Topological structure of single-phase isolation type integrated vehicle-mounted charging system without electrolytic capacitor and control method of topological structure

Abstract

The invention discloses a topological structure of a single-phase isolation type integrated vehicle-mounted charging system without an electrolytic capacitor and a control method of the topological structure, the system multiplexes a driving motor stator winding on the basis of an open winding driving system of an electric vehicle, and when the system is switched from a driving operation mode to a charging operation mode, the driving motor stator winding is switched to the charging operation mode. An open winding permanent magnet motor driving system is reconstructed into an isolated AC / DC converter without an electrolytic capacitor through a change-over switch, the isolated AC / DC converter comprises a synchronous rectifier, a dual-active-bridge converter and an active filtering device, phase shifting is controlled through matching of transmission power and network side input power, power factor correction is achieved, and power factor correction is achieved through winding inductive current control. According to the vehicle-mounted power battery integrated vehicle-mounted charging system, the inherent secondary power pulsation is filtered out to realize active filtering, and the torque pulsation suppression of a multiplexing motor winding is realized through a magnetic flux balance method, so that the vehicle-mounted power battery integrated vehicle-mounted charging system with an isolation charging characteristic is obtained, the integrated design of a driving charging function is realized, and the reliability and the safety of the integrated charging system are improved.

Description

Technical Field

[0001] The present invention relates to the field of power electronics and electric drive technology, and in particular to a topological structure of a single-phase isolated integrated vehicle charging system without electrolytic capacitors and a control method thereof. Background Art

[0002] At present, the common on-board chargers for electric vehicles charge the battery pack by converting the grid-side AC power supply. However, since they are installed on electric vehicles, they increase the weight of the vehicle, occupy the space inside the vehicle, and reduce the vehicle's cruising range, which is contrary to the goal of lightweighting the entire vehicle. The integrated on-board charging solution that reuses the electric vehicle motor windings and drive system power devices changes the motor winding connection mode by switching switches when charging the car, reconstructs the motor windings and drive system into an AC / DC converter, and converts the grid-side AC power supply into DC power that meets the charging voltage level of the electric vehicle, thereby realizing the integration of the drive charging system. Compared with traditional on-board chargers, this integrated on-board charging system achieves the same charging effect as the on-board charger while saving volume and weight by time-sharing the drive system and motor windings, and has high practical value.

[0003] 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. In addition, the secondary pulsating power problem inherent in the rectification process of the single-phase power grid usually requires the addition of electrolytic capacitors or other passive devices to filter it out. This is contrary to the goal of highly integrated integrated charging systems, limiting the large-scale development and application of integrated charging systems.

[0004] Therefore, it is an urgent problem to realize an isolated integrated on-board charging system without adding additional power devices, power frequency transformers and passive devices. Summary of the invention

[0005] Purpose of the invention: The present invention provides a topological structure of an electrolytic capacitor-free single-phase isolated integrated on-board charging system and a control method thereof, so as to realize the electrical isolation of the integrated on-board charging system and improve the reliability and safety of charging.

[0006] Technical solution: The topology of the single-phase isolated integrated vehicle charging system without electrolytic capacitor described in the present invention includes: an open-winding permanent magnet synchronous motor, a dual three-phase inverter, a power battery, a bus capacitor, a high-frequency transformer, a winding switching switch K 1 , K 2 , K 3 And single-phase grid switch G 1 The open-winding permanent magnet synchronous motor three-phase winding leads to the center tap, which is divided into L a1 , La2 , L b1 , L b2 , L c1 , L c2 There are six windings in total; the winding switching switch is a double-pole double-throw switch, which is switched according to the driving mode or the charging mode.

[0007] Furthermore, in the driving mode, the three-phase single-phase grid switching switch G 1 Disconnect, winding switch K 1 , K 2 , K 3 The two windings of each phase are connected in series and connected to the dual three-phase inverter. The power battery and bus capacitor drive the open-winding permanent magnet synchronous motor with the dual three-phase inverter of the isolation bus. In the charging mode, the winding switching switch K 1 , K 2 , K 3 And single-phase grid switch G 1 Close the circuit, connect the two sections of each phase winding of the motor in parallel, and reconstruct the system topology into an isolated single-stage AC / DC converter without electrolytic capacitors. The single-phase grid AC power outputs DC power with secondary pulsating power through the isolation converter, and the secondary pulsating power is filtered out through the active filter circuit to charge the power battery.

