AVR means automatic voltage regulator. An excitation system can operate on AVR mode, or power factor control mode, or reactive power control mode, or field voltage control mode, or field current control mode.

If you want to represent the AVR response, please refer to the IEEE Std. 421.5(2016), IEEE Recommended Practice for Excitation System Models for Power System Stability Studies.

https://standards.ieee.org/standard/421_5-2016.html

Not exactly PSCAD (EMTP-type) models, but you should start with the IEEE Std. 421.5 - IEEE Recommended Practice for Excitation System Models for Power System Stability Studies

https://standards.ieee.org/content/ieee-standards/en/standard/421_5-2016.html

I used IEEE Std for Excitation system but i am not able to control active and reactive power of Synchronous Generator L.T.G. Lima

Excitation systems do not control active power: that is the turbine control (with or without speed governor response). Excitation systems in AVR mode control terminal voltage and, in doing so, change the reactive power output of the generator.

You can follow this link: https://hvdc.ca/webhelp/Master_Library_Models/Machines/Exciter_Models/Exciter_Models.htm

terminal voltage is not controlled using this exciter models. Umesh Chaudhary