Reactive Power Management and Voltage Control by using STATCOM

1. University of Turkish Aeronautical
Association
Faculty of Engineering
EEE department
Supervision
Prof. Dr. Ibrahim Mahariq
TURKEY - ANKARA 2016

2. CONTENTS
• Introduction
• Definition of reactive power.
• Need for reactive power compensation.
• Definition of FACTS devices.
• Definition of STATCOM.
• Basic principle of operation of STATCOM.
• STATCOM , reactive power management and voltage
control in transmission lines.
• Conclusion .

3. Introduction
AC transmission lines are used to transfer electrical power from power generating stations
to the distribution system, which then supplies electrical power to consumers. Since the
power generating stations in an AC power network can be quite far from the centers of energy
consumption, AC transmission lines often have to transfer electrical power over great
distances.
Generation, transmission and distribution of electrical energy

4. Introduction
This complication in the grid, coupled with the fact that AC
transmission lines are primarily inductive, has many effects on the
operation of AC transmission lines. One of the main effects of this
complication is a significant voltage drop occurring at the receiver end
of AC transmission lines .
Simplified equivalent circuit of an AC transmission line
transferring power from a generating station (sender
end) to a distribution station (receiver end).
- The line inductive reactance 𝑋 𝐿 is represented by the
inductance and the distribution station is represented
by the load.
- The voltage 𝐸𝐿 across the inductance:
𝑬 𝑳=𝑰 𝑳 × 𝑿 𝑳 where 𝑰 𝑳 = the line current
- The voltage 𝐸𝐿𝑜𝑎𝑑 (receiver voltage):
𝑬 𝑳𝒐𝒂𝒅=𝑬 𝑮𝒆𝒏.- 𝑬 𝑳
-Therefore, the higher the line current 𝐼𝐿 and the line
inductive reactance 𝑋 𝐿 , the higher the voltage drop
𝐸𝐿 across the line and the lower the voltage
𝐸𝐿𝑜𝑎𝑑 across the load.

5. The voltage drop occurring across the ac transmission line must
be continually compensated in order to maintain the receiver
voltage equal to the sender voltage.
Introduction
-This is commonly achieved using capacitors
connected in parallel to the line at the receiver end.
However, using shunt-capacitor substations for
reactive power and voltage compensation of long AC
transmission lines has some drawbacks. The primary
drawback is potential difficulty in coordinating
operation at all substations along the line to achieve
proper voltage compensation.
- A number of different systems have been
developed to diminish or eliminate the drawbacks
of using shunt capacitor substations for voltage
compensation of AC transmission lines. These
systems are part of flexible ac transmission
systems (commonly abbreviated as FACTS) device
family, one of the most common FACTS devices,
the static synchronous compensator (commonly
abbreviated as STATCOM).
Bank of shunt capacitors used to compensate the
voltage at substations installed
along an AC transmission line.

6. Definition of the reactive power
Reactive power is the power that supplies the stored energy in
reactive elements. Power, as we know, consists of two
components, active and reactive power. The total sum of active
and reactive power is called as apparent power.
Current vector diagram
Power vector diagram
- In current vector diagram, the current vector can be split into two
components :
- For most electrical loads like motors, the current I is lagging behind
the voltage V by an angle ϕ.
𝐼 𝑎 is called the "active" component of the current.
𝐼𝑟 is called the "reactive" component of the current.
- The previous diagram was drawn up for currents also applies to
powers, by multiplying each current by the common voltage V.
Apparent power: S = V x I (kVA)
Active power: P = V x Ia (kW)
Reactive power: Q = V x Ir (kvar)

7. - Analogy to explain the reactive power.
- Take a boat on a canal, pulled by a horse .
- The fact that the horse is not walking straight in front of the boat.
Consequences:
• The fact that the rope is pulling at the flank of the horse and not
straight behind it, and limit the horse’s capacity to deliver work.
•The turned rudder leads to extra losses.
- The vector representation of the force to pull the boat is similar to
the vector representation of power in an electric system.
Definition of the reactive power

