pajce
Electrical
- Jan 18, 2007
- 40
There are 3 different ways we can model generators in PSS software.
1. PV Machine
2. Constant Power
3. Induction machine with negative active power
When are we supposed to use which model and why???
1. I noticed that when I use PV machine model machine (generator) pumps out as many +/- VAR’s as needed to keep generator terminal voltage at preset value. I don’t have problem with this, since all generators are exactly working this way in reality. Problem I have with this is that I noticed Reactive Power Flow is going in different direction that I would expect. It is going from source of lower voltage to the source of higher voltage. (Generator was set at 1.0 pu, and source at TS was set at 1.0 pu too) I expect that reactive power flow should always be going from higher to lower voltage bus in the system. In all fairness this is happening with models only when I have utility source and generator source on the same model Generator source far downstream of the utility bus). Please explain how am I suppose to interpret these results? I noticed that by playing with the generator scheduled voltage in p/u. I can swing this reactive energy flow in the opposite direction, and then it is in the correct direction (relative to the voltage magnitude). Which p.u. setting I should chose if setting in the field is not known?
2. Constant Model, same issues when I have generators and utility on the same feeder. Reactive power flow wrong. Additional problem is High Voltage that shows in proximity to the generators.
3. Induction machine with negative active power model? When are we supposed to use this? This is motor NEMA or IEC, but there is option for entering negative WATTS, so it is working as a generator??? This is so little information for accurate model in my mind. What is this option for??
From all above mentioned, summarized question is - when are we supposed to use what model and how do we interpret VAR flow results on the model???
1. PV Machine
2. Constant Power
3. Induction machine with negative active power
When are we supposed to use which model and why???
1. I noticed that when I use PV machine model machine (generator) pumps out as many +/- VAR’s as needed to keep generator terminal voltage at preset value. I don’t have problem with this, since all generators are exactly working this way in reality. Problem I have with this is that I noticed Reactive Power Flow is going in different direction that I would expect. It is going from source of lower voltage to the source of higher voltage. (Generator was set at 1.0 pu, and source at TS was set at 1.0 pu too) I expect that reactive power flow should always be going from higher to lower voltage bus in the system. In all fairness this is happening with models only when I have utility source and generator source on the same model Generator source far downstream of the utility bus). Please explain how am I suppose to interpret these results? I noticed that by playing with the generator scheduled voltage in p/u. I can swing this reactive energy flow in the opposite direction, and then it is in the correct direction (relative to the voltage magnitude). Which p.u. setting I should chose if setting in the field is not known?
2. Constant Model, same issues when I have generators and utility on the same feeder. Reactive power flow wrong. Additional problem is High Voltage that shows in proximity to the generators.
3. Induction machine with negative active power model? When are we supposed to use this? This is motor NEMA or IEC, but there is option for entering negative WATTS, so it is working as a generator??? This is so little information for accurate model in my mind. What is this option for??
From all above mentioned, summarized question is - when are we supposed to use what model and how do we interpret VAR flow results on the model???