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Compared to the conventional boost power factor correction (PFC) converter, a totem-pole bridgeless PFC has high efficiency because it does not have an input diode rectifier stage, but a current spike may occur when the polarity of the grid voltage changes. This paper proposes a digital control algorithm for bridgeless totem-pole PFC with a simple control structure based on the phase angle of grid voltage. The proposed algorithm has a PI-based double-loop control structure and performs DC-link voltage and input inductor current control. Rectifying switches operate based on the proposed rectification algorithm using phase angle information calculated through a single-phase phase-locked loop (PLL) to prevent current spikes. The feed-forward duty ratio value is calculated according to the polarity of the grid voltage and added to the double-loop controller to perform appropriate power factor control. The performance and feasibility of the proposed control algorithm are verified through a 3 kW hardware prototype. [ABSTRACT FROM AUTHOR]

There has been no research conducted thus far on the semiconducting behaviour of biomaterials. In this study, we present an n-type semiconducting biomaterial composed of amorphous kenaf cellulose fibre (AKCF) paper with a voltage-controlled N-type negative resistance. The AKCF generates an alternating-current wave with a frequency of 40.6 MHz from a direct-current voltage source at its threshold voltage (electric field of 5.26 kV/m), which is accompanied by a switching effect with a four-order resistance change at 293 K. This effect is attributed to the voltage-induced occurrence of strong field domains (electric double layers) at the cathode and depletion at the anode of the AKCF device. The proposed AKCF material presents considerable potential for applications in flexible/paper electronic devices such as high frequency power sources and switching effect devices. [ABSTRACT FROM AUTHOR]

In this paper, the influence of the stiffness and damping of real elastic shafts on the behavior of a multidrive system driving a tissue paper machine is investigated. The drive system consists of four dc motors, where two of them drive the Yankee drying cylinder and the other two drive the presses section. Six-pulse thyristor bridge power converters that are connected to the same power transformer supply the motors. The inertias of the motors and the driven machines, in conjunction with the shaft stiffness, form mechanical resonators. Thus, resonance phenomena may occur, which may lead to undesirable results. This particular case results to two three-mass and one five-mass systems. This paper presents an analysis of the resonance frequencies of two sections of the machine during startup and machine production, considering the shaft stiffness (shaft diameter, length, and thickness). The elastic shafts eliminate the ripple of the motor electromagnetic torque, which is transferred to the driven machine. The behavior of elastic shafts with different stiffness in the transmission system is studied. Moreover, the steady state and dynamic behavior of the system considering the influence of the elastic shafts and vibration analysis were investigated using simulation. A model algorithm for system simulation was developed using the MATLAB/SIMULINK software. Characteristic simulation results are presented and are expressed in terms of speed and torque response. Considering the resonance frequency analysis and simulation results, mechanical design guidelines can be given for the most significant drive components in order to avoid torsional oscillation resonance phenomena and minimize torsional oscillations of the drive system. [ABSTRACT FROM AUTHOR]

This paper introduces a new hybrid DC–DC converter with enhanced voltage gain and synchronized multiple output capabilities, specifically tailored for smart grid applications. The proposed converter is based on the integration of non-isolated Zeta and Mahafzah converters, comprising a single controlled switch, two diodes, three inductors, and two coupling capacitors. The primary objective of this novel hybrid converter is to improve voltage gain as compared to conventional Zeta and Mahafzah topologies. By achieving higher voltage gain at lower duty cycles, the converter effectively reduces voltage stress on semiconductor switches and output diodes, thereby enhancing overall performance and reliability. A comprehensive examination of the hybrid converter's operating principle is presented, along with detailed calculations of duty cycle and switching losses. The paper also explores the converter's application in smart grids, specifically in the context of renewable energy systems and electric vehicles. Two distinct scenarios are analyzed to evaluate the converter's efficacy. Firstly, the converter is assessed as a DC–DC converter for renewable energy systems, highlighting its relevance in sustainable energy applications. Secondly, the converter is evaluated as an electric vehicle adapter, showcasing its potential in the transportation sector. To validate the converter's performance, extensive simulations are carried out using MATLAB/SIMULINK with parameters set at 25 kW, 200 V, and 130 A. The simulation results demonstrate the converter's ability to efficiently supply multiple loads with opposing energy flows, making it a promising technology for optimized grid management and energy distribution. Moreover, the paper investigates the total harmonic distortion (THD) of the grid current, focusing on its impact in smart grid environments. Notably, the new hybrid converter topology achieves a THD of 21.11% for the grid current, indicating its ability to effectively mitigate harmonics and improve power quality. Overall, this research introduces a cutting-edge hybrid DC–DC converter that enhances voltage gain and synchronizes multiple outputs, specifically catering to the requirements of smart grid applications. The findings underscore the converter's potential to significantly contribute to the advancement of efficient and resilient power conversion technologies for smart grids, enabling seamless integration of renewable energy systems and electric vehicles into the grid. [ABSTRACT FROM AUTHOR]

This paper proposes a Symmetric High Voltage-Gain (SHVG) boost converter control for photovoltaic system applications. The concept is based on a multilevel boost converter configuration, which presents an advantage compared to a classic boost converter such as the ability to transfer a high amount of power with less stress on the power electronics components in the high voltage-gain conditions. This advantage allows the power losses in the converter to be reduced. A mathematical-based voltage model of the PV system using variable series resistance depending on solar irradiance and the temperature is proposed. This model is connected to an SHVG boost converter to supply the load's power. A control strategy of the DC-bus voltage with maximum power point tracking (MPPT) from the PV system using PI controllers is developed. The contributions of the paper are focused on the SHVG operating analysis with the passive components' sizing, and the DC-bus voltage control with maximum power point tracking of the PV systems in dynamic operating conditions. The performances of the proposed control are evaluated through simulations, where the results are interesting for high-power photovoltaic applications. [ABSTRACT FROM AUTHOR]

This paper proposes a single-phase, transformer-less, seven-level inverter that utilizes eight switches, three capacitors, and two diodes to produce seven voltage levels with triple boosting ability. The availability of the common-ground point eliminates the leakage current in PV applications. The proposed Transformer-Less Triple-Boosting Seven-Level Inverter (TLTB7LI) has the ability to feed different types of loads from non-unity to unity power factors. The voltage balancing of capacitors takes place naturally without the need for auxiliary circuits and complicated control strategies. This paper investigates the appropriateness of the proposed TLTB7LI for grid-connected application. The Peak Current Controller (PCC) is employed to generate the switching pulses and regulate the active/reactive power transfer between the converter and the output, which guarantees the high quality of injected current to the output. Moreover, the operational principles, its control technique, as well as the design procedure of the key components of the proposed inverter have been presented. The superiority of the proposed inverter over existing counterparts has been verified through comparative analysis. The simulation and experimental analysis validated the proper operation of the proposed TLTB7LI. [ABSTRACT FROM AUTHOR]

