阅读说明：本技术 一种电动车永磁同步电机反电动势抑制方法及系统 (Method and system for restraining back electromotive force of permanent magnet synchronous motor of electric vehicle ) 是由 张大双 宋宏贵 周建刚 普刚 钟亮 李俊 于 2020-11-26 设计创作，主要内容包括：本发明公开了一种电动车永磁同步电机反电动势抑制方法及系统,涉及电动车技术领域,该方法包括以下步骤：若电动车处于电机高速掉电或故障高速拖车状态,且电机的当前转速大于预设转速,则根据母线电容的电压调节励磁电流和转矩电流,控制三相桥式电路中的开关器件的通断,使母线电容的电压在预设的电压范围内,直至电机的当前转速不大于预设转速。本发明中的电动车永磁同步电机反电动势抑制方法及系统,在保护母线电容和三相桥式电路中的开关器件不受损坏的同时,使整车有足够的时间利用制动系统将车速降为零,不会降低电机效率,不会导致电机过热,也不会增加维护成本。(The invention discloses a method and a system for restraining back electromotive force of a permanent magnet synchronous motor of an electric vehicle, which relate to the technical field of electric vehicles and comprise the following steps: if the electric vehicle is in a state that the motor is in high-speed power failure or high-speed trailer failure, and the current rotating speed of the motor is greater than the preset rotating speed, the exciting current and the torque current are adjusted according to the voltage of the bus capacitor, and the on-off of a switch device in the three-phase bridge circuit is controlled, so that the voltage of the bus capacitor is in a preset voltage range until the current rotating speed of the motor is not greater than the preset rotating speed. According to the method and the system for inhibiting the back electromotive force of the permanent magnet synchronous motor of the electric vehicle, disclosed by the invention, the capacitance of a bus and a switching device in a three-phase bridge circuit are protected from being damaged, meanwhile, the whole vehicle has enough time to reduce the vehicle speed to zero by using a braking system, the efficiency of the motor cannot be reduced, the motor cannot be overheated, and the maintenance cost cannot be increased.)

1. The method for inhibiting the back electromotive force of the permanent magnet synchronous motor of the electric vehicle is characterized by comprising the following steps of:

if the electric vehicle is in a state that the motor is in high-speed power failure or high-speed trailer failure, and the current rotating speed of the motor is greater than the preset rotating speed, the exciting current and the torque current are adjusted according to the voltage of the bus capacitor, and the on-off of a switch device in the three-phase bridge circuit is controlled, so that the voltage of the bus capacitor is in a preset voltage range until the current rotating speed of the motor is not greater than the preset rotating speed.

2. The method for suppressing the back electromotive force of the permanent magnet synchronous motor of the electric vehicle as claimed in claim 1, wherein the exciting current and the torque current are adjusted according to the voltage of the bus capacitor, and the on-off of a switching device in a three-phase bridge circuit is controlled to make the voltage of the bus capacitor within a preset voltage range, and the method comprises the following specific steps:

acquiring the voltage of a bus capacitor;

judging whether the voltage of the bus capacitor is greater than a preset first voltage:

if yes, adjusting exciting current I_dAnd torque current I_qIn which the excitation current I_dHas a regulation interval of [ -2 Ψ ]_f/(3L_d)，-Ψ_f/(3L_d)]Torque current I_q＝I_d/20，Ψ_fIs a permanent magnet flux linkage of an electric machine, L_dIs a direct-axis inductance of the motor;

if not, judging whether the voltage of the bus capacitor is smaller than a preset second voltage, wherein the preset second voltage is smaller than a preset first voltage: if yes, adjusting exciting current I_dAnd torque current I_qIn which the excitation current I_dHas a regulation interval of [ -psi [ -phi ]_f/(20L_d)，0]Torque current I_q＝I_d(ii) a If not, adjusting the exciting current I_dAnd torque current I_qThe current value is maintained.

3. The back electromotive force suppression method of a permanent magnet synchronous motor according to claim 2, characterized in that:

a predetermined first voltage U₁For the battery voltage U of the electric vehicle_b120% of;

a predetermined second voltage U₂For the battery voltage U of the electric vehicle_b80% of the total.

