阅读说明：本技术 一种用于电机主动短路控制的方法 (Method for active short circuit control of motor ) 是由 王元宵 陈守川 于 2021-01-04 设计创作，主要内容包括：本发明公开了一种用于电机主动短路控制的方法,该方法在电机主动短路时能够抑制暂态电流,该方法的具体步骤为：a、当电机需要进入安全状态时,电机控制器记录电机在当前时刻的转子位置角θ-i,并计算反电动势线电压；b、计算电机在下一时刻的反电动势线电压；c、通过判断任意两相的反电动势线电压处于波峰或波谷时,先进行两相短路,剩余第三相为开路相并进入步骤d；否则回到步骤a；d、计算电机的开路相在当前时刻的反电动势相电压；e、计算电机的开路相在下一时刻的反电动势线电压；f、通过判断开路相的反电动势相电压处于波峰或波谷时,对开路相进行短路；否则回到步骤d。本发明的方法通过判断反电动势线电压在波峰或波谷时刻进行短路。(The invention discloses a method for controlling active short circuit of a motor, which can restrain transient current when the motor is actively short-circuited, and comprises the following specific steps: a. when the motor needs to enter a safe state, the motor controller records the rotor position angle theta of the motor at the current moment i And calculating the back electromotive force line voltage; b. calculating the back electromotive force line voltage of the motor at the next moment; c. d, when the back electromotive force line voltages of any two phases are judged to be in wave crests or wave troughs, firstly carrying out two-phase short circuit, and enabling the rest third phase to be an open-circuit phase and entering the step d; otherwise, returning to the step a; d. calculating the back electromotive voltage phase voltage of the open-circuit phase of the motor at the current moment; e. calculating the back electromotive force line voltage of the open-circuit phase of the motor at the next moment; f. when the back electromotive force phase voltage of the open-circuit phase is judged to be in a wave crest or a wave trough, the open-circuit phase is subjected to short circuit; otherwise, go back to step d. The method of the invention judges whether the back electromotive force line voltage is at the peak or notAnd short circuit is carried out at the wave trough moment.)

1. A method for active short circuit control of a motor, characterized by: the method can restrain transient current when the motor is in active short circuit, and comprises the following specific steps:

a. when the motor needs to enter a safe state, the motor controller records the rotor position angle theta of the motor at the current moment_iCalculating the back electromotive force line voltage of the motor at the current moment;

b. the motor controller calculates a rotor position angle theta of the motor at the next time_i+1And according to theta_i+1Calculating the back electromotive force line voltage of the motor at the next moment;

c. on the basis of the step a and the step b, when the back electromotive force line voltages of any two phases are judged to be in wave crests or wave troughs, firstly carrying out short circuit on the two phases, and carrying out step d when the remaining third phase is an open-circuit phase; otherwise, returning to the step a;

d. the motor controller records the rotor position angle theta of the motor at the current moment_iCalculating the back electromotive voltage phase voltage of the open-circuit phase of the motor at the current moment;

e. the motor controller calculates a rotor position angle theta of the motor at the next time_i+1And according to theta_i+1Calculating the back electromotive voltage phase voltage of the open-circuit phase of the motor at the next moment;

f. on the basis of the step d and the step e, when the back electromotive force phase voltage of the open-circuit phase is judged to be in a wave crest or a wave trough, the open-circuit phase is subjected to short circuit; otherwise, go back to step d.

2. The method for active short circuit control of an electric machine of claim 1, wherein: the back electromotive force line voltage of the motor in the step a at the current moment is as follows:

in the formula (1), U_AB(i) Representing the AB back EMF line voltage at the present time; u shape_BC(i) Representing the BC back emf line voltage at the present time; u shape_CA(i) The CA counter electromotive force line voltage represents the current moment; u shape_LRepresenting the line voltage amplitude; 90 deg. represents the phase voltage of the back electromotive force leading the rotor position angle theta_iThe degree of (d); represents; 30 ° represents the degree by which the back emf line voltage lags the back emf phase voltage.

3. The method for active short circuit control of an electric machine of claim 2, wherein: the rotor position angle theta of the motor in the step b and the step e at the next moment_i+1The rotor position angle theta of the motor in the step a and the step d at the current moment_iThe mutual relationship of (A) and (B) is as follows: theta_i+1＝2θ_i-θ_i-1In the formula [ theta ]_i-1The rotor position angle at the previous time.

