CN110667437B - Equalizing circuit based on switch capacitor and LC resonance unit and control method - Google Patents
Equalizing circuit based on switch capacitor and LC resonance unit and control method Download PDFInfo
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- CN110667437B CN110667437B CN201911014474.0A CN201911014474A CN110667437B CN 110667437 B CN110667437 B CN 110667437B CN 201911014474 A CN201911014474 A CN 201911014474A CN 110667437 B CN110667437 B CN 110667437B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
- B60L58/00—Methods or circuit arrangements for monitoring or controlling batteries or fuel cells, specially adapted for electric vehicles
- B60L58/10—Methods or circuit arrangements for monitoring or controlling batteries or fuel cells, specially adapted for electric vehicles for monitoring or controlling batteries
- B60L58/18—Methods or circuit arrangements for monitoring or controlling batteries or fuel cells, specially adapted for electric vehicles for monitoring or controlling batteries of two or more battery modules
- B60L58/22—Balancing the charge of battery modules
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
- B60L58/00—Methods or circuit arrangements for monitoring or controlling batteries or fuel cells, specially adapted for electric vehicles
- B60L58/10—Methods or circuit arrangements for monitoring or controlling batteries or fuel cells, specially adapted for electric vehicles for monitoring or controlling batteries
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
- H02J7/0013—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries acting upon several batteries simultaneously or sequentially
- H02J7/0014—Circuits for equalisation of charge between batteries
- H02J7/0019—Circuits for equalisation of charge between batteries using switched or multiplexed charge circuits
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
- B60L2240/00—Control parameters of input or output; Target parameters
- B60L2240/40—Drive Train control parameters
- B60L2240/54—Drive Train control parameters related to batteries
- B60L2240/547—Voltage
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/60—Other road transportation technologies with climate change mitigation effect
- Y02T10/70—Energy storage systems for electromobility, e.g. batteries
Abstract
The invention discloses an equalizing circuit and a control method based on a switch capacitor and an LC resonance unit, wherein the equalizing circuit comprises more than two switch capacitor units which have the same structure and are respectively provided with a battery; the device also comprises an LC resonance unit and a battery; after the batteries configured by all the switch capacitor units are connected in series, the anode is connected to the cathode of the battery configured by the LC resonance unit. There are two modes of operation: in the mode 1, when the maximum voltage difference between the batteries exceeds a mode switching threshold, the switched capacitor unit works to realize energy transmission among all the batteries, so that the voltage difference between the batteries is quickly reduced to the mode switching threshold; and in the mode 2, when the maximum voltage difference between the batteries is smaller than or equal to the mode switching threshold value, the LC resonance unit works, so that the equalizing circuit still has larger equalizing current when the voltage difference between the batteries is smaller, and the equalizing speed is ensured. Different equalization speeds can be obtained by controlling the switching threshold values of the two modes so as to meet the requirements of different occasions.
Description
Technical Field
The invention relates to the technical field of lithium battery voltage equalization, in particular to an equalization circuit based on a switch capacitor and an LC resonance unit and a control method.
Background
As an environment-friendly vehicle, a pure electric vehicle has been studied and applied in a large amount. The lithium battery is one of ideal power sources of a power system of a pure electric vehicle due to the advantages of high energy density, low self-discharge rate, no memory effect and the like. However, because the rated voltage of a single lithium battery is low, typically not exceeding 4.2V, a large number of lithium batteries are typically used in series to provide a sufficiently large voltage to the load. Due to the reasons of production and manufacture, the battery monomers have inconsistency in performances such as internal resistance, voltage, capacity and the like, and meanwhile, the inconsistency is aggravated due to the difference of ambient temperature and the aging of the battery in the use process of the battery, so that the waste of the battery capacity is caused, and the service life of the battery is reduced. In order to solve such inconsistency problem, to extend the service life of the battery, it is necessary to add an equalization circuit to the battery pack.
