A Vehicle-mounted Battery Charging and Heating Control Method Based on Phase-shifted Full-bridge Synchronous Rectification

Abstract

The present invention provides a vehicle-mounted battery charging and heating control method based on phase-shifted full-bridge synchronous rectification. Based on the existing power electronic components in common vehicle-mounted chargers, only one power switch device and two relays need to be added to the secondary side of the transformer to build the circuit structure required by the method. Through the relays, the corresponding topologies for implementing internal AC heating, DC charging, and discharging control of the battery can be obtained flexibly. By performing closed-loop feedback control on the PWM modulation process, the present invention can rapidly heat the battery in extremely cold environments for vehicles. Compared with the prior art, the process is easier to control and can significantly improve the heating efficiency and uniformity.

Description

Technical Field

[0001] The present invention belongs to the technical field of on-vehicle battery charging and heating, and particularly relates to a control method for on-vehicle battery charging and heating based on phase-shifted full-bridge synchronous rectification. Background Art

[0002] Since the on-vehicle battery cannot always maintain the normal range required during use and its performance often decays in a low-temperature environment, in the prior art, external heating devices are mainly set up or the battery is used to execute an AC heating cycle to cope with the cold environment. However, there are still many deficiencies in these prior arts. For example, external heating devices will occupy space in the vehicle and increase costs, and the heating efficiency generally cannot meet the need for rapid temperature rise. Although the internal AC heating of the battery achieved by using the three-phase windings in the vehicle motor has improved heating efficiency, it is prone to generate additional torque, leading to safety hazards such as motor stalling. Therefore, how to effectively combine the advantages of the two battery heating methods to balance the temperature rise rate, energy consumption efficiency and safety is an important problem to be solved in this field. Summary of the Invention

[0003] In view of this, the present invention provides a control method for on-vehicle battery charging and heating based on phase-shifted full-bridge synchronous rectification. First, the following circuit structure is built using the secondary circuit of the on-vehicle charger transformer:

[0004] Both ends of the secondary winding in the secondary circuit are respectively connected to the collectors of the first and second switching tubes, and the emitters of the two switching tubes are both connected to the negative line of the secondary output; two paths are led out from the midpoint of the secondary winding. One path is connected to the negative line of the secondary output through a secondary inductor and a current sensor, and the other path is connected to the emitter of the third switching tube. The collector of the third switching tube is connected to the positive electrode of the battery module E2 through a single-pole single-throw relay SW1 and the first contact of a single-pole double-throw relay SW2; the second contact of SW2 is connected to the negative line of the secondary output, and its common contact is connected to the negative electrode of the battery module E1; the positive electrode of the battery module E1 is connected to the positive line of the secondary output, and the negative electrode of the battery module E2 is connected to the negative line of the secondary output. Each battery module is respectively connected in parallel with a capacitor;

[0005] After the above structure is built, the voltage, current and temperature data of the power battery are collected and the SOC is calculated, and it is judged whether there is a charging or driving demand, and the following corresponding controls are respectively executed:

[0006] First, it is judged whether the temperature of the power battery is too low and there is a heating requirement. If the judgment result is yes, the relay SW1 is controlled to close and the common contact of the relay SW2 is connected to the second contact, so that no current is output from the primary side of the transformer, and the secondary circuit forms a bidirectional buck-boost circuit form. PWM modulation is performed to control the on-off of the three switching tubes in the secondary circuit, so as to switch the current direction in the loop and make the battery module execute an AC internal heating cycle;

[0007] If it is judged that heating is not required, the relay SW1 is controlled to disconnect and the common contact of the relay SW2 is connected to the first contact to enter the charging mode or the discharging mode; in the charging mode, the primary and secondary circuits of the transformer form a phase-shifted full-bridge synchronous rectification module, and the industrial-frequency AC power supply is input through the vehicle charging interface and PWM modulation is performed for rectification, and then the battery module is charged directly; in the driving mode, the power battery is controlled to perform the vehicle power-on operation, output electric energy to the vehicle motor inverter and drive the motor to work.

