Multilevel Multiphase Feedforward Space-Vector Modulation Technique

Multiphase converters have been applied to an increasing number of industrial applications in recent years. On the other hand, multilevel converters have become a mature technology mainly in medium- and high-power applications. One of the problems of multilevel converters is the dc voltage unbalance of the dc bus. Depending on the loading conditions and the number of levels of the converter, oscillations appear in the dc voltages of the dc link. This paper presents a feedforward modulation technique for multilevel multiphase converters that reduces the distortion under balanced or unbalanced dc conditions. The proposed modulation method can be applied to any multilevel-converter topology with any number of levels and phases. Experimental results are shown in order to validate the proposed feedforward modulation technique.Ministerio de Ciencia e Innovación DPI2009-07004Ministerio de Eduación y Ciencia TEC2007-6187

The Essential Role and the Continuous Evolution of Modulation Techniques for Voltage-Source Inverters in the Past, Present, and Future Power Electronics

The cost reduction of power-electronic devices, the increase in their reliability, efficiency, and power capability, and lower development times, together with more demanding application requirements, has driven the development of several new inverter topologies recently introduced in the industry, particularly medium-voltage converters. New more complex inverter topologies and new application fields come along with additional control challenges, such as voltage imbalances, power-quality issues, higher efficiency needs, and fault-tolerant operation, which necessarily requires the parallel development of modulation schemes. Therefore, recently, there have been significant advances in the field of modulation of dc/ac converters, which conceptually has been dominated during the last several decades almost exclusively by classic pulse-width modulation (PWM) methods. This paper aims to concentrate and discuss the latest developments on this exciting technology, to provide insight on where the state-of-the-art stands today, and analyze the trends and challenges driving its future

Conventional Space-Vector Modulation Techniques versus the Single-Phase Modulator for Multilevel Converters

Space-vector modulation is a well-suited technique to be applied to multilevel converters and is an important research focus in the last 25 years. Recently, a single-phase multilevel modulator has been introduced showing its conceptual simplicity and its very low computational cost. In this paper, some of the most conventional multilevel space-vector modulation techniques have been chosen to compare their results with those obtained with single-phase multilevel modulators. The obtained results demonstrate that the single-phase multilevel modulators applied to each phase are equivalent with the chosen wellknown multilevel space-vector modulation techniques. In this way, single-phase multilevel modulators can be applied to a converter with any number of levels and phases avoiding the use of conceptually and mathematically complex space-vector modulation strategies. Analytical calculations and experimental results are shown validating the proposed concepts

Selective Harmonic Mitigation Technique for Cascaded H-Bridge Converters With Nonequal DC Link Voltages

Multilevel converters have received increased interest recently as a result of their ability to generate high quality output waveforms with a low switching frequency. This makes them very attractive for high power applications. A Cascaded HBridge converter is a multilevel topology which is formed from the series connection of H-Bridge cells. Optimized pulse width modulation techniques such as Selective Harmonic Elimination (SHE-PWM) or Selective Harmonic Mitigation (SHM-PWM) are capable of pre-programming the harmonic profile of the output waveform over a range of modulation indices. Such modulation methods may however not perform optimally if the DC links of the Cascaded H-Bridge Converter are not balanced. This paper presents a new SHM-PWM control strategy which is capable of meeting grid codes even under non-equal DC link voltages. The method is based on the interpolation of different sets of angles obtained for specific situations of imbalance. Both simulation and experimental results are presented to validate the proposed control method

Multilevel multiphase space vector PWM algorithm

In the last few years, interest in multiphase converter technology has increased due to the benefits of using more than three phases in drive applications. Besides, multilevel converter technology permits the achievement of high power ratings with voltage limited devices. Multilevel multiphase technology combines the benefits of both technologies, but new modulation techniques must be developed in order to take advantage of multilevel multiphase converters. In this paper, a novel space vector pulsewidth modulation (SVPWM) algorithm for multilevel multiphase voltage source converters is presented. This algorithm is the result of the two main contributions of this paper: the demonstration that a multilevel multiphase modulator can be realized from a two-level multiphase modulator, and the development of a new two-level multiphase SVPWM algorithm. The multiphase SVPWM algorithm presented in this paper can be applied to most multilevel topologies; it has low computational complexity and it is suitable for hardware implementations. Finally, the algorithm was implemented in a low-cost field-programmable gate array and it was tested in a laboratory with a real prototype using a five-level five-phase inverter.Ministerio de Educación y Ciencia | Ref. ENE2006-0293

Modulated model predictive control for a 7-level cascaded h-bridge back-to-back converter

