Energy storage system parallel battery cluster charge state equalization system, method and medium

Abstract

The present invention discloses a system, method and medium for equalizing the state of charge of parallel battery clusters of an energy storage system. The system comprises a battery energy management system, a host computer system, a control system and a state of charge equalization circuit; the battery energy management system is used for real-time detection of the state of charge of different battery clusters; the control system is used for comparing and calculating reference values ​​for equalizing the state of charge of different parallel battery clusters and reference values ​​for output currents of the battery clusters required for maintaining and equalizing the state of charge; the state of charge equalization circuit is used for controlling the polarity and magnitude of the output voltage of each parallel battery cluster to achieve equalization control of the state of charge of the parallel battery clusters.

Description

Technical Field

[0001] The present invention belongs to the technical field of power batteries, and in particular relates to a state of charge equalization system, method and medium for parallel battery clusters of an energy storage system. Background Art

[0002] Electric vehicle battery accidents occur frequently, and the main problem lies in the battery management system. Once the microcontroller crashes or loses control, if the vehicle system is in a charging state, the system will directly overcharge and catch fire.

[0003] Due to the inconsistency of the current battery system production specifications, there are differences between cells in the battery cluster. As the number of charge and discharge times increases, this difference will make the capacity difference between cells greater. Because the battery cluster has a "barrel effect", that is, the characteristics of the battery cluster are determined by the worst battery, if the capacity of the battery cluster is unbalanced, it will affect the performance of the entire battery cluster. At present, for the main components of the balancing system, resistance balancing and energy storage balancing are the more commonly used balancing methods for lithium-ion power batteries that do not require external energy. However, in the resistance balancing method, there are problems such as the difficulty in selecting the size of the resistor and thermal management. Energy storage balancing uses the battery to charge and discharge energy storage elements such as inductors or capacitors, and uses relays or switching devices to switch the energy storage elements between unbalanced batteries to achieve energy transfer between batteries. Although the efficiency of energy storage balancing is high, the current is uncontrollable during the balancing process, which may damage the battery. Summary of the invention

[0004] The main purpose of the present invention is to overcome the shortcomings and deficiencies of the prior art and to provide a system, method and medium for equalizing the state of charge of a parallel battery cluster in an energy storage system.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A state of charge equalization system for a parallel battery cluster of an energy storage system, comprising a battery energy management system, a host computer system, a control system and a state of charge equalization circuit;

[0007] The battery energy management system is used to detect the charge status of different battery clusters in real time;

[0008] The control system is used to compare and calculate the charge state equalization reference value of different parallel battery clusters and the battery cluster output current reference value required to maintain and equalize the charge state;

[0009] The state of charge balancing circuit is used to control the polarity and magnitude of the output voltage of each parallel battery cluster, thereby achieving balanced control of the state of charge of the parallel battery clusters.

[0010] Furthermore, the charge state equalization reference value is specifically:

[0011] The battery energy management system uploads the actual state of charge and maximum available capacity of each parallel battery cluster; when the maximum available capacity of different parallel battery clusters is the same but the state of charge is different, the host computer system compares the real-time state of charge of different battery clusters and takes the average value as the reference value for the state of charge balance of each battery cluster required to maintain the system state of charge balance.

[0012] Furthermore, when the maximum available capacity and state of charge of different parallel battery clusters are different, the host computer system controls the state of charge of each parallel battery cluster to change according to a certain rule during the charging and discharging process according to the different control principles of this energy storage system, and uses this as the state of charge reference value of the state of charge balancing process.

[0013] Furthermore, the state of charge equalization circuit is a DC converter with bidirectional power transmission and bipolar voltage output.

[0014] Furthermore, the control system compares the real-time state of charge of each parallel battery cluster with the state of charge reference value given by the host computer system. If the difference is less than a certain constant γ, its state of charge balancing circuit is locked; otherwise, the state of charge balancing circuit is connected and controlled by the control system to achieve balanced control of the state of charge between different parallel battery clusters.