[0008] Further, the battery modules E1 and E2 are specifically connected in series by closing the common contact and the first contact of the relay SW2 in the charging mode, and are disconnected from each other in the heating mode; in the heating mode, the first and second switching tubes in the secondary circuit synchronously perform the on-off actions and cooperate with the third switching tube, so that the battery modules E1 and E2 exchange power with the secondary inductor to perform an AC internal heating cycle, and the heat is synchronously transferred to E2 during the temperature rise of E1.

[0009] Further, in the heating mode, by collecting the voltage and temperature of each battery module in real time and calculating the optimal heating current amplitude, the errors between the calculation results and the actual output currents of each module are respectively tracked, and the reference voltage command of PWM modulation is provided to achieve closed-loop feedback control;

[0010] In the charging mode, by collecting the voltage and temperature of each battery module in real time and calculating the charging current and voltage amplitudes, the errors between the calculation results and the actual currents and voltages of each module are respectively tracked, and the reference voltage command of PWM modulation is provided to achieve closed-loop feedback control.

[0011] Further, the closed-loop feedback control in the heating mode or the charging mode can select PID control or fuzzy control to obtain the reference voltage command.

[0012] The vehicle-mounted battery charging and heating control method based on phase-shifted full-bridge synchronous rectification provided by the present invention only needs to add a power switch device and two relays to the secondary side of the transformer on the basis of the existing power electronic components in a common vehicle-mounted charger to build the circuit structure required by the method. Through the relays, the corresponding topologies for implementing internal AC heating, DC charging, and discharging control of the battery can be obtained flexibly. By performing closed-loop feedback control on the PWM modulation process, the present invention can rapidly heat the battery of the vehicle in extremely cold environments, and its process is easier to control and can significantly improve the heating efficiency and uniformity compared with the prior art. Brief Description of the Drawings

[0013] Figure 1 It is a schematic flowchart of the method provided by the present invention;

[0014] Figure 2 It is a schematic circuit diagram of the system built in the method provided by the present invention;

[0015] Figure 3 It is a schematic diagram of vehicle-mounted charging and AC heating control of the present invention;

[0016] Figure 4 It is a membership function diagram of the input current error and error differential of the fuzzy control performed based on the present invention;

[0017] Figure 5 It is a membership function diagram of the output reference regulation voltage of the fuzzy control performed based on the present invention;

[0018] Figure 6 It is a simulation result diagram of the internal AC heating process performed based on the present invention. Detailed Embodiments

[0019] The technical solutions of the present invention will be described clearly and completely below with reference to the accompanying drawings. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0020] A vehicle-mounted battery charging and heating control method based on phase-shifted full-bridge synchronous rectification provided by the present invention first uses the secondary circuit of the vehicle-mounted charger transformer to build the following circuit structure as shown in Figure 2 shown:

[0021] The two ends of the secondary winding in the secondary circuit are respectively connected to the collectors of the first and second switching transistors Q5 and Q6, and the emitters of Q5 and Q6 are both connected to the negative line of the secondary output; two paths are led out from the midpoint of the secondary winding. One path is connected to the negative line of the secondary output through a secondary inductor and a current sensor, and the other path is connected to the emitter of the third switching transistor Q7. The collector of Q7 is connected to the positive pole of the battery module E2 through a single-pole single-throw relay SW1 and the first contact of a single-pole double-throw relay SW2; the second contact of SW2 is connected to the negative line of the secondary output, and its common contact is connected to the negative pole of the battery module E1; the positive pole of the battery module E1 is connected to the positive line of the secondary output, and the negative pole of the battery module E2 is connected to the negative line of the secondary output. Each battery module is connected in parallel with a capacitor.

[0022] After the above structure is built, the voltage, current, and temperature data of the power battery are collected and the SOC is calculated to determine whether there is a charging or driving requirement and respectively execute the following corresponding controls as Figure 1 shown:

[0023] First, it is judged whether the temperature of the power battery is too low and there is a heating requirement. If the judgment is yes, the relay SW1 is controlled to close and the common contact of the relay SW2 is connected to the second contact, so that no current is output from the primary side of the transformer, and the secondary circuit forms a bidirectional buck-boost circuit form. PWM modulation is performed to control the on and off of the three switching transistors in the secondary circuit to switch the current direction in the loop so that the battery module executes an AC internal heating cycle.

