Enhanced Single-Loop dq Control Based on Inductor Current Feed-Forward and Virtual Damping for Nonlinear Load Application

With the recent increase in demand for power electronics-based commercial products, the influx of nonlinear loads into the ac system has increased. In applications, such as standalone inverter systems or uninterrupted power supplies, ensuring sinusoidal load voltage becomes critical when such nonlinear loads are connected. This new development drives power electronics engineers to develop new techniques to mitigate the harmonic effects of these nonlinear loads. Passive filtering of the harmonics leads to costly and bulky systems. Thus, harmonic mitigation must be performed through control and modulation schemes. This article develops an enhanced single-loop direct-quadrature control scheme with inductor current feed-forward and synchronous reference frame-based active selective harmonic elimination to suppress the harmonic effects induced by the nonlinear loads on the output voltage of the standalone inverter systems. The proposed control scheme is analyzed theoretically in the frequency domain, and the design procedure for the control scheme is presented. The proposed control scheme is tested experimentally on an H-bridge-based standalone inverter system operated under different nonlinear loading conditions against its counterparts to prove its efficacy.