PROJECT TITLE :

A Space-Vector PWM-Based Voltage-Balancing Approach With Reduced Current Sensors for Modular Multilevel Converter

ABSTRACT:

Arm voltage and submodule (SM) capacitor voltage balancing may be a key factor for the safe and reliable operation of modular multilevel converters (MMCs). The arm voltage balancing is achieved through a zero-sequence voltage controller in carrier pulse-width modulation (CPWM). In this study, a dual space-vector pulse-width modulation (SVPWM) technique is proposed for an MMC, that eliminates the external controller for arm voltage balancing. During this approach, the three-phase top and bottom arms are independently controlled using SVPWM. Furthermore, the capacitor voltage balancing will be achieved using redundant switching vectors. But, this can increase the computational load on the house-vector modulator. Therefore, an external capacitor voltage-balancing approach is proposed to reduce the computational complexity. The proposed approach uses the direction of load current instead of the arm current in SM selection method. As such, the specified range of current sensors is reduced to fiftypercent in an exceedingly three-phase system. The proposed modulation and voltage-balancing approach are simulated and experimentally verified on the MMC system with 3-level flying capacitor (3L-FC) SMs. Simulation and experimental results show the successful balancing of the arm voltage and SM capacitors voltage.