Power System Frequency Regulation in Low Inertia Systems

Abstract

Abstract Electrifying industries is an emerging trend that aims to replace traditional fossil-fuel-based energy sources with renewable electricity in various sectors. Several industrial installations around the world, offshore and onshore, are abandoning reliance on fossil-fuel based power generators by connecting to the public grid directly or through power from shore interconnection. In many cases those installations are and lead to an island network configuration or what is commonly known as micro grid constituted of the load, the renewable generator plant and the transmission system. The objective of this work is to investigate frequency regulation in this configuration. In the presence of classical power generators based on synchronous machines an island grid caters for the power system stability among others, frequency regulation, through the inherit characteristics of the synchronous machines. In the absence of synchronous generators- based power plants, frequency stability becomes more critical as the entire power system inertia is reduced due to the absence of rotating machines both on the generation, especially in the case of solar generation, and load side, i.e. power electronics connected motors. The power system frequency regulation has to be achieved through careful coordination and cooperation of the different power electronic devices controllers such as solar generation converters, battery energy storage systems (BESS) converters and HVDC converters, in case present. This investigation is achieved by the means of RMS based dynamic system simulations. The investigation shows that the ability of the synchronous machine prime mover to regulate the power system frequency through its governor action and avoid critical frequency excursions through inherit kinetic inertia is significantly reduced due to renewable energy displacement of synchronous machine power generation. Additionally, the speed of measurement and response to frequency events of the power electronics-based devices is detrimental to system survival. The investigation shows that the coordination of the solar generation and BESS along with their respective droops and coordination with other power electronic devices in the power system, such as HVDC transmission with grid forming functionalities, is essential. Frequency regulation in lower inertia power systems is essential to maintain system and process operation and reliability. The investigation gives an outlook into realizing industrial installation in remote locations without connection to an existing public grid relying solely on sustainable sources of power generation.