AC4A Excitation System

Implements IEEE type AC4A excitation system model

Library

Simscape / Electrical / Specialized Power Systems / Electrical Machines / Synchronous Machine Control

Description

This block models an ac alternator connected to a thyristor rectifier to produce the field voltage Vf required by the Synchronous Machine block. A voltage regulator controls the thyristors and the excitation system stabilization is accomplished by a series lead-lag compensator.

Controllers Tab

Low-pass filter time constant: The time constant Tr of the first-order system representing the stator terminal voltage transducer. Default is 20e-3.
Voltage regulator gain and time constant: The gain Ka and time constant Ta of the first-order system representing the main regulator. Default is [200 0.015].
Voltage regulator input limits: The voltage regulator input limits VImin and VImax, in p.u. Default is [-10 10].
Voltage regulator output limits: The voltage regulator output limits VRmin and VRmax, in p.u. Default is [-4.53 5.64].
Transient gain reduction lead and lag time constants: The time constants Tb and Tc of the first-order system representing the lead-lag compensator. Default is [10 1.0].

Exciter and Rectifier Tab

Rectifier loading factor Kc: The gain Kc represents the rectifier loading factor proportional to the commutating reactance. Default is 0.

Initial Values Tab

Initial values of terminal voltage and field voltage: The initial values of terminal voltage Vt0 and field voltage Efd0, both in p.u. Initial terminal voltage is normally set to 1 pu. The Vt0 and Efd0 values can be determined using the Powergui Load Flow tool. Default is [1 1].
Sample time: Specify a value greater than zero to discretize the block at the given sample time. Set to -1 to inherit the simulation type and sample time parameters of the Powergui block. Default is 0.

Ports

Vref: The reference value of the stator terminal voltage, in p.u.
Vt: The measured value in p.u. of the stator terminal voltage of the controlled Synchronous Machine block.
Ifd: The measured value in p.u. of the stator field current of the controlled Synchronous Machine block.
Vstab: Connect this input to a power system stabilizer to provide additional stabilization of power system oscillations. When you do not use this option, connect to a Simulink^® ground block. The input is in p.u.
Efd: The field voltage to apply to the Vf input of the controlled Synchronous Machine block. The output is in p.u.

References

[1] “IEEE Recommended Practice for Excitation System Models for Power System Stability Studies.” IEEE Standard, Vol. 421, No. 5, 2005 (Revision of IEEE 521.5-1992).

Version History

Introduced in R2012b