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Analysis and Comparison of Two Wireless Battery Charger Arrangements for Electric Vehicles Giuseppe Buja, Rupesh K. Jha, Manuele Bertoluzzo, Mude K. Naik Chinese Journal of Electrical Engineering    2015, 1 (1): 50-57.   Abstract （102）      PDF       Knowledge map    The paper deals with wireless battery chargers (WBCs) for plug-in electric vehicles (PEVs) and analyzes two arrangements for the receiver of a series-series resonant WBC. The first arrangement charges the PEV battery in a straightforward manner through a diode rectifier. The second arrangement charges the PEV battery through the cascade of a diode rectifier and a chopper whose input voltage is kept constant. Figures of merit of WBCs such as efficiency and sizing factor of both the power source and the transmitter/receiver coils are determined. Afterwards, they are discussed and compared with reference to the case study of WBC for an electric city car. A proposal to optimize the efficiency of the second arrangement by a suitable selection of the chopper input voltage is presented. Measurements on the efficiency of the two arrangements are included to support the theoretical results. Reference | Related Articles | Metrics

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Novel Wind Power Grid-connection System Using Inductive Filtering Technology* Juan Ni, Sijia Hu, Yong Li, Jinjie Lin, Qianyi Liu, Peiyao Liu, Lihong Dong Chinese Journal of Electrical Engineering    2022, 8 (3): 102-111.   DOI: 10.23919/CJEE.2022.000029 Abstract （216）      PDF       Knowledge map    Herein, a novel wind power grid-connection system based on inductive filtering is proposed to improve grid-connection compatibility, and is implemented in a 50-MW real system. First, the topology and wiring configuration of the proposed system are discussed. Thereafter, an equivalent circuit and mathematical model are established to reveal the filtering characteristics and resonance damping mechanism of the proposed system. Finally, a 50-MW wind farm-based experimental study, which is conducted to validate the effectiveness and availability of the system is discussed. The experimental results show that the main harmonics, power factor, voltage fluctuation, and flicker satisfy national standards. Reference | Related Articles | Metrics

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Benefits of High-voltage SiC-based Power Electronics in Medium-voltage Power-distribution Grids* Fred Wang, Shiqi Ji Chinese Journal of Electrical Engineering    2021, 7 (1): 1-26.   DOI: 10.23919/CJEE.2021.000001 Abstract （457）      PDF       Knowledge map    Medium-voltage (MV) power electronics equipment has been increasingly applied in distribution grids, and high-voltage (HV) silicon carbide (SiC) power semiconductors have attracted considerable attention in recent years. This paper first overviews the development and status of HV SiC power semiconductors. Then, MV power-converter applications in distribution grids are summarized and the benefits of HV SiC in these applications are presented. Microgrids, including conventional and asynchronous microgrids, that can fully demonstrate the benefits of HV SiC power semiconductors are selected to investigate the benefits of HV SiC in detail, including converter-level benefits and system-level benefits. Finally, an asynchronous microgrid power-conditioning system (PCS) prototype using a 10 kV SiC MOSFET is presented. Reference | Related Articles | Metrics

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Robust Predictive Current Control of Induction Motors Based on Linear Extended State Observer Yongchang Zhang, Xing Wang, Haitao Yang, Boyue Zhang and Jose Rodriguez Chinese Journal of Electrical Engineering    2021, 7 (1): 94-105.   DOI: 10.23919/CJEE.2021.000009 Abstract （380）      PDF       Knowledge map    Model predictive current control can achieve fast dynamic response and satisfactory steady-state performance for induction motor (IM) drives. However, many motor parameters are required to implement the control algorithm. Consequently, if the motor parameters used in the controller are not accurate, the performance may deteriorate. In this paper, a new robust predictive current control is proposed to improve robustness against parameter mismatches. The proposed method employs an ultra-local model to replace the mathematical model of the IM. Additionally, to improve the control performance, a linear extended state observer is developed for disturbance estimation. Experimental tests confirm that satisfactory tracking performance can still be obtained although the motor parameters may not be accurately set in the controller. Reference | Related Articles | Metrics

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Comparative Analysis on the Stability Mechanism of Droop Control and VID Control in DC Microgrid* Gang Lin, Wei Zuo, Yong Li, Jiayan Liu, Shaoyang Wang, Pengcheng Wang Chinese Journal of Electrical Engineering    2021, 7 (1): 37-46.   DOI: 10.23919/CJEE.2021.000003 Abstract （388）      PDF       Knowledge map    Voltage resonance and fluctuation deteriorate the stability of DC microgrids (DC-MGs) and restrict their popularization. Conventional droop control cannot suppress voltage fluctuation and damp oscillations. Therefore, new control methods, namely, droop+filter control and virtual inertia and damping control, are proposed. These methods differ owing to the addition of low pass filter (LPF) and virtual inertia loop. In this study, the stability of these control methods is investigated comprehensively to understand their differences arising from the use of LPF and inertia loop as well as the underlying dynamic stability mechanism. The leading causes of voltage instability in DC-MGs regulated by droop control are first presented. Subsequently, control methods for solving this issue are compared and their simplified small-signal models are constructed. Based on eigenvalue analysis, the DC-MG is equivalent to a third-order system. Different control effects can be acquired by changing the control parameters and the location of the eigenvalues; furthermore, they can be used to understand the dynamic stability. Eigenvalue analysis can provide parameter design guidelines. Finally, the simulation results verify the validity of the theoretical analysis. Reference | Related Articles | Metrics

