The control module corresponding to the first battery cluster disconnects the connection between the first battery cluster and the DC bus; the first battery cluster is any battery cluster with uneven charge.

[0093] After the first battery cluster is disconnected from the DC bus, the restrictions on charging and discharging of the energy storage converter are lifted.

[0094] Specifically, if there are battery clusters with uneven power levels, the main control unit will control the energy storage converter to prohibit charging and discharging when the energy storage system is fully charged (triggering the charging restriction condition) or fully discharged (triggering the discharging restriction condition). Then, it will send a switch module disconnection command and a converter module start command to the cluster-level control unit corresponding to the first battery cluster. The cluster-level control unit corresponding to the first battery cluster will disconnect the main contactor of the switch module corresponding to the first battery cluster and control the corresponding converter module to start. After completing the above operations, the cluster-level control unit will send switch module disconnection information and converter module start information to the main control unit. After receiving the switch module disconnection information and converter module start information, the main control unit will release the charging and discharging restriction of the energy storage converter so that other normal battery clusters are still connected to the DC bus and waiting for scheduling operation.

[0095] In one possible implementation, after the main contactor in the control switch module is disconnected, the main control unit obtains the SOC value of each battery cluster and determines the charging and discharging strategy after removing the first battery cluster based on the SOC value of each battery cluster.

[0096] In one possible implementation, after S102, the method provided in this embodiment further includes:

[0097] S201: Determine whether the first battery cluster has completed power balancing; the first battery cluster is any battery cluster with unbalanced power.

[0098] S202: If the first battery cluster has completed power balancing, determine whether the total voltage of the first battery cluster is the same as the bus voltage of the DC bus.

[0099] S203: If the total voltage of the first battery cluster is the same as the bus voltage of the DC bus, then control the switch module corresponding to the first battery cluster to close the connection between the first battery cluster and the DC bus, and control the converter module corresponding to the first battery cluster to turn off.

[0100] In one possible implementation, the specific implementation process of S201 includes:

[0101] Determine whether the first battery cluster triggers a preset prohibition condition; the preset prohibition condition includes a charging prohibition condition or a discharging prohibition condition.

[0102] If the first battery cluster triggers the preset prohibition condition, it is determined that the first battery cluster has completed power balancing, and the converter module corresponding to the first battery cluster is controlled to prohibit charging and discharging.

[0103] In this embodiment, the preset prohibition conditions include charging prohibition conditions and / or discharge prohibition conditions.

[0104] In this embodiment, if the battery cluster is balanced by charging, the three-phase power distribution terminal rectifies and boosts the AC power through the converter module before sending it to the first battery cluster.

[0105] Correspondingly, when the cluster-level control unit corresponding to the first battery cluster detects that the total voltage of the first battery cluster has reached the full-charge voltage threshold, it triggers a charging-discharge restriction condition and controls the corresponding converter module to prohibit charging and discharging. The cluster-level control unit sends the charging-discharge restriction trigger command and the total voltage of the battery cluster to the main control unit. After detecting the charging-discharge restriction trigger command, the main control unit determines that the first battery cluster has completed power balancing and determines whether the total voltage of the first battery cluster is the same as the bus voltage of the DC bus. If the total voltage of the first battery cluster is the same as the bus voltage of the DC bus, it sends a switch module closing command and a converter module closing command to the cluster-level control unit corresponding to the first battery cluster. The cluster-level control unit controls the main contactor of the switch module to close and controls the corresponding converter module to close. Then, it sends the switch module closing information and the converter module closing information to the main control unit. The main control unit controls the energy storage converter to release the prohibition on charging and discharging based on the switch module closing information and the converter module closing information, so as to realize the access of the battery cluster.

[0106] The above method can reconnect the battery clusters to the DC bus when they are fully charged, and the control method is simple and precise.

[0107] In this embodiment, if the battery cluster is balanced by discharging, the first battery cluster will step down the DC voltage and invert it through the converter module before being delivered to the three-phase power distribution terminal of the energy storage system.

