Chapter 13 - Reactive Compensation and Harmonic Suppression of UHVDC Systems

Abstract

Currently, ordinary thyristor converter valves are used in UHVDC transmission systems. The thyristor is a low-frequency semiconductor device without self-turning-off capability and requires a large amount of reactive power in operation (around 30%–50% of the DC transmission power). This requires the installation of AC and DC filters on the AC and DC sides of converters, respectively, as the AC filter can supply the reactive power required for the converter while meeting filtering requirements. Apart from the use of AC filters to supply reactive power, this chapter considers when additional reactive power compensation equipment, such as electrostatic capacitors, condensers, or static VAR compensators, may be necessary. The composition and type of filters, along with principles for selection, development, and performance of filtering technologies are also discussed. The chapter also provides analysis of the source of harmonics that may occur on both the AC and DC sides during operation of converters, which results in distortion of voltage and current waveforms on both sides and how these can be suppressed.