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Review of General Modeling Approaches of Power Converters* Dong Yan, Chenglin Yang, Lijun Hang, Yuanbin He, Ping Luo, Lei Shen, Pingliang Zeng Chinese Journal of Electrical Engineering    2021, 7 (1): 27-36.   DOI: 10.23919/CJEE.2021.000002 Abstract （389）      PDF       Knowledge map    The modeling approaches of power converters occupy an important position in power electronic systems and have made considerable progress over the past years. Continuous modeling approaches and linearization techniques are reviewed, including the state-space average model, generalized average model, averaged small-signal model, and describing function method. A Buck converter with PWM modulation and voltage-mode control is taken as an example to compare the advantages and disadvantages of different methods through simulation analysis. Moreover, the corresponding equivalent circuit with an intuitive physical meaning of state-space average model, generalized average model, and averaged small-signal model is given. The results point out that the generalized average model can improve the modeling accuracy based on the state-space average model. In the linearization techniques, the averaged small-signal model reflects accuracy at low frequencies, but introduces phase lag in the high-frequency region. The describing function method is derived from harmonic linearization, which takes into account the sideband effect and improves the modeling accuracy at high frequencies. Reference | Related Articles | Metrics

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Review of Inductance Identification Methods Considering Inverter Nonlinearity for PMSM* Qiwei Wang, Jiqing Xue, Gaolin Wang, Yihua Hu, Dianguo Xu Chinese Journal of Electrical Engineering    2024, 10 (2): 1-15.   DOI: 10.23919/CJEE.2023.000046 Abstract （2148）      PDF       Knowledge map    Permanent magnet synchronous motors (PMSMs) are widely used in high-power-density and flexible control methods. Generally, the inductance changes significantly in real-time machine operations because of magnetic saturation and coupling effects. Therefore, the identification of inductance is crucial for PMSM control. Existing inductance identification methods are primarily based on the voltage source inverter (VSI), making inverter nonlinearity one of the main error sources in inductance identification. To improve the accuracy of inductance identification, it is necessary to compensate for the inverter nonlinearity effect. In this study, an overview of the PMSM inductance identification and the related inverter nonlinearity self-learning methods are presented. Reference | Related Articles | Metrics

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Optimal Rotor Poles and Structure for Design of Consequent Pole Permanent Magnet Flux Switching Machine Wasiq Ullah, Faisal Khan, Muhammad Umair Chinese Journal of Electrical Engineering    2021, 7 (1): 118-127.   DOI: 10.23919/CJEE.2021.000011 Abstract （347）      PDF       Knowledge map    Permanent magnet flux switching machines (PMFSM) have attracted significant research interest and are considered as competent candidates when higher torque density is primary requirement. However, conventional PMFSMs uses excessive rare earth PM volumes which ultimately increases machine the machine weight and PM cost. Moreover, the PMs extended at the stator yoke results in stator leakage flux which degrades the performance. To suppress the leakage flux and diminish the PM volume, the consequent pole PMFSM (CPPMFSM) with flux bridges and barriers encompassing partitioned circumferential and radial magnetized PMs is proposed, thereby ensuring an alternate magnetic path for the working harmonics which improves the modulation effect and flux distribution. Moreover, the influence of the rotor pole number on seven different rotor structures namely, curved rotor, trapezoidal rotor, wide rotor tooth tip, wide rotor base width, rectangular segmented and eccentric rotors are investigated based on the electromagnetic performance and stress distribution. Finite element analysis (FEA) reveals that the 12S-13P CPPMFSM with a wider rotor base offers comparatively better electromagnetic performance. Compare to the conventional PMFSM, the proposed CPPMFSM reduces the PM volume which minimizes the overall machine cost and weight, suppresses the torque ripples by 16.49%, diminishes total harmonic distortion (THD) by 35.24% and decreases cogging torque by 32.88%. Furthermore, the torque and power density are enhanced by 7.028% and 7.025% respectively. Reference | Related Articles | Metrics

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Current Loop Disturbance Suppression for Dual Three Phase Permanent Magnet Synchronous Generators Based on Modified Linear Active Disturbance Rejection Control* Dezhi Xu, Hu Yao, Yang He, Wenxiang Zhao Chinese Journal of Electrical Engineering    2024, 10 (1): 101-113.   DOI: 10.23919/CJEE.2023.000018 Abstract （151）      PDF       Knowledge map    A modified four-dimensional linear active disturbance rejection control (LADRC) strategy is proposed for a dual three-phase permanent magnet synchronous generator (DTP-PMSG) system to reduce cross-coupling between the d and q axis currents in the d-q subspace and harmonic currents in the x-y subspace. In the d-q subspace, the proposed strategy uses a model-based LADRC to enhance the decoupling effect between the d and q axes and the disturbance rejection ability against parameter variation. In the x-y subspace, the 5th and 7th harmonic current suppression abilities are improved by using quasi-resonant units parallel to the extended state observer of the traditional LADRC. The proposed modified LADRC strategy improved both the steady-state performance and dynamic response of the DTP-PMSG system. The experimental results demonstrate that the proposed strategy is both feasible and effective. Reference | Related Articles | Metrics

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Design Optimization and Comparison of Linear Magnetic Actuators under Different Topologies* Zhijian Ling, Jinghua Ji, Tao Zeng, Wenxiang Zhao Chinese Journal of Electrical Engineering    2020, 6 (1): 41-51.   DOI: 10.23919/CJEE.2020.000003 Abstract （316）      PDF       Knowledge map    In this study, several types of linear actuators that adopt different permanent-magnet (PM) topologies are studied and compared. These linear actuators are based on the concept of PM magnetic screw transmission, which offers high force density, high reliability, and overload protection. Using different magnetic configurations and assembly methods, these linear actuators are designed and optimized for a fair comparison. Initially, based on the operating principle and maximum thrust force, the surface-mounted magnetic screw is described and optimized. Furthermore, the embedded magnetic screw, Halbach array magnetic screw, and field modulated magnetic screw are investigated and compared. Their electromagnetic performances, such as thrust force, torque, magnetic losses, and demagnetization effects are analytically assessed and verified using finite-element analysis. Finally, a prototype of the surface-mounted magnetic screw is developed to validate the predictions. Reference | Related Articles | Metrics

