Description
This module is based on the IEEE std 412.5 type ST2A excitation system model [1]. The excitation system uses both terminal current and terminal voltage. The effects of commutation and rectifier loading are account in the model.
Mask and Parameters
AVR Parameters
Expanding the "ST2A diagram" displays the block diagram in the parameters window.
| Name | Description | Unit | |
|---|---|---|---|
Tr | Regulator input filter time constant | pu | |
Kf | Excitation control system stabilizer gain | pu | |
Tf | Excitation control system stabilizer time constant | pu | |
Ka | Voltage regulator gain | pu | |
Ta | Regulator time constant | pu | |
Vrmax | Maximum voltage regulator output | pu | |
Vrmin | Minimum voltage regulator output | s | |
Exciter Parameters
Expanding the "Exciter diagram" displays the block diagram in the parameters window.
| Name | Description | Unit | |
|---|---|---|---|
Te | Exciter time constant | s | |
Ke | Exciter constant related to self-excited field | - | |
Kc | Rectifier loading factor proportional to commutating reactance | - | |
EFDmax | Maximum exciter output voltage | pu | |
Kp | Potential circuit real part gain coefficient | - | |
Kj | Potential circuit imaginary part gain coefficient | - | |
Initial Values Mask Parameters
Name | Unit | Description |
Ifd0 | pu | Synchronous machine field current initial value |
Efd0 | pu | Exciter output voltage initial value |
The parameters Ifd0 and Efd0 can be set manually by entering a numerical value. It can also be set automatically, based on load flow calculations, by entering a referenced synchronous machine variable. For instance, if the name of the synchronous machine on which the excitation system is connected is “SM1”:
- If a thermal machine or a hydraulic machine is used, Ifd0 shall be set as “=SM1.IfdInit” multiplied by the synchronous machine parameter Xad = Xd – Xl, and Efd0 shall be set as “=SM1.EfdInit”;
- If a pu standard or pu fundamental machine is used, Ifd0 shall be set as “=SM1.IF_Init” and Efd0 shall be set as "=SM1.EFD_Init".
The HYPERSIM simulation option Set Initial Conditions must be checked for the automatic initialization to work properly.
Inputs and Outputs and Signals Available for Monitoring
Inputs
| Name | Description | Unit |
|---|---|---|
Voel | Overexcitation limiter output* | pu |
Vc1 | Signal proportional to compensated terminal voltage If the Load Compensator block is not used upstream from the exciter block, then Vc1 is equal to Vt (main alternator terminal voltage) | pu |
Vuel | Underexcitation limiter output* | pu |
Vref | Voltage regulator reference voltage | pu |
Vs | Is defined as the output voltage of a Power System Stabilizer (PSS) [1]. | pu |
Ifd | Synchronous machine field current** | pu |
Id | Active component of generator terminal current or component from load compensator | pu |
Iq | Reactive component of generator terminal current or component from load compensator | |
Vd | Active component of generator terminal voltage or component from load compensator | |
Vq | Reactive component of generator terminal voltage or component from load compensator |
*Vuel and Voel is normally an input to this excitation system but the user has the option to use a fixed constant value directly in the mask by choosing internal in the mask option.
*A switch allows the users to select UEL input locations (Vuel)
- Summation point ( voltage error )
- Take-over at voltage regulator input
**If a Synch. Machine (Hydraulic or Thermal) from the Network Machines and Generators library is used, the machine observable Ifd must be multiplied by the synchronous machine parameter Xad = Xd – Xl prior to its input to the exciter. This multiplication is not needed if a Synchronous Machine (pu Standard) or (pu Fundamental) is used.
Outputs
| Name | Description | Unit |
|---|---|---|
| Efd | Exciter output voltage | pu |
References
1. “IEEE Recommended Practice for Excitation System Models for Power System Models for Power System Stability Studies,” IEEE Standard 421.5-2005.