CN115864606A - Active equalization circuit and control method thereof - Google Patents
Active equalization circuit and control method thereof Download PDFInfo
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- CN115864606A CN115864606A CN202310121108.5A CN202310121108A CN115864606A CN 115864606 A CN115864606 A CN 115864606A CN 202310121108 A CN202310121108 A CN 202310121108A CN 115864606 A CN115864606 A CN 115864606A
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Abstract
The invention provides an active equalization circuit and a control method thereof, wherein the active equalization circuit comprises a plurality of basic units, each basic unit comprises two adjacent batteries, a switch component and an energy storage component, the batteries in all the basic units are sequentially connected in series to form a battery pack, when two batteries in the battery pack are in an energy imbalance state, the corresponding basic unit transmits energy between the two batteries through the energy storage component according to an energy transmission path gated by the switch component, so that the energy balance between the two batteries is achieved. 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, under the condition that the energy of any two batteries is unbalanced, the energy can be transferred between the two batteries through the energy storage assembly according to a transmission path switched on by the switch assembly, and therefore the energy balance between the two batteries is realized. And in the balancing process, the number of participating devices is small, 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, a battery system is widely applied to the fields of automobiles, energy storage and the like, and the market demand for battery capacity is higher and higher along with the development of new energy industries. In order to increase the battery capacity, the number of series-parallel connection of the batteries is increasing, but the voltage inconsistency of the single batteries in the battery system can seriously affect the battery capacity, so-called short plate effect is caused, and the reliability of the battery system is affected by the over-charge or over-discharge of the individual single batteries.
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 exerted, each battery is ensured to be fully charged or discharged at the same time, and the service life of the system is prolonged.
As shown in fig. 1, the topology is a switching matrix type active equalization circuit topology, which mainly includes a switching matrix circuit and an isolated bidirectional power supply, the switching 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 aim to solve the problems of more participating 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, and when two batteries in the battery pack are in an energy imbalance state, the corresponding basic unit performs energy transfer 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 module includes two switch tubes, the energy storage module includes the inductance, the one end of inductance is connected the middle node of two adjacent batteries, the other end of inductance is connected the middle node of two switch tubes, under the state that two adjacent batteries energy is unbalanced, electric quantity in the high energy battery is stored and transfer to in the low energy battery to the inductance.
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 unit; under the condition that two batteries with unbalanced energy belong to different basic units respectively, the corresponding control switches are 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 transferred to the low-energy battery.
Preferably, the equalization operation of the active equalization circuit comprises a half-bridge switching mode, a CUK switching mode and an extended switching 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, carrying out energy transfer on 2N and 2N +1+2k batteries between different basic units, wherein N is more than or equal to 1, and K is more than or equal to 0; under the expansion conversion mode, the 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, the first basic unit comprises a first battery and a second battery, a first switch tube and 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 to the sixth battery in sequence, the first switch tube is connected in series to the sixth switch tube in sequence, and the first capacitor, the second capacitor and the third capacitor are connected in series in sequence.
Preferably, the first base unit operates in the half-bridge switching mode in case of an energy imbalance between the first and second batteries; when the voltage of the first battery is higher than that of the second battery, the first switch tube is conducted, the second switch tube is disconnected, the energy of the first battery is transferred to the first inductor, then the first switch tube is disconnected, the second switch tube is conducted, 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 switched on, the first switch tube is switched off, the energy of the second battery is transferred to the first inductor, then the second switch tube is switched off, the first switch tube is switched on, and the first inductor transfers the energy to the first battery.
Preferably, the first and third base units operate in a CUK conversion mode in the event of an energy imbalance between the second and fifth batteries; 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 switched on, other switch tubes and control switches are switched off, the energy of the second battery is transferred to the first inductor and the third inductor, then the fifth switch tube is switched on, other switch tubes and control switches are switched off, and the third inductor transfers the energy to the fifth battery; when the voltage of the second battery is lower than the voltage of the fifth battery, the fifth switching tube, the first control switch and the third control switch are connected, other switching tubes and the control switches are disconnected, the energy of the fifth battery is transferred to the first inductor and the third inductor, then the second switching tube is connected, other switching tubes and the control switches are disconnected, and the first inductor transfers the energy to the second battery.
