Active equalization unit of energy storage battery pack and energy storage battery pack

Abstract

An energy storage battery pack active equalization unit and an energy storage battery pack, the energy storage battery pack active equalization unit comprises a controller, an MUX chip, a plurality of MOS tubes, a plurality of isolation transformers and a plurality of constant current pumps, the controller and the MUX chip are connected in series, the MUX chip is electrically connected with the plurality of parallel MOS tubes, each MOS tube is connected with the isolation transformer and the constant current pump in series and then is connected to a battery monomer of the energy storage battery pack, and the isolation transformers are electrically connected with the isolation transformers. The isolation transformer is arranged between the MOS tube and the constant flow pump; the number of the MOS tubes, the number of the isolation transformers and the number of the constant flow pumps are the same as the number of the battery monomers in the energy storage battery pack, and the number of the battery monomers is at least two. The isolation transformer transmits the primary side current to the constant flow pump after the primary side current is subjected to electricity-magnetism-electricity isolation, and the constant flow pump pumps the current into the battery pack for charging. The utility model has the advantages of strong insulating property and high reliability, and solves the problems of easy insulation breakdown and easy damage of wiring open-circuit devices when the existing product is used in high-voltage energy storage occasions.

Description

Technical Field

[0001] This utility model belongs to the field of energy storage battery technology, and in particular relates to an active balancing unit for energy storage battery packs and an energy storage battery pack. Background Technology

[0002] The battery pack of an energy storage system consists of many individual lithium batteries. Due to individual differences in the batteries, the battery voltage will be inconsistent during operation, which will affect the overall battery capacity and charging efficiency. To solve this problem, the batteries need to be balanced.

[0003] Currently, there are two methods: passive balancing and active balancing. Passive balancing consumes the energy of a battery with a higher voltage through a resistor, which results in low battery life and excessive heat generation. Active balancing can extend battery life more efficiently and reduce the heat generated by passive balancing. However, active balancing generally has the problem of high cost.

[0004] To reduce the cost of active balancing, prior art 1 (CN115483738A) discloses a switchable active balancing method, and prior art 2 (CN115622187A) further discloses a circuit that uses PMOS (MOSFET) as a control switch for switching. However, prior art 1 and prior art 2 use a switching method, which has two problems: 1) Due to the voltage limitation of the switching device, it is difficult to apply to high-voltage energy storage, such as high-voltage energy storage above 1500VDC; 2) The control of the switching device is complex, and there is a risk of damage caused by the transient conduction of the switching device due to timing competition during switching.

[0005] To address the aforementioned issues, prior art 3 (CN113193618A) discloses the use of thyristors instead of MOSFETs or IGBTs to increase the maximum breakdown voltage of a single unit for applications up to 1500VDC. However, the improvement in withstand voltage is limited, and the thyristor still suffers from breakdown issues when applied to voltages exceeding 1500VDC.

[0006] Existing technology 4 (CN112060972B) adopts an active balancing circuit based on a constant power transformer. Through a chip select chip, only one transformer is turned on at a time. The charge pump on the main side of the transformer acts as a self-excited source to replenish the battery cells connected to the secondary side of the transformer. Through communication via an isolated CAN chip, it can withstand a maximum high voltage of 3500V. However, this method has the following problems: when the connection with the battery is open due to poor contact or other reasons, the energy output by the charge pump acting as a self-excited source through the transformer cannot be discharged and continues to accumulate. The voltage on the secondary side of the transformer continues to rise, eventually leading to overvoltage damage to the device. Utility Model Content

[0007] The purpose of this invention is to solve the problems of insulation breakdown of switching devices and easy damage of open-circuit devices in high-voltage energy storage applications.

[0008] The objective of this utility model is achieved through the following technical solution:

[0009] The first aspect of this utility model provides an active balancing unit for an energy storage battery pack, including a controller, a MUX chip, multiple MOSFETs, multiple isolation transformers, and multiple constant current pumps.

[0010] The controller and the MUX chip are connected in series. The MUX chip is electrically connected to multiple parallel MOSFETs. Each MOSFET is connected in series with an isolation transformer and a constant current pump and then connected to a battery cell of the energy storage battery pack. The isolation transformer is located between the MOSFET and the constant current pump.

[0011] The number of MOSFETs, isolation transformers, and constant current pumps is the same as the number of individual battery cells in the energy storage battery pack, with at least two individual battery cells.

[0012] Preferably, the controller includes a microcontroller chip.

[0013] Preferably, the MUX chip has a periodic cyclic dynamic conduction structure.

[0014] Preferably, the MUX chip has an 8-to-1 or 16-to-1 conduction structure.

[0015] Preferably, the MOS transistor is an N-channel MOS transistor.

