Utility Power Supply Research Articles

Mitigation of CM conducted EMI in flyback converter using balancing capacitors

The offline Switched Mode Power Supply (SMPS) draw non-sinusoidal line current from the utility power supply, thereby introducing unwanted harmonics and also generate significant electromagnetic interference (EMI). Power factor correction (PFC) converters can be used to improve the power factor. But they also generate EMI in both Differential Mode (DM) and Common Mode (CM). In this paper, the EMI generated by the flyback PFC converter is addressed. A lumped circuit model for CM conducted EMI generated in a flyback converter, including the HF transformer's parasitics and the components, is considered. The parasitics of the HF transformer are calculated and measured experimentally. Using them, the resonant frequencies of the flyback converter are calculated for validation. A technique for determining the required balancing capacitor to mitigate CM conducted EMI is presented. A novel technique by splitting this balancing capacitor with their mid-point grounded for further reduction of this EMI is presented. This technique can eliminate the C y capacitors of the EMI line filter connected between line/neutral to the ground. Hence for the same amount of CM conducted EMI mitigation, the size and the cost of EMI line filters are reduced. Theoretical analysis, simulation results, and experimental verifications are presented.

Cost Efficient Real Time Electricity Management Services for Green Community Using Fog

The computing devices in data centers of cloud and fog remain in continues running cycle to provide services. The long execution state of large number of computing devices consumes a significant amount of power, which emits an equivalent amount of heat in the environment. The performance of the devices is compromised in heating environment. The high powered cooling systems are installed to cool the data centers. Accordingly, data centers demand high electricity for computing devices and cooling systems. Moreover, in Smart Grid (SG) managing energy consumption to reduce the electricity cost for consumers and minimum rely on fossil fuel based power supply (utility) is an interesting domain for researchers. The SG applications are time-sensitive. In this paper, fog based model is proposed for a community to ensure real-time energy management service provision. Three scenarios are implemented to analyze cost efficient energy management for power-users. In first scenario, community’s and fog’s power demand is fulfilled from the utility. In second scenario, community’s Renewable Energy Resources (RES) based Microgrid (MG) is integrated with the utility to meet the demand. In third scenario, the demand is fulfilled by integrating fog’s MG, community’s MG and the utility. In the scenarios, the energy demand of fog is evaluated with proposed mechanism. The required amount of energy to run computing devices against number of requests and amount of power require cooling down the devices are calculated to find energy demand by fog’s data center. The simulations of case studies show that the energy cost to meet the demand of the community and fog’s data center in third scenario is 15.09% and 1.2% more efficient as compared to first and second scenarios, respectively. In this paper, an energy contract is also proposed that ensures the participation of all power generating stakeholders. The results advocate the cost efficiency of proposed contract as compared to third scenario. The integration of RES reduce the energy cost and reduce emission of CO 2 . The simulations for energy management and plots of results are performed in Matlab. The simulation for fog’s resource management, measuring processing, and response time are performed in CloudAnalyst.

A performance comparison of transformer-less grid tied PV system using diode clamped and neutral point shorted inverters

Grid tied photovoltaic (PV) system is an operation mode of PV system working together with utility power supply to provide power to the power load. Conventionally, transformer is used together with the power inverter. The power transformer works as galvanic insolation amongst PV system and power grid. It works also to raise the voltage of power inverter. However, use of transformer will add system complexity, price, weight and size of the entire system. Transformer-less system is an alternative to make the system simpler and more practical in use. The paper discusses performance of transformer-less grid tied PV systems using diode clamped and neutral point shorted inverters. Effects of transformer elimination to the feat of the grid tied PV system especially harmonics content and leakage current of PV system were examined and analyzed. The performance was also compared with the traditional system using H-bridge inverter. The leakage currents did not flow in the system applying diode clamped inverter, and neutral point shorted inverter. In case of harmonics content, the diode clamped inverter injected less harmonics components than the neutral point shorted inverter. The neutral point shorted provides a simpler inverter circuit in the transformerless systems. Normal 0 false false false MS X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman",serif;}

A logistic mapping-based encryption scheme for Wireless Body Area Networks

In recent years, data security becomes a critical issue restricting the wider acceptance of Internet of Things (IoT) devices and Cyber-physical systems since they have limited hardware resources and power supply while high data security protection requires relatively large hardware resources and power supply utilization. This contradiction is particularly prominent in the field of Wireless Body Area Networks (WBANs) which is a segment of the IoT field. WBANs are dedicated to transmit and process biomedical data collected from human beings, any kind of tampering or hacking may cause severe consequences to users. However, the limited computing ability and battery supply of biomedical sensors attached or implanted in the users restrict the security protection strength of the data in WBANs. In this paper, a quantized Logistic mapping-based stream encryption scheme for WBANs is proposed. Meanwhile, Power spectral entropy (PSD) and Peak-to-average Power Ratio (PAPR) analysis of the quantized chaotic sequences have been performed to evaluate the chaotic characteristic among different quantization precision to resolve the ineffectiveness of Lyapunov factor in quantized systems. This encryption scheme utilizes chaotic systems with different quantization precision based on the security requirement of every individual communication, which leads to higher hardware and power efficiency. Finally, the proposed encryption scheme is implemented with VHDL and synthesized using SMIC 60 CMOS technology. The evaluation results illustrate that the proposed encryption scheme has the advantages of high-security performance and high-efficiency hardware resources utilization.

