1. Ph.D Theses
Permanent URI for this collectionhttps://idr.nitk.ac.in/handle/1/11
Browse
34 results
Search Results
Item Enhanced control of Photovoltaic Power Converters under Mismatching Conditions(National Institute of Technology Karnataka, Surathkal, 2019) Ramana, Vanjari Venkata.; Venkatesaperumal, B.Exhausting fossil fuel, a huge increase in oil prices, global warming, damage to environment, increasing energy demand are major problems being faced. In order to avoid these problems, power generation is being done using renewable energy sources. Among the renewable energy sources, solar photovoltaic (PV) is dominant because of long operational life, lesser emission, decreasing cost of solar photovoltaic panels. Photovoltaic sources exhibit unique maximum power point under uniform conditions. Under mismatching conditions, there will be multiple peak points because of the presence of bypass diodes. Maximum power point tracking algorithm is used to track the maximum power from the PV source. This thesis presents a literature review of maximum power point tracking (MPPT) algorithms for tracking the global peak. The methodology employed for tracking maximum power point is classified as empirical methods, perturbation methods, model-based methods, artificial intelligence methods, evolutionary computing methods, scanning-based methods, and modified perturbation methods. Based on the literature survey, research gaps are identified and are presented as objectives for this thesis. Four maximum power point tracking algorithms capable of tracking global peak under mismatching conditions are proposed. The first algorithm is based on searching technique and bisection method in which zone wise division of characteristics is performed based on open circuit voltage and panel characteristics. It is a duty ratio based control method and the value of duty ratio is calculated based on bisection method until the global peak is detected. Once the global peak is detected, conventional perturb and observe method is used to retain the operating point at GP. The second algorithm is based on current control in which reference current is moved in the forward and backward direction by multiplying or dividing PV current with 0.9. The movement of PV current is continued in the backward direction until the operating voltage is less than minimum voltage below which there is no chance of occurrence of global peak. After that, the perturbation of PV current is continued in the forward direction until the operating current is less than minimum current below iiiwhich there is no chance of occurrence of global peak. During the process of perturbation, the maximum power point is identified and a conventional algorithm is used to retain the operating point at that point. The third algorithm uses reference voltage control and reference current control to track the global peak. The choice to use voltage or current control is made using a decision variable. The algorithm operates in the current control mode to find the nearest peak and operates in voltage control mode to identify the inflection point. Initially, the voltage below which there is no chance of occurrence of the global peak is identified and it is initialized as the reference voltage. Then the succeeding peak is identified using reference current control. Once the peak is determined, reference voltage control is used to identify the inflection point. This process is continued until the operating PV current is less than the minimum possible current. The fourth algorithm tracks the global peak by sampling variations in the transient period during charging of the input capacitor. The algorithm operates in three stages viz., scanning, correcting and retaining the operating point at MPP. In the scanning stage, the maximum power and voltage at maximum power are identified by changing the value of duty ratio from maximum to minimum value. The correcting stages bring the operating point close to the voltage at maximum power point by varying the duty ratio and retaining stage maintains the operating point at MPP. The simulation studies of all the four MPPT algorithms are performed in MATLAB. All the methods are compared with recent existing MPPT methods in the literature. Hardware implementation is performed using solar array simulator, the boost converter, and resistive load.Item Investigation on Multi-cell and Hybrid Multilevel Inverters with Minimum Number of DC sources(National Institute of Technology Karnataka, Surathkal, 2019) Venkataramanaiah J.; Suresh, Y.From the energy saving perspective, it is essential to adopt highly efficient DC to AC conversion (inverter) system for high power and medium voltage applications. Indeed the conventional two-level inverters cannot handle high power system unless series/parallel arrangements of semiconductor switching devices are used. However, these reformations have severe problems such as misfiring the gating pulses, voltage unbalances between the series connected devices and so on. Again to get rid of these problems, large snubber capacitors and resistors (passive elements) are connected