[0008] Furthermore, in the charging mode, the system topology is reconstructed into an isolated single-stage AC / DC converter without electrolytic capacitors, and the three-phase inverter 1 is reconstructed into the primary bridge arm of the transformer, in which the switch tube S 1 , S 2 , S 5 , S 6 and parallel winding L a1 , L a2 Reconstructed into a synchronous rectifier, reuse the switch tube S 5 , S 6 , and the switch tube S 3 , S 4 Reconstructed into a primary full-bridge circuit, through the parallel winding L c1 , L c2 Connect the primary side of the high-frequency transformer; the three-phase inverter 2 is reconstructed into the secondary side bridge arm of the transformer, in which the switch tube S 7 , S 8 , S 11 , S 12 Reconstructed into a secondary full-bridge circuit, connected to the secondary side of the high-frequency transformer, and reused the switch tube S 7 , S 8 , and the switch tube S 9 , S 10 and parallel winding L b1 , L b2Reconstructed into an H-bridge active filter circuit; the primary full-bridge circuit, the secondary full-bridge circuit and the high-frequency transformer form a dual active bridge converter; the synchronous rectifier converts the single-phase grid AC power into a pulsating DC bus voltage, outputs DC power through the subsequent dual active bridge converter, and filters out the secondary pulsating power through the H-bridge active filter circuit to realize isolated single-phase integrated charging of the battery pack; in the charging process of each phase winding in the topology, the current of the parallel winding is equal in magnitude and direction, and the generated magnetic flux is offset, so that the magnetic flux generated in the three-phase winding of the motor is zero, achieving magnetic flux balance, thereby eliminating the electromagnetic torque generated by the reused motor winding.

[0009] Furthermore, in the synchronous rectifier, the switch tube S 1 , S 2 The power frequency switch bridge arm, the switch tube S 5 , S 6 The high-frequency switch bridge arm has a duty cycle of 0.5, so that the AC side voltage is boosted and converted into a pulsating DC bus voltage with twice the amplitude; the switch tube high-frequency switch of the dual active bridge converter regards the pulsating DC bus voltage as a constant voltage during the switching cycle, and its primary full-bridge circuit reuses the switch tube S 5 , S 6 , while the switch tube S 4 , S 5 With switch tube S 3 , S 6 Complementary conduction, duty cycle is 0.5, the secondary full-bridge circuit switch tube S 7 , S 12 With switch tube S 8 , S 11 Complementary conduction, by controlling the switch tube S 3 , S 4 , S 5 , S 6 And switch tube S 7 , S 8 , S 11 , S 12 The phase shift angle adjusts the transmission power of the dual active bridge converter; the H-bridge active filter circuit reuses the switch tube S 7 , S 8 , and the switch tube S 7 , S 8 It is a high-frequency switch bridge arm with a duty cycle of 0.5. 9 , S 10 The duty cycle of the parallel B-phase winding is controlled to filter out the secondary power pulsation.

[0010] Accordingly, a control method for a topological structure of a single-phase isolated integrated vehicle charging system without electrolytic capacitors comprises the following steps:

[0011] Step 1: Collect the instantaneous value of the single-phase grid voltage u g , instantaneous current value i g , instantaneous value of B-phase parallel winding current i b , output voltage U o ;

[0012] Step 2: Calculate the instantaneous value of the single-phase grid voltage u through the phase-locked loop g The phase angle θ g , and at the same time determine the instantaneous value of the grid side voltage u g When the switch S 2 conduction, instantaneous value of grid side voltage u g When it is negative, the switch tube S 1 Conductivity;

[0013] Step 3: Calculate the charging voltage set value and actual output voltage U of the power battery o The difference is filtered out through a notch filter to remove the secondary pulsation component, and the output is shifted by a factor k after passing through a proportional-integral controller;

[0014] Step 4: In the phase shift calculation module, the phase shift coefficient k and the grid side voltage phase angle θ are used to calculate the phase shift coefficient k and the grid side voltage phase angle θ. g , calculate the displacement ratio D;

[0015] Step 5: Set the switch signal with a constant duty cycle of 0.5 to drive the switch tube S 3 , S 4 , S 5 , S 6 , switch tube S 3 , S 6 , respectively with S 4 , S 5 Complementary conduction, the switching signal is phase-shifted according to the calculated phase shift D and then drives the switch tube S 7 , S 8 , S 11 , S 12 , switch tube S 7 , S 12 Respectively with S 8 , S 11 Complementary conduction;

[0016] Step 6: Calculate the given value of the current of the B-phase parallel winding and convert the instantaneous value of the current i b With given value Subtract 0.5 from the proportional-integral controller to get the switch S 9 The duty cycle, S 9 , S 10 Complementary conduction.

