The Research Of The New Electric Energy Meter System For Electric Locomotive

In this paper, a new design scheme of electric energy metering system for electric locomotive is put forward. By comparing with traditional electric energy metering equipments, this scheme has its unique advantages in some aspects. The kernel of this system is made of DSP and CPLD. This scheme has made full use of the DSP's digital operational ability, and raised the precision and real time performance of the system. On the other hand, CPLD centralize the digital hardware logic of the system, so that the structure of the system is simplified. As a part of CPLD logic, the keyboard logic is realized reliably and high efficiencyly by VerilogHDL hardware describe language and FSM.Then the electric energy metering is carried out by CS5460A, which is a ASIC on meter. By digital dignal processing, this chip can calculate and acquire the true RMS of the voltage and current,and the value of the active power which will not lose the harmonic energy. At last, after lots of calibrations and experiments, the electric energy metering precision is 0.1 class.Because of actual operation condition of electric locomotive, the important data is preserved in the NVRAM as some records, and when the locomotive comes back to the station, those records will be uploaded into the computer to form database files by wireless communication. For reliable communication, a channel model is founded and the reasons of communication error are discussed.At Last, a wireless communication protocol is given.It is proofed by experiments that the product which is made from the scheme can work very well , and can meet the demand of electric energy metering for electric locomotive.Finally, in order to get rid of the disadvantages of foreground/background system, another scheme is given. In this scheme, uC/OS-II—a real-time embedded operating system kernel—becomes the core, all the funcations of the electric energy metering system are partitioned into some tasks, every task is endowed a different priority, and a new especial task is set up to monitor other tasks to avoid errors in the system. If the scheme can be applied into the system, the stability and reliability will be enhanced remarkably.