Impedance Source Matrix Converters and Control E-Book

Yushan Liu

• Herausgeber: John Wiley & Sons
• Kategorie: Wissenschaft und neue Technologien
• Sprache: Englisch

Seitenzahl: 448

Veröffentlichungsjahr: 2024

Beschreibung

Technical resource presenting the latest power conversion solutions to advance the role of AC-AC power electronics in various applications.

Compiling state-of-the-art research from around the world, Impedance Source Matrix Converters and Control provides a rich diversity of scientific work experience and scholarly approaches on the fundamentals and advances of power electronic converters for motor drives, renewable energies, and industry applications. The reader will be able to apply the learnt design approaches in this book for building and researching the future generation of efficient power electronic converters: more efficient, more reliable, less expensive, lighter, and less voluminous.

The text introduces impedance source matrix converters in four distinct parts, covering the basics, converter topology, control, and applications. Its main focus is on the detailed understanding of advanced concepts related to fundamentals of impedance source matrix converters, and provides associated models, analysis, modulation, and final design and optimization control.

Additional tables, questions/answers, tutorials, PowerPoint presentations, and selected simulation and experimental results are discussed in order to impart seamless reader comprehension.

Written by four highly qualified academics with significant experience in the field, Impedance Source Matrix Converters and Control covers sample topics such as:

• Operating principles and modulation methods for impedance source direct/indirect matrix converters and 3-1-phase matrix converters
• Optimum operation control of LC filter integrated impedance source indirect matrix converters and comparison and control strategies of typical impedance source matrix converters
• Design and improvement in the electricity supply’s reliability, efficiency, compact volume, power quality, and sustainability
• Challenges and key technologies within the field of impedance source matrix converters, and solutions and directions for further research and applications

Impedance Source Matrix Converters and Control is an essential resource on the latest developments in the field for researchers, postgraduate students, and graduate students studying power electronics and renewable energy conversion. The text is also a useful reference for R&D engineers involved with the development of power converters/inverters.

Leseprobe

IEEE Press445 Hoes LanePiscataway, NJ 08854

IEEE Press Editorial BoardSarah Spurgeon, Editor-in-Chief

Moeness Amin

Jón Atli Benediktsson

Adam Drobot

James Duncan

Ekram Hossain

Brian Johnson

Hai Li

James Lyke

Joydeep Mitra

Desineni Subbaram Naidu

Tony Q. S. Quek

Behzad Razavi

Thomas Robertazzi

Diomidis Spinellis

Impedance Source Matrix Converters and Control

Yushan Liu

Beihang University, Beijing, China

Xiao Li

Beihang University, Beijing, China

Baoming Ge

Ford Motor Company, Michigan, USA

Haitham Abu-Rub

Hamad bin Khalifa University, Doha, Qatar

Frede Blaabjerg

Aalborg University, Aalborg East, Denmark

Copyright © 2025 by The Institute of Electrical and Electronics Engineers, Inc. All rights reserved.

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About the Authors

Yushan Liu received the BSc degree in automation from Beijing Institute of Technology, Beijing, China, in 2008, and the PhD degree in electrical engineering from the School of Electrical Engineering, Beijing Jiaotong University, Beijing, China, in 2014. She has been a postdoctoral fellow and an assistant research scientist in the Department of Electrical and Computer Engineering, Texas A&M University at Qatar, Doha, Qatar, from 2014 to 2017. She is currently an associate professor in the School of Automation Science and Electrical Engineering, Beihang University, Beijing, China. She has published over 100 journal and conference papers, one book, and one book chapter in her area of expertise. Her research interests include, but not limited to, power electronics, impedance source inverters, cascade multilevel converters, photovoltaic power integration, and model predictive control. Dr. Liu received the “Beijing Science and Technology Nova” from Beijing Municipal Science and Technology Commission, the “Research Fellow Excellence Award” from Texas A&M University at Qatar, and the “Excellent Doctoral Dissertations” prize from Beijing Jiaotong University. She is an associate editor of the IEEE Transactions on Industrial Electronics and the IEEE Open Journal of Industrial Electronics Society. She served the Power Electronics Devices and Components Committee of IEEE Industry Applications Society as the secretary and vice chair in 2020–2023.

