CN115864606B - Active equalization circuit and control method thereof - Google Patents
Active equalization circuit and control method thereof Download PDFInfo
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- CN115864606B CN115864606B CN202310121108.5A CN202310121108A CN115864606B CN 115864606 B CN115864606 B CN 115864606B CN 202310121108 A CN202310121108 A CN 202310121108A CN 115864606 B CN115864606 B CN 115864606B
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Abstract
The invention provides an active equalization circuit and a control method thereof, wherein each basic unit comprises two adjacent batteries, a switch assembly and an energy storage assembly, the batteries in all the basic units are sequentially connected in series to form a battery pack, the two batteries in the battery pack are in an energy imbalance state, and the corresponding basic units transmit energy between the two batteries through the energy storage assembly according to an energy transmission path gated by the switch assembly so as to achieve energy equalization between the two batteries. Through the cascade connection of a plurality of independent basic units, each basic unit comprises two adjacent batteries, a switch assembly and an energy storage assembly, and under the condition of energy unbalance of any two batteries, energy transfer can be carried out between the two batteries through the energy storage assembly according to the transmission path of the switch assembly, so that energy balance between the two batteries is realized. Few participation devices are used in the equalization process, and the conversion efficiency is high.
Description
Technical Field
The invention relates to the technical field of battery management, in particular to an active equalization circuit and a control method thereof.
Background
At present, the battery system is widely applied in the fields of automobiles, energy storage and the like, and with the development of new energy industry, the demand of the market for battery capacity is higher and higher. In order to increase the battery capacity, the number of battery strings and parallel connections is continuously increasing, but the voltage inconsistency of the unit batteries in the battery system can seriously affect the battery capacity, so-called short-circuit effect is caused, and the individual unit batteries are easy to overcharge or overdischarge, so that the reliability of the battery system is affected.
Therefore, an active equalization technology is generally adopted to transfer the electric energy of the single battery with higher voltage to the single battery with lower voltage, so that real-time equalization during charging and discharging is realized, the potential of each battery is developed, each battery is ensured to be simultaneously full or empty, and the service life of the system is prolonged.
As shown in fig. 1, the active equalization circuit topology of the switch matrix mainly comprises a switch matrix circuit and an isolated bidirectional power supply, wherein the switch matrix circuit is used for gating the battery with the highest voltage and the battery with the lowest voltage, and the bidirectional power supply realizes the electric energy transmission between the two batteries.
Disclosure of Invention
The invention aims to provide an active equalization circuit and a control method thereof, which are used for solving the problems of more participation devices and low equalization efficiency in the prior equalization technology.
In one aspect, the invention provides an active equalization circuit, which comprises a plurality of basic units, wherein each basic unit comprises two adjacent batteries, a switch assembly and an energy storage assembly, the batteries in all the basic units are sequentially connected in series to form a battery pack, the two batteries in the battery pack are in an energy imbalance state, and the corresponding basic units transmit energy between the two batteries through the energy storage assembly according to an energy transmission path gated by the switch assembly so as to achieve energy equalization between the two batteries.
Preferably, the switch assembly comprises two switch tubes, the energy storage assembly comprises an inductor, one end of the inductor is connected with the middle node of the two adjacent batteries, the other end of the inductor is connected with the middle node of the two switch tubes, and in the state that the energy of the two adjacent batteries is unbalanced, the inductor stores the electric quantity in the high-energy battery and transfers the electric quantity to the low-energy battery.
Preferably, the switch assembly further comprises a control switch, the energy storage assembly further comprises a capacitor, one end of the control switch is connected with the middle node of the two switch tubes, the other end of the control switch tube is connected with the capacitor, and the capacitor is connected with the adjacent basic units; under the condition that two batteries with unbalanced energy respectively belong to different basic units, the corresponding control switch is communicated with an energy transmission path between the two batteries, and the electric quantity in the high-energy battery is stored through the corresponding inductor and is transferred to the low-energy battery.
Preferably, the equalization operation of the active equalization circuit includes a half-bridge conversion mode, a CUK conversion mode and an extended conversion mode; in the half-bridge conversion mode, energy transfer is carried out on two adjacent batteries in each basic unit; under the CUK conversion mode, energy transfer is carried out on the 2N and 2N+1+2k batteries among different basic units, wherein N is more than or equal to 1, and K is more than or equal to 0; and in the expansion conversion mode, energy transfer is carried out on the 2N-1 and 2N+2 (k+1) batteries among different basic units, wherein N is more than or equal to 1, and K is more than or equal to 0.
Preferably, the plurality of basic units are a first basic unit, a second basic unit and a third basic unit, wherein the first basic unit comprises a first battery, a second battery, a first switch tube, a second switch tube, a first inductor, a first control switch and a first capacitor; the second basic unit comprises a third battery, a fourth battery, a third switching tube, a fourth switching tube, a second inductor, a second control switch and a second capacitor; the third basic unit comprises a fifth battery, a sixth battery, a fifth switching tube, a sixth switching tube, a third inductor, a third control switch and a third capacitor; the first battery is connected in series with the sixth battery in sequence, the first switch tube is connected in series with the sixth switch tube in series with the first capacitor, the second capacitor and the third capacitor are connected in series in sequence.
