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High Power PWM rectifiers
Valouch, Viktor ; Šimek, Petr ; Škramlík, Jiří
High power, high voltage PWM rectifiers with low swirching frequency are analyzed in terms of attainable powers exchangedwith the grid and of their current frequency spectra. Four-level PWM rectifiers with rated powers S = 2, 4, 8 MVA and the switching frequency 800 Hz per one switching element are considered, thus the controlller sampling frequency 1600 Hz is used. Selected results of simulation as wellas experimental tests are presented.
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Software Phase Lock Loops of PWM Rectifiers
Šimek, Petr ; Škramlík, Jiří ; Valouch, Viktor
In the paper the properties of three PLL techniques (known under names DSC-, DDSRF- a FVAVG-PLL) for different states of the feeding three-phase voltage system are assessed. As a crucial quality criterion of synchronization to the positive component of the fundamental harmonic voltage the errorbetween an estimated and real angle of the positive component of the fundamental harmonic voltage vector was selected. Two sampling periods Ts=0.05 ms and 0.5 ms as well as two gain values of a PL-type compensator were treated.
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Control of Parallel Active Filter by Using dSpace 1103A
Paclt, Zdeněk ; Šimek, Petr ; Valouch, Viktor
This work shows that nonlinear control technique of a shunt active filter is well suited to compensate for characteristic current harmonics that are generated by nonlinear loads. The proposed control is based on two inner current loops and an outer dc bus voltage regulator loop. There is no interaction between inner and outer loops in addition to good performance in both steady-state and transient operation. Active filters represent a modern and effective resource for suppresing interfering phenomena in the electrical supply.
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Avenue foundation in extreme conditions special respect to soil quality
Šimek, P. ; Šimek, Miloslav
Quality of soil environment is an important factor which substantially influences growth of plants. Present paper deals on general features and main parts of soils. The importance of soil air content and composition of soil air together with main principles of movement of gases in soil are described. Soil aeration status, namely low oxygen concentration, both low and high carbon dioxide concentrations and higher ethylene concentrations directly influence plants. Changes in amount and composition of soil air impact a number of soil physical and chemical properties, and by this mechanism also influence plant growth and behaviour.
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