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

Implementation of a closed loop SHMPWM technique for three level converters

High power converters are built using high-voltage and high-current rated semiconductors. The commutation of these devices imply large amounts of energy per cycle leading to very low switching frequency in order to avoid a high rise on the semiconductors temperature. The consequence is high harmonic distortion generated by the converter. Grid codes requirements specify the maximum admitted harmonic distortion. The well-known selective harmonic elimination pulse width modulation (SHEPWM) technique has proved to be useful in eliminating some of the undesired harmonics without increasing the switching frequency, leaving the rest of them free. The solution to the rest of harmonics is to add bulky and expensive filters. Recently, the method named selective harmonic mitigation pulse width modulation (SHMPWM) has been introduced. The aim of this technique is to mitigate the amplitude of the undesirable harmonics, to acceptable values to meet the grid code, considering a larger number of harmonics. In this paper a practical implementation of this technique in a closed loop scheme is presented. The experimental results using a 150 kW three-level diode-champed converter show that the output signals meet the EN 50160 and CIGRE WG 36-05 grid codes. Comparisons between SHMPWM and SHEPWM are included in the experiments, showing the superior performances of the SHMPWM technique

Recent advances in high-power industrial applications

The industrial electronics market is continuously changing following the users demand. This paper introduces the current industrial electronics applications and is focused in the medium-voltage high-power ones. The multilevel approach is the most attractive solution to achieve the challenges that medium voltage-high power applications arise. Several commercial examples are introduced and some of the last research advances related to multilevel power electronic converters are presented in this paper

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

New trends and topologies for high power industrial applications: The multilevel converters solution

This paper reviews briefly the current scenarios where power electronics converters are being applied. In the paper, the main focus moves towards the high power applications, reviewing the different alternatives and topologies. The multilevel approach is studied in more depth, showing that is a good solution to the challenges that medium voltage-high power applications pose. Several industry examples are introduced and the most suitable modulation techniques for multilevel high power converters are explained. Among them, the recent selective harmonic mitigation method appears as a good solution to achieve a high performance. Finally the conclusions are addressed

Selective harmonic mitigation: limitations of classical control strategies and benefits of model predictive control

Selective harmonic mitigation pulsewidth modulation (SHMPWM) combined with model predictive control (MPC) is a promising approach for grid-connected power converters. SHMPWM can guarantee grid code compliance in steady state, e.g. grid harmonic injection, with a reduced output converter filter, while MPC improves dynamic response and allows grid code compliance in the event of grid transients. This paper presents a survey of the MPC strategies already published in the literature developed for their use with SHMPWM. The existing strategies fall into two categories: direct model predictive control with an implicit selective harmonic mitigation modulator, and direct model predictive control based on finite control set (FCS-MPC). One representative control strategy of each group is compared to each other and to the performance of classical proportional- integral (PI) controllers combined with SHMPWM. The goal is to identify the potential benefits of MPC for grid-connected power converters, and determine the main advantages and limitations of the two selected state-of-the-art control strategies. Their performance is assessed through Hardware-in-the-Loop (HIL) experimental results in terms of real-time implementation, harmonic content grid code compliance, dynamic response and performance under grid transients.This work is part of the projects PID2019-110956RB-I00 and TED2021- 132604B-I00, funded by MCIN/AEI/10.13039/501100011033 and by the European Union NextGenerationEU/PRTR. It has also been partially supported by Ingeteam Power Technology and the Public University of Navarre

Real-Time Selective Harmonic Mitigation Technique for Power Converters Based on the Exchange Market Algorithm

Hand-in-hand with the smart-grid paradigm development, power converters used in high-power applications are facing important challenges related to efficiency and power quality. To overcome these issues, the pre-programmed Pulse-Width Modulation (PWM) methods have been extensively applied to reduce the harmonic distortion with very low power switching losses for high-power converters. Among the pre-programmed PWM techniques, Selective Harmonic Elimination (SHE) has been the prevailing solution, but recently, Selective Harmonic Mitigation (SHM) stands as a superior alternative to provide further control of the harmonic spectrum with similar losses. However, the large computational burden required by the SHM method to find a solution confines it as an off-line application, where the switching set valid solutions are pre-computed and stored in a memory. In this paper, for the first time, a real-time implementation of SHM using an off-the-shelf mid-range microcontroller is presented and tested. The Exchange Market Algorithm (EMA), initially focused on optimizing financial transactions, is considered and executed to achieve the SHM targets. The performance of the EMA-based SHM is presented showing experimental results considering a reduced number of switching angles applied to a specific three-level converter, but the method can be extrapolated to any other three-level converter topology.Ministerio de Ciencia e Innovación de España TEC2016-78430-RJunta de Andalucía P18-RT-1340Fondo Nacional de Investigación de Qatar NPRP 9-310-2-13

Multilevel Converters: An Enabling Technology for High-Power Applications

| Multilevel converters are considered today as the state-of-the-art power-conversion systems for high-power and power-quality demanding applications. This paper presents a tutorial on this technology, covering the operating principle and the different power circuit topologies, modulation methods, technical issues and industry applications. Special attention is given to established technology already found in industry with more in-depth and self-contained information, while recent advances and state-of-the-art contributions are addressed with useful references. This paper serves as an introduction to the subject for the not-familiarized reader, as well as an update or reference for academics and practicing engineers working in the field of industrial and power electronics.Ministerio de Ciencia y Tecnología DPI2001-3089Ministerio de Eduación y Ciencia d TEC2006-0386

Model predictive control: a review of its applications in power electronics

Model-based predictive control (MPC) for power converters and drives is a control technique that has gained attention in the research community. The main reason for this is that although MPC presents high computational burden, it can easily handle multivariable case and system constraints and nonlinearities in a very intuitive way. Taking advantage of that, MPC has been successfully used for different applications such as an active front end (AFE), power converters connected to resistor inductor RL loads, uninterruptible power supplies, and high-performance drives for induction machines, among others. This article provides a review of the application of MPC in the power electronics area