In this paper, we propose an improved boost converter with functions of adjustable output voltages and currents. The DC sources of electronic products using batteries have become indispensable equipment. These charging sources of the diverse batteries must be provided by switching power converters. To obtain functions of adjustable output voltages and currents, a conventional boost converter is usually accepted. However, the power semiconductor devices (power switches and power diodes) of the conventional boost converter are operated at high frequency, which causes high power losses, high temperatures, and low conversion efficiency. To overcome these disadvantages, a passive lossless snubber is incorporated in the conventional boost converter to reduce power losses and increase conversion efficiency. In this paper, we propose an improved boost converter to implement functions of adjustable output voltages and currents. We compare the performance and efficiency between the conventional and improved boost converter with functions of adjustable output voltages and currents. Theoretical analysis and experimental results confirmed that the improved boost converters with functions of adjustable output voltages and currents has lower power losses, lower temperatures and higher conversion efficiency than the conventional boost converter. [ABSTRACT FROM AUTHOR]

This paper studies the stability of a real-world wind farm, Bison Wind Generation System (BWGS) in the state of North Dakota in the United States. BWGS uses an AC collector grid rated at 34.5 kV and a symmetrical bipolar high-voltage DC (HVDC) transmission grid rated at ±250 kV. The HVDC line transfers a total power of 0.5 GW, while both the HVDC rectifier and inverter substations use line-commuted converters (LCCs). The LCC-based rectifier adopts constant DC current control to regulate HVDC current, while the inverter operates in constant extinction angle control mode to maintain a fixed HVDC voltage. This paper proposes a frequency scan-based approach to obtain the d–q impedance model of (i) BWGS AC collector grids with Type 4 wind turbines that use permanent magnet synchronous generators (PMSGs) and two fully rated converters, and (ii) an LCC-HVDC system. The impedance frequency response of the BWGS is acquired by exciting the AC collector grid and LCC-HVDC with multi-sine voltage perturbations during its steady-state operation. The resulting voltage and current signals are subjected to a fast Fourier transform (FFT) to extract frequency components. By analyzing the impedance frequency response measurement of BWGS, a linear time–invariant (LTI) representation of its dynamics is obtained using the vector fitting (VF) technique. Finally, a Bode plot is applied, considering the impedance of the BWGS and grid to perform stability analyses. This study examines the influence of the short circuit ratio (SCR) of the grid and the phase lock loop (PLL) frequency bandwidth on the stability of the overall system. The findings provide valuable insights for the design and verification of an AC collector and LCC-based HVDC transmission systems. The findings suggest that the extraction of the impedance model of a real-world wind farm, achieved through frequency scanning and subsequent representation as an LTI system using VF, is regarded as a robust, suitable, and accurate methodology for investigating the dynamics, unstable operating conditions, and control interaction of the wind farm and LCC-HVDC system with the AC grid. [ABSTRACT FROM AUTHOR]

This paper proposes an improved zero-current distortion compensation (IZCDC) method for the Vienna rectifier. The conventional zero-current distortion compensation (ZCDC) method modifies the reference voltages by adding an offset voltage to compensate for the zero-current distortion (ZCD). However, the reference voltages occasionally exceed the linear modulation region by the offset voltage added at the driving start-point of the Vienna rectifier, where the modulation index of phase voltage is relatively large. This causes a hard-start of the Vienna rectifier accompanied by a serious surge and distortion in the phase current. In this paper, the IZCDC method is proposed for achieving the soft-start of the Vienna rectifier. When the overmodulation occurs, the proposed method modifies the conventional offset voltage to the IZCDC component, which is involved in the adjustment of the variance of the phase current, only for a certain phase among the three phases. As the IZCDC component regulates the variance of the phase current to zero, surge and distortion in the phase current can be mitigated. As a result, the Vienna rectifier starts its operation softly while ensuring its normal operation in the transients. The effectiveness of the proposed method is verified through simulations and experimental results. [ABSTRACT FROM AUTHOR]

The reliability of power electronic switching components is of great concern for many researchers. For their usage in many mission profiles, it is crucial for them to perform for the duration of their intended lifetime; however, they can fail because of thermal stress. Thus, it is essential to analyze their thermal performance. Non-linear switching action, bifurcation and chaotic events may occur in DC-DC power converters. Consequently, they show different behaviors when their parameters change. However, this is an opportunity to study these bifurcation phenomena and the existence of chaos, e.g., in boost converters, on their performance as the effects of load variations (mission profiles) on the system's behavior. These variations generate many non-linear phenomena such as periodic behavior, repeated period-doubling bifurcations and chaos in the MOSFET drain-source current. Thus, we propose, for the first time, an analysis of the influence of chaos on the junction temperature. First of all, this paper provides a step-by-step procedure to establish an electrothermal model of a C2M0080120D MOSFET with integrated power loss. Then, the junction temperature is estimated by computing the power losses and a thermal impedance model of the switch. Additionally, this model is used to investigate the bifurcation and chaotic behavior of the MOSFET junction temperature. The paper contributes by providing a mathematical model to calculate several coefficients based on experimental data and thermal oscillations. Estimation of the number of cycles to failure is given by the Coffin–Manson equation, while temperature cycles are counted using the rainflow counting algorithm. Further, the accumulated damage results are calculated using the Miner's model. Finally, a comparison is made between the damage accumulated during different mission profiles: significant degradation of the MOSFET's lifetime is pointed out for chaotic currents compared to periodic ones. [ABSTRACT FROM AUTHOR]

To reduce the current harmonics on the input side of a multi-pulse rectifier, this paper proposes a low harmonic current source series multi-pulse rectifier based on an auxiliary passive injection circuit at the DC side. The rectifier only needs to add an auxiliary passive injection circuit on the DC side of the series 12-pulse rectifier, which can change its AC input voltage from 12-step waves to 24-step waves. We analyzed the working mode of the rectifier, optimized the optimal turn ratio of the injection transformer from the perspective of minimizing the total harmonic distortion (THD) value of the input voltage on the AC side, and analyzed the diode open circuit fault in the auxiliary passive injection circuit. Test verification shows that, after using the passive harmonic injection circuit, the THD value of the input voltage of the AC side of the rectifier is reduced from 14.03% to 4.86%. The THD value of the input current is reduced from 5.30% to 2.16%. The input power factor has been increased from 98.86% to 99.83%, and the power quality has been improved. [ABSTRACT FROM AUTHOR]

Three-phase voltage PWM rectifier is a multivariable, strong coupling, nonlinear multi-input and multi-output system. In the design of rectifier control systems, with PI control it is difficult to achieve the ideal control effect, the dynamic performance is poor, and the parameter computation is complex. Moreover, the traditional sliding mode control voltage outer loop suffers from the problem of chattering, which is difficult to solve. Responding to the above issues, a new type of variable speed reaching law is proposed, which is applied to the voltage outer loop sliding mode control, while the feedback linearization principle is introduced to the current inner loop, and a new type of double closed-loop sliding mode control system is obtained by applying the two theories to the design of the sliding mode controller. A simulation model is established in MATLAB/Simulink to compare the PI control, the SMC control and the V-SMC control strategy proposed in this paper (voltage outer loop V-SMC current inner loop FLC-SMC control), and the simulation results show that the rectifier under the new dual-closed-loop sliding mode control strategy has the advantages of good dynamic performance, strong robustness and strong anti-interference ability. At the same time, compared with the traditional sliding mode control strategy, the vibration suppression effect under the proposed control strategy is obvious. Finally, a 10 kW rectifier control system is built on a semi-physical hardware-in-the-loop experimental platform to further verify the correctness and superiority of the proposed control strategy. [ABSTRACT FROM AUTHOR]