4. The method for active short circuit control of an electric machine according to claim 3, characterized in that: the back electromotive force line voltage of the motor in the step b at the next moment is as follows:

in the formula (2), U_AB(i +1) represents the AB counter electromotive force line voltage at the next time; u shape_BC(i +1) represents the AB counter electromotive force line voltage at the next time; u shape_CA(i +1) represents the AB counter electromotive force line voltage at the next time.

5. The method for active short circuit control of an electric machine of claim 4, wherein: the two-phase short circuit determination conditions in step c are specifically as follows:

if U is_AB(i-1)≤U_AB(i)≤U_AB(i +1), the voltage of the AB opposite electromotive force line is a wave crest, and the AB phase meets the short-circuit condition;

or if U_AB(i-1)≥U_AB(i)≥U_AB(i +1), the line voltage of the AB reverse electromotive force is a waveValley, AB phase meets the short circuit condition;

or if U_BC(i-1)≤U_BC(i)≤U_BC(i +1), the voltage of the BC phase reverse electromotive force line is a wave crest, and the BC phase meets the short-circuit condition;

or if U_BC(i-1)≥U_BC(i)≥U_BC(i +1), the voltage of the BC phase reverse electromotive force line is a wave trough, and the BC phase meets the short-circuit condition;

or if U_CA(i-1)≤U_CA(i)≤U_CA(i +1), the voltage of the CA opposite electromotive force line is a wave crest, and the CA phase meets the short-circuit condition;

or if U_CA(i-1)≥U_CA(i)≥U_CA(i +1), the voltage of the CA counter electromotive force line is a trough, and the CA phase meets the short-circuit condition.

6. The method for active short circuit control of an electric machine of claim 1, wherein: the back electromotive force phase voltage of the open-circuit phase of the motor in the step d at the current moment is as follows:

U_{opening device}(i)＝U_Pcos(θ_i+90°+120°) (3)

In the formula (3), U_{Opening device}(i) Representing the open-circuit opposite electromotive force phase voltage at the current moment; u shape_PRepresenting a phase voltage magnitude; 90 deg. represents the phase voltage of the back electromotive force leading the rotor position angle theta_iThe degree of (d); 120 ° indicates that the open-phase voltage leads by 120 °.

7. The method for active short circuit control of an electric machine of claim 6, wherein: and e, the back electromotive voltage phase voltage of the open-circuit phase of the motor in the step e at the next moment is as follows:

U_{opening device}(i+1)＝U_Pcos(θ_i+1+90°+120°) (4)

In the formula (4), U_{Opening device}(i +1) represents the open-circuit counter electromotive voltage phase voltage at the next time.

8. The method for active short circuit control of an electric machine of claim 7, wherein: the conditions for determining the short circuit of the open-circuit phase in the step f are specifically as follows:

if U is_{Opening device}(i-1)≤U_{Opening device}(i)≤U_{Opening device}(i +1), the open-circuit phase voltage of the opposite electromotive force is a wave crest, and the open-circuit phase meets the short-circuit condition;

or if U_{Opening device}(i-1)≥U_{Opening device}(i)≥U_{Opening device}(i +1), the open-circuit phase voltage of the opposite electromotive force is a wave crest, and the open-circuit phase meets the short-circuit condition.

Technical Field

The invention relates to the technical field of electric automobile control, in particular to a motor control technology of an electric automobile, and specifically relates to a method for motor active short circuit control.

Background

The driving motor of an electric vehicle (a pure electric vehicle, a hybrid electric vehicle, a fuel cell vehicle, etc.) mostly adopts a permanent magnet synchronous motor to pursue higher efficiency, energy density and reliability.

When a vehicle runs, if a complete vehicle system has serious uncontrollable faults (such as battery over-temperature, failure of a device of a controller, and the like), the controller needs to immediately stop controlling the permanent magnet motor. If the permanent magnet motor is in a high-speed rotation state in the running process of a vehicle before a fault occurs, and the high-speed permanent magnet motor which is out of control after the vehicle is stopped generates overhigh back electromotive voltage at the three-phase end of the motor by the permanent magnet on the rotor, such as Ea, Eb and Ec shown in figure 1. The back electromotive voltage is proportional to the motor speed, i.e., the higher the vehicle speed before the fault is, the higher the motor speed is, and the higher the back electromotive voltage is.

