Improvement in control and gain aspects of impedance source inverters and converters

Power electronics have revolutionized the concept of power control for power conversion and for control of electrical motor drives. Power electronics has been extensively used in industrial applications since it was first discovered in 1902. Power conversion is one of the most important and prominent applications of power electronics. Impedance source networks cover the entire spectrum of electric power conversions from DC-AC (e.g. inverters), to phase and frequency conversion (AC-AC) in a wide range of applications. A wide variety of topologies and control methods using different impedance source networks have been presented in the literature to overcome the limitations and problems of traditional voltage source and current source as well as various classical buck–boost, unidirectional, and bidirectional converter topologies. Proper implementation of the impedance-source network with appropriate switching configurations and topologies reduces the number of power conversion stages in the system power chain, which may improve the reliability and performance of the power system. The main focus of this thesis is to study and analyze different impedance source inverters and their control methods, and the development of improved impedance source power systems that will comprise advanced circuitry and provide higher voltage gains needing less complex systems that together provide more cost-efficient solutions. The systems under considerations would have high frequency electrical isolation and voltage clamping across the DC-link inverter bridge that would resulting in better protection, lower overall system losses, and increased efficiencies. Then parallel techniques will be discussed, analyzed and implemented for the class of impedance source inverters. This parallel operation of ZSIs leads to reduced components stress across the inverter bridges by sharing the currents, interleaving, ease of maintenance, modularity, higher reliability, and (N+1) redundancy. The scope of impedance source networks is not limited to inverters (i.e., DC-AC power conversion), but covers a wide range of electric power conversion applications including (DC-DC and AC-AC converters). Thus, the last part of this research project will include the development of a new class of transformer based impedance source AC-AC converters with novel control strategies to increase the input to output gains and to improve the conglomerate characteristics of the AC-AC converters. Validation of the proposed structures will be done virtually using the Saber, PSIM simulations, and physically using experimental hardware prototypes. Several KW power systems will be fabricated and implemented using a DSP-kit based on the TMS320f28335 processor. Modified modulation schemes will be applied to control the switching of active devices. Furthermore, clamping techniques by minimizing the high frequency loop via clamping diode will be applied to the proposed inverters to limit the voltage overshoots caused by the leakage inductance energy. The better performance of improved impedance source network (with added benefits of HF isolation and parallelization) to design more resilient and efficient converter topology for various applications such as adjustable speed drives, distributed generation systems, super-capacitor energy storage systems, uninterruptable power supply, dc circuit breakers, electric vehicles, avionics, and electronic loads will attract researchers and professional engineers to explore it in depth

소용량 수동 소자와 직류단 보조 에너지 저장 회로를 가지는 교류 전동기 구동 시스템에 관한 연구

학위논문 (박사)-- 서울대학교 대학원 : 전기·컴퓨터공학부, 2015. 8. 하정익.In power conversion system, passive components such as grid filter inductor and DC-link capacitor have been widely used. However, they have several problems that they occupy too many spaces in the entire and an electrolytic capacitor which is commonly used in DC-link has a low reliability due to its high failure rate. To reduce or replace them, novel control methods or topologies using extra active devices with low-power-rating have been proposed, and these methods match to a trend of cost reduction of high-performance switching devices. Hence this dissertation proposes control method for diode rectifier-fed system equipping small passive components and an auxiliary circuit called as DC-link shunt compensator (DSC). Owing to the absence of the electrolytic capacitor, the proposed structure is robust in terms of component failure. Moreover the diode rectifier-fed system using the proposed method can satisfy grid regulations such as IEC 61000-3-12 or -3-2 without power factor correction (PFC) or heavy grid filter inductor. The proposed method includes the grid current shaping and system operating methods which improve grid current harmonics and system performances, respectively. This dissertation also presents implementation methods by using either motor drive inverter or DSC. The former is the most cost-effective way to realize proposed method but it necessarily degrades output performances such as torque quality and system efficiency. The latter requires auxiliary switching devices and small passive components, but it has advantages in not only output performances but also system efficiency by cooperation of DSC. The proposed DSC operating strategy is presented in detail and corresponding design guideline is also provided. In this dissertation, the DSC operating method is considered for both single- and three-phase diode rectifier-fed systems. In the case of the diode rectifier system using small passive components, the waveform of DC-link voltage is totally different in accordance with the gird phase, thus the corresponding control algorithms for both single- and three-phase inputs are also established respectively. This dissertation proposes each dedicated control method and discusses the feasibility. As a practical implementation example, boost converter is selected for the structure of DSC, and the validity of proposed methods are verified by simulation and experimental results.Abstract i List of Figures vi List of Tables xi 1 Introduction 1 1.1 Backgrounds and Motivations 1 1.2 Objectives 3 1.3 Dissertation Outlines 6 2 Conventional Motor Drive System 8 2.1 Review of Motor Drive System with Passive Components 8 2.1.1 DC-Link Capacitor 9 2.1.2 Grid Harmonic Regulations and Grid Filter Inductor 14 2.1.3 Limitation of Passive Components 24 2.2 Diode Rectifier Systems with Small DC-Link Capacitor ? State of the Art and Challenges 27 2.2.1 Review of Conventional Small DC-Link Capacitor System 27 2.2.2 Limitation of Conventional Systems 38 2.3 Conventional Systems with Auxiliary Circuit for Reducing Passive Components 40 2.3.1 Current Injection Topologies 41 2.3.2 Series Compensation Topologies 43 2.3.3 Parallel Compensation Topologies 45 3 Grid Current Shaping and DSC Operating Methods in Three-Phase Diode Rectifier System 50 3.1 Grid Current Shaping Method for Three-Phase System 53 3.1.1 Operating Principle of Proposed Control Method 53 3.1.2 System Stability Analysis 61 3.2 Implementation Based on Motor Drive Inverter 63 3.2.1 Control Block Diagram 64 3.2.2 Effect on the Motor Drive System 69 3.3 Three-Phase System with DSC 73 3.3.1 System Configuration 74 3.3.2 Control Method 76 3.3.3 System Design Guideline 83 3.4 Simulation and Experimental Results 87 3.5 Discussions 101 4 Grid Current Shaping and DSC Operating Methods in Single-Phase Diode Rectifier System 104 4.1 Conventional Single-Phase Small DC-Link Capacitor System 105 4.1.1 Control Method [26] 105 4.1.2 Limitation of Single-Phase Small DC-Link Capacitor System 108 4.2 Single-Phase System with DSC 109 4.2.1 System Configuration 109 4.2.2 Operating Concept 111 4.2.3 Partial Power Assistance Operating Strategy 116 4.2.4 Control Method 121 4.2.5 System Design Guideline 126 4.3 Simulation and Experimental Results 128 4.4 Discussions 141 4.4.1 System Operating Strategies 141 4.4.2 Availability of single-phase DSC system 143 5 Conclusion and Future Works 147 Appendix 150 A.1 Case Study 1: Implementation Cost of Three-Phase DSC System 150 A.2 Case Study 2: Implementation Cost of Single-Phase DSC System 152 References 155 초 록 167Docto

Técnicas avanzadas de modulación para la reducción de la distorsión armónica total (DAT) en fuentes auxiliares para ferrocarril

Doctor por la Universidad Carlos III de Madrid. Programa en Ingeniería Eléctrica, Electrónica y AutomáticaPresidente: Emilio Olias Ruiz.- Secretario: Emilio José Bueno Peña.- Vocales: Marta María Hernando Álvarez, Enrique Romero Cadaval, Aurelio García Cerrad