阅读说明：本技术 一种永磁同步电机预测电流控制的计算延时补偿方法 (Calculation delay compensation method for prediction current control of permanent magnet synchronous motor ) 是由 姚绪梁 张飞洋 王景芳 黄乘齐 马赫 关琦 刘铜振 侯逸飞 罗兴鸿 邓日熹 于 2021-07-12 设计创作，主要内容包括：本发明公开了一种永磁同步电机预测电流控制的计算延时补偿方法,采样并计算得到定子电流和电压分量；将采样转速与给定转速之间差值经PI控制器输出得到q轴电流给定值,d轴电流采用的控制方式,再经逆Park变换得到电流给定值；得到预测模型,将采样参数代入预测模型得到预测电流和辅助电流,获得算法执行时间；利用算法执行时间预测由计算延时引起电流变化,并对电流采样值进行补偿；将补偿后电流代入预测模型计算下一时刻预测值,并利用价值函数进行遍历寻优,将最优电压矢量对应开关管驱动信号输出给逆变器以控制电机运行。本发明无需过采样以及不过分增加算法复杂度,对采样电流进行合理补偿解决计算延时所带来的控制性能下降问题。(The invention discloses a calculation delay compensation method for permanent magnet synchronous motor prediction current control, which comprises the steps of sampling and calculating to obtain stator current and voltage components; outputting the difference value between the sampling rotating speed and the given rotating speed through a PI controller to obtain a q-axis current given value, and adopting d-axis current The given current value is obtained through inverse Park conversion; obtaining a prediction model, substituting the sampling parameters into the prediction model to obtain a prediction current and an auxiliary current,obtaining algorithm execution time; predicting current change caused by calculating delay by using algorithm execution time, and compensating a current sampling value; substituting the compensated current into a prediction model to calculate a predicted value at the next moment, traversing and optimizing by using a value function, and outputting a driving signal of a switching tube corresponding to the optimal voltage vector to an inverter to control the motor to operate. The invention does not need oversampling and does not excessively increase algorithm complexity, and reasonably compensates the sampling current to solve the problem of control performance reduction caused by calculation delay.)

1. A calculation delay compensation method for permanent magnet synchronous motor prediction current control is characterized by comprising the following steps:

step 1: sampling three-phase stator current, rotor position information, a given rotating speed and a switching tube driving signal of the permanent magnet synchronous motor at the moment k, and obtaining stator current and voltage components under an alpha beta static coordinate system through Clark transformation;

step 2: the sampling rotation speed in the step 1With a given rotational speedThe difference value between the two is output by a PI controller to obtain a q-axis current given valued-axis current adoptionOfObtaining a current given value under an alpha beta static coordinate system through inverse Park transformation;

and step 3: establishing a mathematical model of the permanent magnet synchronous motor, discretizing the mathematical model to obtain a prediction model, substituting sampling parameters in the past moment into the prediction model to calculate to obtain a prediction current and an auxiliary current at the k moment, and combining the sampling current at the k moment and the discrete control period duration to obtain algorithm execution time at the k-1 moment;

and 4, step 4: predicting the current change caused by calculation delay in the k moment by using the algorithm execution time obtained in the step 3, and compensating the current sampling value of the k moment;

and 5: and (4) substituting the compensated current in the step (4) into a prediction model to calculate a predicted value at the next moment, performing traversal optimization by using a value function, and outputting a switching tube driving signal corresponding to the optimal voltage vector to an inverter to control the motor to operate.

