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

Design of Power Supply for Aircraft Model

Diplomová práca, ktorú držíte v rukách, sa zaoberá návrhom elektrického generátoru pre modely lietadiel na diaľkové ovládanie poháňané spaľovacím motorom. Takýmto modelom je dodávaná energia pomocou batérií, ktoré sa musia po vybití vymieňať. Motiváciou tejto práce bolo potlačiť potrebu pristávania za účelom dobíjania batériových paketov. Práca vyvíja niekoľko analýz a simulačných modelov pre riešenie tohto problému.The Master’s thesis you are holding in your hands deals with design of electrical generator for remote control aircraft models powered by combustion engine. Such models are energized by batteries that have to be exchanged after discharge. The motivation of this thesis was to suppress the need for landing in order to recharge the battery packs. The thesis develops several analysis and simulation models for solution of this problem.

Development of a Supercapacitor based Surge Resistant Uninterruptible Power Supply

Uninterruptible Power Supplies (UPSs) provide short-term power back-up to sensitive electronic and electrical equipments, where an unexpected power loss could lead to undesirable outcomes. They usually bridge the connected equipment between the utility mains power and other long term back-up power systems like generators. A UPS also provides a “clean” source of power, meaning they filter the connected equipment from distortions in electrical parameters of the mains power like noise, harmonics, surges, sags and spikes. A surge resistant UPS or SRUPS is one that has the capability to withstand surges, which are momentary or sustained increases in the mains voltage, and react quickly enough to offer protection to the connected equipment from the same. Usually UPSs run off battery power when the utility mains power is absent. But the SRUPS developed in this design project uses super capacitors instead of battery packs. The reason for this is that the high energy-densities and medium power-densities offered by super capacitors allow for it to serve two purposes. One is to provide the DC power to operate the UPS in the absence of mains power, as an alternative to batteries. Secondly, super capacitors can withstand heavy momentary high current/voltage surges due to its high energy-density characteristics. Also as the life-time of super capacitors is much higher than that of conventional batteries and as they do not need regular topping-up or inspection, the end result is a truly maintenance-free UPS. Most commercial UPSs do not have inherent surge protection capabilities. The UPS is one entity while a discrete surge protection module is inserted between the utility mains and the UPS to provide for transient surge suppression. In the proposed SRUPS, the super capacitor, because of their inherent capability to absorb transient surges, forms a protective front end to the actual UPS rather than needing to have the involvement of discrete protection devices

CMOS indoor light energy harvesting system for wireless sensing applications

Dissertação para obtenção do Grau de Doutor em Engenharia Electrotécnica e de ComputadoresThis research thesis presents a micro-power light energy harvesting system for indoor environments. Light energy is collected by amorphous silicon photovoltaic (a-Si:H PV) cells, processed by a switched-capacitor (SC) voltage doubler circuit with maximum power point tracking (MPPT), and finally stored in a large capacitor. The MPPT Fractional Open Circuit Voltage (VOC) technique is implemented by an asynchronous state machine (ASM) that creates and, dynamically, adjusts the clock frequency of the step-up SC circuit, matching the input impedance of the SC circuit to the maximum power point (MPP) condition of the PV cells. The ASM has a separate local power supply to make it robust against load variations. In order to reduce the area occupied by the SC circuit, while maintaining an acceptable efficiency value, the SC circuit uses MOSFET capacitors with a charge reusing scheme for the bottom plate parasitic capacitors. The circuit occupies an area of 0.31 mm2 in a 130 nm CMOS technology. The system was designed in order to work under realistic indoor light intensities. Experimental results show that the proposed system, using PV cells with an area of 14 cm2, is capable of starting-up from a 0 V condition, with an irradiance of only 0.32 W/m2. After starting-up, the system requires an irradiance of only 0.18 W/m2 (18 mW/cm2) to remain in operation. The ASM circuit can operate correctly using a local power supply voltage of 453 mV, dissipating only 0.085 mW. These values are, to the best of the authors’ knowledge, the lowest reported in the literature. The maximum efficiency of the SC converter is 70.3% for an input power of 48 mW, which is comparable with reported values from circuits operating at similar power levels.Portuguese Foundation for Science and Technology (FCT/MCTES), under project PEst-OE/EEI/UI0066/2011, and to the CTS multiannual funding, through the PIDDAC Program funds. I am also very grateful for the grant SFRH/PROTEC/67683/2010, financially supported by the IPL – Instituto Politécnico de Lisboa

