Power Electronic Equipment Research Articles

Research on static voltage stability enhancement for new energy station based on grid-forming control strategy

The advent of novel power systems has given rise to a multitude of safety and stability concerns associated with the integration of emerging energy sources and power electronic equipment. The active support of the grid-forming control strategy represents an effective solution to the voltage and frequency stability issues associated with the weak damping and low inertia inherent to high-ratio new energy systems. Firstly, a static voltage stability index based on critical impedance is proposed for assessment of the static stability margin of a new energy grid-connected system, based on the static voltage stability theory of a traditional single-unit single-load system. Secondly, an analysis is conducted of the control principle of the grid-forming control converter and its impedance characteristics. In conclusion, a method for enhancing the static voltage stability margin of grid-connected new energy stations through parameter control of grid-forming converters is presented. The simulation verification of the single-feed and multi-feed systems demonstrates the efficacy and accuracy of the methodology presented in this study.

Adaptive Virtual Synchronous Generator Control Strategy Based on Frequency Integral Compensation

With the increasing proportion of power electronic equipment in the power system, improving the inertia and damping characteristics of the system through virtual synchronous generator (VSG) control technology has become a hot research topic. In terms of adjusting the output frequency, traditional primary frequency modulation control cannot ensure that the output frequency is maintained within the safe operating range when the load disturbance is large, so secondary frequency modulation with the integral link is usually adopted. However, the fixed integral coefficient cannot solve the contradiction between system regulation time and frequency oscillation. In this paper, a strategy of coordinated adaptive control based on the integral coefficient, moment of inertia, and damping coefficient is proposed. According to the offset of frequency and the change rate of the frequency offset, the value of parameters is determined, and the specific parameter setting method is determined. Finally, the correctness of the proposed control strategy is verified on a simulation platform and a semi-physical experimental platform.

Performance Evaluation of Solar PV Integrated with Custom Power Device under Various Load Conditions

The non-linear properties and rapid switching of power electronic equipment are the primary causes of power quality issues in power systems, particularly in the power distribution systems. The widespread use of delicate equipment, which continuously pollutes the environment, is making power quality problems worse. The increasing integration of renewable energy sources into the generation mix and the decarburization of the economy have created new challenges for smart grid technology, requiring creative solutions such as energy storage systems and smart transformers. This article describes a solar photovoltaic integrated unified power quality conditioner (UPQC) that uses a deep learning method based on neural networks and a novel compensating technique. Here, two Deep Neural Network algorithms are used, one in the solar PV system to obtain the maximum power under various irradiance situations, and the other to manage the UPQC under various load conditions. When compared to the conventional UPQC based on PQ Theory, DNN-UPQC produces superior results in terms of reducing total harmonic distortion. This iterative strategy, which is focused on soft computing, provides faster convergence to the target condition while maintaining the updating weight within a predetermined limit. PV-based UPQC has been connected individually to reduce voltage sag, swell, and unbalance in variable load conditions. The system's dynamic and steady state performance are assessed by modelling it with a MATLAB-Simulink in different load condition.

Power system frequency nadir prediction based on data-driven and power-frequency polynomial fitting

As the proportion of renewable energy and power electronics equipment continues to rise, the level of rotational inertia decreases considerably, resulting in severe frequency stability challenges to the power grid. It is of great significance to accurately predict the frequency nadir following a large disturbance. This paper proposes a novel data-model fusion-driven approach for the prediction of frequency nadir. As the physics-driven part, a Simplified Prediction Model (SPM) based on power-frequency polynomial fitting is developed to quickly produce the frequency nadir. As the data-driven part, Back Propagation Neural Network (BPNN) is deployed to correct the errors of the SPM to achieve more accurate results. This serial integration scheme not only obtains the final prediction result with higher accuracy, but also meets the computational efficiency requirements of online prediction. Compared with existing integration-driven methods, SPM only focuses on the active power-frequency characteristics of the system, which retains the most critical effects and greatly reduces the dependence of BPNN on sample data quality. Case studies on a modified IEEE 39-bus system verify the effectiveness of the proposed approach.

