阅读说明：本技术 一种交流伺服系统高响应电流控制方法 (High-response current control method for alternating current servo system ) 是由 赵云 廖政斌 王泽飞 菜美东 宋茂良 于 2019-10-14 设计创作，主要内容包括：本发明属于电流控制技术领域,公开了一种交流伺服系统高响应电流控制方法及控制系统,采用电流控制周期内PWM占空比双次刷新的方式减小电压输出滞后；采用电流预测控制算法,将本时刻采样的电流通过预测控制算法得到下一时刻的预测电压并作为电流环的输出,抵消采样延时；并针对dq轴电压耦合采用复矢量解耦控制。仿真试验表明,对比于常规的PI调节器,本发明具有更优的电流响应特性；本发明改善了电流环性能,提高了响应,在某些高响应的应用场合能很好地满足快速性要求；本发明得出的解耦后的电流预测中,电流环带宽最宽,其响应最快。(The invention belongs to the technical field of current control, and discloses a high-response current control method and a high-response current control system for an alternating current servo system, wherein voltage output lag is reduced by adopting a PWM duty ratio double-refresh mode in a current control period; adopting a current prediction control algorithm, obtaining the predicted voltage of the current sampled at the moment through the prediction control algorithm and using the predicted voltage as the output of a current loop to offset sampling delay; and complex vector decoupling control is adopted for dq axis voltage coupling. Simulation tests show that compared with a conventional PI regulator, the current-controlled type PI regulator has a better current response characteristic; the invention improves the current loop performance, improves the response, and can well meet the requirement of rapidity in certain high-response application occasions; in the decoupled current prediction obtained by the invention, the current loop bandwidth is widest, and the response is fastest.)

1. The high-response current control method of the alternating current servo system is characterized in that the high-response current control method of the alternating current servo system obtains predicted voltage of the next moment by current sampled at the moment through a current prediction control algorithm and uses the predicted voltage as the output of a current loop, sampling delay is offset, and complex vector decoupling is adopted for controlling dq axis voltage coupling;

the method for controlling complex vector decoupling specifically comprises the following steps:

decoupling of a dq-axis voltage equation is realized by taking the error quantity of the q axis as compensation of a d-axis integral term and taking the error quantity of the d axis as compensation of a q-axis integral term;

current is given in the k period

2. The method for controlling the high response current of the ac servo system as claimed in claim 1, wherein before the current sampled at the current moment is passed through the current predictive control algorithm to obtain the predicted voltage at the next moment and used as the output of the current loop, the following steps are performed: and voltage output lag is reduced by adopting a PWM duty ratio double refreshing mode in a current control period.

3. The method for controlling the high response current of an ac servo system as claimed in claim 1, wherein the current predictive control algorithm is:

the voltage and flux linkage equation of the permanent magnet synchronous motor under a rotating coordinate system is as follows:

u_d、u_qthe voltages of a direct axis and a quadrature axis of the permanent magnet synchronous motor are obtained; i.e. i_d、i_qDirect and quadrature currents; psi_d、ψ_qThe magnetic flux linkage is a direct-axis magnetic flux linkage and a quadrature-axis magnetic flux linkage; l is_d、L_qDirect axis and quadrature axis inductors; r is a stator resistor; psi_fIs a permanent magnet flux linkage.

The surface-mounted synchronous motor is provided with L_d＝L_qThe state equation for current derived from the voltage equation is:

taking the current of the motor as a state space variable, and converting into the following state space variable according to a state equation:

u is at t₀Constant between t, let t₀Kt, t (k +1) t, yielding:

x(k+1)＝A_φx(k)+A^-1(A_φ-I)Bu(k)+A^-1(A_φ-I)D(k)

in the above formula, the first and second carbon atoms are,

sinω_eT_s≈ω_eT_s，

by current predictive control principle

in the formula: l is₀，R₀，ψ_f0Are all motor parameters.

4. An ac servo high-response current control system of the ac servo high-response current control method as claimed in claim 1.

5. An information data processing terminal for implementing the high-response current control method of the AC servo system as claimed in any one of claims 1 to 3.

6. A computer-readable storage medium comprising instructions that, when executed on a computer, cause the computer to perform the method of high-response current control for an ac servo system according to any one of claims 1 to 3.

Technical Field

The invention belongs to the technical field of current control, and particularly relates to a high-response current control method for an alternating current servo system.

