An Analysis of the Impact on Frequency Response with Penetration of ‎RES in Power System and Modified Virtual Inertia Controller

The power system in upcoming years will face issues of power frequency instability due to an increase in the share of Renewable Energy Sources (RES). The RESs are integrated into the power system through the power electronic converters. The operation and control of RES are drastically different than the conventional energy sources. This paper is focused on the effect of a rise in the share of RES on power system frequency stability and its possible solutions. The RESs are not taking part in the frequency regulation process in case of disturbance. Despite this, they generate disturbances in the power system caused by the intermittent nature of input energy. The RES doesn’t have extra active power for the frequency regulation as they already operate at their maximum power point. These power electronic-based generators don’t contain inertia like conventional generators. The inertia-less systems adversely affect the Rate of Change of Frequency (RoCoF) and frequency nadir. This is demonstrated on IEEE 9-bus system with different scenarios. According to that analysis, the RES should provide an inertial response during disturbances. In this paper, the proposed Modified Virtual Inertia Control (M-VIC) technique emulates inertia like conventional generators by using external Energy Storage Systems (ESS). In M-VIC the inertial response is replicated by controlling the rate and duration of power provided by ESS. The proposed technique is more effective to reduce the frequency nadir and RoCoF with better utilization of ESS. To demonstrate this, the PV integrated single-area power system model is simulated in MATLAB R2019a.