Preferably, in case of an energy imbalance of the first and second batteries, the first base unit operates in the half-bridge conversion mode; when the voltage of the first battery is higher than that of the second battery, the first switch tube is turned on, the second switch tube is turned off, the energy of the first battery is transferred to the first inductor, then the first switch tube is turned off, the second switch tube is turned on, and the first inductor transfers the energy to the second battery; when the voltage of the first battery is lower than the voltage of the second battery, the second switch tube is turned on, the first switch tube is turned off, the energy of the second battery is transferred to the first inductor, then the second switch tube is turned off, the first switch tube is turned on, and the first inductor transfers the energy to the first battery.
Preferably, in case of energy imbalance of the second and fifth batteries, the first and third base units operate in CUK conversion mode; when the voltage of the second battery is higher than that of the fifth battery, the second switch tube, the first control switch and the third control switch are turned on, the other switch tubes and the control switch are turned off, the energy of the second battery is transferred to the first inductor and the third inductor, then the fifth switch tube is turned on, the other switch tubes and the control switch are turned off, and the third inductor transfers the energy to the fifth battery; when the voltage of the second battery is lower than that of the fifth battery, the fifth switch tube, the first control switch and the third control switch are turned on, the other switch tubes and the control switch are turned off, the energy of the fifth battery is transferred to the first inductor and the third inductor, then the second switch tube is turned on, the other switch tubes and the control switch are turned off, and the first inductor transfers the energy to the second battery.
Preferably, in case of energy imbalance of the first and fourth batteries, the first and second base units operate in an extended conversion mode; when the voltage of the first battery is higher than that of the fourth battery, the first switch tube, the first control switch and the second control switch are turned on, the other switch tubes and the control switch are turned off, the energy of the first battery is transferred to the first inductor and the second inductor, then the fourth switch tube is turned on, the other switch tubes and the control switch are turned off, and the energy of the second inductor is transferred to the fourth battery; when the voltage of the first battery is lower than that of the fourth battery, the fourth switching tube, the first control switch and the third control switch are turned on, the other switching tubes and the control switch are turned off, the energy of the fourth battery is transferred to the first inductor and the second inductor, then the first switching tube is turned on, the other switching tubes and the control switch are turned off, and the first inductor transfers the energy to the first battery.
On the other hand, the invention also provides a control method of the active equalization circuit, which is applied to any one of the active equalization circuits, and comprises the following steps:
collecting the battery voltage of each battery in the battery pack;
judging whether the energy unbalance situation of the two batteries exists according to the battery voltage; and
and under the condition of energy unbalance between the two batteries, controlling the corresponding basic units to gate the energy transmission paths, and transferring energy between the two batteries so as to achieve energy balance between the two batteries.
Preferably, the specific steps include:
s10: collecting the voltages of all batteries, and obtaining the highest voltage battery and the lowest voltage battery;
s20: judging whether the pressure difference between the highest voltage battery and the lowest voltage battery is larger than a preset unbalanced voltage value, if so, executing S30, and if not, not actively balancing;
s30: judging whether the pressure difference between two adjacent batteries in each basic unit is larger than the unbalanced voltage value, if so, transferring energy to the two adjacent batteries in a half-bridge conversion mode; if not, executing S40;
s40: judging whether the voltage difference between the 2N and 2N+1+2k batteries is larger than the unbalanced voltage value, if so, performing energy transfer on the 2N and 2N+1+2k batteries in a CUK conversion mode, and if not, executing S50;
s50: judging whether the voltage difference between the 2N-1 and 2N+2 (k+1) batteries is larger than the unbalanced voltage value, if so, performing energy transfer on the 2N-1 and 2N+2 (k+1) batteries in an expansion conversion mode, and if not, executing S60;
s60: and selecting an adjacent battery in a basic unit where the highest voltage battery or the lowest voltage battery is positioned as a bridging battery, firstly carrying out energy transfer on one battery of the highest voltage battery and the lowest voltage battery and the bridging battery in a half-bridge conversion mode, and then carrying out energy transfer on the bridging battery and the other battery in a CUK conversion mode or an expansion conversion mode.
The beneficial effects of the invention are as follows: through the cascade connection of a plurality of independent basic units, each basic unit comprises two adjacent batteries, a switch assembly and an energy storage assembly, and under the condition of energy unbalance of any two batteries, energy transfer can be carried out between the two batteries through the energy storage assembly according to the transmission path of the switch assembly, so that energy balance between the two batteries is realized. Few participation devices are used in the equalization process, and the conversion efficiency is high.
Specifically, each basic unit is respectively connected with two adjacent batteries and two switching tubes through an inductor, so that energy balance can be carried out on the two adjacent batteries, and each basic unit can simultaneously carry out balance work without interference, and has the advantages of short power path and high balance efficiency; the number of the used switching tubes is small, and the cost is low.
