4 sonuçlar
Arama Sonuçları
Listeleniyor 1 - 4 / 4
Yayın Improving the calibration time of traffic simulation models using parallel computing technique(Institute of Electrical and Electronics Engineers Inc., 2019-06) Dadashzadeh, Nima; Ergün, Murat; Kesten, Ali Sercan; Zura, MarijanThe calibration procedure for traffic simulation models can be a very time-consuming process in the case of a large-scale and complex network. In the application of Evolutionary Algorithms (EA) such as Genetic Algorithms (GA) and Particle Swarm Optimization (PSO) for calibration of traffic simulation models, objective function evaluation is the most time-consuming step in such calibration problems, because EA has to run a traffic simulation and calculate its corresponding objective function value once for each set of parameters. The main contribution of this study has been to develop a quick calibration procedure for the parameters of driving behavior models using EA and parallel computing techniques (PCTs). The proposed method was coded and implemented in a microscopic traffic simulation software. Two scenarios with/without PCT were analyzed using the developed methodology. The results of scenario analysis show that using an integrated calibration and PCT can reduce the total computational time of the optimization process significantly-in our experiments by 50%-and improve the optimization algorithm's performance in a complex optimization problem. The proposed method is useful for overcoming the limitation of computational time of the existing calibration methods and can be applied to various EAs and traffic simulation software.Yayın Statistical analysis of bus transportation networks of Istanbul(World Scientific Publishing Co Pte Ltd, 2016) Çoban, Veysel; Atan, Sabri TankutTransportation networks such as railway, airport and bus networks are the real-world networks whose inherent statistical properties characterize and differentiate the networks. In order to understand the network characteristics of bus transportation networks (BTNs) of Istanbul, we analyzed its network properties such as degree distributions, clustering coefficients and assortativity. BTNs of Istanbul is defined into three networks as the existence and nonexistence of the metrobus and existence of third- bridge. They are also graphically represented within C-, L- and P-Space topologies that are defined with the connection of the bus stops or routes. Statistical results obtained from network properties reflected the characteristics of the BTNs of Istanbul and give an information about the effects of the metrobus lines and third bridge on the BTNs in Istanbul.Yayın An active discharge scheme for DC-bus capacitors in EV powertrain(Institute of Electrical and Electronics Engineers Inc., 2025-07-18) Sezer, Mustafa Murat; Norwood, Daniel; Geiger, John; Hava, Ahmet Masum; Akın, BilalDuring the emergency situations, key-OFFs, or maintenance, discharging the inverter dc-bus capacitor voltage within seconds is imperative due to safety concerns (inverter not used to control motor). Conventional discharge methods rely on external resistors, additional switches, or motor windings, increasing cost, space requirements, and control complexity. This article presents a cost-effective and space-efficient solution that enables fast capacitor discharge by operating the inverter's SiC mosfets-either discrete devices or power modules-in linear mode. The proposed method utilizes a constant power tracking approach with pulse frequency modulation to safely discharge the high-voltage bus capacitor without external components. When the car is off, the proposed scheme discharges a 1000-V dc bus within 1 s using a single low-side SiC switch to test a worst-case scenario. In practice, all six devices can be used to share thermal stress, and the discharge time can be extended to 5 s as suggested by safety standards. Optimal operating conditions, including gate-source voltage (V{GS}) and pulse width (t{ON}}), are identified for different mosfets from various vendors. To assess long-term reliability, devices undergo more than 200 000 discharge cycles, with intrinsic parameter monitoring and failure analysis conducted to determine degradation mechanisms. The findings help establish safe operating conditions, ensuring robust and reliable integration of the proposed discharge method within the main powertrain inverter.Yayın Analysis and design of a resistor-less DC-bus active discharge and dynamic braking scheme using IGBTs in the active region(Institute of Electrical and Electronics Engineers Inc., 2026-04) Sezer, Mustafa Murat; Deshmukh, Akshay Vijayrao; Hava, Ahmet Masum; Akın, BilalDuring shutdowns, emergency conditions, and dynamic braking, fully discharging the dc-bus capacitor or clamping the dc-bus voltage in industrial systems is typically managed using power resistors and additional switches. This conventional approach increases system cost, size, and complexity. This article introduces a compact, cost-effective, resistor-less method for two functions: 1) active discharge and 2) dynamic braking in low-power industrial systems. The proposed technique operates IGBTs in their active region with low gate-emitter voltages ($V_{\text {GE}}$ ), creating high impedance in the discharge path to limit current. For active discharge, a constant-power strategy is implemented using pulse frequency modulation (PFM), where the on-time (t_{\text {on}}$ ) of each pulse is fixed and the pulse frequency is ramped up to accelerate energy dissipation. This approach enables complete discharge of a 600-V dc-bus within 1 s, handled entirely by a single IGBT. The method is validated across three different IGBT vendors, showing consistent results and long-term reliability with no parameter degradation after over 200000 completed discharge cycles. For dynamic braking, the PFM method with fixed pulse frequency enables continuous power dissipation between 50 and 150 W for over 30 min. It effectively replaces conventional internal braking resistors typically rated from 20 to 200 W with resistance values of 5-$120~\Omega $. The system can also tolerate brief overloads up to 50% beyond IGBT current ratings for 10-20 s, providing sufficient time to complete braking without failure, as confirmed by test results. All these benefits are achieved through a simple gate driver modification that supplies partial $V_{\text {GE}}$ levels (3-10 V), eliminating bulky resistors, reducing cost by at least 50%, and saving space-making the solution ideal for high-volume industrial applications.
