Condition Monitoring of Power Electronic Systems through Data Analysis of Measurement Signals and Control Output Variables

A major disadvantage of existing condition monitoring methods is the need for additional sensors and measuring equipment. In this work, this disadvantage is eliminated by completely avoiding additional hardware. Instead, software-based methods from the field of machine learning are used. Therefore, measurement signals and control output variables are utilized which are acquired and processed in any power electronic system for the purpose of converter control. The publication focuses on two main converter components: power semiconductors and DC link capacitor. For each component, the aging mechanisms that have been studied in the literature are explained. Based on the aging mechanisms, the degradation indicators are identified. Then, a converter model is built that allows the variation of degradation indicators in order to analyze their effects on the available data set. These findings form the basis for mathematical models, which detect future failure mechanisms of this type during converter operation. The test setup must offer the possibility of generating reproducible failure cases in various components with the aid of additional failure equipment. Finally, failure mechanisms are intentionally introduced at the test bench in order to validate the methodology of the developed approach

Novel Controls of Photovoltaic (PV) Solar Farms

Solar Farms are absolutely idle in the night and even during daytime operate below capacity in early mornings and late afternoons. Thus, the entire expensive asset of solar farms remains highly unutilized. This thesis presents novel technologies for utilization of PV solar farm inverter in nighttime for providing multiple benefits to power systems, as well as accomplishing the same objectives during the daytime from the inverter capacity left after production of real power. The new technology transforms a solar farm inverter functionally into a dynamic reactive power compensator known as STATCOM, and termed PV-STATCOM. A novel coordinated control of PV-STATCOMs is proposed for loss reduction in a distribution network. The saved energy is substantial and can be used for powering several homes annually. The second novel PV-STATCOM control involves a temporary curtailment of real power production and utilization of the available reactive power capacity to prevent the instability of a critical induction motor load. The third novel PVSTATCOM control is employed to significantly enhance the power transfer limit of a long transmission line both in the nighttime and also during daytime even when the solar farm is producing a large amount of real power. A new technique for short circuit current management is developed for a conventional PV solar farm that can potentially solve the problem due to which several solar farms have been denied connectivity in Ontario. This thesis has contributed to two patent applications and presented first time implementations of another two filed patents. A generalized PV solar system model in EMTDC/PSCAD software has been developed and validated with manufacturer\u27s datasheet. Another contribution of this thesis is the first time harmonics impact study of the largest solar farm in Canada, in the distribution utility network of Bluewater Power, in Sarnia, Ontario. This thesis makes a strong case for relaxing the present grid codes to allow solar farms to exercise these novel controls. This technology can open up new avenues for solar farms to earn revenues apart from the sale of real power. This will require appropriate agreements between the regulators, network utilities, solar farm developers and inverter manufacturers

Development of Si Device Based Power Converters for High Temperature Operation in HEV Applications

In this dissertation, the feasibility of operating Si devices at 200 ˚C [degree Celsius] is investigated and the guidelines on the development of a high temperature Si converter for operating with 105 ˚C high temperature liquid coolant in hybrid electrical vehicle (HEV) applications are provided. First, the characterization of a Si IGBT operating at 200 ˚C junction temperatures is presented. It is shown that the commercial 175 ˚C Si IGBT under test can be successfully switched at an elevated junction temperature of 200 ˚C with increased but acceptable losses. Second, a comprehensive evaluation of Si IGBT ruggedness at high temperature operation is provided through experiments. The important criteria considering latch-up immunity, short circuit capability, and avalanche capability are given to ensure the safe and reliable operation of Si IGBTs at 200 ˚C. Third, the feasibility of operating Si devices based converters continuously at the junction temperature of 200 ˚C is demonstrated. A Si IGBT phase-leg module is developed for 200 ˚C operation utilizing high temperature packaging technologies and appropriate thermal management. Fourth, a method is proposed to measure the junction temperatures of IGBTs during the converter operation using IGBT short circuit current. The calibration experiments show that the short circuit current has good sensitivity, linearity and selectivity, making the method suitable for use as temperature sensitive electrical parameter (TSEP). By connecting a temperature measurement unit to the converter and giving a short circuit pulse during the converter operation, the IGBT junction temperature can be measured. Fifth, a 30 kW Si IGBT based three-phase converter has been developed for operating at the junction temperature of 200 ˚C with the high temperature coolant in HEV applications. The experimental results demonstrate that the three-phase converter can operate at junction temperature of 200 ˚C with the 105 ˚C high temperature coolant, thus eliminating the need for the additional 65 ˚C coolant in HEV. Additionally, the emerging 600 V GaN HEMT is investigated as a potential replacement of Si devices for high efficiency and high temperature in future HEV applications

Challenges and New Trends in Power Electronic Devices Reliability

The rapid increase in new power electronic devices and converters for electric transportation and smart grid technologies requires a deepanalysis of their component performances, considering all of the different environmental scenarios, overload conditions, and high stressoperations. Therefore, evaluation of the reliability and availability of these devices becomes fundamental both from technical and economicalpoints of view. The rapid evolution of technologies and the high reliability level offered by these components have shown that estimating reliability through the traditional approaches is difficult, as historical failure data and/or past observed scenarios demonstrate. With the aim topropose new approaches for the evaluation of reliability, in this book, eleven innovative contributions are collected, all focusedon the reliability assessment of power electronic devices and related components