CN103731082B - A kind of permanent-magnetic synchronous motor stator magnetic linkage method of estimation based on Direct Torque Control - Google Patents

Abstract

This paper discloses a closed-loop flux linkage estimation method applied to a direct torque control system of a permanent magnet synchronous motor. Use the voltage and current signals measured by real-time sampling to calculate according to the calculation formula of the voltage method flux linkage to obtain a preliminary estimated flux linkage, and then use the PI regulator to perform dynamic closed-loop correction with the target control flux linkage as the input to make it Finally track the upper target to control the magnetic link. The given control flux linkage of direct torque control is used as the target control flux linkage amplitude in the flux linkage estimator, the rotor position angle is obtained by using the position sensor, and the angle information is dynamically compensated as the angle information of the target control flux linkage . Through the closed-loop adjustment of the voltage method flux linkage estimator, it can effectively eliminate the flux calculation deviation caused by the DC bias and the initial integral value of the integral link, and accurately estimate the real flux linkage. In the actual direct torque control system It has good rapidity and robustness.

Description

A Method for Estimating Stator Flux Linkage of Permanent Magnet Synchronous Motor Based on Direct Torque Control

technical field

The invention relates to a method for estimating flux linkage of a permanent magnet synchronous motor, in particular to a method for estimating stator flux linkage of a permanent magnet synchronous motor based on direct torque control.

Background technique

In the field of motor dynamic control, direct torque control technology is more and more applied to permanent magnet synchronous motors, asynchronous machines and other new motors because of its fast and accurate control performance. In direct torque dynamic control, the two direct control objects are torque and flux linkage, both of which are calculated from changes in voltage, current, position information, and motor parameters, because torque is determined by flux linkage and other parameters Therefore, the calculation of the two control objects is essentially the accurate calculation of the flux linkage of the motor.

Flux linkage calculation methods can generally be divided into voltage calculation method and current calculation method. The voltage calculation method is relatively simple. It uses the stator voltage equation and is calculated by an integrator; the current method uses the rotor voltage equation and substitutes it in to obtain the flux linkage calculation equation. The theoretical model of the voltage method is simple, but in practical applications, there are some problems, such as the influence of the stator resistance change at low speed, the initial value of the integral, and the DC bias in the sampling signal. The current calculation method also has shortcomings. The current method relies more on the motor parameters, and during the operation of the motor, with the change of temperature and speed, the motor parameters will also change to a certain extent. In addition, it is affected by the time constant of the rotor at high speed, resulting in The current method flux calculation is not as accurate as the voltage method. According to the characteristics of the voltage method and the current method, the calculation methods of the low-speed current method and the high-speed voltage method can be used, and the conversion between the two can be realized through a filter, but this method is more complicated and can be performed within the working area of the two methods. , to achieve accurate calculations. Many scholars have made many improvement methods according to the characteristics of voltage method and current method, such as adding low-pass filter method, high-low pass filter matching method, closed-loop correction method, Kalman filter method, etc., these methods have improved to a certain extent. The accuracy of the flux linkage estimation is improved, but it also brings some problems. The method of adding a filter can eliminate the initial integral error and attenuate the DC offset, but it will bring a phase amplitude offset. The combination of high and low pass filters can make the low pass On the basis of the filter, the effect of flux linkage estimation is improved to a certain extent, but more parameters are introduced. The closed-loop correction method has a good effect in steady state, but in the actual direct torque control system, the effect of direct torque control in dynamic state It will interact with the calculation effect of the flux linkage. The result of the double influence makes the entire control system easily lose stability. The calculation method of the flux linkage with the filter also has the problem of poor dynamic effect. The Kalman filter alleviates it to a certain extent. The shortcomings of the current method are eliminated, but the dependence on the motor parameters in the calculation of the flux linkage cannot be avoided. For motors with large changes in motor parameters under different working conditions, there will still be large calculation errors. Adding the Kalman filter also requires relatively complex calculations.

Contents of the invention

Purpose of the invention: Aiming at the above prior art, a permanent magnet synchronous motor stator flux estimation method based on direct torque control is proposed, through the closed-loop adjustment of the voltage method flux estimator, it can effectively eliminate the direct current bias of the integral link. , Integrate the flux calculation deviation caused by the initial value, and accurately estimate the real flux.

