Power System Dynamics and Control Presentation on Unit 3

POWER SYSTEM DYNAMICS AND CONTROL
UNIT 3
POWER SYSTEM STABILIZERS
DEPARTMENT OF ELECTRICAL ENGINEERING
Represented By:
CHAITRA NITIN PANAT
EPS Mtech 2nd Sem

CONTENT:
1. Power System Stability
2. Classification
3. Power system Stabilizer & types
4. Basic Concept Of Control Signals in PSS
5. Structure and Tuning
6. Field implementation & Operating Experiences
7. Advantages & Disadvantages
8. Applications
9. Future Trends
10. Conclusion
11. Reference

POWER SYSTEM STABILITY
1. Power system stability is the ability of an electric
power system for a given initial operating condition, to
regain a state of operating equilibrium after being
subjected to a physical disturbance , with most system
variables bounded so that practically the entire system
remains intact.
2.It is used to define the ability of the system to bring
back its operation to steady state condition within a
minimum possible time after having undergone any
transience or disturbance.

POWER SYSTEM STABILIZER
1.The Power System Stabilizer (PSS) is a
supplementary excitation controller used to damp
generator electro-mechanical oscillations in order to
protect the shaft line and stabilize the grid. It also
damps generator rotor angle swings, which are of
greater range in frequencies in power system.
2.The disturbance may be caused by the even small
change in reference voltage of the automatic voltage
regulator / exciter which results in ever increasing rotor
oscillations.

TYPES
1. Speed based stabilizer
2. Frequency based stabilizer
3. Power based stabilizer

Basic Concept of Control Signals in PSS

The choice of control signal for PSS can be based on
following criteria:
a. Signal must be obtained from local measurements and
easily synthesized.
b. The noise content of the signal must be minimal .
Otherwise complicated filters are required which can
introduce their own problems.
c. The PSS design based on a particular signal must be
robust and reject noise. This implies that lead
compensation must kept to a minimum to avoid
amplifying the noise.

Basic components of Power system stabilizer:
1. Washout block
2. Phase Compensation block
3. Gain block
4. Torsional Fiter
5. Stabilizer Output Limiter

SELECTION OF PSS PARAMETERS:
The overall excitation control system is designed so as
to:
1. Enhance system transient stability.
2. Maximize the damping of the local plant mode as
well as inter area mode oscillations without
compromising the stability of other modes.
3. Not adversely affect system performance during
major system upsets which cause large frequency
excursions
4. Minimize the consequences of excitation system
malfunction due to component failures.

Field Implementation and Operating Experiences of PSS
1. Measure the open loop frequency response without PSS.
This involves obtaining the transfer function between the
terminal voltage and AVR input in frequency domain.
2. Select PSS time constants by trial & error.
3. The early operating experience with speed input stabilizers
showed the need for torsional filtering to eliminate
unfavorable interactions at torsion frequency.
4. The frequency input stabilizers are susceptible to noise
generated by arc furnace loads located close to the power
stations.

Advantages & Disadvantages:
1. Improved damping of the system.
2. The dynamic stability of a system is improved.
3. Reduced power losses.
4. Time consuming tuning of PSS.
5. Non optimal damping in the entire operating range.

Applications:
1. Used in various motors.
2. Industrial applications.
3. Controlling System.
4. Stability Control.
5. Voltage Control.
6. Frequency Control.

Future Trends Of PSS :
1. Research efforts in academic institutions and
industry have been directed at better approaches to
tuning of PSS using analytical techniques.
2. Another direction of investigation is the possibility of
coordinated tuning of PSS in several locations using the
general multi-machine system.
3. The present practice in tuning PSS is to select a
tuning condition of the system and select the
parameters for satisfactory performance under all
possible operating conditions.

CONCLUSION :
1. The state space design was better than root locus and
frequency response methods and is used in present study.
2. The elements of state vector were obtained by using field
circuit dynamics and effects of AVR.
3. The generalized model of a system was obtained by
considering transmission networks, loads, variety of excitation
system, prime mover models, HVDC link , etc.
4. The selection of PSS parameters to maximize the damping
of local plant mode was explained.
5. The various optimization techniques for tuning of PSS
parameters were summarized.

REFERENCE :
1. Kundur, P. (1994). Power System Stability and Control,
McGraw Hill
2. Anderson,P.M.;& Fouad,A.A(2003).Power System Control
and Stability , John Wiley & sons.
3. www.bing.com
4. www.google.com
5. www.wikipedia.com

Power System Dynamics and Control Presentation on Unit 3

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