Xiao Li received the BSc degree in automation from Harbin Institute of Technology, China, in 2012, and the PhD degree in electrical engineering from Texas A&M University, College Station, TX, USA, in 2017. From 2017 to 2020, he has worked with Intersil Co., participating in multiple technology programs, including power module design and application of wide-bandgap power devices. After that, he joined Efficient Power Conversion Co. as a senior application engineer, focusing on application of gallium nitride power devices into power electronics systems. Since 2021, he has been with Beihang University, Beijing, China, and now the Associate Professor. Dr. Li’s research interests include power electronics, modeling and application of wide-bandgap power devices, and electric energy conversion and control technology.

Baoming Ge received the PhD degree in electrical engineering from Zhejiang University, Hangzhou. He was a postdoctoral researcher in Tsinghua University, a research associate professor in Michigan State University, and a professor in Beijing Jiaotong University. Also, he worked in Texas A&M University and the University of Coimbra. He is the technical expert of power electronics in Ford Motor Company, MI. His main research interests include power electronics, power converters and inverters, electric drives, hybrid/electric vehicles, renewable energy generation, and energy storage systems. He has published more than 230 journal and conference papers, three books, and two book chapters, and he has been granted more than 60 patents.

Haitham Abu-Rub received the MSc degree from Gdynia Maritime Academy, Gdynia, Poland, in 1990; the PhD degree from the Technical University of Gdansk, Gdansk, Poland, in 1995, both in electrical engineering; and the PhD degree in humanities from Gdansk University, Gdansk, in 2004. Since 2006, he has been with Texas A&M University at Qatar, Doha, Qatar, where he is currently with Hamad bin Khalifa University. He has co-authored more than 600 journal and conference papers, seven books, and seven book chapters. His main research interests include energy conversion systems, smart grid, renewable energy systems, electric drives, and power electronic converters. Dr. Abu-Rub is the recipient of many prestigious national and international awards and recognitions. He is fellow of the IEEE.

Frede Blaabjerg was with ABB-Scandia, Randers, Denmark, from 1987 to 1988. From 1988 to 1992, he got the PhD degree in electrical engineering at Aalborg University in 1995. He became an assistant professor in 1992, an associate professor in 1996, and a full professor of power electronics and drives in 1998 at AAU Energy. From 2017 he became a Villum Investigator. He is honoris causa at University Politehnica Timisoara (UPT), Romania, in 2017, and Tallinn Technical University (TTU), Estonia, in 2018.

His current research interests include power electronics and its applications such as in wind turbines, Photovoltaic (PV) systems, reliability, Power-2-X, power quality, and adjustable speed drives. He has published more than 600 journal papers in the field of power electronics and its applications. He is the co-author of eight monographs and editor of fourteen books in power electronics and its applications, e.g., the series (four volumes) Control of Power Electronic Converters and Systems published by Academic Press/Elsevier.

He has received 38 IEEE Prize Paper Awards, the IEEE PELS Distinguished Service Award in 2009, the EPE-PEMC Council Award in 2010, the IEEE William E. Newell Power Electronics Award 2014, the Villum Kann Rasmussen Research Award 2014, the Global Energy Prize in 2019, and the 2020 IEEE Edison Medal. He was the editor-in-chief of the IEEE transactions on power electronics from 2006 to 2012. He has been distinguished lecturer for the IEEE Power Electronics Society from 2005 to 2007 and for the IEEE Industry Applications Society from 2010 to 2011 as well as 2017 to 2018. In 2019–2020, he served as the president of the IEEE Power Electronics Society. He has been vice president of the Danish Academy of Technical Sciences. He was nominated in 2014–2021 by Thomson Reuters to be the most 250 cited researchers in Engineering in the world.

Preface

A significant challenge to current utility grids is to integrate various energy sources, particularly renewable energy sources and energy storage elements into the network by using power electronics devices. A matrix converter directly connects an AC source to an AC load/source without using intermediate energy storage. It has attracted the attention of academia and industry because of the simple and compact power circuit without dc-link capacitor, output voltage with variable amplitude and variable frequency, sinusoidal input/output currents, and unity power factor operation at input side. Design and improvement in reliability, efficiency, compact volume, power quality, and sustainability of the electricity supply are new challenges. The use of matrix converter topologies with wide voltage gain capability will easily make the system reaching such goals.