to each switch for compensating transient voltages and static charge balance. Nevertheless, these passive elements cause a higher switching loss and relatively long switching time. On the other hand, total harmonic distortion of the output voltage waveform of traditional two-level inverters is one of the severe problems as the power ratings of the devices goes high. In this critical situation, the multi-level inverters (MLIs) are successfully introduced to overcome all the issues as mentioned earlier for medium and high power applications. Ever since the inception of MLIs, cascaded H-bridge (CHB), neutral point clamped (NPC) and flying capacitor converters are among the earliest topologies that are deemed to be well-established. Each of them has advantages and disadvantages. An NPC-MLI requires additional clamping diodes for its extension whereas, CHB-MLI and flying capacitor MLI needs many isolated DC sources to generate a multistep output and multiple capacitors respectively. Since then, many derivatives and refinements to these classic topologies have been proposed. The motivation for this research work stems out from the demand to generate a substantial number of voltage levels while keeping the device count as low as possible. Therefore, by taking advantage of the basic MLI configurations, a few schemes emanating as a result of combining two or more MLIs in part or fully, referred to as hybrid MLIs are proposed. The offered solutions exhibit considerable topological improvements with reduced control complexity. In the present thesis, we have mainly concentrated on designing a novel hybrid multilevel inverter which can provide an inbuilt isolation for gridiiiconnected, FACTS devices and standalone applications. This MLI can attain nineteen level output waveform with only 12 semiconductor switches. Moreover, it can be extended to n number levels where the switch count is further reduced enormously. In addition to that, a new PWM switching technique is introduced to refine the harmonic profile of the proposed MLI’output voltage waveform. The new PWM can efficiently operate at a very low switching frequency. Thereby, the switching losses of the proposed configuration are minimised drastically. Later, we have kept consistent efforts to derive a new power circuit from our first proposed configuration. Herein the device count is further reduced from 12 to 10 switches to produce the same nineteen level output waveform. In addition to that, an innovative controlling approach is implemented which is a simple fundamental switching strategy so-called ‘FSQS’technique. Moreover, the switching technique can achieve the least harmonic distorted output voltage waveform, and it can be applied to any topology and ‘n’number of output levels. On the other hand, motor drive applications always prefer the efficient MLIs without any transformer involvement in their structures. In fact, most of the power drives are still running with traditional MLIs where the part count is a significant limitation. Thereby we designed a new MLI topology which can attain the modularity with less circuit complexity. It has been named as a multi-cell MLI where the power cell is built asymmetrically. In fact, the part count of the proposed configuration is an appreciable rate compared to the traditional and recent MLIs for the equivalent level generations. In the end, the thesis is devoted to design three unique configurations and two new modulation techniques to address the full range of MLI applications. All developed configurations and schemes are simulated extensively in MATLAB/Simulink. After that, the topologies are verified experimentally by advanced DSP controller and OPAL-RT (Real Time) Simulator on a prototype setup for recording the corresponding output voltage, current, and the THD resultsItem Grid Connection of Wind-Solar Hybrid Renewable Energy System, with Active Power Filter Functionality(National Institute of Technology Karnataka, Surathkal, 2019) Jayasankar, V. N.; Vinatha, U.The incorporation of the abundantly available wind and solar energy to the grid using power electronic converter based interfaces makes a reliable hybrid renewable energy system. Assigning harmonic mitigation property to the grid interfacing inverter to mitigate the current harmonics created by the non-linear loads at the load centres, is a cost-effective solution. The inverter controller consists of an outer DC-link voltage control loop and an inner current harmonic mitigation loop. The limitations of existing DC-link voltage controllers are poor stability margin, steady-state error and chattering problem. The widely used pq theory based inner loop controller offers poor performance under non-ideal grid voltage conditions. The conventional low pass filter based fundamental component extraction methods used in pq theory possess some limitations such as additional time delays and low-frequency oscillations. The main focus of this research is the design, simulation, implementation and analysis of a grid-tied wind-solar hybrid renewable energy system with shunt and series active filtering