Theses supervised by Prof. Dr. Mehmet Tümay
20 theses · Çukurova University
Modeling and analysis of custom power park by PSCAD/EMTDC program
The advances in power electronics based devices to improve power quality have been increased the interest on Custom Power Park (CPP). CPP concept means the integration of multiple CP Devices within the Industrial/Commercial Park, which offers customers high quality of power at the distribution system voltage level. CPP is one of the most useful solutions to prevent voltage sags/swells and harmonics from distribution lines.In this thesis, CPP has been modeled by using PSCAD/EMTDC program. CPP is composed of Static Transfer Switch (STS) and Dynamic Voltage Restorer (DVR). The operation principles of STS and DVR have been explained in detail and then they have been modeled with PSCAD/EMTDC program. Simulation results have been comprehensively investigated. Different types of faults are applied for STS and DVR in CPP and the response of the system for these disturbances are examined.
Response tests of load-frequency control in thermal power plants regarding Union for the co-ordination of Transmission of Electricity (UCTE) policies
Active and reactive power flows are independent from each other and they are controlled by different methods in an interconnection system. The control of active power is closely related to frequency control and the control of reactive power is related to voltage control. Frequency control is a necessary parameter in order to both indicate energy quality of electricity network and join Turkish interconnected system to Union for the Co-ordination of Transmission of Electricity (UCTE). UCTE in Europe mainland is a huge organization and has own policies. The most important parameter of those policies is load-frequency control. The interconnection of Turkish electrical network with UCTE network is an ongoing project since the end of 90?s and tests are persisting in both hydro power plants and thermal power plants chosen as references in Turkey via TEİAŞ.The goal of this thesis is to investigate primary load-frequency control involved in UCTE policies for thermal power plants. Turbine controller of reference power plant is modeled and simulated by using Matlab/Simulink program in the thesis. Load-frequency performance of reference power plant is achieved by the field test. The results of tests are transferred into computer via Digsilent software and results of tests are compared with results of simulations.
Implementation of voltage quality disturber controller with digital signal processor
Electrical machines and power electronic devices become more sensitive to power quality variations. Because of the production losses end users have an increased awareness of power quality issues. Custom power devices (CPD) such as Dynamic Voltage Restorer (DVR), Active Power Filter (APF) and Static Transfer Switch (STS) supply a level of reliability and power quality that is needed by electric power customers sensitive to power quality variations.The basic purpose of this thesis is modelling of the Power Quality Disturber-Voltage in order to evaluate performance of CPDs. Proposed PQD-V has an ability of producing voltage sag, swell, phase shifted voltage and voltage with defined harmonic order.Proposed model is simulated in Matlab/Simulink for different cases. Experimental study of the model is also performed. Simulation and experimantal results are compared in order to evaluate performance of the system.
Voltage quality enhancement with custom power park
In the recent years, power electronics based Custom Power (CP) devices that solve these problems attract attention. However, the system formed by putting together the CP devices in an industrial/commercial power park is known as Custom Power Park (CPP). The CPP provides continuous and high quality power to the customers having sensitive loads.In this thesis, a CPP is designed, simulated and made experimental analysis to enhance the voltage quality. The CP devices which are modeled, made experimental analysis and put together in a prototype low voltage power park are Dynamic Voltage Restorer (DVR) and Static Transfer Switch (STS). A new voltage compensation method is proposed for the DVR. However, a new sag detection method is presented for the DVR. The same detection method is also proposed for the STS. The proposed control methods are used for both devices in simulations and experimental setup and get successful results. Finally, the STS and the DVR are integrated to a power park prototype and the CPP is set up. The voltage quality improvements with the help of this CPP are examined against various fault scenarios.The publications made as a result of these studies will contribute to scientific literature. Besides, it will also contribute to become conscious about a new country wide progress ?finding solutions to the electric power quality problems? and this will also contribute to the using of power quality devices in our country.
Renewable energy sources
At the end of 20th and the beginning of 21th century, energy demand has increased and scientists attempted to find solutions for compensating this energy demand. On the other hand, with the increase of energy demand and consumption, scientist had to face another issue that our World?s energy resources are very limited and increasing demand is consuming our limited resources and polluting our World. This challenged the scientists to find new solutions like renewable energy sources that compensate our world?s energy demand without polluting and consuming limited energy sources.In this dissertation, information on technologies of renewable energy resources is given. Wind and solar energy are emphasized but geothermal, hydropower, wave, tidal, biomass and hydrogen energies are also discussed. Current information and proposals on renewable energy applications, policies, laws, institutions and R&D studies in Turkey are given.
