Energy transfer system and method between battery packs of energy storage system

Abstract

The present invention discloses an energy transfer system and method between battery PACKs of an energy storage system. In the system, the output end of each battery PACK is connected to a PACK controller; the two ends of the battery cluster are respectively connected to the output positive bus and the output negative bus, and the output positive bus and the output negative bus are connected to the energy storage converter PCS; the system also includes a balancing bus; each battery cluster is configured with an energy transfer circuit, and the energy transfer circuit includes a reactor L, a switch K1, and a switch K2. After the switch K1 and the switch K2 are connected in parallel, they are connected in series with the reactor L. The reactor L is connected to the battery cluster, the switch K1 is connected to the output bus, and the switch K2 is connected to the balancing bus. The present invention optimizes the topological structure of the energy storage system through the balancing bus and the energy transfer circuit, and can transfer the energy of the fault-free battery PACK in the battery cluster that exits due to a fault, thereby solving the problem of capacity and power loss.

Description

Technical Field

[0001] The present invention relates to the technical field of energy storage systems, and in particular to a system and method for transferring energy between battery PACKs in an energy storage system. Background Art

[0002] In the energy storage system, single cells are connected in series and parallel to form a battery box, and battery boxes are connected in series and parallel to form a battery cluster. Multiple battery clusters are directly connected in parallel to the same DC busbar. In the current energy storage system, for the energy storage system solution with battery PACK-level control, the DC bus can be connected in parallel to a centralized PCS, so the fault handling scheme is different. For battery PACK-level control, only in a few energy storage systems can some manufacturers add DC / DC module control schemes to the battery PACK to achieve battery PACK-level management. This DC / DC module scheme is costly and has high losses, and has not been used in large energy storage systems; the energy transfer scheme based on battery module-level control has not been used by any manufacturer yet. In the energy storage system, when a battery module fails, the faulty battery PACK can be removed to continue operation; when the number of faulty PACKs exceeds the redundant number of the battery cluster, the battery cluster exits operation. For the energy storage system solution with battery PACK-level control, when the battery cluster exits operation, it leads to waste of energy stored in the non-faulty battery PACK in the battery cluster and waste of capacity of the energy storage system. Summary of the invention

[0003] The purpose of the present invention is to provide an energy transfer system and method between battery PACKs in an energy storage system, aiming at a battery PACK-level controlled energy storage system, and solving the energy transfer problem of a fault-free battery PACK in a battery cluster that has exited due to a fault.

[0004] To achieve the above object, the present invention provides the following solutions:

[0005] An energy transfer system between battery PACKs of an energy storage system, comprising a plurality of battery clusters connected in parallel to the same DC busbar, each battery cluster comprising a plurality of battery PACKs arranged in series, parallel or series-parallel, characterized in that the output end of each of the battery PACKs is connected to a PACK controller;

[0006] The DC busbar includes an output positive busbar and an output negative busbar, and the two ends of the battery cluster are respectively connected to the output positive busbar and the output negative busbar, and the output positive busbar and the output negative busbar are connected to the energy storage converter PCS; the system also includes a balancing busbar;

[0007] Each battery cluster is configured with an energy transfer circuit, which includes a reactor L, a switch K1, and a switch K2. The switches K1 and K2 are connected in parallel and then connected in series with the reactor L. The reactor L is connected to the battery cluster, the switch K1 is connected to the output bus, and the switch K2 is connected to the balancing bus.

[0008] Furthermore, each battery cluster is provided with a cluster controller, the PACK controller is communicatively connected with the cluster controller of the battery cluster in which it is located, and the cluster controller controls the on and off of the switches K1 and K2.

[0009] Furthermore, a plurality of battery clusters are combined to form a battery stack, and each battery stack is provided with a stack controller, the cluster controller is communicatively connected with the stack controller of the battery stack in which it is located, and the stack controller controls the charging and discharging of each battery cluster in the battery stack through the energy storage converter PCS.

