377 research outputs found
Supplemental material for Validation of claims-based algorithms for pulmonary arterial hypertension
No full textSupplemental material for Validation of claims-based algorithms for pulmonary arterial hypertension by Ravikanth Papani, Gulshan Sharma, Amitesh Agarwal, Sean J. Callahan, Winston J. Chan, Yong-Fang Kuo, Yun M. Shim, Andrew D. Mihalek and Alexander G. Duarte in Pulmonary Circulation</p
Performance evaluation of control strategies for grid connected wind power generator
No full textDissertation submitted in fulfillment of the requirements for the degree of Master of Engineering: Electrical Power Engineering, Durban University of Technology, Durban, South Africa, 2022.South Africa is currently experiencing a significant load-shedding situation because of
rising electricity demand. The renewable energy power producer (RPP) sector is
growing rapidly to become an important source of power in South Africa and nations
across the globe. Companies within this sector provide a variety of clean energy
sources, including wind, solar, hydroelectric, biomass and geothermal. Despite its
ability to support the power system and conserve the environment that sustains life,
the rising usage of renewable distributed generators (RDGs) poses power quality
problems in the overall distribution network, such as the voltage instability at buses,
the increase in voltage/current harmonics distortions, etc. The technical requirements
for connecting RDGs to the power system have been defined in standard grid code to
ensure the safe, secure and proper functioning of the overall power system. The
specifications defined in the grid code include the limit of voltage variations (i.e., +/-1
pu), the limit of frequency variations (i.e., +/-5%), and the limit of current/voltage
harmonic distortions (i.e., total harmonic distortion voltage (THDv) of 0.1% and total
harmonic distortion current (THDi) of 5%), and a power factor limit of Pf = (0.9-0.95).
Additionally, RDGs must remain connected throughout a fault condition and assist in
voltage recovery.
In this dissertation, control strategies for grid connected wind energy conversion
system (WECS) are investigated for dynamic performance evaluation. This work
focuses on the doubly fed induction generator (DFIG) – based WECS incorporating a
proportional integral (PI) controller; the permanent magnet synchronous generator
(PMSG) – based WECS incorporating a PI controller; DFIGb-based WECS
incorporating a voltage source converter (VSC) with a fuzzy-logic controller, the
proportional integral derivative (PID), and fuzzy-PID controller. A comparative
analysis of the different WECS topologies was further conducted in terms of the
steady-state error, the percentage overshoot, and the settling time of the
voltage/current or power output signals and dc-link voltage signals.The VSC was
selected as compared to the line-commutated converters (LCCs) because of the
commutation that is not dependent on voltage and current AC signals. The grid-side
converter was applied to regulate DC-link voltage and reactive power to their reference
values. The rotor side converter provided rotor speed regulation on the DFIG to control the power output signal. The vector control method was used for the dynamic
performance analysis. The simulations were done using MATLAB/SIMULINK. From
the simulation results, it was found that the DFIG-based WECS incorporating a fuzzyPID controller performed efficiently compared to the other topologies of WECS.
Load frequency control of a hydro dominating interconnected power system
No full textSubmitted in fulfilment of the requirements for the degree of Master of Engineering in Electrical Power Engineering, Durban University of Technology, Durban, South Africa, 2020.Energy is one of the vital figures that impact the development of civilization in the 21st century. It has been projected that by the year 2050, global energy needs will be satisfied by renewable sources. Among these renewable energy resources hydropower is available worldwide with relatively cheaper accessibility for most of the communities. Nevertheless, hydropower's control architecture raises concern for the system operators in terms of preserving the Load Frequency Control (LFC) services due to the elongated response time of hydro turbines in catering for the varying load demands. The varying load demands are inevitable in the power system due to different clients’ energy consumption patterns at different times. This, therefore, places changing control framework requests as per the requirement of diverse clients. Hence, the research proposes and demonstrates the connection of the hydro-hydro framework through the AC tie- line for LFC. The Linear Quadratic Regulator (LQR) is a plan for hydro overseeing framework in discrete mode. The application derived is displayed through closed- loop feedback gains and closed-loop eigenvalues. In the expansion model, the positive effect of a Unified Power Flow Controller (UPFC) and Redox Flow Battery (RFB) in LFC studies is investigated.
