Guide for Planning DC Links Terminating at AC Locations Having Low Short-Circuit Capacities
|Publication Date:||26 June 1997|
Part I of the guide discusses the effects of various aspects of the ac/dc interactions on the design and performance of dc schemes where the ac system appears as a high impedance at the ac/dc interface bus; i.e., low and very low short-circuit (short-circuit ratio [SCR]) conditions. AC systems having zero or inadequate mechanical rotational inertia, such as island schemes with no or with limited local generation, are also considered. Environmental, siting, and construction issues are not addressed. General issues, such as steadystate reactive compensation and ac and dc Þlter requirements, are not in the scope of this guide, but would be included in a complete study for a particular dc scheme design. In order to assist those not familiar with dc transmission and convertors, a brief description of basic rectiÞer and inverter operation is given in Annex A of Part I.
Part II of this guide, which is bound together with Part I, considers how the ac/dc interaction phenomena described in Part I should be taken into account in the planning and the preliminary design of ac/dc systems having low or very low SCR values.
The purpose of Part I of this guide is to address factors required to be considered in the design of dc transmission schemes in the context of system interactions resulting from dc links terminating at ac system locations having low short-circuit capacities relative to dc power infeed and for cases where the inertia of the ac system is too low for satisfactory operation. The following ac/dc interactions are considered: power, voltage, and frequency instabilities; harmonic resonance-related instabilities; subsynchronous torsional interactions; temporary overvoltages; and recoveries from ac and dc faults.