Liuchen Chang

University of New Brunswick, Fredericton, New Brunswick, Canada

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Publications (167)88.42 Total impact

  • Source
    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.
    Electric Power Systems Research 09/2015; 126:68–77. DOI:10.1016/j.epsr.2015.05.001 · 1.60 Impact Factor
  • Source
    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.
    Electric Power Components and Systems 06/2015; 43(8-10). DOI:10.1080/15325008.2014.999142 · 0.66 Impact Factor
  • Source
    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
    IEEE Transactions on Industrial Electronics 01/2015; DOI:10.1109/TIE.2015.2420627 · 6.50 Impact Factor
  • IEEE Transactions on Power Delivery 01/2015; DOI:10.1109/TPWRD.2015.2418580 · 1.66 Impact Factor
  • 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.
    IEEE Transactions on Sustainable Energy 10/2014; 5(4):1328-1336. DOI:10.1109/TSTE.2014.2327067 · 3.84 Impact Factor
  • Meiqin Mao · Peng Jin · N.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.
    IEEE Transactions on Sustainable Energy 07/2014; 5(3):938-946. DOI:10.1109/TSTE.2014.2313882 · 3.84 Impact Factor
  • 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.
    2014 IEEE 5th International Symposium on Power Electronics for Distributed Generation Systems (PEDG); 06/2014
  • 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.
    2014 IEEE 5th International Symposium on Power Electronics for Distributed Generation Systems (PEDG); 06/2014
  • 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.
    2014 IEEE 5th International Symposium on Power Electronics for Distributed Generation Systems (PEDG); 06/2014
  • 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.
    2014 IEEE 5th International Symposium on Power Electronics for Distributed Generation Systems (PEDG); 06/2014
  • 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.
    2014 IEEE 5th International Symposium on Power Electronics for Distributed Generation Systems (PEDG); 06/2014
  • 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.
    2014 International Power Electronics Conference (IPEC-Hiroshima 2014 ECCE-ASIA); 05/2014
  • Meiqin Mao · Yong Ding · Shiting Weng · Liuchen Chang
    2014 International Power Electronics Conference (IPEC-Hiroshima 2014 ECCE-ASIA); 05/2014
  • Meiqin Mao · Zheng Dong · Yong Ding · Liuchen Chang
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    ABSTRACT: The precise output power control and seamless transit of micro-source converters (MSCs) between grid-tied and islanded operation modes are of great significance for the stability of voltage and frequency, and power flow control in a microgrid. The wireless droop control method (WDCM) is one of the effective methods for MSCs to share loads dynamically and automatically and realize the “plug and play” function. But this method strongly rely on the local voltage and current sampling signals of MSC to dynamically control its output power, therefore the voltage drop induced by the line impedance will cause errors in output power control of MSCs and induce the system unstable. To realize the accurate power tracking and sharing, as well as the automatic seamless transition between grid-tied and islanded modes of microgrid, an accurate output power control method based on local measurement and unified control algorithm is proposed. In this method, two virtual impedances and an on-line estimated power compensation conductance are designed to form a unified controller for MSC, which uses the refined droop control method. The controller is valid for all types of line impedance and loads, besides, the sampling points of voltage and current required are located at the local MSC output terminals, thus increasing the modularity, reliability and flexibility of the controller. Finally, the validity of the improved control scheme is verified by simulation and experiment.
    2014 International Power Electronics Conference (IPEC-Hiroshima 2014 ECCE-ASIA); 05/2014
  • Riming Shao · Rong Wei · Liuchen Chang
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    ABSTRACT: This paper proposes a complete maximum power point tracking (MPPT) solution for grid-connected photovoltaic (PV) systems. The proposed MPPT algorithm is a multi-stage algorithm combined with the golden section search (GSS) method and two other commonly used methods: the perturb and observe (P&O) and the incremental conductance (INC). The GSS method is used for its fast convergence time and robustness. The GSS mechanism, as well as the whole multistage MPPT strategy, is described in this paper. Finally, the results of simulations and experiments are given to verify the good performance of the system.
    2014 IEEE Applied Power Electronics Conference and Exposition - APEC 2014; 03/2014
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    ABSTRACT: This paper presents a novel neural network-based approach to short-term, multi-step-ahead wind speed forecasting. The methodology combines predictions from a set of feed forward neural networks whose inputs comprehend a set of 11 explanatory variables related to past averages of wind speed, direction, temperature and time of the day, and their outputs represent estimates of specific wind speed averages. Forecast horizons range from 30 minutes up to 6:30 hours ahead with 30 minutes time steps. Final forecasts at specific horizons are combinations of corresponding neural network predictions. Data used in the experiments are telemetric measurements of weather variables from five wind farms in eastern Canada, covering the period from November 2011 to April 2013. Results show that the methodology is effective and outperforms established reference models particularly at longer horizons. The method performed consistently across sites leading up to more than 60% improvement over persistence and 50 % over a more realistic MA-based reference.
    Proceedings of the 2013 12th International Conference on Machine Learning and Applications - Volume 02; 12/2013
