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Power factor of wind power generation system.

At an oil storage depot with a standard engine driven three phase generator

some time ago had to investigate why generator failed,stored energy electrical and electronic parts damaged. The conclusion was that the old chunky power factor Hand/Off/Auto switch someone had switched it to hand; the generator did not like this stored energy  on start up (generator exciter diodes blown and other electronics damaged). What I am asking only out of interest could the same thing ever happen if the supply was solely fed by wind powered generator?  Not really talking about wind farm supply as this would be like mains supply and would need standard PF correction at the user end because of changing current and voltage values.


 Oil or gas engine driven three phase generators have inbuilt PF and don’t need existing PF correction I don't know about small scale wind power . Looking up some information on the web, As written on the web site below Seems a bit completed with Self turned fuzzy logic controller (whatever that is) and Power factor improvement of wind power generation system through control of grid side converter.

Any engineer has a knowledge  of the requirements for PF with wind supply at the consumer end. only out interest thank you.

Thanks jcm


This is a good site for types of wind generators.


core.ac.uk/.../53188636.pdf

  • Hi JCM I don't think the PF unit would of damaged the generator as they have discharge resistors built in which usually discharge the capacitors in about 5 minutes. Unless of course you mean that this unit is normally across the mains and hen gets auto transferred to the genset in which case I'm not sure what would happen
  • I think you have a few concepts confused here.


    Generators don't have "inbuilt power factor ". Power factor is a property of the load which is imposed upon the supply.


    Are you thinking, perhaps, of reading the rating plate on a genset which may say something like 400V, 80A 55kVA 0.8pf ? This doesn't mean that the genset "corrects" the pf factor to 0.8 - its telling you something about how the genset has been designed. A diesel genset consists of two main parts: a prime mover (ie. the engine) & the alternator. Both come in a range of sizes. The prime mover provides the mechanical power (ie. the kW ) & the alternator provides the current & the voltage. Now most real loads don't have a pf=1. Real loads (going back a few years) have an average pf of around 0.8. So the designer has used this to help him size his equipment. In the example above, the alternator is capable of delivering 80A @ 400V. This equates to 55kVA. The designer has used the stated pf to come up with an engine that can deliver 0.8 * 55 = 44kW ... and that's what he has fitted. ie. the 55KVA genset is only sized to deliver 44kW. What would happen is you applied a load of 55kVA with a pf = 1 (ie. 55kW)? The answer is that the engine would not be man enough to do this, the govenor would not be able to provide enough fuel & the speed (and hence frequency) would fall. Eventually it may stall.


    To answer you second part - it is not wise to use pf correction kit with a genset. This is not because of stored energy (any energy stored in the cap bank would be gone a few seconds after switching off due to discharge resistors) but is to do with other characteristics of the gen supply. A generator has a much higher impedance than the grid supply. It also has a much higher reactance. When a pf correction bank is used with a genset it is possible that the capacitance of the pf correction bank & the inductance of the genset will form a resonant circuit. This can result in the terminal voltage of the generator being raised well above the 400V expected and will confuse the AVR. It is this phenomenon, in my opinion, which resulted in your blown rectifier diodes and damaged AVR.


  • There is a possible source of confusion here, Some inverter designs can be programmed to effectively provide a complex source impedance when feeding into a stiffer supply , such as a solar panel driving the grid -  by pushing more current at one or other of the flanks of the sinewave than at the peak . This looks like the generation of reactive power, and can be very useful for grid stabilisation. This is sometimes expressed as an equivalent power factor, being a phase shift between I and V.