Voltage dynamic balance management system of power lithium battery pack

Abstract

The invention provides a voltage dynamic balance management system of a power lithium battery pack, which relates to a charging and discharging balancing circuit of a series power battery pack. The voltage dynamic balance management system comprises a microprocessor, Hall sensor modules, channel selecting modules, a switch driving circuit module and a DC/DC (Direct Current/Direct Current) transformer, wherein the microprocessor is used for gating a single battery in the battery pack by a first channel selecting module; an input end of the DC/DC transformer is connected with two ends of the battery pack; an output end of the DC/DC transformer is connected with two ends of the single battery by the switch driving circuit module and the switch driving circuit module; an input end of a first Hall sensor module is connected with a charging current input end and a discharging current output end of a charging and discharging switch; an output end of the first Hall sensor module is connected with the microprocessor; an input end of a second Hall sensor module is connected with a balancing charging current output end of the switch driving circuit module; an output end of the second Hall sensor module is connected with an input port of the microprocessor; an input end of the switch driving circuit module is connected with an output end of a second channel selecting module; and an output end of the circuit driving circuit module is connected with two ends of the single battery of the battery pack.

Description

technical field [0001] The invention relates to a charge-discharge equalization circuit for series-connected power battery packs, in particular to an automatic voltage balance management system for the charge-discharge process of series-connected power lithium battery packs. Background technique [0002] With the modularization of large-scale lithium battery packs and the wide application of medium-sized lithium battery packs, the cycle performance and safety performance of battery packs have become the main factors restricting the development, due to the inconsistency between the individual cells in the battery pack , and the difference of single cells caused by continuous charge and discharge cycles will accelerate the decay of the capacity of some single cells. The capacity of the battery pack is determined by the minimum capacity of the single battery, so these differences will shorten the service life of the battery pack. At present, the matching requirements of batter...

AI Technical Summary

Problems solved by technology

The shortcomings of the above charging equalization circuit are as follows: 1. The shortcomings of using parallel resistors for charging and shunting to realize charging equalization: it belongs to the energy dissipation type, and there are energy waste and thermal management problems; 2. The main / sub charging unit is used to charge separately. Disadvantages of charging equalization: each single battery needs a separate charging module, resulting in complex circuit structure and high cost; 3. Disadvantages of using coaxial coils for energy conversion to achieve charging equalization: each monomer All batteries need a secondary winding, which is costly, and the use of coaxial coils for energy conversion has a certain amount of energy dissipation. In actual use, the circuit structure is complex and not suitable for cascading; 4. Use relay switching signals for energy conversion. Insufficiency of conversion to achieve charge balance: each single battery corresponds to two relay switches, resulting in too large a charge balance circuit, and spark oxidation is likely to occur when the relay switch is switched, resulting in an increase in the contact internal resistance of the switch contact and power consumption Larger, the energy supplement is realized by the inverter power supply circuit, the cost is high, and the circuit realization structure is relatively complicated

Disadvantages of using the main / sub-discharge unit to discharge separately to achieve discharge balance: each single battery needs a separate discharge module, resulting in a complex circuit structure and high cost; in summary, the discharge balance method is used in battery packs. It can be used in the early stage. In the case of large changes in battery performance in the later stage, during the charging process, the charging voltage of the battery with a large internal resistance of the single battery will be higher than that of other batteries, thus increasing the possibility of overcharging.

[0012] The deficiencies of the above dynamic equalization circuit are as follows: the shortcomings of the first three points have been stated in the above single equalization method, and the fourth point uses the inductive energy storage element to realize the dynamic equalization circuit of the energy transfer method. Energy transfer between adjacent batteries, so there must be multiple transmissions during the equalization process, and the equalization time is long, which is not suitable for multi-string battery packs

[0014] Among them, the Chinese Patent Publication No. CN201611789 discloses an equalization scheme for a lithium battery pack equalizer charger, which uses a main charging circuit and N single-string charging circuits to charge the battery pack at the same time. When the battery pack reaches a predetermined standard voltage, the main charging circuit The charging circuit stops working, and the N single-string charging circuits continue to charge the single-string batteries that do not meet the standard, until each string of batteries reaches the standard voltage. The disadvantage of this scheme: it can only achieve charging balance, but not discharge balance. Purpose: Each single battery needs a separate charging module, which is unnecessary and the circuit is more complicated and costly to implement; there is no voltage collection for each single battery, and the balance of the single battery can only be based on experience, and the error larger

