Performance evaluation of partial mixing anaerobic digester

N. Stalin and H. J. Prabhu

All fermentation reactions are autocatalytic in nature. In autocatylic reactions, the products act as a catalyst. Fermentation reactions are carried out in the reactors, during this reaction it generate methane gas or biogas. In the exiting biogas plants gas production per m3 of volume is less and Hydraulic Retention Time is more than 60 days and additional power required for circulation of slurry in the digester. The exiting biogas plants are constructed based on either mixed flow or Plug flow model where the self circulating biogas plant designed based on mixed flow followed by plug flow reactor. It gives a better performance than either mixed or plug flow reactors, because of partial mixing. The autocatalytic reaction requires partial pumbing for fast reaction, which need the source of power. The fermentation process takes nearly 60 days to complete, it is a very slow reaction. For self-mixing, the density difference is to be maintained in the reactor. The difference in density can either be created by pumping or by bubbling biogas through the reactor, requiring additional power. The increase in microbe concentration could be achieved by immobilizing microbes on carriers. The immobilized bacteria in the central column increase the biogas production rate and hence the lower density is maintained than the outside column. An increase in concentration in some section of the digester could lead to more generation of gas. The bubbling gas reduces the bulk density considerably causing hydrostatic pressure difference in density is responsible for the circulation of slurry in the digester. In order to achieve this, a tube of diameter roughly to one third of the diameter and volume equal to 10.7% of total volume is fitted at the centre of digester. It is filled with washed and broken burnt bricks. The bricks act as an adsorbent, immobilizing microbes. In addition, the bricks acting as bio filters increase the gas generation by 60%. Two digesters having an effective volume of 200 litres- One digester is constructed with central tube filled with biofilters and another digester constructed without central tube. 3.5 Kg of cow dung with 3.5 liters of water is added daily. On steady state condition, this recycle reactor has yielded nearly 60% increases in gas generation compare with conventional model, proving our assumption namely “Self circulation by density difference or a partial mixing digester would perform well”.

Simulation of D-STATCOM and DVR in power systems

S.V Ravi Kumar and S. Siva Nagaraju

A Power quality problem is an occurrence manifested as a nonstandard voltage, current or frequency that results in a failure or a mis-operation of end user equipments. Utility distribution networks, sensitive industrial loads and critical commercial operations suffer from various types of outages and service interruptions which can cost significant financial losses. With the restructuring of power systems and with shifting trend towards distributed and dispersed generation, the issue of power quality is going to take newer dimensions. In developing countries like India, where the variation of power frequency and many such other determinants of power quality are themselves a serious question, it is very vital to take positive steps in this direction .The present work is to identify the prominent concerns in this area and hence the measures that can enhance the quality of the power are recommended. This work describes the techniques of correcting the supply voltage sag, swell and interruption in a distributed system. At present, a wide range of very flexible controllers, which capitalize on newly available power electronics components, are emerging for custom power applications. Among these, the distribution static compensator and the dynamic voltage restorer are most effective devices, both of them based on the VSC principle. A DVR injects a voltage in series with the system voltage and a D-STATCOM injects a current into the system to correct the voltage sag, swell and interruption. Comprehensive results are presented to assess the performance of each device as a potential custom power solution.

Object detection of speckle image base on curvelet transform

Nguyen Thanh Binh and Nguyen Chi Thanh

The speckle degrades quality of the image and makes interpretations, segmentation of objects harder.  In this paper, we present a method for object detection of speckle image base on curvelet transform.  The approximate properties and the high directional sensitivity of the curvelet transform make the new method for object detection of speckle image. We construct a method segmentation that provides a sparse expansion for typical images having smooth contours.

