Switching Losses Research Articles

High-Efficient Direct Power Control Scheme Using Predictive Virtual Flux for Three-Phase Active Rectifiers

In recent years, the pulse-width-modulation (PWM) converter has been found to have extensive applications in renewable energy, industrial fields, and others. The high efficiency requirement is crucial to operating a PWM rectifier in various applications, in addition to the fundamental control objectives of sinusoidal grid currents and the correct DC bus voltage. Additionally, in practical application, another issue arises when the grid voltage frequently experiences distortion, leading to a distorted grid current and a significant rise in total harmonic distortion (THD). To resolve these problems, a model predictive virtual flux-based direct power control (MPVFDPC) with improved power loss performance is proposed based on an integrated switching state predetermination strategy. The proposed MPVFDPC for PWM rectifier inherits the merits of both virtual flux control and direct power control, which have fast dynamic performance and the grid current THD is considerably decreased under distorted grid voltage states. The proposed technique aims to minimize switching loss under ideal and distorted grid voltage states by exploiting the discontinuous modulation concept by using a switching state predetermination strategy. The MPVFDPC with switching state predetermination strategy is proven by employing it in experiments as well as simulations in comparison with previous models: predictive direct power control (Conv. MPDPC) and conventional MPVFDPC (Conv. MPVFDPC). The acquired waveforms and quantitative data are employed to prove the effectiveness of the developed algorithm.

Resonant step-down DC-DC converter based on GaN power integrated circuits and SiC diodes

In the paper results of the operation and efficiency of a DC-DC resonant converter with a switched capacitor topology, equipped with GaN transistors and SiC diodes are presented. Investigated problems are related to the optimization of the DC- DC power electronic converter in order to achieve miniaturization, a simplified design and high efficiency. The proposed system operates at a high frequency with low switching losses. The proposed design helps to achieve uniform heating of the transistors and diodes, as demonstrated by the results of the thermal imaging measurements. The GaN transistors are integrated in one package with dedicated gate drivers and used to simplify the drivers circuitry and increase the power density factor of the proposed device. In the high-frequency design presented in the paper, the converter is implemented without electrolytic capacitors. The results included in the paper contain waveforms recorded in the power circuit at ZVS operation when switching on the transistors. It occurs when the system operates above the frequency of current oscillations in the resonant circuit of the switched capacitor. Efficiency characteristics and a voltage gain curve of the converter versus its output power are presented as well. Results of efficiency and quality of waveforms are important because they allow to characterize the tested system for the implementation using WBG devices. The use of integrated GaN modules to minimize elements in the physical system is also unique to this model and it allows for very short dead-time use, operation in ZVS mode at low reverse-conduction losses.

The Behaviours of Various DC Choppers during Shading Occurrence in PV Systems

This paper investigates how the DC choppers behave during the shading occurrence at different time intervals of the year. Three types of DC choppers are implemented during the same shading conditions and intervals of time. The studied parameters are the duty cycle, output power, current, and switch losses. The mathematical model is built and implemented using the MATLAB/Simulink platform. The obtained results show that the SEPIC converter has the highest rate of duty cycle, which means more switching losses are generated. Concerning the average output power, the Modified Single Ended Primary Converter (MSEPIC) has the highest rate, while the Boost Converter has the lowest rate. The MPP power, duty cycle, and switching losses are studied under various shading rates. The duty cycle has the highest rate on the SEPIC converter, while MSEPIC has the lowest rate. Despite that, the switching losses are tremendously high at MSEPIC compared to SEPIC converters. Furthermore, simulation studies show that Boost and SEPIC converters have better performance in frequent cloudy weather conditions.

