Research on Dynamic Interaction and Stability of Rectifier/Inverter Control Loop in Hybrid Cascade HVDC System
In order to study the interaction between the converter control systems of rectifier and inverter of hybrid cascaded high voltage direct current(HVDC)system,the state space model of hybrid cascaded HVDC system is established.The multi-input-multi-output transfer function model of the system is obtained based on the state space model.Then,the equivalent single-input-single-output feedback control model is established according to the multivariable feedback control theory for different research objectives.On this basis,the interaction between different control loops is quantitatively analyzed and the effects of system strength,electrical distance and control parameters on the interaction between the control loops are revealed.It is concluded that the interaction between the control loops is enhanced when the SCR of rectifier or inverter decreases,and the dynamic interaction between the line commutated converter(LCC)and multilevel modular converter(MMC)control loops on the inverter side is enhanced when the length of the AC tie line is shortened,and the parameters of each control loop restrict each other.Finally,the detailed electromagnetic transient simulation model of hybrid cascaded HVDC system is built on PSCAD/EMTDC to verify the effectiveness of the established single-input-single-output feedback control model and the correctness of the theoretical analysis results.
hybrid cascaded high voltage direct current(HVDC)systemmultivariate feedback control theoryinteraction effectsingle-input-single-output feedback control model