Preferably, the first and second base units operate in an extended conversion mode in the event of an energy imbalance between the first and fourth batteries; 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 switched on, other switch tubes and control switches are switched off, the energy of the first battery is transferred to the first inductor and the second inductor, then the fourth switch tube is switched on, other switch tubes and control switches are switched off, and the second inductor transfers the energy to the fourth battery; when the voltage of the first battery is lower than that of the fourth battery, the fourth switch tube, the first control switch and the third control switch are switched on, other switch tubes and the control switches are switched off, the energy of the fourth battery is transferred to the first inductor and the second inductor, then the first switch tube is switched on, other switch tubes and the control switches are switched off, and the first inductor transfers the energy to the first battery.
On the other hand, the present invention further provides a control method of an active equalization circuit, which is applied to any one of the above active equalization circuits, and the control method includes:
collecting the battery voltage of each battery in the battery pack;
judging whether the energy imbalance of the two batteries exists or not according to the battery voltage; and
and under the condition of energy imbalance between the two batteries, controlling the corresponding basic unit to gate an energy transmission path, and performing energy transfer 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 acquiring a highest voltage battery and a lowest voltage battery;
s20: judging whether the pressure difference between the highest-voltage battery and the lowest-voltage battery is larger than a preset unbalance voltage value or not, if so, executing S30, and if not, not performing active equalization;
s30: judging whether the pressure difference between two adjacent batteries in each basic unit is greater than the unbalance voltage value, if so, performing energy transfer on the two adjacent batteries in a half-bridge conversion mode; if not, executing S40;
s40: judging whether the voltage difference between the 2N and the 2N +, 1+2k battery is larger than the unbalanced voltage value, if so, performing energy transfer on the 2N and the 2N +, 1+2k battery in a CUK conversion mode, and if not, executing S50;
s50: judging whether the pressure difference between the 2N-1 and 2N +2 (k + 1) batteries is larger than the unbalance voltage value, if so, performing energy transfer on the 2N-1 and 2N +2 (k + 1) batteries in an extended conversion mode, and if not, executing S60;
s60: and selecting the adjacent battery in the basic unit where the highest-voltage battery or the lowest-voltage battery is located 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 extended conversion mode.
The invention has the beneficial effects that: 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, under the condition that the energy of any two batteries is unbalanced, the energy can be transferred between the two batteries through the energy storage assembly according to a transmission path switched on by the switch assembly, and therefore the energy balance between the two batteries is realized. And in the balancing process, the number of participating devices is small, and the conversion efficiency is high.
Specifically, each basic unit is respectively connected with two adjacent batteries and two switching tubes through inductors, so that energy balance can be performed on the two adjacent batteries, each basic unit can perform balance work simultaneously, mutual interference is avoided, the power path is short, and the balance efficiency is high; the number of the used switching tubes is small, and the cost is low.
Specifically, adjacent basic units are connected through capacitors, and an energy transmission path between two basic units is switched on by controlling a switch, so that energy transfer can be performed between any two batteries in different basic units. Energy balance can be carried out point to point among the odd and even batteries of different basic units without multi-stage transmission, so that the risk of energy attenuation is reduced, and the balancing speed is high. And two odd batteries or two even batteries are converted only twice without using an isolating device, so that 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 three working modes are combined to realize the energy equalization of the whole battery pack.
Meanwhile, the active equalization circuit provided by the invention is standardized, modularized and small in volume, the number of batteries is convenient to expand, the number of battery strings is not limited, the upper limit of the working voltage of the battery pack can be greatly improved, the consumption of participating devices is small, the cost is low, and the miniaturization is easy to realize.
Drawings
The above and other objects, features and advantages of the present invention will become more apparent from the following description of the embodiments of the present invention with reference to the accompanying drawings.
