A robust model reference adaptive controller for UPS applications

A novel robust control approach to obtain a nearly sinusoidal PWM inverter output voltage for a single-phase uninterruptible power supply (UPS) has been investigated. In the proposed scheme, a voltage source inverter and its corresponding RLC load-filter are controlled, based on the robust model reference adaptive control (RMRAC). Different to the other presented control strategies, such as dead-beat, one sampling ahead preview (OSAP) and adaptive repetitive controller, this scheme is able to compensate unfavorable errors, switching cyclic fluctuating loads and also unmodeled dynamics loads. An on-line adaptive learning algorithm is described which guarantees steady-state controller stability. The principles, stability, robustness, and special features of the control scheme are discussed and the UPS system is presented. Experimental results are presented to verify the feasibility and performance of the proposed approach.