Tseng King Jet

Review of high speed electrical machines in gas turbine electrical power generation

The concept of a More Electric Aircraft (MEA) demands a highly optimized airframe power system which is achieved by replacing pneumatic and hydraulic systems with energy efficient electrical systems. With increasing power offtake requirements, the More Electric Engine (MEE) could play a key role in future MEA, where more electrical power will be drawn from gas turbine shaft using the conventional gear driven electrical machine, which is known to present inefficiencies and reliability issues. Embedding an electrical machine directly at the engine shaft would help eliminate the need for the accessory gearbox along with potentially improving the reliability and efficiency of the whole system. However embedding the electrical machine presents significant design challenges to meet the key requirements. Some of these include: the necessity of the electrical machine to operate in high temperatures and high vibration environments, the mechanical constraints such as space limitations, and the need to operate at high speeds. Other requirements include the need for high power density, high torque density, high efficiency and maintenance-free operation of the electrical machines. At present, different electrical machine topologies have been developed for a number of challenging industrial and automotive applications where some of the requirements and criteria have been partially met. In this paper the detailed investigation and the trade study carried out of the various electrical machine topologies to understand their advantages, constraints and drawbacks is presented to provide a preliminary evaluation of their suitability for meeting the stringent requirements of embedded machines in aerospace applications.

A synchronous reference frame based control of an unified power flow controller

The unified power flow controller (UPFC) device, which has the capability of controlling real power flow and reactive power flows at sending end and receiving end of a transmission line, was originally proposed by L. Gyugi (see IEE Proceedings, vol.139, no.4, p.323-31, 1992). According to this scheme, an AC voltage vector generated by a GTO-based inverter is injected in series with the phase voltage in the transmission line. In this paper a robust H/sub /spl infin// controller is used to control line currents in both the shunt and series inverters of the UPFC. The line current controller is designed to ensure robust performance and internal stability of the UPFC against disturbances and unstructured parameter variations. Conventional PI control system performance is compared with the H/sub /spl infin// control to highlight their contrasting features.

Online junction temperature estimation of IGBT modules for Space Vector Modulation based inverter system

This paper presents a junction temperature estimation model for space vector modulated IGBT inverter system for a real time implementation. Advances in power electronics, control systems, motor drives, and electrical machines helped in developing new technologies of Variable speed constant frequency (VSCF) system for more aircraft application. It is estimated that about 21% of the faults in the variable speed drive system are due to failure of power devices, Most of the inverters use insulated gate bipolar transistor so these applications require well designed thermal management systems to ensure the protection of IGBTs from thermal runaway. Therefore estimating the junction temperature has become essential to predict the fault and to assist in IGBT heath monitoring system. The proposed junction temperature estimation method is based on the power loss approach. Electro-thermal models for the commonly used Space Vector Modulation (SVM) techniques namely the alternate SVM and the Null V0V7 SVM are developed. The efficacy of the proposed junction temperature estimation model is verified using the measured junction temperature from the experimental setup.

Comparison of power cycling and thermal cycling effects on the thermal impedance degradation in IGBT modules

Insulated gate bipolar transistor (IGBT) devices have gained leading position in traction and aerospace applications. The failure of these switches (IGBT) can reduce the efficiency of the system. Two most dominated failure mechanisms of IGBTs are solder fatigue and bond wire lift off. One of the major effects which influence these failure mechanisms is thermal impedance characteristics, which depends on the heat dissipation in the junction. In traction or aerospace application, the operational loads are not always constant. It results in the temperature cyclic in power converter, meaning that change in the device junction temperature. This change in temperature degrades the transient thermal resistance, and induces a mechanical stress especially at contacting surfaces of materials with different coefficient of thermal expansion. This may lead to degradation or complete failure of these components. The aim of this paper is to identify thermal impedance variation due to power cycling and thermal cycling. More importantly which temperature cyclic nature causes degradation in the thermal impedance, and its relation to semiconductor module failure mechanism.

Review on application of additive manufacturing for electrical power converters

Additive manufacturing(AM) or 3D printing is one of the fastest growing technologies that has been successfully implemented in various fields. The technique of building components by addition of material rather than the conventional subtractive manufacturing has opened up new realm of product design possibilities. From using AM for prototyping purpose it has evolved to make working parts it started replacing the conventional machines from the production lines. All the engineering disciplines, medical applications, fashion and jewelery designs, hobbyist etc. utilizes 3D printing to build efficient prototypes and products. In this paper, potential application of 3D printing for parts of electrical power converters has been identified and discussed. Surge in the dependence of electromechanical machines had urged to improve the performance of electrical power converters and their form factor. High power density requirements, compactness, rugged environments of usage poses challenges for the converters design. The promising AM technology and their material capabilities could improve the converter design features and assist to meet the requirements. This paper highlights the potential of AM which improved the performance of parts used for thermal management, passive electrical components, PCB construction and other constructional features of the power converters.

