An Unidirectional Single Stage Single Phase Soft-Switched Resonant High Frequency Link Inverter

In this article, a single stage high frequency link unidirectional single phase inverter topology is reported for the application of grid integration of solar and fuel cells. The inverter supports only unity power factor operation. The converter is realized using a parallel resonant structure followed by a full bridge unfolder. This avoids undesirable voltage stress caused by parasitic ringing in pulsewidth modulation (PWM)-based approach. A hybrid modulation strategy, variable frequency modulation in most part of the line cycle, fixed frequency PWM near the zero crossing of line cycle is adopted here. The proposed modulation strategy provides the conditions for zero voltage switching over most part of the line cycle and ensures that the variation of the switching frequency of the converter is within an acceptable range. A state plane-based exact analysis is used for modulator implementation and design of the converter. Also, a design procedure is given that ensures minimization of the component stresses over the line cycle. The operation of converter is experimentally verified using a 3 kW hardware prototype.