Design and Experimental Validation Of FPGA Based Digital Control Scheme Of The Nearest Level Modulation Method For Modular Multilevel Converter Topology

Modular multilevel converter (MMC) has become a preferable circuit topology for industrial applications, where the nearest level modulation (NLM) technique is mostly used to control the arm voltages of the MMC. Implementation of the NLM method on MMC topology using digital control techniques is gaining importance among researchers because of flexible design, full controllability, re-configurable property and modular realization. In order to achieve this aim, field programmable gate arrays (FPGAs) are preferred thanks to their benefits such as high speed performance and parallel processing ability. Accordingly, in this article, FPGA based control scheme of the NLM method was proposed for single-phase five-level MMC topology. In this context, very high-speed integrated circuit hardware description language (VHDL) modules were designed to achieve the proposed architectural design of the NLM method by presenting each VHDL module and algorithm used in the implementation. The architectural steps of the FPGA realization of the NLM method were presented in detail. Gate signals of the switching devices of the MMC topology were observed in simulation environment. Finally, in order to validate the applicability of the digital control scheme of the NLM method, an experimental setup was built using single-phase five-level MMC topology and experimental findings were presented. According to the obtained results of this study, the outcomes including gate signals, arm voltages and output voltages with currents were presented for various modulation index values using the RL load.