Due to the increase in decentralised energy production in low voltage grids, the voltage stability is at risk if power is fed back into the high voltage levels. This leads to an increased usage of voltage control elements. The interaction between these control systems must be studied to avoid unwanted effects and thus, ensuring the system stability. This thesis analyses the occurance of stable, self-preservative oscillations in an electrical grid with an regulated distribution transformer (RDT) and local voltage control systems. For this purpose, the harmonic balance method is applied and the nonlinear behavior of the RDT is modelled. The model includes the effects of multiple taps and the time delay during the tap change of the RDT. On this basis, two criteria on the occurance of stable oscillations due to a RTD are defined. Furthermore, two local voltage control systems of a SMA- and a KACO-inverter are analysed in regard to possible oscillations with an RDT.
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Due to the increase in decentralised energy production in low voltage grids, the voltage stability is at risk if power is fed back into the high voltage levels. This leads to an increased usage of voltage control elements. The interaction between these control systems must be studied to avoid unwanted effects and thus, ensuring the system stability. This thesis analyses the occurance of stable, self-preservative oscillations in an electrical grid with an regulated distribution transformer (RDT)...
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