153 research outputs found
Dependent Failures And Failure Propagation In Electric Power Systems
Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2013Thesis (M.Sc.) -- İstanbul Technical University, Institute of Science and Technology, 2013Biz toplam kesinti sayısı dağılımını, cascading sürecinden sonra dallanma yöntemi ve yayılma ortalamasına göre tahmin ettikAn initial number of lines outaged can lead to a cascading propagation of further outages. We estimate the amount by which line outages propagate from standard utility data that is reported to TEİAŞ. We estimate the distribution of the total number of outages after cascading from the amount of propagation and a probabilistic branching process model of the cascading.Yüksek LisansM.Sc
Multi-physics design optimisation of a GaN-based integrated modular motor drive system
Here, a multi-physics approach is presented for the design optimisation of an integrated modular motor drive (IMMD). The system is composed of a modular permanent magnet synchronous motor (PMSM) and a GaN-based modular motor drive power stage. The multi-physics model includes motor drive inverters and DC-link capacitor bank (electrical model), stator windings and rotor magnets (electromagnetic model), heat sink (thermal model), and a geometrical model. The main purpose of the design optimisation is to obtain the highest power density possible, which is quite critical in integrated drives. Due to the integrated structure, the system has several interdependencies and parameters are selected based on those relationships. An 8kW IMMD system design is proposed from the developed optimisation tool and evaluated. The resultant system has a power density of 0.71kW/lt, drive efficiency of 98.3%, and motor efficiency of 96.6%
Superconducting generators for large off shore wind turbines
This thesis describes four novel superconducting machine concepts, in the pursuit
of finding a suitable design for large offshore wind turbines. The designs should be
reliable, modular and light-weight. The main novelty of the topologies reside in using
a single loop shaped stationary superconducting field winding, which eliminates the
rotating transfer couplers and electric brushes or brushless exciters. Furthermore, the
electromagnetic forces in the superconducting wire are also eliminated, which simplifies
the design and manufacturing of the cryostat and the support structure.
Among the four topologies presented, the claw pole type machine is the most promising
one. The rotor of the machine composes of claw-poles made from laminated electrical
sheets, the superconducting field winding and the armature winding are stationary. The
machine is analysed using 3D FEA simulations and a small linear machine prototype
is manufactured to verify the simulations.
For large scale applications, a double-sided claw pole machine is proposed, which has
balanced magnetic attraction forces in the rotor. The machine has a modular cryostat
structure, which increases the availability of the machine. Thus, even if a fault occurs
in the cryocoolers or in the armature coils, the rest of the machine can operate at
partial load until the maintenance is performed. Moreover, it is much easier to replace
the faulty parts, as full disassemble of the machine is not required, and a small on-site
crane can be used. As a result, it offers operational advantages over the existing
superconducting topologies.
A 10 MW, 10 rpm generator design is presented, which has a diameter of 6.6 m and
an axial length of 1.4 m. The total active mass of the generator is 58 tonnes, and
the structural mass is 126 tonnes, which gives a total mass of 184 tonnes. There are
four independent cryostats and two independent armature windings in the machine
to improve modularity. The biggest advantage of the design is the significantly less
superconducting wire usage compared to any other designs; 10 MW machine just needs
15 km of MgB2 wire at 30 K. Thus, it is believed that the proposed topology is a very
cost effective and suitable candidate for a successful entry to the wind turbine market
Feasibility of quasi-square-wave zero-voltage-switching bi-directional dc/dc converters with gan hemts
There are trade-offs for each power converter design which are mainly dictated by the switching component and passive component ratings. Recent power electronic devices such as Gallium Nitride (GaN) transistors can improve the application range of power converter topologies with lower conduction and switching losses. These new capabilities brought by the GaN High Electron Mobility Transistors (HEMTs) inevitably changes the feasible operation ranges of power converters. This paper investigates the feasibility of Buck and Boost based bi-directional DC/DC converter which utilizes Quasi-Square-Wave (QSW) Zero Voltage Switching (ZVS) on GaN HEMTs. The proposed converter applies a high-switching frequency at high output power to maximize the power density at the cost of high current ripple with high frequency of operation which requires a design strategy for the passive components. An inductor design methodology is performed to operate at 28 APP with a switching frequency of 450 kHz. In order to minimize the high ripple current stress on the output capacitors an interleaving is performed. Finally, the proposed bi-directional converter is operated at 5.4 kW with 5.24 kW/L or 85.9 W/in3 volumetric power density with air-forced cooling. The converter performance is verified for buck and boost modes and full load efficiencies are recorded as 97.7% and 98.7%, respectively
Non-Invasive Real-Time Diagnosis of PMSM Faults Implemented in Motor Control Software for Mission Critical Applications
This paper presents a non-intrusive, real-time, online Condition Monitoring and FaultDiagnosis system for Permanent Magnet Synchronous Machines. The system utilizesonly the motor drive's built-in sensors, such as current and voltage sensors, to detectthree types of faults: inter-turn short circuit, partial demagnetization, and staticeccentricity. The proposed solution adopts a hardware-free approach, utilizingcurrent/voltage signature analysis to optimize cost-effectiveness. It requires a smallmemory and short execution time, allowing it to be implemented on a simple motorcontroller with limited memory and calculation power. The system is designed forcritical mission applications, and therefore, computation load, code size, memoryallocation, and run-time optimization are key focuses for real-time operation. Theproposed method has a high detection accuracy of 98%, is computationally efficient,and can accurately detect and classify the fault. The system provides immediateinsights into motor health without interrupting the drive operation
Can you text what is happening? Integrating pre-trained language encoders into trajectory prediction models for autonomous driving
In autonomous driving tasks, scene understanding is the first step towards
predicting the future behavior of the surrounding traffic participants. Yet,
how to represent a given scene and extract its features are still open research
questions. In this study, we propose a novel text-based representation of
traffic scenes and process it with a pre-trained language encoder.
