Design and Implementation of Sensorless WECS with SSA-SMO and SS-HOSMC

Abstract

Sensor-less control of wind energy generator and production of optimum wind energy are two important aspects focused in this paper. A soft switching adaptive sliding mode observer (SSA-SMO) is used for wind energy conversion system (WECS) interfaced to the grid. The SSA-SMO is used as back electromotive force estimator of permanent magnet synchronous generator (PMSG) during the estimation of rotor position and speed. Unlike the traditional SMO, this observer replaces the discontinuous signum function with hyperbolic tangent function for smooth operation and chattering reduction. With the knowledge of prevailing stable condition, the observer gains are tuned online. Moreover, precise estimation of rotor position and speed, is achieved with reduced steady state error. A soft switching higher order sliding mode controller (SS-HOSMC), is used for adapting the shaft speed according to the incident wind speed, which confirms the optimum wind energy production at variable wind speed. This SS-HOSMC is robust as well as contributes in chattering reduction. Field oriented control (FOC) is used for implementing machine side converter control, whereas a simple phase locked loop (PLL) less control is implemented for dealing with power quality issues and DC link voltage regulation, which is requisite need for power flow from wind generator to the grid. The controls are simulated as well as tested on a test bed of WECS tied to the grid.