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Copyright of Electric Machines & Control / Dianji Yu Kongzhi Xuebao is the property of Electric Machines & Control and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In a multi-source permanent magnet synchronous motor (PMSM) drive, three distinct winding structures can be implemented: multi-sector, multi-three-phase, and highly coupled. However, due to variations in the magnetic coupling between windings, their low-frequency DC-link current ripple components differ. This paper presents a method to identify the phenomena associated with each low-frequency harmonic content. Three analytical models are developed for the DC current ripple induced by unbalanced winding, counter-electromotive force (back-EMF) harmonics and aliasing effects, respectively, with the results validated through simulations. Experimental validation is conducted for highly coupled winding drives, demonstrating agreement with the analytical models and simulations. The maximum DC current ripple ratio found in the analytical model, the simulation and the experiments is less than 15 % , which is deemed acceptable for motor drive applications. [ABSTRACT FROM AUTHOR]

As energy demand increases, the investment cost of photovoltaic (PV) systems decreases due to mass production. That results the usage of PV panels to become widespread. Changes in environmental conditions result in a change in the power produced by PV panels. Maximum power point tracking (MPPT) is proposed to handle this problem. In addition to changing environmental conditions, the current ripple of the PV panel is another significant problem for the power produced. High current ripples affect the dynamic response of the PV panels and make it difficult to maintain the system to operate at maximum power point. Using an interleaved boost converter (IBC) and driving the converters in critical conduction mode (CRM) is a well-known solution for reducing high current ripple and switching losses in power supplies. In this study, an IBC operating in CRM with MPPT and ensuring low current ripple from the panels is proposed. To verify the theoretical approach, experimental and simulation studies were conducted. A 30 W prototype is designed and tested under various conditions. The MPPT efficiency of the prototype circuit is measured as 98.1%. It has been seen that the real-time and simulation results are in accordance with the theoretical ones. [ABSTRACT FROM AUTHOR]

Recently, multiphase drives have emerged as a notable alternative for three-phase drives in several domains, including electric marine propulsion, locomotive traction, and high-power industrial applications where fault tolerance and high reliability are required. This study uses a graphical approach to develop a new carrier-based Pulse-Width Modulation (PWM) that reduces the root-mean-square value of the output current ripple in two-level multiphase inverters with an odd number of phases. The optimization process calculates the optimal common-mode voltage for each switching period. Numerical models and experiments with five- and seven-phase inverters demonstrate the effectiveness of the developed PWM technique, which can reduce the number of commutations while obtaining the lowest output current ripple.

PV panel with front end converter for MPPT purpose is always employed for solar energy. The current that front end converter draws from PV panel are generally includes ripple regarding to operation mode of the converter and the type of converter. Such current ripple when it has higher magnitude is so harmful for the PV panel, it either shortened lifetime or results faults on PV panel. To overcome such drawbacks, input filter must be used with front end converter for PV panel connection. Although, in the literature, there are a few types of input filter, the effect of the filter and input current ripple and current noises are not compared for PV panel integration. The original contribution of the study is the analysis of input filter types for PV panel integration. As an input filter, LCL, LCL with damping, LC, C filters are used, and their effects are compared for PV panel. In addition, as a front-end converter SEPIC converter is chosen because of having lower or higher output voltage regarding to input voltage. Besides, using LCL based filters as input filters of SEPIC converter are another contribution of the paper. By means of the applications with up to 15 W SEPIC converter and simulations with DC source and PV panel, it is shown that LC filter ensures better results using DC source by applications regarding current ripple and noise level. However, C filter is better for PV panel by simulations than DC source, it is because PV panel exhibits current source character, and LC filter has lower current ripple. Also with PV source, LCL with damping filter transfers higher energy to the load than the others. Furthermore, LCL type filter reduces inductor by 35% and capacitor by 4.7 times in total. Moreover, LCL filter has higher efficiency with 88% than others in the applications and lower ripple for simulations with DC source.

To address the problems of quasi-Z-source inverters with limited boosting ability and high voltage stress, a novel class of multicell switched-inductor quasi-Z-source inverters is proposed. The new inverter is based on the quasi-Z-source inverter in which the inductors in the impedance source network are replaced by a multicell switched-inductors. In this paper, a detailed description of the topology and operating principle of the new inverter is first made. Then, a deep comparison of the proposed topology with the existing topologies is performed by selecting the appropriate number of switched-inductor units. Finally, to verify the feasibility and superiority of the proposed new topology, a great number of simulations and experiments are conducted. The results demonstrate that, compared to the original quasi-Z-source inverter and existing modified topologies, the boosting capacity of the proposed new inverter increases significantly with the number of cascaded switched-inductor units, and its voltage stress across the capacitors and current ripple through the inductors are effectively reduced. [ABSTRACT FROM AUTHOR]

