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AC8B
Description
This module is based on the IEEE Std 412.5 type AC8B excitation system model [1]. The block diagram of this excitation system model includes an AC alternator with non-controlled rectifiers. The model presents alternate options for the under excitation limiter input.
Mask and Parameters
AVR Parameters
Expanding the "AC8B diagram" displays the block diagram in the parameters window.
Name | Description | Unit | |
|---|---|---|---|
Tr | Regulator input time constant. This input filter is not part of the standard and there are no typical values recommended. It was added for flexibility. NB This parameter can be set to zero if the filter is not used. |
| s |
Tdr | Derivative time constant control PID |
| s |
Kpr | Proportional gain PID control |
|
|
Kdr | Derivative gain PID control |
|
|
Kir | Integral gain PID control |
|
|
Ka | AVR filter gain |
| - |
Ta | AVR filter time constant |
| s |
VRmax | Maximum regulator internal voltage |
| pu |
VRmin | Minimum regulator internal voltage |
| pu |
Exciter Parameters
Expanding the "Exciter diagram" displays the block diagram in the parameters window.
Name | Description | Unit | |
|---|---|---|---|
Ke | Exciter constant related to self-excited field |
| - |
Te | Exciter time constant |
| s |
Kc | Rectifier loading factor |
| - |
Kd | Demagnetizing factor |
| - |
Se1, Se2 | Exciter saturation factor at the corresponding Vex |
| pu |
Ve1, Ve2 | Exciter voltage for the exciter saturation function |
| pu |
VEmin | Minimum exciter output voltage |
| pu |
Vfemax | Maximum exciter field current |
| pu |
Initial Values Mask Parameters
Name | Description | Unit | |
|---|---|---|---|
Ifd0 | Synchronous machine field current initial value |
| pu |
Efd0 | Exciter output voltage initial value |
| pu |
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 |
|---|---|---|
Vc1 | Signal proportional to compensated terminal voltage If a load compensator block is not used upstream from the exciter block, then Vc1 is equal to Vt (main alternator terminal voltage) | pu |
Vref | Voltrage regulator reference voltage | pu |
Vs | Is defined as the output voltage of a power system stabilizer (PSS) | pu |
Ifd | Synchronous machine field current* | pu |
*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.