4. A back electromotive force suppressing method for a permanent magnet synchronous motor according to claim 3, characterized in that: according to the formula n_t＝60U₁/(2πΨ_f) Calculating to obtain a preset rotating speed n_t。

5. The method for suppressing the back electromotive force of the permanent magnet synchronous motor of the electric vehicle as claimed in claim 1, wherein:

acquiring message information of the vehicle control unit and the current rotating speed of the motor;

and judging whether the electric vehicle is in a high-speed motor power-off state or a fault high-speed trailer state according to the message information, and judging whether the current rotating speed of the motor is greater than a preset rotating speed.

6. The utility model provides an electric motor car PMSM back electromotive force suppression system which characterized in that includes:

a three-phase bridge circuit connected to the motor;

a bus capacitor connected to the three-phase bridge circuit;

a motor controller configured to:

if the electric vehicle is in a state that the motor is in high-speed power failure or high-speed trailer failure, and the current rotating speed of the motor is greater than the preset rotating speed, the motor controller is used for adjusting exciting current and torque current according to the voltage of the bus capacitor and controlling the on-off of a switch device in the three-phase bridge circuit to enable the voltage of the bus capacitor to be within a preset voltage range until the current rotating speed of the motor is not greater than the preset rotating speed.

7. The system for suppressing back electromotive force of a permanent magnet synchronous motor of an electric vehicle as claimed in claim 6, wherein:

the motor controller is used for acquiring the voltage of the bus capacitor;

the motor controller is used for judging whether the voltage of the bus capacitor is greater than a preset first voltage:

if yes, the motor controller is used for adjusting the exciting current I_dAnd torque current I_qIn which the excitation current I_dHas a regulation interval of [ -2 Ψ ]_f/(3L_d)，-Ψ_f/(3L_d)]Torque current I_q＝I_d/20，Ψ_fIs a permanent magnet flux linkage of an electric machine, L_dIs a direct-axis inductance of the motor;

if not, the motor controller is used for judging whether the voltage of the bus capacitor is smaller than a preset second voltage, wherein the preset second voltage is smaller than a preset first voltage: if yes, the motor controller is used for adjusting the exciting current I_dAnd torque current I_qIn which the excitation current I_dHas a regulation interval of [ -psi [ -phi ]_f/(20L_d)，0]Torque current I_q＝I_d(ii) a If not, the motor controller is used for adjusting the exciting current I_dAnd torque current I_qThe current value is maintained.

8. The back electromotive force suppression system of a permanent magnet synchronous motor according to claim 7, characterized in that:

a predetermined first voltage U₁For the battery voltage U of the electric vehicle_b120% of;

a predetermined second voltage U₂For the battery voltage U of the electric vehicle_b80% of the total.

9. The back electromotive force suppression system of a permanent magnet synchronous motor according to claim 8, characterized in that: preset speed n_t＝60U₁/(2πΨ_f)。

10. The system for suppressing back electromotive force of a permanent magnet synchronous motor of an electric vehicle as claimed in claim 6, wherein:

the motor controller is used for acquiring message information of the whole vehicle controller and the current rotating speed of the motor;

the motor controller is used for judging whether the electric vehicle is in a motor high-speed power-off or fault high-speed trailer state or not according to the message information and judging whether the current rotating speed of the motor is greater than a preset rotating speed or not.

Technical Field

The invention relates to the technical field of electric vehicles, in particular to a method and a system for restraining back electromotive force of a permanent magnet synchronous motor of an electric vehicle.

Background

With the development of society, the electric vehicle as a new energy vehicle meets the development trend of energy conservation and environmental protection. The permanent magnet synchronous motor is the first choice of the driving motor of the electric vehicle due to the advantages of high power/torque density, high efficiency and the like. However, the permanent magnet synchronous motor adopts permanent magnet excitation, and when the vehicle is abnormally powered off in high-speed running or needs to maintain a high-speed fault trailer, back electromotive force is generated on a motor winding. Because the back electromotive force is in direct proportion to the rotating speed of the motor, when the back electromotive force is larger than the maximum voltage which can be borne by a switching device (mainly adopting an IGBT) of a three-phase bridge circuit and a bus capacitor of a main circuit, the switching device and the bus capacitor can be damaged.

In the correlation technique, to the damage problem that the electric motor car PMSM counter electromotive force may cause for switching device and bus capacitance, mainly there are 2 kinds of technical scheme at present:

scheme 1: when the motor is designed, the permanent magnetic flux linkage value is reduced through the magnetic circuit design, and the value of the motor no-load counter electromotive force of the high-speed abnormal power failure or high-speed fault trailer is controlled in a proper range.

