Dr. Pengyu Fu received his B.S. degree and Ph.D. degree in electrical engineering from North China Electric Power University, Beijing, China, in 2014 and 2019, respectively. From 2019, he is working as a researcher at the Center for High Performance Power Electronics of the Ohio State University, Columbus, OH, USA.
Currently, Dr. Fu is a lead research scientist at the High Voltage Laboratory of the Ohio State University (OSU), where he focuses on the development of advanced power electronics and high voltage systems. His current research interests include high voltage and dielectric insulation, plasmas, electromagnetic compatibility, high voltage power module packaging and characterization, high voltage power electronics for aerospace power and lunar and terrestrial power grid applications.
Dr. Fu has published numerous research papers in high-impact journals and conferences, focusing on the development of advanced power electronics and high voltage systems for future electrified aircraft. He has delivered several tutorials and presentations in the leading conferences on the topics of high voltage for the electrified aircrafts. His work has received recognitions and he has been invited as the topic chair on electric aircraft propulsion technologies for 2023 IEEE Energy Conversion Conference and Expo (ECCE).
In addition to his research work, Dr. Fu is also an active member of the Institute of Electrical and Electronics Engineers (IEEE). He is passionate about mentoring and inspiring the next generation of researchers and engineers and actively participates in various teaching activities to promote science and engineering education.
Electrification in the aviation industry is gaining significant attention as the world strives towards a more sustainable future. One of the emerging trends in electrified aircraft is the use of high voltage systems to 1-10 kV DC range.
The transition towards high voltage systems in electrified aircraft is driven by two main factors. First, as more and more systems onboard aircraft are electrified, the demand for power has significantly increased (MW class). This includes electric propulsion, as well as other electrical systems such as avionics, environmental control systems, and lighting. High voltage systems can handle more power and deliver it more efficiently than traditional low voltage systems (270 VDC), making them suitable for meeting the growing demand for power in electrified aircraft. Second, there is a strong need for lightweight, compact, and efficient electrical power systems onboard aircraft. High voltage systems can help reduce the size, weight, and power loss of the electrical power system. This is because high voltage systems require less current to deliver the same amount of power as low voltage systems, which results in smaller power distribution wires, lighter electrical machine windings and lower conduction loss.
However, high voltage at flight altitude (30,000-50,000 ft) presents four major challenges to the safety and reliability of the aircraft electrical power system.
The first challenge is partial discharge (including corona and surface discharge) and arcing (including flashover and sparkover) under high voltage at flight altitude. As the altitude increases, the air pressure decreases, and the dielectric strength of the air tends to decrease according to Paschen’s law. This can lead to the inception of partial discharge and arcing at lower voltage, which can degrade the electrical insulation of components in the aircraft power system and potentially cause catastrophic failures.
The second challenge is dielectric material aging due to cavity discharge, treeing and breakdown phenomena under DC voltage and pulse width modulation (PWM) voltage generated by power electronics. For DC voltage, space charge accumulation will play a key role in the material aging process. When a high DC voltage is applied to an insulating material, charge carriers (electrons and/or ions) can become trapped in the material, creating a space charge region. This space charge region can accumulate over time, leading to a local electric field intensification. The intensified electric field can lead to the local breakdown of insulation material and accelerate the aging. For PWM voltage, high frequency (>10 kHz) and high dv/dt (>10 V/ns) effect will impact the lifetime of the insulation material. High frequency will affect the discharge mechanism and potentially accelerate the thermal induced ageing. High dv/dt will reduce the partial discharge inception voltage and lead to more severe partial discharge events, which may cause a quicker insulation deterioration over the time.
The third challenge is electrical insulation coordination of the on-board power system, including cables and their connectors, power electronics, and electrical machines. High voltage systems require careful insulation coordination to prevent partial discharge and arcing under normal working conditions and transient over-voltage conditions. Key insulation characteristics and their coordination need to be examined for aviation application, including partial discharge test voltage, maximum repetitive peak insulation voltage, maximum transient isolation voltage, maximum withstand isolation voltage and maximum surge isolation voltage. Minimum creepage and clearance distances, as well as comparative tracking index, must be reconsidered for aviation applications, as design guidelines for these factors at low air pressure are not well-established.