[0010] Furthermore, the switch K1 and the switch K2 are automatically controlled mechanical switches or semiconductor switches.

[0011] Furthermore, each of the PACK controllers is provided with a voltage detection module and a temperature detection module. The voltage detection module is used to collect the voltage of a single cell of the battery PACK, and the temperature detection module is used to collect the operating temperature of the battery PACK.

[0012] The present invention also provides an energy storage system battery PACK energy transfer method, which is applied to the above energy storage system battery PACK energy transfer system, comprising the following steps:

[0013] When the energy storage system operates normally, all switches K1 in the energy storage system are closed, all switches K2 are opened, the output positive bus and the output negative bus are put into operation, and charging or discharging is performed through the energy storage converter PCS;

[0014] When the energy storage system fails, determine whether the battery PACK redundancy in each battery cluster is exhausted, use the battery cluster with exhausted battery PACK redundancy as the energy transfer battery cluster, disconnect the switch K1 connected to the energy transfer battery cluster, exit operation, close the switch K2 connected to the energy transfer battery cluster, and at the same time, select any normally operating battery cluster as the energy receiving battery cluster, close the switch K2 connected to the energy receiving battery cluster, and disconnect the switch K1 connected to the energy receiving battery cluster, and put the balancing bus into operation;

[0015] Transferring energy from the energy transfer battery cluster to the energy receiving battery cluster via a balancing bus;

[0016] After the energy transfer is completed, the switch K2 connected to the energy transfer battery cluster and the energy receiving battery cluster is disconnected, and the switch K1 connected to the energy receiving battery cluster is closed, and the energy receiving battery cluster continues to operate normally.

[0017] Furthermore, the method further comprises the step of determining whether a failure occurs in the energy storage system:

[0018] Each battery PACK controller collects the single cell voltage and operating temperature of the battery PACK, and compares them with the set voltage and temperature threshold ranges;

[0019] When at least one of the collected single cell voltage and the operating temperature of the battery PACK exceeds a set threshold range, it is determined that the battery PACK has a fault and fault information is obtained;

[0020] The PACK controller sends the fault information to the cluster controller, and the cluster controller removes the faulty battery PACK and exits operation.

[0021] Furthermore, the determining whether the battery PACK redundancy in each battery cluster is exhausted specifically includes:

[0022] Each battery cluster is configured with N battery PACKs. In order to match the voltage and power of the battery cluster with the PCS, the actual number of battery PACKs required is at least Nn, where n is the set redundancy number and 0 is the power consumption. <n<N;

[0023] When the number of failed battery PACKs is greater than n, the redundancy is considered to be exhausted.

[0024] Furthermore, the energy of the energy transfer battery cluster is transferred to the energy receiving battery cluster through the balancing bus, specifically including:

[0025] By controlling each PACK controller of the energy transfer battery cluster, the output voltage and output current of the energy transfer battery cluster are controlled;

[0026] Controlling the output voltage and output current of the energy receiving battery cluster by controlling each PACK controller of the energy receiving battery cluster;

[0027] The stack controller of the energy storage system coordinates and controls the cluster controllers of the energy transfer battery cluster and the energy receiving battery cluster to discharge the energy transfer battery cluster and charge the energy receiving battery cluster, thereby transferring the energy of the energy transfer battery cluster to the energy receiving battery cluster.

[0028] Furthermore, the energy transfer is determined to be complete based on:

[0029] When the cell voltage of any battery PACK in the energy transfer battery cluster reaches the lower protection threshold or the cell voltage of any battery PACK in the energy receiving battery cluster reaches the upper protection threshold, the energy transfer is considered to be completed.