Active protection scheme based on high‐frequency current for distribution networks with inverter‐interfaced distributed generators

AbstractWith the high penetration and flexible access of inverter‐interfaced distributed generators (IIDGs), it is gradually becoming difficult for traditional protection schemes to meet the requirements for the safe operation of distribution networks (DNs). Active protection schemes based on power electronic equipment provide a new approach. On the basis of the controllability of voltage source converters, a method for active high‐frequency signal injection and a selection principle for the corresponding control parameters are proposed. Considering the impact of T‐connected load branches on the protected line, the high‐frequency current characteristics at the three terminals during internal and external faults are analysed. On this basis, an active protection scheme based on high‐frequency current is proposed for DNs with IIDGs. The performance of the proposed scheme is verified via PSCAD/EMTDC simulation software. The test results show that the proposed scheme can reliably trip during internal faults and identify faulty phases, which has better endurance to fault resistance.

Enhanced DC surface discharge characteristics of epoxy composites treated by dielectric barrier discharge plasma fluorination and its mechanisms

Surface flashover is a destructive high-voltage discharge phenomenon greatly limiting the update of modern power electronic and electrical equipment. Surface plasma treatment is a high-energy, eco-friendly, and convenience method, it changes the surface properties and owns potential to improve flashover voltage. In the present work, plasma fluorination (PF) technique are used to treat EP/Al2O3 composites, surface morphology, element and bonds content, surface trap, conductivity, charging, and DC flashover voltage are tested and simulated, the effects of plasma on surface discharge are explained through the investigation from microscopic molecular reactions to macroscopic flashover characteristics. It indicates the 20 min PF modified sample exhibits the superior DC flashover performance, increasing by 17 % compare to untreated sample. During PF modification, the epoxy chains are degraded and fluorinated, the degradation rather than fluorination of molecular chains introduce large amounts of shallow traps into the composites, accelerating carriers’ migration and improving surface conductivity, causing surface charges to dissipate through surface conductance. Consequently, the surface electric field distortion degree reduces, and the subsequent gas ionization and plasma formation in the gas phase is suppressed, leading to the improvement of DC flashover voltage after PF modifications.

Sensor Fusion-Based Pulsed Controller for Low Power Solar-Charged Batteries with Experimental Tests: NiMH Battery as a Case Study

Solar energy is considered the major source of clean and ubiquitous renewable energy available on various scales in electric grids. In addition, solar energy is harnessed in various electronic devices to charge the batteries and power electronic equipment. Due to its ubiquitous nature, the corresponding market for solar-charged small-scale batteries is growing fast. The most important part to make the technology feasible is a portable battery charger and the associated controllers to automate battery charging. The charger should consider the case of charging to be convenient for the user and minimize battery degradation. However, the issue of slow charging and premature battery life loss plagues current industry standards or innovative battery technologies. In this paper, a new pulse charging technique is proposed that obviates battery deterioration and minimizes the overall charging loss. The solar-powered battery charger is prototyped and executed as a practical, versatile, and compact photovoltaic charge controller at cut rates. With the aid of sensor fusion, the charge controller is disconnected and reconnects the battery during battery overcharging and deep discharging conditions using sensors with relays. The laboratory model is tested using a less expensive PV panel, battery, and digital signal processor (DSP) controller. The charging behavior of the solar-powered PWM charge controller is studied compared with that of the constant voltage–constant current (CV–CC) method. The proposed method is pertinent for minimizing energy issues in impoverished places at a reasonable price.