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Rotor Position Estimation for Single- and Dual- Three-Phase Permanent Magnet Synchronous Machines Based on Third Harmonic Back-EMF under Imbalanced Situation Jiaming Liu, Zi-Qiang Zhu Chinese Journal of Electrical Engineering    2017, 3 (1): 63-72.   Abstract （86）      PDF       Knowledge map    In this paper, an improved rotor position estimation strategy based on third harmonic back-EMF for single- and dual-three-phase permanent magnet synchronous machines (PMSMs) under imbalanced situation is proposed. Due to the imbalanced machine impedance, back-EMF or sensing resistor network, the measured triplen harmonic back-EMF will contain certain fundamental component distortion which may severely deteriorate the performance of rotor position estimation. With the aid of the fundamental component compensator, this distortion can be significantly compensated, and the rotor position estimation error can be minimized considerably. The proposed strategy has been implemented on a dSPACE platform with a prototype of dual-three-phase PMSM with serious imbalanced parameters, and operate at single- and dual-three-phase conditions. The experimental results prove that the proposed strategy can significantly improve the steady-state and dynamic performance of rotor position estimation under imbalanced situation. Reference | Related Articles | Metrics

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Dual-Coupled Robust Wireless Power TransferBased on Parity-Time-symmetric Model Gongjun Liu, Bo Zhang Chinese Journal of Electrical Engineering    2018, 4 (2): 50-55.   Abstract （108）      PDF       Knowledge map    The characteristics of the wireless power transfer(WPT) system vary under different transfer distances. As distance increases, efficiency drops off sharply, limiting the wider use of WPT technology. In order to mitigate this problem, this paper proposes a novel dual-coupled WPT system, where both electric-coupled mechanism and magnetic-coupled mechanism are utilized to enhance the transfer efficiency. Furthermore, a Parity-Time(PT)-symmetric circuit is utilized to realize robustness of the system. The coupled-mode model of the system is established and the expressions of operating frequency, transfer efficiency and output power are deduced. Analysis results indicate that in the unbroken PT-symmetric state, compared with single-coupled systems, the proposed system can keep constant performance within a longer distance; in broken PT-symmetric state, the proposed system has higher transfer efficiency. Simulated results and comparative results are in accordance with the theoretical analysis. Within 1.4m, this scheme can transfer power with constant efficiency of 77% and constant output power of 70W. Reference | Related Articles | Metrics

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Influence of Rotor Iron Bridge Position on DC-winding-induced Voltage in Wound Field Switched Flux Machine Having Partitioned Stators Zhongze Wu, Z. Q. Zhu, Chao Wang, Wei Hua, Kai Wang, Wentao Zhang Chinese Journal of Electrical Engineering    2021, 7 (3): 20-28.   DOI: 10.23919/CJEE.2021.000022 Abstract （353）      PDF       Knowledge map    In this study, the influence of the position of the rotor iron bridge on the DC-winding-induced voltage pulsation in a partitioned stator wound field switched flux machine is investigated. Analytical and finite element (FE) analyses show that both the open-circuit and on-load DC-winding-induced voltages can be minimized by positioning the rotor iron bridge adjacent to the inner air gap closer to the DC winding. This is due to a smoother inner air-gap magnetic reluctance while maintaining the average electromagnetic torque at 92.59% of the maximum value. The analyzed machine with the rotor iron bridge adjacent to the inner air gap is prototyped, and the experimental results validate the analytical and FE results. Reference | Related Articles | Metrics

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Research on Protection of Tuning Area Equipment Disconnection in the ZPW-2000A Track Circuit* Yunshui Zheng, Zhanyi Shu, Shenglin Gao Chinese Journal of Electrical Engineering    2021, 7 (1): 106-117.   DOI: 10.23919/CJEE.2021.000010 Abstract （284）      PDF       Knowledge map    To overcome the problem of tuning area faults influencing the normal operation of the ZPW-2000A track circuit, protector models are established to protect the track circuit from interference. First, the parameters of the protector models are calculated according to the circuit resonance principle. Second, a four-terminal network model of the track circuit in a normal state is established according to transmission-line theory and the transmission equations are derived. Third, the rail voltage is simulated, and an experimental platform is built to verify the models. Finally, the transmission equations of the protectors are derived, and the variation of the rail voltage is analyzed. The results indicate that tuning area faults have significant influence on the rail voltage. However, the installation of protectors can effectively reduce the influence, and not bear on the normal operation and maintenance of the track circuit, which significantly improves the protection ability of the track circuit against tuning area faults. Reference | Related Articles | Metrics

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Vibration Reduction and Torque Improvement of Integral-slot SPM Machines Using PM Harmonic Injection* Jinghua Ji, Deyou Liu, Yu Zeng, Tong Liu, Wenxiang Zhao Chinese Journal of Electrical Engineering    2023, 9 (4): 41-53.   DOI: 10.23919/CJEE.2023.000028 Abstract （173）      PDF       Knowledge map    This study aimed to improve the vibration and torque of an integral-slot surface-mounted permanent magnet (SPM) machine by optimizing the shape of the harmonically injected permanent magnet (PM). First, the effect of the third harmonic injected into the sinusoidal PM shape on the electromagnetic performance of a 36-slot/12-pole SPM machine was investigated, including the torque performance and vibration response. It was found that the Sin+3rd harmonic-shaped PM had a contrary effect on the torque and vibration performance of the integral-slot machine, which improved the torque capability but worsened the vibration performance. Second, the response surface model and Barebones multi-objective particle swarm optimization algorithm based on a trade-off between the average torque and vibration were implemented to determine the optimal harmonic injection. Subsequently, the performances of the optimal Sin+3rd-shaped and eccentric PM machines were compared, showing the excellent torque and vibration performance of the adopted method. Finally, a prototype was manufactured and tested to verify the results of the theoretical analysis. Reference | Related Articles | Metrics

