Optimization of PWM for the Overmodulation Region of Two-Level Inverters

Abstract

Three optimized PWM techniques for the overmodulation region of two-level inverter-fed ac drives are introduced and investigated from harmonic loss minimization point of view. The optimization is elaborated for the lowest loss-factor, which is proportional to the square of rms value of current harmonics. The loss-factors are computed for different switching numbers as the function of the motor fundamental voltage. It is shown that, respect to the motor heating and torque ripples, the acceptable drive condition can be guaranteed by relatively low value of inverter switching frequency up to 96-97% of maximal possible motor voltage. Furthermore, it is shown that, the so-called Three vector methods have considerably better performance in the lower part of the overmodulation region than the so-called Two vector method for the same number of switching. The performance of the techniques is compared with other existing PWM techniques. The paper discusses the implementation details of the proposed optimal PWM techniques. The theoretical results are verified by experimental and simulation tests.

Optimization of PWM for overmodulation region of two-level inverters

“…Both the two vector and the three vector method were implemented on a 16-bit µC (dsPIC33EP512MU810) and on a 32-bit DSP (TMS320F28379D). The experimental results using the µC are presented in [31]. In the current paper the results using the DSP are introduced.…”

“…To compare the proposed two optimized PWM techniques with other techniques available in the literature, the V W T HD values are calculated for a few γ values (5,7,9,13,21,31). The calculation is done by simulating the motor drive system presented previously using Matlab/Simulink and using the FFT() function to determine the harmonics.…”

Investigative uses of overmodulation techniques in modular multilevel cascaded converter

“…The most effective controlling and modulation techniques introduced for this type of inverter are multilevel Sinusoidal pulse width modulation (SPWM), multiple particular harmonic eliminations, and space vector pulse width modulation (SVPWM) for the Modular multilevel cascaded converter (MMCC) scale-up controlling technique, in which more no. of sub-modules can be proposed by a small progressive group of sub-modules [2]. The MMCC has achieved substantial awareness and growth owing to its optimistic benefits such as superior output performance, higher modulation parameters, easy expandability, and low level of current and voltage rating demand for the power converter switches [3], [4].…”

An Improved Overmodulation Strategy for a Three-Level NPC Inverter Considering Neutral-Point Voltage Balance and Common-Mode Voltage Suppression

“…Typically, an inverter can operate in the overmodulation region to fully exploit the DCbus voltage, which can provide significant voltage improvement in many applications [7,8]. This is crucial for improving the output performance of the inverters, especially in the motor drive systems [9].…”