[0016] Preferably, the constant current pump includes a diode, a capacitor, a Zener diode, and a resistor;

[0017] The negative terminal of the diode is connected to the capacitor, and the Zener diode and the resistor are connected in series and then in parallel with the capacitor.

[0018] Preferably, it also includes a driver, which is disposed between the controller and the MUX chip and connected in series.

[0019] Preferably, the isolation transformer is a transformer with a sandwich winding structure.

[0020] Preferably, it also includes overcurrent protection, which includes a sampling resistor and an amplifier connected in series. The sampling resistor is electrically connected to an isolation transformer, and the output of the amplifier is electrically connected to a controller.

[0021] The second aspect of this utility model provides an energy storage battery pack.

[0022] This includes the active balancing unit for energy storage battery packs, as described above.

[0023] This utility model has the following outstanding beneficial effects:

[0024] 1. This utility model ensures effective isolation between the switching device and the high-voltage side by placing the isolation transformer in front of the switching device. The isolation transformer adopts a sandwich winding method, which makes the insulation performance as high as 3000VDC. It has a wide range of applications and high reliability. It solves the problem that the switching device is prone to insulation breakdown and open circuit device damage when used in high-voltage energy storage applications, and reduces the application cost.

[0025] 2. This utility model incorporates a MUX chip to charge individual battery cells in rotation, achieving balanced charging of the energy storage battery pack, thereby protecting the energy storage battery pack and extending its service life.

[0026] 3. This utility model is equipped with a driver, which further improves the driving capability of the PWM square wave signal, thereby improving the efficiency of active balancing and reducing the heat generation of the energy storage battery pack. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the active balancing unit of the energy storage battery pack in this embodiment;

[0028] Figure 2 This is a schematic diagram of the constant flow pump principle of the active balancing unit of the energy storage battery pack in this embodiment;

[0029] In the diagram, 1-controller, 2-MUX chip, 3-MOS transistor, 4-isolation transformer, 5-constant current pump, 6-diode, 7-capacitor, 8-Zenith diode, 9-resistor, 10-driver, 11-overcurrent protection. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this utility model clearer, the technical solutions of this utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. The embodiments described in this application are merely some embodiments of this utility model, and not all embodiments. Based on the spirit of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0031] Example 1

[0032] See appendix Figure 1Embodiment 1 of this utility model provides an active balancing unit for an energy storage battery pack, including a controller 1, a MUX chip 2, multiple MOSFETs 3, multiple isolation transformers 4, and multiple constant current pumps 5. The controller 1 and the MUX chip 2 are connected in series. The MUX chip 2 is electrically connected to multiple parallel MOSFETs 3. Each MOSFET 3 is connected in series with the isolation transformer 4 and the constant current pump 5 and then connected to a battery cell in the energy storage battery pack. The isolation transformer is positioned between the MOSFET 3 and the constant current pump 5. The controller 1 outputs a control signal to control the connection between the MUX chip 2 and the MOSFETs 3. The isolation transformer 4 transmits the primary current to the constant current pump 5 after electro-magnetic-electro-isolation. The constant current pump 5 pumps the current into each battery cell of the energy storage battery pack for charging. The number of MOSFETs 3, isolation transformers 4, and constant current pumps 5 are all the same as the number of battery cells in the energy storage battery pack, with at least two battery cells.

[0033] In a preferred but non-limiting embodiment of this invention, the controller 1 includes a microcontroller (MCU) chip. The control signal output by the controller 1 is a PWM square wave signal with a duty cycle between 1% and 50%. The MUX chip 2 is an 8-to-1 or 16-to-1 chip with a periodic cyclic conduction structure, allowing the PWM square wave signal to connect to the corresponding conducting lines, thereby achieving balanced charging of each battery cell in the energy storage battery pack. The MOSFET 3 is an N-channel MOSFET with a parasitic capacitance of less than 1 nF. The isolation transformer 4 uses a sandwich winding method and has an insulation withstand voltage greater than or equal to 3000 VDC.

[0034] Unlike existing products where the switching devices are directly located on the high-voltage side of the battery, in this embodiment of the invention, the switching devices such as the MOSFET 3 and the MUX chip 2 are isolated from the high-voltage side of the battery by an isolation transformer 4. The isolation transformer is located before the switching devices to prevent the switching devices from breaking down. Because the breakdown voltage of the isolation transformer can be made very high, it solves the problem of low withstand voltage of existing switching devices such as MOSFETs, IGBTs, and thyristors, which are prone to insulation breakdown. Moreover, the isolation transformer does not have the problem of transient conduction of the switch, thus solving the problem of damage caused by transient conduction of the switch in existing products.

