Electrical energy can be obtained by burning coal (thermal power plant), by using nuclear fuel (nuclear power plant) or by using the power of water (hydro power plant). In these cases, the energy obtained by the sources put a shaft of an electrical generator in motion. The generator generates electrical energy – see Figure 1. In the installation, excitation system for the generator is used. The system turns on an uncontrolled rectifier, thyristor-controlled rectifier or AC thyristor regulator dependent on the generator type. The obtained energy is transmitted using a transmission system towards consumers. The transmission yet is made mainly in high-voltage AC energy form (HVAC). In different parts of the transmission network the voltage value may be different. There are so-called high-voltage (420 kV, 220 kV, 110 kV, etc) and medium voltage (20 kV, 6.6 kV, etc.) systems. General consumers consume electrical energy from so-called low-voltage systems (230V, 50Hz or 110V, 60Hz). During the transmission the type of energy does not change, only the value of the voltage changes using transformers.
TopConversion In The Process Of Electrical Generation
Electrical energy can be obtained by burning coal (thermal power plant), by using nuclear fuel (nuclear power plant) or by using the power of water (hydro power plant). In these cases, the energy obtained by the sources put a shaft of an electrical generator in motion. The generator generates electrical energy – see Figure 1. In the installation, excitation system for the generator is used. The system turns on an uncontrolled rectifier, thyristor-controlled rectifier or AC thyristor regulator dependent on the generator type.
Figure 1. Generation of electrical energy
The obtained energy is transmitted using a transmission system towards consumers. The transmission yet is made mainly in high-voltage AC energy form (HVAC). In different parts of the transmission network the voltage value may be different. There are so-called high-voltage (420 kV, 220 kV, 110 kV, etc) and medium voltage (20 kV, 6.6 kV, etc.) systems. General consumers consume electrical energy from so-called low-voltage systems (230V, 50Hz or 110V, 60Hz). During the transmission the type of energy does not change, only the value of the voltage changes using transformers.
The processes of obtaining electrical energy using renewable energy sources have their features studied in the next Chapter 9.
The processes, occurring in the transmission lines for AC electrical energy, are connected with the type and the mode of operation of the consumers. Also, these processes often cause different in types disturbances of the quality of electrical energy. Furthermore, some limitations have to be monitored. The limitations are connected with both energy quality and capabilities of the corresponding transmission system, and they are:
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Steady-state power transfer limit
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Contingency limit
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Voltage stability limit
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Dynamic voltage limit
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Transient stability limit
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Power system oscillation damping limit
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Inadvertent loop flow limit
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Thermal limit
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Short-circuit current limit
The benefits of control in the process of electrical energy transmission can be marked as:
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Increase loading and more effective use of transmission corridors
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Added power flow control
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Improved power system stability
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Increased system security
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Increased system reliability
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Added flexibility in sitting new generation facilities
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Elimination or deferral of the need for new transmission lines
The achievements in the field of Power Electronics allow the use of power electronic converters in the processes of transmission of electrical energy with a purpose to observe the mentioned limits (Asprund, 2008). Incorporating such converters gives certain flexibility of energy transmission; therefore, the systems using such converters are called Flexible AC Transmission Systems (FACTS).
Thus, FACTS enhance controllability and increase power transfer capability. Thoroughly, FACTS are systems containing semiconductor converters, information and control technologies (software), and interconnecting conventional equipment that creates intelligence into the network by providing enhanced-power system performance, optimization, and control (Hingorani, 2000). The advantages of FACTS to a construction of new transmission lines are less infrastructure investment, environment impact, and implementation time.