Adaptive discontinuous zero sequence signal for modular multilevel converter applications

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.