Analysis and implementation of a modified robust model reference adaptive control with repetitive controller for UPS applications

Usually, the design of control systems begins taking in account nominal models. If there is any change in the characteristics of these models, the system performance deteriorates. Therefore, it is expected that control systems must have robust stability. In this work, a modified robust model reference adaptive control scheme with a repetitive controller (RMRAC-RP) for uninterruptible power supply (UPS) applications is presented. In the proposed scheme, a voltage source PWM inverter and its corresponding RLC load-filter are controlled by RMRAC-RP in order to obtain a nearly sinusoidal output voltage for a single-phase UPS. The modified scheme guarantees that the closed-loop plant is globally stable in the presence of unmodeled dynamics and cyclic fluctuating loads. The proposed theoretical formulations are verified by system analysis and both simulated and experimental results are presented.