Balancing method of battery cluster of energy storage system and related equipment thereof

Abstract

The invention relates to an equalization method for a battery cluster of an energy storage system and related equipment thereof. In the device, an electronic current limiter is connected in series with a battery cluster of the energy storage system, and the electronic current limiter changes the resistance of the electronic current limiter to adjust the internal resistance of the battery cluster; the input side of the bidirectional flyback DC-DC converter is connected with the battery cluster through a switch Qx, and the output side of the bidirectional flyback DC-DC converter is connected with a DC bus or an energy storage battery; the bidirectional flyback DC-DC converter controls electric quantity balance between the battery cluster and other battery clusters connected to the direct current bus in parallel when the energy storage system is in a standing state. According to the invention, the problem of unbalanced electric quantity among the battery clusters of the energy storage system in the prior art is solved, and the electric quantity balance of the energy storage system under all working conditions is realized.

Description

Technical Field

[0001] The present application relates to the technical field of energy storage systems, and in particular to a method for balancing a battery cluster of an energy storage system and related equipment. Background Art

[0002] In medium and large energy storage systems, multiple battery clusters are usually connected in parallel to form a large-capacity battery energy storage system with a common DC bus. However, due to differences in the age of the battery clusters in the system or differences in internal and external line impedance, the charging and discharging speeds of the battery clusters are inconsistent. Usually, some battery clusters are discharged, while others have more remaining power, or some battery clusters are full, while others can still be charged with more power. This is the "barrel short board effect" between large-scale battery clusters caused by the mismatch between the differences in battery cells in the traditional energy storage architecture and the fixed series-parallel battery grouping method. This inconsistency leads to a reduction in the available power of the energy storage system. If it is not controlled, it will lead to problems such as accelerated aging of some battery clusters.

[0003] With regard to the problem of unbalanced charge among battery clusters in energy storage systems in related technologies, no effective solution has been proposed so far. Summary of the invention

[0004] The energy storage system battery cluster balancing method and related equipment provided in the embodiments of the present application at least solve the problem of unbalanced power among battery clusters in the energy storage system in the related art.

[0005] A balancing device for a battery cluster of an energy storage system includes: an electronic current limiter and a bidirectional flyback DC-DC converter, wherein: The electronic current limiter is connected in series with the battery cluster of the energy storage system, and the electronic current limiter is used to change the resistance of the electronic current limiter to adjust the internal resistance of the battery cluster; The input side of the bidirectional flyback DC-DC converter is connected to the battery cluster via switch Qx, and the output side is connected to the DC bus or the energy storage battery; the bidirectional flyback DC-DC converter is used to control the charge balance between the battery cluster and other battery clusters connected in parallel to the DC bus when the energy storage system is in a static state.

[0006] In some of the embodiments, the electronic current limiter includes: at least one group of two charging semiconductor electronic switches Q1 and discharging semiconductor electronic switches Q2 with freewheeling diodes connected back to back; preferably, the charging semiconductor electronic switch Q1 and the discharging semiconductor electronic switch Q2 are bipolar junction transistors, field effect transistors or insulated gate bipolar transistors; preferably, the electronic current limiter includes multiple groups of two charging semiconductor electronic switches Q1 and discharging semiconductor electronic switches Q2 with freewheeling diodes connected back to back.

[0007] In some of the embodiments, a diode D1 is connected in reverse parallel between the collector of the charging semiconductor electronic switch Q1 and the DC bus, and a diode D2 is connected in reverse parallel between the collector of the discharging semiconductor electronic switch Q2 and the DC bus.

[0008] In some of the embodiments, relays K6 and K2 are connected in parallel between the input and output ends of the electronic current limiter.

[0009] In some of the embodiments, the device further includes a control unit, which is connected to the electronic current limiter and the bidirectional flyback DC-DC converter respectively, and the control unit is used to control the electronic current limiter by any of the following methods: Method 1: Obtaining a charging instruction and setting a charging current; in response to the charging instruction, controlling the discharge semiconductor electronic switch Q2 to be saturated and turned on, and controlling the gate voltage of the charging semiconductor electronic switch Q1 to control the charging current according to the difference between the charging current of the battery cluster and the set charging current; Obtaining a discharge instruction and setting a discharge current; in response to the discharge instruction, controlling the charging semiconductor electronic switch Q1 to be saturated and turned on, and controlling the gate voltage of the discharging semiconductor electronic switch Q2 according to the difference between the discharge current of the battery cluster and the set discharge current to control the discharge current; Method 2: Obtaining a charging instruction and setting an internal resistance; in response to the charging instruction, controlling the discharge semiconductor electronic switch Q2 to be saturated and turned on, obtaining a target charging current according to a difference in resistance between the collector and the emitter of the charging semiconductor electronic switch Q1 relative to the set internal resistance, and controlling a gate voltage of the charging semiconductor electronic switch Q1 according to a difference in the charging current of the battery cluster relative to the target charging current to control the charging current, wherein the resistance between the collector and the emitter of the charging semiconductor electronic switch Q1 is determined based on a voltage between the collector and the emitter of the charging semiconductor electronic switch Q1 and the charging current; Obtain a discharge instruction and set an internal resistance; in response to the discharge instruction, control the charging semiconductor electronic switch Q1 to be saturated and turned on, obtain a target discharge current according to a difference in resistance between the collector and the emitter of the discharging semiconductor electronic switch Q2 relative to the set internal resistance, and control a gate voltage of the discharging semiconductor electronic switch Q2 according to a difference in the discharge current of the battery cluster relative to the target discharge current to control the discharge current, wherein the resistance between the collector and the emitter of the discharging semiconductor electronic switch Q2 is determined based on a voltage between the collector and the emitter of the discharging semiconductor electronic switch Q2 and the discharge current; Method 3: Acquire a set internal resistance; when it is detected that the voltage difference between the DC bus and the battery cluster is greater than the set value, simultaneously control the charging semiconductor electronic switch Q1 and the discharging semiconductor electronic switch Q2 to be saturated and turned on; when it is detected that the voltage difference between the DC bus and the battery cluster is not greater than the set value, obtain the target charge and discharge current according to the numerical difference between the voltage across the electronic current limiter and the target voltage, and according to the numerical difference between the charge and discharge current of the battery cluster and the target charge and discharge current, simultaneously control the gate voltage of the charging semiconductor electronic switch Q1 and the discharging semiconductor electronic switch Q2 to control the charge and discharge current, wherein the target voltage is determined based on the set internal resistance and the charge and discharge current.

[0010] In some of the embodiments, the device further comprises a control unit, the control unit being configured to: When the energy storage system is in a static state and the voltage difference between the DC bus of the energy storage system and the battery cluster exceeds a preset voltage value, the charging semiconductor electronic switch Q1 is disconnected, and the switch Qx is turned on to control the bidirectional flyback DC-DC converter to exchange electric energy from the DC bus or the energy storage battery to the battery cluster; until the voltage value at both ends of the electronic current limiter is less than the set value, the switch Qx is disconnected, the charging semiconductor electronic switch Q1 is turned on, and the current limiting control of the charging current of the battery cluster is achieved by controlling the gate voltage of the charging semiconductor electronic switch Q1.

