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.

THANK YOU