Symmetric Multi-Level Boost Inverter with Single DC Source Using Reduced Number of Switches

In this paper a novel multilevel boost DC to DC converter with H-Bridge inverter circuit for single DC source is proposed. The proposed scheme has two stages: the first one is a multilevel boost converter which gives a multilevel dc output for a single dc source and the second level is a H-Bridge converter which converts multilevel DC to multilevel AC at required frequency. This DC-DC converter not only reduces the DC source but also reduces the switches, diodes and capacitors. This leads to decrease of the amount and the inverter space installation in order to increase the required output voltage by increasing the number of capacitors and diodes in the DC to DC converter. Comparison between the number of power switches for the suggested topology and other topologies in the recent literature is presented. Simulation results are conveyed through MatLAB/Simulink domain and the working of the suggested converter is realized

DC side and AC side cascaded multilevel inverter topologies: A comparative study due to variation in design features

This paper presents a comparative study between DC side and AC side cascaded topologies for the hybrid modular multilevel converter (MMC) which are becoming popular in recent years. A multilevel converter with half or full bridge sub modules connected across DC link is another alternative for high-voltage applications as it has the same number of sub modules and footprint as AC side cascaded topology with the same DC link voltage and AC side voltage. The compared AC side cascaded structure offers a two-level converter as the high voltage stage and cascaded H-bridge (which is full bridge) sub modules with electrically isolated DC sources or capacitors for the low voltage stages which has number of features suitable for HVDC application. The comparison aspects are investigated against 6 different converter sub module number and configuration options for losses, harmonic profile of the output voltage, and the DC fault current characteristics (before blocking the IGBT gate signals during the DC fault) with the same input DC voltage and the same load for both (DC and AC side) topologies. The major results and findings of this investigation are presented, compared and discussed

Fault blocking converters for HVDC transmission : a transient behaviour comparison

A thorough comparison of the transient behaviours of two state-of-the-art converters suitable for HVDC transmission is presented. The Alternate Arm and Mixed-Cell Modular Multilevel Converter topologies both have DC fault blocking capability and are selected for the comparison. Converter performance is evaluated and compared under various transient conditions including charging sequence, unbalanced operation, and DC fault recovery. The study is conducted using high-fidelity converter simulation models, integrating detailed controllers that reflect real-scale projects. The main findings of the study assist in the selection of the most suitable converter, given specific performance specifications such as capacitor voltage ripple, cell capacitor requirements, and response during transient operation

High Power Density and High Efficiency Converter Topologies for Renewable Energy Conversion and EV Applications

This dissertation work presents two novel converter topologies (a three-level ANPC inverter utilizing hybrid Si/SiC switches and an Asymmetric Alternate Arm Converter (AAAC) topology) that are suitable for high efficiency and high-power density energy conversion systems. The operation principle, modulation, and control strategy of these newly introduced converter topologies are presented in detail supported by simulation and experimental results. A thorough design optimization of these converter topologies (Si/SiC current rating ratio optimization and gate control strategies for the three-level ANPC inverter topology and component sizing for the asymmetric alternate arm converter topology) are also presented. Performance comparison of the proposed converter topologies with other similar converter topologies is also presented. The performance of the proposed ANPC inverter topology is compared with other ANPC inverter topologies such as an all SiC MOSFET ANPC inverter topology, an all Si IGBT ANPC inverter topology and mixed Si IGBT and SiC MOSFET based ANPC inverter topologies in terms of efficiency and cost. The efficiency and cost comparison results show that the proposed hybrid Si/SiC switch based ANPC inverter has higher efficiency and lower cost compared to the other ANPC inverter topologies considered for the comparison. The performance of the asymmetric alternate arm converter topology is also compared with other similar voltage source converter topologies such as the modular multilevel converter topology, the alternate arm converter topology, and the improved alternate arm converter topology in terms of total device count, number of switches per current conduction path, output voltage levels, dc-fault blocking capability and overmodulation capability. The proposed multilevel converter topology has lower total number of devices and lower number of devices per current conduction path hence it has lower cost and lower conduction power loss. However, it has lower number of output voltage levels (requiring larger ac interface inductors) and lacks dc-fault blocking and overmodulation operation capabilities. A converter figure-of-merit accounting for the hybrid Si/SiC switch and converter topology properties is also proposed to help perform quick performance comparison between different hybrid Si/SiC switch based converter topologies. It eliminates the need for developing full electro-thermal power loss model for different converter topologies that would otherwise be needed to carry out power loss comparison between different converter topologies. Hence it saves time and effort

