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A Study on the Evolution of Solid State Transformer Technologies and Applications
Nithin Kolli,Sanket Parashar,Raj Kumar Kokkonda,Apoorv Agarwal,Anup Anurag,Subhashish Bhattacharya 전력전자학회 2023 ICPE(ISPE)논문집 Vol.2023 No.-
The advancements in power electronics have enabled the building of solid-state transformers (SSTs) to meet the demands of smart grids. An SST is an AC/AC solid-state power conversion system. Typically these SSTs can be classified based on various parameters like series/parallel interconnection, number of power conversion stages, degree of phase modularity, etc. This paper presents a survey of the work carried out to date on SSTs with multi-stage power conversion. Furthermore, the paper highlights the SSTs that enable medium voltage grid interconnection, which is enabled by high voltage (HV) SiC power devices. The design, control, development, and testing of SST with HV SiC 10 kV MOSFETs and 15 kV SiC IGBTs are presented, and a pilot demonstration for the Navy of a medium voltage (MV) 4160 V, 100 kVA SST for “Mobile Utility Support Equipment (MUSE)” based applications enabled by SiC 10 kV MOSFETs will be discussed. A Medium-Voltage Asynchronous Microgrid Power Conditioning System (Microgrid PCS), or MV-MV SST, enabled by HV SiC series-connected power devices to connect, disconnect, and enable power flow between asynchronously connected microgrids and grids is presented. The paper addresses the developed SST prototypes and provides analysis based on the related applications. The analysis also discusses the challenges and future trends regarding the implementation of SST.
The Need for Rebuilding the Temple in Haggai 1:1-11 : An Impetus for Temple-centered Life
anuel G. M. Kollie 삼육대학교 신학연구소 2020 신학과 학문 Vol.28 No.-
When Israel returned from their exile sojourn, The rebuilding of the destroyed temple in the post-exilic era was yet God’s priority. The need for the rebuilding of the various temples created an impetus for a temple-centered life at all times by God. These moves seemed to be paramount in God’s mission to reconnect the spiritual state of Israel as peculiar people. This paper aims to exegetically investigate Haggai 1:1-11 in order to established the reasons why God had shown so much interest in a temple center life for His people, the usefulness and sacredness of the temple, and the theological implication of a temple-centered life for Christian believers.
Comparison of ANN- and GA-based DTC eCAR
Banda, Gururaj,Kolli, Sri Gowri The Korean Institute of Power Electronics 2021 JOURNAL OF POWER ELECTRONICS Vol.21 No.9
In this paper, an artificial intelligence (AI)-integrated direct torque control (DTC) scheme is developed for an electric vehicle (EV or eCAR) propulsion motor drive. In addition, a comparison is made between adaptive neural network (ANN) and genetic algorithm (GA)-based torque controllers. The integration of AI into EVs has attracted the attention of many researchers in terns if drive control, dynamic stability, speed estimation, and energy management strategies. Amidst the various motor drive control strategies, DTC schemes with space vector pulse width modulation (SVPWM) have gained prominence due to its fast torque (speed) control capability. The smooth control of a DTC-eCAR propulsion motor is accomplished by the use of AI algorithms. The applications of ANN and GA algorithms for tuning the torque controller are tested and the behavior of an eCAR in terms of drive range, percentage of state of charge (SOC), and energy consumption for different driving conditions is observed using MATLAB simulations.
Sanket Parashar,Nithin Kolli,Raj Kumar Kokkonda,Subhashish Bhattacharya 전력전자학회 2023 ICPE(ISPE)논문집 Vol.2023 No.-
This research article presents a thorough investigation of the 3 Level - 3 Phase (3L-3P) Neutral Point Clamped (NPC) Dual Active Bridge (DAB) topology for designing Medium Voltage (MV) DC isolators. An equivalent circuit model is utilized to provide a detailed analysis of the switching transition at specific operating points, including α = 60° , 0 < φ < 90° (φ≠ 60° ) α = 60°, φ = 60°. These operating points not only ensure optimal performance but also minimize the Common Mode (CM) current injected into the operating environment. The article also employs the model to evaluate the minimum current required for Zero Voltage Switching (ZVS) operation, snubber current during turn transition, and the loss in the snubber resistor. Furthermore, the article proposes a dynamic voltage balancing algorithm that significantly reduces DC offset by 80% and switching losses by 50% through precise turn-off Vds mismatch across MOSFETs and Diodes within a specified limit of 100V. The accuracy of the model used in the proposed algorithm is validated through experimental turn-off waveforms of SiC MOSFET at 1.75kV. The article introduces experimental test benches to examine the impact of base plate capacitance (Cbs) on the voltage mismatch and snubber losses in the 3L pole, providing valuable insights into the behavior of the topology under various conditions. The experiments are conducted up to 6kV DC bus voltage, and the snubber loss and dynamic voltage mismatch across series connected MOSFETs and diodes are evaluated and validated through the theoretical model.
