Decarbonization targets in the energy transition and growing environmental awareness drive the integration of renewable energy, which requires increased flexibility and fast control equipment such as voltage source converter-based high voltage direct current (VSC-HVDC) in the power grid. The resulting new layout of the hybrid AC/DC power system also poses new challenges to power system operators. Therefore, this dissertation focuses on how to take the controllable advantages of the HVDC system to enhance the operation security of the AC/DC hybrid power system. One long-term solution is selecting the appropriate access scheme of the VSC-HVDC system for better utilization of controllability and flexibility provided by VSC-HVDC. Another clue is the adjustment of the active power set-point for the VSC-HVDC system during the operation process. First, the optimal access scheme for the VSC-HVDC system in the power system is investigated in detail. A method of access points selection and capacity configuration (APSCC) for the VSC-HVDC system is proposed from actual feasibility, security, and economy perspectives. Then, a joint corrective measure (JCM) by collaborative optimization of the VSC-HVDC and DES devices for improving the power system security is presented. Post-contingency power flow violations in the hybrid AC/DC power system can be cured by the proposed JCM method. Additionally, a voltage angle droop (VAD) control for the VSC-HVDC system is investigated to participate in the optimization operation of the power system for mitigating the overall loading of the hybrid AC/DC systems. Finally, a dynamic corrective control (DCC) method which takes advantage of the HVDC system to regulate power flow distribution is developed.weiterlesen