33 research outputs found
Undetectable GPS-Spoofing Attack on Time Series Phasor Measurement Unit Data
The Phasor Measurement Unit (PMU) is an important metering device for smart
grid. Like any other Intelligent Electronic Device (IED), PMUs are prone to
various types of cyberattacks. However, one form of attack is unique to the
PMU, the GPS-spoofing attack, where the time and /or the one second pulse (1
PPS) that enables time synchronization are modified and the measurements are
computed using the modified time reference. This article exploits the
vulnerability of PMUs in their GPS time synchronization signal. At first, the
paper proposes an undetectable gradual GPS-spoofing attack with small
incremental angle deviation over time. The angle deviation changes power flow
calculation through the branches of the grids, without alerting the System
Operator (SO) during off-peak hour. The attacker keeps instigating slow
incremental variation in power flow calculation caused by GPS-spoofing
relentlessly over a long period of time, with a goal of causing the power flow
calculation breach the MVA limit of the branch at peak-hour. The attack is
applied by solving a convex optimization criterion at regular time interval, so
that after a specific time period the attack vector incurs a significant change
in the angle measurements transmitted by the PMU. Secondly, while the attack
modifies the angle measurements with GPS-spoofing attack, it ensures the
undetectibility of phase angle variation by keeping the attack vector less than
attack detection threshold. The proposed attack model is tested with Weighted
Least Squared Error (WLSE), Kalman Filtering, and Hankel-matrix based
GPS-spoofing attack detection models. Finally, we have proposed a gradient of
low-rank approximation of Hankel-matrix based detection method to detect such
relentless small incremental GPS-spoofing attack
Estimating Relevant Portion of Stability Region using Lyapunov Approach and Sum of Squares
Traditional Lyapunov based transient stability assessment approaches focus on
identifying the stability region (SR) of the equilibrium point under study.
When trying to estimate this region using Lyapunov functions, the shape of the
final estimate is often limited by the degree of the function chosen, a
limitation that results in conservativeness in the estimate of the SR. More
conservative the estimate is in a particular region of state space, smaller is
the estimate of the critical clearing time for disturbances that drive the
system towards that region. In order to reduce this conservativeness, we
propose a methodology that uses the disturbance trajectory data to skew the
shape of the final Lyapunov based SR estimate. We exploit the advances made in
the theory of sum of squares decomposition to algorithmically estimate this
region. The effectiveness of this technique is demonstrated on a power systems
classical model.Comment: Under review as a conference paper at IEEE PESGM 201
Critical Clearing Time Sensitivity for Inequality Constrained Systems
From a stability perspective, a renewable generation (RG)-rich power system
is a constrained system. As the quasistability boundary of a constrained system
is structurally very different from that of an unconstrained system, finding
the sensitivity of critical clearing time (CCT) to change in system parameters
is very beneficial for a constrained power system, especially for
planning/revising constraints arising from system protection settings. In this
paper, we derive the first order sensitivity of a constrained power system
using trajectory sensitivities of fault-on and post-fault trajectories. The
results for the test system demonstrate the dependence between ability to meet
angle and frequency constraints, and change in power system parameters such as
operating conditions and inertia.Comment: To appear in IEEE PES General Meeting 201
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Application of Advanced Early Warning Systems with Adaptive Protection
This project developed and field-tested two methods of Adaptive Protection systems utilizing synchrophasor data. One method detects conditions of system stress that can lead to unintended relay operation, and initiates a supervisory signal to modify relay response in real time to avoid false trips. The second method detects the possibility of false trips of impedance relays as stable system swings “encroach” on the relays’ impedance zones, and produces an early warning so that relay engineers can re-evaluate relay settings. In addition, real-time synchrophasor data produced by this project was used to develop advanced visualization techniques for display of synchrophasor data to utility operators and engineers
Transient Stability Assessment of Cascade Tripping of Renewable Sources Using SOS
There has been significant increase in penetration of renewable generation
(RG) sources all over the world. Localized concentration of many such
generators could initiate a cascade tripping sequence that might threaten the
stability of the entire system. Understanding the impact of cascade tripping
process would help the system planner identify trip sequences that must be
blocked in order to increase stability. In this work, we attempt to understand
the consequences of cascade tripping mechanism through a Lyapunov approach. A
conservative definition for the stability region (SR) along with its estimation
for a given cascading sequence using sum of squares (SOS) programming is
proposed. Finally, a simple probabilistic definition of the SR is used to
visualize the risk of instability and understand the impact of blocking trip
sequences. A 3-machine system with significant RG penetration is used to
demonstrate the idea.Comment: To appear in PESGM 2018, Portland, OR, 201