IEC TS 63529 ED1

DC side harmonics & filtering in HVDC transmission systems

Scope

IEC TS 63529:2025, which is a Technical Specification, is intended to inform and guide the harmonic design of the DC side of HVDC projects. It considers all aspects of AC current and voltage occurring on the DC circuit and also the interaction with adjacent systems.
The switching action in HVDC converters results in a wide spectrum of harmonics. These range from the fundamental frequency to the radio frequency range. Traditionally the specification of DC side harmonic performance has been limited to the frequency range of interest for induced audible noise on nearby telephone systems. Often a limit of 50th harmonic has been applied, corresponding to 2 500 Hz or 3 000 Hz on 50 Hz and 60 Hz systems respectively. Occasionally the range has been extended to 5 000 Hz. This frequency range has corresponded to the spectrum of characteristic harmonic generation from thyristor line commutated converters (LCC).
The introduction of HVDC voltage sourced converters (VSC) has meant that although the magnitude of DC side harmonic generation from these converters is generally lower, the generated spectrum of interest extends to higher frequencies.
The scope of this document therefore covers the frequency range up to approximately 5 000 Hz. Higher frequencies are mentioned only when relevant. The scope excludes the much higher frequency ranges appropriate to PLC communication and the radio interference spectra.