A novel phaselet-based approach for fault detection and location in HVDC lines

Recently, the popularity of direct current (DC) transmission has surged due to a 30 % reduction in power electronics equipment costs over the last decade. High-Voltage Direct Current (HVDC) transmission lines experience fluctuations in both nominal and faulty states, posing challenges for fault location methods, particularly those based on traveling waves, resulting in imprecise outcomes with an average error margin of ±2 %. This paper investigates a novel fault detection and location approach utilizing wavelet and phaselet transforms. The proposed method focuses on traveling waves in HVDC transmission lines, where the phaselet transform effectively eliminates undesired fluctuations in line currents, improving fault detection accuracy by up to 15 %. By leveraging the traveling time in the faulty line, the exact fault location is calculated with an accuracy of 98.5 %, independent of transmission line parameters, making it applicable to any DC line. Additionally, the method's precision is minimally affected by fault resistance, with <0.5 % deviation even in nonlinear scenarios. Sensitivity analysis conducted on various parameters, including mother wavelet patterns, suggests the optimal solution for each fault type, enhancing detection speed by 20 %. The proposed method is validated using the Cigre HVDC benchmark, confirming its accuracy, speed, and robustness in fault detection and location in HVDC lines. The main contribution of this paper is an accurate, fast, and robust phaselet-based algorithm that reduces fault location errors to <1 % and is applicable to all types of bipolar and monopolar HVDC systems, delivering reliable results for both ground and line faults.

Current Research Status and Future Trends of Vibration Energy Harvesters.

The continuous worsening of the natural surroundings requires accelerating the exploration of green energy technology. Utilising ambient vibration to power electronic equipment constitutes an important measure to address the power crisis. Vibration power is widely dispersed in the surroundings, such as mechanical vibration, acoustic vibration, wind vibration, and water wave vibration. Collecting vibration energy is one of the research hotspots in the field of energy. Meanwhile, it is also an important way to solve the energy crisis. This paper illustrates the working principles and recent research progress of five known methods of vibrational energy harvesting, namely, electromagnetic, piezoelectric, friction electric, electrostatic, and magnetostrictive vibrational energy harvesters. The strengths and weaknesses of each method are summarised. At the end of the article, the future trends of micro-nano vibrational energy collectors are envisioned.

Junction temperature monitoring of silicon carbide MOSFET based on turn‐off voltage spike

AbstractBecause of the advantages of high switching speed, silicon carbide (SiC) devices are widely used in high‐power power electronic equipment. Real‐time monitoring of junction temperature is very important for the safe operation of equipment. There have been many studies on traditional junction temperature monitoring methods based on Si IGBT, but the dynamic characteristics of SiC MOSFETs are changed due to their different physical structure and parasitic parameters, which make the traditional methods no longer applicable. In this paper, the junction temperature can be extracted from the switching process of SiC MOSFET by using the turn‐off voltage spike as the index of thermosensitive electrical parameter (TSEP). In addition, the effect of working voltage, current, and different materials on turn‐off voltage spike is also studied. The simulation platform of Ansys/Simplorer and the experimental test platforms are built, and the theory of junction temperature detection based on turn‐off voltage spike is verified. The simulation and experimental results show that turn‐off voltage spike is a feasible TSEP, which can be used to extract junction temperature of SiC MOSFET with good linearity and instantaneity.

A Novel Contact Resistance Model for the Spherical–Planar Joint Interface Based on Three Dimensional Fractal Theory

In order to obtain the contact resistance of relay contacts more accurately, a novel contact resistance model for the spherical–planar joint interface is constructed based on the three-dimensional fractal theory. In this model, three-dimensional fractal theory is adopted to generate a rough surface at microscopic scale. Then, using contact mechanics theory, the deformation mechanism of asperities on rough surfaces is explored. Combined with the distribution of asperities, a contact resistance model for the planar joint interface is established. Furthermore, by introducing the surface contact coefficient, cross-scale coupling between the macro-geometric configuration and micro-surface topography is achieved, and a contact resistance model for the spherical–planar joint interface is constructed. After that, experiments are conducted to verify the accuracy of the proposed model, and the maximum relative error of the proposed model is 8.44%. Ultimately, combining numerical simulation analysis, the patterns of variation in contact resistance influenced by factors such as macroscopic configuration and microscopic topography are discussed, thereby revealing the influence mechanism of the contact resistance for the spherical–planar joint interface. The proposed model provides a solid theoretical foundation for the optimization of relay contact structures and improvements in manufacturing processes, which is of great significance for ensuring the safe and stable operation of power systems and electronic equipment.

