Brazils fast growing economy and population, combined with hosting the 2014 FIFA World Cup and 2016 Olympic Games, means an additional 47,000 km of transmission lines, or $27 billion of investment between 2012 and 2021 is needed. The majority of these investments will be dedicated to transporting the electricity coming from large hydro plants in the north of the country to the south-eastern region where the consumption centers are located.
Quest for clean and renewable power is increasing globally year by year. Governments are looking at different ways to solve their energy crisis; interconnection of HVDC systems is one in that. Lots of investment is going into connecting different power grids and thousands of Megawatts of power is being sent everyday across these grids.
The first long distance High Voltage Direct Current was sent in 1882 over 57 km and only 1.5kW was sent in Germany. Now the longest transmission is the Rio Madeira transmission link in Brazil which has a length of 2385km and sends 7.1GW of power.
In these 130 years the concept of Direct Current has again come into relevance with people realising its advantages over long distance transmission and how the problems that were earlier faced can be overcome. Thomas Edison popularised the concept of DC everywhere but it never really caught the imagination of the people. Now after numerous researches and new innovations in this field, the industries are again looking at HVDC to overcome the problems of HVAC transmission.
The average size of the HVDC transmission systems has increased in the recent years. The market for this transmission system is also increasing with more countries getting involved with the project and installing more HVDC grids.
HVDC has various advantages like for long distances it is much cheaper to transmit power, the transmission losses are less for larger distances, they do not have any maximum transmission distance and one of the very big advantage is that it allows the power to be transferred from one AC grid to another having different frequencies. This helps in linking incompatible grids, brings stability and increases the economy.
The main concerns with HVDC are that its converter stations are expensive and the system of controlling the power flow must be well communicated so the multi-terminal systems are costly. There are big companies getting involved in the HVDC market and are coming up with innovative ideas to solve some of the issues concerning this market.
In HVDC the basic process at the transmitting end is to convert the AC to DC and at the receiving end convert this DC back to AC. These conversions can be done by using rectifiers and inverters. The other important devices used in this are filters, thyristors, Insulated Gate Bijunction Transistor (IGBT) and Voltage Source Converter (VSC). There is a lot of research going on in the VSC field because it is one of the key aspects to reduce the losses. The power can be sent by overhead lines or undersea cables.
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