•  
  •  
 

Keywords

on‑load tap changer；adjustment strategy；no‑load voltage；losses

Abstract

At present, in view of the stable operation of the VSC‑HVDC transmission system under grid voltage fluctuation, the on‑load tap‑changer(OLTP) is generally adjusted to ensure the constant no‑load voltage on the valve side of the transformer. But the method does not take full use of the OLTP, leading to a relatively higher converter loss during normal operation. In this paper, a novel OLTP regulation strategy to effectively reduce converter losses is proposed. Firstly, the principle of the proposed OLTP regulation strategy is analyzed based on the operation characteristics of the VSC‑HVDC system. The maximum modulation ratio limit and the maximum continuous operating voltage limit of transformer valve side are used to comprehensively determine the upper limit of no‑load transformer valve side voltage, and then the OLTP position is calculated according to the actual grid side voltage. Secondly, for a specific example, the reactive power requirements under different AC voltages are analyzed, and then the OLTP requirements under different working conditions are calculated according to the proposed strategy. The converter losses of the novel regulation strategy and the traditional strategy under various transmission powers are calculated and compared, and the losses data show that novel regulation strategy could effectively reduce converter losses. Finally, a PSCAD simulation model of a typical offshore wind power VSC‑HVDC transmission system is established, and the stability and effectiveness of the proposed novel OLTP regulation strategy are verified under two key conditions of AC voltage fluctuation and change in the number of operating transformers.

DOI

10.19781/j.issn.1673-9140.2023.04.004

First Page

35

Last Page

45

Download

Share

COinS