Cross-regulation is one of the critical challenges in single-input and multi-output converters. In this study, new design guidelines and an analytical model for studying the cross-regulation between the dual-outputs of the fly-buck converter are proposed. A small-signal AC model is first established to obtain control over the output and to determine the cross-influence transfer functions of the system. Then, a load regulation coefficient and method for analysing the cross-regulation while considering the load magnitude and load change are proposed to study the characteristics of the fly-buck converter. Finally, to demonstrate the rationality behind the influencing factors over cross-regulation based on the resulting characteristics, a fly-buck converter with double control variables and lower cross-regulation is designed. Simulations and experimental prototypes are implemented to demonstrate the effectiveness of the proposed theoretical analysis.

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Dual-mode photovoltaic power system should be capable of operating in grid-connected (GC) and stand-alone (SA) modes for distributed generation. Under different working modes, the optimal parameters of inverter output filters vary. Inverters commonly operate in GC mode, and thus, a small capacitance is beneficial to the GC topology for achieving a reasonable compromise. A predictive current control scheme is proposed to control the grid current in GC mode and thereby obtain high-performance power. As filter are not optimal under SA mode, a compound control strategy consisting of predictive current control, instantaneous voltage control, and repetitive control is proposed to achieve low total harmonic distortion and improve the output voltage spectrum. The seamless transfer between GC mode and SA mode is illustrated in detail. Finally, the simulation and experimental results of a 4 kVA prototype demonstrate the effectiveness of the proposed control strategy.

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