Low-input-ripple active-filter-type isolated integrated charging system and control method thereof

Abstract

The application discloses a low-input-ripple active filtering type isolated integrated charging system and a control method thereof. The system is based on the open-winding driving system of an electric vehicle and is additionally provided with a diode and a high-frequency transformer. The motor A-phase winding is cross-parallel multiplexed into a network-side current filter through a switching switch, the B-phase winding and the C-phase winding are multiplexed into active filtering energy storage elements, the system is reconstructed into a single-phase isolated AC / DC converter with low input current ripple, and the function of isolating charging of the on-board battery pack is realized. The application designs the cross-parallel topology structure for the integrated charging system based on the low-inductance on-board motor, avoids the problem of excessively large input ripple caused by small multiplexed winding inductance in the traditional integrated charging system method, and improves the safety and reliability of the integrated charging system. Meanwhile, the motor winding is used for energy storage, the output-side filter capacitance value is reduced, the secondary power pulsation of the charging voltage is reduced, and the integration degree of the system is improved.

Description

Technical Field

[0001] This invention relates to an integrated on-board charging system for electric vehicles, specifically to a low-input-ripple active filter type isolated integrated charging system and its control method. Background Technology

[0002] On-board integrated charging systems utilize the time-sharing multiplexing of existing drive system components in electric vehicles, eliminating the need for numerous additional dedicated charging devices. During charging, the system reconfigures the drive system topology into an on-board integrated charger via a switching switch, directly converting grid-side AC power to DC power for efficient charging of the battery. This approach retains the convenience of on-board chargers while significantly reducing the overall vehicle size and weight, making it highly practical. However, it's important to note that on-board integrated charging systems still face several pressing technical challenges in practical applications.

[0003] 1. The inductance value of the high-speed motor on the electric vehicle is usually small. If it is used as a filter inductor, it will result in high total harmonic distortion of the grid current and obvious distortion of the current waveform, which will affect the power quality of the power grid.

[0004] 2. Vehicle-mounted integrated charging systems typically lack electrical isolation, resulting in low charging safety.

[0005] 3. The charging current flowing through the reused motor windings will generate electromagnetic torque, causing the motor to vibrate or rotate, thus reducing charging efficiency.

[0006] 4. The DC power obtained by rectifying the AC power from a single-phase power grid contains second harmonics. It is usually necessary to add additional power devices to filter out the second power pulsation, which leads to an increase in the size and weight of electric vehicles.

[0007] Therefore, how to achieve isolated integrated on-board charging without adding extra isolation equipment and extra filtering devices is an urgent problem to be solved. Summary of the Invention

[0008] Purpose of the invention: To address the above problems, this invention proposes an active filter-type isolated integrated charging system and its control method with low input ripple, which can suppress grid-side current harmonics, improve charging power quality, and realize the function of isolated charging of vehicle battery packs.

[0009] Technical Solution: The technical solution adopted in this invention is a low-input-ripple active filter type isolated integrated charging system, including an electric vehicle open-winding drive system. The electric vehicle open-winding drive system includes an open-winding permanent magnet synchronous motor, a dual three-phase inverter, a power battery, and a bus capacitor. The power battery is connected in parallel with the bus capacitor and is connected to the open-winding permanent magnet synchronous motor through the dual three-phase inverter. The feature is that it also includes a high-frequency transformer, a switching switch, and two diodes connected in parallel at the input terminal of the dual three-phase inverter.

[0010] Among them, the midpoint of the bridge arm formed by the two diodes is connected to the negative terminal of the single-phase power grid, and the positive terminal of the single-phase power grid is connected to the midpoint tap of the A-phase winding through the single-phase power grid switching switch G4.

[0011] One winding of the high-frequency transformer is connected to the midpoints of the first and second bridge arms of the grid-side three-phase inverter of the dual three-phase inverter, respectively. The other winding is connected to the midpoints of the third bridge arm of the grid-side three-phase inverter and the midpoint of the first bridge arm of the battery-side three-phase inverter, respectively. A high-frequency transformer switching switch is connected in series at both ends of the high-frequency transformer for connecting / disconnecting the high-frequency transformer.

[0012] The bus changeover switch G1 is located between the second and third bridge arms of the grid-side three-phase inverter and is used to connect / disconnect the DC buses on both sides of the bus changeover switch G1.

