An Improved MPC Integrating Fuzzy PI of an MMC-HVDC System

Modular multilevel converter (MMC) has been widely used in high-voltage and high-power transmission because of its high efficiency, low harmonics and low switching frequency. Model predictive control (MPC) can well overcome the difficulty of PI controller parameter tuning and overshooting. However, when the traditional MPC is applied in MMC systems with a great number of submodules, the times of rolling optimizations is too many to realize real-time control. And the existing MPC in the MMC system is to replace the inner loop controller with the MPC, and still retain the outer loop PI controller. Therefore, an MPC integrating the fuzzy PI is proposed. The accuracy requirement of parameter tuning of outer loop controller is reduced by the fuzzy PI control, and then the number of rolling optimizations of the inner control system are reduced by the double-layer MPC. Finally, a 101-level MMC-HVDC system is set up in PSCAD/EMTDC to confirm the feasibility and validity of the method.