Dubravko Franković

A dual-axis tracking photovoltaic power plant as an educational tool

Renewable energy sources have become a considerable part of electric transmission networks as well as medium and low voltage distribution networks. Understanding the overall process from design stage up to the installation stage, followed by the commissioning and startup of renewable energy sources plants is essential knowledge that electric engineers nowadays should posses. Therefore, in the first part of the article activities, conducted at the Faculty of Engineering, University of Rijeka, Croatia, necessary for the installation of a fully operational, grid connected photovoltaic power plant with dual-axis tracking system have been described. Consequently, upon photovoltaic plant’s installation and commissioning, students are able to have ‘hands-on’ on a fully functional photovoltaic power plant and perform supervised, ‘live’ measurements and compare it with previously calculated values. Therefore, new – dedicated laboratory sessions have been introduced in an existing subject to make the most of the photovoltaic installation in the teaching process. In the second part, the article is mainly focused on the newly introduced laboratory sessions as well as on the educational framework and methodology. Some of the experiments that our students are able to perform include alternating current and direct current operating values measurements (photovoltaic string and inverter voltages, currents, power, efficiency, etc.), environmental parameters measurements (irradiance, air temperature, wind direction, velocity, etc.) and grounding parameters measurements (soil resistivity, photovoltaic plant’s grounding resistance). The acquired knowledge gained from the activities performed during our educational photovoltaic plant project realization give us the ability to propose a methodology that can be used as the key model for other universities and faculties.

A noninvasive inclusion of synchrophasors in the power system state estimation

Original scientific paper The paper investigates the application of synchronized phasor measurements, which are available from Phasor Measurement Units (PMUs), in the power system state estimation. In order to avoid changes in the type of the input measurements of the classical state estimator, which runs in the control centre, the proposed model utilizes voltage and current phasors to calculate pseudo-measurements such as pseudo-voltages, power flows and power injections. These pseudo-measurements are used together with the voltage phasor magnitudes and the conventional measurements in the iterative procedure. The IEEE 14, 30, 57 and 118 buses test systems as well as the mathematical model of the Croatian transmission power system were used as the test systems. The results of the simulation were compared with the classical state estimator, which uses only conventional measurements. The effect of the voltage phasor angles on the state estimator performance was investigated.

A Synchrophasor Assisted Hybrid State Estimator

Abstract The paper presents a Synchrophasor Assisted Hybrid State Estimator that utilizes the conventional SCADA measurements and the synchrophasors obtained from Phasor Measurement Units (PMUs). To take advantage of the high sampling frequency of the multiple sets of synchrophasors they are preprocessed in a recursive algorithm that provides the state estimate for the power system part observable by PMUs. The results are forwarded to an iterative procedure in which they are combined with SCADA measurements. The given solution was applied on the IEEE test systems with 14, 30 and 57 buses and its performance was compared with other state estimators. The filtering of measurement errors and convergence, while providing improved accuracy of the final state estimates of the developed methodology can be compared with other hybrid state estimators.