Scheme 2: when the motor is suddenly powered off during high-speed running, damage to a switching device and a bus capacitor caused by overhigh counter potential is avoided through three-phase active short circuit; when the trailer is in fault, the speed of the trailer is limited or the power system is disconnected, such as neutral gear engagement or transmission shaft dismounting, so that damage to a switching device and a bus capacitor due to overhigh back electromotive force is avoided.

However, in the scheme 1, the permanent magnet flux linkage value is designed to be too low, so that on one hand, characteristic parameters such as the power factor and the power density of the motor can be reduced, and on the other hand, the output current is increased due to the low permanent magnet flux linkage value when the torque is output in the same way, so that the model selection of a switching device is influenced, the iron loss and the circuit loss of the motor can also be increased, and further the efficiency of the motor is influenced.

The motor falls down when electric motor car high speed operation in scheme 2, adopts the strategy that initiative short-circuit protection reduces the counter electromotive force harm, can not run for a long time, otherwise the last short-circuit current that the counter electromotive force produced can arouse the motor overheated, and the motor is overheated to lead to rotor magnet steel demagnetization risk, also can arouse the overheated damage that leads to of switching device. When a trailer is in fault, the speed limit of the trailer or the dismounting of the transmission shaft can prolong the maintenance time, increase the maintenance workload and further increase the after-sale maintenance cost.

Disclosure of Invention

The embodiment of the invention provides a method and a system for restraining back electromotive force of a permanent magnet synchronous motor of an electric vehicle, which are used for solving the technical problems of motor efficiency reduction, motor overheating or maintenance cost increase of the conventional method and system for restraining the back electromotive force of the permanent magnet synchronous motor of the electric vehicle.

In a first aspect, a method for suppressing back electromotive force of a permanent magnet synchronous motor of an electric vehicle is provided, which includes the following steps:

if the electric vehicle is in a state that the motor is in high-speed power failure or high-speed trailer failure, and the current rotating speed of the motor is greater than the preset rotating speed, the exciting current and the torque current are adjusted according to the voltage of the bus capacitor, and the on-off of a switch device in the three-phase bridge circuit is controlled, so that the voltage of the bus capacitor is in a preset voltage range until the current rotating speed of the motor is not greater than the preset rotating speed.

In some embodiments, the exciting current and the torque current are adjusted according to the voltage of the bus capacitor, and the on-off of a switching device in the three-phase bridge circuit is controlled to make the voltage of the bus capacitor within a preset voltage range, and the specific steps are as follows:

acquiring the voltage of a bus capacitor;

judging whether the voltage of the bus capacitor is greater than a preset first voltage:

if yes, adjusting exciting current I_dAnd torque current I_qIn which the excitation current I_dHas a regulation interval of [ -2 Ψ ]_f/(3L_d)，-Ψ_f/(3L_d)]Torque current I_q＝I_d/20，Ψ_fIs a permanent magnet flux linkage of an electric machine, L_dIs a direct-axis inductance of the motor;

if not, the bus capacitor is judgedWhether the voltage is less than a preset second voltage, wherein the preset second voltage is less than a preset first voltage: if yes, adjusting exciting current I_dAnd torque current I_qIn which the excitation current I_dHas a regulation interval of [ -psi [ -phi ]_f/(20L_d)，0]Torque current I_q＝I_d(ii) a If not, adjusting the exciting current I_dAnd torque current I_qThe current value is maintained.

In some embodiments, the predetermined first voltage U₁For the battery voltage U of the electric vehicle_b120% of; a predetermined second voltage U₂For the battery voltage U of the electric vehicle_b80% of the total.

In some embodiments, the method comprises: according to the formula n_t＝60U₁/(2πΨ_f) Calculating to obtain a preset rotating speed n_t。

In some embodiments, message information of the vehicle control unit and the current rotating speed of the motor are obtained; and judging whether the electric vehicle is in a high-speed motor power-off state or a fault high-speed trailer state according to the message information, and judging whether the current rotating speed of the motor is greater than a preset rotating speed.

In a second aspect, a back electromotive force suppression system for a permanent magnet synchronous motor of an electric vehicle is provided, which includes:

a three-phase bridge circuit connected to the motor;

a bus capacitor connected to the three-phase bridge circuit;

a motor controller configured to:

if the electric vehicle is in a state that the motor is in high-speed power failure or high-speed trailer failure, and the current rotating speed of the motor is greater than the preset rotating speed, the motor controller is used for adjusting exciting current and torque current according to the voltage of the bus capacitor and controlling the on-off of a switch device in the three-phase bridge circuit to enable the voltage of the bus capacitor to be within a preset voltage range until the current rotating speed of the motor is not greater than the preset rotating speed.