Specifically, adjacent basic units are connected through a capacitor, and an energy transmission path between the two basic units is connected through a control switch, so that energy transfer can be performed between any two batteries in different basic units. The energy balance can be carried out point-to-point among the odd-even batteries of different basic units, multi-stage transmission is not needed, the energy attenuation risk is reduced, and the balance speed is high. Only two times of conversion are needed for two odd batteries or two even batteries, an isolation device is not needed, the conversion efficiency is high, and the equalization speed is high.
The active equalization circuit and the control method thereof provided by the invention have three working modes, namely a half-bridge conversion mode, a CUK conversion mode and an expansion conversion mode, and the energy equalization of the whole battery pack is realized by combining the three working modes.
Meanwhile, the active equalization circuit provided by the invention has the advantages of standardization, modularization, small volume, convenient expansion of the number of batteries, no limitation on the number of battery strings, capability of greatly improving the upper limit of the working voltage of the battery pack, less consumption of participating devices, low cost and easiness in realization of miniaturization.
Drawings
The above and other objects, features and advantages of the present invention will become more apparent from the following description of embodiments of the present invention with reference to the accompanying drawings.
FIG. 1 is a schematic diagram of a prior art active equalization circuit of the switch matrix type;
FIG. 2 is a schematic diagram of a Buck-Boost active equalization circuit in the prior art;
FIG. 3 is a schematic diagram of an isolated multi-winding coupled active equalization circuit according to the prior art;
fig. 4 is a schematic diagram of an embodiment of an active equalization circuit according to the present invention;
FIG. 5 is a schematic diagram illustrating the operation of the active equalization circuit of FIG. 4 in a half-bridge conversion mode for energy transfer between two adjacent cells;
FIGS. 6 and 7 are schematic diagrams illustrating the operation of the active equalization circuit of FIG. 4 in performing energy transfer on two cells of the odd-even system in the CUK conversion mode, respectively;
FIGS. 8 and 9 are schematic diagrams illustrating the operation of the active equalization circuit of FIG. 4 in performing energy transfer between two cells in an extended conversion mode;
fig. 10 is a flow chart of a control method of an active equalization circuit provided by the invention;
fig. 11 is a specific flowchart of an embodiment of a control method of an active equalization circuit provided by the present invention.
Description of the embodiments
At present, aiming at an active equalization topology scheme of a battery pack, a basic architecture mostly adopts a bidirectional DCDC power supply conversion circuit. The open Guan Ju array type active equalization circuit topology shown in fig. 1 mainly comprises a switch matrix circuit and an isolated bidirectional power supply, wherein the switch matrix circuit is used for gating the battery with the highest voltage and the battery with the lowest voltage, and the bidirectional power supply realizes electric energy transmission between the two batteries. As shown in fig. 2, the active equalization circuit topology based on the non-isolated Buck-Boost DC/DC conversion circuit is characterized in that a basic unit is a non-isolated Buck-Boost converter, so that energy transfer between two adjacent batteries is realized, but if the batteries to be equalized are non-adjacent batteries, multi-stage transfer is needed if the two batteries are more spaced, energy is attenuated in the transfer process, and the equalization speed is influenced. As shown in fig. 3, the isolated multi-winding coupling active equalization circuit topology is a multi-winding coupling bidirectional single-ended flyback DC/DC converter, and the power transmission between a pair of batteries with the highest electric quantity and the lowest electric quantity is performed at the same time.
Aiming at the problems existing in the prior art, the applicant develops in the dimensions of energy conversion efficiency, balancing speed, volume, cost and the like, and provides an active balancing circuit and a control method thereof, so as to solve the problems of energy attenuation, influence on balancing speed, more participation devices and high cost of a series battery pack in the energy balancing process in the prior art.
In order that the invention may be readily understood, a more complete description of the invention will be rendered by reference to the appended drawings. Preferred embodiments of the present invention are shown in the drawings. The invention may, however, be embodied in different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.
The present invention will be described in detail with reference to the accompanying drawings.
Fig. 4 shows an embodiment of an active equalization circuit provided by the present invention.
Referring to fig. 4, the active equalization circuit provided in the present invention includes a plurality of basic units, for example, three basic units, namely, a first basic unit 110, a second basic unit 120, and a third basic unit 130, where each basic unit includes two adjacent batteries, all the batteries are BT1, BT2, BT3, BT4, BT5, and BT6 in sequence according to the arrangement positions, and the six batteries are connected in series to form a battery pack, that is, each basic unit includes an odd battery and an even battery. Each basic unit further comprises a switch component and an energy storage component, when the energy of two batteries in the battery pack is unbalanced, the corresponding basic unit can transfer energy to the two batteries through the charging and discharging process of the energy storage component according to the energy transmission path gated by the switch component, so that energy balance between the two batteries is realized, few devices are involved in the balancing process, and the balancing efficiency is high.
