Unit No-3 FACTS Technology Subject-Power System Operation Control Class-BE Electrical Engineering SPPU

1. DEPARTMENT OF ELECTRICAL ENGINEERING
JSPMS
BHIVARABAISAWANTINSTITUTEOFTECHNOLOGYANDRESEARCH,
WAGHOLI,PUNE
A.Y. 2020-21 (SEM-I)
Class: B.E.
Subject: Power System Operation Control
Unit No-3 FACTS Technology
Prepared by Prof. S. D. Gadekar
Santoshgadekar.919@gmail.com
Mob. No-9130827661

2. Content
• FACTS-(Flexible AC Transmission System Controller)
• Sources of Reactive Power (VARS)
• Necessity of FACTS Controller
• Classification of FACTS Controller
• STATIC VAR Compensator (SVC)
• Static Synchronous Compensator (STATCOM)
• Thyristor Controlled Series Capacitor (TCSC)
• Unified Power Flow Controller (UPFC)

3. FACTS-(Flexible AC Transmission System Controller)
“It is defined as alternating current transmission
systems incorporating power electronics based and other
static controllers to enhance controllability and increase
power transfer capability.”
It is a system based on power electronic and other static
equipment that provide control of one or more AC
transmission system parameters.

4. Sources of Reactive Power (VARS)
1. Synchronous Machines (Alternator & Motor)
2. Shunt Static Capacitors
3. Series Capacitors
4. Synchronous Condensers
5. FACTS Controllers

5. Necessity of FACTS Controller
∞ |𝑽| < 𝟎°G
𝑬 < 𝜹
Bus 1 Bus 2
𝑷 𝒎
𝑺 𝒔 = 𝑷 𝒔 + 𝒋𝑸 𝒔
𝑺 𝒓 = 𝑷 𝒓 + 𝒋𝑸 𝒓
Generalised Power System
𝑽 𝑺
𝑽 𝑹

6. Necessity of FACTS Controller
There has to maintained sufficient margins in power transfer due to,
• The large interconnected transmission networks are susceptible to
faults caused by lightning discharges and decrease in insulation
clearances by undergrounds.
• The loads in power system vary by the time of day, they are also
subject to variations caused by the weather and other
unpredictable factors. Thus the power flow in a transmission line
can very even under normal steady state conditions.

7. Necessity of FACTS Controller
There has to maintained sufficient margins in power transfer due to,
• The occurrence of contingency (due to tripping of line, generator)
can result in a sudden increase /decrease in the power flow.
• The increase in the loading of the transmission lines sometimes can
lead to voltage collapse due to the shortage of reactive power
delivered at the load centres.
These power transfer margins can not be maintained due to the difficulties in
the expansion of the transmission network caused by economic and
environmental reasons.
The introduction of fast dynamic control over reactive and active power by
high power electronic controllers makes AC transmission network ‘Flexible’
to adapt to the changing conditions.

8. Classification of FACTS Controller
FACTS controller are classified on the basis of
1. Type of connection in the power system network
a. Shunt Connected Controller
b. Series Connected Controller
c. Combined Series-Series
d. Combined Shunt-Series
2. Power Electronic Devices used in the control
a. Variable impedance type controller
b. The VSC based FACTS controller

9. Classification of FACTS Controller
2. Power Electronic Devices used in the control
a. Variable impedance type controller
• Static VAR Compensator-SVC (Shunt)
• Thyristor Controlled Series Capacitor-TCSC (Series)
• Thyristor Controlled Phase Shifting Transformer-
TCPST (Combined Shunt-Series)
b. The VSC based FACTS controller
• Static Synchronous Compensator-STATCOM (Shunt)
• Static Synchronous Series Compensator-SSSC (Series)
• Interline Power Flow Controller-IPFC (Combined
Series-Series)
• Unified Power Flow Controller-UPFC (Combined
Shunt-Series)

10. Static VAR Compensator-SVC
It is a variable impedance device where the current through a
reactor is controlled using back to back connected thyristor valves.
There are two types of SVC-
1. Thyristor Switched Capacitor-Thyristor Controlled Reactor (TSC-
TCR)
2. Fixed Capacitor -Thyristor Controlled Reactor (FC-TCR)
𝐿
|𝑽| < 𝟎°
G
𝑬 < 𝜹
Bus 1 Bus 2
𝑷 𝒎
𝑺 𝒔 = 𝑷 𝒔 + 𝒋𝑸 𝒔
𝑺 𝒓 = 𝑷 𝒓 + 𝒋𝑸 𝒓
𝑽 𝑺
𝑉𝑅
SVC 𝑽 𝑹
∗
+
−
𝑄 𝑟 =
𝑉𝑟
𝑋
|𝑉𝑠 − 𝑉𝑟|

11. Static VAR Compensator-SVC
The SVC is used in two main situations
1. Connected to the power system, to regulate the transmission
voltage.
2. Connected near large industrial loads, to improve power quality.

