# Experimental Study of Radiated Emission Due to Secondary Common-Mode Current in Buck Converters

## Abstract

**:**

## 1. Introduction

## 2. Configuration of Experimental System

^{2}is used for the connection between the buck converter and LISNs. Note that the metal box is connected to the ground plane via LISNs.

## 3. Generation Mechanism of the SCM Noise in the Experimental System

_{DM}is the DM current source; V

_{PCM}is the PCM voltage source; and I

_{PCM}is the PCM current. The impedance between terminals P’–N’ when the three-core cable is disconnected near the input terminal of the buck converter is denoted as Z

_{DM}. Moreover, the impedance between the input terminals of the buck converter and the metal box is Z

_{PCM}, and it is equally distributed to each phase of the buck converter. Z

_{LISN}represents the impedance of LISNs, and Z

_{P}, Z

_{N}, and Z

_{E}represent the impedances of the power lines P, N, and ground line E of the three-core cable, respectively. The impedance between the terminal E and the ground plane near LISNs is represented as Z

_{G}(Z

_{G}is depicted by a dotted line in Figure 2 because it is very small).

_{P}= Z

_{N}= Z

_{E}), the following Equation (1) for the PCM is derived as

_{PCM}is given using

_{P}, V

_{N}, and V

_{E}) are represented as

_{P}, V

_{N}, and V

_{E}, which is the CM voltage of the three-core cable as a whole V

_{SCM}, is given with

_{G}and Z

_{LISN}are not equal, and the right side of Equation (6) is not zero. Thus, it can be considered that the SCM voltage, which is the average voltage given with Equation (6), is caused by the PCM current and the unbalance of the power supply side impedances (Z

_{LISN}≠ Z

_{G}) in this experimental system.

_{SCM}causes the SCM current I

_{SCM}to flow through the entire three-core cable. The buck converter, which is housed in the metal box, is placed on the wooden table whose height is 0.8 m from the floor. Thus, the power converter side has a large SCM impedance to the ground plane. In this case, a standing wave of the SCM current with the power supply side as the antinode and the power converter side as the node is generated depending on the cable length, as shown in Figure 4.

_{PCM}or balancing the power supply side impedances (Z

_{LISN}= Z

_{G}) effectively reduces the SCM noise. For the experimental system in this article, it is necessary to connect an artificial impedance network between the ground line terminal E and the ground plane to achieve the balance of power supply side impedances. However, in practice, the power supply side impedance is not constant over a wide bandwidth. Generally, it is difficult to accurately simulate the frequency characteristics of a power supply side impedance over wide-band frequencies. Moreover, from the viewpoint of preventing electric shock, it is undesirable to connect an impedance balancing component to the ground line of power converters. On the other hand, the PCM current can be suppressed using CM inductors (CMIs) to increase the impedance of the PCM propagation path [20,34]. The following section demonstrates the above-mentioned radiated noise generation mechanism by connecting CMIs to the experimental system and evaluating the impact of CMIs on each CM current and radiated noise based on the experimental results.

## 4. Noise Measurements in the Experimental System

#### 4.1. Common-Mode Currents

_{PCM}and Z

_{SCM}) of each fabricated CMI. The measurements were performed using an impedance analyzer (E4990A, Keysight, Santa Rosa, CA, USA) in the frequency range from 1 kHz to 100 MHz. For the P-CMI, Z

_{PCM}was measured by connecting the terminals of the two windings shorted together to the measurement terminals of the impedance analyzer. Z

_{PCM}and Z

_{SCM}of the fabricated S-CMI were measured according to the connections, as shown in Figure 9a. Figure 9b confirms that the PCM impedance of the P-CMI and the SCM impedance of the S-CMI show similar frequency characteristics due to the equal turn numbers of the two CMIs. Up to about 2 MHz, the impedance increases with a +20 dBΩ/dec slope. Above 2 MHz, the slopes of impedance increase are about +10 dB/Ω due to the complex permeability of the NiZn ferrite core. Note that the PCM impedance of the S-CMI corresponds to the leakage inductance of the S-CMI. The PCM impedance of S-CMI is very small compared to the SCM impedance because of the winding arrangement’s high coupling between the windings. Moreover, it can be confirmed that the winding resistance is dominant from 1 kHz to 10 kHz in the measured PCM impedance of S-CMI.

