CURRENT SOURCE INVERTER(CSI) &VOLTAGE SOURCE INVERTER(VSI)
Presented by- Sadanand.C.PurohitG.E.S.R.H.Sapat College of Engineering, Nasik
(University of Pune), Maharashtra, India
INDEX What is inverter. What is Current source inverter(CSI). Working of CSI. What is Voltage source inverter(VSI). Working of VSI.
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.
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.
CSI
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.
WORKING OF CSI.
For 3 phase CSI
WORKING OF CSIMODE 1
MODE 2
MODE 3
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.
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
VSIAdvantages• Output voltage waveform does not depend
on type of load.• Size is small.Disadvantages• Protection against short circuit is difficult.Application• UPS• 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).
Application of Current Source Inverter
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
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
CHARACTERISTICS. Simple converter topology, Inherent four quadrant operation, Reliability, Motor friendly waveforms with Low dv/dt.
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
Application ofVoltage Source Inverter
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.
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 bus.
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 transmission system.
To enhance the power flow over the transmission line the parameters namely
voltage, impedance or angle must be adjusted.
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.
CONTINUED.. VSI based FACTS devices have several advantages such as :1)being small/compact 2)High response speed3) No harmonic pollution.
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