In each basic unit, the switch assembly comprises two switch tubes and a control switch, and the energy storage assembly comprises an inductor and a capacitor. As shown in fig. 4, the first basic unit 110 includes batteries BT1 and BT2, an inductor L1, switching transistors Q1 and Q2, a control switch S1, and a capacitor C1, one end of the inductor L1 is connected to an intermediate node of the batteries BT1 and BT2, the other end is connected to an intermediate node of the switching transistors Q1 and Q2, one end of the control switch S1 is connected to an intermediate node of the switching transistors Q1 and Q2, the other end is connected to the capacitor C1, and the capacitor C1 is connected to the second basic unit 120. The second basic unit 120 includes batteries BT3 and BT4, an inductor L2, switching transistors Q3 and Q4, a control switch S2, and a capacitor C2, where one end of the inductor L2 is connected to the intermediate node of the batteries BT3 and BT4, the other end is connected to the intermediate node of the switching transistors Q3 and Q4, one end of the control switch S2 is connected to the intermediate node of the switching transistors Q3 and Q4, the other end is connected to the capacitor C2, and the capacitor C2 is connected to the third basic unit 130; the third basic unit 130 includes batteries BT5 and BT6, an inductor L3, switching transistors Q5 and Q6, a control switch S3, and a capacitor C3, where one end of the inductor L3 is connected to the intermediate node of the batteries BT5 and BT6, the other end is connected to the intermediate node of the switching transistors Q5 and Q6, one end of the control switch S3 is connected to the intermediate node of the switching transistors Q5 and Q6, the other end is connected to the capacitor C3, and the capacitors of each basic unit are sequentially connected in series.
In other embodiments, the power of each basic unit may be connected in parallel, and the control switch of each basic unit may be replaced by a bidirectional switch formed by two MOS transistors connected in reverse series.
In this embodiment, all the switching tubes are PWM power MOS tubes, each battery corresponds to one MOS tube, and each MOS tube is serially connected in turn. Each MOS tube and each control switch are connected with a micro control unit (Micro control unit, MCU) (not shown in the figure) and are turned on or off according to the switch control signal of the MCU; each battery is connected with an Analog Front End (AFE) (not shown in the figure), the state of each battery is collected by the AFE chip, and the MCU executes corresponding equalization algorithm to control related circuits according to the state of each battery so as to realize corresponding control and driving of MOS and control switches, thereby realizing energy transfer among all batteries of the whole battery pack.
In this embodiment, the equalization operation of the active equalization circuit includes three modes, i.e., a half-bridge conversion mode, a CUK conversion mode, and an extended conversion mode, where in the half-bridge conversion mode, energy transfer can be performed on two adjacent batteries (e.g., BT1 and BT 2) in the same basic unit, and multiple basic units can operate in the mode at the same time, so that the power path is short and the equalization efficiency is high. In the CUK conversion mode, energy transfer can be performed on the 2N and 2n+1+2k batteries among different basic units, where n=1, 2, and 3. In the extended conversion mode, energy transfer can be performed on the 2N-1 and 2n+2 (k+1) batteries among different basic units, wherein n=1, 2,3. Under the condition that the batteries needing to be subjected to energy transfer are all odd batteries or all even batteries, energy can be carried out by combining multiple conversion modes, for example, the first battery BT1 and the third battery BT3 are all odd batteries, when the voltage of the battery BT1 is highest and the voltage of the battery BT3 is lowest, the corresponding basic unit transfers the energy of the battery BT1 to the battery BT2 in the half-bridge conversion mode, and then the energy of the battery BT2 is transferred to the battery BT3 in the CUK conversion mode, so that the battery BT1 charges the battery BT 3. By analogy, through the combination of the three working modes, the balance work can be carried out on any two batteries in the battery pack, the energy balance of the whole battery pack is realized, the phenomenon of overcharge or overdischarge of the battery pack is avoided, the service life of the battery pack is prolonged, and the battery pack is converted for at most two times, so that the balance efficiency is high and the speed is high.
Referring to fig. 5, an operation diagram of the active equalization circuit for transferring energy between two adjacent cells in the half-bridge conversion mode is shown. As shown in fig. 5 (a) and (b), the energy between the batteries BT1 and BT2 is unbalanced, the energy between the batteries BT3 and BT4 is unbalanced, and the first base unit 110 and the second base unit 120 perform the equalization operation in the half-bridge conversion mode in synchronization. As shown in fig. 5 (a), in a state where the voltage of the battery BT1 is higher than the voltage of the battery BT2, the switching tube Q1 is turned on as a main switch, the switching tube Q2 is turned off, when Q1 is turned on, the battery BT1 transfers energy to the inductor L1, after that, the switching tube Q1 is turned off, the switching tube Q2 is turned on for synchronous rectification, and the inductor L1 transfers energy to the battery BT2, thereby realizing that the battery BT1 charges the battery BT 2. Similarly, in a state where the voltage of the battery BT3 is higher than the voltage of the battery BT4, the battery BT3 can also transfer energy to the battery BT4 synchronously, thereby improving the equalization efficiency. As shown in fig. 5 (b), in a state where the voltage of the battery BT1 is lower than the voltage of the battery BT2, the switching tube Q1 is turned off, the switching tube Q2 is turned on as a main switch, the battery BT2 transfers energy to the inductor L1, and then the switching tube Q2 is turned off, the switching tube Q1 is turned on to perform synchronous rectification, and the inductor L1 transfers energy to the battery BT1, thereby realizing that the battery BT2 charges the battery BT 1. Similarly, in a state where the voltage of the battery BT3 is lower than the voltage of the battery BT4, the battery BT4 can also transfer energy to the battery BT3 synchronously, thereby improving the equalization efficiency. In the process of carrying out balanced work in the half-bridge conversion mode, the control switches of the corresponding basic units are all disconnected.