A Parameter Optimization Design Method for Single-Phase Dual Active Bridge AC-DC Converter

The single-stage dual active bridge (DAB) AC-DC converter has the advantages of high power density, low cost, and simple control; it has a broad potential for application in the field of onboard chargers (OBC). However, the lack of fast and accurate quantitative parameter optimization design methods in single-stage DAB AC-DC converters limits the overall efficiency of the converter. Based on the above problem, in order to improve the overall operating efficiency of the converter by optimizing the parameter transformer ratio and power inductance, this paper proposes a parameter design method considering a multi-timescale strategy by combining the steady-state analysis model of the converter in the line cycle and switching cycle and step-by-step reducing its design space through the constraints on the parameters. The first step is to obtain a safe design space for the parameters under the converter’s transmitted power and current stress constraints. The second step obtains the optimization design space of the parameters under the optimization of conduction loss and switching loss of the converter. Finally, the optimal parameters are determined by the loss analysis model. The proposed parameter optimization method entirely takes into account the steady-state characteristics of the DAB AC-DC converter during the line cycle, and the step-by-step constraints greatly accelerate the parameter design process. In addition, the proposed parameter optimization design method applies to all types of single-stage DAB AC-DC converters, which can be well applied to engineering practice.

A novel approach to modeling and experimenting a solar-fed H6 configuration for battery swapping stations in rural and commercial areas using a dual phase CLLC DC–DC resonant converter

In order to further the use of clean energy, the transition from internal combustion engine (ICE) vehicles to electric vehicles (EVs) was initiated globally. In the coming days, there will be a need for more EV charging stations in rural and commercial areas. The installation of new charging infrastructure for different vehicles with different voltage specifications in order to charge batteries are expensive with limited availability. Also fast charging is not possible in rural areas. To overcome this issue, the battery swapping station is a good option. In this paper, a new solar-powered dual-phase CLLC DC–DC resonant converter is proposed to test battery swapping. An equivalent circuit has been derived analytically, and the optimal design of the magnetic components for the proposed converter has been derived. Simulation has been carried out for the proposed system. The proposed system was tested with a prototype set-up of a 100 W lithium-ion battery bank of equal and unequal voltage levels in an open-loop condition using Analog Discovery-2. Introducing the H6 concept in the proposed converter has the features of low stress across switches, use of higher dc grid voltage, low switching losses due to the dual phase resonant compensation network, and a multi-port isolated output system. Apart from battery swapping applications it can be utilized for Energy Storage Solution [ESS].

Dual‐input step‐up switched‐capacitor multilevel inverter with reduced voltage stress on devices

SummaryThis paper proposes a single‐phase dual‐input step‐up switched‐capacitor multilevel inverter that employs three capacitors, 15 switches, and two diodes to provide 13 voltage levels and triple‐voltage boosting factor in its symmetric form and 37 levels with voltage boosting factor of 3.6 in its asymmetric version. This high boosting factor is accomplished without utilizing any transformer. For each output voltage level, there exists flow paths for both the positive and negative load current directions, which makes the proposed inverter capable of supplying any load type with variety of power factors (zero to unity). The voltage balancing of the capacitors takes place naturally, which tackles the need to auxiliary charge‐balancing circuits or control mechanisms. The proposed inverter can generate negative levels without the end‐side H‐bridge. Moreover, the voltage stress on the semiconductor devices is less than the peak output voltage. The increased number of levels and sinusoidal‐like waveform of the output voltage waveform enhances the quality and lowers the harmonic content of the load voltage and current waveforms, even for resistive loads. As the result, the load‐side filter can be downsized or removed. This paper employs the fundamental frequency method (FFM) as the switching technique, which is simple to implement and also operates the switches at low frequencies, leading to lower switching losses. The ascendancy of proposed inverter over similar counterparts has been investigated through comprehensive comparative analysis. Moreover, the correct performance of the proposed inverter at different modulation indices, and load types as well as during dynamic load changes has been verified by simulation and experimental analysis.

