Abstract
Neutral-point clamped (NPC) three-level grid-tied converter is the key power electronic equipment connecting renewable energy and power grid. High temperature and other factors can lead to current sensor failure, control strategy failure, output current distortion, and even lead to the disconnection of renewable energy. To maintain the normal operation of NPC three-level grid-tied converter with current sensor fault, a model predictive fault-tolerant control strategy based on space voltage vector set and fault phase current reconstruction is proposed. Firstly, the relationship between fault phase current and voltage vector is studied. After the current sensor fault, only 12 out of 27 voltage vectors were found to be able to reconstruct faulty phase currents with a DC current sensor and an AC current sensor. Model predictive current control using the set of these 12 voltage vectors, and fault phase current is directly calculated by DC current and normal phase current, which improves the fault tolerance and stability of the converter system. Finally, simulation and experimental results verified the effectiveness of the proposed method.
Highlights
Neutral-point-clamped (NPC) three-level grid-tied converter serves in high-voltage and high-power applications because of its low harmonic content of output current and high conversion efficiency [1]
Aiming at the current sensor fault of NPC three-level grid-tied converter, an Model predictive control (MPC) strategy based on current reconstruction is proposed
A MPC strategy based on current reconstruction is proposed to ensure the NPC three-level grid-tied converter continuous operation after current sensor fault
Summary
Neutral-point-clamped (NPC) three-level grid-tied converter serves in high-voltage and high-power applications because of its low harmonic content of output current and high conversion efficiency [1]. For the two-level converter, a PWM control strategy using DC-link current to reconstruct the fault phase current is proposed. The current sensor fault tolerance of NPC three-level grid-tied converter has not been further studied. A three-level current reconstruction method for NPC is proposed, in which a shunt resistor is inserted at the neutral point to reconstruct fault phase current according to the current of shunt resistor [25]. Aiming at the current sensor fault of NPC three-level grid-tied converter, an MPC strategy based on current reconstruction is proposed. When AC current sensor fails, the voltage vector of NPC three-level grid-tied converter is analyzed, and the fault phase current is reconstructed by DC-link current. The proposed MPC strategy has good steady-state performance under different loads, and can quickly follow the reference current It ensures the continuous operation of NPC three-level grid-tied converter after current sensor fault
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