FIG. 1 is a schematic diagram of a prior art switching matrix type active equalization circuit;
FIG. 2 is a schematic diagram of a Buck-Boost type active equalization circuit in the prior art;
FIG. 3 is a schematic diagram of a prior art isolated multi-winding coupled active equalization circuit;
FIG. 4 is a schematic diagram of an active equalization circuit according to an embodiment of the present invention;
FIG. 5 is a schematic diagram illustrating the operation of the active balancing circuit shown in FIG. 4 in a half-bridge switching mode to transfer energy between two adjacent cells;
fig. 6 and 7 respectively show the operation diagrams of the active equalization circuit shown in fig. 4 for energy transfer of two odd-even batteries in the CUK conversion mode;
fig. 8 and 9 respectively show the working schematic diagrams of the active equalization circuit shown in fig. 4 for energy transfer of two odd-even batteries in the extended switching mode;
fig. 10 is a flow chart of a control method of an active equalization circuit according to the present invention;
fig. 11 is a flowchart illustrating an embodiment of a control method of an active equalization circuit according to the present invention.
Detailed description of the preferred embodiments
At present, for an active equalization topology scheme of a battery pack, a bidirectional DCDC power conversion circuit is mostly adopted in a basic architecture. The switching matrix type active equalization circuit topology shown in fig. 1 mainly comprises a switching matrix circuit and an isolation bidirectional power supply, wherein the switching 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. As shown in fig. 2, the active equalization circuit topology is based on a non-isolated Buck-Boost DC/DC conversion circuit, a basic unit is a non-isolated Buck-Boost converter, energy transfer between two adjacent batteries is realized, but if a battery to be equalized is a non-adjacent battery and the two batteries are spaced more, multi-level transfer is required, energy may be attenuated in the transfer process, and the equalization speed is affected. As shown in fig. 3, the isolated multi-winding coupled active equalization circuit topology is a bidirectional single-ended flyback DC/DC converter in a multi-winding coupling mode, and a pair of batteries with the highest electric quantity and the lowest electric quantity work at the same time to transfer energy between the batteries.
Aiming at the problems in the prior art, the applicant carries out research and development on the dimensions such as energy conversion efficiency, equalization speed, volume and cost, and provides an active equalization circuit and a control method thereof so as to solve the problems that in the prior art, a series battery pack has energy attenuation, influences equalization speed, and has more participating devices and high cost in the energy equalization process.
To facilitate an understanding of the invention, the invention will now be described more fully with reference to the accompanying drawings. Preferred embodiments of the present invention are shown in the drawings. The invention may, however, be embodied in different forms and should not be construed as limited to the embodiments set forth 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 below with reference to the accompanying drawings.
Fig. 4 is a schematic diagram of an embodiment of the active equalization circuit provided in the present invention.
Referring to fig. 4, the active equalization circuit provided by the present invention includes a plurality of basic units connected in sequence, taking three basic units as an example, which are respectively a first basic unit 110, a second basic unit 120, and a third basic unit 130, each basic unit includes two adjacent batteries, all the batteries are BT1, BT2, BT3, BT4, BT5, and BT6 in sequence according to the arrangement position, and six batteries are connected in series to form a battery pack, that is, each basic unit includes an odd battery and an even battery. When the energy of the 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 assembly according to an energy transmission path gated by the switch assembly, so that energy balance between the two batteries is realized, the number of devices participating in the balancing process is small, 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 base unit 110 includes batteries BT1 and BT2, an inductor L1, switching transistors Q1 and Q2, a control switch S1, and a capacitor C1, wherein one end of the inductor L1 is connected to the intermediate node of the batteries BT1 and BT2, the other end is connected to the intermediate node of the switching transistors Q1 and Q2, one end of the control switch S1 is connected to the 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 base unit 120. The second basic unit 120 includes batteries BT3 and BT4, inductors L2, switching tubes Q3 and Q4, a control switch S2, and a capacitor C2, where one end of the inductor L2 is connected to the middle node of the batteries BT3 and BT4, the other end is connected to the middle node of the switching tubes Q3 and Q4, one end of the control switch S2 is connected to the middle node of the switching tubes 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 comprises batteries BT5 and BT6, inductors L3, switching tubes Q5 and Q6, a control switch S3 and a capacitor C3, wherein one end of the inductor L3 is connected to the middle node of the batteries BT5 and BT6, the other end is connected to the middle node of the switching tubes Q5 and Q6, one end of the control switch S3 is connected to the middle node of the switching tubes 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 can be connected in parallel, and the control switch of each basic unit can be replaced by a bidirectional switch formed by two MOS tubes connected in series in an opposite direction.
