ANovel Non-Isolated Cubic DC-DC Converter with High Voltage Gain for Renewable Energy Power Generation System

In recent years,switched inductor(SL)technology,switched capacitor(SC)technology,and switched inductor-capacitor(SL-SC)technology have been widely applied to optimize and improve DC-DC boost converters,which can effectively enhance voltage gain and reduce device stress.To address the issue of low output voltage in current renewable energy power generation systems,this study proposes a novel non-isolated cubic high-gain DC-DC converter based on the traditional quadratic DC-DC boost converter by incorporating a SC and a SL-SC unit.Firstly,the proposed converter’s details are elaborated,including its topology structure,operating mode,voltage gain,device stress,and power loss.Subsequently,a comparative analysis is conducted on the voltage gain and device stress between the proposed converter and other high-gain converters.Then,a closed-loop simulation system is constructed to obtain simulation waveforms of various devices and explore the dynamic performance.Finally,an experimental prototype is built,experimental waveforms are obtained,and the experimental dynamic performance and conversion efficiency are analyzed.The theoretical analysis’s correctness is verified through simulation and experimental results.The proposed converter has advantages such as high voltage gain,low device stress,high conversion efficiency,simple control,and wide input voltage range,achieving a good balance between voltage gain,device stress,and power loss.The proposed converter is well-suited for renewable energy systems and holds theoretical significance and practical value in renewable energy applications.It provides an effective solution to the issue of low output voltage in renewable energy power generation systems.

Fuzzy Based Interleaved Step-up Converter for Electric Vehicle

This work focuses on the fuzzy controller for the proposed three-phase interleaved Step-up converter(ISC).The fuzzy controller for the proposed ISC converters for electric vehicles has been discussed in detail.The proposed ISC direct current(DC-DC)converter could also be used in automobiles,satellites,industries,and propulsion.To enhance voltage gain,the proposed ISC Converter combines boost converter and interleaved converter(IC).This design also reduces the number of switches.As a result,ISC converter switching losses are reduced.The proposed ISC Converter topology can produce a 143 V output voltage and 1 kW of power.Due to the high voltage gain of this converter design,it is suitable for medium and high-power systems.The proposed ISC Converter topology is simulated in MATLAB/Simulink.The simulated output displays a high output voltage.But the output voltage contains maximum ripples.Fuzzy proposes an ISC Converter which makes closed loop responsiveness and reduces the output voltage ripple.The proposed ISC converter has the lowest ripple output voltage,which is less than 2%,because the duty cycle is regulated using the fuzzy logic controller.It offers high voltage gain,minimal ripple,and low switching loss.The performance of the proposed converter is compared to that of the fuzzy and Pro-portional Integral(PI)controllers implemented in MATLAB.

Novel forward mode AC/AC converters with high frequency link

A circuit configuration and a circuit topologic family of the novel forward mode AC/AC converters with high frequency link are presented. The circuit configuration is constituted of input cycloconverter, high frequency transformer, output cycloconverter, input and output filters. The circuit topologic family includes eight circuit topologies, such as full-bridge-full-wave mode, etc. The bi-polarity phase-shifted control strategy and steady principles are thoroughly investigated. The output characteristics are obtained. By using the bi-polarity phase-shifted control strategy with phase-shifted control between the output cycloconveter and the input cycloconverter, commutation overlap period of the output cycloconverter, and polarity selection of the output filtering inductance current and the input voltage, the leakage inductance energy and the output filtering inductance current are naturally commutated, and surge voltage and surge current of the cycloconverters are overcome. The converters have such advantages as simple topology, two-stage power conversions(LFAC/HFAC/LFAC), bi-directional power flow, high frequency electrical isolation, good output waveforms, and strong ability to stabilize voltage. The converters lay key technical foundation on a new-type of regulated sinusoidal AC power supplies and electronic transformers. The correction and advancement of the converters are well verified by a principle test.

High-Reliability Photovoltaic Converter Based on Improved PSO Algorithm

An improved particle swarm optimization(PSO)algorithm based on dynamic inertia weight and adjustment coefficient is proposed in this paper.The expressions of inertia weight and adjustment coefficient are established based on inter-particle distance and iterations.The improved algorithm is applied to a novel two-stage photovoltaic(PV)converter.The later DC/AC circuit chooses a dual-DC-input multi-level dual-buck inverter.This converter has the advantages of no shoot-through problem and high efficiency.Finally,the validity and effectiveness of the algorithm and the converter are verified with experimental results.

