CN108521243A - A Direct Power Control Method for High Speed Permanent Magnet Synchronous Motor Based on Space Vector Modulation - Google Patents

Abstract

The invention discloses a direct power control method of a high-speed permanent magnet synchronous motor based on space vector modulation. A PI regulator is used instead of a hysteresis controller to realize direct control of instantaneous power. The direct power control method of high-speed permanent magnet synchronous motor based on space vector modulation is based on two PI regulators. The output is based on the phase magnitude of the voltage vector, and the ideal voltage vector is obtained through coordinate transformation and space vector modulation. In this way, the precise control of the stator voltage can be achieved to achieve the goal of controlling the reactive power to zero, and the problem of unfixed switching frequency can be overcome. The invention has simple structure and simple algorithm, can reduce the loss of the motor, improve the operating efficiency of the motor, and can be used in long-term steady-state operation such as a blower with relatively high energy-saving requirements.

Description

A Direct Power Control of High Speed Permanent Magnet Synchronous Motor Based on Space Vector Modulation method

technical field

The invention belongs to the field of motor control, and in particular relates to a direct power control method of a high-speed permanent magnet synchronous motor based on space vector modulation.

Background technique

The permanent magnet synchronous motor uses permanent magnets to provide excitation. Compared with the electric excitation motor, the loss of the excitation system is reduced, and the efficiency and power density of the motor are greatly improved. At the same time, it overcomes the unfavorable factors brought by DC motor brushes and commutators, and its application scope has rapidly developed from the initial military industry to aerospace, industrial automation and other fields.

At present, the more common permanent magnet synchronous motor control methods include vector control method and direct torque control method. The basic principle of vector control is to measure and control the stator current vector of the motor, and to control the excitation current and torque current of the motor according to the principle of magnetic field orientation, so as to achieve the purpose of controlling the motor torque. However, in practical applications, because the rotor flux linkage is difficult to be accurately observed, the system characteristics are greatly affected by the motor parameters, and the vector rotation transformation used in the motor control process is more complicated, making it difficult to achieve the ideal analysis results for the actual control effect. Direct torque control does not indirectly control the torque by controlling the current, flux linkage, etc., but directly controls the torque as the controlled quantity. This algorithm does not require complicated coordinate transformation, but is directly calculated on the coordinates of the motor stator The modulus of the flux linkage and the size of the torque, and the direct tracking of the flux linkage and the torque realizes the PWM pulse width modulation and the high dynamic performance of the system, but the direct torque control method has the problem of large pulsating torque at low speed, and the control The calculation amount and calculation difficulty of the algorithm are very large. Both the vector control method and the direct torque control method have good effects on the dynamic performance of the system, but the content of reactive power has increased.

In the context of building a resource-saving society and facing the situation of energy shortage in our country, finding a new and efficient motor control method has become a research hotspot. As the core component of high-speed power machinery such as blowers, high-speed magnetic levitation motors are in a steady-state operation state most of the time, and do not have high requirements for dynamic performance, but have strict requirements for system energy saving.

In order to reduce the reactive power absorbed by the motor to achieve the goal of saving energy, the direct power control algorithm is used to control the motor. The structure of the direct power control method is simple. By controlling the reactive power of the motor to zero, the ideal goal of the motor power factor close to 1 can be achieved. The direct power control algorithm has the advantages of high power factor, low harmonic distortion, simple algorithm and system structure, etc., and does not need rotating coordinate transformation. The traditional direct power control algorithm uses a combination of a hysteresis comparator and a switch table. Such a composition has the disadvantages that the switching frequency is not fixed, the system sampling frequency is high and the time lag is high, and the stator parameter changes and the inverter switch dead. The control performance of the motor is affected by factors such as the area, the error accumulation of the integrator, and the DC temperature drift. Therefore, it is necessary to propose a new control method for high-speed permanent magnet synchronous motors, which can not only achieve the goal of zero reactive power of the motor, improve the working efficiency of the motor, but also overcome the unfixed switching frequency and the difficult determination of the hysteresis width. To avoid the problem of affecting the motor control performance caused by the hysteresis controller in the traditional direct control method, and further improve the steady-state performance of the motor.

Contents of the invention

The technical problem of the present invention is: the purpose of the present invention is to overcome the deficiencies of the prior art, solve the problems of increased reactive power, large motor loss and low motor efficiency in traditional blowers and other applications, and overcome the problem of unfixed switching frequency . Provide a new method of direct power control of high-speed permanent magnet synchronous motor based on space vector modulation. Technical Support.

