Filter-capacitor current compensation for D-Σ digital controlled single-phase bi-directional inverter with LCL filter to reduce grid-current distortion

This paper presents filter-capacitor current compensation for Division-Summation (D-Σ) digital controlled singlephase bi-directional inverter with LCL filter to reduce grid-current distortion. The single-phase bi-directional inverter allows wide filter-inductance variation and it can operate in grid-connection mode and rectification mode with power factor correction. With the D-Σ digital control, the inverter can cover wide inductance variation and can track sinusoidal inductor current reference precisely. However since there typically exist harmonic voltages, the injected grid current will contain harmonic components. With estimated filter-capacitor current compensation, the grid-current distortion can be improved significantly. Experimental results from a 5 kW single-phase bi-directional inverter have verified the feasibility of the proposed compensation approach.