Different Types Of Converters Research Articles

A bridgeless configured asymmetrical alternating current–direct current converter‐based isolated single‐stage electric vehicle battery charger with supply side power factor enhancement

AbstractAn approach is presented to employ two different types of converters in bridgeless configuration for supply side power factor enhancement of the system. The isolated single‐stage electric vehicle battery charger uses two different converters in a bridgeless configuration to extract the advantages of both converters for supply‐side power factor enhancement. For the negative and positive semi‐cycles of the supply voltage, the power factor‐enhanced asymmetrical alternating current–direct current converter utilises a fourth order single‐ended primary‐inductor converter and a second order buck‐boost converter, respectively. The use of single‐ended primary‐inductor converter and buck‐boost converter in bridgeless configuration reduces the net order of the system with respect to conventional bridgeless‐single‐ended primary‐inductor converter schemes. The buck‐boost converter also needs the supply‐side filter to eradicate the unwanted harmonics in the supply current which increases the order of the system. The usage of both converters presents many benefits like input inductance of the single‐ended primary‐inductor converter can be utilised as a filtering element with a capacitor for the buck‐boost converter. The anti‐parallel diode conduction operation of both switches facilitates the elimination of extra reverse feed diodes (generally used in bridgeless schemes). The single‐stage charger itself comes with the benefit of elimination of extra stages and thus the losses associated with it. The presented charger also witnesses the elimination of the rectifier due to usage of bridgeless configuration. The isolated single‐stage electric vehicle battery charger is also garnished with electrical isolation which adds to the safety standard of the system. To attain power factor enhancement, the asymmetrical alternating current–direct current converter functions in discontinuous current conduction mode in the present work. The elimination of extra‐stages (with respect to two stage charger), a filter, a rectifier, two extra reverse‐feeding diodes, one voltage sensor, one current sensor (with respect to continuous current conduction mode), and electrical isolation not only makes the system compact and safer but also makes the system cheaper. Elaborated mathematical modelling and stability analysis of the presented alternating current–direct current converter using a pole‐zero map and bode plot have been included in the article. The prototype and MATLAB/Simulink model of isolated single‐stage electric vehicle battery charger system with discontinuous current conduction mode control has been built and results of both prototype and MATLAB/Simulink are deployed to verify isolated single‐stage electric vehicle battery charger system's performance during dynamic and steady‐state conditions.

An Adaptable Fault Current Derivative Calculation Method for Derivative Relays in HVDC Grids

This paper presents an adaptable method for fault current derivative calculation in high voltage direct current (HVDC) grids composed of modular multilevel converters (MMCs). The proposed method can be used for current derivative calculation under different fault scenarios including pole-to-pole, pole-to-ground, and pole-to-metallic. The proposed method is adaptable as it can provide accurate fault current derivatives in various grid topologies such as symmetric monopole, asymmetric monopole with ground or metallic return, and bipole with ground or metallic return, as well as grids with different types of converters with and without fault-blocking capability including full-bridge MMCs (FB-MMCs), half-bridge MMCs (HB-MMCs), or a mix of HB- and FB-MMCs. The paper also demonstrates how the proposed current derivative calculation method can be used to form a derivative relay, which is fast, selective, computationally efficient, and insensitive to fault resistance. Furthermore, using the proposed current derivative calculation method, all relay settings are analytically calculated instead of being obtained through time-consuming simulation studies. Simulation results for various fault scenarios, grid topologies, and converter configurations show that the calculation method is accurate and the presented relaying algorithm can detect various faults within 10 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mu$</tex-math></inline-formula> s, even when the fault resistance is as high as 500 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$Upomega$</tex-math></inline-formula> .

A Self-Adaptive Power Flow Analysis Methodology for AC/DC Hybrid System

A self-adaptive methodology is proposed in this study to enable the power flow of an AC/DC hybrid system being uniformly analyzed in an AC framework. Firstly, the DC part of the hybrid system is transformed to its AC equivalent. The external characteristic models of various converters are then formulated as a π-shaped circuit, based on which a self-adaptive algorithm of the AC/DC hybrid power flow can be developed. Finally, the paper compares the proposed method with the unified method validated by different scale hybrid systems with different types of converters and control strategies. The results of case study show that the proposed method performs much more efficiently and reasonably.

