CN203827031U - Battery group equalization circuit based on multi-secondary transformer - Google Patents

Abstract

The utility model discloses a battery pack equalization circuit based on a multi-secondary transformer. The equalization circuit mainly includes a microcontroller, a voltage acquisition module, a multi-secondary transformer, an inverter half-bridge rectifier module and a switch module. The microcontroller selects the balancing module and battery cells that need to be balanced through the voltage data transmitted by the voltage acquisition module, and transfers energy to any battery cell that needs to be balanced through the multi-side voltage converter, even if the battery cell does not belong to the discharge balance module. The adjustable duty cycle PWM driving signal output by the microcontroller can control the size of the equalization current to control the equalization speed. The utility model provides convenience for the expansion of the battery unit and the maintenance and repair of the equalization circuit by modularizing the equalization circuit; the equalization speed is controllable and can adapt to various equalization demands; Inconsistencies within the battery cell improve the overall performance of the battery cell.

Description

A battery pack equalization circuit based on multi-secondary transformer

technical field

The utility model relates to a battery pack equalization circuit based on a multi-secondary transformer.

Background technique

With the advantages of energy saving, environmental protection and low emission, electric vehicles have become the most promising field in the automotive industry. As a key component of electric vehicles, the performance of the power battery unit determines the performance of many aspects of electric vehicles. Due to its relatively high energy density and low self-discharge rate, lithium-ion batteries are widely used in electric vehicles, UPS and other power supply occasions. However, due to the low voltage and small capacity of lithium-ion batteries, they cannot meet the driving power requirements of electric vehicles, so a large number of lithium-ion batteries are generally used in series. However, in the production of lithium-ion battery cells, due to the production process of modern battery factories and other reasons, even the same batch of cells will have obvious differences in capacity and internal resistance. During the use of the battery unit, the difference in the self-discharge rate of the battery unit and the difference in the use environment will also lead to an imbalance in the capacity of the battery unit. The high-frequency charging and discharging environment of electric vehicles accelerates the attenuation of the capacity of some of these unbalanced battery cells, while the capacity of series-connected battery cells is determined by the minimum capacity of the single cells, so these differences will make the use of battery cells Life expectancy is greatly shortened. In the worst case, in a battery unit, if the remaining capacity of one unit is close to 100%, while the remaining capacity of the other unit is 0, then the battery unit can neither be charged nor discharged, and cannot be used at all. . If the power battery unit is in such an unbalanced state for a long time, in addition to greatly reducing the service life of the battery unit, it is also easy to cause battery damage, leakage or even explosion and fire, resulting in loss of personnel and property. In order to avoid the occurrence of these unsafe accidents and enhance the performance of the power battery of electric vehicles, etc., it is necessary to have a balanced method to maintain the balance of the performance of each single battery unit. There are two methods of battery equalization: passive equalization and active equalization. However, passive equalization requires the battery cells to be overcharged for a long time, while lithium-ion batteries cannot be overcharged, so passive equalization is only suitable for lead-acid or nickel-based batteries. , active equalization is the only equalization method suitable for lithium-ion batteries.

At present, active equalization methods can be divided into two categories: energy dissipative and energy non-dissipative:

The energy-consuming equalization method is easy to implement, and essentially consumes the energy of a high-voltage monomer in the form of heat or other energy to reduce its voltage and achieve the purpose of voltage equalization. This creates problems of thermal management and energy waste.

The energy non-dissipative equalization method mainly uses inductors, capacitors, etc. as energy transfer media to realize energy flow between battery cells, and finally achieve equalization.

Chinese invention patent application (Application No. 201010572115.X) discloses a circuit that uses discharge resistors to discharge battery cells to achieve cell balance, mainly including a controller, a battery selection circuit and a discharge resistor. The utility model determines the remaining power of each battery cell according to the collected voltage value, and then controls the battery selection circuit to connect the battery cell with higher power in parallel with the discharge resistor to consume the power of the cell, thereby realizing the power balance of the battery cells . Obviously, this method has energy waste and thermal management problems.

Chinese invention patent application (Application No. 201120421053.2) discloses an inductive battery balancing circuit, in which two adjacent batteries share an inductance, which stores the energy released by the higher monomer, and then transfers it to the adjacent lower energy monomer to achieve equilibrium. However, when the number of battery cells is large, since the energy transfer of this equalization method must be transmitted one by one, the equalization speed is greatly limited.

