Voltage/Var Control using Electric Springs in Distribution Networks

Modern distribution networks (DNs) suffer from unstable conditions, such as fast voltage fluctuations, due to the intermittent nature of integrated renewable energy sources. An emerging type of power electronics-based controller called the electric spring (ES) is believed to be a promising solution for alleviating this instability by performing voltage/var control (VVC). In this paper, instead of investigating distributed control schemes for ESs, as has been done in related literature, we study the system-level effectiveness of the ES in performing centralized VVC in distribution networks. AC power flow models for the ES-equipped bus and the ES-equipped DN are proposed. Based on the models, we formulate a multi-objective VVC problem for the ES-equipped DN. To solve the problem, we propose a second-order cone program relaxation method. Numerical tests are demonstrated through a 34-bus distribution network, validating that the fast VVC provided by ESs can effectively reduce both line losses and bus voltage deviations compared to the conventional VVC method using only slow VVC devices.