Stability improvement and control optimization of isolated two-stage AC-DC-DC converter systems Authors: Feng, Fan -Engineering::Electrical and electronic engineering::Power electronics -Nanyang Technological University

STABILITY IMPROVEMENT AND CONTROL OPTIMIZATION OF ISOLATED TWO-STAGE AC-DC-DC CONVERTER SYSTEMS by FENG FAN

 School of Electrical & Electronic Engineering -2020

 A thesis submitted to the Nanyang Technological University in partial fulfilment of the requirement for the degree of Doctor of Philosophy 2020 

 Abstract: Driven by the ever-increasing energy demand and the desire for carbon footprint reduction, the power industry is under a wave of transformation from the current grid into the smart grid. As the trend of the grid transformation continues, a significantly high penetration level of renewable energy resources, in parallel with other emerging technologies such as the energy storage and electric vehicles, is to be expected. Since many types of renewables and energy storage devices, e.g., solar photovoltaic, batteries and supercapacitors, etc., are treated as DC sources, the multi-stage converter system is usually employed as the interface between the AC grid and DC networks. Specifically, the dual active bridge (DAB)-based two-stage AC-DC-DC converter is highly related to the distributed systems because of its advantages such as the high power density, soft switching properties, galvanic isolation and less passive components. Therefore, the stability and reliability of the two-stage AC-DC-DC converters are at the core of the distributed system operations. However, despite its control benefits, the two-stage AC-DC-DC converter system may suffer instability issues. This thesis aims to investigate and overcome the instability issues of the two-stage AC-DC-DC converter system. First, the existing primary stability criteria and stabilization methods for the non-isolated two-stage converter systems have been reviewed and summarized. The terminal impedances of the sub-converters are useful tools to determine the stability of the two-stage converter systems. The forbidden regions for the voltage-source and current-source systems have been discussed. To satisfy these stability criteria, the terminal impedances of the sub-converters should be modified via passive or active damping methods. The research gap for the isolated two-stage AC-DC-DC converter has been identified as well. To analyze the stability of the DAB-based two-stage AC-DC-DC converter, the full-order impedance model of the DAB converter is derived for the first time in this thesis. Since the high-frequency ac conversion stage of the DAB converter naturally violates the small ripple assumption of the traditional state-space modeling, the generalized averaging approach is applied for the DAB impedance derivation. The derived impedance model can provide fully continuous-time representations that are capable of describing the ac conversion stage of the DAB converter. Furthermore, based on the developed impedance model, the influences of the DAB circuit parameters on the stability of the two-stage converter are analyzed. The analysis results offer instructive implications to fine-tune the design rules of the DAB converters. Bearing the mind that the impedance model of the DAB converter is closely related to the modulation schemes, the impacts of three typical modulation methods on the DAB impedances are analyzed and compared. An interesting phenomenon is found that the open-loop impedances of Single Phase-Shift (SPS)-based and Dual Phase-Shift (DPS)-based DAB converters present the characteristics of the parallel-connected inductor and capacitor, while the open-loop impedance of Cooperative Triple Phase-Shift (CTPS)-based DAB converter presents the resistor characteristics. The optimal modulation scheme in terms of stability performance for the two-stage converter is pointed out. This can help engineers find a more stable modulation scheme of the DAB converter in practical cascaded applications.

VIEW FULL TEXT:

https://dr.ntu.edu.sg/bitstream/10356/142948/2/Final%20Thesis.pdf

Development of AC/DC and DC/DC Converters Applied to DC Power Supply with Wide Range of Input Voltage BY TaeHo Bang -Yonsei University Graduate School 2019-Doctor of Philosophy

Development of AC/DC and DC/DC Converters Applied to DC Power Supply with Wide Range of Input Voltage

 A Dissertation Submitted to the School of Electrical and Electronic Engineering and the Graduate School of Yonsei University in partial fulfillment of the requirements for the degree of Doctor of Philosophy 

TaeHo Bang 

December 2018

 Abstract 

This dissertation presents development of AC/DC and DC/DC converters applied to a DC power supply used for various electric devices from home appliances to electric vehicles. In general, the DC power supply consists of electromagnetic interference (EMI) filter for reducing the EMI noise, AC-DC converter to rectify the AC grid voltage into DC voltage and DC-DC converter to supply the power with the suitable voltage level for each device. The EMI filter is essential part of power supply because high speed switching of the converter devices causes undesirable EMI noise. The boost power factor correction (PFC) has widely used for the AC-DC converter because of its simple structure and low cost. In addition, the ability to cope with various AC grid voltages and conditions in different countries is becoming important for PFC converter topologies from the industrial point of view. Meanwhile, full-bridge DC-DC converter is one of the most frequently used topologies in electric vehicle when electrical isolation is required. Isolated DC-DC full-bridge converters are suitable for low DC-DC converter (LDC) which converts high input voltage of the battery into low output voltage level for suppling the power to load of the electrical vehicle. The efficiency of DC-DC converter in electric vehicle are highly related with overall performances including range distance, weight and charging time. Then, improving efficiency without much additional component becomes very important in converter topologies used in electric vehicle. The buck cascaded buck-boost (BuCBB) PFC converter and isolated full-bridge (FB) converter are studied in this dissertation, respectively. 

