Synchronous Generator Power Factor
Synchronous Generator Power Factor
(OP)
Hello everyone,
I am a new member to this forum and would like to ask a little help from you guys. I am designing a Permanent Magnet Synchronous Generator (PMSG) for a Wind turbine application which is of direct drive (DD) type. Being a DD type PMSG the frequency of the output is very low and hence I had to employ converter Inverter pair to improve the frequency. Now, how do I calculate the power factor (PF) of the PMSG? As the PMSG is not directly connected to the load, I believe that the PF does not depend on the load nature. Can someone help me by providing any equations or any research papers and any other material that can help me finding out the PF of the PMSG.
Thank you very much.
I am a new member to this forum and would like to ask a little help from you guys. I am designing a Permanent Magnet Synchronous Generator (PMSG) for a Wind turbine application which is of direct drive (DD) type. Being a DD type PMSG the frequency of the output is very low and hence I had to employ converter Inverter pair to improve the frequency. Now, how do I calculate the power factor (PF) of the PMSG? As the PMSG is not directly connected to the load, I believe that the PF does not depend on the load nature. Can someone help me by providing any equations or any research papers and any other material that can help me finding out the PF of the PMSG.
Thank you very much.





RE: Synchronous Generator Power Factor
Alan
"The engineer's first problem in any design situation is to discover what the problem really is." Unk.
RE: Synchronous Generator Power Factor
RE: Synchronous Generator Power Factor
=====================================
(2B)+(2B)' ?
RE: Synchronous Generator Power Factor
RE: Synchronous Generator Power Factor
Then you simply use some trigonometry to get the components for voltage and currents (in d- and q-axis). You need also reactances here (X=LI). When you have the components, you can calculate the angle between voltage and current vectors and then you have power factor. It is a bit tricky, and needs understanding of vector diagram presentation of electric machines.
In general, power factor with PMSM is not very important, usually it is more practical to get minimum current. Power factor of PMSM can be set to unity for example, by adjusting the terminal voltage from converter, but usually operation at unity power factor is not practical as it results in higher current and higher (copper) losses. By choosing lower power factor is often more feasible as it results in lower current.
I hope this helps
RE: Synchronous Generator Power Factor
RE: Synchronous Generator Power Factor
where
Power Factor = real power / (Vrms * Irms) [true rms]
Displacement power factor = cos of angle between voltage and fundamental current
Distortion Power Factor = rms of current fundamental / rms of current total
assumes sinusoidal voltage
If you have a full wave bridge rectifier feeding a resistive load, then the currrent in the half-cycle w*t =-Pi/2 to +Pi/2 (which is all we need since the interval Pi/2 to to 3*Pi/2 is half-wave symmetric) looks like:
I(t) = 0 for –Pi/2 < w*t < –Pi/6
I(t) = Imax * sin(w*t) for –Pi/6 < w*t < Pi/6
I(t) = 0 for Pi/6 < w*t < Pi/2
You could calculate the rms and fundamental of the waveform above to get an idea of the distortion power factor if you were feeding a resistive load.
For what purpose will this power factor number be used?
=====================================
(2B)+(2B)' ?
RE: Synchronous Generator Power Factor
I(t) = 0 for –Pi/2 < w*t < –Pi/6
I(t) = Imax * cos(w*t) for –Pi/6 < w*t < Pi/6
I(t) = 0 for Pi/6 < w*t < Pi/2
Rather than doing the algebra I solved it numerically as shown in attached (tab data1... ignore the rest).
Results were:
I1rms = 0.431335137 *Imax
Itotrms = 0.552267595 *Imax
Distortion PF = I1rms/Itotrms = 0.781025613
=====================================
(2B)+(2B)' ?
RE: Synchronous Generator Power Factor
RE: Synchronous Generator Power Factor
=====================================
(2B)+(2B)' ?
RE: Synchronous Generator Power Factor
RE: Synchronous Generator Power Factor
A PMSG feeding a rectifier is similar to line power feeding the input of a common 6-pulse VFD. Maybe you can look at those examples and extract some useful info.
I'm not sure what use the apparent power is beyond sizing the conductors and rectifier. In that case, assuming something like the power factor is -0.7 should suffice.
RE: Synchronous Generator Power Factor
RE: Synchronous Generator Power Factor
RE: Synchronous Generator Power Factor
RE: Synchronous Generator Power Factor
How exactly is the below no "information about it"????
RE: Synchronous Generator Power Factor
When a synchronous gen is paralleled with another stiff source such as a grid, power factor of the gen will vary with the excitation. The voltage (and frequency) will be dictated by the stronger source. I am sure there are books on the subject.
Rafiq Bulsara
http://www.srengineersct.com
RE: Synchronous Generator Power Factor
This is a permanent-magnet generator, so no excitation current is required. It will have much lower inductance than an induction generator, so its displacement power factor will be much higher (0.9 to 0.95 would not surprise me). Distortion power factor could be much lower, as Pete has shown, depending on how the rectification to DC is done. But the rectification definitely "isolates" it from the grid.
Chin2, how are you planning to do the rectification? A simple passive diode bridge is inexpensive, but leads to large distortions (as per Pete's estimations) with the CD bus "gulping" current at the peaks. It may also limit your performance so much as to make the system impractical, because the speed must be high enough to create a back EMF higher than needed to create the grid voltage.
An active front end is more expensive, but virtually eliminates both displacement and distortion power factor concerns, and permits generation over a far larger range of operation. All of the projects of this type I know of use such an active front end.
Curt Wilson
Delta Tau Data Systems
RE: Synchronous Generator Power Factor
If the "rectifier" is an active solution then a good power factor might be the result. Even sinusoidal current at close to unity power factor is possible.
At this point, the origional poster hasn't really given enough details to know what he wants and doesn't seem to know what the load will be. Still, the power factor will be a result of the applied load in this application.
RE: Synchronous Generator Power Factor
jpts, Thank your for taking so much time and effort to give me that file. The power rating of the generator is 4MW.
LionelHutz, The load is not decided yet. but the rectifier inverter pair is used to bump up the frequency of the power output of the generator. The PMSG I am considering is of direct drive type and hence the frequency of it is very low. I got some papers and other documents to support the usage of 0.9 to 0.95 lagging power factor for a generator with a rectifier load. Many papers showed that they have used this high power factor value. Hence, I might end up using the same
At this moment I thank one and all for your support.