Background

Currently, the closest prior art:

an alternating current servo system taking a Permanent Magnet Synchronous Motor (PMSM) as a control object mainly aims at high efficiency, high precision and high response performance, and commonly used control modes comprise PI control and hysteresis control, wherein although the PI control is simple and convenient, the AC axis and the DC axis are coupled to influence the dynamic response of a current loop, although the response of the current loop of the hysteresis control is quick, the switching frequency under the algorithm is not fixed, the output current contains harmonic distortion, and a steady-state error exists. Therefore, in order to improve the current response characteristic of a servo system and ensure the stable current output, documents of high-performance current control strategies of alternating current permanent magnet synchronous motors, precise control methods of permanent magnet synchronous motors and a plurality of problem researches propose methods for double sampling and double PWM refreshing of stator current in one carrier period, and reduce sampling delay to improve the response characteristic of the system; the document 'AC servo system non-time-lag feedback high-performance drive control strategy research' introduces speed instruction feedforward and acceleration instruction feedforward to improve the system response, and reduces the amplitude of a modulation wave and improves the utilization rate of direct current through the injection of third harmonic, so as to improve the system response. However, the above methods are all single in terms of improving the current loop bandwidth response.

In summary, the problems of the prior art are as follows:

(1) the current loop of the alternating current servo system usually uses a PI regulator to control the dq axis current, and the requirement for rapidity cannot be well met in certain high-response application occasions.

(2) The PI controls the coupling of the alternating axis and the direct axis to influence the dynamic response of a current loop.

(3) Although the hysteresis loop control current loop response is fast, the switching frequency under the algorithm is not fixed, the output current contains harmonic distortion, and a steady-state error exists.

The difficulty of solving the technical problems is as follows:

in order to improve the response speed of the current loop, the performance of the DSP is required to be higher by adopting a PWM double-refresh control mode.

The significance of solving the technical problems is as follows:

the invention reduces the time delay of the current loop in the conventional PI algorithm and solves the problem that the rapidity requirement cannot be well met in certain high-response application occasions. In the prior art, current sampling delay, voltage output lag, dq axis voltage coupling and the like can restrict the improvement of the response bandwidth of a current loop, so that the high response characteristic of the current loop of the alternating current servo system is influenced. The current prediction control algorithm can improve the current loop bandwidth and improve the current loop response speed by combining the dq axis complex vector.

Disclosure of Invention

Aiming at the problems in the prior art, the invention provides a high-response current control method for an alternating current servo system.

The invention is realized in this way, a high response current control method of AC servo system, adopt PWM duty cycle two times to refresh (PWM refreshes twice in a current control cycle) mode to reduce the voltage output lag in the current control cycle; adopting a current prediction control algorithm, obtaining the predicted voltage of the current sampled at the moment through the prediction control algorithm and using the predicted voltage as the output of a current loop to offset sampling delay; and complex vector decoupling control is adopted for dq axis voltage coupling.

Further, the current prediction control of the alternating current servo system specifically includes:

the voltage and flux linkage equation of the permanent magnet synchronous motor under a rotating coordinate system is as follows:

u_d、u_qthe voltages of a direct axis and a quadrature axis of the permanent magnet synchronous motor are obtained; i.e. i_d、i_qDirect and quadrature currents; psi_d、ψ_qThe magnetic flux linkage is a direct-axis magnetic flux linkage and a quadrature-axis magnetic flux linkage; l is_d、L_qDirect axis and quadrature axis inductors; r is a stator resistor; psi_fIs a permanent magnet flux linkage.

The surface-mounted synchronous motor is provided with L_d＝L_qL, derived from the equation of voltageThe current-out equation of state is:

taking the current of the motor as a state space variable, and according to the state equation, equation (6) can be converted into:

the general solution is as follows:

u is at t₀Constant between t, let t₀Kt, t ═ k +1) t, given as:

x(k+1)＝A_φx(k)+A^-1(A_φ-I)Bu(k)+A^-1(A_φ-I)D(k) (8)

in the above formula, the first and second carbon atoms are,

at T_sWhen small enough, cos omega_eT_s≈1，

sinω_eT_s≈ω_eT_s，

Therefore, it is not only easy to use

A_φ-I≈AT_sThe resulting current dispersion equation is as follows:

by current predictive control principleAvailable time k control variable u (k):

in the formula: l is₀，R₀，ψ_f0Are all motor parameters in the prediction algorithm.

Further, the complex vector decoupling control specifically includes:

the decoupling of the dq-axis voltage equation is realized by taking the error quantity of the q axis as the compensation of the d-axis integral term and taking the error quantity of the d axis as the compensation of the q-axis integral term.

