The project addresses better understanding of how the reliability of power electronic based power systems is influenced by different stress factors such as temperature, environment and operational planning.
The modern society has to become more energy efficient and uses more renewable generation in order to be sustainable - a key technology in this mission is power electronics, which convert electrical energy from one stage to another. So now the power system is becoming more and more power electronic based.
The project will address better understanding of how the reliability of power electronic based power systems is influenced by different stress factors such as temperature, environment and operational planning.
The project is established in close collaboration with RWTH Aachen, Germany and CALCE, University of Maryland, US
Further, the project aims to develope system models that will enable simulation and design of power electronic based power systems very close to the limits of the devices and enable reliability based design.
The projects aims to develop new methods for ensuring reliable and safe operations of power electronic based power systems. An integrated reliability assessment tool, which can incorporate both the physical characteristics of hardware components and control software optimization at the system level, will be developed for predicting the lifetime of power electronic based power systems. New insights into the mutual interactions of power electronic converters at multiple time scales will be revealed to leverage the control effects of power electronics for power grid stabilization and protection.
Three great technology challenges are faced in the future:
- How to keep a high system reliability when many new power electronic components are introduced into the grid system
- The costs from failure, downtime, and maintenance are bottlenecks to further reduce the Levelized Cost of Energy from renewable generation
- Development of efficient and reliable power electronics products requiring minimum testing time to validate the life expectancy
Meeting these challenges requires the establishment of a new research platform for design and test of power electronic systems and their integration into the grid. The development of modeling and test tools for the activity is only possible by combining several disciplines like electrical engineering, system engineering, power system analysis, physics, statistics for reliability assessment, and control theory. To create this new and better understanding of power electronic system combined with its integration into the grid system, REliable Power Electronic based Power System (REPEPS) has been started.
In CORPE at Aalborg University, a multi-time-scale (from micro-seconds to years) mission profile has been proposed, which so far is limited to temperature as a single stressor at the component level and there is a large gap in research in order to fully assess complete systems with multiple stressors. At the same time, those system models have not been applied in the future grid system where many power electronic devices are connected, such as renewable (mainly photovoltaic and wind) power plants, direct current transmission systems, and high-speed railway networks.
REPEPS will make the ground to enable complete system assessment using a multi-stressors based approach on the power converters as well as making such knowledge applicable in operation of power electronic based power systems.
REPEPS will focus on a multi-disciplinary research on system assessment and reliability in power electronics based power system used in electrical energy systems. The aims are to develop new models and tools by taking advantage of new multi-time scale, multi-stressors (e.g., temperature, voltage, current, humidity) modeling methods, control methods and also resource-effective mission profile (long-term operation conditions) based verification testing methods. Many of the existing models are very limited to be used in system-level reliability assessment and only taking into account one parameter, while I aim to create/develop physics based models, which can handle the most important parameters to be able to assess systems. Fig. 1 shows an overview of the activities to be carried out with six research thrusts. Also a combined electro-thermo-mechanical degradation model is useful for the design in the equipment level and it is feasible also to be used in more complex system analysis. Following research thrusts are proposed to be going on:
Failure mechanism of power electronic and power system components
The major components in a power electronic based power system are defined and a failure mode and effect analysis (FMEA) is carried out to address the most critical components. Models to describe the failures for wear out as well as their behavior during abnormal conditions will be done.
Multi-time scale modeling and system assessment
We will develop models to describe the wear out of the components depending on loading conditions taking into account the most important stressors. The models will be developed so they can also be used in Monte Carlo analysis in order to take into account parameter variation.
Power electronic system modeling and analysis
Terminal behavioral models of power electronic converters, including both small-signal disturbance and large-signal grid faults, will be developed for the system analysis. A multi-frequency modeling framework will be established to reveal the electromagnetic coupling as well as control interactions of multiple converters. The model-order reduction and aggregation techniques will be explored for the analysis of large-scale power electronic based power systems. The impacts of the system-wide instabilities and resonances on the reliability of power electronic converters will be qualified.
Control of power electronic based power system
Control methods for stable operations of power electronic based power systems will be investigated and translated into reliability metrics. Fault control methods of power electronic converters will also be assessed by means of reliability metrics. Cooperative control strategies that considers the reliability indexes will be developed for clustered power converters in renewable power plants, micro-grids, and other power electronic based power systems.
System probabilistic and reliability assessment
Conventional reliability metrics does not take into account wear out of power components when doing power system analysis – here this will be included by assessing the power system dependent on the loading conditions combined with the advanced converter lifetime models. The assessment method is also able to quantify the demands to the individual components before they are connected. The assessment will probabilistic also study generation and loading conditions as well as the parameter variation in the converter.
Validation of the proposed methods
Test will be done at different systems – some of the power converter system modeling of control and reliability will be performed at the CORPE infrastructure. In addition, the power electronic based power system stability will be assessed in a micro-grid provided by the Harmony project. Finally, the methods will be applies in a real grid structure – either a small scale low voltage micro-grid or a more complicated larger scale wind farm system.
These thrusts will be covered with PhDs and also with Post-Docs.
See an overview of the research in REPEPS