#### 4.2. Radiated Emission

## 5. Conclusions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Acknowledgments

## Conflicts of Interest

## Nomenclature

I_{DM} | Differential-mode current |

I_{PCM} | Primary common-mode current |

I_{SCM} | Secondary common-mode current |

V_{E} | Voltage potential of the terminal E for the ground |

V_{N} | Voltage potential of the terminal N for the ground |

V_{P} | Voltage potential of the terminal P for the ground |

V_{PCM} | Primary common-mode voltage |

V_{SCM} | Secondary common-mode voltage |

Z_{DM} | Differential-mode impedance |

Z_{E} | Impedance of the ground wire E |

Z_{G} | Impedance between the terminal E and the ground plane |

Z_{LISN} | Impedance of the line impedance stabilization network |

Z_{N} | Impedance of the power line N |

Z_{P} | Impedance of power the line P |

Z_{PCM} | Primary common-mode impedance |

Z_{SCM} | Secondary common-mode impedance |

## References

- Sengupta, S.; Kumar, A.; Tiwari, S. Transient stability enhancement of a hybrid Wind-PV farm incorporating a STATCOM. In Proceedings of the 2018 3rd IEEE International Conference on Recent Trends in Electronics, Information & Communication Technology (RTEICT), Bangalore, India, 18–19 May 2018; pp. 1574–1580. [Google Scholar]
- Sinha, S.; Chandel, S.S.; Malik, P. Investigation of a building-integrated solar photovoltaic-wind-battery hybrid energy system: A case study. Int. J. Energy Res.
**2021**, 45, 21534–21539. [Google Scholar] [CrossRef] - Biela, J.; Schweizer, M.; Waffler, S.; Kolar, J.W. SiC versus Si—Evaluation of Potentials for Performance Improvement of Inverter and DC–DC Converter Systems by SiC Power Semiconductors. IEEE Trans. Ind. Electron.
**2011**, 58, 2872–2882. [Google Scholar] [CrossRef] - Han, D.; Li, S.; Wu, Y.; Sarlioglu, B. Comparative Analysis on Conducted CM EMI Emission of Motor Drives: WBG Versus Si Devices. IEEE Trans. Ind. Electron.
**2017**, 64, 8353–8363. [Google Scholar] [CrossRef] - Engelmann, D.G.; Sewergin, A.; Neubert, M.; De Doncker, R.W. Design Challenges of SiC Devices for Low- and Medium-Voltage DC-DC Converters. IEEJ J. Ind. Appl.
**2019**, 8, 505–511. [Google Scholar] [CrossRef] - Zhang, B.; Wang, S. A Survey of EMI Reserch in Power Electronics Systems with Wide-Bandgap Semiconductor Devices. IEEE J. Emerg. Sel. Topics Powe Electron.
**2020**, 8, 626–643. [Google Scholar] [CrossRef] - Takahashi, S.; Wada, K.; Ayano, H.; Ogasawara, S.; Shimizu, T. Review of Modeling and Suppression Techniques for Electromagnetic Interference in Power Conversion Systems. IEEJ J. Ind. Appl.
**2022**, 11, 7–19. [Google Scholar] [CrossRef] - Ogasawara, S.; Akagi, H. Modeling and Damping of High-Frequency Leakage Currents in PWM Inverter-Fed AC Motor Drive Systems. IEEE Trans. Ind. Appl.
**1996**, 32, 1105–1114. [Google Scholar] [CrossRef] - Akagi, H.; Hasegawa, H.; Doumoto, T. Design and Performance of a Passive EMI Filter for Use with a Voltage-Source PWM Inverter Having Sinusoidal Output Voltage and Zero Common-Mode Voltage. IEEE Trans. Power Electron.
**2004**, 19, 1069–1076. [Google Scholar] [CrossRef] - Ogasawara, S.; Ayano, H.; Akagi, H. An Active Circuit for Cancellation of Common-Mode Voltage Generated by a PWM Inverter. IEEE Trans. Power Electron.
**1998**, 13, 835–841. [Google Scholar] [CrossRef] - Takahashi, S.; Maekawa, S. Attenuation Characteristics of the Input/Output Coupling Passive EMI Filter on Conducted Emission in Motor Drive Systems. IEEJ J. Ind. Appl.
