In open-loop operation, a disturbance allows you to inject a preset frequency error signal into the speed governor.

The options are the following:

Consider the following example:

Permanent droop B_p = 0.05 of servomotor displacement

Frequency variation dF0 (p.u.) = 0.01

GO Disturbance 

Servomotors shut down and their final displacement will be:

∆X = -∆F = -0.01 = -0,2 p.u. (-20%)

 Bp       0.05 

The test checked that the permanent droop is correct.

• Click on GO Disturbance: the disturbance ends, the frequency error is canceled and servomotors return to the initial position.
• Click on GO Acquis to stop recording signals.

The following sections show examples of opened loop tests. 

Filtered Frequency Step

The filtered frequency step disturbance lets you inject into the speed governor a frequency error step that has passed through a filtered step, using the following procedure:

• Select the Filtered frequency signal step disturbance type.
• Define the frequency step amplitude dF0 (p.u.) in peak size: The preset value is 0.01 p.u.
• Define the amplitude-frequency modulation Fr_sin (Hz). The preset value is 0.075 Hz.
• Define the damping factor Dzeta sinus: The preset value is ζ = 0.1.
• Use the GO BERTA switch to select the servomotor command mode.
• Click on GO Acquis to begin recording acquisition group 2 signals to the data file and increment the test counter.
• Click on GO Disturbance: the frequency signal is injected into the speed governor.
• Examine the following graphs:
  • Servomotor movement
  • Speed variation
  • Simulated mechanical power
  • Simulated electrical power

Consider the following example:

Permanent droop Bp = 0.05 of servomotor displacement.

Frequency error peak amplitude dF0 (p.u.) = 0.01 p.u.

Sinus frequency Fr_sin (Hz) = 0.075 Hz.

Dzeta sinus damping factor ζ = 0,1, ωn = 2π  Fr_sin (Hz), GO Disturbance, Figure 55 shows the expected behavior. Top graph:  simulated speed error and real speed. Bottom graph: servomotor displacement and mean value before disturbance.

• Click GO Disturbance: the disturbance ends, the frequency error is canceled and the servomotors return to the initial position.
• Click GO Acquis to stop recording signals.

Frequency Sinus

The frequency sinus disturbance lets you insert into the speed governor a signal frequency error whose amplitude is frequency modulated, This type of test analyzes the turbine and speed governor frequency behavior.

The procedure is the following:

• Select the Frequency sinus disturbance type
• Define the frequency error amplitude dF0 (p.u.) by peak size: The preset value is 0.01 p.u.
• Define the amplitude-frequency modulation Fr_sin (Hz). The preset value is 0.075 Hz.
• Select the servomotor command mode using the GO BERTA switch.
• Click on GO Acquis to start recording acquisition group 2 signals to the data file and increment the test counter.
• Click on GO Disturbance to insert the disturbance into the simulator.
• Examine the following graphs:
  • Servomotor movement
  • Speed variation
  • Simulated mechanical power
  • Simulated electrical power, s in the following example:

Frequency error peak amplitude  dF0 (p.u.) = 0.02 p.u.,

Amplitude modulation frequency Fr_sin (Hz) = 0.5 Hz

• Click GO Disturbance to stop the disturbance, stop the frequency error and return the servomotors to the initial position.
• Click Go Acquis to stop recording signals.

• Closed Loop Operating Mode - Islanded Grid