Abstract
An effective and accurate power flow algorithm provides control references for active power dispatch and initial steady state operating points, used for stability analysis, short-circuit calculations, and electromagnetic transient simulations, which is not only a fundamental precondition to analyze the system operating conditions, but also the basis to improve the accuracy of power flow and DC voltage control of the multi-terminal voltage source converter-based high voltage direct current (VSC-HVDC). This paper proposes a nodal voltage-based universal steady-state power flow algorithm for the newly-developed bipolar multi-terminal VSC-HVDC (VSC-MTDC). Firstly, as the positive-pole and negative-pole DC network of the bipolar VSC-MTDC can be operated individually, a bipolar power flow alternating iterative method is proposed here to obtain the positive/negative-pole DC network power flow. Secondly, a series of nodal equivalent methods involving various control strategies are proposed for the universal power flow algorithm. Then the detailed calculation procedure and a general MATLAB(TM) program for the universal power flow algorithm is presented. A typical 4-terminal bipolar VSC-MTDC system was built in the PSCAD/EMTDC to verify the validity of the proposed algorithm, and the results are discussed here. Moreover, the calculation results of more complex bipolar VSC-MTDC systems under different operating conditions, employing the proposed universal power flow algorithm, are presented to illustrate its universality and efficiency.
Highlights
The advances in power electronic technology and the need for more flexible power transmission systems have led to the development of voltage source converter-based high voltage direct current (VSC-HVDC) transmission technology
Technology is that it can be extended to multi-terminal VSC-HVDC systems (VSC-MTDC) with radial, circular or meshed topology
This paper has proposed a nodal voltage-based universal steady-state power flow algorithm for the newly-developed bipolar VSC-MTDC system with different structures and topologies under various control strategies, which uses a bipolar power flow iterative method, and a series of nodal equivalent methods according to various control strategies
Summary
The advances in power electronic technology and the need for more flexible power transmission systems have led to the development of voltage source converter-based high voltage direct current (VSC-HVDC) transmission technology. It is a favorite solution for asynchronous grid interconnection, wind power integration, offshore platform power supply and urban power supply [1]. One obvious advantage of VSC-HVDC technology is that it can be extended to multi-terminal VSC-HVDC systems (VSC-MTDC) with radial, circular or meshed topology. It can facilitate the combination of decentralized generation units with large energy consumption centers. The merit of VSC-MTDC is driving real projects all over the world, such as the Tres Amigas Superstation project [2,3] and the Zhoushan 5-terminal MTDC project [4,5]
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