[0108] Correspondingly, when the cluster-level control unit corresponding to the first battery cluster detects that the total voltage of the first battery cluster has reached the discharge voltage threshold, it triggers the discharge restriction condition and controls the corresponding converter module to prohibit charging and discharging. The cluster-level control unit sends the discharge restriction condition trigger command and the total voltage of the battery cluster to the main control unit. After detecting the discharge restriction condition trigger command, the main control unit determines that the first battery cluster has completed power balancing and determines whether the total voltage of the first battery cluster is the same as the bus voltage of the DC bus. If the total voltage of the first battery cluster is the same as the bus voltage of the DC bus, it sends a switch module closing command and a converter module closing command to the cluster-level control unit corresponding to the first battery cluster. The cluster-level control unit controls the main contactor of the switch module to close and controls the corresponding converter module to close. Then, it sends the switch module closing information and the converter module closing information to the main control unit. The main control unit controls the energy storage converter to release the charging and discharging restriction according to the switch module closing information and the converter module closing information, so as to realize the access of the battery cluster.

[0109] The above method can reconnect the battery cluster to the DC bus when the battery cluster to be balanced is depleted. The control method is simple and precise.

[0110] In one possible implementation, another step in S201 includes:

[0111] When the difference between the total voltage of the first battery cluster and the maximum total voltage of the battery cluster in the energy storage system is not greater than a preset voltage threshold, it is determined that the first battery cluster has completed power balancing.

[0112] Specifically, in this embodiment, the conditions for determining that the battery cluster has completed power balancing can include not only full charge and full discharge, but also, during the charging and discharging process, if the total voltage difference between the first battery cluster and the maximum total voltage difference between other battery clusters is not greater than a preset voltage difference, the battery cluster can be connected to the DC bus. Although this method requires precise calculation to determine the timing of the battery cluster connection, it does not require waiting for the timing of other battery clusters to be fully charged / fully discharged, making the scheduling more flexible.

[0113] For example, the preset voltage difference can be 0.1V to 3V.

[0114] In one possible implementation, prior to S202, the method provided in this embodiment further includes:

[0115] Determine whether the energy storage converter is in a first state, where the first state is either a charging state or a discharging state.

[0116] If the energy storage converter is in the first state, then after detecting that the energy storage system has triggered a preset prohibition condition;

[0117] Accordingly, after S203, the method further includes:

[0118] Remove the restrictions on charging and discharging of the energy storage converter.

[0119] In this embodiment, after monitoring that the battery cluster to be balanced has completed the power balancing, it is determined whether other battery clusters are currently charging or discharging. If they are charging or discharging, the charging and discharging of the energy storage converter is prohibited after the energy storage converter stops charging or discharging, and then the battery cluster to be balanced is controlled to be connected to the DC bus. If other battery clusters are not charging or discharging, the energy storage converter has triggered the charging or discharging prohibition condition, and the battery cluster to be balanced can be directly controlled to be connected to the DC bus.

[0120] The above method can achieve high-power equalization management at the battery cluster level, thereby improving equalization management efficiency, avoiding the increase of differences between battery clusters, and equalizing only a single battery cluster. The energy storage system can still carry out normal charging and discharging. It is more flexible in application and can perform equalization management at any time. It is suitable for multiple application scenarios such as power generation-side power stations, grid-side power stations, and power consumption-side power stations.

[0121] It should be understood that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0122] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. An energy storage system, characterized by, The application relates to a controller, an energy storage converter, a plurality of battery clusters and a high-voltage box corresponding to each battery cluster; the high-voltage box comprises a switch module and a converter module. Each battery cluster is connected with a first end of the corresponding switch module and a first end of the converter module, the second end of each switch module is connected with the energy storage converter through a DC bus, and the second end of each converter module is connected with a three-phase power distribution end of the energy storage system. The controller is used for controlling the switch module corresponding to each battery cluster to be balanced to disconnect the corresponding battery cluster to be balanced from the DC bus and starting the converter module corresponding to the battery cluster to be balanced when an electric quantity balancing task is performed, so that the three-phase power distribution end balances the electric quantity of each battery cluster to be balanced. The converter module comprises a rectifier unit and a DC / DC unit. The AC end of the rectifier unit is connected with the three-phase power distribution end, the DC end of the rectifier unit is connected with the first end of the DC / DC unit, and the second end of the DC / DC unit is connected with the corresponding battery cluster. The controller comprises a main control unit, a cluster-level control unit corresponding to each battery cluster and a battery control unit corresponding to each battery in the battery cluster. The main control unit is in communication connection with the energy storage converter and each cluster-level control unit, the cluster-level control unit is in communication connection with the switch module, the converter module and the battery control unit of each battery in the corresponding battery cluster, and the battery control unit is in communication connection with the corresponding battery. The battery control unit is used for acquiring the electric parameters of each battery and sending the electric parameters of each battery to the cluster-level control unit. The cluster-level control unit determines the electric parameters of the corresponding battery cluster based on the electric parameters of each battery and sends the electric parameters of the corresponding battery cluster to the main control unit. The controller is specifically used for performing an electric quantity balancing task when it is monitored that there is a battery cluster with unbalanced electric quantity and taking the battery cluster with unbalanced electric quantity as a battery cluster to be balanced.

