Fault-Tolerant Control of Low Voltage Ride-Through Under Bridge Arm Open-Circuit Fault of NPC Direct-Mounted Energy Storage Converter
Long-term operation of neutral-point-clamped(NPC)direct-mounted energy storage converter may cause the bridge arm open-circuit fault,which causes the shutdown of equipment and affects the low-voltage fault ride-through.In this paper,a virtual bridge arm is formed by directly connecting the faulty phase and the midpoint of the DC bus.The fault-tolerant topology is reconstructed,and a fault-tolerant low voltage ride-through(LVRT)control strategy based on model predictive control is proposed.Considering that the reconstructed fault-tolerant topology structure reduces the utilization rate of the DC side voltage,the maximum output current setting method of the fault-tolerant structure is studied and analyzed.Due to the change of the output characteristics of the fault-tolerant topology during the LVRT process,the model prediction vector analysis is carried out on the current and output volt-age of the direct-mounted fault-tolerant structure of the energy storage converter,and the relationship between the voltage drop and the maximum output current is deduced.In the reconstructed space voltage vector,a vector state that can support LVRT is selected,and the energy storage converter is controlled to allocate active and reactive power according to the LVRT technical specifications to support the power grid voltage.The simulation results verify that the proposed control strategy ensures that the fault-tolerant topology structure can operate during bridge arm faults and the reliability of reactive power support during low voltage ride-through.
low voltage ride-throughmodel predictive controlfault-tolerant controlthree-level neutral-point-clampedenergy storage converter
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