[0015] The Chinese patent publication number is CN101643054B, which discloses an equalization scheme for an automotive power lithium battery management system. The management system consists of a main control board and a protection board. The protection board is placed in each battery pack. The main control board and the protection board The purpose of balancing is achieved through CAN network communication. The disadvantage of this scheme is that the protection board in each single battery needs to be composed of a microprocessor, a CAN gateway connected to the microprocessor, and a dedicated protection chip for lithium batteries. The cost of protecting the battery pack through this hardware structure is relatively high. Compared with the overcharge, overdischarge, and overcurrent protection of the battery pack through software, the software implementation is more direct, simple, and low in cost. reliable and stable

[0016] The Chinese Patent Publication No. CN102111005A discloses an equalization scheme for a non-destructive lithium battery equalization management system and method. The disadvantage of this scheme is that each battery cell requires an equalization circuit and a single-chip microcomputer, and each equalization circuit requires a separate Isolated transformer, the circuit structure is too large and the cost is high

[0017] The Chinese patent publication number is CN202103447U. An energy-compensated lithium battery equalization controller discloses an equalization scheme. The scheme uses the coaxial coil method to use the energy of the entire battery pack to supplement energy for the battery cells with low voltage in the battery pack. , the channel switching circuit is equipped with a high-frequency isolation transformer structure for each battery cell, that is, each cell has a secondary winding. The disadvantage of this scheme is that it can only achieve charge balance, but not discharge balance. ;Each single battery needs a secondary winding, the cost is high, and there is a certain amount of energy dissipation when using coaxial coils for energy conversion. In the actual use process, the circuit structure is complex and not suitable for cascading; Small (1% of battery pack capacity (AH)), slow equalization speed

[0018] The Chinese Patent Publication No. CN101026307A discloses an equalization scheme for the automatic equalization method of charge and discharge of series power lithium battery packs. In this scheme, each single battery is equipped with a charge and discharge equalization control unit, one-to-one control, parallel monitoring until the charging voltage When the set value is reached and discharged, it is found that a single battery is lower than the average voltage of the battery pack and exceeds the lower limit, the inverter circuit is activated, and the DC power of the battery pack itself is used to realize active inverter to generate AC output. The modulation process outputs the AC pulse width modulation signal, and then controls the power of the micro MOS tube to isolate the output through the transformer. After rectification and filtering, the single battery is recharged. The disadvantage of this solution: the charging balance is controlled by a one-to-one structure, and the functional structure is repeated. , not as flexible and simple as the one-to-many structure, each single battery needs an inverter power supply, the cost is high, and the circuit implementation structure is relatively complicated

[0019] Chinese Patent Publication No. CN201438493U discloses an equalization scheme for an equalization device for a vehicle-mounted power battery pack. This scheme connects a battery cell with a high voltage to the input end of a DC / DC power converter through a polarity unit at the charging end. / DC power converter for energy conversion, the output end of the DC / DC power converter is connected to the battery cell with a lower voltage through the polarity unit of the discharge end, and the battery cell with a lower voltage is charged to realize the battery pack Voltage balance, the circuit structure of this scheme is simple, and the control process is relatively simple compared with the above patents. The disadvantage: the energy supplement method is to convert the energy from the high voltage of the single battery to the low voltage of the single battery, and the conversion efficiency is relatively higher than that of the battery pack to the single battery The battery conversion method is low, and the charging and discharging polarity switch is used to control the balance of the polarity of the single battery. Improper control may easily cause the reverse connection of the two ends of the battery single battery, and the switch control amount is large

[0020] The Chinese patent publication number is CN201438493U, which discloses an equalization scheme for a balance management device of a series lithium battery pack. Balanced adjustment of the terminal voltage, the disadvantage of this scheme: the use of cascaded connected transfer switches increases the inconvenience and risk of control, that is, when charging the single battery n, it must be ensured that the front n-1 single batteries correspond to The transfer switches must be cascaded together, and the control is more troublesome. Once a fault or misoperation of an individual transfer switch occurs, it is easy to cause the wrong selection of the balanced cell. In this way, the difference between the cells of the battery pack will be accelerated, and the balance will be lost. the goal of

[0021] To sum up, at present, domestic improved technologies or products for the voltage equalization management of power lithium battery packs cannot give full play to the performance of lithium battery packs. To give full play to the advantages of dynamic equalization, most of them simply combine the existing charge equalization and discharge equalization technologies, so there are still many problems left over from single equalization in the dynamic equalization circuit, and some of them use inductive energy storage components The dynamic equalization circuit that realizes the energy transfer method can only realize the energy transfer between adjacent batteries, so there must be multiple transmissions in the equalization process, and the equalization time is long, which is not suitable for multi-string battery packs, and most of the dynamic equalization controls its The scheme is complicated, the circuit volume is large, the cost is high, and the practical application is difficult

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