In order to solve the problem of battery inconsistency, various equalization circuits and control strategies thereof have been proposed. Existing equalization circuits are largely divided into energy-dissipative and non-energy-dissipative types. The energy dissipation type equalization circuit is small in size and low in cost, but equalization energy is consumed in a heat energy mode, and equalization efficiency is low. The non-energy dissipation type equalization circuit uses non-energy dissipation elements such as a capacitor, an inductor and the like as energy transmission media to realize the transmission of energy from a high-voltage battery to a low-voltage battery. The equalization circuit based on the single converter and the switch group can realize rapid equalization of any two batteries in the battery group, but cannot equalize a plurality of batteries at the same time. Therefore, as the number of unbalanced batteries increases, the equalization speed of the circuit is greatly reduced. The traditional switched capacitor equalization circuit can equalize a plurality of batteries simultaneously, and the equalization speed is higher when the voltage difference between the batteries is larger, but the equalization speed is lower when the voltage difference between the batteries is smaller; in addition, the traditional switched capacitor equalization circuit is only controlled by a pair of control signals with complementary duty ratios, the equalization effect is greatly influenced by the inconsistency of parameters among the batteries and the circuit parameters, the voltage difference among the batteries after equalization is uncontrollable, and the satisfactory equalization effect cannot be realized.
Disclosure of Invention
The invention aims to provide an equalizing circuit based on a switch capacitor and an LC resonance unit and a control method.
The technical scheme for realizing the purpose of the invention is as follows:
an equalizing circuit based on a switch capacitor and an LC resonance unit comprises more than two switch capacitor units with the same structure, wherein each switch capacitor unit is provided with a battery; the switch capacitor unit comprises a capacitor and four MOS tubes; the drain electrode of the first MOS tube is connected with the drain electrode of the third MOS tube and then connected to one end of the capacitor, and the drain electrode of the second MOS tube is connected with the drain electrode of the fourth MOS tube and then connected to the other end of the capacitor; the source electrode of the first MOS tube is connected to the positive electrode of the battery, and the source electrode of the second MOS tube is connected to the negative electrode of the battery; the device also comprises an LC resonance unit, wherein the LC resonance unit is also provided with a battery; the LC resonance unit comprises a resonance capacitor, a resonance inductor and three MOS tubes; the resonance capacitor and the resonance inductor are connected in series to form a resonance branch; the source electrode of the first MOS tube and the drain electrode of the third MOS tube are connected and then connected to one end of the resonance branch, and the source electrode of the second MOS tube and the source electrode of the third MOS tube are connected and then connected to the other end of the resonance branch; the drain electrode of the first MOS tube is connected to the positive electrode of the battery, and the drain electrode of the second MOS tube is connected to the negative electrode of the battery; after the batteries configured by all the switch capacitor units are connected in series, the anode is connected to the cathode of the battery configured by the LC resonance unit; the sources of the third MOS tubes of all the switch capacitor units are connected to the drain electrodes of the third MOS tubes of the LC resonance unit, and the sources of the fourth MOS tubes of all the switch capacitor units are connected to the sources of the third MOS tubes of the LC resonance unit.
The control method of the voltage equalization circuit comprises the following steps of
Detecting the voltage of each battery, and calculating the voltage difference between the highest voltage and the lowest voltage;
when the voltage difference is greater than the mode switching threshold, let V Gsa First MOS tube and second MOS tube for controlling all switch capacitance units, V GSb Controlling the third MOS tube, the fourth MOS tube and the first MOS tube and the second MOS tube of the LC resonance unit of all the switch capacitor units until the voltage difference is smaller than or equal to the mode switching threshold; the V is GSa And V GSb A PWM signal complementary to a pair of frequency fixed duty cycles;
when the voltage difference is less than or equal to the mode switching threshold value, let V GSc Each MOS tube of the switch capacitor unit or the first MOS tube of the LC resonance unit connected with the battery with the lowest control voltage,MOS tube number two, V GSr Three MOS tubes for controlling LC resonance unit, V GSd Controlling each MOS tube of the switch capacitor unit connected with the battery with highest voltage or the first MOS tube and the second MOS tube of the LC resonance unit until the voltage difference is smaller than the equalization termination threshold; the V is GSc 、V GSr And V GSd The periods of the PWM signals are 3/2 of the resonance period of the resonance branch, the conduction time is 1/2 of the resonance period of the resonance branch, and the conduction time is according to V GSc 、V GSr 、V GSd Is a sequential distribution of (a).
The invention has two working modes: in the mode 1, when the maximum voltage difference between the batteries exceeds a mode switching threshold, the switched capacitor unit works to realize energy transmission among all the batteries, so that the voltage difference between the batteries is quickly reduced to the mode switching threshold; and in the mode 2, when the maximum voltage difference between the batteries is smaller than or equal to the mode switching threshold value, the LC resonance unit works, so that the equalizing circuit still has larger equalizing current when the voltage difference between the batteries is smaller, and the equalizing speed is ensured. Different equalization speeds can be obtained by controlling the switching threshold values of the two modes so as to meet the requirements of different occasions. Meanwhile, the invention adopts a control method based on battery voltage, and larger balanced current still exists when the voltage difference between batteries is smaller, so the voltage difference between batteries can be quickly reduced to the set balanced termination threshold value, thereby meeting the requirements of the voltage difference between batteries in different occasions.