The technical solution adopted by the present invention to solve the above-mentioned technical problems is: a direct power control method of a high-speed permanent magnet synchronous motor, comprising the following steps:

(1) Based on the assumption of the ideal condition of the permanent magnet synchronous motor, the basic mathematical model of the three-phase PMSM is established. The ideal conditions are: the three-phase PMSM is an ideal motor; the saturation of the iron core of the motor is ignored; the eddy current and hysteresis loss in the motor are ignored; the current in the motor is a symmetrical three-phase sinusoidal current.

(2) The control target of zero reactive power of the motor is realized by the direct power control algorithm, and the fixed switching frequency is realized by the space vector modulation algorithm. At the same time, the rotor position is estimated by the high-speed permanent magnet synchronous motor rotor position information estimation algorithm, which is directly The implementation of power control provides protection.

The mathematical model of the above-mentioned high-speed permanent magnet synchronous motor is:

In the ABC coordinate system, the stator current and voltage space vectors can be expressed as:

Among them, a=e ^j120° represents the operator space; R _s is the phase resistance; L _s is the equivalent phase inductance, which is the difference between the phase inductance and mutual inductance; ψ _f is the excitation space vector of the permanent magnet; θ _r is the relative A of the permanent magnet The rotation angle of the axis.

The above-mentioned direct power control method is a control algorithm based on a PI regulator that uses the two parameters of the instantaneous active power and the instantaneous reactive power of the motor as control variables. The specific steps of the method are:

(1) In the ABC coordinate system, assume that the state functions of the six switching tubes of the inverter are: S _A , S _B and S _C , which are expressed as:

Then, the three-phase line voltage can be expressed as:

Among them, u _d represents the d-axis voltage, u _AB , u _BC , u _CA represent the three-phase line voltage.

Combined with u _A + u _B + u _C = 0, the three-phase phase voltage vector is obtained as:

Among them, u _A , u _B , u _C represent three-phase phase voltage;

(2) Transform the collected three-phase current signals i _A , i _B and i _C into current vectors i α and _{i β} in the α-β coordinate system through the coordinate transformation method, and the conversion relationship is:

(3) Using the calculation formula of instantaneous power, solve the three-phase instantaneous active power p and reactive power q of the permanent magnet synchronous motor in the α-β coordinate system.

The calculation formula of instantaneous power is:

The three-phase instantaneous active power p and reactive power q are respectively:

(4) Make a difference between the given speed ω ^* and the measured speed ω, and the difference is input to the PI regulator for speed adjustment. The output value of the PI regulator is used as the given value of the instantaneous active power p ^* , and the instantaneous active power Make a difference between p ^* and the actual calculated instantaneous active power p, and the difference is sent to the PI regulator to obtain the voltage vector u _sp , the given value of the instantaneous reactive power q ^* is set to 0, and the instantaneous reactive power q ^* and The instantaneous reactive power q obtained by the actual calculation is subtracted, and the difference is sent to the PI regulator to obtain the voltage vector u _sq .

(5) According to the derivation of the instantaneous power theory of the permanent magnet synchronous motor, the phase angle information θ _s of the voltage vector is obtained.

The instantaneous active power in the ABC coordinate system can be obtained from the scalar product of the instantaneous voltage vector and the current vector, and the instantaneous reactive power can be obtained from the vector product of the two, respectively expressed as:

Among them, u=[u _A ,u _B ,u _C ] ^T and i=[i _A ,i _B ,i _C ] ^T represent the phase voltage vector and the phase current vector respectively.

Therefore, the three-phase input instantaneous active power and instantaneous reactive power of the motor are respectively:

The change of the stator current in the d-q coordinate axis is related to the change of the current amplitude and angle, and when the motor is running in a steady state, the motor torque is stable, and the component of the stator current on the q-axis remains unchanged, so the stator current amplitude does not change , and the stator current vector and the d-axis rotate at the same speed, so the vector angle between the stator current and the d-axis does not change, and, in the process of direct power control, the instantaneous power is required to be 0, and the power factor is 1, so let q=0.

Therefore, the instantaneous active power of the three-phase input of the motor can be written as:

Among them, γ is the angle between the current vector i _s and the q-axis, δ is the angle between the voltage vector u _s and the q-axis, and θ is the angle between the voltage vector and the current vector.

