  We propose a planning method for offshore wind farm electrical collector
system (OWF-ECS) with double-sided ring topology meeting the "N-1" criterion on
cable faults, in which the submarine cables layout of OWF is optimized
considering cable length and power losses. The proposed mixed-integer quadratic
programming (MIQP) model is based on the Capacitated Vehicle Routing Problem
(CVRP) formulation and power network expansion planning, which could
approximate the power losses in OWF-ECS. In addition, cross-avoidance
constraints are proposed to avoid crossing cables, and the minimum k-degree
center tree model is included to improve the convergence. Case studies on OWFs
with 30 and 62 WTs demonstrate the effectiveness of the proposed method.
Considering the potential outage cost in the radial topology, the total cost of
the planning result is reduced by up to 25.9% with reliability improvement. The
cable investment is reduced by 4%~8% with the proposed method compared with
conventional heuristic methods and Google OR-tools. The proposed method/model
can also achieve acceptable computation efficiency and OWF-ECS planning results
with good optimality. Moreover, it could be solved by modern commercial
solvers/optimization software, thus it's easy to use even for large-scale OWF.
