A hybrid fuzzy current regulator for three-phase voltage source PWM-inverter

Abstract

This paper presents a fuzzy logic strategy for the current control of a three-phase voltage source power PWM-inverter. The base of this regulator is a direct digital predictive loop which has a very good dynamic performance, but the steady state performance will heavily depend on the accuracy of the model structure and plant's parameters. To reduce the steady errors and compensate the system uncertainties, a feedforward control loop and a fuzzy logic algorithm are introduced. The direct digital predictive loop with the feedforward loop, which can be seen as a hybrid current regulator, generates the command voltage based on the nominal system conditions, guarantees the system with a very fast dynamic response and a smaller system error. The fuzzy logic algorithm, by measuring the amplitude and phase angle of the system error, generates a modifying signal to correct the gains of the direct digital predictive loop and the feedforward loop. When the difference between the reference and actual signals is larger than a given threshold, therefore it minimizes the effects of system uncertainties. Simulation results are presented to verify the effectiveness of the current regulation algorithm.