Novel series-isolated-parallel wind farm DC collection system with new control strategies

Offshore wind farm (WF) DC collection systems offer significant reductions in weight and size compared to conventional AC systems. Among DC architectures, the series-parallel wind farm (SP-WF) configuration achieves higher efficiency by reducing the number of power conversion stages. However, because SP-WF places the DC-DC converter upstream of the series connection of wind turbines (WTs), it suffers from reduced reliability due to its vulnerability to DC short-circuit faults within the series string. This paper proposes a novel series-isolated-parallel wind farm (SIP-WF) architecture that enhances reliability by integrating a DC-DC converter to isolate each group of series-connected WTs. This isolation provides intrinsic DC fault blocking capability without the need for external DC circuit breakers. Furthermore, as only passive rectifiers are used at each individual WT, the proposed SIP-WF architecture maintains high efficiency. To manage maximum power point tracking (MPPT) across turbines experiencing different wind conditions, two new centralized control strategies are proposed to coordinate multiple WTs using a single DC-DC converter per group. The proposed SIP-WF architecture and control strategies are validated through simulations in MATLAB/Simulink. A comprehensive performance comparison is conducted against existing DC collection topologies. The results demonstrate that SIP-WF achieves a higher net energy yield while reducing cost, system weight, and volume, and offering superior fault tolerance compared to conventional architectures.