In some embodiments, the motor controller is configured to obtain a voltage of a bus capacitor;

the motor controller is used for judging whether the voltage of the bus capacitor is greater than a preset first voltage:

if yes, the motor controller is used for adjusting the exciting current I_dAnd torque current I_qIn which the excitation current I_dHas a regulation interval of [ -2 Ψ ]_f/(3L_d)，-Ψ_f/(3L_d)]Torque current I_q＝I_d/20，Ψ_fIs a permanent magnet flux linkage of an electric machine, L_dIs a direct-axis inductance of the motor;

if not, the motor controller is used for judging whether the voltage of the bus capacitor is smaller than a preset second voltage, wherein the preset second voltage is smaller than a preset first voltage: if yes, the motor controller is used for adjusting the exciting current I_dAnd torque current I_qIn which the excitation current I_dHas a regulation interval of [ -psi [ -phi ]_f/(20L_d)，0]Torque current I_q＝I_d(ii) a If not, the motor controller is used for adjusting the exciting current I_dAnd torque current I_qThe current value is maintained.

In some embodiments, the predetermined first voltage U₁For the battery voltage U of the electric vehicle_b120% of; a predetermined second voltage U₂For the battery voltage U of the electric vehicle_b80% of the total.

In some embodiments, the predetermined speed n_t＝60U₁/(2πΨ_f)。

In some embodiments, the motor controller is configured to obtain message information of the vehicle controller and a current rotation speed of the motor; the motor controller is used for judging whether the electric vehicle is in a motor high-speed power-off or fault high-speed trailer state or not according to the message information and judging whether the current rotating speed of the motor is greater than a preset rotating speed or not.

The technical scheme provided by the invention has the beneficial effects that:

the embodiment of the invention provides a method and a system for inhibiting back electromotive force of a permanent magnet synchronous motor of an electric vehicle. The electric vehicle speed control system has the advantages that the electric vehicle speed control system can ensure that the whole vehicle has enough time to utilize a braking system to reduce the vehicle speed to zero while protecting the bus capacitance and preventing a switching device in a three-phase bridge circuit from being damaged, the motor efficiency can not be reduced, the motor can not be overheated, and the maintenance cost can not be increased.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.

Fig. 1 is a schematic flow chart of a method for suppressing back electromotive force of a permanent magnet synchronous motor of an electric vehicle according to an embodiment of the present invention;

FIG. 2 is a schematic flow chart of step 105 of FIG. 1 according to an embodiment of the present invention;

FIG. 3 shows an embodiment of the present invention providing a reference current I_dAnd torque current I_qCalculating a given current I_sA schematic diagram of (a);

FIG. 4 shows an embodiment of the present invention providing a reference current I_dAnd torque current I_qCalculating a given current I_sAnother schematic of (a);

fig. 5 is a schematic structural diagram of a back electromotive force suppression system of a permanent magnet synchronous motor of an electric vehicle according to an embodiment of the present invention;

in the figure: 1. a three-phase bridge circuit; 2. a bus capacitor; 3. a motor controller; 4. a contactor; 5. a battery.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.

The embodiment of the invention provides a method for inhibiting back electromotive force of a permanent magnet synchronous motor of an electric vehicle, which can solve the technical problems of motor efficiency reduction, motor overheating or maintenance cost increase of the conventional method for inhibiting the back electromotive force of the permanent magnet synchronous motor of the electric vehicle.

A method for restraining back electromotive force of a permanent magnet synchronous motor of an electric vehicle comprises the following steps:

if the electric vehicle is in a state that the motor is in high-speed power failure or high-speed trailer failure, and the current rotating speed of the motor is greater than the preset rotating speed, the exciting current and the torque current are adjusted according to the voltage of the bus capacitor, and the on-off of a switch device in the three-phase bridge circuit is controlled, so that the voltage of the bus capacitor is in a preset voltage range until the current rotating speed of the motor is not greater than the preset rotating speed.

Referring to a flowchart shown in fig. 1, the steps of the method for suppressing back electromotive force of a permanent magnet synchronous motor of an electric vehicle according to an embodiment of the present invention are as follows.

At step 101, the method flow begins.

And 102, acquiring message information of the vehicle control unit and the current rotating speed of the motor.

And 103, judging whether the electric vehicle is in a high-speed motor power-off or fault high-speed trailer state or not according to the message information. If yes, go to step 104; if not, execution ends in step 106.

