Two-stage voltage control of subtransmission networks with high penetration of wind power

Voltage issues are the main factors that limit the penetration level of wind power in subtransmission systems. In this paper, based on different control characteristics, we propose a two-stage coordinated control framework to deal with the negative voltage impacts caused by wind power fluctuations. In the first control stage, on-load tap changers (OLTCs) are used to deal with the voltage variations caused by large wind power fluctuations. In the second control stage, virtual power plants (VPPs) in the subtransmission network are used to handle the remaining slight voltage variations by controlling their reactive power. The second control stage only takes actions to support voltage regulations when control actions of the first control stage cannot meet the control requirements. Control actions of OLTCs and VPPs are obtained through multi-objective optimization based model predictive control and a fully distributed optimal dispatch scheme, respectively. The effectiveness of the proposed control method is tested through case studies based on the IEEE 14-bus test system and IEEE 30-bus test system with wind farms. In addition, through comparison with the traditional control method, our control scheme can reduce the control costs significantly and achieve the control targets at the same time.