Abstract
A DC power support strategy utilizes the flexibility of a High-voltage direct-current (HVDC) system in power modulation to optimize the operating point or compensate the power imbalance caused by a disturbance. The major impediment to the strategy is the difficulty in maintaining DC voltage values at converter stations during the process of DC power support. To overcome the difficulty, a coordinated DC power support strategy for multi-infeed HVDC systems is proposed in this paper. Synchronous condensers are employed to provide dynamic reactive power compensation in sustaining DC voltage values at converter stations. Models are built for the optimal leading phase operation and adjusting excitation voltage reference value of synchronous condensers. Multiple HVDC links are coordinated to participate by using the DC power support factor to rank and select the links. Optimal DC power support values of the participating HVDC links are obtained with a comprehensive stability margin index that accounts for transient stability of the sending-end systems and frequency security of the receiving-end systems. An optimal load shedding model is used to ensure the frequency security of receiving-end systems. Case study results of a provincial power system in China demonstrate the effectiveness and performance of the proposed DC power support strategy.
Highlights
High-voltage direct-current (HVDC) technologies have been extensively applied to long-distance large-scale power transfer worldwide [1]
A coordinated DC power support strategy for multi-infeed HVDC systems is proposed in this paper
The DC power of HVDC links can be effectively modulated to achieve the set values while ensuring the power system stability
Summary
High-voltage direct-current (HVDC) technologies have been extensively applied to long-distance large-scale power transfer worldwide [1]. A comprehensive stability margin index is defined and used to obtain the optimal DC power support values of the participating HVDC links, which accounts for transient stability of the sending-end systems and frequency security of the receiving-end systems. Multiple HVDC links are ranked and selected to participate in the DC power support strategy, for which the feasible range of DC power support values are guaranteed by properly adjusting excitation voltage reference values of SCs. A comprehensive stability index is proposed to quantify the impacts of the DC power support on the sending-end and receiving-end systems, which accounts simultaneously for the transient stability and frequency security issues.
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