Topological circuit of isolated single-phase integrated vehicle-mounted charging system for electric vehicle and control method of topological circuit

Abstract

The invention discloses a topology circuit of an isolated single-phase integrated vehicle-mounted charging system for an electric vehicle and a control method of the topology circuit. The topology circuit comprises an open-winding permanent magnet synchronous motor, a dual three-phase inverter, a power battery pack, a bus capacitor, a high-frequency transformer, a winding change-over switch K1, a winding change-over switch K2 and a bus change-over switch G1, through switching of the winding change-over switch K1, the winding change-over switch K2 and the bus change-over switch G1, the system works in a driving mode or a charging mode, and the system is controlled in combination with a driving control method and a charging control method. According to the invention, electrical isolation of the integrated vehicle-mounted charging system is realized without adding extra power devices and industrial frequency transformers, and the reliability and safety of charging are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of integrated on-board charging of automobiles, and in particular to a topological circuit of an isolated single-phase integrated on-board charging system for electric vehicles and a control method thereof. Background Art

[0002] At present, the common charging of electric vehicles is generally achieved through on-board chargers or off-board independent chargers. Among them, off-board chargers generally charge the battery pack directly through independent ground charging piles, and the charging power is generally above 50kW, but the charging piles occupy a large space, have high construction costs, and are less convenient; while the on-board charger charges the battery pack after converting the grid-side AC power supply, while retaining a large charging power, it takes into account the convenience and economy of charging. However, on-board chargers are usually installed on electric vehicles, which increases the weight of the vehicle, squeezes the limited space in the car, and reduces the vehicle's cruising range, which is contrary to the goal of lightweighting the entire vehicle. Therefore, the integrated on-board charging solution that reuses the electric vehicle motor windings and drive system power devices has received continuous attention from the industry.

[0003] When charging a car, the integrated on-board charging system usually changes the motor winding connection mode by switching the switch, reconstructs the motor winding and the drive system into an AC / DC converter, and converts the grid-side AC power into DC power that meets the charging voltage level of the electric vehicle, thereby realizing the integration of the drive charging system. Compared with the traditional on-board charger, this integrated on-board charging system saves volume and weight while achieving the same charging effect as the on-board charger through time-sharing multiplexing of the drive system and motor windings, and has high practical value.

[0004] At present, since integrated on-board charging systems usually do not have electrical isolation functions, additional power frequency transformers or DAB converters are required in practical applications to achieve electrical isolation of the charging system, which is contrary to the goal of highly integrated integrated charging systems and limits the large-scale development and application of integrated charging systems. Therefore, how to achieve an isolated integrated on-board charging system without adding additional power devices and power frequency transformers is an urgent problem to be solved. Summary of the invention

[0005] Purpose of the invention: The present invention provides a topological circuit of an isolated single-phase integrated on-board charging system for electric vehicles and a control method thereof, which realizes the electrical isolation of the integrated on-board charging system without adding additional power devices and industrial frequency transformers, thereby improving the reliability and safety of charging.

[0006] Technical solution: The topological circuit of an isolated single-phase integrated on-board charging system for electric vehicles described in the present invention includes: an open-winding permanent magnet synchronous motor, a dual three-phase inverter, a power battery pack, a bus capacitor, a high-frequency transformer, a winding switching switch K1, a winding switching switch K2 and a bus switching switch G1; the open-winding permanent magnet synchronous motor has a three-phase winding, and each phase winding leads to a center tap, which is divided into L a1 , L a2 , L b1 , L b2 , L c1 , L c2 There are six windings in total; the dual three-phase inverter is a common bus structure, including 12 switch tubes; the winding switching switch K1 is fixedly connected to the three-phase winding L a1 , L b1 , L c1 The switching end is connected at the grid interface, high-frequency transformer and three-phase winding L a2 , L b2 , L c2 The winding switch K2 is fixedly connected to the three-phase winding L a2 , L b2 , L c2 The switching end is switched between the high-frequency transformer and the midpoint of the three-phase inverter bridge arm; the busbar switching switch G1 has a fixed end connected to the busbar, and the switching end is used to disconnect Q9 and Q 10 Bridge arm, Q 11 and Q 12 The bridge arm and the power battery pack realize electrical isolation between the primary and secondary sides of the charging system; by switching the winding switching switch K1, the winding switching switch K2 and the bus switching switch G1, the system works in the driving mode or the charging mode, and the driving and charging control methods are combined to realize the control of the system.