Design of current disturbance generator by using digital signal processor (DSP)
Electrical machines and power electronic devices become more sensitive to power quality variations. Because of the production losses end users have an increased awareness of power quality issues. Custom power devices (CPD) such as Dynamic Voltage Restorer (DVR), Active Power Filter (APF) and Static Transfer Switch (STS) supply a level of reliability and power quality that is needed by electric power customers sensitive to power quality variations..The basic purpose of this thesis is modelling of the Current Source Disturbance Generator in order to evaluate performance of APFs. Proposed CSDG has an ability of producing source current defined Total Harmonic Distortion (THD) levelProposed model is simulated in Matlab/Simulink for different cases. Experimental study of the model is also performed. Simulation and experimantal results are compared in order to evaluate performance of the system.
Digital signal processor based implementation of custom power device controllers
Custom power can be explained as the power supplied to the customers who do not tolerate any power quality problems that may occur in supplied power using custom power devices. Dynamic Voltage Restorer (DVR) is one of the custom power devices that is connected in series to the system. DVR detects the voltage sags and injects missing portion of voltage to the load. By this way, the load is not affected by voltage sags on the supply. Another custom power device is the Static Transfer Switch (STS) that transfers the supply of the voltage sensitive loads of customers who have two different feeders. When a sag or interruption occurs on one of the feeders, the loads are transferred to the healthy feeder in the shortest time possible. Shunt Active Power Filter (SAPF) is used to eliminate the current harmonics. The purpose of SAPF is to minimize the harmonic level of the source current by generating the harmonics required by the non-linear loads.Power electronics switching devices are widely used in the realization of custom power devices such as DVR, STS and SAPF. To control the power electronic equipments, controller design and development are needed. In this study, the controllers of DVR, STS and SAPF are designed, developed and implemented using Digital Signal Processors (DSP). A new sag detection and voltage compensation method is proposed for the DVR. The sag detection algorithms are also applied to the control of STS. In the implementation of SAPF, the problems caused by the voltage unbalance in instantenous reactive power method are solved. The design of custom power devices are explained in detail. Control algorithms and codes developed are presented.
Unified power quality conditioner: Design, simulation and experimental analysis
Power quality (PQ) problem can be defined as the deviations of the voltage and/or current from the nominal sine wave. PQ problems generally concern with voltage sags/swells and harmonic currents. Custom Power (CP) devices that mitigate these power quality problems have gained more attention in the recent decades. Unified Power Quality Conditioner (UPQC) is one of the CP devices and it mitigates both load current and supply voltage problems, simultaneously.In this study, UPQC and a new topology of UPQC namely OPEN UPQC are designed, modeled and setup experimentally to mitigate voltage sag/swells and harmonic currents. UPQC consists of Dynamic Voltage Restorer (DVR) and Active Power Filter (APF). An improved voltage compensation controller and new sag/swell detection method based on Enhanced Phase Locked Loop (E-PLL) are presented for DVR. Traditional Instantaneous Reactive Power Theory (IRPT) is optimized for APF control algorithm to compensate harmonic load current under unbalanced and distorted supply voltages. Digital Signal Processor based 6 kVA, 230Vline-lineUPQC and OPEN UPQC prototypes have been developed for laboratory tests. UPQC and OPEN UPQC with proposed controller algorithms effectively compensates the sag/swell in supply voltage by keeping the load voltage amplitude at 0.9-1 per unit and eliminates the load current harmonics by keeping supply current at 5%Keyword: Elektrik enerji sistemleri = Electrical energy systems ; Elektrik güç sistemleri = Electric power systems ; Elektriksel analiz = Electrical analysis ; Enerji dağılımı = Energy distribution ; Enerji kalitesi = Energy quality ; Enerji kullanımı = Energy usage
Detection and mitigation methods of power quality disturbances
The voltage sags and harmonic currents are the most common disturbances in the power system. These disturbances are mainly caused by the power electronic-based devices and nonlinear loads used commonly in the industrial plants, commercial and residential areas. The term ?power quality? has emerged with the increasing of the disturbances in the power systems recently. This term is used to express the quality of the electricity service by the electricity authorized and end-users.The power electronic based devices are proposed to mitigate the negative effects of the power quality disturbances and used in the power system applications. The utilization of these devices has increased for the improvement of power quality in recent years. Many methods based on time and frequency domains are proposed by the researchers to control these devices. The control algorithms of these devices perform the analysis of the voltage and current signals simultaneously. The analysis of these signals can be divided into two main topics. The first topic is the detection of the disturbances and the second topic is the generation of the compensation signal for mitigating the disturbances. The fast detection of the disturbances and accurate calculation of the compensation signal are the important issues for the control algorithms of these devices.In this thesis, the control algorithms of conventional methods such as Fourier Transform, Wavelet Transform, Reference-Frame Transformation Methods, Fuzzy Logic and Artificial Neural Networks are examined for the disturbances detection and compensation and illustrated graphically. The advantages and disadvantages of these methods are also analyzed and given in details. In additions, new methods for the harmonic currents extraction, voltage sag detection and compensation for the negative effects of these disturbances are proposed. The performance comparisons of the conventional and proposed methods are realized by using the power quality mitigation devices such as Active Power Filter (APF) and Dynamic Voltage Restorer (DVR) in PSCAD simulation program.
