Yung-Fu Huang

Series resonant type soft-switching grid-connected single-phase inverter employing discontinuous-resonant control applied to photovoltaic AC module

This paper presents a high-frequency transformer link single-phase inverter system using a series resonant softswitching scheme applied to photovoltaic AC modules. The proposed high-frequency transformer link inverter circuit consists of a full-bridge inverter, a series resonant circuit, an isolation transformer with center tap winding in secondary side and low-frequency distribution switches synchronized with a grid voltage. An AC output current is controlled by the discontinuous-resonant action that has constant on-time pulse pattern synchronized with the resonant frequency. Thus, the inverter switches are operated under zero current switching (ZCS). The basic operating principle and fundamental analysis to design the circuit parameters for the proposed inverter are described in the paper. The effectiveness of the proposed inverter is evaluated by using a prototype of 200W output capacity employing 190kHz resonant frequency based on Power MOSFET devices and a frequency modulation controller by MCU. The proposed series resonant inverter employing discontinuous-resonant control achieves maximum efficiency of 94.8% at 200W output power.

Utility-interactive high-frequency flyback transformer link three-phase inverter for photovoltaic AC module

This paper presents a novel utility-interactive high-frequency flyback transformer link three-phase inverter circuit applied to photovoltaic AC module. The proposed inverter consists of a high-frequency flyback transformer driven by two switches configuration in primary side and six change-over switches with reverse block diode in secondary side to supply three-phase currents. The paper describes basic operating principle and fundamental analyses to design the circuit parameters for optimizing and verifying the operating performances of the proposed inverter. The effectiveness of the proposed inverter are evaluated by using a breadboard set-up of 250W output capacity employing 39kHz switching frequency operation based on power MOSFET device and DSP control. And the paper indicates that the well-controlled three-phase sinusoidal balance currents flow to the utility-grid.