functionalities, under different system conditions. A Backstepping controller based outer loop, with enhanced DC-link loss compensation capability is proposed for the shunt active filter to overcome the limitations of the existing DC-link voltage controllers. The limitations of conventional low pass filter based fundamental component extraction methods are overcome by employing a self-tuning filter in the inner loop of the shunt active filter. An additional self-tuning filter is incorporated to improve the effectiveness of pq theory under non-ideal grid conditions. A self-tuning filter and a Fuzzy logic-based voltage controller are employed to control the series active filter effectively. A laboratory prototype of the shunt active power filter is implemented. The control algorithm is realised in Xilinx Basys-3 FPGA. From the simulation and hardware test results under steady-state and dynamic conditions, it is found that the proposed controller offers better stability, robustness and speed compared to other existing control methods.Item Localisation of Partial Discharge Source in Oil Insulation Using Acoustic Emission Technique: Non-Iterative Method, Newton’s Method and Genetic Algorithm(National Institute of Technology Karnataka, Surathkal, 2019) Antony, Deepthi; Punekar, G. S.The power transformers are a vital component of power systems. The condition assessment of transformers is of utmost importance to ensure the reliable operation of the power system. The partial discharges (PD) originating from defects in operating transformers should be detected as early as possible. In large power apparatus like transformers, locating the source of PD is as important as identifying it. The PD source localisation helps in risk assessment and in planning of maintenance activities. The acoustic emission (AE) technique is one of the on-line non-destructive testing (NDT) techniques for PD source localisation in power transformers. The PD source is located by solving a system of non-linear sphere equations obtained by modeling the acoustic emission partial discharge (AEPD) location system mathematically. The algorithms that have been developed to solve the mathematical model of AEPD location system need to be improved due to the various limitations. Hence, the current research proposal aims to address this existing research gap by suggesting new algorithms/modifications in the existing algorithms. Further, the factors which affect the accuracy of PD source localisation will be studied and analysed. According to IEEE standard C.57.127-2007, there are two AEPD location systems: (i) allacoustic system; and (ii) combined acoustic-electrical system. When AE technique is used for PD source localisation in power transformers, the error in PD localisation can occur mainly due to two reasons: (i) the inefficacy of the algorithm used for solving the mathematical model; and (ii) the error in measurement of acoustic signal arrival time from the PD source to various sensors. For an all-acoustic system, a hybrid method combining the advantages of both the iterative and random search algorithms is developed to solve the mathematical model of AEPD location system. The existing non-iterative algorithm is modified/extended so that it works for cases with zero time-differences. The PD localisation experiments in an all-acoustic system are conducted in the diagnostic laboratory of Central Power Research Institute (CPRI), Bangalore. The proposed algorithms are verified using data from laboratory experiments. For the combined acoustic-electrical PD-locator-system, a non-iterative algorithm is devised for the first time. The effect of the sensor positioning on the performance of the method is studied, and some guidelines for the sensor placement on the transformer’s tank wall are suggested. The efficacy of the proposed algorithm is verified by applying to data from published literature. The error in estimating the acoustic signal arrival time from the PD source to the multiple AE sensors results in false localisation of the PD source, irrespective of the algorithm used for the AEPD source localisation in transformers. Two mathematical methods for the identification of such erroneous time measurements are proposed: (i) using discriminant; and (ii) using Jacobian determinant. The verification of the proposed methods are carried out by applying to published data in literature.Item Investigations on Three-Phase Front-End AC-DC Converters for Power Quality Improvement(National Institute of Technology Karnataka, Surathkal, 2019) P, Saravana Prakash.; Kalpana, R.The revolution in power electronics has opened an era for widespread use of power converters of different power rating from few Watts to Mega-Watts. Three-phase AC-DC converters are most widely used power converters as the distributed electric power is AC supply, while the applications based on DC supply as well as variable frequency AC supply, need conversion of AC supply into DC supply. Large current harmonics and poor power factor in the utility interface are common problems in three-phase AC-DC converters. These AC-DC converters are used