[0017] Furthermore, in step 4, the calculation formula of the shift ratio D is:

[0018]

[0019] Furthermore, in step 6, the given value of the current flowing through the B phase winding The calculation formula is:

[0020]

[0021] Among them, P r is the pulsating power component to be filtered out, L b is the parallel inductance value of phase B, L a is the A-phase parallel inductance, ω is the power frequency electrical angular velocity, U g is the voltage amplitude on the grid side, I g is the grid input current amplitude.

[0022] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: the present invention 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; without adding additional passive devices such as electrolytic capacitors, the secondary pulsating power inherent in the single-phase power grid is filtered out, thereby improving the integration of the system. On the basis of the open-winding drive system of the electric vehicle, the stator winding of the drive motor is reused. When the system switches from the drive operation mode to the charging operation mode, the open-winding permanent magnet motor drive system is reconstructed into an isolated AC / DC converter without electrolytic capacitors by switching the switch, thereby obtaining an integrated on-board charging system for on-board power batteries with isolated charging characteristics, realizing the integrated design of the drive charging function, and improving the reliability and safety of the integrated charging system. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a topological schematic diagram of the single-phase isolated integrated vehicle charging system without electrolytic capacitors of the present invention.

[0024] Figure 2 This is the system topology of the present invention in the driving state.

[0025] Figure 3 This is the system topology of the present invention in the charging state.

[0026] Figure 4 This is the system equivalent circuit of the present invention in charging mode.

[0027] Figure 5 This is a system control block diagram of the present invention in charging mode.

[0028] Figure 6 The figure is a comparison waveform diagram of the voltage and current on the grid side before and after adding power factor correction in the present invention.

[0029] Figure 7 This is a comparison diagram of the grid-side current harmonic analysis results before and after adding power factor correction in the present invention.

[0030] Figure 8 The figure is a comparison waveform diagram of the output voltage and current pulsation before and after adding the active filter circuit of the present invention.

[0031] Fig. 9 This is the main waveform diagram of the transformer voltage and current during charging of the present invention.

[0032] Fig.10 This is the main input and output voltage and current waveform diagram of the present invention during charging. DETAILED DESCRIPTION

[0033] like Figure 1 As shown in FIG. 1 , a topological structure of a single-phase isolated integrated vehicle charging system without electrolytic capacitors includes: an open-winding permanent magnet synchronous motor, a dual three-phase inverter, a power battery, a bus capacitor, a high-frequency transformer, a winding switching switch K 1 , K 2 , K 3 And single-phase grid switch G 1 The open-winding permanent magnet synchronous motor three-phase winding leads to the 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 switching switch is a double-pole double-throw switch, which is switched according to the driving mode or the charging mode.

[0034] like Figure 2 As shown, when the electric vehicle is running in the driving mode, the three-phase single-phase grid switch G 1 Disconnect, winding switch K 1 , K 2 , K 3 The two winding sections of each phase are connected in series and connected to a dual three-phase inverter. The power battery and bus capacitor and the dual three-phase inverter of the isolated bus drive the open-winding permanent magnet synchronous motor.

[0035] like Figure 3 As shown, when the electric vehicle is running in charging mode, the winding switching switch K 1 , K 2 , K 3 And single-phase grid switch G 1Close the circuit, connect the two sections of each phase winding of the motor in parallel, and reconstruct the system topology into an isolated single-stage AC / DC converter without electrolytic capacitors. The single-phase grid AC power outputs DC power with secondary pulsating power through the isolation converter, and the secondary pulsating power is filtered out through the active filter circuit to charge the power battery.

