Adaptive digital control for UPS inverter applications with compensation of time delay

Abstract

This paper presents a digital adaptive controller based on the Generalized Minimum Variance (GMV) control approach for high performance single-phase inverters capable of maintaining very low harmonic distortion in the presence of unknown loads which could be linear or nonlinear. The controller gains are determined by minimizing a cost function that reduces both the tracking error and the control signals. The on-line adaptive learning algorithm for the controller guarantees the high robustness of the proposed controller. The principle of operation, stability, robustness, and the special features of the control scheme are discussed. The major advantage of the proposed scheme is its simplicity of implementation. Also, only the output voltage and the load current are required to be sensed. Another important merit of the proposed control scheme is that it can be designed and implemented without knowing the exact parameters of the PWM inverter system. Simulation and experimental results are presented to verify the feasibility of the proposed approach and also its performance.