Journal Articles
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Item Quantifying aquifer properties and freshwater resource in coastal barriers: A hydrogeophysical approach applied at Sasihithlu (Karnataka state, India)(2012) Vouillamoz, J.-M.; Hoareau, J.; Grammare, M.; Caron, D.; Nandagiri, L.; Legchenko, A.Many human communities living in coastal areas in Africa and Asia rely on thin freshwater lenses for their domestic supply. Population growth together with change in rainfall patterns and sea level will probably impact these vulnerable groundwater resources. Spatial knowledge of the aquifer properties and creation of a groundwater model are required for achieving a sustainable management of the resource. This paper presents a ready-to-use methodology for estimating the key aquifer properties and the freshwater resource based on the joint use of two non-invasive geophysical tools together with common hydrological measurements.
We applied the proposed methodology in an unconfined aquifer of a coastal sandy barrier in South-Western India. We jointly used magnetic resonance and transient electromagnetic soundings and we monitored rainfall, groundwater level and groundwater electrical conductivity. The combined interpretation of geophysical and hydrological results allowed estimating the aquifer properties and mapping the freshwater lens. Depending on the location and season, we estimate the freshwater reserve to range between 400 and 700 L m??'2 of surface area (A± 50%). We also estimate the recharge using time lapse geophysical measurements with hydrological monitoring. After a rainy event close to 100% of the rain is reaching the water table, but the net recharge at the end of the monsoon is less than 10% of the rain. Thus, we conclude that a change in rainfall patterns will probably not impact the groundwater resource since most of the rain water recharging the aquifer is flowing towards the sea and the river. However, a change in sea level will impact both the groundwater reserve and net recharge. © Author(s) 2012.Item Investigations on interconnection of wind-solar hybrid Renewable Energy Source to the ideal grid at the distribution level together with power quality improvement features(Universitatea Politehnica din Timisoara blucretiu@yahoo.com, 2015) Gururaj, M.V.; Vinatha Urundady, U.one of the most challenging issues that modern man is facing nowadays is global warming and scarcity of fuel. To find a solution to the above problems the focus of research is directed towards Renewable Energy Sources (RES). Among all available RES the combination of wind-solar RES provides the most reliable solution to the utility as both of them are complimentary to each other. As all the energy sources including RES are scattered across the globe, it becomes necessity to extract available green energy at the distribution as well. Non-linear loads connected at the Point of Common Coupling (PCC) inject current harmonics into the system thereby pollutes the grid environment. Shunt active power filter is found to be one of the feasible solutions in addressing issues related to the non-linear loads. This paper deals with the study of integration of wind-solar hybrid energy system to the grid at the distribution level. Here the active power filter functionality has been added to the interfacing four leg inverter to reduce overall cost of the system. The system is studied under three different cases of RES=0, Load Demandd-Iq control strategy.Item Online voltage estimation and control for smart distribution networks(2016) Raghavendra, P.; Gaonkar, D.N.The increasing deployment of Distributed Generation (DG) technologies introduces power quality challenges to the grid, in particular steady state voltage rise at the connection point forDGunits. In most distribution networks, control and monitoring of grid parameters is missing, as well as system security is at risk. Smart grid technologies have the capability to realize the real-time measurements and on-load voltage controls. With the steady implementation of smart grid technologies throughout the existing distribution networks, the online voltage control can be achieved ensuring the power quality and voltage levels within the statutory limits. This study presents a methodology for the estimation of voltage profile in a smart distribution network with DG for the online voltage control, taking into account different line X/R ratios and laterals. This method is based on maximum and minimum voltage estimation by remote terminal units (RTUs) placed only at DG connected bus and at capacitor connected bus. Voltage regulation is carried out based on RTUs estimated values. This work is tested on two radial distribution networks with/without DGs and laterals. Comparative results for voltage magnitudes