||Study of a High-Precision Analysis Method about EMI Noise for Motor Drive Systems in Inverter Air Conditioners
In order to save energy and improve the efficiency of the power supply system, inverters, which are consists of power semiconductor devices, has gained wideacceptance as an important part in the power system design. When the power semiconductor devices do high-speed switching, the high-frequency leakage currentwill occur. This kind of leakage current backtracks to the utility power source through the ground path and leads to the conducted electromagnetic interference (EMI) noise. In addition, common-mode (CM) noise is the main ingredient of the conducted EMI noise. Furthermore, the accurate modeling of the EMI noise equivalent circuit will be beneficial to the design of effective noise suppression system. This dissertationpresents an equivalent circuit containing non-linear component for inverter-fed drive air conditioner system.By comparing the amplitude of leakage current when the air conditioner is working in different modes, the main effect factors of the CM EMI noise are indentified. Though the analysis of interference conduction mechanism and the waveform of leakage current in inverter-fed drive system, an accurate equivalentcircuit with non-linear resistance is proposed for the first time. Afterward, according to the waveform of the leakage current in the ground path when only one phase of inverter is switching, the parameters of the equivalent circuit are calculated. And the accuracy of this equivalent circuit is verified again, bycomparing the result of simulation with the waveform when two phases of inverter are switching at the same time. Further, the equivalent circuit is indentified again through an optimize software modeFRONTIER to correct the errors during the subjective calculation before. A linear model and a non-linear model are separately discussed. With the results of these two models, the necessity and effectiveness of theintroduction of the non-linear resistance about the common-mode equivalent circuit are confirmed. By analyzing the relationship between the current i and the magnetic flux Ψ in high consonance frequency circuit, this conclusion is verified again. In theend, this thesis proposes a method to estimate the parasitic capacitance when the motor is running and the permittivity of oil and refrigerant mixture in the airconditioner compressor for the first time. A design procedure for EMI problem is proposed. The EMI noise can be predicted and the EMI filter can be designed fromafter assembling to before assembling. The effectivenessof the proposed equivalent circuit is verified, by comparing the simulation result with the experiment waveform.
Hokkaido University（北海道大学）. 博士(工学)