Electrical performance characteristics of high power converters for space power applications

The first goal of this project was to investigate various converters that would be suitable for processing electric power derived from a nuclear reactor. The implementation is indicated of a 20 kHz system that includes a source converter, a ballast converter, and a fixed frequency converter for generating the 20 kHz output. This system can be converted to dc simply by removing the fixed frequency converter. This present study emphasized the design and testing of the source and ballast converters. A push-pull current-fed (PPCF) design was selected for the source converter, and a 2.7 kW version of this was implemented using three 900 watt modules in parallel. The characteristic equation for two converters in parallel was derived, but this analysis did not yield any experimental methods for measuring relative stability. The three source modules were first tested individually and then in parallel as a 2.7 kW system. All tests proved to be satisfactory; the system was stable; efficiency and regulation were acceptable; and the system was fault tolerant. The design of a ballast-load converter, which was operated as a shunt regulator, was investigated. The proposed power circuit is suitable for use with BJTs because proportional base drive is easily implemented. A control circuit which minimizes switching frequency ripple and automatically bypasses a faulty shunt section was developed. A nonlinear state-space-averaged model of the shunt regulator was developed and shown to produce an accurate incremental (small-signal) dynamic model, even though the usual state-space-averaging assumptions were not met. The nonlinear model was also shown to be useful for large-signal dynamic simulation using PSpice

Analysis of Induction Motor Drive Systems

In industry, the induction machine, particularly the cage rotor type, is most typically employed for variable speed applications. Adjustable speed drives use back-to-back AC to DC and DC to AC conversion to alter the speed. This conversion procedure introduces harmonics and reduces power factor at the supply end. It is now more important than ever to design and build a three-phase induction motor drive with higher power quality. A full report on the converter topologies is used for Power Factor Correction at the input side to eliminate harmonics and enhance power factor at the supply side. So the main aim of this study is to improving power quality by raising power factor at input side of an electric drive, hence lowering losses and boosting efficiency

Roadway-Embedded Transmitters and Multi-Pad Receivers for High Power Dynamic Wireless Power Transfer

Electric vehicles (EVs) offer considerable economic and environmental benefits to society. Despite the decreasing vehicle costs and increasing range of newer EVs, the problem of range anxiety still exists. Range anxiety, at its core, is an issue of charging speeds rather than a concern about the driving range. Dynamic wireless charging of EVs is seen as a potential solution to this issue of range anxiety. Further, wireless charging technology also helps the push towards level 5 autonomy and opens new opportunities for how an EV can be utilized. Dynamic wireless power transfer (DWPT) systems typically require a high initial investment due to the scale of deployment needed and require a certain level of EV adoption before they become economically viable. The challenges facing DWPT technologies are broadly categorized into development, deployment and operation challenges. To address the deployment challenges, this dissertation presents the pavement integration of DWPT systems, and the design and validation of concrete-embedded wireless charging pads. To improve infrastructure utilization and address the operation challenge, different vehicle classes need to recharge from the same charging infrastructure. This is made possible by the use of multi-pad receivers, which allow different vehicle classes to receive different power levels using the same charging infrastructure. This work presents a scaled-down version of a multi-pad receiver system to demonstrate the operation and scalability of these modular receivers. To help further reduce the cost of development and implementation of DWPT systems, finite element method (FEM) and circuit simulation models are presented. The time-domain simulations can be used to develop and validate various control and communication schemes without the need for expensive hardware implementation. Finally, leakage magnetic field reduction to ensure safety and compliance for DWPT systems is discussed, and an example system is analyzed using FEM simulations

Power Converters in Power Electronics

In recent years, power converters have played an important role in power electronics technology for different applications, such as renewable energy systems, electric vehicles, pulsed power generation, and biomedical sciences. Power converters, in the realm of power electronics, are becoming essential for generating electrical power energy in various ways. This Special Issue focuses on the development of novel power converter topologies in power electronics. The topics of interest include, but are not limited to: Z-source converters; multilevel power converter topologies; switched-capacitor-based power converters; power converters for battery management systems; power converters in wireless power transfer techniques; the reliability of power conversion systems; and modulation techniques for advanced power converters

Modeling and analysis of power processing systems: Feasibility investigation and formulation of a methodology

A review is given of future power processing systems planned for the next 20 years, and the state-of-the-art of power processing design modeling and analysis techniques used to optimize power processing systems. A methodology of modeling and analysis of power processing equipment and systems has been formulated to fulfill future tradeoff studies and optimization requirements. Computer techniques were applied to simulate power processor performance and to optimize the design of power processing equipment. A program plan to systematically develop and apply the tools for power processing systems modeling and analysis is presented so that meaningful results can be obtained each year to aid the power processing system engineer and power processing equipment circuit designers in their conceptual and detail design and analysis tasks