Experimental investigation on the thermal performance of a large-size aluminum vapor chamber for multi-point heat sources

Abstract With the development of electronic information technology, the integration and power of electronic equipment continue to increase. As an efficient heat transfer element, vapor chambers are widely used in the field of heat dissipation of electronic devices. However, greater challenges have been posed in terms of higher heat dissipation capacity, larger size, and lighter weight. Therefore, a large-scale aluminum vapor chamber with a size of 340 mm×295 mm ×7.5 mm is designed for the heat dissipation of multi-point array heat sources. Multiple parallel porous ribs are sintered to form capillary wicking channels and vapor diffusion paths, which efficiently transfer the heat from the middle of the vapor chamber to the cold plate on the two sides. The transient working characteristics and heat dissipation performance under different working conditions are experimentally investigated. The results show that there is obvious temperature instability, which can be suppressed by the tilt of the vapor chamber and the increase of the heating power. Under the tilt condition, the temperature rises in the vertical direction due to the influence of gravity, while the inclination angle has basically no effect. The vapor chamber can work stably at the total heating power of 2100 W with the smallest thermal resistance 0.03 °C/W. The single-point heat flux can reach 7.3W/cm2 for the 128 heat sources. Compared to a traditional vapor chamber, the proposed aluminum vapor chamber provides a thermal management solution for large-size electronic devices with multiple heat sources.

Knacks of marine predator heuristics for distributed energy source-based power systems harmonics estimation

The power system incorporates renewable energy resources into the main utility grid, which possesses low or no inertia, and these systems generate harmonics due to the utilization of power electronic equipment. The precise and effective assessment of harmonic characteristics is necessary for maintaining power quality in distributed power systems. In this paper, the Marine Predator Algorithm (MPA) that mimics the hunting behavior of predators is exploited for harmonics estimation. The MPA utilizes the concepts of Levy and Brownian motions to replicate the movement of predators as they search for prey. The identification model for parameter estimation of harmonics is presented, and an objective function is developed that minimizes the difference between the real and predicted harmonic signals. The efficacy of the MPA is assessed for different levels of noise, population sizes, and iterations. Further, the comparison of the MPA is conducted with a recent metaheuristic of the Reptile Search Algorithm (RSA). The statistical analyses through sufficient autonomous executions established the accurate, stable, reliable and robust behavior of MPA for all variations. The substantial enhancement in estimation accuracy indicates that MPA holds great potential as a strategy for estimating harmonic parameters in distributed power systems.

Prediction of IGBT Gate Oxide Layer's Performance Degradation Based on MultiScaleFormer Network.

Insulated gate bipolar transistors (IGBTs) are widely used in power electronic devices, and their health prediction problems have attracted much attention in the field of power electronic equipment health management. The performance degradation of IGBT gate oxide is one of the most important failure modes. In order to analyze this failure mechanism and the ease of implementation of a monitoring circuit, the gate leakage current of IGBTs was selected as the fault precursor parameter for the degradation of their gate oxide performance, and feature selection and fusion were carried out by using time domain characteristic analysis, grayscale correlation, Mahalanobis distance, Kalman filter, and other methods. Thus, a health indicator was obtained to characterize the degradation of IGBT performance, which was used to indicate the degree of aging of the IGBT gate oxide layer. In this paper, we propose an improved degradation prediction model called MultiScaleFormer, inspired by advanced design ideas of the iTransformer network architecture, combined with the health parameters of IGBTs to construct a degradation prediction model for the IGBT gate oxide layer. MultiScaleFormer showed the highest fitting accuracy compared with the Long Short-Term Memory (LSTM), Convolutional Neural Network (CNN), Support Vector Regression (SVR), Gaussian Process Regression (GPR), CNN-LSTM, and Transformer models in our experiment. The mean absolute error (MAE) of the MultiScaleFormer prediction was as low as 0.0087. Extraction of the health indicator and the construction and verification of the degradation prediction model were carried out on the dataset released by the NASA-Ames Laboratory. These results demonstrate the feasibility of the gate leakage current as a fault precursor parameter for IGBT gate oxide failure, and the feasibility and accuracy of the MultiScaleFormer prediction model for IGBT performance degradation.

