CSI vs VSI

1. CURRENT SOURCE INVERTER(CSI)
&
VOLTAGE SOURCE INVERTER(VSI)
Presented by- Sadanand.C.Purohit
G.E.S.R.H.Sapat College of Engineering, Nasik
(University of Pune), Maharashtra, India

2. INDEX
 What is inverter.
 What is Current source inverter(CSI).
 Working of CSI.
 What is Voltage source inverter(VSI).
 Working of VSI.

3. INVERTER..
 We use converter as a generic term to refer
power conversion.
 Inverter refers to the converter when the
average flow is from DC to AC side.

4. CURRENT SOURCE INVERTER
 A current-source inverter (CSI) is one in
which the source current is predetermined
and the load impedance determines the
output voltage.
 The supply current cannot change quickly.
 The current is controlled by series dc supply
inductance.

5. CSI

6. CONSTRUCTION...
 The type of operation in this case is Auto-
Sequential Commutated Inverter (ASCI).
 In this circuit, six thyristors, six diodes, three
capacitors are needed here.

7. WORKING OF CSI.
 For 3 phase CSI

8. WORKING OF CSI
MODE 1

9. MODE 2

10. MODE 3

11. CSI....
Advantages
• Thyristor used for commutation are simpler
• The peak current flow through thyristor is limited
to safe value.
Disadvantages
• It needs a extra converter stage.
• At light load it has sluggish performance &
stability problem.
Application
• AC motor drives.

12. VOLTAGE SOURCE INVERTER.
 A voltage-source inverter (VSI) is one in
which the dc input voltage is essentially
constant
 Feedback diodes are necessary.
 Classification:- series, parallel, bridge
inverter

13. VSI
Advantages
• Output voltage waveform does not depend on
type of load.
• Size is small.
Disadvantages
• Protection against short circuit is difficult.
Application
• UPS
• AC drives

14. VOLTAGE SOURCE INVERETER
There are six combinations of conducting switches during an output
cycle:- (Sw5, Sw6, Sw1), (Sw6, Sw1, Sw2), (Sw1, Sw2, Sw3), (Sw2,
Sw3, Sw4), (Sw3, Sw4, Sw5), (Sw4, Sw5, Sw6).

15. Application of
Current Source Inverter

16. CSI FED INDUCTION MOTOR
 A three phase filter capacitor CS is required
for the commutation of switching devices
 CSI drives employ self commutating devices
such as gate turn-off thyristors (GTOs)
 Pulse width modulation (PWM) techniques
can be used to get improved output currents
and voltages

17. CSI FED INDUCTION MOTOR
 It is an attractive solution for high-power
applications due to its regenerative capability.
 A large dc link inductor connected at the
output of the phase controlled rectifier
 Suitable for fan and pump type of load
 smoother set of output voltage waveforms
suitable for driving ac motors

18. CHARACTERISTICS.
 Simple converter topology,
 Inherent four quadrant operation,
 Reliability,
 Motor friendly waveforms with
 Low dv/dt.

19. CONTINUED..
 The current-source inverter (CSI) topology
offers a number of advantages:
1) short-circuit protection,
2) low output voltage
3) instantaneous and continuous
regenerative capabilities.
Disadvantages;
 Poor and variable overall input power factor

20. Application of
Voltage Source Inverter

21. WHAT IS FACTS
 “Alternating current transmission systems
incorporating power electronics based and other
static controllers to enhance controllability and
Available Power Transfer Capacity”.
 The major problems faced by power industries
in establishing the match between supply and
demand are:
1) Transmission & Distribution; supply the electric
demand without exceeding the thermal limit.
2)In large PS, stability problems causing power
disruptions and blackouts leading to huge
losses.

22. VSI BASED FACTS
 FACTS controllers provide fast and reliable
control over the three main transmission
parameters, i.e., voltage magnitude, phase
angle and line impedance to facilitate optimal
power system performance.
 Static synchronous compensator, static
synchronous series compensator and unified
power flow controller are the voltage source
inverter based FACTS devices

23. VSI BASED FACTS
 It is composed of a VSC and its associated
shunt connected transformer with system
bus.
 The transformer is used as a link between
the VSI and the system bus

24. VSI BASED FACTS CONTROLLERS
 Includes dc-ac inverters to exchange shunt
or series reactive power with the
transmission system.
 To enhance the power flow over the
transmission line the parameters namely
voltage, impedance or angle must be
adjusted.

25. FACTS CONTROLLERS
 The shunt connected compensator
(STATCOM) is used to control the
transmission line voltage.
 The series connected compensator (SSSC)
controls the effective line impedance, XL
 The UPFC controls all variables (voltage,
impedance and angle) selectively or
concurrently.

26. CONTINUED..
 VSI based FACTS devices have several
advantages such as :
1)being small/compact
2)High response speed
3) No harmonic pollution.

27. THANK YOU