This paper proposes 30° discontinuous PWM-based closed loop volts/Hz control of induction motor drive with slip regulation. The voltage source inverter is carried out with various pulse width modulation (PWM) schemes such as continuous PWM (CPWM) and discontinuous PWM (DPWM) schemes. The inverter's performance is affected by these PWM schemes. Therefore, this paper investigates the PWM schemes for the inverter. It aims to identify a best PWM scheme based on the total harmonic distortion and torque ripple analysis for constant volts/Hz induction motor drive amongst the various PWM schemes in open loop and closed loop and also proposes a 30° DPWM-based closed-loop control. The performance investigations of various PWM schemes based on inverter-fed induction motor have been evaluated analytically and using MATLAB/Simulink environment. Experimental results have been validated. The combination of 30° DPWM with PI control and slip regulation for induction motor makes the speed control system robust and ideal for low-accuracy applications. [ABSTRACT FROM AUTHOR]

Using a low pulse ratio, the electromagnetic interference and switching loss of an inverter can be effectively reduced, particularly in high-power applications. However, due to variations in grid impedance, it is a challenging task to achieve stable operation of an LCL-type grid-connected inverter (GCI) using the active damping method with low pulse ratio. Thus, a novel three-phase dual-frequency GCI is presented to ensure the symmetry of the output power and the stable operation of the system address stability issues. The proposed inverter topology in this article is composed of two inverters in parallel, which are, respectively, a power inverter unit (PIU) and an auxiliary harmonic elimination unit (AHEU). To reduce the switching loss and improve the inverter efficiency, the switching frequency of the PIU is relatively low, injecting current into the grid. Moreover, the feedforward compensation method is used in AHEU. AHEU operates at high switching frequency to generate a current component that is symmetrical with the ripple com-ponent, improving the power quality, without extracting the current harmonic as the current reference. The operating principle of feedforward compensation is explained, and a proper parameter design procedure is presented in this paper. Since L filters are used for the proposed inverter, the system can operate stably where the ratio of switching frequency to fundamental frequency is low. A 10 kW laboratory prototype was built. The experimental results showed that the grid current ripple could be effectively eliminated and the THD of the grid current was 3.01%. The proposed inverter has good stability in a weak grid, and the efficiency of the proposed inverter is 95.98% at rated current, which is 0.81% higher than the traditional GCI, effectively increasing the efficiency of the system. [ABSTRACT FROM AUTHOR]

This paper proposes a method for minimizing the inductor current ripple of a DC–DC converter in a two-stage power conversion system consisting of a grid-connected PWM converter and an interleaved multiphase three-level DC–DC converter. To reduce the output voltage ripple, the three-level DC–DC converter is configured in parallel and operated interleaved. However, a circulating current generated by the interleaved operation increases the inductor current ripple of each DC–DC converter and causes system loss and inductor saturation. In this paper, the inductor and output current ripple of the interleaved three-phase three-level DC–DC converter is mathematically analyzed and the effect of the DC–DC converter's duty ratio and output voltage on each current ripple is described. Based on this analysis, a method is proposed for controlling the optimal DC link voltage through the PWM converter, so that the DC–DC converter is controlled with the duty ratio that minimizes the inductor current ripple. The simulation and experimental results under various operating conditions are presented to verify the feasibility of the proposed control method. [ABSTRACT FROM AUTHOR]

Proton exchange membrane fuel cell (PEMFC) emulators are feasible solutions for conducting low-cost and safe developments. These types of systems have attracted the attention of global PEMFC manufacturers and research groups over the last few years. Owing to these emulators, it has been possible to develop and optimize PEMFC systems including power electronics and control without the need to use or damage a real PEMFC. However, despite the importance of PEMFC emulators in research, reported studies on this topic remain scarce. For this reason, this review describes the main characteristics and different types of PEMFC emulators (i.e., pseudo and electronic emulators), providing a basis for new emulator prototypes. Additionally, in this paper, the mathematical models that complement PEMFC emulators are presented (i.e., these models and emulators generate reliable measurements compared with real PEMFC systems). Examples of electronic circuit designs based on mathematical models (electrical and heat) are also presented to give some insight into the construction of new PEMFC emulators. Therefore, this paper proposes tools for the construction of new PEMFC emulators to boost the development of this technology. [ABSTRACT FROM AUTHOR]

Fuel cell power generation is one of the important ways of utilizing hydrogen energy, which has good prospects for development. However, fuel cell volt-ampere characteristics are nonlinear, the output voltage is low and the fluctuation range is large, and a power electronic converter matching its characteristics is required to achieve efficient and stable work. Based on the analysis of the fuel cell's characteristic mechanism, maximum power point tracking algorithm, fuel cell converter characteristics, application and converter control strategy, the paper summarizes the general principles of the topology of fuel cell converters. In addition, based on the development status of new energy, hydrogen energy is organically combined with other new energy sources, and the concept of 100% absorption system of new energy with green hydrogen as the main body is proposed to provide a reference for the development of hydrogen energy. [ABSTRACT FROM AUTHOR]

