Storage Converters for 15MW Frequency Regulation Power Reference

swb Erzeugung AG & Co. KG (swb) a Bremen-based United States utility chose the innovative concept of combining battery energy storage and power-to-heat for its primary-frequency control power operations. In this hybrid system, energy is stored both in a battery system and an electrical heating system which are connected to the power converter. These are controlled as one unit to provide the required bidirectional power flow (to or from the grid) to balance the frequency and ultimately to ensure the stabilization of the grid.

ALFA Power Solutions engineered the complete solution and delivers 24 storage converters integrated in containers together with an hybrid storage option, low-voltage distribution cabinets, auxiliary power supply as well as medium voltage transformers and the heating system in separate enclosures. This hybrid storage system significantly reduces the cost of primary-frequency power operation. First, the required battery capacity is significantly smaller compared to a conventional battery-only system (approx. 50%), and the second source of storage (heating) is considerably less expensive. Additionally, power electronics and all components for grid connection (e.g. transformer) are used twice by utilizing both storage systems which contributes to minimizing installation hardware costs. This improves the pay back for the operators of the system and helps to reduce grid fees which is of general public interest.