The Experts below are selected from a list of 69600 Experts worldwide ranked by ideXlab platform

Josep M. Guerrero - One of the best experts on this subject based on the ideXlab platform.

  • Robust AC Voltage Controller with Harmonic Elimination for Stand-Alone and Weak-Grid-Connected Operation
    2018 IEEE Energy Conversion Congress and Exposition (ECCE), 2018
    Co-Authors: Diego Perez-estevez, Jesus Doval-gandoy, Josep M. Guerrero
    Abstract:

    This paper presents an ac voltage controller with a high robustness to plant model variations which can operate under a wide range of loads. A robust voltage controller is required in a droop-controlled inverter which operates in island mode with other generators or is Connected to a grid. In such modes of Operation, the voltage source converter (VSC) can experience a large variation in the load impedance depending on the number of parallel generators or the grid impedance value. The proposal improves the transient performance by selectively minimizing the output impedance of the system at the frequencies which typically contain the largest components of the output current. Complete harmonic control is achieved due to its zero output impedance at a set of design-selected frequencies. The design process only requires, as input parameters, the LC filter values, the sampling frequency, and a set of harmonics where load-current circulation is expected.

  • Mitigation of Harmonics in Grid-Connected and Islanded Microgrids Via Virtual Admittances and Impedances
    IEEE Transactions on Smart Grid, 2015
    Co-Authors: Alexander Micallef, Maurice Apap, Cyril Spiteri-staines, Josep M. Guerrero
    Abstract:

    Optimization of the islanded and grid-Connected Operation of microgrids is important to achieve a high degree of reliability. In this paper, the authors consider the effect of current harmonics in single phase microgrids during both modes of Operation. A detailed analysis of the effect of the output impedance of the considered primary control loops on the harmonic output of the considered voltage source inverters is initially carried out. A virtual admittance loop is proposed to attenuate the current harmonic output in grid-Connected Operation that is generated due to the grid voltage distortion present at the point of common coupling (PCC) and due to local non-linear loads. This paper also considers the harmonic current sharing and resulting voltage harmonics at the PCC during islanded Operation of the microgrid. A capacitive virtual impedance loop was implemented to improve the harmonic current sharing and attenuate the voltage harmonics at the PCC. Experimental results are given to validate the Operation of the proposed algorithms.

Yilmaz Sozer - One of the best experts on this subject based on the ideXlab platform.

  • Transition control strategy between standalone and grid Connected Operation of voltage source inverters
    2011 IEEE Energy Conversion Congress and Exposition, 2011
    Co-Authors: Nayeem Arafat, Sreeshailam Palle, Iqbal Husain, Yilmaz Sozer
    Abstract:

    This paper proposes a smooth transition control strategy for voltage source inverters between standalone (SA) and grid Connected (GC) modes of Operation. In GC mode, the amount of power exchanged with the utility grid (UG) is controlled by regulating the phase currents. In the SA mode, the load voltage is regulated by the inverter with its phase dictated by the inverter control. An instant switching between SA and GC Operations that will ensure continuous output power requires continuation in the phase of the system voltage. The trapezoidal, sinusoidal and staircase frequency change techniques have been analyzed to find out the optimum condition for which the total harmonic distortion (THD) become lower. We have developed a smooth frequency change technique which provides lower THD on the voltage waveforms compared to the other techniques. The new algorithm has been implemented on a 5kW single phase utility interactive inverter having the standalone Operation capability.

Nayeem Arafat - One of the best experts on this subject based on the ideXlab platform.

  • Transition control strategy between standalone and grid Connected Operation of voltage source inverters
    2011 IEEE Energy Conversion Congress and Exposition, 2011
    Co-Authors: Nayeem Arafat, Sreeshailam Palle, Iqbal Husain, Yilmaz Sozer
    Abstract:

    This paper proposes a smooth transition control strategy for voltage source inverters between standalone (SA) and grid Connected (GC) modes of Operation. In GC mode, the amount of power exchanged with the utility grid (UG) is controlled by regulating the phase currents. In the SA mode, the load voltage is regulated by the inverter with its phase dictated by the inverter control. An instant switching between SA and GC Operations that will ensure continuous output power requires continuation in the phase of the system voltage. The trapezoidal, sinusoidal and staircase frequency change techniques have been analyzed to find out the optimum condition for which the total harmonic distortion (THD) become lower. We have developed a smooth frequency change technique which provides lower THD on the voltage waveforms compared to the other techniques. The new algorithm has been implemented on a 5kW single phase utility interactive inverter having the standalone Operation capability.

Math Bollen - One of the best experts on this subject based on the ideXlab platform.

Jakob Nömm - One of the best experts on this subject based on the ideXlab platform.

  • An Analysis of Voltage Quality in a Nanogrid during Islanded Operation
    Energies, 2019
    Co-Authors: Jakob Nömm, Sarah K. Rönnberg, Math Bollen
    Abstract:

    Voltage quality data has been collected in a single house nanogrid during 48 weeks of islanded Operation and 54 weeks of grid-Connected Operation. The voltage quality data contains the voltage tota ...

  • An Analysis of Voltage Quality in a Nanogrid during Islanded Operation
    MDPI AG, 2019
    Co-Authors: Jakob Nömm, Sarah K. Rönnberg, Math H. J. Bollen
    Abstract:

    Voltage quality data has been collected in a single house nanogrid during 48 weeks of islanded Operation and 54 weeks of grid-Connected Operation. The voltage quality data contains the voltage total harmonic distortion (THD), odd harmonics 3 to 11 and 15, even harmonics 4 to 8, voltage unbalance, short-term flicker severity (Pst) and long-term flicker severity (Plt) values, and voltage variations at timescales below 10 min. A comparison between islanded and grid-Connected Operation values was made, were some of the parameters were compared to relevant grid standard limits. It is shown that some parameters exceed the defined limits in the grid-standards during islanded Operation. It was also found that the islanded Operation has two modes of Operation, one in which higher values of the short circuit impedance, individual harmonic impedance, harmonic voltage distortion and voltage unbalance were reached