An optimization approach to determining the power of active filters

The coal grading plants in Vietnam extensively apply asynchronous motors with frequency control. They consume reactive power and non-sinusoidal current from the supply network. The nonsinusoidal currents and voltages lead to additional energy losses in electrical equipments, reduce their service life and cause an economic damage. Because of the low load power factor the companies with such plants pay penalties to power supply utilities. These problems can be solved by the active filters. The paper suggests an optimization algorithm to calculate the power of the active filter, which provides a load power factor corresponding to the normative documents and power quality indices corresponding to the standard requirements. The algorithm is used to calculate the power of the active filter for the coal grading plant owned by the company “Kua Ong-Vinakomin”.

A novel approach for the study and analysis in designing system of smart grid

The designing of the system has made all possible energy resources, conversion efficiency, and also power demand, to control both environmental and economic issues. In this technology, the network will not only get going to integrated and set communicable all over the country but its demand will be tracked by the control centers in different aspect and at high time the usage of power is going to cost higher than the actual rate with intimation given to the customer through notification via SMS or email. Besides, they also assist with the utilities to comply with the countries regulatory for power supply utility grid and local renewable energy sources. From the conventional distribution system, we can see the design for the control of all the constituents as observed to be autonomous with each other. Thus, centralization in control and consolidated functionality are the main challenges discovered by the distribution system. To minimize these matters of concern, the term “distribution system and its responsibilities” came into effect by using information and communications technology (ICT) to power the resolution in circulating distribution systems.

Energy Storage System in Smart Homes of Smart City

The Nanogrid utilizes renewable energy sources, e.g. Solar PV, Wind, etc; which are stochastic in nature. Due to this nature, power reliability is the main issue. To increase the reliability of the power supply and proper utilization of the available resources, Nanogrid should either connected to the utility grid directly or it must have the proper energy storage system. Energy storage system fills the gap between consumers demand and renewable power generation; which is very important issue in technical and economical consideration. The Nanogrid gives new hope of ray to the people living in off grid areas. By using energy storage system we can increase their living standard and enhance socio-economical development. This paper proposes the selection of the proper energy storage device and its calculation, control strategy also suggested for protecting storage device from over voltage and deep discharge.

A Decentralized Energy Trading Framework for Active Distribution Networks with Multiple-Microgrids under Uncertainty

The ever-increasing need for more reliable power supply, cost-effective and environmental-friendly utilization of distributed energy resources will result in formation of multiple microgrids (MMGs) in the near future of distribution system. To achieve this prospective, a coordination among MMGs is necessary. Accordingly, this paper proposes a new non-hierarchical multilevel architecture for the optimal scheduling of active distribution network (ADN) with MMGs. The proposed model is a decentralized decision making algorithm to optimally coordinate the mutual interaction between local optimization problems of ADN and MMGs. A non-hierarchical analytical target cascading (ATC) method is presented to solve the local optimization problems in parallel. Also, underlying risks of the energy trading caused by renewable generation uncertainty are reflected in both the objective functions and the constraints of local optimization problem. The numerical results on modified IEEE 33-bus distribution test system containing two microgrids demonstrate the effectiveness and merits of proposed model.

Feasibility Study of Superconducting Cable Application to Oil/Gas Power Supply Network

In this paper, the static and dynamic behaviors of a power system feeding an oil/gas plant with superconducting (SC) cables are investigated. SC cables have been expected to provide more efficient power supply and less space utilization for power systems compared to conventional cables. On the other hand, their compatibility with the existing power systems has not yet been clarified. In this paper, taking a typical distribution system in an oil/gas plant as an example, we designed high-voltage SC cables and investigated their compatibility with the system from the viewpoint of static and dynamic performances. The voltage distribution under steady-state operation and the transient voltage and current during fault conditions were examined and compared with the case of conventional cables. The results show that, in addition to the efficiency enhancement, SC cables could be applied without any further constraint on circuit breaker duties and insulation coordination requirements.