This proposition moreover shows the joint endeavors of Fuzzy Logic (FL) as well as Proportional Integral Derivative (PID), with control gains well-calculated, through Particle Swarm Optimization (PSO) result into a robust FL-PSO-PID for LFC of the connected hydro framework. The different errors are defined to assess the yield as well as the execution of the FL-PSO-PID. The yield appears through a decline in blunder values as well as minimization in framework responses from accurate estimation for the LFC under various working conditions such as non- linearity, random load alteration, and parametric move as a result of a precise estimate. In the expansion, the effect of energy storage devices is also investigated to understand the enhancement provided frequency control of the hydro system, and the result obtained shows their effectiveness. Finally, the outcomes and future extent of this investigation work have been presented.
Design of control strategies for frequency stability of PV-thermal interconnected power system
No full textSubmitted in the fulfilment of the requirements for the degree of Master of Engineering in Electrical Power Engineering, Durban University of Technology, Durban, South Africa.Renewable energy in particular solar energy is a viable option to meet the increasing energy demand for the modern world. The Solar resource in South Africa is among the highest in the world. With the progression of modern society, both energy demands and energy prices are increasing, which has welcomed the introduction of renewable energy resources as an alternative. However, solar radiation varies over the complete day sometimes over the season, and sometimes over the complete year. Further, the power demand is highly variable in nature. Hence, the generated power should match the customer demands over the period of twenty-four hours, and further, it should be economical for customers and electrical utilities. Hence, this study will focus on integrating PV plants with thermal plants to meet the rising customer power demand. The integration of PV with thermal power plants will bring some new challenges in the domain of power system operation & control which is the frequency of the power system should be restricted to well-defined values. Hence, suitable control strategies are to be developed for the successful and smooth operation of the power system. In this research work, an attempt is made to investigate an interlinked system comprising of a thermal and a PV generation system. The control strategies based on PID controllers and their gains tuned through effective tuning techniques are presented. In addition, the concept of fuzzy logic is used to address the problem of frequency managing of PV-Thermal via effectively designing fuzzy proportional, fuzzy integral, and fuzzy PI built control strategies to ensure the frequency regulation of the energy system. The obtained results are shown via a graphical approach, and the best control design is explore and suggested for the considered system. In addition, the scope for further improvement and possible direction areas are also explored and listed in this report.
Voltage stability in distribution network
No full textSubmitted in fulfilment of the requirements for the degree of Master of Engineering in Electrical Power Engineering, Durban University of Technology, Durban, South Africa, 2020.Voltage stability studies and to maintain the flat voltage profile is quite important in order to maintain the healthy operation of electric power network as well as to provide the quality and cheap electric energy to the modern power users. Further with the advancement of power electronics technologies and its application to design flexible alternating current transmission devices (FACTS) have made it easier to alleviate the voltage stability problem in a quicker and cheaper way in the modern DNs. Therefore, this research work shows an attempt to investigate and solve the problem of voltage instability in the distribution network (DN) with the help of FACTS. All buses and lines are calculated in terms of voltage stability index (VSI) and to identify the optimal location of FACTS. The bus or line with minimum voltage profile in terms of VSI are more sensitive to the voltage collapse and it may further lead to blackouts. Hence, the FACTS are permanently installed at the weakest point to enhance voltage profile and improve the voltage stability in the DN. The present study is tested on standard IEEE-15 bus DN and application results are shown to verify the feasibility of the present studies for DN.
