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Chinese Physics B 2015年第10期24卷 166-171页

作者：焦重庆李月月 state key laboratory of alternate Electrical power system with renewable energy sources North China Electric Power University

According to the reciprocity principle, we propose an efficient model to compute the shielding effectiveness of a rectangular cavity with apertures covered by conductive sheet against an external incident electromagnetic wave. This problem is converted into another problem of solving the electromagnetic field leakage from the cavity when the cavity is excited by an electric dipole placed within it. By the combination of the unperturbed cavity field and the transfer impedance of the sheet, the tangential electric field distribution on the outer surface of the sheet is obtained. Then, the field distribution is regarded as an equivalent surface magnetic current source responsible for the leakage field. The validation of this model is verified by a comparison with the circuital model and the full-wave simulations. This time-saving model can deal with arbitrary aperture shape, various wave propagation and polarization directions, and the near-field effect.

关键词： electromagnetic shielding electromagnetic leakage apertured cavity conductive material

Resonance suppression and electromagnetic shielding effectiveness improvement of an apertured rectangular cavity by using wall losses

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Chinese Physics B 2013年第8期22卷 404-409页

作者：焦重庆朱弘钊 state key laboratory of alternate Electrical power system with renewable energy sources North China Electric Power University

The cavity-mode resonance effect could result in significant degradation of the shielding effectiveness （SE） of a shielding enclosure around its resonance frequencies. In this paper, the influence of coated wall loss on the suppression of the resonance effect is investigated. For this purpose, an equivalent circuit model is employed to analyze the SE of an apertured rectangular cavity coated with an inside layer of resistive material. The model is developed by extending Robinson＇s equivalent circuit model through incorporating the effect of the wall loss into both the propagation constant and the characteristic impedance of the waveguide. Calculation results show that the wall loss could lead to great improvement on the SE for frequencies near the resonance but almost no effect on the SE for frequencies far away from the resonance.

关键词： electromagnetic shielding rectangular cavity wall losses resonance effect

Improved Coordinated Control Approach for Evolved CCC-HVDC system to Enhance Mitigation Effect of Commutation Failure

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Journal of Modern power systems and Clean energy 2021年第2期9卷 338-346页

作者： Chunyi Guo Bo Liu Chengyong Zhao state key laboratory of alternate Electrical power system with renewable energy sources(North China Electric power University) BeijingChina

The evolved capacitor commutated converter(ECCC),embedded with anti-parallel thyristors based dual-directional full-bridge modules(APT-DFBMs),can effectively reduce commutation failure(CF)risks of line-commutated converter-based high voltage direct current(HVDC)and improve the dynamic responses of capacitor-commutated converterbased *** paper proposes an improved coordinated control strategy for ECCC with the following improvements:(1)under normal operation state,series-connected capacitors can accelerate the commutation process,thereby reducing the overlap angle and increasing the successful commutation margin;(2)under AC fault conditions,the ability of ECCC to mitigate the CF issue no longer relies on the fast fault detection,since the capacitors inside the APT-DFBMs can consistently contribute to the commutation process and further reduce the CF probability;(3)the inserted capacitors can output certain amount of reactive power,increase the power factor,and reduce the required reactive power compensation ***,the proposed coordinated control approach is presented in detail,and the extra commutation voltage to mitigate the CFs provided by the proposed control approach and an existing approach is ***,the mechanism of the improved control approach to accelerate commutation process and improve the power factor is analyzed ***,the detailed electromagnetic transient(EMT)simulation in PSCAD/EMTDC is conducted to validate the effectiveness of the proposed coordinated *** results show that the proposed approach can present a further substantial improvement for ECCC,especially enhancing the CF mitigation effect.

关键词： Evolved capacitor commutated converter(ECCC) coordinated control commutation failure power factor

Analysis for magnetic field disturbance of modular multilevel converter based high voltage direct current(MMC-HVDC)converter valve

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High Voltage 2023年第1期8卷 91-101页

作者： Lei Qi Muxue Wang Xiangyu Zhang Hong Shen Hongyu Wang Chongqing Jiao state key laboratory of alternate Electrical power system with renewable energy sources North China Electric Power UniversityBeijingChina

The standardised design and operational reliability enhancement of the flexible DC converter valve are impending with the construction of high shares of renewables and power electronics power system.A power frequency magnetic field calculation model able to obtain the electromagnetic disturbance at the submodule(SM)drive board during normal operation of a flexible DC converter valve is *** of SMs with complex structures in a converter valve tower are simplified by the equivalent to the line current to fulfil calculation accuracy *** addition,a random function is employed to simulate the non-sequential switching process of the *** comparing the calculated results with the measured data obtained from the SM equivalent operation experiment of 2200 V/2150 A,the validity of the calculation model is *** to the final calculations,the influence of non-sequential switching cannot be ignored when recognising the time-domain distribution features of the power frequency magnetic field of the drive ***,engineering design can be guided only by the power frequency magnetic field intensity of the drive board calculated based on SM’s full removal in the valve tower.