The impedance source matrix converters are promising candidates for future generations of the three-three-phase and three-one-phase power conversions. They fulfill the wide voltage gain capability in the compact topologies and overcome the limits of traditional matrix converters. Hence, the high reliability, high efficiency, and low cost can be achieved when using proper topologies and controls. In addition, impedance source matrix converters can be seen as the second type, besides the other type of traditional matrix converters, and these two types build the complete matrix converter family. The recently derived impedance networks with improved voltage gain will be discussed in this book with highlighting the future trends and various applications.

This book brings together the state-of-the-art knowledge and the edge techniques in various stages of research related to the impedance source matrix converters. The book illustrates comprehensive analysis, operating principles, and modulation methods of typical and various impedance source matrix converter topologies developed by the book authors. The book addresses and compares different kinds of typical topologies, in terms of voltage gain analysis, filtering function assessment, parameters design, etc. The innovative design approach and low-frequency power compensation control are detailed for the derived three-one-phase impedance source matrix converter. The book also discusses the model predictive control solution of impedance source matrix converters, overcoming the complexity of duty cycles calculation and composition of traditional modulation. The book also presents applications of impedance source matrix converters to motor drives. It includes the configuration, operation, and results of the discussed topologies and control. Future trends of the research and development in this area are also discussed.

The book encompasses a thorough understanding of the concepts, design, control, and applications of the impedance source matrix converters. Researchers, senior undergraduate and graduate students, and professional engineers investigating vital topics related to power electronic converters will find a high value in the content of the book. They will be able to use the presented design approaches in this book to develop future generation of efficient and reliable power electronics converters/inverters.

Acknowledgment

We would like to take this opportunity to express our sincere appreciation to all the people who directly or indirectly helped in making this book a reality. Our special thanks go to Beihang University for the support provided to realize this effort. Further appreciations go to Ford Motor Company, Hamad bin Khalifa University, and Aalborg University.

We are indebted to our family members for their continuous support, patience, and encouragement without which this book would not have been completed.

Sincerely,Yushan Liu, Xiao Li, Baoming Ge,Haitham Abu-Rub, and Frede Blaabjerg

1Background

1.1 Power Electronics Converter Topologies and Applications in Modern Power Systems

1.1.1 Introduction

In modern society, electrical energy is the most convenient and widely available form of energy, making it the most crucial energy source. However, in recent years, with rapid economic development, global electricity consumption has surged, leading to prominent issues of energy scarcity and environmental pollution. On one hand, electrical energy cannot meet the demands of industrial production and people’s daily lives. On the other hand, extensive reliance on traditional fossil fuels for electricity generation has caused severe environmental problems and inefficient utilization of electrical energy [1].

According to statistics from the International Energy Agency in 2014, from 1973 to 2012, the proportion of coal and oil in global terminal energy consumption decreased by 3.6% and 7.5%, respectively. In contrast, the share of electricity consumption increased from 9.4% to 18.1%, ranking second only to oil, as shown in Figure 1.1. It is projected that by 2030, electricity will constitute 25% of global terminal energy consumption, and by 2050, this share is expected to surpass 50%, as depicted in Figure 1.2 [2–5].

Power electronics technology, serving as the vital link for energy conversion and a necessary means to address environmental pollution in the context of new energy sources, has permeated various aspects of electrical applications. This includes applications in power systems, industry, transportation, aerospace, information technology, and telecommunications, as depicted in Figure 1.3[6]. It has directly or indirectly generated significant economic and societal benefits. In the future, approximately 90% of electrical energy will need to be processed through power electronics technology to enhance energy efficiency and production efficiency, thereby maximizing the utilization of renewable energy sources [7].

AC variable frequency drive technology is a significant application of power electronics in energy-efficient and high-capacity AC transmission control systems. Within this technology, AC converters play a crucial role as integral components of AC speed control systems. Currently, AC converters are extensively employed in high-power AC motor drive systems and power systems [8]. The classification of converters can be seen in Figure 1.4[9].

