Security Evaluation of Voltage Controlled Active Distribution Network at Point of Common Coupling

Voltage control of point of common coupling (PCC) for a combined system with distributed generation (DG) and energy storage (ES) on distribution network side, which can improve the regulation ability of the distribution network to renewable energy and the overall voltage quality. In this paper, extended QV bus type is used to model the power output characteristics of the DG+ES combined system with PCC voltage control. Then, a probabilistic load flow model with QV bus type and an analytical algorithm are proposed to realize the probabilistic modeling of the operation for active distribution network and improve the solving efficiency. Furthermore, the key indicators for the safe operation of distribution network thus as over-limited probability of voltage, confidence range of voltage fluctuation, and the over-limited probability of transmission power are presented to quantify the operation risk. Finally, simulation results are compared and analyzed to demonstrate the rationality and effectiveness of the proposed method and model.

I. Introduction

Compared with traditional distribution network, the load flow and voltage distribution characteristics of active distribution network [1–2] become more complicated due to the large number of distributed generation (DG). At the same time, the inherent randomness and volatility of renewable energy sources such as wind turbine (WT) and photovoltaic (PV) also increase the uncertainty of the load flow of active distribution network significantly, which will bring about short-term voltage quality and transmission power blocking problems that cannot be ignored. With the development and application of energy storage (ES), the combined system composed of DG+ES can effectively control the operating voltage of the PCC point [3–4], which can significantly improve the voltage quality of the distribution network containing large-scale renewable energy [5–6].