Efficient, High Power Density, Modular Wide Band-gap Based Converters for Medium Voltage Application

Recent advances in semiconductor technology have accelerated developments in medium-voltage direct-current (MVDC) power system transmission and distribution. A DC-DC converter is widely considered to be the most important technology for future DC networks. Wide band-gap (WBG) power devices (i.e. Silicon Carbide (SiC) and Gallium Nitride (GaN) devices) have paved the way for improving the efficiency and power density of power converters by means of higher switching frequencies with lower conduction and switching losses compared to their Silicon (Si) counterparts. However, due to rapid variation of the voltage and current, di/dt and dv/dt, to fully utilize the advantages of the Wide-bandgap semiconductors, more focus is needed to design the printed circuit boards (PCB) in terms of minimizing the parasitic components, which impacts efficiency. The aim of this dissertation is to study the technical challenges associated with the implementation of WBG devices and propose different power converter topologies for MVDC applications. Ship power system with MVDC distribution is attracting widespread interest due to higher reliability and reduced fuel consumption. Also, since the charging time is a barrier for adopting the electric vehicles, increasing the voltage level of the dc bus to achieve the fast charging is considered to be the most important solution to address this concern. Moreover, raising the voltage level reduces the size and cost of cables in the car. Employing MVDC system in the power grid offers secure, flexible and efficient power flow. It is shown that to reach optimal performance in terms of low package inductance and high slew rate of switches, designing a PCB with low common source inductance, power loop inductance, and gate-driver loop are essential. Compared with traditional power converters, the proposed circuits can reduce the voltage stress on switches and diodes, as well as the input current ripple. A lower voltage stress allows the designer to employ the switches and diodes with lower on-resistance RDS(ON) and forward voltage drop, respectively. Consequently, more efficient power conversion system can be achieved. Moreover, the proposed converters offer a high voltage gain that helps the power switches with smaller duty-cycle, which leads to lower current and voltage stress across them. To verify the proposed concept and prove the correctness of the theoretical analysis, the laboratory prototype of the converters using WBG devices were implemented. The proposed converters can provide energy conversion with an efficiency of 97% feeding the nominal load, which is 2% more than the efficiency of the-state-of-the-art converters. Besides the efficiency, shrinking the current ripple leads to 50% size reduction of the input filter inductors

A High Step-Up Transformerless DC-DC Converter with New Voltage Multiplier Cell Topology and Coupled Inductor

In this paper, a new high step-up transformerless DC-DC converter based on voltage multiplier and coupled inductor topology is presented. The proposed converter has two stages. In the first stage, a modified boost converter is designed by the coupled inductor and in the second stage, a new voltage multiplier by using a coupled inductor was illustrated. In this converter, high voltage gain can be achieved by adjusting the turn ratio of two coupled inductors and duty cycle which result in three degrees of design freedom. Using a single power switch with low on-resistance in the converter structure leads to simple control and low conduction loss. Also, total voltage stresses of active elements are decreased which cause to increase efficiency. Steady-state performance and theoretical achievements are confirmed by experimental test results on a test setup with one 200 W DC-DC prototype.©2021 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.fi=vertaisarvioitu|en=peerReviewed

Multiport DC-DC Converters for Hybrid Energy Systems

Renewable energy sources (RESs) like solar and wind have gained attention for their potential to reduce reliance on fossil fuels and mitigate climate change. However, integrating multiple RESs into a power grid is challenging due to their unpredictable nature. Power electronic converters can manage hybrid energy systems by controlling power flow between RESs, storages, and the grid. Conventional single input dc-dc converters have limitations such as low efficiency, bulky designs, and complex control systems. Multiport dc-dc converters (MPCs) have emerged as a solution for hybridizing multiple sources, storages, and load systems by providing a common interface. Existing MPCs have limitations such as high component count, limited operational range, complex control strategies and restrictions on the number of inputs to list a few. Thus, there is a need to develop new MPCs that combine the advantages of existing designs while overcoming their limitations. Isolated MPCs with unipolar or bipolar outputs are needed that can accommodate any number of inputs, offer high voltage gain, use fixed magnetic components for galvanic isolation (regardless of the number of ports), and have a simplified control strategy. Additionally, new non-isolated MPCs with unipolar or bipolar outputs are required, featuring reduced component count, simultaneous power transfer and power flow between input ports, high voltage gain, low control complexity, and modular design allowing for arbitrary increase in the number of input ports. There is also an opportunity to apply MPCs in the integration of RESs and storages to ac grids through multilevel inverters for low component count, high efficiency, low harmonics, and higher power density. Further, advances in bipolar MPCs provide the chance to balance the dc bus without requiring a complex control system.acceptedVersio

Analysis and Design of a Soft Switching Z-Source Boost DC-DC Converter

This paper proposes a high step-up fully soft switched Z-source Boost DC-DC converter, which uses two resonant paths to create soft switching conditions for switches and diodes and also increases the voltage gain. The proposed converter only has one switch, so it has a simple structure. Furthermore, its control circuit remains pulse width modulation. Since soft switching conditions are provided for all switching elements, the converter efficiency is very high. This converter also has all advantages of Z-source converters. The converter is analyzed and simulated in PSPICE software. The results confirm the aforementioned advantages and features of the proposed converte

Advanced topologies of high step-up DC-DC converters for renewable energy applications