[0015] Furthermore, if the number of SOC balancing circuits locked during a SOC balancing process is equal to the number of parallel clusters of the energy storage system, that is, all parallel battery clusters do not need to be SOC balancing, the SOC balancing of the energy storage system is completed.

[0016] Furthermore, the polarity and magnitude of the output voltage of each parallel battery cluster are controlled as follows:

[0017] The control system controls the polarity and magnitude of the output voltage of the state of charge balancing circuit according to the relationship between the state of charge reference value and the actual value given by the host computer system. When the actual state of charge is less than the state of charge reference value, the output voltage is negative polarity, and when the actual state of charge is greater than the state of charge reference value, the output voltage is positive polarity.

[0018] The present invention also includes a method for equalizing the state of charge of parallel battery clusters in an energy storage system based on the provided system. The battery energy management system detects and compares the state of charge of different battery clusters in real time. When the state of charge between the battery clusters is unbalanced, the control system calculates and obtains reference values ​​for equalizing the state of charge of different parallel battery clusters, and calculates and generates reference values ​​for the output current of the battery clusters required to maintain the balance of the state of charge, thereby controlling the polarity and size of the output voltage of the state of charge equalization circuit of each parallel battery cluster, thereby achieving balanced control of the state of charge of the parallel battery clusters.

[0019] Furthermore, for parallel battery clusters that require state of charge balancing control, the difference between the current reference value and the actual current is first obtained through the output current reference value deviation and the state of charge deviation curve, and then the output current reference value for charge state balancing of each parallel battery cluster is obtained. If the calculated output current reference value absolute value is greater than the maximum charge and discharge current of the parallel battery cluster, the input and output current reference values ​​of the cluster battery are set to the maximum charge and discharge current size.

[0020] The present invention also includes a computer-readable storage medium storing a computer program, and when the computer program is executed by a processor, the method provided by the present invention is implemented.

[0021] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0022] 1. For a battery cluster that needs to perform state of charge balancing control, the control system of the present invention can control the load short-circuit switch of the corresponding state of charge balancing circuit to be turned off to balance the power of the parallel circuit. For a battery cluster that does not need to perform state of charge balancing control, the control system can control the load short-circuit switch of the corresponding state of charge balancing circuit to be turned on to not balance the power of the parallel circuit.

[0023] 2. For the balancing circuit for charge state balancing control of the access system, the stability of the intermediate bus capacitor voltage and the balance of the bus capacitor energy can be maintained by controlling the switching of the switch tubes of each bidirectional DC / DC converter, and the sum of the output powers of different converters can be controlled to be 0, that is, the series capacitor loss of the charge state balancing circuit of the parallel battery cluster of the energy storage system is 0 when working, so the system efficiency is relatively high. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a structural schematic diagram of the system of the present invention;

[0025] Figure 2 is a flow chart of the method of the present invention;

[0026] Figure 3 It is a graph showing the relationship between the current reference deviation and the state of charge deviation of the parallel battery cluster balancing circuit;

[0027] Figure 4 Schematic diagram of the configuration of the state of charge equalization circuit in an embodiment of the present invention. DETAILED DESCRIPTION

[0028] The present invention is further described in detail below in conjunction with embodiments and drawings, but the embodiments of the present invention are not limited thereto.

[0029] Example

[0030] like Figure 1As shown, the present invention is a parallel battery cluster state of charge equalization system, including a battery energy management system, a host computer system, a control system and a state of charge equalization circuit;

[0031] The battery energy management system is used to detect the charge status of different battery clusters in real time;

[0032] The control system is used to compare and calculate the charge state equalization reference value of different parallel battery clusters and the battery cluster output current reference value required to maintain and equalize the charge state;

[0033] The state of charge balancing circuit is used to control the polarity and magnitude of the output voltage of each parallel battery cluster, thereby achieving balanced control of the state of charge of the parallel battery clusters.

