Universal Power Flow Algorithm for Bipolar Multi-Terminal VSC-HVDC

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.

Combined Operation Analysis of a Saturated Iron-Core Superconducting Fault Current Limiter and Circuit Breaker for an HVDC System Protection

“…In order to perform the experiment of a DCCB combined with a SI-SFCL, a four-terminal MTDC topology suitable for the application of the corresponding protection facility was selected. The four-terminal MTDC is a representative HVDC network configuration and has practical installation cases such as the Zhangbei dc grid project in China [40]. In the lab-scale experiment, since all four terminals could not be implemented, one terminal was mainly expressed, but a lead-acid battery was used to realize a larger amount of energy.…”

Optimal sparse control of interval networks: Voltage source converter based DC grid study

“…© 2021 The Authors. IET Generation, Transmission & Distribution published by John Wiley & Sons Ltd on behalf of The Institution of Engineering and Technology and multi-point voltage controls are developed to administer the challenges [2].…”

“…However, as the network topology becomes too complex, more effective strategies are required. The master-slave, DC voltage droop, amplitude-phase, and multi-point voltage controls are developed to administer the challenges [2].…”

“…One of the significant advantages of Voltage Source Converter for High Voltage Direct Current (VSC‐HVDC) networks is the potential in implementing radial, circular, or meshed topology [1]. Besides, it facilitates the combination of distributed generation units (DG's) with large energy consumption centres [2]. It can also provide several ancillary services to the AC grids owing to its rapid and flexible power control [3].…”

“…It can also provide several ancillary services to the AC grids owing to its rapid and flexible power control [3]. Inversely, such interconnections among tightly controlled active devices (VSCs) will give rise to harmful interactions and possible instability [2]. Another prime topic in this respect is uncertainty that has to be effectively addressed; otherwise, secure operation of the network may be lost.…”