2. The method for compensating for the calculated delay of the predictive current control of the permanent magnet synchronous motor according to claim 1, wherein: step 3, establishing a mathematical model of the permanent magnet synchronous motor, discretizing the mathematical model to obtain a prediction model, substituting the sampling parameters in the past moment into the prediction model to calculate the prediction current and the auxiliary current at the k moment, and combining the sampling current and the discrete control period duration at the k moment to obtain the algorithm execution time at the k-1 moment specifically as follows:

a mathematical model is established for the permanent magnet synchronous motor under an alpha beta static coordinate system, and the complex vector form is as follows:

in the formula u_sAnd i_sStator voltage and current vectors, respectively; r_s、L_sAnd Ψ_fRespectively a stator resistor, a stator inductor and a permanent magnet flux linkage; omega_eIs the rotor electrical angular velocity; theta_eIs the rotor electrical angle;

the mathematical model carries out first-order forward Euler dispersion to obtain a prediction model, and current, voltage and rotating speed sampling values in the k-1 moment are substituted into the prediction model to calculate to obtain predicted current at the k momentComprises the following steps:

in the formula (I), the compound is shown in the specification,the current sampling value at the k-1 moment; t is_sDiscrete control cycle duration;

defining the physical meaning of the auxiliary current at the moment k as the result of the sampling current at the moment k-1 under the continuous action of the voltage vector in the moment k-2 until the moment k, substituting the current and rotating speed sampling values at the moment k-1 and the voltage sampling value at the moment k-2 into a prediction model to calculate to obtain the auxiliary currentComprises the following steps:

assuming that the current change under the action of the actual voltage is linear change conforming to the prediction result, converting the linear change into the relation between the current difference at the moment k and the algorithm execution time at the moment k-1 to obtain the algorithm execution time at the moment k-1Comprises the following steps:

in the formula (I), the compound is shown in the specification,sampled values of the current at time k.

3. The method for compensating for the calculated delay of the predictive current control of a permanent magnet synchronous motor according to claim 1 or 2, wherein: step 4, predicting the current change caused by the calculation delay in the k moment by using the algorithm execution time obtained in the step 3, and compensating the current sampling value at the k moment specifically comprises the following steps:

assuming that the algorithm execution time at the time k is equal to the algorithm execution time at the time k-1, under the continuous action of the voltage at the previous time, the current variation caused by calculation delay at the time kAnd predicting the amount of current changeAnd therefore, the current change amount caused by the calculation delay in the k time is obtainedComprises the following steps:

compensating the current sampling value at the k moment to obtain compensated currentComprises the following steps:

4. the method for compensating for the calculated delay of the predictive current control of a permanent magnet synchronous motor according to claim 3, wherein: and 5, substituting the current compensated in the step 4 into a prediction model to calculate a predicted value at the next moment, performing traversal optimization by using a cost function, and outputting a switching tube driving signal corresponding to the optimal voltage vector to an inverter to control the motor to operate specifically as follows:

calculating the current predicted value of the compensated current at the k +1 moment under the action of each voltage vectorComprises the following steps:

in the formula (I), the compound is shown in the specification,for 7 basic voltage vectors V in a limited control set_iI ═ 0,1, …,6} in the form of a complex vector in the α β coordinate system;

substituting a current predicted value obtained by using the compensated current into a cost function to perform traversal optimization, selecting a basic voltage vector meeting the minimum cost function, and outputting a corresponding switch tube driving signal to an inverter to control the motor to operate, wherein the cost function specifically comprises the following steps:

in the formula (I), the compound is shown in the specification,a complex vector form given to the current.

Technical Field

The invention relates to a calculation delay compensation method for prediction current control of a permanent magnet synchronous motor, and belongs to the field of drive control of permanent magnet synchronous motor systems.

Background

The permanent magnet synchronous motor has the advantages of simple structure, high reliability, high power density and the like, and is widely applied to the fields of national defense industry, production transportation, traction drive and the like. In the field of control of permanent magnet synchronous motor driving systems, model predictive control methods have received much attention due to the advantages of fast dynamic response, simple control structure, capability of performing multi-objective control and nonlinear constraint condition processing, and the like. The finite set prediction current control is used as a classic control strategy, a prediction model is used for calculating a future output result of the system under given different control behaviors in a finite time domain range, and the optimal control behavior is selected by a cost function and then output to act on the system. In each control cycle, the algorithm will re-select the optimal control behavior to be applied according to the above steps based on the new sampling results. However, considering that the control strategy is actually implemented, compared with the traditional vector control strategy, the finite set prediction current control algorithm includes steps of model prediction, traversal optimization and the like, which require a large amount of calculation, so that the execution time of the algorithm is quite long, and the problem of control delay is generated. If the problem of calculating delay between sampling and control application is not considered in the design of the controller, the optimal control effect of the algorithm is influenced, and therefore the running performance of the motor is reduced.