[0034] like Figure 4 As shown, in this embodiment, the state of charge equalization circuit is configured as a DC converter with bidirectional power transmission and bipolar voltage output.

[0035] The battery energy management system uploads the actual state of charge and maximum available capacity of each parallel battery cluster. When the maximum available capacity of different parallel battery clusters is the same but the state of charge is different, the host computer system compares the real-time state of charge of different battery clusters and takes the average value as the reference value for the state of charge balance of each battery cluster required to maintain the system state of charge balance. When the maximum available capacity and state of charge of different parallel battery clusters are different, the host computer system can control the state of charge of each parallel battery cluster according to different control principles of this energy storage system, such as the principle of optimal capacity utilization, to change according to a certain rule during the charging and discharging process, and use this as the reference value for the state of charge balance process.

[0036] The control system compares the real-time state of charge of each parallel battery cluster with the state of charge reference value given by the host computer system. If the difference is very small and less than a certain constant γ, the state of charge balancing circuit is locked; if the difference is large, the state of charge balancing circuits of these parallel battery clusters are connected, and the state of charge balancing control between different parallel battery clusters is achieved through control of the control system. For parallel battery clusters that need to be controlled for state of charge balancing, the current reference value and the actual current difference are first obtained through the output current reference value deviation and state of charge deviation curve, and then the output current reference value for each parallel battery cluster for charge state balancing is obtained. If the calculated output current reference value absolute value is greater than the maximum charge and discharge current of the parallel battery cluster, the input and output current reference value of the cluster battery is set to the maximum charge and discharge current size, effectively protecting the battery system life.

[0037] The control system can control the polarity and size of the output voltage of the state of charge balancing circuit according to the relationship between the state of charge reference value and the actual value given by the host computer system. When the actual state of charge is less than the state of charge reference value, the output voltage is negative polarity, and when the actual state of charge is greater than the state of charge reference value, the output voltage is positive polarity. If the number of balancing circuit locks during a certain state of charge balancing process is equal to the number of parallel battery clusters in the energy storage system, that is, all parallel battery clusters do not need to be balanced for the state of charge, the energy storage system state of charge balancing is completed.

[0038] like Figure 3 As shown, it is assumed that the output current reference value I used by the battery cluster for charge state balancing refi The actual current I i The absolute value of the feedback value deviation is ΔI. If the actual state of charge of the i-th battery cluster is greater than the average state of charge, then in order to reduce the state of charge of the i-th battery cluster, the output current reference value of this battery cluster can be set to I i +ΔI i , increasing its discharge current, the bidirectional converter controls the series capacitor voltage to be negative polarity; otherwise, the output current reference value of this battery cluster is I i -ΔI i , the bidirectional converter controls the series capacitor voltage to be positive polarity.

[0039] like Figure 3 As shown, ΔI i =min{ΔI max ,k·|SOC i -SOC av}, where ΔI max Set ΔI to be the maximum value of the deviation between the output current reference value and the actual output current. max It can not only prevent the sudden reversal of battery current during the control process, but also prevent the occurrence of large current discharge when the battery cluster temperature is too high.

[0040] like Figure 2 As shown, in another embodiment, a method for equalizing the state of charge of parallel battery clusters of an energy storage system based on the above embodiment is also provided, including a battery energy management system detecting and comparing the states of charge SOC1, SOC2, ..., SOC n When the state of charge between battery clusters is unbalanced, the control system calculates the reference value SOC of the state of charge balance of different parallel battery clusters ref1 , SOC ref2 ,……,SOC refn , and then calculate the battery cluster output current reference value I required to maintain the charge state balance ref1 ,I ref2 ,……,I refn, thereby controlling the polarity and magnitude of the output voltage of the charge state balancing circuit of each parallel battery cluster, and realizing balanced control of the charge state of the parallel battery cluster.

[0041] In another embodiment, a computer-readable storage medium is provided, which stores a computer program. When the computer program is executed by a processor, the method of the above embodiment is implemented.