Referring to fig. 6 and 7, an operation schematic diagram of the active equalization circuit for transferring energy to two odd-even cells in CUK conversion mode is shown. As shown in fig. 6, in the state where the voltage of the battery BT2 is highest and the voltage of the battery BT5 is lowest, the switching tube Q2, the control switches S1 and S3 are turned on, and the other switching tubes and the control switches are turned off, at this time, the battery BT2 transfers energy to the inductors L1 and L3, and then the switching tube Q2 is turned off, the switching tube Q5 is turned on for synchronous rectification, and the other switching tubes and the control switches are turned off, and the inductor L3 transfers energy to the battery BT5, thereby realizing that the battery BT2 charges the BT 5. As shown in fig. 7, in the state where the voltage of the battery BT2 is the lowest and the voltage of the battery BT5 is the highest, the switching tube Q5, the control switches S1 and S2 are turned on, and the other switching tubes and the control switches are turned off, at this time, the battery BT5 transfers energy to the inductors L1 and L3, and then the switching tube Q5 is turned off, the switching tube Q2 is turned on for synchronous rectification, and the other switching tubes and the control switches are turned off, so that the inductor L1 transfers energy to the battery BT2, thereby realizing that the battery BT5 charges the BT 2.
Referring to fig. 8 and 9, an operation schematic diagram of the active equalization circuit for transferring energy to two odd-even cells in the extended conversion mode is shown. As shown in fig. 8, in the state where the voltage of the battery BT1 is highest and the voltage of the battery BT4 is lowest, the switching tube Q1, the control switches S1 and S2 are turned on, and the other switching tubes and the control switches are turned off, at this time, the battery BT1 transfers energy to the inductors L1 and L2, and then the switching tube Q1 is turned off, the switching tube Q4 is turned on for synchronous rectification, and the other switching tubes and the control switches are turned off, and the inductor L2 transfers energy to the battery BT4, thereby realizing that the battery BT1 charges the BT 4. As shown in fig. 9, in the state where the voltage of the battery BT1 is the lowest and the voltage of the battery BT4 is the highest, the switching tube Q4, the control switches S1 and S2 are turned on, and the other switching tubes and the control switches are turned off, at this time, the battery BT4 transfers energy to the inductors L1 and L2, and then the switching tube Q4 is turned off, the switching tube Q1 is turned on for synchronous rectification, and the other switching tubes and the control switches are turned off, and the inductor L1 transfers energy to the battery BT1, thereby realizing that the battery BT4 charges the BT 1.
In this embodiment, the voltage inconsistency index is used as an equalization variable, which is not limited, and in alternative other embodiments, the active energy equalization can be implemented by using parameters that are easily thought by those skilled in the art as detection indexes, so as to reduce the switching loss of the equalization circuit, improve the equalization speed, and prolong the service life of the battery pack.
In the above embodiments, all the batteries are secondary batteries, and may be selected from any one of the following lithium ion batteries, lead acid batteries, supercapacitors, or nickel hydrogen batteries.
According to the embodiment of the invention, the novel active equalization circuit is adopted to ensure that the single batteries in the battery pack are not overcharged and overdischarged in the charging and discharging processes, so that the unbalanced phenomenon of the series battery pack is improved, the available capacity of the battery pack is increased, the maintenance and replacement period of the series battery pack is reduced, the service life of the battery pack is prolonged, and the running cost of the battery pack in application scenes such as a hybrid electric vehicle, an electric vehicle and an energy storage power station is reduced.
On the other hand, the present invention also provides a control method of an active equalization circuit, please refer to fig. 10, which shows a flow chart of the active equalization control method provided by the present invention, including:
collecting the battery voltage of each battery in the battery pack;
judging whether the energy unbalance situation of the two batteries exists according to the battery voltage; and controlling the corresponding basic unit to gate the energy transmission path under the condition of energy unbalance between the two batteries, and transferring energy between the two batteries so as to achieve energy balance between the two batteries.
In this embodiment, voltage data acquired by the AFE is fed back to the MCU, the MCU respectively determines whether there is an energy imbalance situation of two batteries in the acquired voltage, and if it is determined that there is an energy imbalance situation, the MCU controls on/off of a switch component of a corresponding basic unit through a switch control signal, so as to select an energy transmission path of the basic unit, and achieve energy balance between the two batteries.