Technical solution: A permanent magnet synchronous motor stator flux linkage estimation method based on direct torque control. When calculating the flux linkage in the initial control cycle, the three-phase voltages U _a , U _b , and U _c of the permanent magnet synchronous motor are measured in real time. and the three-phase current i _a , i _b , i _c , transform the voltage and current in the three-phase rotating coordinate system into the voltage u _α , u _β , current i _α , i _β in the αβ coordinate system; in the direct torque In one control cycle of the control system, the voltage u _α and u _β are integrated and calculated according to the formula (1), and the preliminary estimated flux linkage is obtained

Among them, R _s is the motor stator resistance;

The initial estimated flux linkage and target control flux linkage reference value The DC bias voltage compensation V _α and V _β are obtained through the PI control algorithm; among them, the integral items sum _α and sum _β of the PI control algorithm are obtained according to formula (2):

Among them, K _i is the integral coefficient; sum _α ′ and sum′ _β are the integral items obtained in the previous control cycle of the direct torque control system, and the initial values of sum _α ′ and sum′ _β are both 0; To control the flux reference value for the target:

Among them, ψ ^* is the given control flux linkage of the direct torque control system, ψ ^* is the amplitude of the target control flux linkage; θ is the stator flux angle of the target control flux linkage;

According to formula (3), the DC bias voltage compensation amounts V _α and V _β are obtained:

Among them, K _p is the proportional coefficient;

According to the DC bias voltage compensation amount V _α , V _β , the motor flux linkage estimated by the flux linkage estimator is calculated according to formula (4)

In the next control cycle, use the estimated motor flux linkage of the previous control cycle Replace the initial estimate of the flux linkage Substituting formula (2) into the calculation to form a closed-loop adjustment system; when the closed-loop regulator realizes the target control flux linkage When tracking dynamically, the flux linkage estimator estimates the flux linkage is the exact motor flux linkage.

As a preferred solution of the present invention, the rotor position sensor is used to obtain the rotor position angle γ of the motor under direct torque control, and after closed-loop dynamic compensation is performed on the rotor position angle γ, the stator flux of the target control flux linkage is obtained. Chain angle θ; the dynamic compensation calculation is shown in formula (5):

θ=γ+δ(5)

Wherein, γ is the rotor position angle; δ is the torque angle, and the compensation angle to the rotor position angle is equal to the torque angle;

The calculation of the torque angle is shown in formula (6):

in, for the reason stated Using the target control flux stator flux angle calculated by the arc tangent function; is the estimated motor flux calculated according to the formula (2) The stator flux angle of the motor flux calculated by using the arctangent function;

In the closed-loop compensation process, the accumulator is used to calculate the compensation value periodically, as shown in formula (7):

sum=sum+gel(7)

Wherein sum is the compensation angle accumulator, and its initial value is 0, and gel is the compensation angle of the rotor position angle calculated according to the formula (6); the accumulator memorizes the angle compensation value of the direct torque control system control cycle, And it is substituted into the angle compensation calculation of the next cycle to realize the periodic dynamic compensation of the angle, and the cycle value is set to 0.3-3 electrical cycles of the motor.

Beneficial effects: Compared with the prior art, the present invention utilizes the voltage and current signals measured by real-time sampling, calculates according to the flux calculation formula of the voltage method, obtains a preliminary estimated flux linkage, and then uses it and the target control flux linkage as input The quantity uses the PI regulator for dynamic closed-loop correction, so that it can finally track the upper target control flux linkage. The given control flux linkage of direct torque control is used as the target control flux linkage amplitude in the flux linkage estimator, the rotor position angle is obtained by using the position sensor, and the angle information is dynamically compensated as the angle information of the target control flux linkage . Through the closed-loop adjustment of the voltage method flux linkage estimator, the present invention eliminates the flux linkage DC bias and integral initial value error problems in the flux linkage calculation, effectively improves the accuracy of the flux linkage calculation, and at the same time reduces the Sensitivity to stator resistance in the calculation of flux linkage, compared with the calculation method of adding filter link flux linkage and the closed-loop flux linkage calculation method without angle compensation, the algorithm of the present invention shows better accuracy and robustness in the direct torque control system Stickiness. In the actual direct torque control system, the accuracy of the angle information of the flux linkage is the key link of the stability of the whole control system, so the estimation of the angle information of the target flux linkage should be stable, continuous and accurate, because the rotor position is used in the present invention Angle is the basic angle information of flux linkage estimation, so it has better stability and continuity. Angle compensation can effectively improve the accuracy of flux linkage estimation.