Chance-constrained stochastic congestion management of power systems considering uncertainty of wind power and demand side response

This study proposes a new stochastic model based on chance constraints for network congestion management in the day-ahead power market. By jointly considering the uncertainty of wind power and demand side response, the proposed optimization model can help determine the optimal daily dispatch of generators and demand responsive loads to minimize the risk of transmission congestion. To this end, transmission line congestion probability (TLCP) is constructed in chance constraints to ensure system congestion less than a certain level. The indexes of load loss probability (LLP) and wind curtailment probability (WCP) are proposed and incorporated as chance constraints to achieve a high reliability of power supply and high utilization of wind generation, respectively. In the optimization process, the proposed stochastic optimization model is transformed to an equivalent deterministic model by using the probability distribution of random variables, and the influence of transmission system loss on transmission congestion management is considered. To calculate the satisfaction degree of chance constraints under the determined dispatch of generators and demand responsive loads, the probabilistic power flow based on the cumulant method is used, and the risk of transmission congestion level is quantified by the index, congestion risk value (CRV). Simulation results of a modified PJM 5-bus system and an IEEE 118-bus test system demonstrate the effectiveness of the proposed approach for congestion management in the day-ahead power market.

Low cost residential microgrid system based home to grid (H2G) back up power management

Load shedding is a common scenario in developing countries to mitigate the high-power demand. Normally, a low power backup supply is used for essential home-loads only, viz. essential lighting and fan loads. However, there always is a need of essential backup power supply for household applications during load shedding hours. Currently, rooftop, grid-connected, solar photovoltaic (PV) based inverters are being extensively used for home based backup power supply. These inverters have unidirectional power flow i.e. from generation side (PV source as well as utility grid supply) towards the home-load side. However, during a fully charged battery condition, as charging is done by the utility grid too, the power of solar PV modules gets underutilized as the solar energy is only partially used for charging the battery. The proposed supervisory switching control system, in conjunction with a conventional, low-cost home based inverter/UPS, adds up improved control features which ensure the reliability of the power supply and/or complete utilization of solar energy while operating in economy mode. In economy mode, only solar energy is utilized to meet the load demand during sunshine hours and thereafter. In case of repeated and prolong load shedding, the proposed controller selects a reliable mode of operation where batteries are allowed to be charged both from utility grid as well as solar PV modules. Thus, two modes of control offer maximum harnessing of solar energy as well as better standby power supply, respectively. The proposed controller has been successfully implemented with the residential microgrid (existing home based inverter system for backup power supply). The proposed system also works as home-to-grid (H2G) system to meet load demand and peak load of utility grid during the sunshine hours by islanding the residential microgrid (home-loads System.)

Study on low-frequency voltage fluctuation of traction power supply system introduced by multiple modern trains

As the modern trains have been widely adopted in China high-speed and heavy-haul railways, the low-frequency voltage fluctuation of traction network has been found frequently, which affects both traction power supply system (TPSS) and utility system seriously. In order to investigate such new phenomenon, this paper studies the formation mechanism and potential factors of the low-frequency fluctuation by comparing the results of the impedance-based and simulation methods. Firstly, the impedance-based model of the train-TPSS interaction system is presented with the consideration of concrete configurations. Then, the stability of interaction system under different conditions of system impedances has been studied based on the impedance-based stability analysis method. Besides, the low-frequency fluctuation and potential factors of the train-TPSS system have also been simulated on MATLAB/Simulink platform. The results of both theoretical and simulation analyses quantify the impacts of the equivalent output impedance of TPSS (e.g., catenary length, traction transformer capacity, etc.) and input impedance of the train (e.g., number, operation condition, control parameters, etc.) on low-frequency voltage fluctuations. Finally, the effectiveness of the proposed methods has been verified through sufficient field tests in China electrical railways. And the suppression suggestions are provided to improve the low-frequency voltage fluctuations.

MaxPB

Phase Change Memory (PCM) is one of the promising memory technologies but suffers from some critical problems such as poor write performance and high write energy consumption. Due to the high write energy consumption and limited power supply, the size of concurrent bit-write is restricted inside one PCM chip. Typically, the size of concurrent bit-write is much less than the cache line size and it is normal that many serially executed write units are consumed to write down the data block to PCM when using it as the main memory. Existing state-of-the-art PCM write schemes, such as FNW (Flip-N-Write) and two-stage-write, address the problem of poor performance by improving the write parallelism under the power constraints. The parallelism is obtained via reducing the data amount and leveraging power as well as time asymmetries, respectively. However, due to the extremely pessimistic assumptions of current utilization (FNW) and optimistic assumptions of asymmetries (two-stage-write), these schemes fail to maximize the power supply utilization and hence improve the write parallelism. In this article, we propose a novel PCM write scheme, called MaxPB (Maximize the Power Budget utilization) to maximize the power budget utilization with minimum changes about the circuits design. MaxPB is a “think before acting” method. The main idea of MaxPB is to monitor the actual power needs of all data units first and then effectively package them into the least number of write units under the power constraints. Experimental results show the efficiency and performance improvements on MaxPB. For example, four-core PARSEC and SPEC experimental results show that MaxPB gets 32.0% and 20.3% more read latency reduction, 26.5% and 16.1% more write latency reduction, 24.3% and 15.6% more running time decrease, 1.32× and 0.92× more speedup, as well as 30.6% and 18.4% more energy consumption reduction on average compared with the state-of-the-art FNW and two-stage-write write schemes, respectively.

