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The heterocharge accumulated in the oil‐paper insulation system of the converter transformer will enhance the local electric field and cause insulation deterioration. Numerical simulation is an effective method to analyze heterocharge. Currently, the numerical simulation of heterocharge is mainly based on the bipolar charge transport (BCT) model and the impurity ion transport (IIT) model. However, the effects of temperature, conductivity, and thickness of oil‐impregnated paper on charge transport have not been considered in these models. In view of this, a modified charge transport (MCT) model by introducing the Maxwell–Wagner model and heat conduction equation is proposed in this paper based on the BCT model and IIT model. Then, the influence of multi‐factors (temperature gradient, moisture content, and oil‐impregnated paper thickness) on heterocharge accumulation is investigated by using the MCT model. The simulation results obtained by the MCT model are more consistent with the experimental results than the BCT model, which proves the accuracy and superiority of the MCT model. Moreover, the increase in temperature gradient, moisture content, and oil‐impregnated paper thickness will enlarge the ion dissociation rate, conductivity, and trap density, and thus promote the generation of heterocharge. In that respect, the MCT model is expected to optimize the insulation design and provide a reference for space charge dynamic simulation. [ABSTRACT FROM AUTHOR]

For purposes of technological processes, the power supply is needed. Within thermically processes, entering features are defined, such as production speed for a specific range of products. All mentioned actions demand calculation of power needed for power supply. The type of voltage is determined. The application of alternating and direct voltage is possible. For specific power and type of power supply, a converter is designed. Welding demands alternating voltage at a particular frequency. Such power supplies are realized through transistor inverters which will work at a specific frequency. This paper analyses existing solutions. The main objective of this paper is the representation of the original calculation with more accurate values of inverter components. [ABSTRACT FROM AUTHOR]

Delivering high power quality in single‐phase distribution has witnessed more challenges especially with the increased penetration of single‐phase distributed generation (DG). This paper proposes a smart solid‐state‐based transformer, which aims to replace traditional ones, for single‐phase distribution laterals, and provide load balancing and protection to the three‐phase main feeders, that is based on connecting the single‐phase lateral to the three‐phase main feeder through a power electronics converter. This converter transfers balanced power from and to the three‐phase feeder while automatically regulating the lateral single‐phase voltage, hence, assuring high power quality without requiring any transformer on‐load tap changer. A 7‐level packed‐U‐cells (PUC) single‐phase inverter topology was used to deliver single‐phase regulated sinusoidal voltage to the AC loads, and at the same time, it is able to deliver DC power to DC loads. The simulation and hardware‐in‐the‐loop (HIL) results have shown that the proposed topology delivers high power quality for both AC and DC loads under different operating scenarios. Moreover, the converter can play the role of a solid‐state protection device coordinated with other up‐ and downstream protective devices. Finally, this system can be integrated within the smart grid allowing more flexibility for automation and efficient control of the grid. [ABSTRACT FROM AUTHOR]

The DC distribution network is a low-inertia system, which is very sensitive to load disturbance, system failure, and other factors. By adding virtual capacitance to the converter connected to the power supply, the virtual inertia of the DC power grid can be improved. Firstly, this paper proposes a strategy for adjusting virtual capacitance based on the voltage change rate to achieve adaptive control of virtual inertia, which enables the converter to quickly absorb or release energy during power fluctuations. Secondly, the adaptivity of the strategy is improved and the main control parameters in the proposed control method are qualitatively analyzed. Finally, the four-terminal photovoltaic storage DC distribution network system is constructed. Through Simulink, the adaptive virtual inertia control is incorporated on the battery side to simulate and validate the effectiveness of the strategy and the rationality of parameter analysis. The results show that this method can provide flexible and adjustable inertia support for DC grids and improve the voltage stability of DC grids. [ABSTRACT FROM AUTHOR]

Studies have been conducted on Energy storage systems (ESS) that replaced lithium-ion batteries (LIB) by the thermal runaway of the existing LIB. Using only the supercapacitor (SC) as a direct current power source in applications such as supercapacitor-based ESSs and mobile electric vehicle charging stations (MCSs) reduces the output voltage of the SC linearly. To solve this problem, this paper combines a boost converter capable of achieving regulatable constant voltage from an input of an SC bank to an output of a rectifier and an inductor/capacitor/capacitor (LCC) resonance converter. In this paper, an electrical double-layer capacitor (EDLC) known as SC was constructed as 64.8-V 400-FEDLC for experimental analysis. This EDLC is a high-capacity EDLC bank using 120 EDLCs with 30 serial connections and 4 parallel connections. In addition, resonance compensation circuits are analyzed and designed using a first-order harmonic approximation method (FHA). The analysis shows that the LCC resonance compensation converter is more suitable for EDLC standalone systems as an energy storage system, for LCC resonance converter topologies combined with EDLC discharge characteristics, constant voltage discharge is designed under an efficient discharge strategy, i.e., variable load conditions after the first constant voltage discharge. Based on LCC compensation analysis, the system has an optimum frequency, which allows the system to operate at the maximum efficiency point. By combining constant voltage power characteristics, constant voltage power becomes the same as the optimal power point, and thus high efficiency could be maintained in the constant voltage stage. Finally, the above design is verified through experiments. [ABSTRACT FROM AUTHOR]

This study thoroughly compares multiple single bidirectional and multiport converters (MPCs), highlighting the significant role of MPCs in multi-input and multi-output (MIMO) systems. MPCs offer a more efficient and cost-effective solution than multiple single converters, especially in applications involving photovoltaic (PV), electric vehicles (EVs) with storage systems, and power grids. This research emphasizes the importance of multi-input converters (MICs) in integrating diverse voltage sources. It notes the rising popularity of multi-output DC-DC converters in portable electronics, owing to their reduced component count, lower costs, and compact design. This paper emphasizes comparisons based on diverse aspects and applications, shedding light on recent developments in basic bidirectional converters. Additionally, it delves into the advancements in MPC topologies, focusing on efficiency, reliability, and modularity improvements. These advancements are crucial for harnessing cost reduction, simplicity, and compactness. Furthermore, this paper introduces an innovative multiport DC-DC converter tailored for integrating and managing renewable sources. This new converter design enhances PV system and battery storage performance by reducing power conversion steps, using fewer components, and improving voltage-boosting capabilities. Its unique bidirectional buck-boost structure allows for versatile connections between sources and loads with varying voltage and power requirements. The performance of this novel converter is evaluated through MATLAB/Simulink simulations under different scenarios. Experimental studies further validate its effectiveness, marking a significant contribution to power conversion and management in integrating renewable sources such as DC microgrids. [ABSTRACT FROM AUTHOR]

