To build a resilient and secure microgrid in the face of growing cyber-attacks and cyber-mistakes, we present a software-defined networking (SDN)-based communication network architecture for microgrid operations. We leverage the global visibility, direct networking controllability, and programmability offered by SDN to investigate multiple security applications, including self-healing communication network management, real-time and uncertainty-aware communication network verification, and specification-based intrusion detection. We also expand a novel cyber-physical testing and evaluation platform that combines a power distribution system simulator (for microgrid energy services) and an SDN emulator with a distributed control environment (for microgrid communications). Experimental results demonstrate that the SDN-based communication architecture and applications can significantly enhance the resilience and security of microgrid operations against the realization of various cyber threats.