Drawings
FIG. 1 is a circuit block diagram of the present invention;
FIG. 2 is a control flow diagram of the present invention;
FIG. 3 is a circuit block diagram of an embodiment;
FIG. 4a shows an embodiment in an operating state I;
FIG. 4b shows an embodiment of the working state II;
FIG. 4c shows an embodiment in operation III;
FIG. 4d shows an operating state IV of the embodiment;
fig. 4e shows an operating state v of the embodiment;
FIG. 5 shows the capacitor C in equalization mode 1 according to an embodiment 1 Voltage and current simulation waveforms of (a);
FIG. 6 shows the resonant capacitor C in equalizing mode 2 according to an embodiment r Voltage and current simulation waveforms of (a);
FIG. 7 shows the threshold voltage DeltaV for mode switching according to the embodiment 1 Simulation waveforms of battery voltage at=0.6v;
FIG. 8 shows the threshold voltage DeltaV for mode switching according to an embodiment 1 Simulation waveforms of battery voltage at=0.4v;
FIG. 9 shows the threshold voltage DeltaV for mode switching according to the embodiment 1 Simulation waveform of battery voltage at=0.1v.
Detailed Description
Further details are described below with reference to the drawings.
An equalization circuit based on a switch capacitor and an LC resonance unit, as shown in figure 1, comprises batteries B connected in series in turn 1 ,B 2 ,…,B n Wherein n is a positive integer greater than or equal to 3; the device also comprises n-1 switch capacitor units and 1 LC resonance unit, wherein each switch capacitor unit has the same structure. Battery B 1 ,B 2 ,…,B n-1 Each battery is connected with 1 switch capacitor unit; battery B n Is connected with the LC resonance unit.
And battery B i (i=1, 2, …, n-1) connected i-th switched capacitor unit: comprises 4 MOS tubes Q i1 、Q i2 、Q i3 、Q i4 And 1 capacitor C i The method comprises the steps of carrying out a first treatment on the surface of the MOS tube Q i1 Drain electrode of (d) and MOS transistor Q i3 Is connected to the capacitor C after the drain electrode of the capacitor C is connected i Is a MOS tube Q i2 Drain electrode of (d) and MOS transistor Q i4 Is connected to the capacitor C after the drain electrode of the capacitor C is connected i Is arranged at the other end of the tube; MOS tube Q i1 Source of (c) and battery B i Is connected with the positive electrode of the MOS tube Q i2 Source of (c) and battery B i Is connected with the negative electrode of the battery; MOS tube Q i3 Is connected to the common connection point a, MOS transistor Q i4 Is connected to the common connection point b.
And battery B n Connected LC resonant cells: comprising 1 resonant capacitor C r 1 resonant inductance L r 3 MOS tubes Q n3 、Q n4 And Q r The method comprises the steps of carrying out a first treatment on the surface of the MOS tube Q n3 Drain of (c) and battery B n The positive electrode of which is connected with the source electrode which is connected with the common connection point a; MOS tube Q n4 Drain of (c) and battery B n The negative electrode of which is connected with the source electrode of which is connected with the common connection point b; resonance capacitor C r And resonant inductance L r After being connected in series, one end is connected to the common connection point a, and the other end is connected to the common connection point b; MOS tube Q r Is connected to the common connection point a and the source is connected to the common connection point b.
The equalization circuit based on the switch capacitor and the LC resonance unit has two equalization modes: equalization mode 1 and equalization mode 2.
