Cooperative Scheduling of Electric Springs and On-Load Tap Changers for Volt/Var Control in Active Distribution Networks

Coordinated voltage and reactive power control of the active distribution networks (ADNs) are usually based on discrete regulating devices like the on-load tap changer (OLTC). However, frequent operations of the OLTC are detrimental to its long-term service life. Also, discrete adjustments of OLTC taps cannot meet the requirement of precise volt/var control (VVC). To address this, the emerging electric spring is proposed for joint VVC with the OLTC in ADNs in this paper. First, we develop a time-series optimization model for VVC in ADN. In this model, multiple electric springs and the OLTC are regarded as controllable devices. The objective function comprises minimum power losses and minimum voltage violations. Then, the electric springs contribute to decreasing total tap movements of OLTC, which is represented as a constraint in the proposed model. Case studies are carried out on a modified IEEE-33 test feeder. Simulation results validate the effectiveness and accuracy of the proposed model.