[0011] In some of the embodiments, the device further comprises a control unit, and the control unit is configured to: disconnect the charging semiconductor electronic switch Q1 and the discharging semiconductor electronic switch Q2 when the battery cluster is short-circuited.

[0012] In some of the embodiments, the device further comprises a control unit, the control unit being configured to: When the temperature of the charging semiconductor electronic switch Q1 and / or the discharging semiconductor electronic switch Q2 exceeds a set temperature threshold, controlling the charging semiconductor electronic switch Q1 and the discharging semiconductor electronic switch Q2 to be saturated and turned on; When the temperature of the charging semiconductor electronic switch Q1 and / or the discharging semiconductor electronic switch Q2 continues to exceed a set temperature threshold within a set time period, the relays K2 and K6 are turned on.

[0013] A method for balancing a battery cluster of an energy storage system is applied to the above-mentioned balancing device for the battery cluster of the energy storage system, and the method comprises: Under charging or discharging conditions, the internal resistance of the battery cluster is adjusted by changing the resistance of the electronic current limiter to control the charge balance between the battery clusters of the energy storage system; When the energy storage system is in a static state, the bidirectional flyback DC-DC converter is controlled to exchange electric energy between the DC bus or the energy storage battery and the battery cluster, thereby controlling the charge balance between the battery cluster and other battery clusters connected in parallel to the DC bus.

[0014] An energy storage system includes a DC-AC converter connected in series between a DC bus and an AC line, and a plurality of battery clusters connected in parallel with the DC bus; wherein the battery cluster includes a first battery module and a second battery module connected in series, and the first battery module includes an equalization device of the battery cluster.

[0015] The embodiment of the present application provides a method for balancing a battery cluster of an energy storage system and related equipment. In the present application, an electronic current limiter is connected in series with a battery cluster of the energy storage system, and the electronic current limiter changes the resistance of the electronic current limiter to adjust the internal resistance of the battery cluster; the input side of the bidirectional flyback DC-DC converter is connected to the battery cluster via a switch Qx, and the output side is connected to a DC bus or an energy storage battery; the bidirectional flyback DC-DC converter controls the charge balance between the battery cluster and other battery clusters connected in parallel to the DC bus when the energy storage system is in a static state, which solves the problem of unbalanced charge between battery clusters in the energy storage system in the related art, and realizes charge balance under all working conditions of the energy storage system. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the prior art descriptions. Obviously, the drawings described below are only some embodiments of the present application, and for ordinary technicians in this field, other embodiments can be obtained based on these drawings without creative work.

[0017] Figure 1 It is a schematic diagram of the structure of a balancing device for a battery cluster of an energy storage system according to an embodiment of the present application.

[0018] Figure 2 It is a schematic diagram of a connection method of Q1 and Q2 in an embodiment of the present application.

[0019] Figure 3 It is a schematic diagram of another connection method of Q1 and Q2 in the embodiment of the present application.

[0020] Figure 4 It is a circuit topology diagram of a balancing device for a battery cluster of an energy storage system according to an embodiment of the present application.

[0021] Figure 5 This is a circuit topology diagram of another equalization device for a battery cluster of an energy storage system according to an embodiment of the present application.

[0022] Figure 6 It is a schematic diagram of the circuit topology structure of the control unit of an embodiment of the present application.

[0023] Figure 7 It is a control flow chart of control method 1 of the control unit of an embodiment of the present application.

[0024] Figure 8 It is a control flow chart of control method 2 of the control unit of an embodiment of the present application.

[0025] Fig. 9 This is a flow chart of a master controller of an energy storage system according to an embodiment of the present application controlling current balancing among battery clusters.

[0026] Fig.10 This is a flow chart of balancing control performed by a control unit in a battery cluster according to an embodiment of the present application.

[0027] Fig.11 It is a control flow chart of control method three of the control unit of an embodiment of the present application.

[0028] Fig.12 is a schematic diagram of a reverse diode clamping voltage spike according to an embodiment of the present application.

[0029] Fig.13 It is a flow chart of a method for balancing a battery cluster of an energy storage system according to an embodiment of the present application.

[0030] Fig.14 The flowchart is a flow chart of charging current limiting control performed by a control unit in a battery cluster according to an embodiment of the present application.

[0031] Fig.15 This is a flow chart of the discharge current limiting control performed by the control unit in the battery cluster according to the embodiment of the present application.

[0032] Fig.16 It is a schematic diagram of the structure of the energy storage system of an embodiment of the present application. DETAILED DESCRIPTION

[0033] The embodiments of the present application will be described in more detail below with reference to the accompanying drawings. Although certain embodiments of the present application are shown in the accompanying drawings, it should be understood that the present application can be implemented in various forms and should not be construed as being limited to the embodiments described herein. Instead, these embodiments are provided to provide a more thorough and complete understanding of the present application. It should be understood that the drawings and embodiments of the present application are only for exemplary purposes and are not intended to limit the scope of protection of the present application.

[0034] In order to achieve power balancing among battery clusters of an energy storage system, an embodiment of the present application provides a balancing device for a battery cluster of an energy storage system. Figure 1 is a schematic diagram of the structure of a balancing device for a battery cluster of an energy storage system according to an embodiment of the present application, such as Figure 1As shown, the device includes: an electronic current limiter 10 and a bidirectional flyback DC-DC converter 20, wherein the electronic current limiter 10 is connected in series with a battery cluster 30, and the electronic current limiter 30 is used to change the resistance of the electronic current limiter 10 to adjust the internal resistance of the battery cluster 30; the input side of the bidirectional flyback DC-DC converter 20 is connected to the battery cluster 30 via a switch Qx, and the output side is connected to a DC bus or an energy storage battery; the bidirectional flyback DC-DC converter 20 is used to control the charge balance between the battery cluster 30 and other battery clusters connected in parallel to the DC bus when the energy storage system is in a static state.

[0035] In the related art, a solution for power balancing is to connect a high-power DC-DC converter in parallel to the positive and negative ports of each battery cluster to adjust the charge and discharge current of different battery clusters, so as to solve the problem of unbalanced charge and discharge between battery clusters caused by differences in battery internal resistance or SOC when different battery clusters are connected in parallel. In this solution, since the DC-DC converter is connected in parallel to the battery cluster and the inverter power transmission circuit, all input and output power of the entire battery cluster must be converted by the centralized DC-DC converter, resulting in increased power loss. In the balancing device provided in the above embodiment, the bidirectional DC-DC converter 20 is connected in series between the battery cluster and the DC bus or the energy storage battery; the bidirectional flyback DC-DC converter 20 is connected to the battery cluster through the switch Qx. When the battery cluster is normally charged and discharged, the switch Qx is turned off, and the charge and discharge current no longer passes through the bidirectional flyback DC-DC converter 20. When the battery cluster is in a static state, the switch Qx is turned on, and the bidirectional flyback DC-DC converter 20 is enabled to realize the bidirectional energy exchange between the battery cluster and the DC bus or the energy storage battery to achieve power balancing. Therefore, on the one hand, the above-mentioned bidirectional flyback DC-DC converter 20 does not need to use a high-power DC-DC converter, but can use a small-capacity DC-DC converter to reduce costs. On the other hand, under the charging and discharging conditions, the normal charging and discharging current of the battery cluster no longer passes through the bidirectional flyback DC-DC converter 20, thereby reducing energy loss and avoiding the problem of battery cluster efficiency loss.