 First, the BuCBB PFC converter which operates in wide input voltage range to cope with various grid conditions is developed. The converter can operate in buck or boost mode according to the peak value of input voltage. The converter parameters are properly determined to endure voltage and current stress in all operating ranges. In addition, the EMI filter is used to reduce the high frequency switching noise and guarantee continuous input current in buck mode operation. In addition, switching loss is reduced in all operation range by applying zero-voltage-transient pulse-width-modulation (ZVT-PWM) method. In particular, the power factor (PF) depending on the operation modes of the PFC converter including EMI filter is derived with associated mathematical equations in buck and boost mode, respectively. The performances of proposed PFC converter with wide range of input voltage are evaluated by the simulation and experimental test including PF and input current harmonics in all operating ranges. Finally, the efficiency of proposed PFC converter is compared with that of a conventional buck cascaded buck-boost PFC converter in various conditions. And then, a novel control method for FB converter by using the combined phase-shifted and asymmetric pulse-width-modulation (APWM) method is proposed. It reduces the peak and DC offset values of the input-side current of converter. Then, the overall efficiency is consequently improved by reduced the switching losses in its input-side. Moreover, the zero-voltage switching (ZVS) conditions of switches are satisfied in all operating ranges. The phase-shifted duty ratios corresponding to the output currents of converter are optimally selected based on the loss model analysis. Also, the operational features characterized by the proposed phase-shifted asymmetric pulse-width-modulation (PS-APWM) method are investigated under both the continuous and discontinuous current modes of converter. Then, the effectiveness of proposed PS-APWM method is verified with the simulation and practical hardware experimental results. In particular, the experimental test is carried out in a light load condition. Finally, the efficiency of FB converter controlled by the proposed PS-APWM method is compared with that by the conventional phase-shifted or APWM method, which has been separately applied.

ORIGINAL SOURCE:

http://www.riss.kr/search/detail/DetailView.do?p_mat_type=be54d9b8bc7cdb09&control_no=d64f3903ccdb9036ffe0bdc3ef48d419&keyword=topology%20power%20supply

DOWNLOAD: https://www.mediafire.com/file/f0v5mkub38680y5/Development+of+ACDC+and+DCDC+Converters+Applied+to+DC+Power+Supply+with+Wide+Range+of+Input+Voltage.pdf/file

Resonant isolating transducer with GaN transistors BY Soukup, Dominik-Rezonanční izolující měnič s GaN tranzistory -ZÁPADOČESKÁ UNIVERZITA V PLZNI FAKULTA ELEKTROTECHNICKÁ KATEDRA VÝKONOVÉ ELEKTRONIKY A STROJŮ

 

Title: Rezonanční izolující měnič s GaN tranzistory 

Other Titles: Resonant insulating converter with GaN transistors 

Authors: Soukup, Dominik

 Advisor: Jára Martin, Ing. Ph.D. Referee: Štěpánek Jan, Ing. Ph.D.

 Issue Date: 2021 

Publisher: Západočeská univerzita v Plzni

Abstrakt

Předkládaná diplomová práce se věnuje návrhu a realizaci rezonančního izolujícího měniče s GaN tranzistory. V práci je uvedeno stručné porovnání polovodičových materiálů a rezonančních měničů. Dále se práce zabývá samotným návrhem měniče, který zahrnuje výběr a dimenzování polovodičových součástek, návrh budícího obvodu, mechanický koncept a následnou realizaci. Závěrečná část práce se věnuje oživení a testování prototypového měniče.

Abstract 

The presented diploma thesis deals with the design and implementation of a resonant isolating transducer with GaN transistors. The paper presents a brief comparison of semiconductor materials and resonant converters. Furthermore, the work deals with the design of the converter, which includes the selection and dimensioning of semiconductor components, the design of the excitation circuit, the mechanical concept and subsequent implementation. The final part of the work is devoted to the recovery and testing of a prototype converter.

VIEW FULL TEXT :https://dspace5.zcu.cz/bitstream/11025/46112/1/DP.DS.pdf

Engineering PhD thesis Considering load impedance fluctuations of resonant power conversion system 4-terminal network desig by Jeong Eui-Hoon Seoul National University Graduate School Department of Electrical and Information Engineering

공학박사학위논문

부하 임피던스 변동을 고려한

공진형 전력 변환 시스템의

4 단자 네트워크 설계

서울대학교 대학원

전기∙정보공학부

정 의 훈

Engineering PhD thesis Considering load impedance fluctuations of resonant power conversion system 4-terminal network design 

 Seoul National University Graduate 

School Department of Electrical and Information Engineering

By  Jeong Eui-Hoon

ABSTRACT

Resonant power conversion systems have been widely used for high-frequency power conversion due to the advantage of low switching losses in inverter circuits. Such a system structure has been adopted in various fields such as battery charging, wireless power transmission, plasma driving system, and etc. Resonant power conversion systems operate very efficiently under one driving operation condition, but performance is easily degraded by system variations. In this dissertation, a systematic method for designing a resonant network, which is a key element of a resonant power conversion system, is proposed. The degree of design freedom of a two-port network is analyzed based on the general and mathematical model. This dissertation presents methods utilize the design freedoms to shape the input impedance trajectories to the desired way or to compress the input impedance variations to a certain value when the load impedance varies in a certain range. Based on this theoretical background, a resonant power conversion system with robust characteristics against load impedance is constructed. The proposed method is applied to design the wireless power transfer system that has a robust output characteristic against coil coupling variation. In addition, the proposed method is used to construct a high-frequency power conversion system that maintains impedance matching even with a wide range of load impedance variations. For the design examples, simulation and experimental results are presented to verify the effectiveness and the superiority of the proposed method. 

VIEW FULL TEXT: https://www.mediafire.com/file/hezak1yyth9gs72/resonant+converter.pdf/file

AUTOMATIC CONTROL Kyungpook National University PROF. Choi Byung-Jo-Lecture 24: Loop Gain Shaping and Feedback Compensation Structure