Three-phase Three-level NPC Converter - Objective

This document is intended to teach the students about the Three-Phase Three-Level Neutral-Point Clamped converter, operating in inverter and rectifier modes, using real-time simulation exercises.

A description of the circuit is given first, allowing the student to understand the major components of the scheme, namely, the converter bridge topology, the voltage levels, and waveforms, the PWM generator, the filtering process, the load, the measurements and finally the power flow.

The simulation panels follow, with a thorough description of the different scenarios, the control parameters and buttons, the scopes with their associated waveforms.

Finally, simulation exercises covering the two possible modes (i) inverter and (ii) rectifier are proposed. In inverter mode, the load is a combination in series of a resistance, an inductance, and an AC-source. Additionally, the power flow is shown in real-time. The possibility to add or remove an LC filter, shows the students the impact of harmonics and the benefits of filtering. In rectifier mode, the AC-source on the load side becomes the generator, while the DC source is disconnected and the PWM generator is disabled. The students observe the waveform when the diodes are the sole conducting elements. The possibility to add a resistive load is given again with a full observation of the power flow.