This paper presents a computer-simulation-based design of an in-line, coaxial-to-circular waveguide adapter for converting the coaxial transverse electromagnetic (TEM) mode to the circular waveguide TE11 mode over more than a one-octave bandwidth. The proposed adapter consists of a coaxial-to-rectangular waveguide transformer employing a stepped-ridge converter and a rectangular-to-circular waveguide transformer employing a curved transition. The proposed adapter has been optimized using a commercial simulation tool. The dimensions of the designed adapter are given so that it can be verified by anyone who is interested. The designed adapter operates from 8.00 GHz to 22.95 GHz (2.87:1 bandwidth) with a reflection coefficient of less than −20 dB and a higher-order mode level of less than −25.0 dB. [ABSTRACT FROM AUTHOR]

In hydrogen production, AC‐DC rectifiers must provide a high current and low voltage to the production load. This paper focuses on the efficient performance and elimination of the output ripple in these AC‐DC rectifiers. Unfortunately, efforts to reduce the current ripple often lead to lower efficiency, causing a contradiction. To address this issue, a low‐ripple high‐efficiency AC‐DC rectifier with an auxiliary compensator is proposed in this paper. The proposed rectifier can maximise efficiency while eliminating the current ripple, including the switching ripple and low‐frequency ripple. By incorporating a rectifier‐chopper and a buck circuit with a series‐connected capacitor, the auxiliary compensator, the solution provides an additional flow path for the current ripple at the rectifier output, successfully preventing the ripple from being output to the load. This paper offers a thorough exposition regarding the causative factors and sources of the switching and low‐frequency ripple. Furthermore, a detailed explication of the operating principle of the proposed rectifier system is provided. The losses and costs associated with auxiliary compensators are then analysed for persuasive purposes. Finally, simulation and experimental results verify the feasibility and superiority of the proposed rectifier. [ABSTRACT FROM AUTHOR]

Zero-voltage zero-current switching (ZVZCS) phase-shifted full-bridge (PSFB) converters have been widely used in high-power applications because of their high efficiency, low price, and easy control. Currently, the biggest problem with PSFB converters in operation is their high duty cycle loss. With the increase in current, duty cycle loss grows and degrades their performance. Focusing on this problem, a new ZVZCS PSFB converter is proposed in this paper. This topology adds an auxiliary circuit to minimize duty cycle loss. Moreover, the lagging-leg switches can obtain zero-current switching (ZCS) easily with the help of the circuit. The auxiliary circuit is built of four metal-oxide-semiconductor field-effect transistors (MOSFETs) and an auxiliary transformer, and extra voltage can be added to the primary coils when the direct-current (DC) voltage is small. This paper discusses its operation principles and characteristics, and an experiment of a 2 kW prototype was conducted, the results of which demonstrate the advantages of the presented circuits. [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 paper proposes a simple design scheme for a modular NPC inverter using thermal RC network analysis. The proposed design process is an efficient and straightforward approach to designing the heatsink for a 300 kW modular neutral-point-clamped inverter. The heatsink design plays a crucial role in achieving high power density of a power converter because the weight and size of the heatsink are primarily influenced by its type. The structure and dimensions of the heatsink are mainly determined based on the generated heat by losses of the power semiconductor switches. In this paper, a thermal RC network model was established using parameters from the power switch module and was applied to the simulation of the power converter. The thermal losses of the power semiconductor switches were calculated via this process, and the heatsink was designed according to the calculated thermal losses. The proposed design scheme was analyzed and compared with the thermal fluid dynamic model. To validate the feasibility of the proposed design process, The simulation results were compared with experimental results. [ABSTRACT FROM AUTHOR]

The design and optimization of power converters is a key factor in the growth and development of the power electronics field. However, the process of designing a power converter is not straightforward, and engineers often rely on experience and intuition, sometimes requiring time-consuming computer simulations. This paper presents a tool for the basic design of grid-connected AC–DC converters. The design tool takes specifications and operating conditions for two-level and three-level NPC converter topologies and derives a draft design. The tool calculates the input filter's electrical parameters, the converter's losses, the temperature rise of the power semiconductor devices, and the ripple current and voltage of the DC-link capacitor. In order to validate the proposed design tool, four AC–DC converters using SiC MOSFETs were designed. Based on the design results, simulation models and prototypes were fabricated to verify the performance and confirm that the proposed design tool can be used in the basic design process of converters. [ABSTRACT FROM AUTHOR]

Introduction: Grid-forming control has received increasing attention for being an effective solution to cope with low-inertia and weak damping systems. Owing to the basic characteristics of transient voltage regulation, inertia support and primary frequency regulation (PFR), virtual synchronous generator (VSG) is the most promising candidate of grid-forming control scheme. The damping characteristic plays a significant role in stabilizing when the system is disturbed. However, the traditional approaches for damping emulation pose a number of problems, such as the introduction of phase-locked loop (PLL) that may lead to stability issues, or the blurring of the functional distinction between damping characteristic and primary frequency regulation. Moreover, the grid strength affects the operational characteristics of the converters. Methods: Based on the background of these issues, firstly, an effective transient damping power strategy is proposed in this paper. In contrast to conventional damping approaches, the proposed scheme provides a positive damping during transient period that suppresses the fluctuation of active power, and has no impact on the steady-state frequency droop characteristic. Ulteriorly, based on small-signal models and classical control theory, an parameters adjustment strategy for both active and reactive power control is proposed to considerably enhance the adaptability of the converter to the variations in grid strength. Results and Discussion: The results obtained from PSCAD/EMTDC and hardware-in-the-loop (HIL) platform verify that proposed control strategy exhibits excellent transient damping effect, the decoupling characteristic between fixed damping coefficient and PFR coefficient, and performs well across a broad spectrum of grid strengths. [ABSTRACT FROM AUTHOR]

