Decentralized voltage control in distribution systems by distributed generators

Recently, renewable energy such as wind turbine generator and photovoltaic system are introduced as distributed generators (DGs). Connection of a large amount of distributed generator causes voltage deviation beyond the statutory range in distribution system. Reactive power control of inverter interfaced with DG is one of the solutions against this problem. Additionally, reactive power control has a possibility to contribute for reduction of distribution loss. In this paper, we propose a voltage control method in distribution system by reactive power control of inverters interfaced with DGs. The proposed method has been developed with the aim of reduction of distribution loss and voltage regulation into statutory range without any telecommunications. In the proposed method, each interfaced inverter controls reactive power based on voltage control reference, which is calculated from local measurements. The calculation rule of control reference has been developed using optimal data, which consist of relations between ramdomly given inputs and corresponding optimal outputs calculated by an optimization technique. Simulations are conducted to show the effectiveness of the proposed method.