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The reactive power optimization (RPO) problem of power systems is a mixedinteger nonlinear programming problem, which can be computationally expensive. This paper applies the alternating direction method of multipliers (ADMM) to solve it. By duplicating discrete control variables with one copy allowed to vary continuously, the RPO model is formulated as a modified model in which the objective function and constraints have a separable structure with respect to the continuous and discrete variables, except for the coupling constraint. We then applied the ADMM to solve this model with the separable structure, and hence the original problem is converted into two optimization subproblems, which are nonlinear programming (NLP) and mixedinteger quadratic programming (MIQP) problems, respectively. To improve the convergence of the algorithm, we proposed an extended ADMM by adding the upper and lower limits on state variables into the MIQP subproblem based on the sensitivities obtained in the NLP subproblem. We also established a mechanism to filter out inactive inequality constraints in the MIQP subproblem to improve computational speed. Moreover, numerical results tested on IEEE test systems and a real 739bus system have shown the correctness of the proposed method and its adaptability for power systems with different sizes and configurations..
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http://iet.metastore.ingenta.com/content/journals/10.1049/ietgtd.2017.1257
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