The paper presents the issues related to predicting the amount of energy generation, in a particular wind power plant comprising five generators located in south-eastern Poland. The location of wind power plant, the distribution and type of applied generators, and topographical conditions were given and the correlation between selected weather parameters and the volume of energy generation was discussed. The primary objective of the paper was to select learning data and perform forecasts using artificial neural networks. For comparison, conservative forecasts were also presented. Forecasts results obtained shaw that Artificial Neural Networks are more universal than conservative method. However their forecast accuracy of forecasts strongly depends on the selection of explanatory data

The paper discussed the studies related to the output voltage distortion of frequency inverter depending on its frequency. The changes in the effective value of voltage, THD, harmonics and interharmonics were presented for three different frequencies, lower than 50Hz. Additionally, it was shown how these values change depending on measurement time, presenting waveforms cycle by cycle in graphs, averaged in 10 periods and averaged in 150 periods of the analyzed signal. The studies were conducted in the laboratory area equipped with power quality meter class A.

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SUMMARY This paper presents application of differential equations in modelling and simulation tests of water supply network pumps drive system together with powered water supply pipelines. The description is preceded with an analysis of practically applicable mathematical models representing drive systems with induction motors and PWM converter. Models of electric devices and their elements, from the viewpoint of the methods used to describe the phenomena occurring in them, can be divided into three basic groups: circuit models, semi‐field models, and field models. Each of these groups has its own purpose depending on the complexity of the modelled electric system, the types of devices, and the required accuracy in the reconstruction of processes actually occurring in the system. In the case under consideration, sufficient accuracy is ensured by circuit models. Mathematical models of PWM converter, squirrel‐cage induction motor, and pump together with a pipeline allow to carry out computer simulations of the whole drive system consisting of the above‐listed elements. Simulations of the system of such complexity definitely pose a more difficult problem than simulation of each of the elements performed separately. In the following, mathematical models of individual elements and selected simulation tests of the system are presented. Copyright © 2011 John Wiley & Sons, Ltd.