EPQU Journal Volume 13 Issue 2

Amparo Rico, Enrique Romero Cadaval, María 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. The paper presents a basic and simple procedure to obtain a model from the manufacturer characteristic curves of the photovoltaic cells. MA TLAB ® Simulink® is used as simulation tool to obtain the response of the proposed system to changes in temperature and irradiance.

Zygfryd Głowacz and 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.

Nita R. Patne and 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.

Khaled H. Ahmed, Stephen J. Finney and 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. Analytical expressions for the maximum inductor ripple current are derived. The filter capacitor design depends on the allowable level of switching components injected into the grid. Different passive filter damping techniques to suppress resonance affects are investigated and evaluated. Simulated results are included to verify the derived expressions.

Federico Delfino and 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. The effectiveness of such control scheme is then tested by applying the SSC to a load represented by an induction motor in order to improve its power factor. The whole system is modelled with the aid of the electromagnetic code PSCAD -EM TDC, which allows to describe with high detail all its components. The results of the simulations show the good response of the device, which enables to rapidly increase the power factor of the motor and maintains the Total Harmonic Distortion (THD ) of the injected phase voltages under the threshold value of 8%, as prescribed by CEI EN 50160 3.11.

J. Cusidó, A. Luna, S. Busquets, J. Bordonau, P. Rodríguez, 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. On this defined plane, every turning vector fulfil this property. Simulations and experimental results clearly show method’s efficiency.

Sharmistha Bhattacharyya, Johanna MYRZIK, Jos MEUWSEN

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. It was found from the analysis that voltage quality and power supply availability of a hybrid-grid can be improved by proper selection of energy storage system along with protective and control devices.

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 to determine which part of these harmonics has its origin in the wind turbine. It is shown that also harmonics which originally have zero sequences can 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.

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.

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. Voltages and currents in systems with time-varying loads, although nonperiodic, can be treated as quantities with a disturbed periodicity. These are referred to as semi-periodic quantities. Under such an assumption, the Current Physical Components (CPC) power theory can by used for estimation of the power properties of such loads. In such a case, the CPC power theory provides fundamentals for a quasi-instantaneous generation of reference signals for the compensator control, based both on the frequency- and on the time-domain approach. The paper presents fundamentals of generation of reference signals for unbalanced loads with semi-periodic voltages and currents.