The Controller panel has the following tabs:

• Settings
• PID controller
• Classical controller
• BERTA Stab 1
• BERTA Stab 2
• BERTA Stab 3

Settings Tab

The Settings tab in the Controller panel opens a panel allowing to change the connection parameters to the tested AC generator and several control parameters of the simulation.

Network Connections

The reduced voltage and current outputs from the voltage and current transformers must be measured for the power and frequency calculations. The conditioning gains were adjusted so that the AC voltage signals obtained do not reach the saturation thresholds of the digital numeric converters.

The following example shows how to calculate the grid connection:

• Rated power: 370 MVA.
• Rated voltage: 13.8 kV
• Rated current: 370,000 / √3 / 13,8 = 15480 A
• Voltage transformer: 120 kV/14400 kV = 1/120
• Current transformer: 5A/18000 A = 1/3600
• Voltage (p.u./V): Conversion gain of high AC voltage signal in p.u./V. 
  • Conditioning gain : 0.05 V/V
  • Gain (V/p.u.) = 13.8 kV/120 x 0.05 = 50.5 V/p.u.
  • Gain (p.u./V) = 1/5.75 = 0.1739
• Current (p.u./V): Conversion gain of high AC current signal in p.u./V. 
  • Current probe: 0.4 V/A       
  • Conditioning gain: 5 V/V
  • Gain (V/A) = 2 
  • Gain (V/p.u.) = 15480 A/3600x 2V/A = 8.60 V/p.u.
  • Current parameters (p.u./V) = 1/8.60 = 0.1163

Grid Frequency Deadband (Hz)

Tested Unit Parameters

• H = Inertia constant in MJ/MVA or seconds.
• Ra = Stator resistance in p.u.
• Xq = Quadrature axis synchronous reactance in p.u. (saturated value recommended).
• Rated MVA = Apparent rated power in MVA
• Delta Pm VS Delta Speed: for Islanded system simulations, the coefficient determining the mechanical power fluctuations depending on the rotation speed. Value in p.u./p.u. The default value is zero.
• FO (60 Hz / 50 Hz) = Rated frequency in Hz: 60 or 50

Other Connections - Gains and Offsets

Miscellaneous

PID Controller Tab

This tab opens BERTA’s PID Controller pane. BERTA’s PID controller can be used only if the servomotor chain can be driven directly, bypassing the actual controller.

The PID output signal is used to bypass the speed governor controller to drive directly the gate servomotor chain. The gains, time constants and selections correspond to the diagram model.

To enable this controller, select PID Controller in the top left menu and click the BERTA Cmd red switch.

Classical Tab

This tab opens BERTA’s classic controller, which can only be used if the actuator pilot valve can be driven directly, bypassing the actual controller. The figure below presents BERTA’s classical controller diagram.

Select Classical Controller in the top left menu, and click the BERTA Cmd red switch.

BERTA Stab 1, Stab 2 and Stab 3 Tabs

The BERTA Stab 1, BERTA Stab 2 and BERTA Stab 3 tabs provide access to panels enabling the user to enter the modeling parameters of the Power System Stabilizer (PSS).

Choose the circuit stabilizer model usually in service in the top left box of the diagram. The panels allow adjusting the parameters of the PSS emulation function. This function corrects the simulated electrical load in closed-loop operating mode, i.e. islanded grid simulation. It is inactive in opened loop operating mode.

BERTA Stab 1

This panel shows the load modeling function based on the PSS output signal (valid for any PSS model) and the generic model of a classical PSS. This model is equivalent to the IEEE PSS1A type.

BERTA Stab 2

This panel shows a two-input model equivalent to the IEEE PSS2B type and a model with a gate feedback function specific to hydraulic groups.

BERTA Stab 3

This panel shows a multi-band PSS model equivalent to the IEEE PSS24 type.