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Efficient Operation of Flywheel Energy Storage Units


The feed-in converter SD2R by SIEB & MEYER comes with a dynamic control even for very large masses as well as high output frequencies. This ensures safe and efficient operation of high-speed flywheel energy storage units amongst others. These systems are still under development, but as soon as they are ready to go into series production, they will have distinct advantages over battery storage units in certain applications.

The feed-in system SD2R by SIEB & MEYER provides the power electronics required for the operation of flywheel energy storage units – including the control algorithms necessary for the energy management. This allows high-dynamic charging and discharging of the storage unit. "The energy amount to be stored via flywheel increases proportionally to the inertial mass of the rotating body and square to its speed", Torsten Blankenburg, CTO at SIEB & MEYER, explains. Due to mechanical and electrical limits – e.g. the maximum possible circumferential speed and/or the output frequency of the drive electronics – the two system parameters must be balanced to achieve optimal performance in practice.

Therefore, the drive electronics must be capable of accelerating a great mass to high speeds as well as decelerating it with a controlled braking system. The electronics of SD2R, especially developed for high-speed motors and generators, master this challenge confidently: Powers of up to 100 kVA and speeds of up to 120.000 rpm are possible. The 4 quadrant operation provided by SD2R ensures the energy flow in both directions. During motor operation the energy is stored and during generator operation the energy is released. "In addition, it is essential to reduce the motor losses caused by the drive electronics to a minimum during charging and discharging", says Blankenburg. "Since the flywheel including motor or generator usually operates in vacuo, only small amounts of losses can be dissipated as radiant energy." In this regard the control algorithms developed by SIEB & MEYER make a significant contribution.

Flywheel energy storage units offer a wide range of use: The opportunity to adapt the systems to different power ranges makes them attractive for various stationary applications and possibly some mobile ones. In addition, the rotating storage units contribute to the grid stability by counteracting frequency and voltage fluctuations of the grid. This makes them especially attractive for companies employing sensitive production machines or highly available data processing centers. The greater the part of "fluctuating power sources" in the public electricity generation, the more important technologies that balance these (weather-related) performance fluctuations become.

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