[0013] In drive mode, bus switching switch G1 is closed, connecting the DC buses on both sides, high-frequency transformer switching switch is open, and single-phase grid switching switch G4 disconnects the single-phase grid. The system is equivalent to a common bus drive system for open-winding permanent magnet synchronous motors. The DC power output from the power battery drives the open-winding permanent magnet synchronous motor through a common bus dual three-phase inverter.

[0014] In charging mode, bus switch G1 is open, high-frequency transformer switch is closed to connect the high-frequency transformer, and single-phase grid switch G4 is closed to connect the single-phase grid, thus reconfiguring the open-winding permanent magnet synchronous motor drive system into a single-phase active filter type isolated AC / DC converter.

[0015] In charging mode, the drive signal duty cycles of the switching transistors in the first and second bridge arms of the grid-side three-phase inverter in the dual three-phase inverter are both 0.5 and opposite in phase, suppressing grid-side current harmonics. By interleaving and paralleling two A-phase windings, an interleaved parallel Boost converter is formed, which converts grid-side AC power into a pulsating DC voltage with twice the amplitude. The first and second bridge arm switching transistors of the grid-side three-phase inverter are reused, and together with the third bridge arm switching transistor of the grid-side three-phase inverter and the first bridge arm switching transistor of the battery-side three-phase inverter, a dual active bridge converter is formed to transmit DC power and achieve electrical isolation between the grid side and the battery side.

[0016] In charging mode, the B and C phase windings of the open-winding motor are reused as active filter energy storage elements. The third bridge arm switch of the grid-side three-phase inverter is reused, and together with the third bridge arm switch of the battery-side three-phase inverter and the B phase winding, they are reconfigured into a first active filter circuit. The first bridge arm switch of the battery-side three-phase inverter is reused, and together with the second bridge arm switch of the battery-side three-phase inverter and the C phase winding, they are reconfigured into a second active filter circuit. The first and second active filter circuits are connected in parallel to form an active filter circuit based on the two-phase motor windings. The switching transistors S9 and S2 are determined through a B and C phase current coordinated control strategy. 10 S 11 S 12 The duty cycle is adjusted to suppress torque pulsation and filter out secondary pulsating power.

[0017] By using a B- and C-phase current coordinated control strategy to determine the duty cycle of the second and third bridge arm switches of the battery-side three-phase inverter, torque ripple suppression and secondary ripple power filtering are achieved.

[0018] Based on the grid-side current phase angle, the switching signals of the third bridge arm switch of the grid-side three-phase inverter and the first bridge arm switch of the battery-side three-phase inverter are phase-shifted by phase-shift control to suppress leakage inductance current and better achieve electrical isolation and DC power transmission between the grid side and the battery side.

[0019] This invention provides a control method for the aforementioned low-input-ripple active filter type isolated integrated charging system. In charging mode, the duty cycle of the second and third bridge arm switches of the battery-side three-phase inverter is determined through a B-phase and C-phase current coordinated control strategy to suppress torque ripple and filter secondary ripple power. The B-phase and C-phase current coordinated control strategy includes the following steps:

[0020] (1) Calculate the setpoint i of the B-phase winding current based on the amplitude of the grid-side input AC voltage and AC current and the rotor position. b * and the C-phase winding current setpoint i c * ;

[0021] (2) Set the given value i of the B-phase winding current. b * Subtract the actual value of the B-phase winding current i b The duty cycle of the third bridge arm switch of the battery-side three-phase inverter is obtained through a proportional resonant controller.

[0022] (3) Set the current of the C-phase winding to the given value i c * Subtract the actual value of the C-phase winding current i c The instantaneous value of the current i cSubtracting the two values, the duty cycle of the second bridge arm switch of the battery-side three-phase inverter is obtained through the proportional resonant controller;

[0023] Based on the amplitudes of the grid-side input AC voltage and current and the rotor position, calculate the setpoint values ​​of the B and C phase winding currents, including:

[0024] The formula for calculating the given value of the B-phase winding current is:

[0025] ;

[0026] In the formula, i b * U is the given value for the B-phase winding current. g I g These represent the amplitudes of the grid-side input AC voltage and AC current, respectively. ω is the angular frequency of the grid-side input AC voltage, L is the phase inductance, θ is the rotor position, and t is time.

