Distributed generation: definition, benefits and issues

This paper starts from the observation that there is a renewed interest in small-scale electricity generation. The authors start with a survey of existing small-scale generation technologies and then move on with a discussion of the major benefits and issues of small-scale electricity generation. Different technologies are evaluated in terms of their possible contribution to the listed benefits and issues. Small-scale generation is also commonly called distributed generation, embedded generation or decentralised generation. In a final section, an attempt is made to define the latter concepts more precisely. It appears that there is no consensus on a precise definition as the concept encompasses many technologies and applications.Distributed generation, embedded generation, electricity

Maine Campus September 26 1957

In traction applications, electrical drivetrain components are subjected to unpredictable load and temperature variations depending on the driving cycle and ambient conditions. As performance and power density requirements are getting increasingly stringent, the power electronic devices and electromagnetic actuators are stressed heavily due to temperature cycling effects and face the risk of overheating, compromising lifetime and reliability. To protect the drivetrain from thermally induced failure, a model-based thermal management strategy is proposed in this paper. Critical component temperatures are calculated online with a combined loss and thermal model and are limited progressively by applying constraints to loss-influencing operating variables. Starting from the requested torque, the dq-current setpoint calculation is formulated as a constraint optimization problem in order to protect all drivetrain components while maximizing overall efficiency over the entire torque speed operating range, including field weakening at elevated speed. Unlike conventional approaches, which are often adhoc or based on de-rating, the proposed strategy allows the drivetrain to operate safely at maximum performance limits, without unnecessarily degrading performance.status: publishe

Convex Optimization of PV-Battery System Sizing and Operation with Non-Linear Loss Models

In the literature, when optimizing the sizing and operation of a residential PV system in combination with a battery energy storage system, the efficiency of the battery and the converter is generally assumed constant, which corresponds to a linear loss model that can be readily integrated in an optimization model. However, this assumption does not always represent the impact of the losses accurately. For this reason, an approach is presented that includes non-linear converter and battery loss models by applying convex relaxations to the non-linear constraints. The relaxed convex formulation is equivalent to the original non-linear formulation and can be solved more efficiently. The difference between the optimization model with non-linear loss models and linear loss models is illustrated for a residential DC-coupled PV-battery system. The linear loss model is shown to result in an underestimation of the battery size and cost as well as a lower utilization of the battery. The proposed method is useful to accurately model the impact of losses on the optimal sizing and operation in exchange for a slightly higher computational time compared to linear loss models, though far below that of solving the non-relaxed non-linear problem.Comment: submitted to Applied Energ

Dynamics of Nonlinear Diffusion Processes

The purpose of this thesis is to analyze nonlinear diffusion processes. In particular, some of the results arrived at by Newman and Sagan in their 1981 paper Galactic Civilizations: Population Dynamics and Interstellar Diffusion, will be reproduced by different means. First, a thorough analysis of the linear diffusion equation will be performed in order to test a numerical algorithm that can solve the nonlinear diffusion equation and look at the processes of interest with sufficient accuracy. Once the algorithm is tested and shows good resolution it is used to solve the nonlinear equation. The post processing is then done to compare the numerical results with the analytical solution and then they are related to the results arrived at by Newman and Sagan. More precisely, the timescales over which these processes take place are of great interest. A study of the dynamics of these diffusion processes that take place will bring about a better understanding of the nature of nonlinear diffusion and some of its applications

Performance comparison between SiC and Si inverter modules in an electrical variable transmission application

This paper evaluates the performance of Silicon Carbide MOSFET and Silicon IGBT modules in a threephase inverter for Electrical Variable Transmission systems. For this purpose, two practical inverter setups were developed and compared. An increase of several percentage points is visible over the entire operating range for the Silicon Carbide prototype. The total energy efficiency increased by 3.7% for the rotor and by 11.2% for the stator, for the same test conditions

Analytical switching loss model for superjunction MOSFET with capacitive nonlinearities and displacement currents for DC-DC power converters

A new analytical model is presented in this study to predict power losses and waveforms of high-voltage silicon superjunction MOSFET during hard-switching operation. This model depends on datasheet parameters of the semiconductors, as well as the parasitics obtained from the printed circuit board characterization. It is important to note that it also includes original features accounting for strong capacitive nonlinearities and displacement currents. Moreover, these features demand unusual extraction of electrical characteristics from regular datasheets. A detailed analysis on how to obtain this electrical characteristic is included in this study. Finally, the high accuracy of the model is validated with experimental measurements in a double-pulse buck converter setup by using commercial SJ MOSFET, as well as advanced device prototypes under development.This work was supported by the Asturian Gobernment through the grant Beca Predoctoral “Severo Ochoa” BP14–140. This work was also supported by the project E2 SG, cofunded by grants from Belgium, Italy, Austria, Germany, Spain, The Netherlands, Portugal, Slovakia, The U.K., and the ECSEL