DC-Link Capacitor Optimization in AC–DC Converter by Load Current Prediction

Alternating Current–Direct Current(AC–DC)converters require a high value bulk capacitor or afilter capacitor between the DC–DC conversion stages,which in turn causes many problems in the design of a AC–DC converter.The component package size for this capacitor is large due to its high voltage rating and capacitance value.In addition,the high charging current creates more pro-blems during the product compliance testing phase.The shelf life of these specific high value capacitors is less than that of Multilayer Ceramic Capacitors(MLCC),which limits its use for the highly reliable applications.This paper presents a fea-sibility study to overcome these two problems by adding a few sensing mechan-isms to the typical AC–DC converter topology.In majority of the AC–DC converter,Al-Elko capacitor takes approximately 3%to 5%of the converter size.The proposed method reduces this to approximately 50%size and so it effectively approximates 2%to 3%size reduction in converter size.The proposed method basically works based on the load current prediction method and hence it is highly suitable for the constant load application.Moreover,the converter response time increases in this method,which limit its application in high-speed systems.The high temperature application of Al-Elko capacitor is limited because of its poor performance,which is significantly rectified by replacing the Al-Elko with MLCC as it delivers good performance in high temperature.

Design and Implementation of Bi-Directional DC-DC Converter for Wind Energy System

This paper proposes a design and implementation of the bi-directional DC-DC converter for Wind Energy Conversion System. The proposed project consists of boost DC/DC converter, bi-directional DC/DC converter (BDC), permanent magnet DC generator and batteries. A DC-DC boost converter is interface with proposed wind system to step up the initial generator voltage and maintain constant output voltage. The fluctuation nature of wind makes them unsuitable for standalone operation. To overcome the drawbacks an energy storage device is used in the proposed system to compensate the fluctuations and to maintain a smooth and continuous power flow in all operating modes to load. Bi-directional DC-DC converter (BDC) is capable of transforming energy between two DC buses. It can operate as a boost converter which supplies energy to the load when the wind generator output power is greater than the required load power. It also operates in buck mode which charges from DC bus when output power is less than the required load power. The proposed converter reduces the component losses and increases the performance of the overall system. The complete system is implemented in MATLAB/SIMULINK and verified with hardware.

Improved Dynamic Response of DC to DC Converter Using Hybrid PSO Tuned Fuzzy Sliding Mode Controller

DC/DC switching converters are widely used in numerous appliances in modern existence. In this paper, the dynamic and transient response of phase shift series resonant DC/DC converter are improved using hybrid particle swarm optimization tuned fuzzy sliding mode controller under starting and load step change conditions. The aim of the control is to regulate the output voltage beneath the load change. The model of the hybrid particle swarm optimization tuned fuzzy sliding mode controller is implemented using Sim Power Systems toolbox of MATLAB SIMULINK. Performance of the proposed dynamic novel control under step load change condition is investigated.

Design and Analysis of the Main AC/DC Converter System for ITER

A design of the main AC/DC converter system for ITER is described and the configuration of the main AC/DC converters is presented. To reduce the reactive power absorbed from the converter units, the main AC/DC converters are designed to be series-connected and work in a sequential mode. The structure of the regulator of the converter system is described. A simulation model was built up for the PSCAD/EMTDC code, and the design was validated accordingly. Harmonic analysis and reactive power calculation of the converters units are presented. The results reveal the advantage of sequential control in reducing reactive power and harmonics.

Efficient Single-Stage Bridgeless AC to DC Converter Using Grey Wolf Optimization

