# Design and Application of a Distribution Network Phasor Data Concentrator
## 6 Conclusions  
With the distributed energy, flexible load and electric vehicle charging station (pile) connected to the distribution network on a large scale, the monitoring and control methods of the traditional distribution network have difficulty coping with the new problems faced by the distribution network. Therefore, the synchronous phasor measurement technology in the transmission network WAMS is introduced into the distribution network, and the uMPMUs with the power distribution terminal functions are gradually deployed to each key node in the distribution network. The DPDC for the distribution network communication environment has become more important as a connection node between the uMPMUs and the main station. In view of the current lack of discussion on the design and application of the DPDC, this paper analyzes and compares the DPDC and the traditional PDC in terms of functions, communication methods, and application requirements. The key indicators for evaluating the performance of DPDC are proposed, and a DPDC is designed. The test environment is further designed to perform various evaluations on the DPDC, and the evaluation results are analyzed. The contribution of this paper is summarized below:  
* This paper introduces three basic networking structures of uMPMU-DPDC and illustrates the various communication methods that may exist in the networking. Then, by comparing the PMU and uMPMU, PDC and DPDC from the installation location and main functions, the application requirements of DPDC are obtained. Further to judge the basic performance of DPDC, the key performance indicators of DPDC are provided, namely, the access capability is no less than 20 uMPMU, the time difference tolerance is no less than 150 ms and the data delay is within 3 ms;
* A design method of hardware DPDC is proposed, which uses event-driven mechanism and structured program design, uses libuv to establish TCP connection, and completes the asynchronous non-blocking operation for multi-task through the multi-thread and callback mechanisms. The functions of each software module inside DPDC are introduced, and the data buffer structure and data aggregation mechanism are described in detail. The data aggregation mechanism and data structure ensure the efficiency of data processing and reduce the demand for hardware resources. The hardware configuration and selection of the DPDC are also described;
* The test methods for key performance indicators of DPDC are proposed. Firstly, the development of the test environment and the test software are described. Then test method for key performance indicators and conduct various tests on the DPDC was designed. The test results show that the designed DPDC access capability can reach 20 uMPMUs, the time difference tolerance is not less than 200 ms, and the data delay is less than 1 ms, which meets the requirements of all key performance indicators. Proven that the performance of the designed DPDC meets its application in the distribution network. Further analysis of the test results shows that the main impact on the performance of DPDC is the program mechanism and hardware performance. The designed DPDC uses a multi-threaded and event-driven mechanism. DPDC will call the corresponding callback function for processing when it receives the data. When the data aggregation is completed, it will be sent to the master station immediately to achieve a small delay and the CPU utilization rate is not high. If the time-driven mechanism is used to periodically query the status of each socket in the receiving thread, the DPDC data delay and CPU utilization rate will increase accordingly. The field application of the designed DPDC works well. The further work of the author's team is to expand more distribution sub-station functions and islanded control functions on the DPDC, enabling the DPDC to act as a distributed control sub-station for distribution automation and DER grid-connected control tasks. Conceptualization, W.T. and M.M. ; methodology, W.T. and M.M. ; software, validation, M.M., D.X. and Y.S.