Electrical Engineering

This paper utilizes best first search (BFS) algorithm to determine the optimal placement of phasor measurement units (PMUs) for complete observability of a power system under normal operating conditions. The additional redundancy offered by this method has been removed by applying a pruning technique to further minimize the number of PMUs determined by BFS algorithm. The proposed method has been used to determine the optimal PMU placement solutions for the standard IEEE 14-bus system, IEEE 30-bus system and a practical 246-bus Indian system. The results obtained with the proposed method have been compared with the existing methods such as integer linear programming. It has been found that the proposed method is able to achieve the complete system observability with the minimum number of PMUs required.

Synchronized phasor measurements placement problem is commonly solved by formulating it as a mathematical optimization problem, which is limited by huge computational burden especially for larger systems. This paper proposes a novel intelligent search based approach for placement of phasor measurement units (PMUs) in the power system while maintaining complete observability. The proposed approach works in two stages. Stage I utilizes best first search to identify the possible locations of PMUs in order to obtain system observability and these locations are used as inputs to stage II. Stage II determines the optimal locations of PMUs by applying pruning to the inputs received from stage I, such that the system observability is achieved with the minimum number of PMUs. The proposed approach has been further extended to incorporate the presence of conventional flow measurements. An important feature of the proposed placement method is its capability to handle both single as well as multiple ow measurements connected to a bus. The proposed method has been tested on IEEE 14-bus, IEEE 30-bus and a practical 246-bus Indian networks for system intact condition as well as during single transmission line and single PMU loss. The effectiveness of the proposed method has been demonstrated by comparing the numerical results obtained using the proposed method with the existing methods.

This paper utilizes best first search (BFS) algorithm to determine the optimal placement of phasor measurement units (PMUs) for complete observability of a power system under normal operating conditions. The additional redundancy offered by this method has been removed by applying a pruning technique to further minimize the number of PMUs determined by BFS algorithm. The proposed method has been used to determine the optimal PMU placement solutions for the standard IEEE 14-bus system, IEEE 30-bus system and a practical 246-bus Indian system. The results obtained with the proposed method have been compared with the existing methods such as integer linear programming. It has been found that the proposed method is able to achieve the complete system observability with the minimum number of PMUs required. Keywords—best first search (BFS); observability; optimal placement; phasor measurement unit (PMU); pruning

This paper proposes a human intuition-based concept of Case-Based Reasoning (CBR) for Static Security Assessment (SSA) of power systems. Prior to security assessment, a composite Security Index (SI) defined in terms of line overload and voltage violation, is computed for each training pattern to label them into either secure or insecure class. Out of all phasor measurements obtained using Phasor Measurement Units (PMUs), only the real and reactive power flows, which are identified as relevant features are given as inputs to the proposed CBR system. The proposed approach has been implemented on IEEE 14 bus, IEEE 30 bus and Indian 246 bus networks and the results have been compared with those obtained using Support Vector Machine (SVM) and Artificial Neural Network (ANN) based classifiers. The results indicate that the proposed approach is more efficient, reliable and outperforms the above said classifiers in terms of classification accuracy at a comparable computation cost.

In  this  Paper,  the  dynamic  response  of  multi  area
load  frequency  control  problem  in  a  deregulated  power  system  is
improved  with  a  practical  view  point  for  step  load  changes  in
different  areas  sequentially  and  simultaneously.  In  this  two
assumptions  are  taken  in  power  system  model  in  which  one  is
speed  governor  and  turbine  model  are  taken  separately  and
another  one  is  augmented  speed  governor  turbine  model.  In  the
deregulated  environment  it  is  not  possible  to  access  and  to
measure  all  the  state  variables.  To  solve  this  problem,  in  this
paper  optimal  output  feedback  method  is  proposed.  In  optimal
output  feedback  method,  only  measureable  state  variables  within
each  control  area  is  required  to  use  for  feedback.  The  optimal
control  law  is  determined  by  minimizing  performance  index  of
type  that  integral  of  square  error  under  the  output  feedback
conditions.  The  proposed  method  is  tested  on  two  area  power
system  with  two  contract  scenarios  that  transactions  based  on
free  contracts  and  contract  violation.  The  results  are  compared
with  the  full  state  feedback  method  for  complete  research.  The
results  are  shown  that  when  the  power  demand  changed,
proposed  method  have  good  ability  to  tracking  of  both  contracted
and  un-contracted  demands  in  contracted  violation.  Optimal
output  feedback  method  provides  a  better  control  that  satisfied
the  load  frequency  control  requirements  and  with  a  reasonable
dynamic response.

