High Consistency Detection Method for the Device Current of IGCT Converter Based on Tunneling Magnetoresistance Effect

The commutated converter constructed by fully- controlled integrated gate-commutated thyristors (IGCT) has active turn-off capability, enabling forced commutation to resolve commutation failure. However, their turn-off capacity is limited, and active turn-off above the maximum turn-off current may damage itself, so it is essential to detect the current of the IGCT online. Traditional current sensor based on tunneling magnetoresistance is susceptible to errors caused by the nonuniform magnetic fields in the valve. This article analyzes the distribution pattern of the magnetic field in the valve and establishes a mathematical model of magnetic field change in the magnetic core air gap under nonuniform magnetic field, clarifies the main factors affecting the consistency of the sensor outputs, analyzes the transient interference generated by the active turn off of the IGCT. Combined with the magnetic field distribution results from COMSOL finite element simulation, an anti-interference design method is proposed to achieve high consistency measurement of IGCT current. Finally, experimental tests show that the maximum error of the air-gap magnetic field caused by conductor offset and copper busbar influence is reduced from 11.14% of the traditional structure to 0.69%, and the transient interference during active turn-off is greatly reduced, which verifies the effectiveness of the proposed method.