The frequency converter, known as a thyristor-based AC/AC converter circuit, directly converts AC power of a certain frequency into adjustable-frequency AC power. As it lacks a direct current (DC) stage, it falls into the category of direct-frequency conversion circuits. However, this type of converter has notable drawbacks, with its output upper-frequency limit not exceeding 1/3 to 1/2 of the grid frequency. For single-phase AC circuits, two sets of converters are needed, while three-phase circuits require six sets, resulting in numerous components and highly complex control systems.

Figure 1.1 (a) Comparison of energy consumption structure between 1973 and 2012; (b) Global terminal energy consumption structure from 2010 to 2050.

Figure 1.2 Global terminal energy consumption structure from 2010 to 2050.

AC/DC/AC converter is presently one of the most widely used AC/AC frequency conversion circuits. This converter first rectifies AC power into DC power and then inverts DC power back into AC power. Due to the presence of a DC stage, this circuit falls under the category of indirect-frequency conversion circuits. Depending on whether the intermediate DC stage is composed of capacitors or inductors, it can be classified into voltage-source indirect AC/DC/AC converters and current-source indirect AC/DC/AC converters [8]. Among them, the voltage-source AC/DC/AC converter can be further divided into non-controlled rectifier + inverter (Figure 1.5a), which lacks boosting capability and generates high-input current harmonics, resulting in severe grid pollution. The controlled rectifier + inverter (Figure 1.5b) utilizes a boosting rectifier at the input stage, requiring the addition of an inductor. To mitigate harmonic pollution to the grid, inductor–capacitor (LC) or inductor–capacitor–inductor (LCL) filters need to be designed at the input stage. The primary drawback of both types of converters lies in the intermediate energy storage components, which not only have large volume and high mass but are also challenging to maintain, leading to lower power density in power converters.

Figure 1.3 Application fields of power electronics [6].

Figure 1.4 AC frequency converter classification.

The current-source AC/DC/AC converter Figure 1.6 introduces challenges related to the need for large-capacity flat-wave reactors and issues like current distortion and oscillations caused by AC-side LC filter. In comparison to voltage-source converters, it is more costly and complex to control, thereby limiting its application and research. However, with the advancement of superconducting technology, the current-source converter has found successful applications in superconducting energy storage. Furthermore, it has garnered significant attention in medium-voltage high-power wind power generation and motor drive applications [10, 11].

Figure 1.5 AC/DC/AC voltage-source converter (a) uncontrolled rectifier with inverter, (b) controlled rectifier with inverter.

Figure 1.6 AC/DC/AC current-source converter.

To overcome the drawbacks associated with converters featuring intermediate energy storage components and to enhance the power density and reliability of AC/AC converters, researchers began to explore the possibility of AC/AC converters without the use of DC energy storage elements. It was at this juncture that matrix converter (MC) emerged. MC is an electrical conversion device based on bidirectional switches and utilizes pulse-width modulation to generate the desired output voltage. Among various novel AC power converters, MC has gained significant attention from researchers worldwide due to its simple structure and full silicon integration, among other excellent performance attributes [9]. Depending on their structural characteristics, MCs can be classified into two categories: direct matrix converters (DMCs) and indirect matrix converters (IMCs). IMCs not only inherit the advantageous features of DMC but also possess the advantage of zero-current switching at the rectifier stage, significantly reducing control complexity, making them one of the most promising types of AC power converters. IMCs have further led to the development of three-level MCs and generalized sparse IMCs.

1.1.2 Matrix Converter

MCs have been in development for over 40 years, and substantial progress has been made in key areas such as topology design, modulation strategies, control theory, and device development [12–14].

1.1.2.1 Direct Matrix Converter

The concept of DMCs and bidirectional switches was first proposed by Gugi and Pelly [15]. In 1980, Venturini and Alesina introduced the idea of using transistors to construct bidirectional switches for implementing MCs. They developed a prototype based on this concept and presented a series of attractive results. The topology of a DMC is shown in Figure 1.7. This topology employs nine bidirectional switches to interconnect each input phase with every output phase, allowing for the synthesis of the desired output and input currents through a single-stage transformation. Since each bidirectional switch consists of two antiparallel insulated gate bipolar transistors (IGBTs), a DMC requires a total of 18 IGBT power devices [16].