invariably at the front-end in numerous applications which may or may not be electrically isolated from the AC supply system depending on the rating and nature of the load and also the prevalent ‘Standards’ requirement. The applications such as electrochemical, electrometallurgical and electrical heating process, high voltage direct current systems, adjustable speed drives, battery charging, aerospace and naval equipment’s, uninterrupted power supplies etc., use AC-DC conversion at the front-end. These processing industries and adjustable speed drives are the main applications wherein large amount of power is involved in AC-DC converters. These AC-DC converters are generally diode-based, thyristor-based or self-commutating device-based converters depending on applications, size and cost. The wide spread use of AC-DC converters for various applications have resulted in power pollution leading to failure of sensitive equipment’s, reduced efficiency, etc. This has led to the development of power quality standards and hence attracted attention of many researchers for improving the power quality at AC mains. This research work aims at classifying and investigating different three-phase AC-DC converters that employ diodes. The AC-DC converters are mainly classified on the basis of the circuit configuration used for power quality improvement. They are passive, active and hybrid AC-DC converters. The detailed investigation in each category is carried out based on the circuit configurations and control techniques employed. Also, it has led to the formation ofiv some new AC-DC converter configurations that are investigated for the power quality improvement capability. Firstly, this research work aims at employing multi-pulse techniques for mitigating the power quality problems at the AC mains in front-end AC-DC converters. The multi-pulse technique uses autoconfigured transformer for power quality improvement and hence it is termed as passive technique. The investigations on two types of multi-pulse AC-DC converters is carried out covering a wide range of applications that use three-phase AC supply at the front-end for converting it to DC power. The two type of multi-pulse AC-DC converters are multi-phase staggering autoconfigured transformer and asymmetric multiphase converter. The former uses delta and zig-zag autoconfigured transformer and the latter uses delta connected autotransformer for power quality improvement. The main feature of these multi-pulse AC-DC converters is its ability to reduce current harmonics distortion. In these multi-pulse AC-DC converters the number of pulses (voltage ripples at output of AC-DC converters in one cycle of AC supply voltage or steps in the current at input of AC mains) is increased by using phase staggering (or phase shifting), multi-phase (or phase multiplication) and hybrid of these techniques. Further, the unconventional pulse numbered AC-DC converters having pulse number of 20 is considered for the power quality improvement at AC mains. Secondly, this research work aims at utilizing active front-end AC-DC converter for power quality improvement. The active topologies namely Vienna rectifier and Delta switch rectifier are chosen as front-end AC-DC converters for power quality improvement. The voltage sensorless control technique is proposed for the active front-end AC-DC converters such that the computational complexity and sensing effort have been reduced. The system results in improved power quality parameters with less engineering effort. Finally, this research work also focuses on hybrid front-end AC-DC converter for power quality improvement. The hybrid AC-DC converter uses three-level boost converter as active modulation circuit and zig-zag transformer as passive current injection circuit. The current injection circuit along with the modulation circuit at the output stage increases thev DC-link voltage. Further, the utilised current injection circuit avoids resonance problem and also resulted in less rating. Furthermore, the modulation circuit results in reduced ripple current and device rating. For visualizing the different advantages of the three-phase front-end AC-DC converters, the design and simulation of these converters are carried out in MATLAB/Simulink. The main emphasis of these investigations has been on compactness of configurations, simplicity and reduction in rating of components to reduce the overall cost of these frontend AC-DC converters. A laboratory prototypes of these front-end AC-DC converters are developed to validate the design. A high speed digital processor namely field programmable gate array controller, that consists of EP4CE30F484 processor is used to implement a control scheme for active and hybrid front-end AC-DC converters. The steady-state and transient-state performance of the front-end AC-DC converters are verified by changing the resistive load. These front-end AC-DC configurations and techniques have resulted in improved power quality indices with overall reduced rating and reduction in number of components.Item Effective Utilization and Management of PV and Battery Based