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Multi-objective Model Predictive Control of Grid-connected Three-level Inverter Based on Hierarchical Optimization* Ting Liu, Yong Li, Li Jiang, Jianghu Wan, Jiaqi Yu, Chao Ding, Yijia Cao Chinese Journal of Electrical Engineering    2021, 7 (1): 63-72.   DOI: 10.23919/CJEE.2021.000006 Abstract （322）      PDF       Knowledge map    In order to solve the problem of weighting factors selection in the conventional finite-control-set model predictive control for a grid-connected three-level inverter, an improved multi-objective model predictive control without weighting factors based on hierarchical optimization is proposed. Four control objectives are considered in this strategy. The grid current and neutral-point voltage of the DC-link are taken as the objectives in the first optimization hierarchy, and by using fuzzy satisfaction decision, several feasible candidates of voltage vectors are determined. Then, the average switching frequency and common-mode voltage are optimized in the second hierarchy. The average ranking criterion is introduced to sort the objective functions, and the best voltage vector is obtained to realize the coordinated control of multiple objectives. At last, the effectiveness of the proposed strategy is verified by simulation results. Reference | Related Articles | Metrics

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Fault Tolerant Control of Multiphase Multilevel Motor Drives - Technical Review Zheng Wang, Xueqing Wang, Yibo Wang, Jian Chen, Ming Cheng Chinese Journal of Electrical Engineering    2017, 3 (2): 76-86.   Abstract （148）      PDF       Knowledge map    The multiphase multilevel motor drives are a promising solution for some high-power and high-reliability applications, since they have multiple power conversion routes, a large amount of redundant voltage vectors, higher equivalent switching frequencies and superior harmonic performance. It has great significance to exploit their remedial control strategies in depth to fully utilize their high fault tolerant capabilities. This paper will present an updated technical review of fault tolerant control schemes for multiphase multilevel motor drives. Based on exemplification of the diode neutral-pointclamping three-level (DNPC-3L) inverters and T-type NPC three-level (TNPC-3L) inverters fed asymmetric six-phase PMSM drives, the study is taken for both phase-leg faults and switch faults. Furthermore, the discussion on multiple-switch faults, short-circuit switch faults and switch and leg hybrid faulty conditions are discussed in this paper. Reference | Related Articles | Metrics

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A Critical Topology Review of Power Electronic Transformers: In View of Efficiency Guidong Zhang, Jie Chen, Bo Zhang, Yun Zhang Chinese Journal of Electrical Engineering    2018, 4 (2): 90-95.   Abstract （100）      PDF       Knowledge map    Design of power electronic transformers is a hot research topic and its efficiency improvement is a critical problem all over the world. It is also the largest barrier hindering the application of power electronic transformers in industry. In this paper, the state of power electronic transformers is fully presented in terms of efficiency improvements. It is followed by the efficiency modeling of several typical topologies, and their detailed analysis and comparisons. Then, the corresponding industrial application scope of these topologies is presented, providing theoretical guidance for their industrial applications. Reference | Related Articles | Metrics

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New Technical Trends on Adjustable Speed AC Motor Drives Kouki Matsuse, Daiki Matsuhashi Chinese Journal of Electrical Engineering    2017, 3 (1): 1-9.   Abstract （119）      PDF       Knowledge map    Adjustable speed AC Motor drives have been used extensively in modern industry and transportation which calls for electrical and mechanical energy conversion with wide output power range applications. Because of its modularity and scalability, the drive system can be extended to many different application areas. More recently, adjustable speed AC motor drive applications are spreading not only in industry applications, but also sky and the marine. In this paper, after summarizing the history of adjustable speed AC motor drives and applications, the main issues of AC drive technologies are reviewed and investigated in the paper. Technical issues of adjustable speed AC motor drives including its standardization are surveyed and analyzed for more advancement. Finally, the paper provides the latest technical trends on adjustable speed AC motor drives technologies, and discusses the development of high speed high power PM motor. Reference | Related Articles | Metrics

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Influence of Magnet Shape on the Cogging Torque of a Surface-mounted Permanent Magnet Motor* Min Zhou, Xinxing Zhang, Wenxiang Zhao, Jinghua Ji, Jingning Hu Chinese Journal of Electrical Engineering    2019, 5 (4): 40-50.   DOI: 10.23919/CJEE.2019.000026 Abstract （347）      PDF       Knowledge map    The influence of bread-loaf shaped magnet poles under parallel magnetization on the cogging torque of surface-mounted permanent magnet (SPM) motors is studied. For the SPM motors having magnetic poles with eccentricity and sine harmonic compensation, the electromagnetic performances of integer and fractional slot motors are compared. It is found that the cogging torque and torque ripple of the integer and fractional slot motors can be reduced with the same eccentric magnet pole. The cogging torque and torque ripple of a fractional slot motor can be decreased by sine harmonic compensation, however, the same sine harmonic compensation has a small influence in integer slot motors. By varying the magnetic poles, the contribution of the field harmonics (k = (2n + 1) p), which are a direct result of magnet magnetization, to the cogging torque also changes. The electromagnetic performance of a 3 kW prototype is tested, and it is found that the experimental results validate the theoretical investigation. Reference | Related Articles | Metrics

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Accurate Evaluation of Cooling System Capability of Three-phase IGBT-based Inverter* Dan Zheng, Puqi Ning, Xiaoguang Chai, Wei Sun, Zhijie Qiu, Yuhui Kang, Han Cao, Tao Fan Chinese Journal of Electrical Engineering    2021, 7 (1): 73-78.   DOI: 10.23919/CJEE.2021.000007 Abstract （250）      PDF       Knowledge map    In this paper, an offline evaluation method for the cooling capability of three-phase insulated-gate bipolar transistor (IGBT) inverters is presented, which can better emulate real working conditions. With a properly designed sudden-stop control sequence, the conventional junction temperature monitoring method at a low current is used to calculate the junction temperature before the sudden stop of an inverter. This can solve the challenging switching loss calculation issue in conventional methods. Finally, the feasibility, control sequence, and electrical behaviors of the proposed method are validated through experimental tests. Reference | Related Articles | Metrics