12. Circuit Diagram:-TCR-TSC Configuration SVC
High Voltage Transmission Line or Grid
Step Down Transformer
Potential
Transformer
HP
Filter
Tuned
Filter
Control Unit
𝑽 𝑹𝒆𝒇
+
𝑉𝑅
−
TCR-
Thyristor Control
Reactor
TSC
Thyristor Switched
Capacitor
Low Voltage Bus

13. Circuit Diagram:-FC-TCR Configuration SVC
High Voltage Transmission Line or Grid
Step Down Transformer
Potential
Transformer
HP
Filter
Tuned
Filter
Control Unit
𝑽 𝑹
∗
+
𝑉𝑅
−
TCR-
Thyristor Control
Reactor
Fixed Capacitor

14. V-I Characteristics of FC-TCR SVC V-I Characteristics of TSC-TCR SVC

15. Applications of SVC
• The midpoint located ideal SVC doubles the steady state power limit
and increases the stable angular difference between the synchronous
and the infinite bus from 90°to 180°.
The maximum steady state power across uncompensated line without SVC
corresponds to 𝛿 = 90° is,
𝑃𝑒 =
𝑉1 𝑉2
𝑋
sin 𝛿 −− −1
𝑃𝑚𝑎𝑥 = 𝑉2
𝑋 −− −2
The electrical power flow across the half line section connecting the
generator and SVC is,
𝑃𝑒 =
𝑉1 𝑉2
𝑋
2
sin 𝛿
2 −− −3
𝑃𝑚𝑎𝑥 = 2𝑉2
𝑋 −− −4

16. Applications of SVC
• Enhancement of transient stability.
Uncompensated Power System Network

17. Applications of SVC
• Enhancement of transient stability.
Compensated Power System Network

18. Applications of SVC
• The major applications of SVC is for rapid voltage
regulation and control of dynamic over voltages caused
by load through off, faults or other transients
disturbances.
• Augmentation of power system damping.

19. Advantages of SVC
• Faster Response under transient conditions
• There are no moving parts, hence requires less
maintenance
• There is no problem of loss of synchronism
• A SVC do not contribute to short circuit.

20. Static Synchronous Compensator-STATCOM
It is a shunt connected static compensator, which uses a voltage
source converter (VSC) based on self commutated power
semiconductor devices such as GTO, IGBT, IGCT, MCT etc.
𝐿
|𝑽| < 𝟎°
G
𝑬 < 𝜹
Bus 1 Bus 2
𝑷 𝒎
𝑺 𝒔 = 𝑷 𝒔 + 𝒋𝑸 𝒔
𝑺 𝒓 = 𝑷 𝒓 + 𝒋𝑸 𝒓
𝑽 𝑺
𝑉𝑅
VSC
𝑽 𝒓 𝑹𝒆𝒇𝒆𝒓𝒆𝒏𝒄𝒆
+
−
𝑄 𝑟 =
𝑉𝑟
𝑋
|𝑉𝑠 − 𝑉𝑟|
𝑉𝐷𝐶
+ −
𝐼 𝐷𝐶
DC Energy Source
𝐸𝑆
𝐼𝑠

21. VSC
𝑹𝒆𝒇𝒆𝒓𝒆𝒏𝒄𝒆
𝑽𝒐𝒍𝒕𝒂𝒈𝒆
+
−
𝑽 𝑫𝑪
+ −
𝑰 𝑫𝑪
DC Energy Source
𝑬 𝑺
𝑰 𝒔
𝑬 𝒕 Utility Voltage
Principle of Static Synchronous Compensator (STATCOM)-
The exchange of reactive power between the converter and the ac
system can be controlled by varying the amplitude of the three phase
output voltage, 𝑬 𝑺 of the converter.
VSC−𝑽𝒐𝒍𝒕𝒂𝒈𝒆 𝑺𝒐𝒖𝒓𝒄𝒆
𝑪𝒐𝒏𝒗𝒆𝒓𝒕𝒆𝒓
𝑰 𝒒
𝑬 𝒂𝒄
𝑬 𝑺 > 𝑬 𝒕
𝑬 𝑺 < 𝑬 𝒕
Supplies-Q
Absorbs- Q

