A multi-power quality problems management strategy based on VSCs and switches in AC/DC hybrid LVDN with large PVs

A large scale of distributed photovoltaics is accessed through a low voltage distribution network in a single-phase or two-phase, which causes three-phase unbalance and over-voltage problems. These problems can be solved by using a voltage source converter to realize AC/DC interconnection and flexible power transfer between lines. How to utilize the characteristics of voltage source converters to optimize the power qualities, and fully promote distributed PV systems consumption in low voltage distribution network is an important research point. This paper proposes a power regulation model of VSC. The goal of this model is to adjust and optimize over-voltage and three-phase unbalance problems. By constructing a voltage-power sensitivity calculation model for a three-phase four-wire system and integrating different control modes and adjustment capabilities of voltage source converters, a control strategy based on voltage source converters is proposed to address three-phase unbalance and over-voltage issues. Finally, the simulation results demonstrate the effectiveness of the proposed strategy. This paper proposes a dual-layer control strategy to address voltage unbalances and voltage violations with multiple devices. First layer is pre-day scheduling, which aims to minimize unbalance factors by optimizing the position of phase-changing switches. Second layer is intra-day optimization, which proposes a VSC active and reactive power coordinated control strategy. image