An Original Hybrid Multilevel DC-AC Converter Using Single-Double Source Unit for Medium Voltage Applications:Hardware Implementation and Investigation

In this article, an original hybrid multilevel DC-AC converter configurations are proposed by using single-double source unit for medium voltage applications. The proposed topologies are derived by hybridization of single and double source units with polarity changer and cascaded with full-bridge converter for medium and high voltage applications. Two different hybrid topologies presented and each topology configured for both symmetric and asymmetric method. The proposed hybrid topologies compared with the conventional cascaded H-bridge converter (CHB), and the best topologies recommended for medium voltage applications. The comparison in terms of the number of switches, gate driver circuits, maximum blocking voltage by switches and total peak inverse voltages of switches presented. The proposed topologies require a small installation area and low cost. The validity of the proposed hybrid converter structures is verified by simulation using MATLAB/Simulink and hardware results. The simulation and hardware results show a good agreement with the theoretical approach

A Compact Five-Level Single-Stage Boost Inverter

This article presents a single-stage five-level boost inverter (5L-SBI) topology with reduced power components. The proposed topology falls under the self-balanced switch-capacitors (SCs) type and combines both a DC/DC boost converter and inverter with a switched-capacitor cell. The advantages of proposed topologies include the following: the number of switch counts is reduced, the maximum voltage gain is two times higher than the input voltage, and the capacitor’s charging current is suppressed. Further, the proposed topology cascaded, and three-phase extensions are presented. To attest, the advantages of the proposed topology are thoroughly compared with other recent SCI topologies. The proposed topology is verified under dynamic loading conditions, and the results are presented, considering a 600 W laboratory prototype model

A Switched-Capacitor Multilevel Inverter With Modified Pulsewidth Modulation and Active DC-Link Capacitor Voltage Balancing

Although switched-capacitor (SC) multilevel inverters (MLIs) offer self-voltage balancing of flying capacitors and voltage gain higher than unity, the advantages come at the cost of high current stress and power loss in the SC circuit and dc source. Moreover, the voltage balancing is often restricted to a limited range of modulation indices. Another problem of MLIs with neutral-point clamped (NPC) front end is with dc-link capacitor voltage balancing under unbalanced load conditions, imploring sensor-based closed-loop control. This article proposes a unity gain five-level active-NPC SC-MLI with inrush charging current attenuation and actively balanced dc-link capacitor voltages under all load conditions and over the entire range of modulation index and power factor. The modified pulsewidth modulation (PWM) results in most switches operating at a low switching frequency, minimizing switching losses in the SC circuit. The proposed MLI attains a maximum efficiency of 98.04% at an output power of 510 W. Experiments on a 2 kVA laboratory prototype validate the theoretical analysis. Results from transformerless grid-connected solar photovoltaic (PV) system show that the proposed MLI can inject power into the grid with a unity power factor under conditions of varying irradiance and provide the grid with reactive power as well

Dynamic Analysis of Extendable Hybrid Voltage Lift DC–DC Converter for DC Microgrid

This paper proposes a novel non-isolated high voltage gain dc–dc converter with a boost2 (B2) technique. The derived single-switch hybrid voltage-lift topology generates a higher voltage conversion ratio with less component counts than traditional voltage-lift converters. Furthermore, to show its superiority, the proposed topology is compared with other recent non-isolated dc–dc converters in terms of the number of power components such as inductors, capacitors, diodes, and switches. Moreover, the voltage stress across the power switch is less than the output voltage, which results in using low-rated components and reducing the converter cost. The steady-state analysis of the proposed topology is carried out with the operating modes in continuous and discontinuous conduction modes. The critical inductance for the proposed converter is derived for design considerations. Compared to the other traditional step-up converters, the stresses across the power diodes are highly reduced. The analysis related to the addition of an expander cell with the topology is performed concerning boundary conditions. An efficiency model with loss calculation is presented. Furthermore, the reliability analysis is performed with the military handbook to determine the failure rate of the converter’s components. Finally, the simulation and 50 W prototype model for experimental validation prove the strength of the proposed topology

A New Multilevel Inverter Topology With Reduced Power Components for Domestic Solar PV Applications

Power electronic converters are used to nullify the input fluctuations from a solar photovoltaic unit because of intermittent solar irradiance and to make the terminal voltage grid compatible with the desired frequency. The conventional two-level converters suffer from low power quality and high voltage stress. In this article, a new multilevel inverter topology called Dual Source Multilevel Inverter (DS-MLI) with fewer power switches is proposed for solar PV power conversion systems. It can operate in symmetric and asymmetric operating modes with no cascading. This reduces the switching components required to produce several levels in the staircase voltage waveform. A closed-loop control algorithm is designed using the state-space averaging technique, and we assess the dynamic behaviour of the system under step change. We carry the simulation out in MATLAB environment. The experimental prototype of DS-MLI rated 1 kW is fabricated using FGA25N120-ANTD IGBTs, and an eco-sense made solar PV emulator is used for analysing the performance of DS-MLI while interfacing with solar PV unit. We compare the suggested scheme with its conventional counterpart in the aspects of components required, cost and efficiency, and the results are presented

A New Single Phase Single Switched-Capacitor Based Nine-Level Boost Inverter Topology with Reduced Switch Count and Voltage Stress

Based on the concept of switched-capacitor based multilevel inverter topology, a new structure for a boost multilevel inverter topology has been recommended in this paper. The proposed topology uses 11 unidirectional switches with a single switched capacitor unit to synthesize nine-level output voltage waveform. Apart from the twice voltage gain, self-voltage balancing of capacitor voltage without any auxiliary method along with reduced voltage stress has been the main advantages of this topology. The merits of proposed topology have been analyzed through various comparison parameters including component counts, voltage stresses, cost and efficiency with a maximum value of 98.3%, together with the integration of switched capacitors into the topology following recent development. Phase disposition pulse width modulation (PD-PWM) technique and nearest level control PWM (NLC-PWM) have been used for the control of switches. Different simulation and hardware results with different operating conditions are included in the paper to demonstrate the performance of the proposed topology. - 2013 IEEE.This work was supported in part by the QU High Impact under Grant QUHI-CENG-19/20-2 from Qatar University, and in part by the Qatar National Library, Doha, Qatar.Scopu