The University of ManchesterFaculty of Engineering and Physical SciencesPhD ThesisSupervisory Control Scheme for FACTS and HVDC Based Damping of Inter-Area Power Oscillations in Hybrid AC-DC Power SystemsMelios HadjikyprisJuly, 2015Modern interconnected power systems are becoming highly complex and sophisticated, while increasing energy penetrations through congested inter-tie lines causing the operating point approaching stability margins. This as a result, exposes the overall system to potential low frequency power oscillation phenomena following disturbances. This in turn can lead to cascading events and blackouts.Recent approaches to counteract this phenomenon are based on utilization of wide area monitoring systems (WAMS) and power electronics based devices, such as flexible AC transmission systems (FACTS) and HVDC links for advanced power oscillation damping provision. The rise of hybrid AC-DC power systems is therefore sought as a viable solution in overcoming this challenge and securing wide-area stability.If multiple FACTS devices and HVDC links are integrated in a scheme with no supervising control actions considered amongst them, the overall system response might not be optimal. Each device might attempt to individually damp power oscillations ignoring the control status of the rest. This introduces an increasing chance of destabilizing interactions taking place between them, leading to under-utilized performance, increased costs and system wide-area stability deterioration.This research investigates the development of a novel supervisory control scheme that optimally coordinates a parallel operation of multiple FACTS devices and an HVDC link distributed across a power system. The control system is based on Linear Quadratic Gaussian (LQG) modern optimal control theory. The proposed new control scheme provides coordinating control signals to WAMS based FACTS devices and HVDC link, to optimally and coherently counteract inter-area modes of low frequency power oscillations inherent in the system.The thesis makes a thorough review of the existing and well-established improved stability practises a power system benefits from through the implementation of a single FACTS device or HVDC link, and compares the case -and hence raises the issue-when all active components are integrated simultaneously and uncoordinatedly.System identification approaches are also in the core of this research, serving as means of reaching a linear state space model representative of the non-linear power system, which is a pre-requisite for LQG control design methodology.
|Date of Award||1 Aug 2016|
- The University of Manchester
|Supervisor||Vladimir Terzija (Supervisor) & Joseph Mutale (Supervisor)|
- Coordinated power oscillation damping control, Inter-area oscillations, Linear Quadratic Gaussian (LQG) control, Static Var Compensator (SVC), Thyristor Controlled Series Capacitor (TCSC), Voltage Source Converter (VSC)-High Voltage Direct Current (HVDC)