The over-high back electromotive voltage can be rectified uncontrollably by anti-parallel diodes D1-D6 of a power device in the controller, a direct current capacitor in the controller is charged, and an uncontrolled braking torque is generated, and the braking torque can harm the control of a vehicle and increase the risk of vehicle rollover. Meanwhile, the back electromotive force is rectified to a direct current capacitor C1 in the controller, the voltage of the direct current capacitor can be increased, a power device in the controller is damaged, even a battery pack explodes, and uncontrollable potential safety hazards are generated.

From the safety point of view, in order to suppress the excessively high back electromotive voltage after the high-speed shutdown of the permanent magnet motor, the motor should be brought into an active short-circuit state after the shutdown. For example, the lower power device S2/S4/S6 of the controller is closed, so that the three-phase voltage of the motor is short-circuited at the DC negative pole, the back electromotive force only acts on the three-phase winding inside the motor to generate short-circuit current, and the short-circuit current only exists in the winding inside the motor and the lower tube of the power device, and cannot flow to the DC capacitor C1 or a battery, so that the safety of the rear-stage DC side is not influenced. Similarly, the upper power device S1/S3/S5 of the controller can be closed, so that the three-phase output end of the motor is short-circuited at the direct current positive pole. The effect of the short circuit of the motor to the positive pole or the negative pole of the battery is not different, and the practical application can be determined according to the fault state of the upper tube S1/S3/S5 or the lower tube S2/S4/S6 of the controller.

If the three phases of the motor are simultaneously short-circuited immediately after the fault, the current on the windings L1-L3 inside the motor undergoes a transient state-to-steady state transition process. The steady-state current is influenced by the design parameters of the motor and belongs to uncontrollable factors; the transient current is influenced by the current amplitude before short circuit, the short circuit time and the short circuit mode, and belongs to controllable factors.

The superposition of steady-state and transient currents results in a large current surge, as shown in fig. 2. The controller power device can be damaged by excessive impact current, and the permanent magnet motor magnetic steel can lose magnetism to cause unrecoverable damage, so that the original purpose of safe shutdown cannot be achieved.

In order to reduce transient damage caused by short circuit as much as possible, in CN109905068A, the dq axis given current of the motor is controlled to be adjusted to be a characteristic current before complete short circuit, so as to reduce the output torque of the motor to 0 before active short circuit action, and ensure that excessive impact current is not generated during active short circuit action; and then, after the dq axis given current of the motor is adjusted to be the characteristic current, complete short circuit is carried out.

In CN 108964572 a, the transient transition process of current short circuit is reduced by performing transition through two control phases, and in the transition phase, adjusting the switching state of the power device by detecting the short-circuit current.

The essence of the methods is that before the short circuit is completed, the power device is driven to be repeatedly switched on and off through a control strategy of the controller, so that the aim of controlling the transient current is fulfilled. The methods need to rely heavily on a current sensor and a rotating speed position sensor, and ensure that a driving circuit of the power device is in a good working state. The initial intention of an active short circuit is to quickly enter a safe state in a simple and reliable manner after a vehicle system fails. After failure, it is not necessary to make an active short if the controller itself can also perform a complex control strategy.

In summary, the prior art is too complex and requires too many steps before a safe short circuit.

Disclosure of Invention

The invention aims to solve the problems in the prior art and provides a method for active short circuit control of a motor.

The invention aims to solve the problems by the following technical scheme:

a method for active short circuit control of a motor, characterized by: the method can restrain transient current when the motor is in active short circuit, and comprises the following specific steps:

a. when the motor needs to enter a safe state, the motor controller records the rotor position angle theta of the motor at the current moment_iCalculating the back electromotive force line voltage of the motor at the current moment;

b. the motor controller calculates a rotor position angle theta of the motor at the next time_i+1And according to theta_i+1Calculating the back electromotive force line voltage of the motor at the next moment;

c. on the basis of the step a and the step b, when the back electromotive force line voltages of any two phases are judged to be in wave crests or wave troughs, firstly carrying out short circuit on the two phases, and carrying out step d when the remaining third phase is an open-circuit phase; otherwise, returning to the step a;

d. the motor controller records the rotor position angle theta of the motor at the current moment_iCalculating the back electromotive voltage phase voltage of the open-circuit phase of the motor at the current moment;

e. the motor controller calculates a rotor position angle theta of the motor at the next time_i+1And according to theta_i+1Calculating the back electromotive voltage phase voltage of the open-circuit phase of the motor at the next moment;

f. on the basis of the step d and the step e, when the back electromotive force phase voltage of the open-circuit phase is judged to be in a wave crest or a wave trough, the open-circuit phase is subjected to short circuit; otherwise, go back to step d.