Description of drawings

Figure 1 is a block diagram of direct torque control of a permanent magnet motor;

Figure 2 is an overall block diagram for flux linkage calculation;

Fig. 3 is a functional block diagram for flux linkage angle compensation;

Fig. 4 is the calculation block diagram for flux linkage angle compensation;

Fig. 5 is the flux linkage calculation effect for adopting the method of the present invention to carry out angle compensation;

Figure 6 is the calculation effect of flux linkage without angle compensation;

Figure 7 The change of angle compensation value

detailed description

The present invention will be further explained below in conjunction with the accompanying drawings.

The direct torque control system block diagram of the matlab simulation embodiment of the present invention is as shown in Figure 1, wherein, the parameter of permanent magnet synchronous motor is: number of pole pairs p=2, stator resistance Rs= _2Ω , direct axis inductance _Ld = 31.06mH, quadrature axis inductance L _q =80.69mH, permanent magnet flux linkage The direct torque control system adopts the switch table vector control method, and the control parameters used in the control process are determined according to the characteristics of the control system. In this embodiment, the matlab simulation step length is set to 1×10 ^-5 s, and the DC power supply voltage is set to 700V , in the flux linkage estimator, K _p =100, the integral coefficient K _i =200, the angle compensation period is 0.018s, when the angle compensation is performed, the output limit of the PI regulator is [-120,120], and the control speed setting value is 1300r/ min, the load torque is 40N·m, the given value of the control flux linkage is 1.13Wb, and the voltage sampling contains a DC bias of 3V.

The overall functional block diagram of the flux linkage estimator shown in Figure 2 uses the voltage method to calculate the flux linkage. First, it needs to use the sensor to sample the voltage and current signals, and use the position sensor to sample the rotor position angle γ. In the initial calculation of flux linkage, the three-phase voltage U _a , U _b , U _c of the permanent magnet synchronous motor and the three-phase current _ia , _ib , _ic were measured in real time, and the three-phase rotating coordinate system Transform the voltage and current into the voltage u _α , u _β , current i _α , i _β of the αβ coordinate system; the coordinate transformation formula is shown in the following formula:

$\left[\begin{array}{c}{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}\\ {\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; \&beta;</span>}}\end{array}\right]<span\; class="notranslate">\; =</span>\left[\begin{array}{ccc}\mathrm{<span\; class="notranslate">\; 1</span>}& \mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 2</span>}& \mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 2</span>}\\ \mathrm{<span\; class="notranslate">\; 0</span>}& \sqrt{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 2</span>}& <span\; class="notranslate">\; -</span>\sqrt{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 2</span>}\end{array}\right]\left[\begin{array}{c}{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}\\ {\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}\\ {\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}\end{array}\right]$

$\left[\begin{array}{c}{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}\\ {\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; \&beta;</span>}}\end{array}\right]<span\; class="notranslate">\; =</span>\left[\begin{array}{ccc}\mathrm{<span\; class="notranslate">\; 1</span>}& \mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 2</span>}& \mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 2</span>}\\ \mathrm{<span\; class="notranslate">\; 0</span>}& \sqrt{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 2</span>}& <span\; class="notranslate">\; -</span>\sqrt{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 2</span>}\end{array}\right]\left[\begin{array}{c}{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}\\ {\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}\\ {\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}\end{array}\right]$

In one control cycle of the direct torque control system, the voltage u _α and u _β are integrated and calculated according to formula (1), and the preliminary estimated flux linkage is obtained

Among them, R _s is the motor stator resistance;

The initial estimated flux linkage and target control flux linkage reference value The DC offset voltage compensation V _α and V _β are obtained through the PI control algorithm; a closed-loop adjustment system is formed through the PI regulator, and the sampling error in the digital control system and the initial value error of the integral calculation caused by the position of the motor rotor are analyzed. dynamic correction. Among them, the proportional integral link of the PI controller is calculated according to formula (2) and formula (3); among them, the integral items sum _α and sum _β of the PI control algorithm are obtained according to formula (2):

