TWM537345U - Active balancing system of battery pack - Google Patents

Description

Battery pack active balancing system

This creation is about a power balance technology for rechargeable batteries, and in particular refers to a battery pack active balance system.

Although lithium-ion batteries have good performance and high safety, they must still avoid overcharging, over-discharging or over-temperature conditions. In order to extend battery life and protect users' safety, a battery management system must be constructed (Battery). The Management System (BMS) ensures that the battery operates within a safe range. Basically, the main function of the battery management system is to measure and protect the voltage of a single cell. In the series battery pack, the battery cell may have an inconsistent voltage of the battery due to internal resistance or process. Such a problem may cause the battery pack to be overcharged or over-discharged in advance due to an early failure of the battery cell. The efficiency and longevity of the group.

In fact, there is a slight difference in the internal resistance and capacity of each cell. This difference will gradually increase with the number of charge and discharge cycles. If there is no management, the difference between the cells will be expanded to between the battery module and the module. Therefore, the battery modules cannot be in a consistent state. The inconsistency between the modules will still cause the battery pack to overcharge and over-discharge early. Therefore, the inconsistency between the cells and the modules must be corrected by proper management system to fully realize the performance of the lithium-iron battery. To improve this problem, we must add a balancing mechanism. Know the importance of BMS and balance mechanisms.

There is a certain degree of management system available in low-voltage equipment. For example, battery management technology is already quite mature in various hand-held devices. Major IC companies such as Texas Instruments Texas Instruments, Linear Technology and Maxism have commercial chip products for battery management ICs, and have been widely used in hand-held products, but these exclusive battery management ICs are mostly managed to manage small capacity, small series parallel The battery pack has almost no battery core balancing mechanism built in.

If the battery pack is used in large-scale power storage applications such as high-voltage energy storage systems or electric buses, the problems caused by imbalance between cells or modules will no longer be ignored. For example, electric vehicles are the most People's rickets should be the price and age of the battery, and the reason is that if the existing battery management technology does not actually perform the balance between the cells or between the modules, it will cause the weakest cells to trigger the protection system to stop operation early. Reduce the efficiency of use, or the system does not immediately protect the weakest cells from overcharge/overdischarge, reducing the life of the overall energy storage device.

The current uniform balanced battery technology is mainly divided into two balanced modes: active technology and passive technology. The cell balancing mechanism is an important technology to extend the battery life. The early battery management systems are based on passive balancing. Passive balancing technology mainly achieves the balance effect by consuming battery energy for a long time, and does not actively pull up the single cell power of the lowest voltage or power in the series battery pack, so it is called passive balance method. Although this method is simple and The disadvantage of low cost, but low efficiency and long balance time is less suitable for high capacity battery packs.

The active balancing method charges the smallest voltage cell in the battery pack, raises its voltage to the same voltage as the maximum voltage, and then continues to perform the same action for the remaining cells until all cell voltages are in equilibrium. It can be divided into the following balance modes due to different actuation modes: inductive balance method and capacitive balance method. The inductive balance method or the capacitive balance method is a uniform balanced sub-circuit with an inductor or a capacitor and a switch connected in parallel in the battery pack. The cell that detects the highest voltage or the amount of electricity stores the energy in the inductor or capacitor, and The switching circuit switches it to the cell of the lowest voltage or electric quantity, repeats the same action until the voltage or the electric quantity of all the single cells is evenly balanced, but the energy conversion of this method is limited by the capacity of the inductor or the capacitor, and the balance time is long. It is not applicable where the lithium ion battery can tolerate large current charging and discharging. Multi-winding transformer balancing method: a transformer with a secondary winding for multiple windings and a switching circuit outside each winding, in addition to charging the series battery pack at the same time, the switch can also control the charging of a single battery with a lower voltage or power. Since the number of turns of the multiple windings on the secondary side is the same, it can be regarded as constant voltage charging, and when all the control switches are turned on to charge all the single cells, the battery with higher power will obtain a lower charge, and vice versa. The amount, so the effect of balance can be achieved after charging for a period of time. However, in reality, the coupled windings have mutual inductance and leakage inductance. Even if the number of turns is the same, it is impossible to obtain the same voltage, and the volume will be too large due to multiple windings.