[0036] like Figure 4 As shown, the system equivalent circuit of an isolated single-stage AC / DC converter without electrolytic capacitor in charging mode is characterized in that the three-phase inverter 1 is reconstructed into the primary bridge arm of the transformer, wherein the switch tube S 1 , S 2 , S 5 , S 6 and parallel winding L a1 , L a2 Reconstructed into a synchronous rectifier, reuse the switch tube S 5 , S 6 , and the switch tube S 3 , S 4 Reconstructed into a primary full-bridge circuit, through the parallel winding L c1 , L c2 Connect the primary side of the high-frequency transformer; the three-phase inverter 2 is reconstructed into the secondary side bridge arm of the transformer, in which the switch tube S 7 , S 8 , S 11 , S 12 Reconstructed into a secondary full-bridge circuit, connected to the secondary side of the high-frequency transformer, and reused the switch tube S 7 , S 8 , and the switch tube S 9 , S 10 and parallel winding L b1 , L b2 Reconstructed into an H-bridge active filter circuit.

[0037] The primary full-bridge circuit, the secondary full-bridge circuit and the high-frequency transformer form a dual-active bridge converter; the synchronous rectifier converts the single-phase grid AC power into a pulsating DC bus voltage, outputs DC power through the subsequent dual-active bridge converter, and filters out the secondary pulsating power through the H-bridge active filter circuit to achieve isolated single-phase integrated charging of the battery pack.

[0038] During the charging process of each phase winding in the topology, the currents of the parallel windings are equal in magnitude and direction, and the generated magnetic fluxes are offset, so that the magnetic fluxes generated in the three-phase windings of the motor are all zero, achieving magnetic flux balance, thereby eliminating the electromagnetic torque generated by the reused motor windings.

[0039] During the charging process of each phase winding in the topology, the currents of the two inductors are equal in magnitude and direction, and the magnetic fluxes generated are offset, so that the magnetic fluxes generated in the three-phase windings are all zero, achieving magnetic flux balance, so that no electromagnetic torque is generated, and the motor rotor can remain stationary during the charging process.

[0040] like Figure 5 As shown, the present invention also provides a charging control method for a single-phase isolated integrated vehicle charging system without electrolytic capacitors, characterized in that in the synchronous rectifier, the switch tube S 1 , S 2 The power frequency switch bridge arm, the switch tube S 5 , S 6 It is a high-frequency switch bridge arm with a duty cycle of 0.5, which boosts the AC side voltage and converts it into a pulsating DC bus voltage with twice the amplitude.

[0041] The switch tube of the dual active bridge converter is switched at high frequency, and the pulsating DC bus voltage is regarded as a constant voltage during the switching cycle. The primary full bridge circuit reuses the switch tube S 5 , S 6 , while the switch tube S 4 , S 5 With switch tube S 3 , S 6 Complementary conduction, duty cycle is 0.5, the secondary full-bridge circuit switch tube S 7 , S 12 With switch tube S 8 , S 11 Complementary conduction, by controlling the switch tube S 3 , S 4 , S 5 , S 6 And switch tube S 7 , S 8 , S 11 , S 12 Phase shift angle adjusts the transmission power of dual active bridge converter.

[0042] The H-bridge active filter circuit reuses the switch tube S 7 , S 8 , and the switch tube S 7 , S 8 It is a high-frequency switch bridge arm with a duty cycle of 0.5. 9 , S 10 The duty cycle of the parallel B-phase winding is controlled to filter out the secondary power pulsation.

[0043] The switch tube S 1 , S 2 By judging the grid voltage direction, the switch state is controlled. 3 , S 4, S 5 , S 6 And switch tube S 7 , S 8 , S 11 , S 12 The phase shift angle is controlled by power factor control and voltage regulator. 9 , S 10 The duty cycle is determined by the active filter control strategy, and the implementation steps are as follows:

[0044] (1) Collect the instantaneous value of the single-phase grid voltage u g , instantaneous current value i g , instantaneous value of B-phase parallel winding current i b , output voltage U o ;

[0045] (2) Calculate the instantaneous value of the single-phase grid voltage u through the phase-locked loop g The phase angle θ g , and at the same time determine the instantaneous value of the grid side voltage u g When the switch S 2 conduction, instantaneous value of grid side voltage u g When it is negative, the switch tube S 1 Conductivity;

[0046] (3) Calculate the charging voltage set value and actual output voltage U of the power battery o The difference is filtered out through a notch filter to remove the secondary pulsation component, and the output is shifted by a factor k after passing through a proportional-integral controller;