This research is focused on developing several advanced topologies of high step-up DC-DC converters to connect low-voltage renewable energy (RE) sources, such as photovoltaic (PV) panels and fuel cells (FCs), into a high-voltage DC bus in renewable energy applications. The proposed converters are based on the combinations of various voltage-boosting (VB) techniques, including interleaved and quadratic structures, switched-capacitor (SC)-based voltage multiplier (VM) cells, and magnetically coupled inductor (CI) and built-in-transformer (BIT). The proposed converters offer outstanding features, including high voltage gain with low or medium duty cycle, a small number of components, low current and voltage stresses on the components, continuous input current with low ripple, and high efficiency. This research includes five new advanced high step-up DC-DC converters with detailed analyses. First, an interleaved converter is presented, which is based on the integration of two three-winding CIs with SC-based VM cells. Second, a dual-switch converter is proposed, which is based on the integration of a single three-winding CI with SC-based VM cells. Third, the SC-based VM cells are utilized to present three new Z-source (ZS)-based converters. Fourth, two double-winding CIs and a three-winding BIT are combined with SC-based VM cells to develop another interleaved high step-up converter. Finally, two double-winding CIs and SC-based VM cells are adopted to devise an interleaved quadratic converter with high voltage gain. The operating and steady-state analyses, design considerations, and a comparison with similar converters in the literature are provided for each converter. In addition, hardware prototypes were fabricated to verify the performance of the proposed converters --Abstract, page iv

A review on non-isolated low-power DC-DC converter topologies with high output gain for solar photovoltaic system applications

The major challenges of the high-gain DC–DC boost converters are high-voltage stress on the switch, extreme duty ratio operation, diode reverse-recovery and converter efficiency problems. There are many topologies of high-gain converters that have been widely developed to overcome those problems, especially for solar photovoltaic (PV) power-system applications. In this paper, 20 high-gain and low-power DC–DC converter topologies are selected from many topologies of available literature. Then, seven prospective topologies with conversion ratios of >15 are thoroughly reviewed and compared. The selected topologies are: (i) voltage-multiplier cell, (ii) voltage doubler, (iii) coupled inductor, (iv) converter with a coupled inductor and switch capacitor, (v) converter with a switched inductor and switched capacitor, (vi) cascading techniques and (vii) voltage-lift techniques. Each topology has its advantages and disadvantages. A comparison of the seven topologies is provided in terms of the number of components, hardware complexity, maximum converter efficiency and voltage stress on the switch. These are presented in detail. So, in the future, it will be easier for researchers and policymakers to choose the right converter topologies and build them into solar PV systems based on their needs

Isolated Single-stage Power Electronic Building Blocks Using Medium Voltage Series-stacked Wide-bandgap Switches

The demand for efficient power conversion systems that can process the energy at high power and voltage levels is increasing every day. These systems are to be used in microgrid applications. Wide-bandgap semiconductor devices (i.e. Silicon Carbide (SiC) and Gallium Nitride (GaN) devices) are very promising candidates due to their lower conduction and switching losses compared to the state-of-the-art Silicon (Si) devices. The main challenge for these devices is that their breakdown voltages are relatively lower compared to their Si counterpart. In addition, the high frequency operation of the wide-bandgap devices are impeded in many cases by the magnetic core losses of the magnetic coupling components (i.e. coupled inductors and/or high frequency transformers) utilized in the power converter circuit. Six new dc-dc converter topologies are propose. The converters have reduced voltage stresses on the switches. Three of them are unidirectional step-up converters with universal input voltage which make them excellent candidates for photovoltaic and fuel cell applications. The other three converters are bidirectional dc-dc converters with wide voltage conversion ratios. These converters are very good candidates for the applications that require bidirectional power flow capability. In addition, the wide voltage conversion ratios of these converters can be utilized for applications such as energy storage systems with wide voltage swings

A wide input-voltage range quasi-Z source boost DC-DC converter with high voltage-gain for fuel cell vehicles

A quasi-Z-source Boost DC-DC converter which uses a switched-capacitor is proposed for fuel cell vehicles. The topology can obtain a high voltage gain with a wide input-voltage range, and requires only a low voltage stress across each of the components. The performance of the proposed converter is compared with other converters which use Z-source networks. A scaled-down 400V/400W prototype is developed to validate the proposed technology. The respective variation in the output voltage is avoided when the wide variation in the input voltage happens, due to the PI controller in the voltage loop, and a maximum efficiency of 95.13% is measured

Power Electronics and Energy Management for Battery Storage Systems

The deployment of distributed renewable generation and e-mobility systems is creating a demand for improved dynamic performance, flexibility, and resilience in electrical grids. Various energy storages, such as stationary and electric vehicle batteries, together with power electronic interfaces, will play a key role in addressing these requests thanks to their enhanced functionality, fast response times, and configuration flexibility. For the large-scale implementation of this technology, the associated enabling developments are becoming of paramount importance. These include energy management algorithms; optimal sizing and coordinated control strategies of different storage technologies, including e-mobility storage; power electronic converters for interfacing renewables and battery systems, which allow for advanced interactions with the grid; and increase in round-trip efficiencies by means of advanced materials, components, and algorithms. This Special Issue contains the developments that have been published b researchers in the areas of power electronics, energy management and battery storage. A range of potential solutions to the existing barriers is presented, aiming to make the most out of these emerging technologies