# Characterization of Partial Discharge Activities in WBG Power Converters under Low-Pressure Condition

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## Abstract

**:**

## 1. Introduction

_{2}captured in 2019 was the highest in at least 2 million years. The human role in this transformation is indispensable and has resulted in changes in the atmosphere, ocean, cryosphere, and biosphere [1]. Many countries have devised plans to cut GHG emissions. For instance, the European Commission plans to reduce GHG emissions by at least 55% compared to 1990 and become carbon neutral by 2050 [2].

_{2}emissions [3]. Considering the 3% annual growth rate in the number of air travelers, this industry could be a major obstacle in the path toward a more sustainable future. The studies have revealed the potential of up to a 60% reduction in energy consumption and also GHG emission reduction by at least 90% [4]. To utilize these potentials, electrification in the aviation industry has been started as a sustainable transition. Besides, an electric aircraft is likely to have improved reliability and lower operating costs due to the lower mechanical compartments [5].

^{®}PI film is evaluated. The results show a 50% decrease in PD inception voltage when the pressure drops from 1 Bar to 0.1 Bar. In [20], the silicone conformal coating of printed circuit boards (PCBs) is investigated and shows a 58% decrease in PDIV when the pressure drops from 1 Bar to 0.116 Bar. The authors of [21] show that the PD inception voltage of twisted pair wire at the voltage frequency of 5–200 kHz monotonically declines with the pressure drop (0.2–1 Bar).

- -
- Extending the 2D axisymmetrical models of laboratory electrode geometries to the 3D modeling of real-world cases with multiple voids.
- -
- Tackling the computational cost and convergence issues associated with the 3D modeling of configurations with extremely nonuniform electric field distribution.
- -
- Incorporating the impact of air pressure variation into different characteristics of silicone gel and AlN, as well as the inception and extinction of the discharges.

## 2. FEA Model for PD Analysis

#### 2.1. Introduction to PD Numerical Modeling

#### 2.2. Algorithm

^{®}is then run to find the results of the Poisson and Laplace equations. This step provides the electric field distribution across the geometry (insulation and voids) helping to assess the inception time of discharge activity. The details of the parameters in the algorithm are explained in the following subsections.

#### 2.3. Initial Electron Generation

#### 2.4. PD Inception/Extinction Criterion

## 3. Numerical Results

^{®}. Note that since the dielectric material is not a sealant of the void against the external low-pressure conditions, it is assumed that the pressure of the void matches the external pressure.

#### 3.1. Single-Void Case Study

#### 3.2. Double-Void Case Study

## 4. Conclusions

## Author Contributions

## Funding

## Data Availability Statement

## Conflicts of Interest

## Abbreviations

AlN | Aluminum Nitride |

CO_{2} | Carbon Dioxide |

CSM | Charge Simulation Method |

FDM | Finite Difference Method |

FEA | Finite Element Analysis |

FEM | Finite Element Method |

GHG | Greenhouse Gases |

HV | High Voltage |

IGBT | Insulated Gate Bipolar Transistor |

PCB | Printed Circuit Board |

PI | Polyimide |

PD | Partial Discharge |

PDIV | Partial Discharge Inception Voltage |

PRPD | Phase-Resolved Partial Discharge |

WBG | Wide Bandgap |

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**Figure 6.**The inception electric field versus pressure for an ellipsoidaland void with $800\mu m$ radius in electric field direction.

**Figure 8.**The electric field distribution across the voids’ cross-section (

**a**) before and (

**b**) after PD occurrence.

**Figure 9.**The electric field distribution across the line that connects the voids’ centers (

**a**) before and (

**b**) after PD occurrence.

Quantity | $\mathit{P}=0.5\mathbf{a}\mathbf{t}\mathbf{m}$ | $\mathit{P}=1\mathbf{a}\mathbf{t}\mathbf{m}$ |
---|---|---|

Number of PDs per Cycle | $3.98$ | $2.03$ |

Mean True Charge | $14.14\mathrm{pC}$ | $19.08\mathrm{pC}$ |

Mean Apparent Charge | $2.24\mathrm{pC}$ | $2.78\mathrm{pC}$ |

Maximum True Charge | $17.74\mathrm{pC}$ | $21.87\mathrm{pC}$ |

Maximum Apparent Charge | $3.42\mathrm{pC}$ | $4.00\mathrm{pC}$ |

Mean True Charge per Cycle | $56.28\mathrm{pC}$ | $38.67\mathrm{pC}$ |

Mean Apparent Charge per Cycle | $8.95\mathrm{pC}$ | $5.63\mathrm{pC}$ |

Quantity | $\mathit{P}=0.5\mathbf{a}\mathbf{t}\mathbf{m}$ | $\mathit{P}=1\mathbf{a}\mathbf{t}\mathbf{m}$ | ||
---|---|---|---|---|

0.2 mm Void | 0.3 mm Void | 0.2 mm Void | 0.3 mm Void | |

Number of PDs per Cycle | 4.00 | 3.80 | 0 | 3.80 |

Mean True Charge | 19.73 $\mathrm{pC}$ | 46.82 $\mathrm{pC}$ | - | 28.06 $\mathrm{pC}$ |

Mean Apparent Charge | 3.15 $\mathrm{pC}$ | 8.68 $\mathrm{pC}$ | - | 3.93 $\mathrm{pC}$ |

Maximum True Charge | 20.69 $\mathrm{pC}$ | 48.82 $\mathrm{pC}$ | - | 29.27 $\mathrm{pC}$ |

Maximum Apparent Charge | 3.37 $\mathrm{pC}$ | 9.19 $\mathrm{pC}$ | - | 4.38 $\mathrm{pC}$ |

Total True Charge per Cycle | 78.84 $\mathrm{pC}$ | 177.74 $\mathrm{pC}$ | - | 106.82 $\mathrm{pC}$ |

Total Apparent Charge per Cycle | 12.60 $\mathrm{pC}$ | 32.96 $\mathrm{pC}$ | - | 14.85 $\mathrm{pC}$ |

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**MDPI and ACS Style**

Borghei, M.; Ghassemi, M. Characterization of Partial Discharge Activities in WBG Power Converters under Low-Pressure Condition. *Energies* **2021**, *14*, 5394.
https://doi.org/10.3390/en14175394

**AMA Style**

Borghei M, Ghassemi M. Characterization of Partial Discharge Activities in WBG Power Converters under Low-Pressure Condition. *Energies*. 2021; 14(17):5394.
https://doi.org/10.3390/en14175394

**Chicago/Turabian Style**

Borghei, Moein, and Mona Ghassemi. 2021. "Characterization of Partial Discharge Activities in WBG Power Converters under Low-Pressure Condition" *Energies* 14, no. 17: 5394.
https://doi.org/10.3390/en14175394