van Rosendael, Alexander R.,Maliakal, Gabriel,Kolli, Kranthi K.,Beecy, Ashley,Al’Aref, Subhi J.,Dwivedi, Aeshita,Singh, Gurpreet,Panday, Mohit,Kumar, Amit,Ma, Xiaoyue,Achenbach, Stephan,Al-Mallah, Mou Elsevier 2018 Journal of cardiovascular computed tomography Vol.12 No.3
<P><B>Abstract</B></P> <P><B>Introduction</B></P> <P>Machine learning (ML) is a field in computer science that demonstrated to effectively integrate clinical and imaging data for the creation of prognostic scores. The current study investigated whether a ML score, incorporating only the 16 segment coronary tree information derived from coronary computed tomography angiography (CCTA), provides enhanced risk stratification compared with current CCTA based risk scores.</P> <P><B>Methods</B></P> <P>From the multi-center CONFIRM registry, patients were included with complete CCTA risk score information and ≥3 year follow-up for myocardial infarction and death (primary endpoint). Patients with prior coronary artery disease were excluded. Conventional CCTA risk scores (conventional CCTA approach, segment involvement score, duke prognostic index, segment stenosis score, and the Leaman risk score) and a score created using ML were compared for the area under the receiver operating characteristic curve (AUC). Only 16 segment based coronary stenosis (0%, 1–24%, 25–49%, 50–69%, 70–99% and 100%) and composition (calcified, mixed and non-calcified plaque) were provided to the ML model. A boosted ensemble algorithm (extreme gradient boosting; XGBoost) was used and the entire data was randomly split into a training set (80%) and testing set (20%). First, tuned hyperparameters were used to generate a trained model from the training data set (80% of data). Second, the performance of this trained model was independently tested on the unseen test set (20% of data).</P> <P><B>Results</B></P> <P>In total, 8844 patients (mean age 58.0 ± 11.5 years, 57.7% male) were included. During a mean follow-up time of 4.6 ± 1.5 years, 609 events occurred (6.9%). No CAD was observed in 48.7% (3.5% event), non-obstructive CAD in 31.8% (6.8% event), and obstructive CAD in 19.5% (15.6% event). Discrimination of events as expressed by AUC was significantly better for the ML based approach (0.771) vs the other scores (ranging from 0.685 to 0.701), P < 0.001. Net reclassification improvement analysis showed that the improved risk stratification was the result of down-classification of risk among patients that did not experience events (non-events).</P> <P><B>Conclusion</B></P> <P>A risk score created by a ML based algorithm, that utilizes standard 16 coronary segment stenosis and composition information derived from detailed CCTA reading, has greater prognostic accuracy than current CCTA integrated risk scores. These findings indicate that a ML based algorithm can improve the integration of CCTA derived plaque information to improve risk stratification.</P>
Sayan Acharya,Anup Anurag,Nithin Kolli,Subhashish Bhattacharya 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5
To ramp up the adaptation of the highly optimized high current 1.2 kV Sillicon Carbide (SiC) based Metal Oxide Semiconductor Field Effect Transistor (MOSFET) power modules, a high power three-phase two-level power block is designed which is rated at 100 kVA and operates with 800 V DC bus. The power modules combined with low inductance busbar and optimized loop thermo-syphon based heatsink extracts the full performance of the power electronic switches. In this paper, the design details of the power block is presented. Furthermore, the performance of the power block is qualified by a back-to-back pump back test set up where two power blocks are interconnected via inductors. Furthermore, closed loop voltage and current control are implemented to circulate the desired amount of AC current between the power blocks. Moreover, heat run tests are carried out to quantify the thermal performance of the thermal management system. The experimental results demonstrate the performance benefits of the power block.
A Study on Carbon Sequestration Index as a Tool to Determine the Potential of Greenbelt
Tamanna Parida,Shaik Riyazuddin,Sailesh Ram Agnihotri,Suresh Kumar Kolli,Namuduri Srinivas 인간식물환경학회 2022 인간식물환경학회지 Vol.25 No.4
Background and objective: Carbon is crucial in the biological world, especially in plants. It helps grow plants and stores the absorbed carbon in terms of biomass. In the biogeochemical cycle, carbon gets neutralized in the environment. The increase in population is responsible for the amplified concertation of greenhouse gas (GHG) into the atmosphere, which leads to maximized CO2 concentration, and consequences global temperatures. Trees play a critical role in the sequestration of carbon from the atmosphere. The objective of the present study is to evaluate the potential of carbon sequestration in urban roadside tree species using the Carbon Sequestration Index as a tool (CSI). Methods: Biophysical estimations such as diameter at breast height (DBH), height, and above and below-ground biomass were measured to assess the carbon sequestration potential of a tree. Results: Results revealed that the potential species present in large numbers are Pongamia pinnata, Azadirachta indica, and Spathodea campanulata. Based on Carbon Sequestration Index results, it is found that Pongamia pinnata and Azadirachta indica act as keystone species in this area and are better than others in removing GHG emissions. The study has also considered the requirement of a total number of trees to neutralize the whole GHG emission of the study area. Conclusion: The total GHG emission of our study area is 39599 kg/yr, where 1041 trees are present inside the boundary, and the entire carbon sequestration is 475921.5 kg/yr. Only 86 trees are sufficient to offset the total GHG emission from this area, whereas 955 trees are surplus for this place.