Multi-body dynamic and finite element analysis based shape optimization of flexible connection structure of On-Load Tap Changer for minimizing transient stress using Adaptive Single-Objective method

On-Load Tap-Changer (OLTC) is the only core equipment in the ultra-high voltage (UHV) converter transformer that moves frequently, and flexible connection structure (FCS) is the moveable actuating part of the vacuum interrupter drive mechanism of OLTC. Minimizing the transient stress during the movement of FCS is essential for prolonging its fatigue life, thus is pursued by optimizing the shape of the flexible sheet in this paper. Peak transient stress of FCS is defined as the optimization objective, and eight geometrical parameters controlling the shape of flexible sheet are defined as the optimization variables. A progressive three-stage shape optimization strategy is proposed by combing four techniques: Multi-body Dynamic (MBD), Finite Element Analysis (FEA), Correlation Coefficient Analysis (CCA) and Adaptive Single-objective Optimization (ASO). MBD analysis of the vacuum interrupter drive mechanism and FEA of the FCS are utilized for calculating the transient stress distribution. Spearman CCA is performed to quantitively determine the correlation and sensitivity between the optimization variables and the optimization objective. Shape optimization of FCS using ASO is carried out, and results show that the stress concentration is basically eliminated and the peak transient stress decrease by 34.35% after shape optimization. Further analysis of the FCS with multi-layered flexible sheet is conducted, again demonstrating the effectiveness of the shape optimization on minimizing transient stress.