Conversión de Potencia para un Sistema de Almacenamiento Híbrido Batería-Capacitor

Context: Thanks to the low emissions of CO2 generated by electric systems, those solutions have anincreased attention from industry and academia. However, the electrical storage systems required in alarge amount of applications must to have both high energy and power densities. Method: To meet those requirements, this paper proposes an active hybrid energy storage system(HESS), which is formed by a battery, i.e. the device with high energy density, and a capacitor, i.e. the device with high power capability. The proposed power system also protects the battery by limiting the current derivative. Results: Two sliding-mode controllers (SMC) are designed to regulate both the battery current and the load voltage. The design process guarantees the global stability and safe battery operation. Conclusions: The controller avoids the battery degradation caused by the high-frequency current components since the capacitor assumes those components demanded by the load profile.Contexto: Gracias a las bajas emisiones de CO2 de los sistemas el´ectricos, estos han ganado mucha atenci´on por parte de la industria y la academia. Sin embargo, los sistemas de almacenamiento de energ´ıa requeridos en un sin numero de aplicaciones deben garantizar ser de alta densidad de energ´ıa y potencia. M´etodo: Para satisfacer estos requerimientos, este trabajo propone un sistema de almacenamiento de energ´ıa h´ıbrido (HESS) activo, el cual es formado por una bater´ıa como dispositivo de alta densidad de energ´ıa, y un capacitor como el dispositivo de alta densidad de potencia. Asimismo, la soluci´on propuesta protege la bater´ı a trav´es de la limitaci´on de la derivada de la corriente. Resultados: Se dise˜nan dos controladores por modos deslizantes, uno para la corriente de la bater´ıa y otro para regular el voltaje en la carga. El proceso de dise˜no garantiza la estabilidad global del sistema y una operaci´on segura de la bater´ıa

STUDY OF HIGH LOAD CURRENT POWER SUPPLY DESIGN FOR LOW FREQUENCY SEABED LOGGING APPLICATION

Low frequency, high load current study is very important for Seabed Logging (SBL) application. SBL is currently an emerging method to find hydrocarbon layer beneath the ocean floor. In SBL, a high current low frequency power supply is needed to assist the transmission process that uses Horizontal Electric Dipole (HED). HED emits electromagnetic signal throughout the sea in the expected area containing hydrocarbon layer. This power supply with the ability to produce high current low frequency output is essential for the transmitter to transmit the signal required to the targeted area and its surrounding, and for the receivers to receive back the signal containing accurate data required. In this project, the processes to design and simulate a power supply with the required output for SBL application is explained in details. At the end of this project, a power supply which has high current and low frequency output is completely designed

Performance comparison of different control strategies for the regulation of DC-DC negative output super-lift luo-converter

In last years, dc-dc converters solve the most issues in the industrial application in the area of power electronics, especially renewable energy, military applications and affiliated engineering developments. They are used to convert the DC input that unregulated to regulated output perhaps larger or smaller than input according to the type of converters. This paper presents three primary control method used for negative output Super lift Luo DC-DC converter. These methods include a Voltage mode control (VMC), Current mode control (CMC), and Sliding mode control (SMC). The goal of this article is to study and selected an appropriate and superior control scheme for negative DC-DC converters. The simulation results show the effectiveness of Sliding mode control for enhancing the performance of the negative dc-dc converter. Also, this method can keep the output voltage constant under load conditions. simulation results obtained by the MATLAB/Simulink environment

A new converter topology for high-speed high-starting-torque three-phase switched reluctance motor drive system

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.Switched reluctance motor (SRM) has become a competitive selection for many applications of electric machine drive systems recently due to its relative simple construction and its robustness. The advantages of those motors are high reliability, easy maintenance and good performance. The absence of permanent magnets and windings in rotor gives possibility to achieve very high speeds (over 10000 rpm) and turned SRM into perfect solution for operation in hard conditions like presence of vibrations or impacts. Such simple mechanical structure greatly reduces its price. Due to these features, SRM drives are used more and more into aerospace, automotive and home applications. The major drawbacks of the SRM are the complicated algorithm to control it due to the high degree of nonlinearity, also the SRM has always to be electronically commutated and the need of a shaft position sensor to detect the shaft position, the other limitations are strong torque ripple and acoustic noise effects

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