Abstract:
The complexity of the power system has increased due to recent grid modernization and
active distribution systems. As a result, monitoring and controlling modern power systems have become
challenging. Dynamic security assessment (DSA) in power systems is a critical operational situational
awareness (OpSA) tool for the energy control center (ECC). State-of-the-art (SOTA) DSA has been based
on traditional state estimation utilizing the supervisory control and data acquisition (SCADA) / phasor
measurement units (PMU) and transmission network topology processing (TNTP) based on SCADA
monitoring of relay signals (TNTP-SMRS). Due to the slow data rates of SCADA, these applications cannot
efficiently support an online DSA tool. Furthermore, an inaccurate network model based on TNTP-SMRS
can lead to erroneous DSA. In this paper, a distributed dynamic security assessment (D-DSA) based on multilevel distributed linear state estimation (D-LSE) and efficient and reliable hierarchical transmission network
topology processing utilizing synchrophasor network (H-TNTP-PMU) has been proposed. The tool can be
used in real-time operation at the ECC of modern power systems. D-DSA architecture comprises three levels,
namely Level 1 - component level security assessment (substations and transmission lines), Level 2 - area
level security assessment, and Level 3 - network level security assessment. D-DSA concurrently evaluates
all available substations’ security in the substation security assessment (SSA) and all available transmission
lines’ security in the transmission line security assessment (TSA). Under the area security assessment (ASA),
all SSA and TSA in each area are separately integrated to assess the area SSI (ASI-SSI) and TSI (ASI-TSI).
Subsequently, each area’s area-level security index (ASI) is calculated by fusing ASI-SSI and ASI-TSI.
At the network level security assessment, network SSI (NSI-SSI) and TSI (NSI-TSI) are estimated by fusing
all ASI-SSIs and ASI-TSI, respectively. Network level security index (NSI) is estimated by fusing the NSISSI and NSI-TSI in network security assessment (NSA). Typical results of D-DSA are presented for two
test systems, the modified two-area four-machine power system model and the IEEE 68 bus power system
model. Results indicate that the proposed D-DSA can complete the assessment accurately at the PMU data
frame rate, enabling online security assessment regardless of the network size.