A simulated annealing based hydrothermal system with thyristor controlled phase shifter under open market system

C. Srinivasa Rao, S. Siva Nagaraju and P. Sangameswara Raju

This paper presents the analysis of Automatic Generation Control (AGC) of a two-area interconnected hydrothermal system with Thyristor Controlled Phase Shifter (TCPS) in series with the tie-line under open market system. It also involves the optimization of integral controller employing simulated annealing method. Open transmission access and the evolving of more socialized companies for generation, transmission and distribution affects the formulation of AGC problem. So the traditional AGC two-area system is modified to take into account the effect of bilateral contracts on the dynamics. It is possible to stabilize the system frequency and tie-power oscillations by controlling the phase angle of TCPS which is expected to provide a new ancillary service for the future power systems. A control strategy using TCPS is proposed to provide active control of system frequency. Gain settings of the integral controllers without and with TCPS are optimized using the Simulated annealing technique following a step load disturbance in either of the areas. Analysis reveals that a TCPS is quite capable of suppressing the frequency and tie-power oscillations effectively as compared to that obtained without TCPS

Design of non-uniform filter banks- quadratic optimization with linear constraints

G.A.E. Satish Kumar, P. Chandrasekhar Reddy and B. Stephen Charles

This paper presents methods for the design of non-uniform filter banks. The filter bank structure is obtained from a uniformly modulated filter bank by using an allpass transform which has a lossless frequency function and a nonlinear phase function. The proposed design method includes quadratic optimization with linear constraints. Considered applications are subband adaptive filtering and subband coding. Analysis filter banks and synthesis filter banks are designed in two subsequent stages, and design objectives include minimization of subband aliasing as well as reconstruction output residual aliasing components on an individual basis. This way to formulate design objectives is appropriate for filter banks used in subband adaptive filtering. Other design objectives are to optimize the overall filter bank response for low amplitude and phase distortion. Designs with phase compensation for linear phase overall response are included. Examples are included of filter banks with increasing bandwidth.

A fuzzy-genetic algorithm for optimal capacitor placement in radial distribution systems

P.V. Prasad, S. Sivanagaraju and N.Sreenivasulu

Abstract:

Reduction of total losses in distribution system is very essential to improve the overall efficiency of power delivery. This can be achieved by placing the optimal value of capacitors at proper locations in radial distribution systems. The proposed methodology is a fuzzy-genetic approach. The best location of the capacitor is determined using fuzzy set theory and the sizing of the capacitor is obtained based on genetic algorithm. The objective function is to place the optimal value of capacitors at best locations, which maximizes net savings in the distribution system. The proposed method is very powerful and directly gives the best locations and identifies the optimal size. The proposed method is tested on 15 node and 69 node radial distribution systems.

Measurement resistance of crack sealant asphalt concrete under repeated loading

Ziari Hassan and Khabiri Mohammad Mehdi

In this paper resistance of cracked and crack sealant asphalt samples were studied by varying temperature and time of loading to understand the crack sealant pavement behavior under Iran climatic conditions and to address the problem according to mode of distress. The common cause of pavement distress in Iran is rutting which initiates due to uncontrolled axle load and large variations in temperature. Creep tests were carried out using Universal Testing Machine (UTM-5P) on the mixes prepared in the laboratory. Polymer modified bitumen was used as sealing material and is a unique opportunity to compare the behavior of in crack sealant asphalt concrete. The results of laboratory tests on cracked and crack sealant asphalt concrete under the influence of load and environmental conditions are presented.

Transient stability improvement using UPFC and SVC

S.V Ravi Kumar and S. Siva Nagaraju

With increased power transfer, transient stability is increasingly important for secure operation. Transient stability evaluation of large scale power systems is an extremely intricate and highly non-linear problem. An important function of transient evaluation is to appraise the capability of the power system to withstand serious contingency in time, so that some emergencies or preventive control can be carried out to prevent system breakdown. In practical operations correct assessment of transient stability for given operating states is necessary and valuable for power system operation. Static VAR Compensator is a shunt connected FACTS devices, and plays an important role as a stability aid for dynamic and transient disturbances in power systems. UPFC controller is another FACTS device which can be used to control active and reactive power flows in a transmission line. The damping of power system oscillations after a three phase fault is also analyzed with the analyzation of the effects of SVC and UPFC on transient stability performance of a power system. A general program for transient stability studies to incorporate FACTS devices is developed using modified partitioned solution approach. The modeling of SVC and UPFC for transient stability evaluation is studied and tested on a 10-Generator, 39 - Bus, New England Test System.