Liuchen Chang

University of New Brunswick, Fredericton, New Brunswick, Canada

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Publications (179)102.44 Total impact

  • Ning Liu · Chris Diduch · Liuchen Chang · Jianhui Su
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    ABSTRACT: This paper proposes a passive islanding detection method based on computing a set of frequency-dependent reference impedance magnitudes and comparing them with the measured impedance magnitudes at the point of common coupling (PCC). The reference impedance may be identified online over a selected frequency band from the measured voltage and current at the PCC. Islanding is detected when the magnitude differences between the reference impedance and the measured impedance over the chosen frequency band are smaller than a preset threshold. Robustness of the proposed method is verified in a distribution network, the method avoids misdiagnosing islanding condition as normal condition. Performance analyses are discussed from two perspectives of nondetection zone (NDZ) and fault detection zone. By combining the undervoltage/overvoltage (UV/OV) and underfrequency/overfrequency (UF/OF) methods with the proposed method, the NDZs of UV/OV and UF/OF methods can be reduced.
    No preview · Article · Dec 2015
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    ABSTRACT: This paper presents a passive islanding detection approach based on measurements of the frequency-dependent impedance at the point of common coupling. The approach exploits the presence of harmonics injected by the electric power system (EPS) and harmonics injected by the distributed generator (DG). Models of impedance are developed to characterize the interconnection topology among the DG, the EPS, and the local load. The interconnection topology changes when islanding occurs resulting in a frequency-dependent change of the impedance as seen by the DG. Islanding is detected when certain changes in the impedance magnitude are detected at certain harmonics. The approach is new: 1) an impedance-based analytic model is derived from the interconnection topology and this may be used as a basis for feature extraction and threshold selection; 2) a passive algorithm is proposed as an enhancement to the under/over-frequency (UF/OF) method; 3) a grid impedance parameter space is derived to characterize the detection zone; and 4) a local load parameter space is used to compare the nondetection zone (NDZ) of the proposed method with that of the UF/OF method without the enhancement. The proposed approach is shown to reduce the NDZ when combined with the UF/OF method.
    No preview · Article · Dec 2015 · IEEE Transactions on Power Delivery
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    Tamer Kamel · Yevgen Biletskiy · Liuchen Chang
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    ABSTRACT: The reliability of power electronics converter systems (PECSs) is of paramount importance in industrial, commercial, aerospace, and military applications. Therefore, the knowledge about the fault mode behavior of a converter system is extremely important from the perspective of improved system design, protection, and fault tolerant control. Faults of power switches in PECSs are classified as Short Circuit (S-C) faults, Open Circuit (O-C) faults, and degradation faults. S-C faults in most cases cause an over-current condition that is readily detected and acted upon by standard protection systems such over-current, under-voltage or over-voltage protection. However, the degradation faults as well as O-C faults often do not trigger fault protection, but rather cause system malfunction or performance degradation. Since the standard protection system may not detect these fault types, their diagnoses become critical for PECSs. This paper presents new methods for fault detection, localization, and diagnosis for grid-connected power converters as well as the identification of the unbalance input voltage to the converter. The proposed fault diagnostic algorithms are verified in both; the simulation and the experimental environments in order to evaluate their robustness and effectiveness. The power converter under the study consists of three main subsystems: the three-phase uncontrolled rectifier, the boost chopper, and the single-phase inverter circuits
    Full-text · Article · Oct 2015 · IEEE Transactions on Industrial Electronics
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    Tamer Kamel · Yevgen Biletskiy · Liuchen Chang
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    ABSTRACT: The functionality of power electronic converter systems (PECS) is a cornerstone in various industrial applications. One of the key requirements to ensure reliable functions of PECS is the analysis of their behavior during fault conditions. Characterizing the behavior of PECS during the fault conditions can provide a standpoint for enhancing their control and protection algorithms. Moreover, effective solutions for on-line monitoring for PECS are significant in order to improve the system supervision and management. Consequently, this paper presents fault diagnosis and on-line monitoring schemes for grid-connected single-phase inverters in typical commercial PECS utilized for renewable energy distributed generation. The paper provides fault detection, classification and location of the open circuit (O-C) faults which do not trigger the standard protection systems in the single-phase inverters. The proposed fault diagnostic algorithm is implemented by adaptive neuro fuzzy inference system (ANFIS) algorithm and it is based solely on the inverter output current measurements. Therefore, the proposed algorithm requires much fewer inputs compared to the previous research works. Furthermore, the paper implements an on-line monitoring by using a communication interface board which is connected to graphical user interface (GUI) software through transmission control and internet protocols (TCP/IP). The GUI software integrates the on-line monitoring for the electrical signals of the single-phase inverter, as well as incorporates a real time database for these signals.
    Full-text · Article · Sep 2015 · Electric Power Systems Research
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    Hossein Hojabri · Hossein Mokhtari · Liuchen Chang
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    ABSTRACT: Abstract—A matrix converter is a voltage/current source AC/AC frequency converter. In grid-connected operation of a variable-speed permanent magnet synchronous wind power generator, the matrix converter is normally controlled as a voltage source converter. In this control method, the generator-side voltage is synthesized from the grid-side voltage source. However, in the stand-alone mode of operation, the grid-side stiff voltage source is not available, and the input filter of the matrix converter is unstable. In this article, a new control method is presented that controls a permanent magnet synchronous wind generator in a stand-alone mode with a matrix converter as a current source converter. The proposed method is so fast that it can control the matrix converter small capacitor voltage despite the generator large inductance and without any input filter instability. A multi-pole permanent magnet synchronous wind generator is simulated to prove the performance of the proposed control strategy.
