Search

Enhancement of system resilience of microgrid is important when the system is operated in the islanded mode. The commonly used clean energy in microgrid is the intermittent renewable energy which would deteriorate the system resilience of microgrid. To solve this problem, the residual energy pre-served in the energy storage system is introduced in this paper to extend the time duration of fundamental load demand when the power outage is present. The experiment is implemented in the demo system in the campus of National Central University to verify the performance of proposed management strategy.

Integrated hybrid power systems have become more and more important in recent years. The functioning of medium-temperature proton-conducting solid oxide fuel cell (pSOFC) hybrid system is proposed in this work. The combined system consists of a pSOFC stack, steam methane reformer, compressors, burners, heat exchangers and methanol synthesizing reactor. The excess waste heat of the burner is recovered using heat exchangers. Also, the unutilized hydrogen from SOFC is used for carbon reduction by methanol production. The functioning of configured system is explored by using Matlab/Simulink/Thermolib software. In pSOFC operation, stoichiometric ratio (Sto) of air is maintained 3 and Sto of hydrogen is varied between 1.4 to1.7. Results show that the benefit of carbon reduction depends on methanol production. By using water separator, the methanol production efficiency increases dramatically. In addition, hydrogen transfer membrane is used to increase stack efficiency and control the temperature of stack chamber and reformer. This further improves benefit of carbon reduction. The proposed hybrid system in this work can be used to power huge residential buildings and some factories.

For the development of smart grid, the effective detection of voltage events is a very important task for the power system monitoring. Voltage sags, interruptions, and voltage swells which usually produce large losses in commercial and industrial consumers are the main events in power systems due to the sensitivity of equipments to these voltage variations. In this paper, a hybrid detection method for voltage events by combining the wavelet analysis and adaptive linear combiner (ADALINE) is proposed. The usefulness of the proposed algorithm is demonstrated by a simple laboratory setup with LabVIEW program and actual recorded waveforms. With the help of accurate time locating of the wavelet analysis and correct event classification of ADALINE, power system monitoring could provide accurate and useful information to power grids via the developing advanced metering infrastructure.

Voltage fluctuations caused by rapidly changing loads in the power systems may give rise to noticeable illumination flickers of lighting equipment. The voltage flickers can also cause malfunctions in many electric devices. This paper presents a digital implementation of flickermeter in the hybrid time and frequency domains based on IEC Standard 61000-4-15. In addition, this paper proposes a new demodulation method to extract the voltage envelope. Simulations and actual measurements show that the digital implementation with the proposed method yields relatively accurate flicker measurements. Index Terms--Arc furnace, flickermeter, power quality (PQ), squaring demodulation.

Harmonics and interharmonics may introduce operational problems in electrical and electronic equipment. Therefore, monitoring harmonics/interharmonics for improving the power quality is of importance for both electric utilities and their customers. In this paper, a cascaded two-stage adaptive linear element (ADALINE) structure for both harmonics and interharmonics measurement is proposed. In addition, a simple laboratory setup implemented by MATLAB and the dedicated hardware for measuring power signals is built to verify the performance of proposed method. Results are compared with those obtained by short-time Fourier transform and two other conventional ADALINE-based methods. It shows that the proposed method is with a better accuracy, even if the power frequency deviation and interharmonic components are present in the measured signal. The proposed method also can be adopted for harmonic/ interharmonic compensation devices in real time. Index Terms--Adaptive linear element (ADALINE), frequency deviation, harmonics, interharmouics, nonlinear loads.

This paper presents a new procedure to track the disturbance source location of voltage sags and shunt capacitor switching transients in a power system based on branch current measurements. In the proposed method, the power-quality metering locations are first determined by the sensitivity of the system fault-current level to the fault voltage. Then, a current deviation index for representing the change of each measured branch current rms magnitudes before and after the disturbance is calculated to track the disturbance source location within an area confined by the directions of the top-priority branches. The IEEE 30-bus benchmark system and an actual transmission system with recorded power-quality disturbance events are used to illustrate the usefulness of the proposed method. Simulation results obtained by the proposed method are also compared with those obtained by a previously developed approach and by actual recorded data. By observing the results, it shows that the proposed method is efficient and accurate to track the source area of voltage sags or shunt capacitor switching transients. Index Terms--Fault current, power quality (PQ), shunt capacitor switching transients, voltage sag.