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VSI Drives for 25MW motors

VSI Drives for 25MW motors

VSI Drives for 25MW motors

(OP)
Voltage Source Inverters based on IGBT technology can use Induction motors and also do not require Harmonic filters at the source, I heard. This is unlike the LCI drives which are more common for large motor ratings.
Any experience or views on VSI drives for large motor ratings!!
Thanks in advance.  

RE: VSI Drives for 25MW motors

LCI drives are used with synchronous motors.  

The need for  source side harmonic filter on typical PWM drives is highly dependent on the actual installation conditions.   

RE: VSI Drives for 25MW motors

For 25MW it is unlikely you would use VSI on an induction motor from my limited expereience, it would typically be synchronous motors.
LCI Drives yes but again, these would be Synchronous motors.
The use of IGBT also at that power range is quite limited too I think, more common are IGCT or basic thyristor devices. These would have no specific effect on harmonic distortion either. This would depend on the type of front end used-active front end would therfore minimise THD.

I'm not clear on what your question is. It might be better to start with your application requirements, connected voltage and dynamics required (low speed/high speed/high-low perfromance, regenerative..etc)
There are only a few companies who can support this range and therefore you will get specialist support in this area so I would talk with them, e.g. Siemens, ABB to name a couple of the bigger ones.
 

RE: VSI Drives for 25MW motors

There are a few companies that I know supply large VSI drives. Former Robicon, now Siemens, ABB and Rockwell Automation are among those companies. And there is at least one Chinese company, too.

The use of series connected lower voltage modules and a combination of PWM in the modules and successive build-up of the voltage by activating the modules in sequence (I know, better explanations are possible, but will be quite long) results in low EMI and low harmonics.

Have seen them being used in iron ore mines, paper mills and steel works. No serious problems that I know about.

Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

RE: VSI Drives for 25MW motors

If your main concern is harmonic filtering on the source side you should consider the following:

Both kinds inverters are available with different kinds of front-ends.

For the VSI the standard solution in this power range would be uncontrolled rectifier with 24p design.

The more advanced solution would be an Active front end, using the same devices as the inverter.

For the CSI the standard solution would be a 24-pulse thyristor rectifier, whereas an Active Frontend would use reverse blocking IGCTs.

All Active Frontend versions are expected to be quite expensive and would include a filter to supress the switching frequency harmonics.

The CSI with Thyristor frontend is also expected to need a (classic) harmonic filter in most cases to comply with standards on harmonic current and  to provide power factor correction when operatung at lower than nominal speed.

Therefore the VSI with diode frontend is the only solution that is possible without any filtering on the source side.

For the VSI with Diode Frontend solution there are basicly two variants:

The cascaded cell inverter (Robicon approach) as well as a Three-Level Inverter with one large, split DC-link.

Each of the topologies has it's specific benefits and drawbacks and you really need to consider the application requirements as mentioned by ozmosis.


 

RE: VSI Drives for 25MW motors

We are in the commissioning phase of a 45MW synch motor (60MW for 60 minutes), 4 x 3phase windings, 3000rpm, operated at 100Hz, with 4 x 15 MW Siemens Robicon Perfect Harmony VSI drives. The drive is having small LV drives (called power cells), cascaded, to have a 7.2 kV voltage. Each power cell get the input from secondary winding of a dry-type transformer. In a VFD, there're total 21 power cells, a dry-type transformer with 22 secondary windings (the 22nd winding is for the pre-charge circuit). The secondary windings are phase shifted. There're capability to bypass upto 3 faulted power cells, while maintain output voltage of 7.2kV.
Each VFD connected to one 3 phase winding of the motor. Thus all 4 VFD's are just like supplying 4 motors with 4 stators but only one rotor.
 

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