DC1C
Exc IEEE DC1C model
Context
This voltage regulator model first appeared in the IEEE Std 421.5-2016 [1]. It has been reproduced identically in the IEC 61970-302:2024 version [2]. In the previous standard versions (1992, 2005), its predecessor model was called DC1A. Compared to DC1A, DC1C has additional options for connecting OEL limits and an additional limit \(E_{fd} Min P_u\).
It conludes a DC type rotating exciters’s model, which can be self-excited (buck-boost) or separately excited (as discussed in 1981 IEEE Committe Report). This type of rotating exciter’s system tend to disapear in new synchronous machines. It includes a DC excitation system model as described in [2].
Model use, assumptions, validity domain and limitations
This particular model is used represent field controlled dc commutator exciters with continuously acting voltage regulators (especially direct-acting rheostatic, rotating amplifier, and magnetic amplifier types). As other standard DC excitation models, it includes the loading effects by using a loaded saturation curve (\(S_E(E_{FD})\) is the saturation block). Excitation systems incorporating rotating machines produce a field voltage output (\(E_{FD}\)) which is proportional to the rotating speed of the machine. Since this effect is negligible when speed deviations are small which is the case of dynamic studies of large interconnected power systems, the effect of speed deviations on the output of the dc rotating exciter models is not represented in this latest version of the standard. However, some commercial software may have implemented such speed dependency in their model.
Model inputs and output
The input variables are :
| Variable | Description | Units |
|---|---|---|
| \(U_s P_u\) | measured stator voltage | \({pu}\) (base \(U N_{om}\)) |
| \(U_{s} R_{ef} P_u\) | reference stator voltage | \({pu}\) (base \(U N_{om}\)) |
| \(U O_{el} P_u\) (optional) | output voltage of overexcitation limiter | \({pu}\) (base \(U N_{om}\)) |
| \(U P_{ss} P_u\) (optional) | output voltage of power system stabilizer | \({pu}\) (base \(U N_{om}\)) |
| \(U S_{cl} O_{el} P_u\) (optional) | output voltage of stator current overexcitation limiter | \({pu}\) (base \(U N_{om}\)) |
| \(U S_{cl} U_{el} P_u\) (optional) | output voltage of stator current underexcitation limiter | \({pu}\) (base \(U N_{om}\)) |
| \(U U_{el} P_u\) (optional) | output voltage of underexcitation limiter | \({pu}\) (base \(U N_{om}\)) |
The output signal is \(E_{fd} P_u\), the excitation voltage in \({pu}\) (user-selected base voltage).
Model parameters
| Parameter | Description | Units |
|---|---|---|
| \(A_{Ex}\) | Gain of saturation function | \({pu}\) |
| \(B_{Ex}\) | Exponential coefficient of saturation function | \(-\) |
| \(E_{fd} Min P_u\) | Minimum excitation voltage | \({pu}\) (user-selected base voltage) |
| \(K_a\) | Voltage regulator gain | \({pu}\) |
| \(K_e\) | Exciter field proportional constant | \({pu}\) |
| \(K_f\) | Exciter rate feedback gain | \({pu}\) |
| \({PositionOel}\) | Input location : (0) none, (1) voltage error summation, (2) take-over at AVR output | \(-\) |
| \({PositionScl}\) | Input location : (0) none, (1) voltage error summation, (2) take-over at AVR output | \(-\) |
| \({PositionUel}\) | Input location : (0) none, (1) voltage error summation, (2) take-over at AVR output | \(-\) |
| \(t_A\) | Voltage regulator time constant | \({s}\) |
| \(t_B\) | Voltage regulator lag time constant | \({s}\) |
| \(t_C\) | Voltage regulator lead time constant | \({s}\) |
| \(t_E\) | Exciter time constant | \({s}\) |
| \(t_F\) | Exciter rate feedback time constant | \({s}\) |
| \(t_R\) | Stator voltage filter time constant | \({s}\) |
| \(V_{r} Max P_u\) | Maximum field voltage | \({pu}\) (user-selected base voltage) |
| \(V_{r} Min P_u\) | Minimum field voltage | \({pu}\) (user-selected base voltage) |
Model diagram
Model variant
In the DC1A model :
- the integrator of the second loop (and its output \(E_{fd} P_u\)) is not limited
- there are no stator current limiter and no overexcitation limiter
Open source implementations
This model has been successfully implemented in :
| Software | URL | Language | Open-Source License | Last consulted date | Comments |
|---|---|---|---|---|---|
| Dynawo | Link | Modelica | MPL v2.0 | 24/05/2024 |