Utility model content

In order to solve the above problems, the utility model proposes a battery pack equalization circuit based on a multi-secondary transformer, which realizes the modularization of the equalization circuit and the energy transfer between modules, effectively balancing the lithium-ion battery. power, thereby improving the service life and working performance of the battery unit.

In order to achieve the above object, the utility model adopts the following technical solutions:

A battery pack equalization circuit based on a multi-secondary transformer, including a microcontroller, the microcontroller is connected to a voltage acquisition module, and the voltage acquisition module is connected to an equalization module, and the equalization module includes a battery unit, an inverter module, a multi-secondary transformer and The battery selects the rectifier module. The battery unit includes multiple battery cells, each of which is connected to the voltage acquisition module; where both ends of the battery unit are connected to the inverter module, and the inverter module is connected to the primary side of the multi-secondary transformer. At least one secondary side of the multi-secondary transformer is connected to a battery selection rectification module, and the battery selection rectification module is connected to each monomer in the battery unit.

The equalization modules are connected through an equalization busbar, and the equalization busbar is connected with one secondary side of the multi-secondary side transformer through a switch.

The battery cells are sequentially connected in series to form a battery pack.

The battery selection rectification module includes a battery selection module and a half-bridge rectification module. The input end of the half-bridge rectification module is connected to a secondary side of the multi-secondary transformer, and the output end is connected to each battery cell through the battery selection module.

The inverter module includes two power switch tubes Q ₁ and Q ₂ , and two capacitors C ₁ and C ₂ , wherein the power switch tubes Q ₁ and Q ₂ are connected in series at both ends of the battery unit, and the power switch tubes Q ₁ and Q ₂ is connected in parallel with a diode, capacitors C ₁ and C ₂ are connected in series and connected to both ends of the battery unit, the midpoints of power switch tubes Q ₁ and Q ₂ and the midpoints of the two capacitors C ₁ and C ₂ are respectively connected to multiple Both ends of the primary side of the secondary transformer.

The power switch tubes _Q1 and _Q2 are driven by a switch tube drive module, which is connected to a microcontroller.

The microcontroller is connected to the battery selection rectifier module and the inverter module through a signal line.

The beneficial effects of the utility model are:

1. Modularize the equalization circuit, which makes the equalization circuit easy to expand, convenient for later management and circuit fault maintenance; the equalization circuit has a variety of equalization methods: equalization within the module, equalization between modules, equalization within the module and between modules at the same time, making equalization More targeted and significantly improved efficiency;

2. In the battery unit of an electric vehicle with a large number of battery cells, the equalization circuit balances a certain battery in a targeted manner, which greatly improves the equalization efficiency;

3. The equalization current is controllable, and the equalization speed can be adjusted as required;

4. Effectively improve the inconsistency between battery cells and improve the performance of power batteries.

Description of drawings

Fig. 1 is the composition schematic diagram of the utility model;

Fig. 2 is the working principle diagram of inverter module in the utility model;

Fig. 3 is the working principle diagram of rectification and battery selection module in the utility model;

Fig. 4 is the working principle diagram when the equalization module of the utility model works alone;

Fig. 5 is the working principle diagram of equalization in the equalization circuit module of the present invention and inter-module equalization at the same time;

Fig. 6 is a working principle diagram of the equalization circuit of the present invention;

Fig. 7 is an equalization effect diagram of the equalization circuit of the present invention in a static state of the power battery.

Among them, 1. microcontroller; 2. voltage acquisition module; 3. battery unit; 4. battery selection rectifier module; 5. multi-side transformer; 6. inverter module; 7. selected battery cells to be balanced ; 8. Balance bus; 9. Signal line.

Detailed ways:

Below in conjunction with accompanying drawing and embodiment the utility model is further described.

As shown in Figures 1-4, a battery pack equalization circuit based on a multi-secondary transformer includes a microcontroller 1, the microcontroller 1 is connected to a voltage acquisition module 2, and the voltage acquisition module 2 is connected to an equalization module, and the equalization module Including a battery unit 3, an inverter module 6, a multi-secondary transformer 5 and a battery selective rectification module 4, the battery unit 3 includes a plurality of battery cells, each of which is connected to the voltage acquisition module 2; wherein, the battery unit 4 has two terminal connected to the inverter module 6, the inverter module 6 is connected to the primary side of the multi-secondary transformer 5, one secondary side of the multi-secondary transformer 5 is connected to the battery selection rectifier module 4, and the battery selection rectifier module 4 is connected to each of the battery units 3 battery cell.