Non-Weighted Two-Stage Model Predictive Control Strategy Based on Three-Level NPC Inverter

This paper investigates the asynchronous motors driven by a Three-Level Neutral-Point-Clamped Voltage Source Inverter (3L-NPC-VSI) and aims to achieve control without weight factors and reduce torque ripple. It puts forward a non-weighted two-stage Finite-Control-Set Model Predictive Control (FCS-MPC) strategy. First, a hierarchical optimization method is adopted to address the difficulty of setting weight factors in traditional FCS-MPC applications. The method offers stratified designs of three performance indices, voltage jump, common-mode voltage, and current tracking, obviating the need for weight factor setting and reducing the calculation load of predictions. Secondly, to further mitigate torque ripple, an optimal vector or vector combination is implemented at the current control layer by adhering to the principle of minimal current tracking error. During the selection of the optimal vector combination, the first vector of the combination is chosen to be the vector at the end of the present cycle. This ensures that there is at most one switch within each control period, reducing the switching losses of the two-stage FCS-MPC. Lastly, detailed simulation and experimental analyses are conducted to verify the feasibility and effectiveness of the proposed strategy.

A high step‐up high step‐down coupled inductor based bidirectional DC–DC converter with low voltage stress on switches

AbstractThis paper proposes, a novel soft‐switching bidirectional direct current to direct current (DC–DC) converter based on switched‐capacitor and coupled‐inductor. The proposed converter has a simple structure and utilizes four switches and a three‐winding coupled inductor and can achieve a high voltage conversion ratio in both step‐up/step‐down operations. By employing the switched‐capacitor technique, voltage stress across the power switches is low and therefore low voltage rating switches can be adopted to reduce the losses of their conduction. Soft‐switching characteristic of the proposed converter reduces the switching loss of active power switches and raises the conversion efficiency. This paper presents theoretical analysis for all operating modes of the converter, voltage conversion ratio, voltage and current stresses of all power switches. Finally, to test the validity of theoretical results and demonstrate the performance of the converter, experimental results are provided.

Improving Performance of Solar Array Fed BLDC Drive Using Firefly Algorithm Based High Gain Converter

The improved transient response of PID controller for improved Luo converter supplied Brushless DC (BLDC) motor using solar energy source is extensively investigated. The BLDC drive uses a hybrid PV system and battery-based power generation as a power source to assure continuous power supply to pump water regardless of solar insolation. The PV system serves as the main energy source, and the battery providing as a backup source that discharged its power only during inclement weather or at night if the photovoltaic panel is insufficient to operate the centrifugal pump. The solar panel feeds power into the battery, whenever water to the field is not required, thus there is no need for an extra power source to charge the batteries. The high output voltage gain DC-DC converter does not make any discomfit to the system performance in regards to irradiance variation, switching loss, or power loss by converter or motor side respectively. Moreover, current sensor, voltage sensor, and control circuits are completed excluded which enhance performance and the cost of the system get reduced effectively. A bidirectional charging control allows a bi-directional converter to alter the battery operation mode automatically. The overall system performance is validated using simulation and experimental setup.

NOUVEAU FILTRE DE PUISSANCE ACTIVE SHUNT BASÉ SUR UN ONDULEUR NPC À NEUF NIVEAUX UTILISANT LA STRATÉGIE DE MODULATION MC-LSPWM

This paper presents a novel shunt active power filter (Shunt APF) system based on a nine-level neutral point clamped (NPC) inverter, which can reduce current harmonics under various nonlinear loads. These loads can introduce harmonic currents within the system, which causes excessive power losses and alters the voltage systems' characteristics. Today, multi-level inverters are more suitable for high-voltage applications; their advantages are low harmonic distortions, low switching losses, low electromagnetic interference, and low acoustic noise. The reference signals required to compensate harmonic currents use the synchronous detection method (SDM) with phase disposition sinusoidal pulse width modulation (PD-SPWM) control due to its low complexity and superior performance. The proposed shunt APF configuration simulation is evaluated using MATLAB-Simulink and SimPowerSystem environment with inductive and capacitive non-linear loads. The simulation results show the efficiency of the proposed shunt APF in terms of harmonic compensation and power quality improvement. The results of comparative studies with other less multi-level inverters confirm the superiority of the proposed shunt APF system.