[0027] The formula for calculating the given value of the C-phase winding current is:

[0028] ;

[0029] In the formula, i c * The current of the C-phase winding is given. By controlling the currents of the B-phase and C-phase windings of the open-winding permanent magnet synchronous motor, the energy stored and released by the B-phase and C-phase windings is controlled, reducing the secondary power pulsation on the DC bus voltage. At the same time, in the synchronous rotating coordinate system, the resultant current in the q-axis direction of the motor is 0, and only the current in the d-axis direction is present, thus achieving torque balance and effectively suppressing torque pulsation during the charging process.

[0030] Beneficial Effects: Compared with existing technologies, this invention has the following advantages: Based on the open-winding drive system of an electric vehicle, this invention adds diodes and a high-frequency transformer. By switching on a switch, the A-phase winding of the motor is interleaved and paralleled for multiplexing as a grid-side current filter, and the B and C-phase windings are multiplexed as active filtering energy storage elements. This reconfigures the system into a low-input-current-ripple single-phase isolated AC / DC converter, achieving the function of isolated charging of the on-board battery pack. By interleaving the two sections of the A-phase winding in parallel and controlling the duty cycle of the switching transistor, the secondary current ripple of the input-side switch is reduced, and the grid-side current harmonics are lowered. Through the coordinated control method of the B and C-phase winding currents, the active filtering function is achieved, and torque pulsation during the charging process of the motor windings is suppressed, improving the quality of the output power. This invention designs an interleaved parallel topology for an integrated charging system based on a low-inductance vehicle motor, avoiding the problem of excessive input ripple caused by the small inductance of the reused windings in traditional integrated charging systems, thus improving the safety and reliability of the integrated charging system. At the same time, by storing energy through the motor windings, the capacitance value of the output-side filter capacitor is reduced, thereby reducing the secondary power ripple of the charging voltage and improving the system's integration. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the topology of the single-phase isolated integrated on-board charging system with interleaved parallel windings of the present invention;

[0032] Figure 2 This is the system topology of the present invention in the driving state;

[0033] Figure 3 This is the system topology of the present invention in the charging state;

[0034] Figure 4 This is the system equivalent circuit of the present invention in charging mode;

[0035] Figure 5 This is a system control block diagram of the present invention in charging mode;

[0036] Figure 6 This is a waveform diagram of the two windings of phase A and the grid-side current during the charging process of this invention;

[0037] Figure 7 The graph shows the Fourier analysis results of the grid-side input current during the charging process of this invention.

[0038] Figure 8 This is a comparison waveform diagram of the three-phase current waveform and torque ripple before and after the addition of dual active filter current collaborative control in this invention;

[0039] Figure 9 The following are the main input and output voltage and current waveforms before and after the addition of dual active filter current collaborative control in this invention;

[0040] Figure 10 This is a diagram showing the main waveforms of the transformer voltage and current during the charging process of this invention. Detailed Implementation

[0041] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0042] Please see Figure 1 As shown, this invention provides a low-input-ripple active filter type isolated integrated charging system, including an open-winding drive system for electric vehicles. The open-winding drive system includes an open-winding permanent magnet synchronous motor, a dual three-phase inverter, a power battery, and a bus capacitor. The power battery is connected in parallel with the bus capacitor and is connected to the open-winding permanent magnet synchronous motor through the dual three-phase inverter. Based on the open-winding drive system for electric vehicles, this invention also includes a high-frequency transformer, a switching switch, and two diodes connected in parallel at the input of the dual three-phase inverter.

[0043] The stator of the open-winding permanent magnet synchronous motor contains three-phase windings. The two ends of each phase winding are connected to the midpoint of the inverter bridge arm. A center tap is drawn from phase A winding, dividing phase A winding into L... a1 and L a2 Two windings; the midpoint of the bridge arm composed of two diodes is connected to the negative terminal of the single-phase power grid, and the positive terminal of the single-phase power grid is connected to the midpoint tap of the A-phase winding through the single-phase power grid switching switch G4.

[0044] One winding of the high-frequency transformer is connected to the midpoints of the first and second bridge arms of the grid-side three-phase inverter in the dual three-phase inverter, respectively. The other winding is connected to the midpoints of the third bridge arm of the grid-side three-phase inverter and the midpoint of the first bridge arm of the battery-side three-phase inverter, respectively. The high-frequency transformer is connected to the corresponding switching tube bridge arms via switching switches G2 and G3.

[0045] The bus changeover switch G1 is located between the second and third bridge arms of the grid-side three-phase inverter and is used to connect / disconnect the DC buses on both sides of the bus changeover switch G1.

