Single-stage isolation type bidirectional vehicle-mounted integrated charging system for new energy automobile

Abstract

The invention discloses a single-stage isolation type bidirectional vehicle-mounted integrated charging system for a new energy automobile, and belongs to the field of vehicle-mounted integrated charging. The problems that an existing two-stage isolation type vehicle-mounted charging system is large in size and high in cost and loss are solved. According to the single-stage isolation type bidirectional AC-DC charging and discharging topological structure based on three-phase motor winding reconstruction, aiming at a two-stage topological structure in the prior art, the size, the cost and the loss of the topology are further reduced, the system efficiency is improved, the single-stage isolation type bidirectional AC-DC charging and discharging topological structure has the advantages that the structure is simple, the cost is low, and the cost is low. In addition, the numerical value of the grid-side equivalent filter inductance in the charging and discharging mode can be increased, the motor does not rotate in the charging process, harmonic waves of the grid-side current can be suppressed, and the loss in the motor can be further reduced while the cost is reduced. The method is mainly applied to new energy automobile charging.

Description

Technical Field

[0001] The invention belongs to the field of vehicle-mounted integrated charging. Background Art

[0002] For an isolated integrated charging system that reuses a three-phase permanent magnet synchronous motor and its supporting drive inverter as a corresponding grid-side filter inductor and power converter in charging mode, the existing topology adopts traditional structures such as PFC+DAB or PFC+CLLC. It is equivalent to an isolated DC-DC with one stage of AC-DC connected in series. This two-stage charging system has a complex structure and numerous switching devices, so it is large in size, high in cost, and high in loss. At the same time, for the PFC level, the existing technology is to inject zero-sequence current into the three windings in charging mode to ensure that the motor does not rotate during charging. In this method of torque elimination by injecting zero-sequence current, the winding inductance that acts as a grid-side filter in charging mode is the winding leakage inductance of the motor, and for a three-parallel inverter system, the grid-side equivalent filter inductance value is about one-third of the leakage inductance value of one winding in the case of single-phase and DC input power supply. Too low equivalent grid-side inductance will reduce the quality of electric energy injected into the grid, which will manifest as an increase in grid-side current harmonics. At the same time, excessive current harmonics will increase the losses of switching devices such as motors and inverters. The above problems need to be solved. Summary of the invention

[0003] The purpose of the present invention is to solve the problems of large volume, high cost and high loss of the existing two-stage isolation type on-board charging system. The present invention provides a single-stage isolation type bidirectional on-board integrated charging system for new energy vehicles.

[0004] A single-stage isolated bidirectional on-board integrated charging system for new energy vehicles, including the original on-board drive system and the clamping capacitor C c A single-stage isolated bidirectional AC-DC charging and discharging topology structure constructed by a switching switch, a high-frequency transformer and a full-bridge converter is used to charge or discharge the vehicle battery;

[0005] In the charge and discharge mode, the switching switch is used to change the connection mode of the three-phase winding of the three-phase motor of the original vehicle drive system, and the three-phase winding of the three-phase motor of the original vehicle drive system is reused as the PFC inductor, and the three-phase inverter of the original vehicle drive system is reused as the AC-AC converter. After the industrial frequency AC power output by the single-phase power supply is converted into high-frequency AC power, the clamp capacitor C c It is sent to the high-frequency transformer, where it undergoes voltage conversion and is then sent to the full-bridge converter for rectification. It then passes through the bus capacitor C of the original vehicle drive system. bat After voltage stabilization, the vehicle battery is charged.

