الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
The driving force for the development of power systems is the on-going increase of electrical power demand. The fast development of power electronics based on new and powerful semiconductor devices has led to innovative technologies. These technologies are such as HYDC (High Voltage Direct Current) transmission and FACTS (Flexible AC Transmission). The technical and economical benefits of these technologies represent an alternative to the application in AC systems. These systems can both effectively control power flow through the interconnection independent on system conditions and it can additionally enhance the system stability.
In the second half of the past century, high power HVDC transmission technology has been introduced, offering new dimensions for long distance transmission. This development started with the transmission of power in an order of magnitude of a few hundred MW and was continuously increased to transmission ratings up to 3 • 4 GW over long distances by just one bipolar line. There are several features of HVDC system such as connection of different areas, connection of areas with undersea connection between their countries and etc. These features make HVDC system more effective and more widely used than High Voltage Alternative Current (HV AC) system. A significant advantage of the HVDC interconnection is that power can be transmitted directly between two locations without overloading the existing system. Therefore, HVDC can essentially improve the reliability of complex interconnected systems. Furthermore, HVDC is a fire wall against cascading disturbances and in this way, it prevents blackouts. For these reasons, in some parts of the world, HVDC or hybrid interconnections, consisting of AC and DC interconnections, became already the preferred solution. HVDC has become the dominating technology for long distance transmission of bulk powerThe main objectives of this report are to present the basic fundamentals of the HVDC transmission system, the different technologies of HVDC and the most important applications of HVDC transmission system. National and international practices in such fields are also included. In addition, the role of HVDC transmission system to help prevent outage in different power grids will be demonstrated. As related subjects, we will provide the main ideas of FACTS. A special emphasis is given to operational features of HVDC as compared to those features provided by SVC and UPFC. To understand how the HVDC transmission system achieves the stability and good performance for any system disturbance, we make system simulation using MA TLAB program. In addition, we present different case studies including normal operation, current step test.