The fourth challenge is testing and certification of high voltage systems for use in aircraft. It must consider the unique environmental conditions (> 100 °C operation temperature, high background radiation and high humidity) and potential failure modes at flight altitudes under DC and PWM voltage to ensure safe and reliable operation of the power system. There are no existing test standards that can be directly referenced for the application scenario. Existing test results concerning the environmental conditions at flight altitude and high DC or PWM voltage are rare.
The identified challenges of high voltage systems in aircraft necessitate urgent research needs to address these issues. These research needs can be categorized into four aspects.
The first aspect is the need to study partial discharge inception and dielectric material aging mechanisms, particularly at DC and PWM voltage and the unique environmental conditions at flight attitude. Understanding these mechanisms is crucial to develop effective insulation materials and structures ensuring the reliable high voltage systems for aircraft. Research in this area can help identify potential failure modes and failure mechanism and develop mitigation strategies to prevent catastrophic failures.
The second aspect is the insulation coordination design of the on-board power system, including cables, cable connectors, power electronics, and electrical machines. The insulation coordination design guidelines for all these components need to be established towards the application scenario. Research in the experiment-based design guidelines and computation and simulation aided design tools can contribute to formulate the best practices for the development of high voltage systems for aircraft.
The third aspect is the development of insulation test standards, including testing and measuring techniques, procedures, and conditions. Standards are crucial for ensuring that high voltage systems meet safety and performance requirements of aircraft. Research in this area needs to identify appropriate testing methods and procedures for aircraft high voltage systems, particularly at the unique operation conditions.
The fourth aspect is the development of intelligent online condition monitoring and diagnostics tools for high voltage systems in aircraft. Real-time monitoring and diagnostics can help detect and diagnose potential issues before they escalate into critical failures. Research in this area needs to develop advanced sensing and detection techniques for partial discharge and intelligent diagnostic algorithms for insulation conditions to enable effective online monitoring and diagnostics of high voltage systems.
In the final presentation, the challenges of high voltage at flight altitude will be elaborated. The recent research efforts and outcomes related to this topic from the High Voltage Laboratory at The Ohio State University will be disseminated. The partial discharge related experimental results in cables, power modules and motor windings for aerospace application will be presented in detail to highlight the recent advances on this topic. This presentation aims to provide a comprehensive understanding of the challenges posed by high voltage at flight altitude and the measures to address those challenges.Electrification in the aviation industry is gaining significant attention as the world strives towards a more sustainable future. One of the emerging trends in electrified aircraft is the use of high voltage systems to 1-10 kV DC range.
The transition towards high voltage systems in electrified aircraft is driven by two main factors. First, as more and more systems onboard aircraft are electrified, the demand for power has significantly increased (MW class). This includes electric propulsion, as well as other electrical systems such as avionics, environmental control systems, and lighting. High voltage systems can handle more power and deliver it more efficiently than traditional low voltage systems (270 VDC), making them suitable for meeting the growing demand for power in electrified aircraft. Second, there is a strong need for lightweight, compact, and efficient electrical power systems onboard aircraft. High voltage systems can help reduce the size, weight, and power loss of the electrical power system. This is because high voltage systems require less current to deliver the same amount of power as low voltage systems, which results in smaller power distribution wires, lighter electrical machine windings and lower conduction loss.
However, high voltage at flight altitude (30,000-50,000 ft) presents four major challenges to the safety and reliability of the aircraft electrical power system.
The first challenge is partial discharge (including corona and surface discharge) and arcing (including flashover and sparkover) under high voltage at flight altitude. As the altitude increases, the air pressure decreases, and the dielectric strength of the air tends to decrease according to Paschen’s law. This can lead to the inception of partial discharge and arcing at lower voltage, which can degrade the electrical insulation of components in the aircraft power system and potentially cause catastrophic failures.