Bridgeless single-stage converters are used for efficient(alternative current)AC-(direct current)DC conversion.These converters control generators,likeelectromagnetic meso-and micro-scale generators with low voltage.Power factorcorrection helps increase the factor of the power supply.The main advantage ofthe power factor is it shapes the input current for increasing the real power of theAC supply.In this paper,a two-switch bridgeless rectifier topology is designedwith a power factor correction capability.For the proposed converter topologyto have good power quality parameters,the closed loop scheme,which uses thegrey wolf optimization(GWO)algorithm,is implemented.The successes ofGWO encourage this research to implement GWO in the topology.The performanceof the proposed topology is analyzed under different load conditions.Simulation is carried out using the MATLAB/Simulink environment,and theresults are compared with those of conventional(proportional integral derivative)PID and(particle swarm optimization)PSO controllers.To validate the simulation results,a 350-W hardware prototype is implemented,and the voltage ripple,efficiency,and power factor under different load conditions are analyzed and tabulated.The comparative study clearly indicates that the proposed convertertopology with a closed loop control scheme using the GWO algorithm improves the power factor to 0.9732 and reduces the voltage ripple to 0.12%with a conversion efficiency of 98.25%.

Robust Control Strategy for Inductive Parametric Uncertainties of DC/DC Converters in Islanded DC Microgrid

Direct current(DC) microgrid consists of many parallel power converters that share load currents through the inductance of DC/DC converters. Usually, the inductance parameters are dependent on the physical implementation of the system, and their values may not match their nameplates. Such disparities could lead to unequal response characteristics of the system, which can potentially reduce the performances of the DC microgrid operation. This paper proposes a robust control strategy for inductive parametric uncertainties of DC/DC converters using an optimal control method with integral action. To achieve such a goal, the system model parameters with nominal values are transformed into parametric unmatched uncertainties to form a robust control problem, which is then transformed into a linear quadratic regulator problem. The inductance uncertainties are stabilized with the uncertainty dynamic algebraic Riccati equation(UDARE) using state feedback gain under linear quadratic regulator. The closed-loop control with integral action is adopted to achieve a steady-state error of zero on the DC-link voltage at any uncertainty of the inductive parameter, which subsequently ensures the equal load current sharing. Off-line simulations and real-time validations based on OpalRT have been conducted to demonstrate the effectiveness and robustness of the proposed robust control strategy.

Novel integrated three-port DC/DC converter for different operating modes between renewable energy,electrolyser and fuel cell/battery

Due to the slow dynamic power-regulation characteristics of the electrolyser(EL),a novel integrated three-port DC/DC converter topology based on a phase-shifted full-bridge converter and dual active-bridge converter is proposed in this paper.Especially,the proposed converter can achieve a fast auxiliary response to the EL.This topology has the features of single-stage conversion,high system integration and compatibility with multiple operation modes.The operational principles and a hybrid modulation scheme of the proposed converter are analysed in detail.In addition,the power-transmission characteristics of each port and the soft-switching range are researched.On these bases,six operation modes suitable for a hydrogen energy-storage system are designed.The simulation and a 2-kW scaled-down experimental prototype are established to verify the feasibility and effectiveness of the proposed topology in different operation modes.

Phasor Analytical Model of Non-isolated DC/DC Converter Based on Modular Multilevel Converter for DC Transmission Grids

Non-isolated DC/DC converter based on modular multilevel converter(MMC)technology is expected to play an important role in future DC transmission grids.This paper presents a phasor analytical model for this new family of converters which is suitable for a range of studies like DC grid power flow or DC/DC parametric design.The 30th-order phasor model is derived in 3 coordinate frames:zero sequence(DC),fundamental frequency(dq),and double frequency(d2q2).The second-harmonic current suppression control is included as an option.Additionally,an estimation of the required control signals is presented,and a closed-loop model is developed which facilitates direct calculation of all variables and fast parametric studies.The accuracy of the proposed models is verified against a detailed PSCAD model for a wide range of parameters.The studies illustrate the importance of the second-harmonic components on the model accuracy.Finally,the impact of the converter parameters on the performance is studied,and a basic eigenvalue stability analysis is given.

