A Robust SMOC for Vector Controlled PMSG based Isolated Wind Energy Generating System

Abstract

A battery energy storage (BES) supported isolated wind energy generating system (IWEGS) feeding the load, consisting of mainly a wind turbine and a generator controlled by a robust sliding mode control (SMOC) technique is proposed in this work. The IWEGS consists of a permanent magnet synchronous generator (PMSG), two voltage sourced converters (VSCs) connected back to back, working as machine side VSC (MSVSC) and load side VSC (LSVSC). The MSVSC is responsible for controlling the generated wind power using vector control scheme that uses a speed control unit to regulate its torque. Because of the robustness of the SMOC, it is used to control the speed of the PMSG in the presence of uncertainties in modelling and disturbance that occurs due to variable wind speed. The convergence speed of SMOC, is improved by using a modified reaching law in order to reduce the torque ripple. The LSVSC uses a voltage control scheme that regulates the voltage at common coupling point. The wind exhibits an irregular behavior, thereby requiring a reserve power source for meeting the load demand. An integration of BES improves the system reliability by meeting the excess power required by the load. Moreover, the BES absorbs the surplus power when the demand is not enough. Hence, an uninterrupted power supply is maintained ensuring the overall system utilization. A prototype of PMSG based IWEGS is developed in the laboratory. The control techniques are tested under variable speeds and varying loading conditions.