阅读说明：本技术 基于转矩模型预测的六相永磁容错电机直接转矩控制方法 (Direct torque control method of six-phase permanent magnet fault-tolerant motor based on torque model prediction ) 是由 朱景伟 安达 李想 陈思 郑杰阳 于 2021-09-02 设计创作，主要内容包括：本发明公开了一种基于模型预测转矩控制的六相永磁容错电机直接转矩控制方法,包括：获取采样信息,包括通过光电编码器得到永磁同步电机的转子位置θ,经过计算得到电机的转速信号,电机转速与给定转速的偏差经过PI调节器处理为给定转矩,由给定转矩计算出给定磁链幅值。在模型预测算法中同时预测电机下一时刻的转矩和磁链幅值。转矩和磁链的预测值与其给定值构成价值函数,选取使价值函数最小的空间电压矢量,根据该空间电压矢量控制六相独立H桥逆变器从而对电机进行实时转矩预测控制。(The invention discloses a direct torque control method of a six-phase permanent magnet fault-tolerant motor based on model prediction torque control, which comprises the following steps: and acquiring sampling information, wherein the sampling information comprises the rotor position theta of the permanent magnet synchronous motor obtained through a photoelectric encoder, the rotating speed signal of the motor is obtained through calculation, the deviation of the rotating speed of the motor and the given rotating speed is processed into given torque through a PI regulator, and the given flux linkage amplitude is calculated through the given torque. And simultaneously predicting the torque and flux linkage amplitude of the motor at the next moment in the model prediction algorithm. The predicted values of the torque and the flux linkage and the given values of the torque and the flux linkage form a value function, a space voltage vector which enables the value function to be minimum is selected, and the six-phase independent H-bridge inverter is controlled according to the space voltage vector, so that real-time torque prediction control is conducted on the motor.)

1. A direct torque control method of a six-phase permanent magnet fault-tolerant motor based on model prediction torque control is characterized by comprising the following steps:

collecting rotor position information theta and motor rotating speed n of surface-mounted six-phase permanent magnet fault-tolerant motor, and setting rotating speed n^*The difference value between the actual rotating speed fed back by the motor and the actual rotating speed fed back by the motor is processed by a PI regulator to obtain the given torque of the motor, and then the given torque is based on i_dAnd (5) calculating a given flux linkage amplitude of the motor according to the given torque of the motor to obtain six-phase stator current i of the motor_a(k)、i_u(k)、i_b(k)、i_v(k)、i_c(k)、i_w(k) And obtaining component current i of d-axis and q-axis coordinate systems through coordinate transformation_d(k)、i_q(k)；

Establishing a voltage equation of the motor under a two-phase rotating coordinate system, processing a differential expression of current through an Euler formula, and obtaining a current predicted value i at the next moment_d(k +1) and i_q(k +1) using the predicted current value to obtain a predicted torque value T at the next time_e(k +1) and stator flux linkage predictor | Ψ_s(k+1)|；

Respectively calculating seven groups of different torque predicted values and flux linkage predicted values at the next moment according to seven different voltage vectors by adopting a model predicted torque control algorithm, and tracking the given torque and flux linkage of the motor in a value function through proper weight coefficients; and selecting the optimal voltage vector in a single control period by the minimum cost function, and finally outputting a switching signal corresponding to the optimal voltage vector to the inverter, so that the direct torque control is performed on the motor through the six-phase independent H-bridge inverter.

2. The method of claim 1, wherein: when the direct torque control is performed on the motor: and (3) considering limiting factors of the torque and the flux linkage amplitude in a cost function by adopting a model prediction torque control algorithm, wherein the cost function is as follows:

when the motor has one-phase open circuit fault, no fault-tolerant strategy is applied, and when any two-phase open circuit fault occurs: namely, when two-phase open circuit faults with a spatial angle difference of 60 degrees, two-phase open circuit faults with a spatial angle difference of 120 degrees and two-phase open circuit faults with a spatial angle difference of 180 degrees occur, a group of new alternative space voltage vectors are respectively reselected to realize low-torque ripple operation control of the motor.

Technical Field

The invention relates to the field of motor control, in particular to a direct torque control method of a six-phase permanent magnet fault-tolerant motor based on torque model prediction.