Power Supply System for Telecom Load(National Institute of Technology Karnataka, Surathkal, 2019) Goud, J Saikrishna.; Kalpana, R.One of the major sectors which have seen a rapid growth in the last decade is mobile telecommunications. It has not only become an important part in peoples lives but also playing a part in world business as the entire world is connected by telecommunication networks. The growing power demand and the dwindling fossil fuels resulted in the unreliable power supply, which is the critical challenge facing by telecommunication industries. Currently, telecom towers are using Diesel Generators (DG) as source of supply, which is rather expensive and emits environmental pollutants. This study analyses the solar photovoltaic (PV) system and battery based hybrid power supply system to reduce the usage of DG. The effective utilization and management of the PV and Battery sources increases the efficiency and reliability of the system. Therefore, in this work, a literature review related to maximum power point tracking of PV array, Li-Ion battery aging mechanism and battery state of health (SoH) estimation techniques have been presented. Non-uniform insolation conditions on PV array is the most common phenomenon and it affects the efficiency of the system. Therefore, in this study two global maximum power point tracking (GMPPT) algorithms have been developed. The first GMPPT technique is scanning based two stage hill climbing technique and the second GMPPT technique is artificial bee colony based soft computing technique. Both the techniques have been developed to track the global maximum power point (GMPP) with the fast convergence speed and with the highest tracking accuracy. Moreover, both the GMPPT techniques uses single current sensor for tracking the (GMPP) to reduce the overall cost of the system. The proposed GMPPT techniques are experimentally validated and its performance characteristics are compared with other GMPPT techniques proposed in literature. Battery is the important power source in the PV and battery based hybrid power supply system. Therefore, reliable power supply to the telecom load depends on the health of the battery. Hence, the knowledge of battery aging mechanism is very vital and helps to configure the right time to replace the battery. In this study, mathematical model of a Li-Ion batiiitery with aging parameters and two SoH estimation algorithms have been developed. The first SoH estimation technique measures the degradation in capacity of the battery over a period and thus estimates the life. The second method estimates the life of the battery by measuring the DC resistance. Both the techniques have been validated using MATLAB/Simulink platform and an experimental prototype. The telecom load operates in a pulsed-power mode intermittently, also the power consumption depends on signal traffic. Maintaining the constant voltage at the DC load terminals during the pulsed power operation is the biggest challenge. Therefore, in this study, Type II compensator is developed to regulate the load voltage with fast response time. The stability analysis of system with Type II compensator is analyzed using the MATLAB/Simulink tool. Moreover, the developed voltage regulator system has been tested for various load and also input voltage varying conditions.Item Design and Control of LowVoltage Dynamic Voltage Restorers employing Semi-Z-Source Inverters(National Institute of Technology Karnataka, Surathkal, 2019) Remya, V. K.; Parthiban, P.Industries have attained tremendous growth rate in recent years with the advent of computers, sensitive equipment and control systems. Most of the processes involving these devices are disturbed and sometimes damaged by the voltage quality problems. Dynamic Voltage Restorer (DVR) is a power electronic converter based device that protects the sensitive loads from experiencing the power quality problems. The main objective of the research work is to find an alternative to the commonly used Full-Bridge (FB) inverter in the DVR structure. The research work here presents two novel topologies of constant dc-link type DVR based on a) semi-Z-source inverter and b) differential semiZ-source inverter. The semi-Z-source inverter offers the same output voltage range as the FB inverter with reduced number of switches. The differential semi-Z-source inverter gives double the output voltage range with four semi-conductor switches compared to the FB inverter. The Modified Sinusoidal Pulse Width Modulation Technique (MSPWM) is used for generating the switching pulses for the semi-Z-source inverter and differential semi-Z-source inverter. The two DVR topologies proposed effectively mitigate the voltage sag by employing feed-forward control and modified feed-back control. The numerical simulations of the proposed DVR topologies for different voltage disturbances are carried out in MATLAB/ Simulink environment. The application of semi-Z-source inverter and differential semi-Z-source inverter as DVR inverter is validated by the results obtained from the laboratory prototype. The MSPWM for the independent