23 December 2025, Volume 44 Issue 12

    

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Treatise and Report
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  Characteristic analysis of AC excitation variable frequency drive system for Mach-level very-high-speed electromagnetic propulsion

  XU Zehao，LI Zixin，SUN Baiyan, GAO Fanqiang，CUI Xiang，LI Yaohua

  Advanced Technology of Electrical Engineering and Energy. 2025, 44(12): 1-10. https://doi.org/10.12067/ATEEE2504055

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  Conventional electromagnetic propulsion system usually drives high power linear motor directly by full-capacity inverters, which limits the scalability and speed range of the system due to the high cost of the full-capacity inverters. This paper proposes a novel AC excitation variable frequency drive system to reduce the inverter capacity in Mach-level very-high-speed electromagnetic propulsion system. The proposed drive system provides variable voltage with variable frequency by inverter during low-speed operation, whereas in high-speed operation the proposed drive system provides variable voltage with variable frequency by AC excitation machine. In this paper, an analysis of the relationship of inverter capacity and linear motor capacity is investigated and a system parameters design method is proposed to realize a minimum inverter capacity. Besides, the control strategy of AC excitation variable frequency drive system is analyzed. A simulation model of AC excitation variable frequency drive system is established in PSIM environment. According to the simulation results, the control strategy is effective and the nominal capacity of the inverter has a significant reduction compared with the nominal capacity of the linear motor.
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  A flyback micro-inverter with active clamp and power decoupling

  FANG Longjue, LIN Guoqing

  Advanced Technology of Electrical Engineering and Energy. 2025, 44(12): 11-19. https://doi.org/10.12067/ATEEE2411034

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  A flyback micro-inverter with active clamp and power decoupling circuit is proposed. This circuit incorporates an auxiliary winding on the primary side of the transformer to transfer the power double-frequency pulsation to an energy storage capacitor, thereby reducing the low-frequency ripple in the input current and decreasing the capacitance of the input filter capacitor. Additionally, this energy storage capacitor serves as a clamping capacitor, absorbing the leakage inductance energy of the transformer and enabling zero-voltage switching (ZVS) of the main switch. This paper provides a detailed analysis of the circuit’s operating principle and control strategy, along with the design process for key parameters. An 80W micro-inverter prototype was built for experimentation, and the experimental results confirm the feasibility of the proposed scheme.
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  Optimization study of losses in large horizontal evaporatively cooled hydro generators

  LI Shuai，DU Fangmian, WANG Yu, RUAN Lin

  Advanced Technology of Electrical Engineering and Energy. 2025, 44(12): 20-27. https://doi.org/10.12067/ATEEE2410009

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  With the continuous increase in the unit capacity of bulb-type units, the demand for efficient cooling is becoming more and more intensive. In order to solve the heat generation problem of large-capacity bulb-type hydro generators, this paper proposes a self-circulating evaporative cooling system based on a ring-shaped cold plate as its horizontal structure. A matching ring-shaped cold plate structure was designed based on a 50 MW bulb-type hydro generator. The relationship between the physical properties of the cold plate, the wall thickness and its layout between rows, and the overall length of the motor and the stator loss of the motor is analyzed. The comparative analysis results show that, on the premise of ensuring the necessary circulation characteristics of the evaporative cooling working fluid, when the wall thickness of the annular cold plate is reduced to less than 10mm, the influence of cold plate losses on the overall motor losses can be ignored. The research results of this paper may provide some theoretical support for large-capacity evaporative cooling tubular hydro generators, and may also provide reference for the design methods of other annular cold plate systems with liquid cooling.
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  Optimization study on corona-proof structure of stator wire rod end of large-capacity hydro generator

  HUANG Jiaxin，ZOU Maojuan, CHEN Jinxiu, LIU Feihui, BAI Yong, ZENG Yuhao

  Advanced Technology of Electrical Engineering and Energy. 2025, 44(12): 28-39. https://doi.org/10.12067/ATEEE2410025