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Fault-tolerant Deadbeat Model Predictive Current Control for a Five-phase PMSM with Improved SVPWM* Suleman Saeed, Wenxiang Zhao, Huanan Wang, Tao Tao, Faisal Khan Chinese Journal of Electrical Engineering    2021, 7 (3): 111-123.   DOI: 10.23919/CJEE.2021.000030 Abstract （475）      PDF       Knowledge map    The main drawbacks of traditional finite set model predictive control are high computational load, large torque ripple, and variable switching frequency. A less complex deadbeat (DB) model predictive current control (MPCC) with improved space vector pulse-width modulation (SVPWM) under a single-phase open-circuit fault is proposed. The proposed method predicts the reference voltage vector in the α-β subspace by employing the deadbeat control principle on the machine predictive model; thus, the exhaustive exploration procedure is avoided to relieve the computational load. To perform the constant switching frequency operation and achieve better steady-state performance, a modified SVPWM strategy is developed with the same conventional structure, which modulates the reference voltage vector. This new approach is based on a redesigned and adjusted post-fault virtual voltage vector space distribution that eliminates the y-axis harmonic components in the x-y subspace and ensures the generation of symmetrical PWM pulses. Meanwhile, the combined merits of the DB, MPCC, and SVPWM methods are realized. To verify the effectiveness of the proposed control scheme, comparative experiments are performed on a five-phase permanent magnet synchronous motor (PMSM) drive system. Reference | Related Articles | Metrics

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MESO-based Robustness Voltage Sliding Mode Control for AC Islanded Microgrid Hao Pan, Qingfang Teng, Dangdang Wu Chinese Journal of Electrical Engineering    2020, 6 (2): 83-93.   DOI: 10.23919/CJEE.2020.000013 Abstract （274）      PDF       Knowledge map    A new modified extended state observer (MESO)-based robustness voltage sliding mode control (SMC) strategy is proposed for an AC islanded microgrid under system uncertainties including system parameter and load variation. First, the disturbance effect on the system is regarded as a lumped uncertainty, and a state space model of the uncertain islanded microgrid system is established. Then, a modified extended state observer is designed to estimate external disturbances and internal perturbation. Finally, considering the lumped uncertainty, a sliding mode controller with a multi-power reaching law is proposed to enable the output voltage of the system to track its reference voltage rapidly and accurately, and to enhance the robustness of the system. The simulation results confirm that the proposed robustness voltage control strategy can perform satisfactory voltage control and demonstrate a strong capability to reject parameter and load variation. Reference | Related Articles | Metrics

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Fast Online Diagnosis of Open-circuit Switching Faults in Flying Capacitor Multilevel Inverters Majid T. Fard, Waqar A. Khan, Jiangbiao He, Nathan Weise, Mostafa Abarzadeh Chinese Journal of Electrical Engineering    2020, 6 (4): 53-62.   DOI: 10.23919/CJEE.2020.000030 Abstract （406）      PDF       Knowledge map    Flying capacitor multilevel (FCML) inverter is an attractive power converter topology which provides high-quality staircase output voltage waveforms by cascading flying capacitor cells. However, the large number of semiconductor devices utilized in the FCML inverters degrades the hardware reliability, which may constrain such converters from being applied in safety-critical applications. Targeting at open-circuit switching faults, a fast online fault diagnostic method for FCML inverters is presented. Conventional phase-shifted PWM (PSPWM), which can naturally balance the voltage across flying capacitors, is used as the modulation method in this work. Hence, to retain the simplicity feature of the PSPWM, the proposed diagnostic method is developed so that it does not require any voltage measurements of flying capacitors. Only the output AC voltage and current data along with the switching PWM signals from the microcontroller are needed to detect an open-circuit switching fault, and all such sensory data is typically available in the inverter, requiring no additional sensors or hardware for the implementation of this diagnostic method. The detection process takes 5% of the fundamental period of the inverter output signals to diagnose the faulty switch. Simulation and experimental results are presented to verify the effectiveness of the proposed diagnostic method. Reference | Related Articles | Metrics

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A Novel Soft-start Method for SVG Based on D-axis Orientation* Shicheng Zheng, Ying Shu, Mengmeng Qi, Jiahong Lang, Xuefeng Hu Chinese Journal of Electrical Engineering    2021, 7 (1): 55-62.   DOI: 10.23919/CJEE.2021.000005 Abstract （262）      PDF       Knowledge map    In this paper, a novel method for shock-free soft-start is proposed. The novel method can realize the aim of no-overshoot and inrush of current during the entire soft-start process, thus the start process is safe, stable, and reliable. When the uncontrolled rectification stage ends, a sinusoidal signal synchronized with the grid voltage is generated through dq coordinate transformation and D-axis orientation, then the signal is transmitted to the three-phase inverter bridge. The AC voltage output of the inverter bridge is superimposed on both ends of the soft-start resistor along with the grid. The open-loop control method is adopted to gradually reduce the modulation ratio of the sinusoidal PWM wave until the capacitor voltage on the DC side reaches the rated voltage value, then the soft-start resistor is removed, which means the shock-free soft-start process is completed. Experimental results prove the effectiveness and feasibility of the control strategy proposed in this paper. Reference | Related Articles | Metrics

