Three-phase grid-connected inverters interface for alternative energy sources with unified constant-frequency integration control

A new control approach for three-phase grid-connected inverters is presented. The inverter stage is a standard three-phase half bridge. During each 60/spl deg/ of line cycle, the three-phase half bridge can be de-coupled into parallel-connected dual-buck inverter. Based on one-cycle control, a unified constant-frequency integration controller (UCI) is proposed for the dual-buck inverter. The controller is comprised of an integrator with reset, along with some linear and logic components. No multipliers are required. Low current distortion and unity-power-factor are achieved in the control loop. The input to the inverter can be fuel cells, photovoltaic power, wind power, etc. The three-phase currents injected to the grid are sinusoidal. The simplicity and performance of the proposed inverter make it a good candidate for grid-connected alternative energy generation.