In this paper, a novel coordinated control method is proposed to handle the negative voltage impacts on weak sub-transmission systems, which are caused by wind power fluctuations. Firstly, wind variations are divided into large and small fluctuations. Then, according to the different control characteristics of on-load tap changers (OLTCs) and static compensators (STATCOMs), the OLTCs are used to minimize the impacts caused by large fluctuations, while the STATCOMs are used to eliminate the impacts introduced by small fluctuations. The model predictive control (MPC) and a consensus based distributed control techniques are adopted to design the control schedules of OLTCs and STATCOMs, respectively. It is shown that by the coordination of OLTCs and STATCOMs, voltage violations of points of interconnection (POIs) are eliminated, and voltage fluctuations at unregulated load buses are mitigated. The effectiveness of our proposed control scheme is presented through a case study on the modified IEEE 14-bus test system with a real wind power profile. According to the simulation results, it turns out that the proposed approach can reduce the operation number of OLTCs significantly, and decrease the required capacity of STATCOMs dramatically by comparison with the existing control scheme.
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