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  The end of the stator bars in large hydro-generators represents a weak link of the unit’s insulation system. The anti-corona performance imposes limitations on the further expansion of the unit’s capacity and voltage. At present, a three-segment nonlinear anti-corona structure is commonly employed at the ends of large-capacity and high-voltage units, which can satisfy the anti-corona requirements of units under normal environmental conditions. However, in high-altitude environments, the required value of the corona inception voltage for the stator bars increases, so that a design solution with an enhanced anti-corona capability is essential to ensure the long-term safety, and stable operation of the units. In light of this, the influence law of the design parameters of the anti-corona layer on the anti-corona performance is explored, and the optimized design scheme is proposed. First, a three-dimensional parametric electromagnetic simulation model of the end of the stator bar is established. Then, simulation calculations are carried out to analyze the electric-field distribution of the anti-corona layer, and the sensitivity of various design parameters to the anti-corona performance is explored. The key influencing factors for anti-corona design are identified, and an optimized design scheme is proposed based on the genetic algorithm. The research findings indicate that parameters such as the nonlinear coefficient of the anti-corona layer, the low resistance intrinsic conductivity, the intrinsic conductivity of the nonlinear anti-corona layer, and the thickness of the anti-corona layer have a significant impact on the anti-corona performance. By using the genetic algorithm, an improved design scheme with superior anti-corona effects can be obtained. Compared with the initial scheme, the maximum electric-field strength of the anti-corona layer of the optimized scheme is reduced by 34.69%. This research provides valuable references for the anti-corona optimum design of the stator bar ends.
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  A hybrid compensation system compound control strategy based on adaptive active damping

  LI Zhijun, WANG Yaxin, LEI Huilin

  Advanced Technology of Electrical Engineering and Energy. 2025, 44(12): 40-49. https://doi.org/10.12067/ATEEE2403011

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  In order to improve the quality of power supply and the ability of stable operation of power system, the method of additional damping is usually used to suppress the harmonic resonance generated by the system. Compared with passive damping, the active damping strategy not only has well harmonic suppression effect, but also has the advantages of low loss and easy realization, so it has been widely used in recent years. However, the traditional active damping strategy mainly adopts the fixed control parameter design, which may cause the harmonic resonance problem when the working condition changes greatly. To solve this problem, based on the compound control strategy composed of harmonic compensation and resonance suppression in hybrid compensation system, an adaptive additional active damping composite control strategy is proposed in this paper. Firstly, we establish the parallel resonance equivalent model of the hybrid compensation system, and analyze the shortcomings of the traditional compound control strategy. On this basis, the harmonic voltage at PCC point is extracted by the second-order generalized integrator-frequency lock loop (SOGI-FLL), and the harmonic resonance suppression in the power supply system is designed and realized by adapting the parameters of the resonant suppression controller with the method of harmonic content limitation. Finally, the feasibility and effectiveness of the proposed method are verified by simulation experiments.
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  Transient stability analysis for PLL-based DFIG system in DC-link voltage control timescale

  HUANG Fei, LUO Yi, LIAO Qinglong, ZHAO Junguang, CHEN Shiyue, YAO Jun, OUYANG Jinxin, PENG Lian

  Advanced Technology of Electrical Engineering and Energy. 2025, 44(12): 50-59. https://doi.org/10.12067/ATEEE2403053

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  The interaction between the PLL-based DFIG and grid is significantly enhanced during grid short circuit fault, which easily leads to the LOS phenomenon. Therefore, in this article, the nonlinear large signal model in dc-link voltage control timescale of PLL-based grid-connected DFIG system is established. Then, the transient response characteristics of DC-link voltage under different operating conditions are analyzed, and the transient instability mechanism of DC-link voltage during LVRT is revealed. Secondly, the instability forms of DC-link voltage with the moving process of equivalent power angle are analyzed by the energy function, and the influence of the control parameter of the DC voltage control loop, the active current of the stator, and the slip on the transient response characteristics of DC-link voltage are analyzed, respectively. Finally, simulation results validate the effectiveness of theoretical analysis.
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  Quantitative analysis method for system strength of receiving end system based on Thevenin equivalence

  LI Shengnan, GUAN Chang, HE Tingyi, GAO Yuan, LI Chongtao

  Advanced Technology of Electrical Engineering and Energy. 2025, 44(12): 60-69. https://doi.org/10.12067/ATEEE2312025

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  For the quantitative analysis of system strength of receiving end system, the formula of short circuit ratio about the network structure parameters is obtained by deducing the Thevenin equivalent circuit of receiving end system. The power stability of Thevenin equivalent circuit is analyzed. It is shown that the value of short-circuit ratio is related to the equivalent impedance angle, the phase angle difference between grid-connected voltage and Thevenin equivalent potential, and the critical short-circuit ratio under some limit conditions is further discussed. The phase angle difference index is proposed to evaluate system strength of receiving end system, and the standard of dividing system strength of receiving end system by the phase angle difference index is given. The relationship between the phase angle difference index and the potential phase in the generator is analyzed. A simulation example is given to verify the validity of the phase angle difference index in evaluating system strength of receiving end system.
New Technolog Application
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  A hybrid discontinuous pulse width modulation strategy based on improved carrier for three-level inverter

