ST9C

Exc IEEE ST9C 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].

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 \(S N_{om}\), user-selected base voltage)
\(i_t P_u\)	complex current at the terminal	\({pu}\) (base \(S_{Nom}\), \(U N_{om}\))
\(U_s P_u\)	measured stator voltage	\({pu}\) (base \(U N_{om}\))
\(U_{s} R_{ef} P_u\)	reference stator voltage	\({pu}\) (base \(U N_{om}\))
\(u_t P_u\)	complex voltage at the terminal	\({pu}\) (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
\(K_a\)	Voltage regulator gain	\({pu}\)
\(K_{as}\)	Power converter gain proportional to supply voltage	\({pu}\)
\(K_c\)	Rectifier loading factor proportional to commutating reactance	\({pu}\)
\(K_i\)	Potential circuit (current) gain coefficient	\({pu}\)
\(K_p\)	Potential circuit gain	\({pu}\)
\(K_u\)	Gain associated with activation of takeover UEL	\({pu}\)
\({PositionOel}\)	Input location : (0) none, (1) voltage error summation, (2) take-over	\(-\)
\({PositionScl}\)	Input location : (0) none, (1) voltage error summation, (2) take-over	\(-\)
\({PositionUel}\)	Input location : (0) none, (1) voltage error summation, (2) take-over	\(-\)
\({Sw1}\)	If true, power source derived from terminal voltage, if false, independent from terminal voltage	\(-\)
\(t_A\)	Voltage regulator time constant	\({s}\)
\(t_{As}\)	Equivalent time constant of power converter firing control	\({s}\)
\(t_{AUel}\)	Time constant of underexcitation limiter	\({s}\)
\(t_{Bd}\)	Filter time constant of differential part of voltage regulator	\({s}\)
\(t_{Cd}\)	Time constant of differential part of voltage regulator	\({s}\)
\(\Theta_p\)	Potential circuit phase angle	\({rad}\)
\(t_R\)	Stator voltage filter time constant	\({s}\)
\(V_{a} Max P_u\)	Maximum output voltage of limited first order	\({pu}\)
\(V_{a} Min P_u\)	Minimum output voltage of limited first order	\({pu}\)
\(V_{b} Max P_u\)	Maximum available exciter field voltage	\({pu}\) (base \(U N_{om}\))
\(V_{r} Max P_u\)	Maximum field voltage	\({pu}\) (user-selected base voltage)
\(V_{r} Min P_u\)	Minimum field voltage	\({pu}\) (user-selected base voltage)
\(X_l P_u\)	Reactance associated with potential source	\({pu}\) (base \(S_{Nom}\), \(U_{Nom}\))
\(Z_a P_u\)	Dead-band for differential part influence on voltage regulator	\({pu}\) (base \(U N_{om}\))

Model diagram

Figure 1: ST9C block diagram

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