Because γ=θ+δ, and when the reactive power is zero, that is, when the power factor is 1, the power factor angle is zero, that is to say, i _s and u _s should be coaxial, that is, γ=δ. make:

Therefore, the above formula can be changed to:

The phase angle information θ _s of the voltage vector can be determined by γ and the rotor position angle θ _r , which can be expressed as:

θ _s =90°+δ+θ _r (32)

Among them, the expression of δ and θ _r can be expressed as:

Among them, P represents the number of pole pairs of the motor.

(6) Through the coordinate transformation method, using the voltage vector signals u _sp and u _sq output by the PI regulator, and according to the phase angle information θ _s of the voltage vector, the voltage vectors u _sα and u _sβ in the α-β coordinate system are solved, The conversion relationship is:

Among them, θ _s is the angle between the voltage space vector u _s and the α axis.

The above-mentioned direct power control method is a permanent magnet synchronous motor direct power control algorithm based on space vector modulation, and the specific steps of the method are:

(1) Establish a space vector modulation model.

Assuming that the calculated vector is between u _s non-zero vector u _s1 and u _s2 , using u _s1 is equivalent to u _s2 , the equivalent relationship is as follows:

u _s T _s = u _s1 T _s1 + u _s2 T _s2 (35)

Among them, T _s represents the PWM period; T _s1 and T _s2 represent the action time of u _s1 and u _s2 respectively.

(2) The voltage vector u _sα of the α-axis and the voltage vector u _sβ of the β-axis are vector-decomposed to obtain the ideal voltage vectors u _α and u _β , and the equivalent relationship is rewritten in the α-β coordinate system as follows:

Fixed switching frequency can be achieved by solving for exact T _s1 and T _s2 .

(3) The ideal voltage vectors u _α and u _β output three-phase current signals i _A , i _B , i _C through the PWM inverter, thereby adjusting the magnitude of the stator current vector to change the instantaneous reactive power. At the same time, the output three-phase The phase currents i _A , i _B , and i _C undergo coordinate transformation to obtain the current vectors i _α and i _β in the α-β coordinate system, which together with the voltage vectors u _α and u _β are used as the actual calculated instantaneous active power p ^* and instantaneous reactive power The input of power q ^* realizes the closed-loop control of direct power control.

The principle of the invention is: the invention relates to a direct power control algorithm of a high-speed permanent magnet synchronous motor based on a space vector modulation algorithm for long-term steady-state operation and high energy-saving requirements. Firstly, the collected three-phase current signals are transformed into two-phase current signals to obtain the two-phase current signals, and the instantaneous active power and reactive power of the motor are calculated in real time, and then compared with the given instantaneous active power and reactive power respectively. After adjustment by two PI regulators, according to the phase angle of the voltage vector, it is processed through coordinate transformation, and finally the space vector modulation algorithm is used to obtain the ideal voltage vector to control the motor with zero reactive power.

Compared with the prior art, the present invention has the advantages that: the present invention proposes a direct power control algorithm, that is, based on a PI regulator, the two parameters of the instantaneous active power and the instantaneous reactive power of the motor are used as the control quantities, the method is simple, and the The goal of zero reactive power of the motor has greatly improved the operating efficiency and energy-saving indicators of high-speed motors. At the same time, a method combining direct power control and space vector modulation algorithm is proposed, which overcomes the problems that the switching frequency is not fixed and the hysteresis width is not easy to determine. In addition, in the control process, the hysteresis controller output in the traditional direct control method and the stator parameter change at low frequencies caused by the sector where the stator flux linkage needs to be estimated, the switching dead zone of the inverter, and the error accumulation of the integrator are avoided. The problem of affecting the control performance of the motor due to factors such as DC temperature drift and so on, effectively improves the steady-state performance of the motor.

Description of drawings

Fig. 1 is a system structure block diagram of the present invention;

Fig. 2 is a schematic diagram of the coordinate relationship of the present invention;

Fig. 3 is the schematic diagram of the principle of the space vector modulation of the present invention;

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

As shown in Figure 1-3, concrete method of the present invention is as follows:

Specific embodiment one: Referring to Fig. 1 to illustrate this embodiment, a direct power control method of a high-speed permanent magnet synchronous motor described in this method is a method based on a space vector modulation algorithm, including a permanent magnet synchronous motor mathematical model part 1, directly Power control part 2, space vector modulation part 3.