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    ABSTRACT: Power Electronic Converters (PECs) are routinely used to control the energy supplied to electric grids from distributed generators. The operation of PECs involves the control of voltage and current by rapidly switching power semiconductor devices. Rapid switching of these devices causes a certain class of high frequency noise called spikes which in turn are induced into sensor measurements. In addition to PEC control functions, the sensor measurements are also used to detect over current (OI) over voltage (OV) and under voltage (UV) faults. The presence of noise spikes compromises the performance and leads to unnecessary triggering of fault protection circuitry as a result of false detection of over/under voltage and current faults. The development of a new algorithm to remove short time electrical spikes from PEC sensors is the focus of this paper. In such a way, the PEC is unaffected and false OI, OV, and UV alarms are eliminated. The methodology uses the discrete wavelet transform (DWT) to generate a feature space where the spike feature is detected and removed, and the inverse DWT to reconstruct spike-free measurements. A Field-Programmable Gate Array (FPGA)-based interface board is designed to implement the new algorithm within an actual PEC system. The designed FPGA board along with the new algorithm is used in integration of distributed generators into power systems.
    2013 4th IEEE International Symposium on Power Electronics for Distributed Generation Systems (PEDG); 07/2013
  • Meiqin Mao · Yu Cao · Liuchen Chang
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    ABSTRACT: Accurate prediction of short-term wind power is an effective way to rationally adjust the scheduling strategies and to improve the operation stability and economy of microgrid with wind turbines. A new improved prediction method which does not rely on any basic prediction methods is proposed based on analysis of a traditional wind power prediction procedure and in terms of strategy how to use a basic prediction method in wind power prediction procedure. By the proposed method, an additional error prediction model is built to predict the error of the predicted results by the traditional prediction method. And the predicted error value is added back to the predicted results mentioned above to reach the final predicted results. Taking Back propagation (BP) neural network as a basic prediction method, the proposed prediction method is validated by output power prediction of a real wind farm. Support vector machine (SVM) is chosen as another basic prediction method to test the versatility of the proposed improved prediction method. The simulation results show that the proposed wind power prediction method can improve the prediction accuracy by about eight percent. The proposed method does not involve the internal characteristics of any basic prediction methods or require any auxiliary methods, which is quite different from the traditional improved methods available and thus is more universal.
    2013 4th IEEE International Symposium on Power Electronics for Distributed Generation Systems (PEDG); 07/2013
  • Meiqin Mao · Yuefan Liu · Peng Jin · Hui Huang · Liuchen Chang
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    ABSTRACT: For a microgrid consisting of photovoltaic generators and hybrid energy storage systems (HESS) with the battery and supercapacitor (SC) banks, this paper presents a real time energy coordinated control method for both grid-connected and stand alone operation modes. In the proposed method, the low-frequency and high-frequency power of fluctuant loads are decomposed by the algorithm of Fast Fourier Transfer (FFT), and are sent to battery and supercapacitor banks, respectively, thus extending the service life of battery. To achieve the control objectives and realize the smooth transfer of different operation modes for the microgrid, a unified control strategy is designed for the inverter of battery, which enables it to operate at both islanding and grid-connected mode without detecting the operation mode of microgrid in advance. Simulation results show that the power of loads absorbed by battery is smooth, and the supercapacitor can respond to rapid fluctuation of the power of loads. With the unified control strategy, the power flows to grid can be controlled when the microgrid operates at grid-connected mode while the voltage and frequency on AC bus can be stabilized by the inverter of battery at the islanding mode.
    2013 4th IEEE International Symposium on Power Electronics for Distributed Generation Systems (PEDG); 07/2013
  • Meiqin Mao · Hui Huang · Liuchen Chang
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    ABSTRACT: A typical microgrid system comprises photovoltaic generator which usually operates at both grid-connected and intentionally islanding operation modes. In terms of such operation characteristics of the microgrid, this paper proposes an active power control strategy dynamically to balance the energy output and consumption in the microgrid. By the control strategy, the photovoltaic generators may actively curtail their output energy instead of maximum output power by MPPT when the total microgrid system has surplus energy specifically at intentionally islanding operation mode. In order to ensure the stability of the voltage amplitude and frequency at PCC and achieve energy real-time coordinated and balance control, a method by real-time calculating the change of load power according to P-f and Q-V drooping relationship, then assigning to each micro-source by energy dispatching layer is proposed. The simulation results prove that proposed active power control strategy and coordinated method operates effectively to dynamically manage energy of the microgrid.
    2013 4th IEEE International Symposium on Power Electronics for Distributed Generation Systems (PEDG); 07/2013

Publication Stats

2k Citations
88.42 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
    • Xi'an Jiaotong University
      • Department of Mechatronics Engineering
      Xi’an, Shaanxi Sheng, China
    • Huazhong University of Science and Technology
      Wu-han-shih, Hubei, China
  • 2000
    • Beijing Jiaotong University
      • School of Electrical Engineering
      Beijing, Beijing Shi, China