Modeling strategy for EMI filter and flyback transformer

“The switch-mode power supply is key to miniaturizing power adapters. However, the switching nature of the circuit introduces issues in conducted emissions. In a flyback converter, the transformer serves as the path for common mode current flowing from the primary side to the secondary side. Different winding technologies have been invented and implemented to reduce the capacitance between the primary side and the secondary side. But the repeatability of the winding is still poor due to the fluctuations of the winding machine. Thus, the resulting conducted emission has a fluctuation that can lead to failure in the compliance tests. EMI filter is another module implemented to reduce the conducted emissions. Due to the miniaturization, the components inside a filter are closely placed, therefore, strong mutual parasitics. These parasitics degrade the performance of the EMI filter. Overall, it would be beneficial if the performance of the EMI filter and the fluctuation of the transformer can both be analyzed through pre-design simulation. In this dissertation, a model strategy for EMI filters is developed and validated through comparison with measurement. The strategy covers different types of film capacitors, common mode chokes, and circuit topologies. This dissertation also provides an approach to asserting the parasitic capacitance of transformers through 2D analysis. Contradictory to the existing models that relate the parasitic capacitance and conducted emissions, the best-performance capacitance is found not zero. A simplified circuit model is developed to associate the conducted emissions with the parasitic capacitance of the transformer. This circuit model leads to an analytical formulation for evaluating the best-performance parasitic capacitance of the transformer, and its prediction matches with the observed relationship in the measurement. In conclusion, the research in this dissertation clarified the procedure for utilizing computer-aided simulation to guide the design of EMI filters and flyback converters in compact designs”--Abstract, page iv

Computer-Aided Modeling and Analysis of Power Processing Systems (CAMAPPS), phase 1

The large-signal behaviors of a regulator depend largely on the type of power circuit topology and control. Thus, for maximum flexibility, it is best to develop models for each functional block a independent modules. A regulator can then be configured by collecting appropriate pre-defined modules for each functional block. In order to complete the component model generation for a comprehensive spacecraft power system, the following modules were developed: solar array switching unit and control; shunt regulators; and battery discharger. The capability of each module is demonstrated using a simplified Direct Energy Transfer (DET) system. Large-signal behaviors of solar array power systems were analyzed. Stability of the solar array system operating points with a nonlinear load is analyzed. The state-plane analysis illustrates trajectories of the system operating point under various conditions. Stability and transient responses of the system operating near the solar array's maximum power point are also analyzed. The solar array system mode of operation is described using the DET spacecraft power system. The DET system is simulated for various operating conditions. Transfer of the software program CAMAPPS (Computer Aided Modeling and Analysis of Power Processing Systems) to NASA/GSFC (Goddard Space Flight Center) was accomplished

Common-Mode Modeling of Neutral Point Clamped Converter Based Dual Active Bridge

Modern power converters designed with wide-bandgap semiconductors are known to generate substantial conducted electromagnetic interference as a side effect of high edge rate and high frequency switching. With the advancement in power electronic converters, the significant EMI challenges need to be addressed for distribution level power systems. The goal is to provide a computationally efficient method of EMI characterization for conducted emissions for this future generation of power distribution systems. The first step in making this possible is through creating an accurate EMI characterization platform for the neutral point clamped dual active bridge. In this thesis, a formalized common-mode modeling approach is carried out for transforming this mixed-mode power system into its common-mode equivalent circuit. The approach is validated through comparison of time-domain waveforms predicted by detailed mixed-mode and common-mode equivalent models of the representative power distribution system, with a proposed future validation using hardware measurements. The experimental studies highlight the utility of the proposed modeling approach to assess design mitigation strategies

Advanced Battery Technologies: New Applications and Management Systems

In recent years, lithium-ion batteries (LIBs) have been increasingly contributing to the development of novel engineering systems with energy storage requirements. LIBs are playing an essential role in our society, as they are being used in a wide variety of applications, ranging from consumer electronics, electric mobility, renewable energy storage, biomedical applications, or aerospace systems. Despite the remarkable achievements and applicability of LIBs, there are several features within this technology that require further research and improvements. In this book, a collection of 10 original research papers addresses some of those key features, including: battery testing methodologies, state of charge and state of health monitoring, and system-level power electronics applications. One key aspect to emphasize when it comes to this book is the multidisciplinary nature of the selected papers. The presented research was developed at university departments, institutes and organizations of different disciplines, including Electrical Engineering, Control Engineering, Computer Science or Material Science, to name a few examples. The overall result is a book that represents a coherent collection of multidisciplinary works within the prominent field of LIBs

Design of high frequency operating mechatronic systems : tools and methods of characterization of electromagnetic couplings between electromechanic converters and power electronics converters

