Dynamic Modeling, Control and Electromagnetic Transient Simulation of the Modular Cascaded Converters (MCCs)

This paper presents the dc-link capacitor balancing control scheme and effective current regulation algorithms for the modular cascaded converters (MCCs). The analytical model for the dc-link voltage balancing and capacitor energy mechanism are presented. Based on the devised control models, an effective control method is devised for the dc-link capacitor voltages, i.e., the sum capacitor voltage controller (SCVC), difference capacitor voltage controller (DCVC). In order to improve the tracking accuracy of the current regulator, the model predictive current controller (MPCC) is devsied and implemented. To minimize the circulating current, an effective circulating current damping controller (CCDC) is proposed by using a proportional-resonant controller. Digital simulation of the single-phase five-level MCC is carried out using the Electromagnetic Transient Program, which confirms the validity of the devised algorithms.