Influence of active power gradient control of an MMC-HVDC link on long-term frequency stability

摘要

This paper presents a frequency stability analysis of two power systems coupled by a high-voltage direct current (HVDC) system, based on modular multilevel converter (MMC) technology. The effect of the active power gradient (APG) control scheme attached to MMC on the long-term frequency response (time frame of 1 s to 2 min) of the AC synchronous areas is analyzed by considering a typical disturbance like a load shedding, which helps in clearly observing the frequency deviation produced in the power systems considered. The frequency responses are assessed through deterministic software experiments in the time domain, focusing on 1) power systems with similar and different inertias and 2) the effect of varying the APG of the MMC-HVDC system. The simulation results reveal a correlation between APG and the long term frequency response, which becomes more prominent for low-inertia systems.