Cascaded multilevel converters in recent research and applications

Abstract

Abstract. Multilevel converters have been intensively investigated and developed since 1960s and have found successful industrial applications. The aim of this paper is to present state of the art as well as recent research and applications of cascaded multilevel converters, which are a very interesting solution for power distribution systems and renewable energy sources. Cascaded multilevel converters can easily operate at medium and high voltage based on the series connection of power modules (cells), which use standard low-voltage component configurations. Series connections of modules (cells) allow for high quality output voltages and input currents, reduction of passive components and availability of component redundancy. Due to these features the cascaded multilevel converters have been recognized as attractive solutions for high-voltage direct-current (HVDC) transmission, solid state transformers (SST) and photovoltaic (PV) systems.Key words: multilevel converters, cascaded converters, modular multilevel converters, modulation, solid state transformer, photovoltaic systems. Cascaded multilevel converters in recent research and applications M. MALINOWSKIInstitute of Control and Industrial Electronics, Warsaw University of Technology, 75 Koszykowa St., 00-662 Warsaw, Poland for multilevel structures. Among the main benefits one may count a superior harmonic spectrum for a given switching frequency, a lower dv/dt stress at the converter terminals, cables and end windings of transformers/generators, a lower common mode voltage, and substantially lower semiconductor switching losses, particularly at medium to higher switching frequencies. A three-level topology is also a highly competitive alternative to the two-level structure in terms of cost, efficiency, and weight/size [2].The final choice of converter topology for RES depends on type of application, expected power, reliability demand and price. Three-phase multilevel converters, e.g. three-level neutral point clamped (3L-NPC) [3][4][5][6], three-level transistor clamped (3L-TCC) [4] or five-level active neutral point clamped (5L-ANPC) [7][8][9] are most popular in high power applications. However, 3L-NPC converters may be considered even in power range of few hundreds kVA, which was discussed in [2].

Application of Model Predictive Control in Modular Multilevel Converter for MTPA operation and SOC Balancing

“…Multilevel converter topologies first emerged in the late-1960s with the introduction of a voltage-source converter (VSC) named the H-bridge converter [20]. The problems with VSCs include lack of modularity, failure management, reliability, and simple, structure-based design.…”

Analysis and Implementation of Switched Capacitor-based Multi-Level Inverter for Electric Vehicles Applications

“…MLI uses a grid-connected photovoltaic (PV) system without a transformer, as shown in [26]. Additionally, there are numerous topologies that support the use of T-type NPC MLI as a crucial component of the overall structure [27]. Ten switches are needed for the cascade TNPC MLI in conjuction with the FC H-bridge architecture presented in [28], and FC is reported to have the fewest devices.…”

Current THD comparison of different offset injections in the linear modulation range for cascaded H-bridge converters

“…A series connection of multiple modular converter units can be further classified as cascaded multilevel converters [3]. Although many different topologies can be cascaded, a cascaded connection of full bridge (H-bridge) modules in a CHB and that of half-bridge modules (cells) in the modular multilevel converter (MMC) have proven to be the most popular options [4].…”

“…Fig 4. Phase current THD (%) profiles for in-phase disposition (IPD) modulation method for different injections.…”