[0047] (4) In the phase shift calculation module, the phase shift coefficient k and the grid side voltage phase angle θ are used to calculate the phase shift coefficient k and the grid side voltage phase angle θ. g , calculate the displacement ratio D;

[0048] (5) Set a switch signal with a constant duty cycle of 0.5 to drive the switch tube S 3 , S 4 , S 5 , S 6 , switch tube S 3 , S 6 , respectively with S 4 , S 5 Complementary conduction, the switching signal is phase-shifted according to the calculated phase shift D and then drives the switch tube S 7 , S 8 , S 11 , S 12 , switch tube S 7 , S 12 Respectively with S 8 , S 11 Complementary conduction;

[0049] (6) Calculate the given value of the current of the B-phase parallel winding and convert the instantaneous value of the current i b With given value Subtract 0.5 from the proportional-integral controller to get the switch S 9 The duty cycle, S 9 , S 10 Complementary conduction;

[0050] In step (4) of the above control strategy, the calculation steps of the shift phase D are as follows:

[0051] The voltage expression on the grid side is:

[0052] u g =U g sin(ωt),

[0053] i g =I g sin(ωt)

[0054] Among them U g ,I g are the amplitudes of voltage and current respectively. Multiplying the two together gives the power on the grid side:

[0055] p g =U g I g sin(ωt)sin(ωt)

[0056] In the synchronous rectifier, the switch tube S 1 , S 2 The power frequency switch bridge arm, the switch tube S 5 , S 6 The high-frequency switch bridge arm has a duty cycle of 0.5, which boosts the AC side voltage into a pulsating DC bus voltage with twice the amplitude. Therefore, the DC bus voltage U in for:

[0057] U in =2U g |sin(ωt)

[0058] Under single phase shift control, the system transmission power of the dual active bridge converter is:

[0059]

[0060] Among them, U o is the output voltage, f is the system operating frequency, L is the parallel inductance of the C-phase winding, and n is the transformer turns ratio; in order to achieve the power factor correction function, it is necessary to make the grid side power and the converter system transmission power equal, so:

[0061]

[0062] It can be further simplified to:

[0063]

[0064] Therefore, the calculation formula for the shift ratio is as follows:

[0065]

[0066] The calculation formula of the shift ratio coefficient k is:

[0067]

[0068] Since the system operating frequency f, C phase winding parallel inductance L and transformer turns ratio n are constants, when the system is working stably, U o The output voltage is fixed, so the phase shift coefficient k determines the magnitude of the system input current amplitude, thereby determining the system input power. The calculation formula for the phase shift coefficient is as follows:

[0069]

[0070] In step (6) of the above control strategy, the B phase current given value is The calculation steps are as follows:

[0071] Power on the grid side:

[0072]

[0073] The power consumed by the input side winding A phase inductance is:

[0074]

[0075] Where L a is the parallel equivalent inductance of phase A winding, then the input power of the converter is:

[0076]

[0077] It can be seen that the input power of the rectifier consists of a DC component and a secondary power frequency pulsating component. If the secondary pulsating power is to be eliminated, the pulsating component should act completely on the B-phase winding inductance, and the power on the B-phase winding inductance is:

[0078]

[0079] In order to filter out the secondary power frequency pulsation component, p in The pulsating component in p r Equal, it can be obtained that the given value of the inductance current of phase B winding should be:

[0080]

[0081] 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 / Simulink 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:

[0082] Table 1 Simulation setting parameters

[0083]

[0084] like Figure 6 and Figure 7 As shown, the simulation time is set to 0.12s, and power factor correction is added at 0.06s. Figure 6 The voltage and current waveforms on the grid side before and after adding power factor correction are shown in Figure 2. It can be seen that the current sinusoidality is poor and there is zero-crossing distortion before adding power factor correction. After adding power factor correction, it can be seen that the current sinusoidality is high and is basically consistent with the voltage phase, and there is no current distortion. The PFC function is realized and the power consumption requirements of the grid are met. Figure 7 This is a comparison chart of the grid-side current harmonic analysis results before and after adding power factor correction. It can be seen that there are harmonics when power factor correction is added, and the THD is 41.52%. After adding power factor correction, there are basically no current harmonics, and the THD is 2.65%, which meets the harmonic requirements of the power grid.