In this embodiment, whether there is an energy imbalance between the highest voltage battery and the lowest voltage battery in the battery pack is determined according to a voltage difference between the highest voltage battery and the lowest voltage battery, and under the determination criterion, as shown in fig. 11, the specific steps of the control method of the active equalization circuit include:
s10: collecting the voltages of all batteries, and obtaining the highest voltage battery and the lowest voltage battery;
s20: judging whether the pressure difference between the highest voltage battery and the lowest voltage battery is larger than a preset unbalanced voltage value, if so, executing S30, and if not, not actively balancing;
s30: judging whether the pressure difference between two adjacent batteries in each basic unit is larger than the unbalanced voltage value, if so, transferring energy to the two adjacent batteries in a half-bridge conversion mode; if not, executing S40;
s40: judging whether the voltage difference between the 2N and 2N+1+2k batteries is larger than the unbalanced voltage value, if so, performing energy transfer on the 2N and 2N+1+2k batteries in a CUK conversion mode, and if not, executing S50;
s50: judging whether the voltage difference between the 2N-1 and 2N+2 (k+1) batteries is larger than the unbalanced voltage value, if so, performing energy transfer on the 2N-1 and 2N+2 (k+1) batteries in an expansion conversion mode, and if not, executing S60;
s60: and selecting an adjacent battery in a basic unit where the highest voltage battery or the lowest voltage battery is positioned as a bridging battery, firstly carrying out energy transfer on one battery of the highest voltage battery and the lowest voltage battery and the bridging battery in a half-bridge conversion mode, and then carrying out energy transfer on the bridging battery and the other battery in a CUK conversion mode or an expansion conversion mode.
In step S10, the AFE collects voltages Vi (i=1, 2,3 … … n) of all the cells in the battery pack and feeds back to the MCU, and the MCU finds the highest voltage value Vmax and the lowest voltage value Vmin from the fed back voltages, and obtains the corresponding highest voltage cell BTp and lowest voltage cell BTk, that is, vp=vmax, vk=vmin.
In step S20, the MCU may preset an unbalanced voltage value Vth, obtain the differential voltage Δv1 between the highest voltage battery BTp and the lowest voltage battery BTk by the formula Δv1=vp-Vk, determine that if Δv1 > Vth, it is considered that the highest voltage battery BTp and the lowest voltage battery BTk have energy unbalance, and perform the balancing operation, and if Δv1 < Vth, it is considered that the highest voltage battery BTp and the lowest voltage battery BTk do not have energy unbalance, then control does not need to perform active balancing operation.
In step S30, it is determined whether the differential voltage Δv2 between two adjacent cells in each unit cell is greater than the unbalanced voltage value, if Δv2 > Vth of any unit cell, the corresponding unit cell transfers energy to the two adjacent cells in the half-bridge conversion mode, and if Δv2 < Vth of all unit cells, step S40 is performed.
In step S40, it is further determined whether the voltage difference Δv3 between two odd-even batteries not belonging to the same basic unit is greater than the unbalanced voltage value, wherein the two odd-even batteries are 2n and 2n+1+2k batteries, n=1, 2, …; k=0, 1,2, …, i.e. the number of odd cells is higher than the number of even cells (e.g. cells BT2 and BT3, cells BT2 and BT 5). In case Δv3 > Vth, the corresponding basic unit performs energy transfer for the two-section parity in CUK conversion mode, and if Δv3 < Vth, step S50 is performed.
In step S50, it is further determined whether the differential pressure Δv4 between two odd-even batteries not belonging to the same basic unit is greater than the unbalanced voltage value, wherein the two odd-even batteries are 2N-1 and 2n+2 (k+1) batteries, and n=1, 2, …; k=0, 1,2, …, i.e., the number of odd cells is lower than the number of even cells (e.g., cells BT1 and BT4, cells BT1 and BT6, cells BT3 and BT 6). In the case where Δv4 > Vth, the corresponding basic unit performs energy transfer for the two cells in the extended conversion mode, and if Δv4 < Vth, step S60 is performed.
In step S60, regarding that the highest voltage battery BTp and the lowest voltage battery BTk are both odd-numbered batteries or both even-numbered batteries, one other battery is selected as the bridge battery, and the bridge battery and the highest voltage battery BTp or the lowest voltage battery BTk belong to the same basic unit, then one of the highest voltage battery BTp and the lowest voltage battery BTk and the bridge battery are subjected to energy transfer in the half-bridge conversion mode, and then the bridge battery and the other battery are subjected to energy transfer in the CUK conversion mode. For example, when the highest voltage battery is BT1 and the lowest voltage battery is BT3, the battery BT2 may be selected as the bridge battery, and the first basic unit 110 transfers the energy of the battery BT1 to the battery BT2 adjacent thereto in the half-bridge conversion mode, and transfers the energy of the battery BT2 to the battery BT3 in the CUK conversion mode, so as to implement energy conversion between two odd-numbered batteries, and energy conversion between two even-numbered batteries is implemented in a similar manner.