[0046] Please see Figure 2 As shown, when the electric vehicle is running in drive mode, switch G1 is closed to connect the DC bus, switches G2 and G3 are disconnected from the high-frequency transformer, and switch G4 is disconnected from the single-phase power grid. The system is equivalent to a common bus drive system for open-winding permanent magnet synchronous motors. The DC power output from the power battery drives the open-winding permanent magnet synchronous motor through a common bus dual three-phase inverter.

[0047] Please see Figure 3As shown, in charging mode, switch G1 disconnects the DC bus, switches G2 and G3 close to connect the high-frequency transformer, and switch G4 closes to connect the single-phase power grid. This reconfigures the open-winding permanent magnet synchronous motor drive system into a low-input-current-ripple single-phase active-filter isolated AC / DC converter, including a single-phase isolated AC / DC converter based on the interleaved parallel connection of the A-phase windings and an active filter circuit based on the two-phase motor windings. Combined with corresponding charging control methods, this achieves isolated charging of the vehicle battery pack.

[0048] Please see Figure 4 The diagram shows the equivalent circuit diagram of the topology of a low-input-ripple active-filter type isolated integrated charging system in charging mode. The single-phase isolated AC / DC converter based on the interleaved parallel connection of the A-phase windings, in charging mode, uses the A-phase winding of the open-winding permanent magnet synchronous motor as a grid-side filter inductor. The negative terminal of the single-phase grid is connected to the midpoint of the bridge arm formed by diodes D1 and D2, and the positive terminal is connected to the center tap of the A-phase winding. Multiplexed switches S3 and S4 and diodes D1 and D2 are connected to the A-phase winding L... a1 Reconfigured into a first-stage Boost converter, multiplexing switches S1 and S2 and diodes D1 and D2 to connect phase A winding L. a2 It is reconstructed into a second-stage Boost converter.

[0049] The drive signals for switches S1 and S2, and S3 and S4, all have a duty cycle of 0.5 and are out of phase. The two winding segments L of phase A... a1 L a2 The switching current ripples cancel each other out, suppressing grid-side current harmonics. By interleaving and paralleling two A-phase windings, a low-input-ripple interleaved parallel Boost converter is formed, which converts grid-side AC power into a pulsating DC voltage with twice the amplitude. Switches S1, S2, S3, and S4 are reused, and together with switches S5, S6, S7, and S8, they form a dual active bridge converter to transmit DC power and achieve electrical isolation between the grid side and the battery side.

[0050] The active filter circuit based on two-phase motor windings, in charging mode, reuses the B and C phase windings of the open-winding motor as active filter energy storage elements, reuses switching transistors S5 and S6, and is connected to switching transistor S... 11 S 12 And the B-phase winding is reconfigured into an active filter circuit 1, multiplexing switches S7 and S8, and connecting with switches S9 and S1. 10 The C-phase winding is reconfigured into active filter circuit 2. Active filter circuit 1 and active filter circuit 2 are connected in parallel to form an active filter circuit based on the two-phase motor winding. The switching transistors S9 and S2 are determined through a coordinated control strategy of the B and C phase currents. 10 S 11 S 12 The duty cycle is adjusted to suppress torque pulsation and filter out secondary pulsating power.

[0051] Please see Figure 5 As shown, the present invention also provides a charging control method for an active filter-type isolated integrated charging system with low input ripple, the specific implementation steps of which are as follows:

[0052] (1) Calculate the setpoint i of the B-phase winding current according to the current coordinated control strategy. b * and the C-phase winding current setpoint i c * ;

[0053] (2) Collect the actual value of the B-phase winding current i b The actual value of the current i b With the given value i of the B-phase winding current b * Subtracting the values ​​and then subtracting 0.5 after passing through the proportional resonant controller, we obtain the switching transistor S. 11 S 12 Duty cycle;

[0054] (3) Collect the actual value of the C-phase winding current i c The instantaneous value of the current i c With the given value i of the C-phase winding current c * Subtracting the values ​​and then subtracting 0.5 after passing through the proportional resonant controller, we obtain the switching transistors S9 and S2. 10 Duty cycle;