Comparative Analysis of Flux Switching Machines between Toothed Rotor with Permanent Magnet Excitation and Segmented Rotor with Field Coil Excitation

The Flux Switching Machine is one of the novel topologies within the hybrid machine class. It has many advantages such as flux focusing effect, compatibility with simple power converters, high fault tolerance with independent concentrated armature windings, mechanical robustness due to its simple salient pole rotor and high power density. With such attributes the machine is a promising candidate for high speed, high power density applications. It includes toothed rotor with permanent magnet excitation and segmented rotor with field coil excitation. This article reports on comparative studies into the mechanical stress, magnetic flux, back EMF, D axis, Q axis inductance and saliency ratio, loss distribution, efficiency and power density for these topologies via finite element analysis under open circuit and various load conditions. Quantitative simulation results reveal that the segmented rotor with field coil excitation topologies exhibit better electromagnetic performance, among which the 12/7 combination of stator pole and rotor segments exhibits superior EM performances than those of other combinations. Parametric analysis with respect to the aspect ratio and rotor segment arc angle are also performed on 12/7 topology to investigate their relationship with the torque, efficiency and power density.

Online electro-thermal model for real time junction temperature estimation for insulated gate bipolar transistor (IGBT)

This paper proposes an online dynamic electro-thermal model to compute the junction temperature of an IGBT under real time operating conditions. The proposed computational model is based on transient thermal capacitance and power loss calculations. Insulated Gate Bipolar Junction Transistor is popularly used in mission safety critical applications such as aerospace. Usually mission critical application requires well-designed thermal management to ensure the safety of power devices from thermal runaway. Hence, real time estimation of the junction temperature has become more important to develop health monitoring model as well to predict the lifetime of power converter system. In order to analyze the accuracies of the junction temperature estimation method, the results from the proposed dynamic electro thermal model is compared with the experimental results (measured junction temperature) obtained from the laboratory test rig.

Preliminary investigation of electromagnetic and thermal performance of closed stator switched reluctance machines

This paper presents the preliminary investigation results of a novel closed stator slot structure in Switched Reluctance Machines (SRM) to form direct cooling channels inside the stator slots in electromagnetic and thermal aspects. The investigation starts by identifying the current challenges faced by various cooling arrangements for electric machines. Two sets of baseline SRMs, with and without the closed slot structure, are then obtained via the combined optimization process based on FEA and Genetic Algorithm (GA). Coupled simulation between Matlab/Simulink and FEA is conducted to obtain the transient electromagnetic characteristics of the target SRM under Average Torque Control (ATC) scheme. The incurred iron and copper loss are then fed to Lumped Parameter Circuit (LPC) for thermal investigations. The results show that in spite of the increased leakage flux due to the added flux bridges, the proposed closed stator slot structure can improve the thermal performance of SRM and allow for higher stator current densities without exceeding the winding insulation limits. As a result, the power level and power density of the studied SRM is still increased.

System design for the building-integrated microgrid test-bed — A case study

In this paper, we propose a system design for a laboratory test-bed of building-integrated microgrid (BIMG) to facilitate the research needs in relation to the BIMG cyber-physical control system. The system design consists of hardware part (infrastructure) and software part (control platform). Specifically, for the control platform we develop an architecture capable of easily integrate different system components communicating with heterogeneous languages, and make them work together cooperatively, aiming to emulate various BIMG operation scenarios and to test different control algorithms and strategies adapt to those scenarios.

A novel and efficient free oscillating discrete TV power supply

FROSIN (free oscillation smart and intelligent) is a discrete flyback converter based switch mode power supply. One of the main features of this power supply includes minimum switch on loss controlled by a quasi resonant tank circuit and biasing transistor, and standby low power at low frequency. The novelty of this switch mode power supply is low switching frequency at low load. The minimum switch on circuit from the transformer primary lower auxiliary winding is designed in such a way that it provides a delay of half-resonant cycle before the driver circuit switches on the biasing circuit.