Different control strategies for power quality improvement using dynamic voltage restorer

Usually PID controller is used in all closed loop control systems, but owing to difficulties in tuning the parameters with the existing conventional methodologies like Ziegler Nicholas, Cohen-coon etc there is always a need to develop a unique algorithm for PID controller. The existing methods tune controller parameters on trial and error basis. The study includes three different methods for controller tuning namely RST, IMC, and pole placement technique. The proposed control strategies are implemented in cascaded multilevel inverter (CMLI) type dynamic voltage restorer for power quality improvement. Disturbance rejection capability, set point tracking and stability aspects are discussed in the proposed strategies. The case studies are presented to test the performance of the proposed control strategies. The test circuit is developed in Matlab/simulink and the results are presented to validate the proposed strategy.