Multi-population-based differential evolution algorithm for optimization problems

A differential evolution (DE) algorithm is an evolutionary algorithm for optimization problems over a continuous domain. To solve high dimensional global optimization problems, this work investigates the performance of differential evolution algorithms under a multi-population strategy. The original DE algorithm generates an initial set of suitable solutions. The multi-population strategy divides the set into several subsets. These subsets evolve independently and connect with each other according to the DE algorithm. This helps in preserving the diversity of the initial set. Furthermore, a comparison of combination of different mutation techniques on several optimization algorithms is studied to verify their performance. Finally, the computational results on the arbitrarily generated experiments, reveal some interesting relationship between the number of subpopulations and performance of the DE. Centralized charging of electric vehicles (EVs) based on battery swapping is a promising strategy for their large-scale utilization in power systems. In this problem, the above algorithm is designed to minimize total charging cost, as well as to reduce power loss and voltage deviation of power networks. The resulting algorithm and several others are executed on an IEEE 30-bus test system, and the results suggest that the proposed algorithm is one of effective and promising methods for optimal EV centralized charging

Introduction of electric vehicle charging stations to university campuses : A case study for the university of Georgia from 2014 to 2017

Electric vehicles (EVs) are becoming increasingly popular in the United States of America (USA). EVs attract buyers with benefits including energy efficiency and environmental friendliness. As EV usage grows, more public spaces are installing EV charging stations. This paper presents a comprehensive analysis of EV charging station usage at the University of Georgia (UGA) in Athens, Georgia. Three ChargePoint EV charging stations at UGA were used to collect data about each of 3204 charging events that occurred from 10 April 2014 to 20 June 2017. The charging event data included start date, start time, length of parking time, length of charging time, amount of energy delivered, and the postal code entered by the user during ChargePoint account registration. Analytical methods were proposed to obtain information about EV charging behavior, charging station occupancy, and geolocation of charging station users. The methodology presented here was time- and cost-effective, as well as scalable to other organizations that own charging stations. Because this study took place at a university, the results presented here can be used as a reference for EV charging station usage in other college towns in the USA that do not have EV charging stations but are planning to develop EV infrastructure

Which service is better on a linear travel corridor: Park & ride or on-demand public bus?

This paper develops an analytical model to support the decision-making for selection of a public transport service (PTS) provision between park & ride and on-demand public bus (ODPB). The objective of the model is to maximise the total social welfare, which includes consumer surplus and operator’s net profit. The model is solved by a heuristic solution procedure and tested on an idealized linear travel corridor. The case study considers the effects from population density, density distribution, size of residential area, P&R station location, distance from the residential area to centre business area (CBD), as well as the changes of residential area layout and population growth. Results show that P&R fits for low population density area while ODPB is more suitable for high population density area. Population distribution type has little influence on the services’ social welfare. ODPB is a preferable service for the city which does not have advanced metro network. Besides, the investment time for building ODPB service in the planning horizon is discussed with consideration of the development of residential area

Design and Advanced Model Predictive Control of Wide Bandgap Based Power Converters

The field of power electronics (PE) is experiencing a revolution by harnessing the superior technical characteristics of wide-band gap (WBG) materials, namely Silicone Carbide (SiC) and Gallium Nitride (GaN). Semiconductor devices devised using WBG materials enable high temperature operation at reduced footprint, offer higher blocking voltages, and operate at much higher switching frequencies compared to conventional Silicon (Si) based counterpart. These characteristics are highly desirable as they allow converter designs for challenging applications such as more-electric-aircraft (MEA), electric vehicle (EV) power train, and the like. This dissertation presents designs of a WBG based power converters for a 1 MW, 1 MHz ultra-fast offboard EV charger, and 250 kW integrated modular motor drive (IMMD) for a MEA application. The goal of these designs is to demonstrate the superior power density and efficiency that are achievable by leveraging the power of SiC and GaN semiconductors. Ultra-fast EV charging is expected to alleviate the challenge of range anxiety , which is currently hindering the mass adoption of EVs in automotive market. The power converter design presented in the dissertation utilizes SiC MOSFETs embedded in a topology that is a modification of the conventional three-level (3L) active neutral-point clamped (ANPC) converter. A novel phase-shifted modulation scheme presented alongside the design allows converter operation at switching frequency of 1 MHz, thereby miniaturizing the grid-side filter to enhance the power density. IMMDs combine the power electronic drive and the electric machine into a single unit, and thus is an efficient solution to realize the electrification of aircraft. The IMMD design presented in the dissertation uses GaN devices embedded in a stacked modular full-bridge converter topology to individually drive each of the motor coils. Various issues and solutions, pertaining to paralleling of GaN devices to meet the high current requirements are also addressed in the thesis. Experimental prototypes of the SiC ultra-fast EV charger and GaN IMMD were built, and the results confirm the efficacy of the proposed designs. Model predictive control (MPC) is a nonlinear control technique that has been widely investigated for various power electronic applications in the past decade. MPC exploits the discrete nature of power converters to make control decisions using a cost function. The controller offers various advantages over, e.g., linear PI controllers in terms of fast dynamic response, identical performance at a reduced switching frequency, and ease of applicability to MIMO applications. This dissertation also investigates MPC for key power electronic applications, such as, grid-tied VSC with an LCL filter and multilevel VSI with an LC filter. By implementing high performance MPC controllers on WBG based power converters, it is possible to formulate designs capable of fast dynamic tracking, high power operation at reduced THD, and increased power density

Measuring the effect of park-and-ride facilities and interchange station on passenger ridership at the urban rail station in Kuala Lumpur

This paper is to measure the contribution of the park-and-ride facility and interchange station on passenger ridership in Kuala Lumpur using March 2018 passenger ridership, park-and-ride, and interchange station data for each station along Sri Petaling – Ampang lines. The data were gathered and analyzed using correlations and multiple regression. The result found that the interchange station has contributed 38.5% in determining passenger ridership for the Sri Petaling – Ampang lines. Park-and-ride facilities, however, were found to be statistically insignificant in determining passenger ridership. Therefore, the interchange station is crucial for future urban rail development, to increase ridership, improve mobility and uplift public transport modal split. Further studies should identify the irrelevancy of park-and-ride facilities in contributing to passenger ridership for rail lines. A better characteristic of park-and-ride facilities must be formulated to tackle their weaknesses and to improve existing park-and-ride and their future development

Integrated Power/Attitude Control System (IPACS) study. Volume 2: Conceptual designs

For abstract, see N74-22706