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Small disturbance stability analysis of UHVDC hierarchical connection mode system based on jacobian transfer function matrix

As a new topological mode of DC feeding into the receiving power grid, UHVDC hierarchical connection mode has obvious advantages in evacuating the power flow, improving the acceptance capacity and voltage supporting capacity of the receiving end power system. However, compared with the traditional multi-DC infeed mode, the high and low converter buses in the hierarchical connection mode are coupled through the AC network at the receiving end, and the DC converter valves are connected in series, which makes the AC and DC system interaction more complicated in the DC hierarchical connection mode. Therefore, in this paper, according to the topological characteristics of hierarchical DC itself, and considering the dynamic characteristics of DC control, as well as the dynamic characteristics of AC and DC networks, the model of Jacobian transfer function matrix of hierarchical DC system is established, and the validity of the model is verified by MATLAB/Simulink simulation. The results show that the multivariable feedback control system composed of Jacobi transfer function matrix can effectively analyze the stability of small disturbance, and it also lays a foundation for the stability of small disturbance when other power electronic equipment is connected to the power grid.