[0006] Preferably, the switch includes a single-open single-control switch K1, K31 and K 32 , and single-open dual-control K 21 and K 22 ;

[0007] The input ends of the a, b and c phase windings of the three-phase motor are respectively connected to one end of the switch K1 and the second and third AC output ends of the three-phase inverter. The other end of the switch K1 is connected to the first AC output end of the three-phase inverter. The first and second AC output ends of the three-phase inverter are also respectively connected to the single-open single-control switch K1. 31 and K 32 One end is connected to single-open single-control switch K 31 and K 32 The other end is connected to one end and the other end of the primary winding of the high-frequency transformer respectively;

[0008] The two ends of the secondary winding of the high-frequency transformer are connected to the two single-phase AC ends of the full-bridge converter, and the two DC ends of the full-bridge converter are used as single-open dual-control K 21 and K 22 The second selection end;

[0009] The first DC input terminal of the three-phase inverter and the clamping capacitor C c One end and single open double control K 21 The first selection end of the three-phase inverter is connected to the second DC input end of the clamping capacitor C c The other end and the single open dual control K 22 The first selection end is connected to the bus capacitor C bat The two ends of the battery are connected in parallel to the single-open dual-control K 21 and K 22 The fixed end connection;

[0010] In the driving mode, the single-open single-control switch K1 is in the closed state, and the single-open double-control switch K 21 and K 22 Switch to the first selection end, single open single control switch K 31 and K 32 It is disconnected state;

[0011] In charging mode, the two ends of the single-open single-control switch K1 are used to connect to the two charging terminals P of the single-phase power supply respectively. g1 and P g2 connected, and the single-open single-control switch K1 is disconnected, the single-open double-control K 21 and K 22 Switch to the second selection end, single open single control switch K 31 and K 32 In closed state.

[0012] Preferably, the three-phase inverter is a three-phase full-bridge inverter, and the first, second and third AC output terminals of the three-phase inverter are respectively the midpoints of the a, b and c phase half-bridges of the three-phase inverter;

[0013] The a-phase half bridge of the three-phase inverter is composed of power switch tubes S3 and S4 located at the top and bottom, the b-phase half bridge is composed of power switch tubes S5 and S6 located at the top and bottom, and the c-phase half bridge is composed of power switch tubes S1 and S2 located at the top and bottom;

[0014] In the charge and discharge mode, the power switches S1 and S2 are switched on alternately at a grid frequency of 50 Hz, the power switches S3 and S4 are switched on alternately at a 50% duty cycle, and the power switches S5 and S6 are switched on alternately at a 50% duty cycle; and

[0015] When the grid-side voltage Vg is greater than 0, the power switch tube S1 is turned off and the power switch tube S2 is turned on. When the grid-side voltage Vg is less than or equal to 0, the power switch tube S1 is turned on and the power switch tube S2 is turned off. Among them, the grid-side voltage Vg is the industrial frequency alternating current output by the single-phase power supply.

[0016] Preferably, the clamping capacitor C c The voltage across the two ends is V Cc It is twice the grid-side voltage Vg, where the grid-side voltage Vg is the industrial frequency alternating current output by a single-phase power supply.

[0017] Preferably, the high-frequency transformer is implemented by a single-phase half-bridge inverter, and the carriers of the two switching tubes in each branch of the two branches of the single-phase half-bridge inverter are phase-shifted by 180° and modulated by a signal d(t), wherein d(t)=k|sin(ω g t)|; k is a coefficient, and k∈[0,0.5], ω g is the grid angular frequency, and t is the time.

[0018] Preferably, the equivalent filter inductance L of phases a, b and c of the PFC inductor is eqa , L eqb and L eqc They are:

[0019]

[0020] Among them, L σs is the motor winding self-leakage inductance, L m is the mutual leakage inductance between the motor windings, L is the average value of the motor winding self-inductance, L Δ1 is the amplitude of the second harmonic of the motor winding self-inductance, and θ is the rotor position angle.

