Study On Energy Storage Sizing Considering The Capacity Credit Of Intermittent Energy Resources

The contribution of wind resources need to be objectively evaluated in the planning stage of composite power systems,so that the over-investment of generation capacity can be avoided.A notion called capacity credit is developed to quantify the contribution.Meanwhile,battery energy storage systems(BESS)are more widely configured recently to reduce the adverse influence of the uncertainty to enhance wind power capacity,so that the energy structure will gradually transition to an eco-friendlier one.Therefore,a series of researches are carried out in this paper,focusing on improving the deficiencies in the wind power capacity credit evaluation and enhancement.Specific work is as follows:(1)A stochastic scenario generation method is proposed by combining the skew normal mixture model(SNMM)and Vine copulas to draw wind power samples.Vine copulas are used as the link function to join the marginal distribution of different wind power models together.Then the modelling of the marginal distribution and the correlation structure can be decoupled,which enhances the flexibility in modelling and avoids the difficulty in establishing the joint distribution directly.The marginal distribution is constructed by SNMM,which can achieve better balance in complexity and accuracy.This stochastic scenario generation method can apply to joint distribution with different statistical characteristics and provide scenario samples for subsequent capacity credit.(2)An improved cross entropy based importance sampling(CE-IS)method is proposed to cover the correlation between wind power and load in reliability analysis of composite power systems.The method first develops a notion called homogeneous units and utilizes multinomial distribution to model each group of homogeneous units.The optimal parameters are also derived for multinomial distribution to infuse it into the process of CE-IS.Then the joint normal transformation is employed in this method to make the samples drawn by CE-IS correlated to reduce the proportion of useless samples,so that the reliability evaluation can be accelerated.(3)A non-iterative method is proposed to overcome the convergence difficulty and poor accuracy of the secant method when it is combined with the simulation methods of reliability index computation.The smoothing spline method is used to substitute the secant method,by which the fitted curves do not need to cross the interpolation points.Therefore,this method relies much less on the accuracy of a single interpolation point.Besides,no parametric form needs to be designated before fitting,so the proposed method is very flexible in capacity credit evaluation.(4)A capacity credit evaluation method for wind power is developed based on sequential Monte Carlo sampling(SMCS),which is able to cover the temporal properties.The SMCS method is improved by adjusting the reliability parameters of conventional units.Then the smoothing spline method is used again and combined the improved SMCS method to compute the capacity credit of wind power.(5)A sizing strategy for battery energy storage system(BESS)is proposed aiming at enhancing the capacity credit of wind power.Before determining the capacity of BESS,the operating strategy of BESS should be optimized and specified.Therefore,based on the analysis of the characteristics and optimization models of BESS,two control measures are chosen to determine the operating strategies of BESS,which are minimizing the daily peak-valley difference of wind power and maximizing the correlation of wind power and load,respectively.Then a scenario generation and reduction method is developed to construct multiple typical scenarios of wind power and load to ensure the generality of the BESS configuration scheme.Finally,posterior evaluation of capacity credit is performed for the hybrid wind-BESS system,whose results are used to carried out a sensitivity analysis for BESS capacity and the enhanced capacity credit.The sensitivity analysis will support the decision making of the BESS sizing.The proposed method for evaluating and enhancing the capacity credit of wind power can provide theoretical basis for wind-integrated power system planning,which will promote the increase of wind power penetration and improve the energy structure.