Research On Adequacy Reliability Assessment Of Microgrid

In the background of energy shortage and environmental degradation nowadays,microgrids have gained more and more reception in the world.Microgrid is a small power system consisting of distributed generations,energy storages system,loads,monitoring and protection equipments,and it is an autonomous system with self-control,self-protection and self-management.Microgrid is an important part of smart grid.It can utilize distributed generations and energy storages device flexibly and efficiently and solve the grid-connecting problem of distributed generations and energy storages device locally.However,the microgrid brings environmental protection and high efficiency,but also brings a series of operation and control problems.Meanwhile,the flexible operation mode and complicated operation characteristics of microgrid also challenge its reliability assessment.In this paper,considering the flexible operation mode and characteristics of microgrid,the reliability assessment of microgrid adequacy is studied.The main research work is as follows:1)Long-term reliability assessment of islanded microgrid based on Monte Carlo simulation.The characteristics of the reliability evaluation of the microgrid are analyzed,and the sampling model of the sequential Monte Carlo simulation method and the non-sequential Monte Carlo simulation method,as well as the reliability model of the microgrid element,are established.A mixed Monte Carlo simulation method is proposed to solve the problem of sequential charging and discharging process of energy storage system in the non-sequential Monte Carlo simulation method.On this basis,the traditional sequential Monte Carlo simulation method and mixed Monte Carlo simulation method are used to evaluate the long-term reliability of the independent microgrid,and the applicability and the existing problems of the sequential Monte Carlo simulation method and the non-sequential Monte Carlo simulation method in the short-term reliability evaluation are simulated and analyzed.2)Long-term reliability assessment of distribution system containing microgrid based on equivalent nodal model.In view of the characteristics of the microgrid with a certain topology and the integrated access distribution system,a long-term reliability evaluation method based on the equivalent node model for the distribution system of microgrid is proposed.On the basis of the system fault mode partition,the distribution system containing microgrid is transformed into a proposed equivalent node model to simplify the analysis process of the failure mode influence,and the effect analysis of the fault mode is carried out based on the equivalent node model,and the result of the failure mode is obtained.The reliability model of the system components is established and all non-power components are sampled by quasi-sequential Monte Carlo sampling.Under the fault of non-power components,only some load operation mode is used to sample the distributed power and energy storage system by non-sequential Monte Carlo sampling,which reduces the total sampling times of the system components,and can improve the computational efficiency.3)Short-term reliability assessment of isolated island operation microgrid considering static security constraints.Aiming at the difficulty of obtaining time series information by analytic method and non-sequential Monte Carlo simulation method,and the problem that sequential Monte Carlo simulation method can not obtain the system sample effectively in a short time span,the short time sequential state transfer sampling method is proposed.This method has good applicability in short time span,and can effectively get the time series sample of short-term system.On this basis,considering the influence of the microgrid control strategy and static security constraint on the short-term reliability assessment of isolated island operation microgrid,the short-term reliability index values including the index of load average interruption duration are obtained,which has certain engineering application value.4)Short-term reliability assessment of isolated island operation microgrid under master-slave contol based on time-carying dynamic fault tree.Aiming at time-varying feature of short-term reliability and redundant feature of communication system in islanded microgrid under master-slave control,a short-term reliability assessment method based on time-varying dynamic fault tree is proposed.Taking the power supply interruption as the top event,the top event is divided into two classes of two events,direct and indirect events,which are solved separately,and the process of building the tree is simplified.On this basis,the time-varying dynamic fault tree of each load point is established and the probability calculation is carried out.The indexes of loss of load probability and the expected energy not supplied are obtained.This method greatly improves the computation efficiency and has the prospect of online application.