The mathematical model part 1 of the permanent magnet synchronous motor includes a system current vector equation, a voltage vector equation, and a flux linkage equation. The direct power control part 2 is based on a PI regulator, takes the two parameters of the motor's instantaneous active power and instantaneous reactive power as control quantities, and outputs a preliminary control of the voltage vector. During the rotation of the motor rotor, three corresponding coordinate systems are established, namely the ABC coordinate system, the stationary α-β coordinate system and the rotating dq coordinate system. Make a difference between the given speed ω ^* and the measured speed ω, and the difference is input to the PI regulator for speed regulation. The output value of the PI regulator is used as the given value of the instantaneous active power p ^* , and the given value of the instantaneous reactive power q ^* set to 0. In the static α-β coordinate system, the three-phase instantaneous active power and reactive power of the motor are calculated using the voltage vector and current vector information. The instantaneous active power p ^* , reactive power q ^* and the actual calculated instantaneous active power p, reactive power q are respectively made difference, and the difference is sent to two PI regulators for adjustment, and the output of the two PI regulators According to the voltage vector phase angle θ _s , the coordinates are transformed into the static α-β coordinate system, and the voltage vector u _sα of the α axis and the voltage vector u _sβ of the β axis are obtained.

The space vector modulation part 3 is a control algorithm for further obtaining an ideal voltage vector on the basis of direct power control. The voltage vector u _sα of the α-axis and the voltage vector u _sβ of the β-axis are vector-decomposed to obtain the ideal voltage vectors u _α and u _β . This voltage signal outputs three-phase current signals i _A , i _B , i _C through the PWM inverter to adjust the magnitude of the stator current vector to change the instantaneous reactive power. At the same time, the output three-phase current signals i _A , i _B , and i _C undergo coordinate transformation to obtain the current vectors i _α and i _β in the α-β coordinate system, which together with the voltage vectors u _α and u _β are used as the actual calculated instantaneous active power Input of power p ^* and instantaneous reactive power q ^* .

Specific embodiment 2: This embodiment is a further limitation of the direct power control method of high-speed magnetic levitation synchronous motor based on space vector modulation described in specific embodiment 1. The mathematical model part 1 of the permanent magnet synchronous motor includes the system current vector equations, voltage vector equations, flux linkage equations, and electromagnetic torque equations.

In the ABC coordinate system, the stator current, voltage space vector, and stator flux linkage can be expressed as:

Among them, a=e ^j120° represents the operator space; R _s is the phase resistance; L _s is the equivalent phase inductance, which is the difference between the phase inductance and mutual inductance; ψ _s is the flux linkage of the three-phase winding; u _s , R _s , i _s is the phase voltage, resistance and current of the three-phase winding respectively; ψ _f is the excitation space vector of the permanent magnet; θ _r is the rotation angle of the permanent magnet relative to the A axis, and satisfies:

L _s is the stator mutual inductance, L ₃ is the stator leakage inductance.

Specific embodiment three: Referring to Fig. 1 and Fig. 2 to illustrate this embodiment, this embodiment is a further limitation of the direct power control method for high-speed magnetic levitation synchronous motors based on space vector modulation described in specific embodiment one, the direct power control Part 2 includes the following steps:

Step 1, using the states of the switching tubes of the inverter, the three-phase voltage vectors u _A , u _B and u _C are obtained.

In the ABC coordinate system, it is assumed that the state functions of the six switching tubes of the inverter are: S _A , S _B and S _C , which are expressed as:

Then, the three-phase line voltage can be expressed as:

Among them, u _d represents the d-axis voltage, u _AB , u _BC , u _CA represent the three-phase line voltage.

Combined with u _A + u _B + u _C = 0, the three-phase phase voltage vector is obtained as:

Among them, u _A , u _B , u _C represent three-phase phase voltages.

Step 2: Transform the collected three-phase current signals i _A , i _B and i _C into current vectors i _α and i _β in the α-β coordinate system by coordinate transformation method. According to the schematic diagram of the coordinate relationship shown in Figure 2, the conversion relationship is:

Step 3, use the calculation formula of instantaneous power to solve the three-phase instantaneous active power p and reactive power q of the permanent magnet synchronous motor in the α-β coordinate system.