The back electromotive force line voltage of the motor in the step a at the current moment is as follows:

in the formula (1), U_AB(i) Representing the AB back EMF line voltage at the present time; u shape_BC(i) Representing the BC back emf line voltage at the present time; u shape_CA(i) The CA counter electromotive force line voltage represents the current moment; u shape_LRepresenting the line voltage amplitude; 90 deg. representsThe back emf phase voltage leads the rotor position angle theta_iThe degree of (d); represents; 30 ° represents the degree by which the back emf line voltage lags the back emf phase voltage.

The rotor position angle theta of the motor in the step b and the step e at the next moment_i+1The rotor position angle theta of the motor in the step a and the step d at the current moment_iThe mutual relationship of (A) and (B) is as follows: theta_i+1＝2θ_i-θ_i-1In the formula [ theta ]_i-1The rotor position angle at the previous time.

The back electromotive force line voltage of the motor in the step b at the next moment is as follows:

in the formula (2), U_AB(i +1) represents the AB counter electromotive force line voltage at the next time; u shape_BC(i +1) represents the AB counter electromotive force line voltage at the next time; u shape_CA(i +1) represents the AB counter electromotive force line voltage at the next time.

The two-phase short circuit determination conditions in step c are specifically as follows:

if U is_AB(i-1)≤U_AB(i)≤U_AB(i +1), the voltage of the AB opposite electromotive force line is a wave crest, and the AB phase meets the short-circuit condition;

or if U_AB(i-1)≥U_AB(i)≥U_AB(i +1), the voltage of the AB opposite electromotive force line is a wave trough, and the AB phase meets the short-circuit condition;

or if U_BC(i-1)≤U_BC(i)≤U_BC(i +1), the voltage of the BC phase reverse electromotive force line is a wave crest, and the BC phase meets the short-circuit condition;

or if U_BC(i-1)≥U_BC(i)≥U_BC(i +1), the voltage of the BC phase reverse electromotive force line is a wave trough, and the BC phase meets the short-circuit condition;

or if U_CA(i-1)≤U_CA(i)≤U_CA(i +1), the voltage of the CA opposite electromotive force line is a wave crest, and the CA phase meets the short-circuit condition;

or if U_CA(i-1)≥U_CA(i)≥U_CA(i +1), the voltage of the CA counter electromotive force line is a trough, and the CA phase meets the short-circuit condition.

The back electromotive force phase voltage of the open-circuit phase of the motor in the step d at the current moment is as follows:

U_{opening device}(i)＝U_Pcos(θ_i+90°+120°) (3)

In the formula (3), U_{Opening device}(i) Representing the open-circuit opposite electromotive force phase voltage at the current moment; u shape_PRepresenting a phase voltage magnitude; 90 deg. represents the phase voltage of the back electromotive force leading the rotor position angle theta_iThe degree of (d); 120 ° indicates that the open-phase voltage leads by 120 °.

And e, the back electromotive voltage phase voltage of the open-circuit phase of the motor in the step e at the next moment is as follows:

U_{opening device}(i+1)＝U_Pcos(θ_i+1+90°+120°) (4)

In the formula (4), U_{Opening device}(i +1) represents the open-circuit counter electromotive voltage phase voltage at the next time.

The conditions for determining the short circuit of the open-circuit phase in the step f are specifically as follows:

if U is_{Opening device}(i-1)≤U_{Opening device}(i)≤U_{Opening device}(i +1), the open-circuit phase voltage of the opposite electromotive force is a wave crest, and the open-circuit phase meets the short-circuit condition;

or if U_{Opening device}(i-1)≥U_{Opening device}(i)≥U_{Opening device}(i +1), the open-circuit phase voltage of the opposite electromotive force is a wave crest, and the open-circuit phase meets the short-circuit condition.

Compared with the prior art, the invention has the following advantages:

the invention provides a control method capable of restraining transient current when a motor is actively short-circuited, wherein a motor controller calculates the phase of back electromotive force through the rotor position angle of the motor, and performs two-phase short-circuit at the time of wave crest or wave trough by judging the voltage of the back electromotive force; and when the back electromotive force phase voltage of the third phase is at the wave crest or the wave trough, carrying out three-phase short circuit again.