[0036] In addition, unlike some related technologies that use series DC-DC converters to balance the charge between battery clusters under all working conditions, this embodiment uses a series DC-DC converter to balance the charge between battery clusters when the energy storage system is in a static state, and uses an electronic current limiter 10 to balance the charge between battery clusters under charge and discharge conditions, thereby avoiding the problem that the response speed of the entire battery system decreases due to the limited charge and discharge or current and voltage response speed of the DC-DC converter itself, thereby affecting the charge and discharge conversion speed of the entire battery system. This embodiment uses an electronic current limiter, especially an electronic current limiter composed of back-to-back semiconductor transistors, to adjust the charge and discharge current under charge and discharge conditions using the impedance characteristics of the linear region of the semiconductor transistor, thereby achieving zero delay in charge and discharge conversion. The bidirectional flyback DC-DC converter can achieve the ability to achieve wide-range adjustable voltage difference and charge balance when the battery cluster is in a static state. The wide range of voltage difference in this embodiment refers to the voltage difference exceeding the preset voltage value.

[0037] It should be noted that the "stationary state" in this embodiment means that the energy storage system is neither charging nor discharging, but is in a waiting or standby mode. In this state, the energy storage system remains connected but does not perform energy conversion activities, that is, the chemical reaction inside the battery cluster is temporarily stopped or maintained at a very low level.

[0038] It can be understood that, although the electronic current limiter 10 is connected in series between the negative electrode of the battery cluster and the negative electrode of the DC bus, and the bidirectional flyback DC-DC converter 20 is connected in series between the negative electrode of the battery cluster and the positive electrode of the DC bus in this embodiment, the series connection position of the electronic current limiter 10 and the bidirectional flyback DC-DC converter 20 is not limited to this. For example, the electronic current limiter 10 can also be connected in series between the positive electrode of the battery cluster and the positive electrode of the DC bus, and the bidirectional flyback DC-DC converter 20 can also be connected in series between the positive electrode of the battery cluster and the negative electrode of the DC bus.

[0039] In addition, the purpose of the bidirectional flyback DC-DC converter 20 is to achieve bidirectional energy transfer to reduce or increase the power of the battery cluster. The source or destination of the transferred energy can be a DC bus or an energy storage battery. The energy storage battery can be a small-capacity battery, such as a 24V small-capacity energy storage battery, which is used for temporary storage of energy and does not directly participate in the charging and discharging of the energy storage system. In addition, it can be understood that in an embodiment where an energy storage battery is used instead of a DC bus for temporary storage of energy, a small-capacity energy storage battery can be separately provided for each battery cluster, or multiple battery clusters connected in parallel on the DC bus or all battery clusters can share a small-capacity energy storage battery.

[0040] In some of the embodiments, the electronic current limiter 10 includes: at least one group of two charging semiconductor electronic switches Q1 and discharging semiconductor electronic switches Q2 with freewheeling diodes connected back to back; wherein the charging semiconductor electronic switch Q1 is used for charging protection of the battery cluster, and the discharging semiconductor electronic switch Q2 is used for discharging protection of the battery cluster. Figure 2 is a schematic diagram of a connection method of a charging semiconductor electronic switch Q1 and a discharging semiconductor electronic switch Q2 according to an embodiment of the present application, such as Figure 2 As shown, the charging semiconductor electronic switch Q1 and the discharging semiconductor electronic switch Q2 can be located on the same side of the battery cluster and connected to a common node connected to the safety protection ground G. Figure 3 FIG. 1 is a schematic diagram of another connection method of the charging semiconductor electronic switch Q1 and the discharging semiconductor electronic switch Q2 of the embodiment of the present application. Figure 3 As shown, the charging semiconductor electronic switch Q1 and the discharging semiconductor electronic switch Q2 may also be located at different sides of the battery cluster and connected to the positive electrode and the negative electrode of the battery cluster respectively.

[0041] In this embodiment, the impedance characteristics of the semiconductor electronic switch in the linear region are used to achieve the external internal resistance adjustment of the entire battery cluster. The semiconductor electronic switch can be a bipolar junction transistor, a field effect transistor or an insulated gate bipolar transistor. In the scenario of large current (for example, the battery cluster current exceeds 200A) and large voltage (for example, the battery cluster voltage exceeds 1000V), an insulated gate bipolar transistor is preferably used as the semiconductor electronic switch of the above-mentioned electronic current limiter 10.

[0042] In the specific selection, the charging semiconductor electronic switch Q1 and the discharging semiconductor electronic switch Q2 can use semiconductor electronic switches of the same specifications, or semiconductor electronic switches of different specifications or types. At the same time, in the scenario where the battery cluster has high power, in order to improve the overcurrent capacity of the electronic current limiter 10, multiple groups of semiconductor electronic switches connected back to back can be set in parallel.

[0043] When the battery cluster is in the charging and discharging condition, there is a short circuit or other reasons that require the charging circuit or the discharging circuit to be quickly cut off, the charging semiconductor electronic switch Q1 or the discharging semiconductor electronic switch Q2 is quickly turned off to generate flyback energy, which may cause the circuit components to be damaged due to energy impact. For this reason, in some embodiments, a diode D1 is reversely connected in parallel between the collector of the charging semiconductor electronic switch Q1 and the DC bus, and a diode D2 is reversely connected in parallel between the collector of the discharging semiconductor electronic switch Q2 and the DC bus. When the charging semiconductor electronic switch Q1 or the discharging semiconductor electronic switch Q2 is quickly turned off to generate flyback energy, the diode D1 and the diode D2 respectively provide a freewheeling circuit for the flyback energy to protect the circuit components.

[0044] To protect the electronic current limiter, in some embodiments, relays K6 and K2 are connected in parallel between the input and output ends of the electronic current limiter.

[0045] In some of the embodiments, the balancing device further includes a control unit, which is respectively connected to the electronic current limiter and the bidirectional flyback DC-DC converter, and is used to obtain various parameters of the balancing device, the battery cluster, and the energy storage system, and to control the electronic current limiter, the bidirectional flyback DC-DC converter and other components in the balancing device, so as to realize the charge balancing, internal resistance control and related protection functions of the battery cluster under the charging and discharging conditions or in the static state.

[0046] The structure and working process of the embodiment of the present application are described and illustrated below in conjunction with a specific circuit topology diagram.

[0047] Figure 4 is a circuit topology diagram of a balancing device for a battery cluster of an energy storage system according to an embodiment of the present application, such as Figure 4 As shown, the circuit includes a battery cluster BAT5, an IGBT transistor Q1 selected as 300A / 1200V, an IGBT transistor Q2 selected as 300A / 1700V, a gate control signal of transistor Q1 as GCH+, a gate control signal of transistor Q2 as GDIS+, and G as protective grounding. A switch K5 is provided on the positive pole P+ of the DC bus, a switch K7 is provided on the negative pole P- of the DC bus, a relay K6 is connected in parallel between the input and output of the electronic current limiter, and a current sensor Hall3 is used to collect the current value flowing through the electronic current limiter. A diode D1 is connected in reverse parallel between the collector of the transistor Q1 and the positive pole P+ of the DC bus, and a diode D2 is connected in reverse parallel between the collector of the transistor Q2 and the positive pole P+ of the DC bus. The bidirectional flyback DC-DC converter includes a capacitor C6, a switch tube Q5, a winding, and a resistor R2 on the input side; and a capacitor C5, a switch tube Q6, a winding, and a resistor R3 on the output side. A switch Qx with a specification of 20A / 1200V is also connected in series between the input side of the bidirectional flyback DC-DC converter and the negative electrode of the battery cluster BAT5.