An Adaptive Control Strategy for Energy Storage Interface Converter Based on Analogous Virtual Synchronous Generator

In the DC microgrid,the lack of inertia and damping in power electronic converters results in poor stability of DC bus voltage and low inertia of the DC microgrid during fluctuations in load and photovoltaic power.To address this issue,the application of a virtual synchronous generator(VSG)in grid-connected inverters control is referenced and proposes a control strategy called the analogous virtual synchronous generator(AVSG)control strategy for the interface DC/DC converter of the battery in the microgrid.Besides,a flexible parameter adaptive control method is introduced to further enhance the inertial behavior of the AVSG control.Firstly,a theoretical analysis is conducted on the various components of the DC microgrid,the structure of analogous virtual synchronous generator,and the control structure’s main parameters related to the DC microgrid’s inertial behavior.Secondly,the voltage change rate tracking coefficient is introduced to adjust the change of the virtual capacitance and damping coefficient flexibility,which further strengthens the inertia trend of the DC microgrid.Additionally,a small-signal modeling approach is used to analyze the approximate range of the AVSG’s main parameters ensuring system stability.Finally,conduct a simulation analysis by building the model of the DC microgrid system with photovoltaic(PV)and battery energy storage(BES)in MATLAB/Simulink.Simulation results from different scenarios have verified that the AVSG control introduces fixed inertia and damping into the droop control of the battery,resulting in a certain level of inertia enhancement.Furthermore,the additional adaptive control strategy built upon the AVSG control provides better and flexible inertial support for the DC microgrid,further enhances the stability of the DC bus voltage,and has a more positive impact on the battery performance.

Modeling and Control of an Isolated Module Multilevel DC/DC Converter for DC Grid

This paper presents an isolated DC/AC/DC converter using a middle frequency transformer coupling two modular multilevel converters(MMC),suitable for interconnecting DC transmission lines of different voltage levels in high voltage direct current(HVDC)system.The basic operational principle of the isolated module multilevel DC/DC converter(IMMDCC)is analyzed.The dynamic model of IMMDCC is studied in detail and the transient relationship between DC side and AC side of IMMDCC is revealed,which is physically straightforward for understanding the power transfer in IMMDCC.The control strategy in D-Q coordinate system is put forward,and the fault characteristic and corresponding protection method is analyzed.Finally,computer simulation using Matlab/Simulink is performed to verify the dynamic model and the proposed control strategy.The simulation results show good performances and the quick response ability of the proposed control strategy.

Experimental research of heavy ion and proton induced single event effects for a Bi-CMOS technology DC/DC converter

This paper tested and analyzed heavy ion and proton induced single event effects（SEE） of a commercial DC/DC converter based on a 600 nm Bi-CMOS technology. Heavy ion induced single event transients（SET） testing has been carried out by using the Beijing HI-13 tandem accelerator at China Institute of Atomic Energy. Proton test has been carried out by using the Canadian TRIUMF proton accelerator. Both SET cross section versus linear energy transfer（LET） and proton energy has been measured. The main study conclusions are：（1） the DC/DC is both sensitive to heavy ion and proton radiations although at a pretty large feature size（600 nm）, and threshold LET is about 0.06 Me V mg/cm^2;（2） heavy ion SET saturation cross section is about 5 magnitudes order larger than proton SET saturation cross section, which is consistent with the theory calculation result deduced by the RPP model and the proton nuclear reaction model;（3） on-orbit soft error rate（SER） prediction showed, on GEO orbit,proton induced SERs calculated by the heavy ion derived model are 4–5 times larger than those calculated by proton test data.

SUPPRESSING CONDUCTED EMI FROM A DC/DC HIGH POWER CONVERTER BASED ON MIXED-MODE FILTER

Conducted electromagnetic interference (EMI) from a 7.5kVA DC/DC high power converter is investigated to agree with EN class A. Here in some passive methods of suppressing conducted EM Noise, such as mixed-mode (MM) EMI filters, snubbing circuits and other means, are used. Based on measurement, the sources of noise are detected with the characteristics analyzed in detail. The MM EMI filters is valuable means with which low-frequency part and some of the high frequency part of conducted EM Noise can be efficiently reduced. How to lay out the MM filters on both sides of the converter is outlined in detail. In addition, multiple grounding and RDC snubbing circuits are employed to improve the performance in high frequency. The experimental results confirm the methods adopted.

