Enhanced Power System Stability using Fast, Distributed Power Electronics Control

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The increasing penetration of inverter-coupled renewable generation is rapidly changing the dynamics of large-scale power systems. As inverter-connected generation displaces synchronous machines, electric grids lose inertia, voltage support, and oscillation damping. These potential adverse impacts on system stability have received significant attention from system operators, regulators and the research community. System stability often limits power transfer between areas of cheap resources and high load areas. For example, California imports about 25% of its electrical energy from other states, of which significant amount comes from the state of Washington through direct current (DC) interties. In 2017, the average wholesale day-ahead price in Washington State was about 40% lower than the prices in California. The reason for these price differences is mainly due to the stability concerns that limit the amount of power transferred between the two areas. This project proposes new approach that would have substantial economic and environmental benefits by improving stability of systems through more careful control of power electronics. The resulting monetary savings could amount to hundreds of millions for allowing more unconstrained power flow between different regions and higher utilization of of renewable resources. The project will engage undergraduate and graduate students in the proposed research activities and develop new courses integrating control methods in power electronics. This project will develop novel control algorithms and hardware architectures for inverters so they can be deployed in a "plug-and-play" manner and improve the stability of a grid with both power electronic interfaced and synchronous generation. We will accomplish this goal by ensuring that the algorithms and the hardware are robust, completely decentralized and complement the dynamics of the synchronous machines. We study both voltage and frequency controls for a system. In voltage control, we diagnose the shortcomings of existing inverter control methods on the grid today, and engineer novel controllers that preserve stability, avoid adverse interactions, and leverage the algorithmic flexibility of digitally controlled inverters. In frequency control, we adopt a robust control approach to design the time domain response of inverters to explicitly optimize the frequency response and enforce power and energy constraints coming from the resources connected to the inverters. We will construct a testbed for validation and experimentation.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.