Impedance scan and characterization of Type 4 wind power plants through aggregated model

With the rapid increase in planning and commissioning of large offshore wind farms, the use of long HVAC submarine cables to transfer the power has become a necessity. However, the interaction of the HVAC cable capacitance and the inductance of transformers within the wind farm creates multiple resonance points. This, together with grid-connected converter controller unstable operation can cause excessive harmonic emission. In this paper, a method to determine the system stability using the wind farm output impedance and the grid impedance is presented. Further, in order to analyze this instability, the entire wind farm needs to be modeled, which increases the computational burden significantly. Therefore, a methodology to aggregate the collector system of a wind farm, in a manner that preserves the frequency response of the wind farm impedance, will also be presented.