In this embodiment, all the switching tubes are PWM power MOS tubes, each cell corresponds to one MOS tube, and each MOS tube is connected in series in sequence. Each MOS transistor and the control switch are connected to a Micro Control Unit (MCU) (not shown in the figure), and are turned on or off according to a switch control signal of the MCU; each battery is connected with a battery Analog Front End (AFE) (not shown in the figure), the AFE chip collects the state of each battery, and the MCU executes a corresponding equalization algorithm according to the state of each battery to control the relevant circuits to realize corresponding control and driving of the MOS and the control switch, thereby realizing energy transfer between each battery of the whole battery pack.
In this embodiment, the balancing operation of the active balancing circuit includes three types, namely a half-bridge switching mode, a CUK switching mode and an extended switching mode, where in the half-bridge switching mode, energy transfer can be performed on two adjacent batteries (for example, BT1 and BT 2) in the same basic unit, and a plurality of basic units can simultaneously operate in this mode, so that the power path is short and the balancing efficiency is high. In a CUK conversion mode, energy transfer can be carried out on 2N and 2N +1+2k batteries between different basic units, wherein N =1,2,3.. And K =0,1,2.. The batteries with the odd numbers are subjected to energy transfer and the number of the odd numbers is higher than that of the batteries with the even numbers (such as BT2 and BT3, BT2 and BT 5). In the extended conversion mode, energy transfer can be carried out on 2N-1 and 2N +2 (K + 1) batteries between different basic units, wherein N =1,2,3, K =0,1,2, the two odd-even batteries of different basic units are subjected to energy transfer, and the number of the odd-even batteries is lower than that of the even-even batteries (such as BT1 and BT4, BT1 and BT 6). In the case that the batteries requiring energy transfer are all odd batteries or are all even batteries, energy can be transferred in combination with a plurality of conversion modes, for example, the first battery BT1 and the third battery BT3 are both odd batteries, when the voltage of the battery BT1 is the highest and the battery BT3 is the lowest, the corresponding basic unit firstly transfers the energy of the battery BT1 to the battery BT2 in the half-bridge conversion mode, and then transfers the energy of the battery BT2 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 balancing 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, at most, twice conversion is carried out, the balancing efficiency is high, and the speed is high.
Referring to fig. 5, a schematic diagram of an active balancing circuit for energy transfer between two adjacent batteries in a half-bridge switching mode is shown. As shown in (a) and (b) of fig. 5, the energy imbalance between the batteries BT1 and BT2, the energy imbalance between the batteries BT3 and BT4, and the first base unit 110 and the second base unit 120 perform the equalizing operation in the half-bridge switching mode simultaneously. 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 the Q1 is turned on, the battery BT1 transfers energy to the inductor L1, and then the switching tube Q1 is turned off, the switching tube Q2 is turned on to perform synchronous rectification, and the inductor L1 transfers energy to the battery BT2, thereby charging the battery BT1 to the 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 into 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, so 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 into the battery BT3 synchronously, thereby improving the equalization efficiency. During the equalization operation in the half-bridge switching mode, the control switches of the respective basic cells are all switched off.
Referring to fig. 6 and 7, schematic diagrams of the active equalization circuit performing energy transfer on two odd-even batteries in the CUK conversion mode are shown. As shown in fig. 6, in a state where the voltage of the battery BT2 is highest and the voltage of the battery BT5 is lowest, the switching tube Q2 and 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 to perform synchronous rectification, the other switching tubes and the control switches are turned off, and the inductor L3 transfers energy to the battery BT5, so that the battery BT2 charges the battery BT 5. As shown in fig. 7, in a state where the voltage of the battery BT2 is lowest and the voltage of the battery BT5 is highest, the switching tube Q5 and 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 to perform synchronous rectification, the other switching tubes and the control switches are turned off, and the inductor L1 transfers energy to the battery BT2, so that the battery BT5 charges the battery BT 2.
