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Xiaofeng Sun

Bio: Xiaofeng Sun is an academic researcher from Yanshan University. The author has contributed to research in topics: Inverter & AC power. The author has an hindex of 22, co-authored 84 publications receiving 1692 citations.
Topics: Inverter, AC power, Microgrid, Voltage droop, Harmonic


Papers
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Journal ArticleDOI
TL;DR: The findings indicate that the proposed dynamic phasor model is able to predict accurately the stability margins of the system, while the conventional reduced-order small signal model fails.
Abstract: System modeling and stability analysis is one of the most important issues of inverter-dominated microgrids. It is useful to determine the system stability and optimize the control parameters. The complete small signal models for the inverter-dominated microgrids have been developed, which are very accurate and could be found in literature. However, the modeling procedure will become very complex when the number of inverters in microgrid is large. One possible solution is to use the reduced-order small signal models for the inverter-dominated microgrids. Unfortunately, the reduced-order small signal models fail to predict the system instabilities. In order to solve the problem, a new modeling approach for inverter-dominated microgrids by using dynamic phasors is presented in this paper. Our findings indicate that the proposed dynamic phasor model is able to predict accurately the stability margins of the system, while the conventional reduced-order small signal model fails. In addition, the virtual ${\boldsymbol{\omega }}$ -E frame power control method, which deals with the power coupling caused by the line impedance X/R characteristic, has also been chosen as an application example of the proposed modeling technique.

216 citations

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TL;DR: In this article, a dual-bridge LLC resonant converter for wide input applications is proposed and the topology is an integration of a half-bridge (HB) LLC circuit and a full-bridge circuit.
Abstract: This paper proposes a dual-bridge (DB) LLC resonant converter for wide input applications. The topology is an integration of a half-bridge (HB) LLC circuit and a full-bridge (FB) LLC circuit. The fixed-frequency pulsewidth-modulated (PWM) control is employed and a range of twice the minimum input voltage can be covered. Compared with the traditional pulse frequency modulation (PFM) controlled HB/FB LLC resonant converter, the voltage gain range is independent of the quality factor, and the magnetizing inductor has little influence on the voltage gain, which can simplify the parameter selection process and benefit the design of magnetic components as well. Over the full load range, zero-voltage switching (ZVS) and zero-current switching (ZCS) can be achieved for primary switches and secondary rectifier diodes, respectively. Detailed analysis on the modulation schedule and operating principle of the proposed converter is presented along with the converter performance. Finally, all theoretical analysis and characteristics are verified by experimental results from a 120-V to 240-V input 24 V/20 A output converter prototype.

167 citations

Journal ArticleDOI
Xiaofeng Sun1, Baocheng Wang1, Yue Zhou1, Wei Wang1, Huiyuan Du1, Zhigang Lu1 
TL;DR: A novel cascaded seven-level inverter topology with a single input source integrating switched-capacitor techniques is presented, which replaces all the separate dc sources with capacitors, leaving only one H-bridge cell with a real dc voltage source and only adds two charging switches.
Abstract: In this paper, a novel cascaded seven-level inverter topology with a single input source integrating switched-capacitor techniques is presented. Compared with the traditional cascade multilevel inverter, the proposed topology replaces all the separate dc sources with capacitors, leaving only one H-bridge cell with a real dc voltage source and only adds two charging switches. The capacitor charging circuit contains only power switches, so that the capacitor charging time is independent of the load. The capacitor voltage can be controlled at a desired level without complex voltage control algorithm and only use the most common carrier phase-shifted sinusoidal pulse width modulation strategy. The operation principle and the charging–discharging characteristic analysis are discussed in detail. A 1-kW experimental prototype is built and tested to verify the feasibility and effectiveness of the proposed topology.

167 citations

Journal ArticleDOI
TL;DR: In this article, a current-fed LLC resonant converter that is able to achieve high efficiency over a wide input voltage range is derived by integrating a two-phase interleaved boost circuit and a full-bridge LLC circuit together by virtue of sharing the same fullbridge switching unit.
Abstract: This paper proposes a current-fed LLC resonant converter that is able to achieve high efficiency over a wide input voltage range. It is derived by integrating a two-phase interleaved boost circuit and a full-bridge LLC circuit together by virtue of sharing the same full-bridge switching unit. Compared with conventional full-bridge LLC converter, the gain characteristic is improved in terms of both gain range and optimal operation area, fixed-frequency pulsewidth-modulated (PWM) control is employed to achieve output voltage regulation, and the input current ripple is minimized as well. The voltage across the turned-off primary-side switch can be always clamped by the bus voltage, reducing the switch voltage stress. Besides, its other distinct features, such as single-stage configuration, and soft switching for all switches also contribute to high power conversion efficiency. The operation principles are presented, and then the main characteristics regarding gain, input current ripple, and zero-voltage switching (ZVS) considering the nonlinear output capacitance of MOSFET are investigated and compared with conventional solutions. Also, the design procedure for some key parameters is presented, and two kinds of interleaved boost integrated resonant converter topologies are generalized. Finally, experimental results of a converter prototype with 120–240 V input and 24 V/25 A output verify all considerations.