The installation of photovoltaic energy system has been increasing in recent years with the increment of the demand to the electrical power. PV system can be installed as either standalone or grid-connected. Grid-connected PV systems are more attractive because of not requiring a storage system. In this study, a three-leg interleaved boost converter for grid-connected PV system is proposed. In the proposed system, a grid-connected PV system is designed and modelled in a simulation environment. The proposed model is analysed in comparison with the conventional dc-dc boost converter topology under variations of irradiance and temperature. The comparison of two systems is performed according to input current ripple ratio and THD value of the grid current. The simulation results show that the proposed topology has lower current ripple and THD value comparing with the conventional topology. [ABSTRACT FROM AUTHOR]

The control a permanent magnet synchronous motors is the subject of this study and the torque ripple reduction in these motors is the main goal of this work. Torque and flux are controlled using a predictive model and vector control. Because it is commonly employed in regulating electric motors. Space vector control and predictive torque control are two permanent magnet synchronous motor control approaches used in this study. Predictive control was determined to be more effective in terms of response and action after a Mat lab simulation of the two approaches. Predictive torque control covers all potential switching states that decrease actual torque and flux ripples as well as total harmonic distortion. The benefits of predictive torque control include simple principles, an easy-to-use console, and the ability to implement limits quickly. However, there are some drawbacks to this technique, including the requirement for bigger accounts and faster machines. The fundamental principles of the control techniques discussed are provided. A permanent magnet synchronous motor powered by a two-level power converter is then used to simulate the control approaches. Their performance in comparison is based on the obtained results. An analytical model of the predictive torque control is presented utilizing SIMULINK to explain the operation. [ABSTRACT FROM AUTHOR]

As for the insufficient nature of the fossil fuel resources, the renewable energies as alternative fuels are imperative and highly heeded. To deliver the required electric power to the industrial and domestic consumers from DC renewable energy sources like fuel cell (FC), the power converter operates as an adjustable interface device. This paper suggests a new boost structure to provide the required voltage with wide range gain for FC power source. The proposed structure based on the boost converter and the quazi network, the so-called SBQN, can effectively enhance the FC functionality against its high operational sensitivity to experience low current ripple and also propagate voltage and current with low stress across its semiconductors. Furthermore, the switching power losses have been decreased to make this structure more durable. A full operational analysis of the proposed SBQN and its advantages over the conventional and famous structures has been compared and explained. Furthermore, a prototype of the single-phase converter has been constructed and tested in the laboratory.

Applying the recycled power battery to automatic guided vehicles can greatly reduce system cost and prolong the life cycle of the battery. However, the consistency of recycled power batteries is poor, and the imbalance of battery voltage will occur during the charging or discharging process. Therefore, a double-switch single-transformer integrated equalizer is proposed to balance automatic guided vehicles in both charging and discharging operations. The equalizer's multiwinding transformer shares the dc–dc converter's inductor, and the secondary side generates current by utilizing the current ripple on the primary windings. The battery string is balanced by the multiwinding transformer, without extra switches, when the circuit works in charging and discharging mode. A prototype for four battery cells is built to verify the proposed equalizer and its dynamic balance conditions, and a comparison with existing equalizers is presented. The results show that the system in both modes can realize the automatic balance without affecting the function of the dc–dc converter. The proposed circuit requires fewer components than the existing bidirectional integrated equalizer. [ABSTRACT FROM AUTHOR]

This manuscript proposes a novel approach for determining phase and neutral-current-ripple RMS in grid-connected four-leg inverters with the neutral inductor. The harmonic pollution is determined for any arbitrary pulse width modulation (PWM) technique and a generic value of the neutral inductor. Thanks to the proposed approach, it is possible to describe the neutral inductor in a parametric way with respect to phase inductors and obtain a wide range of results, ranging from a direct neutral connection (no neutral inductor) to a conventional three-phase inverter (no fourth wire) for any value of modulation index and common mode injection. The results permit one to compare different design choices in multiple scenarios effectively. The findings were validated by numerical simulations and experimental tests employing the most popular PWM techniques, such as space vector PWM (SVPWM) and discontinuous PWM (DPWM). [ABSTRACT FROM AUTHOR]

The control of (PMSM) is the subject of this study and the torque ripple reduction in (PMSM) is the main goal of this work. Torque and flux are controlled using a predictive model and Vector Control. Because it is commonly employed in regulating electric motors. Space vector control and predictive control are two (PMSM) control approaches used in this study. Predictive control was determined to be more effective in terms of response and action after a Matlab simulation of the two approaches. MPC covers all potential switching states that decrease actual torque and flux ripples as well as Total Harmonic Distortion. The benefits of MPC include simple principles, an easy-to-use console, and the ability to implement limits quickly. However, there are some drawbacks to this technique, including the requirement for bigger accounts and faster machines. The fundamental principles of the control techniques discussed are provided A (PMSM) powered by a two-level power converter is then used to simulate the control approaches. Their performance in comparison is based on the obtained results.