In the equalizing mode 1, the MOS transistor Q in the LC resonance unit n3 、Q n4 The switch capacitor unit works to realize energy transmission among all batteries and reduce the maximum voltage difference among the batteries; the equalization mode 1 has two working states, including
(1) Working state I: energy in battery B i (i=1, 2, …, n-1) and a capacitance C i (i=1, 2, …, n-1);
(2) Working state II: energy in battery B n And capacitor C 1 ,C 2 ,…,C n-1 Transmission between them;
in the equalizing mode 2, MOS tubes and LC resonance units in all the switch capacitor units work, and the battery with the highest voltage transmits energy to the battery with the lowest voltage, so that the quick equalization of the battery voltage is realized; equalization mode 2 has three operating states, including
(1) Operating state III: resonance capacitor C r And resonant inductance L r To battery B with lowest voltage j (j=1, 2, …, n) transmitting energy;
(2) Working state VI: resonance capacitor C r And resonant inductance L r Resonance is generated, resonance capacitance C r The voltage direction of (2) is changed from positive to negative;
(3) Operating state V: battery B with highest voltage k (k=1, 2, …, n, k+.j) to the resonance capacitance C r And resonant inductanceL r Energy is transmitted.
Fig. 2 is a flowchart of a control method of the equalizing circuit based on the switch capacitor and the LC resonance unit, which includes the following detailed control steps
(1) Initializing a system;
(2) Detecting the voltages of all batteries in real time;
(3) Calculating the maximum value V of the battery voltage according to the detection results of all the battery voltages Bmax Minimum value V Bmin And the maximum voltage difference DeltaV between the cells Bmax ；
(4) Determining the maximum voltage difference DeltaV between batteries Bmax Whether or not it is greater than the equalization termination threshold voltage DeltaV 2 If yes, balancing, otherwise ending the balancing process;
(5) When DeltaV Bmax >ΔV 2 At the time, deltaV is judged Bmax Whether or not it is smaller than the mode switching threshold voltage DeltaV 1 If yes, entering an equalization mode 2, otherwise, entering an equalization mode 1;
(6) Returning to the step (2) after the equalization mode 2 or the equalization mode 1 is finished until the maximum voltage difference DeltaV between the batteries in the step (4) Bmax Less than or equal to threshold voltage DeltaV 2 The condition of ending the equalization process is reached;
(7) The equalization process ends.
Specific examples are as follows:
the equalization circuit of 4 batteries is taken as an embodiment, and the circuit structure diagram is shown in fig. 3. Assume an initial battery voltage V B4 >V B3 >V B2 >V B1 And DeltaV Bmax >ΔV 1 . At this time, the equalization circuit operates in equalization mode 1, and the control signal in the equalization mode is a pair of PWM signals V with complementary fixed duty ratios GSa And V GSb . At this time, the operation state of the equalizing circuit is as follows:
(1) Working state I: PWM signal V GSa Is at high level, controls the MOS tube Q 11 、Q 12 、Q 21 、Q 22 、Q 31 、Q 32 Conducting; the rest MOS transistors are turned off; as shown in fig. 4 a. Capacitor C 1 、C 2 、C 3 Respectively to battery B 1 、B 2 、B 3 Energy is transmitted.
(2) Working state II: PWM signal V GSb Is at high level, controls the MOS tube Q 13 、Q 14 、Q 23 、Q 24 、Q 33 、Q 34 、Q 43 、Q 44 Conducting; the rest MOS transistors are turned off; as shown in fig. 4 b. Energy in battery B 4 And capacitor C 1 、C 2 、C 3 And transmitted therebetween.
When the maximum voltage difference between the batteries becomes DeltaV Bmax ≤ΔV 1 When the equalization circuit is operating in equalization mode 2. The control signal in the equalizing mode is three PWM signals V with the same frequency GSc 、V GSd And V GSr The method comprises the steps of carrying out a first treatment on the surface of the The period of the three PWM signals is 3/2 of the resonance period of the LC circuit, the conduction time is 1/2 of the resonance period of the LC circuit, and the conduction time is according to V GSc 、V GSr 、V GSd Is a sequential distribution of (a). At this time, the operation state of the equalizing circuit is as follows:
(1) Operating state III: according to the detected battery voltage, the battery with the lowest voltage is B j (j=1, 2,3, 4); PWM signal V GSc Is at high level, controls the MOS tube Q j1 、Q j2 、Q j3 、Q j4 (when j=1, 2, 3) turn on or MOS transistor Q j3 、Q j4 (when j=4) on; the rest MOS transistors are turned off; resonance capacitor C r And resonant inductance L r To battery B j Energy is transmitted. FIG. 4c shows a battery B 1 Equalizing circuit working state when voltage is lowest, wherein MOS tube Q 11 、Q 12 、Q 13 、Q 14 The other MOS tubes are turned off; resonance capacitor C r And resonant inductance L r To battery B 1 Energy is transmitted.
