DC Voltage Oscillation Stability Analysis of DC-Voltage-Droop-Controlled Multiterminal DC Distribution System Using Reduced-Order Modal Calculation

To reduce the dimensions of a multiterminal DC (MTDC) distribution system connected with multiple voltage source converters (VSCs), a dynamic equivalent model is normally established, assuming that the VSCs are either identical or have a specified topology. These assumptions are inconsistent with practical scenarios, and thus, may lead to errors in the analyzed results. In this study, differences of the VSCs are considered, and a dynamic equivalent model of a DC-voltage-droop-controlled MTDC distribution system is established by reconstructing the dynamics of the VSCs and the DC network. Based on that, a dynamic-reconstruction-based reduced-order modal calculation method is proposed to quickly calculate the DC voltage oscillation mode and determine the stability. For a MTDC distribution system with N different VSCs, the highest dimension is NH + T, where the orders of the VSC and DC network are H and T, respectively. The highest dimension using the proposed method can be reduced to H +1. Finally, the advances of the proposed method are demonstrated by comparing with other reduced-order methods. The conclusions are verified by both a simple example and a large-scale DC distribution system with 100 different VSCs.