Modular single-phase trans-Z-source inverter for multi-input renewable energy system

This paper presents a novel modular single-phase trans-Z-source inverter for the multi-input grid-connected renewable energy (photovoltaic/wind/fuel cell) system in order to simplify the system structure and reduce the cost. The proposed modular single-phase trans-Z-source inverter evolves from the original Z-source inverter by incorporating coupled inductors and center-tapped capacitors and thus making the system neutral available. By utilizing the extra shoot-through state which is prohibited in the conventional voltage-source inverter to avoid short circuit, the proposed inverter can perform DC-DC boost conversion and DC-AC inversion simultaneously based on the single-stage structure. Multiple inverter modules can be flexibly configured in terms of terminal interconnections, and thus they can adapt to multiple energy sources at different voltage levels and power capacities. More importantly, a shared DC bus decouples the AC outputs of the interconnected inverter modules from their inputs and enables the system to supply balanced power to the grid. Circuit modularization and minimum required devices predict a significantly reduced cost; furthermore, the shoot-through operation offers a great EMI immunity and reliability.