In resent years, because of increasing residential photovoltaic systems, voltage unbalance is being caused in distribution systems. It might be difficult to control voltage with allowable range using equipment such as Step Voltage Regulators and Load Ratio control Transformers. Therefore, it is important to suppress voltage unbalance. The method of voltage unbalance suppression using single-phase static capacitors (SCs) was proposed, and the effectiveness of the method was confirmed through experiments carried out on low voltage systems.
In this study, the authors propose the method of distribution line impedance estimation to prevent wrong control when distribution line impedance is changed. And we verify effect of the method by experiments with real-time simulator.