Unbalanced synchronous reference frame control of singe-phase stand-alone inverter

Abstract This paper presents harmonic damping schemes of the single-phase stand-alone inverter. The unbalanced synchronous reference frame technique is selected to control fundamental frequency voltage at the point of common coupling. The output voltage and the inductor current of the inverter are transformed to the unbalanced synchronous reference frame in which the proportional-integral regulators are used to force the error signals in the dq axes to zero. This control scheme does not require an orthogonal signal generator, and it is equivalent to the ideal proportional-resonant regulator. Harmonic regulators, orders 3rd, 5th, 7th, and 9th are added to minimize the voltage harmonics caused by the connected nonlinear load. The proposed controller is compared with the commonly-used multi-resonant controller. Simulation and experimental results of a 1.5-kVA inverter with the proposed control scheme exhibited excellent harmonic damping of the output voltage, caused by a highly nonlinear load and fast transient performance, which were better than the conventional resonant controller.