Strategies for improving ride-through capability of three-terminal HVDC system under AC side fault

This paper considers a three-terminal hybrid DC transmission system in which the rectifier station adopts line-commutated converter (LCC) while the inverter station adopts parallel two-terminal modular multilevel converter (MMC). The focus of this paper is on the improvement of ride-through capability of LCC AC system in the presence of a fault. A strategy for improving the fault ride-through capability based on local information is proposed. First, the mathematical models of different types of converters in a hybrid DC system are established, and the influence of AC faults at the sending end on the DC transmission system is discussed. Second, in the presence of a slight fault on the AC side of LCC, the current margin control is proposed for the load center side MMC2, where the MMC2 maintains the DC port current as the minimum allowable value. Third, if a serious fault on the AC side of LCC causes a significant AC voltage drop, it is proposed that the non-load center terminal MMC1 adopts voltage margin control. In addition, the MMC1 takes over the DC system voltage control so as to maintain MMC2 to absorb minimum power from the DC system, and prevent the load center connected by the MMC2 from removing too many important loads or causing a frequency collapse. Last, a large number of simulation results verify the effectiveness of the proposed methods.

Comparative Study of the Transmission Capacity of Grid-Forming Converters and Grid-Following Converters

The development trend of high shares of renewables and power electronics has increased the demand for new energy converters in the power system, but there is a lack of systematic research on the stability of different types of converters when transmitting power, which is worth exploring in depth. In this study, the power transfer capabilities of grid-forming and grid-following converters are investigated separately through an equivalent circuit diagram and phasor diagram when connected to the grid, and a quantitative relationship between converters’ power transmission limit and short circuit ratio under static stability conditions is obtained, leading to the conclusion that, in terms of power transmission, grid-forming converters are more suitable for weak grids with high damping and low inertia, whereas grid-following converters are more suitable for strong grids with high inertia. The conclusions are further verified by constructing the converter grid-connected models for different grid strengths through the PLECS simulation platform and the real-time simulation RTBOX1 and F28379D launchpad platform.

Artificial Neural Network-based Fault Location in Terminal-hybrid High Voltage Direct Current Transmission Line

In this article, a fault location technique based on artificial neural networks (ANN) for Terminal-Hybrid LCC-VSC-HVDC has been assessed and scrutinized. As is known, in conventional HVDC systems (LCC-based and VSC-based HVDCs), the same type of filter is used on both sides due to the use of similar converters in both sender and receiver terminals. In this article, it is concluded that due to the use of two different types of converters at the both ends of the utilized Terminal-hybrid LCC-VSC-HVDC system, and the use of different DC filters on both sides, fault location using positive and negative pole currents of the rectifier side has much better results than the rest of input signals. Therefore, it will be finalized that by increasing and designing suitable DC filters on the transmission line of HVDC systems, fault localization matter will be remarkably and surprisingly facilitated. Nowadays, the fault location of HVDC transmission lines with a value of more than 1% is generally discussed in most articles. In this research, the fault location with a value of 0.0045%, i.e., a distance of 22.5 meters from the fault point in the most satisfactory case is obtained, which shows the absolute feasibility of the ANN along with the wavelet transform. To validate the proposed method, a ±100 KV, Terminal-hybrid LCC-VSC-HVDC system is simulated via MATLAB. The outcomes verify that the proposed technique works perfectly under various fault locations, resistances, and fault types.

Development of a Didactic Platform for Flexible Power Electronic Converters

Power electronic converters are the subject of several studies and applications. Knowledge about those converters is essential for several technical and undergraduate courses in the field of Electrical Engineering and related areas. The presence of converter modules in laboratories can be beneficial for experimental validations in academic research and educational purposes, for allowing students to have practical contact with different converter topologies and applications. However, the commercially available power converters are generally manufactured for specific applications, with poor versatility and high cost, when applied for academic purposes. For this reason, several laboratories propose the design of versatile converters, mainly for multilevel converter research. Nevertheless, most of these projects present module designs based on half bridge topology due to their low cost. Therefore, this project topology requires more modules to operate as topologies based on a full-bridge converter. Besides, modules based on full-bridge topology can also work in a half-bridge configuration. Thus, this work presents the design of full-bridge modules capable of operating as different types of converters, as well as the project of the dc-link voltage measurement, isolated power supply and bypass circuits. Moreover, this work addresses the heatsink choice, the thermal evaluation for the semiconductor devices and the realization of galvanic isolation between the signal and power circuits.

