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.

Single-insertion technique for anesthetizing the inferior alveolar nerve, lingual nerve, and long buccal nerve for extraction of mandibular first and second molars: a prospective study

Benny Joseph,Nithin Kumar,Suresh Vyloppilli,Shermil Sayd,KP Manojkumar,Depesh Vijaykumar 대한구강악안면외과학회 2020 대한구강악안면외과학회지 Vol.46 No.6

Objectives: Appropriate and accurate local anesthetic (LA) techniques are indispensable in the field of oral and maxillofacial surgery to obtain a satisfactory outcome for both the operating surgeon and the patient. When used alone, the inferior alveolar nerve block (IANB) technique requires supplemental injections like long buccal nerve block for extraction of mandibular molars leading to multiple traumatic experiences for the patient. The aim of this study was to anesthetize the inferior alveolar, lingual, and long buccal nerves with single-needle penetration requiring a minimal skillset such as administering a conventional IANB through introduction of the Benny Joseph technique for extraction of mandibular molars. Materials and Methods: This was a prospective study conducted in the Department of Oral and Maxillofacial Surgery, Kunhitharuvai Memorial Charitable Trust (KMCT) Dental College, Calicut, India. The duration of the study was 6 months, from June to November 2017, with a maximum sample size of 616 cases. The LA solution was 2% lignocaine with 1:100,000 adrenaline. The patients were selected from a population in the range of 20 to 40 years of age who reported to the outpatient department for routine dental extraction of normally positioned mandibular right or left first or second molars. Results: Of the 616 patients, 42 patients (6.8%) required re-anesthetization, a success rate of 93.2%. There were no complications such as hematoma formation, trismus, positive aspiration, and nerve injuries. None of the cases required re-anesthetization in the perioperative period. Conclusion: The Benny Joseph technique can be employed and is effective compared with conventional IANB techniques by reducing trauma to the patient and also requires less technique sensitivity.

Design Optimization and Performance Analysis of a Three-Phase Three-Level MVDC Bidirectional Isolator using Series-Connected 10kV SiC MOSFETs and 10kV SiC JBS diodes

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.

Comparison of the efficacy of amoxicillin-clavulanic acid with metronidazole to azithromycin with metronidazole after surgical removal of impacted lower third molar to prevent infection

Shermil Sayd,Suresh Vyloppilli,Krishna Kumar,Pramod Subash,Nithin Kumar,Sarfras Raseel 대한구강악안면외과학회 2018 대한구강악안면외과학회지 Vol.44 No.3

Objectives: The goal of the study was to investigate the clinical effects of amoxicillin-clavulanic acid (500+125 mg) with metronidazole 400 mg ad-ministered three times daily (Group I) versus azithromycin 500 mg administered once daily and with metronidazole 400 mg three times daily (Group II) for the prevention of postoperative infection following mandibular third molar surgical removal. Materials and Methods: The study design was a single-center prospective study. Patients who reported to the Department of Oral and Maxillofacial Surgery between February 2015 and January 2017 for removal of mandibular third molar were screened, and 108 patients were chosen. One surgeon carried out all procedures. Patients were prescribed antibiotics until the two groups contained a similar number of cases. Results: Our data showed that Group II had fewer incidences of surgical site infection, but with no statistical significance. Conclusion: Although both treatments are used routinely after removal of the mandibular third molar, neither is significantly better than the other.

A Short Preamble-Based Synchronization for QPSK/TDMA Satellite Receiver - Implementation on Multi-core DSP

Dileep K G,Pradeep Goutam,Laxmaiah P,Nithin Kumar S,Hari Prasad S V,Nithin B 대한전자공학회 2017 대한전자공학회 학술대회 Vol.2017 No.1

This paper demonstrates the implementation of a QPSK/Time Division Multiple Access (TDMA) satellite receiver using short preamble-based synchronization in the presence of timing, frequency and phase offsets, and with Additive White Gaussian Noise (AWGN). The detection and estimation of synchronization parameters of the received signal, i.e., frequency, phase and symbol timing, are highly dependent on the preamble of the burst. Moreover, computational complexity and acquisition time of the receiver are directly proportional to the preamble length. The implemented receiver uses a 64-bit short preamble for synchronization and gives better bit error rate (BER) performance at low signal to noise ratio (SNR), close to -3dB. The functional verification of the synchronization algorithm is done using Matlab simulations and the algorithm implementation uses fixed-point C. The receiver design has been prototyped for 4 TDMA channels in Texas Instruments (TI) multi-core C66x DSP. The design and implementation of this receiver have been done for C-DOT indigenous satellite project.