High-Inertia Asynchronous Condenser: A New Tool Cosupporting the Voltage and Frequency of Renewable Energy Stations

Modern power grid suffers from low short-circuit ratio (SCR) and absence of mechanical inertia. Conventional synchronous condensers (SynCons) could not provide sufficient inertia (typicallyH2s). To address these issues, this paper proposes a High Inertia Asynchronous Condenser (HIAC) system, which combines the advantages of SynCons, doubly-fed machines (DFMs), and flywheel energy storage (FES). Adopting AC excitation enables HIAC to achieve wide-range speed regulation (up to ±30%) far exceeding that of traditional synchronous machines (±2%), which results in the provision of high equivalent inertia. Furthermore, the high DC bus voltage of AC excitation significantly enhances power response speed. This paper introduces the operational principles and characteristics of the HIAC, as well as its hierarchical control strategy and active frequency/voltage support strategy. Finally, the effectiveness of the HIAC in supporting the voltage and frequency of renewable energy stations is verified by simulations and experiments. Results proved that the HIAC could prove equivalent inertia that is more than 10 times greater than that of the conventional SynCon and achieved rapid power response of around 20ms