120124399 power system stabilizer 1

7/29/2019 120124399 Power System Stabilizer 1

http://slidepdf.com/reader/full/120124399-power-system-stabilizer-1 1/8

ADVANCED AND EVER ADVANCING

Power SystemStabilizer (PSS)

G e n e r a t o r P o w e r PSS OFF PSS ON

PSS OFF PSS ON

time (sec)

time (sec)

0.85

0.9

0.95

G e n e r a t o r P o

w e r

0.85

0.9

0.95

0 1 2

0 1 2

Step response

Grid one line open



AVR

AVR

+

PSS

K1

K1+K1A

K1+K1A+K1P

∆ Tm

∆ Tm

∆ Tm

∆ ω1

Ms

1

Ms

1

Ms

D

D+DA

D+DA+DP

+ – –

+ – –

+ – –

G

Power

A POWER SYSTEM STABILIZER (PSS) which is installed in the Automatic Voltage Regulator of thGenerator, can improve the power system stability. Therefore the PSS has excellent cosperformance rather than constructions of power system arrangements. MITSUBISHI PSS hasvarious system, such as Analogue / Digital type and ∆ P / ∆ ω / ∆ f input type, and can respond tovarious customer's needs.

Summary of Powersystem stability

Theory of PSS

sSummary

sExplanation on torque vector

Though a generator output power is

decided by the turbine mechanical torque,a generator output power also can bechanged by changing excitation value

transiently. (Fig.1)A PSS detects the changing of generatoroutput power, controls the excitation

value, and reduces the power swingrapidly. (Fig.2)

Fault (3 phase fault, Several cycles open)

Unstable (less dynamic stability)

Stable

Step out (less transient stability)

F a u l t h a p p e n e d

F a u l t c l e a r e d

Transientarea Dynamic area

Constant

Excitation

Block Diag

K1 : Synchronizing TorqueD : Damping TorqueM : Inertia

K1A : Synchronizing Torque bDA : Damping Torque by AV

K1P : Synchroning Torque byDP : Damping Torque by PS

time

Power



Type of PSS

As mentioned before, a PSS detects the changing of generator output power and controls the excitation value.

The type of PSS is identified by the detecting signal. The most simple and typical type is ∆ P input type.And, recently ∆ ω input type and/or ∆ f input type PSS also adopted in order to improve a stability of inter-area mode dueto the recent increase in power system and power re-routing. Each features are as follows;

MultipleInput Type PSS

∆P Signal

∆ω or∆f Signal

Local ModePowerOscillation

Inter-area(Long Cycle)ModePower Oscillation

ComplexPowerOscillation

qIndividual generator oscillates

against the system.

qFrequency is approx. 1 Hz.

qThe whole system oscillates with long-distance and large power transportation

system connection.

qFrequency is 0.2 to 0.5 Hz

qComplex power oscillation mode,such as local mode + inter-area

mode

qPSS of single input, such as

∆P, ∆ ω and ∆ f, etc.

q∆ P type of PSS is more effective.

qPSS of single input, such as ∆ P, ∆ ω and ∆f, etc.

q∆ ω or ∆f type of PSS is more effective.

qMultiple input PSS is more effective.

q∆P + ∆ ω type or ∆ P + ∆ f type of PSS.



New Publication, effective May. 1998.Specifications subject to change without notice.

HEAD OFFICE: MITSUBISHI DENKI BLDG., MARUNOUCHI, TOKYO 100-8310. TELEX: J24532 CABLE: MELCO TOKYO

Improper use of products can cause severe injury or death,

and may result in damage to product and other property.

Please read instruction manual before installing or using product.

Mitsubishi Power System Stabilizer (PSS)

SE-D581-A(9805-2.0)ROD



Integral of Accelerating Power Type PSS(Power System Stabilizer)

time (sec)

P o w e r

AVR without PSS

Step respnse of voltage reference

AVR with PSS

time (sec)

P o w e r

AVR without PSS

AVR with PSS

Power system fault(1 line open after 3 phases grounding)



New Publication, effective Sep. 2001.Specifications subject to change without notice

HEAD OFFICE: MITSUBISHI DENKI BLDG., MARUNOUCHI, TOKYO 100-8310. TELEX: J24532 CABLE: MELCO TOKYO

Improper use of products can cause severe injury or death,

and may result in damage to product and other property.

Please read instruction manual before installing or using product.

SE D779 A(0109 0 5)MDOC

Mitsubishi Integral of Accelerating Power Type PSS (Power System Stabilizer)

AVR

AVR+

PSS

K1

K1+K1A

K1A+DA

K1+D

K1+D

K1+K1A+K1P

1Ms

1Ms

1Ms

S

S

S

D 0

0

0

D+DA

D+DA+DP

Theory of PSS

Though a generator outputpower is decided by theturbine mechanical torque, agenerator output power alsocan be changed by changingexcitation value transiently.(Fig.3)A PSS detects the changingof generator output power,controls the excitation value,and reduces the powerswing rapidly. (Fig.4)

Generator output power

Excitation value

Generator output power

Excitation value

ConstantExcitation

Block Diagram Torque Characteristics

K1 : Synchronizing TorqueD : Damping TorqueM : Inertia

K1A : Synchronizing Torque by AVRDA : Damping Torque by AVR

K1P : Synchroning Torque by PSSDP : Damping Torque by PSS

(Damping Torque)

(Synchronizing Torque)

Resultant Torque

Resultant Torque

By changing of excitation value,generator output power can bechanged transiently

(Fig.3) (Fig.4)

A PSS detects the changing ofgenerator output power, controlsthe excitation value, and reducesthe power swing rapidly.

Summary

Explanation on torque vector

(Stable at D+DA+DP 0)

(Unstable at D+DA 0)

120124399 power system stabilizer 1

Documents