Abstract:
To address the issue of frequency instability caused by power imbalance when HVDC transmission system enters the island operation state, an emergency frequency control method based on dynamic interactive energy is proposed. Firstly, a state-space model for the DC island transmission system is established. According to the response differences of control links, a system energy model is constructed involving the energy storage term, dissipation term, and interaction term using the first integral method. Then, the influence of different energyterms on frequency stability is analyzed, and it is revealed that the positive interaction energy term is the direct factor contributing to the stability of the degraded system. On this basis, with the aim of minimizing the positive interaction energy of the DC island system, a positive interaction energy compensation branch is constructed. This branch dynamically adjusts the rectifier current command value to realize urgent compensation for the power difference of the sending network and achieve rapid stabilization of system frequency fluctuations. Finally, a DC island transmission system model is built on the RT-LAB platform to verify the proposed method. The experimental results demonstrate that the proposed DC island frequency emergency control method can significantly reduce the negative influence of positive interaction energy on system stability and enable the rapid and stable recovery of system frequency.