22. 𝐼𝐿𝑚𝑎𝑥
V-I Characteristic of STATCOM-
𝐼 𝐶
𝑉𝑡
𝐼 𝐶𝑚𝑎𝑥
𝐼𝐿
1.0
0.25
Capacitive
Inductive

23. Applications of STATCOM-
• STATCOM is used to fast regulation of voltage at a load or
an intermediate bus. This will also increase the power
transfer capacity of network.
• The smaller size and faster response of a STATCOM
provides an opportunity to import power from distant
economic generators while the voltage is stabilized with a
local STATCOM.
• The use of multi pulse and or multilevel converters
eliminates the need for harmonic filters in the case of a
STATCOM.

24. Advantages of STATCOM-
• Faster response
• Requires less space as bulky passive components (such as
reactors) are eliminated.
• Inherently modular and relocatable
• It can be interfaced with real power sources such as
battery, fuel cells or SMPS.
• A STATCOM has superior performance during low voltage
condition as the reactive current can be maintained
constant.
In a SVC, the capacitive reactive current drops linearly with
the voltage at the limit of capacitive susceptance.

25. Sr.
No
STATCOM SVC
1 It is a converter based VAR generator,
functions as a shunt connected synchronous
voltage source.
It is a TCR-TSC based VAR generator,
functions as a shunt connected, controlled
reactive admittance.
2 The real and reactive power exchange
between the STATCOM and the ac system
can be controlled independently of each
other. Also any combination of real and
reactive power generation and absorption is
achievable.
The Real power compensation is not
possible using SVC as interfacing suitable
energy storage with ac system for real
power exchange is not possible.
3 The STATCOM can be operated over its full
output current range even at very low,
typically about 0.2 PU system voltage levels.
The maximum attainable corresponding
current of the SVC decreases linearly with
AC system voltage.
4 The transient stability margin obtained with
the STATCOM, due to the better support of
the midpoint voltage is significantly greater.
The transient stability margin is less for the
same rating SVC.
5 Small in size. Large in size as it requires the capacitor and
reactor banks with their associated
switchgear and protection.
Comparison between SVC & STATCOM

26. Sr.
No
STATCOM SVC
6 The maximum VAR generation or absorption
changes linearly with the ac system voltage
The maximum VAR output
decreases with the square of the
voltage
7 Attainable response time and bandwidth of the
closed voltage regulation loop of the STATCOM
are also significantly better than those of the
SVC.
Less for svc system
8 The loss contribution of power semiconductors
and related components to the total
compensator losses is higher for STATCOM.
Lesser for SVC
Comparison between SVC & STATCOM

27. Thyristor Controlled Series Capacitor-TCSC
In this configuration a TCR is used in parallel with a fixed capacitor.
It enables a continuous control over the series compensation.
TCSC provides inherent protection against over voltages. TCSC is
available for application in AC lines of voltage up to 500 kV.
Bus 1 Bus 2
𝑽 𝑺 𝑽 𝑹
𝑄 𝑟 =
𝑉𝑟
𝑋
|𝑉𝑠 − 𝑉𝑟|
TCSC
𝑃𝑒 =
𝑉𝑆 𝑉𝑅
𝑋
sin 𝛿
T1
T2

28. The Reactance of TCSC and current through TCR is Given by,
The Reactance of TCSC (ZTCSC) is given by,
XTCSC =
−jXc ∗ jXTCR
j(XTCR − XC)
XTCSC =
−jXc
(1 −
Xc
XTCR
)
The current through the TCR (ITCR) is given by,
ITCR =
−jXc
j(XTCR − XC)
IL
ITCR =
IL
j(1 −
XTCR
XC
)

29. Compute
XTCSC
XC
and
ITCR
IL
if,
a. XTCR = 1.5XC −−−−− −XTCR > XC
𝐗 𝐓𝐂𝐒𝐂
𝐗 𝐂
=
𝟏
𝟏−
𝐗 𝐜
𝐗 𝐓𝐂𝐑
=
1
1−
1
1.5
XTCSC
XC
= 3.0
𝐈 𝐓𝐂𝐑
𝐈 𝐋
=
𝟏
𝟏−
𝐗 𝐓𝐂𝐑
𝐗 𝐂
=
1
1−1.5
ITCR
IL
= −2.0