inverter operation, rms voltage method for voltage sag detection and DVR inverter control are implemented in Xilinx-Basys-3 FPGA. The voltage sag generation is implemented using Solid State Relays, transformers and PIC microcontroller. The experimental results of voltage sag compensation by proposed DVR approves the application of semi-Z-source inverter as DVR inverter.Item Effective utilization of solar power for isolated water pumping system(National Institute of Technology Karnataka, Surathkal, 2019) Arjun, M.; Venkatesaperumal, B.The imbalance between energy demand and the power generation has led the world to look for alternative solution called Renewable energy sources. Amongst the available energy sources, Photovoltaics (PV) has gained a lot of prominence in the present days due to its reliability and less maintenance. Therefore, the applications of PV have also become multitudiouos ranging from street lights, roof top lighting till satellites. However the major drawback are its high initial costs and low energy conversion efficiency. Therefore, one of the major focus of research lie in development of efficient power electronic converters and controllers. Due to the abundance of solar energy, and adequate requirement of water, research focus has been more on development of PV fed water pumping systems. Over the years of developments in the field of PV pump systems and power electronics technology, several topologies and control strategies have been developed. However, all these studies mentioned above assumes the PV to be receiving uniform irradiance. In an array consisting of a number of panels, it is very much sure that not all panels receive same irradiation. Often some panels are exposed to shades of buildings, clouds, etc., causing multiple peaks in the characteristics of PV array, and is termed as partial shading condition (PSC). Extracting maximum power (MPP) under such conditions becomes more challenging and complex. The non linear behavior of PV, power electronic converters and the load makes the analysis even more difficult. This study on the impact of PSC in PV systems is of high importance especially in the field of water pumping systems because PV fed water pumps are often employed in agricultural sectors where panels are exposed to soiling, shades of trees and clouds. In case of uniform shading, the MPP for varying irradiance occurs near the open circuit voltage region of the PV characteristics. In case of partial shading, the MPP occurs anywhere from short circuit current to open circuit voltage regions. The occurrence of MPP anywhere over such wide range is found to have considerable effects on water pump systems. In case of a two-stage conversion system with an intermediate DC-DC converter, the occurrence of MPP at constant current region will impose iiiproblems such as high voltage stress on MOSFET/IGBT switches due to a higher duty cycle. It may also cause transitions from CCM (continuous conduction mode) to DCM (discontinuous conduction mode) as a result the efficiency falls drastically due to which the pump may even fail to operate though sufficient power is available at the PV terminals. Therefore, this thesis presents the aforementioned effects of partial shading on PV fed motor pump systems. Since majority of the pump systems use induction motor, the pump system considered here for analysis is also an induction motor based. The thesis aims in studying the effects of PSC on double stage water pumping systems by developing mathematical models for PV, MPPT, DC–DC converter and induction motor system. Since the systems are non-linear, the equations governing the systems are also nonlinear and implicit by nature. Therefore, advanced numerical techniques are to be employed to converge at the solution. Therefore, importance is also given to the solution techniques of the developed mathematical equations. To understand, the effect of shading on the converters stability, small signal models are also developed and several interesting observations are reccorded. Finally, the effect of filters connected between the inverter and motor, to mitigate transient over voltages is studied and a cost effective solution is presented. The entire simulation is carried out in MATLAB and verified on a laboratory setup. The results from the mathematical model and experiments are found to agree with each other. In nutshell, this thesis addresses the key points of stand alone water pumping systems and can also be used as a computer aided tool to study the PV fed pumping systems and thus helping in effective utilization of PV power.Item Design and Analysis of Switched Capacitor Converter Topologies for Low Power Applications(National Institute of Technology Karnataka, Surathkal, 2019) Vivekanandan, S.; Jena, Debashisha; P, ParthibanDC - DC converter can be regarded as the heart of any electrical or electronic circuit for buck, boost, inverting or conditioning the target voltage from the available source voltage. Switched Mode Power Supplies (SMPS) are the widely used converters in this segment. Any modern SMPS comprises an energy storage element that