Solutions and Study Methods for Power Grids with Diminishing Inertia

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Renewable energy sources transform our power grids as their share in energy generation grows. While we reap the benefits of energy sustainability, we must also face the adverse impacts of renewable generation on the ability of our power grids to remain stable and resilient to disturbances. The term used to describe this ability is system inertia. Conventional generation chiefly relies on rotary generators for energy conversion. When a disturbance occurs, the load-generation imbalance is rapidly met by the kinetic energy stored in the rotating shaft before the generator's mechanical input is adjusted to regain balance and restore the system frequency. Since the collective rotating mass of generators is enormous, the impact of transients on frequency is often small. In fact, an essentially constant frequency is normally taken for granted and is the underlying assumption in the study and operation of power systems. The growing use of renewables has diluted the share of rotary generation, thus eroding the system inertia. As a result, large frequency swings are appearing at alarming rates. This has major effects on the operation of low-inertia grids and on the methods used to study and design them. Problems related to low inertia have been observed in North America, UK, and Australia, and will grow as we move towards 100% renewable generation. As the inertial energy stored in the grid diminishes, alternative means of energy storage, e.g., battery energy storage systems, are considered. This proposal aims to establish a research program on critical aspects of low-inertia grids wherein energy storage systems are used. The next 5-year cycle of my Discovery program will focus on (i) solutions for integration of energy storage in low-inertia systems and (ii) algorithms for modeling, simulation, analysis and design of low-inertia systems. Diminishing inertia causes difficulty in maintaining stability and preventing cascading failures. My research will create solutions for integration of battery energy storage systems, methods for their optimal placement, and operating schemes to achieve stability and reliability. These will be based on novel power-electronic converters and modern control techniques. To design and study low-inertia systems and to validate solutions, we rely on computer simulations. Existing simulators are ill-prepared for this aim. For example, transient stability simulators that are used for the study of large networks assume an essentially constant frequency, and electromagnetic transient simulators lack the computational efficiency needed to simulate large systems. A major thrust of my program is to create advanced computer simulation methods for the study of large, low-inertia systems with high accuracy and computational efficiency. My program will train 15 HQP, and will involve collaboration with industrial partners who will deploy our results in their products and services, thus disseminating its impact to the general public.