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Power grid
Huangjie Gong, 1/21/2017

Power grid is an interconnected network where electricity comes and goes, just like a plumbing network, where water comes and goes. A complete power grid is always comprised of sources, transmission lines and distribution lines. Source generates electricity. Transmission lines delivere the electricity to distributed demand centers by after the electricity being converted to high voltage. Finally, distribution lines transmit power to individual customers.

Fossil
Typically there are 4 steps to turn fossil energy into electricity. Firstly, heat is created by burning fossil fuel. Then the heat turns the water into steam with high temperature and high pressure. In the third step, the steam pushes the turbine shaft connected to the shaft of generator, where electricity is produced based on Electromagnetic induction. Finally, the steam will be converted to water by cool water nearby and be used again and again. Fossil sources are the mostly used because they are affordable and very reliable, but they may also lead to air pollution and global warming.

Nuclear Power
Nuclear power is based on Electromagnetic induction too. Be different from fossil energy, nuclear power generate heat by nuclear fission in the reactor. Then the heat converts water into steam. Steam pushes the turbines thus the generator generates electricity. Nuclear power pollutes less but it's regarded dangerous especially after the Chernobyl Disaster and Fukushima Daiichi nuclear disaster.

Hydropower
Instead of steam, hydropower take advantages of water flows to push the turbine directly. It costs less and it does nearly no pollution. But it's location based. Famous water power project includes Three Gorges Dam and Hoover Dam.

Wind
Wind power is an important renewable energy. It is based on Electromagnetic induction too. Wind pushes the blades of turbines connected to generator. The generator finally converters wind energy to electricity. Wind power is clean, free, omnipresent and endless. But it depends on the local weather and it always take long time to cover the initial investment.

Solar
Solar panels converts sunshine to electricity. In the solar panel, photons push the electrons to the other side. If the panel's two sides are linked to form a circle, electrons flow to generate electricity. Solar energy has the same advantages as wind energy, but it is not reliable and its capacity is small.

Purpose
The purpose of power management is to gather electricity from different sources and transmit it efficiently to make supply meet demand. Changes of power supply, power losses in the transmission line and load variance are always need to be considered. The ultimate purpose of power management is to generate power cheaply, to transmit power efficiently and to make the power grid stable.

Problems
Power demand differs a lot during the different seasons of a year, so variable source combinations should be considered from long term considering both efficiency and stability. In short term, the problem is always related to stability. Northeast blackout of 2003 is a failure of power management. In the case, power grid is not stable enough to hold a power surge, causing millions people affected eventually. Typical research focus aiming at solve such problems include economic dispatch, distributed energy resource, peak shaving , information security and so on.

Trends
Modern grid is now more smart, more stable and also more complex. Many intelligent algorithms are adopted to control the power system. Auxiliary software such as MATLAB and PSCAD help to design a better grid. Advanced electronic devices make it possible to realize the perfect designs. The roles in the existed power grid will be more complicated, because the conventional 'customer' may be able to sell electricity to the grid generated from its own solar panel or wind turbine when its power is sufficient. There is more communication between different centers, which makes the whole system more efficient. Smart grid becomes more and more popular. They can be linked or isolated from the city grid easily. Modern grid rely much on computer, so it may fail or face cyber attack.