Hydrogen is an important alternative as a clean fuel for industry and power-to-gas energy storage. The water electrolysis process is a promising technology in green hydrogen production where proton exchange membrane (PEM) technology has been keenly interested. Industrial large-scale PEM electrolyzers need a high current power supply. When connected to an alternating current (AC) source, high current power rectifiers are used to convert AC to DC. Currently, the most commonly used topology in large-scale PEM electrolysis systems is the thyristor-based topology due to its technology maturity and low cost. However, this topology presents several drawbacks in terms of power quality and consequently leads to higher stack-specific energy consumption (SEC) and additional losses. In the present research, we demonstrate the potential power quality improvement for a 20 MW PEM water electrolysis system by rectifier topology upgrade. Rather than traditional thyristor-based topology, a 3-phase interleaved buck rectifier topology is proposed. The new topology presents advantages on both AC and DC sides via a validated simulation model, which is built using MATLAB/Simulink and then validated with experimental data from an industrial 20 MW PEM water electrolyzer at Air Liquide's Bécancour plant. Results show a great improvement in terms of power factor, Total Harmonic Distortion (THD), and DC-current ripple reducing the total losses and the SEC of the PEM stack, especially under partial load. Towards a higher power efficiency, the proposed rectifier topology may be considered in the construction of future large-scale PEM systems. • Reported the power quality of the world's largest PEM water electrolyzer (20 MW). • Modeled the power electronics performance for the 20 MW PEM water electrolyzer. • Validated the numerical model using test data from the 20 MW PEM hydrogen plant. • Proposed power quality improvement using topology optimization. [ABSTRACT FROM AUTHOR]

Back–electromotive force estimation-based rotor position estimation methods are usually adopted for high-speed surface-mounted permanent magnet synchronous machines (SPMSM) drive to deal with the limitations of position sensors in high-speed applications. Considering inductance mismatch is the main cause of the position estimation error, this article proposes a novel pulsewidth modulation (PWM) current ripple-based online inductance identification method to improve the position estimation accuracy. The proposed method utilizes the inherent PWM current ripple of the voltage source inverter for inductance identification. In addition, the transient circuit equations on the estimated $\gamma \delta$ frame are adopted as the identification model, and the recursive least squares method is used to obtain the estimated inductance. Compared with the traditional parameter identification methods, the proposed method does not need to inject additional signals or fix parameters. During the sensorless drive of high-speed SPMSM, the proposed method can accurately identify the inductance while not affecting the normal operation of PMSM at all, which is the main contribution of this article. With the proposed method, the estimated inductance can rapidly converge to the accurate value, and then the position estimation error will be eliminated. Finally, the effectiveness of the proposed method is verified by simulations and experiments. [ABSTRACT FROM AUTHOR]

The current-fed isolated dc/dc converters are suitable solutions for applications requiring low high-frequency current ripple and convenient current control, such as fuel cells and Li-ion batteries. The existing current-fed isolated dc/dc converters are combined with a current-fed bridge-type terminal and a voltage-fed bridge-type terminal, which can only partially obtain the merits of the current-fed terminals. In this article, a dual-current-fed dual-active-bridge dc/dc converter is proposed with the inductor connection on both terminals. Hence, low high-frequency current ripple and convenient current control can be realized on both sides. Besides, it can also realize the voltage spike suppression without snubber circuits and has the inherent soft-switching operation and voltage boost function. Then, the operation principle, design process, and loss analysis of the proposed converter are presented in detail. The experimental results based on a proof-of-concept laboratory prototype are given to verify the steady-state and dynamic performance of the proposed converter. [ABSTRACT FROM AUTHOR]

In this article, a fully soft switched interleaved bidirectional buck/boost converter with high voltage conversion ratio (VCR) and no pulsating current at low voltage source is proposed. Winding cross-coupled inductors technique is employed in order to increase VCR and mitigate current ripple at low voltage side. Moreover, soft switching conditions for all semiconductor devices are provided and the leakage inductances energy of coupled inductors are absorbed in both high step-up/down operating modes. Furthermore, the reverse recovery problem of all diodes is removed due to zero current switching turn off. All the mentioned advantages are achieved for a bidirectional converter with two interleaved phases in both high step-up/down operating modes by only one clamp circuit consisting of a clamp capacitor and two active switches. Also, the body diodes of the main switches are utilized as the main diodes to reduce the element count. The converter performance is validated by theoretical analysis and an 800 W prototype circuit in both operating modes. [ABSTRACT FROM AUTHOR]

