A Novel Selective Harmonic Compensation Method for Single-Phase Grid-Connected Inverters

Conventional harmonic compensation techniques have several drawbacks, such as: 1) additional hardware needs; 2) complex control structure; 3) difficulties in parameter tuning; 4) issues in applicability with the reference frame of the fundamental current controller. In addition, most of them are not good enough in terms of compensating harmonics under the light load condition, which can be mainly attributed to the inaccurate detection of harmonics. In order to cope with the abovementioned problems, a novel digital lock-in amplifier (DLA)-based harmonic compensation method is proposed in this article. Since the proposed method can detect harmonics very accurately without additional hardware, it is simple, robust, and easy to implement. The detected amplitude and phase information of a certain harmonic are used to reconstruct the harmonic and it is used to compensate that harmonic through a negative feedback loop. The theoretical background of the DLA, mathematical analysis, simulation, and experimental results are presented to corroborate the validity and feasibility of the proposed harmonic compensation method. A 5-kW single-phase grid connected inverter is built to verify the performance of the proposed harmonic compensation method by a comparison with those of conventional harmonic compensation methods.