The advantages of a DMC include: (i) bidirectional energy flow, achieving four-quadrant operation; (ii) both input and output currents are sinusoidal; (iii) power factor at the input side can be unity for any load; and (iv) no need for a DC energy storage stage, resulting in a compact circuit structure and high integration level [17].

Despite over 40 years of development, MC technology still faces challenges preventing widespread industrial adoption [18]. These challenges include: (i) maximum boost ratio limited to 0.866; (ii) a relatively high number of power devices, leading to complex commutation control; (iii) difficulty in control under abnormal grid voltage conditions due to the absence of an intermediate DC stage, impacting system performance; (iv) interference on the load side directly affects input-side performance, leading to suboptimal electromagnetic compatibility with the grid; and (v) complex protection circuits, large physical footprint, and higher cost.

1.1.2.2 Indirect Matrix Converter

In pursuit of simplifying the structure of DMCs, reducing the count of power switching components, minimizing system energy losses, and alleviating control intricacies, scholars have introduced a category of IMCs, as depicted in Figure 1.8. In this topology, the input-side rectification employs bidirectional switches, while the inversion stage relies on unidirectional switches, necessitating a total of 18 IGBT power devices. The initial conceptualization of this topology was attributed to Wei at University of Wisconsin-Madison [19], USA. Subsequently, researchers, led by Kolar at wiss Federal Institute of Technology in Zurich, expanded and refined this concept, introducing various topological variants such as sparse matrix converters (SMCs), very sparse matrix converters (VSMCs), and ultra sparse matrix converters (USMCs) [20, 21], as illustrated in Figure 1.9. A comprehensive analysis of modulation techniques, commutation strategies, voltage transfer ratios, and switch losses for multiple MCs can be found in Table 1.1, as extensively discussed in [22].

Figure 1.7 DMC circuit diagram.

Figure 1.8 IMC.

IMCs have the potential to overcome the shortcomings of traditional AC-DC-AC PWM inverters and DMCs, making them a promising new category of AC-AC converters. Their advantages primarily manifest in the following ways: (i) they eliminate the need for large energy storage components like bulky inductors or capacitors in the intermediate DC stage; (ii) the rectifier stage switches can achieve zero-current commutation, simplifying the commutation control of the system; (iii) with an intermediate DC stage, mature PWM control methods can be separately applied to the rectifier and inverter stages, reducing control complexity; (iv) under certain constraints, they can reduce the number of switching devices; (v) by using the intermediate DC link as a common bus, they can facilitate multiple inverter outputs, supplying power to multiple AC motor loads [23–26].

In comparison to DMCs, IMCs offer more advantages. However, similar to DMCs, the limited system voltage gain is a significant hindrance to their industrialization.

1.1.2.3 Power Switches of MCs

The main circuit of a MC must employ bidirectional switches, also known as four-quadrant switches. To enable safe commutation and bidirectional power flow, these controllable switches can carry bidirectional current and block bidirectional voltage [27]. Since fully controllable bidirectional switch devices are not yet commercially available, the bidirectional switches used in MCs must be constructed from combinations of unidirectional switches. There are four common structures for bidirectional switches [12, 28, 29], as depicted in Figure 1.10.

Figure 1.10a,b shows antiparallel bidirectional switches with common emitter and common collector configurations, respectively. These bidirectional switches can be composed using two IGBTs (or MOSFETs) with internally integrated antiparallel diodes. These two antiparallel configurations possess the soft-switching capability and are commonly employed. By implementing a four-step commutation strategy [29], these bidirectional switches can control the switching sequence effectively, preventing input short circuits and providing a conduction path for inductive loads, thus avoiding voltage spikes. Each of these bidirectional switch configurations has distinct characteristics in their main circuit operation [12]. Table 1.2 provides a simple comparison of these two structural configurations.

Figure 1.9 Other IMC circuit diagrams: (a) SMC; (b) VSMC; (c) USMC.

Table 1.1 Topologies comparison of MCs.