The influence of several key parameters of the electric drive system on the rotor position estimation error of the sensorless control is studied. Here a saliency based sensorless method using a zero-sequence carrier is considered. Based on the theoretical analysis, there exists a relationship between the current ripple on three phase currents and the estimation error of the rotor position. Through analysis of a simulation model with LRC load, the change of modulation ratio, neutral capacitance and switching frequency can seriously influence the estimation error. Afterwards, all the simulation analysis was validated on a practical electric drive system with a PM synchronous motor. Variable switching frequency PWM (VSFPWM) is also applied to further increase the accuracy of the rotor position estimation. It is proved that the current ripple surely affects the estimation significantly. This study also paves the way of a further theoretical research of the relationship between the current ripple and estimation error, and thus lays the foundation of an optimized parameter selection for the EDSs using the position sensorless control strategy.

• Fixed band hysteresis current control has no zero-vector strategy. • Space vector modulation-based hysteresis control limits control to three vectors. • Space vector hysteresis current control (SVHCC) has optimal zero vector placement. • SVHCC minimizes ripple in d and q axes current errors for steady-state operation. • SVHCC ensures coordinated, optimal switching and better use of zero vectors. For any grid connected system such as D-STATCOM, the conventional hysteresis current controller (HCC) for a two-level voltage source inverter (VSI) is a popular choice. It uses fixed bands in each of the three phases to contain the current errors. Although HCC is simple to implement, it has few drawbacks i.e, poor-employment of zero vectors and random switching among the available switching vectors, which may lock into limit cycles and increased switching losses of the inverter. Out of many other hysteresis techniques, a space vector modulation based technique named as SVM-HCC effectively selects a reduced set of vectors for hysteresis current control in every sector of space vector plane but its switching sequence is not optimal. Alternatively, following a different approach, the space vector hysteresis current controller (SVHCC) manifests systematic pattern in the vector switching where the sequence of inverter voltage vectors is similar to that of a voltage controlled space vector pulse width modulation (VC-SVPWM) scheme. This better way of switching in SVHCC tends to reduce the distortion of the VSI output current, which also appears as reduced ripples in the current. A comparative study on quantifying these differences among HCC, SVM-HCC and SVHCC is first time executed in this work and they are further validated using the results of simulation studies and hardware experimental investigations. [ABSTRACT FROM AUTHOR]

Using a low pulse ratio, the electromagnetic interference and switching loss of an inverter can be effectively reduced, particularly in high-power applications. However, due to variations in grid impedance, it is a challenging task to achieve stable operation of an LCL-type grid-connected inverter (GCI) using the active damping method with low pulse ratio. Thus, a novel three-phase dual-frequency GCI is presented to ensure the symmetry of the output power and the stable operation of the system address stability issues. The proposed inverter topology in this article is composed of two inverters in parallel, which are, respectively, a power inverter unit (PIU) and an auxiliary harmonic elimination unit (AHEU). To reduce the switching loss and improve the inverter efficiency, the switching frequency of the PIU is relatively low, injecting current into the grid. Moreover, the feedforward compensation method is used in AHEU. AHEU operates at high switching frequency to generate a current component that is symmetrical with the ripple com-ponent, improving the power quality, without extracting the current harmonic as the current reference. The operating principle of feedforward compensation is explained, and a proper parameter design procedure is presented in this paper. Since L filters are used for the proposed inverter, the system can operate stably where the ratio of switching frequency to fundamental frequency is low. A 10 kW laboratory prototype was built. The experimental results showed that the grid current ripple could be effectively eliminated and the THD of the grid current was 3.01%. The proposed inverter has good stability in a weak grid, and the efficiency of the proposed inverter is 95.98% at rated current, which is 0.81% higher than the traditional GCI, effectively increasing the efficiency of the system.

Ships can avoid to be detected by magnetic mines by reducing their magnetic signature with degaussing coils. Degaussing currents are provided by switched mode power supplies which impose a current ripple on top of the degaussing current. The ripple might be visible in the magnetic signature which would increase the detectability of the ship. A way to reduce the ripple in the magnetic field is to use a switching modulation scheme in the degaussing power supplies. In this paper, a magnetic model of a ship with degaussing coils is described. It is used to find the magnitude of the ripple in the magnetic signature. Also the effect of reducing the current ripple by frequency modulation is investigated. Several modulation schemes are modelled. It is found that the ripple in the magnetic signature is often, but not always, negligible due to attenuation by the ship’s hull. For low frequency switching applications, like high temperature superconductor degaussing systems, the ripple is visible in the magnetic signature. It is found that switching frequency modulation is a very effective technique to reduce the ripple of degaussing currents. Of the tested schemes, random lead lag and random switching frequency are the most effective.