Time-to-digital converters (TDCs) with superior performance are in high demand in application domains like light detection and ranging (LIDAR), nuclear physics, and time interval counters. One of the interesting architectures for field-programmable gate array (FPGA)-based TDCs is the tapped delay line (TDL) approach with carry chains as delay elements. However, the resolution of TDL-TDCs is limited, and linearity is weakened by the ultra-wide bins that correspond to the FPGA's long routing wires crossing into another clock area. This paper presents wave union TDC using FPGA internal routing wires as delay elements to subdivide ultra-wide bins. The Zynq Evaluation and Development (ZED) board is used to implement and test the wave union types: A (WU-A) and B (WU-B) TDCs. According to experimental data, the WU-A TDC based on an 8 × 128 matrix of counters has a resolution of 5.7 ps, an integral nonlinearity (INL) of 1.1170 LSB (RMS), and a differential nonlinearity of 0.329 LSB (RMS). WU-A TDC improves DNL and INL by 19% and 57%, respectively, over ordinary TDC. The WU-B TDC uses an average of sixteen different time measurements, resulting in an effective resolution of up to 0.356 ps, a DNL of 0.60 LSB (RMS), and an INL of 1.04 LSB (RMS). These characteristics make the TDC suitable for time-of-flight applications such as LIDAR and for other general-purpose scientific instruments. [ABSTRACT FROM AUTHOR]

This paper presents an innovative control scheme designed to significantly enhance the power factor of AC/DC boost rectifiers by integrating an adaptive neuro-fuzzy inference system (ANFIS) with predictive current control. The innovative control strategy addresses key challenges in power quality and energy efficiency, demonstrating exceptional performance under diverse operating conditions. Through rigorous simulation, the proposed system achieves precise input current shaping, resulting in a remarkably low total harmonic distortion (THD) of 3.5%, which is well below the IEEE-519 standard threshold of 5%. Moreover, the power factor reaches an outstanding 0.990, indicating highly efficient energy utilization and near-unity power factor operation. To validate the theoretical findings, a 500 W laboratory prototype was implemented using the dSPACE ds1104 digital controller. Steady-state analysis reveals sinusoidal input currents with minimal THD and a power factor approaching unity, thereby enhancing grid stability and energy efficiency. Transient response tests further demonstrate the system's robustness against load and voltage fluctuations, maintaining output voltage stability within an 18 V overshoot and a 20 V undershoot during load changes, and achieving rapid response times as low as 0.2 s. Comparative evaluations against conventional methods underscore the superiority of the proposed control strategy in terms of both performance and implementation simplicity. By harnessing the strengths of ANFIS-based voltage regulation and predictive current control, this scheme offers a robust solution to power quality issues in AC/DC boost rectifiers, promising substantial energy savings and improved grid stability. The results affirm the potential of the proposed system to set new benchmarks in power factor correction technology. [ABSTRACT FROM AUTHOR]

The utilization of renewable sources connected to a grid to reduce traction substation installation costs and electrified trains' operation energy is a highly promising solution in the electric transportation field. This study proposes a DC traction power supply system integrated with a solar energy system using a DC-DC boost converter and an active rectifier replacing a diode located at the traction substation. The active rectifier not only recovers regenerative braking energy when electric trains operate in braking mode but also transfers solar energy from the DC bus to the grid. With the characteristics of urban railway lines utilizing high-power traction motors and high-voltage DC bus, this paper presents the structure of the Modular Multilevel DC-DC boost converter in the solar energy system employing the Maximum Power Point Tracking (MPPT) algorithm, whereas the modular multilevel active rectifier utilizes the Voltage Oriented Control (VOC) algorithm with three loop circuits: phase-lock loop, current loop, and voltage loop. Simulation results in Matlab/Simulink with parameters collected from the Nhon-Hanoi station urban railway line in Vietnam demonstrate that the PV system produces almost 37% of the energy in the accelerating phase of electric trains. [ABSTRACT FROM AUTHOR]

Rectifier plays a pivotal role in wireless power transfer systems. While numerous studies have concentrated on enhancing efficiency and bandwidth at specific high-power levels, practical scenarios often involve unpredictable power inputs. Consequently, a distinct need arises for a rectifier that demonstrates superior efficiency across a broad range of input power levels. This paper introduces a high-power RF-to-DC rectifier designed for WPT applications, featuring an ultrawide dynamic range of input power. The rectification process leverages a GaN (gallium nitride) high electron mobility transistor (HEMT) to efficiently handle high power levels up to 12.6 W. The matching circuit was designed to ensure that the rectifier will operate in class-F mode. A Schottky diode is incorporated into the design for relatively lower-power rectification. Seamless switching between the rectification modes of the two circuits is accomplished through the integration of a circulator. The proposed rectifier exhibits a 27.5 dB dynamic range, achieving an efficiency exceeding 55% at 2.4 GHz. Substantial improvement in power handling and dynamic range over traditional rectifiers is demonstrated. [ABSTRACT FROM AUTHOR]

The increasing penetration of renewable energy sources (RESs) in transmission and distribution systems presents several challenges for grid operators. In particular, the unpredictable behavior of RESs can disrupt the balance between energy production and load demand, potentially affecting the stability of the entire system. Grid-connected energy storage systems (ESSs) offer a possible solution to manage the uncertainty associated with RESs. In fact, ESSs exchange power with the grid through the adoption of suitable energy management strategies, which are typically implemented by power electronics-based grid interfaces. Unlike other current source converter (CSC) solutions described in the literature, which only interface with a single energy storage device, this paper introduces a novel topology for a three-phase delta-type current source converter (D-CSC), which is capable of integrating three independent ESSs using the same number of semiconductors as traditional CSC solutions. Thus, it considerably enhances the flexibility of a power conversion system (PCS) without increasing the number of converter components. In addition, an innovative energy management control strategy is also introduced. This strategy enables the D-CSC to compensate for energy imbalances arising between the three ESSs, which might be caused by several factors, such as different aging characteristics, converter component tolerances, operating conditions, and temperature drifts. Hence, the D-CSC-based interface is capable of proper grid operation even if the three ESSs have different characteristics, thus opening the possibility of employing this converter to integrate both first and second-life devices. First, the topology of the proposed D-CSC is introduced, followed by a detailed mathematical description of its control strategy. The proper grid operation of the D-CSC was tested under different scenarios, considering the grid integration of three independent superconducting magnetic energy storage systems in a marine vessel. The proposed D-CSC is compared to traditional CSC solutions, highlighting the superior performances of the novel converter topology in terms of efficiency, total harmonic distortion of the output currents, and overall cost reduction for the PCS. [ABSTRACT FROM AUTHOR]

With more and more extensive research and application of wearable devices, their continuous working time has become a prominent problem which is increasingly concerned. Within the limitations of existing battery technology, environmental energy harvesting can be used to enhance the continuous working time of wearable devices. To solve this problem, this paper designs a collection system for heat energy and radiofrequency (RF) energy in the environment. This system designs a thermoelectric collector based on thermoelectric generation, an RF energy collector based on a rectifier antenna, and a mixed energy collection controller based on power trajectory tracking. This system can generate power according to the temperature difference between environment and human body and RF energy in the environment. This system uses the heart rate sampling algorithm to accurately collect the required voltage and current information while saving system energy consumption. The maximum power output algorithm based on power trajectory tracking keeps the maximum power output of the energy collection system at all times. In this paper, two kinds of environmental energy models and a mixed energy acquisition system model are established by MATLAB. After setting reasonable environmental conditions, we get the results to verify the rationality and effectiveness of this environment energy collection system. [ABSTRACT FROM AUTHOR]