**2022**, 11, 709–710. [Google Scholar] [CrossRef] - Wang, A.; Zhang, F.; Gao, T.; Wu, Z.; Li, X. Integrated CM Inductor for Both DC and AC Noise Attenuation in DC-Fed Motor Drive Systems. IEEE Trans. Power Electron.
**2023**, 38, 510–522. [Google Scholar] [CrossRef] - Julian, A.L.; Oriti, G.; Lipo, T.A. Elimination of Common-Mode Voltage in Three-Phase Sinusoidal Power Converters. IEEE Trans. Power Electron.
**1999**, 14, 982–989. [Google Scholar] [CrossRef] - Han, D.; Morris, C.T.; Sarlioglu, B. Common-Mode Voltage Cancellation in PWM Motor Drives With Balanced Inverter Topology. IEEE Trans. Ind. Electron.
**2017**, 64, 2683–2688. [Google Scholar] [CrossRef] - Han, D.; Lee, W.; Li, S.; Sarlioglu, B. New Method for Common Mode Voltage Cancellation in Motor Drives: Concept, Realization, and Asymmetry Influence. IEEE Trans. Power Electron.
**2018**, 33, 1188–1201. [Google Scholar] [CrossRef] - Xie, L.; Yuan, X. Common-Mode Current Reduction at DC and AC Sides in Inverter Systems by Passive Cancellation. IEEE Trans. Power Electron.
**2021**, 36, 9069–9079. [Google Scholar] [CrossRef] - Xie, L.; Yuan, X.; Zhu, H.; Lo, Y.-K. Common-Mode Voltage Cancellation for Reducing the Common-Mode Noise in DC–DC Converters. IEEE Trans. Ind. Electron.
**2021**, 68, 3887–3897. [Google Scholar] [CrossRef] - Xie, L.; Yuan, X. Non-Isolated DC-DC Converters With Low Common-Mode Noise by Using Split-Winding Configuration. IEEE Trans. Power Electron.
**2022**, 37, 452–461. [Google Scholar] [CrossRef] - Hockanson, D.M.; Drewniak, J.L.; Hubing, T.H.; Van Doren, T.P.; Fei, S.; Wilhelm, M.J. Investigation of Fundamental EMI Source Mechanisms Driving Common-Mode Radiation from Printed Circuit Boards with Attached Cables. IEEE Trans. Electromagn. Compat.
**1996**, 38, 557–566. [Google Scholar] [CrossRef] - Roc’h, A.; Leferink, F. Nanocrystalline Core Material for High-Performance Common Mode Inductors. IEEE Trans. Electromagn. Compat.
**2012**, 54, 785–791. [Google Scholar] [CrossRef] - Laour, M.; Tahmi, R.; Vollaire, C. Modeling and Analysis of Conducted and Radiated Emissions due to Common Mode Current of a Buck Converter. IEEE Trans. Electromagn. Compat.
**2017**, 59, 1260–1267. [Google Scholar] [CrossRef] - Takahashi, S.; Ogasawara, S.; Orikawa, K.; Takemoto, M.; Tamate, M. An Active Common-Mode Filter for Reducing Radiated Noise from Power Cables. In Proceedings of the 2017 IEEE 3rd International Future Energy Electronics Conference and ECCE Asia (IFEEC 2017—ECCE Asia), Kaohsiung, Taiwan, 3–7 June 2017; pp. 1753–1758. [Google Scholar]
- Yao, J.; Li, Y.; Zhao, H.; Wang, S.; Wang, Q.; Lu, Y.; Fu, D. Modeling and Reduction of Radiated Common Mode Current in Flyback Converters. In Proceedings of the 2018 IEEE Energy Conversion Congress and Exposition (ECCE), Portland, OR, USA, 23–27 September 2018; pp. 6613–6620. [Google Scholar]
- Zhang, Y.; Wang, S.; Chu, Y. Investigation of Radiated Electromagnetic Interference for an Isolated High-Frequency DC–DC Power Converter With Power Cables. IEEE Trans. Power Electron.
