Decentralized module-oriented realization of pulse-pattern generation, symmetrisation and protection for MMC

Inhalt:
Modular Multilevel Converters (MMC) with a high number of independent modules become more and more important e.g. for energy transfer at high voltages. The connection of offshore wind farms as well as energy transport within the European interconnected grid require independent reactive power control as well as black start capability, making MMC the best choice. The challenges posed by MMC result from controlling several hundred independent states given by the module capacitors and the communication effort needed to transfer the resulting number of switching signals. This paper is the first which suggests a control scheme in which only superordinated set-point and measurement values are transferred to all modules identically, while each module generates its own switching signals based on utilizing a FPGA integrated into the module electronics. The overall effort is reduced considerably, while at the same time dynamic properties can be improved.