Liuchen Chang

University of New Brunswick, Fredericton, New Brunswick, Canada

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Publications (129)47 Total impact

  • 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
  • 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
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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
  • 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
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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
  • Mao Meiqin, Niu Chengyu, Liuchen Chang
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    ABSTRACT: In order to design and test the control algorithms of the actual direct-drive wind generation system (DDWGS) with a permanent magnet synchronous generator (PMSG), it is necessary to reproduce the dynamic performances of wind turbine and PMSG in the lab. After the analysis of the aerodynamic, mechanical model of wind turbine and the electrical model of PMSG, a novel simulator based on three-phase voltage source inverter and DSP for a DDWGS with PMSG is proposed in this paper. Based on Park's transformation, double closed-loop PI control algorithm and space vector PWM, the proposed simulator which eliminates electro-mechanical parts can simulate the external mechanical and electrical characteristics of PMSG. The simulation and experiment results show that the proposed simulator can accurately simulate the external mechanical and electrical characteristics of the actual DDWGS with PMSG under static and dynamic conditions.
    ECCE Asia Downunder (ECCE Asia), 2013 IEEE; 01/2013
  • Meiqin Mao, Wenjian Gong, Liuchen Chang
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    ABSTRACT: A combined prediction method based on ensemble empirical mode decomposition (EEMD) and support vector machine (SVM) is proposed to tackle with the problem of the short-term forecast of photovoltaic system (PVs) hourly output a day ahead. Weather types are divided into abnormal day (weather changed suddenly) and normal day. By the proposed method, firstly, the history data for hourly output of PVs is decomposed into a series of components by using EEMD method. Considering different factors for different type of weather, different models are built and different kernel functions and parameters are chosen to deal with each component of the decomposed data by using SVM. Simulation results show that the proposed classification modeling ideas and EEMD-SVM combination forecasting method enable that the mean absolute percentage error results for the abnormal days is decreased by 5%, and for normal day is decreased by 3% comparing with the traditional SVM method and Back Propagation (BP) neural network method respectively.
    Energy Conversion Congress and Exposition (ECCE), 2013 IEEE; 01/2013
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    ABSTRACT: In this paper, a power-frequency (P-ω) controller is presented for voltage source converters (VSC). The approach is intended for multiple parallel VSCs forming a microgrid operating in both grid-connected and islanded modes. The proposed controller allows a VSC to mimic the operation of a synchronous generator (SG) by implementing the swing equation of SG with a primary frequency controller. In addition, a generalized model of the active power generation dynamics is developed in order to analyze the stability and to design the main control parameters. In contrast with the conventional droop control method, the proposed controller improves the close-loop system dynamic response without changing the frequency accuracy. The obtained results show the good performance of the proposed controller.
    ECCE Asia Downunder (ECCE Asia), 2013 IEEE; 01/2013
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    ABSTRACT: An economic evaluation method and optimal allocation model of the industrial PV microgrids are proposed in this paper. The economic indexes include levelized energy cost, emission reduction benefits and payback period. The optimal model considering various relevant issues such as local insolation level and detailed investment costs is established and applied to improve the configuration of the PV microgrids for four different operation strategies. The optimization problem is solved by Particle Swarm Optimization to obtain the minimum annual energy cost of the system and bring more economic and emission reduction benefits for industrial users. The simulation results based on three months running data of a 500kW industrial PV microgrid in Dongguan City, China, verify that the optimal allocations by the proposed method can meet the technical indicators as well as the economic optimum, thus effectively optimizing industrial PV microgrid in both economic and environmental way. In addition, the added batteries can not only be used to maximize the utilization of renewable energy, but also enhance the system's ability of peak load shifting. Besides, the sensitivity of the impact of different parameters on the system is also performed. The economic evaluation and optimal allocation of the industrial PV microgrids in this paper provide a reference for the application of similar projects.