[0035] See appendix Figure 2In this embodiment, the constant current pump 5 includes a diode 6, a capacitor 7, a Zener diode 8, and a resistor 9. The cathode of the diode 6 is connected to the capacitor 7. The Zener diode 8 and the resistor 9 are connected in series and then in parallel with the capacitor 7. The diode 6 enables unidirectional pumping of AC charge. The pumped charge enters the capacitor 7 to eliminate ripple. Unlike traditional constant current pumps, this constant current pump can solve the problem of excessively high output voltage causing device damage when the wiring between the battery cell is broken or has poor contact. The forward voltage of the Zener diode 8 is greater than the maximum voltage of the battery cell. When the wiring is normal, the Zener diode 8 does not conduct. When the wiring is broken, open circuit, or has poor contact, the output voltage will increase rapidly. At this time, the Zener diode 8 conducts, providing a stable load through the resistor 9, thereby avoiding excessively high output voltage that could damage the device. This solves the problem of easy device damage when the wiring is open in existing products.

[0036] When the voltage of a single battery cell is too low and exceeds the threshold, the internal structure of the MUX chip is transformed into a circuit structure that conducts the abnormal battery cell. This causes the constant current pump 5 on the circuit containing the abnormal battery cell to pump the alternating current output by the isolation transformer 4 of the corresponding channel into the battery cell in one direction, thereby achieving balanced charging.

[0037] In this embodiment, overcurrent protection is also included. The overcurrent protection includes a sampling resistor and an amplifier (not shown in the figure). The sampling resistor and the amplifier are connected in series. The sampling resistor of the overcurrent protection is connected in series to the isolation transformer circuit to monitor the primary charging current of the isolation transformer. The voltage signal across the sampling resistor is output by the amplifier and connected to the controller to realize real-time monitoring of the primary charging current of the isolation transformer. When the sampling resistor detects an overcurrent, all circuits inside the MUX chip are disconnected to stop charging in time and avoid abnormal situations such as overcurrent caused by output short circuit or long-term high-current charging of the isolation transformer.

[0038] These measures have solved the problems of insulation breakdown and open-circuit device damage in existing products used in high-voltage energy storage applications.

[0039] Example 2

[0040] See appendix Figure 1Embodiment 2 of this utility model provides an active balancing unit for an energy storage battery pack, including a controller 1, a MUX chip 2, multiple MOSFETs 3, multiple isolation transformers 4, multiple constant current pumps 5, and a driver 10. The controller 1, driver 10, and MUX chip 2 are connected in series. Multiple parallel MOSFETs are electrically connected to the MUX chip 2. Each MOSFET is connected in series with the isolation transformers 4 and constant current pumps 5 and then connected to a single cell in the energy storage battery pack. The isolation transformers are positioned between the MOSFETs 3 and the constant current pumps 5. The controller 1 outputs a control signal to control the MOSFETs 3. The isolation transformers 4 transmit the primary current to the constant current pumps 5 after electro-magnetic-electro-isolation. The constant current pumps 5 pump the current into each cell of the energy storage battery pack for charging. The number of MOSFETs 3, isolation transformers 4, and constant current pumps 5 are all the same as the number of cells in the energy storage battery pack, with at least two cells per cell.

[0041] In a preferred but non-limiting embodiment of this invention, the controller 1 includes a microcontroller (MCU) chip. The control signal output by the controller 1 is a PWM square wave signal with a duty cycle between 1% and 50%. The MUX chip 2 is an 8-to-1 or 16-to-1 chip with a periodic cyclic conduction structure, allowing the PWM square wave signal to connect to the corresponding conducting lines, thereby achieving alternating and balanced charging of individual battery cells within the energy storage battery pack. The MOS transistor 3 is an N-channel MOS transistor with a parasitic capacitance of less than 1nF. The isolation transformer 4 uses a sandwich winding method and has an insulation withstand voltage greater than or equal to 3000VDC. The rise and fall times of the output signal from the driver 10 are both less than 10ns. Compared to embodiment 1, embodiment 2 of this invention further improves the driving capability of the PWM square wave signal by adding a driver, thereby improving the efficiency of active balancing and reducing heat generation.

[0042] Unlike existing products where the switching devices are directly located on the high-voltage side of the battery, in this example, the switching devices such as MOSFET 3 and MUX chip 2 are isolated from the high-voltage side of the battery by an isolation transformer 4. The isolation transformer is located before the switching devices to prevent the switching devices from breaking down. Because the breakdown voltage of the isolation transformer can be made very high, it solves the problem of low withstand voltage of existing switching devices such as MOSFETs, IGBTs, and thyristors, which are prone to insulation breakdown. Moreover, the isolation transformer does not have the problem of transient conduction of the switch, which solves the problem of damage caused by transient conduction of the switch in existing products.

