Impedance Modeling and Characteristics Analysis of Photovoltaic Generation Considering Photovoltaic Array
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.
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