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A Zero Sequence Voltage Injection Method for Cascaded H-bridge D-STATCOM
Yarlagadda, Srinivasa Rao,Pathak, Mukesh Kumar The Korean Institute of Power Electronics 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.4
Load variations on a distribution line result in voltage fluctuations at the point of common coupling (PCC). In order to keep the magnitude of the PCC voltage constant at its rated value and obtain zero voltage regulation (ZVR), a D-STATCOM is installed for voltage correction. Moreover, the ZVR mode of a D-STATCOM can also be used to balance the source current during unbalanced loading. For medium voltage and high power applications, a D-STATCOM is realized by the cascaded H-bridge topology. In the ZVR mode, the D-STATCOM may draw unbalanced current and in this process is required to handle different phase powers leading to deviations in the cluster voltages. Zero sequence voltage needs to be injected for ZVR mode, which creates circulating power among the phases of the D-STATCOM. The computed zero sequence voltage and the individual DC capacitor balancing controller help the DC cluster voltage follow the reference voltage. The effectiveness of the control scheme is verified by modeling the system in MATLAB/SIMULINK. The obtained simulations are further validated by the experimental results using a dSPACE DS1106 and five-level D-STATCOM experimental set up.
Preliminary Modelling of Plasco Tower Collapse
Yarlagadda, Tejeswar,Hajiloo, Hamzeh,Jiang, Liming,Green, Mark,Usmani, Asif Council on Tall Building and Urban Habitat Korea 2018 International journal of high-rise buildings Vol.7 No.4
In a recent tragic fire incident, the Plasco Tower collapsed after an intense outburst of fire lasting for three and a half hours and claiming the lives of 16 firefighters and 6 civilians. This paper will present continuing collaborative work between Hong Kong Polytechnic University and Queen's University in Canada to model the progressive collapse of the tower. The fire started at the 10th floor and was observed to have travelled along the floor horizontally and through the staircase and windows vertically. Plasco Tower was steel structure and all the steel sections were fabricated by welding standard European channel or angle profiles and no fire protection was applied. Four internal columns carried the loads transferred by the primary beams, and box columns were constructed along the perimeter of the building as a braced tube for resisting seismic loading. OpenSees fibre-based sections and displacement-based beam-column elements are used to model the frames, while shell elements are used for the reinforced concrete floor slabs. The thermal properties and elevated temperature mechanical properties are as recommended in the Eurocodes. The results in this preliminarily analysis are based on rough estimations of the structure's configuration. The ongoing work looks at modeling the Plasco Tower based on the most accurate findings from reviewing many photographs and collected data.
Trinary asymmetric cascaded H bridge (1:3:9) multilevel inverter with self-balanced capacitor
Yarlagadda, Anil Kumar,Verma, Vimlesh The Korean Institute of Power Electronics 2022 JOURNAL OF POWER ELECTRONICS Vol.22 No.9
A single-phase trinary asymmetrical cascaded H-bridge (TACHB) inverter with a level doubling network (LDN) is proposed in this paper. It consists of a LDN and 'n' H bridges, where 'n' represents the number of DC sources. The TACHB-LDN generates N number of levels at the output voltage using log<sub>3</sub>(${\frac{N+1}{2}}$) DC sources, 4+4 log<sub>3</sub>(${\frac{N+1}{2}}$) switches, and a capacitor. The TACHB-LDN gives an improved power quality output when compared with the conventional trinary CHB inverter for a given number of DC sources. A detailed comparison analysis with existing topologies is presented to show the superiority of the proposed topology. The TACHB-LDN is verified in MATLAB/Simulink for the generation of a 17-level output voltage with two DC sources. The phase disposition level shift pulse width modulation (PD-LSPWM) technique is used to generate the required triggering pulse for the converter. The carrier frequency is considered to be the fundamental frequency to ensure low-frequency switching. Conduction and switching loss are analyzed with the help of PSIM software. The obtained simulation results are verified through a prototype model developed in the laboratory using dSPACE 1104. The total harmonic distortion (THD) of the 17-level output voltage waveform is found to be below 5% (IEEE 519 Standard). The efficiency of the prototype model under different loads is observed to be in the range of 93.65-97.35%.