transfers the energy from source to load. Inductors are the widely accepted storage element in most of the present day SMPS. They are capable of carrying larger currents by virtue of their construction in large power converters. However, when it comes to small converters, bulky and heavy inductors often restrict the application in an on chip miniaturization circuit. Capacitor, which is another energy storage element, because of its high energy density and low equivalent series resistance compared to inductors, is promising for efficient on chip application. Switched capacitor converters (SCC) that are using only switches and capacitors popularly known as flying or charge pump capacitors are gaining popularity in on die power management boards. In this thesis, the concept of generalized Fibonacci single input single output (SISO) SCC is discussed and it has more efficiency and less equivalent resistance value. Generalized Fibonacci SCCs are technologically advanced and operate on fixed conversion ratio. Different target ratios of Fibonacci series have already been carried out by researchers to step-up and step-down configuration. But, 1/6 and 5/6 voltage ratios of Fibonacci SCC have not been proposed in the literature. To solve the unsolved voltage ratios two possible cases are considered: 1) Fourteen switches and four flying capacitors using Fi = Fi−1 + Fi−3 series. 2) Generalized Fibonacci SCC network is used and a new series is developed to solve the voltage ratios 1/6 and 5/6 with 12 switches and 3 flying capacitors. Theoretical results and simulation results are validated. To overcome limited voltage ratios, reconfigured dual input and single output (DISO) SCC is developed. A reconfigurable SCC topology with nine/ten CMOS switches and two flying capacitors is developed. It is capable of accepting two input sources simultaneously with an input voltage in the range of 1-2.5 V and delivers the output for 15 conversion ratios. The proposed SCC iiican drive a load current ranging from 10 µA to 10 mA at an open loop efficiency of >90%. One of the important applications of the proposed converter is the utilisation of photovoltaic (PV) or the combination of PV and other direct current sources. The regulation of the output voltage can be achieved either by changing the voltage ratios or using variable switching frequency. DISO requires more space and more capacitors to develop more voltage ratios. To overcome such issues, the dual input dual output (DIDO) converter is developed. A new dual-input and dual-output SCC is designed to operate with two independent voltage sources that provide two different output voltages and generate 56 voltage ratios. The converter is portable to operate with one or two input sources alternatively and have the ability to vary 56 voltage ratios. An efficient low power SCC is designed for input voltage of 1.5 V to 5 V that gives dual output voltages of 1 V to 10 V. The designed converter can operate in both buck and boost modes. SCC has high drive capability of load current from 10 µA to 25 µA that is adjusted by operating frequency. The algorithm is discussed to solve the coupled case of dual input and dual output converter. Another major contribution in this research is the introduction of R- parameters calculation for the coupled case and is deliberated in detail since it includes all conduction and ohmic losses accounting for coupling effects. To validate the performance of designed SCC, modeling and mathematical analysis has been carried out. Finally, an extended version of reconfigurable SISO SCC is designed for driving the white light emitting diodes (WLEDs). The various voltage ratios are selected to control the WLEDs blacklights using the inverted SCC (ISCC), which helps to save the battery life of electronic devices. The major contribution is developing maximum voltage ratios for power converter driver ICs and equivalent resistance (Req) accurate calculation where it includes all conduction and ohmic losses. Furthermore, ISCC experimental results are obtained from prototype model. Accurate R eq analyses validate the accuracy of the proposed topology. It is designed for low voltage of 10 mV to 0.1 V and it provides the output voltage of -100 mV to -0.5 V. Finally, the accurate Req calculation and the results are verified experimentally, particularly, at the transition reivgion (between slow switching limit (SSL) and fast switching limit (FSL)). Theoretical calculation from the model derived concurs well with simulation and experimental findings. Accurate equivalent resistance calculation and average current calculation are compared with existing Req analysis available in the literature.Item Probabilistic Steady-State Analysis of Power Systems With Photovoltaic Generations(National Institute of Technology Karnataka, Surathkal, 2019) Prusty, B Rajanarayan.; Jena, DebashishaRecently, the application of probabilistic methods for power system analyses has become increasingly popular owing to their capability to instill enough confidence in system planner and operator in making more realistic decisions. In the conventional