Low frequency oscillations have been a significant threat to the secure and economic operation of large interconnected power systems. For example, the last decade severe oscillation events have occurred in the interconnected power grid of Continental Europe, with the most recent one on December 3rd 2017, during which the system was operating under low-loading conditions, and two consecutive generation disconnections excited a sustained 0.293Hz oscillation which lasted for more than 10 minutes. Typically, Power System Stabilizers (PSSs) at synchronous generators are used to suppress low frequency oscillations. PSSs use local feedback signals for control, and are usually designed and tuned based on offline simulations using system planning models for several assumed system operating conditions.
With increasing deployment of Phasor Measurement Units (PMUs) and availability of wide area measurements, wide area power oscillation damping (POD) controllers is an emerging technology to suppress low-frequency oscillations. Power electronics based devices such as HVDC and FACTS can be used as actuators for the POD to achieve fast control. In addition, an adaptive design of PODs is highly desirable to account for variations in operating conditions that become increasingly dramatic and frequent, due to the increasing integration of intermittent renewable resources and intense competition of electricity markets.
In addition to low-frequency oscillations, sub-synchronous oscillations can be another grid reliability threat. These sub-synchronous oscillations could be introduced by HVDC/FACTS devices due to either resonance between the device controller and the network, or due to control interactions among power electronic devices that operate electrically close to each other, especially in areas where the grid is relatively weak. A POD can be used as a mitigation measure for these sub-synchronous oscillations as well.
This project aims to design adaptive POD controllers via HVDC links and/or FACTS devices using a novel measurement-driven approach to mitigate low frequency inter-area oscillations and local sub synchronous oscillations. The measurement-driven approach is able to overcome the drawbacks of conventional design approaches and make the POD controller adaptive to varying operating conditions. The adaptive capability of the designed POD controller will be first validated in the GB power grid by simulations. Moreover, the POD controller will be implemented on a generic-purpose hardware platform coupled in a hardware-in-the-loop setup with the RTDS at the National HVDC centre. Realistic operating conditions will be emulated to evaluate the performance of the POD controllers, including random control signal impairments such as varying latencies, data package losses, and measurement noise.