    Preview · Article · Jun 2015 · Electric Power Components and Systems
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    ABSTRACT: Reliability of power electronic systems is of paramount importance in industrial, commercial, aerospace, and military applications. Faults in power converters are classified as short circuit faults, open circuit faults, and degradation faults. Short circuits (S-C) in most cases cause an overcurrent condition that is readily detected and acted upon by standard protection systems. However, open circuit (O-C) faults often do not trigger fault protection, but rather cause system malfunction or performance degradation. Since the standard protection system may not detect the open circuit faults, O-C fault diagnosis becomes critical for power converter. This paper presents new methods for O-C fault detection, localization, and diagnosis for small wind power converters that consist of three subsystems: the three phase rectifier, the dc-dc converter, and the single-phase inverter.
    Full-text · Conference Paper · Jun 2015
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    Tamer Kamel · Yevgen Biletskiy · Liuchen Chang
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    ABSTRACT: The monitoring and supervision of grid-connected solar and wind energy sources with consumers require further improvement of the performance and the stability of energy transfer. Therefore, the effective communication between the power generation and the supervisory nodes of power grids are necessary to manage electrical generation from renewable energy sources. The communication interface, which is presented in this paper, transfers data about the state of power generation nodes to supervisory nodes to control the power grid. The data is also visualized for possible human intervention; therefore, this paper presents data communication and Graphical User Interface (GUI) for single-phase grid connected power electronic converter. The data communication interface board is responsible for receiving the measurements of the electrical parameters of the converter and the digital statuses, which determine either the converter is in normal or fault condition, and specify the fault type if the converter is faulted as well
    Full-text · Conference Paper · Jun 2015
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    Tamer Kamel · Y. Biletskiy · Liuchen Chang
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    ABSTRACT: DC filters are responsible for more than half of the failures in the power electronic converters. One approach to improving the reliability and maintainability of the converters is to include failure diagnosis for the DC filters within the power converter. DC filters failures may be classified as sudden faults which may take the form of breakdown faults resulting from a blown capacitor fuse and gradual faults caused by capacitor aging. This paper presents a fault detection and location for the capacitor aging faults in the DC filters of the power converters. The proposed fault diagnosis is based on the adaptive neuro-fuzzy inference system (ANFIS) algorithm. The inputs to the ANFIS unit are only the input voltage of the converter as well as the voltages across the DC filters. The output of the ANFIS unit is utilized as an index in order to identify the capacitor aging fault in the power converter. Then, it locates the fault within the two DC filters installed in the power converter
    Full-text · Conference Paper · May 2015
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    Tamer Kamel · Yevgen Biletskiy · Liuchen Chang
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    ABSTRACT: This paper presents real time diagnosis for open circuited (O-C) and unbalance faults in power electronic converters (PECs) connected to residential small wind systems grid-tied. The spectrum analysis along with the DC components of the voltage and current measurements available in the converter are utilized for the O-C fault detection, classification and localization of the power switching devices in the PEC, as well as the identification of the unbalance input voltage to the converter. The proposed methodologies in this paper require much fewer inputs compared to the previous researches; therefore, they avoid any additional sensors or hardware which include further costs and expenses on such systems. The experimental evaluations for the proposed algorithms are provided and demonstrate the effectiveness and the robustness of the proposed diagnostic algorithms in this paper. The PEC under study consists of three main subsystems; uncontrolled three-phase rectifier, boost chopper, and single-phase inverter.
    Full-text · Article · Jan 2015 · IEEE Transactions on Industrial Electronics
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    Full-text · Article · Jan 2015 · IEEE Transactions on Power Electronics
  • Meiqin Mao · Peng Jin · Liuchen Chang · Haibo Xu
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    ABSTRACT: This paper proposes an optimal design model of microgrids with small-scale photovoltaic systems (SS-PVs) and storage batteries for industries along with three economic evaluation indicators. The proposed indicators are levelized energy cost, emission reduction benefits, and payback period. They are combined to comprehensively evaluate economic performances and investment risk of the microgrids. The optimal model considering local solar insolation level, environment benefits, different operation modes, and initial investment costs is formulated and applied to obtain the optimal configuration of the microgrids with SS-PVs by particle swarm optimization (PSO) method. The simulation results based on 4-month real operation data of a 500-kW PV microgrid for industries in Guangdong, China, have verified that the optimal design by the proposed method can meet the technical requirements as well as the economic performances, thus effectively optimizing the microgrid with SS-PVs for industries in both economic and environmental aspects. Furthermore, the sensitivity analysis of the impact of different parameters on the system is also performed. The results provide a reference for the application of similar projects.
    No preview · Article · Oct 2014 · IEEE Transactions on Sustainable Energy
  • Meiqin Mao · Zheng Dong · Yong Ding · Liuchen Chang

