Yu Zhang

Huazhong University of Science and Technology, Wu-han-shih, Hubei, China

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Publications (41)14.49 Total impact

  • Yu Zhang · Yongxian Yi · Peimeng Dong · Fangrui Liu · Yong Kang ·

    01/2015; DOI:10.1109/JESTPE.2015.2421339

  • Journal of power electronics 09/2014; 14(5):1047-1056. DOI:10.6113/JPE.2014.14.5.1047 · 0.78 Impact Factor
  • Yu Zhang · Mi Yu · Fangrui Liu · Yong Kang ·
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    ABSTRACT: By regulating the inverter output current every switching cycle, instantaneous current-sharing control strategies are usually employed in paralleled modular uninterruptible power supplies (UPSs). In this paper, virtual impedance, which is usually utilized in the droop method, is firstly introduced to the instantaneous current-sharing control strategy to achieve good load current-sharing performance. The instantaneous circulating current model of the paralleled system is developed and the circulating impedance is derived as well to clearly identify the intrinsic nature of unequal sharing of load current. By inserting the virtual impedance to the circulating impedance with the help of proper control strategy, good current-sharing capability can be obtained. The parallel inductor, e.g., coupled inductor, which is generally added at the output of each inverter to reduce the circulating current among modules, can be, therefore, eliminated, contributing to reduced weight, volume, and cost. In the meantime, the system output-voltage regulation performance, e.g., amplitude and waveform quality, is not affected by the introduction of the virtual impedance. The designation of the virtual impedance is provided and its implementation is simple but rather effective. Experimental results are also provided to verify the feasibility of the proposed method.
    IEEE Transactions on Power Electronics 01/2013; 28(1):432-440. DOI:10.1109/TPEL.2012.2200108 · 6.01 Impact Factor
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    ABSTRACT: Due to multifeedback of state variables, a discrete state-space controller offers outstanding control bandwidth as well as control stability for popular LCL-type grid-connected inverters, while the grid current is still vulnerable to the grid-voltage harmonics. The feedforward of grid voltage, usually employed in continuous controllers to solve such a problem, is too complicated to be applied for the discrete state-space controller. By means of continuous transformation, a full grid-voltage feedforward (GVFF) decoupling strategy is successfully proposed in this paper to make the feedforward possible for the discrete state-space controller. Based on the transfer function analysis and comparison of discretized and continuous system, comprehensive verification is also provided to verify the effectiveness of the derivation of the GVFF path. Subsequently, the robustness analysis of the proposed strategy to the grid impedance is also performed. Moreover, a grid-voltage estimator instead of the measured voltage is employed for the full GVFF, which not only retains the important information of grid voltage but also eliminates the influence of accompanied noises. The distinct features of the proposed feedforward controller plus implementation strategy are the super steady waveform, dynamic response, and robustness to the variation of grid impedance. Besides, the complexity of the algorithm is moderate and the computational burden is not significantly increased. Finally, simulation and experimental results are provided to verify the feasibility and validity of the proposed strategy.
    IEEE Transactions on Power Electronics 10/2012; 27(10):4234-4247. DOI:10.1109/TPEL.2012.2190524 · 6.01 Impact Factor
  • Yu Zhang · Jun Guo · Lu Cheng · Rui Liu ·
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    ABSTRACT: Wenchuan Earthquake has caused substantial damage to reinforced concrete columns, in order to improve their lateral stiffness, wing walls are added to repair and strengthen the columns. Based on engineering practice, the mechanical calculations of normal section bearing capacity on damaged reinforced concrete columns strengthened by wing walls have been conducted, and based on the N-M curves of various special-shaped columns, the influence laws of different azimuths and different axial compression ratios on bearing capacity of normal section have been analyzed, therefore mechanical properties of special-shaped sections have been obtained, which provides reference information for engineering technology.
    01/2012; 446-449:561-565. DOI:10.4028/www.scientific.net/AMR.446-449.561
  • Yu Zhang · L. Teixeira · Yong Kang ·
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    ABSTRACT: The large-scale wind power may influence the stability of the power system when its penetration level exceeds some limit and some disturbance as the short circuit happen. To study and preview this phenomenon before connect the wind farm into the grid, the use of simulation method has been a good tool. This paper evaluated the stability analysis of the power system in Santiago Island, Cape Verde, considering a 9.25 MW wind farm installed and connected into the 40 MW grid. The simulation results by MATLAB/Simulink® show the stable performance of power system under short circuit fault. The effect of STATCOM is also evaluated.