Çok seviyeli paralel melez aktif filtre'nin modellenmesi ve analizi
In industrial areas, the harmonics and other power quality problems which is created by nonlinear loads not only have some bad effects such as system loss, efficiency drop, shortenning the life of circuit elements but also cause material and natural problems. Therefore, the solutions of reducing power quality problems is required to get both economically and high quality electrical energy. The solution of harmonic distortion generated by nonlinear loads is a quite serious problem. One of these solutions is hybrid active power filters. The main aim of the development of hybrid active power filter is to reduce the cost and capacity of active filter by using passive filter that filters the dominant harmonics caused by non-linear loads and supplies reactive power requirement. In this thesis, Hybrid Active Power Filter is modeled in PSCAD/EMTDC. The developed topology is a multilevel topology that achieves both harmonic and reactive power compensations. All controllers are written by FORTRAN programming language. According to the results obtained using PSCAD/EMTDC, it is observed that Multilevel Parallel Hybrid Active Power Filter can compensate both harmonic and reactive power successfully.
Design and simulation of thyristor switching system for reactive power control and motor power efficiency control
Nowadays, the majority of the increasing energy consumption is consumed by industrial organizations that are constantly growing and evolving. A large part of the energy used in industry is consumed by electric motors. As a result of work to be done on the efficiency of electric motors, large declines in energy consumption values can be established. In this study, a new motor drive which is designed to provide efficiency in asynchronous motor that is the most commonly used industry is presented. The driver is modeled in PSCAD/EMTDC. Designed driver provides energy-efficiency in motors which operating at lightly loads. The proposed methods provide superior performance compared to conventional methods. The aim of the thesis is that design and simulation a motor drive which provide energy efficiency in 7.5 kW induction motor. The performance and provided efficiency values of the proposed motor driver are investigated with different simulation studies by PSCAD program.
Modeling of fast dc charger for electric vehicles and integration to grid
Energy consumption is increasing gradually with worldwide industrialization. The increase in consumption of energy creates a big amount of demand for production which is supplied by fossil fuels. The consumption of fossil fuels leads to environmental pollution. Additionally, limited petroleum reserves are remained. There is an enormous amount of fossil fuel consumption by internal combustion vehicles that are the most widely used vehicles worldwide. In addition to this, electric vehicles are clean, silent and simple to operate. Because of these reasons, the demand for electric vehicles is increasing. In this thesis, charger circuit for electric vehicles and its integration to grid are studied. In the study, significant charger modeling topologies in the literature are investigated. Advantages and disadvantages of these topologies are discussed. Among these topologies, one of the most common (constant current-constant voltage) topology is used. The best advantage of the studied topology is recharging the battery in the most appropriate manner. Data of Çukurova University's infrastructure is used for the system. Additionally, in the study we will examine the current drawn by the system, whether the infrastructure is adequate or not. If the results of the examination are found to be inadequate, then we should determine where new infrastructure systems will be needed. Also, the performance of charging station and grid for different cases are analyzed; response of multiple synchronous charging is also investigated.