    No preview · Conference Paper · Sep 2014
  • Meiqin Mao · Peng Jin · Nikos D. Hatziargyriou · Liuchen Chang
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    ABSTRACT: Energy management systems for microgrids (EMS-MG) play an important role in ensuring their stable and economic operation. This paper presents a multiagent-based hybrid EMS-MG (HEMS-MG) with both centralized and decentralized energy control functionalities. Based on this framework, three-level hierarchical energy management strategies are presented, in which a cooperation method with contract net protocol and multifactor evaluation mechanisms are applied. A coordinated energy management framework is realized by the combination of autonomous control of local distributed energy resources at the local level with coordinated energy control at the central level of the microgrid. A novel simulation platform for the HEMS-MG is designed in terms of the client–server frame and implemented under the C++ Builder environment. To prove the effectiveness and benefits of the proposed control system, an example of generation cooperation control of a laboratory microgrid is provided. The simulation results show that the proposed control system is an effective way to manage and optimize microgrid operation.
    No preview · Article · Jul 2014 · IEEE Transactions on Sustainable Energy
  • Riming Shao · Rong Wei · Liuchen Chang
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    ABSTRACT: This paper proposes an improved current control algorithm for single-phase grid-connected inverters. The new algorithm has a superior performance over commonly used predictive current control methods. Conventional predictive control suffers from the inherent control delay in a digital control system. The proposed control algorithm applies an appropriate digital controller to compensate for the influence of control delay. This paper introduces the design approaches for the digital current control, including system modeling, discretization, and disturbance decoupling techniques. Design case studies of both the conventional predictive current control and improved current control are presented in this paper. These two methods were both implemented on a 10kW grid-connected inverter for comparative studies. All the analytical and experimental results given in the paper have verified the effectiveness and superiority of the proposed current control algorithm.
    No preview · Conference Paper · Jun 2014
  • Jintao Liao · Jianhui Su · Liuchen Chang
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    ABSTRACT: This paper presents a novel inverter topology that is applied to single-phase grid-connected photovoltaic systems. The proposed topology has an active decoupling function, which not only eliminates the double line frequency ripple power in the dc-link but also accepts large voltage ripple across the decoupling capacitor in order to reduce the requirement of the decoupling capacitance. Traditionally, bulky electrolytic capacitors are employed in passive decoupling of power, which limits the system lifespan. The reduction of the decoupling capacitance makes it possible for using long life film capacitors in photovoltaic systems. The simulation results verify the operation of the proposed topology and its control strategy.
    No preview · Conference Paper · Jun 2014
  • Meiqin Mao · Fengming Mei · Peng Jin · Liuchen Chang
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    ABSTRACT: In order to achieve the interoperability among different devices made from different manufacturers, IEC61850 protocol is applied to the energy management system of microgrids (MEMS) in this paper to make the standardization of data communication among the microgrid. The communication system model of three layers for the microgrid is proposed and applied into microgrids. And the IEC61850-based data model for a microgrid is established based on the characteristics of IEC61850 standard modeling, the real-time data in MEMS and objective-oriented concept. In the proposed data model, the whole distributed generation (DG) unit or a load unit is considered as a logical physical device with different data nodes. A wind generating unit is taken as an example to illustrate the proposed modeling process in detail. The proposedIEC61850 Client and Server based communication system and corresponding testbed are also developed in this paper. The test results verify that the proposed method provides an effective technical way for the equipment integration, operation analysis and intelligent control in microgrids.
    No preview · Conference Paper · Jun 2014
  • Meiqin Mao · Zheng Dong · Ying Dong · Hui Huang · Liuchen Chang
