Shifted Carrier Pulse Width Modulation Research Articles

Analytical Modelling and Optimization of Output Voltage Harmonic Spectra of Full-Bridge Modular Multilevel Converters in Boost Mode

This article develops a new closed-form analytical solution to the harmonic spectrum of the full-bridge (FB) modular multilevel converter (MMC) with phase shifted carrier pulse width modulation. It considers FB-MMC operation in boost mode where the negative-voltage states of the FB submodules (SMs) are utilized to extend the ac operating voltage range and/or reduce the dc link voltage which is known to reduce the energy storage requirement. The solution is based on double Fourier series expansion in two variables. The harmonic distribution of the output voltage is analyzed and the effects of the modulation index and the number of SMs on the output voltage harmonics are revealed. The influence of the upper/lower arm carrier phase shift angle is also investigated. Using the analysis, selection of the number of SMs, the modulation index and the upper/lower arm carrier phase shift angle are specified for output voltage harmonic minimization. The findings are verified by simulation and experimental results.

Comparison of Multicarrier PWM Techniques for Cascaded H-Bridge Multilevel Inverter

<p>One of the preferred choices of electronic power conversion for high power applications are multilevel inverters topologies finding increased attention in industry. Cascaded H-Bridge multilevel inverter is one of these topologies reaching the higher output voltage, power level and higher reliability due to its modular topology. Level Shifted Carrier Pulse Width Modulation (LSCPWM) and Phase Shifted Carrier Pulse Width Modulation are used generally for switching cascaded H-bridge (CHB) multilevel inverters. This paper compares LSCPWM and PSCPWM in terms of total harmonics distortion (THD) and output voltage among inverter cells. Simulation for 21-level CHB inverter is carried out in MATLAB/SIMULINK and simulation results are presented.</p>

A simple modular multilevel inverter topology for the power quality improvement in renewable energy based green building microgrids

The advent of multilevel inverter topologies paves path for the realization of renewable energy based microgrids for various classes of consumers. But, these topologies are offering concerns with design complexity, power quality, dv/dt stresses, capacitor voltage balancing, etc. In view of these challenges, this paper proposes a simple Modular Cascaded Multilevel Inverter with modified Uni-Polar Shifted Carrier Pulse Width Modulation (MCMI-mUPSC PWM) topology for microgrids. The proposed MCMI topology eliminates the use of clamping diodes, capacitors, and requires only 1/4th (25%) of the DC input voltage that is used in any conventional topology to produce the same amount of output voltage. This leads to the reduction in switching devices’ rating and dv/dt stresses. The proposed mUPSC PWM reduces the magnitude of hazardous lower order harmonics by shifting them to higher order components around the region of integral multiples of switching frequency. Thus, the proposed MCMI-mUPSC PWM topology simplifies the design of multilevel inverters along with aforesaid advantages. For the analysis, microgrid modelling and simulations are carried out in MATLAB/Simulink®. The effectiveness of the proposed topology is evaluated by calculating various power quality indices under dynamic and non-linear loading conditions. These indices are compared with the conventional topology with respect to standard tolerances. From results, it is observed that the proposed topology has improved the power quality along with the elimination of some of the inherent problems of the multilevel inverters. This enhances the plausibility of microgrid installations towards smart and net-zero energy buildings.

English

english

Flying‐capacitor stacked multicell multilevel voltage source inverters: analysis and modelling

The aim of this study is to investigate the natural voltage balancing dynamics of the single/three-phase stacked multicell converters (SMCs). First, explicit analytic solutions for switching functions’ implicit equations, which are, utilised in modulating of the SMCs operated under phase disposition phase shifted carrier pulse width modulation (PD-PSC-PWM) technique whereas being initiated from the Kepler's transcendental equation, are derived. Next, utilising above-mentioned calculated Kapteyn (Fourier–Bessel)-based infinite series, a time-variant differential equation-based analytical model for single/three-phase SMCs is suggested. This strategy reduces to a model that can facilitate the analytic investigation of the start-up behaviour, dynamic response and natural voltage balancing phenomenon for SMCs owning any number of voltage-levels and phase numbers. Furthermore, it is also inferred that under the PD-PSC-PWM modulation technique, the flying-capacitor (FC) voltages balance naturally for higher number of stacks and cells, hence substantiating that the natural balancing exists for high-level SMCs. Moreover, precise analysis of the experimental observations reveals that settling time of the FC voltages in the positive and negative stacks positioned in the immediate vicinity of the SMC's midpoint is higher than the settling time of the FC voltages in the correspondent positive and negative stacks outlying the SMC's midpoint.

I.E.E. current papers

The multilevel converter, (MC) had been recommended for high- and medium-level power applications for decades. It is one of the most popular converters due to its ability to decrease the harmonic distortion in the output waveform without decreasing the converter power output. This paper presents the basic concept of four different types of multilevel converter: the neutral-point clamped, flying capacitor, cascaded H-bridge and modular. This paper also reviews five different modulation techniques for multilevel converters: pulse width modulation, space vector pulse width modulation, phase shifted carrier pulse width modulation, sinusoidal pulse width modulation and selective harmonic elimination pulse width modulation. In addition, recent publications regarding developments and improvements of fundamental concern to MCs and modulation techniques are reviewed in this paper. The implementation of MCs within renewable energy systems is also discussed here.