A backstepping control to improve compensating performance for transformer-less dynamic voltage restorers

Power quality problems such as voltage sags are presently important issues in the industrial field. The dynamic voltage restorer (DVR) is a series compensation device that mitigates voltage sag problems. Due to the nonlinearity of the DVR dynamic characteristics, the compensating performance of the DVR is affected much by its control strategy. In this paper, a backstepping control is proposed to improve compensating performance of the transformer-less DVR. The backstepping control is to construct a passivation output and a storage function to be used as a Lyapunov function. Thus, the system with the proposed controller is to be asymptotically stable. Simulation studies were conducted to show that the proposed backstepping DVR control is very effective in damping the system oscillations and improving the compensating performances.