Adaptive discontinuous zero sequence signal for modular multilevel converter applications

Abstract

This work proposes a technique to inject a discontinuous zero sequence signal (D-ZSS) into voltage modulation of the modular multilevel converter arms. The core of the technique is the clamping of the arm voltages to a particular level and interval, in such a way that reduces the number of switching events on the instants that the load stress on the semiconductors is high, and consequently the dissipated energy. The clamping voltage and interval has some degrees of freedom which are also discussed. The description of the methodology is complemented with its simulation. Either in steady-state or in dynamic converter operation this technique is able to reduce the switching events and the correspondent total losses up to 6.6%. Hence contributing to a more efficient VSC-HVdc solution.Postprint (published version

Modulation techniques applied to medium voltage modular multilevel converters for renewable energy integration: A review

“…In the discontinuous ZSS an offset is added to the modulation index target in such a way that voltage generated at the VSC's output is clamped to a particular voltage level. In the literature it is shown that its possible to clamp the converter voltages over 30, 60, and 120 degrees intervals [33,34,47], and during those intervals the switching events are avoided [48,49]. The impact of the combination between the modulation techniques and the ZSS presented on the modular multilevel converter performance was also analyzed and presented in Section 4.…”