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Resonance Mechanism Analysis of Large-scale Photovoltaic Power Plant* Jinjie Lin, Yong Li, Sijia Hu, Qianyi Liu, Jing Zhang, Shaoyang Wang, Lihong Dong, Juan Ni Chinese Journal of Electrical Engineering    2021, 7 (1): 47-54.   DOI: 10.23919/CJEE.2021.000004 Abstract （376）      PDF       Knowledge map    To analyze the resonance mechanism of a photovoltaic (PV) power plant, a simplified impedance model of the PV power plant is first established. The structure of the PV power plant is then introduced, and the reason for the resonance is obtained by analyzing the on-site situation and measured data of the PV power plant. Finally, a simple and effective solution is proposed based on the structure of the PV power plant and its existing facilities. The results of the engineering experiments and the stable operation of the PV power plant verify the effectiveness of the proposed method. Reference | Related Articles | Metrics

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Review of Low Carrier Ratio Converter System* Mai Xu, Yang Zhang, Da Luo, Anping Shen Chinese Journal of Electrical Engineering    2021, 7 (1): 79-93.   DOI: 10.23919/CJEE.2021.000008 Abstract （409）      PDF       Knowledge map    With the rapid development of new energy power generation and high-power traction technology, the voltage and power levels of converter devices have been continuously improved, and the application of high-power converters is becoming increasingly widespread. However, high-power converters are affected by switching losses and heat dissipation, meaning they are not suitable for high carrier conditions. Therefore, research of low carrier ratio converter systems has received increased attention. Based on existing research, the problems of large current harmonics, low observation accuracy, and poor stability that may occur at low carrier ratios are explained. In addition, the topologies, modulation strategies, and control methods of the low carrier ratio converter system are analyzed and classified. Finally, future research directions of low carrier ratio converter systems are proposed. Reference | Related Articles | Metrics

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Wavelet Synchro-squeezing Transform and Dynamic Threshold Supported Symmetrical Power Swing Technique for Modern Transmission Network Monalisa Biswal, Kumar Raja Andanapalli, Papia Ray Chinese Journal of Electrical Engineering    2024, 10 (2): 30-43.   DOI: 10.23919/CJEE.2024.000064 Abstract （604）      PDF       Knowledge map    Distance relays are prone to symmetrical power swing phenomenon. To mitigate this issue, a dynamic threshold-supported algorithm is proposed. A single logic is not supposed to be secure for all cases. Thus, a supervisory algorithm, as proposed in this study, can aid in the improvement of the immunity of the relay during swing cases and be sensitive to symmetrical faults. In the developed stages, a three-phase power signal was used and processed in two different steps: (i) extraction of the effective intrinsic mode function (IMF) selected from the Kurtosis analysis using the wavelet synchro-squeezing transform, and (ii) estimation of the average Euclidean distance index using the absolute values of the decomposed IMF’s. The adaptive threshold facilitated resistance to swing situations. At the onset of a symmetrical fault, the proposed algorithm efficiently discriminated among events using a dynamic threshold. The IEEE 39-bus test system and Indian Eastern Power Grid networks were modelled using PSCAD software, and cases were generated to test the efficacy of the method. The impact of the proposed method on a large-scale wind farm was also evaluated. A comparative analysis with other existing methods revealed the security and dependability of the proposed method. Reference | Related Articles | Metrics

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Defect Detection in c-Si Photovoltaic Modules via Transient Thermography and Deconvolution Optimization* Zekai Shen, Hanqi Dai, Hongwei Mei, Yanxin Tu, Liming Wang Chinese Journal of Electrical Engineering    2024, 10 (1): 3-11.   DOI: 10.23919/CJEE.2023.000043 Abstract （313）      PDF       Knowledge map    Defects may occur in photovoltaic (PV) modules during production and long-term use, thereby threatening the safe operation of PV power stations. Transient thermography is a promising defect detection technology; however, its detection is limited by transverse thermal diffusion. This phenomenon is particularly noteworthy in the panel glasses of PV modules. A dynamic thermography testing method via transient thermography and Wiener filtering deconvolution optimization is proposed. Based on the time-varying characteristics of the point spread function, the selection rules of the first-order difference image for deconvolution are given. Samples with a broken grid and artificial cracks were tested to validate the performance of the optimization method. Compared with the feature images generated by traditional methods, the proposed method significantly improved the visual quality. Quantitative defect size detection can be realized by combining the deconvolution optimization method with adaptive threshold segmentation. For the same batch of PV products, the detection error could be controlled to within 10%. Reference | Related Articles | Metrics

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Spiral Vector Modeling of Brushless Doubly-fed Induction Machines with Short-circuited Rotor Windings Peng Han, Ming Cheng, Zhiwei Zhang, Peng Peng Chinese Journal of Electrical Engineering    2021, 7 (3): 29-41.   DOI: 10.23919/CJEE.2021.000023 Abstract （296）      PDF       Knowledge map    A unified spiral vector model is presented that can be used to assist the finite element method-based performance analysis of brushless doubly-fed induction machines with various short-circuited rotor windings. Specifically, magnet-free brushless doubly-fed induction machines working in doubly-fed or singly-fed synchronous mode are investigated. A dynamic model in spiral vector notation is developed, based on which the torque-angle and power-angle characteristics are derived. It is shown that the investigated brushless machines are equivalent to a traditional non-salient-pole synchronous machine with brushes. By introducing a conversion factor, they can also be analyzed with methods similar to the conventional phasor theory. A comparison is made between the brushless doubly-fed induction machine and non-salient-pole wound-field synchronous machine with brushes, revealing that the performance of the brushless machine degrades faster when the laminated core is saturated. A scaled-down prototype is tested to validate the effectiveness of the theoretical analysis. Reference | Related Articles | Metrics

