Table Of ContentCPSS Power Electronics Series
Huafeng Xiao · Ruibin Wang ·
Chenhui Niu · Yun Liu · Kairong Qian
High-Frequency
Soft-Switching
Transformerless
Grid-Connected
Inverters
CPSS Power Electronics Series
Series Editors
Wei Chen, Fuzhou University, Fuzhou, Fujian, China
Yongzheng Chen, Liaoning University of Technology, Jinzhou, Liaoning, China
Xiangning He, Zhejiang University, Hangzhou, Zhejiang, China
Yongdong Li, Tsinghua University, Beijing, China
Jingjun Liu, Xi’an Jiaotong University, Xi’an, Shaanxi, China
An Luo, Hunan University, Changsha, Hunan, China
Xikui Ma, Xi’an Jiaotong University, Xi’an, Shaanxi, China
Xinbo Ruan, Nanjing University of Aeronautics and Astronautics, Nanjing Shi,
Jiangsu, China
Kuang Shen, Zhejiang University, Hangzhou, Zhejiang, China
Dianguo Xu, Harbin Institute of Technology, Haerbin Shi, Heilongjiang, China
Jianping Xu, Xinan Jiaotong University, Chengdu, Sichuan, China
Mark Dehong Xu, Zhejiang University, Hangzhou, Zhejiang, China
Xiaoming Zha, Wuhan University, Wuhan, Hubei, China
Bo Zhang, South China University of Technology, Guangzhou Shi, Guangdong,
China
Lei Zhang, China Power Supply Society, Tianjin, China
Xin Zhang, Hefei University of Technology, Heifei Shi, Anhui, China
Zhengming Zhao, Tsinghua University, Haidian Qu, Beijing, China
Qionglin Zheng, Beijing Jiaotong University, Haidian, Beijing, China
Luowei Zhou, Chongqing University, Chongqing, Sichuan, China
This series comprises advanced textbooks, research monographs, professional
books, and reference works covering different aspects of power electronics, such as
Variable Frequency Power Supply, DC Power Supply, Magnetic Technology, New
Energy Power Conversion, Electromagnetic Compatibility as well as Wireless
Power Transfer Technology and Equipment. The series features leading Chinese
scholars and researchers and publishes authored books as well as edited
compilations. It aims to provide critical reviews of important subjects in the field,
publish new discoveries and significant progress that has been made in develop-
ment of applications and the advancement of principles, theories and designs, and
report cutting-edge research and relevant technologies. The CPSS Power
Electronics series has an editorial board with members from the China Power
Supply Society and a consulting editor from Springer.
Readership: Research scientists in universities, research institutions and the
industry, graduate students, and senior undergraduates.
· · ·
Huafeng Xiao Ruibin Wang Chenhui Niu
·
Yun Liu Kairong Qian
High-Frequency
Soft-Switching
Transformerless
Grid-Connected Inverters
Huafeng Xiao Ruibin Wang
College of Electrical Engineering College of Electrical Engineering
Southeast University Southeast University
Nanjing, Jiangsu, China Nanjing, Jiangsu, China
Chenhui Niu Yun Liu
China Huaneng Jiangsu Company College of Electrical Engineering
Nanjing, Jiangsu, China Southeast University
Nanjing, Jiangsu, China
Kairong Qian
China Huaneng Jiangsu Company
Nanjing, Jiangsu, China
ISSN 2520-8853 ISSN 2520-8861 (electronic)
CPSS Power Electronics Series
ISBN 978-981-19-3037-9 ISBN 978-981-19-3038-6 (eBook)
https://doi.org/10.1007/978-981-19-3038-6
© The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature
Singapore Pte Ltd. 2022
This work is subject to copyright. All rights are solely and exclusively licensed by the Publisher, whether
the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse
of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and
transmission or information storage and retrieval, electronic adaptation, computer software, or by similar
or dissimilar methodology now known or hereafter developed.
The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication
does not imply, even in the absence of a specific statement, that such names are exempt from the relevant
protective laws and regulations and therefore free for general use.
The publisher, the authors, and the editors are safe to assume that the advice and information in this book
are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or
the editors give a warranty, expressed or implied, with respect to the material contained herein or for any
errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional
claims in published maps and institutional affiliations.
This Springer imprint is published by the registered company Springer Nature Singapore Pte Ltd.
