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Thermal cycling is one of the main sources of aging and failures in power electronics. A possibility to reduce the stress to semiconductors is to control the amount of losses that occur in the device during operation. This work presents an active thermal controller that aims at reducing the junction temperature variations in the case of variable power profile. The switching frequency of the converter...
This paper presents a non-contact measurement of irradiance on plane of array (POA) and cell temperature for PV systems. The idea is motivated from the diode model of PV, where POA irradiance and cell temperature are proportional to the photocurrent and modified ideality factor, respectively. Based on the recent progress of diode model identification, the photocurrent and modified ideality factor...
Building energy efficiency has increasing focus worldwide. The heating, ventilation, air-conditioning (HVAC) devices account for highest energy consumption in buildings in Singapore. Multipoint sensing information in the various scenario is critical to optimize the HVAC operation, and increase the energy efficiency of the air-conditioning. A software called FloVENT® is used for simulation of room...
Fuel cells, especially the proton exchange membrane fuel cell, are promising energy converters that can be used for various applications (transportation, mobile and stationary applications). Although, they have a limited lifespan due to degradation mechanisms (chemical and mechanical stresses) that are not completely understood. Consequently, researches have been conducted to estimate the Remaining...
This paper deals with the validation of a simplified first order thermal model in machine operative conditions for the prediction of the winding temperature during overload duty. The machine used for the model validation is a 10 kW automotive starter-generator prototype for mini-hybrid powertrain. The functionalities required to the machine are mainly transitory operative conditions such as engine...
Understanding the operation of a building is key for improving it and reducing energy waste. However, today this is a mostly manual task for which domain experts use visual tools to analyze the large amounts of building data. We show how to automate this task by means of pattern extraction techniques. These allow human operators to simply consider well defined data patterns rather than vast amounts...
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...
An optimized state of charge (SOC) estimation method is critical for energy control strategy in hybrid energy system. For an embedded system, the executed algorithm should be less time consuming and also robust on measurement noise from sensors. Moreover, the estimation method should also be insensitive to initial SOC for the purpose of avoiding battery relaxing time in real application. The proposed...
Solar photovoltaic (PV) energy has grown significantly during the last years. However, despite of the increase in installed capacity penetration, this energy source still arises important concerns due to the variability of power production. The short-term effects such as cloud shadowing and supply interruptions, as well as long-term effects such as dust accumulation, seasonal variation and ageing...
Multi-rotor systems have been developed into better performance for mature applications. Due to lift to weight balance on motor power and battery energy, they are limited in payload and flight endurance. Since gasoline power has 44 times better energy density than battery, integration of gas engine and DC brushless motor into a vertical take-off and landing (VTOL) system will gain much higher lift...
Today, battery electric vehicles as well as stationary battery system demand lithium-ion batteries. Lithium titanate battery cells with their excellent charge and discharge rate capabilities in combination with their long lifetime have become an attractive option for these kinds of applications. However, to ensure safe operation of lithium batteries — especially in high power applications — temperature...
Recently, efficient energy management systems have been in high demand to reduce overall energy consumption. In particular, energy consumption in the civilian sector is increasing considerably. Therefore, the effective use of energy in this sector should be emphasized. To do so, the introduction of a Home Energy Management System (HEMS) is effective because such systems allow households to control...
Mathematical model of laser heating with induction pre- and/or post-heating is presented and solved. The purpose of this combined way of heat treatment is to reduce residual mechanical stresses in the surface layers of the processed material produced by high temperature gradients at the spots heated by the laser beam. The 3D model takes into account all important nonlinearities including the temperature...
A simple adaptive linear current derating strategy for safe operation at low coolant flow rates and optimum operation at temperatures close to the allowed maximum operating junction temperature for electric drivetrain inverters is presented. An inverter junction temperature observer is implemented to calculate the maximum junction temperature which is used as an input to the derating strategy. Results...
This paper presents a method for evaluations and measurements of a high frequency nanocrystalline core transformer for power converters. An experimental platform is set up to measure the B-H characteristics of the core and the performances of the transformer with a frequency range up to 100 kHz. Using the measured B-H characteristics, a 3D FEM model of the transformer is built to simulate the performances...
Dynamic line ratings (DLR) can increase power transmission capacity of power lines. The use of DLR becomes effective, if DLR is possible to be known beforehand, e.g., a day-ahead for the different hours of the following day. Power line ampacity, and thus DLR, is dependent on weather conditions, mainly wind and temperature — in this order of significance. Thus, DLR can be forecasted based on weather...
In this paper, we present a system to estimate the health of a lead-acid car battery and warn the driver of upcoming battery failure in the near future. Most existing lead-acid battery state of health (SOH) estimation systems measure the battery impedance by sensing the voltage and current of a battery. However, current sensing is costly for parts and/or labor. A method to estimate SOH by sensing...
In this paper, we propose a stand-alone, battery powered, wireless temperature sensor that can be used for diagnostic purposes in harsh industrial environments, including magnetic interferences and very low pressure (vacuum). Being easily mountable and removable during machine stoppage, this autonomous temperature sensor can be used at any location in a machine to gather temperature data over a period...
Air conditioning systems need permanent monitoring of the mass and energy flows in the air ducts to assess their proper operation and detect and correct changes that may occur with time. This is a prerequisite for energy efficiency and demanded by recent legislation such as the Energy Performance of Buildings Directive issued by the European Union. Such distributed monitoring systems require low-cost...
This paper investigates the energy efficiency of Li-ion battery used as energy storage devices in a micro-grid. The overall energy efficiency of Li-ion battery depends on the energy efficiency under charging, discharging, and charging-discharging conditions. These three types of energy efficiency of single battery cell have been calculated under different current rates. The relations of the energy...
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