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Bakhtvar, Mostafa
Preferred name
Bakhtvar, Mostafa
Official Name
Bakhtvar, Mostafa
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Now showing 1 - 3 of 3
- PublicationPower system planning for high renewables penetration: voltage stability and system frequency aspects(University College Dublin. School of Electrical and Electronic Engineering , 2016)
; The installed capacity and the grid access request for renewables is anticipated to continue rising in the EU and US in the coming years. The scarcity of reactive power and synchronous inertia are two inherent consequences of high penetration of renewables in the power system. This raises voltage security concerns, and may endanger rotor angle and frequency stability. In order to foresee these challenges, it is essential to carry out extensive planning and operation studies. Thus, new methodologies and innovative metrics are required to ensure secure and reliable operation of power systems.In this thesis, a multi-operating condition AC voltage stability constraint optimal power flow framework has been presented for transmission system planning. This framework captures multiple wind and demand operating conditions within an optimal power flow tool. The voltage stability constrained optimal power flow was applied to wind capacity allocation. It was shown that the capacity allocation pattern affects steady state voltage stability and the total allocated wind capacity. This indicates that a well-chosen allocation of wind capacity is not only in line with the trend of renewables integration in power systems but also enables limiting the occurrence probability of insecure operating points that may require costly remedies.A procedure for wind capacity allocation has been presented based on the finding on the effects of the pattern of wind capacity allocation on voltage stability. This benefits from the potential of an optimal wind capacity allocation for enhancing the voltage stability margin. Unit commitment was employed to take into account the reduction of the available reactive power sources at each operating condition for wind capacity allocation. By setting the wind capacity target and tracking the loadability margin, it was shown how the risk for a reduction in loadability margin may increase with allocation of wind generation. This procedure showed that specific locations in the system are favored for capacity allocation. It also identified weak areas in the network that experience a reduction in the loadability margin as a result of the allocation of the wind capacity. The methodology can help system operators prioritize network access and investment in the network to enhance the integration of renewables.Further, this thesis focused on the power system frequency aspect of renewables integration. Synchronous inertia acts as a means of immediate frequency support in power imbalances. Renewables often inject power into the network through power electronic converters. As such, synchronizing torque and synchronous inertia are not available in the power from renewables. Reduced levels of synchronizing torque raise concerns on rotor speed behavior under power imbalance events. The interaction of generators has been investigated by deriving the synchronizing torque coefficient matrix from the multi-machine Heffron-Philips model. It was shown that the reactive power output of the generators can be used to control the elements of the synchronizing torque coefficient matrix. It was identified that the varying levels of synchronizing torque affect the rate of change rotor speed of generators following a loss of generation event. Furthermore, the effect of rotor speed deviation due to synchronizing torque was presented from the system frequency perspective. This provides a foundation for system operators to establish strategies that benefit from the synchronizing torque coefficient matrix characteristics for controlling the frequency behavior.622 - PublicationAllocation of Wind Capacity Subject to Long Term Voltage Stability ConstraintsIncreasing wind capacity integration results in displacement of active power from conventional generators and a reduction in reactive power sources available. As such, voltage stability may become a concern in certain periods for power system operation particularly in weaker areas of the network. Thus, it is of importance to consider the AC constraints for optimal wind generation planning (long term) in order to decrease the possibility of a wind capacity allocation that requires costly remedies from the power system operation perspective (short term). In this work, a procedure is proposed for wind capacity allocation with the aim of benefiting from the potential of an optimal wind capacity allocation for enhancing the voltage stability margin. The procedure is based on a multi operating conditions voltage stability constrained optimal power flow. The wind capacity target is set and the loadability margin is tracked. The results will show the applicability of the proposed procedure and will emphasize the effects of the pattern of wind capacity allocation on the loadability margin. This will result in a wind capacity allocation that enhances the minimum loadability margin among the possible future operating conditions considered for planning. The procedure uses the Maximin concept for this purpose.
537Scopus© Citations 16 - PublicationOptimal Allocation of Wind Generation Subject to Voltage Stability ConstraintsIn power systems the occurrence probability of operating points close to network limits may be increased as a result of high wind penetration. Consequences of such scenarios include inefficient exploitation of both wind and economic resources. A well chosen allocation of wind capacity not only is in line with the trend of renewables integration in power systems but also allows for limiting the occurrence probability of unsafe operating points that may require costly remedies. In this work, a voltage stability constrained optimal power flow (VSC-OPF) framework is presented for transmission system planning and applied to wind capacity allocation. This framework captures multiple wind and demand scenarios within the OPF. The pattern of wind capacity allocation is studied in order to assess its impact on voltage stability and the total wind capacity allocation. The results emphasize the effect of the capacity allocation pattern on improvement of voltage stability.
335Scopus© Citations 1