| HVDC transmission system has the characteristics of large capacity and long distance power transmission, which plays an important role in the regional power grid interconnection. Thus, its running state strongly influences the sending and receiving terminal power grid operation state. Reasonable maintenance strategy for the HVDC transmission system can bring remarkable positive influences, which can improve the operation efficiency of the interconnected power grid. Otherwise, it may also affect interconnected power grid’s safety, stability and reliability, which cause economic losses. Therefore, it has become one of research focus on the HVDC transmission system safety, reliability and economic operation.Based on sufficient understanding of its function, this study decomposes the functional structure of the HVDC transmission system. Based on this clue, this study calculates its real-time reliability and simplifies the HVDC transmission system interconnected sending and receiving terminal power grid model. Additionally, this study also researches the HVDC transmission system-centered maintenance strategy with power grid operation risk and builds power grid condition based maintenance model considering association sets’opportunistic maintenance. The main works are as follows:(1) The universal generation function method is introduced for the HVDC transmission system real time reliability calculation. As an efficient calculation method for discrete random variables composition calculus, the universal generating function can obtain probability distribution function of the HVDC transmission system states in a hierarchy through merging similar items and recursively calling typical logical structure function. Comparing to the system state-transition method based on the Markov model, the universal generating function method can reduce the middle states number and decrease the calculation intensity, which has obviously advantages in calculation intensity, flexibility, feasibility and calculation errors referring to calculating system real-time reliability.(2) The HVDC transmission system function is decomposed into serial-and-parallel combinations of 6 main subsystems based on the fully understanding of it. Each subsystem state probability distribution function can be calculated by the Markov model considering its structure and standby model. And the universal generating function is used to calculate the HVDC transmission system reliability. The obtained explicit function between the HVDC transmission system reliability and equipment’ reliability makes the calculation of its reliability on the given maintenance schedule be possible, which is also the fundamental of the HVDC transmission system maintenance strategy for the further decision-making.(3) The optimization research is on the center of HVDC transmission system maintenance strategy. The sending and receiving terminal power grid interconnected by the HVDC transmission system is simplified into two nodes model. And simultaneously the sending and receiving terminal power grid operation risk is explored. According to this study, a whole maintenance strategy is researched firstly. Then, further considering the maintenance resources limitation, the local maintenance strategy is researched. The equipment’ importance ranking model, the reliability tracing model and the reliability sensitivity analysis model are applied to recognize its weakness. The reliability sensitivity analysis model is selected to recognize its weakness. At last, equipment’ maintenance effects are considered to the impacts of HVDC transmission system maintenance, and the total risk of HVDC transmission system maintenance is calculated considering the equipment’ maintenance cost, which further improve the economy of HVDC transmission system condition based maintenance.(4) When the system maintenance schedule is given, researches on the scene of equipments failures before their maintenance schedule are considered. Considering equipments’ opportunistic maintenance caused by equipments failures in the association sets, the modified system state-transition method is used to calculate association sets availability function and associated equipments expected maintenance times. Based on it, system condition-opportunity maintenance model is built on the aim of the minimal system operation risk. |
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