Background

The permanent magnet synchronous motor is a high-performance motor excited by permanent magnets, and becomes a main execution motor of an alternating current servo control system with the advantages of high efficiency, small torque ripple and the like. A symmetrical surface-mounted six-phase permanent magnet fault-tolerant motor is a novel motor developed on the basis, and six-phase symmetrical isolation windings are adopted and are respectively driven by six H-bridge inverters. This structure makes it possible to have an excellent fault tolerance. Six H-bridge inverters theoretically have 3⁶729 voltage vectors, but can be finally simplified to 62 space voltage vectors with different angles and amplitudes. Control of such machines often employs current hysteresis control and conventional direct torque control. When the motor breaks down, although the fault-tolerant control effect can be achieved, the steady-state performance of the motor in normal operation and fault states is slightly poor. The application of model predictive control in the control of the surface-mounted six-phase permanent magnet fault-tolerant motor is few, most of the model predictive control is current predictive control, and the model predictive control is insufficient in the aspects of rapid torque following and suppression of torque pulsation in a fault state.

Disclosure of Invention

Aiming at the problems, the invention provides a direct torque control method of a six-phase permanent magnet fault-tolerant motor based on model prediction torque control. The method has the characteristic that the algorithm is easy to realize, can effectively reduce the torque ripple of the motor in a normal state and a fault state, and specifically comprises the following steps:

collecting rotor position information theta and motor rotating speed n of surface-mounted six-phase permanent magnet fault-tolerant motor, and givingSpeed n^*The difference value between the actual rotating speed fed back by the motor and the actual rotating speed fed back by the motor is processed by a PI regulator to obtain the given torque of the motor, and then the given torque is based on i_dAnd (5) calculating a given flux linkage amplitude of the motor according to the given torque of the motor to obtain six-phase stator current i of the motor_a(k)、i_u(k)、i_b(k)、i_v(k)、i_c(k)、i_w(k) And obtaining component current i of d-axis and q-axis coordinate systems through coordinate transformation_d(k)、i_q(k)；

Establishing a voltage equation of the motor under a two-phase rotating coordinate system, processing a differential expression of current through an Euler formula, and obtaining a current predicted value i at the next moment_d(k +1) and i_q(k +1) using the predicted current value to obtain a predicted torque value T at the next time_e(k +1) and stator flux linkage predictor | Ψ_s(k+1)|；

Respectively calculating seven groups of different torque predicted values and flux linkage predicted values at the next moment according to seven different voltage vectors by adopting a model predicted torque control algorithm, and tracking the given torque and flux linkage of the motor in a value function through proper weight coefficients; and selecting the optimal voltage vector in a single control period by the minimum cost function, and finally outputting a switching signal corresponding to the optimal voltage vector to the inverter, so that the direct torque control is performed on the motor through the six-phase independent H-bridge inverter.

Further, when the direct torque control is performed on the motor: and (3) considering limiting factors of the torque and the flux linkage amplitude in a cost function by adopting a model prediction torque control algorithm, wherein the cost function is as follows:

when the motor has one-phase open circuit fault, no fault-tolerant strategy is applied, and when any two-phase open circuit fault occurs: namely, when two-phase open circuit faults with a spatial angle difference of 60 degrees, two-phase open circuit faults with a spatial angle difference of 120 degrees and two-phase open circuit faults with a spatial angle difference of 180 degrees occur, a group of new alternative space voltage vectors are respectively reselected to realize low-torque ripple operation control of the motor.

Due to the adoption of the technical scheme, the direct torque control method of the six-phase permanent magnet fault-tolerant motor based on model prediction torque control, provided by the invention, predicts the torque and flux linkage of the motor under a two-phase rotating coordinate system. With i_dThe idea of being zero is to build a relationship for a given flux linkage and torque. The torque of the motor is directly controlled through model prediction, so that the torque control effect of the motor is very good, and the stable output of the motor torque can be ensured no matter in fault-free operation or in relatively common one-phase/two-phase open-circuit faults. And the low-torque ripple running of the motor in a fault state can be realized without adding any fault-tolerant algorithm from the fault-free running to the one-phase open-circuit fault-tolerant running. Therefore, the control complexity is greatly reduced, and the real-time performance of motor control is improved. Even when two-phase open circuit with a spatial angle difference of 60 degrees, two-phase open circuit with a spatial angle difference of 120 degrees and two-phase open circuit with a spatial angle difference of 180 degrees occur, the motor can operate with low torque pulsation in a fault state only by respectively using a set of new alternative voltage vectors.

Drawings

In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments described in the present application, and other drawings can be obtained by those skilled in the art without creative efforts.

