Design For Reliability Of PLC Platform For MW Wind Turbine Generator System

At present, the disposable energy consumption of coal resources is in the proportionof over70%in our country, and the coal consumption is growing nearly200million tonsper year. Pollutant emissions continue to rise, thus causing the environmental pollutionproblem more and more serious. Wind power, as a kind of renewable energy with featuresof being safe, reliable and friendly to environment, must be the first choice of new energy.However, at present, China’s wind power industry, due to shortage of key technology ofPLC controller which having been highly dependent on imports, has been bothered withhigh cost of PLC controller. Therefore, PLC controller with independent intellectualproperty rights and high reliability, has a great meaning for realizing the localization rateof wind turbine, thus the quality of the the wind turbine will be improved, and the cost ofthe whole machine will be decreased.This paper is combined with some part of the R&D project “the localization ofPLC-based control system for MW class wind turbine”. In view of the PLC operating in aharsh environment and requiring high reliability, a dual-processor-based redundancyarchitecture for PLC is proposed. The co-processors of the main/standby modules transmitthe synchronization data, and realize the state synchronization of main/standby PLC.When the master PLC broke down, the redundancy PLC can take over the mastershipquickly, so as to realize non-stop working.Related theories of reliability were investigated, different redundant fault-tolerancemethods to improve the efficiency of PLC reliability were compared, and an applicableredundant fault-tolerance method were proposed. Based on the analysis of hardwarefunction diagnosis method and software function diagnosis method, the top-down methodfor spotting the fault of a failed module is proposed by detecting the heartbeat atdifferent layers. By using a combination of the improved heartbeat detection method andPUSH and PULL strategies, misjudgment rate in fault diagnosis can be reducedsubstantially. This is a good choice as high reliability and real time capability can beachieved simultaneously but avoiding too much communication.The data synchronization between the master/standby PLC is also designed andrealized in this paper. Based on detailed study of the traditional redundancy PLC datasynchronization method, a monitor-record type data synchronization method is proposed.In this method, the master PLC monitors the input data of I/O module through theco-processor. Once new data is to be read, the co-processor will record the new data immediately and combine with the status data of PLC, then transfer to hot standby PLC.Hot standby PLC implements the same control program as master PLC does, and the samestate of master PLC and standby PLC are achieved,as well with the synchronization.The monitor-record type data synchronization method does not involves too muchdata synchronization and does not take too much time of CPU. The synchronous data issmall for the recording type data synchronization method and it doesn’t occupy too muchCPU resources. When the master PLC fails, hot standby PLC takes over the mastershipautomatically, and thus a robust PLC is achieved with a higher reliability compared tosingle PLC.