Optimisation of Virtual Inertia Control and Parameter Stability Analysis of PMSG-Based Wind Turbine

Currently, high power permanent magnet synchronous generator (PMSG) wind turbines and even renewable energy generation systems are connected to the AC bus through a power converter, and the turbines need to pass through a step-up transformer as well as a very long transmission line in order to deliver the energy to the grid. The long transmission lines make the grid impedance larger and the grid characteristics weaker. Virtual inertia control is analogous to traditional thermal power units in that the virtual inertia embedded in the unit is added to the grid system, which is widely used because of its excellent performance in dealing with frequency support problems under weak grid characteristics. Conventional virtual inertia control involves adding frequency variations to the power command to simulate the characteristics of a synchronous generator. However, in traditional wind turbines, the power command has a large delay because it needs to be sent through the main control system. Based on the traditional virtual inertia control, this paper proposes the virtual inertia optimization control by superimposing the additional command of power regulation on the current loop command to speed up the system inertia response and optimize the frequency support characteristics. Then the influence of relevant control parameters on inertia response speed and frequency stability is analyzed in combination with control system theory. Finally, the simulation model is built on the MATLAB/Simulink to verify the support ability and stability analysis conclusion of the optimal control strategy for power grid frequency.