Sliding mode control for DC-AC converter

Abstract

The aim of this study is to design a sliding mode controller (SMC) for DC-AC converter to track the desired AC voltage under load variation. In order to design the controller, a set of differential equations describing the plant need to be established to obtain state-space equation of the system. The state variables of the control system are the variables which come from the energy storage elements, such as the inductor current or capacitor voltage. In converters, the level of current is a function of load and most of the time is nonlinear. The suggested controller does not need current sensors and only the desired AC voltage is used as reference. Variation of resistive load is considered as uncertainty and it causes that system to become unstable, so that output voltage has not the ability to track reference sinusoidal voltage. The effect of load changing on the system is compensated effectively by SMC. Two indices are considered for measuring the existing error between output and reference voltage which are integral of absolute error (IAE) and integral of total control power (ITCP). Also, two gains from SMC are optimized by using GA optimization technique in order to minimize the error. Finally, the results are compared with existing PID controller which is implemented to the system. From simulation, it is observed that SMC is more robust, fast and stable against perturbations in contrast to PID controller in DC-AC converter.