ST5C

Exc IEEE ST5C model

This article is incomplete, some sections must be written.

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 version (2005), its predecessor model was called ST5B. Compared to ST5B, ST5C has additional options for connecting OEL and UEL inputs.

Model use, assumptions, validity domain and limitations

To be completed

Model inputs and output

The input variables are :

Variable	Description	Units
\(I_r P_u\)	rotor current	\({pu}\) (base \(S_{Nom}\), user-selected base voltage)
\(U_s P_u\)	measured stator voltage	\({pu}\) (base \(U_{Nom}\))
\(U_{s} R_{ef} P_u\)	reference stator voltage	\({pu}\) (base \(U_{Nom}\))
\(U O_{el} P_u\) (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
\(K_c\)	Rectifier loading factor proportional to commutating reactance	\({pu}\)
\(K_r\)	Gain of voltage after overexcitation and underexcitation limitations	\({pu}\)
\({PositionOel}\)	Input location : (0) none, (1) voltage error summation, (2) take-over at AVR input	\(-\)
\({PositionScl}\)	Input location : (0) none, (1) voltage error summation, (2) take-over at AVR input	\(-\)
\({PositionUel}\)	Input location : (0) none, (1) voltage error summation, (2) take-over at AVR input	\(-\)
\(t_1\)	Inverse timing current constant	\({s}\)
\(t U_{B1}\)	Second lag time constant	\({s}\)
\(t U_{B2}\)	First lag time constant	\({s}\)
\(t U_{C1}\)	Second lead time constant	\({s}\)
\(t U_{C2}\)	First lead time constant	\({s}\)
\(t O_{B1}\)	Second lag time constant (overexcitation limitation)	\({s}\)
\(t O_{B2}\)	First lag time constant (overexcitation limitation)	\({s}\)
\(t O_{C1}\)	Second lead time constant (overexcitation limitation)	\({s}\)
\(t O_{C2}\)	First lead time constant (overexcitation limitation)	\({s}\)
\(t_R\)	Stator voltage filter time constant	\({s}\)
\(t U_{B1}\)	Second lag time constant (underexcitation limitation)	\({s}\)
\(t U_{B2}\)	First lag time constant (underexcitation limitation)	\({s}\)
\(t U_{C1}\)	Second lead time constant (underexcitation limitation)	\({s}\)
\(t U_{C2}\)	First lead time constant (underexcitation limitation)	\({s}\)
\(V_{r} Max P_u\)	Maximum field voltage	\({pu}\) (user-selected base voltage)
\(V_{r} Min P_u\)	Minimum field voltage	\({pu}\) (user-selected base voltage)

Model diagram

Figure 1: ST5C block diagram

Model variant

In the ST5B model :

• the overexcitation and underexcitation limitation voltages are applied at the AVR input
• there is no stator current 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

References

1.

Electrical TI of, Engineers E (2016) IEEE recommended practice for excitation system models for power system stability studies. IEEE Std 4215-2016

2.

Commission IE (2024) Energy management system application program interface (EMS-API) part 302: Common information model (CIM) dynamics. IEC 61970-302