First, we show that text-based representations, combined with classical
rasterized image representations, lead to descriptive scene embeddings. Second,
we benchmark our predictions on the nuScenes dataset and show significant
improvements compared to baselines. Third, we show in an ablation study that a
joint encoder of text and rasterized images outperforms the individual encoders
confirming that both representations have their complementary strengths
Autonomous fault detection and diagnosis for permanent magnet synchronous motors using combined variational mode decomposition, the Hilbert-Huang transform, and a convolutional neural network
Centralized Microgrid Control System in Compliance with IEEE 2030.7 Standard Based on an Advanced Field Unit
The necessity for the utilization of microgrids emerges from the integration of distributed energy resources, electric vehicles, and battery storage systems into the conventional grid structure. In order to achieve a proper operation of the microgrid, the presence of a microgrid control system is crucial. The IEEE 2030.7 standard defines the microgrid control system as a key element of the microgrid that regulates every aspect of it at the point-of-interconnection with the distribution system, and autonomously manages operations such as the transitions of operating modes. In this paper, a microgrid control system is developed to achieve real-time monitoring and control through a centralized approach. The controller consists of a centralized server and advanced field units that are also developed during this work. The control functions of the centralized server ensure the proper operation during grid-connected and island modes, using the real-time data received via the advanced field unit. The developed server and the field unit constitute a complete system solution. The server is composed of control function and communication, database, and user interface modules. The microgrid control functions comprise dispatch and transition core-level functions. A rule-based core-level dispatch function guarantees the security of supply to critical loads during the islanded mode. The core-level transition function accomplishes a successful transition between the operation modes. Moreover, a communication framework and a graphical user interface are implemented. The presented system is tested through thecases based on the IEEE 2030.8 standard
Analysis of clinical and demographic characteristics of patients presenting with renal colic in the emergency department
<p>Abstract</p> <p>Background</p> <p>Renal colic (RC), is one of the most severe pain patterns which is most commonly diagnosed and managed in the emergency department (ED). This study is designed to evaluate the characteristics of adult patients presenting with pain and diagnosed with RC in the ED, length of stay in the ED and hospital and factors affecting these variables.</p> <p>Methods</p> <p>All consecutive adult patients who presented with side pain, flank pain, abdominal or groin pain and consequently diagnosed with urolithiasis or RC were analyzed retrospectively. Sociodemographic data, times of admission into and discharge from the ED, adjunctive complaints, results of laboratory investigations, findings on examination, treatment and drugs administered were noted.</p> <p>Results</p> <p>A total of 235 patients with a diagnostic code of urolithiasis were enrolled. Physicians were more likely to order radiological and laboratory investigations for female patients and those without hematuria in urinalysis. The peak incidence of patients diagnosed with RC (p = 0.001) was noted in August, while the winter had the lowest frequency of relevant admissions. The peak frequency was between 06:00 and 08:00. Women stayed longer in the ED (p = 0.001). Absence of hematuria in urinalysis was associated with increased length of stay (p = 0.007).</p> <p>Conclusion</p> <p>Although RC is a common ED presentation for which the emergency physician has no guidelines in terms of diagnosis and management, there is no exact pattern to guide ordering investigations. Patients with atypical presentations stay longer in the ED and are likely to undergo additional tests in management.</p
- …