Analysis of a seven‐level asymmetrical hybrid multilevel converter for traction systems

Abstract

A medium-voltage high-power electric traction system, due to its non-linear nature results in serious power quality issues in power system such as low-power factor and high-harmonic distortion. To mitigate the aforementioned problems, this study presents a seven-level asymmetrical hybrid multilevel converter that can be implemented using a single dc source and two capacitors. The proposed converter is a series connection of a five-level cascaded module (CM) converter with an H-bridge cell to meet the demand of medium-voltage high-power traction applications with improved power factor at minimum harmonic distortion. A modulation scheme presented will operate an H-bridge cell and a CM with a fundamental frequency and highfrequency switching, respectively. The unbalancing of dc-link capacitors voltages due to active power transfer requires corrective control action including current control, voltage control and voltage balancing that has been proposed to keep the dclink capacitor voltage balanced. Working principle of the proposed topology and its mathematical analysis is presented in this work. The effectiveness of the controlled pulse-width modulation strategy and stability of the proposed control method have been validated through simulation and experimental results.

Review of reduced‐switch multilevel inverters for electric vehicle applications

“…Ali et al 41 developed a seven‐level hybrid asymmetric MLI for electric traction systems. The structure comprised an H‐bridge cell in series with a five‐level cascaded module (CM) converter.…”

Optimal design of a cascaded rectangular‐type and circle‐type multilevel inverters with a new switching technique

“…They are widely used in modern technology [1, 2], and play a critical role in diverse power system applications, for instance, renewable energy applications, especially in photovoltaic systems [3–8] and high‐voltage direct current [9, 10]. Moreover, MLIs are an adequate solution in various applications related to electrical motor drives such as conveyors [11, 12], traction [13–20], mine hoists [21] and marine propulsion [22–26]. Due to their efficient conversion of dc to ac, MLIs have extended their application to industrial and power quality devices such as magnetic resonance imaging [27], induction heating power supply [28], flexible ac transmission systems [29–32], solid‐state transformers [33–36], static compensators [37–40], active filters [41–44], dynamic voltage restorers [45–48], unified power quality conditioners [49–52] and unified power flow controllers (UPFC) [53–55].…”

ZVS/ZCS Vienna rectifier topology for high power applications

“…flying capacitor (FC), neutral point clamped (NPC), cascaded H-bridge (CHB) etc. provide bidirectional power flow capability [11][12][13]. The increasing usage of front-end converters have caused power quality-related issues such as distorted line voltage, overheating, damage, or even malfunction of equipment that are undesirable and unacceptable [9].…”