The present invention provides a rotor position angle theta based on the current cycle_iCalculating the current weekBack emf of the period and rotor position angle theta of the next period_i+1Then according to the rotor position angle theta of the next cycle_i+1And calculating the back electromotive force of the next period, and judging that the voltage is in a wave crest or a wave trough by combining the calculated values of the back electromotive force of the current period and the back electromotive force of the previous period.

The method of the invention has the advantages of less external conditions, high reliability, simple short-circuit decision process and less calculation amount, is convenient for the motor controller to quickly respond under the condition of emergency failure of the driving system, and improves the safety of the system.

The method can quickly enable the motor system to enter a steady-state short-circuit state, and avoids transient current caused in the short-circuit process, so that the controller can be protected from causing secondary faults in the short-circuit process.

Drawings

FIG. 1 is a schematic diagram of a motor control system of an electric vehicle according to the prior art;

FIG. 2 is a simulation graph of transient current overshoot caused by direct short circuit of a motor of an electric vehicle;

FIG. 3 is a schematic diagram of a single-phase short circuit condition employed in the present invention;

FIG. 4 is a simulation graph of the back EMF voltage and the short circuit current in the short circuit state when the instantaneous angle of the back EMF is 90 degrees according to the present invention;

fig. 5 is a simulation graph of the back electromotive voltage and the short-circuit current in a short-circuit state when the instantaneous angle of the back electromotive force is 270 ° according to the present invention;

FIG. 6 is a simulation graph of the back EMF voltage and the short circuit current in the short circuit state when the instantaneous angle of the back EMF is 180 degrees according to the present invention;

FIG. 7 is a simulation graph of back EMF voltage and short circuit current in a short circuit state when the instantaneous angle of back EMF is 0 degrees according to the present invention;

FIG. 8 is a short circuit flow diagram of a method of the present invention for active short circuit control of a motor;

fig. 9 is a simulation graph of a short-circuit current when the method for active short-circuit control of a motor according to the present invention is implemented.

Detailed Description

The following first describes the control principle adopted by the method for controlling the active short circuit of the motor provided by the invention.

As shown in fig. 3, the nature of the active short circuit to the pm machine is via a switch Sw at t₀An alternating current power supply E is in short circuit connection with an inductor L at any moment, wherein E is the counter electromotive force of the motor, L is the winding inside the motor, and Sw is a power device inside the motor controller. The change of the back electromotive force of the permanent magnet motor along with the time t is E (t-t)₀)＝ωφcos(ω(t-t₀)+θ_E0) Where ω is the rotational angular velocity of the motor rotor, θ_E0Is t₀The instantaneous angle of the back electromotive force at the moment phi is the flux linkage of the permanent magnet motor.

According to the circuit principle, the short-circuited current expression is as follows:

in formula (5)The method is a steady-state alternating current component expression, and the amplitude of the steady-state alternating current component expression is only related to motor parameters; in the formulaThe amplitude of the transient DC component expression is not only related to motor parameters, but also is mainly related to the instantaneous angle theta of the back electromotive force at the moment of short circuit_E0It is related. If the transient component is as small as possible, the short-circuit current is directly led to the steady state, and only theta is needed_E0And 0 ° or 180 °, that is, when the back electromotive force is the maximum or minimum value.

Fig. 4-7 show simulation graphs of back emf voltage and short circuit current at different short circuit times, respectively, and it can be seen that if short circuit occurs at the time of maximum or minimum back emf, the current immediately enters steady state with no transient current; the transient component of the current will be large if short-circuited near the back emf zero crossing.

Since the short-circuit logic of a three-phase motor is similar to the single-phase principle. However, the three-phase motor has no uniform angle, so that two phases need to be short-circuited first, and then three phases need to be short-circuited.

The invention is further described with reference to the following figures and examples.

As shown in fig. 8-9: a method for active short circuit control of a motor specifically comprises the following steps:

a. when the vehicle needs to enter a safe state, the motor controller records the rotor position angle theta of the motor at the current moment_i；

b. The motor controller calculates the back electromotive force line voltage of the motor at the current moment:

in the formula (1), U_AB(i) Representing the AB back EMF line voltage at the present time; u shape_BC(i) Representing the BC back emf line voltage at the present time; u shape_CA(i) The CA counter electromotive force line voltage represents the current moment; u shape_LRepresenting the line voltage amplitude; 90 deg. represents the phase voltage of the back electromotive force leading the rotor position angle theta_iThe degree of (d); represents; 30 degrees represents the degree of the back electromotive force line voltage lagging the back electromotive force phase voltage;

