Permanent-magnet synchronous machine control method and device, and permanent-magnet synchronous machine control system

1. A permanent-magnet synchronous machine control method, comprising:

obtaining a d-axis current i d and a q-axis current i q in a permanent-magnet synchronous machine control loop at a current moment;

obtaining a fifth-order harmonic current i d5th and a seventh-order harmonic current i d7th in the d-axis current i d in the permanent-magnet synchronous machine control loop at the current moment, and a fifth-order harmonic current i q5th and a seventh-order harmonic current i q7th in the q-axis current i q in the permanent-magnet synchronous machine loop at the current moment;

calculating four harmonic voltages based on the fifth-order harmonic current i d5th , the seventh-order harmonic current i d7th , the fifth-order harmonic current i q5th , and the seventh-order harmonic current i q7th , wherein the four harmonic voltages comprise a d-axis-fifth-order harmonic voltage u d5th , a q-axis fifth-order harmonic voltage u q5th , a d-axis seventh-order harmonic voltage u d7th , and a q-axis seventh-order harmonic voltage u q7th ;

subtracting the fifth-order harmonic current i d5th and the seventh-order harmonic current i d7th from the d-axis current i d to obtain a first current i d k on a d axis; and subtracting the fifth-order harmonic current i q5th and the seventh-order harmonic current i q7th from the q-axis current i q to obtain a second current i q k on a q axis;

subtracting the d-axis fifth-order harmonic voltage u d5th and the d-axis seventh-order harmonic voltage u d7th from a d-axis voltage corresponding to each switch state of an inverter to obtain a first voltage on the d axis in each switch state, and subtracting the q-axis fifth-order harmonic voltage u q5th and the q-axis seventh-order harmonic voltage u q7th from a q-axis voltage corresponding to each switch state of the inverter to obtain a second voltage on the q axis in each switch state;

determining a d-axis current i d k+1 at a next moment in each switch state based on the first current i d k , the second current i q k , and the first voltage in each switch state; and determining a q-axis current i q k+1 at the next moment in each switch state based on the first current i d k , the second current i q k , and the second voltage in each switch state; and

determining a control policy of the permanent-magnet synchronous machine based on the d-axis current i d k+1 at the next moment in each switch state and the q-axis current i q k+1 at the next moment in each switch state.

2. The method according to claim 1 , wherein the obtaining a fifth-order harmonic current i d5th and a seventh-order harmonic current i d7th in the d-axis current i d in the permanent-magnet synchronous machine control loop at the current moment, and a fifth-order harmonic current i q5th and a seventh-order harmonic current i q7th in the q-axis current i q in the permanent-magnet synchronous machine loop at the current moment comprises:

obtaining a three-phase current in the permanent-magnet synchronous machine control loop at the current moment;

transforming the three-phase current into a d-axis current and a q-axis current in a fifth-order rotating coordinate system based on a coordinate transformation algorithm and a phase angle of a fifth-order harmonic;

filtering the d-axis current and the q-axis current in the fifth-order rotating coordinate system by using a filter, so as to obtain the fifth-order harmonic current i d5th and the fifth-order harmonic current i q5th ;

transforming the three-phase current into a d-axis current and a q-axis current in a seventh-order rotating coordinate system based on the coordinate transformation algorithm and a phase angle of a seventh-order harmonic; and

filtering the d-axis current and the q-axis current in the seventh-order rotating coordinate system by using the filter, so as to obtain the seventh-order harmonic current i d7th and the seventh-order harmonic current i q7th .

3. The method according to claim 1 , wherein a formula for calculating the d-axis fifth-order harmonic voltage u d5th is: u d5th =5w e L q i q5th +R s i d5th ;

a formula for calculating the q-axis fifth-order harmonic voltage is:

u q5th =−5 w e L d i d5th +R s i q5th ;

a formula for calculating the d-axis seventh-order harmonic voltage is:

u d7th =−7 w e L q i q7th +R s i d7th ; and

a formula for calculating the q-axis seventh-order harmonic voltage is:

u q7th =7 w e L d i d7th +R s i q7th ,

wherein, w e represents an electrical angular velocity, R s represents a stator resistance, L d represents a d-axis inductance parameter, and L q represents a q-axis inductance parameter.

4. The method according to claim 1 , wherein the determining a control policy of the permanent-magnet synchronous machine based on the d-axis current i d k+1 at the next moment in each switch state and the q-axis current i q k+1 at the next moment in each switch state comprises:

obtaining a d-axis reference current i d ref and a q-axis reference current i q ref based on an MTPA and a torque current distribution policy of flux weakening control; and

calculating a cost function corresponding to each switch state based on the d-axis current i d k+1 at the next moment in each switch state, the q-axis current i q k+1 at the next moment in each switch state, the d-axis reference current i d ref , and the q-axis reference current i q ref ,

wherein, a switch state with a lowest cost function is the control policy of the permanent-magnet synchronous machine.

