A Hybrid Cable Connection Structure for Wind Farms With Reliability Consideration

The collector system in wind farm has a large number of cables. When one of the cable fails, the power generated by the wind turbine (WT) cannot be collected into the substation through the faulty cable. That would make the profits for the wind farm reduced. Therefore, it is necessary to find a more reliable cable structure, which can transfer power as much as possible even if the cable failure occurs. In this paper, a new cable connection method is proposed in two main steps to improve both the reliability of the cable connection and the economic. Two different wind farms with the same climatological information and high voltage substation location are investigated and compared in the case study. In the first step, the minimum spanning tree (MST) algorithm is adopted to connect all wind turbines (WTs) to the substation. The cables used in collector system are the 33-kV middle voltage alternating current (MVAC) cables. Then the power production generated by WTs is transmitted from substation to the high voltage substation via a 132-kV transmission cable. The initial cable connection layout is obtained in the first step and the total trenching length is optimized to be minimum. In addition, cable selection in each branch can be determined based on the cable current carrying capacity. In the second step, reliability assessment is implemented by analyzing the expected energy not supplied (EENS). Based on EENS, the evaluation index <inline-formula> <tex-math notation="LaTeX">${LPC}_{rel}$ </tex-math></inline-formula> is obtained. This index takes both reliability and economy into account. Additional cables found by particle swarm optimization (PSO) algorithm are added to the initial cable connection layout. Finally, a cable layout called hybrid structure is formed. What is more, by adding additional cables, the <inline-formula> <tex-math notation="LaTeX">${LPC}_{rel}$ </tex-math></inline-formula> is reduced by 1.5&#x0025;. The simulation results clearly indicate that the proposed method is better when the cable failure is considered.