A New Approach to the Modulation and DC-Link Balancing Strategy of Modular Multilevel AC/AC Converters

Modular multilevel AC/AC converters have been examined for high powers and voltages applications such as traction converters and interphase power controllers. It can also operate directly on a transmission line for voltage regulation and reactive power control . This paper presents a modulation technique aiming at an independent control over the AC voltages as well as reactive power of the AC/AC converter, having the capability of controlling the transferred active power from the input source to the load. Moreover, the DC-links of a modular AC/AC converter needs to be regulated for proper operation under various load conditions. The proposed modulation technique embraces a DC voltage balancing strategy based on the engaged switching instants. PSCAD simulation results are presented to validate the proposed modulation technique for both open-loop and closed-loop control