In this paper, a hybrid control method with adaptive phase-shifting modulation (PSM) and pulse-frequency modulation (PFM) is proposed to optimize the steady-state performance of an LLC resonant converter in wide voltage-gain range application. For the primary-side switches under the hybrid control method, zero-voltage switching (ZVS) performance is maintained over wide voltage-gain range and the turn-off loss is reduced; therefore, the converter reconciles wide voltage-gain range and high efficiency. Mode characteristics under different phase-shifting-angle-θ and switching-frequency-fs combinations is analyzed, and then the soft-switching characteristic is revealed. By introducing time domain analysis, the turn-on current of the primary-side switches is calculated, and thus the ZVS boundary of different θ and fs combinations is inferred. In addition, to acquire the optimum steady-state operation of the converter, the turn-off current is calculated; by making the converter work near to the minimum turn-off current operating point, the turn-off loss can be reduced greatly. With the principles of achieving ZVS performance and minimizing turn-off current, the phase-shifting angle θ of PSM is designed to be adaptive to the reference output voltage, no additional circuits are needed, and the two control degrees (θ and fs) are simplified to one (fs). The simulation and experiment are developed to verify the feasibility and effectiveness of the hybrid control method; the results show that ZVS performance is maintained at wide voltage-gain range and the turn-off current of the hybrid control method is reduced to that of the single PFM, and thus the turn-off loss is reduced. The efficiency comparison validates the fact that the hybrid control method has less power loss than single PSM and single PFM. [ABSTRACT FROM AUTHOR]

Using modularized power converters with scalable energy storage in particle accelerators can be further enhanced with controls that can be adapted to optimise different design targets, such as to minimise the front‐end stage peak current, the depth of discharge of electrolytic capacitors or the thermal cycling of semiconductors. This paper proposes a control system that is able to individually adjust the power flow of the converter modules under pre‐defined load profiles, and hence separates the use of energy storage and grid connection even under rapid cycling. The paper briefly summarises the characteristics of the modular converter and proposes four energy control strategies that have been validated by simulation as well as experimentally on a 800 kW full scale prototype. It is shown that by applying each strategy, the corresponding design objectives can be achieved, for example, optimal utilisation of the energy storage systems or minimised current stress in the semiconductors. [ABSTRACT FROM AUTHOR]

Power converters can convert the electrical energy output by power source into specific forms required by target device. They are widely used in various fields such as electrification, transportation, and power systems, and are the core components of the systems. Power converters are composed of power semiconductor devices (such as IGBTs), which are prone to failure due to abnormal conditions and aging degradation, leading to power converter faults. Therefore, over the past twenty years, extensive fault diagnosis methods for power converters have been studied and proposed. Among them, symmetry-based methods have the characteristics of rapid diagnosis speed and strong robustness, but so far there's no systemic summary of such methods. Therefore, this paper reviews the relevant research on fault diagnosis of power converters based on symmetry in recent years, analyzes the mathematical principles of these methods, and compares their diagnostic performance. In addition, two factors that may have an influence on the symmetry are pointed out. This paper provides references and suggestions for the future development and research of power converter fault diagnosis. [ABSTRACT FROM AUTHOR]

This article presents a detailed analysis of a previously introduced boost converter based on cascaded capacitor connections. The analyzed converter maintains the same voltage gain as its conventional double-boost converter counterpart. The main advantage of the redesigned converter is that it requires smaller capacitors, rated to a lower voltage, due to the cascaded connection. This makes it suitable for various applications, including distributed generation and microgrids. This paper conducts the mathematical modeling of the converter with large signal models and the equilibrium operation in continuous conduction mode, employed to implement a control scheme. Even though the individual capacitor voltage ripple reaches high values, for voltage gains above five, the output voltage ripple is lower compared with that of other converters. The analysis also includes a comparative study with the conventional double dual boost converter. Simulations assess the proposed topology's ability to effectively minimize the switching ripple in the output voltage, even with smaller capacitors. Finally, experimental results are also provided to confirm the functionality of the proposed converters under various operational conditions, which confirm its suitability for low-voltage generator applications. [ABSTRACT FROM AUTHOR]

Voltage source converters (VSCs) have emerged as the key components in modern power systems, facilitating efficient energy conversion and flexible power flow control. Understanding the fundamental circuit model of VSCs is essential for their accurate modeling and analysis in power system studies. A basic voltage source converter circuit model connected to an LC filter is essential because it lowers the harmonic distortions and enhances the overall power quality of the micro-grid. This guarantees a clean and steady power supply, which is necessary for the integration of multiple renewable energy sources and sensitive loads. A comprehensive methodology for developing a basic circuit model of VSCs, focusing on the key components and principals involved, is presented in this paper. The methodology includes the modeling of space vector pulse-width modulation (SVPWM) as well as the direct quadrature zero synchronous reference frame. Different design controls, including the design of current control loop in the S-domain, the design of the direct current (DC) bus voltage control loop in the S-domain, and the design of the alternating current (AC) voltage control loop in the S-domain, are explored to capture the dynamic behavior and control strategies of VSCs accurately. The proposed methodology provides a systematic framework for modeling VSCs, enabling engineers and researchers to analyze their performance and assess their impact on power system stability and operation. Future studies can be conducted by using case studies and simulation scenarios to show the efficiency and applicability of the developed models in analyzing VSC-based power electronics applications, including high-voltage direct current (HVDC) transmission systems and flexible alternating current transmission systems (FACTS). The significance of this work lies in its potential to advance the understanding and application of VSCs, contributing to more resilient and efficient power systems. By providing a solid foundation for future research and development, this study supports the ongoing integration of renewable energy sources and the advancement of modern electrical infrastructure. [ABSTRACT FROM AUTHOR]