The recently proposed novel unidirectional multilevel rectifier, a three single-phase star-connected multilevel rectifier, has the characteristic of having a large number of DC-side capacitors and a complex capacitor voltage balancing control structure under conventional carrier-based phase-shift sine wave pulse-width modulation (SPWM). Hence, a space vector pulse-width modulation (SVPWM) algorithm for the novel multilevel rectifier is proposed in this paper, which can quickly balance the capacitor voltage without an additional voltage balancing control structure. Firstly, it divides the space vectors of the rectifier, then it determines the two basis voltage vectors that synthesize the output reference voltage. After that, based on the analysis of the relationship between switching states and the charge–discharge of capacitors, the final action sequences of redundant vectors are determined according to the principle of keeping the capacitor charge–discharge time consistent. Thus, the capacitor voltages can be automatically balanced without an additional voltage balancing control structure. Finally, simulation and experimental results validated the feasibility and effectiveness of the proposed SVPWM algorithm. The results also show improvements in current quality, capacitor voltage balance and the fluctuation of the neutral point voltage on the DC-link, allowing for further reduction in the overall volume and cost of the rectifier. [ABSTRACT FROM AUTHOR]

The main aim of this study is the development of a fast and secure charging system for electric vehicles. Recently, many different charging methods have been introduced. The main charging methods are the induction charging method and the conduction charging method. In this paper, the conduction charging method is employed. With regard to the conduction method, there are three levels of charging. At level 1, there is single-phase charging, while both single-phase and three-phase charging occur at level 2. Lastly, at level 3, a three-phase AC charging method, DC conduction charging method, and AC/DC conduction charging method is focused. The level 3 charging method is the main focus of this paper. Toward this end, a 12-diode rectifier or 12-pulse rectifier with a firing angle of zero degrees having two bridges is used for AC to DC conversion, while a SEPIC converter is used for DC-to-DC conversion. The design presented in this paper was simulated and verified using MATLAB/Simulink, and the results show that the Total Harmonic Distortion (THD) of the input current was reduced, and that overall efficiency was improved. [ABSTRACT FROM AUTHOR]

A miniature and high-efficiency interface circuit based on parallel synchronous switch harvesting on capacitors (P-SSHC) for piezoelectric energy harvesting (PEH) is proposed in this paper. This interface circuit consists of a two-stage synchronous rectifier and the P-SSHC circuit. The two-stage synchronous rectifier, composed of a negative voltage converter (NVC) and an active diode (AD), achieves higher efficiency compared with the full-bridge rectifier (FBR). In addition, the two-stage synchronous rectifier detects the zero-crossing moment of the input current; therefore, an extra current zero-crossing detection circuit is eliminated, which simplifies the structure of the interface circuit, reduces power consumption and improves peak converting efficiency. The P-SSHC circuit aims to improve the power extraction capability of the rectifier. The P-SSHC achieves considerable voltage flipping efficiency with very small volume compared to the parallel synchronized switch harvesting on inductor (P-SSHI), which is more suitable for volume sensitive applications. The proposed interface circuit is designed in SMIC 0.35 μ m CMOS process. Simulation results show that it achieves a 2. 9 7 × output power improvement compared with FBR for the case of a 3.4 V open-circuit voltage, the voltage flipping efficiency is as high as 83.6% and the peak power converting efficiency is up to 91.5%. The overall volume of the capacitors used in this paper is only 0.6 mm3, which is much smaller than the inductor used by conventional P-SSHI interface circuit. [ABSTRACT FROM AUTHOR]

This paper presents the development of an Air‐Cored Axial Flux Permanent Magnet Generator (ACAF PMG) integrated for direct battery charging scheme for urban and rural micro‐wind turbine applications rated at 1 kW. The proposed generator has a Single Stator Double Rotor configuration with a relatively short axial length. In this paper, the analytical model for generator sizing is presented and the main parameters are defined. Novel analytical model is presented to determine the required number of turns for each phase in order to produce a balanced voltage in the three phases. The generator is electromagnetically analyzed using Finite Element model and simulated using Matlab/Simulink to predict its performance under several operating conditions. The effect of retainment ring type on the generator performance is also demonstrated. The machine is harnessed to a battery bank via a three‐phase fully controlled converter using six bridge thyristors to regulate the output voltage delivered from the generator to the battery. Generator model and simulation results are validated via experimental tests. The preliminary experimental results showed a good match with the simulation results. Moreover, the proposed machine is compared favourably with other counter machines of similar configuration and power ratings in terms of machine size, power‐to‐weight ratio, and voltage regulation. This paper therefore demonstrates the concrete benefits of utilizing the axial flux PMG in scavenging energy to generate electrical power from micro wind turbines. [ABSTRACT FROM AUTHOR]

Introduction. Recently, the number of high and medium voltage applications has increased dramatically. The connection between these different applications requires series-parallel combinations of power semiconductors. Multilevel converter topologies provide major advantages to these applications. In this paper, a grid-connected photovoltaic system with a hybrid energy storage system using a five-level neutral point clamped inverter is studied. Although the multilevel inverter has many advantages over the two-level inverter, it has a high probability of experiencing an open circuit fault. In this context, the five-level inverter has 24 controllable switches, one of which may experience an open circuit fault at any time. Therefore, it plays an important part in the reliability and robustness of the whole system. The novelty of this paper presents an approach to accurately detect the open circuit fault in all insulated gate bipolar transistors of a five-level neutral point clamped inverter in a photovoltaic power generation application with a hybrid energy storage system. Purpose. Before using fault-tolerant control to ensure service continuity, fault diagnosis techniques must first be used, which are the crucial phase of reliability. Methods. A detection method based on the maximum and minimum error values is proposed. These errors are calculated using the expected and measured line-to-line pole voltages. Results. The open circuit fault detection method is implemented using MATLAB/Simulink. Simulation results showed the accuracy of detecting the open circuit fault in all insulated gate bipolar transistors in a short time. Moreover, this method is adaptable to several applications and is also robust to transient regimes imposed by solar irradiation and load variations. [ABSTRACT FROM AUTHOR]

This paper presents a compact stacked RF energy harvester operating in the WiFi band with multi-condition adaptive energy management circuits (MCA-EMCs). The harvester is divided into antennas, impedance matching networks, rectifiers, and MCA-EMCs. The antenna is based on a polytetrafluoroethylene (PTFE) substrate using the microstrip antenna structure and a ring slot in the ground plane to reduce the antenna area by 13.7%. The rectifier, impedance matching network, and MCA-EMC are made on a single FR4 substrate. The rectifier has a maximum conversion efficiency of 33.8% at 5 dBm input. The MCA-EMC has two operating modes to adapt to multiple operating conditions, in which Mode 1 outputs 1.5 V and has a higher energy conversion efficiency of up to 93.56%, and Mode 2 supports a minimum starting input voltage of 0.33 V and multiple output voltages of 2.85–2.45 V and 1.5 V. The proposed RF energy harvester is integrated by multiple-layer stacking with a total size of 53 mm × 43.5 mm × 5.9 mm. The test results show that the proposed RF energy harvester can drive a wall clock (30 cm in diameter) at 10 cm distance and a hygrometer at 122 cm distance with a home router as the transmitting source. [ABSTRACT FROM AUTHOR]

