Inertia estimation in eletric power systems with photovoltaic parks through the use of simulated voltage signals from EMTP

The growing number of electrical power plants based on renewable energy and their interconnection to the power grid through power electronics devices has derived into the appearance of new issues in the design, operation, and control of the electric power systems. One of the most commonly observed phenomena in power systems with penetration of renewable energy is the decrease of the total system inertia. The effect of such an inertia decrease is reflected as a higher variation in the frequency of the system when it is subjected to real power perturbations like generation loss or load (dis)connections. In this paper, an electric power system with several synchronous generators and a photovoltaic (PV) park is simulated in the EMTP software to obtain three-phase voltage signals similar to those obtained by a phasor measurement unit (PMU) in real power systems. Moreover, a method is proposed to compute frequency signals from the measured three-phase voltages and to utilize them for estimating the global system inertia. The proposed method is then applied to a 2-area, 4-machine, 1-PV park power system, where the 5% of the real power of the system is injected by the PV park. The synchronous generators are represented in detail and equipped with exciters and governors. The results show that the proposed method performs adequately, providing estimations of the global inertia that change according to the percentage of penetration of the renewable energy. Comparations of the estimations with and without the PV park are pointed out, and the main points to work on in future developments are provided.