104, judging whether the current rotating speed n of the motor is greater than the preset rotating speed n or not_tIf yes, go to step 105, if no, go to step 106 and end. Wherein the preset rotating speed n_tCan be according to the formula n_t＝60U₁/(2πΨ_f) Is calculated to obtain U₁Is a predetermined first voltage, U₁Can be the battery voltage U of the electric vehicle_b120% of (i) (%), Ψ_fIs the permanent magnet flux linkage of the motor.

And 105, adjusting the exciting current and the torque current according to the voltage of the bus capacitor, controlling the on-off of a switching element in the three-phase bridge circuit, and adjusting the voltage of the bus capacitor within a preset voltage range. After step 105 is executed, the process returns to step 104 to continue the execution.

Further, referring to the flowchart shown in fig. 2, in step 105, the exciting current and the torque current are adjusted according to the voltage of the bus capacitor, and the on/off of the switching device in the three-phase bridge circuit is controlled to make the voltage of the bus capacitor within a preset voltage range, specifically including the following steps:

at step 501, the process begins.

Step 502, obtaining the voltage U of the bus capacitor_dc。

Step 503, determining the voltage U of the bus capacitor_dcWhether it is greater than a preset first voltage U₁If yes, go to step 504; if not, go to step 505;

step 504, adjusting the exciting current I_dAnd torque current I_qIn which the excitation current I_dHas a regulation interval of [ -2 Ψ ]_f/(3L_d)，-Ψ_f/(3L_d)]Torque current I_q＝I_d/20，L_dIs the direct-axis inductance of the motor. Referring to fig. 3, assume that a given current I is used to control the motor_s，I_sSatisfy the relation I_s ²＝I_d ²+I_q ²At this time, due to I_dThe generated back electromotive force epsilon is lower than the voltage U of the bus capacitor although the motor rotating speed is higher_dcAt the moment, the bus capacitor is in a discharge state, so that the voltage U of the bus capacitor is enabled_dcAnd decreases.

Step 505, determining the voltage U of the bus capacitor_dcWhether or not it is less than a preset second voltage U₂In which a predetermined second voltage U is applied₂Is less than a preset first voltage U₁. If yes, go to step 506; if not, go to step 507. Wherein the preset second voltage U₂Can be the battery voltage U of the electric vehicle_b80% of the total.

Step 506, adjusting the exciting current I_dAnd torque current I_qIn which the excitation current I_dHas a regulation interval of [ -psi [ -phi ]_f/(20L_d)，0]Torque current I_q＝I_d. See FIG. 4, where I is_dSmaller, less weakening effect on the magnetic field generated by the permanent magnet of the motor, higher rotating speed of the motor, and higher generated back electromotive force epsilon than the bus capacitor voltage U_dcSo as to charge the bus capacitor by using the counter electromotive force to ensure that the voltage U of the bus capacitor_dcAnd (4) rising.

Step 507, adjusting the exciting current I_dAnd torque current I_qThe current value is maintained.

In summary, according to the method for suppressing back electromotive force of a permanent magnet synchronous motor of an electric vehicle in the embodiment of the present invention, under the condition that the electric vehicle is in a high-speed power-down or fault high-speed trailer state of the motor and the current rotation speed of the motor is greater than the preset rotation speed, the exciting current I is adjusted according to the voltage of the bus capacitor_dAnd torque current I_qControlling the on-off of the switch device in the three-phase bridge circuit to make the voltage U of the bus capacitor_dcAt a predetermined first voltage U₁And a preset first voltage U₂And fluctuating until the current rotating speed of the motor is not more than the preset rotating speed. The electric vehicle speed control system has the advantages that the electric vehicle speed control system can ensure that the whole vehicle has enough time to utilize a braking system to reduce the vehicle speed to zero while protecting the bus capacitance and preventing a switching device in a three-phase bridge circuit from being damaged, the motor efficiency can not be reduced, the motor can not be overheated, and the maintenance cost can not be increased.

Referring to fig. 5, an embodiment of the present invention provides a back electromotive force suppression system for a permanent magnet synchronous motor of an electric vehicle, including: three-phase bridge circuit 1, bus capacitor 2 and motor controller 3.