The present paper provides a comparison of different optimization techniques applied to the model-based design of a Buck Zero Voltage Switching (ZVS) Quasi-Resonant DC-DC Converter. The comparison was made both on the basis of the duration of the optimization procedures and in terms of guaranteeing the performance of the power electronic device. The main task of the paper is to present various techniques based on the use of mathematical software for the optimal design of Quasi-Resonant DC-DC converters. These topologies were chosen because in them, the design is carried out according to computational procedures, in which several iterations are often necessary for the successful completion of the process. An optimization procedure with a target function reference curve of the output voltage was used. In this way, the optimization is performed without the need for a complete design of the device but only by using base ratios, design constraints, and past experience to determine initial values and intervals of change in circuit parameters. This is also the main advantage of the used optimization of the reference curve type of the output, compared to applying other objective functions, such as achieving minimum losses or maximum efficiency of the device. [ABSTRACT FROM AUTHOR]

This paper presents a low-ripple and high-efficiency buck–boost DC–DC converter with delta-sigma modulator controller that converts 1.8 V to 1.2 V and 3.3 V. A current and voltage closed-loop controller has been designed to achieve better performance simultaneously such as lower settling-time, steady-state error and over shoot and under shoot. The converter is started in the current controller mode initially, when the output voltage approaches the desired value, the power stage is controlled with the voltage controller mode. PI compensator and a third-order delta-sigma modulator are utilized in the voltage mode. Also, the closed-loop stability of the designed converter has been analyzed with Lyapunov method using converter nonlinear model. This work has been simulated in MATLAB-SIMULINK environment. The performance results show that the maximum efficiency of the closed-loop DC–DC converter is 90% at 5 MHz switching frequency, and the output voltage ripple is 0.5% and 0.6% for the buck and boost modes, respectively. Also, the simulation results demonstrate the closed-loop stability of the converter in the presence of 10% load variation. [ABSTRACT FROM AUTHOR]

Most coupled inductor‐based step‐up DC–DC converters encounter a significant voltage overshoot on their power switch due to the leakage inductance of the coupled inductor. So, they need additional bulky snubber circuits or a sophisticated procedure for coupled inductor design to reduce that effect. This paper proposes an improved coupled inductor‐based DC–DC converter, which provides a high quadratic voltage conversion ratio without excessive voltage stresses on the power switch. An active clamp circuit that operates with the zero‐voltage switching (ZVS) feature has been utilized for this aim. This feature allows the main power switch to be selected from low voltage ratings and low on‐resistance MOSFETs, which reduces conduction loss. The topology also benefits from continuous input current, high gain, high efficiency, and an appropriate number of components compared with the produced gain. In this article, the theory and operation of this converter are described by proposing the dc and small‐signal models, loss model, and continuous and discontinuous current modes (CCM and DCM) relations. Experimental results are represented to evaluate the performance of the proposed topology. For this purpose, a 240 V/240 W prototype has been designed and fabricated. Results confirm the above claims. [ABSTRACT FROM AUTHOR]

Power grids are progressing, and the possibility of incorporating DC grids toward hybrid AC/DC grids is gaining increasing relevance, as several technologies available nowadays are operating natively in DC. This paper proposes a topology of a full-controlled bidirectional dual-stage interleaved converter for interfacing hybrid AC/DC grids. The topology is based on a dual-stage architecture, constituted by an AC/DC converter and by a DC/DC converter, both based on interleaved power converters. On the AC side, which is connected to the main AC power grid, the proposed dual-stage architecture operates with sinusoidal current in phase or phase opposition with the voltage, meaning a bidirectional operation. In addition, it has the possibility of interfacing with other AC loads, such as domestic electrical appliances, or with an AC microgrid. The DC link, formed by the AC/DC power stage, is interfaced with a DC power grid, which provides numerous advantages, e.g., for interfacing battery electric vehicles directly charged in DC, as well as other DC loads, such as renewable energy sources. The DC/DC power stage is considered for interfacing with an energy storage system, which is capable of bidirectional power exchange with the DC grid or with the AC grid through the AC/DC power stage. A complete laboratory prototype was designed and developed, with the unified control algorithms implemented on a digital signal processor. The experimental results validated the operation of the full-controlled bidirectional dual-stage interleaved converter based on the specifications for the hybrid AC/DC grid, such as bidirectional operation, synchronization with the AC power grid, predictive current control, interleaved operation on both AC/DC and DC/DC power stages, DC-link voltage control for the DC grid, as well as the operation with different power levels. [ABSTRACT FROM AUTHOR]

In this paper, an interleaved DC–DC step-up converter with improved characteristics based on a voltage multiplier rectifier is presented. The proposed converter is presented and analyzed for two different operating duty regions including operating region 1 (0 < D ≤ 0.5), and operating region 2 (0.5 ≤ D < 1). This converter can be used in various applications such as energy storage, electric vehicles, and renewable energy systems. This converter is composed of two stages: an interleaved boost stage and a voltage multiplier rectifier stage, which collectively forms its general structure. The interleaved boost stage is a type of two-phase boost converter that transforms the input DC voltage into a high-frequency AC square waveform. This waveform can be readily filtered using smaller capacitors. The square-shaped voltage waveform from the interleaved boost stage is rectified and converted to a high DC voltage by the Voltage Multiplier Rectifier (VMR) stage. The operating regions, the evaluation of the steady-state condition, the voltage gain of the proposed converter's parasitic and ideal models as well as its losses and efficiency analysis have been evaluated. The proposed converter has an efficiency of 97% at the output power of 150 W. The proposed converter is simulated to convert a voltage of 25–159.5 V and to validate the mathematical relationships and simulation results, a laboratory prototype has been developed. The simulation and experimental results show the precision of the performance of the proposed interleaved boost converter. [ABSTRACT FROM AUTHOR]

This paper recommends new design for non-isolated semi-quadratic buck/boost converter with two similar structure that includes the following features: (a) the continuous input current has made it reasonable for PV solar applications and reduced the value of the capacitors in the input filter reducing the input ripple as well as EMI problems; (b) the topology is simple, and consists of a few numbers of components; (c) the semiconductor-based components have lower current/voltage stresses in comparison with the recently recommended designs; (d) semi-quadratic voltage gain is D (2 − D) / (1 − D)2; (e) 94.6 percent from the theoretical relations and 91.8 percent from the experimental for the output power of 72W, the duty of 54.2 percent, and output voltage of 72 V are the efficiency values in boost mode; (f) 89.3 percent from the theoretical relations and 87.2 percent from the experimental for the output power of 15W, the duty of 25.8 percent, and output voltage of 15 V are the efficiency values in buck mode. One structure is the continuous output current and negative output polarity, and other structure is positive output polarity. The recommended topologies have been studied in both ideal and non-ideal modes. The continuous current mode (CCM) is the suggested mode for the proposed converters. Moreover, the requirements of CCM have been discussed. The various kinds of comparisons have been held for voltage gain, efficiency, and structural details, and the advantages of the suggested design have been presented. A small-signal analysis has been completed, and the suitable compensator has been planned. Finally, PLECS simulation results have been associated with the design considerations. [ABSTRACT FROM AUTHOR]

