Journal Volume 13 Issue 2

Quasi-Instantaneous Generation of Reference Signals for Hybrid Compensator Control

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Leszek S. Czarnecki

Power variation of a customer load can disturb other loads in distribution systems and compensators for such loads are sometimes needed. Voltages and currents in systems with such loads can be asymmetrical, nonperiodic, distorted and even unpredictable. Consequently, reference signals for the compensator control have to be generated in a situation where the power properties of the load are not well specified.

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Electromagnetic Coupling of the Electrical Drive – EMC (Part I)

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Irena Kováčová, Dobroslav Kováč

The paper deals with the general analysis of one part of the electromagnetic compatibility (EMC) problem - the electromagnetic coupling applied in the field of power electrical systems. Theoretical analysis of above mentioned problem, based on the impact investigation of the electromagnetic wave propagation, is described in part I. Obtained results can be used for predictive stating of EMC quality of individual new electrotechnical products.

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Wind Turbine Harmonics Caused by Unbalanced Grid Currents

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Klaus-Dieter Dettmann, Steffen Schostan, Detlef Schulz

For wind turbines that feed into public grids, limits for voltage and current harmonics must be assured. To verify that the actual levels are valid, measurements are necessary. Problems can occur in determining which part of these harmonics has its origin in the wind turbine. It is shown that harmonics which originally have zero sequences can also be transferred over a delta-star-transformer, if the currents of the wind turbine are asymmetric due to unbalanced loads. Measurements in an existing wind turbine configuration are discussed, which confirm the described effects.

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Influences of a “Hybrid Grid” on the Network’s Voltage Quality and Supply Reliability

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Sharmistha Bhattacharyya, Johanna Myrzik, Jos Meeuwsen

The electricity is a basic need for functioning of modern society. In the deregulated electricity market, delivering quality power to the clients is a challenge for the utilities. In this paper, a “hybrid grid” is discussed that consists of centralized generations and localized distributed generations which may be comprised of small-scale conventional and sustainable sources. Energy storage option is also integrated in the hybrid-grid. Simulations are done on a test network, using “Power-Factory” software.

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Power Injection Control System and Experimental Model based on Manufacturer Characteristic Curves for a Photovoltaic Generation

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Amparo Rico, Enrique Romero Cadaval, Maria Isabel Milanés Montero

This paper attempts to validate the performance of a power injection control block for Photovoltaic Generation Systems (PVGS). This device uses a control module based on detecting the power injected into the supply by the inverter, instead of measuring the power generated by the PVGS. The performance is evaluated using the concept of Maximum Energy Curve that takes into account both transient and permanent control performance.

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Mathematical Model of DC Motor for Analysis of Commutation Processes

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Zygfryd Głowacz, Witold Głowacz

The mathematical model of dc motor was created. In model the commutator is approximated by circuit with variable parameters. Extremely different values are assigned to circuit parameters depending on the angular position of the rotor. Model equations were solved using implicit integration method. Commutation processes of dc motor were investigated with the aid of this model. Presented model can be extended and to take into account another phenomena occurring in dc motor.

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Stochastic Estimation of Voltage Sag Due to Faults in the Power System by Using PSCAD/EMTDC Software as a Tool for Simulation

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Nita R. Patne, Krishnarao L. Thakre

Faults in the power system are major cause of voltage sag. Voltage sag in the power system due to fault can be symmetrical or unsymmetrical. For sensitive loads it is necessary to estimate how many times in year the voltage at their terminal will experience sag to avoid tripping of operation. Several stochastic methods for estimation of number of sags are developed in recent years. In different methods of sag prediction there is need to do lengthy programming or calculations. Here PSCAD/EMTDC software package is used to estimate number of sag with uniform distribution of faults along the lines.

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Passive Filter Design for Three-Phase Inverter Interfacing in Distributed Generation

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Khaled H. Ahmed, Stephen J. Finney, Barry W. Williams

With the growing use of inverters in distributed generation, the problem of injected harmonics becomes critical. These harmonics require the connection of low pass filters between the inverter and the network. This paper presents a design method for the output LC filter in grid coupled applications in distributed generation systems. The design is according to the harmonics standards that determine the level of current harmonics injected into the grid network.

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The Use of the SSC as Reactive Power Compensator

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Federico Delfino, Renato Procopio

The paper deals with the possibility of employing the Custom Power Static Series Compensator (SSC), whose primary aim is to compensate voltage sags, also as a Reactive Power Compensator. The idea arises from the observation that such device does not work for the majority of time and can therefore be usefully employed for other purposes, such as power factor corrections. To this aim, an “ad hoc” control algorithm is developed and thoroughly discussed in the paper.

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Three-level Modulation Techniques to Reduce Instantaneous Common Mode Voltage in Induction Machines

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J. Cusidó, A. Luna, S. Busquets, J. Bordonau, P. Rodriguez, L. Romeral

Problems on inverter motor drives such as bearing currents are introduced due to common mode voltages. Different solutions are proposed on literature, for two-level or multilevel inverter. Instantaneous zero common mode voltage by using a three-level inverted could be achieved. This paper proposes a commutation strategy that allows zero common mode voltage by using medium vectors, and also a new representation as a plane on the commutation space is defined which is called zero common mode voltage plane.

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