关键词： disturbance converter magnetic

Space charge characteristics of silicone elastomer for device packaging under positive square wave voltage

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High Voltage 2023年第2期8卷 401-411页

作者： Jinqiang Zhang Xuebao Li Zhibin Zhao Xiang Cui state key laboratory of alternate Electrical power system with renewable energy sources North China Electric Power UniversityBeijingChina

With the rapid development of power electronic devices towards high voltage and power,the insulation challenges faced by devices have attracted widespread *** elastomer is widely used in device packaging as one insulating material,and the study of its insulating properties is helpful to the reliable operation of *** this end we obtained the space charge characteristics of silicone elastomer under positive square wave voltage by using the pulse-electroacoustic(PEA)*** based on the existing research and IEC standards,the selection criteria of the resistance and capacitance parameters of a PEA system for space charge measurement under square wave voltage are *** this experimental system,the space charge distribution under the positive square wave voltage with different waveform parameters is obtained,and the influences of the waveform parameters on the space charge accumulation are *** amounts of charges under the action of square wave voltage with different waveform parameters are calculated,and the influences of waveform parameters on the amounts of charges are *** addition,the reasons for the difference in the accumulation of positive and negative charges are explained through Schottky injection model,the synthesis reaction and the infrared spectrum of the silicone elastomer.

关键词： charge wave characteristics

A DC Chopper Topology to Mitigate Commutation Failure of Line Commutated Converter Based High Voltage Direct Current Transmission

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Journal of Modern power systems and Clean energy 2020年第2期8卷 345-355页

作者： Chunyi Guo Bo Liu Chengyong Zhao the state key laboratory of alternate Electrical power system with renewable energy sources North China Electric Power UniversityBeijingChina

To reduce the probability of commutation failure(CF)of a line commutated converter based high-voltage direct current(LCC-HVDC)transmission,a DC chopper topology composed of power consumption sub-modules based on thyristor full-bridge module(TFB-PCSM)is ***,the mechanism of the proposed topology to mitigate CF is analyzed,and the working modes of TFB-PCSM in different operation states are ***,the coordinated control strategy between the proposed DC chopper and LCC-HVDC is designed,and the voltage-current stresses of the TFB-PCSMs are ***,the ability to mitigate the CF issues and the fault recovery performance of LCC-HVDC system are studied in PSCAD/*** results show that the probability of CF of LCC-HVDC is significantly reduced,and the performances of fault recovery are effectively improved by the proposed DC chopper.

关键词： Line commutated converter based high-voltage direct current(LCC-HVDC)transmission DC chopper power consumption sub-module based on thyristor full-bridge module(TFB-PCSM) commutation failure(CF) fault recovery capability

The study of disturbance sources energy size identification based on free energy theory

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Science China(Technological Sciences) 2018年第2期61卷 242-249页

作者： bi tianshu qin junda state key laboratory of alternate electrical power system with renewable energy sources north china electric power universityBeijing 102206China

The influence of power system disturbance on safety and stability is serious. Therefore, it is very important to identify the disturbance quickly and accurately. However, until now there is no unilbrm standard evaluation of disturbances on the energy impact strength, also no appropriate method to quantitatively and quickly assess the size of the disturbance energy. In this paper, the relationship between energy enthalpy and free energy in thermodynamics field is introduced into the description of disturbance free energy. And a new method based on energy entropy theory is proposed. In order to analyze the energy characteristics of various types of disturbances in power systems, an amended method of energy entropy is proposed. The free energy of each disturbance is described. Finally, the proposed theory is validated using the standard IEEE 39-bus system. The disturbance free energy is calculated under 5 kinds of disturbances. The proposed method provides a new idea to analyze the disturbance propagation and describe the impact strength of disturbance.