As research into data centers progresses, the importance of resonant switched-capacitor converters in power supply design becomes more evident. Practical applications reveal that the values of resonant capacitors and inductors may deviate from their nominal values due to various factors, leading to resonant frequency instability. This instability poses a challenge to power electronics technology, affecting system reliability and performance. This paper analyzes the effect of frequency deviation on system functionality, identifies the relationship between output voltage and switching frequency, and proposes a self-tracking frequency strategy to address this issue. Through experimental validation, this approach shows that it maintains synchronization between switching and resonant frequencies, reducing losses associated with frequency misalignment. Simulation and experimental results validate the converter's stable operation and its ability to achieve zero-voltage and zero-current switching. [ABSTRACT FROM AUTHOR]

An introduction is presented in which the editor discusses various reports within the issue on topics including non inverting buck boost converter, design of power for power amplifiers and design of power amplifiers for wireless communication system.

The operational stability of grid‐connected converters is affected by unbalanced grid voltage, which often leads to overcurrent. The traditional control method maintains the grid‐into current within the rated limit by adjusting the current reference value. However, this method limits the output active power of the converters and affects their reliability, which can cause active power shortage or even disconnection of the power grid. To deal with this issue, this paper proposes an effective control strategy. First, the interaction between AC and DC sides of the converters under unbalanced voltage conditions is analysed. Second, the resilience is defined and elaborated. Third, considering various constraints such as the grid‐into current harmonics, power fluctuations and DC side voltage fluctuations, the operation resilience range of the converters is calculated. Based on the resilience range, an optimal operating point is selected and an optimal strategy is developed. Compared with the traditional strategy, the proposed strategy allows improving the maximum active power output capacity and resilience of the grid‐connected converters under unbalanced grid conditions, while simultaneously limiting the power fluctuations and grid‐into current distortions within an allowable range. Last, simulation and experimental results show the effectiveness and feasibility of the proposed strategy. [ABSTRACT FROM AUTHOR]

Solid-state transformer (SST) technology is one of the developing technologies that will be widely used in the future to integrate low-voltage and high-voltage networks with control circuitries and power electronics converters, facilitating renewables integration in smart grid applications. SST technology has crucial key advantageous features, including compact size and weight, low cost, and ease of connection in offshore applications. However, SST technology exhibits a few concerns, such as implementation, protection, economic, and communication compatibility, that need to be addressed. This paper aims to review SST technology with its advanced control schemes and provide future directions for research and development, applications, and prospects. In line with this, highly cited SST technology papers are examined to derive and summarize concerning issues related to its operation and control with further research development of power grids. Moreover, this review discusses the assessment and state-of-the-art technology of SSTs in different applications, focusing on configurations, control circuitry, and their drawbacks and benefits. Numerous issues and challenges of SST technology are explored to identify the existing knowledge gaps and potential future recommendations. All these critical analyses, information, and evaluations would benefit power engineers and researchers in developing and implementing advanced intelligent SST technologies for sustainable energy management in future power systems. [ABSTRACT FROM AUTHOR]

The LLC resonant converter, which is extensively utilized across various industrial fields, significantly depends on its parameters for performance optimization. This paper establishes a time-domain analytical model for the LLC resonant converter under Pulse Frequency Modulation (PFM) and proposes a multi-objective parameter optimization design method with stepwise constraints. The proposed method limits the resonant capacitor voltage while ensuring that the converter meets the voltage gain requirement and realizes Zero-Voltage Switching (ZVS). The converter's performance is then optimized with the objective of minimizing the switching frequency range, the resonant inductor current, and the RMS value of the switching current on the secondary side. Compared with the existing methods, the proposed method has the advantages of comprehensive consideration and wide application scenarios. Finally, a 1200 W experimental prototype was fabricated, with experimental results verifying the feasibility of the proposed optimization design method and demonstrating that the prototype's maximum efficiency reaches 96.54%. [ABSTRACT FROM AUTHOR]

The utilization of switched inductors, involving parallel charging and series discharging of inductors, is extensively embraced in diverse DC–DC converters for attaining high voltage gain; nevertheless, the stress on switch voltage and diode current escalates considerably with an increased count of inductors integrated into the switched inductors network. In the classical multistage switched inductor converter, the switch voltage aligns with the output voltage, and the diode experiences a high current as the number of stages increases. This research recommends a DC–DC multistage converter for energy conversion and high voltage gain with low stress. In this paper, a novel multistage switched inductor converter is introduced and designed to attain higher voltage gain while mitigating the stresses on switch voltage and diode current. The proposed circuit is created by replacing the standard multistage switched inductor converter's possible diodes with power switches. All of the switching devices are connected in such a way that the output voltage and input current are shared by all of the switches and diodes, respectively. As a consequence, the voltage stress on switches and the current stress on diodes are comparatively low, resulting in a high efficiency compared to a typical multistage switched inductor converter. It's interesting to note that the proposed converter and a typical multistage switched inductor converter both require the same amount of components. Different operation modes, analysis, a non‐ideal model, and a comparison of the suggested and recently constructed converters are discussed. The effectiveness and performance of the circuit are validated experimentally. [ABSTRACT FROM AUTHOR]