In high-series applications, the battery packs are usually distributed and managed in a modular manner. Even if the battery management system provided by the current market can balance the cells in the module, it cannot ensure the balance between the modules. The inconsistency between the modules still causes the inconsistency of the battery pack's working state, so the balance existing only in the module still falls short.

The battery pack application environment with large capacity and high serial-parallel number is very different from that of 3C hand-held applications, but currently there are high-series, high-voltage battery pack applications on the market, especially for the balance strategy between modules. But there is still no perfect management system. This phenomenon does not have much impact on low-voltage or consumer electronics. However, if the battery pack is used in large-scale storage applications such as energy storage systems and electric buses, it will no longer be ignored. Derived between the questions.

In order to solve the shortcomings of the prior art, the present invention provides a battery pack active balancing system. The present invention utilizes an external power source or a series battery pack itself as a power source, and can be switched with a switch circuit that can switch to any single cell. Active balancing of a single cell. The power supply can use the external power supply or the reverse power electronic converter to isolate the same charging power supply and convert the voltage into a charging voltage of a single battery, and continue to increase the voltage of the lowest voltage battery. Balanced energy charging, the active balancing method of this creation can be performed when the battery pack is charged, discharged or left, and the goal of battery pack balancing can be achieved in a short time.

The present invention is a battery pack active balancing system, comprising: a battery pack comprising a plurality of battery cells connected in series with each other; a buck converter connected to the battery pack, having a first side winding and The first side winding induces a second side winding; a main switch unit is connected to the battery pack and the buck converter; a battery voltage sensing unit is connected to the battery pack for sensing the electric The individual voltages of the core unit; the plurality of battery core switching units are respectively connected to the battery cells and connected to the second side winding of the buck converter; a control unit is connected to the main switch unit, the battery core a voltage sensing unit and the battery cell switching units.

In an embodiment of the present invention, the method further includes: an external power source connecting the battery pack and the main switch unit.

In one embodiment of the present invention, the external power source is a commercial power source.

In one embodiment of the present invention, the external power source is a wind power generation system, a solar power generation system, or another type of renewable energy power generation system.

In one embodiment of the present invention, the cell switch unit is a photorelay.

In one embodiment of the present invention, each of the cell units has a positive and negative pole connected to a cell switch unit.

In one embodiment, the battery active balancing system of the present invention has a two-stage charging mode; the first phase is a series charging (series charging) phase, and when the battery pack lacks power, the external power source will charge the battery pack. That is, the charging current I ₁ flows from the external power source into the entire battery pack, and the control unit performs voltage measurement of the individual single cell units by the cell voltage sensing unit, and detects the cell unit with the lowest voltage. At the same time, the external power supply outputs power to the buck converter, and the buck converter reduces the voltage of the power to 5V as externally balanced power I ₂ ; when the lowest voltage of the cell unit and the highest voltage cell unit voltage If the difference exceeds a balance set value (for example, 30 mV), the control unit will enable the two cell switch units corresponding to the cell unit of the lowest voltage, and the buck converter notifies the current of the external balance power I ₂ to the Among the cell units of the lowest voltage, the current on the cell unit of the lowest voltage is I ₁ +I ₂ , and the current of other cell units is I ₁ , thereby rapidly pulling the cell of the lowest voltage. single The power, which is the same until the average voltage of the battery pack. The end condition of the first stage is that after any single cell in the battery pack exceeds a high voltage setting value (for example, 3.6V), the series charging is cut off, and the cutoff condition setting can avoid overcharging of any single cell in the battery pack. In the embodiment, in one embodiment of the present invention, the battery pack usually has a capacity of 80% or more after the first stage (string charging phase) is turned off.

In an embodiment of the battery active balancing system of the present invention, when any of the cells reaches the high voltage setting value (3.6V) when the first phase is charged in series, the charging phase of the second phase is entered, for each battery cell. Balanced charging; when entering the charging phase, the control unit will sort according to the voltage level of each cell unit, and perform balanced charging of individual single cells from low to high, when the cell unit that is balanced and charged reaches a high voltage. The set value (for example, 3.6V), the balance of the next cell unit is performed in order from low to high, until the entire battery pack After the cell units are fully balanced, the charging is terminated. The control unit determines that the battery pack completes the two-stage charging method according to the message via each of the battery cells, that is, ends a complete two-stage charging.

