Capacitor bank protection via constraint WLS dynamic state estimation method (CWLS-DSE)

Abstract

A dynamic state estimation (DSE) based protection algorithm using weighted least square (WLS) method was introduced recently. In this paper, the DSE-based protection algorithm using constraint weighted least squares (CWLS) method is applied to capacitor bank protection. This approach monitors the health status of the capacitor bank by fitting real time measurements to the capacitor bank dynamic model via dynamic state estimation. Virtual measurements are added to the measurements set by considering the physical laws that must be obeyed by the capacitor bank (i.e. KVL, KCL). Virtual measurements can be handled as measurements with high accuracy or as constraints to the dynamic state estimation. The CWLS method treats the virtual measurements as constraints while the WLS method treats them as highly accuracy measurements. Comparison of capacitor bank protection results using unconstraint WLS and CWLS is provided. It is shown that the proposed method can detect internal faults and issue the trip signal correctly The use of CWLS provides a more sensitive protection for capacitor banks.