This paper deals with the control and performance improvement of parallel-operated voltage-source inverters (VSIs) controlled as virtual synchronous generators (VSGs). In publications regarding the parallel-operated VSGs, transmission lines are considered to be mainly inductive. However, less analytical works have been done regarding the control of paralleled VSGs in low-voltage grids with dominant resistive impedances. Once VSIs are controlled as VSGs in a microgrid with more resistive transmission lines, swing equation and system representation for the power-angle synchronization will change leading to a new control structure. Therefore, this paper deals with the control of parallel-operated converter-based VSGs in low-voltage grids with dominant resistive line impedances. In this way, the VSG representation, comprising the swing equation and V-P droop characteristic, for applications in highly resistive microgrids is presented, in which the swing equation and VSG frequency are related to reactive power. Then, the V-P droop characteristic is modified and an enhanced P-V droop characteristic for proper sharing of active power between the VSGs in highly resistive microgrids is proposed. Next, the VSG control is modified so that the R/X ratio at the VSG output increases and thus the decoupled control of active/reactive powers in relatively inductive cases is realized as well. [ABSTRACT FROM AUTHOR]

The voltage source converter-based multi-terminal DC transmission (VSC-MTDC) system can use additional frequency control to respond to the frequency change of faulty AC system. However, the control coefficient of traditional additional frequency control is mostly fixed, and the control flexibility is insufficient, so it cannot be adjusted adaptively according to the frequency change of the system. Therefore, a frequency control strategy of the VSC-MTDC system based on fuzzy logic control is proposed. Based on the DC voltage slope controller, this strategy introduces an additional frequency controller based on fuzzy logic control, takes the frequency deviation and frequency change rate as the additional controller input, and dynamically adjusts the control quantity through the fuzzy logic control link to realize the adaptive adjustment of the VSC-MTDC system to the AC system's frequency. Finally, a three-terminal flexible HVDC system is built on the PSCAD/EMTDC simulation platform for simulation verification. The results show that the proposed control strategy can effectively use the flexible DC system to support the frequency of the AC system and significantly improve the frequency stability of the faulty AC system. [ABSTRACT FROM AUTHOR]

This paper proposes an interleaved coupled‐inductor high step‐up direct current (DC)–DC converter. This converter uses a coupled inductor (CI), a voltage multiplier (VM) integrated with a regenerative passive lossless clamp circuit to enhance the voltage conversion ratio. The interleaved structure is used as the front stage of the proposed converter to reduce the input current ripple. The proposed converter has benefits such as low voltage stress across semiconductor elements, high voltage gains, and continuous input current, which makes it suitable for applications such as renewable energy sources. In addition, to reduce the negative effects of leakage inductance and recover the energy stored in it, a diode‐capacitor clamp circuit is used. Moreover, a comprehensive analysis has been done on the details of the performance of the proposed converter in different operation modes. Also, its design, the voltage and current equations of all the elements, and efficiency analysis are obtained. In addition, a comprehensive comparison has been made with some similar converters. The experimental results of a prototype with 260 W 96.9% is presented to validate the performance of the proposed converter. [ABSTRACT FROM AUTHOR]

In some applications of microgrids and distributed generation, it is necessary to feed islanded or stand-alone loads with high-quality voltage to provide low total harmonic distortion (THD). To fulfil these demands, an L C filter is usuallyconnected to the output terminals of power electronics converters. A cascaded voltage and current control loop with pulse-width modulation schemes are used to regulate the voltages and currents in these systems. However, these strategies have some drawbacks, particularly when multiple-input–multiple-output plants (MIMO) are controlled using single-input–single-output (SISO) design methods. This methodology usually produces a sluggish transient response and cross–coupling between different control loops and state variables. In this paper, a model predictive control (MPC) strategy based on the concept of optimal switching sequences (OSS) is designed to control voltage and current in an L C filter connected to a three-level neutral-point clamped converter. The strategy solves an optimisation problem to achieve control of the L C filter variables, i.e., currents and output voltages. Hardware-in-the-loop (HIL) results are obtained to validate the feasibility of the proposed strategy, using a PLECS–RT HIL platform and a dSPACE Microlab Box controller. In addition to the good dynamic performance of the proposed OSS–MPC, it is demonstrated using HIL results that the control algorithm is capable of obtaining low total harmonic distortion (THD) in the output voltage for different operating conditions. [ABSTRACT FROM AUTHOR]

The high potentiality of integrating renewable energies, such as photovoltaic, into a modern electrical microgrid system, using DC-to-DC converters, raises some issues associated with controller loop design and system stability. The generalized state space average model (GSSAM) concept was consequently introduced to design a DC-to-DC converter controller in order to evaluate DC-to-DC converter performance and to conduct stability studies. This paper presents a GSSAM for parallel DC-to-DC converters, namely: buck, boost, and buck-boost converters. The rationale of this study is that modern electrical systems, such as DC networks, hybrid microgrids, and electric ships, are formed by parallel DC-to-DC converters with separate DC input sources. Therefore, this paper proposes a GSSAM for any number of parallel DC-to-DC converters. The proposed GSSAM is validated and investigated in a time-domain simulation environment, namely a MATLAB/SIMULINK. The study compares the steady-state, transient, and oscillatory performance of the state-space average model with a fully detailed switching model. [ABSTRACT FROM AUTHOR]

The main contribution of this paper is the assets of the current and voltage ripples in a buck converter with an LED load. The results indicate that the ripples are different and that it is possible to reduce the passive filter concerning the model of the LED as a simple resistance. The paper presents the design and simulation of a buck converter as a power supply for an LED lamp. Modeling the LED as a resistor and a voltage source (SVRM), the equations to calculate the components of the circuit using the SVRM model are presented, where the Fourier series and phasors are used to calculate the output filter. The equations are validated with SPICE simulations. The results indicate that the SVRM model for the LED load affects the calculation of the output filter of the buck converter as well as the voltage and current ripples, making it a more precise design alternative to the proposed development. [ABSTRACT FROM AUTHOR]

An introduction is presented in which the editor discusses various reports within the issue on industrial electronics topics including induction machines, synchronous machines, and power components and power converters.