[0024] If it is judged that heating is not required, the relay SW1 is controlled to disconnect and the common contact of the relay SW2 is connected to the first contact to enter the charging mode or the discharging mode; in the charging mode, the primary and secondary circuits of the transformer form a phase-shifted full-bridge synchronous rectification module, and the industrial-frequency AC power is input through the vehicle's charging interface and PWM modulation is performed for rectification and then DC charging of the battery module; in the driving mode, the power battery is controlled to perform vehicle power-on operation, output electric energy to the vehicle motor inverter and drive the motor to work.

[0025] In a preferred embodiment of the present invention, the battery modules E1 and E2 are specifically formed in series by the closing of the common contact and the first contact of the relay SW2 in the charging mode, and are disconnected from each other in the heating mode; in the heating mode, the switching transistors Q5 and Q6 in the secondary circuit synchronously perform the actions of conduction and cut-off and cooperate with the third switching transistor Q7, so that the battery modules E1 and E2 and the secondary inductor transfer electric power to each other to execute an AC internal heating cycle, and heat is synchronously transferred to E2 during the temperature rise process of E1.

[0026] As Figure 3As shown, in a preferred embodiment of the present invention, the heating mode realizes closed-loop feedback control by collecting the voltage and temperature of each battery module in real time, calculating the optimal heating current amplitude, tracking the errors between the calculation results and the actual output current of each module respectively, and providing a reference voltage command for PWM modulation;

[0027] In the above control strategy, by using the temperature and state of charge of the battery to be heated collected, the optimal AC heating current frequency and amplitude I can be calculated in real time Amp . The optimal AC heating current can be an AC current that ensures the maximum heat generation rate of the starting battery, less power consumption, and less damage to the battery. The heat generation rate Q is calculated as follows:

[0028]

[0029] In the formula, R re is the real part of the battery impedance that varies with the battery temperature T and current frequency f, and can be obtained through off-line electrochemical impedance spectroscopy.

[0030] The maximum safe operating value of the AC heating current amplitude can be set as:

[0031]

[0032] In the formula, U oc is the open-loop voltage of the battery at the current temperature and state of charge; U max is the maximum allowable terminal voltage of the battery in the current state; U min is the minimum allowable terminal voltage of the battery in the current state.

[0033] The charging mode realizes closed-loop feedback control by collecting the voltage and temperature of each battery module in real time, calculating the charging current and voltage amplitude, and tracking the errors between the calculation results and the actual current and voltage of each module respectively, and providing a reference voltage command for PWM modulation.

[0034] In a preferred embodiment of the present invention, the closed-loop feedback control in the heating mode or charging mode can select PID control or fuzzy control to obtain the reference voltage command. Here, taking fuzzy control as an example, the process of current closed-loop control is described:

[0035] Based on the fuzzy control theory, set the fuzzy domain and fuzzy inference method. According to the error E between the input target current and the actual current and the differential EC of the error, calculate and output the reference voltage U ref . Construct the fuzzy language sets for E, EC, and the reference voltage U ref The fuzzy language set is {NB, NM, NS, ZO, PS, PM, PB}, and the subset elements represent negative large, negative medium, negative small, zero, positive small, positive medium, and positive large respectively. The membership functions of E and EC are shown inFigure 4 as shown;

[0036] Reference voltage U ref is used as the only fuzzy control output quantity, and its value is related to the maximum voltage command V max of the system regulation. The universe of discourse is expressed as: {-V max , -2*V max / 3, -V max / 3, 0, V max / 3, 2*V max / 3, V max}, and its membership function is shown in Figure 5 ;

[0037] In this example, the triangular membership function commonly used in engineering is adopted as the membership function of the fuzzy control system subset. By selecting an appropriate universe of discourse according to the system stability conditions, fuzzy inference can be carried out. The specific fuzzy rule table is shown in Table 1 as follows:

[0038] Table 1 Fuzzy control rule table

[0039]

[0040] According to the result of the fuzzy control output, defuzzification processing is performed on the fuzzy output quantity. The weighted average method is used to calculate the weighted average of each element and its corresponding membership degree in the fuzzy quantity to obtain the accurate output quantity of the reference regulation voltage. Then, through PWM pulse width modulation, a PWM control signal is output, and thus each switching tube in the built system can be controlled.