    Energy Conversion Congress and Exposition (ECCE), 2013 IEEE; 01/2013
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    T. Kamel, Y. Biletskiy, C.P. Diduh, Liuchen Chang
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    ABSTRACT: This paper provides new methods to detect and investigate the failure in the DC filter of the power rectifier. The proposed diagnoses techniques are interested in two types of capacitor faults; capacitor aging and capacitor open circuit O.C. faults. The required inputs for the methods are the ripple of the DC voltage of the capacitors as well as the loading and the supply conditions.
    Electrical & Computer Engineering (CCECE), 2012 25th IEEE Canadian Conference on; 01/2012
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    T. Kamel, Y. Biletskiy, C.P. Diduh, Liuchen Chang
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    ABSTRACT: This paper presents a fault detection, classification, and diagnoses for all the successive stages of the power electronic converter, including; the three phase rectifier, the dc-dc converter, and finally the single phase inverter. The paper provides a number of proposed algorithms for the open circuit fault diagnoses of these stages. The inputs of these algorithms are the voltage and current measurements of these stages after they undergo certain signal processing so that the inputs of the proposed algorithms could efficiently reflect the fault occurrence and behaviour.
    Electrical & Computer Engineering (CCECE), 2012 25th IEEE Canadian Conference on; 01/2012
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    T. Kamel, C. Diduch, Y. Bilestkiy, Liuchen Chang
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    ABSTRACT: DC filters are responsible for more than half of the failures in electric power converters. One approach to improving the reliability, performance and maintainability is to include failure diagnosis logic within the power converter. DC bus capacitor failures may be classified as gradual faults caused by capacitor aging and sudden faults which may take the form of breakdown faults resulting from a blown capacitor fuse, and open circuit O-C faults. This paper presents new methods to detect and isolate failures in the DC filters of power converters caused by capacitor aging and O-C faults.
    Energy Conversion Congress and Exposition (ECCE), 2012 IEEE; 01/2012
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    ABSTRACT: This paper proposes a detection method for open-circuit faults in a 3-phase uncontrolled rectifier that forms the input stage of a single-phase current controlled power converter. The rectifier is driven by a 3-phase wind generator with variable amplitude and frequency. The algorithm is based on fault signatures embedded within the output voltage ripple of the rectifier. It is demonstrated that seven different classes of open circuit faults can be detected and isolated.
    Power Electronics for Distributed Generation Systems (PEDG), 2012 3rd IEEE International Symposium on; 01/2012
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    ABSTRACT: Power converters are widely used to control the power energy generated by distributed generators in power grids. The operation of power converters involves monitoring and adjustment of voltage and current by power devices, which are switching rapidly. The rapid switching causes spikes that can result in the false detection of voltage faults. This present paper describes a method to detect and remove spikes from power converter sensors that allows power converter to be not affected. The methodology behind the present work is the use of discrete wavelet transform enabling spike detection and removal.
    Electrical & Computer Engineering (CCECE), 2012 25th IEEE Canadian Conference on; 01/2012
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    ABSTRACT: Economic performances of a microgrid with multi-energy are effected by many factors such as the configuration of microgrid systems for the specific installation sites and cluster of loads, operation modes and dispatching schedules of the microgrid, the electricity market, energy policy and alike. And the configuration of the microgrid is the premise of all factors. This paper presents an optimization model to quantitatively evaluate the economic impacts of different installation sites on microgrids with multi-energy. In this model, optimal configuration schemes for microgrids installed at typical sites are designed by particle swarm optimization method. The economic performances of optimal configuration schemes are evaluated by the operation simulation with the proposed indexes. Those typical installation sites mentioned above belong to different regions which are divided into the five-level classifications in terms of the richness of wind and solar resource and the distributions of loads in China. The calculation results may be used for the decision-making references by the decision-makers.