5. The method according to claim 1 , wherein the inverter is a two-level inverter, and the two-level inverter comprises eight switch states.

6. A permanent-magnet synchronous machine control device, characterized in that the device comprises:

a first obtaining module, configured to obtain a d-axis current i d and a q-axis current i q in a permanent-magnet synchronous machine control loop at a current moment;

a second obtaining module, configured to obtain a fifth-order harmonic current i d5th and a seventh-order harmonic current i d7th in the d-axis current i d in the permanent-magnet synchronous machine control loop at the current moment, and a fifth-order harmonic current i q5th and a seventh-order harmonic current i q7th in the q-axis current in the permanent-magnet synchronous machine loop at the current moment;

a first calculation module, configured to calculate four harmonic voltages based on the fifth-order harmonic current i d5th , the seventh-order harmonic current i d7th , the fifth-order harmonic current i q5th , and the seventh-order harmonic current i q7th , wherein the four harmonic voltages comprise a d-axis fifth-order harmonic voltage u d5th , a q-axis fifth-order harmonic voltage u q5th , a d-axis seventh-order harmonic voltage u d7th , and a q-axis seventh-order harmonic voltage u q7th ;

a second calculation module, configured to subtract the fifth-order harmonic current i d5th and the seventh-order harmonic current i d7th from the d-axis current i d to obtain a first current i d k on a d axis; and subtract the fifth-order harmonic current i q5th and the seventh-order harmonic current i q7th from the q-axis current i q to obtain a second current i q k on a q axis;

a third calculation module, configured to subtract the d-axis fifth-order harmonic voltage u d5th and the d-axis seventh-order harmonic voltage u d7th from a d-axis voltage corresponding to each switch state of an inverter to obtain a first voltage on the d axis in each switch state; and subtract the q-axis fifth-order harmonic voltage u q5th and the q-axis seventh-order harmonic voltage u q7th from a q-axis voltage corresponding to each switch state of the inverter to obtain a second voltage on the q axis in each switch state;

a fourth calculation module, configured to determine a d-axis current i d k+1 at a next moment in each switch state based on the first current i d k , the second current i q k , and the first voltage in each switch state; and determine a q-axis current i q k+1 at the next moment in each switch state based on the first current i d k , the second current i q k , and the second voltage in each switch state; and

a determining module, configured to determine a control policy of the permanent-magnet synchronous machine based on the d-axis current i d k+1 at the next moment in each switch state and the q-axis current i q k+1 at the next moment in each switch state.

7. The device according to claim 6 , wherein the second obtaining module is specifically configured to obtain a three-phase current in the permanent-magnet synchronous machine control loop at the current moment; transform the three-phase current into a d-axis current and a q-axis current in a fifth-order rotating coordinate system based on a coordinate transformation algorithm and a phase angle of a fifth-order harmonic; filter the d-axis current and the q-axis current in the fifth-order rotating coordinate system by using a filter, so as to obtain the fifth-order harmonic current i d5th and the fifth-order harmonic current i q5th ; transform the three-phase current into a d-axis current and a d-axis current in a seventh-order rotating coordinate system based on the coordinate transformation algorithm and a phase angle of a seventh-order harmonic; and filter the d-axis current and the q-axis current in the seventh-order rotating coordinate system by using the filter, so as to obtain the seventh-order harmonic current i d7th and the seventh-order harmonic current i q7th .

8. The device according to claim 6 , wherein a formula for calculating the d-axis fifth-order harmonic voltage u d5th is: u d5th =5w e L q i q5th +R s i d5th ;

a formula for calculating the q-axis fifth-order harmonic voltage u q5th is:

u q5th =−5 w e L d i d5th +R s i q5th ;

a formula for calculating the d-axis seventh-order harmonic voltage u d7th is:

u d7th =−7 w e L q i q7th +R s i d7th ; and

a formula for calculating the q-axis seventh-order harmonic voltage u q7th is:

u q7th =7 w e L d i d7th +R s i q7th ,

wherein, w e represents an electrical angular velocity, R s represents a stator resistance, L d represents a d-axis inductance parameter, and L q represents a q-axis inductance parameter.

9. The device according to claim 6 , wherein the determining module is specifically configured to obtain a d-axis reference current i d ref and a q-axis reference current i q ref based on an MTPA and a torque current distribution policy of flux weakening control; and calculate a cost function corresponding to each switch state based on the d-axis current i d k+1 at a next moment in each switch state, the q-axis current i q k+1 at the next moment in each switch state, the d-axis reference current i d ref , and the q-axis reference current i q ref , wherein, a switch state with a lowest cost function is the control policy of the permanent-magnet synchronous machine.

10. A permanent-magnet synchronous machine control system, comprising: an electric machine controller, a permanent-magnet synchronous machine, and an inverter, wherein

the electric machine controller is connected to the permanent-magnet synchronous machine and the inverter separately;

the permanent-magnet synchronous machine is further connected to the inverter; and

the electric machine controller is configured to perform the method according to claim 1 .