In power system dynamic analysis, especially voltage analysis at load disconnection, it is known that the turbine generator model considering quadrature axis transient reactance Xq’ (called LGT = 5 in CRIEPI’s Power System Analytical Tools (CPAT)) is more accurate than ignoring Xq’ (called LGT = 4 in CPAT). However, in power system analysis in Japan, LGT = 4 seems to be used as the model for the turbine generator rather than LGT = 5. It seems to be primarily because there is no significant difference between them in rotor angle stability analysis. However, it is not clear whether there is great difference between them in the analysis on the inverters trip in grid fault. In such an analysis, the change of frequency of inverters connection node is mainly important. In this paper, the impacts of Xq’ of the turbine generator on the frequency change after grid fault are investigated. Through the time-domain simulations, it was found that the frequency change in grid fault of LGT = 4 tend to be larger than that of LGT = 5, indicating that there is a clear difference between the results of frequency analysis using LGT = 4 and LGT = 5. © 2024 The Institute of Electrical Engineers of Japan.
