Survey of DC-DC Non-Isolated Topologies for Unidirectional Power Flow in Fuel Cell Vehicles

The automobile companies are focusing on recent technologies such as growing Hydrogen (H2) and Fuel Cell (FC) Vehicular Power Train (VPT) to improve the Tank-To-Wheel (TTW) efficiency. Benefits, the lower cost, `Eco\u27 friendly, zero-emission and high-power capacity, etc. In the power train of fuel cell vehicles, the DC-DC power converters play a vital role to boost the fuel cell stack voltage. Hence, satisfy the demand of the motor and transmission in the vehicles. Several DC-DC converter topologies have proposed for various vehicular applications like fuel cell, battery, and renewable energy fed hybrid vehicles etc. Most cases, the DC-DC power converters are viable and cost-effective solutions for FC-VPT with reduced size and increased efficiency. This article describes the state-of-the-art in unidirectional non-isolated DC-DC Multistage Power Converter (MPC) topologies for FC-VPT application. The paper presented the comprehensive review, comparison of different topologies and stated the suitability for different vehicular applications. This article also discusses the DC-DC MPC applications more specific to the power train of a small vehicle to large vehicles (bus, trucks etc.). Further, the advantages and disadvantages pointed out with the prominent features for converters. Finally, the classification of the DC-DC converters, its challenges, and applications for FC technology is presented in the review article as state-of-the-art in research

Development of novel non-isolated unidirectional DCDC multistage power converter configurations for renewable energy applications- hardware implementation and investigation studies

Abstract: In the last decades, there is a rapid development towards new energy sources due to the increasing demand of energy and cost of the fossil fuels. Renewable energy sources getting more popular day by day due to government support and carbon dioxide (CO2) emission reduction policy to reduce greenhouse gas emissions. Photovoltaic energy generation is the excellent example of energy generation through various serious parallel arrangement of a small voltage generating cells or modules. There are directly use of synchronous generators to transfer power to grid from hydro energy plant, geothermal energy plant, bio-fuel energy plants. However, the photovoltaic energy generation systems requires the power electronic converters system to satisfy the demand of realtime application or electric grid. Therefore, for real-time applications or before feeding energy to the grid via inverter, photovoltaic systems linked with DC-DC converters, which have high-voltage conversion ratio capability. Thus, DC-DC power converter is the paramount constituent in the photovoltaic power conversion stage. This research work carried out in focusing on hardware implementation and investigation studies of novel non-isolated unidirectional DC-DC multistage power converter configurations for renewable energy application. The comprehensive review of various unidirectional non-isolated DC-DC multistage power converters are presented and it is found that not all of them have the capability to convert low voltage into high voltage, thus not suitable for photovoltaic energy applications. It is investigated that there is a scope to design new DC-DC multistage power converter topologies configurations with high voltage conversion ratio by employing a new arrangement of reactive elements and semiconductor devices. A new breed of DC-DC multistage power converters called “X-Y converter family” proposed for photovoltaic application by utilizing the switchedinductor, the switched capacitor, the voltage lift switch capacitor and modified voltage lift switched capacitor, voltage doubler and multiplier boosting techniques. The derivation of voltage conversion ratio, advantage of each converter of X-Y family and hierarchy of X-Y family is discussed. The research work also proposed a new DC-DC multistage power converter without a magnetic component for photovoltaic application by utilizing the concept of switched capacitors. An original Transformer and Switched Capacitor (T-SC) based multistage power converter proposed for high-voltage/lowcurrent photovoltaic applications by combining the feature of the boost converter, transformer and switched capacitor. New Nx IMBC (Nx Interleaved Multilevel Boost Converter) or Cockcroft Walton (CW) Voltage Multiplier based Multistage/Multilevel Power Converter (CW-VM-MPC) converter topologies are presented to achieve maximum voltage conversion ratio by utilizing the feature of Cockcroft Walton (CW) voltage multiplier. Moreover, the proposed multistage power converter compared with each other as well as recently proposed multistage power converters in term of voltage conversion ratio, number of devices and costs.D.Eng. (Electrical and Electronic Engineering

Development of controllers using FPGA for fuel cells in standalone and utility applications

