Hybrid controller strategy for optimization of cumulated thermal stresses, induced in X-rays tube for medical use

This work presents a new control strategy of the power supply, in favor of equipment intended for the medical use. Several research investigations have been reserved for the service of this supply type, but there are still some disadvantages, which have challenged their high performance in the practical side, in particular the problems which concern the weight, the size and especially, the efficiency of these installations and this, on the cost side, energy balance, and lifetime of this equipment. A control technique is presented to overcome these constraints; its principle is based on the deduction of a hybrid control of which two controllers are simultaneously used for the same radiological dose, known by the fuzzy logic and the PID which have already been tested [1], [3]. This hybrid control has been greatly enhanced and developed, thanks to its robustness against the various intolerable dynamic states applied to the system and also to the unpredictable external disturbances

Medical Grade High Frequncy Power Distribution Units

The focus of this thesis is to design, model, build, and test a series resonance converter that uses a high frequency isolation transformer, offering significant reduction in size and cost, for powering a Computed Tomography (CT) scanner. The design increases the power quality for the load by isolating the grid side disturbances, and providing regulated desired voltage. The proposed architecture also allows for an optimized point of integration with an UPS, a regulated DC bus to improve waveform fidelity of x-ray generator, and active monitoring and control of the power architecture. Conventional CT systems use a 60Hz transformer, which not only occupies large footprints but also uses large amounts of copper and iron with increasing cost trajectory. In comparison to the traditional Power Distribution Units (PDU), the medical grade high frequency PDU presented in this thesis provides higher power quality and performance at a lower cost. The new CT systems possess unprecedented performance capability in terms of rotational speed and x-ray voltage modulation ( Ultra-Fast kV ) fidelity. In order to achieve such capabilities, a tightly regulated high power DC bus (700VDC, 150kW) is required. The system implemented in this thesis satisfies these new requirements. Design requirements, proposed architecture and controls, modeling, implementation and test results of the proposed system, including thermal analysis and electromagnetic compatibility, are presented in details in this thesis

Improvements in Design of Local Fluorescent Electronic Ballasts in Compliance With the Related Local and International Standards

The fluorescent electronic ballast has been in the market for a long time but has not created any great impact in the illumination industry due to its high initial cost of investment compared to the conventional magnetic ballast. With the advancement in power electronics and utilization of power semiconductor which is available commercially today, it is now possible to implement almost every type of desired conversion of current, voltage or frequency and availability of electronic components with higher power ratings. Thus, it is now possible to manufacture an economically priced, light weight, lower watt-loss and high quality with maximum performance electronic ballast which is compatible with all types of fluorescent luminaries. This study is undertaken to improve the design of existing locally manufactured electronic ballasts. The study indicated that many of these commercial electronic ballasts only have partial or minimum compliance requirements or none at all to the related local and international standards, namely MS IEC 928, MS IEC 929 and EMC requirements as stipulated by SIRIM Berhad. From a survey on nine different ballast manufacturers, only seven manufacturers conducted two tests on MS IEC 928 and MS IEC 929 and only two manufacturers conducted a complete list of tests to ascertain whether their product comply with the related local and international standards. Since electronic ballast is listed as one of the electrical controlled items by the Department of Electricity and Gas Supply of Malaysia (DEGSM), it is crucial that the EMC test be imposed prior to ballast approval. A directive was issued by the Malaysian government on the 3rd of July 1998 to implement energy conservation and to promote the use of energy efficient equipment specifically on lighting luminaries and lighting control systems. DEGSM noted the limitations of fluorescent ballast watt-loss hence, this study is undertaken to meet the implementation of energy conservation regulations/act in the near future

A new and improved control of a power electronic converter for stabilizing a variable speed generation system using an embedded microcontroller

A new and improved stabilizer was developed for the variable speed generation (VSG) system. The VSG system exhibits periodic oscillations which sometimes leads to a loss of synchronism. After careful study, a simple but effective strategy to stabilize the system was implemented with real time digital feedback control. The VSG system consists of an engine, which is the prime mover, driving a doubly fed machine (DFM), which is the generator. The stator of the DFM is directly connected to the grid while the rotor is connected to the grid through a power electronic converter. The converter used in this study is a series resonance converter (SRC), but the proposed method may also be applied to other kinds of converters. The stabilizer senses the RPM of the engine, the feedback signal, and controls the rotor current amplitude and frequency of the doubly fed machine. Control was implemented using the 80C196KB microcontroller. The software consists of a mix of "C" and assembly language. Speed being an important factor in the implementation, care was taken to minimize the control loop times. The important features of the hardware and software developed for the stabilizer are: (1) 12 MHz controller board (2) Real time digital band pass filter (3) Instantaneous rotor speed measurement (4) Interrupt driven measurement and control loops (5) User defined setup parameters (6) IBM PC based real time serial communication The performance of the VSG system was studied with and without the stabilizer. A significant improvement in the stability of the system was noticed over the entire region of operation