The beauty and future promise of UPFC in power quality improvement was authenticated on the IEEE-15 bus DN carried out using MATLAB software tool, five different scenarios were considered by increasing the load up to 40% at an interval of 10% from its nominal operating load. With the aim of determining the impact of UPFC on bus voltage and system losses, the load flow analysis was contributed on each scenario with and without UPFC placement in the DN. After UPFC placement there was a significant enhancement of voltages of all busses as well as weakest bus voltage jump from 0.5750 to 0.9750 p.u. and shifting that bus as well as system from voltage instability to stable zone. The active and reactive power loses were decrease by 9.83% and 27.27% that fulfil the beauty of the UPFC installation in the DNs as well as it promise to mitigate the voltage instability problem of the modern DNs
Coordinated control of conventional power sources and plug-in hybrid electric vehicles for a hybrid power system
No full textSubmitted in fulfilment of the requirements of the degree of Master of Engineering in Electrical Engineering at the Durban University of Technology, Durban, South Africa, 2022.Globally, the requirement for renewable and clean energy technologies is becoming vastly
popular. With the high implementation of solar and wind energy systems, together with plugin hybrid electric vehicle (PHEV) aggregators, energy costs can be minimised, greenhouse gas
emissions decrease, and overall maintenance becomes reduced. The constant increase of load
demand is becoming a challenge for the current power systems, with difficulties including
stability concerns and excessive regulations by the government. Due to irradiance and wind
speed fluctuations, the solar and wind energy system’s non-linearity affects the existing power
system stability. The growth of the electric vehicle industry has also shed new light on potential
auxiliary services that can be provided, as and when required, to the power system. Hence, this
research examines the potential control strategies that are required to maintain the system in
steady-state conditions after disturbances that occur with higher penetration of renewable
energy systems (RESs) and PHEVs. The case study models a isolated two-area thermal type
power system that is interconnected through an AC tie-line. Three scenarios are modelled,
simulated and analysed. The first scenario models a isolated thermal power system with PHEVs
with two areas which utilises a fractional order proportional integral derivative (FOPID)
controller in each area. The resulting model is analysed to see the effects of PHEVs coupled
with FOPID on the power system. The second scenario models a isolated two-area thermal
power system with RES and utilises a fuzzy type-2 (FT2) FOPID controller in each area. The
RES penetration istested for its non-linearity effect on the isolated power system, and the error
is reduced by an advanced controller that uses artificial intelligence techniques. The third
scenario is modelled as an isolated two-area thermal power system with PHEVs and RES
coupled with neural network predictive controller (NNPC) in each area. The three scenarios
are simulated in MATLAB/Simulink with results displayed graphically and numerically. The
results show that the integration of PHEVs for load and/or storage in the multi-area power
system, and the proposed control methods for each scenario, have the best dynamic response
with the least error, no oscillations and the fastest response to steady state condition.
Application of optimal control for power systems considering renewable energy technologies
No full textDissertation submitted in fulfilment of the requirements for the degree of Master of Engineering in Electrical Power Engineering, Durban University of Technology, Durban, South Africa, 2021.Over the last decade, power generation from renewable energy sources such as wind, hydro and solar energies have substantially increased globally and in South Africa. Of all the renewable energy sources, wind energy appears to be the most promising, considering design and costs. However, due to the intermittent nature of wind, the increased integration of wind energy into existing power systems raises several control challenges related to load frequency control (LFC) and tie-line power system stability. The stability of modern power systems, incorporating wind energy generations, will be significantly enhanced with the development of LFC strategies based on modern control theory, which is the focus of this research.
This thesis presents the design, modelling and analysis, of two LFC control strategies for interconnected power systems, having wind power integrations. The first design is an optimal control strategy, based on error minimization through full state vector feedback, for a two-area interconnected power system consisting of hydro-thermal generations. The second design is a model predictive control (MPC) strategy, based output vector feedback of system state parameters, for a two-area interconnected power system consisting of thermal generations in each area. Both designs include the active power support from doubly fed induction generator based wind turbines (DFIG) in conjunction with the combined effort of a thyristor control phase shifter (TCPS) and super conducting magnetic energy storage unit (SMES). Both control strategies were simulated in MATLAB Simulink and positive results were obtained. The results show that the optimal control strategy is enhanced with power integrations using DFIG based wind turbines combined with the TCPS-SMES units and the MPC strategy is very robust and provides better dynamic performances even with parameter variations and generation rate restrictions.
