In recent years, due to the increasing of distributed energy resources (DERs) in distribution system, power companies experience new challenges in grid operation, i. e. reverse power flow, protection coordination, volt/var coordination and so on. Conventional grid operation softwares are not designed for these operation scenarios. It is key for the next-generation tools to provide better situational awareness and effective way to manage the impacts of DERs on grid reliability. Conventional DER management systems are often developed in a vertically integrated way, that data communication structure, user interface and analytical functions are deeply coupled together. It typically requires significant efforts to add new functions or integrate with third-party tools. In this paper, an innovative internet of thing (IoT) data analytical framework is proposed featuring an open end-to-end architecture. The proposed data framework enables efficient monitoring, analyzing and coordinating of various distributed grid resources in real time. Its hierarchical layered design consists of edge computing layer, IoT data management layer, and modular application layer. A Proof of Concept PV management system is developed based on this proposed IoT framework for a commercial PV fleet owner. This online PV management system provides real-time monitoring of PV fleet across multiple sites. Different analytical functions are integrated onto this framework, e. g. performance analysis, PV power forecasting, etc.