Developing a synthetic inertia function for smart inverters and studying its interaction with other functions with CHIL testing

Abstract

Due to the increasing burden on the traditional control systems, inverter-based resources (IBR) is required to take part in grid stability efforts. This is the key to increasing the share of IBRs in the power grid and ensuring that issues related to reduced inertia are handled properly. There have been some efforts towards developing frequency control for smart inverters such as frequency–watt​ mode. However, a fully functioning synthetic inertia mode combined with a smart inverter has not been developed yet. In this paper, a novel function is developed for implementing synthetic inertia in smart inverters as a combination of several control modes. Then, the operating curves of these control modes are varied to investigate their impact on the synthetic inertia’s performance and stability. These operations are tested both with lab equipment and controller hardware in the loop (CHIL) testing to study the accuracy of the latter. Once accuracy is established, further CHIL tests have been performed to investigate the interaction between the developed synthetic inertia function and other smart inverter functions such as Volt-Var Control. Results show that there is no negative impact on either of the functions and they can be safely activated simultaneously.

Keywords

• Virtual inertia
• Volt-var control
• Rate of change of frequency (RoCoF)
• Frequency–watt
• Inverter-based resource (IBR)