Battery-Supercapacitor Energy Storage Systems for Electrical Vehicles: A Review

The current worldwide energy directives are oriented toward reducing energy consumption and lowering greenhouse gas emissions. The exponential increase in the production of electrified vehicles in the last decade are an important part of meeting global goals on the climate change. However, while no greenhouse gas emissions directly come from the operations of the electrical vehicles, the electrical vehicle production process results in much higher energy consumption and greenhouse gas emissions than in the case of a classical internal combustion vehicle; thus, to reduce the environment impact of electrified vehicles, they should be used for as long as possible. Using only batteries for electric vehicles can lead to a shorter battery life for certain applications, such as in the case of those with many stops and starts but not only in these cases. To increase the lifespan of the batteries, couplings between the batteries and the supercapacitors for the new electrical vehicles in the form of the hybrid energy storage systems seems to be the most appropriate way. For this, there are four different types of converters, including rectifiers, inverters, AC-AC converters, and DC-DC converters. For a hybrid energy storage system to operate consistently, effectively, and safely, an appropriate realistic controller technique must be used; at the moment, a few techniques are being used on the market.

Design of LLC resonant converter with silicon carbide MOSFET switches and nonlinear adaptive sliding controller for brushless DC motor system

Introduction. The high voltage gain DC-DC converters are increasingly used in many power electronics application systems, due to their benefits of increased voltage output, reduced noise contents, uninterrupted power supply, and ensured system reliability. Most of the existing works are highly concentrated on developing the high voltage DC-DC converter and controller topologies for goal improving the steady state response of brushless DC motor driving system and also obtain the regulated voltage with increased power density and reduced harmonics, the LLC resonant DC-DC converter is implemented with the silicon carbide MOSFET switching devices Problem. Yet, it facing the major problems of increased switching loss, conduction loss, error outputs, time consumption, and reduced efficiency. Also the existing works are mainly concentrating on improving the voltage gain, regulation, and operating performance of the power system with reduced loss of factors by using the different types of converters and controlling techniques. The goal of this work is to obtain the improved voltage gain output with reduced loss factors and harmonic distortions. Method. Because, this type of converter has the ability to generate the high gain DC output voltage fed to the brushless DC motor with reduced harmonics and loss factors. Also, the nonlinear adaptive sliding controller is implemented to generate the controlling pulses for triggering the switching components properly. For this operation, the best gain parameters are selected based on the duty cycle, feedback DC voltage and current, and gain of silicon carbide MOSFET. By using this, the controlling signals are generated and given to the converter, which helps to control the brushless DC motor with steady state error. Practical value. The simulation results of the proposed LLC silicon carbide MOSFET incorporated with nonlinear adaptive sliding controller controlling scheme are validated and compared by using various evaluation indicators.

Electric Vehicle Motor, Converter, Controller and charging station with challenges and Configurations: Review

Electric vehicles (EVs) are an emerging technology that enhances the ecology and environmental respect around the world through the automobile industry. The impact of electric vehicles mainly depends upon the efficient output of batteries and power converters. Converters and controllers used in the EVs have many drawbacks such as large switching loss, reduced dynamic response, increased current stress, and a larger number of components. The effectiveness of controllers, converters, and motors should be necessary to achieve reliable output power from the storage systems. Therefore it is necessary to choose the appropriate converter, controller, and motor to get efficient output. This review paper explores different types of converters, power controllers, EV motors, and charging stations with its advantage and disadvantage. A comparison was made on various types of Electric vehicles, power converters, EV controllers, charging stations, and motor with their commercial demand. Finally, this review article explores the challenges and gives suggestions for future electric vehicle development and application. Keywords : Electric Vehicle, DC-DC Converter, Controllers, Modulation Techniques, Solar Charging Station, EV Motors.