deterministic methods, consideration of a few typically stressed operating conditions are inadequate in solving the present uncertainty problems which are majorly confronted due to the enormous integration of renewable generations along with the conventional load powers. Probabilistic steady-state analysis (PSSA) refers to the adaptation of probabilistic load flow (PLF) to address the aforementioned uncertainties for characterizing the uncertainties in the power system variables referred to as result variables. Among the many renewable sources, photovoltaics (PVs) have experienced a globally increasing significance as its cost per unit is decreasing day by day. PV generation is intermittent and variable with a higher level of uncertainty; their integration to power system greatly affects the power system variables which is a significant concern in the power system studies. Hence, a study focusing on the various aspects of power systems with integration of such renewable resources is the need of the hour. Therefore, this thesis is dedicated towards the PSSA of PV integrated power systems to examine various uncertainty issues that are likely to be combated in transmission systems. The primary requirements for PSSA are mainly of threefold which include uncertainty modeling, power system model development, and application of an uncertainty handling method. This thesis aims at the improvement of each of these facets through suitable modifications and eventually resulting in an elegant PSSA. For the uncertainty modeling, use of the historical record of inputs yields realistic models. For power system expansion and operational planning, such models use the daily time step data corresponding to the time of the year concerning the study of interest. The span of the chosen time series ranges from few months to few years depending on the study requirement or data availability. The daily time series of PSSA inputs such as load iiipower, PV generation, ambient temperature, etc. exhibit complex patterns that are periodic, encompassing predictable components. It is vital to separate such components from the raw data to characterize the unpredictable residuals referred to as preprocessing. In this regard, methods for preprocessing using multiple linear regression is proposed, and are compared with state of the art methods using the data collected from various places in India and USA. The rationale involved in the development of such models is deliberated in detail. Finally, a scenario-based spatiotemporal probabilistic model is developed by adopting the proposed preprocessing, transformation techniques, principal component analysis, and a suitable time series model capable of accurately modeling the trend in the variance of uncertain inputs. Risk-based power system studies considering PV generations facilitate in delimiting the permissible penetration by executing essential steps to hedge systems risks. On this line, a risk assessment of PV arrays integrated to New England 39-bus transmission system is carried out. An improved system model is developed by accounting for the effect of environmental conditions, predominantly, the ambient temperature on the branch parameters by considering the electro-thermal coupling effect. The PLF that embodies the above effect in system model is referred to as temperature-augmented PLF (TPLF). It considers uncertainties in PV generation, aggregate load power, and ambient temperature along with their associated correlations for risk assessment. The effect of increased PV penetrations and variation in TPLF model parameters on the statistics of result variables is analyzed in detail. The expected system over-limit risk indices are calculated and are analyzed for different PV penetrations and input correlations. In general, operational studies require a faster estimation of PSSA. One of the ways to achieve this is through the use of an uncertainty handling method that obtains accurate results in less time. On this line, efforts are made to devise two hybrid methods for PLF and TPLF simulations. Here, \hybrid" refers to the suitable amalgam of two uncertainty handling methods in part or as a whole through suitable modifications. As the thesis focuses on the larger transmission systems, cumulant method is chosen as ivone of the potential methods for hybridization. It is seen that, based on a comprehensive result analysis, the proposed hybrid methods exhibit improved performance in the approximation of multimodal probability distributions of the result variables. For all the above studies, PSSA is carried out on various transmission systems such as New England 39-bus test system, IEEE 14-bus, 57-bus 118-bus test systems, and Indian utility 62-bus test system. MATLAB 7.10 is used to develop the corresponding programming codes for various analyses. Finally, with the aid of the obtained results, the research work in this thesis demonstrates that the proposed models and methods for PSSA are potentially challenging candidates which facilitate in making sensible decisions regarding the planning and operation of PV-integrated power systems.