Observer-Based Anomaly Detection of Synchronous Generators for Power Systems Monitoring

Abstract

This paper proposes a rigorous anomaly detection scheme, developed to spot power system operational changes which are inconsistent with the models used by operators. This novel technique relies on a state observer, with guaranteed estimation error convergence, suitable to be implemented in real time, and it has been developed to fully address this important issue in power systems. The proposed method is fitted to the highly nonlinear characteristics of the network, with the states of the nonlinear generator model being estimated by means of a linear time-varying estimation scheme. Given the reliance of the existing dynamic security assessment tools in industry on nominal power system models, the suggested methodology addresses cases when there is deviation from assumed system dynamics, enhancing operators' awareness of system operation. It is based on a decision scheme relying on analytical computation of thresholds, not involving empirical criteria which are likely to introduce inaccurate outcomes. Since falsealarms are guaranteed to be absent, the proposed technique turns out to be very useful for system monitoring and control. The effectiveness of the anomaly detection algorithm is shown through detailed realistic case studies in two power system models.

Time-domain Dynamic State Estimation for Unbalanced Three-phase Power Systems

“…The measurement model consists of two parts, viz. the voltage measurement equation (11) and the current measurement equation (13). The voltage measurement equation describes which of the bus voltages are being measured.…”

“…The current measurement equation may describe the measurements of bus currents and line currents (expressed through bus currents). The basis for the validity of the measurement models (11) and ( 13) is fast-sampled and time-synchronized sampled value measurements [7]. Phasor measurement units (PMUs) provide such measurements with a high signal-tonoise ratio (SNR) and typical sampling times between 0.15 and 0.2 [26].…”

“…This voltage measurement acts as a reference for the voltage estimates and constitutes the voltage measurement vector m v Î R 3 . From this, we can directly formulate a measurement equation (11).…”

“…Reference [10] presents a DSE based on an unknown input observer to estimate the dynamic states of reheater sections and storage systems. Another observer-based DSE approach can be found in the anomaly detection scheme from [11]. In [12], the unscented Kalman filter (UKF) is used to estimate the dynamic states of generators and power system stabilizers.…”

“…automated design of the estimator of(16) Input: model(10) with measurements(11) and(13) 1: Set up (14) and(15) 2: Calculate E and F from (19) and(20), respectively 3: Specify the eigenvalues of N 4: Calculate Z from (21) by pole placement techniques 5: Calculate N and L from (21) and (22), respectively 6: Return(NLFE) …”