Module 2 : Frequency Control in a Power System
Lecture 8a : A Brief Review of Feedback Control Systems
Objectives
In this lecture you will learn the following
What are feedback control systems ?
Transfer Function Representation of linear systems
Proportional and Integral Controllers
What is a feedback control system ?
Before we move on to study frequency control of a power system, we will study about another phenomena known as voltage instability. To get a better
understanding of frequency control and voltage instability, we will first briefly review the topic of feedback control systems.
What does one mean by a feedback control system and why/when is it necessary? To understand this let us take a simple example.
Let us suppose that you wish to buy 1 kg of rice from your grocer. If all rice grains were of the same weight, it would be possible (although by a very tedious
process!) to calculate how many grains are required. However, not only will this be time consuming, but it is also true that there are uncertainties in the grain
weight. Therefore, rather than follow this procedure the grocer will put some rice into his weighing pan (counter balanced by 1 kg standard weight) and
depending on the extent of imbalance, he will incrementally add or reduce grain in the pan. A seasoned grocer may even hold some grain in his fist and
gradually pour it by monitoring the position and rate at which the pan moves. By doing this, he can speed up the process of weighing the rice. This is a
manual feedback control system. The major components are shown below:
Components of a feedback control system
We saw in the previous slide that a feedback system can be used to quickly perform the task of weighing 1 kg of rice.It was a manual feedback
which involved a human being as the controller and actuator. While a controller decides on what control actions are to be taken based on the
feedback obtained by a sensor, an actuator is a device that converts the command of a controller into appropriate actions.
Lecture 8a : A Brief Review of Feedback Control Systems
Objectives
In this lecture you will learn the following
What are feedback control systems ?
Transfer Function Representation of linear systems
Proportional and Integral Controllers
What is a feedback control system ?
Before we move on to study frequency control of a power system, we will study about another phenomena known as voltage instability. To get a better
understanding of frequency control and voltage instability, we will first briefly review the topic of feedback control systems.
What does one mean by a feedback control system and why/when is it necessary? To understand this let us take a simple example.
Let us suppose that you wish to buy 1 kg of rice from your grocer. If all rice grains were of the same weight, it would be possible (although by a very tedious
process!) to calculate how many grains are required. However, not only will this be time consuming, but it is also true that there are uncertainties in the grain
weight. Therefore, rather than follow this procedure the grocer will put some rice into his weighing pan (counter balanced by 1 kg standard weight) and
depending on the extent of imbalance, he will incrementally add or reduce grain in the pan. A seasoned grocer may even hold some grain in his fist and
gradually pour it by monitoring the position and rate at which the pan moves. By doing this, he can speed up the process of weighing the rice. This is a
manual feedback control system. The major components are shown below:
Components of a feedback control system
We saw in the previous slide that a feedback system can be used to quickly perform the task of weighing 1 kg of rice.It was a manual feedback
which involved a human being as the controller and actuator. While a controller decides on what control actions are to be taken based on the
feedback obtained by a sensor, an actuator is a device that converts the command of a controller into appropriate actions.