[0030] According to the specific embodiments provided by the present invention, the energy storage system battery PACK energy transfer system and method provided by the present invention disclose the following technical effects:

[0031] 1. By adding a balancing bus, an energy transfer channel is provided for the faulty cluster and the non-faulty battery cluster, so that energy transfer between different battery clusters can be realized; energy can be transferred out of the faulty cluster through the balancing bus, and energy can also be transferred into the normal cluster, so that the non-faulty battery modules in the faulty battery cluster can be effectively utilized;

[0032] 2. Through the coordination of switch K1 and switch K2, when a battery PACK failure causes the battery cluster to exit operation, the energy of the battery PACK that has not failed can be transferred by controlling the on and off of different switches to change the topology structure, thereby solving the problem of capacity and power loss. Energy can also be transferred from the normal cluster to the faulty cluster to effectively utilize the battery capacity of the faulty cluster;

[0033] 3. The invention has a more obvious effect when the number of battery cells connected in series is greater. It can be used in both low-voltage and high-voltage situations. The higher the voltage, the more obvious the effect.

[0034] 4. The invention has a more obvious effect in long-term energy storage, realizing an energy storage system in which only the energy of the faulty battery PACK is lost after a battery PACK failure occurs;

[0035] 5. This invention can greatly reduce the number of operation and maintenance times and reduce the operation and maintenance costs of the energy storage system. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0037] Figure 1 A hardware topology diagram of a control system for an energy transfer system between battery PACKs of an energy storage system according to an embodiment of the present invention;

[0038] Figure 2 It is a principle block diagram of the control system of the energy transfer system between battery PACKs of the energy storage system of the present invention;

[0039] Figure 3A schematic diagram of various switch states of the energy storage system in normal operation according to an embodiment of the present invention;

[0040] Figure 4 Schematic diagram of the states of various switches when a failure occurs in the energy storage system according to an embodiment of the present invention. DETAILED DESCRIPTION

[0041] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0042] The purpose of the present invention is to provide an energy transfer system and method between battery PACKs in an energy storage system, aiming at a battery PACK-level controlled energy storage system, and solving the energy transfer problem of a fault-free battery PACK in a battery cluster that has exited due to a fault.

[0043] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0044] like Figure 1-2 As shown, the energy transfer system between battery PACKs of the energy storage system provided by the present invention comprises: a plurality of battery clusters connected in parallel to the same DC busbar, each battery cluster comprising a plurality of battery PACKs arranged in series, parallel or series-parallel, characterized in that the output end of each battery PACK is connected to a PACK controller; for example, Figure 1 Each battery cluster has N battery PACKs connected in series;

[0045] The DC busbar includes an output positive busbar and an output negative busbar, and the two ends of the battery cluster are respectively connected to the output positive busbar and the output negative busbar, and the output positive busbar and the output negative busbar are connected to the energy storage converter PCS; the system also includes a balancing busbar;

[0046] Each battery cluster is configured with an energy transfer circuit, which includes a reactor L, a switch K1, and a switch K2. The switches K1 and K2 are connected in parallel and then connected in series with the reactor L. The reactor L is connected to the battery cluster, the switch K1 is connected to the output bus, and the switch K2 is connected to the balancing bus.

[0047] Among them, Figure 2As shown, each battery cluster is provided with a cluster controller, and the PACK controller is connected to the cluster controller of the battery cluster in which it is located, and the cluster controller controls the on and off of the switches K1 and K2. Multiple battery clusters are combined to form a battery stack, and each battery stack is provided with a stack controller, and the cluster controller is connected to the stack controller of the battery stack in which it is located, and the communication mode includes wired communication and wireless communication mode, and the wired communication mode is CAN bus, 485 bus, Ethernet and the like; the stack controller controls the charging and discharging of each battery cluster in the battery stack through the energy storage converter PCS.

[0048] The switches K1 and K2 are mechanical switches or semiconductor switches controlled automatically. The mechanical switches include mechanical switches such as contactors, circuit breakers, relays, etc.; the semiconductor switches include IGBTs, IGCTs, MOSFETs, triodes, etc.

