The increasing penetration of intermittent renewable energy sources can be a significant source of instability for transmission grids that are already operating close to their limits, especially in periods of peak demand. The use of dynamic energy storage systems operating in combination with fast-acting grid interface electronics offers an alternative to the traditional approach to grid frequency regulation based on maintaining a margin of spinning reserve.
The first commercially available energy storage solution for grid applications is ABB’s DynaPeaQ system that combines SVC Light technology with Saft’s advanced Li-ion battery systems. The system provides the optimum mix of active and reactive power to support grids under high stress conditions. Not only are grid voltage and stability controlled with high dynamic response, the active power element enables a number of new services to be added including black start capability and peak load support.
230 V high power module
A complete dynamic energy storage system comprises:
- Power transformer
- SVC Light
- Battery system
- AC and DC high voltage equipment
- Control and protection system
- Auxiliary power equipment
Li-ion batteries
Since high power applications and series connected IGBTs are used to adapt the voltage level, the pole-to-pole voltage is high. Therefore, a number of Li-ion batteries are connected in series to provide the required voltage level in a battery string. To obtain higher power and energy, a number of parallel battery strings may be added.
The battery system comprises cassette-mounted Li-ion modules. An array of battery modules will provide the necessary rated DC voltage as well as storage capacity for each specific application.
Saft’s Li-ion battery technology offers a number of key features:
- High energy density
- Very short response time
- High power capability both in charge and discharge
- Excellent cycling capability
- High round trip efficiency
- High charge retention
- Maintenance free design
Scalable design
The energy storage system is highly scalable. At present, rated power and capacity are typically in the 20 MW range for tens of minutes, but the technology permits up to 50 MW for periods of 60 minutes and more.