Improved Design of a SiC MOSFET Gate Drive with Crosstalk Suppression Capability

For high-frequency switching applications, silicon carbide (SiC) devices are more suitable than silicon-based devices, which is conducive to improving the efficiency and power density of power electronic equipment. However, as the switching frequency increases, the influence of parasitic parameters on the switching characteristics of devices becomes increasingly apparent. When SiC metal-oxide-semiconductor field-effect transistors (MOSFETs) are applied in bridge circuits, the crosstalk problem easily occurs with the complementary conduction of upper and lower transistors, which seriously limits the promotion of SiC MOSFETs. However, the existing crosstalk suppression drive circuit tends to increase the switching loss, switching delay, and control complexity; therefore, a gate drive with crosstalk suppression capability is proposed. In this paper, the gate drive has two features: a negative voltage to shut down the SiC MOSFET; and an adjustment of the gate-source equivalent impedance. To accomplish this goal, the mechanism of crosstalk voltage generation is analyzed. Furthermore, the operation principle of the gate drive is analyzed, and the parameters of the gate drive are designed. Eventually, the proposed gate drive is verified by an LTspice simulation and experimental platform. The results prove that the gate drive can suppress the crosstalk voltage without affecting the switching speed.

Harmonic voltage measurement based on capacitive equipment dielectric equivalent model and responding current

Abstract With the increasing proportion of new energy and the power electronic equipment in the power grid, accurate measurement of harmonic voltage has become increasingly important for power quality monitoring. In order to solve the problem of high-precision measurement of harmonic voltage in the power grid, this manuscript proposes a high-precision harmonic voltage measurement method based on the dielectric equivalent model (DEM) of capacitive equipment and its responding current. Based on DEM, a voltage-current transfer function of the capacitive device is established, and harmonic voltage is reconstructed with the responding current. Considering the dielectric relaxation characteristics of capacitive device other than a pure capacitor model, this manuscript analyzes the fitting performance of different equivalent capacitance models and improves the traditional pure capacitance model to a more suitable DEM for harmonic voltage reconstruction. The DEM parameters of capacitive devices are obtained through the frequency domain spectroscopy (FDS) and intelligent parameter identification algorithms, which improved the measurement accuracy of harmonic voltage and reduced computational complexity. The harmonic voltage testing platform is established to test the simulated high-voltage harmonics and the harmonic voltage of the actual grid voltage. The results show that the proposed harmonic voltage measurement method can meet the high-precision reconstruction of harmonic voltage in the frequency range of 50~2500Hz, and the system testing error with sensors is less than 2%. The testing accuracy is higher than traditional voltage transformers and testing systems based on pure capacitance models.

Influence of the foam-fin structure on the thermal performance of a coupled phase change liquid cooling module

