| Wind, solar, tidal power, geothermal energy and other renewable energy are developing and enlarging. The power demand of offshore drilling platform, isolated island and other passive load are also increasing fast. All of these have brought new demands to the transmission technology of current power system. VSC-HVDC is a new kind of HVDC which is based on Voltage Sourced Converters (VSC) Technology. By using IGBT or GTO in VSC and the pulse width-modulation (PWM) technology, VSC-HVDC can make passive inversion realized and transmit power to passive load in DC. At the same time, this type of transmission technology can control phase and amplitude output from convertor station. Therefore, it makes the power flow control conveniently. Besides, this type of transmission technology can make the renewable generation and distributed generation parallel in to network by its own conversion and transmission. Therefore the VSC-HVDC transmission technology will have an obvious advantage in feeding the renewable energy, distributed generation to grid, powering to island, city, interconnecting asynchronous AC network and other fields.This topic mainly studies the transmission technology of VSC-HVDC applying on passive power supply network, which is based on the power system development background. After reading, researching and analyzing lots of literature, the main works includes the following:1) The steady state and transient mathematical model which supplies power to passive power network are established according to the VSC-HVDC transmission principle. The control mode and strategy are identified which is suitable to supply power to passive power supply network;2) The SVPWM pulse theory is mastered and realized in the PSCAD for simulation. The model of VSC-HVDC supplying power to the passive network and small power system are established. The simulations of various operating conditions are operated in PSCAD, the operation characteristic of VSC-HVDC supply to passive network and small power system are analyzed respectively, The results show that the system design is correct and the reliability of VSC-HVDC supply to weak power systems is higher than the passive network one by the same control strategy;3) In order to verify the reliability and stability of the VSC-HVDC supplying power to passive network, in this paper, the system static stability is analyzed. According to the characteristic of VSC-HVDC, the power flow calculation is made, the small disturbance analysis mathematical model is established, and the system parameters are analyzed. The results show that when the small disturbance happens in the VSC-HVDC system which supplies power to passive network, it can operate reliably, stably. |
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