    Power and Energy Engineering Conference (APPEEC), 2012 Asia-Pacific; 01/2012
  • Hong Tao Shan · Yuan Ling Cai · Yu Zhang ·
    [Show abstract] [Hide abstract]
    ABSTRACT: Interleaving Parallel is the unique technology with the combination of SPWM modulation technology with multiple technology. This paper was researched the interleaving parallel rectifier technology in restraining the AC side current ripple in detail, and compared current ripple in the AC side between the single rectifier and the interleaving parallel rectifier. The research was deduced that current ripple in the AC side of the interleaving parallel rectifier was lessened than the same parameters of the single rectifier. The relevant simulations were verified the characteristic of restraining the current ripple in the AC side in interleaving High-Frequency rectifier was effective.
    10/2011; 354-355:1363-1366. DOI:10.4028/www.scientific.net/AMR.354-355.1363
  • Hong Tao Shan · Yong Kang · Xue Juan Kong · Yu Zhang ·
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    ABSTRACT: Digital controlled SPWM inverter has become main-stream in development of SPWM inverter control strategy. But the traditional PID control strategy realized in digital control can’t achieve better performance than in analog control. Process of the zero-order hold & one-step-delay control were researched the effect of zero-order hold & one-step-delay control on the stability of digital control SPWM inverter with quantitative analysis in this paper. Finally relevant simulations and experiments were verified the validity of the theoretical analysis.
    10/2011; 347-353:564-567. DOI:10.4028/www.scientific.net/AMR.347-353.564
  • Luis Teixeira · Yu Zhang · Yong Kang ·
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    ABSTRACT: Wind Power System connected to electric grid has been increased in the last years. In order to investigate its dynamic behavior and influence into the grid, simulation method can be used to study the performance of overall power systems. In this paper, the Power System in Cape Verde is modeled and simulated with MATLAB/Simulink<sup>®</sup> considering Wind Farm. The model of wind turbine DFIG, the diesel generator, the transmission line and the load are presented on details. It is implementing in environment block for SimPowerSystems Phaser Models. The simulation results for Santiago Island case study are shown and discussed.
    Power and Energy Engineering Conference (APPEEC), 2011 Asia-Pacific; 04/2011
  • Yu Zhang · Mi Yu · Fangrui Liu · Shuming Li · Jianwei Wang · Yong Kang ·
    [Show abstract] [Hide abstract]
    ABSTRACT: The current-sharing control strategies based on phasors are commonly used in parallel inverter systems. However, their low regulation speed, low accuracy and incapable of restraining the instantaneous circulating currents make them be more and more replaced by instantaneous control methods. In this paper, the transient model of circulating currents between parallel inverters is discussed, and an instantaneous current-sharing control method is proposed based on virtual impedance, which is realized through instantaneous circulating currents feedback. The virtual impedance will not influence output characteristic of whole parallel system. Simulations and experiments show this method achieves good performance and is suitable to high performance modular UPS system.
    01/2011; DOI:10.1109/IECON.2011.6119510
  • Mingyu Xue · Yu Zhang · Fangrui Liu · Yong Kang · Yongxian Yi ·
    [Show abstract] [Hide abstract]
    ABSTRACT: Due to the attractive harmonic elimination capability, LCL filter is widely adopted in the grid-connected converters. Combined with complete state feedback control, PI current controller of the converters offers almost full controllability, resulting in super grid current waveform. By proposing an optimal pole and zero placement strategy for the PI state-space controller in this paper, the dominant poles and non-dominant poles are carefully specified to ensure system stability even in worst cases of low LCL resonant frequency and weak grid. With the proposed method, the high-order system behaves like a typical second-order system. The obtained maximum bandwidth varies with the filter size and the control burden is moderate. The computer aid design (CAD) based selection of control parameters is also provided with simplicity and adaptability. Moreover, only grid current is required as the state variable with the developed reduced-order state observer. Experimental results are provided to verify the feasibility and validity of the proposed method.
  • Source
    Luis Teixeira · Yu Zhang · Yong Kang ·