A high performance adaptive on-time controlled valley-current-mode DC–DC buck converter

This paper presents an AOT-controlled(adaptive-on-time,AOT)valley-current-mode buck converter for portable application.The buck converter with synchronous rectifier not only uses valley-current-mode control but also possesses hybridmode control functions at the same time.Due to the presence of the zero-current detection circuit,the converter can switch freely between the two operating modes without the need for an external mode selection circuit,which further reduces the design difficulty and chip area.The converter for the application of high power efficiency and wide current range is used to generate the voltage of 0.6–3.0 V with a battery source of 3.3–5.0 V,while the load current range is 0.05–2 A.The circuit can work in continuous conduction mode with constant frequency in high load current range.In addition,a stable output voltage can be obtained with small voltage ripple.In pace with the load current decreases to a critical value,the converter transforms into the discontinuous conduction mode smoothly.As the switching period increases,the switching loss decreases,which can significantly improve the conversion efficiency.The proposed AOT controlled valley current mode buck converter is integrated with standard 0.18μm process and the simulation results show that the converter provides well-loaded regulations with power efficiency over 95%.When the circuit switches between the two conduction modes drastically,the response time can be controlled within 30μs.The undershoot voltage is controlled within 25 mV under a large current hopping range.

Zero-voltage switching converter absorbing parasitic parameters for super high frequency induction heating

This paper presents a novel mega-Hz-level super high frequency zero-voltage soft-switching converter for induction heating power supplies. The prominent advantage of this topology is that it can absorb both inductive and capacitive parasitic components in the converter. The switch devices operate in a zero-voltage soft-switching mode. Consequently, the high voltage and high current spikes caused by parasitic inductors or capacitors oscillation do not occur in this circuit, and the high power loss caused by high frequency switching can be greatly reduced. A large value inductor is adopted between the input capacitor and the switches, thus, this novel converter shares the benefits of both voltage-type and current-type circuits simultaneously, and there are no needs of dead time between two switches. The working principles in different modes are introduced. Results of simulation and experiments operated at around 1 MHz frequency verify the validity of parasitic components absorption and show that this convener is competent for super high frequency applications.

Recent Developments of Modulation and Control for High-Power Current-Source-Converters Fed Electric Machine Systems

The pulse-width-modulated(PWM)current-source converters(CSCs)fed electric machine systems can be considered as a type of high reliability energy conversion systems,since they work with the long-life DC-link inductor and offer high fault-tolerant capability for short-circuit faults.Besides,they provide motor friendly waveforms and four-quadrant operation ability.Therefore,they are suitable for high-power applications of fans,pumps,compressors and wind power generation.The purpose of this paper is to comprehensively review recent developments of key technologies on modulation and control of high-power(HP)PWM-CSC fed electric machines systems,including reduction of low-order current harmonics,suppression of inductor–capacitor(LC)resonance,mitigation of common-mode voltage(CMV)and control of modular PWM-CSC fed systems.In particular,recent work on the overlapping effects during commutation,LC resonance suppression under fault-tolerant operation and collaboration of modular PMW-CSCs are described.Both theoretical analysis and some results in simulations and experiments are presented.Finally,a brief discussion regarding the future trend of the HP CSC fed electric machines systems is presented.

Analysis of Soft-Switched High Frequency AC-AC Converter for Induction Motor Drive

The systematic mathematical analysis of the high frequency soft-switched AC-AC converter is proposed for variable frequency induction machine load in this paper. Both PWM and square-wave modes of operation have been considered. The frequency relation and phase unbalance problem due to discrete time integral half-cycle switching has been discussed in the beginning. Then, generalized Fourier series have been derived for output voltage, output current and supply current in two modes.The analytical results help to understand tbe converter characteristics, design optimally a convertermachine system of arbitrary capacity considering the various trade-off parameters.

Tunable circularly-polarized turnstile-junction mode converter for high-power microwave applications

Frequency tunability has become a subject of concern in the field of high-power microwave（HPM） source research.However, little information about the corresponding mode converter is available. A tunable circularly-polarized turnstilejunction mode converter（TCTMC） for high-power microwave applications is presented in this paper. The input coaxial TEM mode is transformed into TE（10） mode with different phase delays in four rectangular waveguides and then converted into a circularly-polarized TE（11） circular waveguide mode. Besides, the rods are added to reduce or even eliminate the reflection. The innovations in this study are as follows. The tunning mechanism is added to the mode converter, which can change the effective length of rectangular waveguide and the distance between the rods installed upstream and the closest edge of the rectangular waveguide, thus improving the conversion efficiency and bandwidth. The conversion efficiency of TCTMC can reach above 98% over the frequency range of 1.42 GHz–2.29 GHz, and the frequency tunning bandwidth is about 47%. Significantly, TCTMC can obtain continuous high conversion efficiency of different frequency points with the change of tuning mechanism.