[0048] Figure 5 is a circuit topology diagram of another equalization device for a battery cluster of an energy storage system according to an embodiment of the present application. Figure 5 and Figure 4 The difference is that in order to improve the overcurrent capacity of the electronic current limiter, a group of back-to-back semiconductor electronic switches Q3 and Q4 are added, wherein the specification of Q3 is the same as that of Q1, and the specification of Q4 is the same as that of Q2.

[0049] To control Figure 4 Take the electronic current limiter shown as an example. Figure 6 is a schematic diagram of the circuit topology structure of the control unit of an embodiment of the present application, such as Figure 6 As shown, the control unit includes a microcontroller MCU and sensors for collecting various working parameters of the electronic current limiter, such as the current sensor Hall1 (equivalent to Figure 4 The current sensor Hall3 in the device), the voltage collection pins AD1 and AD2, and the voltage collection module, control pins DA1, DA2, DO1, DO2, DO3, etc. Figure 6 The relay K2 in the Figure 4 Relay K6 in.

[0050] The working process of the equalizing device is described and illustrated below.

[0051] When the battery cluster does not require balancing and short-circuit protection, the control unit controls the two back-to-back semiconductor electronic switches Q1 and Q2 in the electronic current limiter to be in a saturated conduction state, which does not affect the charging and discharging functions of the battery system.

[0052] When the battery cluster needs balancing and short-circuit protection, the control unit controls the gate voltage of two back-to-back semiconductor switches Q1 and / or Q2 in the electronic current limiter to control the internal resistance of the battery cluster, thereby achieving battery balancing.

[0053] In one scenario, the master controller of the energy storage system sends instructions to the control units of each battery cluster to indicate whether the current operating condition is charging or discharging, and at the same time indicates the current set charging current (under charging condition) or set discharging current (under discharging condition) of each control unit. In this scenario, both the charging current and the discharging current are directly issued by the master controller and are in a planned charging or discharging state. In this scenario, the control unit does not need to autonomously detect the current operating condition of the energy storage system, and the real-time control requirements of the electronic current limiter can be met by the closed-loop control of the proportional-integral controller.

[0054] In this scenario, the control unit can use the following method to perform closed-loop control on the electronic current limiter. The corresponding control flow chart is as follows: Figure 7 As shown, a PI controller is used for control. Method 1 includes the following steps: obtaining a charging instruction and setting a charging current; in response to the charging instruction, controlling the discharge semiconductor electronic switch Q2 to be saturated and turned on, and controlling the gate voltage of the charging semiconductor electronic switch Q1 to control the charging current according to the difference between the charging current of the battery cluster and the set charging current; obtaining a discharging instruction and setting a discharging current; in response to the discharging instruction, controlling the charging semiconductor electronic switch Q1 to be saturated and turned on, and controlling the gate voltage of the discharging semiconductor electronic switch Q2 to control the discharging current according to the difference between the discharging current of the battery cluster and the set discharging current.

[0055] refer to Figure 4 and Figure 7After the control unit receives the charging instruction from the main controller, the control unit outputs a driving voltage ≥10V to drive the Gate12+ signal so that Q2 is in a saturated conduction state. If the control unit receives an instruction containing a set charging current from the main controller, the control unit detects the current data of the main circuit through the current sensor Hall1. If it is detected that the current charging current exceeds the set charging current, the control unit immediately reduces the driving voltage Gate11+ of the gate of Q1, so that the on-resistance of Q1 increases, and the current flowing through the battery cluster BAT5 decreases, and gradually approaches the set charging current through repeated adjustments; if it is detected that the current charging current is lower than the set charging current, the control unit immediately increases the driving voltage Gate11+ of the gate of Q1, so that the on-resistance of Q1 decreases, and the current flowing through the battery cluster BAT5 increases, and gradually approaches the set charging current through repeated adjustments, so that the charging current flowing through the battery cluster is controllable. If the control unit detects that the amplitude of Gate11+ has reached the control limit, it stops adjusting the driving voltage Gate11+ and maintains the driving voltage value at the control limit state.

[0056] After the control unit receives the discharge instruction from the main controller, the control unit outputs a driving voltage ≥10V to drive the Gate11+ signal so that Q1 is in a saturated conduction state. If the control unit receives an instruction containing a set discharge current from the main controller, the control unit detects the current data of the main circuit through the current sensor Hall1. If it is detected that the current discharge current exceeds the set discharge current, the control unit immediately reduces the driving voltage Gate12+ of the gate of Q2, so that the on-resistance of Q2 increases, the current flowing through the battery cluster BAT5 decreases, and gradually approaches the set discharge current through repeated adjustments; if it is detected that the current discharge current is lower than the set discharge current, the control unit immediately increases the driving voltage Gate12+ of the gate of Q2, so that the on-resistance of Q2 decreases, the current flowing through the battery cluster increases, and gradually approaches the set discharge current through repeated adjustments, so that the discharge current flowing through the battery cluster is controllable. If the control unit detects that the amplitude of Gate12+ has reached the control limit, it stops adjusting the driving voltage Gate12+ and maintains the driving voltage value at the control limit state.

[0057] In another scenario, the main controller of the energy storage system sends instructions to the control units of each battery cluster to indicate whether to enter the charging or discharging condition. In this scenario, the charging and discharging conditions are planned, but the charging current or discharging current is not set and is in an unplanned fluctuating state.

[0058] In this scenario, the control unit can use method 2 to perform dual closed-loop control on the electronic current limiter. Since the outer loop control response is relatively slow and the bandwidth is low (in this embodiment, the outer loop bandwidth is one tenth of the inner loop bandwidth), while the inner loop control response is relatively fast and the bandwidth is large, the outer loop is used for resistance control and the inner loop is used for current control in method 2. The corresponding control flow chart is as follows: Figure 8 As shown, two PI controllers are used for control. Method 2 includes the following steps: obtaining a charging instruction and setting an internal resistance; in response to the charging instruction, controlling the discharge semiconductor electronic switch Q2 to be saturated and turned on, obtaining a target charging current according to the difference between the resistance between the collector and the emitter of the charging semiconductor electronic switch Q1 and the set internal resistance, and controlling the gate voltage of the charging semiconductor electronic switch Q1 according to the difference between the charging current of the battery cluster and the target charging current to control the charging current, wherein the resistance between the collector and the emitter of the charging semiconductor electronic switch Q1 is determined based on the voltage between the collector and the emitter of the charging semiconductor electronic switch Q1 and the charging current; obtaining a discharging instruction and setting an internal resistance; in response to the discharging instruction, controlling the charging semiconductor electronic switch Q1 to be saturated and turned on, obtaining a target discharging current according to the difference between the resistance between the collector and the emitter of the discharging semiconductor electronic switch Q2 and the set internal resistance, and controlling the gate voltage of the discharging semiconductor electronic switch Q2 according to the difference between the discharging current of the battery cluster and the target discharging current to control the discharging current, wherein the resistance between the collector and the emitter of the discharging semiconductor electronic switch Q2 is determined based on the voltage between the collector and the emitter of the discharging semiconductor electronic switch Q2 and the discharging current.