**2019**, 34, 9632–9643. [Google Scholar] [CrossRef] - Yao, J.; Wang, S.; Luo, Z. Modeling, Analysis, and Reduction of Radiated EMI Due to the Voltage Across Input and Output Cables in an Automotive Non-Isolated Power Converter. IEEE Trans. Power Electron.
**2022**, 37, 5455–5465. [Google Scholar] [CrossRef] - Ma, Z.; Wang, S.; Sheng, H.; Lakshmikanthan, S. Modeling, Analysis and Mitigation of Radiated EMI Due to PCB Ground Impedance in a 65 W High-Density Active-Clamp Flyback Converter. IEEE Trans. Ind. Electron.
**2023**, 70, 12267–12277. [Google Scholar] [CrossRef] - Nobunaga, T.; Toyota, Y.; Iokibe, K.; Koga, L.R.; Watanabe, T. Evaluation of Pigtail Termination of STP Cable Using Model Equivalent Circuit of Four-Conductor Transmission Systems. In Proceedings of the 2013 International Symposium on Electromagnetic Theory, Hiroshima, Japan, 23–24 May 2013; pp. 222–225. [Google Scholar]
- Vincent, M.; Klingler, M.; Riah, Z.; Azzouz, Y. Influence of Car Body Materials on the Common-Mode Current and Radiated Emissions Induced by Automotive Shielded Cables. In Proceedings of the 2015 IEEE International Symposium on Electromagnetic Compatibility (EMC), Dresden, Germany, 16–22 August 2015; pp. 726–731. [Google Scholar]
- Zhang, N.; Kim, J.; Nah, W. Novel Extended Mixed-Mode S-Parameters and Mode Conversion of Four-Conductor Lines. In Proceedings of the 2015 Asia-Pacific Symposium on Electromagnetic Compatibility (APEMC), Taipei, Taiwan, 25–29 May 2015; pp. 712–715. [Google Scholar]
- Instruction Manual for Line Impedance Stabilization Network Model LI-325C 10 kHz to 400 MHz. Available online: https://documentation.com-power.com/pdf/LI-325C-2.pdf (accessed on 22 October 2023).
- Foissac, M.; Schanen, J.; Vollaire, C. “Black Box” EMC Model for Power Electronics Converter. In Proceedings of the 2009 IEEE Energy Conversion Congress and Exposion, San Jose, CA, USA, 20–24 September 2009; pp. 3609–3615. [Google Scholar]
- Bishnoi, H.; Baisden, A.C.; Mattavelli, P.; Boroyevich, D. Analysis of EMI Terminal Modeling of Switched Power Converters. IEEE Trans. Power Electron.
**2012**, 27, 3924–3933. [Google Scholar] [CrossRef] - Amara, M.; Vollaire, C.; Ali, M.; Costa, F. Black Box EMC Modeling of a Three Phase Inverter. In Proceedings of the 2018 International Symposium on Electromagnetic Compatibility (EMC EUROPE), Amsterdam, The Netherlands, 27–30 August 2018; pp. 642–647. [Google Scholar]
- Yao, J.; Li, Y.; Zhao, H.; Wang, S. Design of CM Inductor Based on Core Loss for Radiated EMI Reduction in Power Converters. In Proceedings of the 2019 IEEE Applied Power Electronics Conference and Exposition (APEC), Long Beach, CA, USA, 25–29 February 2019; pp. 2673–2680. [Google Scholar]

**Figure 9.**CM impedance measurements of the fabricated CMIs. (

**a**) Measurement configurations of the S-CMI; (

**b**) measured CM impedances.

**Figure 12.**Configuration of a monopole antenna constructed when the S-CMI is connected to the three-core cable.

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**MDPI and ACS Style**

Takahashi, S.
Experimental Study of Radiated Emission Due to Secondary Common-Mode Current in Buck Converters. *Appl. Sci.* **2023**, *13*, 11735.
https://doi.org/10.3390/app132111735

**AMA Style**

Takahashi S.
Experimental Study of Radiated Emission Due to Secondary Common-Mode Current in Buck Converters. *Applied Sciences*. 2023; 13(21):11735.
https://doi.org/10.3390/app132111735

**Chicago/Turabian Style**

Takahashi, Shotaro.
2023. "Experimental Study of Radiated Emission Due to Secondary Common-Mode Current in Buck Converters" *Applied Sciences* 13, no. 21: 11735.
https://doi.org/10.3390/app132111735