Anil Kumar Sharma's scientific contributions

HVDC power transmission is coming up with merits to replace the EHV-AC system. The controller inverter operation can successfully regulate the power in HVDC link leading to fulfillment ofpower demand in A.C. networks caused by sudden rise in loading. Since overloading and unloading both lead to the departure of operating frequency below or above normal, its control for normalization isexercised through control of power flow in HVDC Link. Also the same is achieved by adjusting firing delay angle intelligently. This paper aims at providing automation to frequency normalization after it hasundergone changes from normal value of 50 Hz, due to sudden and sustained increase in load or due to working of generations at increased loads in H.V.D.C transmission systems. It is planned to automate the restoration of departed frequency to normal value by arranging the change in firing delay angle i.e. α of the converter of H.V.D.C. link till the increased load demand is met with. An adaptive control system has been devised which controls the firing delay angle on the basis of decisions given by a fuzzy controller. Also the fuzzy controls are decided by the departure in frequency from normal. The results have been found to be encouraging.

In this paper the current mode approach called “Current Conveyor (CCII+)” has been incorporated to design and simulate the circuit for producing two amplitude matched anti-phase sine waveforms which are frequently used in various communication and instrumentation systems. PSpice simulation has been used to depict the output waveforms. The power supply used is ±2.5 V which can be easily incorporated with CMOS IC technology. The designed circuit has been simulated at variousfrequency ranges and the waveforms are obtained after the circuit is optimized.

The electrocardiogram (ECG) is quite important tool to find out more information about the heart. The main tasks in ECG signal analysis are the detection of QRS complex (i.e. R wave), and the estimation ofinstantaneous heart rate by measuring the time interval between two consecutive R-waves. After recognizing R wave, other components like P, Q, S and T can be detected by using window method. In this paper, we describe a QRS complex detector based on the Dyadic wavelet transform (DyWT) which is robust in comparison with time- varying QRS complex morphology and to noise. We illustrate the performance of the DyWT-based QRS detector by considering problematic ECG signals from Common Standard for Electrocardiography (CSE) database. We also compare and analyze its performance to some of the QRS detectors developed in the past.

In this paper a modified CMOS positive second-generation current conveyor (CCII+) based resistance-capacitance (RC) Sinusoidal Oscillator operating over a wide frequency range is described. The proposed circuit consists of two CCII+, two buffers, four resistors and two capacitors. The oscillation conditions and the frequency of oscillations can be adjusted independently by two control resistors. Though the CCII's are available from commercial monolithic IC's viz. AD 844, PA 630, PA 630A and CCII01, but user doesn't have the access to control high frequency response, linear current gain, large output impedance, current biasing etc, in the basic internal circuit. The designed RC oscillator is desirable for VLSI realization. The power supply voltage used in the circuit were balanced and adjusted to Vdd = + 2.5V and VSS = -2.5 V. The output waveforms presented and the results discussed in the paper are the simulated outcomes of the proposed circuit, carried out using CADENCE and OrCAD Version-10 software.

Summary The life of a transformer is basically the life of dielectric of the transformer. Many a times the transformers don't survive their normal life though they work under non-faulty and normal operating conditions. This is because of the slow but continuous degradation of the quality of dielectric. The process is known as ageing process. The breakdown test of the transformer using H.V. supply does not give the reasons which leads to the failure of the transformer much before the expiry of nominal expected life. Also the H.V. testing is destructive & therefore un economical. The researchers have therefore focused on nondestructive testing of H.V. dielectrics such as c-Tan δ testing, partial discharge testing and insulation resistance measurement under d.c. voltage etc. In the present work the Tan δ measurements of the dielectric have been made at regular intervals of time. The monitoring of Tan δ reveals that with usage, its value keeps on increasing and when it crosses the threshold value, the dielectric of the transformer and therefore the transformer ceases to survive its useful life. Efforts have been made to estimate the life of transformer using the mathematical model and also using the MATLAB based ANN. It is basically the back-propagation network in ANN, which has been used. Also the use of ANN successfully maps all the factors affecting the life of dielectric and yield's reliable information about the life of dielectric. The mathematical model uses the fuzzy c- mean value of Tan δ, while the ANN is required to be trained before testing it, for providing the life of the transformer.