基于扰动观测器的五相永磁同步电机开路和短路容错矢量控制

Disturbance-Observer-Based Field-Oriented Control of Five-Phase PMSM under Open-Circuit and Short-Circuit Faults

针对反电动势含有3次谐波的五相永磁同步电机(PMSM)开路和短路故障导致转矩脉动大的问题,该文提出一种基于扰动观测器的矢量控制(DOB-FOC)策略。该策略基于降阶正交变换矩阵在同步旋转坐标系上建立PMSM开路故障情况下的基波模型,将3次谐波反电动势、短路电流等作为扰动信号。在此基础上,设计扰动观测器,观测出以上扰动导致的转矩脉动,将其转化为q轴补偿电流前馈到q轴电流指令中,有效地抑制了故障导致的转矩脉动,并且实现了PMSM在开路和短路故障情况下的平稳无扰运行。仿真和实验结果验证了所提容错策略的有效性。

The unbalanced phase currents of a multiphase permanent magnet synchronous motor(PMSM)generate large torque fluctuations when an open-circuit or short-circuit fault occurs,which causes the whole system to oscillate or even not continue operating.A novel field-oriented control strategy based on disturbance-observer(DOB-FOC)is proposed to restrain torque fluctuations in the five-phase PMSM with third harmonic back electromotive forces(EMF)under open-circuit and short-circuit fault conditions.Firstly,a fundamental PMSM model with open-circuit fault is built in the synchronous rotating frame using an orthogonal reduced-order transformation matrix.The third harmonic back EMF and short-circuit current are recognized as disturbances.Secondly,a disturbance observer is designed.Then,a feedforward compensatory current obtained from the estimated disturbances is added to the q-axis current reference.Finally,the torque fluctuations caused by the fault can be restrained effectively,and the PMSM with the proposed strategy can operate well under open-circuit and short-circuit faults.Simulation shows that when the third harmonic back EMF is 0 or 20%of the fundamental amplitude,DOB-FOC can effectively suppress the fluctuating torque caused by open-circuit and short-circuit faults.Therefore,whether the back EMF contains the third harmonics,the faulty motor with DOB-FOC has a similar steady-state performance in healthy conditions.Experimental results demonstrate the feasibility and effectiveness of the proposed strategy.When the open-circuit or short-circuit fault occurs,the proposed DOB-FOC strategy is activated at once,and the fluctuating torque is restrained to 0.14 N·m and 0.19 N·m,respectively.When the load steps between 3 N·m and 5 N·m,the d-axis current almost remains unchanged,the q-axis current is like that under healthy conditions,and the response time is 170 ms.During the reference speed step changes,the DOB-FOC strategy significantly reduces the fault impact on the speed performance.Its dynamic performance is similar to that under healthy conditions,and its response time is 240 ms.The following conclusions can be drawn from the theoretical analysis,simulation,and experimental results.(1)The proposed strategy can effectively suppress the fluctuating torque caused by the third harmonic back EMF under open-circuit or short-circuit faults.(2)DOB can effectively estimate torque fluctuations caused by short-circuit current and observe the disturbance caused by two-phase faults without additional hardware support.(3)The proposed strategy is suitable for PMSM with only fundamental back EMF or third harmonic back EMF.