At present, the proportion of new energy access in the power system is increasing, and wind power is the key support for achieving energy security, green and low-carbon. Compared with overhead lines, power cables shows more than 20 times capacitance effect at the same voltage level. The result makes threats of the safe and reliable operation of offshore wind farms. Therefore, under AC grid connection of large-scale offshore wind farms, harmonic amplification factors and harmonic control methods are studied. Firstly, the harmonic state space model of high-voltage submarine cables and wind turbines of offshore wind farms is established. The harmonic amplification mechanism of offshore wind farms is analyzed, when they are connected to the grid. Then, harmonic suppression method with energy storage based APF(Active Power Filter) is analyzed. Finally, taking an offshore wind power grid-connected project as a case, the Simulink simulation model is built. The correctness and effectiveness of the theoretical analysis and method are verified.

The monitoring and fault prediction of power substations is one of the most important issues for critical nodes in future smart grid. An accurate prediction and real-time evaluation of the operational status for substation equipment can improve the stability and reliability of the power grid, reduce fault risks, and ensure the safe operation of the power system. In practice, however, the challenges such as the vast amount of data generated, the complexity of equipment interactions, and the need for timely and accurate fault detection pose significant hurdles. A novel method is proposed for state prediction and real-time evaluation of substation metering systems in this paper. It aims to predict state quantities and evaluate actual performance based on these predictions. By systematically sampling and preprocessing environmental and metering data, applying advanced clustering and imbalance learning techniques, and utilizing a decision tree-neural network hybrid algorithm, the proposed method addresses these challenges and enhances the accuracy and reliability of substation monitoring.

The real-time digital measurement technique is one of the most important issues for the smart power substation. To enhance the ability of substations to measure electric power and to address the challenges of substation metering data not being able to be centrally computed and the difficulty of handling massive multi-time frequency data computation at the power substation. A new digital power measurement method is proposed based on the Hanning window function to reduce the spectral leakage. The signal is converted from the time domain to the frequency domain using a fully-phase fast Fourier transform, and harmonic parameters are obtained through polynomial approximation-based single-spectrum interpolation. The calculation accuracy is enhanced by using a variable forgetting factor Recursive Least Squares algorithm, with coefficients updated through an adaptive linear combiner, significantly improving the speed and accuracy of the measurement for power substation.

With the increasing application of multi-port converters in electrical engineering, the design demand for multi-winding transformers is also rapidly rising. The complex electromagnetic parameters and structural optimization of multi-winding transformers have become a significant engineering challenge. Additionally, as the voltage levels of power electronic converters increase, managing the enhanced insulation levels of transformers while addressing the resulting increase in leakage inductance has become another critical issue. This study focuses on a three-winding transformer within a half-bridge LLC topology. Using an iterative approach that combines parameter calculation and software simulation, we optimize the transformer model by adjusting the winding arrangement to balance insulation and leakage inductance. The goal is to enhance the insulation capability of the transformer while achieving balanced leakage inductance between the two equivalent windings of the three-winding transformer. The effectiveness of the calculation method and design scheme is validated through simulation analysis and experimental testing.

Busbars integrate conductors, insulation, and terminals, facilitating the seamless connection of capacitors, power devices, and other components. A well-engineered busbar design minimizes parasitic elements, which is crucial for maintaining stable system performance. This article combines SiC MOSFET power modules, Si IGBT power modules, and discrete Si IGBT devices. By employing an optimization strategy, it refines the placement of components, the laminate sequencing, the positioning of terminals and capacitors to reduce the parasitic parameters of the current commutation loop(CCL), leading to an enhanced PCB laminated busbar design. To improve current-carrying capacity between the inner and outer PCB layers while minimizing inductance, via-in-pad technology is utilized. According to Q3D simulation, the parasitic inductance of the large CCLs are reduced to just 58.93 nH and 59.39 nH.

In order to limit the voltage spikes caused by leakage inductance of transformer, the RCD snubber is usually used in flyback converter. However, when the clamping diode in the RCD snubber turns off, the residual energy that stored in the intrinsic capacitance can’t be absorbed entirely, which causes the high frequency oscillations between the leakage inductance of the transformer and intrinsic capacitance. These oscillations will become new CM noise sources, and generate unexpected CM noises. In this paper, a ferrite bead is connected in series with the diode of the RCD snubber, and a RC buffer is connected in parallel with the MOSFET, in order to absorb the residual energy entirely. This kind of circuit is called RCD-L-RC snubber, and the goal of this paper is to analyze the RCD-L-RC snubber circuit operation and the CM EMI in a multi-winding flyback converter. Finally, the theoretical analysis is well verified by experiments.

Dynamic thermal monitoring at of IGBT modules is a key technology to enhancing the reliability of high-power converters. However, most existing thermal model-based methods suffer from temperature estimation errors due to variations in model parameters and inaccuracies in loss calculations. To address this issue, this paper proposes an adaptive Kalman filter-based 3-D thermal monitoring method for IGBT modules. Firstly, a 3-D reduced-order thermal model for the IGBT module is established, enabling real-time estimation of temperatures. Secondly, a feedback loop is introduced using an adaptive Kalman filter to correct the thermal model. Simulation results demonstrate that, when confronted with deviations in thermal model parameters and loss calculations, the proposed adaptive Kalman filter-based thermal monitoring method can improve temperature estimation accuracy compared to open-loop thermal models.

With the development of distributed photovoltaic industry, household photovoltaic and energy storage equipment has gradually become a research hotspot. The non-isolated inverter topology can cater well to the characteristics of miniaturization and compactness of household inverters. However, non-isolated inverters have problems of electromagnetic compatibility and stability due to common mode current in parasitic capacitors. Otherwise, power fluctuations of twice the fundamental frequency on the AC side will be coupled to the DC side. This paper presents a non-isolated inverter with common mode current suppression and active power decoupling.

Zero-voltage-switching(ZVS) is widely used to increase the efficiency of converters. It is influenced by some nonidealities, including the MOSFET’s junction capacitance and the dead-time. The buck converters may lose the ZVS operation when the junction capacitance incompletely charges or discharges during the dead-time. This paper aims to discuss the influence of nonlinear junction capacitance and dead-time on the ZVS region of buck converters and propose a method to get the boundary condition of ZVS, considering the interaction of these nonidealities. A 600V buck converter based on SiC MOSFET is built. The experimental results prove the correctness of the ZVS critical conditions with inductance and dead-time.

Hybrid Si/SiC switches(HyS) have garnered substantial attention owing to their cost-effectiveness and high efficiency. Nevertheless, their utilization poses challenges as conventional driving methods cannot accommodate their multifaceted control degrees of freedom. Consequently, exploring a driving method capable of implementing diverse control strategies is crucial for practical applications of HyS. To this end, this paper proposes a driving method for HyS based on SPWM modulation. The method can realize all kinds of control strategies of HyS while maintaining a simple peripheral circuit design. Furthermore, the method takes into account the effect of power factor so that the HyS converter is able to operate at power factor-1 to 1. The driving method proposed in this paper makes it possible for the HyS converter to be put into application.