[0021] Advantages of the present invention:

[0022] The present invention proposes a single-stage isolated bidirectional AC-DC charging and discharging topology structure based on reconstruction of three-phase motor windings. This topology is aimed at the two-stage topology structure in the prior art, and further reduces the volume, cost and loss, thereby improving the system efficiency. The single-stage isolated bidirectional AC-DC charging and discharging topology structure can also improve the value of the grid-side equivalent filter inductance in the charging and discharging mode. The motor does not rotate during the charging process, and the harmonics of the grid-side current can be suppressed. While reducing costs, it can further reduce the loss inside the motor and further improve the efficiency of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram of the structure of the single-stage isolated bidirectional on-board integrated charging system for new energy vehicles according to the present invention; wherein L s is the leakage inductance of the primary winding of the high-frequency transformer;

[0024] Figure 2 is an equivalent circuit diagram of the vehicle-mounted integrated charging system of the present invention in the driving mode;

[0025] Figure 3 It is an equivalent circuit diagram of the vehicle-mounted integrated charging system of the present invention in the charging mode.

[0026] Figure 4 is the switch state and voltage waveform of the primary side of the high-frequency transformer; among them, S 1，4 Indicates power switch tubes S1 and S4, S 2,3 Represents power switch tubes S2 and S3, V g,peak Indicates the grid side voltage V g The peak voltage, V a,b The voltage between the midpoint a of the a-phase bridge arm and the midpoint b of the b-phase bridge arm of the three-phase inverter, V Cc Represents the clamping capacitor C c The voltage across the terminals;

[0027] Figure 5 It is the switch state and voltage waveform of the secondary side of the high-frequency transformer; among them, is the carrier of switch tube S9, is the carrier of switch tube S7, V cd is the voltage between the midpoints c and d of the two bridge arms of the full-bridge converter, V bat is the battery voltage;

[0028] Figure 6 It is the simulation waveform diagram under G2V mode; Among them, Figure 6 a is the input voltage and current waveform of the single-phase power supply input to the three-phase motor in G2V mode; Figure 6 b is the clamp capacitor voltage and battery current waveform; Figure 6 c is the current waveform of phase a and phase b of the three-phase motor; Figure 6 d is for Figure 6 c is the waveform after enlargement;

[0029] Figure 7 It is the simulation waveform diagram under V2G mode; Among them, Figure 7 a is the input voltage and current waveform diagram of the single-phase power supply input to the three-phase motor in V2G mode; Figure 7 b is the clamp capacitor voltage and battery current waveform; Figure 7 c is the current waveform of phase a and phase b of the three-phase motor; Figure 7 d is for Figure 7 c is the waveform after enlargement;

[0030] Figure 8 This is the simulation result diagram of the motor torque under single-phase AC charging. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0033] Combination Figure 1 The present embodiment describes a single-stage isolated bidirectional on-board integrated charging system for new energy vehicles, comprising an original on-board drive system and a clamping capacitor C c , switching switches, high-frequency transformers and full-bridge converters to build a single-stage isolated bidirectional AC-DC charging and discharging topology to charge or discharge the vehicle battery;

[0034] In the charge and discharge mode, the switching switch is used to change the connection mode of the three-phase winding of the three-phase motor of the original vehicle drive system, and the three-phase winding of the three-phase motor of the original vehicle drive system is reused as the PFC inductor, and the three-phase inverter of the original vehicle drive system is reused as the AC-AC converter. After the industrial frequency AC power output by the single-phase power supply is converted into high-frequency AC power, the clamp capacitor C c It is sent to the high-frequency transformer, where it undergoes voltage conversion and is then sent to the full-bridge converter for rectification. It then passes through the bus capacitor C of the original vehicle drive system. bat After voltage stabilization, the vehicle battery is charged.

[0035] In specific applications, the high-frequency transformer may generally refer to a transformer with a frequency higher than 20 kHz, and in specific applications, the turns ratio of the primary side to the secondary side may be n:1, where n is an integer.

[0036] The single-stage isolated bidirectional AC-DC charging and discharging topology structure constructed in this embodiment is aimed at the two-stage topology structure in the prior art, and further reduces the volume, cost and loss, thereby improving the system efficiency.