[0085] like Figure 8 As shown, the simulation time is set to 0.8s, and active filter control is added at 0.4s. Figure 8 The charging voltage waveform and current waveform of the power battery before and after adding active filtering control. It can be seen that the peak-to-peak value of the second harmonic of the charging voltage of the power battery reached 65.2V before adding active filtering, and the peak-to-peak value of the second harmonic after adding active filtering was reduced to 21.5V, which was 67.02% less than before filtering, and the average charging voltage was always stable at 800V.

[0086] like Fig. 9 As shown in the figure, after adding power factor correction and active filtering control strategies, the simulation time is set to 0.5s, and the steady-state waveforms of 0.2s-0.3s and 0.215s-0.21505s are intercepted, which are the primary-secondary voltage difference of the transformer and the transformer inductor current waveform, respectively. 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 the high-frequency transformer.

[0087] like Fig.10As shown, the steady-state waveform of 0.2s-0.3s is intercepted. The figure shows the grid-side input voltage, the front-stage bus capacitor voltage, the power battery charging voltage and the power battery charging current waveform. It can be seen that the voltage fluctuation is small in the steady state, and it has good steady-state performance.

[0088] Through the above specific embodiments, the feasibility of the single-phase isolated integrated on-board charging system topology without electrolytic capacitor and its control method proposed by the present invention is verified. Based on the open-winding drive system of the electric vehicle, the system reuses the stator winding of the drive motor. When the system switches from the drive operation mode to the charging operation mode, the open-winding permanent magnet motor drive system is reconstructed into an isolated AC / DC converter without electrolytic capacitor by switching the switch, including a synchronous rectifier, a dual active bridge converter and an active filter device. The power factor correction is realized by matching the transmission power and the grid-side input power. The active filtering is realized by filtering the inherent secondary power pulsation through the winding inductance current control. The torque pulsation of the reused motor winding is suppressed by the flux balance method, thereby obtaining an integrated on-board charging system with isolated charging characteristics for on-board power batteries, realizing the integrated design of the drive charging function, and improving the reliability and safety of the integrated charging system.

Claims

1. A topology structure of a single-phase isolated integrated vehicle charging system without electrolytic capacitor, characterized in that: include: An open-winding permanent magnet synchronous motor, a dual three-phase inverter, a power battery, a bus capacitor, a high-frequency transformer, winding switching switches K1, K2, K3 and a single-phase grid switching switch G1; the open-winding permanent magnet synchronous motor three-phase winding leads out a center tap and is divided into L a1 , L a2 , L b1 , L b2 , L c1 , L c2 There are six windings in total; the winding switching switch is a double-pole double-throw switch, which is switched according to the driving mode or the charging mode.

2. The topology structure of the electrolytic capacitor-free single-phase isolated integrated vehicle charging system according to claim 1, characterized in that: In driving mode, the three-phase single-phase grid switching switch G1 is disconnected, and the winding switching switches K1, K2, and K3 connect the two winding sections of each phase in series and connect them to the dual three-phase inverter. The power battery and bus capacitor drive the open-winding permanent magnet synchronous motor with the dual three-phase inverter of the isolation bus; in charging mode, the winding switching switches K1, K2, K3 and the single-phase grid switching switch G1 are closed, and the two sections of each phase winding of the motor are connected in parallel, reconstructing the system topology into an isolated single-stage AC / DC converter without electrolytic capacitors. The single-phase grid AC power outputs DC power with secondary pulsating power through the isolation converter, and the secondary pulsating power is filtered out by the active filter circuit to charge the power battery.

3. The topology structure of the electrolytic capacitor-free single-phase isolated integrated vehicle charging system according to claim 1, characterized in that: In charging mode, the system topology is reconstructed into an isolated single-stage AC / DC converter without electrolytic capacitors, and the three-phase inverter 1 is reconstructed into the primary bridge arm of the transformer, in which the switch tubes S1, S2, S5, S6 and the parallel winding L a1 , L a2 Reconstructed into a synchronous rectifier, reused switch tubes S5 and S6, and reconstructed into a primary full-bridge circuit with switch tubes S3 and S4, and connected through the parallel winding L c1 , L c2 Connect the primary side of the high-frequency transformer; the three-phase inverter 2 is reconstructed into the secondary side bridge arm of the transformer, in which the switch tubes S7, S8, S 11 , S 12 Reconstructed into a secondary full-bridge circuit, connected to the secondary side of the high-frequency transformer, reused switch tubes S7 and S8, and switch tubes S9 and S 10 and parallel winding L b1 , L b2 Reconstructed into an H-bridge active filter circuit; the primary full-bridge circuit, the secondary full-bridge circuit and the high-frequency transformer form a dual active bridge converter; the synchronous rectifier converts the single-phase grid AC power into a pulsating DC bus voltage, outputs DC power through the subsequent dual active bridge converter, and filters out the secondary pulsating power through the H-bridge active filter circuit to realize isolated single-phase integrated charging of the battery pack; in the charging process of each phase winding in the topology, the current of the parallel winding is equal in magnitude and direction, and the generated magnetic flux is offset, so that the magnetic flux generated in the three-phase winding of the motor is zero, achieving magnetic flux balance, thereby eliminating the electromagnetic torque generated by the reused motor winding.