The calculation formula of instantaneous power is:

The three-phase instantaneous active power p and reactive power q are respectively:

Step 4, according to the block diagram of the direct power control algorithm shown in Figure 1, the given speed ω ^* is compared with the measured speed ω, and the difference is input to the PI regulator for speed regulation, and the output value of the PI regulator is used as the instantaneous active power p ^* given value of . Make a difference between the instantaneous active power p ^* and the actual calculated instantaneous active power p, and send the difference to the PI regulator to obtain the voltage vector u _sp . The given value of instantaneous reactive power q ^* is set to 0, and the difference between instantaneous reactive power q ^* and the calculated instantaneous reactive power q is made, and the difference is sent to the PI regulator to obtain the voltage vector u _sq .

Step five, using the derivation of the instantaneous power theory of the permanent magnet synchronous motor, and according to the schematic diagram of the coordinate relationship shown in Figure 2, the phase angle information θ _s of the voltage vector is obtained.

The three-phase instantaneous power in the d-q coordinate system can be calculated according to the complex power definition method:

S=p+jq=u _s ×i _s * (44)

Among them, S represents the complex power; p represents the instantaneous active power; q represents the instantaneous reactive power; i _s ^* represents the complex conjugate of i _s .

The instantaneous active power in the ABC coordinate system can be obtained from the scalar product of the instantaneous voltage vector and the current vector, and the instantaneous reactive power can be obtained from the vector product of the two, respectively expressed as:

Among them, u=[u _A ,u _B ,u _C ] ^T and i=[i _A ,i _B ,i _C ] ^T represent the phase voltage vector and the phase current vector respectively.

The voltage vector u _s is rewritten in the dq coordinate system as follows:

in, Represents the stator flux linkage in the dq coordinate system. Therefore, it can be concluded that the instantaneous active power and instantaneous reactive power of the three-phase motor input are:

Since i _s can also be expressed as So its differential can be expressed as:

Among them, θ ₁ represents the angle between the current vector i _s and the d axis.

Therefore, it can be seen from the above formula that the change of the stator current in the d-q coordinate axis is related to the change of the current amplitude and angle, and when the motor is running in a steady state, the motor torque is stable, and the component of the stator current on the q axis is not Change, so the stator current amplitude does not change, and the stator current vector and the d-axis rotate at the same speed, so the vector angle between the stator current and the d-axis does not change. Moreover, in the process of direct power control, the instantaneous power is required to be 0 and the power factor is 1, so let d=0, that is:

Among them, γ is the angle between the current vector i _s and the q axis.

Therefore, the instantaneous active power of the three-phase input of the motor can be written as:

Among them, δ is the angle between the voltage vector u _s and the q axis, and θ is the angle between the voltage vector and the current vector.

Because γ=θ+δ, and when the reactive power is zero, that is, when the power factor is 1, the power factor angle is zero, that is to say, i _s and u _s should be coaxial, that is, γ=δ. make:

Therefore, the above formula can be changed to:

The phase angle information θ _s of the voltage vector can be determined by γ and the rotor position angle θ _r , which can be expressed as:

θ _s =90°+δ+θ _r (54)

Among them, the expression of δ and θ _r can be expressed as:

Among them, P represents the number of pole pairs of the motor.

Step 6, through the coordinate transformation method, use the voltage vector signals u _sp and u _sq output by the PI regulator, and calculate the voltage vectors u _sα and u _sβ in the α-β coordinate system according to the phase angle information θ _s of the voltage vector. According to the schematic diagram of the coordinate relationship shown in Figure 2, the conversion relationship is:

Among them, θ _s is the angle between the voltage space vector u _s and the α axis.

Specific embodiment four: referring to Fig. 1, Fig. 2, Fig. 3 to illustrate this embodiment, this embodiment is a further limitation to the direct power control method of high-speed magnetic levitation synchronous motor based on space vector modulation described in specific embodiment one, said Space vector modulation part 3 includes the following steps:

Step 1, establishing a space vector modulation model.

Assuming that the calculated vector is between u _s non-zero vector u _s1 and u _s2 , using u _s1 is equivalent to u _s2 , according to the schematic diagram of space vector modulation in Figure 3, the equivalent relationship is as follows:

u _s T _s = u _s1 T _s1 + u _s2 T _s2 (57)

Among them, T _s represents the PWM period; T _s1 and T _s2 represent the action time of u _s1 and u _s2 respectively.

