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Analysis of Three-Phase Delta-Connected Converter for Compensation of Unsymmetrical Loads
Bejvl, Martin ; Šimek, Petr ; Valouch, Viktor ; Hauptmann, R.
The paper presents possibilities of compensation of general single-phase load connected to the three-phase grid. The compensation is to ensure a symmetrical and pure active load of the three-phase grid. It is documented that after the proposed compensation it is possible to draw symmetrical and pure active current from all phases. A set of multi-level voltage converters is considered as a compensation device. The paper presents a way of determining the reference currents for the converter in its two branches and proposes a method of controlling the converter so that the active power from the grid is equal to the active load of the load. This methodology is documented by the results of a series of simulations for static and dynamic modes of the system.
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Experimental investigation of fault tolerant converter connected to unbalanced grid
Valouch, Viktor ; Šimek, Petr ; Škramlík, Jiří
A model of the three-phase voltage converter for simulation of its modes of operation in standard as wellas fault states is presented. The presented model can be used to simulate steady-states and also transients at dc and ac side of the grid-connected converter. Based on simulation, an algorithm was designed to identify and localize a fault in some phase of the three-phase converter. Rules how to modify hardware, and control and modulation strategies to hold the converter in operation after the fault are presented and tested. the algorithm was experimentally verified.
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Control Strategy of Grid Connected Converter under Unbalanced Conditions
Lettl, J. ; Bejvl, Martin ; Valouch, Viktor
Current-controlled voltage source converters are widely used in grid-connected applications. The negative sequence component of the grid voltage causes pulsating components in powers transmitted through the converterand ripple of the dc voltage in the intermediate circuit. Two strategies of the current reference calculation for a dual current controller were developed and tested in the Matlab/Simulink environment and experimentally verified as well.
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