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The paper presents a new four-level voltage source converter (VSC). Compared to conventional four-level converters, this proposed converter has fewer components and can be used for a higher power density system in low and medium voltage applications. Its principles and advantages are studied in this paper. The effect of various redundant switching states on the voltages of flying capacitors is analyzed...
The paper proposes a three phase nine level T-type neutral point clamped (9L-T-NPC) inverter for medium voltage induction motor drive. The primary objective of the proposed inverter is to improve the output voltage quality with reduced number of devices and passive components. The generation of nine levels in the output pole voltage is achieved using only ten switches per phase. Although the similar...
A capacitor voltage-balancing control strategy based on switching state redundancies is proposed for the hybrid stacked five-level converter. In order to obtain the balancing properties for flying capacitors, a hybrid model in state-space representation is established by considering the continuous and discrete variables. The proposed balancing strategy can control the flying capacitor voltages to...
This paper proposes two hybrid asymmetric cascaded multilevel inverters. Both inverters consist of the series connection of a three-level (3L) H-bridge cell and a nine-level (9L) H-bridge cell with an unequal dc voltage ratio of 1:8. The topologies of the 9L H-bridge cell are based on modular multilevel cascade converter (MMCC) with double-star chopper cells (DSCC). Both the proposed inverters can...
The three-level T type inverter has been extensively used in photovoltaic (PV) generation. Various PV panels in cascaded connection normally require unequal dc voltage to accomplish separate maximum power point tracking (MPPT). This paper proposes a DPWM-controlled three-level T type inverter for two strings of PV panels in cascaded connection. The proposed modulation is developed based on the so-called...
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...
This paper introduces an asymmetric cascaded multilevel inverter consisting of series-connected two nine-level (9L) H-bridge cells, which are based on modular multilevel cascade converter (MMCC) with double-star chopper cells (DSCC). An unequal dc voltage ratio of 1:2 is used, so that the proposed topology can generate 25 output voltage levels. A modulation strategy for the inverter is proposed. A...
This paper develops an alternate arm converter (AAC) high-voltage direct current (HVDC) terminal model that is compatible with the existing benchmark models of modular multilevel converter (MMC) based HVDC and dc-grid benchmark models. The developed model is a first step towards an AAC-based point-to-point transmission system and the future development of multi-converter, multiterminal benchmark models...
A quasi single-stage power factor correction converter, which is composed of a three-level (TL) Boost converter and a DC-DC transformer (DCX), is presented and analyzed in this paper. The DC output load is connected to one of the dividing capacitors of the TL Boost converter, so that the load voltage can be lower than the peak amplitude of the AC line voltage and part of the AC input power can be...
The paper presents a dual output AC-DC converter as a suitable candidate in emerging DC distribution systems. In accordance with the need of vast range of DC loads and standard distribution levels, the proposed Dual Output PFC Rectifier has been designed to provide simultaneous boost and buck outputs. In addition, the design ensures that the rectifier operates at unity power factor while maintaining...
In this paper, we propose a backstepping based nonlinear control strategy to ensure the transient performances for the Modular Multilevel Converter (MMC), especially under the emergencies like changing load and operating mode. According to the backstepping control technique, the control input is derived from the Lyapunov stability theory and the established mathematical model. Meanwhile, it can be...
A transformer-less Modular Multilevel DC-DC converter for High Voltage Direct Current (HVDC) applications is proposed in this paper. This topology is suitable for interfacing two HVDC links at different voltage levels using only conventional half bridge submodules. The uniqueness of the proposed converter is in its symmetry in performance in the event of reversal of polarity of one of the DC links...
Testing and verification of high-level and low-level control, modulation, fault handling and converter co-ordination for modular multilevel converters (MMCs) requires development of experimental prototype converters. In this paper, we provide a a complete overview of the MMC-based experimental prototype at UNSW Sydney (The University of New South Wales) including the structure of the sub-modules,...
Due to the three-phase-to-three-leg direct matrix converter (3 × 3 MC) cannot be achieved with unbalanced load, then the three-phase-to-four-leg direct matrix converter (3 × 4 MC) is introduced. A novel modulation strategy is proposed to ensure the capability of 3 × 4 MC with arbitrary loads, which is development by using fixed voltage vectors and one zero vector. Considering the harm of common-mode...
Performance of multilevel inverters (MLI) are distinguished because of their low harmonic waveform generation, low filtering requirements on AC side and high voltage application. Among different (MLI) topologies, cascaded multi-level inverters (CMLI) are easier to implement and are much more cost effective. The main drawback of multilevel inverters is requirement of more than one isolated DC source...
The working performance of modular multilevel converters (MMC) is directly affected by the circulating current. This paper presents a circulating current suppressing technique based on internal model control (IMC) applied in conventional NLM modulation scheme and double loop upper control hierarchy. According to the instantaneous energy balance between AC and DC sides, the mathematical model of circulating...
This paper presents a unified control design approach involving four topologies of shunt active power filters (SAPF), which can be applied to three-phase four-wire distribution systems. The SAPF structures are deployed by means of the following inverter topologies: full-bridge composed of three modules, four-legs, split-capacitor and neutral point clamped. The SAPFs are compared to each other through...
Recent research on high voltage and power DC/DC converter mainly focus on the face-to-face topology based on modular multilevel converters (MMC). The topology consists of two MMC which are coupled by a transformer. It is easy to extend the module number according to the voltage level. However, the present modulation method in this topology cannot regulate the voltage transformation ratio on two dc...
Recently, a novel hybrid multilevel inverter topology, the EDA5, was presented. The novel inverter topology comprises of two floating capacitors and 16 active switches to achieve five-level output voltage waveform and achieves higher efficiency at low-modulation index compared to a five-level Active Neural Point Clamped (5L-ANPC) converter. In this work, a full SiC MOSFET version of the inverter is...
The modular multilevel converter (MMC) is most widely acclaimed converter topology for high-voltage, high-power applications. Several multilevel submodules have been proposed to replace the conventional two-level submodules for MMC, allowing the reduction in the foot-print size of the converter for the same number of output voltage levels. Among them, the three-level flying capacitor (3L-FC) submodule...
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