MULTILEVEL INVERTERS

By Vaishnavi

NEED FOR MULTILEVEL INVERTER

High Power application

Staircase waveform

Input Current

Switching Frequency

Renewable Energy sources

Only disadvantage – More Switches, Cost

BASIC CONCEPT

Use of Power SemiconductorSwitches in series - with several lower voltage dc sources - staircase voltage waveform

Lower voltage dc sources – Capacitors, Batteries, PV cells

TYPES OF MULTILEVEL INVERTERS

Diode Clamped Multilevel Inverter

Flying Capacitor Multilevel Inverter

Cascade Multilevel Inverter

DIODE CLAMPED MULTILEVEL INVERTER

Let, m number of nodes or levelsThen, We require,

(m-1) Capacitors2(m-1) Switching Devices

Example :-m= 6

Therefore, Capacitors – 5 Switching Devices - 10

CIRCUIT DIAGRAM OF 6- LEVEL INVERTER

SWITCHING STATES

LINE VOLTAGE WAVEFORM OF SIX LEVEL CONVERTER

FEATURES OF DIODE CLAMPED INVERTER

High Voltage rating for blocking diodes

Unequal Switch device Rating

Capacitor Voltage Unbalance

Advantage & Disadvantage

ADVANTAGES

Harmonic Content is less-filters avoidedEfficiency – HighControl method - simple

DISADVANTAGES

Difficult to control the real power of individual converterNeed for more clamping diodes

Thank You