| Modern power electronic converter is the core equipment which supporting the application likes new energy power generation,flexible DC transmission,electric traction,and electric vehicles.As a key component of the power electronic converter,the failure rate and reliability of HV power IGBT devices directly affect the performance and stability of the equipments.Two-phase cooling technology has shown excellent heat dissipation capability in the application of power electronic devices.Through the application of two-phase cooling on the power semiconductor device,its junction temperature and case temperature can be effectively controlled,which improves the reliability of the device.This paper aims to realize the immersion application of two-phase cooling with FC-72 refrigerant in the HV power IGBT device package.The advanced insulation investigation is significant for the boiling-induced two-phase flow in the complex field environment of the HV package.In this paper,the discharge statistical characteristics of the two-phase flow are obtained in several electrical conditions.The relationship between the bubble motion and the discharge pattern of the two-phase flow is revealed.A method is established for calculating the phase-resolved discharge characteristics of the two-phase flow to realize the phase pattern calculation of the two-phase flow under different voltage waveform.The research also promots the cognition of the discharge characteristics and mechanism of the surface discharge along with the dielectric interface under the effect of two-phase flow,which can provide a reference for the insulation design for the two-phase cooling in the application of HV power IGBT device package.First,a chamber for the insulation test of two-phase is developed,which realizes several test conditions and generation strategies of the two-phase flow.Combined with the standard partial discharge(PD)test system,a test platform,which can provide ±40 kV arbitrary test voltage waveforms,is constructed.To overcome the limitations of the standard PD test circuit under the pulse voltage test,an optical-coupling PD test strategy is proposed,which realizes the long recording and analysis of the PD test under the pulse voltage.Based on the schlieren and the gray-scale quantization method,the evaluation methods for the flow pattern and bubble characteristic are proposed,which provides an analysis method for the two-phase flow.Then,the partial discharge characteristics under the effect of the passing two-phase flow are obtained.By comparing the PD characteristics with a static liquid environment,the effect of the passing two-phase flow on the discharge is obtained.According to the force analysis of the bubble in the non-uniform electric field,the calculation for the bubble trajectory is accomplished.The relationship between the bubble trajectory and the range of the ionization area verifies the mechanism of the flow effect on the discharge.The calculation method for the bubble motion also provides a new way for the PD analysis of two-phase flow.The discharge characteristics of the two-phase flow and the statistical PD characteristics developing with the flow intensity are acquired.The characteristics of the discharge increment in the two-phase flow imply the discharge inside the bubbles.Furthermore,a calculation method for the PD phase-resolved pattern of the two-phase flow is proposed.By comparing the measured PD characteristic with the calculated result under the power frequency voltage,the unipolar AC-DC combined voltage,and the unipolar pulse voltage,the correctness of the calculation method is verified,which further demonstrates the two-phase flow discharge mechanism.Finally,as for the interface insulation in the package,we investigate the creeping discharge characteristics under the influence of two-phase flow.By comparing the creeping discharge patterns under the two bubble-existing conditions,the creeping discharge mechanism at the bubble-attaching interface is revealed assisted with the bubble behavior.The charged interface composition and development process in the creeping discharge is revealed,which demonstrates the mechanism of creeping discharge of the bubble interface.Based on the test method of creeping discharge under two-phase flow and the cognition of the mechanism of creeping discharge at the bubble interface,the insulation characteristics of the HV fast recovery diode under the two-phase cooling condition have proceeded.The insulation capability of power devices under two-phase cooling is realized,which lays the foundation for the insulation design and the application of two-phase cooling in HV power devices. |
PDF Full Text Request