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A full bridge modular multilevel converter (FBMMC) can work in buck and boost modes. It is thus suitable for grid-connected applications in which the dc link voltage varies over a wide range. In this work the emphasis is set on the steady-state analysis of the grid-connected FBMMC under different levels of the dc link voltage. Two control strategies for the dc capacitor voltage are considered and...
A capacitor voltage balancing method for a three phase modular multilevel DC-DC converter (MMDC) is proposed in the paper. The MMDC is derived from a three phase DAB and a modular multilevel converter (MMC) and inherits desirable features of both topologies. To guarantee stable operation of the MMDC, submodule (SM) capacitor voltages are required to be balanced. The proposed balancing method is to...
In this paper, an asymmetric mixed MMC topology of multilevel converter for bipolar HVDC transmission systems is introduced. Among the existing MMC topologies for the bipolar HVDC systems, the asymmetric mixed MMC topology provides the benefits of: a lower number of submodule cells, fewer switching devices and lower conduction losses. Furthermore, the HVDC based on asymmetric mixed MMC can be flexibly...
The modular multilevel converter (MMC) has become the most promising converter technology for high power applications. However, to get more number of levels in the output voltage, a conventional MMC requires large number of submodules. The main technical challenges of an MMC, with a large number of submodules, are the requirement of large number of semiconductor switches, submodule capacitors and...
This paper introduces a new insertion index selection method to control a Back-to-Back Modular Multilevel Converter (MMC) laboratory platform. The test bench is based on a Power-Hardware-In-the-Loop (PHIL) setup constructed from two 6kVA, 3-phase, 10 cells per arm MMC systems connected in Back-to-Back configuration. The proposed insertion index selection method uses the arithmetic mean of available...
Real-time simulation is an important tool of validating the performance of the modular multilevel converter (MMC). By using the field programmable gates array (FPGA), MMC valves with hundreds of sub-modules and the large number of inputs and outputs can be simulated in real-time. In the traditional FPGA based real-time simulation, only the MMC valves are implemented on FPGA, while the rest parts including...
In recent years medium voltage direct-current (MVDC) grids have gained significant attention. This paper presents a new isolated modular multilevel converter (MMC)-based dc/dc converter for connecting such networks. The proposed converter can connect DC grids with different voltage levels and control power flow among them. The proposed isolated dc/dc converter has fewer components compared to conventional...
A modular multilevel converter (MMC) configuration is presented as a medium-voltage high-power drive for variable-speed applications incorporating symmetrical six-phase machines. The topology employs six standard MMC phase-legs feeding two isolated groups of three-phase machine windings, each with 60° spatial phase-displacement. A novel concept of ripple-power decoupling between adjacent sub-modules...
Hot reserved redundant sub-modules significantly increase the reliability of MMC systems equipped with considerable sub-modules. This paper presents a fault-tolerant operation scheme for an MMC with a distributed control architecture. The MMC output, internal dynamics and the average capacitor voltages are balanced and well-regulated while asymmetrical sub-modules in arms are bypassed due to faults...
Fault tolerant operation can significantly improve the reliability of a Modular Multilevel Converter (MMC), but the precondition is that a fast and accurate fault detection and localization method has been embedded into the MMC control system. This paper proposes a fault diagnosis method used in a distributed control architecture, which makes the local controllers capable of identifying the switching...
This paper proposes a new modular multilevel converter with symmetric bidirectional DC fault blocking capability for high voltage direct current transmission systems. The new modular multilevel converter is composed of novel submodules, which is developed from a three-level T-type converter combined with some clamp circuits. The proposed novel submodule can output three voltage levels with six IGBTs,...
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