Search Results (3,632)

Multilevel active bridge converters are potential candidates for many modern high-power DC applications due to their ability to integrate multiple sources while minimizing weight and volume. Therefore, this paper deals with an analytical, simulation-based, and experimentally verified investigation of their circulating current behavior, power factor performance, and power loss characteristics. A high-frequency link analysis framework is developed to characterize voltage, current, and power transfer waveforms, providing insight into reactive power generation and its impact on overall efficiency. By introducing a modulation-based control approach, the proposed converters significantly reduce circulating currents and enhance the power factor, particularly under varying phase-shift conditions. Compared to quadruple active bridge topologies, the discussed multilevel architectures offer reduced transformer complexity and improved power quality, making them suitable for demanding applications such as electric vehicles and aerospace systems. Full article

The Honeycomb Distribution Network is a new distribution network architecture that utilizes the Smart Power-Exchange Station (SPES) to enable power interconnection and mutual assistance among multiple microgrids/distribution units, thereby supporting high-proportion integration of distributed renewable energy and promoting a sustainable energy transition. To promote the continuous and reliable operation of the Honeycomb Distribution Network, this paper proposes a Hierarchical Switching Control Strategy to address the issues of DC bus voltage (U_dc) fluctuation in the SPES of the Honeycomb Distribution Network, as well as the state of charge (SOC) and charging/discharging power limitation of the energy storage module (ESM). The strategy consists of the system decision-making layer and the converter control layer. The system decision-making layer selects the main converter through the importance degree of each distribution unit and determines the control strategy of each converter through the operation state of the ESM’s SOC. The converter control layer restricts the ESM’s input/output active power—this ensures the ESM’s SOC and input/output active power stay within the power boundary. Additionally, it combines the Flexible Virtual Inertia Adaptive (FVIA) control method to suppress U_dc fluctuations and improve the response speed of the ESM converter’s input/output active power. A simulation model built in MATLAB/Simulink is used to verify the proposed control strategy, and the results demonstrate that the strategy can not only effectively reduce U_dc deviation and make the ESM’s input/output power reach the stable value faster, but also effectively avoid the ESM entering the unstable operation area. Full article

Among other uses, DC-DC converters are employed in the auxiliary power modules (APMs) of electric vehicles (EVs), connecting the high-voltage traction battery to the low-voltage auxiliary system (AS). Traditionally, the APM is an isolated two-port, two-level (2L) DC-DC converter, and the auxiliary loads are fed at a fixed voltage level, e.g., 12 V in passenger cars. Dual-active-bridge (DAB) converters are commonly used for this application, as they provide galvanic isolation, high power density and efficiency, and bidirectional power flow capability. However, the auxiliary loads do not present a uniform optimum supply voltage, hindering overall efficiency. Thus, a more flexible approach, providing multiple supply voltages, would be more suitable for this application. Multiport DC-DC converters capable of feeding auxiliary loads at different voltage levels are a promising alternative. Multilevel neutral-point-clamped (NPC) DAB converters offer several advantages compared to conventional two-level (2L) ones, such as greater efficiency, reduced voltage stress, and enhanced scalability. The series connection of the NPC DC-link capacitors enables a multiport configuration without additional conversion stages. Moreover, the modular nature of the ML NPC DAB converter enables scalability while using semiconductors with the same voltage rating and without requiring additional passive components, thereby enhancing the converter’s power density and efficiency. This paper proposes a modulation strategy and decoupled closed-loop control strategy for the generalized multiport 2L-NL NPC DAB converter interfacing the EV traction battery with the AS, and its performance is validated through hardware-in-the-loop testing and simulations. The proposed modulation strategy minimizes conduction losses in the converter, and the control strategy effectively regulates the LV battery modules’ states of charge (SoC) by varying the required SoC and the power sunk by the LV loads, with the system stabilizing in less than 0.5 s in both scenarios. Full article

