  With dramatic breakthroughs in recent years, machine learning is showing
great potential to upgrade the toolbox for power system optimization.
Understanding the strength and limitation of machine learning approaches is
crucial to decide when and how to deploy them to boost the optimization
performance. This paper pays special attention to the coordination between
machine learning approaches and optimization models, and carefully evaluates
how such data-driven analysis may improve the rule-based optimization. The
typical references are selected and categorized into four groups: the boundary
parameter improvement, the optimization option selection, the surrogate model,
and the hybrid model. This taxonomy provides a novel perspective to elaborate
the latest research progress and development. We further compare the design
patterns of different categories, and discuss several key challenges and
opportunities as well. Deep integration between machine learning approaches and
optimization models is expected to become the most promising technical trend.