4. The topology structure of the electrolytic capacitor-free single-phase isolated integrated vehicle charging system according to claim 3, characterized in that: In the synchronous rectifier, the switch tubes S1 and S2 are the industrial frequency switch bridge arms, and the switch tubes S5 and S6 are the high-frequency switch bridge arms with a duty cycle of 0.5, so that the AC side voltage is boosted and converted into a pulsating DC bus voltage with twice the amplitude; the switch tube high-frequency switch of the dual active bridge converter regards the pulsating DC bus voltage as a constant voltage during the switching cycle, and its primary full-bridge circuit reuses the switch tubes S5 and S6, while the switch tubes S4 and S5 are complementary to the switch tubes S3 and S6, with a duty cycle of 0.5, and its secondary full-bridge circuit switch tubes S7 and S 12 With switch tube S8, S 11 Complementary conduction, by controlling the switch tubes S3, S4, S5, S6 and the switch tubes S7, S8, S 11 , S 12 The phase shift angle adjusts the transmission power of the dual active bridge converter; the H-bridge active filter circuit reuses switch tubes S7 and S8, and the switch tubes S7 and S8 are high-frequency switch bridge arms with a duty cycle of 0.5, and the switch tubes S9 and S 10 The duty cycle of the parallel B-phase winding is controlled to filter out the secondary power pulsation.

5. A control method for the topological structure of the single-phase isolated integrated vehicle charging system without electrolytic capacitor 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 、B phase parallel winding current instantaneous value i b , output voltage U o ; Step 2: Calculate the instantaneous value of the single-phase grid voltage u through the phase-locked loop g The phase angle θ g , and at the same time determine the instantaneous value of the grid side voltage u g When the switch S2 is turned on, the instantaneous value of the grid voltage u g When it is negative, the switch tube S1 is turned on; Step 3: Calculate the charging voltage set value and actual output voltage U of the power battery o The difference is filtered out through a notch filter to remove the secondary pulsation component, and the output is shifted by a factor k after passing through a proportional-integral controller; Step 4: In the phase shift calculation module, the phase shift coefficient k and the grid side voltage phase angle θ are used to calculate the phase shift coefficient k and the grid side voltage phase angle θ. g , calculate the displacement ratio D; Step 5: Set a switch signal with a constant duty cycle of 0.5 to drive switch tubes S3, S4, S5, and S6. Switch tubes S3 and S6 are turned on complementary to S4 and S5, respectively. The switch signal is phase-shifted according to the calculated shift ratio D and then drives switch tubes S7, S8, and S9. 11 , S 12 , switch tube S7, S 12 Respectively with S8, S 11 Complementary conduction; Step 6: Calculate the given value of the current of the B-phase parallel winding and convert the instantaneous value of the current i b With given value Subtract 0.5 from the proportional-integral controller to get the duty cycle of switch S9. 10 Complementary conduction.

6. The control method of the topological structure of the single-phase isolated integrated vehicle charging system without electrolytic capacitor as claimed in claim 5, characterized in that: In step 4, the calculation formula for the shift ratio D is:

7. The control method of the topological structure of the single-phase isolated integrated vehicle charging system without electrolytic capacitor as claimed in claim 5, characterized in that: In step 6, the given value of the current flowing through the B phase winding The calculation formula is: Among them, P r is the pulsating power component to be filtered out, L b is the parallel inductance value of phase B, L a is the A-phase parallel inductance, ω is the power frequency electrical angular velocity, U g is the voltage amplitude on the grid side, I g is the grid input current amplitude.

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