2. The energy storage system of claim 1, wherein, The controller is specifically used for performing an electric quantity balancing task when it is monitored that there is a battery cluster with unbalanced electric quantity and taking all the battery clusters in the energy storage system as battery clusters to be balanced.

3. The energy storage system of claim 1, wherein, The rectifier unit comprises a first diode, a second diode, a third diode, a fourth diode, a fifth diode and a sixth diode.

4. The energy storage system of claim 1, wherein, The negative poles of the first diode, the second diode and the third diode are connected with the DC end positive pole of the rectifier unit, the positive pole of the first diode is connected with the A phase of the three-phase power distribution end and the negative pole of the fourth diode, the positive pole of the second diode is connected with the B phase of the three-phase power distribution end and the negative pole of the fifth diode, the positive pole of the third diode is connected with the C phase of the three-phase power distribution end and the negative pole of the sixth diode, and the positive poles of the fourth diode, the fifth diode and the sixth diode are connected with the DC end negative pole of the rectifier unit. The DC / DC unit comprises a first capacitor, a second capacitor, a first inductor, a first switch unit, a second switch unit, a third switch unit and a fourth switch unit.

5. The energy storage system of claim 1, wherein, ​ The first end of the first inductor is connected with the first positive end of the DCDC unit, the second end of the first inductor is connected with the first end of the first switch unit, the first end of the third switch unit and the first end of the first capacitor respectively, the second end of the first switch unit is connected with the first end of the second switch unit, the second end of the second switch unit and the second end of the first capacitor are connected with the negative end of the DCDC unit respectively, the second end of the third switch unit is connected with the first end of the fourth switch unit, and the second end of the fourth switch unit is connected with the second positive end of the DCDC unit; the first end of the second capacitor is connected with the first end of the second switch unit, and the second end of the second capacitor is connected with the second end of the third switch unit.

6. The energy storage system of claim 1, wherein, The current conversion module further comprises a buffer unit; The buffer unit comprises a first switch, a seventh diode, a second resistor, a buffer switch and a fuse; The first end of the first switch is connected with the positive end of the direct current end of the rectification unit and the anode of the seventh diode respectively, the cathode of the seventh diode is connected with the first end of the buffer switch, the second end of the buffer switch is connected with the first end of the second resistor, the second end of the second resistor is connected with the first end of the fuse, and the second end of the fuse is connected with the second end of the first switch and the first positive end of the DCDC unit respectively.

7. The energy storage system of claim 1, wherein, The switch module comprises a main contactor; the first end of the main contactor is connected with the battery cluster, and the second end of the main contactor is connected with the direct current bus; The controller is specifically used for controlling the main contactor of the switch module corresponding to the battery cluster to be disconnected when it is monitored that there is a battery cluster with unbalanced electric quantity.

8. The energy storage system of claim 1, wherein, The main control unit determines whether there is a battery cluster with unbalanced electric quantity based on the electric parameters of each battery cluster and the electric parameters of each battery, and sends a switch module closing instruction and a current conversion module starting instruction to the cluster-level control unit of a target battery cluster when there is a battery cluster with unbalanced electric quantity; the target battery cluster is any battery cluster with unbalanced electric quantity; The cluster-level control unit of the target battery cluster is used for controlling the corresponding switch module to disconnect the connection between the battery cluster and the direct current bus according to the switch module closing instruction, and starting the corresponding current conversion module according to the current conversion module starting instruction.

9. The energy storage system of claim 8, wherein, The main control unit is further used for controlling the energy storage current converter to be prohibited from charging and discharging before sending the switch module closing instruction and the current conversion module starting instruction to the cluster-level control unit of the target battery cluster, and releasing the prohibition of charging and discharging of the energy storage current converter when the current conversion module starting information sent by the cluster-level control unit corresponding to the target battery cluster is monitored.

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