estimated with different methodology are presented. The reported simulation results show that the method presented is capable of estimating the voltage profile along the distribution network with DGs for the online voltage control, considering different line X/R ratios and laterals. © The Author(s) 2016.Item Impact of Different PQ Models of Wind Turbine Generating Units (WTGUs) on System Voltage Performance(Walter de Gruyter GmbH info@degruyter.com, 2017) Moger, T.; Dhadbanjan, T.This paper presents the voltage performance analysis of the system with various types of wind turbine generating units (WTGUs). A detailed voltage performance analysis is carried out by considering the different PQ models used for computing the reactive power output of the WTGUs (fixed/semi-variable speed and variable speed WTGUs). The different PQ models of fixed/semi-variable speed WTGUs incorporated for the studies are voltage dependent model, voltage independent model, power factor based model, and PX model. In addition, the variable speed WTGUs are also considered in different fixed power factor mode of operation. Based on these models, a comparative analysis is presented. A modified 27-bus equivalent distribution test system with dispersed wind generation is considered for the studies. Further, the case studies have been carried out by considering the various wind power output levels of WTGUs to examine its impact on system voltage performance. From the comparative analysis, the power factor based model can be the best choice over the other models (which are based on voltages) for the system studies with fixed/semi-variable speed WTGUs. © 2017 Walter de Gruyter GmbH, Berlin/Boston 2017.Item Design and Implementation of a Sensorless Multilevel Inverter with Reduced Part Count(Institute of Electrical and Electronics Engineers Inc., 2017) Sandeep, N.; Yaragatti, R.Y.This letter proposes a single-phase nine-level (9L) inverter topology suitable for grid-connected renewable energy systems. The proposed inverter is realized using a T-Type neutral-point-clamped inverter connected in cascade to a floating capacitor (FC) H-bridge. Additionally, two low-frequency switches are added across the dc-link enabling the inverter to generate a 9L waveform. A sensorless voltage control based on redundant switching state is developed and embedded with PWM controller, which is responsible for regulating the FC voltage at one-quarter of the dc source voltage. The proposed PWM technique employs the generation of 9L waveform without using any voltage sensor, thereby reducing the complexity of the overall control scheme. This, in turn, will make the overall system appealing for various industrial applications. In comparison to conventional and recent topologies, generation of the 9L waveform using a lower number of components is the notable contribution. Another important feature of the proposed inverter is that if FC H-bridge fails, it can be bypassed, and the inverter can still operate as a 5L inverter at its nominal power rating. Furthermore, a comprehensive comparison study is included which confirms the merits of the proposed inverter against those of other state-of-The-Art topologies. Finally, simulation and experimental results are included for validating the feasibility of the proposed system. © 1986-2012 IEEE.Item Operation and Control of an Improved Hybrid Nine-Level Inverter(Institute of Electrical and Electronics Engineers Inc., 2017) Sandeep, N.; Yaragatti, R.Y.This paper proposes a new nine-level inverter for medium- and high-power applications. The proposed topology comprises of a three-level (3L) active neutral-point-clamped (ANPC) inverter connected in series with a floating capacitor (FC) fed H-bridge. Besides, two additional switches operating at line frequency are appended across the dc link of the 3L ANPC structure. Compared with conventional hybrid cascaded inverters, the primary advantage of this addition is doubling of the resulting root mean square output voltage. This amelioration is achieved while preserving the standard 3L ANPC and H-bridge structures with minimum topological modification. A simple logic-gate-based voltage balancing scheme is developed to regulate the FC voltage. The proposed voltage balancing method is independent of load power factor, inverter modulation index, and can balance the voltage across FC instantaneously. The step-by-step formulation of logical expressions for the generation of gating pulses is deliberated in detail and can be generalized for any n-level inverter. Further, simulation results as well as the experimental measurements obtained from the laboratory prototype are presented to validate the effectiveness and practicability of the proposed configuration. Finally, the notable merits of the proposed