With increasing distribution generation resources integrated

the power distribution network has become an active distribution network (ADN) with definite controllability and its optimal operation is essentially an optimal power flow (OPF) problem with various discrete controllable devices. However

owing to the nonconvexity and nonlinearity of the model

a highly efficient method of solving this kind of problem is the focus of this area. Since the on-load tap changer (OLTC) is an important controllable device in ADN

its strategy has a significant influence on power system operation

especially at the voltage level. Therefore

developing highly efficient methods to solve OPF problems in ADN with OLTC is exceedingly necessary. Based on the branch flow model

an OPF model with OLTC in ADN is developed. An exact linearization modeling method for OLTC using piecewise linear technique is proposed

and the applicability of a second-order cone relaxation method for solving the corresponding OPF problem is demonstrated. A case study based on the modified IEEE system shows the effectiveness of the proposed modeling method of OLTC and the high efficiency of the second-order cone relaxation method in solving the OPF problem in ADN with OLTC. This work is supported by National Natural Science Foundation of China (No. 51321005)

Special Grant Program of China Electric Power Research Institute (No. 5202011304HH)

and National Basic Research Program of China (973 Program) (No. 2013CB2282010).