[0049] Each of the PACK controllers is provided with a voltage detection module and a temperature detection module. The voltage detection module is used to collect the voltage of a single cell of the battery PACK, and the temperature detection module is used to collect the operating temperature of the battery PACK.

[0050] Stack controller (SC): A battery stack-level controller that coordinates and controls the charge and discharge of each battery cluster;

[0051] Cluster controller (CC): a cluster-level controller that coordinates the operations of various controllers within a battery cluster;

[0052] PACK controller (PC): A battery PACK-level controller that controls the charging and discharging of the battery PACK, and also has functions such as battery voltage and temperature collection. In addition to being able to control the charging and discharging of the battery PACK, each battery PACK controller also has the function of collecting information such as battery temperature and voltage. Each PACK controller will set the battery temperature and voltage collection value and a reasonable range. When the collection value is greater than the set range, a corresponding fault will be reported. The PAKC controller (PC) controls the charging and discharging power by forming a DCDC (DC to DC converter) through power electronic devices.

[0053] Battery PACK: includes battery modules, battery management units, fire sensors and electrical and structural components required for integration. Among them, the battery module is a battery assembly consisting of battery cells connected in series, parallel or series-parallel, and has only one pair of positive and negative output terminals. It should also include components such as housing, management and protection devices.

[0054] For example, the various controllers mentioned in the present invention may adopt FPGA or CPLD with high real-time performance, etc., and a processing chip with good operating performance may be selected according to actual use requirements.

[0055] The present invention also provides an energy storage system battery PACK energy transfer method, which is applied to the above energy storage system battery PACK energy transfer system, comprising the following steps:

[0056] When the energy storage system operates normally, all switches K1 in the energy storage system are closed, all switches K2 are opened, the output positive bus and the output negative bus are put into operation, and charging or discharging is performed through the energy storage converter PCS, such as Figure 3 As shown;

[0057] When the energy storage system fails, determine whether the battery PACK redundancy in each battery cluster is exhausted, use the battery cluster with exhausted battery PACK redundancy as the energy transfer battery cluster, disconnect the switch K1 connected to the energy transfer battery cluster, exit operation, close the switch K2 connected to the energy transfer battery cluster, and at the same time, select any normally operating battery cluster as the energy receiving battery cluster, close the switch K2 connected to the energy receiving battery cluster, and disconnect the switch K1 connected to the energy receiving battery cluster, and put the balancing bus into operation; other battery clusters operate normally;

[0058] For example, if the battery PACK redundancy of battery cluster 1 is exhausted, K1 of battery cluster 1 is disconnected and K2 is closed; at the same time, K1 of battery cluster 2 is disconnected and K2 is turned on, and the balancing bus is put into operation. The operating status is as follows: Figure 4 shown.

[0059] Transferring energy from the energy transfer battery cluster to the energy receiving battery cluster via a balancing bus;

[0060] After the energy transfer is completed, the switch K2 connected to the energy transfer battery cluster and the energy receiving battery cluster is disconnected, and the switch K1 connected to the energy receiving battery cluster is closed, and the energy receiving battery cluster continues to operate normally.

[0061] The method further comprises the step of determining whether a failure occurs in the energy storage system:

[0062] Each battery PACK controller collects the single cell voltage and operating temperature of the battery PACK, and compares them with the set voltage and temperature threshold ranges;

[0063] When at least one of the collected single cell voltage and the operating temperature of the battery PACK exceeds a set threshold range, it is determined that the battery PACK has a fault and fault information is obtained;

[0064] The PACK controller sends the fault information to the cluster controller, and the cluster controller removes the faulty battery PACK and exits operation.

[0065] The step of determining whether the battery PACK redundancy in each battery cluster is exhausted specifically includes:

[0066] Each battery cluster is configured with N battery PACKs. To meet the matching of the battery cluster voltage and power with the PCS, the actual number of battery PACKs to be invested is at least N - n, where n is the set redundancy number, 0 < n < N. For example, n can take the value of 2;

[0067] When the number of faulty battery PACKs is greater than 2, it is considered that the redundancy is exhausted.