The above summary and the following detailed description and drawings are intended to further illustrate the manner, means and effects of the present invention in achieving its intended purpose. Other purposes and advantages of this creation will be set forth in the following description and illustration.

A, B‧‧‧ battery pack

B0~B15‧‧‧ batteries

11, 23‧‧‧ buck converter

12‧‧‧Main switch unit

13‧‧‧Battery voltage sensing unit

14, 22‧‧‧ Battery Switch Unit

15‧‧‧Control unit

16, 21‧‧‧ External power supply

S11~S17, S21~S28‧‧‧ flow

FIG. 1 is a schematic diagram of the architecture of the active battery balancing system of the present invention.

FIG. 2 is a schematic diagram of an embodiment of a battery pack active balancing system of the present invention.

FIG. 3 is a flow chart of the battery pack active balancing mechanism in the charging state of the present embodiment.

4 is a flow chart of the active balancing mechanism of the battery pack in the discharge state of the present embodiment.

The embodiments of the present invention are described below by way of specific specific examples, and those skilled in the art can readily appreciate the other advantages and effects of the present invention from the disclosure herein.

Please refer to FIG. 1 , which is a schematic diagram of the battery pack active balancing system architecture of the present invention. As shown in the figure, the battery active balancing system includes: a battery pack A, which comprises a plurality of battery cells connected in series; a buck converter 11 is connected to the battery pack A, having a first side winding and the first The second winding of the side winding is sensed; a main switch unit 12 is connected to the battery pack A and the buck converter 11; a battery voltage sensing unit 13 is connected to the battery pack A for sensing The individual voltages of the battery cells; the plurality of battery cell units 14 are respectively connected to the battery cells in the battery pack A, and are connected to the second side winding of the buck converter 11; a control unit 15 The main switch unit 12, the cell voltage sensing unit 13 and the cell switch units 14 are connected to each other; an external power source 16 is connected to the battery pack A and the main switch unit 12.

In one embodiment of the present invention, the buck converter 11, the main switch unit 12, the cell voltage sensing unit 13, the cell switch unit 14 and the control unit 15 are integrated into a BMS circuit board.

In an embodiment of the present invention, the main switch unit 12 can be switched between on and off states, and when the state is "on", the positive and negative poles of the external power source and the positive pole of the first side winding of the buck converter are connected. When the state is "off" with the negative electrode, the positive and negative electrodes of the battery pack and the positive and negative electrodes of the first side winding of the buck converter are connected.

In an embodiment of the present invention, the positive and negative poles of each of the battery cells in the battery pack A are respectively connected to a battery core switch unit 14, and the battery core switch unit 14 and the buck converter 11 The positive electrode of the two side windings is connected to the negative electrode.

In one embodiment of the present invention, the control unit 15 controls the individual voltages of the respective cell units measured by the cell voltage sensing unit 13. The switching operation of the main switch unit 12 and the battery cell switching units 14 is performed to achieve the effect of balancing the voltages of the respective cell units.

In one embodiment of the present invention, the external power source is a commercial power source, and may be a wind power generation system, a solar power generation system, or another type of renewable energy power generation system. The external power supply is used as an external balanced power (balanced power supply) of the active balancing system of the battery pack to balance the power (voltage, power) unevenness between the battery cells. In an embodiment of the present invention, The battery pack itself can be used as externally balanced power.

The battery active balancing system of the present invention is a separate external balanced power (external power supply) with a switching circuit method (the buck converter, the main switching unit, the battery voltage sensing unit, and the battery switching unit) And the control unit) to overcome the disadvantages of the aforementioned balanced balancing method. The external power supply can use an external power supply or use a flyback power electronic converter to isolate the same charging power supply to ground, and convert the voltage into a single battery charging voltage, directly to a lower voltage (or power) The cell unit performs a uniform balanced charging of larger energy. At the same time, the battery active balancing system of the present invention continuously detects the minimum voltage of the cell unit, and pulls the electric power to the same as the sub-low voltage cell unit, because the balance current is large, and the balance can be reached in a short time. The effect.