Multilevel Current Source Converters for High Power Medium Voltage Applications

In medium voltage high power applications,multi-level current source converters(CSCs)are good candidate to increase system power region,reliability,and the quality of output waveforms.Compared with widely researched voltage source multi-level converters(MLCs),the current source MLCs have the advantages of inherent short-circuit protection,high power capability and high quality of output current waveforms.The main features of MLCs include reduced harmonics,lower switching frequency and reduced current stress on each device which is a particularly important for high power application with low voltage and high current requirements.This paper conducts a general review of the current research about MLCs in higher power medium voltage application.The different types of parallel structure based MLCs and the modulation methodologies will be introduced and compared.Specifically,the circuit analysis of the common-mode(CM)loop for parallel structures will be conducted,the common-mode voltage(CMV)and circulating current suppression methods developed on the base of multilevel modulations will be addressed.

Intelligent Fuzzy Based High Gain Non-Isolated Converter for DC Micro-Grids

Renewable electricity options, such as fuel cells, solar photovoltaic,and batteries, are being integrated, which has made DC micro-grids famous.For DC micro-grid systems, a multi input interleaved non-isolated dc-dcconverter is suggested by the use of coupled inductor techniques. Since itcompensates for mismatches in photovoltaic devices and allows for separateand continuous power flow from these sources. The proposed converter hasthe benefits of high gain, a low ripple in the output voltage, minimal stressvoltage across the power semiconductor devices, a low ripple in inductorcurrent, high power density, and high efficiency. Soft-switching techniquesare used to realize that the reverse recovery issue of the diodes is moderated, the leakage energy is reused, and no new scheme is appropriated. Toreduce conduction losses, minimum voltage rating MOSFETs with a low ONresistance can be utilized. The converter can supply the required power fromthe load in the absence of one or two resources. Furthermore, due to the highgain of boosting voltage, the converter works in an Adaptive Neuro-FuzzyInference System (ANFIS). The operation principle, steady-state analysis ofthe proposed converter, is given and simulated utilizing MATLAB/Simulinksimulation software.

A Novel Single Switch High Gain DC-DC Converter Topology for Renewable Energy Systems

Renewable energy with sources such as photovoltaic(PV)or fuel cells can be utilized for the generation of elec-trical power.But these sources generate fewer voltage values and therefore require high gain converters to match with DC bus voltage in microgrids.These high gain converters can be implemented with switched capacitors to meet the required DC bus voltage.Switched capacitors operate in a series and parallel combination during switch-ing operation and produce high static gain,limits reverse voltage that appears across the components.A novel converter is proposed that satisfies all the features such as high voltage gain,only one switch,forces less potential stress cross the components,ripple current is less.These features of the proposed converter are verified through MATLAB/SIMULINK.

The Implementation of a High Efficiency Full-Bridge Converter

A high efficiency full-bridge converter is investigated and implemented in this paper. The measured data result from the other converter implemented by IC UCC3895 is to compare with that of the previous converter. This full-bridge converter proposed and implemented converter can obtain about 96% power efficiency in conversion procedure when compared with that of 90%, which were ever published by the conventional techniques. Apart from, the L-C resonance circuits were developed and embedded into the popular PWM (pulse width modulation) power converter, which is referred as the soft-switching, so as to down sizing the volume of the IC which can totally reduces the power losses caused in the duration of a semi-con- ductor switching.

Bifurcation and chaos in high-frequency peak current mode Buck converter

Bifurcation and chaos in high-frequency peak current mode Buck converter working in continuous conduction mode（CCM） are studied in this paper. First of all, the two-dimensional discrete mapping model is established. Next, reference current at the period-doubling point and the border of inductor current are derived. Then, the bifurcation diagrams are drawn with the aid of MATLAB. Meanwhile, circuit simulations are executed with PSIM, and time domain waveforms as well as phase portraits in i_L–v_C plane are plotted with MATLAB on the basis of simulation data. After that, we construct the Jacobian matrix and analyze the stability of the system based on the roots of characteristic equations. Finally, the validity of theoretical analysis has been verified by circuit testing. The simulation and experimental results show that,with the increase of reference current I_（ref）, the corresponding switching frequency f is approaching to low-frequency stage continuously when the period-doubling bifurcation happens, leading to the converter tending to be unstable. With the increase of f, the corresponding Irefdecreases when the period-doubling bifurcation occurs, indicating the stable working range of the system becomes smaller.

