An improved power-frequency admittance model of multi-machine parallel system with VSG as the main power supply

In order to solve the power frequency oscillation problem in the virtual synchronous generator (VSG) multi-machine parallel system, a power-frequency "admittance" model is proposed, which can comprehensively describe the powerfrequency response characteristics, but does not consider the primary frequency modulation function. With the massive access of new energy and the continuous penetration of power electronic equipment, there will inevitably be a system with new energy as the dominant power source, which mainly uses VSG technology to connect the power system. At this time, VSG must play a primary frequency modulation function, and the above model is no longer applicable. Based on the multimachine parallel system with VSG as the main power supply, the power-frequency "admittance" model of VSG participating in the primary frequency control of the system is established. The factors and mechanisms that affect the power frequency oscillation of the VSG in the system are analyzed through the transfer function, and the effectiveness of the model and frequency oscillation characteristics is verified by PSCAD/EMTDC simulation.