Among them, K _i is the integral coefficient; sum _α ′ and sum′ _β are the integral items obtained in the previous control cycle of the direct torque control system, and the initial values of sum _α ′ and sum′ _β are both 0; To control the flux reference value for the target:

Among them, ψ ^* is the given control flux linkage of the direct torque control system, ψ ^* is the amplitude of the target control flux linkage; θ is the stator flux angle of the target control flux linkage;

According to formula (3), the DC bias voltage compensation amounts V _α and V _β are obtained:

Among them, K _p is the proportional coefficient;

According to the DC bias voltage compensation amount V _α , V _β , the motor flux linkage estimated by the flux linkage estimator is calculated according to formula (4)

When the closed-loop regulator achieves the target control flux linkage During dynamic tracking, the DC bias voltage compensation V _α and V _β are both 0, and the preliminary estimated flux linkage is the exact motor flux linkage

Among them, the given control flux linkage ψ ^* of the direct torque control system is used as the target control flux linkage amplitude, and the given value of the flux linkage within the rated speed operating range of the motor is given according to the principle of the highest efficiency and the smallest loss. , when the motor speed is higher than the rated speed, the flux linkage amplitude is given according to the field weakening algorithm; the given amplitude of the target control flux linkage is shown in the following formula:

$\left\{\begin{array}{c}{\mathrm{<span\; class="notranslate">\; \&psi;</span>}}^{<span\; class="notranslate">\; *</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; l</span>}}<span\; class="notranslate">\; )</span>\\ {\mathrm{<span\; class="notranslate">\; \&psi;</span>}}^{<span\; class="notranslate">\; *</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; f</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; Te</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span>\\ {\mathrm{<span\; class="notranslate">\; \&psi;</span>}}^{<span\; class="notranslate">\; *</span>}<span\; class="notranslate">\; <</span>\frac{\mathrm{<span\; class="notranslate">\; \&rho;</span>}}{\mathrm{<span\; class="notranslate">\; \&rho;</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&phi;</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}}\end{array}\right.$

Among them, P _l is the loss power of the motor, ρ = quadrature axis inductance/direct axis inductance, that is, the saliency of the motor, Te is the electromagnetic torque of the motor, and f(P _l ) is the calculation amplitude of flux linkage based on the principle of minimum loss value, φ _f is the permanent magnet flux linkage. When the motor runs above the rated speed, the target control flux linkage setting amplitude is calculated according to the flux-weakening algorithm f'(Te,n), and the two calculation functions are related to the characteristics of the motor itself and the actual control algorithm target. For motors with unequal inductance between AC and D axis, the maximum value constraint is established according to the principle of the linearity of the motor torque and torque angle change.

Figure 3 shows the vector schematic diagram of angle compensation. The angle information of the target control flux linkage is measured by the position sensor. Because the measured position information signal is not an accurate flux linkage calculation angle information signal, the position information needs to be corrected. The signal is angle compensated to obtain the stator flux linkage angle θ. Use the rotor position sensor to obtain the rotor position angle γ of the motor under direct torque control, and after performing closed-loop dynamic compensation to the rotor position angle γ, obtain the stator flux linkage angle θ of the target control flux linkage; the dynamic Compensation calculation is shown in formula (5):

θ=γ+δ(5)

Wherein, γ is the rotor position angle; δ is the torque angle, and the compensation angle to the rotor position angle is equal to the torque angle;

The calculation of the torque angle is shown in formula (6):

in, for the reason stated Using the target control flux stator flux angle calculated by the arc tangent function; is the estimated motor flux calculated according to the formula (2) The stator flux angle of the motor flux calculated by using the arctangent function;

Figure 3 is the stator flux linkage, which includes the flux linkage generated by the stator current and permanent magnet flux linkage after magnetic field modulation It can be seen from Fig. 3 that in the αβ coordinate system, the stator flux linkage angle decomposed into two coordinate axes is the sum of the rotor position angle γ and the torque angle δ. Combined with Figure 3, the torque equation of the motor can be obtained:

