Frequency-Domain Modeling and Control of Three-Phase Single-Stage High-Frequency Isolated DC-AC Converter

The three-phase single-stage (3P1S) high-frequency (HF) isolated dc-ac converter is a multifrequency coupling system. The mathematical model that describes the harmonic characteristics of the converter is not analyzed so far. In this article, the combined harmonic state-space (HSS) and extended description function (EDF) modeling method is proposed and the full-order linear model in the frequency domain of this type of converter is originally derived. The systematic modeling process is analyzed and the simulation results verify the correctness of the model. Based on the built model, the harmonic characteristics and the negative effect of the nonideal grid voltage on the current quality are revealed. Meanwhile, a compound controller based on proportional-resonant (PR)-iterative learning is proposed. The compound controller does not need to know the harmonic frequency and tracks the error in real time. Hence, the proposed controller achieves the optimal control of the grid current and the resistance to the harmonic disturbances on the grid voltage. Combined with the built model, the characteristics of the proposed controller are analyzed in detail. The experiments validate the effectiveness and feasibility of the proposed control strategy.