8. Need for reactive power compensation
Voltage control and reactive power management
are two aspects of a single activity that both
supports reliability and facilitates commercial
transactions across transmission networks. On an
alternating-current (AC) power system, voltage is
controlled by managing production and absorption
of reactive power.
If reactive power decreases
Apparent
power
decreases
Losses in
transmission
line
decrease
Voltage
drop
decreases
composition of the total power of a transmission grid

9. Reactive power compensation by using capacitors
principle of reactive power compensation using low voltage power capacitor
-Reactive power compensation is commonly achieved using capacitors connected
in parallel to the line at the receiver end. However, using shunt-capacitor
substations for voltage compensation of long ac transmission lines has some
drawbacks.

10. Reactive
power
compensation
Improvement
in voltage
Improves
system
power
factor
Reduction
in system
losses
Saves cost
Reduction
of KVA
demand
Higher load
capability
Benefits of reactive power compensation :

11. Definition of FACTS devices
FACTS ( Flexible Alternating Current Transmission System) :AC transmission systems
incorporating the power electronic-based to enhance controllability and increase power transfer
capability.
FACTS Controllers :A power electronic based system and other static equipment that provide
control of one or more AC transmission parameters (series impedance, shunt impedance,
current, voltage and phase angle ).
FACTS technology provides
Increase
loading
capacity
Of
transmission
lines
Prevent
blackouts
Improve
generation
productivity
Reduce
circulating
reactive
power
Improves
system
stability
limit
Reduce
voltage
flicker
Reduce
system
damping
and
oscillations
Control
power flow
FACTS technology provides the opportunity to :

12. Classification of FACTS devices
The classification of the FACTS Controllers done on the basis of their types of arrangement in the Power
system:
FACTS
SERIES
SSSC
Static
Synchronous
series
Compensator
TSSC
Thyristor
Controlled
Series
Compensator
TCSC
Thyristor
Controlled
Series
Capacitor
SHUNT
SVC
Static Var
Compensator
STATCOM
Static
synchronous
Compensator
SERIES-
SERIES
IPFC
Interline
Power flow
controller
SERIES-
SHUNT
UPFC
unified
power flow
controller

13. Some FACTS controllers

14. Working principle of FACTS
Single line diagram between a generation station
and load
Consider a transmission line connecting generating
station to a load .
Assuming the line to be lossless and ignoring the line
charging, the power flow (P= real power) and (Q=reactive
power) given by :
𝑷 =
𝑽 𝟏 𝑽 𝟐
𝑿
(𝐬𝐢𝐧 Ѳ) 𝐐 =
𝐕 𝟏
𝐗
(𝑽 𝟏 -𝐕𝟐 COS Ѳ),
Where Ѳ = Ѳ 𝟏 - Ѳ 𝟐 and X= the series line reactance.
- FACTS can control the real power and reactive
power flow by controlling one or more of the
components (𝑽 𝟏 , 𝑽 𝟐 , X , Ѳ ) .

15. A static compensator (STATCOM), also known as
static synchronous compensator, is a member of the
flexible alternating current transmission system
(FACTS) devices. It is a power-electronics-based
regulating device which is composed of a voltage
source converter (VSC).
STATCOM is a shunt connected reactive
compensation equipment which is capable of
generating and/or absorbing reactive power whose
output can be varied so as to maintain control of
specific parameters of the electric power system.
Definition of STATCOM
(STATCOM)

16. Structure of STATCOM
The main components of STATCOM are :
1- A three-phase step-down transformer.
2- A three-phase PWM rectifier/inverter.
- A three-phase bridge
- A three-phase filter.
- Line inductors.
- A controller.
3-A large capacitor ( 𝑪 𝑩𝒖𝒔) is used as a dc power
source for the three-phase PWM rectifier/inverter.