High step-up quasi-Z-source DC–DC converters with single switched capacitor branch

Aiming to integrate the respective merits of the switched-capacitor converter and the quasi-Z-source converter. An novel high step-up quasi-Z-source DC–DC converter with a single switched-capacitor branch is proposed. Compared to other high boost DC–DC converters,the proposed converter can provide higher output voltage gain, lower current stress across the switches, and lower voltage stress across the output diodes by using the same or similar passive and active components. Therefore, the efficiency and reliability of the converter can be improved.The topological derivation, operating principle, parameter selection, and comparison with other DC–DC converters are presented. Finally, both simulations and experimental results are given to verify the characteristics of the proposed converter.

A zero-voltage zero-current soft switching DC/DC converter

A novel three-level zero-voltage zero-current switching(ZVZCS)DC/DC converter is proposed in this paper.A tapped-inductor is used to replace the normal out-put filter inductor,so that the circulating current in the zero-state can be reset to zero.The reset voltage and the re-set time can be set conveniently just by simply changing the winding ratio of the tapped inductor.The converter achieves a zero-current tuning off for inner switching,and a zero-voltage tuning on for outer switching.No circulating current exists in the zero state,so that the loss in the on-state is reduced,and the efficiency can be improved.The experimental results verify that the ZVZCS has low voltage stress,zero-voltage and zero-current switching.

Modeling, Analysis and Simulation of a High-Efficiency Battery Control System

This paper explains step-by-step modeling and simulation of the full circuits of a battery control system and connected together starting from the AC input source to the battery control and storage system.The three-phase half-controlled rectifier has been designed to control and convert the AC power into DC power.In addition,two types of direct current converters have been used in this paper which are a buck and bidirectional DC/DC converters.These systems adjust the output voltage to be lower or higher than the input voltage.In the buck converters,the main switch operates in conduction or cut-off mode and is triggered by a Pulse-Width Modulated(PWM)signal.The output and input voltage levels ratio are used to calculate thePWMsignal’s duty cycle.Therefore,the duty cycle indicates the operation mode of the converter in steady-state operation.In this study,we analyze and control of a buck converter with the PWM signal.Besides,the bidirectional DC/DC converter has been achieved and optimized by PI control methods to control the battery charging and discharging modes.The simulation has been applied via the Matlab/Simulink environment.The results show the activity of each part of the designed circuits starting from the converters and the battery control system in charge and discharge modes.

An Efficient MPPT Tracking in Solar PV System with Smart Grid Enhancement Using CMCMAC Protocol

Renewable energy sources like solar,wind,and hydro are becoming increasingly popular due to the fewer negative impacts they have on the environment.Because,Since the production of renewable energy sources is still in the process of being created,photovoltaic(PV)systems are commonly utilized for installation situations that are acceptable,clean,and simple.This study presents an adaptive artificial intelligence approach that can be used for maximum power point tracking(MPPT)in solar systems with the help of an embedded controller.The adaptive method incorporates both the Whale Optimization Algorithm(WOA)and the Artificial Neural Network(ANN).The WOA was implemented to enhance the process of the ANN model’s training,and the ANN model was developed using the WOA.In addition to this,the inverter circuit is connected to the smart grid system,and the strengthening of the smart grid is achieved through the implementation of the CMCMAC protocol.This protocol prevents interference between customers and the organizations that provide their utilities.Using a protocol known as Cross-Layer Multi-Channel MAC(CMCMAC),the effect of interference is removed using the way that was suggested.Also,with the utilization of the ZIGBEE communication technology,bidirectional communication is made possible.The strategy that was suggested has been put into practice,and the results have shown that the PV system produces an output power of 73.32 KW and an efficiency of 98.72%.In addition to this,a built-in regulator is utilized to validate the proposed model.In this paper,the results of various experiments are analyzed,and a comparison is made between the suggested WOA with the ANN controller approach and others,such as the Particle Swarm Optimization(PSO)based MPPT and the Cuckoo Search(CS)based MPPT.By examining the comparison findings,it was determined that the adaptive AI-based embedded controller was superior to the other alternatives.