Extremely Low Frequency PS-PWM Based Technique for Cascaded H-Bridge Converters With Grid Voltage Compensation Capability

Cascaded H-Bridge Converters (CHB) are good candidates for many industrial applications. Among the modulation techniques that can be applied to CHB converters, the Phase-shifted PWM method (PS-PWM) provides very good harmonic quality being the most popular modulation technique at the expense of presenting high switching losses. On the contrary Block Switching technique as well as Selective Harmonic elimination/mitigation (SHE/SHM) techniques provides lower switching frequency and losses with a lower harmonic quality. Additionally with these techniques the converter operation becomes stiff. In this work a modification of PS-PWM based on an extremely low frequency carrier is proposed with the objective of achieving both low switching losses and an acceptable harmonic quality, simultaneously. The main advantage of the proposed solution is the capability of adjusting the phase-shift angle among the carriers to compensate for harmonic grid voltage disturbance. Several experimental results have been reported to demonstrate the good performance of the proposed modulation technique.

A Hybrid PWM Strategy for Switching Loss Reduction in Three-Level Inverters

The advanced bus-clamping PWM (ABCPWM) sequences are well known to reduce line current THD in a three-level neutral point-clamped inverter. This paper deals with ABCPWM sequences employed optimally to achieve minimum switching loss throughout the linear operating region in a three-level inverter. The work extensively analyzes the performance of these sequences in terms of inverter switching loss and compares them with centered space vector modulation PWM (CSVPWM). Based on the analysis, a hybrid PWM scheme termed as <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">switching loss reduction</i> is proposed by optimally employing ABCPWM sequences in conjunction with variation in power factors. At a given average switching frequency, the proposed hybrid scheme reduces inverter switching loss compared to CSVPWM and the recently proposed discontinuous PWM-based optimization strategy at all power factors and modulation indices. With this scheme, switching loss reduces to 22% to 36% compared to CSVPWM and a maximum of 12% reduction than the existing optimization strategy. Furthermore, the scheme gives lower harmonic distortion compared to these two existing PWM schemes near high modulation indices and near unity power factor load. The theoretical, simulated, and real-time simulation results are presented with experimental results using TMS320F28335 DSP controller for validating the proposed work.

Optimal Design of LCC Resonant Converter With Phase Shift Control for Wide Input/Output Voltage Ranges in Fuel Cell System

This paper proposes an optimal design of an LCC resonant converter with a phase shift control for a fuel cell system which has wide input and output voltage ranges. The proposed optimal design focuses on the circulating energy minimization by adjusting the transformer turns ratio according to the maximum gain of resonant tank. This makes the root mean square (RMS) value of resonant current and turn-off current stationary even though the resonant tank change. Thus, designers can select resonant tank optimized for the converter specifications without considering the conduction and switching losses. By the proposed optimal design, the efficiency degradation at worst case, which is a significant issue of the fuel cell system with wide output voltage range, can be minimized. In addition, for the fuel cell converter with wide input voltage range, a phase shift control which operates the full-bridge inverter with a constant effective duty cycle according to the fuel cell voltage is proposed. This control scheme improves the light-load efficiency without deteriorating the rated-load efficiency by reducing the circulating current and switching frequency. The validity of the proposed works is confirmed by experimental results of the 30kW LCC resonant converter.

LLC resonant converter analysis in PO mode

The PO mode under time-domain analysis is a kind of discontinuous conduction mode (DCM) which is beneficial to reduce the switching loss of the converter, but the calculation of the gain and frequency characteristics of the converter in this mode is cumbersome and difficult to be solved. Based on the analysis method of time domain approximation, the PO operating mode characteristics of the LLC resonant converter are analyzed, and a simple and accurate voltage gain calculation formula is theoretically deduced. Simple analytical expressions for the PO mode power boundary conditions are given based on the voltage variations of the magnetizing inductance and capacitance. A simulation model of the studied converter is established, and the simulation can prove that the proposed voltage gain formula and PO mode boundary conditions are correct.

