Research On Reliability And Its Sensitivity Of Wind Power System Based On NSTPNT

Due to the intermittency,the accuracy of the wind power forecast is inadequate.With the increasing of the wind power integration,quantifying the impact of the wind power forecast error(WPFE)and improving the reserve configuration may help to ensure the reliability of the power system.The modeling to the wind turbine generator can be regarded as the fundamental research of the reliability of the power system.In this paper,the reliability estimation and the reserve configuration of the wind power system considering the WPFE and the reliability modeling to the wind turbine generator are studied.The main work is as follow:1)Considering the unknown distribution of the WPFE,the non-standard third-order polynomial normal transformation(NSTPNT)method is newly proposed.And the analytical expressions of the polynomial coefficients are derived.The WPFE is transformed into the polynomial of the normal random variable whose expectation and the standard deviation are same as that of the WPFE.By substituting the WPFE into the optimal load curtailment considering the reserve,the reliability of the power system is estimated.The sensitivities of the reliability indices with respect to the distribution parameters of the WPFE,including the expectation and the standard deviation,are established respectively,thus the impact of the WPFE on the reliability is quantified.2)With multiple wind farms integrated to power system,the unknown distribution and the correlation of the WPFE make it difficult to calculate the reliability and its sensitivities.The univariate non-standard third-order polynomial normal transformation which ignores the correlation is extended into the multivariate case by deriving the analytical expression of the correlation coefficients before and after the transformation based on the cross product.The transformation between the normal and the non-normal random vectors is established.Besides,for reliability and sensitivity analysis,the sample of the WPFE is usually manually generated instead of the historical data,which means that the correlation control methods should be used to ensure that the samples have the same correlation with the historical data.Thus a genetic algorithm based correlation control technique is introduced to draw the sample of the WPFE.Considerig the correlation among different wind farms,the impacts of the WPFE on the reliability and its sensitivities with respect to the distribution parameters are analyzed.3)The existing correlation control techniques are either inaccurate or computationally expensive,which decelerates the reliability estimation.A hybrid method for correlation control based on the NSTPNT method and the genetic algorithm with local search is proposed to reduce the calculation effort while ensuring the accuracy.With the derated output,the wind farms provide the active power reserve and contribute to power system reliability.However,the capability of reserve provision is limited by the WPFE.The analytical sensitivity model of power system reliability with respect to the derated proportion of the wind farms and the reserve capacity provided by the conventional generators is proposed.The coordination model describing the relationship among the expected demand not served and the reserves of the wind power and the conventional generators is proposed.4)The repair time of the components of the wind turbine generator may not follow the exponetial distribution,which means that the state transitions cannot be modeled by the Markov process.The NSTPNT method is applied to model the distribution of the repair time.And the reliability model of the wind turbine generator is established based on the semi-Markov process(SMP).To solve that,the time-domain expression of the availability is represented by the alternating series of its s-domain expression.And the Euler summation is introduced to calculate the numerical result.Based on the alternating series and the Euler summation,the semi-analytical sensitivity of the availiability with respect to the failure rate and the mean time to repair is proposed.The impact of the non-exponential repair time of the components on the reliability of the wind turbine generator within different time horizons is analyzed.