[0059] refer to Figure 4 and Figure 8After the control unit receives the charging instruction from the master controller, it outputs a driving voltage of ≥10V to drive the Gate12+ signal so that Q2 is in a saturated conduction state. If it receives an instruction from the master controller containing a set internal resistance, the control unit detects the current data of the main circuit through the current sensor Hall1 and detects the voltage between the collector and emitter of Q1 through the voltage sensor. If it is detected that the resistance obtained by dividing the voltage between the collector and emitter of Q1 by the current charging current is less than the set internal resistance, the control unit immediately reduces the driving voltage Gate11+ of the gate of Q1, so that the on-resistance of Q1 increases, and the current flows through the battery cluster B. The current of AT5 becomes smaller, and gradually approaches the set internal resistance through repeated adjustments. If it is detected that the resistance obtained by dividing the voltage Vce between the collector and emitter of Q1 by the current charging current exceeds the set internal resistance, the control unit immediately increases the driving voltage Gate11+ of the gate of Q1, so that the on-resistance of Q1 is reduced, and the current flowing through the battery cluster BAT5 becomes larger, and gradually approaches the set internal resistance through repeated adjustments, so that the charging current flowing through the battery cluster can be controlled. If the control unit detects that the amplitude of Gate11+ has reached the control limit, it stops adjusting the driving voltage Gate11+ and maintains the driving voltage value at the control limit state.

[0060] After the control unit receives the discharge instruction from the main controller, it outputs a driving voltage ≥10V to drive the Gate11+ signal so that Q1 is in a saturated conduction state. If it receives an instruction containing a set internal resistance from the main controller, the control unit detects the current data of the main circuit through the current sensor Hall1, and detects the voltage Vce between the collector and emitter of Q2 through the voltage sensor. If it is detected that the resistance obtained by dividing the voltage between the collector and emitter of Q2 by the current discharge current is less than the set internal resistance, the control unit immediately reduces the driving voltage Gate12+ of the gate of Q2, so that the on-resistance of Q2 increases, and the current flows through The current of the battery cluster BAT5 decreases, and gradually approaches the set internal resistance through repeated adjustments. If it is detected that the resistance obtained by dividing the voltage between the collector and emitter of Q2 by the current discharge current exceeds the set internal resistance, the control unit immediately increases the drive voltage Gate12+ of the gate of Q2, so that the on-resistance of Q2 is reduced, and the current flowing through the battery cluster becomes larger. By repeatedly adjusting the battery cluster, the set internal resistance is gradually approached, so that the discharge current flowing through the battery cluster can be controlled. If the control unit detects that the amplitude of Gate12+ has reached the control limit, it stops adjusting the drive voltage Gate12+ and maintains the drive voltage value at the control limit state. Fig. 9 and Fig.10 The control flow of the energy storage system master controller and the control flow of the control unit are shown respectively.

[0061] In another scenario, the main controller of the energy storage system no longer indicates the operating conditions to be entered by the control units of each battery cluster, nor does it indicate the set charge and discharge currents of each battery cluster. At this time, the charge and discharge operating conditions and charge and discharge currents in the energy storage system are switched or fluctuated unplanned.

[0062] In this scenario, the control unit can use method three to perform dual closed-loop control and one open-loop control on the electronic current limiter. Since the outer loop control responds relatively slowly and has a lower bandwidth (in this embodiment, the outer loop bandwidth is one tenth of the inner loop bandwidth), while the inner loop control responds relatively faster and has a larger bandwidth, method three uses the outer loop for voltage control and the inner loop for current control; since the closed-loop control responds slowly, in order to avoid overcurrent protection of the energy storage system caused by excessive voltage difference between the bus voltage and the battery cluster when switching between charging and discharging conditions, an open-loop control is added to the dual closed-loop control of the electronic current limiter, so that when the voltage difference between the bus voltage and the battery cluster is too large, the semiconductor electronic switch in the electronic current limiter is controlled to be saturated and turned on, thereby improving the overcurrent capacity for instantaneous large currents. The corresponding control flow chart is shown below. Fig.11 As shown, two PI controllers are used for closed-loop control. Fig.11 In the example, Abs represents the absolute value operation; V CE Represents the voltage across the electronic current limiter; the current charge and discharge current and the feedback V CE The voltages are processed by low-pass filtering; loop current limiting measures are adopted in the outer loop PI controller to prevent the loop current value from exceeding the limit value; Udc is the DC bus voltage, and Vbat is the voltage of the battery cluster.

[0063] Method three includes the following steps: obtaining a set internal resistance; when it is detected that the voltage difference between the DC bus and the battery cluster is greater than the set value, simultaneously controlling the charging semiconductor electronic switch Q1 and the discharging semiconductor electronic switch Q2 to be saturated and turned on; when it is detected that the voltage difference between the DC bus and the battery cluster is not greater than the set value, obtaining the target charge and discharge current according to the numerical difference between the voltage at both ends of the electronic current limiter and the target voltage, and according to the numerical difference between the charge and discharge current of the battery cluster and the target charge and discharge current, simultaneously controlling the gate voltage of the charging semiconductor electronic switch Q1 and the discharging semiconductor electronic switch Q2 to control the charge and discharge current, wherein the target voltage is determined based on the set internal resistance and the charge and discharge current.

[0064] refer to Figure 4 and Fig.11, the control unit uses the same control quantity to control Q1 and Q2 at the same time. The control unit collects the DC bus voltage and the voltage of the battery cluster. When it detects that the voltage difference between the DC bus and the battery cluster is greater than the set value, the control unit outputs a drive voltage of ≥10V to drive Q1 and Q2 to a saturated conduction state. When the voltage difference is greater than the set value, it indicates that the energy storage system may be in a state of conversion between charging and discharging conditions. If it is not controlled at this time, the instantaneous high current of the energy storage system may cause overcurrent protection; at this time, saturating Q1 and Q2 at the same time increases the overcurrent capacity and avoids the overcurrent protection problem during the switching process.

[0065] When the voltage difference between the DC bus and the battery cluster is detected to be less than the set value, the balancing control starts. If the control unit receives the instruction containing the set internal resistance from the main controller, it detects the current data of the main circuit through the current sensor Hall1 and detects the voltage V at both ends of the electronic current limiter through the voltage sensor. CE ; If V is detected CE The value of is less than the voltage value obtained by multiplying the set internal resistance and the current charge and discharge current. The control unit immediately reduces the driving voltage of the gates of Q1 and Q2, which increases the overall on-resistance of Q1 and Q2 and reduces the current flowing through the battery cluster BAT5. Through repeated adjustments, V CE The value gradually approaches the voltage value obtained by multiplying the set internal resistance and the current charge and discharge current; if V CE The value of is greater than the voltage value obtained by multiplying the set internal resistance and the current charge and discharge current. The control unit immediately increases the driving voltage of the gates of Q1 and Q2, so that the overall on-resistance of Q1 and Q2 decreases, and the current flowing through the battery cluster BAT5 increases. Through repeated adjustments, V CE The value gradually approaches the voltage value obtained by multiplying the set internal resistance and the current charge and discharge current, so that the discharge current flowing through the battery cluster can be controlled. If the control unit detects that the amplitude of the gate drive voltage of Q1 or Q2 has reached the control limit, it stops adjusting the drive voltage and maintains the drive voltage value at the control limit state.