Impact of Strength and Proximity of Receiving AC Systems on Cascaded LCC-MMC Hybrid HVDC System

The cascaded hybrid LCC-MMC inverter is considered as a feasible option to mitigate the commutation failure problem of conventional LCC-HVDC while maintaining bulk power transmission capability. However, the coupling between different types of converters may result in instability when the inverter integrates with weak AC systems. This paper establishes a small-signal model of the cascaded LCC-MMC inverter based hybrid HVDC system and validates the model against PSCAD/EMTDC. Through eigenvalue analysis, the impact of the strength and proximity of receiving AC systems on the small-signal stability is investigated, and the stable zone of the strength of receiving AC systems is identified. Besides, a supplementary coupling mitigation control is proposed to tackle the instability problem under weak AC systems integration. Both analytical results and time-domain simulations demonstrate the validity of the supplementary control.

Transient energy protection based on wavelet packet transform for hybrid bipolar HVDC transmission system

In hybrid bipolar DC transmission systems with different types of converters at each pole, the transient high-frequency component of the voltage signal under a single-pole grounding fault and an inter-pole fault is significantly different for internal and external faults because of smooth-wave reactors on both sides of the DC line. Based on these characteristics, a single-ended electrical quantity protection scheme based on transient energy is proposed. First, the voltage fault component is extracted and then processed by using a wavelet packet transform to obtain the transient energy in each frequency band. Second, the protection criterion is determined based on the ratio between low-frequency energy and the sum of high-frequency energy. After the setting principle is given, the influence of the protection scheme under high transition resistance is analysed. The protection scheme is implemented in MATLAB and tested based on fault data obtained from a hybrid bipolar HVDC transmission model built in PSCAD under different operating conditions. The effectiveness of the proposed protection method is verified by simulation tests under different fault types at different fault distances. The proposed method can provide strong tolerance to high transient resistance, accurately identify internal/external faults and automatically identify fault poles.

Power sharing in hybrid microgrids with multiple DC subgrids

Control strategies are prominent for the efficient and stable operation of emerging hybrid microgrids (HMGs), where bidirectional dc/dc converters (BDCs) are used to connect multiple dc subgrids to a common dc bus, and bidirectional interlinking converters (BICs) are used to exchange power between the dc and ac sides. Conventional droop controls may not be able to provide accurate power sharing in such sophisticated HMGs. In this paper, a framework is proposed for accurate power sharing among BDCs and BICs using existing harmonics at dc networks and a multi-dimensional droop control. In particular, we employ the frequency of available harmonics as global variables at the dc subgrids and the common dc bus to design a droop control approach for accurate power sharing among BDCs. It outperforms the existing voltage-based droop approaches when practical situations of HMGs, such as different cable resistance of BDCs, are considered. For the BICs, we propose a multi-dimensional droop as an integrated control strategy to adjust the power exchanged between dc and ac sides as well as the power of the BIC’s energy storage system. As a result, not only the converters are operated in a more economical and flexible manner, but also their overstressing and spurious loading are avoided resulting in better maintenance and more robust operation. An HMG with different types of converters and subgrids is used to evaluate the proposed features.

Performance Analysis of DC-DC Converters for Solar Water Pumping System Employing Switched Reluctance Motor Drive

The grail of this paper is to investigate the performance of various DC-DC converters for solar based water pump system incorporating switched reluctance motor drive. The Converters used are CUK converter, Buck-Boost converter and Boost converter respectively. The speed of the switched reluctance motor is regulated by the mid-point converter along with the various DC-DC converters. The Switched reluctance motor is adopted over other motors because of its low inertia, ease of control, speed range is wide, less losses as there is no windings nor permanent magnets Present on the rotor. In order to operate the solar PV array at its optimum level we employ maximum power point tracking (MPPT) and specifically Perturb and Observe control method is employed in this project. The proposed system deals with the design, modeling and simulation of three different types of converters using MATLAB/Simulink environment. The applicability of this system can be analyzed by the simulated results.

Modern Aircraft Electronic Power Converters

The article points out to changes in on-board aircraft power converters, which are necessary due to weight reduction and improvement of reliability and maintenance. The paper presents the evolution from old rotary converters to modern solid state converters and describes their advantages. There is also the mention about electro-magnetic interference (EMI), which is introduce during the conversion and how could it be reduced for different types of converters. The operational principle of various power inverters is simulated in MATLAB to figure out different output waveforms quality which could be reached by such a conversion.

