This document discusses active and reactive power flow control using a Static Synchronous Series Compensator (SSSC). The SSSC injects a controllable voltage in series with a transmission line to regulate power flow. It can control both real and reactive power flow to improve transmission efficiency. The SSSC consists of a voltage source converter connected to the line via a transformer. It provides advantages like power factor correction, load balancing, and reducing harmonic distortion.

1. ACTIVE AND REACTIVE POWER FLOW
CONTROL USING STATIC
SYNCHRONOUS SERIES
COMPENSATOR
Under the Guidance of Presented by:
G. Sujatha Y.Divya
Dept of EEE (17251D5415)

2. CONTENTS
•INTRODUCTION
•STATIC SYNCHRONOUS SERIES COMPENSATOR
•Need for Active and Reactive power flow control
•SSSC as power flow control
•Control scheme of SSSC
•Operating principle of SSSC
•Advantages of SSSC
•Conclusions

3. INTRODUCTION TO FACTS
•A flexible alternating current transmission system is
a system composed of static equipment used for
the ac transmission of electrical energy.
•It is meant to enhance controllability and increase
power transfer capability of the network. It is generally
a power electronics based system.
•FACTS Increase the reliability of AC grids and reduce
power delivery costs.
•FACTS improve transmission quality and efficiency of
power transmission by supplying inductive or reactive
power to the grid.

4. INTRODUCTION TO SSSC
•A SSSC is a kind of flexible ac transmission system,
which consists of a solid-state voltage source
inverter coupled with a transformer that is connected in
series with a transmission line.
•This device could inject an almost sinusoidal voltage in
series with the line.
•This injected voltage could be considered as an inductive
or capacitive reactance, which is connected in series with
the transmission line.
•This feature can provide controllable voltage
compensation.

5. Static Series Synchronous Compensator

6. Need for Active and Reactive Power
Flow Control
•Reactive power flow is the unwanted power which
decreases the efficiency of transmission line.
•Due to the reactive power many harmonics are existed
in power systems.
• Hence Reactive Power Flow Control is needed.
•Active Power Flow control is required to supply the rated
power to the load.

7. SSSC as power flow controller
•SSSC consist of a voltage source converter with a dc
storage capacitor which is connected in series to a
transmission line for compensation.
• It will inject a voltage to the transmission line thus it can
provide necessary compensation.
•It can transfer both active and reactive power to the
system, permitting it to compensate for the resistive and
reactive voltage drops maintaining high effective X/R
that is independent of the degree of series
compensation.

8. Power Flow in SSSC

9. Representation of SSSC in a transmission
line
The voltage drop across the line (see phasor diagram) is given by
The magnitude of the current is obtained as
Let us consider a simple system with transmission line
connected to constant voltage source at the two ends

10. The power flow (P) in the line is given by
The reactive power supplied at the two ends of the line are
equal (Q). The expression for Q is given by
The line current with variable series compensation is given
by
This shows that only way of power reversal is by increasing
the compensation level, kse above 1.0
(overcompensation).

11. Basic Control Scheme of SSSC
• Closed-loop control applied in SSSC
• Vq and α (phase angle of Vq) controlled
• Controlling real and reactive power
• Synchronising fundamental frequency of
line voltage
• α from phase-locked loop
• Vdc controlled by Vq andα
• Feedback signals
• Line current, Vq, Vdc
• Control reference signals
• VqRRef, VqQRef, VdcRef

12. Basic Control Scheme of SSSC
Magnitude
and angle
computer
α
Vdc
VdcRef
Real and
reactive voltage
computer
VqQ VqP
|VqQRef |
VpRef
Phase-
shifter
± π /2
θ
Gate
Pattern
logic
θ + α
Vq
Vq
Error
amplifier
Error
amplifier
VqRRef
V qR
ABS
VqQRef
Phase-
locked
loop
i
Polarity
detector
DC/AC
Switching
Converter
Cu
Vdc
I
Vq

13. Operating principle of SSSC
•The SSSC is a series connected synchronous voltage source
that can vary the effective impedance of a transmission line by
injecting a voltage containing an appropriate phase angle in
relation to the line current.
• It has the capability of exchanging both active and reactive
power with the transmission system.
• The SSSC comprises a multi phase VSC with a dc energy
storage controller and functional representation of active reactive
power flow as shown in Figure.

14. Operating Principle of SSSC

16. Advantages of SSSC
The SSSC is typically applied to correct the voltage during a
fault in the power system. However, it also has several
advantages :
•Power factor correction through continuous voltage injection
and in combination with a properly structured controller.
•Load balancing in interconnected distribution networks.
•It can also help to cover the capacitive and reactive power
demand.
•Power flow control.
•Reduces harmonic distortion by active filtering.

17. Conclusions
•The SSSC is capable of internally generating a controllable
compensating voltage over any capacitive or inductive range
independent of the magnitude of the line current.
•The SSSC has the ability to be interfaced with an external dc
power supply. The external dc power supply is used to provide
compensation for the line resistance.
• The SSSC with energy storage can increase the effectiveness
of the power oscillation damping by modulating the amount of
series compensation in order to increase or decrease the
transmitted power.
•The SSSC is able to control the power flow in the transmission
line. It can also injects fast changing voltage in series with the
line irrespective of the magnitude and phase of the line current.