${\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; em</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 3</span>}\mathrm{<span\; class="notranslate">\; p</span>}<span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; \&psi;</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; |</span>}{{\mathrm{<span\; class="notranslate">\; 4</span>}\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}}{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; q</span>}}}<span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; \&psi;</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}}{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; q</span>}}\mathrm{<span\; class="notranslate">\; sin</span>}\mathrm{<span\; class="notranslate">\; \&delta;</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; \&psi;</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; |</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; q</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; sin</span>}\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&delta;</span>}<span\; class="notranslate">\; ]</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 7</span>}<span\; class="notranslate">\; )</span>$

Among them, T _em is the electromagnetic torque of the motor, δ is the angle between the stator and rotor flux linkage, that is, the torque angle, p is the number of pole pairs of the stator winding, L _d is the direct axis inductance of the motor, L _q is the quadrature axis inductance of the motor, ψ _s is the amplitude of stator flux linkage. It can be seen from formula (7) that the torque is a physical quantity related to the torque angle, and its specific relationship is determined according to the corresponding parameters of the motor. And when other parameters of the motor remain unchanged, the torque of the motor is proportional to sin δ, that is, δ is in the range of 0-90 degrees. As the torque of the motor increases, the torque angle will also increase. The flux angle is the sum of the torque angle and the rotational speed position angle. If no angle compensation is performed, it is equivalent to directly taking the rotational speed position angle as the flux linkage angle. When the stator flux linkage amplitude is constant, the Under normal circumstances, because the torque angle is small, it will not bring a large error. If the torque angle is large in the case of high torque, it will bring a large flux calculation error, so that the entire DTC The control system cannot achieve the expected effect, so it is necessary to perform accurate angle compensation. For permanent magnet motors with a saliency ratio not equal to 1, the torque angle is relatively large in the case of high torque operation. If angle compensation is not used, Flux linkage calculation errors will also be large.

In the closed-loop compensation process, the accumulator is used to calculate the compensation value periodically, as shown in formula (8):

sum=sum+gel(8)

Wherein sum is the compensation angle accumulator, and its initial value is 0, and gel is the compensation angle of the rotor position angle calculated according to the formula (6); the accumulator memorizes the angle compensation value of the direct torque control system control cycle, And it is substituted into the angle compensation calculation of the next cycle to realize the periodic dynamic compensation of the angle, and the cycle value is set to 0.3-3 electrical cycles of the motor.

As shown in Figure 4, it is the specific process of flux linkage angle compensation. First, calculate the phase of the calculated flux linkage and the set flux linkage, according to the calculation characteristics of the tangent angle, and the sequence relationship between the calculated flux linkage and the set flux linkage phase , considering the angle difference between the two according to the situation, as shown in Figure 4, the motor flux linkage will be estimated Using the arctangent function to calculate the stator flux angle, the target control flux Use the target control flux stator flux angle calculated by the arctangent function, and then make a difference between the two, because the angle difference should be between [-π/2, π/2] under normal working conditions of the motor , so beyond this range, according to the specific situation, add a tangent angle period π, or decrease a period π, specifically when the difference between the two is less than -π/2, you should increase a period, when the two When the difference is greater than π/2, one cycle should be reduced, which ensures that the difference between the two outputs must fall within the interval [-π/2, π/2]. Because the entire direct torque control system requires a certain action response time, it is necessary to set a compensation cycle, and compensate once in each cycle. The cycle value setting generally selects 0.3-3 electrical cycles of the motor, and sets a compensation range. Long action threshold, update the compensation value within this range. If it is not within this range, that is, when the phase difference between the target control flux linkage and the calculated flux linkage is not large, there is no need to update the compensation value, and the value obtained in the previous compensation cycle is used. Angle compensation value, the compensator adopts an accumulator mode, because when the angle difference between the actual value and the calculated value is gel, if the compensation value is gel, the phase difference between the actual flux linkage and the calculated flux linkage will be close to zero after the compensation period , the compensation angle in the next compensation cycle will be close to zero, and then the phase difference between the two will recover in the next compensation cycle. In the actual direct torque control system, the final phase difference between the two will stabilize to gel/2, The advantage of using an accumulator is that as long as the phase difference between the calculated flux linkage and the actual flux linkage is locked and compensated, the compensation value will be stored in the accumulator, thereby stabilizing the actual and accurate phase difference and performing angle compensation. The phase difference between the flux linkage and the actual flux linkage falls within the set range. In addition, it is necessary to limit the output value of the accumulator to prevent a large compensation deviation from causing the entire control system to lose stability.