Effective thermal management is key to ensuring the reliable operation of high power electronic equipment. In this study, the strategy of phase transition and liquid cooling coupling applied to transient high power electronic equipment has been examined. In order to improve the performance of the phase changing material (PCM) in temperature control, the effects of the coupling structure have been addressed with a consideration of fin, copper foam (CF), graphite foam (GF), fin-copper foam (FCF) and fin-graphite foam (FGF) structures in heat dissipation. In this study, pure paraffin wax (PPW) was used as phase change material to prepare heat sinks based on the above five structures. The experimental study investigates the impact of different thermal conductivity strategies on temperature control characteristics, with a focus on cold capacity recovery and the combined phase change and liquid cooling, using pure paraffin wax module as a reference. The results have revealed that the fin-foam coupling structure delivers a better PCM performance than the single fin or foam structure. Operating at a heating power of 10 W, 15 W and 20 W, the temperature control time of the FGF structure was increased by 13.6 %∼14.6 % relative to the GF structure. At 15 °C with flow rates of 1 L/min, 1.5 L/min, 2 L/min liquid cooling conditions, the cooling capacity recovery time was reduced by 18.8 %, 17.2 %, 19.7 %, respectively. In the phase-change liquid-cooling coupling temperature control experiment, the final temperature increase in the FGF system was 11.7 °C -15.2 °C lower than that of the GF system under the same water temperature and volume flow for a 50 W heat source. The incorporation of fins also enhanced the thermal conductivity strengthening capability of the copper foam and reduced the cold recovery time. Based on the comprehensive evaluation, the FGF structure demonstrates superior temperature control performance and cold recovery characteristics of PCM, making it an optimal strengthening method. Following closely are the FCF, GF, Fin and CF structures. Compared to pure paraffin modules, these five modules exhibit varying degrees of improvement in temperature control and cold capacity recovery efficiency. This study provides guidance for optimizing heat sink design based on PCM in electronic applications.

High Power Density Buck Boost DC/DC Converter Using SIC MOSFET

Abstract High power density is an advance in power electronics. Third generation wide-bandgap semiconductor devices (WBG SICs) offer significantly improved performance compared to standard silicon devices. SIC MOSFET is commonly used in power electronic equipment such as converters due to its low resistance, excellent thermal stability, and rapid switching speed. Increasing the switching frequency effectively reduces the circuit size. This article uses SIC MOSFET and STM32 single-chip MCU to design a high power density and higher frequency buck boost converter and establish a simulation model in LTspice. The driving circuit designed for SIC MOSFET is intended to maximize the converter’s reliability. Synchronous rectification applies to enhance the converter efficiency. Compared to other types of converters, the size of the converter is reduced, achieving the goals of lightweight and high power density of DC/DC converters.

An Equivalent Modeling Method for Wideband Magnetic Radiation Interference of Power-Electronic Equipment

As more and more new power electronics with high switching frequencies are used in power-electronic equipment on ships and other platforms, the wideband radiation that power-electronic equipment gives off could affect sensitive equipment on the platform. Therefore, it is crucial to accurately model and characterize its wideband radiation properties to predict the wideband field distribution near such equipment. The traditional equivalent dipole method is commonly used to model power-electronic equipment at a single frequency. It is difficult to apply this method to wideband applications, and the precision of equivalent dipole array modeling at each frequency is insufficient. Additionally, acquiring the near-field phase data necessary for comparable modeling through practical measurement is frequently difficult. To solve the above problems, this paper proposes an equivalent dipole hybrid modeling method for power-electronic equipment’s broadband radiation characteristics. Starting with the near-field data at finite frequency points in a wideband, the method employs a global optimization algorithm to find the best equivalent dipole array, which characterizes the power-electronic equipment’s radiation characteristics. Furthermore, the interpolation technique is used to predict the wideband radiation properties of power-electronic equipment. Finally, test and numerical examples demonstrate the method’s accuracy and effectiveness.

Dynamic phasor model of HVDC links for linear analysis of dynamic performance

This paper presents a linearized HVDC link model, which was implemented in PacDyn software and is applicable to dynamic performance studies of power electronic equipment considering electrical network electromagnetic transients, differently from electromechanical studies where the network dynamics is usually neglected. The proposed HVDC model was developed employing equivalent switching functions concepts and dynamic phasors. Simulations and results for small and large-scale test systems are presented. Model validation is performed through comparisons between results obtained by PacDyn and PSCAD. In sequence, there are practical examples of controller tunning considering adverse dynamic interaction mitigation between HVDC Link and electrical grid. The final results on a large-scale model of the Brazilian power system demonstrate that the proposed HVDC model can be used in actual engineering studies.