Resilient and Sustainable Tie-Line Bias Control for a Power System in Uncertain Environments

Interconnected power systems with large-scale penetration of photovoltaic (PV) power introduce frequency and tie-line power flow fluctuations. This is due to the variability and uncertainty characteristics of PV power. This makes automatic generation control (AGC) to be more challenging. In other words, maintaining system frequencies and tie-line power flows at the desired values, also known as “tie-line bias control” is difficult. In this paper, an enhanced tie-line bias control method is proposed by predicting PV power generation and bus frequencies. A cyber-physical two-area power system with a large PV plant consisting of phasor measurement units (PMUs) is studied. The use of synchrophasor networks consisting of PMUs can enable smooth power system operations overcoming the challenges of PV power variability and uncertainty. However, the use of PMUs in power system control creates vulnerabilities for cyber-attacks that could jeopardize the power system operations. It is shown that the frequency prediction using a virtual synchrophasor network (VSN) can mitigate the impact(s) of denial of service (DoS) attacks on physical PMUs. Enhanced AGC performance is investigated under different weather and load conditions including a weather profile during the “Great American Eclipse” of August $21^{st}, 2017$. Typical results indicate that the enhanced AGC structure provides a resilient and sustainable tie-line bias control in uncertain environments.