Topology

No. of switches

No. of diodes

Minimum No. of isolated drive power supplies

DMC

18

18

6

IMC

18

18

8

SMC

15

18

7

VSMC

12

30

10

USMC

9

18

7

Figure 1.10 Different bi-directional switch configuration of MCs, (a) Common emitter IGBT, (b) Common collector IGBT, (c) RB-IGBT, (d) Diode bridge switch cell.

Table 1.2 Characteristics of bi-direction configurations.

Common emitter

Common collector

Isolated power supply of gate drive circuitry

9

6

Detect all IGBT terminals

Yes

Cannot detect collector

Advantages

Overcurrent protection and reliable drive can be achieved by monitoring the collector–emitter voltage

Input and output voltage and current transformers can be powered by gate drive circuitry

Figure 1.10c represents antiparallel bidirectional switches featuring Reverse Blocking IGBT (RB-IGBT) [30–32]. Compared to other bidirectional switches, RB-IGBTs exhibit symmetric voltage blocking capability, low switch conduction loss, high power density, and reduced switch device size, enhancing overall system efficiency. However, their driver circuit design is intricate, and they suffer from relatively high switching losses [33], which has limited their current usage.

The bidirectional switches shown in Figure 1.10d consist of a bridge circuit composed of diodes and IGBTs. This configuration offers the lowest cost and does not encounter the four-step commutation issue. Its driver circuitry is relatively simple. However, it has the drawback of higher conduction losses due to the presence of two diodes and one IGBT in the conduction path, resulting in increased conduction losses.

1.1.2.4 Research Status of MCs

Based on the relevant literatures, researchers all over the world have primarily focused their efforts on various aspects of MCs:

Research on Novel Circuit Topologies:

To simplify MC structures and reduce control complexity, researchers have proposed several derivative topologies, including: (i) single-switch-based matrix AC/AC converters [34]; (ii) SMC series, such as SMC, VSMC, and USMC, which vary based on the number of single-phase switches used in IMCs [25, 35]; and (iii) three-phase four-wire MCs designed for unbalanced loads [36].

Introduction of Innovative Modulation Methods:

To improve output waveform quality and reduce input-side harmonic content, researchers have introduced a series of novel modulation methods, including: (i) phase voltage-phase voltage direct transformation switching function modulation algorithms [37]; (ii) dual-space vector modulation (SVM) algorithms based on input line voltage–output line voltage direct transformation [26, 38]; (iii) dual-line voltage modulation algorithms [39, 40]; and (iv) output current hysteresis current modulation methods aimed at tracking output circuit currents [41, 42].

Research on Control Methods under Abnormal Operating Conditions:

MCs lack a DC energy storage element, making the input-side disturbances directly affect the output side. In response, researchers have proposed methods such as using auxiliary diode clamp circuits to buffer energy storage capacitors [43] and improved modulation methods for unbalanced power supply conditions [44, 45].

Application of Advanced Control Algorithms:

In recent years, scholars all over the world have explored the application of advanced control theories in MCs, including: (i) robust control for MC systems [46, 47]; (ii) sliding-mode control for MCs [48, 49]; and (iii) predictive control for MCs [50–53].

Application Research on New Power Electronic Devices:

To further reduce converter switching loss, numerous companies in Europe, the United States, Japan, and elsewhere have developed Reverse Blocking IGBTs (RB-IGBTs). The systems built using these devices have effectively reduced overall system losses [54–56]. Additionally, the emergence of power electronic switching devices based on new materials like SiC and GaN has significantly increased switching frequencies, and lowered the system losses [57, 58].

Developed Prototypes:

