Rapid Power Compensation-Based Frequency Response Strategy for Low-Inertia Power Systems

To reduce the frequency deviation and the rate of change of frequency (RoCoF) in a low-inertia power system, some converters are required to provide the frequency response (FR) power normally associated with the frequency deviation and/or the RoCoF, by droop/inertia/PD control. In this article, a rapid power compensation (RPC)-based FR strategy is developed to optimize the ability to compensate grid imbalance power, by fully exploiting the converter idle capacity. To this end, first, mathematical proof demonstrated the improved performance of the RPC strategy in terms of frequency deviation suppression versus droop control, and in terms of RoCoF suppression versus inertia control, with identical converter capacity limit. Moreover, it is proven that the RPC strategy can achieve consistent FR performance with respect to the optimal PD control, i.e., it can maximize the suppression of frequency deviation and RoCoF simultaneously, yet avoiding the limitations due to unknown grid parameters. Finally, by analyzing the operation modes and identifying the pertinent switching logic, the detailed implementation of the proposed RPC strategy is developed. Its superb FR performance is verified by the experiment results in a two-converter low-inertia system, and simulation results in an IEEE four-machine two-area system.