EMI modeling of half-bridge inverter using a generalized terminal model

Abstract

A generalized terminal model has been proposed to predict the conducted electromagnetic interference (EMI) from a boost converter. The results of conducted emissions have shown a good agreement up to 50 MHz. The same technique was also successfully applied to extract a terminal model of buck converter. This paper extends the generalized terminal modeling approach to a larger class of power converters by attempting to model a dc-ac converter from the dc terminal side. Modeling the terminal behavior of an ac system is more challenging than it is for dc-dc converters because of the timevarying converter operating point. The proposed technique is applied to a single-phase half-bridge inverter to show its versatility in modeling conducted emissions from ac systems. Measured and predicted conducted emissions from a half-bridge inverter are in a good agreement within 6 dB up to 30 MHz.

EMC models for power electronics: From converter design to system level

“…The investigation of the network property may be facilitated by using the common mode and differential mode separation, as explained in [5]. Furthermore, to enhance the identification of the elements, this DM/CM basis is also suitable [6]. The equations of the "Black Box" model expressed in the DM/CM are provided by (1): From these equations it is worth noting that the common mode quantities do not depend on the differential mode ones provided that Z pg and Z ng are equal.…”

“…As explained in [6], the main purpose of this approach is the network analysis. The investigation of the network property may be facilitated by using the common mode and differential mode separation, as explained in [5].…”

“…First, due to the identification difficulties of the Black Box, stressed in [5] and [6], it would be a good way to obtain the model, if the converter realization is perfectly known. Even if this is not the case, a first estimate of the model parameters may be obtained from the basic knowledge of the converter components, what may be a good starting point for the identification.…”

“…Figure 11 shows the comparison of the various impedances of the Black Box model, with and without a DM input capacitor Z 0 ( figure 7). The capacitor value for Z 0 has been chosen identical as Z 6 . Not surprisingly, the impedances Z pg and Z ng are not affected, whereas Z pn is modified.…”

“…Moreover, another intrinsic difficulty of the "Black Box" modeling has to be highlighted for this study. Indeed, the model identification is tricky [5], and the results are very sensitive to the modifications of the converter parameters [6] or operating point [7]. Thus, a formal link between the "comprehensive model", including the full knowledge of the converter, and the "black box" one may allow a better identification of the parameters, if those are known.…”