[0037] For further information, see Figure 1 , the switch includes single-open single-control switch K1, K 31 and K 32 , and single-open dual-control K 21 and K 22 ;

[0038] The input ends of the a, b and c phase windings of the three-phase motor are respectively connected to one end of the switch K1 and the second and third AC output ends of the three-phase inverter. The other end of the switch K1 is connected to the first AC output end of the three-phase inverter. The first and second AC output ends of the three-phase inverter are also respectively connected to the single-open single-control switch K1. 31 and K 32 One end is connected to single-open single-control switch K 31 and K 32 The other end is connected to one end and the other end of the primary winding of the high-frequency transformer respectively;

[0039] The two ends of the secondary winding of the high-frequency transformer are connected to the two single-phase AC ends of the full-bridge converter, and the two DC ends of the full-bridge converter are used as single-open dual-control K 21 and K 22 The second selection end;

[0040] The first DC input terminal of the three-phase inverter and the clamping capacitor C c One end and single open double control K 21 The first selection end of the three-phase inverter is connected to the second DC input end of the clamping capacitor C c The other end and the single open dual control K 22 The first selection end is connected simultaneously;

[0041] Bus capacitance C bat The two ends of the battery are connected in parallel to the single-open dual-control K 21 and K 22 The fixed end connection;

[0042] See also Figure 2 In the driving mode, the single-open single-control switch K1 is closed, and the single-open double-control switch K 21 and K 22 Switch to the first selection end, single open single control switch K 31 and K 32It is disconnected state;

[0043] See also Figure 3 In charging mode, the two ends of the single-open single-control switch K1 are used to connect to the two charging terminals P of the single-phase power supply respectively. g1 and P g2 connected, and the single-open single-control switch K1 is disconnected, the single-open double-control K 21 and K 22 Switch to the second selection end, single open single control switch K 31 and K 32 When charging, the energy is transferred from the charging gun of the AC charging pile as a single-phase power source through the motor winding, and after the three-phase inverter effectively controls the industrial frequency AC power output of the single-phase power source and the current output of the single-phase power source, the energy is transferred to the high-frequency transformer and the full-bridge converter. The full-bridge converter provides a wide range of voltage regulation capabilities to smoothly and safely transfer the input energy to the battery.

[0044] The specific structure of a single-stage isolated bidirectional AC-DC charging and discharging topology is given in the preferred embodiment. The switching switch is used to change the connection mode of the winding to realize the working mode of the integrated charging system. In addition, the single-stage isolated bidirectional AC-DC charging and discharging topology can also improve the value of the grid-side equivalent filter inductance in the charging and discharging mode. The motor does not rotate during the charging process, and the harmonics of the grid-side current can be suppressed. While reducing costs, the internal losses of the motor can be further reduced, thereby further improving the efficiency of the system.

[0045] Further, the three-phase inverter is a three-phase full-bridge inverter, and the first, second and third AC output terminals of the three-phase inverter are respectively midpoints of the a, b and c phase half-bridges of the three-phase inverter;

[0046] The a-phase half bridge of the three-phase inverter is composed of power switch tubes S3 and S4 located at the top and bottom, the b-phase half bridge is composed of power switch tubes S5 and S6 located at the top and bottom, and the c-phase half bridge is composed of power switch tubes S1 and S2 located at the top and bottom;

[0047] In the charge and discharge mode, the power switches S1 and S2 are switched on alternately at a grid frequency of 50 Hz, the power switches S3 and S4 are switched on alternately at a 50% duty cycle, and the power switches S5 and S6 are switched on alternately at a 50% duty cycle; and

[0048] When the grid-side voltage Vg is greater than 0, the power switch tube S1 is turned off and the power switch tube S2 is turned on. When the grid-side voltage Vg is less than or equal to 0, the power switch tube S1 is turned on and the power switch tube S2 is turned off. Among them, the grid-side voltage Vg is the industrial frequency alternating current output by the single-phase power supply.