140 citations

Journal ArticleDOI
TL;DR: In this article, the leakage current elimination of a three-phase four-leg PV inverter is investigated with the common-mode loop model established, the generation mechanism of leakage current is clearly identified Different typical carrier-based modulation methods and their corresponding commonmode voltages are discussed.
Abstract: Eliminating the leakage current is one of the most important issues for transformerless three-phase photovoltaic (PV) systems In this paper, the leakage current elimination of a three-phase four-leg PV inverter is investigated With the common-mode loop model established, the generation mechanism of the leakage current is clearly identified Different typical carrier-based modulation methods and their corresponding common-mode voltages are discussed A new modulation strategy with Boolean logic function is proposed to achieve the constant common-mode voltage for the leakage current reduction Finally, the different modulation methods are implemented and tested on the TMS320F28335 DSP +XC3S400 FPGA digital control platform The experimental results verify the effectiveness of the proposed solution

139 citations


Cited by
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Journal ArticleDOI
TL;DR: The many different techniques for maximum power point tracking of photovoltaic (PV) arrays are discussed in this paper, and at least 19 distinct methods have been introduced in the literature, with many variations on implementation.
Abstract: The many different techniques for maximum power point tracking of photovoltaic (PV) arrays are discussed. The techniques are taken from the literature dating back to the earliest methods. It is shown that at least 19 distinct methods have been introduced in the literature, with many variations on implementation. This paper should serve as a convenient reference for future work in PV power generation.

5,022 citations

Journal ArticleDOI
TL;DR: A novel variable step-size incremental-resistance MPPT algorithm is introduced, which not only has the merits of INC but also automatically adjusts the step size to track the PV array MPP.
Abstract: Maximum power point (MPP) tracking (MPPT) techniques are widely applied in photovoltaic (PV) systems to make PV array generate peak power which depends on solar irradiation. Among all the MPPT strategies, the incremental-conductance (INC) algorithm is widely employed due to easy implementation and high tracking accuracy. In this paper, a novel variable step-size incremental-resistance MPPT algorithm is introduced, which not only has the merits of INC but also automatically adjusts the step size to track the PV array MPP. Compared with the variable step-size INC method, the proposed scheme can greatly improve the MPPT response speed and accuracy at steady state simultaneously. Moreover, it is more suitable for practical operating conditions due to a wider operating range. This paper provides the theoretical analysis and the design principle of the proposed MPPT strategy. Simulation and experimental results verify its feasibility.

599 citations

Journal ArticleDOI
TL;DR: In this paper, a classification scheme for MPPT methods based on three categories: offline, online and hybrid methods is introduced, which can provide a convenient reference for future work in PV power generation, is based on the manner in which the control signal is generated and the PV power system behavior as it approaches steady state conditions.
Abstract: In recent years there has been a growing attention towards use of solar energy. The main advantages of photovoltaic (PV) systems employed for harnessing solar energy are lack of greenhouse gas emission, low maintenance costs, fewer limitations with regard to site of installation and absence of mechanical noise arising from moving parts. However, PV systems suffer from relatively low conversion efficiency. Therefore, maximum power point tracking (MPPT) for the solar array is essential in a PV system. The nonlinear behavior of PV systems as well as variations of the maximum power point with solar irradiance level and temperature complicates the tracking of the maximum power point. A variety of MPPT methods have been proposed and implemented. This review paper introduces a classification scheme for MPPT methods based on three categories: offline, online and hybrid methods. This classification, which can provide a convenient reference for future work in PV power generation, is based on the manner in which the control signal is generated and the PV power system behavior as it approaches steady state conditions. Some of the methods from each class are simulated in Matlab/Simulink environment in order to compare their performance. Furthermore, different MPPT methods are discussed in terms of the dynamic response of the PV system to variations in temperature and irradiance, attainable efficiency, and implementation considerations.

549 citations

Journal ArticleDOI
TL;DR: A novel MPPT algorithm is proposed by introducing a particle swarm optimization (PSO) technique that uses only one pair of sensors to control multiple PV arrays, thereby resulting in lower cost, higher overall efficiency, and simplicity with respect to its implementation.
Abstract: Multiple photovoltaic (PV) modules feeding a common load is the most common form of power distribution used in solar PV systems. In such systems, providing individual maximum power point tracking (MPPT) schemes for each of the PV modules increases the cost. Furthermore, its v-i characteristic exhibits multiple local maximum power points (MPPs) during partial shading, making it difficult to find the global MPP using conventional single-stage (CSS) tracking. To overcome this difficulty, the authors propose a novel MPPT algorithm by introducing a particle swarm optimization (PSO) technique. The proposed algorithm uses only one pair of sensors to control multiple PV arrays, thereby resulting in lower cost, higher overall efficiency, and simplicity with respect to its implementation. The validity of the proposed algorithm is demonstrated through experimental studies. In addition, a detailed performance comparison with conventional fixed voltage, hill climbing, and Fibonacci search MPPT schemes are presented. Algorithm robustness was verified for several complicated partial shading conditions, and in all cases this method took about 2 s to find the global MPP.

527 citations

01 Jan 2008
TL;DR: In this paper, a comparative study of ten widely-adopted MPPT algorithms is presented, and their performance is evaluated on the energy point of view, by using the simulation tool Simulink®, considering different solar irradiance variations.
Abstract: Many maximum power point tracking techniques for photovoltaic systems have been developed to maximize the produced energy and a lot of these are well established in the literature. These techniques vary in many aspects as: simplicity, convergence speed, digital or analogical implementation, sensors required, cost, range of effectiveness, and in other aspects. This paper presents a comparative study of ten widely-adopted MPPT algorithms; their performance is evaluated on the energy point of view, by using the simulation tool Simulink®, considering different solar irradiance variations. Key-Words: - Maximum power point (MPP), maximum power point tracking (MPPT), photovoltaic (PV), comparative study, PV Converter.

444 citations