Impedance Modeling and Stability Analysis of Wind Farm through HVDC Transmission System Considering Commutation Overlap Characteristic

LCC-HVDC is vital for efficiently transmitting large-scale wind power over long distances. However, integrating substantial wind power into the AC grid can weaken the grid's strength, leading to stability issues when the LCC-HVDC sending end is connected to such a weak grid. Traditional models often overlook the rectifier side transformer's leakage inductance and the non-instantaneous commutation process, potentially skewing stability analysis outcomes. To address this, we approximate the commutation current as linearly varying to simulate the actual commutation process and employ a 3-D Fourier transform to develop an LCC-HVDC transmission admittance model that accounts for this phenomenon. By integrating the model with the direct-drive wind farm admittance and grid impedance, and using the equivalent SISO impedance conversion method, an integrated system impedance model is established. The influence of LCC commutation overlap on system stability is analyzed by an example, and verified by PSCAD simulation model.