Design of intelligent utility-interactive inverter with AI detection

A power supply system applying for micro-grid is designed with grid-connected operation and autonomous operation modes. Through a novel anti-island (AI) detection method, the current status of electricity network can be detected quickly and the operation mode of inverter will be ascertained. Based on analysis of transition between grid-connected operation and autonomous operation modes, the output conditions of inverter are adjusted optimally and a seamless transition process will be acquired. All transitions are conducted in zero-crossing in order to reduce the voltage ripple of sensitive load. Adopting the main circuit topology with H-bridge, through a line frequency isolating transformer, the inverter is connected to the grid by a switch. Double closed-loop is adopted to the control of the inverter, which can reduce the harmonic of output voltage and current. A 3 kVA prototype is established in laboratory to verify the feasibility of this scheme.