Research Of The Effect Of Series Compensation On Erpu Line To Operation Character Of Sichuan Power Network

With the developing and expanding of Power System, the length and transmitting power of the transmission and distribution line are also increasing. So for the medial and low voltage electrical networks, the voltage quality always cannot be satisfied with users' needs because of the increase of the line impedance and transmission power; For the high voltage and long distance line, the transmission capacity of lines is always affected by the limit of static stabilization and dynamic stabilization. In order to develop Power System more, faster, better and economically, using series capacitance to compensate lines' impedance is a effective measure of improving voltage quality and transfer capacity.Series compensation is divided into fixed series compensation and controlled series compensation. The later belongs to FACTS. In AC transmission system, using series capacitance' capacitive impedance to compensate lines' impedance to shorten electrical distance of different generators, increase the synchronous moment, improve the stability of Power System, reduce voltage decreasing and relative power angles. Thereby improving stable level of Power System, increasing transmission capacity of transmission line and improving electrical networks' actual transmission ability.The controlled series has a inductance circuit, which is controlled by thyristor valve, is in series with series capacity, so it produce a manipulative additive current, achieving the control of equivalent capacitive-reactance of series compensation capacitance; namely, adjust series compensation capacitance smoothly and control dynamic response through controlling thyristor valve's trigger angle. Using controlled series compensation can farther improve the transmission ability of electrical networks and the stability of Power System, restrain low frequency oscillation and sub-synchronous resonance.Ertan hydroelectric plant is the biggest hydroelectric plant station of 20 century in our country, the capacity of all the generator is 3300MW. The least electrical power is 1000MW. The gross electrical power of a year is 17 billon kW.h. But Ertan hydroelectric plant is far away from Sichuan main network. The flow which is transmitted from Ertan hydroelectric plant into main network, is close to the line's single phase permanence stable limit. Therefore, the line's anti-jamming ability is poor. It is very difficult to widen transmission passageway from Ertan to Zhaojue. In order to strengthen the anti-jamming ability of Erzi line, enlarge its transmission capacity and assure the stability of Sichuan network, consider using series capacity of certain capacity doubtless has certain theoriesand practical meaning.Combined with the facts of Sichuan power network, the main analysis and research in this paper are as follows:(1) The transmission character of EHV transmission long line with compensation.(2) The practical situation and problems of Sichuan power network.(3) Feasible schemes to improve transmission ability of Ertan hydroelectric plant andthe necessity of using series compensation.(4) Accurate mathematical model is established. Analyse the influence of series compensation through stable-state analysis and dynamic numeric simulation.