Method for the voltage estimation in large-scale distributed generators under power fluctuations

The use of grid-connected distributed generators (DGs) is increasing rapidly in Japan. In the distribution system with large-scale DG installations, the reverse power flow from DGs leads to a decrease in the line voltage due to the changes in the voltage phase; this is not well-known as the voltage drop phenomenon. As a result, it is difficult to estimate distribution voltages with the conventional voltage-estimation method based on only the measured information when the power flow in the distribution system is different from the measured voltage. To address the estimation problem, in this paper, we propose a simple voltage-estimation method that integrates the facility information about the medium-voltage power distribution system with the measured information. Numerical simulations have been performed to validate this method using the distribution system model and the conventional voltage estimation model. The proposed method achieves a voltage estimation with higher accuracy as compared to that estimated by the conventional method.