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Widen the Zero-Voltage-Switching Range and Secure Grid Power Quality for An EV Charger Using Variable-Switching-Frequency Single-Dual-Phase-Shift Control Qi Tian, KevinBai Chinese Journal of Electrical Engineering    2018, 4 (1): 11-19.   Abstract （135）      PDF       Knowledge map    Compared to conventional electrical-vehicle(EV) on-board chargers utilizing a front-end Power-Factor-Correction(PFC) + an isolated DC/DC converter, which limits the wall-tobattery efficiency to ~94%, a new control strategy using variable switching frequency(VSF) and variable phase shifts frees the PFC stage thereby getting rid of the DC link capacitor and further increasing the system efficiency and power density. The challenge is to secure zero-voltage-switching (ZVS) turn-on for all switches within the full-power range. In this paper a novel VSF single-dualphase- shift(SDPS) control strategy is proposed, which consists of three control freedoms, i.e., two phase shifts and one variable switching frequency to secure ZVS and achieve PFC simultaneously. ZVS boundaries are pictured and compared among single-phase-shift(SPS), dual-phase-shift(DPS) and the proposed single-dual-phase-shift(SDPS) control. Simulation results and experimental validation through a level-2 EV on-board charger indicate that by using the proposed SDPS control, both ZVS and PFC are secured not only for the heavy load but also for the light load, without sacrificing the system efficiency. Reference | Related Articles | Metrics

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Stability-improvement Method of Cascaded DC-DC Converters with Additional Voltage-error Mutual Feedback Control* Zhongya Guo, Hong Li, Chen Liu, Yangyang Zhao, Wenzhe Su Chinese Journal of Electrical Engineering    2019, 5 (2): 63-71.   Abstract （178）      PDF       Knowledge map    The interaction between the source and load converters in cascaded DC-DC converters may cause instability. Thus, improving the stability of cascaded DC-DC converters is important. To solve the above-mentioned problem, a flowchart to improve the control method is established by calculating the eigenvalue sensitivity of a time-domain model of cascaded DC-DC converters. Further, an additional voltage-error mutual feedback control method is firstly proposed based on the flowchart provided in this study to improve the stability of cascaded DC-DC converters. Subsequently, the influence of the proposed mutual feedback control on the stability of cascaded DC-DC converters is analyzed. Finally, the effectiveness of the proposed control method is verified by simulation and experiment. Reference | Related Articles | Metrics

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A Novel Boost Four-Leg Converter for Electric Vehicle Applications Xiaoyu Jia, Huaibao Wang, Baocheng Wang, Xiaoqiang Guo, Xiaoyu Wang Chinese Journal of Electrical Engineering    2017, 3 (1): 79-83.   Abstract （80）      PDF       Knowledge map    Integrating the electric vehicle into grid or microgrid has been receiving more and more attention in recent years. Typically, the electric vehicle (EV) chargers with their power batteries have been developed for vehicle-to-home(V2H) applications, acting as a backup generation to supply emergency power directly to a home. Traditional EV chargers in V2H applications mainly consist of DC/DC and DC/AC stages, which complicate the control algorithm and result in low conversion efficiency. In order to solve this problem, a novel EV charger is proposed for V2H applications. It can boost the battery voltage and output AC voltage with only one-stage power conversion. Also, the DC, 1-phase and 3-phase loads can be fed with the proposed single-stage EV charger. The system control strategy is also provided to deal with versatile load variations. Finally, the performance evaluation results verify the effectiveness of the proposed solution. Reference | Related Articles | Metrics

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Modular Design Method for Motor Drives Dong Jiang, Puqi Ning, Rixin Lai, Zhihao Fang, Fred Wang Chinese Journal of Electrical Engineering    2018, 4 (1): 1-10.   Abstract （157）      PDF       Knowledge map    This paper introduces the concept of modular design methodology for hardware design and development of motor drives. The modular design process is first introduced separating the hardware development into three parts: controller, mother board and phase-leg module. The control and circuit function can be decoupled from the phase-leg module development. The hardware update can be simplified with the phase-leg module development and verification. Two design examples are used to demonstrate this method: a DC-fed motor drive with Si IGBTs and an AC-fed motor drive with SiC devices. Design of DC-fed motor drive aims at developing the converter with customized IGBT package for high temperature. Experience with development of the converter with commercial IGBTs simplifies the process. As the AC-fed motor drive is a more complex topology using more advanced devices, the modular design method can simplify and improve the development especially for new packaged devices. Also, the modular design method can help to study the electromagnetic interference (EMI) issue for motor drives, which is presented with an extra design example. Reference | Related Articles | Metrics

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Black-box Modeling of Converters in Renewable Energy Systems for EMC Assessment: Overview and Discussion of Available Models* Lu Wan, Abduselam H. Beshir, Xinglong Wu, Xiaokang Liu, Flavia Grassi, Giordano Spadacini, Sergio A. Pignari Chinese Journal of Electrical Engineering    2022, 8 (2): 13-28.   DOI: 10.23919/CJEE.2022.000011 Abstract （343）      PDF       Knowledge map    The development of renewable energy systems interfaced with the grid by power electronic converters leads to increasing issues of electromagnetic coexistence between power and communication lines, as well as severe power quality issues, such as total harmonic distortion at the consumer side. Therefore, high-frequency modeling of renewable energy systems is of great importance to guide the design and development of distribution networks involving renewable sources. Owing to system complexity, black-box modeling approaches offer more advantages than traditional circuit modeling, as far as electromagnetic compatibility (EMC) analysis and filter design are the targets. In this study, different black-box modeling techniques for power converters are introduced and systematically analyzed. First, the general theory of black-box modeling is explained. Subsequently, three different modeling approaches are compared in terms of accuracy and the required experimental setup. Finally, the possible limitations of black-box modeling of power converters are investigated and discussed. Reference | Related Articles | Metrics

