Warning 157 | [Various software] | Ambiguous power factor command

Relevant software:

PSS®E

PowerFactory

Emitted message:

Provided power factor command is ambiguous - unclear if injecting or absorbing

Description:

This warning is raised when a power factor command is provided with a value very close to zero. When the power factor approaches zero, it becomes unclear how to determine appropriate active power (P) and reactive power (Q) values for the simulation.

Power factor values near zero (e.g., less than an absolute value of 0.01) create computational challenges. Some examples:

• If both active and reactive power are near zero, the value of power factor becomes extremely sensitive to small changes in apparent power.
• If active power is near zero, the reactive power value is indeterminate (i.e. it is unclear whether the reactive power is injecting or absorbing).

Possible impact:

• Your generating system may not be able to achieve the desired power factor when it's extremely close to zero due to the indeterminate reactive power value.
• Very small changes in power factor near zero can result in large swings in reactive power, potentially causing generator instability.
• This can lead to unpredictable reactive power dispatch from the generator or load, affecting voltage levels at the point of connection and surrounding buses.

Potential fixes:

tip

Wherever possible, if you are completing tests in power factor control that require very low active power setpoints - consider using fixed reactive power (Q) control instead of power factor control.

• Switch to fixed reactive power control: Instead of specifying a power factor near zero, directly specify the reactive power value you want to achieve.
  • For example, use a Q= command with the specific MVAR value instead of using a power factor command.
• Choose a more reasonable power factor: If you must use power factor control, consider using a value further from zero (e.g., 0.1 instead of 0.01).