A Fully Symmetrical Three-port Hybrid Converter for PV Systems

Hybrid power converters with DC and AC outputs are promising solutions to increase the utilization of various types of renewable energy, e.g., solar PV, due to the reduction of conversion stages. To achieve high reliability, this paper proposes a fully symmetrical hybrid converter with three output ports, i.e., two DC ports and one AC port for PV applications. The proposed converter adopts symmetrical boost inductors placed in the positive and negative rails of the low-voltage DC port, while it employs symmetrical synchronization rectifier switches at the high-voltage DC port. In addition, highly efficient and reliable inverter concept (HERIC) (also being symmetrical) operates as a switch or an inverter to generate DC and AC voltages simultaneously. The fully symmetrical structure can achieve flexible power control and good power loss distribution. A modulation method with deadtime is dedicatedly proposed for the fully symmetrical structure to achieve low leakage currents between both the DC ports and the AC port, which enhances the grid integration of solar PV energy. Simulations and experimental tests have been carried on a 1.5 kW prototype to verify the effectiveness of the fully symmetrical hybrid converter in terms of good power loss distribution between the devices and low leakage currents.