Analysis on controllable boundary of grid-connected converter during fault ride through considering multi-converters coupling

Renewable energy grid-connected converters are rapidly increasing their proportion of electrical power generation, renewable energy generation systems lacking synchronous power sources, only rely on converters to support voltage after fault. However, the reactive power regulation range of the converter during fault is related to various factors such as the electrical constraints of the equipment and fault types, and it will change with the current injection process, which may cause the converter to go off-grid when the injection current exceeding the boundary. To address this problem, this paper takes the voltage and current of converters as the basic constraints to derive the controllable boundary of reactive current reference during fault and puts forward an iterative calculation method of controllable boundary considering the multi-converters coupling, to improve the accuracy of the boundary. Based on that, this paper will analyze the further influence of the electrical limit of devices, fault types, grid strength on the boundary, which can provide a design basis for the reactive current reference of the converters during fault. Finally, the accuracy of the controllable boundary calculation proposed in this paper is verified by MATLAB/Simulink simulation.