This paper reviews the state of the art on bandpass Σ Δ modulators (BP- Σ Δ Ms) intended to digitize radio frequency (RF) signals. A priori, this is the most direct way to implement software-defined radio (SDR) systems since the analog/digital interface is placed closer to the antenna, thus reducing the analog circuitry and doing most of the signal processing in the digital domain. In spite of their higher programmability and scalability, RF BP- Σ Δ M analog-to-digital converters (ADCs) require more energy to operate in the GHz range as compared with their low-pass (LP) counterparts. This makes conventional direct conversion receivers (DCRs) the commonplace approach due to their overall smaller energy consumption. This paper surveys some circuits and systems techniques which can make RF ADCs and SDR-based transceivers more efficient and feasible to be embedded in mobile terminals. [ABSTRACT FROM AUTHOR]

Emerging electric vehicle (EV) technology requires high-voltage energy storage systems, efficient electric motors, electrified power trains, and power converters. If we consider forecasts for EV demand and driving applications, this article comprehensively reviewed power converter topologies, control schemes, output power, reliability, losses, switching frequency, operations, charging systems, advantages, and disadvantages. This article is intended to help engineers and researchers forecast typical recharging/discharging durations, the lifetime of energy storage with the help of control systems and machine learning, and the performance probability of using AlGaN/GaN heterojunction-based high-electron-mobility transistors (HEMTs) in EV systems. The analysis of this extensive review paper suggests that the Vienna rectifier provides significant performance among all AC–DC rectifier converters. Moreover, the multi-device interleaved DC–DC boost converter is best suited for the DC–DC conversion stage. Among DC–AC converters, the third harmonic injected seven-level inverter is found to be one of the best in EV driving. Furthermore, the utilization of multi-level inverters can terminate the requirement of the intermediate DC–DC converter. In addition, the current status, opportunities, challenges, and applications of wireless power transfer in hybrid and all-electric vehicles were also discussed in this paper. Moreover, the adoption of wide bandgap semiconductors was considered. Because of their higher power density, breakdown voltage, and switching frequency characteristics, a light yet efficient power converter design can be achieved for EVs. Finally, the article's intent was to provide a reference for engineers and researchers in the automobile industry for forecasting calculations. [ABSTRACT FROM AUTHOR]

The article presents abstracts on technical topics involving the magnetooptical attributes of sputtered garden ferrite film, high-efficiency downsized power conversion equipment and power supply system topology.

This paper presents a novel control strategy to significantly reduce the high-frequency transformer loss in a modular solid-state transformer (SST) based converter system. The modular SST design is based on an ac–dc power-electronic building block comprised of an H-bridge at the ac input and a bidirectional soft-switching isolated dc–dc converter with a medium-voltage insulated high-frequency transformer. The ac terminals of input H-bridges are connected in series and directly coupled to the medium-voltage ac line, while the output dc terminals are all connected in parallel at a low voltage. The key innovation described in this paper, without sacrificing the output performance, is the control scheme that reduces core and winding losses associated with the dc–dc resonant stage by turning off the selected dc–dc converters in synchronism with the line voltage. The prototype for the test described in this paper is based on a modular SST where each module is rated at 50 kVA, with a 200 kHz transformer using 1.7 kV silicon carbide discrete mosfets, but the described control concepts are more broadly applicable to similar topologies. [ABSTRACT FROM AUTHOR]

Offshore Wind Farms (WFs) with significant capacities have been installed recently all over the world. In order to transmit the WF power to the onshore grid, High Voltage Direct Current (HVDC) transmission system is appropriate technology. This paper analytically studies the impact of system parameters, controllers, and operating conditions on the dynamic behavior of HVDC transmission systems based on three-level neutral point clamped Voltage Source Converters (VSC). Also, it investigates modeling, control, and stability analysis of VSC-HVDC systems connected to the offshore wind farms. The VSCHVDC system comprises offshore and onshore converters and high-voltage dc transmission lines. The paper extracts VSC-HVDC system dynamics on the dc side and argues the interaction between onshore converter control and HVDC transmission line dynamics. Moreover, the paper presents a controller design for the dc-link voltage regulation by the onshore converter and examines the impacts of HVDC line length and dc voltage control bandwidth (BW) on the system stability through the modal analysis and time domain simulations. [ABSTRACT FROM AUTHOR]

This paper describes a groundbreaking design of a three-phase interleaved boost converter for PV systems, leveraging parallel-connected conventional boost converters to reduce input current and output voltage ripple while improving the dynamic performance. A distinctive feature of this study is the direct connection of a Li-Ion battery to the DC link, which eliminates the need for an additional charging circuit, which is a departure from conventional approaches. Furthermore, the combination of an MPPT controller and a closed-loop fuzzy controller with a current control mode ensures accurate switching signal generation for all three phases. The meticulously tuned system exhibits a remarkably low ripple content in the output voltage, surpassing calculated values, and demonstrates a superior dynamic performance. The investigation extends to a comprehensive analysis of losses, encompassing inductor copper loss and semiconductor conduction loss. In all scenarios, the converter exhibits an efficiency exceeding 93%, highlighting its robust performance as an effective solution for PV systems. [ABSTRACT FROM AUTHOR]

The DC/DC converters are commonly used in DC microgrids to achieve the desired performance of a system under different operating conditions. The dynamics of an isolated DC microgrid with solar photovoltaic panels, battery, and constant power load is a fractional nonlinear model; thus, the complex nonlinear method should be applied for controller design and stabilizing the system. In multi-input multi-output systems with non-linear elements, non-linear control methods should be used, but this paper presents a straightforward technique for designing decentralized controllers for the buck, boost, and buck-boost converters in an isolated DC microgrid to stabilize the system and implement Maximum Power Point Tracking (MPPT) control of the solar photovoltaic panels. The presented methods consider the nonlinear decentralized feedback linearizing control for the nonlinear system. Depending on the performance of the converters in the system, proper dynamic models are introduced for the converters, and decentralized controllers are determined. Various scenarios are simulated and compared to conventional methods. The results indicate that the settling time of the output variables and the overvoltage of the DC-link voltage are reduced by less than 30% compared to other techniques. [ABSTRACT FROM AUTHOR]

This paper presents the design and application of a boost converter operated in continuous conduction mode for 15 W, with a 25 kHz switching frequency using an inductor-capacitor-inductor (LCL), pi, inductor capacitor (LC) with damping, and LC electromagnetic interference filters. Also, modeling and analysis of the boost converter in terms of state space and small signal are given. Furthermore, the effect of each filter on differential mode (DM) noise and control characteristics is presented using root locus and bode diagrams, which are not detailed in the literature for the boost converter. All results obtained from applications and simulations are compared. Moreover, frequency spectrums are given to compare DM noises. As a result, from a control point of view, the LCL filter provides better results, and for reducing DM noise, the LC and pi filters are superior to others. Besides, the LCL filter reduces the inductor value by 30% compared to other filters. [ABSTRACT FROM AUTHOR]

