Abstract
A centralized grid-connected photovoltaic (PV) station is a widely adopted method of neutral grounding using resistance, which can potentially make pre-existing protection systems invalid and threaten the safety of power grids. Therefore, studying the fault characteristics of grid-connected PV systems and their impact on power-grid protection is of great importance. Based on an analysis of the grid structure of a grid-connected PV system and of the low-voltage ride-through control characteristics of a photovoltaic power supply, this paper proposes a short-circuit calculation model and a fault-calculation method for this kind of system. With respect to the change of system parameters, particularly the resistance connected to the neutral point, and the possible impact on protective actions, this paper achieves the general rule of short-circuit current characteristics through a simulation, which provides a reference for devising protection configurations.
Highlights
At present, photovoltaic (PV) technology is anticipated to be one of the main candidates playing an important role among the diversity of renewable energy sources
The inverter control strategy is usually adopted as an average positive-sequence control (APSC), which improves the power quality of the output current by filtering the double frequency caused by the negative-sequence component [10]
The PV inverter can adjust the output of active and reactive power according to the demands of the power grid, and the PV power station should have a low-voltage ride through (LVRT)
Summary
Photovoltaic (PV) technology is anticipated to be one of the main candidates playing an important role among the diversity of renewable energy sources. PQ-controlled IIDG, which is a group of controlled current sources, can reflect the various fault responses of a PQ-controlled IIDG under different control strategies by adjusting the parameters of the model These studies, have not yet considered the interaction between the IIDG and networks, so they cannot provide a solution to short-circuit currents in a distribution grid with multiple IIDGs. The fault characteristics of IIDGs were analyzed using simulations in [15,16]. This paper proposes a short-circuit calculation model for a grid-connected PV power station with neutral grounding resistance and a fault-calculation method suitable for this system, which enables research on the relationship of fault current changes with system parameters, especially the neutral grounding resistance It provides a reference for devising subsequent protection configurations.
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