Toroidal transformer design optimization for the application of high-frequency power converters = 고주파 전력 변환기의 적용을 위한 토로 이달 변압기 설계 최적화

국문 초록 (Abstract)

고주파 기반의 인버터는 동력 전달을 위한 재생 가능 에너지 원으로 사용됩니다. 그러나 고주파 링크 변압기에서 발생하는 권선 간 높은 기생 커패시턴스에 의한 공통 모드 노이즈 전류의 증가로 인해 전력 품질이 저하됩니다. 이 빠른 전압 과도 응답은 고조파 왜곡 및 변압기 과열로 이어지며, 이는 전원 공급 장치 고장 또는 기타 여러 가지 전기 위험 요인을 유발합니다. 이 논문은 절연 전원 공급 장치에 대한 기존 및 제안 된 토로이드 변압기 설계 간의 비교 연구를 제시합니다. 하프 브리지 고주파 (10 kHz) 소용량 DC-AC 인버터가 전원과 함께 설계되었습니다. 680 W 태양 광 모듈 재생 시스템이 구축되었습니다. Matlab-FFT 분석을 사용한 FEM 시뮬레이션을 사용하여 코어의 자속 분포를 결정하고 총 고조파 왜곡 (THD)을 계산했습니다. GWInstek LCR 미터와 Fluke VT04A는 네 개의 변압기 프로토 타입 모두에서 권선 간 정전 용량과 온도를 측정했습니다. 토로이드 형 코어 변압기의 수정 된 설계는 냉각제 또는 외부 회로를 사용하지 않고도 온도 상승에 대한 저항력을 향상시키면서 기생 커패시턴스를 87 % 줄입니다. 접근법의 타당성을 확인하기 위해 권선 간 용량의 수학적 유도와 함께 실험을 수행했습니다.

다국어 초록 (Multilingual Abstract)

The high-frequency-based inverter is used in renewable energy power sources for power transmission. However, power quality is compromised as a result of the increase in common mode noise currents by the high inter-winding parasitic capacitance in high-frequency link transformers. This fast voltage transient response leads to harmonic distortion and transformer overheating, which causes power supply failure or many other electrical hazards. This paper presents a comparative study between conventional and modified toroid transformer designs for isolated power supply. A half bridge high-frequency (10 kHz) small power DC–AC Voltage inverter was designed along with power source; a 680 W solar module renewable system was built. An FEM-simulation with Matlab-FFT analysis was used to determine the core flux distribution and to calculate the total harmonics distortion (THD). A GWInstek LCR meter and Fluke VT04A measured the inter-winding capacitance and temperature in all four transformer prototypes, respectively. The modified design of a toroid ferrite core transformer offers more resistance to temperature increase without the use of any cooling agent or external circuitry, while reducing the parasitic capacitance by 87%. Experiments were conducted along with a mathematical derivation of the inter-winding capacitance to confirm the validity of the approach

목차 (Table of Contents)

• 1. INTRODUCTION 1
• 1.1. Introduction 4
• 1.2. References 4
• 2. BASIC PRINCIPLES AND THEORY OF TRANSFORMERS 8
• 2.1. Principal of Operation 8
• 2.2 Operation of Transformer
• 2.2.1 Equivalent Circuit of a Transformer………………………………………….13
• 2.3. Types of Transformer………………………………………………………………17
• 2.3.1 Transformer in Power Systems………………………………………………19
• 2.3.2 Special Types of Transformer……………………………………………..…21
• 2.3.2.1 Instrumental Transformer ………………………………………......21
• 2.3.2.2 Autotransformer…………………………………………………….26
• 2.3.2.3 Transformer Taps ……………………………………………….....26
• 2.3.3 Transformer Connection………………………………………………….…28
• 2.4 Technical Points of Transformer ………………………………………………….33
• 2.4.1 Transformer Temperature Control ………………………………………..33
• 2.4.1.1 Renown Transformer Temperature Control Methods ……………….35
• 2.5. Core Material and Shapes…………………………………………………………40
• 2.6 Losses in Transformers…………………………………………………………....41
• 2.7. Definition of Power Converter 51
• 2.6. Total Harmonics Distortion in Power Systems 53
• 2.7. References 58
• 3. Toroidal Transformer Design Optimization 62
• 3.1. Toroid Ferrite Core 62
• 3.2. Minimization of Parasitic Capacitance in Toroidal Transformer 64
• 3.2.1 Fabrication…………………………………………………………………..64
• 3.2.1.1 Case 1: Conventional Toroid Core Tranformer with 1800 Sector Winding
• 3.2.1.2 Case 2: Modified Toroid Core Transformer with 1800 Sector Winding
• 3.2.1.3 Case 3: Conventional 3600 Wound Toroid Core Transformer
• 3.2.1.4 Case 4: Modified 3600 Wound Toroid Core Transformer
• 3.3. Enlargement of leakage inductance in Toroidal Transformer …………………..67
• 3.3.1 Leakage inductance in Toroidal Transformer……………………………….68
• 3.3.2 Sectored winding effects on Toroidal Transformer leakage inductance …....68
• 3.3.3 High permeability material effect on Toroidal Transformer leakage inductance
• 3.3.3.1 What is Ferrofluid……………………………………………………....70
• 3.4 B-H curve for transformer core material (ferromagnetic 77 material)……..71
• 3.4.1 Determination of B-H Curve of Core Material of Transformer ………71
• 3.4.2 DC Magnetization Curve …………………………………………….71
• 3.4.3 Hysteresis Loop……………………………………………………….73
• 3.3.4 B-H curve for ferrite 77 material, core which have used in all prototypes in our toroidal transformer design………………………………………………………..75
• 3.5. References…………………………………………………………………...…75
• 4. TEST PLATFORM ………………………………………………………………….78
• 4.1. High Frequency Toroid Transformer’s Parasitic Capacitance Minimization for Standalone solar Photovoltaic (PV) High-Frequency Link-Based Inverter……………………..……78
• 4.1.1 Renewable Energy Source On and Off Grid System……………………….78
• 4.1.2 Circuit Operation……………………………………………………………79
• 4.1.3 Calculation of the Toroid Transformer Inter-Winding Capacitance………..80
• 4.1.4 Experimental Setup…………………………………………………………85
• 4.1.5 Results and Discussion……………………………………………………...88
• 5. CONCLUSIONS………………………………………………………………94
• Abstract (Korean)……………………………………………………………………....95
• Acknowledgements……………………………………………………………………..97