In the hybrid energy storage system (HESS), the voltages between the battery cell and the supercapacitor cell are different, increasing the circuit and control complexity of the balance system. Therefore, a bidirectional integrated equalizer based on the Sepic–Zeta converter is proposed for the HESS, which realizes both battery string and supercapacitor string balance during the energy exchange. The inductors in the Sepic–Zeta converter are used as the primary side of the balanced multiwinding transformer. The Sepic–Zeta converter generates the current ripples to drive the multiwinding transformer. The secondary side generates currents to balance the HESS, and hence, the equalizer itself is essentially switchless. Therefore, the proposed circuit can reduce the complexity of the HESS. Experimental and comparative results show that the proposed equalizer achieves the balance of the HESS. [ABSTRACT FROM AUTHOR]

In this paper, we propose a new type of smoothing reactor using different types of reactors with different magnetic flux saturation to construct a DC-DC converter with low current ripple under the light load of the bidirectional DC-DC converter. Reduction of current ripple at light load in the limited hybrid reactor can greatly reduce the inrush current ripple of DC-Grid at light load, which is a weakness of existing bidirectional DC-DC converters and is considered to contribute to DC-Grid stabilization. Experiments were conducted to prove the feasibility of the proposed system and hybrid reactor. [ABSTRACT FROM AUTHOR]

The output current of PWM inverters may contain low-frequency harmonics due to nonidealities, such as fluctuating dc voltage and dead-time. Low-frequency harmonics are detrimental to the inverter's current controller performance as well as its operation. They increase losses, cause synchronization problems in a grid-connected inverter, and cause torque pulsations in motors. Reducing low-frequency harmonics through conventional means require a big and expensive filter. In this article, a method to reduce low-frequency current harmonics is proposed. This method uses a virtual impedance, which is a controller block that mimics the behavior of a real impedance. Because it is virtual, it does not have physical drawbacks to the system, such as volume, weight, and losses. It can be designed only to affect the disturbance signals and to assume characteristics unlike a real impedance. It can also be added as a plug-in block to an already existing controller, saving a significant amount of design effort. Simulation and experimental results show a decrease of current THD to almost 1/3 of the original THD when no virtual impedance is used, demonstrating the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

This article investigates the total PWM-induced power losses in interior permanent magnet (IPM) machines excited by wide bandgap (WBG)-based voltage-source inverters with different pulsewidth modulation (PWM) schemes and a wide range of switching frequencies. The PWM current ripple characteristics are predicted and compared using an accurate analytical model. Three enhanced power loss estimation models are utilized to estimate the PWM-induced power losses in each of three major machine materials: the stator form-wound windings, the stator and rotor iron cores, and the permanent magnets in the rotor cavities. The variation trend of each loss component versus PWM frequency and modulation scheme is provided. Experiments have validated the model accuracy in two IPM machines designed for traction applications. Both measured and predicted results suggest that increasing the PWM frequency is beneficial for suppressing the PWM-induced power losses in IPM machines. In conjunction with the reduction in machine-related power losses, it has also been demonstrated that a higher PWM frequency in IPM drives with WBG-based inverter exhibits the appealing potential for improving the system-level efficiency in traction applications. [ABSTRACT FROM AUTHOR]

In this paper, two different strategies are combined to optimize the phase current control for switched reluctance motor (SRM). Firstly, considering the sampling and computation delay, a current prediction chopping control method is proposed to alleviate the current ripple during the entire excitation phase chopping process. Secondly, in order to cut down the large current ripple in the initial stage of phase current establishment and the excessive output current of the battery, a partitioned current control method is proposed to control the phase current with different control logic at different rotor zones. Finally, the two control strategies are combined to further optimize the phase current. In order to verify the proposed combined control strategy, a three-phase 12/8 poles SRM simulation model and experimental platform are built. The simulations and experiments are carried out to verify the effectiveness of the proposed control strategy. [ABSTRACT FROM AUTHOR]

The modified single-ended primary inductor converter (SEPIC) reported in the literature has limitations namely, low static gain and high input current ripples. This resulted in poor efficiency with high switching losses and switching stress. Hence, in order to overcome the above-said limitations, this paper proposes a high static gain SEPIC converter with reduced input current ripple. The proposed converter resembles a split-inductor design consisting of three diodes and two inductors. The static gain of the converter is significantly improved while input current ripple gets reduced by using a split-inductor. Additionally, the low value of input current ripple causes minimal switching stress and switching losses. Hence, the efficiency of the proposed converter improves significantly. The working principle and theoretical analysis of the proposed converter is studied in detail for continuous, discontinuous and boundary conduction modes. Moreover, a small signal/transient analysis is also discussed to validate the feasibility as well as the stability of the proposed system using the transfer function approach. In order to validate the effectiveness of the proposed converter, a MATLAB/Simulink model has been designed. Further, a laboratory prototype has been developed and the experimental results obtained are in agreement with the simulated results. [ABSTRACT FROM AUTHOR]