Investigation and analysis of switching ripple filters for three-phase four-wire Shunt Active Power Filter
There are many studies of Shunt Active Power Filters (SAPF) in the literature and applications of SAPF in industry while Active Power Filter (APF) has different topologies. SAPF is mostly preferred to be used as current source controlled, and used for compensating of harmonic currents, reactive power and unbalance of load current. Shunt APFs, which are acting as a current source, can also be used for the compensation of neutral current. Voltage Source Inverters (VSIs) are used while compensating these power quality problems. Since VSIs are fired by high switching frequencies, high frequency harmonics occur at point of coupling connection. Switching ripple filters are used to reduce the effects of high frequency harmonics. In this thesis, different switching ripple filters are investigated by constituting design and comparing their performances. In this thesis, LCL and LLCL filters are focused on. Besides, different passive and active damping methods are examined and compared with respect to damping capability and ripple suppresion performances. All controllers are written in Matlab Function block via C programming language. Accordingly, the results are obtained by using MATLAB/SIMULINK, it is observed that Switcihing Ripple Filters can mitigate switching ripples successfully through LCL and LLCL filter with different damping methods.
Modelling and analysis of bidirectional dc-dc converter
Bidirectional dc-dc converters are used a lot of industrial areas such as electric vehicles, uninterruptable power supplies, fuel cells, solar panel cells as energy sources are searched in order to improve the quality of power at the transmission and distribution lines and other areas. All of these industrial applications give importance on system loss, efficiency drop, shortening the life of circuit elements. Thus, it should be improved control systems in order to prevent power losses as far as possible and efficiency of bidirectional power flow is very important for high quality electrical energy. Owing to different types of control methods provide bidirectional power flow and each of these has different algorithm. Nowadays, these control methods are improved by increasing complexity of mathematical equations or exchanging better equipments. In the light of these works, comparing of common used control methods provides contribution to efficiency studies at bidirectional dc-dc converter literature. The main aim of this thesis work, applying different phase shift control methods on single phase isolated bidirectional full bridge dc-dc converter and comparing these control methods on efficiency way by reducing cost with or without using snubber capacitors. In this thesis, Isolated Bidirectional DC-DC Converter topology is modelled and all controllers are written by FORTRAN programming language. According to the results, it is observed that efficiency results of DPS and EPS are almost equal and higher than SPS without using snubber capacitors. This statement shows the discovered and innovative way of this thesis work. Key words: Bidirectional DC-DC Converter, Phase Shift Control Methods, Efficiency, Comparison.
Modelling and analysis of modular cascaded multilevel converter based shunt hybrid active power filter for large scale photovoltaic system interconnection
Modular multilevel converters are promising candidates for next generation of efficient, robust and reliable inverters in large scale photovoltaic system. A modular cascaded multilevel converter based shunt hybrid active power filter (SHAPF) for three phase grid-connected large scale PV systems is presented in this thesis. The main contribution of this thesis is to model and control of grid interfaced large scale photovoltaic system with embedded hybrid active power filter functions. In proposed system, the features of hybrid active power filter has been amalgamated in the control circuit of the voltage controlled voltage source inverter interfacing the photovoltaic system to the grid. As a result, the same inverter part of SHAPF is utilized to inject power generated from photovoltaic source to the grid and also to act as hybrid active power filter to compensate harmonics and reactive power demand. With using compensation ability, the grid currents are sinusoidal and in phase with grid voltages. The whole system is modeled in PSCAD/EMTDC. The simulation results are demonstrated to verify the operation and the control system of the proposed system.
Design and experimental verification of resonance damping methods for a shunt active power filter with LCL filter
A Shunt Active Power Filter (SAPF) with LCL filter is designed and constructed in order to examine and apply various damping methods for the resonance issue of LCL filter. In this thesis work, by this means, passive damping (PD) method, active damping (AD) method and auxiliary converter based damping method are investigated and compared according to power losses, resonance damping performance, impact on harmonic compensation and implementation cost. A converter based active damper (CBAD) method is proposed in this thesis to suppress the resonance of LCL filter. Additionally, the design of LCL filter for SAPF is presented and the constraints of the design are conducted and explained in detail. In this thesis study, the implemented SAPF with LCL filter prototype is designed to compensate dominant low order harmonic currents of six pulse rectifiers up to 15A. In the scope of this thesis, a control algorithm is developed and applied to the SAPF with LCL filter prototype. The performances of LCL filter interfaced SAPF with the developed control algorithm and the applied damping methods are verified in the steady-state and dynamic situations with comprehensive experimental results.