Improvement of Ga2O3 vertical Schottky barrier diode by constructing NiO/Ga2O3 heterojunction

The high critical electric field strength of Ga2O3 enables higher operating voltages and reduced switching losses in power electronic devices. Suitable Schottky metals and epitaxial films are essential for further enhancing device performance. In this work, the fabrication of vertical Ga2O3 barrier diodes with three different barrier metals was carried out on an n–-Ga2O3 homogeneous epitaxial film deposited on an n+-β-Ga2O3 substrate by metal−organic chemical vapor deposition, excluding the use of edge terminals. The ideal factor, barrier height, specific on-resistance, and breakdown voltage characteristics of all devices were investigated at room temperature. In addition, the vertical Ga2O3 barrier diodes achieve a higher breakdown voltage and exhibit a reverse leakage as low as 4.82 ×10−8 A/cm2 by constructing a NiO/Ga2O3 heterojunction. Therefore, Ga2O3 power detailed investigations into Schottky barrier metal and NiO/Ga2O3 heterojunction of Ga2O3 homogeneous epitaxial films are of great research potential in high-efficiency, high-power, and high-reliability applications.

A Switched-Capacitor Multilevel Inverter With Modified Pulsewidth Modulation and Active DC-Link Capacitor Voltage Balancing

Although switched-capacitor (SC) multilevel inverters (MLIs) offer self-voltage balancing of flying capacitors and voltage gain higher than unity, the advantages come at the cost of high current stress and power loss in the SC circuit and DC source. Moreover, the voltage balancing is often restricted to a limited range of modulation index. Another problem of MLIs with neutral-point clamped (NPC) front end is with DC-link capacitor voltage balancing under unbalanced load conditions, imploring sensor-based closed-loop control. This paper proposes a unity gain five-level active-NPC SC-MLI with inrush charging current attenuation and actively balanced DC-link capacitor voltages under all load conditions and over the entire range of modulation index and power factor. The modified pulse-width modulation results in most switches operating at a low switching frequency, minimizing switching losses in the SC circuit. The proposed MLI attains a maximum efficiency of 98.04% at an output power of 510 W. Experiments on a 2 kVA laboratory prototype validate the theoretical analysis. Results from transformerless grid-connected solar PV system show that the proposed MLI can inject power into the grid with a unity power factor under conditions of varying irradiance and provide the grid with reactive power as well.

TECHNIQUE DE CONTRÔLE INTÉGRÉE OPTIMISÉE POUR VAUTOUR AFRICAIN POUR APPLICATION DE POMPE À MOTEUR À INDUCTION À ENROULEMENT OUVERT À ALIMENTATION PV

Open-end winding induction motors (OEWIM) have gained much attention, and they are used for solar photovoltaic (PV) fed pumping applications as a compromise alternative to multi-level inverters. Solar irradiance conditions further exacerbate the nonlinear control problem, resulting in significant loss of power and low reliability, which affects motor operation. To overcome these issues, this paper presents an optimized integrated control technique-based PV integrated three-level dual inverter fed Open-end winding induction motors for pumping application. An integrated African vulture optimization algorithm and scalar coupled pulse width modulation (AVO-SCPWM) based control techniques are proposed to extract the maximum power from the solar PV source and control the induction motor pump. Here, the AVO-based maximum power point tracking (MPPT) technique adjusts the modulation index (ma) by insolation and temperature. The proposed technique balances the zero-sequence current, reduces THD, and reduces the switching losses over the inverter. The proposed work is evaluated in MATLAB/Simulink software and compared with the existing conventional induction motor (IM), Conventional OEWIM Drive, and scalar decoupled PWM-based IM techniques under two climatic conditions. Thus, the simulation results demonstrate that the proposed technique accomplishes better than the existing techniques.