[0041] Figure 6 Fig. shows the simulation results of the current closed-loop AC heating process for the first module in an example. The current of the battery module E1 presents a continuous sine waveform, and the current of the battery module E2 presents a pulsed square wave with an amplitude that varies sinusoidally. Therefore, the heat generation rate of E1 is greater than that of E2. During the heating process, the heat of E1 can be transferred to E2 by using a liquid cooling plate. When the temperature difference between E1 and E2 is greater than the set threshold, the heating process can be paused, and after the temperatures of the two tend to be the same, the AC heating is continued.

[0042] It should be understood that the magnitudes of the sequence numbers of the steps in the embodiments of the present invention do not mean the order of execution. The execution order of each process should be determined according to its function and internal logic, and should not constitute any limitation to the implementation process of the embodiments of the present invention.

[0043] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirits of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A vehicle-mounted battery charging and heating control method based on phase-shifted full-bridge synchronous rectification, characterized in that: First, use the secondary circuit of the on-vehicle charger transformer to build the following circuit structure: Both ends of the secondary winding in the secondary circuit are respectively connected to the collectors of the first and second switching tubes, and the emitters of the two switching tubes are both connected to the negative line of the secondary output; two paths are led out from the midpoint of the secondary winding. One path is connected to the negative line of the secondary output through a secondary inductor and a current sensor, and the other path is connected to the emitter of the third switching tube. The collector of the third switching tube is connected to the positive electrode of the battery module E2 through a single-pole single-throw relay SW1 and the first contact of a single-pole double-throw relay SW2; the second contact of SW2 is connected to the negative line of the secondary output, and its common contact is connected to the negative electrode of the battery module E1; the positive electrode of the battery module E1 is connected to the positive line of the secondary output, and the negative electrode of the battery module E2 is connected to the negative line of the secondary output. Each battery module is connected in parallel with a capacitor; After the above structure is built, collect the voltage, current, and temperature data of the power battery and calculate the SOC, and judge whether there is a charging or driving demand and respectively execute the following corresponding controls: First, judge whether the temperature of the power battery is too low and there is a heating demand. If the judgment is yes, control the relay SW1 to close and the common contact of the relay SW2 to be connected to the second contact, so that no current is output from the primary side of the transformer, and the secondary circuit forms a bidirectional buck-boost circuit form. Execute PWM modulation to control the on and off of the three switching tubes in the secondary circuit to switch the current direction in the loop so that the battery module executes an AC internal heating cycle; If it is judged that heating is not required, control the relay SW1 to open and the common contact of the relay SW2 to be connected to the first contact to enter the charging mode or the discharging mode; in the charging mode, the primary and secondary circuits of the transformer form a phase-shifted full-bridge synchronous rectification module, input the industrial-frequency AC power supply through the on-vehicle charging interface and execute PWM modulation for rectification and then charge the battery module directly; in the driving mode, control the power battery to perform the vehicle power-on operation, output electric energy to the vehicle motor inverter and drive the motor to work.

2. The method according to claim 1, wherein: The battery modules E1 and E2 are specifically connected in series by the closing of the common contact and the first contact of the relay SW2 in the charging mode, and are disconnected from each other in the heating mode; in the heating mode, the first and second switching tubes in the secondary circuit synchronously perform the actions of conduction and cut-off and cooperate with the third switching tube, so that the battery modules E1 and E2 and the secondary inductor transfer electric power to each other to execute an AC internal heating cycle, and heat is synchronously transferred to E2 during the heating process of E1.

3. The method according to claim 1, characterized in that: In the heating mode, by collecting the voltage and temperature of each battery module in real time and calculating the optimal heating current amplitude, track the errors between the calculation results and the actual output currents of each module respectively, and provide the reference voltage command of PWM modulation to achieve closed-loop feedback control; In the charging mode, by collecting the voltage and temperature of each battery module in real time and calculating the charging current and voltage amplitude, track the errors between the calculation results and the actual currents and voltages of each module respectively, and provide the reference voltage command of PWM modulation to achieve closed-loop feedback control.

4. The method according to claim 3, wherein: Closed-loop feedback control in the heating mode or charging mode can select PID control or fuzzy control to obtain a reference voltage command.

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