Disturbance observer-based digital control for single-phase UPS inverters

Design and analysis of disturbance observer-based deadbeat control for single-phase inverter applications are presented in this paper. Load current can be estimated by the disturbance observer, which is basically structured with the first order equation in this case and is regarded as a relatively simple method in comparison with the conventional full-order Luenberger observer. Also, an inherent one-step delay problem appearing in the deadbeat control method is overcome by a simple prediction technique proposed. Output voltage dip is reduced by the feedforward control with the change rate of the estimated load current involved in the deadbeat current control loop. The proposed algorithms are verified by the respective simulation and experiment results