Module 7 : Power System Structures
Lecture 35 : Concluding Notes
Objectives
In this lecture you will learn the following
A summary of what we learnt in the entire course
What are future challenges and trends in power system operation and control ?
We have come to the concluding part of this course. We started out in this course by reviewing the basic
power system structure, operational objectives and the ways to achieve them.
We re-iterate the basic objectives here in a concise sentence
A power system should supply quality power, on demand, to a consumer economically and
with minimal ecological impact.
Quality power implies that a consumer is given a supply with a practically constant voltage magnitude and
frequency. The supply is also reliable, which means that barring a very large (and rare) disturbance or a
sequence of disturbances, "the lights are always on".
The power system operation is controlled by a mix of automatic feedback and manual control actions. Real
time operation of a power system is monitored by a "system operator" who has several "schedulable"
quantities at his disposal. These quantities are scheduled to maximize economic benefit for a consumer and
also to ensure security.
So is there any thing more to be "done" ? Yes. Although we have learnt all about operational and control
objectives, there is scope to improve the way a system is operated. With concerns about ecological impact, it
has become difficult (and expensive) to build new transmission lines and add generation. As a result, the focus
is to utilize our resources even more optimally, while still satisfying all constraints. With changes in power
system structure ("de-regulation") from a vertically integrated utility structure to a market based one, there is
a greater need for flexibility to accomodate "power transactions" and also ensure fair access of common
resources (such as the transmission network) for all players.
These challenges can be tackled with newer technologies -- we will discuss some of these soon -- and by
better analytical techniques.
Some New Technologies
Often new ideas which have been proposed either recently or long before become viable economically due to
advances in materials and manufacturing techniques. Amongst the recent technologies which are likely to
impact power system operation and control are:
a) Wide Area Measurement Systems (WAMS): We introduced Wide Area Measurement Systems in Module
6. This communication technology can allow for fast control. Most automatic controllers in a power system use
locally measured feedback systems for control, e.g., Automatic Voltage Regulators and Governors. In fact, AGC,
which uses feedback signal from the tie -lines to control generation, is the only control which uses non-local
measurements. AGC itself is a slow control (it acts over several minutes) and therefore the communication
requirements are quite modest. It is expected that fast wide area measurements may allow for superior
emergency control schemes which need to be executed in a very short time.
b) Power Electronics : Although HVDC has been around for a fairly long time, new converter topologies using
voltage source converters offer a promise of increased flexibility in control. These converters use devices (like
Gate Turn-off Thyristors) which can be turned off by a gate signal (unlike thyristors). This implies that there is
an extra degree of freedom in their control. Voltage source converters as well as variable impedance controllers
based on thyristors, like TCSC, which we learnt in Module 4, are now commercially available.
Can you do a survey of recent literature on both these technologies ?
Lecture 35 : Concluding Notes
Objectives
In this lecture you will learn the following
A summary of what we learnt in the entire course
What are future challenges and trends in power system operation and control ?
We have come to the concluding part of this course. We started out in this course by reviewing the basic
power system structure, operational objectives and the ways to achieve them.
We re-iterate the basic objectives here in a concise sentence
A power system should supply quality power, on demand, to a consumer economically and
with minimal ecological impact.
Quality power implies that a consumer is given a supply with a practically constant voltage magnitude and
frequency. The supply is also reliable, which means that barring a very large (and rare) disturbance or a
sequence of disturbances, "the lights are always on".
The power system operation is controlled by a mix of automatic feedback and manual control actions. Real
time operation of a power system is monitored by a "system operator" who has several "schedulable"
quantities at his disposal. These quantities are scheduled to maximize economic benefit for a consumer and
also to ensure security.
So is there any thing more to be "done" ? Yes. Although we have learnt all about operational and control
objectives, there is scope to improve the way a system is operated. With concerns about ecological impact, it
has become difficult (and expensive) to build new transmission lines and add generation. As a result, the focus
is to utilize our resources even more optimally, while still satisfying all constraints. With changes in power
system structure ("de-regulation") from a vertically integrated utility structure to a market based one, there is
a greater need for flexibility to accomodate "power transactions" and also ensure fair access of common
resources (such as the transmission network) for all players.
These challenges can be tackled with newer technologies -- we will discuss some of these soon -- and by
better analytical techniques.
Some New Technologies
Often new ideas which have been proposed either recently or long before become viable economically due to
advances in materials and manufacturing techniques. Amongst the recent technologies which are likely to
impact power system operation and control are:
a) Wide Area Measurement Systems (WAMS): We introduced Wide Area Measurement Systems in Module
6. This communication technology can allow for fast control. Most automatic controllers in a power system use
locally measured feedback systems for control, e.g., Automatic Voltage Regulators and Governors. In fact, AGC,
which uses feedback signal from the tie -lines to control generation, is the only control which uses non-local
measurements. AGC itself is a slow control (it acts over several minutes) and therefore the communication
requirements are quite modest. It is expected that fast wide area measurements may allow for superior
emergency control schemes which need to be executed in a very short time.
b) Power Electronics : Although HVDC has been around for a fairly long time, new converter topologies using
voltage source converters offer a promise of increased flexibility in control. These converters use devices (like
Gate Turn-off Thyristors) which can be turned off by a gate signal (unlike thyristors). This implies that there is
an extra degree of freedom in their control. Voltage source converters as well as variable impedance controllers
based on thyristors, like TCSC, which we learnt in Module 4, are now commercially available.
Can you do a survey of recent literature on both these technologies ?