Control Scheme Influence on the Performance of Shunt Active Power Filter based on Five-level NPC Inverter in Steady and Transient Conditions

This paper presents an investigation on the performance of shunt active power filter (Shunt APF) systems based on five-level neural point clamped (NPC) inverter in steady and transient conditions adopting a fuzzy control scheme. The shunt APF is operated as a current source connected in parallel with the non-linear loads to inject compensates current harmonics into the AC source. The multi-level inverters have gained considerable interests in last year’s. Five-level inverter is recommended in medium and high voltage applications; their advantages are low harmonic distortions, low switching losses, low electromagnetic interference, low voltage stress of power semiconductors and low acoustic noise. Secondly fuzzy logic has been widely used in various industrial applications. To benefit from these advantages a shunt active power filter based on five-level (NPC) inverter using fuzzy control scheme is presented in this work. To identify the reference currents, synchronous detection method (SMD) is adopted. Proportional integral voltage controller is used to maintain the dc voltage across capacitor constant and reduce inverter losses. The simulation is performed using MATLAB-Simulink software and SIMPOWERSYSTEM toolbox. The obtained results in steady and transient states illustrate the performances and the effectiveness of the proposed shunt APF system.

Direct maximum power injection control of grid-connected PV micro-inverter systems connected to the grid

The increasing use of fossil fuels such as gas and oil has caused many environmental problems, including air pollution, depletion of underground resources, the destructive phenomenon of global warming, destruction of the ozone layer, and many other problems for the environment. Photovoltaic systems are one of the most promising solutions to overcome these problems. Due to the low voltage of solar panels and the higher controllability of photovoltaic systems against changes in sunlight intensity during the day, DC-DC power converters are required. In this project, the aim is to design and build a DC-DC converter with the ability to provide high voltage gain at a suitable efficiency for a 1-string photovoltaic system with the ability to track the maximum power point 2. The designed converter is designed and analyzed with the ability to provide a voltage gain of 5/6 at the critical operating point, a minimum efficiency of 94%, and a power of 500 watts. This converter uses classical soft switching, so the switching losses are reduced, which in turn increases the efficiency of the converter. This converter has a lower voltage stress on the switch (4/0) than the existing techniques. On the other hand, while new converters use a large number of switches and magnetic cores in the cell to provide high gain, this converter uses the least number of switches and magnetic cores to achieve high gain. Also, the passive elements of this converter, such as inductor and capacitor, are in the order of a few microhenries and farads, and therefore the size of these components is also reduced. In addition, due to the high gain provided in lower duty cycles, the efficiency of the switch is increased, and therefore cheaper switches can be used. Also, due to the reduction in the size of passive elements, the size of the magnetic core is also reduced, which in turn optimizes the converter economically.

A Novel Asymmetric Trench SiC Metal-Oxide-Semiconductor Field-Effect Transistor with a Poly-Si/SiC Heterojunction Diode for Optimizing Reverse Conduction Performance.

In this paper, a novel asymmetric trench SiC MOSFET with a Poly-Si/SiC heterojunction diode (HJD-ATMOS) is designed to improve its reverse conduction characteristics and switching performance. This structure features an integrated heterojunction diode, which improves body diode characteristics without affecting device static characteristics. The heterojunction diode acts as a freewheeling diode during reverse conduction, reducing the cut-in voltage (Vcut-in) to a lower level than conventional asymmetric trench SiC MOSFET (C-ATMOS), while maintaining a similar breakdown voltage. Meanwhile, the split gate structure reduces gate-to-drain charge (Qgd). Through TCAD simulation, the HJD-ATMOS decreases Vcut-in by 53.04% compared to the C-ATMOS. Both Qgd and switching loss are reduced, with a decrease of 31.91% in Qgd and 40.29% in switching loss.