Tribrid energy storage system for frequency support with stage-specific control in a complex interconnected power system with HVDC link

The shift from hazardous fossil fuels to renewable energy has resulted in reduced inertia and poor frequency control within electrical power systems eliciting instability and exposure to system wide blackouts. Energy storage systems (ESS) have been proposed as a compelling solution for improved frequency stability in a reduced inertia power system. The adoption of different ESS types contributing to frequency support presents a control challenge. This paper proposes and utilizes Tribrid Energy Storage System (TESS) with controllers contributing to a specific frequency response stage referred to as stage-specific control. The TESS consisted of a Supercapacitor Energy System (SCES) contributing to the inertia response stage, an Electrical Vehicle (EV) contributing to the supplementary control loop, and a Battery Energy Storage System (BESS) contributing to the inertia and supplementary control loop. The power system evaluation model design was based on a Malaysia-Thailand interconnected system, considering a monopolar HVDC tie line. The simulation focused on the effects of the TESSs in Malaysia’s region and the propagating effect in Thailand’s region. Six cases were assessed with different types of loads, RE power mix, and inertia levels. The system demonstrated effectiveness in reducing frequency Nadir, oscillation, and settling time, while in Thailand, the improvement was to the oscillatory component of the frequency response. Standard deviation calculation illustrates an average improvement of 80.13 %, 71.80 %, and 53.72 % in Malaysia’s frequency, tie line power, and Thailand’s frequency, respectively. Sensitivity analysis demonstrated the effectiveness of the system in different power plants. The research indicates the importance of the utilization and configuration of ESS controls in contributing to frequency support.