  ZHAO Yonghui, LI Shangkun, YANG Xiaohua, ZHANG Fan, LI Jiajin

  Advanced Technology of Electrical Engineering and Energy. 2025, 44(12): 70-80. https://doi.org/10.12067/ATEEE2404057

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  In the application of three-level inverters, the problems of switching loss, common mode voltage and neutral point balance have attracted attention. In order to solve these problems, a hybrid discontinuous pulse width modulation strategy based on improved carrier is proposed. The discontinuous pulse width modulation strategy can be used as a solution to reduce switching losses, but the traditional discontinuous pulse width modulation strategies cause high common mode voltage. The proposed strategy in this paper adopts discontinuous pulse width modulation with low common mode voltage when neutral-point potential is balanced, and switches discontinuous pulse width modulation according to the midpoint potential when the midpoint potential is unbalanced to realize the midpoint potential balancing quickly. At the same time, the strategy is implemented based on improved carrier, which further reduces the common mode voltage ripple. Finally, the effectiveness of the proposed strategy is verified by simulation and experiment.
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  Short-term photovoltaic power forecasting based on deep learning algorithm

  HU Kun , DING Lei, GUO Nan, YU Dongsheng, DU Qingcan

  Advanced Technology of Electrical Engineering and Energy. 2025, 44(12): 81-106. https://doi.org/10.12067/ATEEE2407060

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  To enhance the accuracy and reliability of photovoltaic power prediction, this paper proposes a short-term photovoltaic irradiance prediction model based on the improved grey wolf optimizer (GWO), variational mode decomposition (VMD), particle swarm optimization (PSO), and long short term memory (LSTM). First, LGWO optimizes the key decomposition parameters K and α1 of VMD to construct a parameter optimization model. Then, LSTM predicts each mode parameter decomposed by the optimized VMD. Simultaneously, the improved PSO, using root mean square error as the objective function, optimizes the neural network parameters, including the number of LSTM hidden layers, LSTM iterations, and LSTM learning rate. This ultimately improves the prediction accuracy and reliability of the model. Finally, the output modeling and prediction analysis of a photovoltaic power plant in Gansu Province are conducted. The results show that, compared with the traditional LSTM prediction model, the proposed algorithm significantly improves the prediction accuracy.
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  Intelligent evaluation method for corrosion of transmission lines based on near-infrared spectroscopy

  WU Tian，WU Feng，QIU Zhonghua, XU Guowei, LI Peng，ZHU Shu，YAN Yanhong

  Advanced Technology of Electrical Engineering and Energy. 2025, 44(12): 107-120. https://doi.org/10.12067/ATEEE2504053

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  Steel core aluminum conductor (ACSR) operating under harsh environmental conditions for a long time is prone to severe corrosion, which can affect the safe and stable operation of the power grid. Therefore, a rapid and non-destructive method for conductor corrosion detection and intelligent evaluation is urgently needed. In this study, salt spray corrosion experiments were conducted to simulate transmission lines with different service durations. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) were used to observe the microstructure and analyze the element composition of new conductors and ACSR samples corroded for 48 h, 168 h, 336 h, 504 h, 720 h, 1 080 h, and 1 440 h respectively. The corrosion process and near-infrared spectral characteristics of the conductors were studied through microscopic analysis. Based on near-infrared spectroscopy (NIRS) technology, 720 sets of NIRS data were collected from conductors with varying degrees of salt spray corrosion. The obtained spectra were preprocessed using five methods: raw spectra, standard normal variate (SNV), multiplicative scatter correction (MSC), first derivative (D1), and asymmetric least squares (ALS) baseline correction. Five machine learning algorithms including Least Squares Support Vector Machine (LSSVM), Random forest (RF), partial least squares (PLS), K-nearest neighbors (KNN), and one-dimensional convolutional neural network (1D-CNN) were adopted to build classification models for corrosion degree recognition of ACSR. Model hyperparameters were optimized, and the classification performances of different modeling methods were comparatively analyzed. Experimental results indicate that near-infrared spectroscopy combined with machine learning models can effectively identify transmission lines with different corrosion states, providing a new approach and technical means for intelligent, non-destructive monitoring and evaluation of transmission line corrosion.