Multilevel Converters are known to have many advantages for electricity network applications. In particular Cascaded H-Bridge Converters are attractive because of their inherent modularity and scalability. Predictive control for power converters is advantageous as a result of its applicability to discrete system and fast response. In this paper a novel control technique, named Modulated Model Predictive Control, is introduced with the aim to increase the performance of Model Predictive Control. The proposed controller address a modulation scheme as part of the minimization process. The proposed control technique is described in detail, validated through simulation and experimental testing and compared with Dead-Beat and traditional Model Predictive Control. The results show the increased performance of the Modulated Model Predictive Control with respect to the classic Finite Control Set Model Predictive Control, in terms ofcurrent waveform THD. Moreover the proposed controller allows a multi-objective control, with respect to Dead-Beat Control that does not present this capability

A Modified Carrier-Based Advanced Modulation Technique for Improved Switching Performance of Magnetic-Linked Medium-Voltage Converters

© 1972-2012 IEEE. The high-frequency magnetic link is gaining popularity due to its lightweight, small volume, and inherent voltage balancing capability. Those features can simplify the utilization of a multilevel converter (MLC) for the integration of renewable energy sources to the grid with compact size and exert economic feasibility. The modulation and control of the MLC are crucial issues, especially for grid-connected applications. To support the grid, the converter may need to operate in an overmodulation (OVM) region for short periods depending upon the loading conditions. This OVM operation of the converter causes increased harmonic losses and adverse effects on the overall system efficiency. On top of that, the size and cost of filtering circuitry become critical to eliminate the unwanted harmonics. In this regard, a modified OVM scheme with phase-disposed carriers for a grid-connected high-frequency magnetic-link-based cascaded H-bridge (CHB) MLC is proposed for the suppression of harmonics and the reduction of converter loss. Furthermore, with the proposed OVM technique, the voltage gain with the modulation index can be increased up to the range which is unlikely to be achieved using the classical ones. Extensive simulations are carried out with a 2.24 MVA permanent magnet synchronous generator based wind energy conversion system, which is connected to the 11 kV ac grid through a high-frequency magnetic-link and a five-level CHB MLC. A scaled down laboratory prototype is implemented to validate the performance of the converter

Selective Harmonics Elimination in Multilevel Inverter Using Bio-Inspired Intelligent Algorithms

Multilevel inverters are powerful electronic devices that are used for the conversion of DC input voltage into AC output voltage and mostly used in medium and high voltage operations. In these operations, pulse width modulation (PWM) frequency is distorted because of electromagnetic interference (EMI) and switching losses which are caused by dv/dt stress. To achieve a pure sinusoidal waveform at output of multilevel inverter is a primary purpose so that a smaller number of harmonic contents are produced. Selective harmonic elimination PWM technique is used in cascaded multilevel inverter for the mitigation of lower harmonics by solving nonlinear transcendental equations and maintains the required fundamental voltage. An objective function is derived from SHE problem to calculate switching angles. For the solution of objective function, optimization approach such as bio-inspired intelligent algorithms are used. In this paper, Genetic Algorithm (GA), Particle Swarm Optimization (PSO) and Bee Algorithm (BA) are used to determine the optimum switching angles for cascaded multilevel inverters to get low total harmonic distortion (THD) in output voltage. These computed angles are analyzed in MATLAB simulation model to authenticate the results. And there will be direct comparison among these algorithms

Space-vector PWM with common-mode voltage elimination for multiphase drives

Switching common-mode voltage (CMV) generated by the pulse width modulation (PWM) of the inverter causes common-mode currents, which lead to motor bearing failures and electromagnetic interference problems in multiphase drives. Such switching CMV can be reduced by taking advantage of the switching states of multilevel multiphase inverters that produce zero CMV. Specific space-vector PWM (SVPWM) techniques with CMV elimination, which only use zero CMV states, have been proposed for three-level five-phase drives, and for open-end winding five-, six-, and seven-phase drives, but such methods cannot be extended to a higher number of levels or phases. This paper presents a general (for any number of levels and phases) SVPMW with CMV elimination. The proposed technique can be applied to most multilevel topologies, has low computational complexity and is suitable for low-cost hardware implementations. The new algorithm is implemented in a low-cost field-programmable gate array and it is successfully tested in the laboratory using a five-level five-phase motor drive.Ministerio de Ciencia e InnovaciónEuropean CommissionMinisterio de Economía y Competitividad | Ref. DPI2012-31283Ministerio de Economía y Competitividad | Ref. DPI2015-6541

Multilevel multiphase space vector PWM algorithm with switching state redundancy

Multilevel multiphase technology combines the benefits of multilevel converters and multiphase machines. Nevertheless, new modulation techniques must be developed to take advantage of multilevel multiphase converters. In this paper, a new space vector pulsewidth modulation algorithm for multilevel multiphase voltage source converters with switching state redundancy is introduced. As in three-phase converters, the switching state redundancy permits to achieve different goals like extending the modulation index and reducing the number of switchings. This new algorithm can be applied to the most usual multilevel topologies; it has low computational complexity, and it is suitable for hardware implementations. Finally, the algorithm was implemented in a field-programmable gate array, and it was tested by using a five-level five-phase inverter feeding a motor.Ministerio de Educación y Ciencia | Ref. ENE2006-0293