Modeling of doubly-fed induction generator based power supply system for aircraft applications
With developing aircraft technologies, there has been a significant increase in electrical equipment in aircraft. The increase in the electrical equipment used in aircraft caused an increase in energy demand. Therefore, the implementation of stronger and more reliable electricity generation, transmission, and storage methods has become an imperative concern for aircraft. In this thesis study, it has been studied to adapt the doubly-feed induction generator which produces constant output at variable speeds by eliminating the mechanical constant speed drive in the turbine generator, which is the main electric source of the aircraft. Firstly, the structure of DFIG has been researched and comprehended and its working principle has been assimilated. Afterwards, DFIG which can operate in isolated regions, designed for the production of electricity aircraft. Flyback converter, inverter and a asynchronous generator are used for modeling of the system. Keywords: Aircraft electric generation systems, Wind tribune types, Generator types, Doubly-Fed Induction Generator, Variable speed constant frequency and voltage, Flyback converter, Standalone operation, DFIG
Büyük pil paketi için aktif dengeleme sistemi
Nowadays, the tendency towards electric vehicles is increasing and various studies are being carried out in order to eliminate the shortage of battery life. One way to improve battery life is to overcome imbalances in battery packs. The imbalances due to structural differences arising from production and changing operating conditions, reduces the utilization of available energy. Passive and active equalization methods are preferred in order to overcome these imbalances. Due to the slow equalization and energy inefficiency of passive balancing circuits, the trend towards active balancing circuits is increasing. In this thesis, an active cell balancing model and a new active cell balancing algorithm that is able to transfer excess energy to the cells with weak energy via the charge transfer-bus (CTS) is proposed for a electric heavy commercial vehicle (EHCV) equipped with large battery packs (LBPs). To test and evaluate the performance of the active balancing system (AcBS), an active balancing circuit (AcBC) that includes 11 modules which consist of 16 cells equipped with bidirectional dc-dc converters and switch matrixes have been simulated in MATLAB/SIMULINK environment. The study has been carried out in two stages. In the first study, a model is presented for LBPs which can be applied in EHCVs. CTS is used for transferring excess charge from source cell to destination cell. Unlike topologies in literature, presented model doesn't need for external storage element because it uses the existing vehicle battery to buffer the CTS. The presented LBP model consists of 176 cells connected in series. Thus, twenty-two bidirectional dc-dc (BiDC) converters are used in the simulation because every 8 cells are combined with one dc-dc converter. Controlling the switching signals of BiDC converters involves high runtime/complexity. Therefore, current sources are used instead of dc-dc converters by simplifying the model in the simulation. In the second study, a new balancing algorithm is proposed. Compared to existing approaches, the algorithm with features of fast balancing, smaller voltage imbalance range, and multiple charge transfers is suitable for LBPs. By comparing the proposed algorithm with the existing algorithm, the presented algorithm has been shown to have better results for LBPs. Key words: Active balancing, large battery pack, heavy electric vehicle.
Modelling and analysis of a dc electric spring with z-source DC-DC converter
In this thesis, a DC-Microgrid that is supplied from renewable energy sources (RESs) is developed and presented. To keep the DC-Microgrid voltage stable, a DC Electric Spring (DCES) is applied to model to remove voltage fluctuations due to intermittent generation of Renewable Energy Sources. The fluctuating voltage of the system input power is absorbed by the series connected Non-Critical Load and DC Electric Spring branch. In order to maintain a stable DC voltage for Critical Load, the voltage quality on Non-Critical Load can be sacrificed. DC Electric Spring tracks the supply side voltage continuously and generates required voltage from battery bank thanks to Half-Bridge DC-DC Converter and Z-Source Converter.The key advantage of Z-Source Converter is the high level voltage gain and satisfies low battery bank costs. System is modelled in MATLAB/Simulink and simulation results are presented.
Modelling and analysis of hybrid regenerative power system combining with grid and solar energy
In this thesis, the Hybrid Regenerative Power System (HRPS) was studied and operated at low powers with a designing a new Central Energy Management System (CEMS). It is suitable for the critical AC & DC loads and efficient thanks to the regenerative effect. Firstly, equipments in the power system were created and operated seperately and the results of these equipments were obtained in different cases. HRPS consists of a bidirectional inverter connected with LCL filter and grid, a bidirectional isolated DC-DC converter connected with batteries and an isolated unidirectional DC-DC converter connected to photovoltaic panels and combining AC & DC loads. After the HRGS topology emerged, an innovative, efficient, unique rule-based CEMS is created. It can automatically manage power flow scenarios in order to operate power system efficiently and accurately by evaluating load demands and power balances in the system. Power flow scenarios were first run alone according to different situations and then they were operated together with CEMS using real irradiance and temperature spectrums. Then, how efficient the power system is in itself was calculated according to the results obtained and when compared to the literature, it was emphasized in which cases it has advantageous than the other energy management systems.