Reliability Oriented Circuit Design For Power Electronics Applications

Research output: Book/ReportPh.D. thesisResearch

Abstract

Highly reliable components are required in order to minimize the downtime during the lifetime of the converter and implicitly the maintenance costs. Therefore, the design of high reliable converters under constrained reliability and cost is a great challenge to be overcome in the future. The temperature variation of the semiconductor devices plays a key role in the robustness design and reliability of power electronics converters. This factor has a major impact on the power converters used in renewable energy systems, like solar and wind energy applications, due to the fluctuating nature of the mission profile. The mission profile variations introduce converter current changes which further cause device junction temperature variations that significantly reduce the reliability of the semiconductor devices. Therefore, in order to achieve reliability improvement and cost reduction of the renewable energy technology, a reliability-oriented design tool is of great interest. This tool is expected to perform the long-term (e.g. one year) electrothermal and then the reliability aspect analysis of the switching devices in the new generation of power converters. Besides this, another important method for improving the reliability is by active thermal control of the power electronic devices.

The work developed during the Ph.D. studies the above mentioned topics, and is divided into two main parts: the first part develops a reliability-oriented design tool which is using a long term real-field mission-profile as input and the second part propose an advanced gatedriver concept for enhancing the reliability of the power electronics devices. Chapter 1 introduce the emerging challenges of a design tool for reliability and which are the main methods for achieving active thermal control of the devices. To overcome the emerging challenges described in Chapter 1, the first part of the thesis focuses on the proposed reliability tool and it is presented in Chapter 2 and Chapter 3. In this part is introduced a novel concept of assessing the reliability of power semiconductor devices by considering the device degradation and the mission profile operating conditions. The detailed modeling process of the tool is presented in Chapter 2. Afterwards the translation process from the Detailed Simulation Model (DSM) to the Long Term Simulation Model (LTSM) in order to consider the mission profile impact on device thermal loading is presented.

Chapter 3 presents the electro-thermal model validation and the reliability studies performed by the proposed tool. The chapter ends with a detailed lifetime analysis, which emphasizes the mission-profile variation and gate-driver parameters variation impact on the PV-inverter devices lifetime. Moreover, the impact of the mission-profile sampling time on the lifetime estimation accuracy is also determined.

The second part of the thesis introduced in Chapter 4, presents a novel gate-driver concept which reduces the dependency of the device power losses variations on the device loading variations. The proposed gate-driver is able dynamically and accurately to control the gateresistance and gate-voltage in order to preserve constant the device losses dissipation, implicitly also the device temperature. In order to proof the concept, the hardware implementation of the proposed active thermal control has been done. The chapter ends with a detailed lifetime analysis, which emphasizes the mission profile variation and advanced gate-driver strategy impact on the converter device lifetime.

The main contribution of this project is in developing of a novel reliability oriented design tool for the next generation of power converters. The tool introduces a novel concept of assessing the reliability of power semiconductor devices by considering the device degradation related to the real field operating conditions. Moreover, the project it also introduces a novel gate-driver concept which reduces the dependency of the device power losses (implicitly temperature) variations on the device loading variations, enhancing the reliability of power electronics devices.
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Highly reliable components are required in order to minimize the downtime during the lifetime of the converter and implicitly the maintenance costs. Therefore, the design of high reliable converters under constrained reliability and cost is a great challenge to be overcome in the future. The temperature variation of the semiconductor devices plays a key role in the robustness design and reliability of power electronics converters. This factor has a major impact on the power converters used in renewable energy systems, like solar and wind energy applications, due to the fluctuating nature of the mission profile. The mission profile variations introduce converter current changes which further cause device junction temperature variations that significantly reduce the reliability of the semiconductor devices. Therefore, in order to achieve reliability improvement and cost reduction of the renewable energy technology, a reliability-oriented design tool is of great interest. This tool is expected to perform the long-term (e.g. one year) electrothermal and then the reliability aspect analysis of the switching devices in the new generation of power converters. Besides this, another important method for improving the reliability is by active thermal control of the power electronic devices.

The work developed during the Ph.D. studies the above mentioned topics, and is divided into two main parts: the first part develops a reliability-oriented design tool which is using a long term real-field mission-profile as input and the second part propose an advanced gatedriver concept for enhancing the reliability of the power electronics devices. Chapter 1 introduce the emerging challenges of a design tool for reliability and which are the main methods for achieving active thermal control of the devices. To overcome the emerging challenges described in Chapter 1, the first part of the thesis focuses on the proposed reliability tool and it is presented in Chapter 2 and Chapter 3. In this part is introduced a novel concept of assessing the reliability of power semiconductor devices by considering the device degradation and the mission profile operating conditions. The detailed modeling process of the tool is presented in Chapter 2. Afterwards the translation process from the Detailed Simulation Model (DSM) to the Long Term Simulation Model (LTSM) in order to consider the mission profile impact on device thermal loading is presented.

Chapter 3 presents the electro-thermal model validation and the reliability studies performed by the proposed tool. The chapter ends with a detailed lifetime analysis, which emphasizes the mission-profile variation and gate-driver parameters variation impact on the PV-inverter devices lifetime. Moreover, the impact of the mission-profile sampling time on the lifetime estimation accuracy is also determined.

The second part of the thesis introduced in Chapter 4, presents a novel gate-driver concept which reduces the dependency of the device power losses variations on the device loading variations. The proposed gate-driver is able dynamically and accurately to control the gateresistance and gate-voltage in order to preserve constant the device losses dissipation, implicitly also the device temperature. In order to proof the concept, the hardware implementation of the proposed active thermal control has been done. The chapter ends with a detailed lifetime analysis, which emphasizes the mission profile variation and advanced gate-driver strategy impact on the converter device lifetime.

The main contribution of this project is in developing of a novel reliability oriented design tool for the next generation of power converters. The tool introduces a novel concept of assessing the reliability of power semiconductor devices by considering the device degradation related to the real field operating conditions. Moreover, the project it also introduces a novel gate-driver concept which reduces the dependency of the device power losses (implicitly temperature) variations on the device loading variations, enhancing the reliability of power electronics devices.
Original languageEnglish
PublisherDepartment of Energy Technology, Aalborg University
ISBN (Print)978-87-92846-52-5
StatePublished - 2015
Publication categoryResearch

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