The Dadda algorithm is a parallel structured multiplier, which is quite faster as compared to array multipliers, i.e., Booth, Braun, Baugh-Wooley, etc. However, it consumes more power and needs a larger number of gates for hardware implementation. In this paper, a modified-Dadda algorithm-based multiplier is designed using a proposed half-adder-based carry-select adder with a binary to excess-1 converter and an improved ripple-carry adder (RCA). The proposed design is simulated in different technologies, i.e., Taiwan Semiconductor Manufacturing Company (TSMC) 50 nm, 90 nm, and 120 nm, and on different GHz frequencies, i.e., 0.5, 1, 2, and 3.33 GHz. Specifically, the 4-bit circuit of the proposed design in TSMC's 50 nm technology consumes 25 uW of power at 3.33 GHz with 76 ps of delay. The simulation results reveal that the design is faster, more power-energy-efficient, and requires a smaller number of transistors for implementation as compared to some closely related works. The proposed design can be a promising candidate for low-power and low-cost digital controllers. In the end, the design has been compared with recent relevant works in the literature. [ABSTRACT FROM AUTHOR]

This paper proposes a novel approach for low-power applications for the fast estimation of filter capacitor value and the output performance parameters such as average, and Root Mean Square (RMS) values for the voltage and current considering single-phase full-wave, three-phase half-wave and three-phase full-wave rectifier circuits. For this aim, the novel equations in this work are derived for the average output voltage and rms ripple voltage separately for each of the above-mentioned three rectifier types. Then % ripple factors for each rectifier type are calculated using newly derived equations and plotted versus the newly introduced Normalized Time Constant (NTC). Besides, considering the peak supply voltage as the base voltage, the Per Unit (p.u.) output average voltage and rms ripple voltage for each of the rectifier circuits are computed and plotted versus NTC. These graphs will be normalized graphs since the output values of these graphs have turned into independent of both supply voltage amplitude and supply frequency. Normalized graphs are set up only once for each type of the rectifier circuit. Then, and for a pre-selected ripple factor value, the corresponding NTC value is obtained by straightforward reading from the graphs set up between the % ripple factor and NTC. Once the NTC value has been acquired, using the formula of NTC leads to finding the capacitor value required for the pre-selected ripple factor with one simple step calculation. Furthermore, the p.u. values of the average output voltage and rms ripple voltage values that correspond to the same NTC value are obtained by reading them from the set-up graphs directly. Finally, the efficiency of the proposed method is demonstrated through design examples for each type of rectifier circuit. The three design examples highlight how the output performance values can be obtained easily, accurately and swiftly. Furthermore, the viability of the graphical approach is verified by the experimental results which demonstrate the suitability of the derived equations in the proposed method. [ABSTRACT FROM AUTHOR]

The flame of converter mouth can well reflect the change of temperature and composition of molten steel in the furnace. The flame characteristics of converter mouth collected by device can well predict the smelting process of converter. Based on the flame spectrum data set of converter mouth, this paper uses the BEADS algorithm and rough set attribute reduction algorithm optimized by genetic algorithm to extract the features of 2048-dimensional wavelength data. Through the model, eight indexes that contribute greatly to temperature and carbon content are selected, which are f-507, f-520, f-839, f-1073, f-1371, f-1528, f-1727 and f-1826. The MIC coefficients of the eight indicators with temperature and carbon content are calculated, and the MIC coefficients of the variables is small, and the selected indicators are representative. There was a significant correlation between temperature and C content. In BP neural network of temperature prediction model, it is found that the prediction accuracy of the training set is 0.99, the prediction accuracy of the test set is 0.99, the prediction accuracy of the verification set is 0.99, and the prediction accuracy of the whole set is 0.99. Through statistics, it is found that the hit rate of the temperature model in the range of ± 5 K is 88.7%, and the hit rate in the range of ± 10 K is 98.4%. and the RMSE parameter analysis shows that the average prediction error is 3.85 K. In BP neural network of carbon content prediction model, it is found that the prediction accuracy of the training set is 0.99, the prediction accuracy of the test set is 0.99, the prediction accuracy of the verification set is 0.98, and the prediction accuracy of the whole set is 0.99. Through statistics, it is found that the hit rate of the carbon contents model in the range of ± 0.05% is 94.0%, and the hit rate in the range of ± 0.10% is 98.3%, and the RMSE parameter analysis shows that the average prediction error is 0.021%. Finally, the universality of the model is verified by MIV algorithm. [ABSTRACT FROM AUTHOR]

Constant current (CC) charging and constant voltage (CV) charging are the two main charging stages of lithium-ion batteries in wireless charging systems. The traditional LCC-LCC topology has a high degree of design freedom. The conversion from CC to CV output is usually achieved through composite topology or frequency switching, which results in high control complexity and increases system cost. This paper proposes a wireless power transfer (WPT) system with CC and CV output characteristics based on topology reconstruction. Based on the LCC-LCC topology, by introducing one MOSFET in the rectifier and one AC switch which consists of two MOSFETs connected in reverse series to reconfigure the topology, the conversion from CC to CV mode can be achieved without complicated control methods and additional components. In addition, the proposed system works at a fixed operating frequency point, which can effectively avoid frequency bifurcation phenomenon. Therefore, the proposed system features a simple structure, easy control, low cost, and high robustness. In addition, ZPA operation can be realized in both CC and CV modes, ensuring high transmission efficiency. An experimental prototype with a rated power of 480 W is built, and a maximum efficiency can reach 93.5%, which verifies the feasibility of the system. [ABSTRACT FROM AUTHOR]

In this paper, the application and design of a high-power factor isolated Ćuk converter-based LED driver are realized for up to 50 W power. For the power switch of the PFC isolated Ćuk converter, traditional Si and silicon carbide (SiC) MOSFETs, which are wide bandgap semiconductors, are used and compared. The application is conducted using a dsPIC30F4011 microcontroller including PI voltage control. A current sensor is added to limit maximum current. Moreover, PI control parameters are selected by genetic algorithm to avoid a complex mathematical procedure for controller design. The power LED model derived in this paper is used for the PI parameter selection process. In addition, the input side inductor of the converter is operated in discontinuous conduction mode, and the switching frequency of the power switch is 57 kHz. With the experimental setup, the total harmonic distortion (THD) of grid voltage and current, power LED voltage and current, switch voltage, and input side inductor current are shown for both the SiC and Si MOSFETs and compared. It is concluded from the application that the SiC-based driver gives better results than the Si-based driver on the basis of THD and efficiency. Further, both applications provide limits of IEC61000-3-2 C class standard. [ABSTRACT FROM AUTHOR]

