Resilient DC Voltage Control for Islanded Wind Farms Integration Using Cascaded Hybrid HVDC System

To integrate large-scale islanded onshore wind power with different sizes, this paper proposes an integration system based on the cascaded hybrid HVDC transmission system, which consists of LCC and several MMCs in series connection at the DC side of the rectifier. A large-scale wind farm is connected with one LCC and one MMC while several small-scale wind farms are connected with MMCs directly. Owing to the hierarchical integration arrangement, the operating flexibility can be improved with reduced capacity and the number of step-up interfacing transformers. A resilient DC voltage control is proposed for the integration system to adaptively redistribute power among the converters during wind power fluctuations. Firstly, the topology and operating characteristics of the wind power integration system are introduced. Then, a resilient DC voltage control is proposed to ensure stable operation during wind power curtailments. Finally, a simulation model of the hybrid cascaded HVDC transmission system is built in PSCAD/EMTDC to verify the effectiveness. The research results show that the system provides a new option for long-distance transmission of large-scale islanded wind power.

I. Introduction

To overcome the challenges of climate change and environmental degradation, integration of large-scale wind farms will still grow significantly, given that many countries launched renewable energy targets, such as the European Green Deal by European Commission [1] and 2050 carbon-neutral by the United Kingdom [2]. Wind power has become a mainstream source of clean, cost-competitive energy around the world in the last decades. In 2020, more than 93 GW of wind energy capacity had been installed globally, where 93.4% of capacity is onshore wind power [3]–[5].