Abstract
Modular multilevel converters (MMCs) are considered very promising converters due to their modularity structure and high reliability from fault-tolerant. A fault within a submodule (SM) is one of the main issues in half-bridge MMCs with substantial switching devices. In this paper, an adaptive carrier based phase disposition pulse width modulation (PDPWM) technique for MMCs, which uses only one carrier having flexibility with fault-tolerant capability, is presented. The energy-based control is also used in this study to regulate the balancing of SMs during and after a fault. In order to investigate the performance of the proposed method, a laboratory single-phase MMC prototype has been built by using four SMs to generate nine-level. The single-phase MMC prototype is tested by assuming one of the SMs in the failure condition. The result revealed that the proposed method had been successfully applied to the MMC prototype to control the upper and lower arm during the failure. In addition, the reference command will correct the fault according to the adaptive carrier and the computational burden is lesser since it only uses one single carrier.
Highlights
Selective harmonic elimination (SHE) is a low switching frequency modulation based on harmonic elimination theory, which can generate less THD compared to other techniques
This paper presents a modulation technique for Modular multilevel converters (MMCs) based on phase disposition PWM (PDPWM) with 2N + 1 level output voltage
The flexibility of the adaptive carrier signal can act as a fault-tolerant control strategy for MMC based half-bridge SM
Summary
MMCs have become a highly attractive topology due to their various advantages, such as remarkable advancement in designing hierarchical scheme, easy to balance. Redundant SM is placed and operated at the same time, when an SM fails, only the faulty SM is skipped, and the other SM does not change and can work symmetrically or asymmetrically Most of these strategies use CPS-PWM, PDPWM and nearest level modulation (NLM). An adaptive carrier PDPWM method based on the centralized capacitor voltage balancing is presented This method has the following features, only one voltage reference and one carrier are needed for each arm, thereby considerably decreasing computational burden requirement compared to the CPS-PWM and conventional PDPWM. The operation principle of the MMC is to control the upper and lower arm voltages of the sinusoidal with a DC offset up to half of the DC link voltage with an opposite phase of 180◦. The controller locally regulates each arm to keep the individual capacitor voltage between the upper and lower arms identical
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