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    ABSTRACT: The short circuit fault can affect the stability of the power system mainly when a wind power is added. In some situation, the wind gust can happening simultaneity, which can became more complex and serious. Inclusively, the wind farm can be power off and disconnecting from the electrical grid. To study and preview this phenomenon before connect the wind farm into network grid, the use of simulation method has been a good tool. The power system of Santiago Island, Cape Verde, considering a wind farm with 9.35 MW of power installed, near of 40 MW-diesel plant and connected into the electrical networks is used as a case study in this paper. The simulation results by MATLAB/Simulink® showed a stable performance of power system and a protected wind farm under a situation of wind gust and short circuit fault.
  • Lu Cheng · Qiaofu Chen · Yu Zhang · Yali Xiong ·
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    ABSTRACT: In this article a novel controllable reactor based on regulating the transformer's primary equivalent impedance by controlling its secondary voltage source inverter load is proposed. When the secondary current of a transformer is forced to be proportional to and in inverse phase with its primary current, the primary side of the transformer exhibits a linear adjustable reactance with respect to the proportion coefficient. The voltage source pulse width modulation (PWM) inverter connected to the secondary side of the transformer provides the required secondary current. In order to realise a large-capacity reactor, a transformer with multiple secondary windings is used to reduce the capacity requirement of each PWM inverter. A large-capacity (800 kVA) prototype is fabricated. The experimental results verify the characteristics of the novel controllable reactor – linear reactance tuning, few harmonics and fast response.
    International Journal of Electronics 01/2011; 98(1):25-40. DOI:10.1080/00207217.2010.497649 · 0.46 Impact Factor
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    ABSTRACT: Almost all cryptographic storage systems need re-encryption when revoking users. These systems differ from each other only in the timing of re-encryption. As re-encryption is an expensive operation, it is significant to avoid re-encryption. To avoid re-encryption in cryptographic storage systems, field programmable gate array (FPGA) and application-specific integrated circuit (ASIC) hardware module have been integrated into encrypt-on-disk object store system in this paper, letting private key never leave the hardware module and object key existing only in hardware module in plaintext. Anyone who does not know private or object key, so when revoking users, just needs to modify access control list (ACL) to delete the privileges of the users. To facilitate file sharing and key management, a group is adopted. In the system, almost all computationally expensive cryptographic operations are through FPGA/ASIC hardware module. Once a creator revokes some users, objects do not need re-encryption. How to use ACL and FPGA/ASIC hardware module to authenticate and authorise is also described. And the procedure of object store and the distribution of metadata are detailed. Finally, an encrypt-on-disk object store prototype system is implemented using FPGA in software solution with tested and effective performance.
    International Journal of Parallel Emergent and Distributed Systems 04/2010; 25:105-122. DOI:10.1080/17445760802429577
  • Yu Zhang · Dan Feng ·
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    ABSTRACT: Active storage is a promising solution for data processing. Many existing active storage systems utilize spare CPU processing power on the storage controllers to execute active service. The software approach is very flexible for various applications, but the performance is quite low for computational-intensive service tasks. This paper presents a low power SoC-based hardware solution for high performance active storage. The basic idea is incorporating flexible reconfigurable accelerators in storage controllers for efficient active service processing. In order to reduce the reconfiguration latency, we also proposed hybrid configuration prefetching and configuration caching algorithms according to the task pattern. In the experiments, we presented results on applications such as data security, data compression and image processing with our FPGA prototype for an active storage processor.
    Reconfigurable Computing: Architectures, Tools and Applications, 6th International Symposium, ARC 2010, Bangkok, Thailand, March 17-19, 2010. Proceedings; 01/2010
  • Luis Teixeira · Yu Zhang · Yong Kang ·
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    ABSTRACT: The generation of electricity based in the renewable energy sources has becoming a more significant in the last years because of continues increase on energy demand and fossil oil energy dependence, additional to preoccupation of environmental. Wind and PV power systems to generate electricity in The Republic of Cape Verde are analyzed in this paper. The power electronics converters and electrical generators are investigated and proposed to meet all requirements of wind and solar PV power system. The cost of electricity, the fuel importation reduction and the GHG emissions were estimated and compared with conventional diesel generation.