A Zero Sequence Voltage Injection Method for Cascaded H-bridge D-STATCOM
Srinivasa Rao Yarlagadda,Mukesh Kumar Pathak 전력전자학회 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.4
Load variations on a distribution line result in voltage fluctuations at the point of common coupling (PCC). In order to keep the magnitude of the PCC voltage constant at its rated value and obtain zero voltage regulation (ZVR), a D-STATCOM is installed for voltage correction. Moreover, the ZVR mode of a D-STATCOM can also be used to balance the source current during unbalanced loading. For medium voltage and high power applications, a D-STATCOM is realized by the cascaded H-bridge topology. In the ZVR mode, the D-STATCOM may draw unbalanced current and in this process is required to handle different phase powers leading to deviations in the cluster voltages. Zero sequence voltage needs to be injected for ZVR mode, which creates circulating power among the phases of the D-STATCOM. The computed zero sequence voltage and the individual DC capacitor balancing controller help the DC cluster voltage follow the reference voltage. The effectiveness of the control scheme is verified by modeling the system in MATLAB/SIMULINK. The obtained simulations are further validated by the experimental results using a dSPACE DS1106 and five-level D-STATCOM experimental set up.
RP를 이용한 용접비드 형상예측 시스템 개발에 관한 연구
손준식,김일수,Yarlagadda, Prasad K.D.V.,박창언,성백섭,이진구,정호성 한국공작기계학회 2002 한국공작기계학회 춘계학술대회논문집 Vol.2002 No.-
Generally, the use of robots in manufacturing industry has been increased during the past decade. GMA (Gas Metal Arc) welding is an actively growing area and many new procedures have been developed for use with high strength alloys. One of the basic requirement for welding applications is to study relationships between process parameters and bead geometry. The objective of this paper is to develop a new approach involving the use of neural network and multiple regression methods in the prediction of bead geometry for GMA welding process and to develop an intelligent system that enables the prediction of bead geometry using Rapid Prototyping (RP) in order to employ the robotic GMA welding processes. This system developed using MATLAB/SIMULINK, could be effectively implemented not only for estimating bead geometry, but also employed to monitor and control the bead geometry in real time.
Shrutika L. Wadgaonkar,Yarlagadda V. Nancharaiah,Claus Jacob,Giovanni Esposito,Piet N.L. Lens 한국미생물학회 2019 The journal of microbiology Vol.57 No.5
Delftia lacustris is reported for the first time as a selenate and selenite reducing bacterium, capable of tolerating and growing in the presence of ≥ 100 mM selenate and 25 mM selenite. The selenate reduction profiles of D. lacustris were investigated by varying selenate concentration, inoculum size, concentration and source of organic electron donor in minimal salt medium. Interestingly, the bacterium was able to reduce both selenate and selenite under aerobic conditions. Although considerable removal of selenate was observed at all concentrations investigated, D. lacustris was able to completely reduce 0.1 mM selenate within 96 h using lactate as the carbon source. Around 62.2% unaccounted selenium (unidentified organo-selenium compounds), 10.9% elemental selenium and 26.9% selenite were determined in the medium after complete reduction of selenate. Studies of the enzymatic activity of the cell fractions show that the selenite/selenate reducing enzymes were intracellular and independent of NADPH availability. D. lacustris shows an unique metabolism of selenium oxyanions to form elemental selenium and possibly also selenium ester compounds, thus a potential candidate for the remediation of selenium-contaminated wastewaters in aerobic environments. This novel finding will advance the field of bioremediation of selenium-contaminated sites and selenium bio-recovery and the production of potentially beneficial organic and inorganic reactive selenium species.