High Interference-Resistant Magnetic Field Probe for Non-Invasive Current Distribution Monitoring in Press Pack IGBTs of HVDC Valves
Yuanfang Lu, Hong Shen, Zhonghao Dongye, Mingyang Li, Hui Su, Xiangyu Zhang, Lei Qi
Abstract
Current imbalance in press pack insulated-gate bipolar transistor (PP IGBT) impacts the device's lifespan and high-voltage direct-current (HVDC) valves' safe operation. The external magnetic field can reveal the internal current distribution of PP IGBT, warning current imbalance. However, the compact structure and high-frequency electromagnetic environment of HVDC valves introduce significant interferences in monitoring, involving both busbar current interference, device <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dv/dt</i> interference and eddy current interference from the probe. This article proposes a high interference-resistant magnetic field probe featuring a bipolar coil structure and comb structure shielding, which is decoupled from busbar current, reduces <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dv/dt</i> interference and avoids additional eddy current interference. Following a detailed theoretical analysis, a series of experiments was conducted. The results demonstrate that the proposed probe is sensitive to the current distribution in PP IGBTs, with busbar interference limited to 2 mV and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dv/dt</i> interference reduced to 2.9%, while eddy current interference is effectively canceled. These findings validate the feasibility of the proposed method.