Research On Contingency Reserve Strategy Of Receiving-End Power Grid Integrated With UHAVDC Transmission System

The improving of voltage class is helpful to reduce the loss and improve the economy of power transmission. Considering the development of clean energy and the requirement of power transmission from the western region of China to its eastern region simultaneously, UHV transmission system is developing rapidly, which greatly improves the ability of power system to allocate the nationwide resource.Based on the background of UHVDC transmission system being commissioned, this paper analyses its influence on the reserve requirement of receiving-end power grid. This paper also classifies the existing reserve strategy and discusses the advantages and disadvantages of them. Based on the above, this paper puts forward the contingency reserve strategy of receiving-end power grid integrated with UHVDC transmission system.Firstly, from the point of maintaining power system steady-state operating, aiming at the characteristic of the occurred failure of the UHVDC transmission system will improve the secondary reserve requirement of receiving-end power grid, based on the basic conceptions of power system reliability, to improve the economy of power system on the basis of maintaining the system reliability, taking the relationship between the cost and benefit of reserve as the breakthrough point, this paper puts forward the secondary reserve strategy based on the cost-benefit analysis, which can further improve the reliability and economy of power system by considering the reserve of load side and tie-line side.Secondly, based on the secondary reserve strategy, from the point of maintaining frequency transient security of power system after failure occurred, aiming at the characteristic of the occurred failure of the UHVDC transmission system may result in the included primary reserve when the secondary reserve is determined is hard to maintaining frequency transient security of power system even though the determined secondary reserve is enough, to meet the limit of maximum frequency deviation and maximum steady frequency deviation after failure occurred, this paper discusses the necessity to increase the primary reserve on the basis of determined secondary reserve based on the cost-benefit analysis and puts forward the primary reserve strategy considering frequency transient security of power system after failure occurred.Finally, the result of the example shows:the determined secondary reserve based on the cost-benefit analysis is helpful to improve the economy of power system on the basis of maintaining the system reliability; the determined secondary reserve capacity is approximately equal to the sum of the monopolar fault capacity of UH VDC transmission system and a main generator capacity; it can further improve the reliability and economy of power system by considering the reserve of load side and tie-line side; the facts such as the probability of monopolar fault, the probability of bipolar fault, the VOLL, the price of standard coal and the reserve capacity of load side will influence the result of optimal secondary reserve. The included primary reserve when the secondary reserve is determined is hard to maintaining frequency transient security of power system and needs to be increased according to the variation process of frequency after failure occurred; it will significantly improve frequency transient security and economy of power system by taking the method of emergency load shedding after failure occurred; the facts such as the time delay of governor, the margin limit of primary frequency control, the regulation speed of primary frequency control, the coefficient of generating unit and the moment of emergency load shedding will influence the result of optimal primary reserve.