(2) Working state VI: PWM signal V GSr Is at high level, controls the MOS tube Q r Conducting; the rest MOS transistors are turned off; as shown in fig. 4 d; resonance capacitor C r And resonant inductance L r Resonance is generated, resonance capacitance C r The voltage direction of (2) is changed from positive to negative.
(3) Operating state V: according to the detected battery voltage, the battery with the highest voltage is B k (k=1, 2,3,4, k+.j); PWM signal V GSd Is at high level, controls the MOS tube Q k1 、Q k2 、Q k3 、Q k4 (when k=1, 2, 3) turn-on or MOS transistor Q k3 、Q k4 (when k=4) on; the rest MOS transistors are turned off; battery B k To resonance capacitor C r And resonant inductance L r Energy is transmitted. FIG. 4e shows a battery B 4 The equalization circuit working state when the voltage is highest, wherein the MOS tube Q 43 、Q 44 The other MOS tubes are turned off; battery B 4 To resonance capacitor C r And resonant inductance L r Energy is transmitted.
FIG. 5 shows the capacitor C in equalization mode 1 according to an embodiment 1 Voltage and current simulation waveforms of (a); FIG. 6 shows the equalizing capacitance C in equalizing mode 2 according to an embodiment r Voltage and current simulation waveforms of (a); FIG. 7 shows the threshold voltage DeltaV for mode switching according to the embodiment 1 Simulation waveforms of battery voltage at=0.6v; FIG. 8 shows the threshold voltage DeltaV for mode switching according to an embodiment 1 Simulation waveforms of battery voltage at=0.4v; FIG. 9 shows the threshold voltage DeltaV for mode switching according to the embodiment 1 Simulation waveform of battery voltage at=0.1v. The waveforms of fig. 5 and 6 are at the mode switching threshold voltage Δv 1 Obtained with =0.4v. Simulation parameters of the circuit: capacitor C 1 、C 2 、C 3 Are 200 mu F, and the parasitic resistance of each capacitor branch is 120mΩ; the resonance capacitance is 10F, the resonance inductance is 4.7H, and the parasitic resistance of each resonance branch is 120mΩ; the switching frequency of the equalization mode 1 is 50kHz, and the switching frequency of the equalization mode 2 is 15.5kHz; equalization termination threshold voltage DeltaV 2 =1 mV; replacing the battery with a capacitance of 0.2F; an initial voltage of V B1 ＝3.0V、V B2 ＝3.2V、V B3 ＝3.4V、V B4 ＝3.6V。
As shown in fig. 5, when the equalization circuit is operating in equalization mode 1, the circuit has two operating states, operating states I and ii. In the operating state I, the current direction is negative, i.e. the current flows out of the capacitor C 1 Energy is transferred from capacitor C 1 To battery B 1 Capacitance C 1 Is a voltage drop of (2); in state II, the direction of current is positive, i.e. current flows into capacitor C 1 Energy is supplied from battery B 4 To capacitor C 1 Capacitance C 1 Is increased.
As shown in fig. 6, when the equalization circuit is operating in equalization mode 2, the circuit has three operating states, operating states iii, iv and v. In the working state III, the resonant capacitor C flows r The current of (2) decreases from zero to a minimum value and then becomes zero, and the energy is from the equalizing capacitor C r To battery B 1 Resonance capacitor C r Is a voltage drop of (2); in the working state IV, the resonant capacitor C r And resonant inductance L r Resonance occurs and flows through the resonance capacitor C r Is negative, resonance capacitance C r Is reversed in the voltage direction; in the operating state V, the resonant capacitor C flows r The current of (a) rises from zero to a maximum value and becomes zero again, and the energy is from battery B 4 To the equalizing capacitance C r Resonance capacitor C r Is increased.
