An Improved Sliding Mode Variable Structure Control Algorithm and Its Application on PWM Rectifier

The ordinary PWM rectifier using the SMVSC (sliding mode variable structure control) is unstable before reaching the sliding surface and has non-removable buffeting, which leads to the contradiction between stability and rapidity. The VSC (variable structure control) is analyzed based on reaching law and a new method is proposed to achieve a better result in this chapter by combining the VSC with fuzzy control to regulate the reaching law of outer voltage loop. This method is compared with SMVSC without using fuzzy control and classical PI control by simulation under MATLAB/SIMULINK. The results show that this new method has the advantages in response time, overshoot, and system buffeting. The simulation results prove that this method can solve the contradiction between stability and rapidity, and it can be used in situations demanding high quality of direct current.