Performance Analysis of the Multi-Level Boost Converter (MLBC) connected in a Photovoltaic System

The paper concentrates on a comparison between two DC/DC converters topologies, the conventional Boost and the Multi Level Boost Converter (MLBC), for connecting into PV systems. Several performance criteria are included as part of this comparison process for both converters under varying climatic conditions (irradiation and/or temperature). The DC/DC converters' function is to serve as an interface between PV generator and load. We apply MPPT (Maximum Power Point Tracking) control with duty cycle adjustment using PWM technique for extracting the highest achievable output power from PV generator. The multilevel boost converter (MLBC), which is capable of monitoring and maintaining an equal voltage on all N output levels, along with controlling the input current. MATLAB/Simulink simulation results highlight the performance of the Multi-Level Boost Converter (MLBC) converter topology, to match the GPV voltage to the load

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

Steady-state performance of state-of-the-art modular multilevel and alternate arm converters with DC fault-blocking capability

This paper presents a comparison of the steady-state behaviour of four state-of-the-art HVDC converters with DC fault-blocking capability, based on the modular multilevel and alternate arm converter topologies. AC and DC power quality, and semiconductor losses are compared, whilst considering different operating conditions and design parameters, such as the number of cells and component sizing. Such comparative studies have been performed using high-fidelity converter models which include detailed representation of the control systems, and of the converter thermal circuit. The main findings of this comprehensive comparison reveal that, the mixed cell modular converter offers the best design trade-off in terms of power losses and quality, and control range. Moreover, it has been established that the modular converter with a reduced number of cells per arm and with each cell rated at high voltage (i.e. 10-20 kV), tends to exhibit higher switching losses and relatively poor power quality at the DC side

Novel multilevel hybrid inverter topology with power scalability

In this paper, a novel multilevel hybrid inverter is presented. The inverter is based on 2 floating capacitors and 16 active switches for five-level voltage waveform between the output of the inverter and neutral point of DC link. The proposed inverter structure, switching states and commutation scheme for different output voltage levels are presented. The proposed topology is simulated and verified experimentally. The simulation results show that proposed topology can achieve higher efficiency in comparison to state-of-the-art hybrid topologies due to reduced conduction and switching losses at low modulation index and light load conditions. Experimental results show that the converter is successfully operated up to 1 kV DC link voltage and 12 kW output power

Design Optimization & Control of High Power Density Converters using Wide Band Gap Devices

In this dissertation various converter topologies are proposed and evaluated in view of the state of art solutions to optimize power density and converter efficiency for several applications including photovoltaic solar energy harvesting, energy storage, wind power generation, and medium voltage adjustable speed drives. The first part of the dissertation, presents a comparison between mitigation techniques for double line frequency ripples in single phase micro-inverters based on Wide Band Gap devices. A topology based on an auxiliary DC-AC stage is adopted based on optimizing both power density and efficiency to achieve the pressing needs for the next generation of micro-inverters as announced by Google’s Little Box Challenge. An accurate yet simple control algorithm is proposed that provides a ripple-free DC current. Experimental results demonstrate the effectiveness of the presented topology and control algorithm to achieve high power density (55.8 W/in^3) micro-inverter rated at 2kW. In the second part of the dissertation a new class of multilevel converters, namely Interconnected Modular Multilevel Converter (IMMC), is introduced and studied in detail. The IMMC provides a new framework for DC-DC and DC-AC conversion exploiting Wide Band Gap devices in a modular structure, achieving high power density in high voltage applications. The performance of the proposed IMMC is evaluated through theoretical analysis and experiments

Modified half-bridge modular multilevel converter for HVDC systems with DC fault ride-through capability

One of the main challenges of voltage source converter based HVDC systems is DC faults. In this paper, two different modified half-bridge modular multilevel converter topologies are proposed. The proposed converters offer a fault tolerant against the most severe pole-to-pole DC faults. The converter comprises three switches or two switches and 4 diodes in each cell, which can result in less cost and losses compared to the full-bridge modular multilevel converter. Converter structure and controls are presented including the converter modulation and capacitors balancing. MATLAB/SIMULINK simulations are carried out to verify converter operation in normal and faulty conditions