Nonlinear Control Design of a Two-Level ConverterBased HVDC System Interconnecting 50 Hz and 60 Hz Power Grids

In this study, the design of a nonlinear control strategy to stabilize the VSC-HVDC system is addressed. This strategy is designed to: (i) regulate the voltage of the HVDC cable; (ii) control the active power at the inverter station; and (iii) perform power factor correction (PFC) in both power grids located at the terminals of the HVDC system. Since, the VSCHVDC system is strongly nonlinear, the control of the active power at both the rectifier and inverter stations is addressed using a nonlinear control approach based on Lyapunov theory. A PI controller on the rectifier station’s is used to regulate the HVDC cable voltage. The system performances are evaluated by numerical simulation performed in MATLAB/SimPowerSystems environment. The results confirm that the proposed controller successfully achieves its control objectives and provides good dynamic performance during transient conditions, ensuring the stability of the VSC-HVDC system.