[0049] Therefore, regardless of the power level, the clamp capacitor C cThe voltage across the two ends is V Cc The grid voltage Vg is twice the grid voltage Vg, where the grid voltage Vg is the industrial frequency AC output of the single-phase power supply. The power switch state and voltage waveform of the primary side of the high-frequency transformer are as follows: Figure 4 shown. Figure 4 It shows that the switch tubes S1 and S4 have the same driving waveform, and the switch tubes S2 and S3 also have the same driving waveform and are complementary to the switch tubes S1 and S4. Cc The voltage waveform has a peak value of 2V g,peak The input voltage V ab It is related to the working state of the switch tube. When the switch tubes S1 and S4 are turned on, V ab V Cc ; When the switch tubes S2 and S3 are turned on, V ab -V Cc .

[0050] Further information Figure 5 , the high-frequency transformer is implemented by a single-phase half-bridge inverter, and the carriers of the two switching tubes in each branch of the two branches of the single-phase half-bridge inverter are phase-shifted by 180° and are modulated by the signal d(t), wherein,

[0051] d(t)=k|sin(ω g t)| (1);

[0052] Where k is a coefficient, and k∈[0, 0.5], ω g is the grid angular frequency, and t is the time.

[0053] Figure 5 Given, the carrier of carrier switch tube S7 The carrier of switch S9 The phase difference is 180 degrees when the modulation wave d(t) is greater than the carrier wave When the modulation wave d(t) is greater than the carrier wave When the switch tube S7 is turned on, the switch tube S8 is turned on complementary to the switch tube S7. 10 The switch tube S7 is complementary to the switch tube S9. 10 At the same time, the transformer secondary voltage V cd is the load voltage V bat ; When the switch tube S8 and the switch tube S9 are turned on at the same time, the secondary voltage V cd -V bat , in other cases V cd is 0.

[0054] Furthermore, the inductance of the motor winding reconstructed as the grid-side filter inductor is analyzed. The grid-side filter inductor reconstructed as the PFC inductor has the following specific analysis process:

[0055] For a three-phase motor, the expressions of winding self-inductance and mutual inductance are as follows:

[0056]

[0057]

[0058] Among them, L σs is the self-leakage inductance of the motor winding. The values ​​of the windings of each phase of the three-phase motor are equal. m is the mutual leakage inductance between motor windings, which is mainly the slot mutual leakage inductance, L is the average value of the motor winding self-inductance, L Δ1 is the amplitude of the second harmonic of the motor winding self-inductance, and θ is the rotor position angle.

[0059] The inductance matrix of a three-phase winding motor is expressed as follows:

[0060]

[0061] The motor winding current in charging mode can be expressed as:

[0062] i s =[i sa i sb i sc ] T (7);

[0063] The stator winding flux ψ along the motor phase abc axis sm , m = a, b, c can be calculated from the equivalent inductance L of the motor winding eqm and rotor permanent magnet flux ψ fm To express:

[0064]

[0065] Using the stator inductance matrix L ss The magnetic flux represented by the second term of the above equation Expand:

[0066] ψ ss =L ss i s (9);

[0067] Therefore, the motor winding equivalent inductance L eqss It can be expressed as:

[0068] L eqss =[L eqa ,L eqb ,Leqc ] T =ψ ss . / i s (10);

[0069] In the formula, ψ ss ——The stator flux generated by the motor winding current excitation;

[0070] . / ——Represents the division operator of corresponding elements in the matrix.

[0071] according to Figure 3 , the absolute value of the current flowing through phase c is twice that of phase a and phase b, then we can get:

[0072] i sc =-2i sa =-2i sb =I m cos(ω g t) (11);

[0073] Among them, I m is the peak value of the grid-side current.

[0074] Substituting formula 11 into formula 10, the equivalent filter inductance can be calculated based on the above inductance matrix:

[0075] The equivalent filter inductance L of phases a, b and c of the PFC inductor eqa , L eqb and L eqc They are:

[0076]

[0077] Therefore, it can be seen that the equivalent inductance at this time includes the self-inductance of the winding. Therefore, compared with the case of zero-sequence current injection, the equivalent inductance has been greatly improved, which is beneficial to reduce the grid-side current harmonics and improve the system charging efficiency.