The equalization modules are connected through an equalization bus 8, and the equalization bus 8 is connected with one secondary side of the multi-secondary transformer 5 through a switch.

The battery cells 3 are serially connected in series to form a battery pack.

The battery selection rectification module 4 includes a battery selection module and a half-bridge rectification module, the input end of the half-bridge rectification module is connected to a secondary side of the multi-secondary transformer 5, and the output end is connected to each battery cell through the battery selection module connect.

The inverter module 6 includes two power switch tubes Q ₁ and Q ₂ and two capacitors C ₁ and C ₂ , wherein the power switch tubes Q ₁ and Q ₂ are connected in series at both ends of the battery unit 3, and the power switch tube Q ₁ and _Q2 are respectively connected in parallel with a diode, capacitors _C1 and _C2 are connected in series to both ends of the battery unit 3, the midpoints of the power switch tubes _Q1 and _Q2 and the midpoints of the two capacitors _C1 and _C2 are respectively It is connected to both ends of the primary side of the multi-secondary transformer 5 .

The power switch tubes Q ₁ and Q ₂ are driven by a switch tube drive module, and the switch tube drive module is connected to the microcontroller 1 .

The microcontroller 1 is connected to the battery selection rectifier module 4 and the inverter module 6 through a signal line 9 .

As shown in Figure 2, the inverter module uses the half-bridge inverter principle. The switching tubes Q ₁ and Q ₂ are controlled by the PWM signal with adjustable duty cycle. When Q ₁ and Q ₂ are turned on and off periodically, the primary side of the transformer will be periodically connected in parallel to both ends of C ₁ and C ₂ , thus generating Alternating current;

As shown in Figure 3, the rectification module adopts the half-bridge rectification principle. After the primary side of the multi-secondary transformer 5 has an alternating current passing through it, an induced electromotive force is generated on its secondary side. The middle tap of the secondary side is used as the negative terminal of the output voltage, and the terminal rectified by the diodes D ₁ and D ₂ is used as the positive terminal of the output voltage. The positive and negative ends of the output voltage are respectively connected to the busbar, and connected to the battery cell through the selection function of the switches S ₁ , S ₂ , S ₃ , and S ₄ to realize energy transmission.

Embodiment one:

Taking a battery pack composed of 8 battery cells as an example, every 4 battery cells is a battery unit. The microcontroller adopts digital signal processor DSP, the voltage acquisition module adopts the voltage acquisition integrated chip of the chip company, and the switch tube driving signal in the inverter module comes from the IR2110 driver.

As shown in Figure 4, B ₁ , B ₂ , B ₃ , B ₄ , B ₅ , B ₆ , B ₇ , and B ₈ form a battery pack, among which B ₁ , B ₂ , B ₃ , and B ₄ belong to the balance module 1. B ₅ , B ₆ , B ₇ , and B ₈ belong to the second equalization module. The secondary side of the multi-secondary transformer T ₁ in the balancing module 1 is connected to the secondary side of the multi-secondary transformer T ₂ in the balancing module 2 after passing through the switch S.

State 1, as shown in Figure 4, assumes that B ₂ and B ₆ are low-voltage monomers that need to absorb energy. The total voltage of balance module 1 and balance module 2 is similar, the switch S is turned off, and the balance in the module is carried out: the overall energy of balance module 1 is inverted by the inverter module, and then directly transmitted to the module's own half-bridge rectifier through T ₁ module, under the control of the microcontroller, _B2 is selected to be connected to the output terminal of the half-bridge rectifier module to receive the transmitted energy; the equalization process of the equalization module two is the same as that of the equalization module one. The intra-module equalization of the equalization module 1 and the equalization module 2 can be performed simultaneously or independently depending on the situation.

State 2, as shown in Figure 5, assumes that B ₆ is a low-voltage monomer that needs to absorb energy. The total voltage of balance module 1 is relatively high, switch S is closed, balance module 1 releases energy to battery cell B ₆ of balance module 2: the energy released by balance module 1 is input to T ₁ after inversion, and a secondary side of T ₁ The coil is transmitted to the secondary coil of T ₂ through the balanced bus bar, and the secondary coil connected to the rectifier circuit in T ₂ will generate an induced electromotive force at this time, and the energy will be transmitted to the selected battery cell B ₆ after passing through the half-bridge rectifier module .

