AVR control on generators
AVR control on generators
(OP)
Question is if a large industrial turbine is running on Automatic voltage control can you then run in var control or power factor control on top of that? and if so what are the benefits of running var or pf control on top of AVR?
THanks for any imput!
THanks for any imput!
FLORIDA,
BIGDOG50






RE: AVR control on generators
With a regulator in normal voltage control mode, it is adjusting the excitation to try to maintain a setpoint voltage on the generator output (or at whatever point you connect to the voltage input). If the generator is running isolated, off the grid, this makes sense.
However, consider the situation of a generator tied to the power grid or another larger generator. The single generator is not large enough to change the grid voltage in most cases. So even a very small voltage error signal will cause the regulator to drive the excitation to maximum (or minimum) trying to get the voltage input back to the setpoint, but the generator just can't do it. So the generator excitation will swing from min to max as the voltage varies. For these situations, you must switch from voltage control to Var or PF control. In these modes, the setpoint is the kVAR output of the machine or its output power factor. Now the voltage can vary (within limits) and the regulator will be happy and making excitation adjustments to maintain a constant generator power factor or VAR output.
RE: AVR control on generators
but wt will happen if suddenly Grid Parallel info is missed.
Then AVR will Autometic will come to Voltage Droop mode.
We can chose either VARmode or PF mode.
in PF mofe Basically AVR Export the KVAR to maintain the
PF of parrelel system. It calulate the KVAR on the basis of PF value.
while in VAR mode it directly upply the KVAR as per the setting values
bye
RE: AVR control on generators
It is important that the AVR switches back to Voltage droop / control mode whenever the connection with grid is lost and the generator is islanded with the plant load.
If my understanding is right, the modern day AVRs can perform this act if an apprpriate digital input (representing loss of grid connection) is wired to it.
Hope the above is useful.
RE: AVR control on generators
FLORIDA,
BIGDOG50
RE: AVR control on generators
You should refer to the instruction manual for your AVR for more information on the required inputs.
But the AVR should not remain in VAR/PF mode when off-line.
RE: AVR control on generators
As for DPC's comment about the AVR maxing for small changes in system voltage, that is what the Line Drop Compensator or Voltage Droop function prevents. This is from a electrical utility perspective so if you are talking about a 50 kW unit do whatever you want. If you are from an electrical utility I would advise against having this conversation with someone from the WECC as it is a requirment for all interconnected generators above 10MW to run with the AVR in voltage control mode.
RE: AVR control on generators
RE: AVR control on generators
He did say it was an industrial turbine. pf/var control is the norm for cogen and other smaller generators tied to the grid. Industrial generators are interested in using their generators to improve their overall pf, not in helping the utility maintain their grid voltage.
The AVR can be kicked back to voltage control on system voltage excursions through appropriate relaying if required.
In the case of a system voltage collapse, the industrial generator is going to be rapidly tripped off the grid by the undervoltage relay that the utility made them put in anyway.
RE: AVR control on generators
RE: AVR control on generators
However, Bigdogs problem is shutting down. It seems that the AVR is set to control al all times the breaker is in, it could be that it is set to constant VARs and not pf. Thus as the turbine is backed off the VARs stay constant with reducing load. Reverse power has nothing to do with the AVR only the governor. I would suggest that you switchout the VAR controller on shut down.
RE: AVR control on generators
BIGDOG50
FLORIDA,
BIGDOG50