In microgrids, battery chargers/dischargers are used to manage power flow between the battery and the DC bus and to regulate the DC bus voltage, ensuring safe operating conditions for sources and loads. These actions contribute to enhancing the sustainability of the microgrid by improving energy efficiency, extending battery life, and ensuring reliable operation. The classical converter adopted to implement the battery chargers/dischargers is the boost converter, which avoids high current harmonic injection into the battery because of its continuous input current. But due to the discontinuous output current, it introduces high current harmonics into the DC bus. This also occurs in Sepic, Zeta, or other DC/DC converters with discontinuous input or output currents. One exception is the Cuk converter, which has both continuous input and output currents. However, in the Cuk converter, the intermediate capacitor voltage is higher than the input and output voltages, thus imposing high stress on the semiconductors and requiring a costly capacitor with high energy storage. Therefore, this paper proposes the design of a battery charger/discharger based on a non-electrolytic capacitor boost converter. This topology provides continuous input and output currents, which reduces harmonic component injection, extends battery life, and increases operation efficiency. Moreover, it requires a lower intermediate capacitor voltage, thereby enhancing reliability. The design of this battery charger/discharger requires an adaptive sliding-mode controller to ensure global stability and accurate bus voltage regulation. A formal stability analysis and design equations are provided. The proposed solution is validated through detailed simulations, while the adaptive sliding-mode controller is specifically tested using a detailed software-in-the-loop approach. Full article

This article presents a neural network-based control method for maintaining the required output voltage of a synchronous buck converter. The goal was to replace a traditional PID controller with a neural network that calculates the duty cycle based on real-time data. Several versions of the neural network were tested. The final version, which included the input voltage, reference, and output current as inputs and compensated for dead time, was successfully validated on real hardware. It was able to respond to changes in load and input voltage within a limited operating range. Full article

In order to meet the needs of grid integration of various renewable energy sources and promote long-distance power transmission, a hybrid multi-infeed DC system architecture consisting of a line-commutated converter (LCC) and a modular multilevel converter (MMC) is constructed. Focusing on the issue of traditional differential protection refusing to operate under high-resistance grounding faults and failing under symmetrical faults, a dual-criteria protection mechanism is proposed in this paper. By integrating current differential and voltage criterion, the accurate identification of various types of AC line faults can be realized. A hybrid DC system simulation model was built on MATLAB, the sampled data was decoupled, and the differential quantity was calculated to test the dual-criteria protection mechanism. The simulation results show that the proposed protection mechanism can effectively identify various faults within the hybrid DC multi-feed system area and faults outside the area and has robustness to complex working conditions such as high-resistance grounding and three-phase short circuits, which improves the sensitivity, selectivity, and adaptability of the protection. This method is designed for AC line protection under the disturbance of multi-infeed DC systems. It is not directly applicable to pure DC microgrids. The concept can be extended to AC/DC hybrid microgrids by adding DC-side protection criteria and re-calibrating thresholds. Full article

With the rapid rise in electric vehicle (EV) adoption, the deployment of EV charging infrastructure—particularly fast-charging stations—has expanded significantly to meet growing energy demands. While fast charging offers the advantage of reduced charging time and improved user convenience, it imposes considerable stress on existing power distribution systems due to its high power and current requirements. This study investigated the impact of EV fast charging on power quality within Thailand’s distribution network, emphasizing compliance with accepted standards such as IEEE Std 519-2014. We developed a control-oriented EV-charging station model in power systems computer-aided design and electromagnetic transients, including DC (PSCAD/EMTDC), which integrates grid-side vector control with DC fast-charging (CC/CV) behavior. Active/reactive power setpoints were mapped onto $dq$ current references via Park’s transformation and regulated by proportional integral (PI) controllers with sinusoidal pulse-width modulation (SPWM) to command the voltage source converter (VSC) switches. The model enabled dynamic studies across battery state-of-charge and staggered charging schedules while monitoring voltage, current, and total harmonic distortion (THD) at both transformer sides, charger AC terminals, and DC adapters. Across all scenarios, the developed control achieved grid-current THDi of <5% and voltage THD of <1.5%, thereby meeting IEEE 519-2014 limits. These quantitative results show that the proposed, implementation-ready approach maintains acceptable power quality under diverse fast-charging patterns and provides actionable guidance for planning and scaling EV fast-charging infrastructure in Thailand’s urban networks. Full article