Specifically, when the highest voltage battery BTp and the lowest voltage battery BTk are both odd-numbered batteries, a battery having a low number of bits may be selected as the first target battery, and an adjacent battery in the same basic unit as the first target battery may be selected as the bridge battery, for example, when the highest voltage battery is BT1 and the lowest voltage battery is BT5, the number of bits of the battery BT1 is low, and BT2 is selected as the first target battery. When both the highest voltage battery BTp and the lowest voltage battery BTk are even-numbered batteries, the battery BT (p-1) in the same basic unit as the highest voltage battery BTp may be selected as the bridge battery.
The active equalization circuit control method in this embodiment is applied to the active equalization circuit shown in fig. 4, and by using the topology structure of the basic unit and the cascade design of the adjacent basic units, the corresponding working mode can be selected under the condition of energy unbalance between any two batteries, and the switching of the energy paths is realized by the switching control signals, so that the energy is transferred from the higher battery to the lower battery, the energy transfer is performed between the two batteries, and the voltage balance between the two batteries is achieved, so that the phenomena of overcharge and overdischarge of each battery in the charging and discharging processes are avoided, and the unbalanced problem of the series battery is improved.
It should be noted that in the description of the present invention, it should be understood that the terms "upper," "lower," "inner," and the like indicate an orientation or a positional relationship, and are merely for convenience of describing the present invention and simplifying the description, and do not indicate or imply that the components or elements referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the present invention.
Furthermore, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.
Finally, it should be noted that: it is apparent that the above examples are only illustrative of the present invention and are not limiting of the embodiments. Other variations or modifications of the above teachings will be apparent to those of ordinary skill in the art. It is not necessary here nor is it exhaustive of all embodiments. And obvious variations or modifications thereof are contemplated as falling within the scope of the present invention.
Claims (7)
1. An active equalization circuit comprising a plurality of basic cells, characterized in that:
each basic unit comprises two adjacent batteries, a switch assembly and an energy storage assembly, the batteries in all the basic units are sequentially connected in series to form a battery pack, and when the two batteries in the battery pack are in an energy imbalance state, the corresponding basic units transmit energy between the two batteries through the energy storage assembly according to an energy transmission path gated by the switch assembly so as to achieve energy balance between the two batteries;
the switch assembly comprises two switch tubes, the energy storage assembly comprises an inductor, one end of the inductor is connected with the middle node of the two adjacent batteries, the other end of the inductor is connected with the middle node of the two switch tubes, and the inductor stores electric quantity in the high-energy battery and transfers the electric quantity to the low-energy battery in a state that the energy of the two adjacent batteries is unbalanced;
the switch assembly further comprises a control switch, the energy storage assembly further comprises a capacitor, one end of the control switch is connected with the middle node of the two switch tubes, the other end of the control switch is connected with the capacitor, and the capacitor is connected with the adjacent basic units; under the condition that two batteries with unbalanced energy belong to different basic units respectively, the corresponding control switch is communicated with an energy transmission path between the two batteries, and the electric quantity in the high-energy battery is stored through the corresponding inductor and is transferred to the low-energy battery;
the equalization work of the active equalization circuit comprises a half-bridge conversion mode, a CUK conversion mode and an expansion conversion mode; in the half-bridge conversion mode, energy transfer is carried out on two adjacent batteries in each basic unit; under the CUK conversion mode, energy transfer is carried out on the 2N and 2N+1+2k batteries among different basic units, wherein N is more than or equal to 1, and K is more than or equal to 0; and in the expansion conversion mode, energy transfer is carried out on the 2N-1 and 2N+2 (k+1) batteries among different basic units, wherein N is more than or equal to 1, and K is more than or equal to 0.
2. The active equalization circuit of claim 1, wherein: the plurality of basic units are a first basic unit, a second basic unit and a third basic unit, wherein the first basic unit comprises a first battery, a second battery, a first switch tube, a second switch tube, a first inductor, a first control switch and a first capacitor; the second basic unit comprises a third battery, a fourth battery, a third switching tube, a fourth switching tube, a second inductor, a second control switch and a second capacitor; the third basic unit comprises a fifth battery, a sixth battery, a fifth switching tube, a sixth switching tube, a third inductor, a third control switch and a third capacitor; the first battery is connected in series with the sixth battery in sequence, the first switch tube is connected in series with the sixth switch tube in series with the first capacitor, the second capacitor and the third capacitor are connected in series in sequence.
3. The active equalization circuit of claim 2, wherein: in the event of an imbalance in the first and second battery energies, the first base unit operates in the half-bridge conversion mode;
when the voltage of the first battery is higher than that of the second battery, the first switch tube is turned on, the second switch tube is turned off, the energy of the first battery is transferred to the first inductor, then the first switch tube is turned off, the second switch tube is turned on, and the first inductor transfers the energy to the second battery;
when the voltage of the first battery is lower than the voltage of the second battery, the second switch tube is turned on, the first switch tube is turned off, the energy of the second battery is transferred to the first inductor, then the second switch tube is turned off, the first switch tube is turned on, and the first inductor transfers the energy to the first battery.
