Dynamic sliding model control for direct torque control of PMSM based on expected space vector modulation
Firstly, to minimize the ripples of the electric magnetic torque and flux linkage produced in the conventional direct torque control (DTC) system for permanent magnet synchronous motors (PMSM); this paper proposes a expected space vector modulation (ESVM) strategy of DTC. The expected voltage was produced by SVM. PI controller was used in flux and torque controller, instead of hysteresis comparator and switching table in conventional direct torque control. Secondly, to chattering reduction and advance state-dynamic performance of PMSM servo system, a dynamic sliding mode controller was designed. By constructing new switching function with integral term, the first order or high order derivative of control output were introduced in switching function. Dynamic sliding mode control laws with time continuum essentially was obtained. The experimental results show that the steady state and dynamic performance of the proposed DTC based on DSMC are improved dramatically, compared with system of the basic DTC or general SMC.