c. the motor controller calculates a rotor position angle theta of the motor at the next time_i+1，θ_i+1＝2θ_i-θ_i-1In the formula [ theta ]_i-1The rotor position angle at the last moment;

d. the motor controller calculates the back emf line voltage of the motor at the next moment:

in the formula (2), U_AB(i +1) represents the AB counter electromotive force line voltage at the next time; u shape_BC(i +1) represents the AB counter electromotive force line voltage at the next time; u shape_CA(i +1) representsThe AB opposite electromotive force line voltage at the next moment;

e. judging whether a condition meeting two-phase short circuit exists at present:

if U is_AB(i-1)≤U_AB(i)≤U_AB(i +1), the voltage of the AB opposite electromotive force line is a wave crest, and the AB phase meets the short-circuit condition;

or if U_AB(i-1)≥U_AB(i)≥U_AB(i +1), the voltage of the AB opposite electromotive force line is a wave trough, and the AB phase meets the short-circuit condition;

or if U_BC(i-1)≤U_BC(i)≤U_BC(i +1), the voltage of the BC phase reverse electromotive force line is a wave crest, and the BC phase meets the short-circuit condition;

or if U_BC(i-1)≥U_BC(i)≥U_BC(i +1), the voltage of the BC phase reverse electromotive force line is a wave trough, and the BC phase meets the short-circuit condition;

or if U_CA(i-1)≤U_CA(i)≤U_CA(i +1), the voltage of the CA opposite electromotive force line is a wave crest, and the CA phase meets the short-circuit condition;

or if U_CA(i-1)≥U_CA(i)≥U_CA(i +1), the voltage of the CA opposite electromotive force line is a wave trough, and the CA phase meets the short-circuit condition;

f. c, short-circuiting the two phases meeting the condition, and enabling the rest third phase to be an open-circuit phase and entering the step g; otherwise, returning to the step a and repeating the steps a to f;

for example: if the AB phase meets the short-circuit condition, the AB phase is short-circuited, and the C phase is still open-circuited; if the BC phase meets the short-circuit condition, the BC phase is short-circuited, and the A phase is still open-circuited; if the CA phase meets the short-circuit condition, the CA phase is short-circuited, and the B phase is still open-circuited;

the following steps take the short-circuited AB phase as an example:

g. the motor controller calculates the back electromotive voltage phase voltage of the C phase of the motor at the current moment:

U_C(i)＝U_Pcos(θ_i+90°+120°) (3)

in the formula (3), U_C(i) Representing the phase voltage of the C opposite electromotive force at the current moment; u shape_PRepresenting a phaseA voltage amplitude; 90 deg. represents the phase voltage of the back electromotive force leading the rotor position angle theta_iThe degree of (d); 120 deg. indicates that the C phase voltage leads by 120 deg..

h. The motor controller calculates the back electromotive voltage phase voltage of the C phase of the motor at the next moment:

U_C(i+1)＝U_Pcos(θ_i+1+90°+120°) (4)

in the formula (4), U_C(i +1) represents the phase voltage of the counter electromotive force of C at the next time;

i. judging whether a condition meeting the three-phase short circuit exists at present:

if U is_{Opening device}(i-1)≤U_{Opening device}(i)≤U_{Opening device}(i +1), the phase voltage of the opposite electromotive force of the C phase is a wave crest, and the C phase meets the short-circuit condition;

or if U_{Opening device}(i-1)≥U_{Opening device}(i)≥U_{Opening device}(i +1), the phase voltage of the opposite electromotive force of the C phase is a wave crest, and the C phase meets the short-circuit condition;

if the two conditions are not met, returning to the step g and repeating the steps g to i;

j. and (5) short-circuiting all three phases of ABC to finish the short-circuiting process.

It can be seen from fig. 9 that the current does not overrun during the transient process from the two-phase short circuit to the three-phase short circuit.

The method has the advantages of less external conditions, high reliability, simple short-circuit decision process and less calculation amount, is convenient for the motor controller to quickly respond under the condition of emergency failure of the driving system, and improves the safety of the system; and the motor system can be quickly led to enter a steady-state short-circuit state, so that the transient current caused in the short-circuit process is avoided, and the secondary fault caused in the short-circuit process of the controller can be protected.

The above embodiments are only for illustrating the technical idea of the present invention, and the protection scope of the present invention cannot be limited thereby, and any modification made on the basis of the technical scheme according to the technical idea proposed by the present invention falls within the protection scope of the present invention; the technology not related to the invention can be realized by the prior art.