[0055] The phase-shift control section includes: acquiring the actual value u of the single-phase grid side voltage. g The phase angle θ of the power grid is calculated using a phase-locked loop. g The duty cycle of switching transistors S1-S8 is 0.5, and the given value I is based on the grid-side current amplitude. g *and grid phase angle θ g Calculate the absolute value of the given grid current I g *|sinθ g | and theoretical phase shift angle *; Collect actual value of grid-side current i g Calculate the absolute value of the actual current on the grid side |i g |Absolute value of the grid-side given current I g *|sinθ g The difference between these values ​​is reflected in the phase shift angle deviation output by the proportional resonant controller. Using phase shift angle deviation Theoretical phase shift angle *Compensation is performed to obtain the actual phase shift angle. The switching signals of switching transistors S5, S6, S7, and S8 are phase-shifted. Phase shift angle. The calculation steps are as follows:

[0056] grid-side input AC voltage u g and i g They are respectively:

[0057] ;

[0058] Among them U g I g These represent the amplitudes of the input AC voltage and current, respectively. Given the angular frequency of the input voltage, the input power of the AC power supply can be expressed as:

[0059] ;

[0060] In the interleaved parallel single-phase isolated AC / DC converter based on the A-phase winding, diodes D1 and D2 are naturally turned on, and high-frequency switching transistors S1 and S2 are also turned on. 2、 With duty cycles of 0.5 for S3 and S4, the AC input voltage is converted into a pulsating DC voltage with twice the voltage amplitude. Therefore, the DC bus voltage U... in for:

[0061] ;

[0062] The system transmission power of the dual active bridge converter under single-phase-shift control is:

[0063] ;

[0064] Where n is the transformer turns ratio, U o Let f be the output voltage, f be the switching frequency, and L be the transformer leakage inductance. The power factor correction function is achieved by ensuring that the grid-side power and the power transmitted by the dual active bridge converter are equal. Therefore:

[0065] ;

[0066] Therefore, the theoretical formula for calculating the phase shift angle is as follows:

[0067] ;

[0068] To control the grid-side input current, the grid-side input current needs to be collected and processed by a proportional resonant controller to obtain the phase shift angle deviation. The theoretical phase shift angle is compensated for by the phase shift angle deviation and then used to control the phase shift of the converter.

[0069] In step (3) of the above control strategy, the calculation steps for the setpoint values ​​of phase B and phase C currents are as follows:

[0070] The grid-side current flows from the center point of phase A winding into both winding sections. The magnitudes of the currents in the two winding sections and the total current of phase A are:

[0071] ;

[0072] The currents in the two windings are equal in magnitude but opposite in direction. The magnetic flux of the A-phase winding is balanced, so no pulsating torque can be generated.

[0073] When the rotor position is θ, in order to achieve torque balance, the q-axis currents need to be controlled to cancel each other out, and the combined current vector is sent to the d-axis. The A-phase current is 0, therefore the B and C-phase currents need to satisfy the following current relationship:

[0074] ;

[0075] From the power expression on the grid side, it can be seen that the input power includes a DC component and a secondary power frequency pulsation component. The secondary power frequency pulsation component is applied to the B and C phase winding inductances to eliminate the secondary pulsation power. The power on the B and C phase winding inductances is:

[0076] ;

[0077] Where L is the phase inductance, combining the above two equations, we can obtain the expressions for the currents of phases B and C as follows:

[0078] ;

[0079] By distributing the B and C phase currents through a current-coordinated control strategy, the currents in the q-axis direction of the motor cancel each other out, achieving torque balance. At the same time, the power stored in the B and C phase windings is controlled to suppress secondary pulsating power.

[0080] Case simulation effect:

[0081] Based on the aforementioned low-input-ripple active filter type isolated integrated charging system topology and its control method, an isolated single-phase integrated on-board charging system was built in Matlab / Simulink software. The key parameter settings during the simulation verification process are as follows:

[0082] Table 1 Simulation Setting Parameters

[0083]

[0084] Please see Figure 6 , Figure 7 As shown, the simulation duration was set to 0.12s, and the current waveforms from 0.06s to 0.12s and from 0.09625s to 0.09628s were captured. Figure 6 The diagram shows a comparison between the winding current and the grid-side input current of the two interleaved parallel sections of phase A. Since the armature winding inductance of the motor is only 0.6mH, the winding current ripple is as high as 5.6A. By adopting the topology structure of the two interleaved parallel sections of winding, the switching secondary ripple of the grid-side input current can be reduced to 0.3A. Figure 7 The Fourier analysis results of the grid-side input current are shown in the figure. The THD of the grid-side current is 1.66%, which indicates that the present invention can effectively reduce the switching harmonic content of the grid-side input current during charging.