[0068] Among them, the energy of the energy transfer battery cluster is transferred to the energy receiving battery cluster through the equalizing bus; in this process, by controlling each PACK controller of the energy transfer battery cluster, the output voltage and output current of the energy transfer battery cluster can be controlled; the battery PACK controller is a power electronic converter topology in the form of a DC / DC. By coordinating and controlling each battery PACK controller of the battery cluster through the battery cluster level controller, the control of the output voltage and current of the battery cluster can be realized;

[0069] By controlling each PACK controller of the energy receiving battery cluster, the output voltage and output current of the energy receiving battery cluster can be controlled;

[0070] Through the stack controller of the energy storage system, the cluster controllers of the energy transfer battery cluster and the energy receiving battery cluster are coordinated and controlled to realize the discharge of the energy transfer battery cluster and the charging of the energy receiving battery cluster, and the energy of the energy transfer battery cluster is transferred to the energy receiving battery cluster.

[0071] Finally, the judgment basis for the completion of the energy transfer is as follows:

[0072] When the cell voltage of any battery PACK in the energy transfer battery cluster reaches the lower limit protection threshold or the cell voltage of any battery PACK in the energy receiving battery cluster reaches the upper limit protection threshold, it is regarded as the completion of the energy transfer.

[0073] Example: Taking lithium iron phosphate batteries as an example, the lower limit protection threshold can be set to 2.5V and the upper limit protection threshold can be set to 3.6V; when the cell voltage in any battery PACK in the battery cluster reaches 2.5V or 3.6V, it is regarded as the completion of the energy transfer.

[0074] The energy transfer system and method between battery PACKs of the energy storage system provided by the present invention, on the one hand, optimizes the topological structure of the energy storage system, and provides energy transfer channels for faulty clusters and non-faulty clusters by adding a balancing bus; on the other hand, by controlling the on and off of switches, energy transfer is coordinated between battery clusters. The present invention can realize the transfer of energy between faulty battery clusters and non-faulty battery clusters; the more battery sections are connected in series, the more obvious the effect is, and it can be used in both low-voltage and high-voltage occasions. The higher the voltage, the more obvious the effect is; in long-term energy storage, the effect is more obvious, and the energy storage system is realized, and after a battery PACK failure occurs, only the energy of the faulty battery PACK is lost; the present invention can greatly reduce the number of operation and maintenance of the energy storage system and reduce the operation and maintenance costs.

