Three-layer voltage/var control strategy for PV cluster considering steady-state voltage stability

Different from the distributed photovoltaic (PV) system, large-scale PV cluster is regarded as a weakly connected sending-end system, encountering severe voltage issues. This paper proposes a three-layer voltageivar control (VVC) strategy for the coordination of WC devices in PV cluster, which considers not only voltage deviation, but also steady-state voltage stability (SVS) of the system. The central approaches are adopted into the former two layers. In the first layer, capacitor banks and on-load tap changer are scheduled based on 30-min interval PV active power forecast. In the second layer, PV inverters and static synchronous compensator (STATCOM) are scheduled based on 10-min interval PV active power forecast. Considering computation effort and communication delay, in the third layer, the PV inverters and STATCOM continue to respond to real-time PV active power via the local approach. For improving the application performance of the centralized approaches, model prediction control is applied in the first control layer for enhancing robustness of the control. The sensitivity analysis is used for reducing optimization time in the second layer. Simulation results indicate that the proposed VVC strategy is effective for PV cluster to ensure the voltage within the safe range and improve SVS of the whole PV cluster. (C) 2019 Elsevier Ltd. All rights reserved.