[0085] Please see Figure 8 As shown, Figure 8 The main input and output voltage waveforms before and after the addition of dual active filter current coordinated control are shown in the following order: grid-side input voltage, grid-side input current, pulsating DC bus voltage, and power battery charging voltage. It can be seen that the input current and input voltage are in phase, and the charging system has a high power factor. The average value of the power battery charging voltage remains at 400V. Before the addition of active filtering, its second harmonic peak-to-peak value reached 128V, and after the addition of active filtering, it dropped to 30V, and the second harmonic content was reduced by 76.56%.

[0086] Please see Figure 9 , Figure 9 To illustrate the three-phase current waveforms and torque pulsation waveforms before and after the addition of dual active filter current coordinated control, before the addition of current coordinated control, the A-phase current exhibits high-frequency switching secondary pulsation characteristics, while the B and C phase windings have no current output and only contain switching secondary torque pulsation with a peak-to-peak value of 0.13 Nm. After the addition of current coordinated control, the A-phase current still maintains high-frequency switching secondary pulsation characteristics, while the B and C phase currents change from 0 to a sinusoidal waveform, absorbing secondary power pulsation and achieving torque balance. The system torque pulsation always contains only switching secondary components, with no additional low-frequency pulsation, and the motor rotor remains stationary.

[0087] Please see Figure 10 As shown, the simulation duration was set to 0.12s, and steady-state waveforms were captured from 0.06s to 0.12s and from 0.09625s to 0.09628s. Figure 10 The waveforms of the transformer primary and secondary voltages and the transformer leakage inductance voltage and current are shown respectively. It can be seen that the leakage inductance current can be controlled by phase shift control, thereby achieving electrical isolation between the grid side and the battery side and DC power transmission.

[0088] The above specific implementation cases verify the feasibility of the low-input-ripple active filtering isolated integrated charging system topology and its control method. This system adds diodes and a high-frequency transformer to the open-winding drive system of an electric vehicle. By switching on a switch, the A-phase winding of the motor is interleaved and paralleled for multiplexing as a grid-side current filter, and the B and C-phase windings are multiplexed as active filtering energy storage elements. This reconfigures the system into a low-input-current-ripple single-phase isolated AC / DC converter, enabling isolated charging of the on-board battery pack. Specifically, by interleaving the two sections of the A-phase winding in parallel, the secondary current ripple of the input-side switch is reduced, and grid-side current harmonics are lowered. The coordinated control method of the B and C-phase winding currents achieves active filtering and suppresses torque pulsation during motor winding charging, improving the quality of the output power. This invention designs an interleaved parallel topology for an integrated charging system based on a low-inductance vehicle motor, avoiding the problem of excessive input ripple caused by the small inductance of the reused windings in traditional integrated charging systems, thus improving the safety and reliability of the integrated charging system. At the same time, by storing energy through the motor windings, the capacitance value of the output-side filter capacitor is reduced, thereby reducing the secondary power ripple of the charging voltage and improving the system's integration.

Claims

1. A low-input-ripple active-filter isolated integrated charging system, comprising an open-winding drive system for electric vehicles, wherein the open-winding drive system comprises an open-winding permanent magnet synchronous motor, a dual three-phase inverter, a power battery, and a bus capacitor, wherein the power battery is connected in parallel with the bus capacitor and is connected to the open-winding permanent magnet synchronous motor through the dual three-phase inverter, characterized in that: It also includes a high-frequency transformer, a switching switch, and two diodes connected in parallel at the input of the dual three-phase inverter; Among them, the midpoint of the bridge arm formed by the two diodes is connected to the negative terminal of the single-phase power grid, and the positive terminal of the single-phase power grid is connected to the midpoint tap of the A-phase winding through the single-phase power grid switching switch G4. One winding of the high-frequency transformer is connected to the midpoints of the first and second bridge arms of the grid-side three-phase inverter of the dual three-phase inverter, respectively. The other winding is connected to the midpoints of the third bridge arm of the grid-side three-phase inverter and the midpoint of the first bridge arm of the battery-side three-phase inverter, respectively. A high-frequency transformer switching switch is connected in series at both ends of the high-frequency transformer for connecting / disconnecting the high-frequency transformer. The bus changeover switch G1 is located between the second and third bridge arms of the grid-side three-phase inverter and is used to connect / disconnect the DC buses on both sides of the bus changeover switch G1.