[0078] Verification test:

[0079] The technical effects of the present invention are illustrated by the following verification tests, specifically:

[0080] The simulation results in charging mode (i.e. G2V mode) and discharging mode (i.e. V2G mode) are given. In G2V mode, the input voltage and current as well as the clamp capacitor voltage and battery current waveforms are as follows: Figure 6 Specific Figure 6 In a, the input current and input voltage are in phase, which verifies that this topology and control method can achieve the PFC function; Figure 6 b Verifies that the clamping capacitor voltage is a steamed bun wave and its peak value is the grid-side voltage peak value V g，peakand the battery current is positive in G2V mode, that is, the battery is in charging state; Figure 6 c reflects that the current magnitude and phase of phase a and phase b in the G2V mode are not exactly the same, which is caused by the fact that the equivalent impedance of phase a and phase b are not exactly the same; Figure 6 d reflects that the a-phase current waveform and the b-phase current waveform in the G2V mode differ by 180 degrees at high frequency, which verifies the accuracy of the control method.

[0081] In V2G mode, the input voltage and current as well as the clamp capacitor voltage and battery current waveforms are as follows: Figure 7 As shown, the specific Figure 7 In a, the input current and input voltage are in the same and opposite directions, that is, the power factor is -1, which verifies that this topology and control method can realize the V2G function; Figure 7 b Verifies that the clamping capacitor voltage is a steamed bun wave and its peak value is the grid-side voltage peak value V g，peak twice, and the battery current is negative in V2G mode, that is, the battery is in a discharging state; Figure 7 c reflects that the current magnitude and phase of phase a and phase b are not exactly the same in V2G mode, which is caused by the fact that the equivalent impedance of phase a and phase b are not exactly the same; Figure 7 d reflects that the a-phase current waveform and the b-phase current waveform in the V2G mode differ by 180 degrees at high frequency, which verifies the accuracy of the control method.

[0082] The torque simulation results based on this integrated topology at a charging power of 6.6kW are also given, such as Figure 8 It can be seen that the average torque of the motor in the charging mode is substantially zero, and the motor does not rotate, which verifies the effectiveness of the present invention.

[0083] Although the present invention is described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the present invention. It should therefore be understood that many modifications may be made to the exemplary embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims. It should be understood that the various dependent claims and features described herein may be combined in a manner different from that described in the original claims. It should also be understood that features described in conjunction with individual embodiments may be used in other described embodiments.

Claims

1. Single-stage isolated bidirectional on-board integrated charging system for new energy vehicles, characterized in that: Including the original vehicle drive system and the clamping capacitor C c A single-stage isolated bidirectional AC-DC charging and discharging topology structure constructed by a switching switch, a high-frequency transformer and a full-bridge converter is used to charge or discharge the vehicle battery; In the charge and discharge mode, the switching switch is used to change the connection mode of the three-phase winding of the three-phase motor of the original vehicle drive system, and the three-phase winding of the three-phase motor of the original vehicle drive system is reused as the PFC inductor, and the three-phase inverter of the original vehicle drive system is reused as the AC-AC converter. After the industrial frequency AC power output by the single-phase power supply is converted into high-frequency AC power, the clamp capacitor C c It is sent to the high-frequency transformer, where it undergoes voltage conversion and is then sent to the full-bridge converter for rectification. It then passes through the bus capacitor C of the original vehicle drive system. bat After voltage stabilization, the vehicle battery is charged.

