Study On Online Uninterrupted Power Supply Based On Improved Repetitive Control

With the progress of science and technology, high technology products arewidely used in people’s daily life. Because of these products can not operatenormally without power supply, people are more and more attention to the quality ofpower supply. The main problems of power supply system are the efficiency andstability of power source. Uninterruptible power supply (UPS) is designed anddeveloped to solve these issues. The ideal UPS can effectively improve the powerfactor and realize switching perfectly when the utility power is abnormal. It canoutput high quality electric power to maintain loads normal operation. Therefore theresearch on UPS has very important theoretical and practical significance.Based on understanding of the present research situation and development athome and abroad of UPS，the on-line type UPS system with improved repetitivecontrol method is put forward by the author. In this dissertation, the simulationmodels of inverter circuits, active power factor correction circuit and the batteryboost circuit are established and analyzed on Saber platform. UPS inverter iscontrolled by the PI control, traditional repetitive control and improved repetitivecontrol with PI respectively. The hardware circuits are built based on the simulationwith digital signal processor (DSP), including the Wien Bridge circuit, thesynchronous square-wave signal with dead zone, the logical combination circuit, thedrive circuit and power main circuit. A/D sampling part, the control part and the partof PWM generator of the system are programmed by software. Simulation andexperimental results show that: PI control can respond quickly, but the results ofcontrol are poor. Output voltage can follow the given voltage traditional underrepetitive control, but with poor capability of rejection disturbance and slow reactionspeed. Improved repetitive control with PI strategy has very good control effect. Theoutput voltage can track a given signal fast and accurate, and this system can restrain the load disturbance effectively. The results also verify that the design idea of systemis correct and the scheme is feasible.