The registered company address is: 152 Beach Road, #21-01/04 Gateway East, Singapore 189721,
Singapore
Contents
1 Introduction ................................................... 1
1.1 Development History of Soft-Switching Inverters ............... 1
1.2 Resonant DC-Link Inverters ................................. 3
1.2.1 Origin and Configuration of RDCLI .................... 3
1.2.2 Conventional RDCLI ................................. 3
1.2.3 Actively Clamped RDCLI ............................. 5
1.2.4 Parallel RDCLI ...................................... 6
1.3 Resonant Pole Inverters ..................................... 8
1.3.1 Origin and Configuration of RPI ....................... 8
1.3.2 Conventional RPI .................................... 8
1.3.3 Auxiliary Resonant Commutated Pole Inverter ........... 9
1.4 Freewheeling Resonance Tank Inverters ....................... 12
1.4.1 FRTI with Single-Quadrant Resonance Networks ......... 12
1.4.2 FRTI with Two-Quadrant Resonance Networks ........... 13
References ..................................................... 14
2 High-Frequency Transformerless Grid-Connected Inverters
and Related Issues .............................................. 17
2.1 High-Frequency Operation Requirements for TLIs .............. 17
2.1.1 High Power Density and Low Volume ................... 18
2.1.2 Low Cost ........................................... 18
2.1.3 High Performance .................................... 19
2.2 Switching Loss Issue ........................................ 19
2.2.1 Origin of Switching Loss .............................. 19
2.2.2 Semiconductor Related Solutions ....................... 20
2.2.3 Circuit Related Solutions .............................. 21
2.3 EMI Issue ................................................. 21
2.4 Reactive Power Issue ....................................... 22
References ..................................................... 22
v
vi Contents
3 Zero-Current-Transition TLIs with Switching-Loss-Free ........... 25
3.1 ZCT Trajectory and Implementing Cells
with Self-compensation Mode ................................ 25
3.2 SLF-H6 Inverter ............................................ 28
3.2.1 Derivation of SLF-H6 Topology ........................ 28
3.2.2 Operation Principle ................................... 30
3.2.3 Conditions for Achieving SLF-H6 ...................... 34
3.2.4 Parameter Design of Resonant Components .............. 35
3.2.5 Experimental Verification ............................. 36
3.3 SLF-HERIC Inverter ........................................ 41
3.3.1 Derivation of SLF-HERIC Topology .................... 41
3.3.2 Operation Principle ................................... 42
3.3.3 Conditions for Achieving SLF-HERIC .................. 47
3.3.4 Experimental Verification ............................. 48
References ..................................................... 51
4 Zero-Current-Transition TLIs with Full Power Factor Range ...... 53
4.1 Two-Quadrant ZCT Resonance Network ....................... 53
4.1.1 Implementing Cells of ZCT Trajectory
with Load-Related Radius ............................. 54
4.1.2 Derivation of TQ-ZCT-RN ............................ 55
4.2 SLF-HERIC-FPF Inverter ................................... 57
4.2.1 Application of TQ-ZCT-RN in HERIC Topology ......... 57
4.2.2 Operation Principle ................................... 58
4.2.3 Performance Analysis ................................ 63
4.2.4 Experimental Verification ............................. 66
4.3 SLF-H6-FPF Inverter ....................................... 69
4.3.1 Application of TQ-ZCT-RN in H6 Topology ............. 69
4.3.2 Operation Principle ................................... 70
4.3.3 Experimental Verification ............................. 75
4.4 ZCT-H5-FPF Inverter ....................................... 77
4.4.1 Application of TQ-ZCT-RN in H5 Topology ............. 77
4.4.2 Operation Principle ................................... 79
4.4.3 Experimental Verification ............................. 88
References ..................................................... 94
5 Zero-Voltage-Transition TLIs with Single-Quadrant Resonance
Networks ...................................................... 95
5.1 ZVT Trajectory and Implementation Cells ..................... 95
5.2 ZVT-HERIC Inverter ....................................... 97
5.2.1 Derivation of ZVT-HERIC Topology ................... 97
5.2.2 Operation Principle ................................... 98
5.2.3 Conditions for Achieving ZVT ......................... 102
5.2.4 Parameter Design of Resonant Components .............. 103
5.2.5 Experimental Verification ............................. 104
5.3 ZVT-H5 Inverter ........................................... 110
Contents vii
5.3.1 Derivation of ZVT-H5 Topology ....................... 110
5.3.2 Operation Principle ................................... 111
5.3.3 Experimental Verification ............................. 115
5.4 ZVT-H6 Inverter ........................................... 118
5.4.1 Derivation of ZVT-H6 Topology ....................... 118
5.4.2 Operation Principle ................................... 119
5.4.3 Experimental Verification ............................. 123
References ..................................................... 129
6 Zero-Voltage-Transition TLIs with Two-Quadrant Resonance
Networks ...................................................... 131
6.1 Two-Quadrant ZVT Resonance Networks ...................... 131
6.1.1 New Equivalent Structure of ZVT Cells ................. 131
6.1.2 Derivation of TQ-ZVT-RN ............................ 133
6.2 ZVT-HERIC-FPF Inverter ................................... 134
6.2.1 Application of TQ-ZVT-RN in HERIC Topology ......... 134
6.2.2 Operation Principle ................................... 136
6.2.3 Performance Analysis ................................ 140
6.2.4 Experimental Verification ............................. 143
6.3 ZVT-H6-FPF Inverter ....................................... 150
6.3.1 Application of TQ-ZVT-RN in H6 Topology ............. 150
6.3.2 Operation Principle ................................... 152
6.3.3 Experimental Verification ............................. 155
References ..................................................... 162
Chapter 1
Introduction
Abstract Soft-switching technology can reduce switching loss and improve
switching frequency of inverters. In this chapter, the conventional soft-switching
implementation methods of inverters are reviewed at first, and then a new soft-
switching inverter architecture is presented by means of the technical characteristics
of non-isolated photovoltaic grid-connected inverter.