关键词： free energy disturbance identification energy identification energy entropy

Resilience-oriented Restoration Strategy by Offshore Wind power Considering Risk

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CSEE Journal of power and energy systems 2023年第6期9卷 2052-2065页

作者： Junjie Rong Ming Zhou Gengyin Li the state key laboratory of alternate Electrical power system with renewable energy sources North China Electric Power UniversityBeijing 102206China

Global climate changes have created intense naturaldisasters such as typhoons, which may cause serious damage topower systems. As an emerging renewable energy resource, offshore wind power has great potential in power systems resilienceenhancement with its rapid start-up capability and developmentof anti-typhoon technology. In this paper, a restoration strategyby offshore wind power considering risk is proposed to speedup the restoration process and enhance system resilience. Specifically, a failure risk model of an individual wind turbine andthen the whole wind farm is built for predicting severe weather’simpact, with focus on failure probability. Further, a quantificationmodel of resilience enhancement and risk cost, based on customerinterruption cost assessment method, is introduced. Then, a twostage optimized decision-making model is proposed to solve thescheme of offshore wind power and conventional power unitsin load restoration process. Case studies are undertaken on amodified IEEE RTS-79 system and results indicate the proposedrestoration strategy can shorten duration of restoration andreduce customers’ economic losses meanwhile ensuring systemsafety.

关键词： Load restoration offshore wind power optimized decision-making resilience enhancement risk

Time-domain Finite Element Method for Transient Electric Field and Transient Charge Density on Dielectric Interface

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CSEE Journal of power and energy systems 2022年第1期8卷 143-154页

作者： Teng Wen Xiang Cui Xuebao Li Hao Ma Zhibin Zhao state key laboratory of alternate Electrical power system with renewable energy sources North China Electric Power UniversityBeijing 102206China

This paper is devoted to solving the transient electric field and transient charge density on the dielectric interface under the electroquasistatic(EQS)field conditions with high *** proposed method is suitable for both 2-D and 3-D ***,the governing equations represented by scalar electric potential are discretized by the nodal finite element method(FEM)in space and the finite difference method in ***,the transient constrained electric field equation on the boundary(TCEFEB)is derived to calculate the normal component of the transient electric field intensities on the Dirichlet boundary and dielectric interface as well as the transient charge density on the dielectric ***,a 2-D numerical example is employed to demonstrate the validity of the proposed ***,the comparisons of the numerical accuracy of the proposed method in this paper with the existing FEMs for electric field intensity and charge density on the dielectric interface are *** results show that the numerical accuracy of the proposed method for calculating the normal component of transient electric field intensities on the Dirichlet boundary and dielectric interface as well as the transient charge density on the dielectric interface is close to that of nodal electric potential and an order of magnitude higher than those of existing FEMs.

关键词： Electroquasistatic field composite insulation structure transient constrained electric field equation on the boundary finite element method interface charge time-domain

Characterization of Electric Field Distribution Within High Voltage Press-packed IGBT Submodules Under Conditions of Repetitive Turn-on and Turn-off

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CSEE Journal of power and energy systems 2022年第2期8卷 609-620页

作者： Teng Wen Xiang Cui Sijia Liu Xuebao Li Zhibin Zhao state key laboratory of alternate Electrical power system with renewable energy sources North China Electric Power UniversityBeijing 102206China

The high-voltage high-power press-packed IGBT(PPI)devices are the key component of the DC transmission apparatus.A PPI device is composed of several PPI *** general,the PPI submodule works in a state of repetitive turn-on and turn-off,and the corresponding working voltage is the positive periodic square waveform(PPSW)voltage,which is much different from the conventional AC or DC *** addition,insulation capability is one of the most critical challenges in the design and fabrication of PPI *** improve the insulation capability of the device,composite insulation structures with multiple dielectrics are usually *** the PPSW voltage,it is essential to analyze the transient electric field to solve the insulation challenge of the PPI ***,the electric field of the PPI is often calculated under the electrostatic field or DC ***,the transient characteristics of the electric field are ***,this paper focuses on the analysis of the transient characteristics of the electric field of the PPI submodule under the PPSW *** influences of the waveform parameters of the PPSW voltage on the transient characteristics are demonstrated in *** study is significant for the insulation analysis and design of the PPIs.

关键词： Electroquasistatic field FEM IGBT positive periodic square waveform voltage transient electric field