FIG. 1 is a topology structure diagram of a six-phase H-bridge inverter of a six-phase permanent magnet fault-tolerant motor according to the invention

FIG. 2 is a common coordinate system diagram of a six-phase permanent magnet fault-tolerant motor according to the present invention

FIG. 3 is a space voltage vector diagram selected by the six-phase permanent magnet fault-tolerant motor of the present invention

FIG. 4 is a block diagram of a direct torque control system of a six-phase permanent magnet fault-tolerant motor based on model predictive torque control according to the present invention

FIG. 5 is a torque waveform of the six-phase permanent magnet fault-tolerant motor of the present invention during normal operation

FIG. 6 is a rotation speed waveform of a six-phase permanent magnet fault-tolerant motor according to the present invention during normal operation

FIG. 7 is a torque waveform diagram of the six-phase permanent magnet fault-tolerant motor in the invention when the A-phase open circuit fault occurs

FIG. 8 is a waveform diagram of the rotation speed of the six-phase fault-tolerant permanent magnet motor when an A-phase open circuit fault occurs

FIG. 9 is a torque waveform diagram of A, U two-phase open-circuit fault of the six-phase permanent magnet fault-tolerant motor in 0.2s and the fault-tolerant strategy added in 0.35s

FIG. 10 is a torque waveform diagram of A, U two-phase open-circuit fault of the six-phase permanent magnet fault-tolerant motor in 0.2s and the fault-tolerant strategy added in 0.35s

FIG. 11 is a torque waveform diagram of A, B two-phase open-circuit fault of the six-phase permanent magnet fault-tolerant motor in 0.2s and the fault-tolerant strategy added in 0.35s

FIG. 12 is a torque waveform diagram of A, B two-phase open-circuit fault of the six-phase permanent magnet fault-tolerant motor in 0.2s and the fault-tolerant strategy added in 0.35s

FIG. 13 is a torque waveform diagram of a six-phase permanent magnet fault-tolerant motor in which A, V two-phase open-circuit fault occurs at 0.2s and a fault-tolerant strategy is added at 0.35s

FIG. 14 is a rotation speed waveform diagram of A, V two-phase open-circuit fault of the six-phase permanent magnet fault-tolerant motor in 0.2s and fault-tolerant strategy added in 0.35s

Detailed Description

In order to make the technical solutions and advantages of the present invention clearer, the following describes the technical solutions in the embodiments of the present invention clearly and completely with reference to the drawings in the embodiments of the present invention:

as shown in fig. 1, the topology structure diagram of the surface-mounted six-phase permanent magnet fault-tolerant motor H-bridge inverter adopts six phases for independent control and no neutral point connection, so that electrical isolation can be effectively realized, and influence caused by an electrical coupling fault relative to a normal phase is avoided when a fault occurs; fig. 2 shows a six-phase stationary coordinate system, a two-phase stationary coordinate system and a two-phase rotating coordinate system of the surface-mounted six-phase permanent magnet fault-tolerant motor; fig. 3 shows voltage vectors selected by a surface-mounted six-phase fault-tolerant permanent magnet motor under control of a six-phase H bridge, where V1, V2, V3, V4, V5, V6, and V7 are candidate space voltage vectors in normal operation and one-phase open circuit operation, and V1 ', V2', V3 ', V4', V5 ', V6', and V8 represent candidate voltage vectors in two-phase open circuit operation. Therefore, the candidate space voltage vector when the two phases are open is uniformly represented by Vx' (x ═ 1, 2, 3, 4, 5, and 6) in the figure; fig. 4 shows a block diagram of a direct torque control system of a six-phase permanent magnet fault-tolerant motor based on model-based predictive torque control, and the control method includes the following steps:

s1: acquiring feedback information: the method comprises the steps that the rotor position theta of the permanent magnet fault-tolerant motor is obtained through a sensor, and the rotating speed n of the motor can be obtained through calculation of a rotor position signal. Will give a rotation speed n^*After the difference is made with the current rotating speed n of the motor, the given torque value of the motor can be obtained through the processing of a PI regulatorThen, the maximum current ratio control is adopted by the given torque to calculate the given flux linkage amplitude | psi_s ^*L. Acquired current value i of six-phase stator current_a(k)、i_u(k)、i_b(k)、i_v(k)、i_c(k)、i_w(k) The current value i under the two-phase rotating coordinate system can be obtained through coordinate transformation_d(k)、i_q(k)。

S2: in a two-phase stationary frame, the motor may establish the following voltage equation:

wherein R is_sResistance of the stator winding of a dynamo-electric machine, omega_rIs the angular velocity u of the motor rotor_d、u_q、Ψ_sd、Ψ_sqThe voltage and the flux linkage under the two-phase rotating coordinate system of the motor are respectively.