One embodiment of the battery active balancing system of the present invention is shown in FIG. 2, which is used to explain the operation principle of the active balanced circuit channel (ie, balanced charging) of the present invention. In practical application, lithium iron phosphate is used. Take the battery as an example. The maximum balance current of the battery active balancing system of this creation can reach 6A, and the voltage difference of the battery after balancing is not more than 30mV. This embodiment uses an external power source 21 (solar, wind or utility), or the battery pack B itself can be used as a balanced power source. The battery pack B is composed of 16 groups of cells (B0, B1, ..., B14, B15) connected in series. With 32 sets of photo relays as the cell switch unit 22, that is, the positive and negative poles of each cell are connected to a set of cell switch units 22. When charging, switch the correct battery cell to balance the individual cells. The charging process can be divided into the following two stages: (1) Serial charging: When the entire battery pack lacks power, the external power supply 21 will perform battery pack B. the charging operation, i.e. flow from the external power source 21 I ₁ current into the whole string of battery B is charged, a microcontroller (not shown) for a single individual cell voltage measurement at this stage, and the lowest detected voltage The battery core is simultaneously reduced to 5V by an external power supply 21 through a buck converter 23 as externally balanced power; when the lowest voltage of the cell and the highest voltage cell voltage difference exceeds the equilibrium set value (for example, 30mV) The microcontroller (control unit) will enable the two battery cell switching units corresponding to the lowest voltage cell, and the buck converter 23 will inject the I ₂ current into the lowest voltage cell, at which time the minimum voltage The current on the cell is I ₁ +I ₂ , and the current of the other cells is I ₁ , so that the cell of the lowest voltage can be quickly pulled up until the voltage is the same as the average voltage of the battery 21 . (2) sub-charging: When any cell reaches the high voltage setting value (for example, 3.6V) during the first stage charging, it will enter the second stage of each cell to balance the charging; when entering the sub-charging stage, the microcontroller will According to the voltage level of each cell, the voltage is sorted, and the single cell is balancedly charged from low to high. When the balanced cell voltage reaches the high voltage setting value (3.6V), the next battery is sorted according to the order. The balance of the core works until the cells of the entire battery pack are fully balanced, and the charging is terminated. In this embodiment, a main switch unit (not shown) can be connected to the buck converter. This creation ensures that even if the lithium iron phosphate battery has a large capacity or internal resistance difference, all the series cells can be fully charged, and no charge can be overcharged. The balance of the discharge can also effectively extend the battery. The time of use, with the charge and discharge balancing strategy of this creation, can achieve the effect of the extended range without adding any hardware.

3 is a flow chart of the active balancing mechanism of the battery pack in the charging state of the present embodiment. During the charging phase, the voltage S11 of each cell unit is continuously measured, and the voltage of any cell unit is monitored to be greater than or equal to The voltage setting value S12, if the voltage of any of the cell units is greater than the high voltage setting value, according to the voltage level of each cell unit, the cell units are sequentially balanced from the low voltage to the high voltage to the high voltage setting value S13 (ie, In the above-mentioned sub-charging phase), if the voltage difference between any of the cell units of the lowest voltage and the cell unit of the highest voltage exceeds the equilibrium set value S14 before the voltage of any of the cell units is greater than the high voltage set value, The system first confirms whether the cell unit of the lowest voltage is receiving the balancing operation S15, and if not, turns on the balanced charging function S16 (ie, the above-mentioned series charging phase) until the voltage of the lowest voltage cell unit and the average of each cell unit When the voltage is the same, the balanced charging S17 is turned off, and it is continuously detected whether the voltage difference between the cell unit of any lowest voltage and the cell unit of the highest voltage exceeds the balance setting value.

4 is a flow chart of the active balancing mechanism of the battery pack in the discharge state of the present embodiment, in which the battery cells are continuously measured during the discharge phase. Voltage S21, determining (finding) the highest voltage cell unit and the lowest voltage cell unit S22; determining whether the voltage difference between the highest voltage cell unit and the lowest voltage cell unit is higher than the balance set value S23; if so, judging Whether the voltage of the lowest voltage cell unit is lower than the equilibrium starting value S24 (that is, the system setting must give a balanced voltage starting value); if so, whether the voltage of the lowest voltage cell unit is lower than the low voltage setting value S25, lower than the low voltage setting value means that the cell unit may be degraded, so it is no longer balancedly charged; if the voltage of the lowest voltage cell unit is between the balance starting value and the low voltage setting value, it is turned on. Balance function (balance charging function) S26, balance charging the battery unit of the lowest voltage until the balance cell unit and the battery voltage minimum cell unit (the lowest voltage other than the cell unit in the balance) After the pressure difference is greater than the balance cutoff value S27, the balancing function S28 is turned off.

