Civil Engineering Reference
In-Depth Information
FIGURE 10-24
Flywheel configuration with rotor outside enclosing the motor generator and the bearing.
electrical machines can be used, the synchronous machine with variable
frequency converter or the permanent magnet brushless DC machine.
The machine voltage varies over a wide range with speed. The power
electronic converters provide interface between widely varying machine
voltage and the fixed bus voltage. It is possible to design the discharge
converter and the charge converter with input voltage varying over 1 to
3 ranges. This allows the machine speed to vary over the same range. That
is, the low rotor speed can be one-third of the full speed. Since the energy
storage is proportional to the speed squared, the flywheel state of charge at
low speed can be as low as 0.10. That means 90 percent of the flywheel energy