[0007] Furthermore, when the electric vehicle is in the driving mode, the winding switching switch K1 and the three-phase winding L a2 , L b2 , L c2 The winding switch K2 is connected to the midpoint of the three-phase inverter bridge arm, so the three-phase winding L a1 , L b1 , L c1 With three-phase winding L a2 , L b2 , L c2 Connected, three-phase winding L a2 , L b2 , L c2 It is connected to the midpoint of the three-phase inverter bridge arm, and at the same time the bus switch G1 is closed. The DC power output by the power battery is inverted into three-phase AC power through the common bus dual three-phase inverter to drive the open-winding permanent magnet synchronous motor.

[0008] Furthermore, when the electric vehicle is in charging mode, the winding switching switches K1 and K2 are closed, the winding structure is reconstructed and connected to the single-phase grid and high-frequency transformer, and the bus switching switch G1 is disconnected, and the system is reconstructed into a single-phase PWM rectifier and a dual active bridge converter; the single-phase grid and the winding L a1 and L b2 Connected, winding L b2 With winding L a2 Connected, winding L a2 With winding L b1 connected, the switch tubes Q1, Q2, Q3, Q4 and the winding L a1 , L a2 , L b1 , L b2 Reconstructed into the single-phase PWM rectifier; high-frequency transformer and switch tubes Q7, Q8, Q9, Q 10 and winding L c1 , L c2 connected, the switch tubes Q5, Q6, Q7, Q8 and the winding L c1 Reconstructed into a primary full-bridge circuit, switch tubes Q9, Q 10 , Q 11 , Q 12 and winding L c2 Reconstructed into a secondary full-bridge circuit, the primary full-bridge circuit, the secondary full-bridge circuit and the high-frequency transformer are reconstructed into the dual-active bridge converter; the single-phase grid AC outputs DC power through the PWM rectifier, and the bus capacitor is reused for filtering to obtain high-voltage DC power, and the DC power is output through the subsequent dual-active bridge converter to realize isolated single-phase integrated charging of the battery pack.

[0009] Accordingly, a control method for a topological circuit of an isolated single-phase integrated on-board charging system for an electric vehicle comprises the following steps:

[0010] Step 1: Collect the instantaneous value of the single-phase grid voltage U g , instantaneous current value I g 、Power battery positive and negative voltage U dc , busbar capacitor voltage U C ;

[0011] Step 2: Calculate U through the phase-locked loop g The phase angle θ g The difference between the given value and the actual value of the bus capacitor voltage is calculated by the proportional integral controller and θ g Multiply them to get the grid-side current given value, and the current error is modulated by the proportional resonant controller to get the duty cycle of the switch tubes Q1, Q2, Q3, and Q4. The switch tubes Q1 and Q4 are turned on complementary to Q2 and Q3 respectively.

[0012] Step 3: Generate a switch signal with a primary constant duty cycle of 0.5 to drive switch tubes Q5, Q6, Q7, and Q8. Switch tubes Q5 and Q8 are turned on complementary to Q6 and Q7 respectively; the difference between the given value and the actual value of the charging voltage of the high-voltage power battery is passed through a proportional-integral controller to obtain the inter-bridge shift ratio, and the primary switch signal is phase-shifted to obtain the switch tubes Q9 and Q8. 10 , Q 11 , Q 12 , switch tube Q9, Q 12 Respectively with Q 10 , Q 11 Complementary conduction;

[0013] Step 4: Connect the motor windings L in series a1 , L a2 , L b1 , L b2 As the input inductor, the winding L a1 , L a2 And winding L b1 , L b2 The currents are equal in magnitude and opposite in direction, and the magnetic flux generated is canceled; the high-frequency transformer has a turns ratio of 1:1, and the winding L c1 , L c2 Connect to the same terminal of the transformer so that the winding L c1 , L c2 The currents are equal in magnitude and opposite in direction, and the magnetic flux generated is canceled out; the magnetic flux generated in the three-phase windings is zero, so no electromagnetic torque is generated and the motor rotor can remain stationary.