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    ABSTRACT: The controller based on unified control strategy for the DC/AC converters in a photovoltaic microgrid (PV-MG) is proposed for both grid-connected and islanding mode operation and seamless switching. The unified controller is designed by combining the power PI regulator with droop control to realize the current control and voltage control at the grid-connected and islanding modes respectively, and the automatic and seamless switching between the two modes of PV-MG can be realized. According to the step response dynamic index and stability constraints, the parameters of the controller are optimized with root locus methods. The Matlab/Simulink simulation reslults show the feasibility and effectiveness of the proposed control algorithm.
    No preview · Conference Paper · Jun 2014
  • Shuang Xu · Craig Church · Riming Shao · Liuchen Chang
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    ABSTRACT: This paper presents a new method for estimation of energy cost for grid-connected small wind power systems (SWPSs), which integrates the wind resources, turbine power curves, system component losses and costs, and reliability into a comprehensive model. For each of these aspects, models were established. Various structural options of small wind power system components at both fixed speed and variable speed operation were considered. Through Monte-Carlo based simulations, a statistical estimation of energy costs of a typical 30kW small wind power system was obtained for the life cycle operation. The simulation results can give consumers an overview of how much they need to invest for a small wind power system during its installed lifetime. Furthermore, the results of different structural options can serve as a lookup table to provide the cost effectiveness of different structural types of small wind power systems, and also provide a benchmark for future research works on energy cost evaluation.
    No preview · Conference Paper · Jun 2014
  • Du Yan · Liuchen Chang · Meiqin Mao · Jianhui Su · Ning Liu
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    ABSTRACT: In islanding microgrid, the impact of line impedance on the proportional power sharing cannot be neglected if multi-inverters are operated to form a microgrid. In this paper, an improved droop controller is proposed to reduce the unexpected dynamic and steady power sharing errors caused by the mismatching of line impedance. With this proposed combined compensation, the power quality, the dynamic and steady performances are benefited. The design principle of the parameters in the proposed controller is also presented. The simulation and experimental results are provided to validate the proposed controller and the parameters design methodology.
    No preview · Conference Paper · May 2014
  • Meiqin Mao · Yong Ding · Shiting Weng · Liuchen Chang
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    ABSTRACT: A control strategy for direct-drive PMSG wind generation system based on three phase current source converter (CSC-DPMSG-WGS) is presented in this paper. By the proposed method, once unbalanced grid voltage fault happens, the generator-side converter limits the power which flows to DC-link rapidly, meanwhile the grid-side converter controls the positive and negative sequence currents respectively with a dc current closed loop to eliminate the power ripples of twice times fundamental frequency caused by unbalanced grid fault to maintain dc current stable. By coordinated control of generator-and grid-side converters, the stability of the CSC-DPMSG-WGS may be improved so that low voltage ride-through capability for CSC-DPMSG-WGS may be realized. Simulation results are provided to verify the proposed control strategy.
    No preview · Conference Paper · May 2014

Publication Stats

2k Citations
102.44 Total Impact Points

Institutions

  • 1994-2015
    • University of New Brunswick
      • Department of Electrical & Computer Engineering
      Fredericton, New Brunswick, Canada
  • 2007-2014
    • Hefei University of Technology
      • School of Electrical Engineering & Automation
      Luchow, Anhui Sheng, China
    • East China JiaoTong University
      Jiangxi, Gansu Sheng, China
  • 2005
    • Huazhong University of Science and Technology
      Wu-han-shih, Hubei, China
    • Xi'an Jiaotong University
      • Department of Mechatronics Engineering
      Xi’an, Shaanxi Sheng, China
  • 2000
    • Beijing Jiaotong University
      • School of Electrical Engineering
      Beijing, Beijing Shi, China
  • 1991
    • Queen's University
      • Department of Electrical & Computer Engineering
      Kingston, Ontario, Canada