Power Reserve from Photovoltaics for Improving Frequency Response in the Isolated System

Abstract

Appropriate frequency response is an issue of great importance in power system management, especially in an islanded one. An energy-based method for assessing a system’s response, which is needed to prevent under frequency load shedding (UFLS), is introduced. Renewable generation, such as wind turbine (WT) and photovoltaic (PV) facilities, reduces the ability of the power system to resist power imbalances and increases the risks of consumer disconnections by UFLS system, and even of total collapse. To estimate the amount of additional fast power reserve, an equation was developed, relating the moment of inertia, the system demand dynamics, and the available response of synchronous generating units. Clustering units based on their ability to respond to frequency changes in low inertia conditions allows the potential synchronous response to be assessed, providing information of its deficiency in a defined system state. The proposed method was applied to the Israeli power system and up to 307 MW response needed from PV facilities was found for the 350 MW contingency, when the percentage of renewable energy reached 30% of the annual energy production. This study focused on proportional frequency response (PFR) and step frequency response (SFR) that PV facilities can provide. Using this method may contribute to the adoption of PV facilities into the power system without a detrimental impact on frequency response and may even improve the reliability of electricity supply.

Keywords

• frequency response
• power system
• frequency nadir
• photovoltaic plants