  • Hongtao Shan · Yu Zhang · Mi Yu · Yong Kang · Yongqiao Liu · Min Yin · Hongbo Li ·
    [Show abstract] [Hide abstract]
    ABSTRACT: Distributed-logic-control is an independent parallel inverter control technique. The strategy to restrain circulating currents based on distributed-logical-control is researched in the paper. The conventional method by power regulation to restrain the circulating current is affected by the parallel impedance and has such disadvantages in the response speed and harmonic component of circulating current. The strategy to restrain circulating current based on tracing transient average current feedback was proposed in the paper. Its impedance characteristic and the current sharing principle are analyzed. This strategy can reduce the system output impedance, while increase the impedance between parallel inverters. The novel strategy of restraining circulating currents is adopted by the combination of tracing transient average current feedback control and power adjusting strategy. The relevant experiments on the novel strategy were made in parallel inverter with distributed-logical-control, and the validity of the novel strategy was verified.
    Electrical Machines and Systems, 2009. ICEMS 2009. International Conference on; 12/2009
  • Mingyu Xue · Fangrui Liu · Yong Kang · Yu Zhang ·
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    ABSTRACT: As the development of distributed generation technology, the renewable energy resources are widely transformed to electricity and transferred to the utility through grid-connected converters. Islanding detection is a mandatory function for the converters. It usually injects perturbations to the converter output to improve the effectiveness of islanding detection. The current research is mainly based on individual converter, while the islanding detection strategies in multiple grid-connected converters operation are investigated in this paper. The characteristics of commonly used active frequency drift and active phase shift islanding detection methods in multi-inverter systems are explored. The design principle of the two islanding detection strategies and the corresponding parameters selection rule are also presented. It provides a basic guidance for the islanding detection design in multiple grid-connected converters.
    Power Electronics and Motion Control Conference, 2009. IPEMC '09. IEEE 6th International; 06/2009
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    ABSTRACT: Compared with analog control, digital control adopted in PWM inverter possesses the evident advantages but the traditional PID control strategy which is realized in digital method often can't achieve better performance than in analog control. In past references, there is hardly quantitative analysis on the effect of digital process on the performance of PWM inverter. This paper did a creative research about the zero-order-hold process and one-step-delay control effect on the performance of PWM inverter. The process of zero-order-hold and one-step-delay control were analyzed why the digital process influences PWM inverter's performance in this paper. The process of zero-order-hold and one-step-delay control varies the system's stability with sample time. Zero-order-hold reduces the stable scope to a large extent compared with analog control, and limits the performance improvement of digital control system. One-step-delay with different sample time brings different influence on the system stability. Finally relevant experiments in a single phase inverter verify the theoretical analysis on the effect of digital process on the performance of PWM inverter.
  • Yu Zhang · Fangrui Liu · Yong Kang ·
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    ABSTRACT: Based on the instantaneous symmetric components transformation, this paper derived the dynamic equations of three-phase inverters with magnetic couples caused by three-pole reactors and three-pole transformers. The equations are in term by the instantaneous symmetric components, and take into account of the magnetic couples in three-phase inverters, which are simple to be solved and realize decouples of magnetic couples between three phase equations. The equations show that the magnetic couples have influences on inverters in unbalance condition, which should be considered in designation.

Publication Stats

208 Citations
14.49 Total Impact Points


  • 2005-2013
    • Huazhong University of Science and Technology
      • • School of Electrical and Electronic Engineering
      • • State Key Laboratory of Advanced Electromagnetic Engineering and Technology
      • • Department of Applied Power Electronics Engineering
      • • School of Computer Science and Technology
      Wu-han-shih, Hubei, China
  • 2008
    • Huazhong (Central China) Normal University
      Wu-han-shih, Hubei, China
  • 2006
    • University of Electronic Science and Technology of China
      Hua-yang, Sichuan, China