Palikir three-phase power frequency inverter

Three-phase inverters play a crucial role in converting direct current (DC) power into alternating current (AC) in various applications, from industrial machinery to renewable energy systems. Understanding the fundamental workings of these inverters is essential for appreciating their significance and diverse applications.

The DC power source of the three-phase current-type inverter, i.e., the DC current source, is achieved through a variable voltage source using current feedback control. However, employing only current feedback cannot reduce the power ripple in the inverter input voltage caused by switch actions, resulting in current fluctuations.

However in three-phase inverters, this voltage is distributed across three phases to create a balanced three-phase AC output . There are two primary conduction modes in both single-phase and three-phase inverters i.e.. 120-degree conduction mode and the 180-degree conduction mode.

A three-phase Voltage Source Inverter (VSI) with SPWM (Sinusoidal Pulse Width Modulation) is a type of inverter that converts DC voltage into three-phase AC voltage with sinusoidal waveforms. It works by varying the pulse width of a high-frequency carrier signal according to the instantaneous amplitude of a reference sinusoidal waveform.

Considering inverter states in which one switch in each half-bridge is always on (for current continuity at the load) there are 23 = 8 switch state possibilities for the 3-phase inverter. We give each state a vector designation and a associated number corresponding to whether the top or bottom switch in each half-bridge is on.

In a three-phase inverter, the pole voltage , which represents the voltage applied to the load, is equivalent to the pole voltage in a half-phase inverter used in single-phase applications . However in three-phase inverters, this voltage is distributed across three phases to create a balanced three-phase AC output .