In the recent years, increase in consumption of energy, instability of crude oil price and global climate change has forced researchers to focus more on renewable energy sources.Though there are different renewable energy sources available (such as photovoltaic and wind energy), they have some major limitations. The potential techniques which can provide renewable energy are fuel cell technology which is better than other renewable sources of energy. Solid oxide fuel cell (SOFC) is more efficient, environmental friendly renewable energy source. This dissertation focuses on load/grid connected fuel cell power system (FCPS) which can be used as a backup power source for household and commercial units. This backup power source will be efficient and will provide energy at an affordable per unit cost. Load/grid connected fuel cell power system mainly comprises of a fuel cell module, DCDC converter and DC-AC inverter. This thesis primarily focuses on solid oxide fuel cell (SOFC) modelling, digital control of DC-DC converter and DC-AC inverter. Extensive simulation results are validated by experimental results. Dynamic mathematical model of SOFC is developed to find out output voltage, efficiency, over potential loss and power density of fuel cell stack. The output voltage of fuel cell is fed to a DC-DC converter to step up the output voltage. Conventional Proportional-Integral (PI) controller and FPGA based PI controller is implemented and experimentally validated. The output voltage of DC-DC converter is fed to DC-AC inverter. Different pulse width modulation-voltage source inverter (PWM-VSI) control strategy (such as Hysteresis Current Controller (HCC), Adaptive-HCC, Fuzzy-HCC, Adaptive Fuzzy-HCC, Triangular Carrier Current Controller (TCCC) and Triangular Periodical Current Controller (TPCC)) for DC-AC inverter are investigated and validated through extensive simulations using MATLAB/SIMULINK. This work also focuses on number of fuel cells required for application in real time and remedy strategies when one or few fuel cells are malfunctioning. When the required numbers of fuel cells are not available, DC-DC converter is used to step up the output voltage of fuel cell. When there is a malfunction in fuel cell or shortage of hydrogen then a battery is used to provide backup power

Performance Analysis Of Hybrid Ai-Based Technique For Maximum Power Point Tracking In Solar Energy System Applications

Demand is increasing for a system based on renewable energy sources that can be employed to both fulfill rising electricity needs and mitigate climate change. Solar energy is the most prominent renewable energy option. However, only 30%-40% of the solar irradiance or sunlight intensity is converted into electrical energy by the solar panel system, which is low compared to other sources. This is because the solar power system\u27s output curve for power versus voltage has just one Global Maximum Power Point (GMPP) and several local Maximum Power Points (MPPs). For a long time, substantial research in Artificial Intelligence (AI) has been undertaken to build algorithms that can track the MPP more efficiently to acquire the most output from a Photovoltaic (PV) panel system because traditional Maximum Power Point Tracking (MPPT) techniques such as Incremental Conductance (INC) and Perturb and Observe (P&Q) are unable to track the GMPP under varying weather conditions. Literature (K. Y. Yap et al., 2020) has shown that most AIbased MPPT algorithms have a faster convergence time, reduced steady-state oscillation, and higher efficiency but need a lot of processing and are expensive to implement. However, hybrid MPPT has been shown to have a good performance-to-complexity ratio. It incorporates the benefits of traditional and AI-based MPPT methodologies but choosing the appropriate hybrid MPPT techniques is still a challenge since each has advantages and disadvantages. In this research work, we proposed a suitable hybrid AI-based MPPT technique that exhibited the right balance between performance and complexity when utilizing AI in MPPT for solar power system optimization. To achieve this, we looked at the basic concept of maximum power point tracking and compared some AI-based MPPT algorithms for GMPP estimation. After evaluating and comparing these approaches, the most practical and effective ones were chosen, modeled, and simulated in MATLAB Simulink to demonstrate the method\u27s correctness and dependability in estimating GMPP under various solar irradiation and PV cell temperature values. The AI-based MPPT techniques evaluated include Particle Swarm Optimization (PSO) trained Adaptive Neural Fuzzy Inference System (ANFIS) and PSO trained Neural Network (NN) MPPT. We compared these methods with Genetic Algorithm (GA)-trained ANFIS method. Simulation results demonstrated that the investigated technique could track the GMPP of the PV system and has a faster convergence time and more excellent stability. Lastly, we investigated the suitability of Buck, Boost, and Buck-Boost converter topologies for hybrid AI-based MPPT in solar energy systems under varying solar irradiance and temperature conditions. The simulation results provided valuable insights into the efficiency and performance of the different converter topologies in solar energy systems employing hybrid AI-based MPPT techniques. The Boost converter was identified as the optimal topology based on the results, surpassing the Buck and Buck-Boost converters in terms of efficiency and performance. Keywords—Maximum Power Point Tracking (MPPT), Genetic Algorithm, Adaptive Neural-Fuzzy Interference System (ANFIS), Particle Swarm Optimization (PSO