Here, an ultra‐high gain quadratic boost DC–DC converter (UQBC) based on the conventional quadratic boost converter (CQBC) and a three‐winding coupled inductor (TWCI) has been proposed. It benefits from an extensive voltage gain range and low voltage stress on semiconductors. In addition, the converter requires a reasonable number of components. This structure is suitable for connecting renewable DC power sources like fuel cells to a DC‐bus in DC microgrids. Unlike CQBC, the produced conversion ratio has been improved to [1+n+m+d(1+n)]/(1−d)2 thanks to integrating a TWCI into CQBC. As a result, the proposed quadratic boost converter gives a better step‐up factor than previously presented quadratic boost converters (QBC). Meanwhile, the employed improvement method has not adversely affected some critical parameters like voltage stress on semiconductors or the input current ripple. This paper presents the mathematical analysis and operating principle of the proposed topology for both continuous and discontinuous current modes (CCM and DCM). Experimental results are represented to validate the converter theory and its performance. Results indicate that a high gain and efficiency have been obtained. Also, the voltage stress on the power switch is reduced by one‐fourth by choosing a proper duty cycle and winding coefficient. [ABSTRACT FROM AUTHOR]

The utilization of fuel cells (FC) in automotive technology has experienced significant growth in recent years. Fuel cell hybrid electric vehicles (FCHEVs) are powered by a combination of fuel cells, batteries, and/or ultracapacitors (UCs). By integrating power converters with these power sources, the FCHEV system can overcome the limitations of using them separately. The performance of an FCHEV is influenced by the efficiency of the power electronics converter controller, as well as the technical efficiency of the power sources. FCHEVs need intricate energy management systems (EMSs) to function effectively. Poor EMS can lead to low efficiency and accelerated fuel cell and battery degradation. The literature discusses various types of EMSs such as equivalent consumption minimization strategy, classical PI controller, fuzzy logic controller, and mutative fuzzy logic controller (MFLC). It also discusses a systematic categorization of FCHEV topologies and delves into the unique characteristics of these topologies. Furthermore, it provides an in-depth comparative study of EMSs applied in FCHEVs, encompassing rule-based, optimization-based, and advanced learning-based approaches. However, comparing different EMSs can be challenging due to the varying vehicle and system parameters, which might lead to false claims being made regarding system performance. This review aims to categorize and discuss the various topologies of FCHEVs, highlighting their pros and cons, and comparing several EMSs based on performance metrics such as state of charge (SOC) and FC deterioration. This paper seeks a deeper comprehension of the recent advancements in EMSs for FCHEVs. It offers insights that can facilitate a more comprehensive grasp of the current state of research in this field, aiding researchers in staying up to date with the latest developments. [ABSTRACT FROM AUTHOR]

This paper investigates the starting current of an AC/DC/DC converter, consisting of a threephase diode bridge rectifier and a synchronous buck converter. The use of microprocessors in such converters increases the total cost and also reduces reliability due to EMI phenomena. For this reason, by removing the microprocessor, a start-up plan including a limiting starting resistor and then soft starting the switching module is proposed in this paper. By modeling the system under different operating modes, a solution is presented to minimize the circuit startup period, which includes minimizing the bypass time of the startup resistor and reducing the switching soft startup period as possible. The proposed method has been implemented on a 15-kW converter feeding from a three-phase 380 V power grid and provides up to 300 Vdc/50 Adc to supply an electroplating pool. The results show that the sequential startup procedure, including using a 50 ohm/1500 w resistor for 3 seconds, and then bypassing it, then soft start switching after half a second and during 1.5 s, can move this circuit to a steady state in 5 seconds, keeping current in all parts below half rated current. [ABSTRACT FROM AUTHOR]

The primary objective of this paper is to address the adverse effects of active power fluctuations on grid-connected converters. One of the challenges in integrating high levels of solar photovoltaic power into the utility grid is the lack of inertia from converter-based resources. This paper proposes a solution to this challenge by synthesizing additional inertia and damping properties using power electronics converters. They emulate the inertia and damping properties of synchronous generators. The paper discusses different approaches to achieving effective damping control in grid-connected converters. It proposes a genetic algorithm optimization tool to optimize virtual damping and inertia parameters. The goal is to suppress oscillations and ensure stable grid operation. The proposed method is evaluated in both time-domain and frequency-domain analyses. The simulation results demonstrate the validity of the optimization technique and implementation procedure. Using virtual inertia and damping properties ensures stable grid operation and improves the integration of solar photovoltaic power into the utility grid. The paper provides a detailed discussion of the approach, optimization tool, and simulation results, highlighting the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

Electromagnetic compatibility issues must be considered from the early steps in the design of electronic devices. A specific topic is the near-field emission generated by the device due to the traces on a printed circuit board and the specific routing. The analysis of near-field emission is essential to detect potential electromagnetic interference with nearby devices. This problem is crucial in high power density applications. Therefore, especially in these applications, it is necessary to optimize the circuit and the layout to minimize the generated noise. The design and construction of systems able to scan volumes to determine the spatial distribution of electrical E and/or magnetic B fields in the near-field region of a device under test is a very complex process. The realization of equipment that explores a given surface at a given distance from the device is easier. The main purpose of this paper is to show how it is possible to build a cheap two-dimensional scanner, starting from simple hardware not explicitly designed for near-field scan operations. The presented firmware and software solution can map, with good accuracy, the spatial distribution of fields B and E on a fixed plan close to the board. Finally, the developed system has been used in a GaN-based bi-directional DC/DC Converter. [ABSTRACT FROM AUTHOR]

This paper proposes a novel emulation system for emulating the power system in the fuel cell electric vehicle. The major purpose of the proposed emulation system is to test the dc–dc converter between the fuel cell and high-voltage powertrain. The bidirectional buck–boost type dc–dc converter is applied in the emulation system as the basic elements. A modularized approach is presented for easily scaling up and down the power level of the emulation system. Meanwhile, an energy loop structure is implemented in the proposed emulation system for power capability boosting purpose. Because of the proposed energy loop configuration, the emulation system offers long-term running capability with high power rating without the grid connection. A neutral current control mechanism is applied in this paper to further enhance the long-term testing capability as well as extending the lifespan for the battery packages. The simulation studies are proposed in this paper to validate the control mechanisms of the emulation system. A 10 kW hardware prototype has been built and the experimental tests are presented for validating the functionalities of the emulation system. [ABSTRACT FROM AUTHOR]

