Optimal PMU Placement and Signal Selection for Monitoring Critical Power System Oscillations

In this thesis, a strategy for phasor measurement unit (PMU) optimal placement and signal selection is proposed for monitoring critical oscillations in electric power systems. A robust indicator, mode in output proportion factor (MOPF), is introduced for identify critical PMU locations and signal channels, in order to better monitor power system oscillations with specific oscillation modes. Based on the proposed MOPF, a two-layer algorithm is presented. This algorithm could benefit system operators and planners in the following two ways: 1) it identifies existing PMU devices and signal channels, which provides the best observability for critical oscillation modes; 2) it suggests optimal locations for further PMU deployments, in order to enhance the observability for critical oscillation modes. The performance of proposed algorithm is illustrated via a modified 16-machine-68-bus system and NPCC-140-bus system. Based on the proposed algorithm, all modes of interest can be observed sufficiently under various disturbances. Therefore, the proposed algorithm can be applied to prioritize or deploy PMUs to observe critical oscillation modes in power systems

A magnetically driven origin for the low luminosity GRB 170817A associated with GW170817

The gamma-ray burst GRB 170817A associated with GW170817 is subluminous and subenergetic compared with other typical short GRBs. It may be due to a relativistic jet viewed off-axis, or a structured jet, or cocoon emission. Giant flares from magnetars may possibly be ruled out. However, the luminosity and energetics of GRB 170817A is coincident with that of magnetar giant flares. After the coalescence of the binary neutron star, a hypermassive neutron star may be formed. The hypermassive neutron star may have magnetar-strength magnetic field. During the collapse of the hypermassive neutron star, the magnetic field energy will also be released. This giant-flare-like event may explain the the luminosity and energetics of GRB 170817A. Bursts with similar luminosity and energetics are expected in future neutron star-neutron star or neutron star-black hole mergers.Comment: 6 pages, 1 figure, accepted in Research in Astronomy and Astrophysic

Non-intrusive Enforcement of Decentralized Stability Protocol for IBRs in AC Microgrids

This paper presents decentralized, passivity-based stability protocol for inverter-based resources (IBRs) in AC microgrids and a non-intrusive approach that enforces the protocol. By "non-intrusive" we mean that the approach does not require reprogramming IBRs' controllers to enforce the stability protocol. Implementing the approach only requires very minimal information of IBR dynamics, and sharing such information with the non-IBR-manufacturer parties does not cause any concerns on intellectual property privacy. Enforcing the protocol allows for plug-and-play operation of IBRs, while maintaining microgrid stability. The proposed method is tested by simulating two networked microgrids with tie lines and two IBRs modeled in the electromagnetic transient (EMT) time scale. Simulations show that oscillations with increasing amplitudes can occur, when two stable AC microgrids are networked. Simulations also suggest that the proposed approach can mitigate such a system-level symptom by changing less than 2 percent of energy produced by IBRs.Comment: This manuscript has been submitted to IEEE Transactions on Smart Gri