An Introduction to Distribution-Level Solar Energy

Solar energy has been widely used in power generation.With the development of solar energy,the distributed photovoltaic power generation and the distributed grid-connected PV systems become the center of attention.This paper provided a brief introduction to distribution-level solar energy.Firstly,the development of solar energy was analyzed,and the distributed photovoltaic power generation was discussed.Secondly,the distributed grid-connected PV systems and basic theory of photovoltaic solar channel were analyzed.In order to ensure PV power is connected to grid stably and reliably,some related aspects such as the establishment of mathematical model for solar photovoltaic cell,the analysis of I-V characteristics of solar photovoltaic cell,and the tracking of its maximum power point(MPPT)to control the behaviour of the DC/DC converter were discussed.Finally,a simulation model was necessary to be established by using PSCAD/EMTDC function module to verify and simulate the mathematical model and control strategies,and some suggestions were put forward for the sustainable development of solar energy.

Regenerative Braking Strategy for Motor Hoist by Ultracapacitor

Rising concern in environmental issues on global scale has made energy saving in powered equipment a very important subject.In order to improve the energy efficiency and driving range of a motor hoist,a regenerative braking system is designed and discussed.The system takes a unique ultracapacitor-only approach to energy storage system.The bi-directional bride DC？DC converter which regulates current flow to and from the ultracapacitor operates in two modes：boost and buck,depending on the direction of the flow.In order to provide constant input and output current at the ultracapacitor,this system uses a double proportional-integral（PI） control strategy in regulating the duty cycle of PWM to the DC？DC converter.The permanent magnet synchronous motor（PWSM） drive system is also studied.The space vector pulse width modulation（SVPWM） technique,along with a two-closed-loop vector control model,is adopted after detailed analysis of PMSM characteristics.The overall model and control strategy for this regenerative braking system is ultimately built and simulated under the MATLAB and Simulink environment.A test platform is built to obtain experimental results.Analysis of the results reveals that more than half of the gravitational potential energy can be recovered by this system.Simulation and experimentation results testify the validity of the double PI control strategy for interface circuit of ultracapacitor and SVPWM strategy for PMSM.

Operation, Analysis and Experiments of DC Transformers Based on Modular Multilevel Converters for HVDC Applications

This paper studies the operation,analysis and experiments of multilevel high frequency link transformers(MHFLT)based on modular multilevel converters(MMC)for high voltage DC applications.The multilevel dual active phase shift is proposed to operate the MHFLT using a high switching frequency,which brings about many advantages and makes the operation quite different from that of the traditional DC transformer(DCT)based on a dual active bridge and the fundamental frequency MMC widely used in flexible HVDC transmission.Specifically,MHFLT is suitable for high voltage levels,which is due to its good switching characterization,ability to cut itself off from an external fault,and it can also achieve redundancy operations when a sub-module fault occurs.In this paper,the operation,modulation method,multilevel high frequency link voltage,current,and power characterization,high frequency commutation,and switching characterization are analyzed comprehensively;the pulse rotation and distributed delay control,and fault handling strategies of MHFLT are then proposed.Finally,a prototype is built,and the experimental results verify the correctness and effectiveness of the proposed solution.

Critical Transient Processes of Enhancement-mode GaN HEMTs in High-efficiency and High-reliability Applications

Wide-bandgap devices,such as silicon-carbide metal-oxide-semiconductor field-effect transistors(MOSFETs)and gallium-nitride high electron mobility transistors(HEMTs),exhibit an excellent figure of merits compared to conventional silicon devices.Challenges of applying such fast switches include accurate extraction and optimization of parasitics especially when 6high-efficiency operation,all of which require the comprehensive understanding of such switch especially its interaction with peripheral circuits.Particularly for the enhancement-mode GaN HEMTs without the intrinsic body diode,when reverse conducting,its high voltage drop causes a high dead-time loss,which has rarely a concern in silicon devices.This paper focuses on 650V/30~60A enhancement-mode GaN HEMTs provided by GaN Systems,analytically models its switching behaviors,summarizes the impact of parasitics and dead time,and applies it in two DC/DC converters.Systematic design rules are generated not only for soft switching but also for hard switching applications.