考虑大规模风电并网的电力系统随机潮流

Probabilistic Load Flow Method Considering Large-scale Wind Power Integration

提出一种考虑大规模风电并网的电力系统随机潮流算法。该方法针对大规模风电注入功率波动性强的特点,在当前结合半不变量和级数展开的随机潮流计算方法基础上,采用分段线性化手段减小潮流方程线性化误差,提高系统状态量的半不变量求解精度;引入C型Gram-Charlier级数,避免在含大规模风电的系统中采用A型Gram-Charlier级数逼近系统状态量概率密度函数会出现负值的问题。为求分段线性化后系统状态量的半不变量,根据半不变量的定义,推导得出了分段线性函数因变量的半不变量与自变量分布之间的定量关系,此关系可方便地考虑风场有功、无功注入相关性。对IEEE 30节点系统的测试表明:所提算法与蒙特卡罗法计算结果是一致的,而计算速度则要快得多;与当前半不变量法相比,结果计算精度得到了较大提高。该算法可快速、准确地求解含大规模风电并网的电力系统随机潮流,具有较好的实际应用价值。

A probabilistic power load flow（PLF） method considering large-scale wind power integration was proposed in this paper.The method,based on the current PLF method and using semi-invariant and series expansion,can make improvements in two aspects.First,piecewise linearization model was used to reduce the power flow model linearization error and improve calculation accuracy of dependent variable semi-invariant.Second,C-type Gram-Charlier series was introduced into the proposed algorithm to avoid getting the negative value of probalibity density function（PDF） of node voltage or branch power when the A-type Gram-Charlier series expansion was used to estimate distribution of random variables in probabilistic load flow calculation with large-scale wind power.To obtain semi-invariant of state variables,the inter-relationship between semi-invariant of dependent variable and distribution of independent variable in piecewise linearization model was derived on the basis of the definition of semi-invariants and the relationship can describe the correlation conveniently between active and reactive power of wind farm.Finally,the calculation on the IEEE 30-bus test system indicates that the proposed PLF method can obtain the same results as Monte Carlo simulation method with much higher speed and has much higher accuracy than the current PLF method using semi-invariant.The proposed method can solve PLF problem of power system with large-scale wind power integration quickly and accurately,and has some practical value.