[0066] exist Fig.11 In the control flow chart shown in the figure, since V CE The voltage is of a smaller magnitude. To improve control accuracy, V CE The voltage value and the value of the product of the set internal resistance and the current charge and discharge current are amplified by 10 times at the same time.

[0067] The above embodiments provide a method for controlling charging and discharging using an electronic current limiter in different scenarios, achieving rapid response and precise control, and can effectively avoid unexpected fluctuations in the DC bus voltage caused by sudden increases or decreases in load of the energy storage system.

[0068] In some of the embodiments, the control unit is used to disconnect the charging semiconductor electronic switch Q1 and turn on the switch Qx to control the bidirectional flyback DC-DC converter to exchange electric energy from the DC bus or the energy storage battery to the battery cluster when the energy storage system where the battery cluster is located is in a static state and the voltage difference between the DC bus of the energy storage system and the battery cluster exceeds a preset voltage value; until the voltage value at both ends of the electronic current limiter is less than a set value, the switch Qx is disconnected, the charging semiconductor electronic switch Q1 is turned on, and the current limiting control of the charging current of the battery cluster is achieved by controlling the gate voltage of the charging semiconductor electronic switch Q1.

[0069] refer to Figure 4 , the bidirectional flyback DC-DC converter can realize bidirectional transport of energy. In this embodiment, the bidirectional flyback DC-DC converter is mainly used to control the charge and discharge of the battery cluster when the voltage difference between the battery cluster and the battery bus is large, so as to realize the capacity adjustment of the battery cluster in the static state of the energy storage system (that is, the battery cluster system is not charged or discharged externally). For example, when the output end of the bidirectional flyback DC-DC converter of each battery cluster is connected to the DC bus or 24V power supply, and when the energy storage system is in the static stage and the DC bus voltage is high, the battery cluster that needs to be calibrated for capacity or SOC is first identified. For the battery cluster that needs to be calibrated for capacity or SOC, the control unit controls Q1 to be disconnected, Qx to be turned on, controls the duty cycle of Q5 and Q6, and the switching power supply works. The MCU detects the voltage across the electronic current limiter by detecting the AD1 and AD2 ports. If the voltage is less than the set value, Qx is disconnected and Q1 is controlled to start current limiting control.

[0070] In some of the embodiments, the control unit is used to turn off the charging semiconductor electronic switch Q1 and the discharging semiconductor electronic switch Q2 when the battery cluster is short-circuited, wherein a diode D1 is connected in reverse parallel between the collector of the charging semiconductor electronic switch Q1 and the DC bus, and a diode D2 is connected in reverse parallel between the collector of the discharging semiconductor electronic switch Q2 and the DC bus to provide a freewheeling circuit for the flyback energy generated by turning off the charging semiconductor electronic switch Q1 and the discharging semiconductor electronic switch Q2.

[0071] refer to Figure 6 When the MCU detects the Hall1 current and finds that the battery cluster is short-circuited, the MCU controls QC and QD to conduct through DO1 and DO2, lowering the drive voltage of Q1 and Q2, thereby quickly cutting off the charging or discharging circuit. The diodes D1 and D2 (reference Figure 4 ) provides a freewheeling circuit for the flyback energy generated by the rapid shutdown of Q1 and Q2. Fig.12 is a schematic diagram of a reverse diode clamping voltage spike according to an embodiment of the present application, such as Fig.12As shown, L1 and L2 represent the inductance of the circuit. The voltage spike formed by the flyback energy generated by the rapid shutdown of Q1 and Q2 flows to the positive or negative electrode of the DC bus after being clamped by the reverse diode.

[0072] In some of the embodiments, the control unit is used to increase the gate voltage of the charging semiconductor electronic switch Q1 and the discharging semiconductor electronic switch Q2 when the temperature of the charging semiconductor electronic switch Q1 and / or the discharging semiconductor electronic switch Q2 exceeds a set temperature threshold, so that the charging semiconductor electronic switch Q1 and the discharging semiconductor electronic switch Q2 enter a saturated conduction state; and turn on the relay K2 (K6) when the temperature of the charging semiconductor electronic switch Q1 and / or the discharging semiconductor electronic switch Q2 continues to exceed the set temperature threshold within a set time.

[0073] refer to Figure 4 and Figure 6 When the MCU of the control unit detects that the temperature of Q1 and Q2 exceeds the set threshold, the control unit will immediately increase the gate voltage of Q1 and Q2, control Q1 and Q2 to quickly enter the saturated conduction state, reduce the on-resistance, thereby reducing the heat generation of the device and protecting the device from damage due to overheating. If Q1 and Q2 still heat up severely within the set time in the saturated conduction state, the control unit closes the high-power relay switch K2 or K6 to bypass the current and reduce the current stress of Q1 and Q2.

[0074] This embodiment further provides a method for balancing a battery cluster of an energy storage system, which is applied to the above-mentioned balancing device for the battery cluster of the energy storage system. Fig.13 FIG. 1 is a flow chart of a method for balancing a battery cluster of an energy storage system according to an embodiment of the present application. Fig.13 As shown, the process includes the following steps: Step S1301, under a charging condition or a discharging condition, the internal resistance of the battery cluster is adjusted by changing the resistance of the electronic current limiter to control the charge balance between the battery clusters of the energy storage system.

[0075] Step S1302, when the energy storage system is in a static state, the bidirectional flyback DC-DC converter is controlled to exchange electric energy between the DC bus or the energy storage battery and the battery cluster, thereby controlling the charge balance between the battery cluster and other battery clusters connected in parallel to the DC bus.

[0076] Continue to refer Fig. 9 The control flow of the energy storage system master controller is shown.

[0077] If the energy storage system is in a static state, the main controller of the energy storage system collects real-time data from the control units and battery management systems in each battery cluster. The main controller sorts the battery clusters according to the SOC of each battery cluster and calculates the battery clusters that need to be balanced. The main controller sends a balancing control command to the control unit in the corresponding battery cluster. In response to the balancing control command, the control unit in the battery cluster controls the bidirectional flyback DC-DC converter to start adjusting the energy of the battery cluster. If the balancing of each battery cluster meets expectations, the main controller ends the balancing process of the energy storage system in a static state, otherwise it enters the next round of power balancing in a static state.

[0078] If the energy storage system is in the charging and discharging condition, the main controller of the energy storage system collects the real-time data of the control unit and the battery management system in each battery cluster, calculates the optimal charging and discharging current of each battery cluster, and sends the current control command to the control unit in the battery cluster based on the optimal charging and discharging current. After a delay of a period of time to wait for the control unit in each battery cluster to control the electronic current limiter to perform current limiting control, the main controller determines whether the charging and discharging current of each battery cluster meets expectations. If the charging and discharging current of each battery cluster meets expectations, the main controller ends the balancing processing of the energy storage system under the charging and discharging condition (each battery cluster continues to perform current limiting control according to the received current control command); if the charging and discharging current of each battery cluster does not meet expectations but the gate voltage of the electronic current limiter in the battery cluster has reached the control limit, the main controller also ends the balancing processing of the energy storage system under the charging and discharging condition (each battery cluster continues to perform current limiting control according to the received current control command), otherwise it enters the next round of current limiting control under the charging and discharging condition.