[0014] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: without adding additional power devices and industrial frequency transformers, the electrical isolation of the integrated on-board charging system is achieved, thereby improving the reliability and safety of charging; on the basis of the open-winding drive system of the electric vehicle, the stator winding of the drive motor is reused, and a high-frequency transformer and a switching switch are added to obtain an isolated integrated on-board charging system; when the system switches from the driving operation mode to the charging operation mode, the stator winding, the drive system and the high-frequency transformer are reconstructed into a single-phase PWM rectifier cascade dual active bridge converter topology through the switching switch; the torque pulsation suppression of the reused winding motor is achieved through the flux balancing method, and the inductor current is controlled to achieve power factor correction; the phase-shift control method is used to achieve isolated charging of the power battery, thereby improving the system integration and control performance, and realizing the integrated design of the driving and charging functions. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 The topological circuit structure diagram of the isolated single-phase integrated on-board charging system for electric vehicles of the present invention is shown.

[0016] Figure 2It is a topological structure diagram of the present invention in the driving state.

[0017] Figure 3 It is a topological structure diagram of the present invention in the charging state.

[0018] Figure 4 FIG. 4 is an equivalent circuit diagram of the present invention in charging mode.

[0019] Figure 5 It is the overall control block diagram of the present invention in charging mode.

[0020] Figure 6 This is a waveform diagram of the front-stage bus capacitor voltage and the power battery charging voltage in the present invention.

[0021] Figure 7 This is a voltage and current waveform diagram of the grid side during steady-state charging of the present invention.

[0022] Figure 8 This is a diagram showing the harmonic analysis results of the grid-side current during steady-state charging of the present invention.

[0023] Fig. 9 The waveform diagram of the transformer primary-secondary voltage difference and the transformer inductor current during steady-state charging of the present invention.

[0024] Fig.10 The waveform diagram of the current and system torque of the three-phase two-segment winding during charging of the present invention. DETAILED DESCRIPTION

[0025] like Figure 1 As shown, a topological circuit of an isolated single-phase integrated on-board charging system for electric vehicles includes: an open-winding permanent magnet synchronous motor, a dual three-phase inverter, a power battery pack, a bus capacitor, a high-frequency transformer, a winding switching switch K1, a winding switching switch K2 and a bus switching switch G1;

[0026] The open-winding permanent magnet synchronous motor has a three-phase winding, and each phase winding leads to a center tap, which is divided into L a1 , L a2 , L b1 , L b2 , L c1 , L c2 There are six windings in total; the dual three-phase inverter is a common bus structure and includes 12 switch tubes;

[0027] The open-winding permanent magnet synchronous motor has a three-phase winding, and each phase winding leads to a center tap, which is divided into L a1 , L a2 , L b1 , L b2 , L c1 , L c2There are six windings in total; the dual three-phase inverter is a common bus structure and includes 12 switch tubes;

[0028] The winding switch K1 is fixedly connected to the three-phase winding L a1 , L b1 , L c1 The switching end is connected at the grid interface, high-frequency transformer and three-phase winding L a2 , L b2 , L c2 The winding switching switch K2 is fixedly connected to the three-phase winding L a2 , L b2 , L c2 The switching end is switched between the high-frequency transformer and the midpoint of the three-phase inverter bridge arm; the busbar switching switch G1 has a fixed end connected to the busbar, and the switching end is used to disconnect Q9 and Q 10 Bridge arm, Q 11 and Q 12 The bridge arm and the power battery pack realize electrical isolation of the primary and secondary sides of the system;

[0029] The isolated single-phase integrated on-board charging system for electric vehicles can make the system work in driving mode or charging mode by switching the winding switching switch K1, the winding switching switch K2 and the bus switching switch G1, and the system can be controlled by combining the driving and charging control methods.

[0030] like Figure 2 As shown, when the electric vehicle is in driving mode, the winding switching switch K1 and the three-phase winding L a2 , L b2 , L c2 The winding switch K2 is connected to the midpoint of the three-phase inverter bridge arm, so the three-phase winding L a1 , L b1 , L c1 With three-phase winding L a2 , L b2 , L c2 Connected, three-phase winding L a2 , L b2 , L c2 It is connected to the midpoint of the three-phase inverter bridge arm, and at the same time the bus switch G1 is closed. The DC power output by the power battery is inverted into three-phase AC power through the common bus dual three-phase inverter to drive the open-winding permanent magnet synchronous motor.

