tailieunhanh - Nonlinear sliding mode control for three phase UPS

In this paper, a nonlinear sliding mode control with variable damping ratio for uninterrupted power system (UPS) is proposed. In this type of sliding mode controller, the sliding surface is designed with the continuous changed parameters. By this way, the system can have the fast responses without overshoot by giving a low damping ratio at initial time and a high damping ratio as the output reaches the set point. | Research NONLINEAR SLIDING MODE CONTROL FOR THREE-PHASE UPS Vu Thi Thuy Nga Abstract In this paper a nonlinear sliding mode control with variable damping ratio for uninterrupted power system UPS is proposed. In this type of sliding mode controller the sliding surface is designed with the continuous changed parameters. By this way the system can have the fast responses without overshoot by giving a low damping ratio at initial time and a high damping ratio as the output reaches the set point. The stability of the system is guaranteed by Lyapunov criteria. Finally a three-phase UPS control system is setup in several modes via Matlab Simulink software. Simulation results indicate that the proposed control algorithm have the good effectiveness under the conditions of balanced load unbalanced load suddenly changed load and nonlinear load as well as the system uncertainties. Keywords Nonlinear surface Nonlinear sliding mode controller UPS. 1. INTRODUCTION Nowadays with the development of technology the uninterrupted power system UPS is become more important day by day to supply continuous power to critical loads such as computer systems medical equipment etc. A good UPS not only supplies continuous AC power to loads but it also should guarantee that the AC power is disturbance free load independent low THD etc. In order to satisfy that strict requirements besides the development of the hardware the software . algorithm control also has a countable contribution. In recent years there are some advanced control methods have been developed instead of PI controller which is not easy to accomplish good performances for UPS under some conditions. In the dead-beat 1 2 control the good performances with high quantity output voltage and fast dynamic response are achieved however this controller require exactly information about system parameters. In 3 a model predictive control MPC with load observer is proposed. This controller guarantees a small steady-state error reduces the