Thermal System Oriented Simulation of Aircraft Electrical Environmental Control Systems Including its Electric Coupling

A flexible numerical platform based on libraries has been developed within the Dymola/Modelica framework to simulate Environmental Control Systems (ECS). The goal was to build up a flexible tool to analyse complex systems including their thermal and electrical perimeters at both steady and transient conditions focusing on three key characteristics: numerical robustness, optimal time consumption, and high accuracy. This document aims to underline both the most relevant features of the numerical tool and the main challenges addressed during its development. Some illustrative simulations are shown in order to highlight the tool capabilities.Peer ReviewedPostprint (published version

Low-cost I-V tracer for photovoltaic modules and strings

This paper presents new developments of a robust and low-cost instrument-less than 600 (sic)-for monitoring and processing I-V and P-V characteristics of photovoltaic (PV) modules and high voltage strings. The characteristics can be traced on an oscilloscope or using a developed a LabVIEW application. It is a simple instrument because only fundamental electronic circuits are used. The equipment consists of a flexible configuration, developed from a previous work, based on a fast varying load based on a power MOSFET. The MOSFET was controlled by means of suitable gate-source voltage control signal in order to improve the tracing of I-V and P-V characteristics on an oscilloscope. The contribution of this work includes new developments of a previous I-V tracer in order to be use with high voltage strings and a low-cost DAQ monitoring system based on two applications developed in LabVIEW-one for PV modules and the other for PV strings. On the other hand, the robustness for high voltage strings was strongly improved in view of field tests for fault diagnosis analysis. Experimental results obtained with the new instrument are presented with modules and different strings available with voltages up to 1000 volt

Modeling and control of cascaded bridgeless multilevel rectifier under unbalanced load conditions

“The goal of this project is to model and control a novel unidirectional cascaded multilevel bridgeless rectifier as an active front end in medium and high voltage applications. This topology has many advantages over a conventional cascaded H-bridge rectifier, such as lower implementation cost, higher reliability, and greater flexibility with similar power quality. The complete design process of the proposed converter is developed step by step in order to meet all the desired objectives. The steady-state mathematical model is used to develop a method for the voltage balancing of dc cells. Power factor analysis is discussed to mathematically derive requirements for the number of partially controlled and fully controlled H-bridges in the proposed H-bridge converter. Power loss, efficiency, and cost comparison studies between the traditional cascaded H-Bridge converter and the proposed bridgeless converter demonstrate the advantages. After exploring various well-established control methods, a novel control strategy is proposed to achieve dc voltage balancing, fast and robust grid synchronization, power factor correction, and elimination of zero crossing current distortion under both balanced and unbalanced load conditions. The converter can also be used for reactive power compensation in a grid tied power system if a sufficient number of fully controlled H-bridge modules are included. Processor-In-the-Loop (PIL) simulation has been the utilized to validate the performance of discrete control structure. Simulation and experimental results validate the models and control method”--Abstract, page iii

Robustness and balancing of parallel connected power devices : SiC vs. CoolMOS

Differences in the thermal and electrical switching time constants between parallel connected devices cause imbalances in the power and temperature distribution thereby reducing module robustness. In this paper, the impact of electro-thermal variations (gate and thermal resistance) between parallel connected devices on module robustness is investigated for 900V-CoolMOS and 1.2kV-SiC MOSFETs under clamped inductive switching (CIS) and unclamped inductive switching (UIS). Under CIS, the difference in the steady-state junction temperature (ΔTJ) and switching energy (ΔESW) between the parallel connected devices for a given difference in the gate and thermal resistance (ΔRG & ΔRTH) is used as the metric for determining robustness to electrothermal variations i.e. how well the devices maintain uniform temperature in-spite of switching with different rates and thermal resistances. Under UIS conditions, the change in the maximum avalanche current/energy prior to device failure as a function of the ΔTJ and ΔRG between the parallel connected devices is used as the metric. Under both CIS and UIS, SiC devices show better performance with minimal negative response to electrothermal variations between the parallel connected devices. Finite element models have also been performed showing the dynamics of BJT latch-up during UIS for the different technologies