Current Source Inverter and Voltage Source Inverter
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
What is inverter.
What is Current source inverter(CSI).
Working of CSI.
What is Voltage source inverter(VSI).
Working of VSI.
We use converter as a generic term to refer
Inverter refers to the converter when the
average flow is from DC to AC side.
CURRENT SOURCE INVERTER
A current-source inverter (CSI) is one in
which the source current is predetermined
and the load impedance determines the
The supply current cannot change quickly.
The current is controlled by series dc supply
• Thyristor used for commutation are simpler
• The peak current flow through thyristor is limited
to safe value.
• It needs a extra converter stage.
• At light load it has sluggish performance &
• AC motor drives.
VOLTAGE SOURCE INVERTER.
A voltage-source inverter (VSI) is one in
which the dc input voltage is essentially
Feedback diodes are necessary.
Classification:- series, parallel, bridge
• Output voltage waveform does not depend on
type of load.
• Size is small.
• Protection against short circuit is difficult.
• AC drives
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).
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
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
Simple converter topology,
Inherent four quadrant operation,
Motor friendly waveforms with
The current-source inverter (CSI) topology
offers a number of advantages:
1) short-circuit protection,
2) low output voltage
3) instantaneous and continuous
Poor and variable overall input power factor
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
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
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
VSI BASED FACTS
It is composed of a VSC and its associated
shunt connected transformer with system
The transformer is used as a link between
the VSI and the system bus
VSI BASED FACTS CONTROLLERS
Includes dc-ac inverters to exchange shunt
or series reactive power with the
To enhance the power flow over the
transmission line the parameters namely
voltage, impedance or angle must be
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
VSI based FACTS devices have several
advantages such as :
2)High response speed
3) No harmonic pollution.