Resistance compression networks (RCNs) have attracted special attention in the field of wireless power transmission (WPT) since they were put forward. A lot of research work has been done in rectifier basing on RCN for the purpose of increasing conversion efficiency. It is reported that many kinds of rectifiers containing RCN which operate in various circuit and physical forms are proposed. RCN and all kinds of modified versions are studied deeply in this paper, the rectifiers related to which are analyzed also. The results show that RCN only plays the role of bandpass filter (BPF) in the rectifying circuit, which does not reach the original idea of the first proposer. We have different understandings of the rectifying circuits presented in other papers. [ABSTRACT FROM AUTHOR]

The maximum efficiency point of an inductive power link depends on its load power consumption and the distance between the transmitter and the receiver. Matching networks (MNs) and adjustable ac–dc converters have been proposed in the literature as a means to achieve and track this maximum efficiency point. Most of the published papers in inductive power transmission only use one of these two methods without considering a joint design. In this paper, we analyze and compare both methods proposing a general joint design which exploits the advantages of each method. A proof-of-concept system was developed following the proposed flow, built and tested. This system, with a regulated output voltage, presents improvements in measured efficiencies of up to 80% (from 9.2% to 16%) at the largest distances, thus maximizing the distance range. The same approach can be used to maximize output dc voltage, instead of the link efficiency. The proposed system using our designed MN achieved a maximum output voltage that was 90% higher (from 1.36 to 2.59 V) than the case where only a step-up converter was used. [ABSTRACT FROM AUTHOR]

The inherent second harmonic power pulse in single-phase grid-connected rectifiers leads to a noticeable output voltage ripple and thus results in the degradation of the system. A novel second harmonic suppression control is introduced in this paper to address this issue. The key point of the proposed control lies in the real-time prediction of the phase-shifted full-bridge (PSFB) converter's desired duty cycle through accurate PSFB converter modeling. By accurately predicting the ideal duty cycle, the proposed control facilitates a significant enhancement in the control loop's gain specifically at the second harmonic frequency, thereby improving the overall system performance. To validate the theoretical analysis, a series of simulations and experiments were conducted. The results demonstrate the effectiveness of the proposed second harmonic suppression control in mitigating second harmonic output voltage ripple. [ABSTRACT FROM AUTHOR]

To effectively eliminate the impacts of both matched and mismatched power disturbances in a three-phase PWM rectifier, this paper proposes a robust direct power control (RDPC) method with a single-loop control structure. Firstly, a nonlinear power model of the three-phase PWM rectifier is established. Then, using the exact feedback linearization method, a linearized power model including matched and mismatched power disturbances is derived and achieves the decoupling of active and reactive power. Secondly, to regulate the DC bus voltage, a sliding-mode controller (SMC) combined with a nonlinear disturbance observer (NDO) is proposed. The proposed SMC combined with an NDO (SMC + NDO) method features a single-loop control structure, which enables a faster response and simpler structure compared to the dual-loop DPC method. By incorporating estimated mismatched power disturbance into the sliding-mode surface, it overcomes the SMC's defect in incompletely suppressing mismatched disturbances and enables the simultaneous regulation of voltage and active power. Additionally, it effectively reduces sliding-mode chattering. To regulate reactive power, a sliding-mode controller based on the exponential convergence law is designed to suppress matched reactive power disturbances. Finally, the simulation and experimental comparative results demonstrate that the proposed controller exhibits stronger robustness against matched and mismatched power disturbances, as well as a better performance under the constant power load (CPL). [ABSTRACT FROM AUTHOR]

One of the early design decisions for DC‐DC converters is the choice of an appropriate magnetic core material. Powder cores in particular are suitable due to their saturation flux density of up to 1.5 T. However, high DC currents constitutes a significant problem since the winding cross‐section rises with the current, which consequently increases AC losses due to skin effects. Another challenge is the reduction of winding layers to decrease proximity losses. This paper presents an improved single‐layer winding design procedure for DC‐DC converter powder cores. The procedure determines the optimum number of parallel cores and stacks. This way, the procedure enables a predefined maximum wire cross‐section for copper loss optimisation and single‐layer winding. The introduced approach defines the optimum switching frequency as a trade‐off between core loss and core volume. Finally, experimental tests with two setups validate 27 kW DC‐DC converters and hence the design procedure using Si‐IGBTs and SiC‐MOSFETs. The results demonstrate that SiC‐MOSFETs reduce core volume by a factor of 3 compared to Si‐IGBTs. Further, the SiC setup reaches high efficiencies of up to 98.53% compared to 98.17% for the Si‐based converter. [ABSTRACT FROM AUTHOR]

This paper presents electronically tunable current conveyors using low-voltage, low-power, multiple-input operational transconductance amplifiers (MI-OTAs). The MI-OTA is realized using the multiple-input bulk-driven Metal Oxide Semiconductor transistor (MIBD-MOST) technique to achieve minimum power consumption. The MI-OTA also features high linearity, a wide input range, and a simple Complementary Metal Oxide Semiconductor (CMOS). Thus, high-performance electronically tunable current conveyors are obtained. With the MI-OTA-based current conveyor, both an electronically tunable differential difference current conveyor (EDDCC) and a second-generation electronically tunable current conveyor (ECCII) are available. Unlike the conventional differential difference current conveyor (DDCC) and second-generation current conveyor (CCII), the current gains of the EDDCC and ECCII can be controlled by adjusting the transconductance ratio of the current conveyors. The proposed EDDCC has been used to realize a voltage-to-current converter and current-mode universal filter to show the advantages of the current gain of the EDDCC. The proposed current conveyors and their applications are designed and simulated in the Cadence environment using 0.18 μm TSMC (Taiwan Semiconductor Manufacturing Company) CMOS technology. The proposed circuit uses ±0.5 V of power supply and consumes 90 μW of power. The simulation results are presented and confirm the functionality of the proposed circuit and the filter application. Furthermore, the experimental measurement of the EDDCC implemented in the form of a breadboard connection using a commercially available LM13700 device is presented. [ABSTRACT FROM AUTHOR]

Magnetostrictive alloys hold great promise for Energy Harvesting applications due to their inherent durability. However, their implementation often results in usable voltage ranges that fall significantly below common electronic standards like 1.6, 3.3, and 5 volts. Consequently, the utilization of electronic circuits becomes essential to amplify the voltage and enhance energy conversion efficiency. Over the past few decades, numerous conversion techniques have been devised for other intelligent materials, such as piezoelectrics, some of which have even made their way into commercial products. Surprisingly, there is a dearth of specialized techniques, if not a complete absence, tailored to magnetostrictive devices. Among potential solutions, a suitable AC–DC Boost converter stands out as a highly promising candidate for addressing this challenge, but this solution has never been fully characterized. Then, this paper presents thorough experimental validations of such a converter, driven by a real-time Arduino board equipped to measure source time periods and operate under various conditions. We present several cases demonstrating the circuit's substantial potential for enhancing energy harvesting from magnetostrictive materials. [ABSTRACT FROM AUTHOR]

