Controlling small wind farm power factor
Controlling small wind farm power factor
(OP)
Small 9 MW wind farm is connecting to a 44kV distribution line. The power utility requires that at the point of interconnection, the wind facility maintains a fixed power factor of 0.97 at all times (inductive, the wind facility imports reactive power from the utility grid).
There are 4 turbines, with full a AC/DC/AC conversion, capable of operating in the power factor regulation range of +/0.90, measured at the LV side (inverter output), and where the PF and/or voltage control takes place in the inverter itself.
The collector system is 34.5kV, so each turbine is equipped with a step up transformer and there is also common 44/34.5kV transformer at the interconnecting substation.
Some wind turbine suppliers can also provide a common controller, a sort of common AVR, which is located at the interconnecting substation, connected to station PTs and CTs, and which can be operate the wind facility in either fixed voltage mode or fixed power factor mode. The controller communicates to individual wind turbines via a communication link (usually FO) and sends signals to local inverter controllers.
However, it this particular case the wind turbine is unable to supply such "common" controller at the interconnecting substation, so a system with the same functionality would have to be designed using standard third party equipment, i.e., power factor/voltage monitoring devices, capable of sending an appropriate feedback signal to each turbine controller to adjust its own power factor to whatever is needed in order to maintain the station PF at the preset level.
Has anyone worked on something similar and can provide some hints? North American market, 60Hz. Thank you.
There are 4 turbines, with full a AC/DC/AC conversion, capable of operating in the power factor regulation range of +/0.90, measured at the LV side (inverter output), and where the PF and/or voltage control takes place in the inverter itself.
The collector system is 34.5kV, so each turbine is equipped with a step up transformer and there is also common 44/34.5kV transformer at the interconnecting substation.
Some wind turbine suppliers can also provide a common controller, a sort of common AVR, which is located at the interconnecting substation, connected to station PTs and CTs, and which can be operate the wind facility in either fixed voltage mode or fixed power factor mode. The controller communicates to individual wind turbines via a communication link (usually FO) and sends signals to local inverter controllers.
However, it this particular case the wind turbine is unable to supply such "common" controller at the interconnecting substation, so a system with the same functionality would have to be designed using standard third party equipment, i.e., power factor/voltage monitoring devices, capable of sending an appropriate feedback signal to each turbine controller to adjust its own power factor to whatever is needed in order to maintain the station PF at the preset level.
Has anyone worked on something similar and can provide some hints? North American market, 60Hz. Thank you.






RE: Controlling small wind farm power factor
Rafiq Bulsara
http://www.srengineersct.com
RE: Controlling small wind farm power factor
Rafiq Bulsara
http://www.srengineersct.com
RE: Controlling small wind farm power factor
RE: Controlling small wind farm power factor
S&C is selling a bunch of these to windfarms in this region, based on RTO requirements. But 9 MW is probably a little too small for something like this. I believe about the lowest price point for the DSTAT system is about $1M.
O.97 is pretty standard around here.
David Castor
www.cvoes.com
RE: Controlling small wind farm power factor
Also, this particular WTG can work at any PF between +/-0.90 including unity, but unity is not the requirement of the utility.
The utility does its own modeling and determines what constant PF is required on the imbedded generator side, and that math is based on the load on that line, other generators connected to the same line, voltage regulation at the remote TS, compensators on their side (if any), maximum allowable voltage, market rules re VAR flow, etc. The number therefore will differ from case to case. This is the standard practice of this utility, others may do it differently.
Whatever is required, unity or something else, the PF at the point of the connection is not the same PF as at any of the 4 wind turbine outputs – there are two transformers and several km of cable impedance in-between.
The utility requirement is to keep the contact PF at the point of connection, which obviously requires IT equipment and a PF controller to be located at that interconnection station. And then, some sort of communication link will feedback digital or analog signals (whatever is is suitable) to the wind turbine controllers, which are several kilometers away.
RE: Controlling small wind farm power factor
The actual question is related to selecting some hardware which will act as the group PF controller at the substation end and which will provide a feedback to individual turbine PF controllers to adjust as required so that 0.97 at the substation is maintained at all times and at any active power output. Except when there is no wind and WTs are not running and become small loads of about 10kW.
RE: Controlling small wind farm power factor
We see these DSTAT units even on DFIG wind farms, IIRC.
David Castor
www.cvoes.com
RE: Controlling small wind farm power factor
We will do modeling to confirm whether the turbine PF regulation range is satisfactory (it should be – cable capacitance should be partly offset by reactance of two transformers – one at each cable end), and provided that the regulation range will do, then we still need to design a system which act as station group PF regulator.
RE: Controlling small wind farm power factor
Pozdrav iz Srbije
PS Djora te često pominje.
Greetings from Serbia and happy New Year . . .
RE: Controlling small wind farm power factor
You'll be better off using the utility metering data than installing your own equipment. Aside from the costs involved, there will be much less chance of billing disagreements if everyone is using the same numbers.