Multi-Time-Scale Volt/var Control in Distribution networks with the Coordination of PV Inverters and Capacitor Banks

Abstract

With the increasing penetration of photovoltaics (PVs) in distribution networks, PV inverters and capacitor banks (CBs) should be well utilized for volt/var control and tackle fluctuations and uncertainty introduced by PVs. This paper proposes a multi-time-scale volt/var control method to coordinate PV inverters and CBs, where the complementarity between the minute and second-level control promotes the economic and secure operations of distribution networks. Firstly, the model of volt/var optimization (VVO) is constructed to minimize network losses and CB operations, and PV inverters are set to reserve some reactive regulation capacity used for real-time control. According to VVO, the model predictive control is carried out to consider future fluctuations, which decides the current 5-minute control for all devices to achieve economic operations. To avoid second-level uncertainties resulting in possible voltage violations, the real-time control further adaptively adjusts MPC control values, which rapidly drives the reactive power regulation abilities of all PV inverters to ensure voltage security and maintains that the control results almost do not deviate from the MPC results to ensure economy. Case studies based on a modified 17-node distribution network verify the effectiveness of the proposed method.