ψ_sd＝L_di_d+ψ_f

ψ_sq＝L_qi_q (2)

Wherein L is_d、L_qAre d, q-axis inductances, Ψ, respectively_fIs the permanent magnet flux linkage of the motor rotor. Substituting equation 2 into equation 1 results in the following differential equation for current:

the continuous differential equation under the two-phase rotating coordinate system can be converted into a discrete state equation by using a forward Euler formula:

after the predicted value of the current in the next cycle is obtained according to the formula 4, the predicted values of the torque and flux linkage in the next cycle can be calculated according to the following formula:

T_e(k+1)＝n_pψ_fi_q(k+1)

maximum torque current ratio of the non-salient pole permanent magnet synchronous motor: will i_dSubstituting 0 into equation (5) yields the relationship between torque and flux linkage:

s3: predicting u in equation (equation 4) for discrete states_dAnd u_qThe voltage vector is the d-q axis voltage obtained after coordinate transformation of the alternative voltage vector. Different alternative space voltage vectors are selected under different running states of the motor as shown in tables 1-4.

TABLE 1 candidate space voltage vector table under no-fault and one-phase open-circuit fault

Table 2 candidate space voltage vector table under two-phase open circuit fault with 60 ° phase difference space angle

Table 3 candidate space voltage vector table under two-phase open circuit fault with 120 ° phase difference space angle

Table 4 candidate space voltage vector table under 180 ° phase difference space angle two-phase open circuit fault

The different space voltage vectors are substituted into the formula (4), and seven groups of predicted values of the torque and flux linkage amplitude of the next period can be obtained through the formula (5). And then calculating a corresponding cost function through the following formula, and finally selecting the space voltage vector corresponding to the minimum cost function as output. The alternative space voltage vectors shown in the table 1 are used when the motor runs without faults and one-phase open-circuit faults occur, and fault-tolerant control strategies are added when the two-phase open-circuit faults occur under different conditions, namely the alternative space voltage vectors shown in the tables 2-4 are respectively adopted.

S4: each phase winding of the motor adopts an H-bridge inverter as a drive, and each phase winding is controlled by four bridge arms together. The working rule of the H-bridge is shown in table 5, when each cycle starts, the six-phase independent H-bridge inverter receives the trigger pulse, and keeps the working state of each bridge arm unchanged in the whole cycle until the trigger pulse of the next cycle arrives.

TABLE 5H bridge inverter bridge arm switch state table

S5: simulation experiment verification: firstly, simulation verification is carried out on the motor in a normal running state, the given rotating speed of the motor is 250r/min, the load torque is rated torque 23 N.m, and the waveforms of the motor torque and the rotating speed are respectively shown in fig. 5 and 6. And then carrying out simulation verification on the condition that the motor fails under the same simulation condition. Single-phase open circuit fault: when the motor has an open-circuit fault in the phase A at 0.2s, fig. 7 and 8 are torque and rotating speed waveform diagrams before and after the motor has a one-phase open-circuit fault respectively. A. U two phase open circuit fault: a, U two phases of the motor have open circuit faults at 0.2s, and a fault-tolerant control strategy is added at 0.35s, namely a space voltage vector table shown in a table 2 is adopted. Fig. 9 and 10 are torque and rotation speed waveforms of the motor after A, U two-phase open circuit fault is generated and a fault-tolerant strategy is added. A. B, two-phase open circuit fault: a, B two phases of the motor have open circuit faults at 0.2s, and a fault-tolerant control strategy is added at 0.35s, namely a space voltage vector table shown in a table 3 is adopted. Fig. 11 and 12 are torque and rotation speed waveforms of the motor after A, B two-phase open circuit fault is generated and a fault-tolerant strategy is added.

A. V two-phase open circuit fault: a, V two phases of the motor have open circuit faults at 0.2s, and a fault-tolerant control strategy is added at 0.35s, namely a space voltage vector table shown in a table 4 is adopted. Fig. 13 and 14 are torque and rotation speed waveforms of the motor after A, V two-phase open circuit fault is generated and a fault-tolerant strategy is added.

Simulation results show that by adopting a torque model prediction control strategy, the six-phase permanent magnet fault-tolerant motor can complete rapid start and stable operation in a normal state, can still stably operate with lower torque pulsation when one phase and two phases are open, and greatly improves the stability of an electric propulsion system taking the six-phase permanent magnet fault-tolerant motor as a core. The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be considered to be within the technical scope of the present invention, and the technical solutions and the inventive concepts thereof according to the present invention should be equivalent or changed within the scope of the present invention.