PWM 2 Level Inverter

PWM 2 Level Inverter

PWM 2-Level Inverter

A 2-Level Inverter is the most basic form of a voltage source inverter (VSI). It converts DC input voltage into an AC output voltage by switching semiconductor devices (MOSFETs, IGBTs, or thyristors). The term “2-level” means the inverter output can assume only two distinct voltage levels:

+Vdc/2and−Vdc/2+V_{dc}/2 \quad \text{and} \quad -V_{dc}/2+Vdc​/2and−Vdc​/2

When Pulse Width Modulation (PWM) control is applied, the inverter generates an output waveform that approximates a sinusoidal wave by varying the duty ratio of the switches.

Working Principle

• Each phase leg of the inverter has two switches.
• At any instant, one switch in the leg is ON, and the other is OFF.
• The output voltage is switched between +Vdc/2 and –Vdc/2.
• Using PWM techniques, the switches are controlled such that the average value of the output follows a sinusoidal reference.

PWM Techniques for 2-Level Inverter

1. Sinusoidal PWM (SPWM) → A sinusoidal reference compared with a high-frequency triangular carrier.
2. Space Vector PWM (SVPWM) → Optimized switching sequence based on space vector representation.
3. Selective Harmonic Elimination (SHE-PWM) → Switching angles chosen to cancel specific harmonics.

Advantages

• Simple structure and easy control.
• Widely used in low and medium power applications.
• Good dynamic response with PWM control.

Limitations

• Produces high harmonic distortion compared to multilevel inverters.
• Requires large filters to smoothen the output.
• High switching losses at high frequency.

Applications

• Industrial motor drives (induction & synchronous motors)
• UPS systems
• Renewable energy integration (solar PV, wind systems)
• Traction and EV applications