Interconnecting offshore wind farms using multiterminal VSC-based HVDC

This paper presents a large off shore wind farm interconnected to the grid using a multiterminal HVDC link. The 200W wind farm consists of 100 individual 2MW turbines connected using 25 VSC (Voltage Source Converter) converters to a common DC bus. The transmission system converters enable variable speed operation and therefore additional converters are not needed with individual generators, implying savings in converter costs. The paper presents PSCAD simulation of the proposed concept for various changes in wind speeds. The results confirm the ability to operate at optimum coefficient of performance and no synchronization problems occur even for severe wind speed changes. Further tests with faults on AC grid demonstrate satisfactory recoveries. The proposed concept may enable integration of large offshore wind farms at considerable distances, and using optimal number of converters.