The battery-operated active balancing system of this creation combines full-time (charging, discharging, standing) and full battery packs (active balancing for any series cell unit). Regardless of the external power supply, the voltage of each cell unit is continuously monitored to determine whether to open the balanced circuit channel. The battery active balancing system of the present invention has the following operation modes: when there is an external power source, when the battery pack is charged: when the battery pack is charged by the external power source, the integrated BMS circuit board of the present invention (built-in buck converter, main switch) The unit, the cell voltage sensing unit, the plurality of cell switch units and the control unit) convert the high voltage external power source to a low voltage power source, and balance the discrete minimum piezoelectric core (when the main switch unit state is "on"); One battery reaches high power The voltage setting stops the series charging, but the balancing mechanism continues to operate, and the balancing logic is switched to the respective batteries according to the high and low voltages, and the battery pack reaches the set protection voltage (high voltage setting value).

When there is an external power supply and the battery pack is discharged: This creation can perform a balancing mechanism for delaying the over-discharge of the cells, when the voltage state of each cell is excessively discrete (the individual differential pressure is too large), and the voltage of the cell is lower than the set balance. When the value is set, the battery pack active balancing mechanism of the creation is started, and the external power supply is delayed for the battery that needs assistance, and the battery is over-discharged (the state of the main switch unit is "on"), so as to reach the series battery at the same time. Put the state, that is, delay the weakest cell early and over discharge.

When there is an external power supply and the battery pack is stationary: when the battery pack is stationary and when the voltage state of each battery cell is excessively discrete (individual pressure difference is too large), this creation can activate the battery pack active balancing mechanism (when the main switch unit state is "On"), the discrete low voltage cells are balanced from the external power supply to the average voltage of the battery pack.

When there is no external power supply and the battery pack is discharged: This creation can perform the balance mechanism of delayed cell over-discharge. When the voltage state of each cell is excessively discrete (the individual differential pressure is too large) and the voltage of a single cell is lower than the set balance. At the initial value, the battery pack active balancing mechanism of the creation is started (the state of the main switch unit is "off" at this time), and the battery pack is overcharged by the entire battery pack for the weakest battery cell to reach the series battery core. At the same time, it reaches the over-discharge state (that is, the cell with the weakest complementary delay is the weakest cell early release).

When there is no external power supply and the battery pack is stationary: when the battery pack is stationary and when the voltage state of each battery cell is excessively discrete, the battery pack of this creation is activated actively. The balance mechanism (when the main switch unit state is "off"), the weakest battery is replenished to the equal voltage condition with the entire battery pack.

In summary, the present invention provides a battery pack active balancing system. The present invention utilizes an external power source or a series battery pack itself as a power source, and can be switched with a switching circuit corresponding to any single cell for individual single power. The active balance of the core. The power supply can use the external power supply or the reverse power electronic converter to isolate the same charging power supply and convert the voltage into a charging voltage of a single battery, and continue to increase the voltage of the lowest voltage battery. Balanced energy charging, the active balancing method of this creation can be performed when the battery pack is charged, discharged or left, and the goal of battery pack balancing can be achieved in a short time. This creation ensures that even if the battery has a large capacity or internal resistance difference, all series cells can be fully charged, and no charge will be overcharged. The balance of discharge can also effectively extend the battery life. With this creation of the battery active balancing system and its charging and discharging balancing strategy, the battery life can be increased without adding any additional hardware.

The above-described embodiments are merely illustrative of the features and functions of the present invention, and are not intended to limit the scope of the technical content of the present invention. Any person skilled in the art can modify and change the above embodiments without departing from the spirit and scope of the present invention. Therefore, the scope of protection of this creation should be as listed in the scope of the patent application described later.