Three-phase bridge circuit 1 is connected with the motor, and bus electric capacity 2 is connected with three-phase bridge circuit 1, and motor controller 3 is configured as: if the electric vehicle is in a state that the motor is in high-speed power failure or high-speed trailer failure, and the current rotating speed of the motor is greater than the preset rotating speed, the motor controller 3 adjusts exciting current and torque current according to the voltage of the bus capacitor 2, and controls the on-off of a switch device in the three-phase bridge circuit to enable the voltage of the bus capacitor to be within a preset voltage range until the current rotating speed of the motor is not greater than the preset rotating speed.

Specifically, the motor controller 3 obtains message information of the vehicle controller and the current rotating speed of the motor, judges whether the electric vehicle is in a high-speed motor failure state or a fault high-speed trailer state according to the message information, and judges whether the current rotating speed of the motor is greater than a preset rotating speed. Wherein the preset rotating speed n_tCan be according to the formula n_t＝60U₁/(2πΨ_f) Is calculated to obtain U₁Is a preset first voltage U₁Can be the battery voltage U of the electric vehicle_b120% of (i) (%), Ψ_fIs the permanent magnet flux linkage of the motor. When the electric vehicle is in a state that the motor is in high-speed power failure or the electric vehicle is in a state of a fault high-speed trailer, the contactor 4 in the figure 5 is disconnected, and the electric vehicle battery 5 and the bus capacitor 2 do not form a loop.

Further, the motor controller 3 determines the voltage U of the bus capacitor_dcWhether it is greater than a preset first voltage U₁：

If yes, the motor controller 3 adjusts the exciting current I_dAnd torque current I_qIn which the excitation current I_dHas a regulation interval of [ -2 Ψ ]_f/(3L_d)，-Ψ_f/(3L_d)]Torque current I_q＝I_d/20，Ψ_fIs a permanent magnet flux linkage of an electric machine, L_dIs the direct-axis inductance of the motor. Referring to fig. 3, assume that a given current I is used to control the motor_s，I_sSatisfy the relation I_s ²＝I_d ²+I_q ²At this time, due to I_dThe generated back electromotive force epsilon is lower than the voltage U of the bus capacitor although the motor rotating speed is higher_dcAt the moment, the bus capacitor is in a discharge state, so that the voltage U of the bus capacitor is enabled_dcAnd decreases.

If not, the motor controller 3 judges the voltage U of the bus capacitor_dcWhether or not it is less than a preset second voltage U₂In which a predetermined second voltage U is applied₂Is less than a preset first voltage U₁: if not, the motor controller 3 adjusts the exciting current I_dAnd torque current I_qMaintaining the current value; if yes, the motor controller adjusts the exciting current I_dAnd torque current I_qIn which the excitation current I_dHas a regulation interval of [ -psi [ -phi ]_f/(20L_d)，0]Torque current I_q＝I_d. See FIG. 4, where I is_dSmaller, less weakening effect on the magnetic field generated by the permanent magnet, higher rotating speed and higher generated back electromotive force epsilon than the bus capacitor voltage U_dcSo as to charge the bus capacitor by using the counter electromotive force to ensure that the voltage U of the bus capacitor_dcAnd (4) rising.

According to the counter electromotive force suppression system of the permanent magnet synchronous motor of the electric vehicle, under the condition that the electric vehicle is in a high-speed power-off or fault high-speed trailer state of the motor and the current rotating speed of the motor is greater than the preset rotating speed, the motor controller 3 adjusts the exciting current I according to the voltage of the bus capacitor_dAnd torque current I_qControlling the on-off of the switch device in the three-phase bridge circuit to make the voltage U of the bus capacitor_dcAt a predetermined first voltage U₁And a preset first voltage U₂And fluctuating until the current rotating speed of the motor is not more than the preset rotating speed. The electric vehicle speed control system has the advantages that the electric vehicle speed control system can ensure that the whole vehicle has enough time to utilize a braking system to reduce the vehicle speed to zero while protecting the bus capacitance and preventing a switching device in a three-phase bridge circuit from being damaged, the motor efficiency can not be reduced, the motor can not be overheated, and the maintenance cost can not be increased.

In the description of the present invention, it should be noted that the terms "upper", "lower", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, which are merely for convenience in describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed in a specific orientation, and operate, and thus, should not be construed as limiting the present invention. Unless expressly stated or limited otherwise, the terms "mounted," "connected," and "connected" are intended to be inclusive and mean, for example, that they may be fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.

It is to be noted that, in the present invention, relational terms such as "first" and "second", and the like, are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.

The foregoing are merely exemplary embodiments of the present invention, which enable those skilled in the art to understand or practice the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.