Analysis of PWM Method for TFC (3L-NPC)

In modern power industry, one of the important stages of development is the development and implementation of decentralized gas turbine power plants with electrical equipment based on electric machine-valve complexes. One of the enterprises engaged in this activity is JSC «GT Energo», where the link between the generator with 6000 rpm and the power system is a thyristor frequency converter. Improvement of pulse width modulation (PWM) methods for controlling power converters is one of the most important tasks for power electronics. The purpose of this article is to analyze the existing PWM methods and to choose the most effective one based on the analysis performed. There are many methods that differ in the implementation and resulting power quality. Sinusoidal PWM as well as the method of 3 harmonics addition PWM (THIPWM) are used in the article. However, the total harmonic distortion (THD) is high when using these methods. The most effective methods are space vector PWM (SVPWM) and optimal pulse width modulation (OPM). Compared with carrier-based methods, the control strategy for selective elimination and mitigation of harmonics (SHEPWM and SHMPWM) leads to a significant improvement in the performance of converters.