This paper presents a novel technique for thermally compensating the power output of a DC-DC converter that supplies automotive lighting/signaling systems with multiple LED branches. The method ensures stable bias voltage for the current drivers controlling each branch, maintaining consistent power consumption across a wide temperature range. This issue has been minimally addressed in existing literature, providing few solutions which are too complex for industrial production. The approach proposed is simple and involves incorporating a temperature-sensitive thermistor into the DC-DC converter’s control loop, enabling the output voltage to adjust with ambient temperature. Different control loop configurations are explored, demonstrating that a simple resistor-thermistor network can approximate the desired voltage response under diverse thermal conditions. The power dissipated in the current drivers is kept within a controlled range, improving system efficiency and reducing heat loss. Additionally, it minimizes the need for additional current drivers, lowering the cost of these systems, improving battery life of the DC-DC converter, and decreasing CO₂ emissions. For the case studies analyzed, an optimized configuration with appropriate resistor values and thermistor models achieves a 75% relative reduction in power dissipation by the current driver and a 50% improvement in the relative efficiency of the LED branch system. Full article

Given the decline in fossil energy reserves and the need for less pollution, achieving carbon zero is challenging in major industrial sectors. However, the emergence of large-scale hydrogen production systems powered by renewable energy sources offers an achievable option for carbon neutrality in specific applications. When combined with energy storage systems, static power converters are crucial in these production systems. This paper offers a comprehensive review of various power converter topologies, focusing on AC– and DC–bus architectures that interface battery storage units, electrolyzers, and fuel cells. The evaluation of DC/AC, AC/DC, and DC/DC converter topologies, considering cost, energy efficiency, control complexity, power level suitability, and power quality, represents a significant advancement in the field. Furthermore, the subsequent exploration of battery aging behavioral modeling, characterization methods, and real-time parameter estimation of the battery’s equivalent electrical circuit model enhances our understanding of these systems. Large-scale hydrogen production systems most often use an AC–bus architecture. However, DC–bus configuration offers advantages over AC–bus architecture, including high efficiency, simpler energy management, and lower system costs. In addition, MVDC or HVDC DC/DC converters, including isolated and non-isolated designs based on multiple cascaded DABs and MMC-type topologies, have also been studied to adapt the DC–bus to loads. Finally, this work summarizes several battery energy storage projects in the European Union, specifically supporting the large-scale integration of renewable energy sources. It also provides recommendations, discussion results, and future research perspectives from this study. Full article

This paper provides an in-depth review of degradation mechanisms and condition monitoring methods for critical components in modular multilevel converter (MMC) high-voltage direct current (HVDC) systems, including insulated gate bipolar transistors (IGBTs), metallized film capacitors, and cross-linked polyethylene (XLPE) DC cables. This study systematically evaluates the strengths and limitations of existing technologies, while also projecting future trends in technological advancements. By exploring the multi-fields-coupled degradation processes of these components, the mechanisms of switching oscillations, and the flexible and controllable applications of MMC, this review offers valuable insights for improving the accuracy, real-time performance, and reliability of component condition monitoring. The findings aim to contribute to the advancement and broader application of MMC HVDC systems in modern power networks. Full article

The instantaneous AC-side output power of a two-stage single-phase inverter pulsates at twice the output voltage frequency, inducing second harmonic current (SHC) in the front-end DC–DC converter. While conventional SHC mitigation methods mainly focus on controller optimization for PWM-controlled DC–DC converters, LLC resonant converters, which have been widely adopted in two-stage single-phase inverters for high efficiency and soft-switching characteristics, lack tailored solutions due to frequency modulation complexities. To address this gap, this paper first analyzes the propagation mechanism of the SHC in terms of converter output impedance. Then, by simultaneously lowering the open-loop gain and increasing the output impedance of the DC–DC converter at 2f_N, this paper proposes a hybrid SHC mitigation strategy that achieves low SHC and fast dynamic performance for frequency-modulated LLC converters. Finally, a 28 V DC to 220 V/50 Hz AC inverter was developed, and the experimental results verified the effectiveness of the proposed control strategy. Full article