Referring to fig. 8 and 9, schematic diagrams of the active equalization circuit performing energy transfer on two odd-even batteries in the extended conversion mode are shown. As shown in fig. 8, in a 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 to perform synchronous rectification, the other switching tubes and the control switches are turned off, and the inductor L2 transfers energy to the battery BT4, so that the battery BT1 charges the battery BT 4. As shown in fig. 9, in a 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 and 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 to perform synchronous rectification, the other switching tubes and the control switches are turned off, and the inductor L1 transfers energy to the battery BT1, so that the battery BT4 charges the battery BT 1.
In this embodiment, the voltage inconsistency index is used as the equalization variable, which is certainly not limited thereto, and in alternative other embodiments, a parameter that is easily thought by a person skilled in the art may also be used as the detection index to implement active energy equalization, 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-described embodiment, 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.
The embodiment of the invention ensures that the single batteries in the battery pack do not have overcharge and overdischarge in the charging and discharging processes by adopting a new active balancing circuit, so as to improve the unbalance phenomenon of the series battery pack, improve the available capacity of the battery pack, reduce the maintenance and replacement period of the series battery pack, prolong the service life of the battery pack and reduce the running cost of the battery pack in application scenes such as hybrid electric vehicles, energy storage power stations and the like.
On the other hand, the present invention further 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 imbalance of the two batteries exists or not according to the battery voltage; and under the condition of energy imbalance between the two batteries, controlling the corresponding basic unit to gate an energy transmission path, and performing energy transfer 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 between the two cells in the acquired voltage, and if it is determined that there is an energy imbalance, the MCU controls the on/off of the switch assembly of the corresponding basic unit through the switch control signal to select the energy transmission path of the basic unit, thereby achieving energy balance between the two cells.
In this embodiment, whether there is a situation of energy imbalance between two batteries is determined according to a voltage difference between a highest-voltage battery and a lowest-voltage battery in a battery pack, and under the determination criterion, as shown in fig. 11, a control method of an active equalization circuit specifically includes the steps of:
s10: collecting the voltages of all batteries, and acquiring a highest voltage battery and a lowest voltage battery;
s20: judging whether the pressure difference between the highest-voltage battery and the lowest-voltage battery is larger than a preset unbalance voltage value or not, if so, executing S30, and if not, not performing active equalization;
s30: judging whether the pressure difference between two adjacent batteries in each basic unit is greater than the unbalance voltage value, if so, performing energy transfer on the two adjacent batteries in a half-bridge conversion mode; if not, executing S40;
s40: judging whether the voltage difference between 2N and 2N +1+2k batteries is larger than the unbalance 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 pressure difference between the 2N-1 and 2N +2 (k + 1) batteries is larger than the unbalance voltage value, if so, performing energy transfer on the 2N-1 and 2N +2 (k + 1) batteries in an extended conversion mode, and if not, executing S60;
s60: and selecting the adjacent battery in the basic unit where the highest-voltage battery or the lowest-voltage battery is located 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 extended conversion mode.
In step S10, the AFE collects voltages Vi (i =1,2,3 \ 8230; \8230; \ 8230; (n)) of all the cells in the battery pack and feeds back the voltages 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, i.e., vp = Vmax, vk = Vmin.
In step S20, the MCU may preset an imbalance voltage value Vth, obtain a voltage difference Δ V1 between the highest-voltage battery BTp and the lowest-voltage battery BTk through a formula Δ V1= Vp-Vk, and determine that, if Δ V1 > Vth, it is determined that there is an energy imbalance between the highest-voltage battery BTp and the lowest-voltage battery BTk, and balancing needs to be performed, then step S30 is executed, and if Δ V1 < Vth, it is determined that there is no energy imbalance between the highest-voltage battery BTp and the lowest-voltage battery BTk, then active balancing is not needed.
In step S30, it is respectively determined whether the voltage difference Δ V2 between two adjacent batteries in each basic unit is greater than the unbalanced voltage value, if Δ V2 of any basic unit is greater than Vth, the corresponding basic unit performs energy transfer on the two adjacent batteries in the half-bridge conversion mode, and if all the basic units are Δ V2 < Vth, step S40 is executed.
