Local control method and simulation analysis of hybrid AC/DC low-voltage distribution networks with high-proportion photovoltaics

Abstract

Driven by the goal of energy transformation and carbon neutralization, more and more distributed photovoltaics (PVs) are integrated into low-voltage distribution networks (LVDNs). However, the integration of high-proportion PVs may lead to overload problem of distribution transformer (DT) and voltage violation problem, bringing many challenges to the safe and stable operation of LVDN. DC distribution network has the advantages of large transmission capacity and flexible power regulation, which can also realize the interconnection and power transfer between AC low-voltage lines. Therefore, structures and control methods suitable for hybrid AC/DC LVDN are proposed to alleviate the above problems caused by PVs. Firstly, the structure of hybrid AC/DC LVDN is analyzed, including the structure with parallel DC line within distribution area and the structure of DC-interconnected distribution networks between distribution areas. Secondly, a local control method of voltage source converter (VSC) is proposed for the comprehensive improvement of overload problem of DT and voltage violation problem. Finally, an actual LVDN is used to verify the effectiveness of the proposed structure and control method of hybrid AC/DC LVDN. According to the simulation results, the proposed structure of hybrid AC/DC LVDN and VSC control method can improve the voltage level and overload problems of LVDN, decrease the power loss and increase proportion of PV accommodation.