[0042] It should also be noted that in this specification, terms such as "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of more restrictions, an element defined by the sentence "comprises a ..." does not exclude the presence of other identical elements in the process, method, article or device including the element.

[0043] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A state of charge equalization system for parallel battery clusters in an energy storage system, characterized in that: Including battery energy management system, host computer system, control system and charge state equalization circuit; The battery energy management system is used to detect the charge status of different battery clusters in real time; The control system is used to compare and calculate the charge state equalization reference value of different parallel battery clusters and the battery cluster output current reference value required to maintain and equalize the charge state; The charge state equalization reference value is as follows: The battery energy management system uploads the actual state of charge and maximum available capacity of each parallel battery cluster; when the maximum available capacity of different parallel battery clusters is the same but the state of charge is different, the host computer system compares the real-time state of charge of different battery clusters and takes the average value as the reference value for the state of charge balance of each battery cluster required to maintain the system state of charge balance; When the maximum available capacity and state of charge of different parallel battery clusters are different, the host computer system controls the state of charge of each parallel battery cluster to change according to a certain rule during the charging and discharging process according to the different control principles of this energy storage system, and uses this as the state of charge reference value of the state of charge balancing process; The state of charge balancing circuit is used to control the polarity and magnitude of the output voltage of each parallel battery cluster, thereby achieving balanced control of the state of charge of the parallel battery clusters.

2. The energy storage system parallel battery cluster state of charge equalization system according to claim 1, characterized in that: The charge state equalization circuit is a DC converter with bidirectional power transmission and bipolar voltage output.

3. The energy storage system parallel battery cluster state of charge equalization system according to claim 1, characterized in that: The control system compares the real-time state of charge of each parallel battery cluster with the state of charge reference value given by the host computer system. If the difference is less than a certain constant γ, its state of charge balancing circuit is locked; otherwise, the state of charge balancing circuit is connected and controlled by the control system to achieve balanced control of the state of charge between different parallel battery clusters.

4. The energy storage system parallel battery cluster charge state equalization system according to claim 3, characterized in that: If the number of SOC balancing circuits locked during a SOC balancing process is equal to the number of parallel clusters of the energy storage system, that is, all parallel battery clusters do not need to be SOC balancing, the SOC balancing of the energy storage system is completed.

5. The energy storage system parallel battery cluster state of charge equalization system according to claim 1, characterized in that: The polarity and magnitude of the output voltage of each parallel battery cluster are controlled as follows: The control system controls the polarity and magnitude of the output voltage of the state of charge balancing circuit according to the relationship between the state of charge reference value and the actual value given by the host computer system. When the actual state of charge is less than the state of charge reference value, the output voltage is negative polarity, and when the actual state of charge is greater than the state of charge reference value, the output voltage is positive polarity.

6. A method for equalizing the state of charge of a parallel battery cluster of an energy storage system based on the system according to any one of claims 1 to 5, characterized in that: The battery energy management system detects and compares the charge states of different battery clusters in real time. When the charge states of the battery clusters are unbalanced, the control system calculates the charge state balance reference values ​​of the different parallel battery clusters, and calculates the battery cluster output current reference values ​​required to maintain the charge state balance, thereby controlling the polarity and size of the output voltage of the charge state balance circuit of each parallel battery cluster, and realizing the balanced control of the charge state of the parallel battery clusters.

7. The method for equalizing the state of charge of a parallel battery cluster in an energy storage system according to claim 6, characterized in that: For parallel battery clusters that require state of charge balancing control, the difference between the current reference value and the actual current is first obtained through the output current reference value deviation and state of charge deviation curve, and then the output current reference value for charge state balancing of each parallel battery cluster is obtained. If the calculated output current reference value absolute value is greater than the maximum charge and discharge current of the parallel battery cluster, the input and output current reference values ​​of the cluster battery are set to the maximum charge and discharge current size.

8. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the method as claimed in any one of claims 6 to 7 is implemented.

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