Regenerative/Dynamic Breaking operation for AC Motor

Regnerative braking in AC drives takes place a the DC link side. The DC l;ink acts as an energy buffer that either deliver power to the drive or takes back energy from the drive. The D clink should of course be equipped with battery for storage or with a bidirectional grid converter, a so callled Active Front End.

Regnerative braking for AC machines with field oriented control is fairly simple. Only the current iq has to be reversed, which in principle is take care of by the speed control in the drive. If the drive is equipped with an active Front End,. the regenerated energy can flow into the grid. If the DC link is powered from a rectifier, a brake resistor with IGBT has to be added to the DC link.

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In factorie where a lot of AC drives are operating a shared DC link can share regenerated energy from one drive with another drive connected to the same DC link. If a second drive is started at the moment of stopping the first drive, enrgy can be shared and extra energy has to be transmitted to the grid.

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The AC drives build from discrete components with field oriented control a, but also the AC drives modeled as a single block can regenerate energy. No extra modeling efforts are required, since the regeneration is naturally prpovided by the field oriented control.


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