MODELING, DESIGN, AND IMPLEMENTATION OF HIGH GAIN POWER ELECTRONIC DC-DC CONVERTERS FOR NANOGRID APPLICATIONS

Nanogrids are nothing but power distribution systems that are based on renewable energy sources and are apt for low-power home applications. Nanogrids are considered to be the building cells of a Microgrid. Nanogrid is intended for feeding domestic loads (of the order of 100 W to 5 kW) from renewable energy sources such as wind farms, roof-top solar photovoltaic, biomass, and fuel cell, etc. Nonetheless, the voltages produced by these renewable energy sources are small and not sufficient enough to be utilized in all the applications. Hence, it is necessary to include high gain and high-efficiency DC-DC converters in the system. To interface the generators and the loads, power electronic converters are employed within a Nanogrid. The power system grid is also linked to the Nanogrid using these converters. The most fundamental characteristics of the high-gain DC-DC converters are high efficiency, high-voltage gain, and low voltage/current stress on switching components. A comprehensive literature review of various boosting methods is disseminated in this research work. After a detailed investigation, five new DC-DC power converter topologies have been designed and developed to achieve high gain factors with reduced switch ratings and low cost for use in Nanogrids. The proposed converters cannot only reduce voltage/current stresses across the switching components significantly but also achieve a higher voltage gain at moderate duty cycles with a lesser number of components. Moreover, the proposed converters are designed in such a way that they can maintain a continuous input current, and hence making them useful for power conversion in the battery, fuel cell, and solar PV applications. By using boosting technique five novel high voltage gain DC-DC converters are developed and presented in the dissertation, namely: 1. modified Switched Inductor Boost Converter (mSIBC) with reduced switch voltage stress, 2. Transformer-less Boost Converter (TBC) with reduced voltage stress, 3. Switched-Inductor based DC-DC Converter with reduced switch current stress, 4. Novel High Gain Active Switched Network-Based Converter, and 5. Double Stage Converter with low current stress for Nanogrid The detailed theoretical analysis of the voltage conversion ratio, parameter design, continuous and discontinuous conduction mode, and advantages are presented. In addition, a detailed comparative study of each converter topology is also given. The functionality of the proposed power converters is tested in real-time by developing Laboratory prototypes of the proposed converters and the theoretical analysis is validated by obtaining the experimental results. The proposed converter configurations are simulated in MATLAB as well, to verify the theoretical analysis. Simulation results of all the proposed converters are presented indicating clear evidence of the expected predictions in close proximity with experimental results

Modeling, Analysis, and Design of a PV-Based Grid-Tied Plug-In Hybrid Electric Vehicle Battery Pack Charger

Ever-increasing fossil fuels consumption in recent decades has emitted tremendous amounts of greenhouse gases, a big part of which cannot be absorbed by natural processes happening in nature. These gases have increased earth temperature by absorbing extra radiations from sunlight and turning them into heat. Global warming has had terrible effects for all creatures around the world and can threat life on Earth in future. Utilization of green or renewable energies during the recent years is getting more popular and can be a solution to this serious problem. A big source of these pollutants is transportation sector. Electrification of transportation can noticeably reduce greenhouse gasses if the electricity is obtained using renewable energy sources. Otherwise, it will just shift the problem from streets to fossil fuel power plants. Electric vehicles (EVs) were introduced around one century ago; however, they were replaced by internal combustion engine cars over time. Nevertheless, recently they are getting more interest because of their superior performance and clean operation. Solar electricity which can be obtained using photovoltaic panels is one of the easiest ways as long as sun is available. They can be easily mounted on the roofs of buildings or roof tops of parking slots generating electric power to charge the battery pack of the EVs while providing shade for the cars. Since solar energy is intermittent and variable, power grid should be involved to ensure enough power is available. Conventional solar chargers inject power to the grid and use grid as the main source because of its reliability and being infinite. Hence, they use grid as a kind of energy storage system. This approach can lead to problems for grid stability if solar panels are utilized in large scales and comparable to the grid. In this work, a solar powered grid-tied EV/PHEV charger is introduced which uses all the available power from PV panels as the main energy source and drains only the remaining required power from the grid. The proposed configuration provides great flexibility and supports all the possible power flows. To design an efficient system the load should be known well enough first. A comprehensive study has been done about behavior, characteristics and different models of different chemistries of batteries. Specific phenomena happening in battery packs are outlined. A novel maximum power point tracking (MPPT) technique has been proposed specifically for battery charging applications. A specific configuration involving DC link coupling technique has been proposed to connect different parts of the system. Different possible topologies for different parts of the proposed configuration have been considered and the suitable ones have been selected. Dual active bridge topology is the heart of this configuration which acts as the bidirectional charger. A detailed state space modeling process has been followed for the power converters and various small signal transfer functions have been derived. Controllers have been designed for different power converters using SISO design tool of Matlab/Simulink. Different modes of operation for the charger including constant current mode (CCM) and constant voltage mode (CVM) have been analyzed and appropriate cascade controllers have been designed based on required time domain and frequency domain characteristics. Finally, simulation tests have been conducted and test results have been graphed and analyzed for different modes of operation, all possible power flows and various voltage and current set points