Virtual Synchronous Generators (VSG), as an effective mean to improve the frequency and voltage regulation ability of the renewable power, had aroused wide concern. Researchers have proposed several VSG implementations, which can be classified into two categories: voltage-controlled VSG and current-controlled VSG. Voltage-controlled VSG have been extensively studied. However, few researches focused on current-controlled VSG. In this paper, we concentrated on the current-controlled VSG and its stability problem. Firstly, a small-signal model of current-controlled VSG was established to identify the oscillation modes of grid-connected VSG system. Moreover, the developed model was used to investigate damping characteristics of the system under various scenarios and with different control parameters. The results revealed that stability of VSG system was sufficiently impacted by virtual inertia and phase lock loop in VSG. Under some unfavourable conditions, currentcontrolled VSG would contribute to high-frequency or subsynchronous oscillation.

DESCRIPTION Typically electronics has been defined in terms of three fundamental elements such as resistors, capacitors and inductors. These three elements are used to define the four fundamental circuit variables which are electric current, voltage, charge and magnetic flux. Resistors are used to relate current to voltage, capacitors to relate voltage to charge, and inductors to relate current to magnetic flux, but there was no element which could relate charge to magnetic flux. To overcome this missing link, scientists came up with a new element called Memristor. These Memristor has the properties of both a memory element and a resistor (hence wisely named as Memristor). Memristor is being called as the fourth fundamental component, hence increasing the importance of its innovation. Its innovators say ―memrisrors are so significant that it would be mandatory to re-write the existing electronics engineering textbooks.‖

The idea of reducing the gate length of the metal-oxide semiconductor field-effect transistor (MOSFET) has been the leading stimulus for the growth of the integrated circuit industry. This chapter presents the current CMOS technology and its future advancements. The scaling concept and technology advancements in VLSI are discussed. Additionally, the transistor models and associated device modeling approaches are included. Herein, we discussed various aspects of CMOS integration into analog circuits for various architectures implementation and their desired improvements to work for futuristic 5G applications. The basic MOSFET device structure and modeling of MOSFETs for different signals and on different platforms considering various parasitics effects have been presented to make a way for the advanced research understanding of different works of modeling and proposed architectures in terms of simulation for their implementation for 5G. We expect that the future of CMOS with 5G will accompany different solutions arising with scaling issues and also provide various alternatives to make smooth incorporation of 5G into the wireless world.

Farmed poplar could meet the human demand for transparent wood-based composites to replace glass, avoiding the consumption of natural forest resources. We removed the lignin of poplar using a potassium hydroxide (KOH) and deionized water solution, the waste black liquor could be converted into compound potassium fertilizer after being neutralized by phosphoric acid. Polyurethane (PU) was then added to the lignin-stripped poplar and hardened, the transparent poplar-based composite (TPC) has stable transparency at high temperatures, and flexibilityit elongates (about 15%) before breaking. These properties could provide more uses in hot environments requiring a flexible shape. The TPC PU provides transmittance of 85%, haze of 83%, and anisotropic light diffraction.

Cel-Celem artykułu jest analiza samooceny jako jednego z narzędzi systemu kontroli zarządczej i jej praktyczne wykorzystanie w zarządzaniu JST. Metodologia badania-Przeprowadzono analizę samooceny zarówno z punku widzenia formalnych zasad jej funkcjonowania, jak i zagadnień merytorycznych. Omówione zostały obowiązujące regulacje prawne na poziomie przepisów powszechnie obowiązującego prawa krajowego. Wykorzystano również wnioski z obserwacji oraz doświadczeń wdrażania kontroli zarządczej wynikające z pracy zawodowej autorki artykułu. Wynik-Sformułowane zostały postulaty pozwalające na efektywne i skuteczne wykorzystanie samooceny kontroli zarządczej w nowoczesnym modelu zarządzania JST. Oryginalność/wartość-Samoocena jest niezmiernie istotnym elementem zarządzania JST. Stanowi ona nierozerwalny element kontroli zarządczej, a tym samym nowoczesnego modelu działania jednostek sektora finansów publicznych.

This paper presents an application of Empirical Wavelet Transform (EWT) to the power signals for estimation of Power quality Indices (PQIs). This technique first estimates the frequency components present in the distorted signal, computes the boundaries and extracts mono components based on the boundaries computed. Several stationary and non-stationary signals have been analyzed to show the effectiveness of this technique. The PQIs obtained with the proposed technique has been compared with Discrete Wavelet Technique (DWT) and the proposed technique is found to be effective and superior over DWT. The results confirm that the EWT efficiently extracts the mono-component signals from the time varying distorted signal and hence this technique would be suitable for real time PQ indices estimation.

This paper proposes a new tunable-Q wavelet transform (TQWT) based feature extraction for classification of power quality (PQ) disturbances. The filters are designed to extract the fundamental frequency component from the complete voltage/current signal. This is achieved by tuning the Q-factor (Q) and redundancy (r) of the wavelet by primarily investigating the presence of interharmonics near the fundamental frequency. To test the effectiveness of the proposed scheme, the system is verified with noise-added disturbance signals generated in MATLAB and finally on some practical signals. The proposed methodology is computationally efficient as the traditional PQ analyzers.