At present, domestic and foreign researches on methods for solving the problem of calculation delay in model predictive control can be divided into indirect compensation methods and direct compensation methods. The indirect compensation method usually adopts a dead-beat control method, and the method reduces the calculated amount of the algorithm by avoiding the step of traversing optimization so as to achieve the purpose of indirect compensation, however, the method does not completely eliminate the influence of calculation delay, which means that the indirect compensation method is not the optimal solution for solving the problem of calculation delay. The two-step prediction is used as the most classical compensation method in the direct compensation method, model prediction and traversal optimization are carried out on the basis that the prediction model obtains the state variable through calculation in the previous step, and the optimal control quantity is registered and output until the starting time of the next moment. Although the method has been widely adopted in Model Predictive Control, a new Compensation method is proposed, for example, Jinqiu Gao et al in new comprehensive Strategy for Calculation Delay of fine Control Set Model Predictive Control in PMSM propose a new direct Compensation method, which adopts an oversampling mode to obtain the Current variation in the algorithm execution time, thereby compensating the Current sampling value at the Current moment. However, the method needs to perform current sampling twice in one control period, which increases the influence caused by sampling errors on the one hand, and on the other hand, the difficulty of hardware implementation is increased by adopting an oversampling manner and not fixing the second sampling time, which is undoubtedly a defect and a problem existing in the method. Therefore, on the premise of not increasing the sampling times and not excessively increasing the calculation amount and complexity of the algorithm, a simple and reliable calculation delay compensation method is urgently needed to be researched to improve the control performance of the system.

Disclosure of Invention

Aiming at the prior art, the technical problem to be solved by the invention is to provide a method for compensating the calculation delay of the prediction current control of the permanent magnet synchronous motor, which can reasonably compensate the sampling current to solve the problem of the reduction of the control performance caused by the calculation delay on the premise of not needing oversampling and not excessively increasing the complexity of an algorithm.

In order to solve the technical problem, the invention provides a method for calculating time delay compensation of permanent magnet synchronous motor prediction current control, which comprises the following steps:

step 1: sampling three-phase stator current, rotor position information, a given rotating speed and a switching tube driving signal of the permanent magnet synchronous motor at the moment k, and obtaining stator current and voltage components under an alpha beta static coordinate system through Clark transformation;

step 2: the sampling rotation speed in the step 1With a given rotational speedThe difference value between the two is output by a PI controller to obtain a q-axis current given valued-axis current adoptionObtaining a current given value under an alpha beta static coordinate system through inverse Park transformation;

and step 3: establishing a mathematical model of the permanent magnet synchronous motor, discretizing the mathematical model to obtain a prediction model, substituting sampling parameters in the past moment into the prediction model to calculate to obtain a prediction current and an auxiliary current at the k moment, and combining the sampling current at the k moment and the discrete control period duration to obtain algorithm execution time at the k-1 moment;

and 4, step 4: predicting the current change caused by calculation delay in the k moment by using the algorithm execution time obtained in the step 3, and compensating the current sampling value of the k moment;

and 5: and (4) substituting the compensated current in the step (4) into a prediction model to calculate a predicted value at the next moment, performing traversal optimization by using a value function, and outputting a switching tube driving signal corresponding to the optimal voltage vector to an inverter to control the motor to operate.