Characterization and Modeling of High Power Microwave Effects in CMOS Microelectronics

The intentional use of high power microwave (HPM) signals to disrupt microelectronic systems is a substantial threat to vital infrastructure. Conventional methods to assess HPM threats involve empirical testing of electronic equipment, which provides no insight into fundamental mechanisms of HPM induced upset. The work presented in this dissertation is part of a broad effort to develop more effective means for HPM threat assessment. Comprehensive experimental evaluation of CMOS digital electronics was performed to provide critical information of the elementary mechanisms that govern the dynamics of HPM effects. Results show that electrostatic discharge (ESD) protection devices play a significant role in the behavior of circuits irradiated by HPM pulses. The PN junctions of the ESD protection devices distort HPM waveforms producing DC voltages at the input of the core logic elements, which produces output bit errors and abnormal circuit power dissipation. The dynamic capacitance of these devices combines with linear parasitic elements to create resonant structures that produce nonlinear circuit dynamics such as spurious oscillations. The insight into the fundamental mechanisms this research has revealed will contribute substantially to the broader effort aimed at identifying and mitigating susceptibilities in critical systems. Also presented in this work is a modeling technique based on scalable analytical circuit models that accounts for the non-quasi-static behavior of the ESD protection PN junctions. The results of circuit simulations employing these device models are in excellent agreement with experimental measurements, and are capable of predicting the threshold of effect for HPM driven non-linear circuit dynamics. For the first time, a deterministic method of evaluating HPM effects based on physical, scalable device parameters has been demonstrated. The modeling presented in this dissertation can be easily integrated into design cycles and will greatly aid the development of electronic systems with improved HPM immunity

Study of a Symmetrical LLC Dual-Active Bridge Resonant Converter Topology for Battery Storage Systems

A symmetrical LLC resonant converter topology with a fixed-frequency quasi-triple phase-shift modulation method is proposed for battery-powered electric traction systems with extensions to other battery storage systems. Operation of the converter with these methods yields two unique transfer characteristics and is dependent on the switching frequency. The converter exhibits several desirable features: 1) load-independent buck-boost voltage conversion when operated at the low-impedance resonant frequency, allowing for dc-link voltage regulation, zero-voltage switching across a wide load range, and intrinsic load transient resilience; 2) power flow control when operated outside the low-impedance resonance for integrated battery charging; 3) and simple operational mode selection based on needed functionality with only a single control variable per mode. Derivation of the transfer characteristics for three operation cases using exponential Fourier series coefficients is presented. Pre-design evaluation of the S-LLC converter is presented using these analytical methods and corroborated through simulation. Furthermore, the construction of a rapid-prototyping magnetics design tool developed for high-frequency transformer designs inclusive of leakage inductance, which is leveraged to create the magnetic elements needed for this work. Two 2kW prototypes of the proposed topology are constructed to validate the analysis, with one prototype having a transformer incorporating the series resonant inductance and secondary clamp inductance into the transformer leakage and magnetizing inductance, respectively. A test bench is presented to validate the analysis methods and proposed multi-operational control scheme. Theoretical and experimental results are compared, thus demonstrating the feasibility of the new multi-mode operation scheme of the S-LLC converter topology

Modeling and control of a high power soft-switched bi-directional DC/DC converter for fuel cell applications

This work presents a new high power, bi-directional, isolated dc-dc converter for a fuel cell energy management system that will be fitted into a test vehicle being built by Ford Motor Company. The work includes two parts. The first part is to propose a new topology and analyze the principles of the circuits operation. Design guidelines with detailed circuit simulations are presented to verify the feasibility of the new circuit topology. Based on the conceptual understanding of the converter, the mathematical model is also derived to design a control system that achieves soft start up and meets the performance requirements. The second part is to fabricate a 1.6 kW prototype converter in the laboratory. Using the prototype, the steady state performance of the open loop system was tested to verify the analysis and simulation results. A dual half-bridge topology is presented to implement the required power rating using the minimum number of devices. Unified zero-voltage-switching (ZVS) is achieved in either direction of power flow to eliminate switching losses for all devices, increase the efficiency of the system and reduce the electromagnetic interference (EMI). Compared to the other soft-switched dc-dc converters, neither a voltage-clamping circuit nor extra switching devices and resonant components are required in the proposed circuit for soft-switching implementation. All these new features allow efficient power conversion and compact packaging. Different start-up schemes are proposed to successfully limit the in-rush current when the converter is started in the boost mode of operation. The full control system including the start-up scheme is developed and verified using simulation results based upon the average model. A 1.6 kW prototype of the converter has been built and successfully tested under full power. The experimental results of the converter\u27s steady-state operation confirm the simulation analysis