In step S40, it is further determined whether the voltage difference Δ V3 between two odd-even batteries not belonging to the same basic unit is greater than the unbalanced voltage value, where the two odd-even batteries are 2N and 2n +1+2k batteries, N =1,2, \ 8230; k =0,1,2, \ 8230, i.e. the number of bits of the odd cells is higher than the number of bits of the even cells (e.g. cells BT2 and BT3, cells BT2 and BT 5). In the case where Δ V3 > Vth, the corresponding basic unit performs energy transfer on the two parities in the CUK conversion mode, and if Δ V3 < Vth, step S50 is performed.
In step S50, it is further determined whether a voltage difference Δ V4 between two odd-even batteries not belonging to the same basic unit is greater than an unbalanced voltage value, where the two odd-even batteries are 2N-1 and 2n +2 (k + 1) batteries, N =1,2, \8230; k =0,1,2, \ 8230, i.e. the number of bits of the odd cells is lower than that of the even cells (e.g. cells BT1 and BT4, cells BT1 and BT6, cells BT3 and BT 6). In the case where Δ V4 > Vth, the corresponding base unit performs energy transfer of the two odd-even batteries in the extended conversion mode, and if Δ V4 < Vth, step S60 is performed.
In step S60, if it is determined that the highest-voltage battery BTp and the lowest-voltage battery BTk are both odd-numbered batteries or even-numbered batteries, one of the other batteries is selected as a bridge battery, 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 a half-bridge conversion mode, and then the bridge battery and the other battery are subjected to energy transfer in a 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, the first base unit 110 first transfers the energy of the battery BT1 to the battery BT2 adjacent to the battery BT1 in the half-bridge conversion mode, and then transfers the energy of the battery BT2 to the battery BT3 in the CUK conversion mode, so as to implement the energy conversion between the two odd-numbered batteries, and implement the energy conversion between the two even-numbered batteries in the same manner.
Specifically, when the highest-voltage battery BTp and the lowest-voltage battery BTk are both odd-numbered batteries, a battery with a low number of bits may be selected as the first target battery, and a battery adjacent to the first target battery in the same basic unit may be selected as the bridging battery, for example, when the highest-voltage battery is BT1 and the lowest-voltage battery is BT5, the battery BT1 has a low number of bits and is selected as the first target battery, and BT2 is selected as the bridging battery. When both the highest-voltage battery BTp and the lowest-voltage battery BTk are the 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 units and the cascade design of the adjacent basic units, a corresponding working mode can be selected under the condition of energy imbalance between any two batteries, and the switching of the energy path is realized by the switch control signal, so that the energy is transferred from the higher battery to the lower battery, the energy transfer between the two batteries is performed, the voltage balance between the two batteries is achieved, and thus, the phenomena of overcharge and overdischarge of each battery in the charging and discharging processes are avoided, and the problem of unbalance of the series battery pack is solved.
It should be noted that in the description of the present invention, it should be understood that the terms "upper", "lower", "inner", etc. indicate orientation or positional relationship only for convenience in describing the present invention and simplifying description, but do not indicate or imply that the referenced components or elements must have a particular orientation, be constructed and operated in a particular orientation, and therefore should not be construed as limiting the present invention.
Further, in this document, the contained terms "include", "contain" or any other variation thereof are intended to cover a non-exclusive inclusion, so that a process, a method, an article or an apparatus including a series of elements includes not only those elements but also other elements not explicitly listed or inherent to such process, method, article or apparatus. Without further limitation, an element defined by the phrases "comprising a," "8230," "8230," or "comprising" does not exclude the presence of additional like elements in a process, method, article, or apparatus that comprises the element.
Finally, it should be noted that: it should be understood that the above examples are only for clearly illustrating the present invention and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications of the invention may be made without departing from the scope of the invention.
Claims (10)
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 two batteries in the battery pack are in an energy imbalance state, the corresponding basic unit conducts energy transfer between the two batteries through the energy storage assembly according to an energy transmission path gated by the switch assembly, so that energy balance between the two batteries is achieved.
2. The active equalization circuit of claim 1 wherein: the switch module includes two switch tubes, the energy storage subassembly includes the inductance, the one end of inductance is connected the intermediate node of two adjacent batteries, the other end of inductance is connected the intermediate node of two switch tubes under the state of two adjacent battery energy imbalances, electric quantity in the high energy battery is stored to the inductance and transfer to in the low energy battery.
