Experimental Research Of Conducted EMI On Three-phase Rectifier

With the emergence of the global energy crisis and the rapid development of modern power electronics, high-power converter devices'application field is increasingly extensively. As the power electronic systems basic link, the rectifier is more widely used at present. The rectifier, as the power electronic systems basic link, is more widely used at present. The high transient voltage (dv/dt) and high transient current (di/dt), produced by this kind of high power switch device IGBT such as rectifier at the instantaneous of on/off switching, will cause strong electromagnetic interference (EMI). These EMI signals not only reduce rectifier own work efficiency, but also affect the normal operation of other nearby electrical equipments, or even endanger personal safety.At first, this paper introduced the causes and transmission path of three-phase rectifier conducted EMI, and points out that: when the high dv/dt caused by high-frequency switch acts on stray inductance, pulse currents produced in net side will produce differential-mode interference (DM EMI) in a circuit, while when the current flows through the parasitic capacitance at the midpoint of rectifier bridge legs, they generate common-mode interference (CM EMI). Then introduces EMI test instrument in detail, based on the measurement results from precision impedance analyzer, the time-domain modeling simulation analysis of the system is given in Saber. The impact of the components'parasitic parameters to rectifier system is further verified. Finally, the conducted EMI and the near field interference of three-phase rectifier was measured, test results were compared and analyzed. And then detailed introduces conducted EMI test instruments, based on the measurement results which got by precision impedance analyzer, the special simulation tools in Saber are yused for the modeling and simulation of the whole system.The impact of the components'parasitic parameters to rectifier system is further certificated by the simulation results. Lastly, the conducted EMI of three-phase rectifier was measured and the comparison of analysis of tested data was made.Research shows that, under the same conditions, controlled rectifier produced much larger conducted EMI than uncontrolled rectifier, and SVM produced much larger conducted EMI than SPWM; the DM EMI symmetric distribution in switching frequency and multiple nearby, while the CM EMI signals are centralized in switching frequency and odd harmonics nearby; both DM EMI and CM EMI are proportional to switching frequency; the DM EMI vary with the resistance load only at low frequency, but the CM EMI almost no change with resistance loads. We can draw from the experiment: interferences exisiting in the grid side of rectifier is DM interference primarily.