[0079] Through the above process, the master controller of the energy storage system collects the SOC, SOH, current, voltage, fault and other status information of each battery cluster through real-time communication with the control unit of the electronic current limiter in each battery cluster and the BMS; during the charging and discharging operation of the battery system, since the internal resistance and SOC of multiple battery clusters cannot be completely consistent, when the total charging and discharging current value of the energy storage system is constant, there will inevitably be an imbalance in the current between clusters, such as the battery cluster with small internal resistance is allocated a larger current, and the battery cluster with large internal resistance is allocated a smaller current. The master controller calculates the optimal charging and discharging current distribution plan for each battery cluster based on the collected SOC, SOH, current, voltage, fault and other status information of each battery cluster, and sends the distribution plan to the control unit of the electronic current limiter in each battery cluster. The control unit in the electronic current limiter adjusts the driving voltages of Q1 and Q2 according to the received target current, thereby adjusting the DC internal resistance of the battery cluster to achieve the redistribution of the charging and discharging currents of multiple battery clusters. In specific implementation, the maximum operating voltage of the selected discharge switch Q2 is greater than the maximum operating voltage of the energy storage system. This allows the control unit in the electronic current limiter to quickly turn off Q2 when it detects that a discharge overcurrent occurs in the battery cluster, thereby disconnecting the discharge circuit of the battery cluster and preventing the overcurrent fault from expanding.

[0080] Continue to refer Fig.10 The control flow of the control unit is shown.

[0081] When the energy storage system is started and initialized, the MCU controls Q1, Q1, K2, Qx, Q5, and Q6 to be disconnected.

[0082] If the energy storage system is in a static state, depending on the DC bus or energy storage battery connected to the output end of the bidirectional flyback DC-DC converter, the DC bus or energy storage battery is used as the hub of energy exchange for balancing control.

[0083] If the energy storage system is in the charging and discharging condition, the MCU detects the voltage across the electronic current limiter through the AD1 and AD2 ports, detects the temperature of the Q1, Q2 and K2 shells through the AD4, AD5 and AD6 ports, and detects the current through the AD3 port to determine whether the status of each device is normal. If it is abnormal, the protection operation is performed; if it is normal, the charging and discharging control is performed. In the charging and discharging control, the MCU controls Q1 and Q2 to be saturated and turned on, and K2 is closed. At this time, the electronic current limiter does not affect the charging and discharging control process. If the MCU of the control unit receives the current control command from the main controller, it starts the current limiting control according to the current control command.

[0084] Fig.14 FIG. 1 is a flow chart of a control unit in a battery cluster performing charging current limiting control according to an embodiment of the present application. Fig.14As shown, when the current control command received by the MCU of the control unit from the main controller is a charging current limiting control command, the MCU controls K2 to disconnect, and the MCU detects the AD1 and AD2 ports to determine whether the voltage across the electronic current limiter is greater than the set value. If the voltage across the electronic current limiter is greater than the set value, the MCU controls Q1 to disconnect, Qx to turn on, and controls the duty cycle of Q5 and Q6. The switching power supply starts working until the voltage across the electronic current limiter is less than the set value and then disconnects Qx. If the voltage across the electronic current limiter is not greater than the set value, the MCU reduces the voltage amplitude of the drive signal Gate11+ of Q1 by 0.1V, refreshes various real-time data after a delay, and determines whether Q1 and Q2 are overheated. If overtemperature exists, the MCU controls K2 to close; if not, it continues to determine whether a short circuit occurs in the battery cluster; if a short circuit occurs, the MCU controls Q1 and Q2 to disconnect; if no short circuit occurs, it continues to determine whether the charging current reaches the predetermined value indicated by the current control command; if so, it maintains the current drive signal to continue current limiting control; otherwise, it continues to reduce the voltage amplitude of the Q1 drive signal Gate11+ until the Q1 drive signal reaches the adjustment limit.

[0085] Fig.15 FIG. 1 is a flow chart of the discharge current limiting control performed by the control unit in the battery cluster according to an embodiment of the present application. Fig.15 As shown, when the current control command received by the MCU of the control unit from the main controller is a discharge current limiting control command, the MCU controls K2 to disconnect, and the MCU reduces the voltage amplitude of the Q2 drive signal Gate12+ by 0.1V, and refreshes various real-time data after a delay to determine whether Q1 and Q2 are overheated. If there is overheating, the CU controls K2 to close; if there is no overheating, it continues to determine whether the battery cluster has a fault short circuit; if a fault short circuit occurs, the MCU controls Q1 and Q2 to disconnect, and if there is no fault short circuit, it continues to determine whether the discharge current reaches the predetermined value indicated by the current control command. If it reaches it, the current drive signal is maintained to continue the current limiting control, otherwise the voltage amplitude of the Q2 drive signal Gate12+ is continuously reduced until the Q2 drive signal reaches the adjustment limit.

[0086] This embodiment also provides an energy storage system. Fig.16 is a schematic diagram of the structure of the energy storage system of an embodiment of the present application, such as Fig.16 As shown, the energy storage system includes a DC-AC converter connected in series between a DC bus and an AC line, and a plurality of battery clusters connected in parallel with the DC bus. Fig.16The battery clusters are numbered 1#, 2#, ... N# respectively; each battery cluster includes one or more first battery modules 40 (also called smart battery modules) connected in series, and one or more second battery modules 50 (relative to the smart battery modules, called conventional battery modules), wherein the first battery module 40 includes the above-mentioned battery cluster balancing device 100.

[0087] It should be noted that the term "including" and its variations used in the embodiments of the present application are open inclusions, that is, "including but not limited to". The term "based on" means "based at least in part on". The term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one other embodiment"; the term "some embodiments" means "at least some embodiments". The modifications of "one" and "multiple" mentioned in the embodiments of the present application are illustrative and not restrictive. Those skilled in the art should understand that unless otherwise clearly indicated in the context, it should be understood as "one or more".

[0088] The various steps described in the method implementation scheme provided by the embodiments of the present application can be performed in different orders and / or performed in parallel. In addition, the method implementation scheme may include additional steps and / or omit the steps shown. The scope of protection of the present application is not limited in this respect.

[0089] The term "embodiment" in this specification refers to specific features, structures or characteristics described in conjunction with the embodiment that can be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily mean the same embodiment, nor does it mean that it is mutually exclusive with other embodiments and is independent or optional. The various embodiments in this specification are described in a related manner, and the same or similar parts between the various embodiments refer to each other. In particular, for the device, equipment, and system embodiments, since they are basically similar to the method embodiments, the description is relatively simple, and the relevant parts refer to the partial description of the method embodiment.

[0090] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of protection. It should be pointed out that, for a person of ordinary skill in the art, several modifications and improvements can be made without departing from the concept of the present application, and these all belong to the scope of protection of the present application. Therefore, the scope of protection of the present application shall be subject to the attached claims.