The invention also includes:

1. step 3, establishing a mathematical model of the permanent magnet synchronous motor, discretizing the mathematical model to obtain a prediction model, substituting the sampling parameters in the past moment into the prediction model to calculate the prediction current and the auxiliary current at the k moment, and combining the sampling current at the k moment and the discrete control period duration to obtain the algorithm execution time at the k-1 moment, wherein the algorithm execution time is specifically as follows:

a mathematical model is established for the permanent magnet synchronous motor under an alpha beta static coordinate system, and the complex vector form is as follows:

in the formula u_sAnd i_sStator voltage and current vectors, respectively; r_s、L_sAnd Ψ_fRespectively a stator resistor, a stator inductor and a permanent magnet flux linkage; omega_eIs the rotor electrical angular velocity; theta_eIs the rotor electrical angle;

the mathematical model carries out first-order forward Euler dispersion to obtain a prediction model, and current, voltage and rotating speed sampling values in the k-1 moment are substituted into the prediction model to calculate to obtain predicted current at the k momentComprises the following steps:

in the formula (I), the compound is shown in the specification,the current sampling value at the k-1 moment; t is_sDiscrete control cycle duration;

defining the physical meaning of the auxiliary current at the moment k as the result of the sampling current at the moment k-1 under the continuous action of the voltage vector in the moment k-2 until the moment k, substituting the current and rotating speed sampling values at the moment k-1 and the voltage sampling value at the moment k-2 into a prediction model to calculate to obtain the auxiliary currentComprises the following steps:

assuming that the current change under the action of the actual voltage is linear change conforming to the prediction result, converting the linear change into the relation between the current difference at the moment k and the algorithm execution time at the moment k-1 to obtain the algorithm execution time at the moment k-1Comprises the following steps:

in the formula (I), the compound is shown in the specification,sampled values of the current at time k.

2. Step 4, predicting the current change caused by the calculation delay in the k moment by using the algorithm execution time obtained in the step 3, and compensating the current sampling value at the k moment specifically comprises the following steps:

assuming that the algorithm execution time at the time k is equal to the algorithm execution time at the time k-1, under the continuous action of the voltage at the previous time, the current variation caused by calculation delay at the time kAnd predicting the amount of current changeAnd therefore, the current change amount caused by the calculation delay in the k time is obtainedComprises the following steps:

compensating the current sampling value at the k moment to obtain compensated currentComprises the following steps:

3. step 5, substituting the compensated current in the step 4 into a prediction model to calculate a predicted value at the next moment, performing traversal optimization by using a cost function, and outputting a switching tube driving signal corresponding to the optimal voltage vector to an inverter to control the motor to operate specifically as follows:

calculating the current predicted value of the compensated current at the k +1 moment under the action of each voltage vectorComprises the following steps:

in the formula (I), the compound is shown in the specification,for 7 basic voltage vectors V in a limited control set_iI ═ 0,1, …,6} in the form of a complex vector in the α β coordinate system;

substituting a current predicted value obtained by using the compensated current into a cost function to perform traversal optimization, selecting a basic voltage vector meeting the minimum cost function, and outputting a corresponding switch tube driving signal to an inverter to control the motor to operate, wherein the cost function specifically comprises the following steps:

in the formula (I), the compound is shown in the specification,a complex vector form given to the current.

The invention has the beneficial effects that: the invention discloses a calculation delay compensation method aiming at the prediction current control of a permanent magnet synchronous motor, which can effectively solve the problem of system control performance reduction caused by calculation delay, and compared with the prior art, the method can realize the following beneficial effects:

1. the method obtains the algorithm execution time of the previous moment and reasonably compensates the current sampling value of the current moment by analyzing the relation between the difference value between the sampling current and the predicted current in the current moment and the current variable quantity in the algorithm execution time of the previous moment, thereby eliminating the influence of the calculation delay on the control performance of the system.

2. The method only carries out sampling once at the initial moment of each control period, and the algorithm execution time of the previous moment is obtained without an oversampling mode, so that the method not only can reduce the influence of sampling errors caused by two times of sampling, but also can be easily realized in practical application.