The flexible DC transmission project of renewable energy has become an inevitable development trend for large-scale renewable energy grid connection. A two-terminal weak feed (TTWF) AC system is often composed of 100% power electronic equipment. The traditional fault control strategy adopted after a fault in the converter at both terminals of the line limits the fault current and controls the phase, resulting in a decrease in the time-domain distance protection performance. This paper first analyzes the adaptability challenges of time-domain distance protection in TTWF. Based on detailed fault characteristic studies, two improvement approaches are proposed: (1) accounting for phase control effects by equivalently modeling the fault impedance as a series combination of fault resistance and inductance; and (2) incorporating distributed capacitance effects through fault differential equation derivation based on π-type line equivalent models. A novel time-domain distance protection method is subsequently developed, comprehensively considering control strategy impacts and distributed capacitive currents. Simulation tests verify that the proposed method maintains reliable operation under severe conditions, including 300 Ω fault resistance and 30 dB white noise interference, demonstrating significantly improved resistance to fault impedance and noise compared to conventional solutions. Full article

This paper focuses on the Input-Independent Output-Series (IIOS) DC converters within fully DC aggregation systems, which enable independent submodule control and high voltage gain. DC aggregation systems experience output voltage imbalance among submodules due to offshore wind power fluctuations. The proposed isolated DC/DC converter topology incorporates power-balancing capacitors, leveraging intrinsic characteristics to achieve self-power balancing within the system. In addition, this paper proposes an innovative PFMT-PSMN hybrid control strategy that is well-suited for the proposed topology. Firstly, this study performs a time-domain analysis of the intrinsically power-balanced DC series-connected aggregation topology and elucidates the corresponding power-balancing principle. Secondly, based on soft-switching boundary conditions, a hybrid control strategy, PFMT-PSMN, adjusts phase-shift duty cycles to maintain soft-switching conditions while minimizing the system operating frequency. Finally, MATLAB/Simulink simulations validate the power-balancing capability of the intrinsically balanced DC series-connected aggregation system and the effectiveness of the proposed PFMT-PSMN control strategy. Full article

The integration of Internet of Things (IoT) technologies into islanded microgrids has increased their vulnerability to cyberattacks, particularly those targeting critical components such as power converters within an islanded AC microgrid. This study investigates the impact of False Data Injection (FDI) and Denial of Service (DoS) attacks on various power converters, including DC–DC boost converters, DC–AC converters, battery inverters, and DC–DC buck–boost converters, modeled in MATLAB/Simulink. A dataset of healthy and compromised operational parameters, including voltage and current, was generated under simulated attack conditions. To enhance system resilience, a deep learning-based detection and classification framework was proposed. After evaluating various deep learning models, including Deep Neural Networks (DNNs), Artificial Neural Networks (ANNs), Support Vector Machines (SVMs), Long Short-Term Memory (LSTM), and Feedforward Neural Networks (FNNs), the final system integrates an FNN for rapid attack detection and an LSTM model for accurate classification. Real-time simulation validation demonstrated a detection accuracy of 95% and a classification accuracy of 92%, with minimal computational overhead and fast response times. These findings emphasize the importance of implementing intelligent and efficient cybersecurity measures to ensure the secure and reliable operation of islanded microgrids against evolving cyberattacks. Full article

In view of the DC bus voltage fluctuation caused by the short-term periodic power demand of pulsed power loads (PPLs), this paper introduces a power allocation and tracking method for a hybrid energy storage system (HESS) with pulsed loads, aiming to improve the stability of the bus voltage. Firstly, a pulse power allocation and tracking method based on AC and DC components is proposed. Then, by introducing a current estimating method, a reference output current extraction from the AC component is obtained for model predictive control, which is used to control the supercapacitor converter, while the DC power is provided to inform the droop control to drive the battery converter. Finally, a frequency domain model is established to study the suppression effect of the control method on DC bus fluctuations, providing a reliable control scheme for HESS with pulsed power loads. Full article