Novel Converter Topology With Reduced Cost, Size and Weight for High-Power Medium-Voltage Machine Drives: 3x3 Modular Multilevel Series Converter

Abstract

The modular multilevel converter is considered the state-of-the-art power electronic solution for high-power high-voltage applications that require a DC stage and that operate with fixed frequency at their AC terminals. However, in high-power AC-AC variable-frequency applications, it has been proved that this converter topology presents an unnecessarily large number of components and an intolerably high submodule-capacitor voltage ripple at low frequencies. The modular multilevel matrix converter was proposed as a promising alternative for high-power medium-voltage electrical-machine drives since it presented improved performance at low frequencies and a reduced number of components in comparison to the modular multilevel converter resulting in reduced costs and improved efficiency. Even though, the modular multilevel matrix converter is one of the converter solutions that stands out the most for high-power machine drives, it presents some operational drawbacks such the unstable behavior under unbalanced grid conditions and the extremely complex internal control and modulation. Recently, a new converter topology named modular multilevel series converter was proposed presenting attractive operational characteristics such as the high performance at low frequencies, high performance under unbalanced grid conditions, and straightforward control and modulation, which are important advantages compared to the modular multilevel converter and the modular multilevel matrix converter. Nonetheless, as demonstrated in this paper, the modular multilevel series converter presents large component count and poor efficiency. Thus, in this paper, a new converter solution is proposed, which is an enhanced version of the modular multilevel series converter that preserves the previously mentioned advantageous operational characteristics and that presents an improved efficiency and a considerably reduced number of components in comparison to the other three converter topologies, resulting in reduced cost, size and weight.

Systematization of a Multilevel-Topology-Based Linear Amplifier Family for Noiseless DC–AC Power Conversion

“…In this paper, the authors propose the concept of the series of the linear amplifiers based on the circuit topologies of the multi-level converters as one of the novel types of the power conversion circuits. Furthermore, other topologies of the MLLA family with a similar operation principle can be proposed by extending the concept, because many types of multi-level converter topologies have been reported so far [18]- [23]. This means that the other conventional multi-level converter topologies can also be extended as the linear…”

“…The other topologies of the multi-level converters such as an active neutral clamped (ANPC), T-type, stacked multi-cell (SMC) converters, and the other combined topologies [18][21]- [23] can be also extended to the linear amplifiers by modifying the gate circuit configuration like the above three basic topologies. This is because the basic principles of all the multi-level converters are common.…”

Medium-Voltage Seven-Level Multiplexed Converter for AC Applications

“…Multilevel and multicell power converters are currently considered one of the most promising industrial topology solutions thanks to the reduction of losses and, consequently, the efficiency improvement without sacrificing the system's power quality [1]. Over the years, several multilevel topologies, from the simplest to the most complex, have been introduced in literature [2]- [3]. The fundamental characteristics of the multilevel converters, which determine their usability, such as DC bus neutral point voltage balancing and flying capacitor voltage control, are investigated in [4]- [5].…”

“…Consequently, the choice of the flying capacitors to be used can be made on two criteria: 1) current stress and 2) minimizing the peak value of the output voltage ripple. In particular, the voltage ripple is related to the current and the capacitor by the relationship in(2), where IFC is the current…”

New Modular Multilevel DC–DC Converter Derived from Modified Buck–Boost DC–DC Converter

“…Due to the remote location and possibly difficult terrain, the equipment has to be modular for ease of installation. Low cost and high efficiency are also desirable [5][6][7][8]. Specifically for converters interfacing with PV panels and batteries, they must have a low input ripple current to maintain their possible lifetime.…”