S. P. Singh

Bio: S. P. Singh is an academic researcher from Kamla Nehru Institute of Technology. The author has contributed to research in topics: Direct torque control & Vector control. The author has an hindex of 9, co-authored 26 publications receiving 413 citations. Previous affiliations of S. P. Singh include Motilal Nehru National Institute of Technology Allahabad & Regional Institute of Ophthalmology.

Multilevel inverters: A literature survey on topologies and control strategies

Abstract: Multilevel inverters have been attracting in favor of academia as well as industry in the recent decade for high-power and medium-voltage energy control. In addition, they can synthesize switched waveforms with lower levels of harmonic distortion than an equivalently rated two-level converter. The multilevel concept is used to decrease the harmonic distortion in the output waveform without decreasing the inverter power output. This paper presents the most important topologies like diode-clamped inverter (neutral- point clamped), capacitor-clamped (flying capacitor), and cascaded multilevel with separate dc sources. This paper also presents the most relevant modulation methods developed for this family of converters: multilevel sinusoidal pulse width modulation, multilevel selective harmonic elimination, and space-vector modulation. Authors strongly believe that this survey article will be very much useful to the researchers for finding out the relevant references in the field of topologies and modulation strategies of multilevel inverter.

Marker Assisted Breeding to Develop Multiple Stress Tolerant Varieties for Flood and Drought Prone Areas

Abstract: Climate extremes such as drought and flood have become major constraints to the sustainable rice crop productivity in rainfed environments. Availability of suitable climate-resilient varieties could help farmers to reduce the grain yield losses resulting from the climatic extremities. The present study was undertaken with an aim to develop high-yielding drought and submergence tolerant rice varieties using marker assisted introgression of qDTY1.1, qDTY2.1, qDTY3.1 and Sub1. Performance of near isogenic lines (NILs) developed in the background of Swarna was evaluated across 60 multi-locations trials (MLTs). The selected promising lines from MLTs were nominated and evaluated in national trials across 18 locations in India and 6 locations in Nepal. Grain yield advantage of the NILs with qDTY1.1 + qDTY2.1 + qDTY3.1 + Sub1 and qDTY2.1 + qDTY3.1 + Sub1 ranged from 76 to 2479 kg ha− 1 and 396 to 2376 kg ha− 1 under non-stress (NS) respectively and 292 to 1118 kg ha− 1 and 284 to 2086 kg ha− 1 under reproductive drought stress (RS), respectively. The NIL, IR96322–34-223-B-1-1-1-1 having qDTY1.1 + qDTY2.1 + qDTY3.1 + Sub1 has been released as variety CR dhan 801 in India. IR 96321–1447-651-B-1-1-2 having qDTY1.1 + qDTY3.1 + Sub 1 and IR 94391–131–358-19-B-1-1-1 having qDTY3.1 + Sub1 have been released as varieties Bahuguni dhan-1′ and ‘Bahuguni dhan-2’ respectively in Nepal. Background recovery of 94%, 93% and 98% was observed for IR 96322–34-223-B-1-1-1-1, IR 96321–1447-651-B-1-1-2 and IR 94391–131–358-19-B-1-1-1 respectively on 6 K SNP Infinium chip. The drought and submergence tolerant rice varieties with pyramided multiple QTLs can ensure 0.2 to 1.7 t ha− 1 under reproductive stage drought stress and 0.1 to 1.0 t ha− 1 under submergence conditions with no yield penalty under non-stress to farmers irrespective of occurrence of drought and/or flood in the same or different seasons.

Investigation of performance parameters of PMSM drives using DTC-SVPWM technique

Abstract: The direct torque control space vector pulse width modulation (DTC-SVPWM) theory has achieved great success in the speed control of PMSM drives. A DTC-SVPWM technique of PMSM has been presented in this paper. Based on in-depth analysis of PMSM mathematical model in a-b-c frame and α-β frame are established and the operation principle of DTC-SVPWM system, the relationships between the torque and fundamental components. A novel SVPWM technique which has a feature of low harmonic is proposed. The proposed technique is adopted to design the DTC-SVPWM of a three-phase PMSM drives. A large number of simulation results show that the DTC-SVPWM technique of PMSM drives having good dynamic performance. Aiming at the DTC-SVPWM technique in PMSM drives, in this paper explained the theoretical basis of the DTC for PMSM firstly, and then explained the difference between the applications of DTC-SVPWM to PMSM drives. Finally the MATLAB/Simulink models were developed to examine the DTC-SVPWM for PMSM drives for enhancement of performance parameters of such motors. This article is very useful for researchers and scientific engineers for extending the research work in this area.

Relationship of anatomic landmarks with occlusal plane.

Abstract: Purpose : Evaluation of relationship between various anatomical landmarks and the occlusal plane in the natural dentition that could be used for establishing the occlusal plane in complete dentures. Methods : The study comprised of 100 dentulous subjects with all healthy permanent teeth in normal arch form and alignment. Three instruments were custom-made for the purpose : the occlusal plane analyzer to check the parallelism of the ala-tragus lines,and the interpupillary line, the buccinator groove relator and the level analyzer for the level of the linea alba buccalis with the occlusal plane. For the retromolar pad area a metallic scale was used. Results : Within limitations of this study, it was observed that, only 13% subjects showed occlusal plane parallel to the interpupillary line. The posterior reference point of Camper's line was middle point for 72% of males and superior point for 80% of females. Intraorally, 68% of subjects have the occlusal plane at the same level as that of buccinator groove and 77% of the subjects had the occlusal plane at the middle one-third of retromolar pad area. Interpretation and Conclusions : It was concluded that: the occlusal plane is parallel to Camper's plane posterior reference point as the superior point of tragus in females and middle point in males. The occlusal plane is not generally parallel to the interpupillary line. Intra-orally, the level of buccinator groove is reliable, while variations in retromolar pad area make it an unreliable landmark for orienting the occlusal plane.