Cloud-to-Ground Lightning in Malaysia: A Review Study

Lightning has been the major cause of power interruptions in Malaysia. Malaysia is located near the equator having approximately 200 thunder days per year. It is known to be among the highest lightning activity country worldwide. TNB as the main power supply utility in Malaysia has made an effort to reduce the power interruptions via installation of Lightning Detection Network (LDN) in 1994. This paper presents the history leading to modern LDN that capture lightning radiation fields at multiple remote sensors. The network has undergone a series of improvement between 2004 and 2009 in response to evolving detection technologies and requirements. Recent analyses on actual performance of the current LDN are also summarized. The paper includes short and long term requirements for improving the lightning measurements needed to address some open scientific questions and fill the needs of emerging applications.

An Intelligent Power Supply Utilization System Based on Microcontroller for Renewable Energy Applications

The proposed hardware “an intelligent power supply utilization system based on microcontroller for renewable energy applications” is a system in which microcontroller is used to automatically control the power supply of conventional energy source with the help of renewable energy source and power supply utilized in this way is then used to feed to the load. In this system, supply from the mains is altered with the help of microcontroller according to the nonlinear supply from solar energy and this altered power supply of one source is then compensated by another source. This technique will help to maintain the optional power supply to the load from renewable energy source. The control strategy for this kind of power supply utilization is written in the assembly language. The system based on this logic can be used as one of the energy saving option and a tool for promoting and encouraging the renewable energy sources.

High-Resistance Grounded Power-System Equivalent Circuit Damage at the Line–Ground Fault Location—Part I

This paper provides the electrical equivalent circuits of high-resistance grounded (HRG) power systems other than the delta-wye-connected utility power supply transformer included in Part I of this paper. This paper also provides the HRG of a medium-voltage generator for connection to an industrial power system and to a utility power system, and this paper discusses a line-ground fault with fault resistance. Three-line diagrams of ungrounded power systems are also included to illustrate the HRG application and its effect on the ground fault current during the line-ground fault. The damage at the fault location is based on the assumption that the fault remains a line-ground fault until it is cleared by appropriate ground fault protection relays. The fault resistance and the fault current that have an effect on the damage at the fault location are included. This paper provides guidance to update the current edition of the IEEE STD. 142, with respect to HRG systems.

High-Resistance Grounded Power-System Equivalent Circuit Damage at the Line–Ground Fault Location—Part II

This paper provides the electrical equivalent circuits of high-resistance grounded (HRG) power systems other than the delta-wye-connected utility power supply transformer included in Part I of this paper. This paper also provides the HRG of a medium-voltage generator for connection to an industrial power system and to a utility power system, and this paper discusses a line-ground fault with fault resistance. Three-line diagrams of ungrounded power systems are also included to illustrate the HRG application and its effect on the ground fault current during the line-ground fault. The damage at the fault location is based on the assumption that the fault remains a line-ground fault until it is cleared by appropriate ground fault protection relays. The fault resistance and the fault current that have an effect on the damage at the fault location are included. This paper provides guidance to update the current edition of the IEEE STD. 142, with respect to HRG systems.

東京の電気事業と電源開発

東京の電気事業と電源開発

Practical Implementation of an Improved Standby Boost Uninterruptible Power Supply

This paper proposes a single phase pulse-width modulated (PMW) voltage source uninterruptible power supply known as an improved standby boost uninterruptible power supply (ISBUPS) which centers on keeping the output voltage of the inverter system of the UPS at constant voltage of 220V AC and ripple free when utility power supply fails. This concept is achieved by incorporating proportional integral (PI) controller, boost converter and L-C filter at inverter control section. In this research, apart from stabilizing the inverter output voltage of inverter at 220VAC in standby mode, 0.96 modulation index is also realized. The total harmonic distortion of the system is reduced down to 5.05%. This proposed system has its applications at homes, offices and in business centers especially in Nigeria where electrical power instability is high now.

Power generation: Separation activities within the power generation sector

In this article Ken Sutherland reviews the applications for filtration and related separation equipment in the generation of electrical power, for the large scale power supply utilities and dedicated industrial users. This is an end-use sector with significant environmental impact.