Figure 5 and Figure 6 compare the calculation of one-phase flux linkage in the two-phase rotating coordinate system in the case of using the closed-loop flux linkage estimation method in the direct torque control system with and without angle compensation. From the figure It can be seen that angle compensation can effectively improve the estimation effect of flux linkage.

Fig. 7 shows the change of the angle compensation calculation value after adopting the angle compensation method. It can be seen from the figure that the angle compensation value of the system can be quickly locked by using the angle compensation calculation module, and stable and accurate angle compensation for the flux linkage calculation module can be realized.

The above is only a preferred embodiment of the present invention, it should be pointed out that, for those of ordinary skill in the art, without departing from the principle of the present invention, some improvements and modifications can also be made, and these improvements and modifications can also be made. It should be regarded as the protection scope of the present invention.

Claims (1)

1. A permanent magnet synchronous motor stator flux linkage estimation method based on direct torque control is characterized by comprising the following steps: when the flux linkage is calculated in the initial control period, the three-phase voltage U of the permanent magnet synchronous motor is measured in real time_a、U_b、U_cAnd three-phase current i_a、i_b、i_cTransforming the voltage and current in the three-phase rotating coordinate system to the voltage u in the αβ coordinate system_α、u_βCurrent i_α、i_β(ii) a Applying said voltage u according to equation (1) during a control cycle of a direct torque control system_α、u_βIntegral calculation is carried out to obtain preliminary estimation flux linkage

Wherein R is_sIs a motor stator resistor;

flux linking the preliminary estimateAnd a target control flux linkage reference valueObtaining the compensation quantity V of the DC bias voltage by the PI control algorithm_α、V_β(ii) a Wherein, an integral term sum of the PI control algorithm is obtained according to the formula (2)_α、sum_β：

Wherein, K_iIs an integral coefficient; sum_α'、sum'_βIntegral term, sum, derived for a control period on a direct torque control system_α'、sum'_βThe initial values are all 0;control flux linkage reference values for target:

wherein psi^*For a given control flux, psi, of a direct torque control system^*Controlling the flux linkage amplitude as a target; theta is a stator flux linkage angle of the target control flux linkage;

obtaining a rotor position angle gamma of a motor under direct torque control by using a rotor position sensor, and obtaining a stator flux linkage angle theta of the target control flux linkage after performing closed-loop dynamic compensation on the rotor position angle gamma; the dynamic compensation calculation is as shown in equation (5):

θ＝γ+(5)

wherein γ is a rotor position angle; a torque angle, the compensation angle for the rotor position angle being equal to the torque angle;

the torque angle is calculated as shown in equation (6):

wherein,to be composed ofCalculating a target control flux linkage stator flux linkage angle by using an arc tangent function;for the estimated motor flux linkage calculated according to said equation (4)Calculating a stator flux linkage angle of the motor flux linkage by using an arc tangent function;

in the closed-loop compensation process, an accumulator accumulation calculation method is adopted when the compensation value is periodically calculated, as shown in formula (7):

sum＝sum+gel(7)

wherein sum is a compensation angle accumulator having an initial value of 0, and gel is a compensation angle of the rotor position angle calculated according to the formula (6); the accumulator memorizes the angle compensation value of the control period of the direct torque control system and substitutes the angle compensation value into the angle compensation calculation of the next period to realize the periodic dynamic compensation of the angle, and the period value is set to be 0.3-3 electric periods of the motor;

obtaining the DC offset voltage compensation quantity V according to the formula (3)_α、V_β：

Wherein, K_pIs a proportionality coefficient;

according to the compensation quantity V of the DC bias voltage_α、V_βCalculating the estimated motor flux linkage according to the formula (4)

Using the estimated motor flux linkage of the previous control period in the next control periodReplacing preliminary estimated flux linkageSubstituting the formula (2) for calculation to form a closed loop regulating system; when the closed-loop regulator realizes the control of the magnetic linkage to the target Estimated flux linkage of the flux linkage estimator during dynamic trackingNamely the accurate motor flux linkage.