2. The low input ripple active filter type isolated integrated charging system according to claim 1, characterized in that: In drive mode, bus switching switch G1 is closed, connecting the DC buses on both sides, high-frequency transformer switching switch is open, and single-phase grid switching switch G4 disconnects the single-phase grid. The system is equivalent to a common bus drive system for open-winding permanent magnet synchronous motors. The DC power output from the power battery drives the open-winding permanent magnet synchronous motor through a common bus dual three-phase inverter.

3. The low input ripple active filter type isolated integrated charging system according to claim 1, characterized in that: In charging mode, bus switch G1 is open, high-frequency transformer switch is closed to connect the high-frequency transformer, and single-phase grid switch G4 is closed to connect the single-phase grid, thus reconfiguring the open-winding permanent magnet synchronous motor drive system into a single-phase active filter type isolated AC / DC converter.

4. The low input ripple active filter type isolated integrated charging system according to claim 3, characterized in that: In charging mode, the drive signal duty cycles of the switching transistors in the first and second bridge arms of the grid-side three-phase inverter in the dual three-phase inverter are both 0.5 and opposite in phase, suppressing grid-side current harmonics. By interleaving and paralleling two A-phase windings, an interleaved parallel Boost converter is formed, which converts grid-side AC power into a pulsating DC voltage with twice the amplitude. The first and second bridge arm switching transistors of the grid-side three-phase inverter are reused, and together with the third bridge arm switching transistor of the grid-side three-phase inverter and the first bridge arm switching transistor of the battery-side three-phase inverter, a dual active bridge converter is formed to transmit DC power and achieve electrical isolation between the grid side and the battery side.

5. The low input ripple active filter type isolated integrated charging system according to claim 3, characterized in that: In charging mode, the B and C phase windings of the open-winding motor are reused as active filter energy storage elements. The third bridge arm switch of the grid-side three-phase inverter is reused and reconstructed with the third bridge arm switch of the battery-side three-phase inverter and the B phase winding to form the first active filter circuit. The first bridge arm switch of the battery-side three-phase inverter is reused and reconstructed with the second bridge arm switch of the battery-side three-phase inverter and the C phase winding to form the second active filter circuit. The first and second active filter circuits are connected in parallel to form an active filter circuit based on the two-phase motor windings.

6. The low input ripple active filter type isolated integrated charging system according to claim 1, characterized in that: By using a B- and C-phase current coordinated control strategy to determine the duty cycle of the second and third bridge arm switches of the battery-side three-phase inverter, torque ripple suppression and secondary ripple power filtering are achieved.

7. The low input ripple active filter type isolated integrated charging system according to claim 1, characterized in that: Based on the grid-side current phase angle, the switching signals of the third bridge arm switch of the grid-side three-phase inverter and the first bridge arm switch of the battery-side three-phase inverter are phase-shifted by phase-shift control to achieve leakage inductance current suppression.

8. A control method for the low input ripple active filter type isolated integrated charging system as described in claim 1, characterized in that: In charging mode, the duty cycle of the second and third bridge arm switches of the battery-side three-phase inverter is determined through a B-phase and C-phase current coordinated control strategy to suppress torque ripple and filter secondary ripple power. The B-phase and C-phase current coordinated control strategy includes the following steps: (1) Calculate the setpoint i of the B-phase winding current based on the amplitude of the grid-side input AC voltage and AC current and the rotor position. b * and the C-phase winding current setpoint i c * ; (2) Set the given value i of the B-phase winding current. b * Subtract the actual value of the B-phase winding current i b The duty cycle of the third bridge arm switch of the battery-side three-phase inverter is obtained through a proportional resonant controller. (3) Set the current of the C-phase winding to the given value i c * Subtract the actual value of the C-phase winding current i c The instantaneous value of the current i c By subtracting the two values, the duty cycle of the second bridge arm switch of the battery-side three-phase inverter is obtained through the proportional resonant controller.

9. The control method according to claim 8, characterized in that: The formula for calculating the given value of the B-phase winding current is: ； In the formula, i b * U is the given value for the B-phase winding current. g I g These represent the amplitudes of the grid-side input AC voltage and AC current, respectively. ω is the angular frequency of the grid-side input AC voltage, L is the phase inductance, θ is the rotor position, and t is time.

10. The control method according to claim 8, characterized in that: The formula for calculating the given value of the C-phase winding current is: ； In the formula, i c * The given value for the C-phase winding current.

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