This paper proposes a generalized empirical wavelet transform (GEWT) for the recognition of single and combined power quality (PQ) disturbances. The FFT-based frequency estimation is adaptive, requires no prior information and is also capable to diagnose all the PQ disturbances. The improved spectral segmentation followed by an adaptive filter design accurately extracts the fundamental frequency component, thereby enabling the extraction of informative features. Thus, the proposed approach combines the GEWT and a simple rule-based decision tree (DT) for accurate recognition of most significant PQ disturbances. The DT classifier with five features extracted from the GEWT is refined and finally tested on 1200 simulated as well as three real disturbance signals. The proposed scheme is found to be computationally efficient and performs satisfactorily with a good classification accuracy.

Generator is an important component of power system which plays a vital role in the whole system for security and stability. The conventional protection systems will not detect inter turn faults. Longitudinal differential protection detects only inter phase and ground faults. Some large capacity generators are provided with split phase windings to enable transverse differential relay to detect inter turn faults. But this system cannot be retrofit to existing generators. The inter-turn fault protection for stator windings of generators is an important and effective measure to ensure the safe operation of the generator because the inter turn fault may finally lead to ground fault. Therefore, early detection of inter-turn faults would eliminate subsequent damage to adjacent coils and stator core, reducing repair cost and generator outage time. The new Criterion discussed in this paper for detection of inter turn fault is based on the fact that the inter turn fault causes unbalance in t...

Regarding the modern power smart grid, distribution consumers and prosumers are highly concerned about power quality (PQ). In fact, they would prefer to pay higher prices for a reliable and good quality power supply. Unfortunately, utility operators still aim for reliability alone, ignoring the quality of supply voltage and current. There are no clear guidelines for monitoring, penalizing, or implementing PQ-based tariff schemes in LV distribution systems. In addition, the implementation of a PQ-based tariff requires a real-time measuring mechanism at the user end, which is very expensive and difficult to understand for a domestic consumer. This paper presents a novel, low-cost, efficient, and user-friendly smart PQ meter to overcome these issues and limitations. It is essentially a PQ analyzer with energy metering functionality, which implements a novel PQ-based tariff scheme that penalizes consumers violating the PQ limits and provides incentives for a good PQ profile. It measures...

As the local energy sources are mostly uncertain and fluctuating in nature, the ‘energy risk’ due to discrepancies between committed energy transactions and metered measurements is prominent in peer to peer (P2P) markets. We propose a P2P market settlement mechanism which lowers this risk and maximizes the welfare of buyers and sellers. The risk in energy production is modeled using Markowitz portfolio theory and the best point where energy return per unit risk is maximum is obtained from the efficient frontier by using the modified Sharpe ratio. The energy portfolio thus obtained is used as a constraint while optimizing the conflicting prosumer benefits using multi-objective stochastic weight trade-off chaotic non-dominated sorting particle swarm optimization (SWTC-NSPSO). In effect, only a reliable proportion of total energy demand submitted in the bid is cleared in the market, foreseeing the real-time fluctuations. The proposed market settlement mechanism also gives room to the e...

Power system deregulation and shortage of transmission capacities have led to an increase interest in distributed Generation (DG) sources. The optimal location of DGs in power systems is very important for obtaining their maximum potential benefits. This paper presents an algorithm to obtain the optimum size and optimum location of the DGs at any bus in the distribution network using Loss Sensitivity factor. The proposed algorithm is based on power loss minimization in the distribution network. The new algorithm is studied in MATLAB for 33 bus test distribution systems. Results indicate that, if the DGs are located at their optimal locations and have optimal sizes, the total losses in the distribution network are reduced by 27%. The results can be used as a look-up table, which can help design engineers when inserting DGs into the distribution networks

Tracking of instantaneous power quality (PQ) indices is very essential for better characterization of the time-varying voltage and current signals. This paper presents the estimation of time-varying PQ indices for accurate interpretation of disturbances using a generalized empirical wavelet transform (GEWT). This approach is based on adaptive segmentation of Fourier spectrum and followed by an appropriate filter design to extract the individual frequency components. The main emphasis of this work is to estimate the actual frequencies present in the signal by overcoming the problem of spectral leakage. A preliminary investigation of time domain amplitude variation of the signal helps in realizing the presence of low-frequency interharmonics and thereby permitting to extract the fundamental frequency component perfectly. Hence, the GEWT is employed to assess successfully all sorts of power signals having disturbances such as voltage fluctuation, sag, swell, interruption, transients, harmonics, and interharmonics. The robustness and applicability of the GEWT for PQ analysis have been verified by analyzing several distorted signals generated using PSCAD, recorded waveforms available in IEEE database and a few real signals. Finally, the estimated GEWT-based time-varying single phase PQ indices are compared with the indices obtained from IEC defined fast Fourier transform (FFT) and fast S-transform (FST).