System Power Imbalance Estimation Utilizing Linear Component of Local Frequency

This letter indicates that initial transient local frequency deviation is composed of linear component and combination of $(n-1)$ electro-mechanical (EM) modes via solving the initial value problem of ordinary differential equations. It is proved that the linear component of each local frequency deviation is identical to the center of inertia (COI) frequency deviation within the first instants after disturbance. Based on this property, COI frequency and system power imbalance estimation (SPIE) can be fast obtained via least-squares fitting to extract the linear component of local frequency without remote communication. Numerical results of New England 39-bus system verify the correctness of the discovered property and the effectiveness of the proposed method.