[Legacy Report] IEEE UP lecture on "Improved grid resiliency through interactive system control"

---

With growing complexity of power grid interconnections, power systems may become increasingly vulnerable to low frequency oscillations (especially inter-area oscillations) and dependent on stabilizing controls to provide adequate damping. Although local measurements have conventionally been utilized as a control input for stabilizing controls, the damping effect of local signal based controls is limited because local measurements have limited modal observability. In such situations, the use of wide-area signals in which the desired oscillation may be readily observable could be essential in damping inter-area oscillations of a large interconnected system. Incidentally, the ability and potential to use wide-area signals for control purposes has increased since a significant investment has been made in the U. S. in deploying synchrophasor measurement technology.
Fast and reliable communication systems are essential to enable the use of wide-area signals in controls. If wide-area signals find increased applicability in controls the security and reliability of power systems could be vulnerable to disruptions in communication systems. Even though numerous modern techniques have been developed to lower the probability of communication errors, communication networks cannot be designed to be always reliable.
Given this background the motivation of this work is to build resiliency in the power grid controls to respond to failures in the communication network when wide area control signals are used. In the proposed work, two approaches, 1) building resiliency in the physical system and 2) building resiliency in the cyber system are presented respectively to counteract communication failures. The approach to the solution in both methods is motivated by considering the use of a robustly designed supplementary damping control (SDC) framework associated with a static VAr compensator (SVC). When there is no communication failure, the designed controller guarantees enhanced improvement in damping performance. When the wide-area signal in use is lost due to a communication failure, however, the resilient control provides the required damping of the inter-area oscillations by either utilizing another wide-area measurement through a healthy communication route or by simply utilizing an appr
opriate
local control signal. With the proposed control included, the system is stabilized regardless of communication failures, and thus the reliability and sustainability of power systems is improved. The proposed approaches can be extended without loss of generality to the design of any resilient controller in power systems. In this work the approach is designed and demonstrated on a specific controller.
In addition to improving the control resiliency in response to communication failures, this work also presents the work of adding robustness to counteract the impact of uncertainties including variation of system operating conditions and transmission delays. Linear fractional transformation is utilized to model the uncertainties and a synthesis framework is proposed to design an optimal controller robust to the considered uncertainties.
Small signal stability analysis and nonlinear time domain simulations are employed to evaluate the proposed approaches. The results obtained have demonstrated that the designed controllers indeed improve system stability and wide-area grid resiliency in response to communication failures and delay uncertainty.

---

---

---

---