High frequency resonance characteristics analysis of voltage-source virtual synchronous generator and suppression strategy

The voltage-source virtual synchronous generator is a grid-forming type power electronic control technology and is able to support converters that have the ability of inertial, primary frequency and voltage regulation. Firstly, the authors build the small-signal model of the voltage-source virtual synchronous generator and conventional converters, compare and analyse the characteristics of the high-frequency resonance modes, the results show that the voltage-source virtual synchronous generator has almost the same high-frequency resonance characteristics as the conventional converter. Secondly, the different control parameters and power grid strength that affect the high-frequency resonance characteristic are analysed with eigenvalue, and the mechanism of voltage-source VSG that caused high-frequency resonance is derived. The leading factor that causes high-frequency resonance is power grid strengths, and the authors proposed introducing virtual impedance into the front-end channel of the current inner loop control strategy to suppress resonance for the voltage-source virtual synchronous generator based on the theoretical analysis with the small-signal model and eigenvalue analysis. In addition, the electromagnetic transient simulation model and RT-LAB controller-in-loop platform are built, and the simulation and experiment results indicate the effectiveness of the virtual impedance control strategy. Similarly with conventional converters, the resonance mode of high-frequency resonance of voltage-source VSG exists, and the damping ratio is small. The dominant factors of HFR of voltage-source VSG is grid-side parameters. Based on the generated mechanism of HFR and the dominant factors, the novelty control strategy of voltage-source VSG is proposed by introducing virtual impedance into the front-end channel of the current inner loop of voltage-source VSG, as reshaping the control configuration. In addition, root locus analysis based on the small-signal model of voltage-source VSG, electromagnetic transient simulation and RT-LAB controller-in-loop experimental verified that this proposed method is effective on suppression HFR of voltage-source VSG.image