3. The method is a direct compensation method for the calculation delay on the premise of not excessively increasing the calculation amount and complexity of the algorithm, and the control strategy of the method is simple in structure, easy to implement and good in control effect.

Drawings

FIG. 1 is a control schematic block diagram of the proposed method of the present invention;

FIG. 2 is a flow chart of an implementation of the proposed method of the present invention;

FIG. 3 is a schematic diagram of the derivation algorithm execution time;

FIG. 4 is a schematic of a current trace that takes into account the calculated delay;

FIG. 5 is a schematic diagram of a current trajectory under the calculation delay compensation method according to the present invention;

FIG. 6 is a graph of algorithm execution time simulation in a preferred embodiment of the present invention;

FIG. 7 is a current response simulation under a finite set predictive current control method without regard to computational delay;

FIG. 8 is a current response simulation under a finite set predictive current control method without computational delay compensation;

FIG. 9 is a current response simulation diagram in a preferred embodiment of the invention.

Detailed Description

The invention is further described with reference to the drawings and the detailed description.

As shown in fig. 1 and 2, a method for compensating for a calculated delay for a predicted current control of a permanent magnet synchronous motor specifically includes the following steps:

step 1: sampling three-phase stator current, rotor position information, given rotating speed and switching tube driving signals of the permanent magnet synchronous motor at the moment k, and obtaining stator current and voltage components under an alpha beta static coordinate system through Clark transformation:

in the formula (I), the compound is shown in the specification,is the three-phase stator current of the motor;andstator current and voltage components under an alpha beta static coordinate system respectively;is a switch tube driving signal; v_dcIs the bus voltage.

Step 2: the sampling rotation speed in the step 1With a given rotational speedThe difference value between the two is output by a PI controller to obtain a q-axis current given valued-axis current adoptionAnd obtaining the current given value under the alpha beta static coordinate system through inverse Park transformation. Wherein the q-axis current is givenAnd the given current value in the alpha beta static coordinate system is as follows:

in the formula, k_pAnd k_iProportional gain and integral gain of the PI controller respectively;for electricity in dq rotating coordinate systemsA flow setpoint;the current given value is in an alpha beta static coordinate system.

And step 3: and establishing a mathematical model of the permanent magnet synchronous motor, and discretizing the mathematical model to obtain a prediction model. Substituting the sampling parameters in the past moment into the prediction model to calculate the predicted current and the auxiliary current at the k moment, and combining the sampling current and the discrete control period duration at the k moment to obtain the algorithm execution time at the k-1 moment, wherein the specific mode is as follows:

firstly, a mathematical model is established for the permanent magnet synchronous motor under an alpha beta static coordinate system, and the complex vector form is as follows:

in the formula u_sAnd i_sStator voltage and current vectors, respectively; r_s、L_sAnd Ψ_fRespectively a stator resistor, a stator inductor and a permanent magnet flux linkage; omega_eIs the rotor electrical angular velocity; theta_eIs the rotor electrical angle.

Further, carrying out first-order forward Euler dispersion on the mathematical model to obtain a prediction model with short dispersion step length, substituting the current, voltage and rotating speed sampling values in the k-1 moment into the prediction model to calculate to obtain the predicted current at the k momentComprises the following steps:

in the formula (I), the compound is shown in the specification,the current sampling value at the k-1 moment; t is_sIs a discrete control cycle duration.