A‧‧‧Battery Pack

11‧‧‧Buck Converter

12‧‧‧Main switch unit

13‧‧‧Battery voltage sensing unit

14‧‧‧Battery switch unit

15‧‧‧Control unit

16‧‧‧External power supply

Claims (9)

A battery pack active balancing system includes: a battery pack comprising a plurality of battery cells connected in series with each other; a buck converter connected to the battery pack, having a first side winding and the first side a second side winding of the winding induction; a main switch unit connecting the battery pack and the buck converter; a battery voltage sensing unit connecting the battery pack for sensing an individual of the battery cells Voltage; a plurality of cell switch units respectively connected to the cell units and connected to the second side winding of the buck converter; a control unit connected to the main switch unit, the cell voltage sensing unit With these cell switch units. The battery pack active balancing system of claim 1, further comprising: an external power source connecting the battery pack and the main switch unit. The battery pack active balancing system of claim 2, wherein the external power source is a utility power. The battery-operated active balancing system of claim 2, wherein the external power source is a wind power generation system, a solar power generation system, or another type of renewable energy power generation system. The battery pack active balancing system of claim 1, wherein the battery cell switching unit is a photo relay. The battery pack active balancing system according to claim 1, wherein the battery pack active balancing mechanism of the battery active balancing system is in a charging state: continuously measuring the voltage of each of the battery cells during the charging phase And monitoring whether the voltage of any of the cell units is greater than the high voltage setting value. If the voltage of any of the cell units is greater than the high voltage setting value, the voltages of the cells are sorted according to the voltage level of the cells, from low voltage to high voltage. Balancing each cell unit to a high voltage setting value; if the voltage difference between any cell unit of the lowest voltage and the cell unit of the highest voltage exceeds the equilibrium setting value before the voltage of any cell unit is greater than the high voltage setting value, The system first confirms whether the cell unit of the lowest voltage is receiving the balancing operation, and if not, the balance charging function is turned on until the voltage of the lowest voltage cell unit is the same as the average voltage of each cell unit, then the balance charging is turned off, and the detection continues. Measure whether the voltage difference between any of the lowest voltage cell units and the highest voltage cell unit exceeds the equilibrium setting. The battery-operated active balancing system according to claim 1, wherein the active balancing mechanism of the battery pack active balancing system in the discharging state is: continuously measuring the voltage of each of the battery cells in the discharging phase Determining whether the highest voltage cell unit and the lowest voltage cell unit are; determining whether the voltage difference between the highest voltage cell unit and the lowest voltage cell unit is higher than a balance setting value; if so, determining whether the voltage of the lowest voltage cell unit is Lower than the balance start value; if yes, determine whether the voltage of the lowest voltage cell unit is lower than the low voltage set value; if the voltage of the lowest voltage cell unit is between the balance start value and the low voltage set value, Then turn on the balance charging function, right The lowest voltage battery cell is balancedly charged until the voltage difference between the cell unit in the balance and the lowest cell unit of the battery pack voltage (the lowest voltage other than the cell unit in the balance) is greater than the equilibrium cutoff value. Turn off the balance charging function. The requested item battery active balance of the system 2, the lack of power when the battery pack, the external power source to the battery charging operation, i.e., _an entire string into the battery charging current from an external source flows I, by the control unit Performing voltage measurement of the individual single cell units by the cell voltage sensing unit, and detecting the lowest voltage cell unit, and the external power source outputs power to the buck converter, the buck converter The voltage of the power is reduced to 5V, which is regarded as the external balanced power I ₂ ; when the voltage difference between the lowest voltage cell unit and the highest voltage cell unit exceeds a balanced set value, the control unit will enable the lowest voltage cell unit Corresponding cell switching unit, the buck converter is responsive to the current of the external balanced power I ₂ to the lowest voltage cell unit, and the current on the lowest voltage cell unit is I ₁ +I _2, the current of the other unit cell was I _1, thereby quickly lift amount of the minimum unit cell voltage, until it is the same as the average voltage of the battery pack, the battery pack according to any one cell more than a single high After the pressure set value, the charging cutoff. The battery active balancing system according to claim 8, wherein any of the cells reaches the high voltage setting value, the control unit sorts according to the voltage level of each battery cell, and performs individual single electricity from low to high. Balanced charging of the core, when the battery unit that is balanced and charged reaches the high voltage setting value, it is low according to The highest level is used to balance the next cell unit until the entire cell unit of the entire battery pack is fully balanced, that is, the end of charging.