This dissertation explores circuit, control, and optimization techniques for power electronics with the objective of enabling high performance electric networks for a variety of important applications. The motivation for this work is driven in part by societal-scale trends towards systems that are increasingly dominated by power electronics, including applications such as renewable energy integration, vehicle electrification, power management for mobile devices, and data center power delivery. A key approach demonstrated in this dissertation is the design of switching power converter circuits that naturally coordinate with larger networks in order to achieve system-level benefits, whether with respect to efficiency, power quality, or reliability. A central goal of this work is to have this coordination realized in a decentralized or autonomous fashion, such that scalability, modularity, and resiliency can be achieved inherently. In the first part of this dissertation, we explore techniques for improving the power quality of electric networks with high penetrations of switching power converters, in particular, techniques that can minimize aggregate power converter harmonics in an optimal sense while also eliminating the need for communication between distributed converters. In the second part of this dissertation, we explore methods for improving the reliability and fault tolerance of such networks, in particular, model- and estimation-based strategies that transform power converters into active probes that can detect, identify, and diagnose faults in real-time. Together, these contributions demonstrate how power electronics can be designed and collectively controlled and optimized to enable highly efficient, robust, and resilient electric networks.