· ·
Keywords Transformerless inverter Soft-switching configuration Resonant
· ·
DC-link inverter Resonant pole inverter Freewheeling resonance tank inverter
1.1 Development History of Soft-Switching Inverters
The concept of soft switching was firstly proposed by Professor Fred C. Lee, who is
an internationally renowned power electronics expert, in the early 1980s. Nowadays,
soft-switching techniques have been widely used in DC-DC converter applications
[1]. However, when soft switching was transplanted into the inverter, there were
considerable difficulties, for example, the interaction of multiple resonant processes
makes the circuit difficult to work. Until the late 1980s, Professor Divan of the Univer-
sity of Wisconsin (now Georgia Institute of Technology) proposed the landmark reso-
nant DC-link inverter (RDCLI) [2] and resonant pole inverter (RPI) [3], which open
up new ideas for the research of converter soft-switching technology, as shown in
Fig. 1.1 [2–22]. After more than 30 years, researchers have proposed various types of
inverter soft-switching improved topologies based on basic RDCLI and freewheeling
RPI, and have some applications in isolated systems and independent systems [23].
With the rapid increase in the demand for grid-connected renewable energy, such
photovoltaic grid-connected systems require higher conversion efficiency and lower
costs to reduce the cost of electricity and the initial investment. A photovoltaic
power generation system based on Transformerless Grid-Connected Inverter (TLI)
is widely used in distributed photovoltaic power generation. In the TLI system, the
photovoltaic array is electrically connected to the power grid. At the same time,
the large-area photovoltaic array forms a large parasitic capacitance to the ground.
Thus, a circuit with a lower impedance is formed for the common-mode voltage
source of the switching frequency scale, and there is a larger common-mode current
© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 1
H. Xiao et al., High-Frequency Soft-Switching Transformerless Grid-Connected Inverters,
CPSS Power Electronics Series, https://doi.org/10.1007/978-981-19-3038-6_1
2 1 Introduction
Soft-switching inverter
Resonant DC link Resonant pole Freewheeling resonance
inverter (RDCLI) inverter (RPI) tank inverter (FRTI)
Parallel RDCLI Series RDCLI Parallel RPI Series RPI Zero-Voltage Zero-current
FRTI FRTI
CPoRnvDeCntLioI[n4]a l CoRnDveCnLtiIo[8n]al ARCPI[15] ConRvePnIt[9i]o nal ZVT-HERIC[20] ZCS-HERIC[22]
Paper[5] ACRDCLI[9] ZCT-PWM[12] ZVT-PWM[16] Auxiliary ZVT-H5[21] ZCS-H5[22]
diode RPI[19]
QImRpDrCovLeId[2] QRDCLI[6] MAinCimRuDmC vLoIl[t10a]g e Δ-Snubber[13] Y-Snubber[17] ZVT-H6-I[21] ZCS-H6-I[22]
Double coupled Transformer ZVT-H6-II[21] ZCS-H6-II[22]
QIPmRpDroCvLeId[ 3] QPRDCLI[7] ACCoRmDpCoLsiIt[e11 ] inductRoPr Ia[u14x] iliary auRxPiIli[a18r]y
Fig. 1.1 Technology tree of soft-switching inverters
(leakage current) [3]. This leakage current will endanger the safety of personnel and
equipment. Therefore, TLI products sold on the market must comply with leakage
current standards, such as VDE 0126-1-1, IEEE 1547, etc.
When the RDCLI and RPI are directly applied to TLI structure, the high-frequency
time-varying common-mode voltage may act on the parasitic capacitance, resulting
in the leakage current which may exceed the allowable range [24]. As a result, if we
want to use soft-switching technology in TLI, we must avoid generating common-
mode voltages. While the common-mode voltage of RDCLI and RPI soft-switching
inverter topologies cannot be kept constant. In other words, if it is forced to change
the drive timing of a constant common-mode voltage, the working timing of their
resonant network will be destroyed, and the soft-switching operation will be lost. The
Southeast University team proposed a freewheeling resonance tank inverter (FRTI)
[22], as shown in the third branch of Fig. 1.1, and successfully introduced two types of
soft-switching concepts of zero-current transition (ZCT) and zero-voltage transition
(ZVT) into the inverter architecture. However, the soft switching of high-frequency
tube can only be realized under the condition of unit power factor. Therefore, the
team further improved the FRTI architecture, constructed a topological architecture
that can support the dual-quadrant resonant network, and achieving the full power
factor of the high-frequency switch tube soft-switching operation. This article will
discuss the TLI soft-switching technology in detail based on the FRTI architecture.
