Accurate estimation of power imbalance (e.g. loss of generation size) during frequency disturbance events is of vital importance for effective power system monitoring and control. Conventional methods for power imbalance estimation are mainly based on the swing equation, where the size of power imbalance is calculated using the measured Rate of Change of Frequency (RoCoF) and the inertia level of the system. With the increasing penetration of renewable generation, the system inertia has decreased significantly. Inertia emulation is considered as a promising solution for enhancing frequency stability in future power systems. However, the emulated inertia, acting in a similar manner of true inertia, could have an impact on the measured RoCoF, which will subsequently affect the accuracy of the power imbalance estimation using conventional methods. Therefore, this paper presents a comprehensive evaluation of the impact of such emulated inertial response on the RoCoF behaviour during frequency disturbances, thus the impact on the accuracy of power imbalance estimation. A new power imbalance estimation method that takes into account of the impact of emulated inertia is proposed. Case studies using both an analytical model and a microgrid model simulated in a real-time simulator are presented, which demonstrate that the proposed power imbalance estimation method could achieve significantly higher estimation accuracy compared to conventional methods, thus offering an effective solution for estimating frequency disturbance sizes in systems with emulated inertia.

frequency stability,Phasor Measurement Units,inertia emulation,renewable generation