4. The active equalization circuit of claim 2, wherein: in the event of an energy imbalance of the second and fifth batteries, the first and third base units operate in a CUK conversion mode;
when the voltage of the second battery is higher than that of the fifth battery, the second switch tube, the first control switch and the third control switch are turned on, the other switch tubes and the control switch are turned off, the energy of the second battery is transferred to the first inductor and the third inductor, then the fifth switch tube is turned on, the other switch tubes and the control switch are turned off, and the third inductor transfers the energy to the fifth battery;
when the voltage of the second battery is lower than that of the fifth battery, the fifth switch tube, the first control switch and the third control switch are turned on, the other switch tubes and the control switch are turned off, the energy of the fifth battery is transferred to the first inductor and the third inductor, then the second switch tube is turned on, the other switch tubes and the control switch are turned off, and the first inductor transfers the energy to the second battery.
5. The active equalization circuit of claim 2, wherein: in the event of an imbalance in the first and fourth battery energies, the first and second base units operate in an extended conversion mode;
when the voltage of the first battery is higher than that of the fourth battery, the first switch tube, the first control switch and the second control switch are turned on, the other switch tubes and the control switch are turned off, the energy of the first battery is transferred to the first inductor and the second inductor, then the fourth switch tube is turned on, the other switch tubes and the control switch are turned off, and the energy of the second inductor is transferred to the fourth battery;
when the voltage of the first battery is lower than that of the fourth battery, the fourth switching tube, the first control switch and the third control switch are turned on, the other switching tubes and the control switch are turned off, the energy of the fourth battery is transferred to the first inductor and the second inductor, then the first switching tube is turned on, the other switching tubes and the control switch are turned off, and the first inductor transfers the energy to the first battery.
6. A control method of an active equalization circuit applied to the active equalization circuit according to any one of claims 1 to 5, the control method comprising:
collecting the battery voltage of each battery in the battery pack;
judging whether the energy unbalance situation of the two batteries exists according to the battery voltage; and
and under the condition of energy unbalance between the two batteries, controlling the corresponding basic units to gate the energy transmission paths, and transferring energy between the two batteries so as to achieve energy balance between the two batteries.
7. The control method of the active equalization circuit according to claim 6, comprising the specific steps of:
s10: collecting the voltages of all batteries, and obtaining the highest voltage battery and the lowest voltage battery;
s20: judging whether the pressure difference between the highest voltage battery and the lowest voltage battery is larger than a preset unbalanced voltage value, if so, executing S30, and if not, not actively balancing;
s30: judging whether the pressure difference between two adjacent batteries in each basic unit is larger than the unbalanced voltage value, if so, transferring energy to the two adjacent batteries in a half-bridge conversion mode; if not, executing S40; s40: judging whether the voltage difference between the 2N and 2N+1+2k batteries is larger than the unbalanced voltage value, if so, performing energy transfer on the 2N and 2N+1+2k batteries in a CUK conversion mode, and if not, executing S50;
s50: judging whether the voltage difference between the 2N-1 and 2N+2 (k+1) batteries is larger than the unbalanced voltage value, if so, performing energy transfer on the 2N-1 and 2N+2 (k+1) batteries in an expansion conversion mode, and if not, executing S60;
s60: and selecting an adjacent battery in a basic unit where the highest voltage battery or the lowest voltage battery is positioned as a bridging battery, firstly carrying out energy transfer on one battery of the highest voltage battery and the lowest voltage battery and the bridging battery in a half-bridge conversion mode, and then carrying out energy transfer on the bridging battery and the other battery in a CUK conversion mode or an expansion conversion mode.
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| CN102522790A (en) * | 2011-12-05 | 2012-06-27 | 中电普瑞科技有限公司 | Equalization device for series battery packs |
| WO2013003869A1 (en) * | 2011-06-15 | 2013-01-03 | De Vries Ian Douglas | Capacitively coupled cell balancer with a common ac bus |
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| TW201246751A (en) * | 2011-05-12 | 2012-11-16 | Lite On Clean Energy Technology Corp | A battery system and a battery equalizer |
| CN114884150A (en) * | 2022-04-06 | 2022-08-09 | 盐城工学院 | E-type lithium battery equalizer based on bidirectional Cuk chopper circuit |
| CN115693838B (en) * | 2022-09-29 | 2023-09-08 | 上海交通大学 | Battery system and method with inter-battery state equalization and fault bypass functions |
| CN115663973A (en) * | 2022-11-21 | 2023-01-31 | 杭州协能科技股份有限公司 | Active equalization circuit and method for battery pack |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| WO2013003869A1 (en) * | 2011-06-15 | 2013-01-03 | De Vries Ian Douglas | Capacitively coupled cell balancer with a common ac bus |
| CN102522790A (en) * | 2011-12-05 | 2012-06-27 | 中电普瑞科技有限公司 | Equalization device for series battery packs |
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