Analysis on Supercapacitor Assisted Low Dropout (SCALDO) Regulators

State-of-the-art electronic systems employ three fundamental techniques for DC-DC converters: (a) switch-mode power supplies (SMPS); (b) linear power supplies; (c) switched capacitor (charge pump) converters. In practical systems, these three techniques are mixed to provide a complex, but elegant, overall solution, with energy efficiency, effective PCB footprint, noise and transient performance to suit different electronic circuit blocks. Switching regulators have relatively high end-to-end efficiency, in the range of 70 to 93%, but can have issues with output noise and EMI/RFI emissions. Switched capacitor converters use a set of capacitors for energy storage and conversion. In general, linear regulators have low efficiencies in the range 30 to 60%. However, they have outstanding output characteristics such as low noise, excellent transient response to load current fluctuations, design simplicity and low cost design which are far superior to SMPS. Given the complex situation in switch-mode converters, low dropout (LDO) regulators were introduced to address the equirements of noise-sensitive and fast transient loads in portable devices. A typical commercial off-the-shelf LDO has its input voltage slightly higher than the desired regulated output for optimal efficiency. The approximate efficiency of a linear regulator, if the power consumed by the control circuits is negligible, can be expressed by the ratio of Vo/Vin. A very low frequency supercapacitor circulation technique can be combined with commercial low dropout regulator ICs to significantly increase the end-to-end efficiency by a multiplication factor in the range of 1.33 to 3, compared to the efficiency of a linear regulator circuit with the same input-output voltages. In this patented supercapacitor-assisted low dropout (SCALDO) regulator technique developed by a research team at the University of Waikato, supercapacitors are used as lossless voltage droppers, and the energy reuse occurs at very low frequencies in the range of less than ten hertz, eliminating RFI/EMI concerns. This SCALDO technique opens up a new approach to design step-down, DC-DC converters suitable for processor power supplies with very high end-to-end efficiency which is closer to the efficiencies of practical switching regulators, while maintaining the superior output specifications of a linear design. Furthermore, it is important to emphasize that the SCALDO technique is not a variation of well-known switched capacitor DC-DC converters. In this thesis, the basic SCALDO concept is further developed to achieve generalised topologies, with the relevant theory that can be applied to a converter with any input-output step-down voltage combination. For these generalised topologies, some important design parameters, such as the number of supercapacitors, switching matrix details and efficiency improvement factors, are derived to form the basis of designing SCALDO regulators. With the availability of commercial LDO ICs with output current ratings up to 10 A, and thin-prole supercapacitors with DC voltage ratings from 2.3 to 5.5 V, several practically useful, medium-current SCALDO prototypes: 12V-to-5V, 5V-to-2V, 5.5V-to-3.3V have been developed. Experimental studies were carried out on these SCALDO prototypes to quantify performance in terms of line regulation, load regulation, efficiency and transient response. In order to accurately predict the performance and associated waveforms of the individual phases (charge, discharge and transition) of the SCALDO regulator, Laplace transform-based theory for supercapacitor circulation is developed, and analytical predictions are compared with experimental measurements for a 12V-to-5V prototype. The analytical results tallied well with the practical waveforms observed in a 12V-to-5V converter, indicating that the SCALDO technique can be generalized to other versatile configurations, and confirming that the simplified assumptions used to describe the circuit elements are reasonable and justifiable. After analysing the performance of several SCALDO prototypes, some practical issues in designing SCALDO regulators have been identified. These relate to power losses and implications for future development of the SCALDO design

Power Management Circuits for Energy Harvesting Applications

Energy harvesting is the process of converting ambient available energy into usable electrical energy. Multiple types of sources are can be used to harness environmental energy: solar cells, kinetic transducers, thermal energy, and electromagnetic waves. This dissertation proposal focuses on the design of high efficiency, ultra-low power, power management units for DC energy harvesting sources. New architectures and design techniques are introduced to achieve high efficiency and performance while achieving maximum power extraction from the sources. The first part of the dissertation focuses on the application of inductive switching regulators and their use in energy harvesting applications. The second implements capacitive switching regulators to minimize the use of external components and present a minimal footprint solution for energy harvesting power management. Analysis and theoretical background for all switching regulators and linear regulators are described in detail. Both solutions demonstrate how low power, high efficiency design allows for a self-sustaining, operational device which can tackle the two main concerns for energy harvesting: maximum power extraction and voltage regulation. Furthermore, a practical demonstration with an Internet of Things type node is tested and positive results shown by a fully powered device from harvested energy. All systems were designed, implemented and tested to demonstrate proof-of-concept prototypes