[0031] like Figure 3 and Figure 4 As shown in the figure, when the electric vehicle is in charging mode, the winding switching switches K1 and K2 are closed, the winding structure is reconstructed and connected to the single-phase grid and high-frequency transformer, and the bus switching switch G1 is disconnected, and the system is reconstructed into a single-phase PWM rectifier and a dual active bridge converter; the single-phase grid and the winding La1 and L b2 Connected, winding L b2 With winding L a2 Connected, winding L a2 With winding L b1 connected, the switch tubes Q1, Q2, Q3, Q4 and the winding L a1 , L a2 , L b1 , L b2 Reconstructed into the single-phase PWM rectifier; high-frequency transformer and switch tubes Q7, Q8, Q9, Q 10 and winding L c1 , L c2 connected, the switch tubes Q5, Q6, Q7, Q8 and the winding L c1 Reconstructed into a primary full-bridge circuit, switch tubes Q9, Q 10 , Q 11 , Q 12 and winding L c2 Reconstructed into a secondary full-bridge circuit, the primary full-bridge circuit, the secondary full-bridge circuit and the high-frequency transformer are reconstructed into the dual-active bridge converter; the single-phase grid AC outputs DC power through the PWM rectifier, and the bus capacitor is reused for filtering to obtain high-voltage DC power, and the DC power is output through the subsequent dual-active bridge converter to realize isolated single-phase integrated charging of the battery pack.

[0032] like Figure 5 As shown, a charging control method for an isolated single-phase integrated on-board charging system for electric vehicles, the series motor winding L a1 , L a2 , L b1 , L b2 , by controlling the phase of the inductor current to achieve power factor correction; by controlling the amplitude of the inductor current to achieve output voltage control of the single-phase PWM rectifier; by controlling the switch tubes Q5, Q6, Q7, Q8 and the switch tubes Q9, Q 10 , Q 11 , Q 12 The output voltage of the dual active bridge converter is controlled by the phase shift angle; the current of each phase winding is controlled to achieve flux balance and suppress the torque pulsation of the multiplexed winding motor; the control strategy includes the following steps:

[0033] (1) Collect the instantaneous value of the single-phase grid voltage U g , instantaneous current value I g 、Power battery positive and negative voltage U dc , busbar capacitor voltage U C ;

[0034] (2) Calculate U through the phase-locked loop g The phase angle θ gThe difference between the given value and the actual value of the bus capacitor voltage is calculated by the proportional integral controller and θ g Multiply them to get the grid-side current given value, and the current error is modulated by the proportional resonant controller to get the duty cycle of the switch tubes Q1, Q2, Q3, and Q4. The switch tubes Q1 and Q4 are turned on complementary to Q2 and Q3 respectively.

[0035] (3) Generate a switching signal with a primary constant duty cycle of 0.5 to drive the switch tubes Q5, Q6, Q7, and Q8. The switch tubes Q5 and Q8 are respectively turned on complementary to Q6 and Q7; the difference between the given value and the actual value of the charging voltage of the high-voltage power battery is passed through a proportional-integral controller to obtain the inter-bridge shift ratio, and the primary switch signal is phase-shifted to obtain the switch tubes Q9 and Q8. 10 , Q 11 , Q 12 , switch tube Q9, Q 12 Respectively with Q 10 , Q 11 Complementary conduction;

[0036] The method controls the current of each phase winding to achieve flux balance and suppress the torque pulsation of the multiplexed winding motor, which is characterized in that the series motor winding L a1 , L a2 , L b1 , L b2 As the input inductor, the winding L a1 , L a2 And winding L b1 , L b2 The currents are equal in magnitude and opposite in direction, and the magnetic flux generated is canceled; the high-frequency transformer has a turns ratio of 1:1, and the winding L c1 , L c2 Connect to the same terminal of the transformer so that the winding L c1 , L c2 The currents are equal in magnitude and opposite in direction, and the magnetic flux generated is canceled out; the magnetic flux generated in the three-phase windings is zero, so no electromagnetic torque is generated and the motor rotor can remain stationary.

