Real-Time Coordinated Control of Low-Voltage DC Distribution Network With Soft Opening Point

In low-voltage dc distribution networks (DDNs), the load terminals typically employ voltage-source inverters to provide ac supply to the consumers. These load terminals can potentially experience poor voltage regulation especially in the presence of intermittent photovoltaic sources and uncoordinated charging patterns of plugged-in electric vehicles. Variations in power absorption and generation at different points can potentially create significant voltage drop/rise at the load terminals and may reduce the power quality at the ac side of the loads. In order to mitigate this issue, this article suggests a real-time coordinated supervisory control strategy that estimates the present state of the network and generates a set of references for the controllable sources such that the load voltage deviations are minimized. This article also proposes a power-electronic-converter-based soft open point (SOP) that provides a seamless connection of the remote end and gives an additional degree of freedom to control the circulating current among the feeders. Detailed description and control strategy of the SOP is presented. Steady-state analysis carried out on a three-feeder DDN is presented with and without the proposed SOP. Real-time simulation with an Ethernet-based transmission control protocol/Internet protocol communication system along with experimental results is presented to validate the implementation and effectiveness of the control strategy.