Analysis and Design of Single Switch Hybrid Step-Up Converter

A Single Switch Hybrid Step-up Converter with high voltage gain, which is suitable for renewable energy system, is proposed in this paper. The proposed converter consists of one switched diode-inductor cell and a capacitor. While switching, both are charged in parallel from the input source and discharged in series to the output. In order to obtain extra voltage gain at lower duty cycle, the voltage multiplier cell is integrated with the proposed converter. The main advantages of the converter are high voltage gain, reduced voltage stress, simple structure and low output voltage ripples. The operating principle and steady state theoretical analysis are presented. A 250 W prototype converter is implemented with 12 V input and 120 V output to verify the design and analysis of this converter and it has an efficiency of over 90% in all operations.

Design of High Efficiency DC-DC Converter for Photovoltaic Solar Home Applications

The solar energy conversion system is very interesting alternative on supplement the electric system generation, due to the persistent cost reduction of the overall system and cleaner power generation. To obtain a stable voltage from an input supply （PV cells） that is higher and lower than the output, a high efficiency and minimum ripple DC-DC converter required in the system for residential power production. Buck-boost converters make it possible to efficiently convert a DC voltage to either a lower or higher voltages. Buck-boost converters are especially useful for PV maximum power tracking purposes, where the objective is to draw maximum possible power from solar panels at all times, regardless of the load. This paper analyzes and describes step by step the process of designing, and simulation of high efficiency low ripple voltage buck-boost DC-DC converter for the photovoltaic solar conversion system applicable to a （typical） single family home based on battery-based systems. The input voltage can typically change from （20 V） initially, down to （5 V）, and provide a regulated voltage within the range of the battery （12 V）. PLECS simulation results provide strong evidences about the high efficiency, minimum ripple voltage, high accuracy, and the usefulness of the system of the proposed converter when applied to either residential or solar home applications.

Fundamental Study of High Step-down Non-isolated Multicellular DC-DC Converter for Future DC Distribution Systems

A novel high step-down non-isolated DC-DC converter has been proposed. The proposed converter consists of highly efficient non-isolated cell converters using bidirectional semiconductor power devices, and these cell converters are connected in ISOP （input series and output parallel）. The non-isolated ISOP converter achieves high step-down ratio of D/N, operating N cell converters under the duty ratio olD. Availability of the proposed converter has been shown by developing the 48 V-12 V laboratory prototype using two 24 V-12 V cell converters. Design consideration for the 48 V-3 V multicellular converter using four 12 V-3 V cell converters has been also conducted, and the potential to approach the efficiency of 97% has been discussed. The proposed topology is suitable for the POL （point of load） converters in the highly efficient next generation DC distribution system for data centers.

An Optoelectronic High-voltage Probe for Measuring Impulse Voltage Distribution of HVDC Converter Valve

A high-voltage optoelectronic probe is developed for measuring impulse voltage distribution along thyristor units in the HVDC converter valve.The dimension of the resistive voltage divider is optimized by means of numerical computation of electric field.A pulse frequency modulation(PFM) mode is adopted for the data transmission link because of its immunity to high-intensity electromagnetic interference.Experimental results indicate that the linearity deviation for the whole measuring system is within ±0.15%,and therefore it can meet requirements specified by IEC60700-1.

High Frequency Transformers for DC/DC Converter Used in Solar PV System

This paper presents and investigates planar and coaxial high frequency power transformers used for DC/DC converters in a three phase photo voltaic （PV） power systems. The winding structure including a Faraday shield between the primary and secondary windings is designed to minimize eddy current losses, skin and proximity effects, and to reduce the leakage inductance, and the inter winding coupling capacitance. Finite Element Method is employed to analyze the magnetic flux and eddy current distributions. The two different kinds of prototype high frequency transformers are designed and tested. The simulation and experiment results are demonstrated and compared with non-shielded transformers. The shielded transformers have achieved the expected results with a relatively small coupling capacitance, compared with the conventional high frequency transformer. This shield decreases the inter-winding coupling capacitance Cps. The topology of this shield has to be such that it acts as a Faraday screen while avoiding eddy current generation.

Numerical simulation of the flow field of a flat torque converter

A flexible flat torque converter was proposed to fulfill the requirement of miniaturization and power density maximization for automobiles.Constructed by two arcs joined by lines,the torus was designed directly from design path.The influence of flatness on the performance of the torque converter was evaluated.The software CFX and standard k-ε model were adopted to simulate the internal flow fields of the torque converter under different flatness ratios.The results indicated that the performance of the torque converter got worse as the flatness declined,but the capacity of pump increased.The efficiency and the torque ratio dropped slightly as the flatness ratio decreased.So the torque converter could be squashed appropriately to get high power density without too much efficiency sacrifice.But when the flatness ratio was below 0.2,there was a significant drop in the efficiency.