Step 2: Carry out vector decomposition of the voltage vector u _sα of the α-axis and the voltage vector u _sβ of the β-axis to obtain ideal voltage vectors u _α and u _β . According to the schematic diagram of space vector modulation in Figure 3, the equivalent relationship is rewritten in the α-β coordinate system as follows:

Fixed switching frequency can be achieved by solving for exact T _s1 and T _s2 .

Step three, according to the block diagram of the direct power control algorithm based on space vector modulation shown in Figure 1, the ideal voltage vectors u _α and u _β output three-phase current signals i _A , i _B , i _C through the PWM inverter, so that Adjust the magnitude of the stator current vector to change the instantaneous reactive power. At the same time, the output three-phase currents i _A , i _B , and i _C undergo coordinate transformation to obtain the current vectors i _α and i _β in the α-β coordinate system, which together with the voltage vectors u _α and u _β are used as the actual calculated instantaneous active power The input of p ^* and instantaneous reactive power q ^* realizes the closed-loop control of direct power control.

The present invention can be used as a new type of direct power control method of high-speed magnetic levitation synchronous motor based on space vector modulation. It overcomes the problems that the switching frequency is not fixed and the hysteresis width is not easy to determine. This method is simple in engineering, does not need a hysteresis controller and complex flux angle calculation, and improves the operating efficiency of the high-speed permanent magnet synchronous motor.

Parts not described in detail in the present invention belong to the well-known technology in the art.

Claims (3)

