An integrated and comprehensive theory of PWM The selection of the best algorithm for optimum pulse width modulation is an important process that can result in improved converter efficiency, better load (motor) efficiency, and reduced electromagnetic interference. However, the identification of the best approach is a complex process requiring extensive mathematical manipulation. Pulse Width Modulation for Power Converters: Principles and Practice is the first single-volume resource written to help researchers in the field attain a working knowledge of the subject. The authors bring together todays seemingly diverse approaches into a single integrated and comprehensive theory of modulation. The book provides a generalized approach to the fundamentals of PWM, looking at:
Active switch pulse width determination
Active switch pulse placement within a switching period
Active switch pulse sequence between phase legs and across switching periods
The main benefit of this generalized concept is that once the common threads are identified, the selection of a modulation strategy for any converter topology becomes immediately clear, leaving only secondary factors, such as practical performance, cost, and difficulty of implementation to consider. Additionally, it allows the performance of any particular converter topology and PWM strategy to be quickly and easily identified without complex and time-consuming analysis. Pulse Width Modulation for Power Converters: Principles and Practice enables the reader to achieve optimum PWM results for any application.
"Pedro Rodriguez is with the Universitat Politecnica De Catalunya (UPC), Colom 1, 08822 Terrassa, Barcelona, Spain (em: email@example.com). because their harmonic spectrum exhibits no base band harmonics ; only carrier band (or switching frequency) harmonics and groups of side band harmonics placed around multiples of the switching frequency . If the switching frequency is high, the filter resonant frequency may be chosen low enough such that any significant side-band harmonics are above the resonant frequency; yet high enough that it will not present a challenge to the current control loop stability –. "
[Show abstract][Hide abstract] ABSTRACT: This paper describes the design procedure and performance of an LCL grid filter for a medium-voltage neutral-point clamped converter to be adopted for a multimegawatt (multi-MW) wind turbine. The unique filter design challenges in this application are driven by a combination of the medium-voltage converter, a limited allowable switching frequency, component physical size and weight concerns, and the stringent limits for allowable injected current harmonics. Traditional design procedures of grid filters for lower power and higher switching frequency converters are not valid for a multi-MW filter connecting a medium-voltage converter switching at low frequency to the electric grid. This paper demonstrates a frequency-domain-model-based approach to determine the optimum filter parameters that provide the necessary performance under all operating conditions given the necessary design constraints. To achieve this goal, new concepts, such as virtual-harmonic content and virtual filter losses are introduced. Moreover, a new passive-damping technique that provides the necessary damping with low losses and very little degradation of the high-frequency attenuation is proposed.
"In order to determine the switching of the CHB, several modulation strategies have been developed. Multi-carrier based pulse width modulation (PWM) (such as level-shifted PWM and phase-shifted PWM), spacevector modulation (SVM), hybrid modulation or time-based modulation techniques have been applied to CHB achieving a high performance –. Each modulation technique is focused on the optimization of some converter feature such as switching losses reduction, maximum effective switching frequency, even power distribution among the power cells, common-mode voltage minimization, minimum computational cost, etcetera. "
[Show abstract][Hide abstract] ABSTRACT: Multilevel cascaded H-bridge converters have found industrial application in the medium-voltage high-power range. In this paper, a generalized modulation technique for this type of converter based on a multidimensional control region is presented. Using the multidimensional control region, it is shown that all previous modulation techniques are particularized versions of the proposed method. Several possible solutions to develop a specific implementation of the modulation method are addressed in order to show the potential possibilities and the flexibility of the proposed technique. In addition, a feedforward version of this technique is also introduced to determine the switching sequence and the switching times, avoiding low harmonic distortion with unbalanced dc voltages. Experimental results are shown in order to validate the proposed concepts.
[Show abstract][Hide abstract] ABSTRACT: Space vector pulse width modulation (SVPWM) is an optimum pulse width modulation technique for an inverter used in a variable frequency drive applications. It is computationally rigorous and hence limits the inverter switching frequency. This paper discusses a time equivalent SVPWM and neural Network based SVPWM technique for a three-phase voltage source inverter in under modulation region. A neural network has the advantage of very fast implementation of an SVPWM algorithm that can increase the inverter switching frequency. The scheme has been simulated and comparative study is given with the existing PWM schemes. The simulation results are given to validate the concept of proposed schemes. Index Terms -Voltage source inverter (VSI), Time equivalent SVPWM, Artificial neural network (ANN), Total harmonic distortion (THD) and Weighted THD.
IEEE India International Conference on Power Electronics (IEEE IICPE-2010),; 01/2011
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