[0043] See appendix Figure 2In this embodiment, the constant current pump 5 includes a diode 6, a capacitor 7, a Zener diode 8, and a resistor 9. The cathode of the diode 6 is connected to the capacitor 7. The Zener diode 8 and the resistor 9 are connected in series and then in parallel with the capacitor 7. The diode 6 enables unidirectional pumping of AC charge. The pumped charge enters the capacitor 7 to eliminate ripple. Unlike traditional constant current pumps, this constant current pump can solve the problem of excessively high output voltage causing device damage when the wiring between the battery cell is broken or has poor contact. The forward voltage of the Zener diode 8 is greater than the maximum voltage of the battery cell. When the wiring is normal, the Zener diode 8 does not conduct. When the wiring is broken, open circuit, or has poor contact, the output voltage will increase rapidly. At this time, the Zener diode 8 conducts, providing a stable load through the resistor 9, thereby avoiding excessively high output voltage that could damage the device. This solves the problem of easy device damage when the wiring is open in existing products.

[0044] When the voltage of a single battery cell is too low and exceeds the threshold, the internal structure of the MUX chip is transformed into a circuit structure that conducts the abnormal battery cell. This causes the constant current pump 5 on the circuit containing the abnormal battery cell to pump the alternating current output by the isolation transformer 4 of the corresponding channel into the battery cell in one direction, thereby achieving balanced charging.

[0045] In this embodiment, overcurrent protection is also included. The overcurrent protection includes a sampling resistor and an amplifier (not shown in the figure). The sampling resistor and the amplifier are connected in series. The sampling resistor of the overcurrent protection is connected in series to the isolation transformer circuit to monitor the primary charging current of the isolation transformer. The voltage signal across the sampling resistor is output by the amplifier and connected to the controller to realize real-time monitoring of the primary charging current of the isolation transformer. When the sampling resistor detects an overcurrent, all circuits inside the MUX chip are disconnected to stop charging in time and avoid abnormal situations such as overcurrent caused by output short circuit or long-term high-current charging of the isolation transformer.

[0046] These measures have solved the problems of insulation breakdown and open-circuit device damage in existing products used in high-voltage energy storage applications.

[0047] This utility model embodiment also provides an energy storage battery pack, including the energy storage battery pack active balancing unit as described above.

[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of this utility model and not to limit it. Although the utility model has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of this utility model. Any modifications or equivalent substitutions that do not depart from the spirit and scope of this utility model should be covered within the protection scope of the claims of this utility model.

Claims

1. An active balancing unit for an energy storage battery pack, comprising a controller (1), a MUX chip (2), multiple MOSFETs (3), multiple isolation transformers (4), and multiple constant current pumps (5), characterized in that: The controller (1) and the MUX chip (2) are connected in series. The MUX chip (2) is electrically connected to multiple parallel MOS transistors (3). Each MOS transistor (3) is connected in series with the isolation transformer (4) and the constant current pump (5) and then connected to the battery cell of the energy storage battery pack. The isolation transformer is located between the MOS transistor (3) and the constant current pump (5). The number of MOSFETs (3), isolation transformers (4) and constant current pumps (5) are the same as the number of individual battery cells in the energy storage battery pack, and the number of individual battery cells is at least 2.

2. The active balancing unit for energy storage battery packs according to claim 1, characterized in that: The controller (1) includes a microcontroller chip.

3. The active balancing unit for energy storage battery packs according to claim 1, characterized in that: The MUX chip (2) has a periodic dynamic conduction structure.

4. The active balancing unit for energy storage battery packs according to claim 3, characterized in that, The MUX chip (2) has an 8-to-1 or 16-to-1 conduction structure.

5. The active balancing unit for energy storage battery packs according to claim 1, characterized in that: The MOS transistor (3) is an N-channel MOS transistor.

6. The active balancing unit for energy storage battery packs according to claim 1, characterized in that: The constant flow pump (5) includes a diode (6), a capacitor (7), a Zener diode (8), and a resistor (9); The negative terminal of the diode (6) is connected to the capacitor (7), and the Zener diode (8) and the resistor (9) are connected in series and then in parallel with the capacitor (7).

7. The active balancing unit for energy storage battery packs according to claim 1, characterized in that: It also includes a driver (10) which is disposed between the controller (1) and the MUX chip (2) in series connection.

8. The active balancing unit for energy storage battery packs according to claim 1, characterized in that: The isolation transformer (4) is a transformer with a sandwich winding structure.

9. The active balancing unit for energy storage battery packs according to claim 1, characterized in that: It also includes overcurrent protection (11), which includes a sampling resistor and an amplifier connected in series. The sampling resistor is electrically connected to the isolation transformer (4), and the output of the amplifier is electrically connected to the controller (1).

10. An energy storage battery pack, characterized in that: Includes the active balancing unit for energy storage battery packs as described in any one of claims 1-9.

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