Research On Several Important Issues Of Reliability In Electricity Market

With the development of power system and the acceleration of power system deregulation,the problem of power system reliability in the deregulated environment is turning into a hot issue in the domain.Thus,research on power grid reliability and safety is of great engineering value and practical significance.Several major issues in power system reliability analysis are presented in this dissertation.The main contents and the related conclusions of this dissertation are outlined as follows:This paper discusses the particularity of hybrid AC/DC power system.Based on the reliability model of a bipolar HVDC system,one DC line is equivalent to two AC lines, so that an AC/DC system can be transformed to an equivalent pure AC system,and the failure of DC systems with monopolar total outage or bipolar total outage can be analyzed with the equivalent of being failure AC lines,and evaluated with suitable AC transmission reliability assessment software.Furthermore,analysis on the reliability of Yunnan power grid is carried out by using this method.In the field of research of the existing adequacy assessment in composite system, there are already many assessment methods based on a variety of different methods. When all of the methods are used in the same issue of reliability assessment,mutual differences often arise in the assessment results.To solve this problem,the paper presents an evidential reasoning(ER) approach to adequacy assessment in composite system.It is more effective to evaluate the level of reliability factors in composite system on the basis of the Dempster-Shafer's evidence theory.It can be seen from the results that the ER approach is a suitable solution to tackle the MADM problem of adequacy assessment.This paper presents a novel approach to solve an optimal power flow problem with embedded security cost(OPF-SC),where the major aim is to minimize the total operating cost,taking into account both operating security cost and power system constraints.In addition,OPF-SC problem includes the cost of interrupting customer load and the cost of generator ramping.The algorithm handles the objective function and constraints separately,and adopts both directional and random search mechanism.It can avoid falling into local optimal point,which may appear in previous bionics random algorithms due to uncertainness of some parameters and/or without guiding search direction.Results on systems from the specialized literature are adopted to validate the proposed approach. Numerical simulation on the five-bus power system has shown that the proposed method is efficient in solving OPF-SC problems for large-scale power systems. In this paper,a new voltage-reactive power optimization method is introduced, which considers the equipment operational cost and confines the number of operated equipment in each optimization.This paper presents a method of reactive power optimization using the hybrid intelligent algorithm(HIA),the hybrid intelligent algorithm is applied to the IEEE 30-bus system and the computing results prove the method of reactive power optimization which is based on the Hybrid Intelligent algorithm in this paper is effective and valuable in theory and practice.Electric price is the fulcrum controlling power trade and plays a role in price guidance of electricity market.Based on nonparametric theory for conditional heteroskedasticity function,an improved method of electricity price forecasting is proposed.On the basis of real electricity price time series,conditional variance function is modeled for stochastic volatility,and the model is determined by means of non-parametric estimation.In the nonparametric estimation process,an iterate algorithm is introduced to overcome the problem that volatility is unobserved latent variable so that the confidence of estimated conditional variance function is weak.On the study of stochastic volatility of day-ahead electricity price in Humb spot in California,the forecasting is made.And the results of test show that the proposed method has the capability of forecasting electricity prices characteristic of volatility clustering,and improves the accuracy of price spikes forecasting.