Design and Implementation of a Voltage Harmonic Elimination Control Method for the Single-Phase Inverter

Single-phase voltage-source converters are widely used in power conversion systems like grid-interfaced photovoltaic arrays. This paper presents a control method for the single-phase inverter that is looking to reduce the harmonic content of the output voltage, especially for the situation when the inverter feeds a crest-factor load. In this case, the currents are non-sinusoidal and relatively distorted; as a result, the THD is higher than the specification allows. The method proposed uses a voltage controller followed by a current controller-both are implemented in the stationary reference frame. The voltage controller uses a harmonic elimination method based on modulation-demodulation. This approach regulates the fundamental of the voltage and is also used to attempt the elimination of some higher order harmonics. In the simulations and experiments shown in the paper, the regulation and harmonic elimination scheme is implemented for the fundamental and for the 3rd, 5th and 7th harmonics of the voltage. The scheme can be expanded further to eliminate the harmonics of even higher order. It is shown that the control method proposed significantly reduces the Total Harmonic Distortion (THD) of the output voltage, from 5.8% (at full load, uncompensated) to 1.6% (at full load, with compensation). The control method proposed is validated with simulations and experimental tests.