As shown in fig. 7, when the threshold voltage Δv 1 When the voltage distribution is=0.6v, the equalization circuit only works in the equalization mode 2, the equalization time of the circuit is 0.081s, and the average voltage of the battery after equalization is 3.277V; as shown in fig. 8, when the threshold voltage Δv 1 When the voltage distribution is=0.4v, the equalization circuit works in the equalization mode 1 first, and works in the equalization mode 2 after the maximum voltage difference between the batteries is smaller than 0.4V, the equalization time of the circuit is 0.072s, and the average voltage of the battery after equalization is 3.282V; as shown in fig. 9, when the threshold voltage Δv 1 When the voltage distribution is=0.1v, the equalization circuit is firstly operated in the equalization mode 1, and when the maximum voltage difference between the batteries is smaller than 0.4V, the equalization circuit is operated in the equalization mode 2, the equalization time of the circuit is 0.146s, and the average voltage of the battery after equalization is 3.294V. Comparing the three simulation results, it can be known that: equalization mode 1 equalizes fast when the voltage difference between the batteries is large, and equalizes slow when the voltage difference between the batteries is small; the speed advantage of the equalization mode 2 is obvious when the voltage difference between the batteries is smaller, and the speed is slower than that of the equalization mode 1 when the voltage difference between the batteries is larger; and is also provided withThreshold voltage DeltaV 1 The larger the working range of the equalization mode 2 is, the lower the average voltage after the circuit is equalized is, and the lower the equalization efficiency of the circuit is; by adjusting the threshold voltage DeltaV 1 The equalization speed and the equalization efficiency of the circuit can be adjusted according to the requirement.
In summary, the equalization circuit and the control method based on the switch capacitor and the LC resonance unit can solve the problem that the equalization speed is low when the voltage difference between batteries is smaller in the traditional switch capacitor equalization circuit through switching of two equalization modes, and solve the problem that the equalization circuit based on a single converter and a switch group can only equalize two batteries at the same time and has low equalization speed. In addition, the invention can control the voltage difference between the batteries after the equalization is finished, and solves the problem that the voltage difference is uncontrollable after the equalization of the traditional switched capacitor equalization circuit.
Claims (2)
1. An equalizing circuit based on a switch capacitor and an LC resonance unit is characterized by comprising more than two switch capacitor units with the same structure, wherein each switch capacitor unit is provided with a battery; the switch capacitor unit comprises a capacitor and four MOS tubes; the drain electrode of the first MOS tube is connected with the drain electrode of the third MOS tube and then connected to one end of the capacitor, and the drain electrode of the second MOS tube is connected with the drain electrode of the fourth MOS tube and then connected to the other end of the capacitor; the source electrode of the first MOS tube is connected to the positive electrode of the battery, and the source electrode of the second MOS tube is connected to the negative electrode of the battery;
the device also comprises an LC resonance unit, wherein the LC resonance unit is also provided with a battery; the LC resonance unit comprises a resonance capacitor, a resonance inductor and three MOS tubes; the resonance capacitor and the resonance inductor are connected in series to form a resonance branch; the source electrode of the first MOS tube and the drain electrode of the third MOS tube are connected and then connected to one end of the resonance branch, and the source electrode of the second MOS tube and the source electrode of the third MOS tube are connected and then connected to the other end of the resonance branch; the drain electrode of the first MOS tube is connected to the positive electrode of the battery, and the drain electrode of the second MOS tube is connected to the negative electrode of the battery;
after the batteries configured by all the switch capacitor units are connected in series, the anode is connected to the cathode of the battery configured by the LC resonance unit; the sources of the third MOS tubes of all the switch capacitor units are connected to the drain electrodes of the third MOS tubes of the LC resonance unit, and the sources of the fourth MOS tubes of all the switch capacitor units are connected to the sources of the third MOS tubes of the LC resonance unit.
2. The control method of an equalization circuit according to claim 1, comprising
Detecting the voltage of each battery, and calculating the voltage difference between the highest voltage and the lowest voltage;
when the voltage difference is greater than the mode switching threshold, let V GSa First MOS tube and second MOS tube for controlling all switch capacitance units, V GSb Controlling the third MOS tube and the fourth MOS tube of all the switch capacitor units and the first MOS tube and the second MOS tube of the LC resonance unit until the voltage difference is smaller than or equal to the mode switching threshold; the V is GSa And V GSb A PWM signal complementary to a pair of frequency fixed duty cycles;
when the voltage difference is less than or equal to the mode switching threshold value, let V GSc Each MOS tube of the switch capacitor unit or the first MOS tube and the second MOS tube of the LC resonance unit connected with the battery with the lowest control voltage, V GSr Three MOS tubes for controlling LC resonance unit, V GSd Controlling each MOS tube of the switch capacitor unit connected with the battery with highest voltage or the first MOS tube and the second MOS tube of the LC resonance unit until the voltage difference is smaller than the equalization termination threshold; the V is GSc 、V GSr And V GSd The periods of the PWM signals are 3/2 of the resonance period of the resonance branch, the conduction time is 1/2 of the resonance period of the resonance branch, and the conduction time is according to V GSc 、V GSr 、V GSd Is a sequential distribution of (a).
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