    Power Electronics for Distributed Generation Systems (PEDG), 2012 3rd IEEE International Symposium on; 01/2012
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    ABSTRACT: A novel control method based on the proportional resonant differential (PRD) control is proposed for the grid-connected current source inverter (CSI) used in the direct drive permanent magnet synchronous wind generation system. By the optimal design of the parameters of the PRD controller in two-phase stationary frame, the CSI system can realize zero steady-state error control and effectively damp the resonance caused by its output LC filter just by feeding back the grid-connected current. This not only greatly simplifies the controller design but also enhances the stability of the system. Simulation results show grid-connected CSI with this method has fast dynamic response and good steady-state performances.
    Power Electronics for Distributed Generation Systems (PEDG), 2012 3rd IEEE International Symposium on; 01/2012
  • Riming Shao, M. Kaye, Liuchen Chang
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    ABSTRACT: Abstract-The power converter is a critical component of a distributed generation (DG) system, particularly for a renewable energy based distributed generator. With the rapid development and growing applications of DG systems, power converters have evolved from a traditional "power conversion device" to a "system integrator". This paper outlines the basic and advanced building blocks of power converters for distributed generation systems, with an emphasis on the new algorithms developed especially for grid-connected single-phase power converters in small wind turbines and photovoltaic systems. A grid-connected power converter should feed power of a high quality into a grid with a low total harmonic distortion (THD), and fast dynamic response to the variations of a renewable energy resource. The newly developed space vector based pulse width-modulation (PWM) with predictive current control provides a direct cycle-by-cycle regulation of the current waveform feeding into the grid. Effective anti-islanding is an essential function of a power converter, in compliance with the grid interconnection requirements. As active islanding detection methods exert disturbances to the grid and passive islanding detection methods generally have large non-detection zones, new and hybrid islanding detection methods have been developed. A power spectral density method has been developed to continuously monitor and identify the possible features of an islanding formation. Maximum power extraction from renewable energy resources is vitally important for distributed generators. Many algorithms have been developed for maximum power point tracking (MPPT) of photovoltaic and wind energy systems. A new MPPT method has been developed by integrating the fast extremum-finding method of Golden Section Search (GSS) into a multi-stage MPPT algorithm. The proposed MPPT algorithm provides fast response (in the order of 40 msec) and high tracking accuracy (99.9%) as compared to the existing algorithms.
    Power Electronics and ECCE Asia (ICPE & ECCE), 2011 IEEE 8th International Conference on; 07/2011
  • Source
    Hossein Madadi Kojabadi, Liuchen Chang
    Wind Turbines, 04/2011; , ISBN: 978-953-307-221-0
  • Source
    Wind Turbines, 04/2011; , ISBN: 978-953-307-221-0
  • Mao Meiqin, Dong Wei, Liuchen Chang
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    ABSTRACT: This paper presents a general multi-agent based model for the hierarchical and distributed energy control of a Microgrid. In this model, the agents under three different levels are classified and defined in detail. And based on the model, a novel simulation platform for the energy management system of the Microgrid (EMS-MG) is designed in terms of Client-Server and implemented under C++ Builder environment. Taking the generation automatic control for example and by the proposed model and implemented EMS-MG, a simulation result is shown to illustrate the operation process of the simulation platform and present the benefits of the proposed method.
    01/2011;

Publication Stats

1k Citations
47.00 Total Impact Points

Institutions

  • 1994–2011
    • University of New Brunswick
      • Department of Electrical & Computer Engineering
      Fredericton, New Brunswick, Canada
  • 2007
    • Hefei University of Technology
      Luchow, Anhui Sheng, China
    • East China JiaoTong University
      Jiangxi, Gansu Sheng, China
  • 2005
    • Huazhong University of Science and Technology
      Wu-han-shih, Hubei, China
  • 2000
    • Beijing Jiaotong University
      • School of Electrical Engineering
      Beijing, Beijing Shi, China
  • 1995
    • Tsinghua University
      Peping, Beijing, China