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A microgrid is a hybrid power system consists of several distributed generation resources and local loads, which provide the solution to supply premium power to remote or specific areas. However, some undesired effects are accompanied with their installations and operations, such as imbalance, voltage fluctuation, and harmonics, as well as inter-harmonics. To the aspect of voltage quality, the switching on and off of the distributed generation resources may cause power fluctuation, hence the associated power quality disturbances are produced and affect the connected power system. To the design of a hybrid power system such as an ac or dc microgrid, it is necessary to perform computer simulation for the planning and study. Before the actual system is built, all potential responses of the system should be known and then the design can be modified to avoid negative impacts to the system. This paper presents an application of the real-time simulation tool for power quality studies of the dc micro grid planning. Experiences of modeling a dc microgrid components are presented and simulation results are reported. [ABSTRACT FROM AUTHOR]

The effective harmonics estimation for measuring power signals has become an important issue in the power quality assessment. By reviewing those commonly used Kahnan filter-based models, some limitations for harmonics estimation can be observed. In this paper an extended real model of Kalman filter combined with a resetting mechanism for accurately tracking time-varying harmonic components of power signals is presented. The usefulness of the proposed algorithm is demonstrated by a simple laboratory setup with LabVIEW program and the dedicated hardware for harmonics monitoring. Results show that the proposed method can achieve more accurate and robust measurement of harmonic amplitudes and phase angles for the time-varying power signals among compared methods while the uncertainty testing performances required by LEC Standard 61000-4-30 are satisfied. [ABSTRACT FROM AUTHOR]

This paper presents an efficient approach for tracking the location of the electric utility shunt capacitor bank that generates switching transients by a limited number of power quality (PQ) meters. The approach is based on measuring the voltage-disturbance energy variations at the meter buses and phase angle changes at the connected branch current due to the reactive power supplied by the switched-on utility capacitor. Both measured energy and phase angle variations are used to identify the location of the switched capacitor through a rule-based tracking algorithm. The proposed method is then tested with the IEEE 30-bus transmission system to show its usefulness. [ABSTRACT FROM AUTHOR]