Further, the physical meaning of the auxiliary current at time k is defined as the result of the sampling current at time k-1 under the continuous action of the voltage vector at time k-2 until time k. Substituting the current and rotating speed sampling values at the k-1 moment and the voltage sampling values at the k-2 moment into a prediction model to calculate to obtain the auxiliary current at the k momentComprises the following steps:

further, the algorithm execution time in the k-1 moment is obtained according to the relation between the sampling current and the difference value between the prediction current and the auxiliary current at the k moment and the relation between the algorithm execution time and the discrete control period duration at the k-1 momentDue to the short discrete step size, the current change under the effect of the actual voltage can be considered as a linear change according with the predicted result. As shown in FIG. 3, the line segments ab and ed represent the predicted current and the actual current, respectively, as a function of voltage over time k-1. Therefore, the line ab and the line ed in fig. 3 are considered to be parallel, and Δ abc and Δ edc are found to be similar according to the triangle similarity theorem. And according to the fact that the ratio of any corresponding line segment of the similar triangle is equal to the similarity ratio, the ratio of the line segment bc to the line segment dc is equal to the ratio of the line segment am to the line segment en, the ratio is converted into the relation between the current difference value at the moment k and the algorithm execution time at the moment k-1, and the algorithm execution time at the moment k-1 can be obtainedComprises the following steps:

in the formula (I), the compound is shown in the specification,sampled values of the current at time k.

And 4, step 4: predicting the current change caused by calculation delay in the k moment by using the algorithm execution time obtained in the step 3, and compensating the current sampling value of the k moment, wherein the specific mode is as follows:

first, it can be assumed that the algorithm execution time at time k is equal to the algorithm execution time at time k-1. In addition, since the straight lines of the line segments ab and ed in fig. 3 are parallel, it can be considered that the current variation caused by the calculation delay in the time k is under the continuous action of the voltage at the previous timeAnd predicting the amount of current changeAre equal. Therefore, the current change amount caused by the calculation delay in the k time is obtainedComprises the following steps:

further, the current sampling value at the time k is compensated to obtain compensated currentComprises the following steps:

and 5: substituting the compensated current in the step 4 into a prediction model to calculate a predicted value at the next moment, performing traversal optimization by using a value function, and outputting a switching tube driving signal corresponding to the optimal voltage vector to an inverter to control the motor to operate, wherein the specific mode is as follows:

first, after calculating compensationThe current obtains a current predicted value at the k +1 moment under the action of each voltage vectorComprises the following steps:

in the formula (I), the compound is shown in the specification,for 7 basic voltage vectors V in a limited control set_iI | ═ 0,1, …,6} in the form of a complex vector in the α β coordinate system.

And further, substituting a current predicted value obtained by using the compensated current into a cost function to perform traversal optimization, selecting a basic voltage vector meeting the minimum cost function, and outputting a corresponding switch tube driving signal to the inverter to control the motor to operate. The specific form of the cost function is as follows:

in the formula (I), the compound is shown in the specification,a complex vector form given to the current.

Further, comparing fig. 4 and fig. 5, it can be found that under the finite set predictive current control method without calculating the delay compensation, the voltage vector selected by the algorithm may not be optimal, resulting in the degradation of the control performance of the system. However, the calculation delay compensation method provided by the invention can reasonably compensate the sampling current at the current moment in the prediction process, so that the action effect of the selected voltage vector is still optimal, and the control performance of the system under the calculation delay is improved.

In the preferred embodiment of the invention, the motor runs under the working condition that the rotating speed is 1000r/min and the load is 2 N.m, the time length of the discrete control period is 100 mu s, and the setting calculation is carried outThe execution time of the method varies from 40 to 60 mus, and the method designed by the present invention was verified by means of the following simulation example. Simulation shows that the calculation delay compensation method provided by the invention can calculate and obtain more accurate algorithm execution time. As shown in FIG. 6, the algorithm execution time t calculated in the method of the present invention_d ^calculatedAlgorithm execution time t set by actual system_d ^realThe simulation curves of (2) are substantially consistent. Therefore, the current sampling value can be reasonably compensated by calculating the current variation of the algorithm execution time within the current moment. Comparing the q-axis current ripple Rip _ i shown in fig. 7, 8 and 9_qAnd q-axis current tracking error Err _ i_qThe method for calculating the time delay compensation aiming at the prediction current control of the permanent magnet synchronous motor can obviously improve the running performance of the motor under the influence of the calculated time delay.