Implementação de lei de comutação restrita para controle de sistemas lineares comutado

A special class of switched linear systems with switching law constrained to logical state-input can be employed to model a wide range of different systems. The present paper presents a new stability analysis and controller design method for this class of hybrid systems. Proposed methods is based on the quadratic Lyapunov function. Stability analysis and design of these systems have resulted in solving a convex optimization problem of Linear Matrix Inequality type. The results of simulation on dc-dc buck converter confirm the effectiveness of proposed method.Se puede emplear una clase especial de sistemas lineales conmutados con ley de conmutación restringida a entrada de estado lógico para modelar una amplia gama de sistemas diferentes. El presente documento presenta un nuevo método de análisis de estabilidad y diseño de controlador para esta clase de sistemas híbridos. Los métodos propuestos se basan en la función cuadrática de Lyapunov. El análisis de estabilidad y el diseño de estos sistemas han dado como resultado la solución de un problema de optimización convexo de tipo de desigualdad de matriz lineal. Los resultados de la simulación en el convertidor dc-dc buck confirman la efectividad del método propuesto.Uma classe especial de sistemas lineares comutados com lei de comutação restrita a entrada de estado lógico pode ser empregada para modelar uma ampla gama de diferentes sistemas. O presente artigo apresenta um novo método de análise de estabilidade e design de controlador para esta classe de sistemas híbridos. Os métodos propostos são baseados na função quadrática de Lyapunov. A análise de estabilidade e o projeto desses sistemas resultaram na solução de um problema de otimização convexa do tipo Desigualdade de Matriz Linear. Os resultados da simulação no conversor dc-dc buck confirmam a eficácia do método proposto

A Global Study of a Contactless Energy Transfer System: Analytical Design, Virtual Prototyping and Experimental Validation

International audienceThis paper presents a design methodology dedicated to a two-winding transformer with large air gap and magnetic cores. To design this kind of components, it is necessary to consider the influence of inductive parameters on electrical magnitudes and the converter, which supplies this magnetic device. Indeed, this kind of a magnetic device has a large leakage inductance and a small magnetizing inductance. Therefore, to transfer the desired power, the transformer needs important reactive energy to magnetize magnetic core and to provide leakage flux. Like inductive parameters can be determined only when geometry is known, sizing has to be iterative. Moreover, resonant converters can be used to compensate inductive behavior, but modify electrical constraints of the transformer. A robust algorithm of design and all necessary tools are presented in order to make it easier to size such components. After the analytical design, 3-D FEM simulations and experimental measurements have been carried out in order to validate the theoretical study. Moreover, the power electronics converter has been optimized in order to improve the efficiency of power transfer. A prototype of 1.6 kW 100 kHz with an air gap of 6 mm has been realized with its converter. The global efficiency is 93.3%

Vf-constrained ηρ-pareto optimization of medium frequency transformers in ISOP-DAB converters

This study deals with ηρ (efficiency-power density) pareto optimisation of medium frequency transformers (MFTs) with considerations of voltage and frequency ( Vf) constraints of semiconductors for mega-watt range input-series output-parallel (ISOP) connected dual-active bridges (DABs). A simple design methodology to include the Litz wire configuration in the optimisation process is proposed. Based on the presented design methodology, the effects of the semiconductors blocking voltage and switching frequency on the ηρ -pareto optimisation are evaluated. First, an idealised optimisation is carried out to understand the general behaviour of the optimum point. Second, brute-force optimisation is utilised to find the practical optimum solution based on the market availability of MFT components. Designing MFTs for a 1 MW 10 kV/600 V ISOP-DAB converter is the subject of numerical studies. The best trade-off between ηρandVf is selected as the final optimal solution and its design correctness is validated using three-dimensional finite-element analysis. Experimental tests on a 3 kW downscaled MFT prototype show that the proposed method is valid in practice

A novel reduction strategy of standby power loss in the multi-oscillated current resonant DC-DC converter considering acoustic noise compatibility

The current resonant type DC-DC converter employs generally the pulse frequency modulation and its magnetizing inductance is set relatively low. For this reason, the magnetizing current through the converter causes a power loss under the light load condition. To solve this problem, a multi-oscillated current resonant type DC-DC converter has been proposed and then the advantage of its control method has been clarified, which can reduce power loss under light load condition and keep low switching noise. This paper deals with a novel reduction strategy of standby power consumption of the converter. As a result, the standby power consumption under no load condition is achieved below 60mW at 100V AC input and 150mW at 240V AC input, respectively. Furthermore, it is clarified that the slope of the resonant current envelope at soft start and end function in the standby mode influence the acoustic noise from the converter.2011 33rd International Telecommunications Energy Conference, INTELEC 2011; Amsterdam; 9 October 2011 through 13 October 201