As power electronic devices become more integrated and MC technology matures, researchers worldwide have developed a variety of prototypes [53]: (i) Siemens in Germany introduced an MC solution for industrial drives in 2001 [23]. (ii) Aalborg University in Denmark developed a 4 kW MC for driving asynchronous motor speed control systems in 2002 [59]. (iii) Fuji Electric in Japan created an RB-IGBT module in 2003, using it to build a 22 kW MC prototype in 2004 [60]. (iv) In collaboration with the military, University of Nottingham in the UK released a 150 kVA MC prototype for military vehicle transmission systems in 2004 [61]. (v) In 2003, University of Nottingham in the UK developed a jet aircraft wing electrohydraulic control system based on an MC [62]. (vi) Several prototypes have emerged at various universities. These include the first domestic MC prototype built using discrete IGBTs by Chen and Lu at Shanghai University in 1998 [63], as well as a constant-frequency sampling current tracking control MC prototype developed by Tang and Fang at Fuzhou University in 1999 [64]. In 2000, Xiangtan University began researching AC/AC MCs and produced an experimental prototype [65]. In 2006, Huang and Sun at Tsinghua University developed a 3.6 kW MC prototype based on RB-IGBT modules [66]. In 2009, she at Huazhong University of Science and Technology developed a 5.5 kW prototype driving an induction motor using discrete IGBTs [67]. In 2010, Li and Mei at North China University of Technology developed an IMC prototype based on dual IGBT modules [68]. To date, researchers worldwide have publicly disclosed MC prototypes, as shown in Table 1.3.

Table 1.3 MC prototype research and development.

Year

Affiliation

Power

Power module

Application

1988

Westinghouse

[28]

22 kW

Bridge Type

Induction Motor Drive

1995

Virginia Tech

[69]

2 kW

Anti-parallel MOSFET

Algorithm Verification

1999

Shanghai University

[63]

2 kW

Discrete IGBT

Algorithm Verification

2001

University of Bologna

[70]

7 kW

IGBT Module

Induction Motor Drive

2002

Aalborg University

[59]

4 kW

IGBT Module

IM Speed Regulation

2002

University of Nottingham

[71]

10 kW

IGBT Module

Induction Motor Drive

2002

University of Nottingham

[72]

30 kVA

IGBT Module

Ground level power supply

2002

University of Karlsruhe

[23]

7.5 kW

IGBT Module

Algorithm Verification

2003

University of Nottingham

[73]

20 kW

IGBT Module

Aircraft aileron control

2004

University of Nottingham

[74]

10 kW

Discrete IGBT

Diesel engine generator power supply

2004

University of Sheffield

[75]

0.7 kW

Anti-tandem MOSFET

PMSM Drive

2005

University of Nottingham

[61]

150 kVA

Discrete IGBT

Electric chariots

2005

Aalborg University

[76]

3 kW

IGBT Module

Induction Motor Drive

2005

University of Nottingham

[77]

30 kVA

Discrete IGBT

IM Speed Regulation

2005

University of Bologna

[78]

10 kW

IGBT Module

Induction Motor Drive

2005

Nagaoka University of Technology and Science

[24]

22 kW

RB-IGBT Module

Induction Motor Drive

2006

Tsinghua University

[66]

3.6 kW

RB-IGBT Module

Induction Motor Drive

2008

University of Stuttgart

[79]

18 kW

Discrete IGBT

Induction Motor Drive

2009

Huazhong University of Science and Technology

[67]

5.5 kW

Discrete IGBT

Induction Motor Drive

2010

North China University of Technology

[68]

2.7 kVA

Two-in-one IGBT Module

Algorithm Verification

Research on Expanding the Gains of MC Systems:

Given the characteristics of MCs, their most significant limitation is that the maximum voltage boost ratio is only 0.866. Many scholars are actively researching methods to improve this aspect. Current research focused on enhancing IMC gain primarily involves improving modulation strategies and adding auxiliary circuits. These approaches include overmodulation methods and combined modulation strategies [80–82]. While the gain improvement is not significant with overmodulation methods, the process is overly complex. On the other hand, adding auxiliary circuits to the intermediate DC bus, such as Boost circuits [83, 84], or Z-source/quasi-Z-source (ZS/QZS) circuits before and after MC, has been rapidly gaining attention in the field of voltage boost due to their structural symmetry and simplified control.

1.2 ZS/QZS Converters

ZS converter was introduced by Peng et al. in 2002 [85], as depicted in Figure 1.11a. By incorporating a ZS circuit between DC source and the inverter, it offers an alternative to traditional voltage-source and current-source inverters. ZS circuit consists of a diode D, two capacitors C1 and C2, and two inductors L1 and L2 interconnected. The distinguishing feature of ZS converter is its ability to achieve both voltage boost/buck and inversion in a single-stage power conversion, resulting in significant cost savings. Moreover, it permits a direct shoot through of the same bridge arm of the inverter, eliminating the need for a dead time, which greatly enhances the system’s immunity to disturbances [86, 87].

