Research On Design Method Of Wind Turbine Safety System Based On Functional Safety

The doubly-fed wind turbine(the following abbreviations wind turbines)often run by control systems,to ensure the safe and effective operation of wind turbines under the specified conditions.When control systems fail to maintain the operation of the wind turbine in a safe range,or operating parameters are out of relative safety limits,the safety system executes safety strategy to fulfill the function of safety protection(the following abbreviations safety function)during the operation.The safety system and control system of wind turbines are independent of each other.When the control system and the security system are in conflict,the control system is subject to the requirements of the safety system.The safety system of wind turbines is carried out by pneumatic,mechanical,electrical and hydraulic systems.These systems are used to reduce the probability of occurrence of hazardous events or mitigate the consequences of hazardous events to achieve the required safety performance.However,affected by their own system structure and hardware reliability,these secure related systems are possible not to execute the security function accurately,which could lead to accident.In this paper,a design method of wind turbines safety system based on functional safety is proposed,which can effectively ensure the safe operation of the security system in the event of danger and reduce the risk of safety accident.The functional safety works depend on the correct exercise of safety related control systems、other safety related systems and external risk reduction design function.This paper also introduces the concept of functional safety to the design method of safety system for evaluating the quantitative performance index of wind turbine safety system.Reducing the safety accident risk could enhance the security of wind turbine performance,unit operation safety,property safety and personal security.(1)By analyzing the failure characteristics of the safety system in the typical safety accidents of wind turbines,this paper presents the research direction、encounters the method and the value of the research.(2)From three aspects,which are evaluation standards,functional safety certification,and safety products,analyzing the present situation of functional safety.Combined with the technical characteristics and development trend of the existing design scheme of the wind turbine safety system,this paper selects the appropriate functional safety standards as the theoretical basis for the wind turbine safety system design methods.(3)Based on functional safety standards,the realization process of wind turbine safety system design is described and the design method is proposed.The design method has clear up that the safety system design iterative process,safety function,general characteristics of risk assessment in determining the system safety performance level in the process of application,and focus on the implementation of the performance level requirement of design method of safety system.This method realizes the safety performance level through some design elements such as the component reliability,system structure constraints and fault diagnosis.By this method,we can effectively avoid or reduce the probability of single fault,common cause failure,random hardware failure and system failure.(4)Selecting the typical fault of wind turbine as an example,using the design method proposed to evaluate the performance of the existing security system design scheme,and analyzing the shortage of the existing design.In the end,a design optimization scheme is proposed,and the safety performance of the wind turbine safety system optimization scheme is quantified and evaluated by software calculation.Through the study on the failure characteristics of safety system for wind turbines,a design method of safety system is proposed based on functional safety.This method could reduce the risk of accidents within the acceptable range by safety performance quantitative evaluation,also improve the safety performance of wind turbines;and provide a practical and scientific method for balancing the relationship among the availability,cost and safety of systems in the design process.