# Development of Energy Storage Systems for High Penetration of Renewable Energy Grids
## 1 Introduction
In [13; 14; 15], these strategies are able to provide inertial support and ensure secure frequency dynamics in isolated microgrids by using battery energy storage systems. These are all control strategies that assist in power system operation, balance with generation and load, recover the system to steady state in an N-1 event, and improve the stability and resilience of the power system. In the transmission and distribution services, battery energy storage systems can strategically charge and discharge energy at different periods. This helps alleviate the pressure on the transmission and distribution systems feeder capacity caused by renewable energy generation systems. Therefore, the goal of alleviating transmission and distribution congestion and improving renewable energy utilization rates is introduced in [16; 17]. Reference [18] introduces a coordinated control strategy to efficiently utilize energy, enhancing the minimum frequency level of the frequency nadir of the system by coordinating wind turbines with permanent magnetic synchronous generators and battery energy storage systems. In [19; 20], a simulation of a power supply system for a weather station, which comprises solar panels, batteries, and inverters, was produced. This simulation resulted in an enhanced reliability of the power system. According to the abovementioned literature, it is understood that battery energy storage systems operate with varying benefits in different power systems under different strategies. However, the current literature lacks a comprehensive comparative analysis of various strategies, making it difficult to compare the advantages and disadvantages of these strategies in detail with the same battery energy storage system specifications. Therefore, this paper focuses on the detailed modeling and design of frequency regulation strategies and virtual inertia strategies based on the WECC second-generation generic model. Subsequently, the simulation conditions are based on the actual equipment locations and capacities of Taiwan's 2025 power system. Finally, according to the proposed WECC second-generation generic model, the three different strategies are simulated in transient using the software PSS/E. These three strategies include dynamic regulation, static regulation, and virtual inertia regulation. According to the simulation results, the capabilities of each strategy are analyzed. The advantages and disadvantages of transmission-scale battery energy storage operating frequency regulation and virtual inertia regulation will help power operators expand the basis for the capacity of battery energy storage systems under different strategies. Next, this paper is divided into four sections. Section 2 introduces the frequency regulation technology, which includes dynamic regulation strategy, static regulation strategy, and virtual inertia strategy. The virtual inertia strategy compares three methods: virtual synchronous machine, swing equation emulation, and synchronverter. Section 3 shows the designs of frequency regulation strategies based on the WECC second-generation generic model. Section 4 shows the results of transient simulations, which consider the capacity of the battery energy storage system, the capacity of renewable energy devices, the load level, and the N-1 level under different strategies. Section 5 contains the conclusion of the paper.