Research On Optimal Control For Dual Induction Motor Dive System Fed By A Five-Leg Inverter

In this paper,the control strategy of dual induction motor drive system fed by a five-leg inverter is studied in order to realize the independent control and high performance operation for both motors.In the conventional control strategy for this system,vector control is adopted for each motor,and half-cycle modulation method is employed for the five-leg inverter.It is very complex with large amount of controller parameters,by using which it is difficult to ensure good performance for both motors.In addition,the voltage transfer ratio is low,which severely limits the speed range and load capacity.An improved deadbeat control strategy based on equalization modulation is proposed.Deadbeat control is used to predict the target reference voltage of each inverter,and the system structure is simplified.And through the redistribution,selection and adjustment of the zero vectors of two inverters,the demand of common leg pulse width is unified and the requirements of both motors are satisfied at the same time.The simulation and experimental results show that the control strategy can not only improve the voltage utilization efficiency of the five-leg inverter,but also reduce the number of the voltage reverse pulse and the switching action,and improve the dynamic performance of the system effectively.Then,in order to simplify the control structure and avoid modulation limit,a wide speed range model prediction flux control strategy is proposed,in which a flux vector synthesized with the flux and torque is designed as the control objective.And DC bus voltage caused by common arm constraints,the control strategy through dynamic adjustment of target flux demand to improve motor speed range by the use of weak magnetic.The simulation and experimental results show that the control strategy can not only improve the steady state performance,but also improve the speed range.Furthermore,this paper proposes a double vector model predictive control strategy of zero vectors interleaved.The control strategy is based on the introduction of double vector(non-zero vector and zero vector),and combined with the requirements of the common leg switch to adjust the two vectors and optimize the switching state distribution.The control strategy not only greatly reduces the number of the predicted voltage vectors in each sampling period but also eliminates the limitation of common leg.The simulation and experimental results show that the proposed control strategy can reduce the calculation,and improve the steady state performance of the system effectively.