2. The single-stage isolated bidirectional on-board integrated charging system for new energy vehicles according to claim 1 is characterized in that: The switch includes single-open single-control switch K1, K 31 and K 32 , and single-open dual-control K 21 and K 22 ; The input ends of the a, b and c phase windings of the three-phase motor are respectively connected to one end of the switch K1 and the second and third AC output ends of the three-phase inverter. The other end of the switch K1 is connected to the first AC output end of the three-phase inverter. The first and second AC output ends of the three-phase inverter are also respectively connected to the single-open single-control switch K1. 31 and K 32 One end is connected to single-open single-control switch K 31 and K 32 The other end is connected to one end and the other end of the primary winding of the high-frequency transformer respectively; The two ends of the secondary winding of the high-frequency transformer are connected to the two single-phase AC ends of the full-bridge converter, and the two DC ends of the full-bridge converter are used as single-open dual-control K 21 and K 22 The second selection end; The first DC input terminal of the three-phase inverter and the clamping capacitor C c One end and single open double control K 21 The first selection end of the three-phase inverter is connected to the second DC input end of the clamping capacitor C c The other end and the single open dual control K 22 The first selection end is connected at the same time, the bus capacitor C bat The two ends of the battery are connected in parallel to the single-open dual-control K 21 and K 22 The fixed end connection; In the driving mode, the single-open single-control switch K1 is in the closed state, and the single-open double-control switch K 21 and K 22 Switch to the first selection end, single open single control switch K 31 and K 32 It is disconnected state; In charging mode, the two ends of the single-open single-control switch K1 are used to connect to the two charging terminals P of the single-phase power supply respectively. g1 and P g2 connected, and the single-open single-control switch K1 is disconnected, the single-open double-control K 21 and K 22 Switch to the second selection end, single open single control switch K 31 and K 32 In closed state.

3. The single-stage isolated bidirectional on-board integrated charging system for new energy vehicles according to claim 2 is characterized in that: The three-phase inverter is a three-phase full-bridge inverter, and the first, second and third AC output terminals of the three-phase inverter are respectively midpoints of the a, b and c phase half bridges of the three-phase inverter; The a-phase half bridge of the three-phase inverter is composed of power switch tubes S3 and S4 located at the top and bottom, the b-phase half bridge is composed of power switch tubes S5 and S6 located at the top and bottom, and the c-phase half bridge is composed of power switch tubes S1 and S2 located at the top and bottom; In the charge and discharge mode, the power switches S1 and S2 are switched on alternately at a grid frequency of 50 Hz, the power switches S3 and S4 are switched on alternately at a 50% duty cycle, and the power switches S5 and S6 are switched on alternately at a 50% duty cycle; and When the grid-side voltage Vg is greater than 0, the power switch tube S1 is turned off and the power switch tube S2 is turned on. When the grid-side voltage Vg is less than or equal to 0, the power switch tube S1 is turned on and the power switch tube S2 is turned off. Among them, the grid-side voltage Vg is the industrial frequency alternating current output by the single-phase power supply.

4. The single-stage isolated bidirectional on-board integrated charging system for new energy vehicles according to claim 2 is characterized in that: Clamping capacitor C c The voltage across the two ends is V Cc It is twice the grid-side voltage Vg, where the grid-side voltage Vg is the industrial frequency alternating current output by a single-phase power supply.

5. The single-stage isolated bidirectional on-board integrated charging system for new energy vehicles according to claim 2 is characterized in that: The high-frequency transformer is implemented by a single-phase half-bridge inverter, and the carriers of the two switching tubes in each branch of the two branches of the single-phase half-bridge inverter are phase-shifted by 180° and modulated by a signal d(t), where d(t)=k|sin(ω g t)|; k is a coefficient, and k∈[0,0.5], ω g is the grid angular frequency, and t is the time.

6. The single-stage isolated bidirectional on-board integrated charging system for new energy vehicles according to claim 2 is characterized in that: The equivalent filter inductance L of phases a, b and c of the PFC inductor eqa , L eqb and L eqc They are: Among them, L σs is the motor winding self-leakage inductance, L m is the mutual leakage inductance between the motor windings, L is the average value of the motor winding self-inductance, L Δ1 is the amplitude of the second harmonic of the motor winding self-inductance, and θ is the rotor position angle.

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