The commutation failure (CF) is the most common fault in line-commutated high voltage direct current (LCC-HVDC) systems that may lead to the transient overvoltage in the sending-side system. In the worst condition, the CF may lead to large-scale wind turbine tripping. To resolve this problem, the mathematical relationship between the reactive power consumed by the rectifier and DC voltage, DC current is derived. Then, a transient overvoltage calculation method is proposed in this paper. Furthermore, the mechanism of transient overvoltage caused by the CF is analyzed; it is revealed that the reason for three times transient overvoltage is the rapid decrease of the reactive power consumed by the rectifier during the CF and the recovery period from the CF. This paper proposes a constant reactive power control (CRPC) to inhibit transient overvoltage of the sending-side AC system. The proposed CRPC can increase the reactive power consumed by the rectifier, reduce the exchange reactive power between AC and DC systems, and suppress the transient overvoltage. A simulation model in PSCAD serves to verify the proposed CRPC on the transient overvoltage suppression in the situation of different fault types, fault duration, fault severity and short circuit ratio (SCR). [ABSTRACT FROM AUTHOR]

The diode‐rectifier (DR)‐based high‐voltage direct current (HVDC) transmission is regarded as a low‐cost alternative to the HVDC transmission for offshore wind farms (OWFs) integration. However, the DR would generate harmonic voltages in the offshore grid, which greatly affects the power quality. To solve this problem, this paper utilizes a parallel‐connected small‐capacity auxiliary converter to suppress the harmonic voltages and provide black‐start energy for the OWFs. In addition, the submodule branches (SMBs) of the auxiliary converter can be used as part of the HVDC chopper. On this basis, a coordinated grid fault ride‐through (FRT) strategy is proposed in this paper. After a grid fault occurs, the HVDC chopper constructed by the auxiliary converter is able to constrain the DC‐link voltage. At the same time, the OWFs are controlled to reduce the output active power. As a result, the cost of the FRT can be significantly reduced. The proposed harmonic voltage suppression and the FRT method are verified through the simulation model in Simulink. [ABSTRACT FROM AUTHOR]

When the wind turbine operates under frequently fluctuating mission profiles, the power semiconductors of its converter will generate low-frequency junction temperature fluctuations, resulting in accumulation of damage to the devices and affecting the converter's lifetime. To address the above issues, an active thermal control (ATC) strategy based on reactive circulating current for the parallel converter of permanent magnet synchronous generator wind power system was proposed in this paper, by introducing reactive circulating current during sudden wind speed drops, the thermal cycle of the power semiconductor can be effectively smoothed. On the other hand, considering the impact of the proposed strategy on the voltage vector and modulation index of the converter, both the machine-side converter (MSC) and the grid-side converter (GSC) during the control process will be analyzed in detail, then the reactive current of GSC will be limited to prevent excessive modulation index and maintain system stability without reducing the filter size. Finally, a 2 MW wind power system is utilized as a benchmark, and both short-term simulation analysis and long-term numerical results reveal the effectiveness of the control strategy proposed in this paper. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive review on the employment of wide bandgap (WBG) semiconductor power devices in wind energy conversion systems (WECSs). Silicon-carbide- (SiC) and gallium-nitride (GaN)-based power devices are highlighted and studied in this review, focusing on their application in the wind energy system. This is due to their premium characteristics such as the operation at high switching frequency, which can reduce the switching losses, and the capability to operate at high temperatures compared with silicon (Si)-based devices. These advantages promote the replacement of the conventional Si-based devices with the WBG semiconductor devices in the new modular converter topologies due to the persistent demand for a more-efficient power converter topology with lower losses and smaller sizes. The main objective of this paper was to provide a comprehensive overview of the WBG power devices commercially available on the market and employed in the modular converter topologies for renewable energy systems. The paper also provides a comparison between the WBG power technologies and the traditional ones based on the Si devices. The paper starts from the conventional modular power converter topology circuits, and then, it discusses the opportunities for integrating the SiC and WBG devices in the modular power converters to improve and enhance the system's performance. [ABSTRACT FROM AUTHOR]

The paper deals with a grid-connected single-phase battery charger integrated with photovoltaic generators (PVGs). The circuit topology consists of a multilevel architecture based on a Cascaded H-Bridge (CHB) rectifier. Its main task is to charge the batteries, primarily from the PVGs, by also assuring to keep their state-of-charge (SOC) balanced. Nevertheless, when the battery SOC overcomes a predefined upper limit, beyond which the charging process could be interrupted, the available PV power can no longer be transferred to the batteries. Therefore, to avoid an undesired curtailment of PV power production, this latter can be supplied to the grid by inverting the system operation. The paper shows how to achieve this result by implementing a dedicated control action based on a multi-step procedure. Numerical investigations are carried out on a 19-level CHB converter implemented in the PLECS environment to validate the feasibility and effectiveness of the proposed control technique. [ABSTRACT FROM AUTHOR]

In low-carbon energy systems, due to the high proportion of renewable energy access, the voltage regulation capacity of the system will decrease. Therefore, in the event of voltage violation, it is easy to cause large-scale renewable energy off-grid and power outages. In order to improve the voltage regulation ability of low-carbon energy system, this paper proposes a two-stage overvoltage suppression strategy for sending-end power grid. Firstly, the principle of overvoltage phenomenon in the sending end power grid of low-carbon energy system with high proportion of renewable energy access is studied, and an overvoltage control strategy composed of two stages of centralized control of rectifier station and flexible resource control of distributed power grid is proposed. Then, the PSO algorithm and consensus algorithm are used to solve the established control model. Finally, a simulation system is established based on actual operating power grid data to verify the proposed control strategy through simulation. The results indicate that the control strategy proposed in this paper can effectively suppress transient overvoltage of AC buses and improve the operational stability of the high proportion of renewable energy sending-end power grid under various operating conditions. In addition, during the daytime overvoltage regulation process, the potential of flexible regulation equipment can be fully utilized. Shortening the duration of voltage exceeding the limit and reducing the peak voltage exceeding the limit can help reduce the renewable energy waste rate of the power grid. [ABSTRACT FROM AUTHOR]

While much attention was given in the literature to improve the fault ride through (FRT) capability of a doubly-fed induction generator (DFIG)-based wind energy conversion system (WECS) during various faults at the grid side, not much attention was given to investigate and improve the performance of the DFIG-WECS under ferroresonance conditions. This paper investigates the impact of ferroresonance on the overall performance of a DFIG-WECS. The paper also presents a new technique to improve the high voltage ride through capability of the investigated system under such condition. The proposed technique relies on incorporating a superconducting coil within the dc-link of the DFIG grid-side and rotor-side converters. Energy exchange between the coil and the system is controlled through regulating the duty cycle of the dc-chopper interfacing the coil with the dc-link. In this regard, a simple but yet effective proportional-integral (PI) controller is employed to regulate the dc-chopper duty cycle. Parameters of the PI controller are optimized using elephant herding optimization algorithm. Simulation results verify the effectiveness of the proposed controller in improving the overall performance of a DFIG-WECS during ferroresonance events. [ABSTRACT FROM AUTHOR]