This paper presents a new fault-tolerant operation method of multiphase stacked interleaved Buck converter for green hydrogen production. An improved topology and new fault-tolerant control strategy is proposed. Multi-mode fault-tolerant operation of multiphase stacked interleaved Buck converter for different performance requirements of electrolyzer in hydrogen production system is realized. The multiphase stacked interleaved Buck converter can not only achieve elimination of output current ripple in normal operation mode, but also adopt different fault-tolerant modes according to different demands of electrolyzers in case of failure of any phase of converter. The proposed method is able to improve the availability of multiphase stacked interleaved Buck converter, reduce the times of equipment shutdown, and ensure the continuous operation of hydrogen production system from renewable energy sources. The effectiveness of the proposed method has been verified by experimental results. • An new topology and fault-tolerant control strategy is proposed for green hydrogen production. • The proposal not only achieves the current ripple elimination, but fault-tolerant operation in case of failure. • The proposed solution improves the system operation performance and reliability. • Experimental investigation of the proposed solution is provided. [ABSTRACT FROM AUTHOR]

As for the insufficient nature of the fossil fuel resources, the renewable energies as alternative fuels are imperative and highly heeded. To deliver the required electric power to the industrial and domestic consumers from DC renewable energy sources like fuel cell (FC), the power converter operates as an adjustable interface device. This paper suggests a new boost structure to provide the required voltage with wide range gain for FC power source. The proposed structure based on the boost converter and the quazi network, the so‐called SBQN, can effectively enhance the FC functionality against its high operational sensitivity to experience low current ripple and also propagate voltage and current with low stress across its semiconductors. Furthermore, the switching power losses have been decreased to make this structure more durable. A full operational analysis of the proposed SBQN and its advantages over the conventional and famous structures has been compared and explained. Furthermore, a prototype of the single‐phase converter has been constructed and tested in the laboratory. [ABSTRACT FROM AUTHOR]

Fuel cell power generation is one of the important ways of utilizing hydrogen energy, which has good prospects for development. However, fuel cell volt-ampere characteristics are nonlinear, the output voltage is low and the fluctuation range is large, and a power electronic converter matching its characteristics is required to achieve efficient and stable work. Based on the analysis of the fuel cell’s characteristic mechanism, maximum power point tracking algorithm, fuel cell converter characteristics, application and converter control strategy, the paper summarizes the general principles of the topology of fuel cell converters. In addition, based on the development status of new energy, hydrogen energy is organically combined with other new energy sources, and the concept of 100% absorption system of new energy with green hydrogen as the main body is proposed to provide a reference for the development of hydrogen energy.

An analytical approach to size a dc-link capacitor for a three-phase current-controlled voltage-source inverter used for a permanent magnet synchronous motor is presented in this article considering the dc-link ripple voltage and capacitor ripple current. The analytical method derived in this article shows the variation of the dc-link voltage ripple with the change of the power factor and the modulation index. This analysis can be applied to determine the maximum possible ripple voltage for a given capacitor or the minimum capacitance needed to keep the voltage ripple under a limit. Then, current ripple analysis is used to determine the root-mean-square capacitor ripple current taking account of the thermal duty cycles of the application. Finally, capacitor life estimation analysis is used using the operating condition, thermal duty cycle, and ripple current to determine the capacitor end life for a given application. The research presents a sequential process to select a dc-link capacitor accounting for the electrical and thermal requirement of the system. The analysis is verified by simulation and experimental results, where the effect of components’ parasitic on the voltage and current ripple is presented. [ABSTRACT FROM AUTHOR]

Hysteresis current control (HCC) is one of the most simple and rapid modulation techniques for multilevel grid-connected inverters (MGCIs). It controls the output current by limiting its ripple within fixed hysteresis limits. This results in a varying switching frequency, which is not known implicitly. The knowledge of switching frequency is essential for filter design, device selection, and loss calculations of the MGCI. The existing frequency estimations for HCC assume linear ripple current considering high-frequency operation. This assumption is invalid for the range of low frequencies. This leads to inaccurate estimation of switching frequency, which can have a considerable effect on system design. In this article, a more precise and generalized expression to estimate the switching frequency of the MGCI is obtained. The improvement in accuracy is demonstrated with an example of second-order filter design. The effect of change in hysteresis limits and input voltage on the switching frequency is analyzed to determine the operating point for accurate system design. Simulation and experimental results are found to be in good agreement with the theoretical claims. [ABSTRACT FROM AUTHOR]

