Multi-Resonant Control-Based Power Flow Scheme for Single-Stage Dual-Port Inverters Under Unbalanced Grid Conditions

Abstract

Since the SSDPI directly interconnects the PV source, battery, and utility grid without an intermediate dc/dc converter, it provides a single power conversion stage with the potential for reduced conversion loss and improved system integration. However, conventional power flow control schemes, which are employed for this topology to manage dc-side power distribution, fail to handle the ripple power caused by unbalanced grid conditions, leading to undesired oscillations in the PV output power. To bridge this gap, this paper proposes a multi-resonant control-based power flow scheme for dc-side power distribution, which can guarantee the constant PV output power through ripple power decoupling even under unbalanced grid conditions. In the proposed scheme, the zero-sequence component is employed as an available control degree to manage port power. Based on this degree, the port power model that exhibits periodic characteristics under unbalanced grid conditions is revealed, which guides the design for a multi-resonant controller embedded with the corresponding periodic internal model. With the proposed controller, the ripple power can be decoupled and fully distributed to the specific dc port, thus yielding constant output power of the dc port connected to the PV. Additionally, the ripple power decoupling ability is analysed. Experiments on a 110 V (rms), 50 Hz system at a 1000 W grid-power reference validate the proposed scheme with Vl=240 V and Vh=360–440 V, corresponding to tested dc-port voltage ratios of δ=0.09–0.33. Across grid-voltage unbalance degrees of γb=0.3–0.7, the maximum measured phase-current THD is 3.41%. At δ=0.2, the measured efficiencies are 95.26%, 95.44%, and 95.35% at 500 W, 800 W, and 1000 W, respectively.