Abstract: Topology of a novel standalone photovoltaic system is proposed, which uses a push-pull output circuit. The system consists of a photovoltaic battery array, a charger, a battery and an inverter. The inverter is used for boosting and inversion so that a DC-DC boost circuit is omitted. The system can supply stable 220 V AC-voltage with a simplified main circuit. Besides, a modulation method based on HF-link SPWM and a control strategy for external voltage RMS loop and instant voltage internal loop is adopted. In this way, size and cost of the device are reduced, and excellent output voltage dynamic response and high steady state output accuracy are achived.

Key words: HF-link, modulation, stand-alone photovoltaic system