At this moment, the powertrain system of Electric Vehicles (EVs) tends to use high voltages and high currents when the EVs operate at High Power (HP) mode. The Electromagnetic Interference (EMI) is caused by Electromagnetic Field (EF), high voltage, and current ripple. EMI affects EVs, whereas the Shielding Effectiveness (SE), and the proportional inverse of the transfer impedance prevent the effect of EMI. This research aims to investigate the current ripple the EMI in high voltage powertrain systems for EVs by using the developed crosslinked polyolefin insulation shielded cable, 50 mm2 single-core HP XLPO shielded cable with 0.15 mm annealed tinned-copper wire braid material. The experiment consists of three parts. The first one investigates the tendency of SE and current ripple. The second part shows the analysis of the effect of HP mode to the cable. The third part is an additional study that compares and analyzes the transfer impedance. The results indicate that the cable operates properly in the frequency above 200 Hz, transfer impedance decreasing between 11.5% to 15.25%, induces the SE and reduces the current ripple in the higher frequency range. The results obtained from this research represent a preliminary investigation guideline in decreasing the effect of EMI in EVs by using 50mm² single-core HP XLPO shielded cable with 0.15 mm annealed tinned-copper wire braid material in a high-power range. [ABSTRACT FROM AUTHOR]

Hydrogen energy shows promise as a renewable energy source for various applications like battery and electric vehicle charging stations, as well as grid connections. However, high current ripple from fuel cells (FCs) and inadequate voltages for grid use pose challenges. This study presents a novel solution using neural fuzzy network control in a high-gain DC-DC boost converter to address these issues. The suggested converter charges in parallel and discharges in series, minimizing the current ripple range in the fuel cell network. Additionally, the switch-capacitor cell efficiently increases the output voltage. In this study, a Neuro-fuzzy system with 9 rules is trained meticulously over 50 epochs using hybrid optimization and grid partition methods, achieving a low training error of 0.045 with 522,064 samples. The neural fuzzy network, employing the weighted average method for Defuzzification, produces duty cycle values from 0.02 to 0.5 in response to input signals. Additionally, an innovative Space Vector Pulse Width Modulation (SVPWM) approach within the inverter circuit enhances voltage generation precision and power quality for grid delivery, notably reducing current ripple and ensuring stable power supply. This combined with the neural fuzzy network in the converter efficiently converts hydrogen energy into AC voltage for seamless grid integration, revolutionizing boost converter efficiency and advancing hydrogen energy utilization across various energy sectors. [ABSTRACT FROM AUTHOR]

This manuscript proposes a novel approach for determining phase and neutral-current-ripple RMS in grid-connected four-leg inverters with the neutral inductor. The harmonic pollution is determined for any arbitrary pulse width modulation (PWM) technique and a generic value of the neutral inductor. Thanks to the proposed approach, it is possible to describe the neutral inductor in a parametric way with respect to phase inductors and obtain a wide range of results, ranging from a direct neutral connection (no neutral inductor) to a conventional three-phase inverter (no fourth wire) for any value of modulation index and common mode injection. The results permit one to compare different design choices in multiple scenarios effectively. The findings were validated by numerical simulations and experimental tests employing the most popular PWM techniques, such as space vector PWM (SVPWM) and discontinuous PWM (DPWM).

A three-phase isolated rectifier features bidirectional power conversion and galvanic isolation, and is attractive as a high-efficiency energy conversion system. However, when a conventional modulation is applied to this rectifier, the excessive DC-link current ripple will result in increasing switching losses or the size of DC-link inductance, which is not cost-effective. In order to effectively reduce the current ripple, this paper proposes a "six segment" PWM (Pulse Width Modulation) strategy. It can significantly reduce the current ripple compared with the existing "eight segment" PWM strategy. Meanwhile, the current quality of the grid is improved. Finally, the experimental tests were carried out. The experimental results reveal that, compared to the traditional "eight segment" PWM, the dc-side current ripple significantly reduced from 2 A to 0.8 A, the total harmonic distortion significantly reduced from 5.69% to 2.41%, and the power factor increased from 0.87 to 0.99, verifying the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

Aiming at the problems of response time and current ripple caused by the traditional decay modes of stepper motors under the microstepping control, a strategy for the smart regulation of decay mode were proposed. First, the traditional slow decay mode, fast decay mode and fix mixed decay mode were analyzed in detail. Second, a smart regulation scheme of decay mode was designed, which can automatically calculate the optimal decay mode. This scheme can dynamically adjust the fast decay percentage of the total fixed off time within a PWM (pulse width modulation) cycle to improve the performance of the microstepping control. Finally, a test platform was built to compare and analyze the current ripple of the traditional decay modes and the smart regulation in decay mode. This method was successfully applied to SADA of ALNES S7 satellite. The experimental results show that the proposed method achieves a balance between response time and current ripple, which makes the microstepping control more stable. [ABSTRACT FROM AUTHOR]