State 3, as shown in Figure 6, assumes that B ₂ and B ₆ are low-voltage monomers that need to absorb energy. The total voltage of the balance module 1 is relatively high, the switch S is closed, and the balance module 1 releases energy to the battery cell B ₂ of its own module and the battery cell B ₆ of the balance module 2: the energy released by the balance module 1 is inverted and input to T _1. Part of the energy output of T ₁ is transferred to the half-bridge rectifier module of its own equalization module through one of the secondary coils, and then the energy is transferred to the battery cell B ₂ , and the other part of the energy is transferred to The secondary coil of T ₂ and the secondary coil of T ₂ connected to the rectifier circuit will generate an induced electromotive force at this time, and the energy will be transferred to the selected battery cell B ₆ after passing through the half-bridge rectifier module.

Which of the balanced states shown in Fig. 4, Fig. 5, and Fig. 6 is in the equalization circuit is judged by the microcontroller after the voltage data is transmitted to the microcontroller by the voltage acquisition module. At the same time, the adjustment of the balance current is realized by adjusting the duty ratio of the PWM signal driving the switching tube of the inverter module by the microcontroller. In an equalization process, multiple states are alternately combined as needed to achieve the effect of quickly equalizing battery energy.

Figure 7 shows the equalization effect of the equalization circuit in the static state of the power battery. Equalization begins, battery B ₈ is in a low voltage state and needs to absorb energy. The balance state of the circuit in the embodiment is in state 1 or state 2 among the above states, that is, one of the balance modules provides energy to battery cells that need to be balanced inside its own module or in other modules. When the arrival time is 40 minutes, when the voltage of battery B ₈ rises to be similar to other batteries, the battery cell with the lowest voltage changes, and the equilibrium state will switch between state 1, state 2, and state 3, and finally achieve a better balance Effect.

Although the specific implementation of the utility model has been described above in conjunction with the accompanying drawings, it does not limit the protection scope of the utility model. Those skilled in the art should understand that on the basis of the technical solution of the utility model, those skilled in the art do not need to Various modifications or deformations that can be made with creative efforts are still within the protection scope of the present utility model.

Claims (7)

1. A battery pack equalization circuit based on a multi-secondary transformer, characterized in that it includes a microcontroller, the microcontroller is connected to a voltage acquisition module, and the voltage acquisition module is connected to an equalization module, and the equalization module includes a battery unit, an inverter module , multi-side transformer and battery selection rectifier module, the battery unit includes multiple battery cells, each of which is connected to the voltage acquisition module; wherein, the two ends of the battery unit are connected to the inverter module, and the inverter module is connected to multiple The primary side of the side transformer and at least one secondary side of the multi-secondary transformer are connected to the battery selection rectification module, and the battery selection rectification module is connected to each monomer in the battery unit. 2. A battery pack equalization circuit based on a multi-secondary transformer as claimed in claim 1, wherein said equalization modules are connected through an equalization busbar, and the equalization busbar is connected to a secondary side of the multi-secondary transformer through a switch. connect. 3. A battery pack balancing circuit based on a multi-secondary transformer as claimed in claim 1, characterized in that: said battery cells are serially connected in series to form a battery pack. 4. A battery pack balancing circuit based on multiple secondary side transformers as claimed in claim 1, wherein the battery selection rectification module includes a battery selection module and a half-bridge rectification module, and the half-bridge rectification module The input end is connected to a secondary side of the multi-secondary transformer, and the output end is connected to each battery cell through the battery selection module. 5. A battery pack balancing circuit based on multi-secondary transformers as claimed in claim 1, characterized in that: the inverter module includes two power switch tubes Q ₁ and Q ₂ , two capacitors C ₁ and C ₂ , wherein, the power switch tubes Q ₁ and Q ₂ are connected in series at both ends of the battery unit, the power switch tubes Q ₁ and Q ₂ are respectively connected in parallel with a diode, and the capacitors C ₁ and C ₂ are connected in series at both ends of the battery unit, the power The midpoints of the switch tubes _Q1 and _Q2 and the midpoints of the two capacitors _C1 and _C2 are respectively connected to the two ends of the primary side of the multi-secondary side transformer. 6. A battery pack balancing circuit based on multi-secondary transformers as claimed in claim 1, characterized in that: said power switch tubes _Q1 and _Q2 are driven by a switch tube drive module connected to a micro-controller device. 7. A battery pack equalization circuit based on a multi-secondary transformer as claimed in claim 1, wherein the microcontroller is connected to the battery selection rectifier module and the inverter module through signal lines.