Capacity Credit Evaluation Of Photovoltaic(PV) Power Generation

Under the dual constraints of energy security and environmental protection,the penetration of photovoltaic(PV)power generation in power systems increases year by year.PV power generation can not only meet the needs of load demand(denoted as "power value"),but also at the same time has an innegligible contribution to the power system capacity adequacy(denoted as the "capacity value").In order to give full play to the importance of PV power generation as a power source,it is necessary to evaluate the capacity value of PV power generation.In this paper,the capacity credit metric is utilized to describe the PV capacity value.This paper is constructed as following five aspects: the temporal-spatial distribution modeling of solar irradiance and PV output power,reliability-based PV capacity credit estimation,general evaluation model for PV capacity credit evaluation,uncertainty analysis and energy system-based measure to improve PV capacity credit.Specific work as follows:(1)The temporal-spatial distribution model of solar irradiance is established considering kinds of affecting factors.A novel model combined with PV module temperature and the first-order low-pass characteristic-based PV output power is built to obtain the PV power generation model,and this model is adaptive for different time and space scales.First,the randomness and inhomogeneity distribution of the solar irradiance caused by cloud shadows is simulated by the Perlin noise and random walk model.In addition,a high-resolution temperature model of PV modules is built,which takes into account the hysteresis effect of module temperature and solar irradiance.Finally,the PV output power model is established by combining the solar irradiance and the PV module temperature model.This model provides reliable data support for the subsequent study of the reliability and capacity credit of PV system.(2)Based on the proposed PV output power model,reliability of the power system with multi-state PV power generation is calculated by using Monte Carlo simulation and universal generating function(UGF)technique.The effective load carrying capacity(ELCC)metric is selected and the two techniques are used to calculate the PV capacity credit for comparision.Sensitivity analysis is also conducted in order to obatian the main factors affecting the PV capacity credit.(3)On the basis of analyzing the factors that affect the PV capacity redit,a universal model for PV capacity credit evaluation based on artificial neural network is established.The diminishing marginal effect between PV penetration increasement and PV capacity credit increasement is found and revealed.What is more,a time-variant PV capacity credit assessment in its lifetime is also simulated considering the degradation of PV system performance.It reveals that PV capacity credit has the characteristic of time variability.This established model allows power system planners to quickly determine the PV capacity value and its impact on the power system.(4)To characterize the impact of uncertainty on PV capacity credit assessment,a three-parameter interval(TPI)number-based uncertainty analysis model for evaluating PV capacity credit is proposed.The UGF model is extended to a TPI-based UGF model(TPIUGF),and the TPIUGF models of conventional generator unit,PV power plant and load are constructed.The PV capacity credit is solved by improved Cuckoo search algorithm.In order to narrow the search space,the golden section technique combined with equal width division is adopted.In order to speed up the convergence rate,a modified interval number-based orthogonal experiment is proposed.The proposed evaluation method of PV capacity credit based on TPI number indicates that the fluctuation range of the capacity credit,and the maximum probability value can provide a reference basis for decision-makers at the same time.(5)The measure to improve PV capacity credit by introducing energy storage system is put forward.Based on the maximum fluctuation model and the wavelet packet decomposition method,the power/capacity configuration of energy storage system(ESS)is determined.Three different ESS control strategies for improving PV capacity credit are proposed,and their effects and degrees of improvement on PV capacity credit are compared.It is pointed out that the control strategy with the aim of improving the PV-load correlation has the best effect.The application of the energy storage can provide an important and alternative way for improving the PV capacity credit and the accommodation of PV power generation in power systems.The proposed evaluation model of PV capacity credit in this paper provides a theoretical reference for the power system planning with large-scale PV power generation integration,especially under the new power supply structure.It also has a certain reference value for PV power generation friendly integration,achieving the coordinated development of PV power and the grid,innovating the future operation management mode of power system.