Demonstration of local autonomous method for reactive power from solar inverters in a full-scale demonstration facility

In Japan, the introduction of renewable energy sources such as photovoltaic (PV) systems has expanded with the launch of the Feed-in Tariff (FIT) scheme in 2012, and further growth in PV deployment is expected as renewable energy becomes a main power source. Appropriate voltage levels in distribution networks have been maintained through autonomous control of voltage regulation devices installed on distribution systems, as well as through control based on local information, such as the constant power factor control by solar inverter of PV. However, a large number of PV systems that have completed certification are still waiting to be connected to the grid. Voltage and power flow fluctuations in distribution systems will become more complex, raising concerns about the difficulty of appropriate distribution system operation, including voltage management, load levelling, and prevention of overloads. The authors have previously evaluated the effectiveness of the developed local autonomous control method through numerical simulations using a bank model composed of multiple feeders. For the practical deployment of the proposed method, it is necessary to implement the control scheme in actual equipment and to verify issues that may arise when the method is applied under system operation managed by a Distribution System Operator (DSO). To achieve the practical deployment, we carried out demonstrations for the proposed method using a full-scale demonstration facility in CRIEPI. Length and width in the demonstration field are 1000m and 600m. Distributing substations and 22kV/6.6kV distribution lines are installed in the demonstration field, and a distribution system configuration can be changed by switches that are installed in distribution lines. In this paper, three low-voltage systems have been constructed in the demonstration field to simulate plural customers with PV systems. Each PV system of the same pole transformer is sharing the information about current state of active and reactive power based on IEC 61850 for a communication protocol to achieve the practical use. To demonstrate the proposed method, we constructed low-voltage systems including R-L simulators for simulating low-voltage lines and bi-directional inverters for simulating residence houses in the full-scale demonstration facility. The practical operability of the distribution system (fundamental characteristics of the proposed metho, normal operation by DSO, abnormal operation of the proposed method) was evaluated by applying the proposed control method at simulated low-voltage systems. Within the scope of this demonstration study, the local autonomous control operated without issues, confirming its practical operability.