FIG. 5 is a structural diagram of a complex vector decoupling control current loop, as shown in the figure, a current is given in the k-th period

And a sampling current i_d(k)、i_q(k) And the angular velocity omega of the motor_e(k) Generation of dq-axis voltages via current predictive control algorithms

Then, the current error is integrated and compensated to realize dq axis decoupling, and the generated voltage is used

6 paths of PWM signals are generated through space vector conversion, and finally, an inverter generates voltage to drive a motor.

The invention also aims to provide the high-response current control system of the alternating current servo system of the high-response current control method of the alternating current servo system.

Another object of the present invention is to provide an information data processing terminal for implementing the high-response current control method for the ac servo system.

Another object of the present invention is to provide a computer-readable storage medium (applicable to a drive) including instructions that, when executed on a computer, cause the computer to execute the ac servo system high-response current control method.

In summary, the advantages and positive effects of the invention are:

the invention adopts different solving methods aiming at different delays, the current loop adopts a current prediction control algorithm to improve the response of the current loop, and the current at the current moment is sampled to obtain the voltage at the next moment, so that the current sampling delay is reduced and the response is improved; the voltage output lag time is shortened by adopting a duty ratio double-refreshing control method; and a complex vector decoupling method is used for dq axis voltage coupling in the current prediction algorithm, so that the current loop performance is further improved, and the response is improved. Simulation tests show that compared with a conventional PI regulator, the current-controlled type PI regulator has a better current response characteristic; the method can well meet the requirement of rapidity in certain high-response application occasions.

In simulation verification, Matlab/Simulink software is used for simulating a current loop by adopting conventional PI regulator control and current prediction control. Motor parameters: the rated current of the motor is 6A, the rated rotating speed is 2000r/min, the rated torque is 5 N.m, the stator resistance is 3.15 omega, the stator inductance is 0.0085H, the stator flux linkage is 0.175Wb, the number of pole pairs of the motor is 4 pairs, and the moment of inertia is 0.008 Kg.m²。

The voltage of a direct current bus is 310V, the current sampling frequency is 20KHz, the carrier frequency is 10KHz, a step instruction with the speed of 1000r/min is given at the moment 0, a constant load of 5 N.m is suddenly added at the moment 0.2 second, three-phase current and dq-axis current waveforms under a PI algorithm and a current prediction control algorithm are obtained as shown in FIG. 6, and current prediction non-decoupling and decoupling dq-axis current are obtained as shown in FIG. 7.

As can be seen in fig. 6(a), the current under the PI control algorithm contains a large amount of harmonics, which is due to the serious hysteresis problem of the algorithm, and the waveform contains a large amount of noise, so that the waveform is non-sinusoidal; (b) the three-phase current waveform of the medium current prediction algorithm is basically sine wave. In the graphs (c) and (d), dq-axis current waveforms are measured by the PI control algorithm and the current prediction algorithm. When the load is suddenly changed, the d-axis current in the current prediction algorithm in (d) is smaller than the d-axis current in the PI control algorithm in (c) when the load is added by 5 N.m at 0.2 second of the motor. In a steady state situation, the dq axis current of the prediction algorithm is less than the dq axis current of the PI control algorithm in the no-load or load current prediction algorithm.

Fig. 7(a) d-axis current waveforms decoupled and un-decoupled are fluctuated when the motor is started, but the fluctuation of the decoupled current prediction control d-axis current is smaller than that of the un-decoupled current, the un-decoupled d-axis current has 1.2A jump when the load is suddenly applied for 0.2 second, and the decoupled current is basically kept constant; (b) the dq axis is decoupled and the q axis current for decoupling has no substantial change. This decoupled approach plays a role in improving current.

The sampling frequency of the single-time refreshing current of the duty ratio is 10KHz, the sampling frequency of the double-time refreshing is 20KHz, the sampling frequency of the current in the current prediction decoupling and decoupling algorithm is 20KHz, the carrier frequency is 10KHz, a step instruction of 1000r/min is given at the speed at the moment 0, and the rotating speed response waveforms under different algorithms are obtained as shown in FIG. 8.

Fig. 8 is a motor rotation speed response waveform under different algorithms, and it can be seen that the rotation speed response of a single refresh with a 10KHz duty ratio of current sampling frequency is the slowest, the duty ratio of the sampling frequency is 20KHz is the second of the rotation speed response of the refresh, the rotation speed response of the current prediction algorithm with the sampling frequency of 20KHz is faster, and the rotation speed response is further improved by the decoupled current prediction algorithm.