[0037] Based on the above-mentioned isolated single-phase integrated on-board charging system topology and control strategy for electric vehicles, an isolated single-phase integrated on-board charging system was built in Matlab / Sumink software, which mainly includes a mathematical model of an open-winding permanent magnet synchronous motor with a center tap, a dual three-phase inverter model, a single-phase PWM rectifier control model, and a dual active bridge converter control model. The key parameter settings during the simulation verification process are shown in Table 1:

[0038] Table 1 Key parameters

[0039]

[0040]

[0041] The simulation duration is set to 1s, such as Figure 6 As shown, the waveforms of the front-stage bus capacitor voltage and the power battery charging voltage are shown. It can be seen that the charging voltage building time of both is less than 0.1s, the voltage fluctuation is small in steady state, and they have good dynamic performance and steady-state performance.

[0042] like Figure 7 and Figure 8 As shown, Figure 7 To intercept the steady-state waveform of 0.2s-0.3s, which are the voltage waveform and current waveform on the grid side, it can be seen that the current sinusoidality is high and is basically consistent with the voltage phase, realizing the PFC function and meeting the power consumption requirements of the grid; Figure 8 This is the result of the grid-side current harmonic analysis. It can be seen that there is basically no current harmonic and the THD is 0.44%, which meets the harmonic requirements of the power grid.

[0043] like Fig. 9 As shown in the figure, the steady-state waveforms of 0.2s-0.20005s are the transformer primary-secondary voltage difference and transformer inductor current waveforms. It can be seen that the inductor current can be controlled by phase shift control, and electrical isolation and energy transfer can be achieved through high-frequency transformers. The steady-state waveforms of 0.2s-0.3s are the current waveforms of the two windings of the three phases A, B, and C and the system torque waveform. It can be seen that the two currents of each phase winding are equal in magnitude and opposite in direction, so the magnetic flux generated cancels each other out, and the torque does not exceed 0.0001N·m, which verifies the effectiveness of the torque pulsation suppression strategy in this scheme.

[0044] Through the above content, the feasibility of the isolated single-phase integrated on-board charging system topology and its control strategy for electric vehicles proposed in the present invention is verified. The isolated single-phase charging system realizes the electrical isolation of the integrated on-board charging system without adding additional power devices and power frequency transformers, thereby improving the reliability and safety of charging. At the same time, by adding a high-frequency transformer to the drive system, the stator winding and drive circuit of the open-winding permanent magnet motor are reconstructed into a single-phase PWM rectifier and a dual-active bridge converter, and the motor torque pulsation is suppressed by the flux balance method, and the power factor correction is realized by inductor current control. The isolated charging of the power battery is realized by phase shift control, thereby improving the system integration and control performance, and realizing the integrated design of drive charging.

Claims

1. A topological circuit of an isolated single-phase integrated on-board charging system for electric vehicles, characterized in that: include: Open-winding permanent magnet synchronous motor, dual three-phase inverter, power battery pack, high-frequency transformer, winding switch K1, winding switch K2 and bus switch G1; the open-winding permanent magnet synchronous motor has a three-phase winding, each phase winding leads to a center tap, which is divided into L a1 , L a2 , L b1 , L b2 , L c1 , L c2 There are six windings in total; the winding switch K1 is fixedly connected to the three-phase winding L a1 , L b1 , L c1 The switching end is connected at the grid interface, high-frequency transformer and three-phase winding L a2 , L b2 , L c2 The winding switch K2 is fixedly connected to the three-phase winding L a2 , L b2 , L c2 The switching end is switched between the high-frequency transformer and the midpoint of the three-phase inverter bridge arm; the busbar switching switch G1 has a fixed end connected to the busbar, and the switching end is used to disconnect Q9 and Q 10 Bridge arm, Q 11 and Q 12 The bridge arm and the power battery pack realize electrical isolation between the primary and secondary sides of the charging system; by switching the winding switching switch K1, the winding switching switch K2 and the bus switching switch G1, the system works in driving mode or charging mode.

2. The topology circuit of the isolated single-phase integrated on-board charging system for electric vehicles according to claim 1, characterized in that: It also includes a dual three-phase inverter, which has a common bus structure and contains 12 switching tubes.

