Power Electronics - Matrix Converters

A matrix converter is defined as a converter with a single stage of conversion. It utilizes bidirectional controlled switch to achieve automatic conversion of power from AC to AC. It provides an alternative to PWM voltage rectifier (double sided).

Matrix converters are characterized by sinusoidal waveforms that show the input and output switching frequencies. The bidirectional switches make it possible to have a controllable power factor input. In addition, the lack of DC links ensures it has a compact design. The downside to matrix converters is that they lack bilateral switches that are fully controlled and able to operate at high frequencies. Its voltage ratio that is output to input voltage is limited.

There are three methods of matrix converter control −

  • Space vector modulation
  • Pulse width modulation
  • Venturi - analysis of function transfer

The Matrix Converter Circuit

The diagram given below shows a single-phase matrix converter.

Matrix Converter Circuit

It contains four bi-directional switches with each switch having the ability to conduct in both forward blocking and reverse voltage.

Space Vector Modulation (SVM)

SVM refers to a method of algorithm used to control the PWM. It creates AC waveforms that drive AC motors at various speeds. In the case of a three-phase inverter having DC supply power, its three main legs at the output are connected to a 3-phase motor.

The switches are under control to ensure that no two switches in the same leg are ON at the same time. Simultaneous ON states could result in the DC supply shorting. This leads to eight switching vectors where two are zero and six are active vectors for switching.