考虑风电随机性的直驱风机风电场等值模型评价方法

Assessment Method for Equivalent Models of Wind Farms Based on Direct-Driven Wind Generators Considering Randomness

近年来,直驱风机风电场引发的电力系统次同步振荡现象成为了研究的热点。然而,尚未有文献对适用于次同步振荡研究的风电场等值模型进行研究。该文提出在考虑风电随机性的情况下评价等值模型适用性的方法。首先,以风电场等值模型与详细模型对应特征根的平均欧氏距离为判别依据,采用二次函数逼近的方法刻画该距离与注入风功率之间的非线性关系,然后利用高斯混合模型刻画风功率的概率分布,并利用高斯混合模型的性质求取上述平均欧氏距离的分布函数。通过计算这一分布的均值和方差可以对不同等值模型进行评价,均值和方差均较小的等值模型在风电随机变化的情况下能更准确地反映真实风电场的动态特性。最后,以聚合等值模型和基于输出倍乘的单机等值模型为例介绍了文中所提评价方法的应用流程。

Recently,the research on the sub-synchronous oscillation(SSO)caused by direct-driven wind generators (DDWG)became a new hot field.However,no existing literatures have discussed the equivalent model of the DDWG-based wind farm for the SSO research.This paper proposed a methodology to evaluate the applicability of different equivalent model considering the randomness of the wind power.First,taking the average Euclid distance between the corresponding eigenvalues of the detailed system and the equivalent system as the criterion,a second-order polynomial was adopted to approximate the nonlinear relationship between the distance and the injected wind power.Then,the distribution of wind power was modeled as a Gaussian mixture model (GMM),and the analytical calculation method of the distribution function of the distance was derived with the help of GMM's properties.By calculating the mathematical expectation and the variance of the distribution,evaluation can be conducted to different equivalent model.The equivalent model with smaller expectation and variance can represent the dynamics of the actual wind farm more accurately.At last,the structure-reservingaggregatedmodelandtheoutput multiplication based equivalent model were taken as examples to explain the evaluation process of the proposed method.