Ravishankar Deekshit

State-feedback control of a voltage source inverter-based STATCOM

STATic synchronous COMpensator (STATCOM) which is used for reactive power control, has the capability for voltage regulation of grid voltage at the point of common coupling (PCC). This is achieved either by injection or absorption of certain amount of reactive power. This control method is efficiently faster in tackling the voltage fluctuating problems[1]. Based on inverter configuration there are two types of STATCOM: Voltage source inverter (VSI) - based and current source inverter (CSI)-based STATCOM[2]. The closed loop feedback controller can be designed to meet different objectives. Conventional Proportional Integral (PI) controllers produce satisfactory response, provided the parameters kp and ki are well tuned. State feedback controller using the d-q reference frame can be designed to give a satisfactory dynamic response. In this paper, state feedback control method is proposed for VSI based STATCOM. Simulation results using MATLAB/Simulink indicate superior dynamic response with the proposed controller.

Performance analysis of a voltage source converter HVDC system connected to an independent power generating station

This paper presents the mathematical model and analysis of a complete VSC-HVDC system. At sending end, AC power is supplied from a generating station to VSC- HVDC and to an AC line connected to Central grid. Constant power controller for the VSC HVDC system is designed to transfer a definite amount of power on DC link. To ensure constant DC voltage in the DC link, DC voltage controller is used in the inverter side of the DC link. In both converters, reactive power controllers are used to ensure the exchange of reactive power between the converter and the AC system. The reactive power requirement at the inverter side of the VSC-HVDC link is derived from the AC voltage controller. Independent control of active and reactive power is implemented in the model. In the literature, very few papers are available which discuss the performance of VSC HVDC implementing all the four controllers. However, in this paper, a detailed mathematical analysis for the system under consideration is discussed. Two level converter structure is employed to analyze the performance of different controllers designed. The simulation results show that, dynamic control of the rectifier and inverter is achieved with fast response. It is also shown that, the power flow control in AC line is improved due to the power controllability in the DC link.

RANDOM NOISE CANCELLATION IN BIOMEDICAL SIGNALS USING VARIABLE STEP SIZE GRIFFITH LMS ADAPTIVE LINE ENHANCER

This paper presents a new method of random noise cancellation for removing artefacts from biomedical signals using an adaptive line enhancer (ALE). The ALE is implemented using proposed time domain variable step size Griffith least mean square (VSGLMS) algorithm. The technique is based on the adaptation of the gradient of the error surface. The method makes both the step size and the gradient free from observation noise and reduces the gradient mis-adjustment error. Here, both the gradient and the scale factor for the step size are free from the input noise effects, which makes the algorithm robust to both stationary and non-stationary observation noise. Further the additional computational load involved for this is marginal. The VSGLMS adaptive filter technique for ALE is tested on noise cancellation of two types of bio-medical signals — separation of electro cardiogram (ECG) signal from a background of electro myogram (EMG) and heart sound signal (HSS) from lung sound signal (LSS). Application of VSGLAM...

A simple algorithm for fast detection and quantification of voltage deviations using space vectors

This paper presents the use of the concept of space vector representation of three phase quantities, effectively in the detection and quantification of voltage disturbances such as sags, swells, and interruptions in three phase supply systems. The algorithm involves the transformation of the space vector along the stationary reference frame α-β, as two alternating components orthogonal to each other. The resultant of these orthogonal components the resultant space vector, is sensed at every sampling instant. The magnitude of the resultant space vector has a fixed value under normal conditions. Deviations from this value during disturbances are measured. This is further processed, to generate a trigger signal. The trigger thus generated, can facilitate classification of the type of disturbance, quantification of its magnitude, instant of occurrence, as well as duration needed for a parameters recorder. This can also be used in conjunction with the main control system of a DVR (Dynamic voltage restorer), or a power line conditioner for mitigation purposes. The test of the algorithm was successfully done in Matlab / Simulink.