From the more electrically operated aircraft, to the hybridization of motor vehicles, all the way to electromechanic cardiac implants, compactness has become the holy grail of modern embedded electrical engineering. Indeed, the power-to-weight ratio demands for electromechanical systems has greatly increased. To meet these high integration needs, power electronic converters find a vector of development by increasing their temperature and operating frequencies but also by reducing the switching time of power switches, thus enabling them to reduce their power losses and thereby reducing their cooling requirements. Electric motors and generators operate with various innovative topologies that meet integration, robustness and reliability needs. Motor windings, particularly, are the first motor components on the battle front. It is at the heart of the winding that occur the exchanges between motor and converter. In terms of electromagnetic compatibility (EMC) for embedded systems, the increased frequency and transient stresses in the form of current and voltage edges from the power electronic assemblies are considered steep challenges. The work presented herein is the result of a close cooperation between the company Novatem and the laboratory Génie de Production of ENIT de Tarbes, through CIFRE funding, in combination with the Labceem platform of IUT of Tarbes. Its aim is to develop predictive models that will serve to determine the consequences of such integration constraints in power mechatronic systems that are in the early stages of design. Conducted disturbances whose HF source is located at the inverter power switches are shaped by the impedances characterizing the coupling path of which the electrical machine is an integral part. This work proposes to develop methods and tools to support the predictive study of electromagnetic compatibility (EMC) of mechatronic assemblies, by attempting to cover a modeling frequency range that goes from 0 to 300 MHz’s. In the first chapter of this work, a literature review is detailed for the definition of the context and boundaries of the study. A second chapter focuses on the analytical modeling of concentrated windings in electric motors. The analytical models that are established allow determination of circuit networks settings to perform time- and frequency- domain simulations. Unlike the widespread behavioral models of electrical machine in the literature, the models that are synthesized here take into account the physical parameters of the coils. The user of such models is offered the opportunity to account for the different winding architectures, by changing core parameters such as geometry, insulation materials or permeability. A third chapter describes the establishment of a rational method for extraction of functional and parasitic parameters in multilayer Power PCBs. This method being of a generic and predictive logic aims to account for physical parameters. Finally, in the last chapter, the previously established tools and methods are applied to the study of a real electric vehicle drive system developed by the company Novatem. The physical and predictive value of these tools allows for execution of virtual experimentations on the motorconverter assembly without the need for prototypes. This chapter illustrates the value of a physical approach to modeling the electromagnetic compatibility of mechatronic systems

Alternative fuel from vegetable oils and animal fats

This study investigated the properties of processing vegetable and animal fat to be used as alternative fuel. The vegetable oil processing industry comprises the abstraction and treating of oils and fats from vegetable sources. Vegetable oils and fats are principally used for human consumption but are also used in animal feed, for medicinal purposes, and certain technical applications. In contrast triglycerides, vegetable waxes lack glycerin in their structure. Although many plant parts may yield oil, in commercial practice, oil is extracted primarily from seeds, for many developing countries, the concept of employing vegetable oils as sources for diesel fuels can be attractive. Often the culture of the appropriate plant is well established, the oil extraction well developed, and handling and storage well defined. Yields per hectare of tropical crops such as palm and coconut oils far exceed the yields of vegetable oils in temperate zones. Also, the production of most tropical vegetable oils has positive energy. A rendering process is performed to remove excess fat from animal carcasses and then turned into oil. Thus, to obtain refined oil, there is process from crude palm oil that involves removal of the products of hydrolysis and oxidation or abstraction process of oil from the palm kernels. After refining, the oil may be split (fractionated) into liquid and solid phases by thermo-mechanical means such as controlled cooling, crystallization, and filtering, the later oil is competing successfully with the more expensive groundnut, corn, and sunflower oils

Data Center Power System Emulation and GaN-Based High-Efficiency Rectifier with Reactive Power Regulation

Data centers are indispensable for today\u27s computing and networking society, which has a considerable power consumption and significant impact on power system. Meanwhile, the average energy usage efficiency of data centers is still not high, leading to significant power loss and system cost. In this dissertation, effective methods are proposed to investigate the data center load characteristics, improve data center power usage efficiency, and reduce the system cost. First, a dynamic power model of a typical data center ac power system is proposed, which is complete and able to predict the data center\u27s dynamic performance. Also, a converter-based data center power emulator serving as an all-in-one load is developed. The power emulator has been verified experimentally in a regional network in the HTB. Dynamic performances during voltage sag events and server load variations are emulated and discussed. Then, a gallium nitride (GaN) based critical conduction mode (CRM) totem-pole power factor correction (PFC) rectifier is designed as the single-phase front-end rectifier to improve the data center power distribution efficiency. Zero voltage switching (ZVS) modulation with ZVS time margin is developed, and a digital variable ON-time control is employed. A hardware prototype of the PFC rectifier is built and demonstrated with high efficiency. To achieve low input current total harmonic distortion (iTHD), current distortion mechanisms are analyzed, and effective solutions for mitigating current distortion are proposed and validated with experiments. The idea of providing reactive power compensation with the rack-level GaN-based front-end rectifiers is proposed for data centers to reduce data center\u27s power loss and system cost. Full-range ZVS modulation is extended into non-unity PF condition and a GaN-based T-type totem-pole rectifier with reactive power control is proposed. A hardware prototype of the proposed rectifier is built and demonstrated experimentally with high power efficiency and flexible reactive power regulation. Experimental emulation of the whole data center system also validates the capability of reactive power compensation by the front-end rectifiers, which can also generate or consume more reactive power to achieve flexible PF regulation and help support the power system

Topology Studies and Control of Microinverters for Photovoltaic Applications

Ph.DDOCTOR OF PHILOSOPH