计及日照强度时间周期特征的光伏并网系统风险评估方法

Risk Assessment Method of PV Integrated Power System Considering Time Periodic Characteristics of Solar Irradiance

目前在含大规模光伏电站的电力系统中长期风险评估中,多采用概率分布模型来模拟日照强度,但该方法无法反映光伏出力及系统风险的时变特征。针对上述不足,以甘肃某光伏电站收集的日照强度数据为样本,对不同时间尺度下的日照强度变化规律进行了分析,用三阶傅里叶函数拟合其月尺度下的变化趋势,用服从三参数威布尔分布的随机变量模拟其日尺度下的波动特征,二者叠加建立日照强度的时间周期特征模型,并验证了该模型的有效性和普适性。根据光电转换关系,进一步建立了光伏电站输出功率的时间周期特征模型,并采用蒙特卡洛模拟法评估光伏并网系统的时变风险。以IEEE-RTS79系统为例,验证了所提方法的有效性。风险评估结果可为电网中长期调度和光伏电站检修决策等提供参考。

Using probability distribution models to simulate solar irradiance is a common method for mid-and long-term risk assessment of PV integrated power system at present. However, it cannot reflect the time-varying characteristics of PV output and system risk. Aiming at above deficiencies, this paper analyzes the time-varying patterns of solar irradiance samples collected in a certain photovoltaic plant in different time scales. The trend of solar irradiance in monthly time scale is fitted with a third-order Fourier function. The fluctuation characteristics of solar irradiance in daily time scale is simulated with a three-parameter Weibull distribution. The time periodic characteristics model of solar irradiance can be represented as superposition of above two parts. Validity and universality of this model is verified through case study. According to the relationship of photoelectric transformation, time periodic characteristics model of photovoltaic output is obtained. Furthermore, the time-varying risk of PV integrated power system is assessed through Monte Carlo simulation. Validity of the proposed method is verified through a case analysis with IEEE-RTS79 system. The result of risk assessment can be applied to mid-and long-term power system dispatching and photovoltaic plant maintenance decision.