Analysis of VSC-HVDC system connected to a weak AC system

Modeling of a VSC-HVDC system is an important step in analyzing the performance of the VSC-HVDC system. In this paper, the modeling details of the converters and the DC transmission line connected to a weak AC system are presented. The weak AC system considered is an island system comprised of synchronous generators and some passive loads. For proper functioning of the system, controllers play a very important role. The details of computing the parameters of different controllers for the system under consideration are also presented in the paper. Simulations are carried out in MATLAB/Simulink/SimPowerSystems to test the performance of the controllers for the model of VSC-HVDC system feeding power to the island system, and the results are presented.

Multiple-output magnetic feedback forward converter with discrete PWM for space application

This paper is aimed at design and development of fixed high frequency Forward Converter Topology operating at resonant reset mode for Space applications. This self-resonant reset mechanism eliminates power loss in the reset circuit, thus simplifying circuitry and increasing efficiency. The galvanic isolation between input and output is implemented with magnetic feedback which is insensitive to component tolerance, radiation and has good temperature stability. Due to unavailability of radiation hardened PWM IC at higher frequency (>500 KHz), discrete PWM controller has been implemented. Hence, magnetic feedback and discrete PWM controller meets the requirements of radiation for DC-DC Converter for space application. The proposed topology is demonstrated with an experimental prototype that delivers three outputs 5V/4A, ±15V/0.667A from an 18-50 V input with better than 75% at full efficiency.

Comparison of characterizing and data analysis methods for detecting abnormalities in ECG

The electrocardiogram (ECG) is an important bioelectrical signal which gives valuable information about the functional aspects of the heart both in normal and abnormal conditions. For several decades a considerable amount of research activity has been directed towards advancement in the clinical diagnosing of this disease using surface ECG and symptoms. This paper compares different methods that have evolved over the years for elimination of different types of noise present in ECG and for characterizing ECG for the detection of myocardial ischemia and infarction which is a life threatening heart disease. The first part of the review gives broad overview of the research undergone in the area of denoising methods deployed and second part describes different types of ischemia and methods to detect the disease using ECG.

Design and implementation of Current mode controlled multiple output flyback converter for military applications

This paper is aimed at the design and implementation of a high frequency, multiple output, and miniaturized converter for military applications. The implementation is done using the flyback topology in order to make the converter module compact. The proposed converter design illustrates how to achieve better line, load and cross regulations using post regulators. The converter is operated at a switching frequency of 400 KHz using UC1843 PWM Controller. A separate output bias winding is used for converter loop feedback. Primary side Current mode control scheme is attained by comparing input current with bias winding output to modulate the width of the pulses generated from PWM circuit. The converter is validated with an experimental setup which delivers three outputs with desired efficiency of 70%. A delay circuit is employed to maintain the time delay between the outputs. The flyback converter design is equipped with start-up series pass regulator circuit, inrush current limiting circuit, under voltage as well as over current protection circuits.

A transformative approach to capstone projects in engineering

Engineering Institutions provide a rich human capital that can source research and innovation. Organizations build further on this, to ultimately realize game changing products that makes a lot of difference in the lives of people. As a part of the engineering curriculum, many exciting capstone projects are currently being executed that contribute to the ecosystem of technological advancement. An explicit direction or vision in these pursuits with tangible benefits to all the stake holders can be brought forth through a transformative alternate approach at the institutional level. This paper presents a new paradigm that can bring about a sea change in the way projects are selected, executed and handed over to the industry /research for consummation on a larger scale. This can also lead to profound and lasting impacts in the learning experience.

DETECTION AND CLASSIFICATION OF SHORT DURATION DISTURBANCES

The smart grid will be rich with technologies and devices that work at every level of power generation, transmission, and distribution. PQ meters, and systemwide PQ monitoring will indeed contribute to clean power reaching the consumer. Consumer participation is a distinctive feature that promises sustained maintenance of power quality. It is in this context that, fast detection algorithms for detection of short duration disturbances play a vital role in the functioning of monitoring devices. The objective of this paper is to explore a simple cost effective method for fast detection and classification of short duration voltage disturbances, including transients applicable to low voltage power supply systems. The concept of space vector representation of three phase quantities, is used and is found effective for detecting most short duration disturbance types without any time delay. The magnitude of the resultant space phasor when sampled, reveals a lot about the disturbance type. The information thus obtained, may be utilized to trigger a disturbance recorder or can even be used to trigger the operation of a power line conditioner or a dynamic voltage restorer.