Method and system for fault positioning and recovery of voltage source converter

A method for fault recovery of a voltage source converter, the method comprising locking the converter when an alternating-current side zero sequence voltage Uo_ac or a direct-current side unbalanced voltage Uo_dc of a voltage source converter station is detected greater than a set first threshold Uo_set1 for longer than a set period of time Δt1;

• during the locking period, for each converter station, determining the converter station as a faulty station when the alternating-current side zero sequence voltage Uo_ac of the converter station is detected greater than a set second threshold Uo_set2 for longer than a set period of time Δt2;
• otherwise, determining the converter station as a non-faulty station;
• and
• unlocking and recovering operation of non-faulty station after the faulty station is positioned, the faulty station can be directly unlocked to recover operation after being put into control of a zero sequence voltage, or the faulty station can be unlocked to recover operation after the alternating-current side zero sequence voltage Uo_ac stays less than or equal to a set third threshold Uo_set3 for longer than a set period of time Δt3.

A system for fault recovery of a voltage source converter, the system comprising a detection module, a locking module, a fault-determining positioning module, and a fault recovery module,

• wherein, the locking module locks the converter when the detection module detects that an alternating-current side zero sequence voltage Uo_ac or a direct-current side unbalanced voltage Uo_dc of a voltage source converter station stays greater than a set first threshold Uo_set1 for longer than a set period of time Δt1;
• during the locking period, for each converter station, if the alternating-current side zero sequence voltage Uo_ac of a converter station is detected greater than a set second threshold Uo_set2 for longer than a set period of time Δt2, the fault determining and positioning module determines the converter station as a faulty station;
• otherwise, the fault determining and positioning module determines the converter station as a non-faulty station;
• and
• the fault recovery module recovers and unlocks operation of non-faulty stations after the faulty station is positioned, the faulty station can be directly unlocked to recover operation after being put into control of a zero sequence voltage, or the faulty station can be unlocked to recover operation after the alternating-current side zero sequence voltage Uo_ac stays no greater than a set third threshold Uo_set3 for longer than a set period of time Δt3.