3. The active equalization circuit of claim 2 wherein: 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 a 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 belong to different basic units respectively, the corresponding control switches are 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 transferred to the low-energy battery.
4. The active equalization circuit of claim 3 wherein: 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 2N and 2N +1+2k batteries among different basic units, wherein N is larger than or equal to 1, and K is larger than or equal to 0;
under the expansion conversion mode, the 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.
5. The active equalization circuit of claim 4 wherein: the multiple 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 switching tube, a second switching 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 to the sixth battery in sequence, the first switch tube is connected in series to the sixth switch tube in sequence, and the first capacitor, the second capacitor and the third capacitor are connected in series in sequence.
6. The active equalization circuit of claim 5 wherein: the first base unit operates in the half-bridge switching mode in case of an energy imbalance between the first and second batteries;
when the voltage of the first battery is higher than that of the second battery, the first switch tube is conducted, the second switch tube is disconnected, the energy of the first battery is transferred to the first inductor, then the first switch tube is disconnected, the second switch tube is conducted, 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 conducted, the first switch tube is disconnected, the energy of the second battery is transferred to the first inductor, then the second switch tube is disconnected, the first switch tube is conducted, and the first inductor transfers the energy to the first battery.
7. The active equalization circuit of claim 5 wherein: in the event of an energy imbalance between 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 switched on, other switch tubes and control switches are switched off, the energy of the second battery is transferred to the first inductor and the third inductor, then the fifth switch tube is switched on, other switch tubes and control switches are switched off, and the third inductor transfers the energy to the fifth battery;
when the voltage of the second battery is lower than the voltage of the fifth battery, the fifth switching tube, the first control switch and the third control switch are connected, other switching tubes and the control switches are disconnected, the energy of the fifth battery is transferred to the first inductor and the third inductor, then the second switching tube is connected, other switching tubes and the control switches are disconnected, and the first inductor transfers the energy to the second battery.
8. The active equalization circuit of claim 5 wherein: in the event of an energy imbalance between 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 switched on, other switch tubes and control switches are switched off, the energy of the first battery is transferred to the first inductor and the second inductor, then the fourth switch tube is switched on, other switch tubes and control switches are switched off, and the second inductor transfers the energy to the fourth battery;
when the voltage of the first battery is lower than the voltage of the fourth battery, the fourth switch tube, the first control switch and the third control switch are connected, other switch tubes and the control switches are disconnected, the energy of the fourth battery is transferred to the first inductor and the second inductor, then the first switch tube is connected, other switch tubes and the control switches are disconnected, and the first inductor transfers the energy to the first battery.
9. A control method of an active equalization circuit applied to the active equalization circuit according to any one of claims 1 to 8, the control method comprising:
collecting the battery voltage of each battery in the battery pack;
judging whether the energy imbalance of the two batteries exists or not according to the battery voltage; and
and under the condition of energy imbalance between the two batteries, controlling the corresponding basic unit to gate an energy transmission path, and performing energy transfer between the two batteries so as to achieve energy balance between the two batteries.
10. The method of claim 9, comprising the steps of:
s10: collecting the voltages of all batteries, and acquiring a highest voltage battery and a lowest voltage battery;
s20: judging whether the pressure difference between the highest-voltage battery and the lowest-voltage battery is larger than a preset unbalance voltage value or not, if so, executing S30, and if not, not performing active equalization;
s30: judging whether the pressure difference between two adjacent batteries in each basic unit is greater than the unbalance voltage value, if so, performing energy transfer on the two adjacent batteries in a half-bridge conversion mode; if not, executing S40;
s40: judging whether the voltage difference between 2N and 2N +1+2k batteries is larger than the unbalance 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 pressure difference between the 2N-1 and 2N +2 (k + 1) batteries is larger than the unbalance voltage value, if so, performing energy transfer on the 2N-1 and 2N +2 (k + 1) batteries in an extended conversion mode, and if not, executing S60;
s60: and selecting the adjacent battery in the basic unit where the highest-voltage battery or the lowest-voltage battery is located 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 extended conversion mode.
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