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Title: Novel controller designs for VSC-HVDC networks
Author: Zhu, Jiebei
Awarding Body: University of Strathclyde
Current Institution: University of Strathclyde
Date of Award: 2013
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Future power system will incorporate much higher penetrations of renewable energy than is presently the case. In particular, large offshore wind energy resources, connected to AC power systems via HVDC and VSC converters, are expected to proliferate. This thesis introduces research in the area of control of multi-terminal HVDC systems, presenting a review of the state of the art and challenges associated with respect to VSC control solutions for HVDC transmission systems. To address one of the identified challenges (effective control of a multi-terminal HVDC system), a direct current matching control strategy is developed and demonstrated. This uses telecommunications to match the input and output powers of the various VSCs. The operation of the scheme is demonstrated through several case studies, and the advantages of the strategy compared to more traditional and other proposed schemes are presented. Another major challenge associated with future power systems is a reduction in s ystem inertia, due to increased levels of energy being provided from renewable sources, which typically provide little or no inertia to the system. Voltage source converters (VSC), used in high voltage direct current (HVDC) transmission applications, are often deliberately controlled in order to de-couple the interconnected systems to prevent propagation of transients and potential for instability between the systems on either side of the VSC interface. However, this can inhibit the provision of much needed support during transients that would otherwise be available from system inertia provided by rotating plant connected to an interconnected system. Accordingly, a novel VSC-HVDC control system, termed "INEC" (INertia Emulation Control) is proposed, which enables a VSC-HVDC system to provide support that emulates the inertia of synchronous generators (SG). The energy to provide the inertial response is sourced from the capacitance of the HVDC connection, which may be augmented by the installation of additional capacitance. The proposed INEC system allows a VSC-HVDC system with a fixed capacitance to emulate a wide range of inertia constants (H) by specifying the amount of permissible DC voltage variation. The scheme is demonstrated through simulations, and its performance is evaluated for transients that include faults and also changes in load.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available