Claims

1. A balancing device for a battery cluster of an energy storage system, characterized in that include: An electronic current limiter, a switch (Qx) and a bidirectional flyback DC-DC converter, wherein: The electronic current limiter is connected in series with a battery cluster of an energy storage system, and the electronic current limiter is used to change the resistance of the electronic current limiter to adjust the internal resistance of the battery cluster; The input side of the bidirectional flyback DC-DC converter is connected to the battery cluster via the switch (Qx), and the output side is connected to a DC power source; The bidirectional flyback DC-DC converter is used to control the charge balance between the battery cluster and other battery clusters connected in parallel to the DC bus when the energy storage system is in a static state.

2. The battery cluster balancing device according to claim 1, characterized in that: The electronic current limiter comprises: at least one set of two charging semiconductor electronic switches (Q1) and discharging semiconductor electronic switches (Q2) having freewheeling diodes connected back to back; Preferably, the charging semiconductor electronic switch (Q1) and the discharging semiconductor electronic switch (Q2) are bipolar junction transistors, field effect transistors or insulated gate bipolar transistors; Preferably, the electronic current limiter comprises a plurality of groups of two charging semiconductor electronic switches (Q1) and two discharging semiconductor electronic switches (Q2) having freewheeling diodes connected back to back.

3. The battery cluster balancing device according to claim 2, characterized in that: A diode (D1) is connected in reverse parallel between the collector of the charging semiconductor electronic switch (Q1) and the DC bus; and / or A diode (D2) is connected in reverse parallel between the collector of the discharge semiconductor electronic switch (Q2) and the DC bus.

4. The battery cluster balancing device according to claim 2, characterized in that: A relay is connected in parallel between the input end and the output end of the electronic current limiter.

5. The battery cluster balancing device according to claim 2, characterized in that: The device further includes a control unit, which is connected to the electronic current limiter and the bidirectional flyback DC-DC converter respectively, and is used to control the electronic current limiter by any of the following methods: Method 1: Obtaining a charging instruction and setting a charging current; in response to the charging instruction, controlling the discharging semiconductor electronic switch (Q2) to be saturated and turned on, and controlling the gate voltage of the charging semiconductor electronic switch (Q1) according to the difference between the charging current of the battery cluster and the set charging current, so as to control the charging current; Obtaining a discharge instruction and setting a discharge current; in response to the discharge instruction, controlling the charging semiconductor electronic switch (Q1) to be saturated and turned on, and controlling the gate voltage of the discharging semiconductor electronic switch (Q2) according to the difference between the discharge current of the battery cluster and the set discharge current, so as to control the discharge current; Method 2: Obtaining a charging instruction and setting an internal resistance; in response to the charging instruction, controlling the discharging semiconductor electronic switch (Q2) to be saturated and turned on, obtaining a target charging current according to a difference in resistance between the collector and the emitter of the charging semiconductor electronic switch (Q1) relative to the set internal resistance, and controlling a gate voltage of the charging semiconductor electronic switch (Q1) according to a difference in the charging current of the battery cluster relative to the target charging current to control the charging current, wherein the resistance between the collector and the emitter of the charging semiconductor electronic switch (Q1) is determined based on a voltage between the collector and the emitter of the charging semiconductor electronic switch (Q1) and the charging current; Obtaining a discharge instruction and setting an internal resistance; in response to the discharge instruction, controlling the charging semiconductor electronic switch (Q1) to be saturated and turned on, obtaining a target discharge current according to a difference in resistance between the collector and the emitter of the discharging semiconductor electronic switch (Q2) relative to the set internal resistance, and controlling a gate voltage of the discharging semiconductor electronic switch (Q2) according to a difference in the discharge current of the battery cluster relative to the target discharge current to control the discharge current, wherein the resistance between the collector and the emitter of the discharging semiconductor electronic switch (Q2) is determined based on a voltage between the collector and the emitter of the discharging semiconductor electronic switch (Q2) and the discharge current; Method 3: Acquire a set internal resistance; when it is detected that the voltage difference between the DC bus and the battery cluster is greater than the set value, simultaneously control the charging semiconductor electronic switch (Q1) and the discharging semiconductor electronic switch (Q2) to be saturated and turned on; when it is detected that the voltage difference between the DC bus and the battery cluster is not greater than the set value, acquire a target charge and discharge current according to the value difference between the voltage at both ends of the electronic current limiter and the target voltage, and according to the value difference between the charge and discharge current of the battery cluster and the target charge and discharge current, simultaneously control the gate voltage of the charging semiconductor electronic switch (Q1) and the discharging semiconductor electronic switch (Q2) to control the charge and discharge current, wherein the target voltage is determined based on the set internal resistance and the charge and discharge current.

6. The battery cluster balancing device according to claim 2, characterized in that: The device also includes a control unit, which is used to: When the energy storage system is in a stationary state and the voltage difference between the DC bus of the energy storage system and the battery cluster exceeds a preset voltage value, the charging semiconductor electronic switch (Q1) is disconnected, the switch (Qx) is turned on, and the bidirectional flyback DC-DC converter is controlled to exchange electric energy from the DC bus or the energy storage battery to the battery cluster; until the voltage value at both ends of the electronic current limiter is less than a set value, the switch (Qx) is disconnected, the charging semiconductor electronic switch (Q1) is turned on, and the current limiting control of the charging current of the battery cluster is achieved by controlling the gate voltage of the charging semiconductor electronic switch (Q1).

7. The battery cluster balancing device according to claim 3, characterized in that: The device further comprises a control unit, which is used to disconnect the charging semiconductor electronic switch (Q1) and the discharging semiconductor electronic switch (Q2) when the battery cluster is short-circuited.

8. The battery cluster balancing device according to claim 4, characterized in that: The device also includes a control unit, which is used to: When the temperature of the charging semiconductor electronic switch (Q1) and / or the discharging semiconductor electronic switch (Q2) exceeds a set temperature threshold, controlling the charging semiconductor electronic switch (Q1) and the discharging semiconductor electronic switch (Q2) to be saturated and turned on; When the temperature of the charging semiconductor electronic switch (Q1) and / or the discharging semiconductor electronic switch (Q2) continuously exceeds the set temperature threshold within a set time period, the relay is turned on.

9. A method for balancing a battery cluster of an energy storage system, applied to a balancing device for a battery cluster of an energy storage system according to any one of claims 1 to 8, characterized in that: The method comprises: Under charging or discharging conditions, the internal resistance of the battery cluster is adjusted by changing the resistance of the electronic current limiter to control the charge balance between the battery clusters of the energy storage system; When the energy storage system is in a static state, the bidirectional flyback DC-DC converter is controlled to exchange electric energy between the DC bus or the energy storage battery and the battery cluster, thereby controlling the charge balance between the battery cluster and other battery clusters connected in parallel to the DC bus.

10. An energy storage system, characterized in that It comprises a DC-AC converter connected in series between a DC bus and an AC line, and a plurality of battery clusters connected in parallel with the DC bus; wherein the battery cluster comprises a first battery module and a second battery module connected in series, and the first battery module comprises a balancing device for the battery cluster as claimed in any one of claims 1 to 8.

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