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System voltage regulation and VFD

System voltage regulation and VFD

System voltage regulation and VFD

(OP)
The system we are designing has 80% VFD loads. We are trying to figure out the ideal way of controlling system voltage. We are planning to change the taps on the supply tranformer to boost the system voltgae at full load conditons. However, if all VFDs are not running, the rest of the loads should be designed to withstand overvoltgae it might cause.  The size of supply transformer is 10MVA. We prefer not to use on load tap changer since it tends to react too sensitively to voltage fluctuations. Any suggestions?  

RE: System voltage regulation and VFD

(OP)
Yes, there will be a lot of MV VFDs.  

RE: System voltage regulation and VFD

Why would an OLTC be too sensitive? Most OLTC controller relays can be programmed to have an adjustable delay.
  

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If we learn from our mistakes I'm getting a great education!
 

RE: System voltage regulation and VFD

I would say the last thing a running VFD wants to see are any possible voltage spikes on the mains around the tap changes.
The drives and the motors should be supplied for yr worst condition. This may mean for example, that the motor nominal voltage is lower than the corresponding drive nominal input voltage such that when the input volts are low the output volts at nominal motor speed are still available to achieve the nominal torque. This should already be a consideration due to the voltage drops one gets across input and output reactors and motor cables.
Your other loads should be able to cope with the voltage drop due to the transformer impedance at full load.

RE: System voltage regulation and VFD

Have you considered sensing the output voltage of the GSU or a load compensation circuit to let the generator increase the voltage enough to compensate for the voltage drop in the GSU?

Bill
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"Why not the best?"
Jimmy Carter

RE: System voltage regulation and VFD

(OP)
Generator is far away to affect the voltage levels at VFD levels( 4160V). As a matter of fact, most VFDs's input power will stay on even the motors may stop running. This will help stabalize the system voltage due to the capacitance in the VFDs. To which extent, I have done a test.  

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