Modular Multilevel Converter with Simplified Nearest Level Control (NLC) Strategy for Voltage Balancing Perspective

摘要

Modularity, low losses, scalability as well as low filtering requirements make the Modular Multilevel Converter (MMC) a best solution besides HVDC implementations. But still the key concern associated with the implementation has been the voltage balancing of capacitors of about their sub - modules (SMs). Even though the MMC does have an attractive configuration with such a variety of notable features, a sophisticated control method is designed for desirable process. Pulse-width modulation (PWM) control strategy of various combinations, such as phase and level-shifted carriers, has been the most popular MMC deployment. However, the difficult positioning of a significant number of SMs as well as a high switching frequency seems to be constraints of PWM techniques. Even so, Nearest Level Control (NLC) provides a lower switching frequency and easier implementation. Due to its flexibility as well as easy implementation, NLC has become the most famous having to balance methodology for MMC SMs. The research article provides an insight that the use of NLC for 5 levels of MMC, where neither individual sub-module status has been required at the gate pulse generation stage. SM Identification is done upon sorting of sub-modules and the logic of a gate voltage level switching could be assessed. Throughout this article the MATLAB simulation has been conducted out on 5 levels of MMC with simplified NLC and the control strategy of PWM. Just on basis of the results obtained, a comparative evaluation between two techniques was carried out.