A comprehensive review on hybrid electric vehicles: architectures and components

Abstract: The rapid consumption of fossil fuel and increased environmental damage caused by it have given a strong impetus to the growth and development of fuel-efficient vehicles. Hybrid electric vehicles (HEVs) have evolved from their inchoate state and are proving to be a promising solution to the serious existential problem posed to the planet earth. Not only do HEVs provide better fuel economy and lower emissions satisfying environmental legislations, but also they dampen the effect of rising fuel prices on consumers. HEVs combine the drive powers of an internal combustion engine and an electrical machine. The main components of HEVs are energy storage system, motor, bidirectional converter and maximum power point trackers (MPPT, in case of solar-powered HEVs). The performance of HEVs greatly depends on these components and its architecture. This paper presents an extensive review on essential components used in HEVs such as their architectures with advantages and disadvantages, choice of bidirectional converter to obtain high efficiency, combining ultracapacitor with battery to extend the battery life, traction motors’ role and their suitability for a particular application. Inclusion of photovoltaic cell in HEVs is a fairly new concept and has been discussed in detail. Various MPPT techniques used for solar-driven HEVs are also discussed in this paper with their suitability.

Assessment of convection, hot-air combined with microwave-vacuum and freeze-drying methods for mushrooms with regard to product quality

Abstract: Summary Combined drying of hot air and microwave-vacuum has been proposed as an alternative method to improve the quality of dried mushrooms, especially the structural and textural properties. In the present study, the effect of different drying methods namely, convective hot-air drying, hot air combined with microwave-vacuum drying and freeze-drying on qualitative attributes of pretreated mushrooms was investigated. The quality assessment was based on colour, texture, density, porosity and rehydration characteristics of the dried mushrooms. Combined drying of hot air and microwave-vacuum resulted in a dried product of superior quality when compared to the slices dried completely by conventional hot air, exhibiting lower overall colour variation, higher porosity, greater rehydration ratio and softer texture. In a dry state, mushrooms with a puffy structure and unique crispy texture were created by the combined drying method, which might be considered as important characteristics for developing nonfat snack-type food products.

A multilevel voltage-source converter system with balanced DC voltages

Abstract: In this paper, a multilevel voltage-source converter system is proposed for high-voltage, high-power applications such as back-to-back interconnection of power systems, large induction motor drives, and electrical traction drives. Multilevel voltage-source converters have a voltage unbalance problem in the DC capacitors. The problem may be solved by use of additional voltage regulators or separate DC sources. However, these solutions are found not to be practicable for most applications. The proposed converter system can solve the voltage unbalance problem of the conventional multilevel voltage-source converters, without using any additional voltage balance circuits or separate voltage sources. The mechanism of the voltage unbalance problem is analyzed theoretically in this paper. The voltage unbalance problem of multilevel converters in the DC capacitors has been solved by the proposed internal connections of the AC/DC and DC/AC converters. The validity of the new converter system is demonstrated by simulation and experiment. >

Multilevel Inverter Topology for Renewable Energy Grid Integration

Abstract: In this paper, a novel three-phase parallel grid-connected multilevel inverter topology with a novel switching strategy is proposed. This inverter is intended to feed a microgrid from renewable energy sources (RES) to overcome the problem of the polluted sinusoidal output in classical inverters and to reduce component count, particularly for generating a multilevel waveform with a large number of levels. The proposed power converter consists of $n$ two-level $(n+1)$ phase inverters connected in parallel, where $n$ is the number of RES. The more the number of RES, the more the number of voltage levels, the more faithful is the output sinusoidal waveform. In the proposed topology, both voltage pulse width and height are modulated and precalculated by using a pulse width and height modulation so as to reduce the number of switching states (i.e., switching losses) and the total harmonic distortion. The topology is investigated through simulations and validated experimentally with a laboratory prototype. Compliance with the $\text{IEEE 519-1992}$ and $\text{IEC 61000-3-12}$ standards is presented and an exhaustive comparison of the proposed topology is made against the classical cascaded H-bridge topology.

A Capacitor Voltage-Balancing Method for Nested Neutral Point Clamped (NNPC) Inverter

Abstract: A capacitor voltage-balancing method for a nested neutral point clamped (NNPC) inverter is proposed in this paper. The NNPC inverter is a newly developed four-level voltage-source inverter for medium-voltage applications with properties such as operating over a wide range of voltages (2.4–7.2 kV) without the need for connecting power semiconductor in series and high-quality output voltage. The NNPC topology has two flying capacitors in each leg. In order to ensure that the inverter can operate normally and all switching devices share identical voltage stress, the voltage across each capacitor should be controlled and maintained at one-third of dc bus voltage. The proposed capacitor voltage-balancing method takes advantage of redundancy in phase switching states to control and balance flying capacitor voltages. Simple and effective logic tables are developed for the balancing control. The proposed method is easy to implement and needs very few computations. Moreover, the method is suitable for and easy to integrate with different pulse width modulation schemes. The effectiveness and feasibility of the proposed method is verified by simulation and experiment.