70,732 research outputs found

    AC line connector with intermediate DC link

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    An electric power transmission system and method that provides a power electronic interface system for connecting a plurality of alternating current transmission lines by one or more direct current transmission lines. The system includes dc-link converters, frequency transformers connected to the converters, and multilevel converters are connected to a direct current transmission line

    Intelligent Electric Power Systems with Active-Adaptive Electric Networks: Challenges for Simulation Tools

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    The motivation of the presented research is based on the needs for development of new methods and tools for adequate simulation of intelligent electric power systems with active-adaptive electric networks (IES) including Flexible Alternating Current Transmission System (FACTS) devices. The key requirements for the simulation were formed. The presented analysis of simulation results of IES confirms the need to use a hybrid modelling approach

    AC loss of ripple current in superconducting DC power transmission cable

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    As a method of largely reducing the transmission loss in the electric power grid, superconducting direct current (DC) power transmission cable has been investigated. Using superconducting DC power transmission cables, large amounts of current and energy can be transferred compared to conventional copper cables. In this case, an alternating current (AC) is converted to DC and superposed AC which is known as ripple current, and the energy loss by the ripple current is generated. Therefore it is desired to estimate the energy loss density for the case of DC current and superposed AC current for a design of DC transmission cable system. In this study, the hysteresis loss for DC current of 2 kA rectified from 60 Hz alternating current is calculated using the Bean model, and coupling loss was also estimated. The diameter of the cable was 40 mm. The ripple currents generated by multi-pulse rectifiers, 6-pulse, 12-pulse, and 24-pulse were considered. It is found that the total AC loss including the hysteresis loss and the coupling loss is considerably smaller than the supposed heat loss of 0.5 W/m which is obtained with a newly developed cable.26th International Symposium on Superconductivity (ISS 2013), November 18-20, 2013, Tokyo, Japa

    Development of three phase back to back converter with current flow control using raspberry Pi microcontroller

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    A High-Voltage Direct Current (HVDC) electric power transmission system uses direct current form the bulk transmission of electrical power, in contrast with the common Alternating Current (AC) systems. For a long-distance transmission, HVDC systems may be less expensive and suffer lower electrical losses. The overall HVDC system is call back-to-back converter. Therefore, this project is to design and to develop a back-to-back converter with Proportional-Integrative-derivative (PID) control current that could be applied for the resistive load. The basic structure of the PID controller makes it easy to regulate the process output. The control technique is called a current control technique by comparing the output current with the reference current. Thus, the PID controller will force the output current to follow the reference current by creating and changing the pulse width modulation (PWM) signals. The PID controller is developed and simulated by using MATLAB/Simulink software and then implemented to the hardware by using Raspberry Pi Microcontroller. The result from the simulation shows that, the load current follows the reference current from 0 amperes until 1 amperes and the results from the experiment shows that the output current at the load follows the reference current from 0 amperes until 0.4 amperes. The high sensitivity of current sensor and also due to very low resolution of analogue to digital converter effect the result in this project. The results explanation of the project can be divided into three categories; simulation, open loop control and closed loop control

    Utilizing Unified Power Flow Controller for Voltage Stability Improvement of the Electric Power Transmission System of Ghana

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    Interconnecting power transmission systems provide reliability of electric power supply. The security of the system is however questioned when a disturbance in any part of the interconnected system causes instability in the entire network. Unified Power Flow Controller (UPFC), which is a member of the flexible alternating current transmission system (FACTS) family, has the capability of controlling active and reactive power flow in a transmission line thereby improving the voltage stability of the system especially at the 500 kV configuration level. The performance of a 161-kV UPFC modelled in SimPowerSystems is tested on Ghana’s power transmission network.  The optimal placement of the UPFC is done using fast voltage stability index (FVSI) and maximum loadability assessment (MLA). The results show that the device improved the connecting bus voltage from 0.88 p.u. to 0.98 p.u. Active power loss in the network was also reduced from 13.40 MW to 10.39 MW when the UPFC was in circuit.Keywords: Ghana, Stability, Transmission system and Unified Power Flow Controller (UPFC

    Application of LFAC {16 2/3Hz} for electrical power transmission system: a comparative simulation study

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    Transmission of electrical power for long distance is one of the major challenges for electrical engineers over the years. The first and foremost target it is to ensure the transport of electric power with minimal losses over the distance. This paper proposes to employ the low frequency alternating current (LFAC) with (16 2/3Hz) instead of the traditional frequency (50Hz) for electrical power transmission based on a simulation study. Two transmission systems have been constructed using MATLAB/Simulink software namely: 50Hz transmission systems and (16 2/3Hz) transmission systems. In addition, three different distances of transport lines have been used to compare the efficiency of the two systems namely: short (50km), medium (150) and long (300km). The result demonstrated that the use of LFAC with (16 2/3Hz) is better than the traditional frequency (50Hz) in term of energy saving

    Nikola Tesla a man who was ahead of his time

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    Nikola Tesla (1856-1943) is a Serbian-American scientist, inventor, and electro and mechanical engineer who provided mankind with a large number of discoveries and inventions. Tesla is most famous for conceiving the rotating magnetic field principle and then using it to invent the induction motor together with the accompanying alternating current long-distance long-electrical transmission system. His patents and theoretical work still form the basis for modern alternating current electric power (AC) systems including the polyphase power distribution system

    Space charges analysis on insulator with uniform layer contamination effect

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    High voltage direct current (HVDC) transmission provides an attractive alternative for bulk power transfer. However, HVDC transmission may have loss about half per unit length of high voltage alternating current (HVAC) at the same amount of power carried. This is due to the space charge formation around the conductor in HVDC cables. It is known that the presence of space charge inside an insulator may distort the local electric field and surface energy. This paper investigates the effect of electrostatics for space charge, electric field and surface energy in the HVDC cable in clean and contaminated conditions. The effect of uniform layer contamination from oil, sandstone and fresh water was conducted on 11 kV XLPE cable using finite element software under electrostatics study. The contamination layer was created around the XLPE cable by multifarious the radius of layer contamination from the conductor. The simulation results show that enlargement of contamination layer radius by 1.0 mm (light), 1.5 mm (medium) and 2.0 mm (heavy) resulted in the reduction of surface energy by 20% and electric field by 22% but increase the space charge amplitude by 76%. The study also found that fresh water can be considered as the worst contamination compared to oil and sandstone
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