Sequential State Estimation Containing the Operating Limits for VSC MTDC System

This paper proposes an improved sequential state estimation method containing the operating limits for VSC MTDC (voltage source converter, multiple-terminal direct current) system. As a fully controlled quick-response power equipment, VSC has a set of strict restrictions to ensure safe operation. However, the conventional SE (state estimation) approach presents challenges when the concerned VSC works on the boundaries. Thus, the SE results may be outside the limits because of dealing with measurement errors. To avoid this problem, the operating limits are considered in the process of SE. First, the safe operating range of VSC are analyzed and drawn in details based on basic state variables. Furthermore, the check of limit violation is implemented inside the sequential method. Once the violation is detected, the corresponding parameter will be set as the boundary value and regarded as high-weighted pseudo-measurement for the following calculation loop. Thus, the accuracy and reasonability of SE can be guaranteed. The proposed method is programmed and tested in MATLAB to show the feasibility and satisfactory efficiency.