In 2008, QZS, an improved topology of ZS converter, was proposed by Peng et al. [88], as shown in Figure 1.11b. This circuit possesses all the characteristics of ZS converter and offers the additional benefit of achieving continuous input current. Furthermore, the QZS network has a shared negative pole for input and output, which aids in suppressing electromagnetic interference (EMI). Due to the advantages of QZS network converter, various impedance network structures based on this architecture have been proposed, primarily aimed at maximizing voltage gain [89–91].

ZS/QZS converters were initially applied to DC/DC and DC/AC converters. Currently, ZS inverters (ZSIs) and QZS inverters (QZSIs) have garnered widespread research interest, especially in applications requiring voltage boosting, leading to significant breakthroughs. Based on available literature, scholars worldwide have primarily focused their research in the following directions:

Improvement of Topological Structures:

Researchers have proposed enhanced ZS and QZS structures, such as extended ZS and QZS [89], switched-inductor-type ZSI structures [90], L–C coupled inductor-based current-fed ZSI (LCCT-ZSI) structures [92], and trans-ZS structures [93]. They have investigated the voltage boost ratios and characteristics of different structures.

Figure 1.11 Classical topology of (a) ZSI; (b) QZSI.

Modulation Algorithm Research:

This includes investigations into modulation techniques like sinusoidal pulse-width modulation (SPWM) [94, 95] and SVM [96, 97].

Model Establishment and Analysis:

By developing state-space average models, scholars have created small-signal models for ZSI/QZSI [98–100], providing mathematical foundations for the study of converter dynamic responses and controller design.

Introduction of Advanced Control Algorithms:

Building upon model analysis, scholars have designed corresponding controllers, including sliding-mode variable structure control [101, 102] and model predictive control [101, 103, 104].

Multi-Level Expansion:

In the field of photovoltaic power generation systems, an extensive research is the ZS multi-level technology. This includes the development and study of cascaded multi-level inverters based on QZS and energy storage-type cascaded multi-level inverters [105–108].

1.3 Advantages of ZS/QZS MCs Compared to Existing Technology

The characteristics of MCs and ZS/QZS converters demonstrate that their integration can effectively enhance the performance of MCs. Currently, through the efforts of researchers, the combination of ZS/QZS with MCs has resulted in several topological structures, primarily including ZS/QZS placed before DMC, referred to as ZS/QZS-DMC converters, ZS/QZS circuits positioned on the DC side of IMCs, known as DC-ZS/QZS-IMC converters, and those located before or on grid side (GS) of IMCs, denoted as GS-ZS/QZS-IMC converters [109–111].

Introducing ZS and QZS networks in front of the DMC, as illustrated in Figure 1.12a,b, respectively, overcomes the issue of low-voltage gain in traditional DMC systems. Furthermore, the ZS network allows the subsequent bridge arms to operate in a direct shoot-through mode, simplifying the commutation process of DMC [109]. However, ZS-DMC exhibits discontinuous input current. On the other hand, QZS-DMC does not suffer from phase-shift issues, possesses a high system voltage gain, lower voltage and current stresses on the switches, and, through structural adjustments, ensures continuous input current, as depicted in Figure 1.12c.

The combination of ZS or QZS with IMC results in ZS/QZS-IMCs that effectively inherit the advantages of IMC. Additionally, by utilizing the voltage boost/buck capability and robustness of ZS/QZS converters, these hybrid systems can overcome the drawbacks of traditional IMC, such as low-voltage gain and poor disturbance rejection. ZS/QZS-IMCs with ZS/QZS networks introduced into IMC can be divided into two categories [110, 111]: the first category is DC-ZS/QZS-IMC, and the second category is GS-ZS/QZS-IMC, as illustrated in Figures 1.13 and 1.14.

DC-Link ZS/QZS-IMCs

The first category of ZS/QZS-IMCs, represented by DC-ZS-IMC and DC-QZS-IMC, is depicted in Figure 1.13