Active control-based protection for a flexible DC system of a PV power plant

Abstract

A flexible DC collection system for a photovoltaic (PV) power plant contains a large number of feeders. When fault occurs, the fault current rapidly increases, causing electronic devices to block to protect themselves. This blockage presents a challenge to the protection because of extremely short data windows. To address this difficulty, a protective method based on active control is proposed. The fault current control principle is analyzed and derived so that DC/DC converters can provide a low-amplitude and controllable post-fault stable current signal. The system protection algorithm is designed based on identifying the direction of the generated current signal. Simulation results indicate that the fault section is accurately distinguished and that the proposed method performs efficiently against transition resistance and noise. A highly reliable and complete protective action can be completed within 5 ms after a fault occurs, with grounding impedance, noise, and distributed capacitance considered. The proposed approach provides a solution for future DC system protection.