17. Basic principle of operation of STATCOM
For two AC sources which have the same
frequency and are connected through a series
inductance, the active power flows from the leading
source to the lagging source and the reactive power
flows from the higher voltage magnitude source to
the lower voltage magnitude source.
Thus, the STATCOM can be used to regulate the
reactive power flow by changing the magnitude of
the VSC voltage with respect to source bus voltage.
𝑸 𝑪 =
𝐕𝑺
𝐗
(𝑽 𝑺 -𝐕𝑪 COS Ѳ)
Where 𝑸 𝑪 is the reactive power which can be generated and/or
absorbed by STATCOM .
AND Ѳ = The phase angle which can be controlled by inverter.

18. Basic principle of operation of STATCOM
- Operation mode of STATCOM at different levels of voltage :

19. The size of STATCOM
- STATCOM has a small size.
The small size of STATCOM makes it possible to transport the
STATCOM in a trailer truck. (Copyright 2012 Guc kalitesi)
STATCOM substation

20. STATCOM , reactive power management and
voltage control in transmission lines
Since 1980 when the first
STATCOM (rated at 20
Mvar) using force-
commutated thyristor
inverters was put into
operation in Japan, many
examples have been
installed and the ratings
have been increased
considerably in reactive
power management and
voltage control in
transmission lines .
Partial list of utility scale of STATCOM
PlacePurpose
Voltage
Level
(KV)
Capacity
MVAR
CountryYear
Installed
S.N
Inumaya substation
Power System and
voltage
Stabilization
154
±80
MVA
Japan
19911
Shin Shinano
Substation
Nagoya
Reactive
compensation
500
50
MVA
Japan19922
VELCO Essex
substation
Dynamic reactive
compensation during
critical contingencies
115
-41 to
+133
USA20013
The Doha South
substation (Qatar) and
Al-Jasra
Substation (Bahrain)
Reactive
compensation and
voltage
Stabilization
400
500
Mvar
between
Qatar
and
Bahrain
20124

21. STATCOM , reactive power management and
voltage control in transmission lines
A 500-Mvar STATCOM is implemented in between Qatar
and Bahrain network which is part of Gulf cooperative
council ,Qatar, Oman, Bahrain, KSA, UAE and Kuwait (GCC)
where the total symmetrical range of the reactive output
from the STATCOM, from full inductive to full capacitive,
could be utilized without applying fixed capacitors to :
1- Regulate voltage on a three-bus 400kV in order to meet
long transmission system operational requirements.
2- Reactive power compensation.
STATCOM between Qatar and Bahrain as an example of
reactive power management and voltage control in
transmission lines.
STATCOM between Qatar and Bahrain

22. Simulation process of STATCOM
During a simulation process (MATLAB) it was observed that the reactive current was oscillating from 0.1 to 0.3
second to maintain reference reactive current to the main certain level of the voltage level.
A simulation process (MATLAB)

23. Simulation process of STATCOM
Indicates STATCOM waveforms (a) reactive power (b) measured and reference
voltage (c) DC voltage
- The reactive current was oscillating form 0.1 to 0.3 second to maintain reference reactive current to main
certain level of voltage level.

24. Simulation process of STATCOM
Receiving end voltages at both sides of Bahrain and Qatar without STATCOM and
ends improved voltages at both sides with STATCOM.
(a) receiving end improved voltage (b) sending end improved voltage(a) receiving end voltage (b) sending end voltage without STATCOM

25. Conclusion
- The benefits of using STATCOM to compensate Reactive power and voltage
control.
1- By using a STATCOM control device both capacitive and inductive modes of operations are
demonstrated.
2- STATCOM has a number of advantages, quick response time, less space requirement and
optimum voltage platform.
3- Tighter control of the voltage at the end of the line.
4- Increased line stability during transients (i.e., during sudden changes in the load at the
receiver end of the AC transmission line), due to the superior quickness of the STATCOM
response.
5- Increased power transfer capability in the power grid.
6- Improved power grid operational reliability.
7- STATCOM installation is small in size but is significantly more expensive.