Advanced Control of Single-Phase Grid-Tied SPGU-BSU Systems for DC Offset Mitigation and Power Quality Enhancement

Abstract

The power system faces several difficulties when a PV array and nonlinear household loads are connected to the main stream. It affects both power quality and grid synchronization during grid-connected and stand-alone modes. Furthermore, the addition of more power electronics devices affects both the grid voltage and current. To mitigate the above issues, this article proposes an integrated setup of a solar power generation unit (SPGU) and a battery storage (BS) system as a distributed energy source. The proposed setup is connected to a single-phase grid and essential nonlinear home loads through a single-phase active rectifier. A modified low-pass SOGI (MLSOGI) is also utilized to create an accurate grid current reference signal and provide a sinusoidal unit voltage template, along with a quick dynamic response and minimal steady-state error. Moreover, a dual-active-bridge (DAB) converter is used as an isolated bidirectional DC-DC converter for a wide range of output voltages. The sudden change in load creates a DC offset in leakage inductance current before the high-frequency transformer of the DAB. This offset may lead to transformer saturation. To address these issues, a duty-ratio control (DRC) is introduced in this paper. The proposed SPGU-BS system, along with a new control strategy, is tested through both MATLAB simulation and a lab prototype.