Optimisation of topology, rating, control and insulation coordination of a large series–parallel DC windfarm

Abstract

This study presents the design of a large DC series‐parallel windfarm that considers the key operational challenges in determining the optimal generator equipment rating and DC transmission voltage control. With this topology, offshore platform is not needed, but wind speed dispersion over windfarms and generator outage possibilities demand generator DC output voltages beyond their ratings. An optimization algorithm is developed along with a complete cost model, which includes operational and capital costs with all topology options, in order to inform design decisions. The results are evaluated on a 100‐generator, 25 × 4, 1 GW, 525 kV test wind farm and performance is verified using detailed PSCAD/EMTDC time‐domain simulation. The key finding is that a positive net present value (NPV) is achieved, avoiding power curtailment even under 3% generator outage, when an overvoltage coefficient of 1.145 pu is utilised on all wind generators, assuming use of a suitable DC transmission voltage control. Further, a wide‐ranging parameter sensitivity analysis is performed, and tower arrangement for insulation requirements is proposed.