3. The topology circuit of the isolated single-phase integrated on-board charging system for electric vehicles as claimed in claim 2, characterized in that: When the electric vehicle is in driving mode, the winding switching switch K1 and the three-phase winding L a2 , L b2 , L c2 The winding switch K2 is connected to the midpoint of the three-phase inverter bridge arm, so the three-phase winding L a1 , L b1 , L c1 With three-phase winding L a2 , L b2 , L c2 Connected, three-phase winding L a2 , L b2 , L c2 It is connected to the midpoint of the three-phase inverter bridge arm, and at the same time the bus switch G1 is closed. The DC power output by the power battery is inverted into three-phase AC power through the common bus dual three-phase inverter to drive the open-winding permanent magnet synchronous motor.

4. The topology circuit of the isolated single-phase integrated on-board charging system for electric vehicles according to claim 1, characterized in that: Also includes bus capacitance.

5. The topology circuit of the isolated single-phase integrated on-board charging system for electric vehicles as claimed in claim 4, characterized in that: When the electric vehicle is in charging mode, the winding switching switches K1 and K2 are closed, the winding structure is reconstructed and connected to the single-phase grid and high-frequency transformer, and the busbar switching switch G1 is disconnected, and the system is reconstructed into a single-phase PWM rectifier and a dual active bridge converter; the single-phase grid and winding L a1 and L b2 Connected, winding L b2 With winding L a2 Connected, winding L a2 With winding L b1 connected, the switch tubes Q1, Q2, Q3, Q4 and the winding L a1 , L a2 , L b1 , L b2 Reconstructed into the single-phase PWM rectifier; high-frequency transformer and switch tubes Q7, Q8, Q9, Q 10 and winding L c1 , L c2 connected, the switch tubes Q5, Q6, Q7, Q8 and the winding L c1 Reconstructed into a primary full-bridge circuit, switch tubes Q9, Q 10 , Q 11 , Q 12 and winding L c2 Reconstructed into a secondary full-bridge circuit, the primary full-bridge circuit, the secondary full-bridge circuit and the high-frequency transformer are reconstructed into the dual-active bridge converter; the single-phase grid AC outputs DC power through the PWM rectifier, and the bus capacitor is reused for filtering to obtain high-voltage DC power, and the DC power is output through the subsequent dual-active bridge converter to realize isolated single-phase integrated charging of the battery pack.

6. A method for controlling a topology circuit of an isolated single-phase integrated on-board charging system for an electric vehicle as claimed in claim 1, characterized in that: The steps include: Step 1: Collect the instantaneous value of the single-phase grid voltage U g , instantaneous current value I g 、Power battery positive and negative voltage U dc , busbar capacitor voltage U C ; Step 2: Calculate U through the phase-locked loop g The phase angle θ g The difference between the given value and the actual value of the bus capacitor voltage is calculated by the proportional integral controller and θ g Multiply them to get the grid-side current given value, and the current error is modulated by the proportional resonant controller to get the duty cycle of the switch tubes Q1, Q2, Q3, and Q4. The switch tubes Q1 and Q4 are turned on complementary to Q2 and Q3 respectively. Step 3: Generate a switch signal with a primary constant duty cycle of 0.5 to drive switch tubes Q5, Q6, Q7, and Q8. Switch tubes Q5 and Q8 are turned on complementary to Q6 and Q7 respectively; the difference between the given value and the actual value of the charging voltage of the high-voltage power battery is passed through a proportional-integral controller to obtain the inter-bridge shift ratio, and the primary switch signal is phase-shifted to obtain the switch tubes Q9 and Q8. 10 , Q 11 , Q 12 , switch tube Q9, Q 12 Respectively with Q 10 , Q 11 Complementary conduction; Step 4: Connect the motor windings L in series a1 , L a2 , L b1 , L b2 As the input inductor, the winding L a1 , L a2 And winding L b1 , L b2 The currents are equal in magnitude and opposite in direction, and the magnetic flux generated is canceled; the high-frequency transformer has a turns ratio of 1:1, and the winding L c1 , L c2 Connect to the same terminal of the transformer so that winding L c1 , L c2 The currents are equal in magnitude and opposite in direction, and the magnetic flux generated is canceled out; the magnetic flux generated in the three-phase windings is zero, so no electromagnetic torque is generated and the motor rotor can remain stationary.

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