The second challenge is dielectric material aging due to cavity discharge, treeing and breakdown phenomena under DC voltage and pulse width modulation (PWM) voltage generated by power electronics. For DC voltage, space charge accumulation will play a key role in the material aging process. When a high DC voltage is applied to an insulating material, charge carriers (electrons and/or ions) can become trapped in the material, creating a space charge region. This space charge region can accumulate over time, leading to a local electric field intensification. The intensified electric field can lead to the local breakdown of insulation material and accelerate the aging. For PWM voltage, high frequency (>10 kHz) and high dv/dt (>10 V/ns) effect will impact the lifetime of the insulation material. High frequency will affect the discharge mechanism and potentially accelerate the thermal induced ageing. High dv/dt will reduce the partial discharge inception voltage and lead to more severe partial discharge events, which may cause a quicker insulation deterioration over the time.
The third challenge is electrical insulation coordination of the on-board power system, including cables and their connectors, power electronics, and electrical machines. High voltage systems require careful insulation coordination to prevent partial discharge and arcing under normal working conditions and transient over-voltage conditions. Key insulation characteristics and their coordination need to be examined for aviation application, including partial discharge test voltage, maximum repetitive peak insulation voltage, maximum transient isolation voltage, maximum withstand isolation voltage and maximum surge isolation voltage. Minimum creepage and clearance distances, as well as comparative tracking index, must be reconsidered for aviation applications, as design guidelines for these factors at low air pressure are not well-established.
The fourth challenge is testing and certification of high voltage systems for use in aircraft. It must consider the unique environmental conditions (> 100 °C operation temperature, high background radiation and high humidity) and potential failure modes at flight altitudes under DC and PWM voltage to ensure safe and reliable operation of the power system. There are no existing test standards that can be directly referenced for the application scenario. Existing test results concerning the environmental conditions at flight altitude and high DC or PWM voltage are rare.
The identified challenges of high voltage systems in aircraft necessitate urgent research needs to address these issues. These research needs can be categorized into four aspects.
The first aspect is the need to study partial discharge inception and dielectric material aging mechanisms, particularly at DC and PWM voltage and the unique environmental conditions at flight attitude. Understanding these mechanisms is crucial to develop effective insulation materials and structures ensuring the reliable high voltage systems for aircraft. Research in this area can help identify potential failure modes and failure mechanism and develop mitigation strategies to prevent catastrophic failures.
The second aspect is the insulation coordination design of the on-board power system, including cables, cable connectors, power electronics, and electrical machines. The insulation coordination design guidelines for all these components need to be established towards the application scenario. Research in the experiment-based design guidelines and computation and simulation aided design tools can contribute to formulate the best practices for the development of high voltage systems for aircraft.
The third aspect is the development of insulation test standards, including testing and measuring techniques, procedures, and conditions. Standards are crucial for ensuring that high voltage systems meet safety and performance requirements of aircraft. Research in this area needs to identify appropriate testing methods and procedures for aircraft high voltage systems, particularly at the unique operation conditions.
The fourth aspect is the development of intelligent online condition monitoring and diagnostics tools for high voltage systems in aircraft. Real-time monitoring and diagnostics can help detect and diagnose potential issues before they escalate into critical failures. Research in this area needs to develop advanced sensing and detection techniques for partial discharge and intelligent diagnostic algorithms for insulation conditions to enable effective online monitoring and diagnostics of high voltage systems.
In the final presentation, the challenges of high voltage at flight altitude will be elaborated. The recent research efforts and outcomes related to this topic from the High Voltage Laboratory at The Ohio State University will be disseminated. The partial discharge related experimental results in cables, power modules and motor windings for aerospace application will be presented in detail to highlight the recent advances on this topic. This presentation aims to provide a comprehensive understanding of the challenges posed by high voltage at flight altitude and the measures to address those challenges.