Performance Characteristics of Various Converters for Non Linear System

Power Extraction from renewable energy sources plays a vital role in this century due to the depletion of non renewable energy sources, socio economic factors and expensive cost .Few examples of renewable energy sources are Solar, wind, Fuel cell and hydraulic forces. Compared to other resources solar energy leads to the best option because of the availability and less design complexity. Different converters are available for extracting the maximum power from the panel. In this paper solar panel voltage is extracted with the use of MPPT algorithm along with Boost, Buck and SEPIC converters and their performance is analyzed. Based on the performance analysis boost converter with PV panel is implemented along with MPPT algorithm. Using MATLAB Simulink 2018 environment PV panel and different types of converter are modeled and its characteristics are evaluated.

Review of GaN HEMT Applications in Power Converters over 500 W

Because of the global trends of energy demand increase and decarbonization, developing green energy sources and increasing energy conversion efficiency are recently two of the most urgent topics in energy fields. The requirements for power level and performance of converter systems are continuously growing for the fast development of modern technologies such as the Internet of things (IoT) and Industry 4.0. In this regard, power switching devices based on wide-bandgap (WBG) materials such as silicon carbide (SiC) and gallium nitride (GaN) are fast maturing and expected to greatly benefit power converters with complex switching schemes. In low- and medium-voltage applications, GaN-based high-electron-mobility transistors (HEMTs) are superior to conventional silicon (Si)-based devices in terms of switching frequency, power rating, thermal capability, and efficiency, which are crucial factors to enhance the performance of advanced power converters. Previously published review papers on GaN HEMT technology mainly focused on fabrication, device characteristics, and general applications. To realize the future development trend and potential of applying GaN technology in various converter designs, this paper reviews a total of 162 research papers focusing on GaN HEMT applications in mid- to high-power (over 500 W) converters. Different types of converters including direct current (DC)–DC, alternating current (AC)–DC, and DC–AC conversions with various configurations, switching frequencies, power densities, and system efficiencies are reviewed.

Advanced Control Strategies of VSC Based HVDC Transmission System: Issues and Potential Recommendations

The converters and their control strategies play an important role in converting, transmitting, and improving the performance of high-voltage direct current (HVDC) system. There are different types of converter and their control strategies being employed in the HVDC system, such as line-commutated converter and voltage source converter (VSC). However, the existing converter controllers have still some limitations on certain deficiencies in certain aspects such as in weak AC grid or at high voltage and power level. Thus, an advanced converter control strategy is very much important in order to ensure optimal power transfer with minimal loss and stable voltage. This paper presents a comprehensive review of the advanced control strategies to address the problems and enhance the performance of the VSC-based HVDC (VSC-HVDC) transmission system. A detailed study on the overview of VSC-HVDC and their converter classifications are investigated. The main contribution of this paper is to carry out the different types of VSC-HVDC control strategies in controlling voltage, current, power, and the control parameters of the HVDC transmission system. This paper also highlights several factors, challenges, and problems of the conventional VSC-HVDC controllers. Furthermore, this paper provides some suggestions for the advanced control for the future research and development of the HVDC system.

Hybrid Dual and NPC Six-Phase Drive Systems

This paper presents two hybrid six-phase machine drive systems. The topologies are considered to be hybrid because two three-phase groups of the machine are fed by different types of converters. The purpose of these topologies is to be alternative configurations, being midway between the conventional six-leg two-level (2L) inverter, composed of 12 switches, and more complex structures, such as the six-leg three-level neutral point clamped (3L-NPC) inverter, composed of 24 switches and 12 clamping diodes, or the conventional 12-leg dual inverter, composed of 24 switches. One of the hybrid topologies is composed of 18 switches and the other is composed of 18 switches and 6 clamping diodes. A comparative study of harmonic distortion, semiconductor losses, and machine torque ripple is performed. Compared with the conventional 2L inverter, the proposed systems provide better performance in terms of harmonic distortion, overall semiconductor losses, and machine torque ripple and are less complex than dual and NPC inverters. Pulse width modulation (PWM) strategy is discussed and simulated. A modification in PWM strategy of the hybrid configurations is performed in order to obtain similar torque ripple to the cases when dual and 3L-NPC converters are used, even with lower number of semiconductor devices. Experimental results are also presented in order to validate the PWM strategy.

Guest Editorial

Guest Editorial