An improved Direct Power Control based on SVM strategy of the Doubly Fed Induction Generator

In this paper we propose a control technique called DPC (Direct Power Control) scheme for the doubly-fed induction generator (DFIG) for variable speed windpower generation. The purpose is to directly control the active and reactive power of the DFIG through the converter. The switching states of this converter are selected from a switch table. The latter is fed by two hysteresis comparators whose inputs are the instantaneous errors obtained from the difference between the reference value and the estimated active and reactive power, which represents the DPC. However, because of the variable switching frequency, the conventional C-DPC has the disadvantage of having a high harmonics rate of the currents generated by the DFIG. To remedy this problem a so-called DPC-SVM strategy is proposed. The proposed DPC-SVM technique based on a space vector modulation reduces the current and power ripples. In this control strategy, the active and reactive power are regulated by two conventional PI type regulators using the “SVM” algorithm, then the switching table and the hysteresis correctors have been eliminated. Simulation results of the proposed controller (C-DPC) and (DPC-SVM) scheme are compared for various step changes in the active/reactive power.