Analysis of communication network challenges for synchrophasor-based wide-area applications

Abstract

Abstract-Wide-area synchrophasor applications inherently depend on the underlying IT and communications infrastructure supporting them. In particular, closed loop control systems for power grid oscillation damping is problematic, as it is a complex mixture of power grid monitoring, communication network properties and overall system stability issues. This article offers a holistic analysis of these fields, proposing a combined requirement on the full system: to keep system delays down to maintain stability. Simulation results to support the analysis findings, also showing how observability of power oscillations is important in combination with system delays related to feedback signals, and finally laying out experimentation plans to be performed in the lab on a complex power-grid model with real PMUs, communication network and controllers interacting with the SmarTS Lab real-time hardware-in-the-loop simulator platform.

Delay-Dependent Stability Control for Power System With Multiple Time-Delays

“…The linear differential algebraic equations (10) and (11) can be transformed into state space model in the following compact form: (12) where is the state variable vector, , is the input vector, and , is the time-varying delay, is the external disturbance input, . The system (12) represents a class of linear systems with multiple time-delays.…”

“…1) To evaluate delay margin, i.e., the allowable time-delay upper bound that guarantees the system to be stable when subjected to small disturbances [9], [10]; 2) To analyze the impact of time-delays on power system, and to find appropriate methods to eliminate their harmful effects [11], [12]; 3) To investigate controller design for power systems, considering the time-delay involved in remote signals from WAMS [13]- [15]. However, most of the above mentioned research focused on the stability analysis or controller design of power system with single delay, even if the wide-area signal is lost due to a communication failure [16].…”

A quantitative method to determine ICT delay requirements for wide-area power system damping controllers

“…The simulations again confirm the analysis carried out in the previous section, since signal 1 (δ 3 − δ 1 ) is the most effective remote signal. If the ETD of a wide-area signal increases, the phase margin of the controller will increase, allowing for more series compensation [15]. …”

A Quantitative Method to Determine ICT Delay Requirements for Wide-Area Power System Damping Controllers

“…The delay depends on the distance between remote measuring sites, the communication carrier, communication protocol and several other factors [13], [14]. Observe that the total delay in a control loop will not be constant due to the properties of packet switched networks [15].…”

“…For controllable devices such as SVCs and TCSCs, RI signals such as magnitudes or phase angle differences of key generator terminal voltages, or a combination of them (such as averaged bus angle differences), which are measured by PMUs, can have better observalility than LI signals [11], [16]. However, as ICT delay increases, the phase margin of the system decreases [15], and thus, this delay has a destabilizing effect which reduces the controllers' damping performance. If the ICT delay is beyond a certain threshold, the performance of the WAPOD controller reduces to a level which is lower than that of the controller using a LI signal.…”