The successful integration of renewable energy sources into power grids often requires the deployment of HVDC (High Voltage Direct Current) systems and/or FACTS (Flexible AC Transmission Systems). More recently, a new FACTS device for shunt compensation has emerged, namely the E‑STATCOM (Enhanced Static Synchronous Compensator), which combines reactive power compensation with fast active power exchange capability through the integration of a supercapacitor-based energy storage system (ESS).

The assessment of the high-frequency (HF) performance of an E‑STATCOM is key to its secure and successful integration into the grid. Therefore, electromagnetic compatibility (EMC), lightning surge, switching transient, and converter passivity studies should be conducted using accurate HF models of the ESS.

This paper presents Hitachi Energy’s recent experience in HF impedance characterization and modelling of supercapacitors for E‑STATCOM applications. Three-dimensional (3D) electromagnetic HF models of supercapacitor assemblies were developed using the software CST. Also using CST, the stray parameters of the various subcomponents were estimated to create equivalent circuit models in PSCAD/EMTDC. The developed HF models (both 3D and circuit) were then validated against laboratory measurements.

The proposed HF models and their validation through frequency-response comparisons, together with selected results from the system-level studies, are presented and discussed.