Andrey Lana, Tuomo Lindh, Pasi Peltoniemi, and Jarmo Partanen
LVDC system, transient state stability, dynamic state stability, pscad, stability conditions, dc distribution
This paper considers stability issues in a low-voltage direct current (LVDC) electricity distribution network with a directional power flow. The network is based on power electronic devices, which bring a well-known instability factor, that is, negative impedance to the system. Each network inverter is designed to be stable when operating alone and in normal conditions; however, an actual LVDC power distribution network consists of interconnected inverters, and is always subject to real-life network events. In this paper, analytical modelling and an analysis of the static and dynamic behaviour of the LVDC network are presented, and dynamic stability criteria are established. Time-domain power system simulation software PSCAD/EMTDC is used in the analysis of the transient and dynamic states of the network and the system transient and dynamic behaviour. The results comply with the DC stability theory. Additionally, the results show that changes in the system operating point do not cause instabilities when system DC capacitors are dimensioned to the maximum power point. The use of DC reactors to smooth the DC voltage could cause instabilities, if the stability condition for the inverter-side DC capacitance is not satisfied. The application of analytical modelling and EMTP modelling to the system stability analysis substantiates the stable system design conditions verified by time-domain simulations.
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