Sequence Impedance Modeling and Stability Analysis for Renewable Energy Power Station

The accessibility of renewable energy power station to weak energy grids is prone to harmonic disturbances and other small disturbance stability problems. Considering the influence of phase locked loop (PLL) and distributed transformer impedance, a harmonic linearization impedance modeling method is adopted to establish a system sequence impedance model for renewable energy power station in the frequency domain; equivalent principle is used to simplify the impedance model of the system to the simplest one-port network; based on the criterion of impedance stability, analyze the stability of the system by considering and investigating the dynamic interaction between the renewable energy power station and the grid; verify the number of parallel inverters and the impact of the bandwidth of the PLL on the stability of the system. The investigation shows that as the bandwidth of the PLL and the number of parallel connected inverters increase, the system stability will gradually deteriorate. The simulation results are also presented to validate the model and impedance stability analysis method.