inverter over the prior art topologies is established through a comprehensive comparative study. © 1972-2012 IEEE.Item An improved control strategy without current sensors for DSTATCOM(Inderscience Publishers, 2018) Saralaya, S.; Manjunatha Sharma, K.M.An improved control strategy based on power balancing algorithm without using current sensors is presented in this paper. The mathematical model of this improved method is discussed. Point of common coupling (PCC) voltage and DC link voltage are taken as voltage commands for reference signal generation. Sinusoidal pulse width modulation is used to generate the pulses for distribution static compensator (DSTATCOM). Proportional integral (PI) controller is used to control the PCC voltage and DC link voltage of the voltage source converter of DSTATCOM. This improved method is tested for different load conditions using PSCAD/EMTDC package. The improved control strategy is validated by simulation results for linear and non-linear load conditions. © © 2018 Inderscience Enterprises Ltd.Item A 20-Pulse Asymmetric Multiphase Staggering Autoconfigured Transformer for Power Quality Improvement(Institute of Electrical and Electronics Engineers Inc., 2018) P, P.; Kalpana, R.; Singh, B.; Bhuvaneswari, G.This letter presents a 20-pulse multiphase staggering autoconfigured transformer (MSAT) for power quality improvement in medium and high power applications. The proposed autoconfigured transformer is a combination of delta and zig-zag transformers. Contrary to the prior art multipulse autoconnected transformers, magnetic rating of the proposed configuration is only 40% of the load rating in addition to improved power quality indices. Moreover, the creation of a neutral point ascribed to inbuilt zig-zag windings supplements as one of the remarkable advantages of the proposed MSAT. Therefore, with this suggested configuration, the performance of zig-zag transformer is accomplished within the autoconfigured transformer. A detailed comparison of the proposed MSAT configuration with that of other multipulse autoconnected transformers in terms of magnetic rating and power quality indices are presented. Further, the feasibility and operability of the proposed MSAT are verified and validated through experimental tests on the laboratory prototype. The test results so obtained complies with the IEEE-519 and IEC 61000-3-2 standards on power quality requirements. © 2017 IEEE.Item Operation and Control of a Nine-Level Modified ANPC Inverter Topology with Reduced Part Count for Grid-Connected Applications(Institute of Electrical and Electronics Engineers Inc., 2018) Sandeep, N.; Yaragatti, U.R.This paper presents a nine-level active-neutral-point-clamped (ANPC) based multilevel inverter (MLI) topology for grid-connected applications requiring only ten switches. The envisaged structure comprises two parts, namely five-level ANPC unit, and a two-level converter leg whose midpoint is used as another ac terminal. An ad hoc switching state redundancy based modulation strategy is used to ensure that the voltage across the flying capacitor is tightly balanced and is implemented using a look-up table further simplifies the control complexity. The performance and effectiveness of the proposed topology with its control scheme are validated through simulations and experimental tests. Comparison with other MLIs is included to highlight the merits of the proposed topology. From the results, it will be shown that the proposed inverter requires the least part count as compared to other topologies with the same performance and output quality. © 1982-2012 IEEE.Item A Switched-Capacitor-Based Multilevel Inverter Topology with Reduced Components(Institute of Electrical and Electronics Engineers Inc., 2018) Sandeep, N.; Yaragatti, U.R.This letter presents an improved sensorless nine-level inverter topology with reduced number of components. It is formed by cascading a three-level T-Type neutral clamped point inverter with a floating capacitor (FC) fed two-level converter unit. Additionally, two line-frequency switches are appended across the dc-link. A simple logic-form equations-based pulse width modulator is designed which is in-charge of maintaining the FC voltage at its reference value without any aid of voltage and current sensor. Thus, the complexity in control of the proposed topology is very minimal. The working principle of the proposed inverter and formulation of logic-form equations is deliberated in detail. Furthermore, experimental results obtained from the developed prototype are presented to validate feasibility and operability of the proposed topology. Finally, a comprehensive comparison with some of the recently reported inverter topologies proving the merits of the proposed topology is included. © 1986-2012 IEEE.