30. Compute
XTCSC
XC
and
ITCR
IL
if,
b. XTCR = 0.75XC −−−−− −XTCR < XC
𝐗 𝐓𝐂𝐒𝐂
𝐗 𝐂
=
𝟏
𝟏−
𝐗 𝐜
𝐗 𝐓𝐂𝐑
=
1
1−
1
0.75
XTCSC
XC
= 3.0
𝐈 𝐓𝐂𝐑
𝐈 𝐋
=
𝟏
𝟏−
𝐗 𝐓𝐂𝐑
𝐗 𝐂
=
1
1−0.75
ITCR
IL
= 4.0

31. Case-1
XTCR = 1.5XC −−−−− −XTCR > XC −−−−− −𝑪𝒂𝒑𝒂𝒄𝒊𝒕𝒊𝒗𝒆 𝑶𝒑𝒆𝒓𝒂𝒕𝒊𝒐𝒏
XTCSC
XC
= 3.0
ITCR
IL
= −2.0
Case-2
XTCR = 0.75XC −−−−− −XTCR < XC −−−−−− −𝑰𝒏𝒅𝒖𝒄𝒕𝒊𝒗𝒆 𝑶𝒑𝒆𝒓𝒂𝒕𝒊𝒐𝒏
XTCSC
XC
= −3.0
ITCR
IL
= 4.0

32. 𝑽 𝑺 𝑽 𝑹
𝑿 𝑻𝑪𝑹
𝑰 𝑳
𝑰 𝑻𝑪𝑹
𝑿 𝒄
𝐗 𝐜<𝐗 𝐓𝐂𝐑 − −𝐂𝐚𝐩𝐚𝐜𝐢𝐭𝐢𝐯𝐞 𝐎𝐩𝐞𝐫𝐚𝐭𝐢𝐨𝐧
𝐗 𝐜 > 𝐗 𝐓𝐂𝐑 − −𝐈𝐧𝐝𝐮𝐜𝐭𝐢𝐯𝐞 𝐎𝐩𝐞𝐫𝐚𝐭𝐢𝐨𝐧

33. Modes of Operation of TCSC
Bypass Mode-
In this mode the thyristor valves are gated for 180 °
conduction in each direction. The flow current in the reactor is
continuous and sinusoidal.
The net reactance of the module is slightly inductive and
TCSC is operating in TSR- (Thyristor Switched Reactor) mode.
Bus 1 Bus 2
𝑽 𝑺 𝑽 𝑹
TCSC
180°
180°
T1
T2

34. Modes of Operation of TCSC
Inserted with thyristor valve blocked mode-
In this mode no current flows through the valves with the
blocking of gate pulses. Here TCSC reactance is same as that of fixed
capacitor.
Bus 1 Bus 2
𝑽 𝑺 𝑽 𝑹
T1
T2
TCSC
Both Thyristor in Blocking Mode

35. Modes of Operation of TCSC
Inserted with vernier control mode-
The Thyristor valves are gated in the region of 𝛼 𝑚𝑖𝑛 < 𝛼 <
90° such that the valves conduct for the part of a cycle.
The effective capacitive reactance increases as the 𝛼 increases
from 0°. And effective inductive reactance increases as 𝛼 reduces from
180°.
Bus 1 Bus 2
𝑽 𝑺 𝑽 𝑹
T1
T2
TCSC
Thyristor Valves Conduct for Part of the Period

36. Unified Power Flow Controller-UPFC
Intermediate Transformer
Shunt
Transformer
VSC-1
Intermediate Transformer
Series
Transformer
VSC-2
Circuit Breaker
SW-1
SW-2
High Voltage Transmission Line

37. Unified Power Flow Controller-UPFC
 UPFC consists of two voltage sources converters (VSC), one shunt
connected and series connected.
 If the switches 1 and 2 are open, the two converters work as STATCOM
and SSSC controlling the reactive current and voltage injected in shunt
and series respectively in the line.
 The closing of switch 1 and 2 enable the two converters to exchange real
power flow between the two converter.
 The provision of a controllable power source on the DC side of the series
connected converter, results in the control of both real and reactive
power flow in the line.