An Interactionless Duo Control Strategy for Bipolar Voltage-Source Converter in Renewables Integrated Multiterminal HVdc Grids

Abstract

The dc voltage and frequency <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$ (PVF)$</tex-math></inline-formula> or modified dc voltage and frequency <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$ (PV^{2}F)$</tex-math></inline-formula> double droop control is commended for its ability to regulate both the dc voltage and the frequency in a decentralized approach. However, a convincing response is not achieved due to an interaction between the droop characteristics of dc voltage and frequency. This interaction affects the dc voltage and frequency support of the ac-system-surrounded multiterminal HVdc (AC-MTdc) grid. To overcome this effect, a Duo control strategy is proposed in this article, which takes advantage of a bipolar voltage-source converter topology in the MTdc grid. The virtue of the proposed control technique is emphasized by comparing it with the existing <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$ PV^{2}F$</tex-math></inline-formula> double droop control along with three case studies and two test systems. The validation of the interactionless Duo control strategy is carried out on a five-terminal CIGRE dc grid benchmark model integrated into a two-area power system (AC-MTdc grid-1) and a New England IEEE 39-bus system (AC-MTdc grid-2). These test systems are simulated in PSCAD/EMTdc software.