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Stability Analysis of Sampled-data Control System and Its Application to Electric Power Market* Tian Zhang, Shenping Xiao Chinese Journal of Electrical Engineering    2020, 6 (1): 61-70.   DOI: 10.23919/CJEE.2020.000005 Abstract （371）      PDF       Knowledge map    The stability of sampled-data systems is investigated using a new type of Lyapunov functional. The interval from the sampling point tk to tk+1 is assumed to be a sampling interval. By fully utilizing the characteristic information on the whole sampling interval, a new two-sided closed-loop Lyapunov functional is proposed, which utilizes the information on both the intervals from the sampling point t to tk and from t to tk+1. Based on the two-sided closed-loop Lyapunov functional and modified free-matrix-based inequality, a less conservative stability criterion is derived for a sampled-data control system, and three numerical examples are provided to verify the effectiveness and reduced conservativeness of the proposed method. Furthermore, the proposed method is applied to solve the stability problem of electric power markets, and the practical significance of reducing the conservativeness is discussed. Reference | Related Articles | Metrics

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PSO-based Optimization for Constant-current Charging Pattern for Li-ion Battery* Yixiao Wang, Yong Li, Li Jiang, Yuduo Huang, Yijia Cao Chinese Journal of Electrical Engineering    2019, 5 (2): 72-78.   Abstract （182）      PDF       Knowledge map    A particle swarm optimization algorithm to search for an optimal five-stage constant-current charge pattern is proposed. The goal is to maximize the objective function for the proposed charge pattern based on the charging capacity, time, and energy efficiency, which all share the same weight. Firstly, an equivalent circuit model is built and battery parameters are identified. Then the optimal five-stage constant-current charge pattern is searched using a particle swarm optimization algorithm. At last, comparative experiments using the constant current-constant voltage (CC-CV) method are performed. Although the charging SOC of the proposed charging pattern was 2.5% lower than that of the CC-CV strategy, the charging time and charging energy efficiency are improved by 15.6% and 0.47% respectively. In particular, the maximum temperature increase of the battery is approximately 0.8 ℃ lower than that of the CC-CV method, which indicates that the proposed charging pattern is more secure. Reference | Related Articles | Metrics

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Route Towards Road Freight Electrification in India: Examining Battery Electric Truck Powertrain and Energy Consumption Sreedhar Madichetty, Avram John Neroth, Sukumar Mishra, B. Chitti Babu Chinese Journal of Electrical Engineering    2022, 8 (3): 57-75.   DOI: 10.23919/CJEE.2022.000026 Abstract （186）      PDF       Knowledge map    Medium-duty/heavy-duty trucks (MD/HDTs) are yet to be included in India’s electric mobility plans. With the improvement of electric vehicle (EV) technologies, there is a growing interest in battery-electric trucks (BETs) from original equipment manufacturers (OEMs). The time is opportune to consider electrification as a future direction for road freight in India. Accordingly, this article presents the results of an energy consumption simulation study of a BET under Indian conditions. This study specifically considered an MDBET over a domestic drive cycle. These energy consumption figures can facilitate future studies that analyze the technical and practical feasibility of BETs in the country. In addition, the article provides the requisite groundwork for BET modeling for a simulation study by reviewing available EV powertrain systems and components. Appropriate powertrain considerations are thereby obtained for a typical medium-duty/heavy-duty battery-electric truck (MD/HDBET) in the Indian context. Reference | Related Articles | Metrics

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Reduced Model of Droop-controlled Converters for Transient Simulation Analysis* Yingjie Tan, Yang Shen, Min Xu, Chao Shen, Jinyong Lei Chinese Journal of Electrical Engineering    2022, 8 (3): 112-122.   DOI: 10.23919/CJEE.2022.000030 Abstract （167）      PDF       Knowledge map    In recent years, the transient stability problems encountered by power grids have increasingly attracted interest due to the connection of renewable energy resources. One of the effective methods for studying the transient characteristics of a system is transient simulation analysis. To reduce the simulation time, especially in a system with numerous renewable energy resources, model reduction has been widely employed. However, when a general reduced model is adopted to analyze different transient characteristics, a tradeoff between accuracy and simulation speed emerges. In this study, reduced model selection is implemented to resolve this problem. Considering the droop-controlled converter as an example, this approach allows the transient simulation analysis of voltage, frequency, and power angle characteristics. First, a full-order model of the droop-controlled inverter is formulated. Thereafter, the singular perturbation method is applied to derive different reduced-order models. Then, considering accuracy and simulation speed simultaneously, the most suitable reduced models for transient angle, voltage, and frequency simulation analyses are determined through time-domain simulation comparison. Finally, the simulation results based on Matlab/Simulink are used to verify the correctness of the reduced model selection. Reference | Related Articles | Metrics

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Implementation of 1.7 kV Silicon Carbide Metal Oxide Semiconductor Field Effect Transistors in Auxiliary Power Supplies for Industrial Applications Xuning Zhang, Gin Sheh Chinese Journal of Electrical Engineering    2020, 6 (3): 46-55.   DOI: 10.23919/CJEE.2020.000018 Abstract （274）      PDF       Knowledge map    An auxiliary power supply (Aux-PS) has become an essential component of electronic equipment for many industrial applications, such as in motor drives, photovoltaic (PV) inverters, uninterruptible power supply (UPS) systems and modular multilevel converters. The introduction of 1 700 V silicon carbide (SiC) metal oxide semiconductor field effect transistors (MOSFETs) is useful for such applications, providing benefits with respect to a low on-state resistance, smaller package, low switching loss and single-switching implementation. A single end flyback Aux-PS is designed for industrial applications with a wide input voltage range using 1.7 kV SiC MOSFETs. The special design tradeoffs involved in the usage of SiC MOSFETs are discussed in detail, such as those with regard to gate driving voltage selection, isolation transformer design considerations, and clamping circuit design details. A 60 W demonstration hardware is developed and tested under different working conditions. The results verify the higher efficiency and better thermal performance of the proposed hardware relative to those of traditional Si solutions. Reference | Related Articles | Metrics