## 5 Experimental Verification
### Experimental Environment  
The experimental environment consists of the PMU Emulator, the distribution network PDC, and the Main station Emulator. The above software and hardware have been developed by the authors of this paper. This type of PDC has been piloted and operated in 220 KV and 35 KV substations in Pudong New Area, Shanghai, China. * PMU Emulator: PMU Emulator is developed on Visual C++ and supports the standard GB/T 26865.2-2011 protocol and the extension method, using Socket multi-channel and multi-thread programming. The software is based on the dialog framework, which can simulate PMUs within 30 units at the same time, and the number of phasors, the number of analog quantities, and the number of digital quantities of each PMU can be modified by the initial configuration file. It can support multiple communication rates, such as 200, 100, 50, 25, 10, 5, and 1 frames/s. Data transmission is based on multimedia timer scheduling, improving uniformity between data frames. Real-time data can vary according to time, or it may change randomly, and can also use dynamic data files from DlgSILENT simulation software output or on-the-spot. The data time of each PMU starts to be generated from the computer time, and the time stamps can be the same, or the time difference between them can be fixed (10-500 ms), to simulate the time difference between different PMU data passing through different channels to PDC. This is run on PC1 in Figure 9. PC1 configuration: Intel (R) Core (TM) i5-3230M processor, 2.6 GHz, 8 G memory. * Distribution network PDC: PDC device hardware adopts platform hardware architecture design, a dual-core dual-thread CPU, Intel (R) Celeron (R) 2980 U, 2 M cache, clocked at 1.60 GHz; the hard disk adopts a Solid State Disk, with a capacity of 480 GB; the memory type is DDR3L, with a memory size of 4 GB; the time interface is RS-485, using IRIG-B timing; and it supports a dual power supply, which can be remotely logged in to through the network port or directly connected to the monitor. The system uses a Linux real-time multitasking operating system that is autonomously tailored. Software support standard GB/T 26865.2-2011 protocol and the extension method, using Socket multi-channel and multi-thread programming, through the select procedure, are employed to complete non-blocking mode communication. The data transfer rate is adjustable and the file is cyclically stored. It can connect no less than 20 \(\upmu\)MPMUs, and is able to communicate with multiple primary stations, supporting high-latency PMU data aggregation and forwarding; that is, stable communication functions in a hybrid networking environment. The PC2 in Figure 9 is used to remotely log in to the PDC. Figure 8: Data priority processing. * Main station Emulator: Main station Emulator is also based on Visual C++ development, based on a single document view structure. It is multi-threaded and can be connected to multiple PMUs or PDCs. Each connection to a PMU or PDC will create a command pipeline, data pipeline, and file pipeline, occupying three sockets. If each socket creates a thread, three threads are created for each sub-station. At the same time, since the data channel transmission rate can reach more than 100 frames/s, for the PC, it is easy to have problems such as insufficient system memory resources. For this reason, a network communication non-blocking mechanism is adopted, and each PMU command, data, and file pipeline shares one thread. The CASyncSocket class is used to determine which ports receive the data and then process them accordingly. The Main station Emulator uses tables to display received PDC messages, time, transmission rate, configuration information, binary values of data, the voltage and current values after the coefficient conversion, and so on. When testing PDC data aggregation and forwarding, the Main station Emulator can parse and display the PDC configuration information and the processed synchronized phasor data, which is helpful for analyzing the PDC function and performance test results.