Simulation Study of Three-Level Inverter with Code Implementation Insights

Three-level inverters represent a widely adopted topology in medium-high voltage power electronics applications, offering superior performance compared to traditional two-level inverters through reduced harmonic content and improved output characteristics. For beginners, simulation provides an intuitive approach to observe fundamental operating principles and key waveforms. In code implementations, one typically models semiconductor switching devices using controlled voltage sources and ideal switches, with gate signals generated through PWM comparison blocks.

Phase voltage analysis forms a critical aspect of understanding three-level inverter output, exhibiting characteristic staircase waveforms with positive, zero, and negative voltage levels per phase. This multi-level output structure effectively minimizes voltage transitions, consequently reducing dv/dt stress on motors and cables. Line voltage derives from differentials between phase voltages, with harmonic characteristics serving as key performance indicators. Simulation code often implements phase voltage calculation using switching state combinations and DC-link voltage parameters, incorporating Fourier analysis functions for THD evaluation.

Load-side current simulation validates control algorithm effectiveness, where ideal current waveforms should approximate sinusoidal shapes. By adjusting PWM modulation strategies (e.g., SPWM or SVPWM), current waveform quality can be optimized. Code implementation typically involves Clarke/Park transformations for SVPWM, requiring sector identification and duty cycle calculation algorithms. Particular attention must be paid to neutral-point potential balance during simulation—a unique technical challenge in three-level topologies often addressed through redundant state selection or feedback control in the modulation algorithm.

For beginners, starting with simple carrier-based modulation and progressively comparing voltage/current waveform differences under various modulation schemes helps build systematic understanding of multi-level converters. Simulation projects commonly begin with basic SPWM implementation using triangular carrier comparison, then advance to SVPWM with space vector decomposition and switching sequence optimization.