IEEE Standard 1547 defines grid connection standards for distributed resources (DRs). This standard sets requirements for harmonic performance, which are particularly relevant when converter-interfaced DRs are considered. Specifically, the standard limits the allowable harmonic current injected by a DR, assuming grid voltage at the point of common coupling (PCC) is harmonic free. In this paper, it is demonstrated, both mathematically and experimentally, that the harmonic current injection of a converter-interfaced DR depends highly on the level of PCC background voltage. This paper presents a mathematical formulation that enables the impact of PCC voltage harmonics on the harmonic current injection of a converter-interfaced DR to be determined via experimental identification of the converters frequency coupling matrix. Experimental tests show that an IEEE 1547-compliant solar inverter with measured total demand distortion (TDD) of 0.66% for an undistorted PCC can produce TDD levels in excess of 20% in the presence of 3% voltage distortion. It is concluded that TDD metrics, as employed in IEEE Standard 1547, provide little insight into the field performance of converter-interfaced DRs when background voltage harmonics are present. Improved FCM-based metrics for assessing the harmonic performance of converter-interfaced DRs in the presence of voltage harmonics are provided. [ABSTRACT FROM PUBLISHER]

Recently, voltage-source converter (VSC)-based high-voltage dc (HVDC) transmission systems have gained more attention. In this paper, a control method for a modular VSC-based HVDC transmission system with high-frequency isolation referred to as high-frequency isolated modular converter is proposed. In the high-frequency isolated modular converter configuration, several floating dc capacitors in all three phases are connected in series, and voltage balancing control of these floating dc capacitors is required. In this paper, an appropriate control structure with the capacitor voltage balancing controller is proposed. The proposed control scheme consists of three layers to control terminal dc bus voltage and balance dc capacitor voltages of each building block. Detailed PSCAD simulation results are presented to evaluate the performance of high-frequency isolated modular converter. Controller hardware-in-the-loop simulation of the high-frequency isolated modular converter is also performed by real-time digital simulator (RTDS), and RTDS results are presented to verify the control structure. Finally, laboratory-scale experimental results are presented to validate the proposed control method. [ABSTRACT FROM PUBLISHER]

The modern power system is experiencing transformation from the rotational-generation-equipment-dominated system to a power-electronics-converter-dominated system, with the increasing penetration of renewable energy resources such as wind and photovoltaic. The power-electronics-based renewable generation, as well as energy storage system, can lead to the reduction of system inertia. As dc systems such as dc microgrids are attracting more attention, the low-inertia issues will challenge their stability. In this paper, a comprehensive review of inertia-enhancement methods in dc power systems is presented. The concept and significance of the inertia in dc systems is firstly introduced, and then the types of inertia-providing sources in dc systems are discussed. After that, the different virtual inertia control strategies applied in power electronics converters are classified and investigated. These virtual inertia control methods are proven to have a great ability to enhance the inertia of a dc system. The challenges and future research direction are discussed at the end of the article. In this paper, the previous research work on the inertia of dc power systems is summarized in detail, the inertia-enhancement methods of DC systems are comprehensively introduced, and the future research directions are prospected. [ABSTRACT FROM AUTHOR]

This paper describes a method to provide low-voltage four-wire three-phase power converters with the capability of unbalance estimation as an ancillary service to the main role that they play in the distribution system (distributed generator, energy storage system, drive, etc.). Typically, dedicated grid/load current sensors are needed to effectively comply with unbalance compensation tasks, increasing system cost and reducing reliability. This is due to the difficulties that arise in the extraction of the zero- and negative-voltage components from the voltages at the point of common coupling, such as the inadequate resolution of full-scaled voltage sensors and limited spectral separation. In this paper, the proposed method does not rely on additional sensors to those typically used in voltage-source converters, and in any case, those sensors are limited to the point of connection of the power converter. Impedance estimation only using converter-side current sensors is implemented by adding a high-frequency voltage excitation over the fundamental command. A new model approach is proposed for the real-time extraction of system impedance using a complex-valued compact form. Considering the voltage source at that frequency to be unique in the grid, it will be proved that the impedance and, thus, the resulting negative-sequence current, which is used for unbalance compensation, can be estimated. For the zero sequence, a special arrangement of the converter voltage sensors together with a repetitive controller is used. [ABSTRACT FROM AUTHOR]

Industrial induction heating (IH) is a key manufacturing process due to its benefits in terms of efficiency, accurate output power control, and high performance. These features have made possible the extension of this technology to a wide range of industries from automotive to aeronautic, domestic, or renewable energies. One of the main challenges still present is the design of a high-performance and cost-effective process for those induction targets with complex geometries exposed to the magnetic field, being the most representative example gears present in most mechanical systems. Usually, in order to optimize the heating process, multifrequency IH systems are used, being often expensive and/or difficult to tune and control. The aim of this paper is, consequently, to propose a family of power converters able to supply the inductor system with two simultaneous frequencies in order to improve the heating process of the induction target. The proposed converter takes advantage of a multiresonant network allowing full control of the output power delivered at each frequency and, at the same time, a compact and cost-effective implementation. The proposed converter is analyzed, designed, and implemented, and experimental verification of its operation is provided in this paper. [ABSTRACT FROM AUTHOR]

Voltage source converter (VSC)-based high-voltage direct current (HVDC) transmission systems have attractive advantages compared to classical thyristor-based HVDC transmission systems. However, VSC-based HVDC transmission systems are vulnerable to dc side fault, and expensive dc circuit breakers are required to protect them against dc fault. This paper proposes a control method of a dc fault-resilient VSC which can be protected against dc fault without using expensive dc circuit breakers. In the VSC configuration, several H-bridge modules are connected in cascade, so the voltage balancing control of several floating dc capacitors is required. In this paper, an appropriate control structure with the capacitor voltage balancing controller is proposed. The appropriate control algorithm for dc fault operation and recovery after dc fault is also proposed. PSCAD simulation results are presented to validate the proposed control structure under normal and dc fault operating conditions. Real-time-digital-simulator results are also presented to verify the control structure. [ABSTRACT FROM PUBLISHER]