The above simulation is to analyze the current loop response from the time domain, and analyze the current loop response from the frequency domain, and by analyzing the magnitude of the closed loop cut-off frequency of the current loop, the larger the closed loop cut-off frequency is, the faster the transient response speed of the system is. A sinusoidal excitation with a certain amplitude is input to the d axis of the system current loop, and the frequency of the excitation is changed until the amplitude is attenuated to 0.707 times of the maximum value, at which time the frequency of the excitation is the bandwidth frequency (also called cut-off frequency) of the system current loop.

In Simulink simulation software, sinusoidal excitation with amplitude of 1A is input to a d-axis of a current loop, system current loop bandwidth frequencies under PI control and current prediction control are respectively obtained by changing excitation frequency, and an output response waveform of the d-axis of the system current loop is shown in fig. 9.

In fig. 9(a), (b), (c) and (d), the d-axis input sinusoidal excitation frequencies of the current loop are 1607Hz, 3183Hz, 4293Hz and 4535Hz respectively, the output response amplitudes are attenuated to 0.707 times of the maximum value, and the decoupled current prediction algorithm current loop bandwidth is widest and the response is fastest.

The invention adds complex vector decoupling on the current prediction control method and further improves the response speed of the current loop.

Drawings

Fig. 1 is a flowchart of a method for controlling a high response current of an ac servo system according to an embodiment of the present invention.

Fig. 2 is a block diagram of a system structure of a current loop conventional PI control according to an embodiment of the present invention.

FIG. 3 is a schematic diagram of a current sampling timing sequence according to an embodiment of the present invention.

Fig. 4 is a block diagram of a current prediction control structure according to an embodiment of the present invention.

Fig. 5 is a block diagram of a complex vector decoupling control structure provided in the embodiment of the present invention.

FIG. 6 illustrates three phase currents and dq axis currents under different algorithms provided by embodiments of the present invention;

in the figure: (a) is three-phase current under PI algorithm; (b) is a three-phase current under current predictive control; (c) is dq axis current under the PI algorithm; (d) is dq-axis current under the current prediction method.

FIG. 7 is a decoupled dq-axis current waveform provided by an embodiment of the invention;

in the figure: (a) is the d-axis current waveform; (b) the q-axis current waveform.

Fig. 8 is a waveform of the speed response under different algorithms provided by an embodiment of the invention.

FIG. 9 is an illustration of excitation and response under different algorithms provided by embodiments of the present invention;

in the figure: (a) is the excitation and response under a single refresh of duty cycle; (b) is the excitation and response under the double refresh of duty ratio; (c) excitation and response before current prediction decoupling; (d) is the excitation and response after the decoupling of the current prediction.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

The current loop of the alternating current servo system usually uses a PI regulator to control the dq axis current, and the requirement for rapidity cannot be well met in certain high-response application occasions. In the prior art, the PI controls the coupling of the alternating axis and the direct axis, and the dynamic response of a current loop is influenced. In the prior art, although the hysteresis loop control current loop response is fast, the switching frequency under the algorithm is not fixed, the output current contains harmonic distortion, and a steady-state error exists.

In order to solve the problems in the prior art, the present invention provides a method and a system for controlling a high response current of an ac servo system, and the present invention is described in detail below with reference to the accompanying drawings.

As shown in fig. 1, in the high-response current control method for the ac servo system according to the embodiment of the present invention, a PWM duty cycle is refreshed twice within a current control period (PWM is refreshed twice within one current control period) to reduce voltage output lag; adopting a current prediction control algorithm, obtaining the predicted voltage of the current sampled at the moment through the prediction control algorithm and using the predicted voltage as the output of a current loop to offset sampling delay; and complex vector decoupling control is adopted for dq axis voltage coupling.

In the embodiment of the present invention, the complex vector decoupling control specifically includes:

the decoupling of the dq-axis voltage equation is realized by taking the error quantity of the q axis as the compensation of the d-axis integral term and taking the error quantity of the d axis as the compensation of the q-axis integral term.

FIG. 5 is a structural diagram of a complex vector decoupling control current loop, as shown in the figure, a current is given in the k-th period

And a sampling current i_d(k)、i_q(k) And angular velocity of the motorω_e(k) Generation of dq-axis voltages via current predictive control algorithms

Then, the current error is integrated and compensated to realize dq axis decoupling, and the generated voltage is used6 paths of PWM signals are generated through space vector conversion, and finally, an inverter generates voltage to drive a motor.

The present invention will be further described with reference to the following examples.