1. a kind of direct power control method based on the high-speed permanent magnet synchronous motor of space vector modulation, is characterized in that, comprises the following steps: (1) Based on the assumption of the ideal condition of the permanent magnet synchronous motor, the basic mathematical model of the three-phase PMSM is established. The established permanent magnet synchronous motor model is: In the ABC coordinate system, the stator current and voltage space vectors can be expressed as: Among them, a=e ^j120° represents the operator space; R _s is the phase resistance; L _s is the equivalent phase inductance, which is the difference between the phase inductance and mutual inductance; ψ _f is the excitation space vector of the permanent magnet; θ _r is the relative A of the permanent magnet the rotation angle of the axis; (2) Through the direct power control algorithm, the voltage vector in the α-β coordinate system is obtained; the given speed ω* and the measured speed ω are made difference, and the difference is input to the PI regulator for speed regulation, and the output value of the PI regulator is used as The given value of instantaneous active power p* and the given value of instantaneous reactive power q* are set to 0, the instantaneous active power p*, reactive power q* and the actual calculated instantaneous active power p, reactive power q The difference is made separately, and the difference is sent to two PI regulators for adjustment. The output of the two PI regulators is based on the phase information of the voltage vector, and the voltage vector u _sα of the α-axis and the voltage vector u _sβ of the β-axis are obtained through coordinate changes. ; (3) Through space vector modulation, the ideal voltage signal is obtained; the voltage vector u _sα of the α axis and the voltage vector u _sβ of the β axis are vector decomposed to obtain the ideal voltage vectors u _α and u _β ; the voltage signal is passed through PWM The inverter outputs three-phase current signals i _A , i _B , i _C to adjust the stator current vector amplitude to change the instantaneous reactive power; at the same time, the output three-phase current signals i _A , i _B , i _C undergo coordinate transformation, The current vectors i _α and i _β in the α-β coordinate system are obtained, together with the voltage vectors u _α and u _β , they are used as the input of the actual calculated instantaneous active power p* and instantaneous reactive power q*. 2. the direct power control method of the high-speed permanent magnet synchronous motor based on space vector modulation according to claim 1, is characterized in that: described direct power control method is a kind of instantaneous active power of motor based on PI regulator and instantaneous reactive power two parameters as the control algorithm of the control quantity, the specific steps of the method are as follows: (1) In the ABC coordinate system, assume that the state functions of the six switching tubes of the inverter are: S _A , S _B and S _C , which are expressed as: Then, the three-phase line voltage can be expressed as: Among them, u _d represents d-axis voltage, u _AB , u _BC , u _CA represent three-phase line voltage; Combined with u _A + u _B + u _C = 0, the three-phase phase voltage vector is obtained as: Among them, u _A , u _B , u _C represent three-phase phase voltage; (2) Transform the collected three-phase current signals i _A , i _B and i _C into current vectors i _α and i _β in the α-β coordinate system through the coordinate transformation method, and the conversion relationship is: (3) Using the calculation formula of instantaneous power, solve the three-phase instantaneous active power p and reactive power q of the permanent magnet synchronous motor in the α-β coordinate system; The calculation formula of instantaneous power is: The three-phase instantaneous active power p and reactive power q are respectively: (4) Make a difference between the given speed ω ^* and the measured speed ω, and the difference is input to the PI regulator for speed adjustment. The output value of the PI regulator is used as the given value of the instantaneous active power p ^* , and the instantaneous active power Make a difference between p ^* and the actual calculated instantaneous active power p, and the difference is sent to the PI regulator to obtain the voltage vector u _sp , the given value of the instantaneous reactive power q ^* is set to 0, and the instantaneous reactive power q ^* and The instantaneous reactive power q obtained by the actual calculation is subtracted, and the difference is sent to the PI regulator to obtain the voltage vector u _sq ; (5) According to the derivation of the instantaneous power theory of the permanent magnet synchronous motor, the phase angle information θ _s of the voltage vector is solved; The instantaneous active power in the ABC coordinate system can be obtained from the scalar product of the instantaneous voltage vector and the current vector, and the instantaneous reactive power can be obtained from the vector product of the two, respectively expressed as: Among them, u=[u _A ,u _B ,u _C ] ^T and i=[i _A ,i _B ,i _C ] ^T represent phase voltage vector and phase current vector respectively; Therefore, the three-phase input instantaneous active power and instantaneous reactive power of the motor are respectively: The change of the stator current in the d-q coordinate axis is related to the change of the current amplitude and angle, and when the motor is running in a steady state, the motor torque is stable, and the component of the stator current on the q-axis remains unchanged, so the stator current amplitude does not change , and the stator current vector and the d-axis rotate at the same speed, so the vector angle between the stator current and the d-axis does not change, and, in the process of direct power control, the instantaneous power is required to be 0, and the power factor is 1, so let q=0; Therefore, the instantaneous active power of the three-phase input of the motor can be written as: Among them, γ is the angle between the current vector i _s and the q-axis, δ is the angle between the voltage vector u _s and the q-axis, and θ is the angle between the voltage vector and the current vector; Because γ=θ+δ, and when the reactive power is zero, that is, when the power factor is 1, the power factor angle is zero, that is to say, i _s and u _s should be coaxial, that is, γ=δ. make: Therefore, the above formula can be changed to: The phase angle information θ _s of the voltage vector can be determined by γ and the rotor position angle θ _r , which can be expressed as: θ _s =90°+δ+θ _r (14) Among them, the expressions of δ and _θr can be expressed as: Among them, P represents the number of pole pairs of the motor. (6) Through the coordinate transformation method, using the voltage vector signals u _sp and u _sq output by the PI regulator, and according to the phase angle information θ _s of the voltage vector, the voltage vectors u _sα and u _sβ in the α-β coordinate system are solved, The conversion relationship is: Among them, θ _s is the angle between the voltage space vector u _s and the α axis. 3. the direct power control method of the high-speed permanent magnet synchronous motor based on space vector modulation according to claim 1, is characterized in that: described direct power control method is a kind of direct power control method based on space vector modulation of high speed permanent magnet synchronous motor Power control algorithm, the concrete steps of this method are: (1) Establish a space vector modulation model Assuming that the calculated vector is between u _s non-zero vector u _s1 and u _s2 , using u _s1 is equivalent to u _s2 , the equivalent relationship is as follows: u _s T _s = u _s1 T _s1 + u _s2 T _s2 (17) Among them, T _s represents the PWM period; T _s1 and T _s2 represent the action time of u _s1 and u _s2 respectively; (2) The voltage vector u _sα of the α-axis and the voltage vector u _sβ of the β-axis are vector-decomposed to obtain the ideal voltage vectors u _α and u _β , and the equivalent relationship is rewritten in the α-β coordinate system as follows: Fixed switching frequency can be achieved by solving accurate T _s1 and T _s2 ; (3) The ideal voltage vectors u _α and u _β output three-phase current signals i _A , i _B , i _C through the PWM inverter, thereby adjusting the magnitude of the stator current vector to change the instantaneous reactive power. At the same time, the output three-phase The phase currents i _A , i _B , and i _C undergo coordinate transformation to obtain the current vectors i _α and i _β in the α-β coordinate system, which together with the voltage vectors u _α and u _β are used as the actual calculated instantaneous active power p* and instantaneous reactive power The input of power q* realizes the closed-loop control of direct power control.