RECENT TRENDS IN POWER SYSTEMS GANESH COLLEGE OF ENGINEERING SALEM RECENT TRENDS IN POWER SYSTEMS A NEW TECHNOLOGY IN A NEW WORLD HVDC LIGHT PRESENTED BY: RAJA.S BOOPATHIRAJA.A SANTHOSH.S

CONTENTS: ABSTRACT INTRODUCTION HVDC HVDC LIGHT PULSE WIDTH MODULATION ADVANTAGES DISADVANTAGES APPLICATIONS CONCLUSIONS REFERENCES

ABSTRACT: This paper describes the updated form of HVDC known as HVDC Light. The HVDC Light technology, is well suited to meet the new markets and its demands and the reasons for this are explained. HVDC Light is the most interesting power transmission system using high voltage direct current. "HVDC Light" which uses pulse width modulation. It extends the economical power range of HVDC transmission down to just a few tens of megawatts (MW).

INTRODUCTION Nowadays there is a huge competition in the electrical industry as a means of achieving cost effective outcomes. So most of the long AC transmission lines in the world are replaced by HVDC transmission lines because of their economical properties. Though HVDC transmission line has many advantages there are some limitations too. So, some of the HVDC transmission lines are replaced by the HVDC Light to meet the limitations of HVDC.

HVDC: HVDC transmission originated in Germany during Second World War. The first commercial line was installed in Sweden in 1954. Some of the specialties of the HVDC Transmission lines are:- Lower investment and lower losses for bulk power transmission Asynchronous interconnections No contribution to Short circuit power Improved transmission in parallel AC circuits Instant and precise power flow control

HVDC LIGHT: HVDC Light was introduced in 1997 by ABB Manufacturers. It is an electric power transmission technology which employs the latest in power semiconductor technology, the IGBT based on voltage source converters cables. The HVDC Light system comprises two converter stations at the ends of the transmission, and an underground cable link between them. HVDC Light is the most interesting power transmission system using high voltage direct current. What makes HVDC Light special? Underground polymer cables Independent control of active and reactive power flow Short delivery time power quality control modular compact design

PULSE WIDTH MODULATION: The operation of the converter is achieved by Pulse Width Modulation (PWM). With PWM it is possible to create any phase angle and/or amplitude (up to a certain limit) by changing the PWM pattern, which can be done almost instantaneously. Thus, PWM offers the possibility to control both active and reactive power independently. This makes the PWM Voltage Source Converter a close to ideal component in the transmission network

PULSE WIDTH MODULATION

The combined active and reactive capabilities can most easily be seen in a P-Q Diagram

HVDC LIGHT CABLES:

HVDC LIGHT CABLES The HVDC Light extruded cable is the outcome of a comprehensive development program. HVDC light cable is made up of polymeric material. The most important material property of the cables: space charge accumulation resistivity electrical breakdown strength. These properties made the cables with high mechanical strength, high flexibility and low weight. Due to the polymeric material it is very strong and robust, as well as being specifically adopted for direct voltage.

ADVANTAGES: It has a standardized design, power ratings up to 200 MW, short delivery times and it is friendly to the environment. HVDC Light is Grid friendly and ecological technology. Harmonics can be eliminated easily using filters. Due to the bipolar arrangement of cables magnetic field is almost zero. It increases efficiency and reduce the emissions. It will be an excellent tool for wind power into the networks.

DISADVANTAGES: The cost of an HVDC transmission system depends on many factors, such as power capacity to be transmitted, type of transmission medium, environmental conditions and other safety, regulatory requirements etc. Even when these are available, the options available for optimal design (different commutation techniques, variety of filters, transformers etc.) render it is difficult to give a cost figure for an HVDC system.

APPLICATIONS: Some applications are: Connecting Wind power farms to the grid Distributed generation Multi terminal DC-grid Interconnecting networks Utilizing existing Rights-Of-Way

CONCLUSIONS It is widely recognized that the role of network services has changed as a result of the introduction of competitive power markets. HVDC Light is a DC transmission technology that has important advantages for application in competitive markets. These advantages include its modularity, standardized design leading to short delivery times, and compact stations and cables reducing environment impacts and controllability giving possibilities to match the power need and/or to control the voltage in the network.

REFERENCES: Luces M.Faulkenberry , Walter Coffer: “Electrical Power Distribution and Transmission” K.R.Padiyar: ”HVDC Power Transmission Systems” Technology and System Interactions.. ASplund G Ericson,K.Drugge:”Electric Power Transmission To Distant Loads By HVDC Light”. Website: ABB-HVDC Light

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