Modeling and performance analysis of artificial intelligence (AI) based controllers for AVR of a synchronous generator (SG)
No full textSubmitted in fulfillment of the requirements of the degree of Master of Engineering in Electrical Engineering, Durban University of Technology, Durban, South Africa, 2022.An automatic voltage regulator (AVR) is an electronic device used to control, adjust, and maintain a constant voltage level at the stator terminals of a synchronous generator (SG). Hence, the voltage stability of a power system network is affected by AVR’s performance. Maintaining constancy and stability of the nominal voltage level in power systems remains a major control problem. Another critical reason for effective control of the generator's terminal voltage is that real line losses are determined by the real and reactive power flows and variation in terminal voltage has a large effect on reactive power flow and thus on these losses.
A large power system consists of several synchronous generators that operate in synchronism; the terminal voltage and frequency are to be kept constant with minimal variation to ensure the stability of the power system. The voltage stability of a synchronous generator is highly affected when the terminal voltage varies above the nominal acceptable range. To maintain a constant voltage at a SG’s terminal, an AVR is used. The performance of an AVR is highly dependent on efficient controller design, which improves the output of the AVR by restoring the voltage of the synchronous generator to its nominal value in the presence of disturbances.
The selection of a suitable controller is one of the most challenging aspects of AVR system design. This study presents the design, modeling, and performance analysis of an AVR system employing a Proportional Integral and Derivative (PID) controller, a Fuzzy Logic controller (FLC), and a Model Predictive Controller (MPC) for the performance enhancement and transient response of the AVR system with these controllers.
Initially, a transfer function is used to develop a mathematical model of an AVR in order to observe its step response when the terminal voltage of a generator is disturbed. A PID controller is then added to the system and tuned to enhance the step response of an AVR. The third model develops and implements an AVR system based on MPC, while the final model implements an FLC for an AVR system. Simulating the models in Matlab Simulink 2021a, the results have demonstrated the need for a controlling mechanism to enhance the dynamic performance of the AVRS, and MPC has shown to be the most effective controller.
Adaptive Intrusion Detection in Edge Computing using Cerebellar Model Articulation Controller and Spline Fit
Get PDFInternet-of-Thing (IoT) faces various security attacks. Different solutions exist to mitigate the intrusion problems. However, the existing solutions lack behind in dealing with heterogeneity of attack sources and features. The future anticipated demand of devices' connections also urge the need of new solutions addressing the concerns of time consumption and complexity. In this article, we show a novel solution for the intrusion detection in IoT framework. We configure the intrusion detection in the edge computing layer so that the effect of the attack is not propagated to the clouds. Our solution uses cerebellar model articulation controller with kernel map. This combination is very new in the direction of intrusion detection; hence, it emphasizes the novelty of our proposed intrusion detection solution. We name our solution as Cerebellar Model Articulation Controller based Intrusion Detection System (CMACIDS). Additionally, we use spline fitting to the kernel mapping for the model fit; this adds on another novel contribution to CMACIDS. The results obtained with our detection system are compared with the state-of-the-art solutions in terms of complexity, false alarms, and precision of detection. The analysis of the comparative study proves the efficiency of the solution and makes CMACIDS suitable for IoT paradigm. </p
Music identification using brain responses to initial snippets
No full textNaturalistic music typically contains repetitive musical patterns that are present throughout the song. These patterns form a signature, enabling effortless song recognition. We investigate whether neural responses corresponding to these repetitive patterns also serve as a signature, enabling recognition of later song segments on learning initial segments. We examine EEG encoding of naturalistic musical patterns employing the NMED-T and MUSIN-G datasets. Experiments reveal that (a) training machine learning classifiers on the initial 20s song segment enables accurate prediction of the song from the remaining segments; (b) β and γ band power spectra achieve optimal song classification, and (c) listener-specific EEG responses are observed for the same stimulus, characterizing individual differences in music perception.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Design Aesthetic
- …