[0075] The principles and implementation methods of the present invention are described in this article using specific examples. The description of the above embodiments is only used to help understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. An energy transfer system between battery PACKs of an energy storage system, comprising a plurality of battery clusters connected in parallel to the same DC busbar, each battery cluster comprising a plurality of battery PACKs arranged in series, parallel or series-parallel, characterized in that: The output end of each battery PACK is connected to a PACK controller; The DC busbar includes an output positive busbar and an output negative busbar, and the two ends of the battery cluster are respectively connected to the output positive busbar and the output negative busbar, and the output positive busbar and the output negative busbar are connected to the energy storage converter PCS; the system also includes a balancing busbar; Each battery cluster is configured with an energy transfer circuit, the energy transfer circuit comprising a reactor L, a switch K1, and a switch K2, the switches K1 and K2 are connected in parallel and then connected in series with the reactor L, the reactor L is connected to the battery cluster, the switch K1 is connected to the output positive bus, and the switch K2 is connected to the balancing bus; Each battery cluster is provided with a cluster controller, the PACK controller is connected to the cluster controller of the battery cluster where it is located, and the cluster controller controls the on and off of the switches K1 and K2; The energy storage system battery PACK energy transfer method applied to the energy storage system battery PACK energy transfer system comprises the following steps: When the energy storage system operates normally, all switches K1 in the energy storage system are closed, all switches K2 are opened, the output positive bus and the output negative bus are put into operation, and charging or discharging is performed through the energy storage converter PCS; When the energy storage system fails, determine whether the battery PACK redundancy in each battery cluster is exhausted, use the battery cluster with exhausted battery PACK redundancy as the energy transfer battery cluster, disconnect the switch K1 connected to the energy transfer battery cluster, exit operation, close the switch K2 connected to the energy transfer battery cluster, and at the same time, select any normally operating battery cluster as the energy receiving battery cluster, close the switch K2 connected to the energy receiving battery cluster, and disconnect the switch K1 connected to the energy receiving battery cluster, and put the balancing bus into operation; The energy of the energy transfer battery cluster is transferred to the energy receiving battery cluster through the balancing bus; specifically including: By controlling each PACK controller of the energy transfer battery cluster, the output voltage and output current of the energy transfer battery cluster are controlled; Controlling the output voltage and output current of the energy receiving battery cluster by controlling each PACK controller of the energy receiving battery cluster; The stack controller of the energy storage system coordinates and controls the cluster controllers of the energy transfer battery cluster and the energy receiving battery cluster, so that the energy transfer battery cluster is discharged and the energy receiving battery cluster is charged, thereby realizing the energy transfer of the energy transfer battery cluster to the energy receiving battery cluster; After the energy transfer is completed, the switch K2 connected to the energy transfer battery cluster and the energy receiving battery cluster is disconnected, and the switch K1 connected to the energy receiving battery cluster is closed, and the energy receiving battery cluster continues to operate normally.

2. The energy transfer system between battery PACKs of the energy storage system according to claim 1, characterized in that: A plurality of battery clusters are combined to form a battery stack. Each battery stack is provided with a stack controller. The cluster controller is communicatively connected with the stack controller of the battery stack in which it is located. The stack controller controls the charging and discharging of each battery cluster in the battery stack through the energy storage converter PCS.

3. The energy transfer system between battery PACKs of the energy storage system according to claim 1, characterized in that: The switches K1 and K2 are automatically controlled mechanical switches or semiconductor switches.

4. The energy transfer system between battery PACKs of the energy storage system according to claim 1, characterized in that: Each of the PACK controllers is provided with a voltage detection module and a temperature detection module. The voltage detection module is used to collect the voltage of a single cell of the battery PACK, and the temperature detection module is used to collect the operating temperature of the battery PACK.

5. The energy transfer system between battery PACKs of the energy storage system according to claim 1, characterized in that: The method further comprises the step of determining whether a failure occurs in the energy storage system: Each battery PACK controller collects the single cell voltage and operating temperature of the battery PACK, and compares them with the set voltage and temperature threshold ranges; When at least one of the collected single cell voltage and the operating temperature of the battery PACK exceeds a set threshold range, it is determined that the battery PACK has a fault and fault information is obtained; The PACK controller sends the fault information to the cluster controller, and the cluster controller removes the faulty battery PACK and exits operation.

6. The energy transfer system between battery PACKs of the energy storage system according to claim 5, characterized in that: The step of determining whether the battery PACK redundancy in each battery cluster is exhausted specifically includes: Each battery cluster is configured with N battery PACKs. In order to match the voltage and power of the battery cluster with the PCS, the actual number of battery PACKs required is at least Nn, where n is the set redundancy number and 0 is the power consumption. <n<N; When the number of failed battery PACKs is greater than n, the redundancy is considered to be exhausted.

7. The energy transfer system between battery PACKs of the energy storage system according to claim 1, characterized in that: The energy transfer is completed based on: When the cell voltage of any battery PACK in the energy transfer battery cluster reaches the lower protection threshold or the cell voltage of any battery PACK in the energy receiving battery cluster reaches the upper protection threshold, the energy transfer is considered to be completed.

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