A Reduced Converter Count Solid State Transformer for Grid Connected Photovoltaic Applications

This paper presents a Solid State Transformer (SST) interface for grid connected Photovoltaic (PV) system. A new method is proposed for Maximum Power Point Tracking (MPPT) through a single phase inverter with phase displacement control. The inverter control variable is redefined such that it can be used for MPPT. Due to this control technique one converter stage for power tracking is eliminated, leading to a reduced component count for the overall system. The high frequency transformer's model parameters are designed for an operating frequency of 20 kHz for simulation studies. The grid side converter is controlled for synchronization and power flow using a Synchronous Reference Frame (SRF) current controller. The overall system is tested in simulation for a panel rating of 1.15 kWp under various insolation conditions and power balance is verified and presented. Testing is carried out under step change in the insolation to evaluate the performance of the SST interface under transient conditions. The proposed system is tracking the maximum power available from the panel and delivering it into the grid with high efficiency. The overall system efficiency and the high frequency transformer efficiencies are presented under various operating conditions.