计及光伏阵列的光伏发电阻抗建模与特性分析

Impedance Modeling and Characteristics Analysis of Photovoltaic Generation Considering Photovoltaic Array

大规模光伏电站并网振荡风险急剧增高,序阻抗建模逐步成为广泛采用的分析方法。目前针对光伏发电的阻抗建模将光伏阵列等效为恒定电流源,未计及光伏阵列自身动态特性的影响。实际光伏发电系统中,光伏阵列输出电压、电流非线性且与幅照度和温度强相关,光伏阵列自身动态对光伏发电阻抗特性的影响存在且不可忽略。该文基于光伏发电交-直流小信号耦合关系,建立及光伏阵列的光伏发电阻抗解析模型,揭示光伏阵列动态特性对光伏发电交流侧阻抗的耦合机理,定量分析直流电容容量、直流电压环、光伏阵列幅照度和温度等因素对耦合特性影响规律。基于控制硬件在环仿真平台,开展计及光伏阵列的光伏发电系统阻抗扫描与振荡复现。研究表明,光伏阵列自身阻抗不可忽略,且与幅照度和温度强相关,通过直流母线耦合至交流端口,最终对光伏发电交流端口阻抗特性产生影响。直流母线电容容量、直流电压环带宽以及幅照度均会影响光伏阵列对光伏发电交流端口阻抗的耦合程度。

The oscillation risk of large-scale photovoltaic(PV)power stations has increased sharply,and sequence impedance modeling has gradually become a widely used analysis method.At present,the impedance modeling of the PV unit equates the PV array as a constant current source,ignoring the impact of its dynamics on its impedance characteristics.However,in the actual PV generation system,the output voltage and current of the PV array are nonlinear and strongly related to the irradiance and temperature.In this paper,the AC-DC small-signal coupling relationship of the PV unit is explained,an impedance model considering the dynamic characteristics of PV array is established,and the coupling mechanism of the PV array dynamic characteristics on the AC side impedance is revealed.The effects of DC capacitance,DC voltage loop,irradiance and temperature on the coupling characteristics are quantitatively analyzed.Based on the control hardware in the loop simulation platform,the impedance scanning and oscillation recurrence are carried out.The research shows that the PV array impedance cannot be ignored,and is strongly related to the irradiance and temperature.It is coupled to the AC port through the DC bus,and ultimately affects the impedance characteristics of the PV unit.The DC bus capacitance,the DC voltage loop bandwidth and the irradiance will affect the coupling characteristics of PV array to the PV unit impedance.