Online diagnosis and selective control method and device for leakage current unusual service conditions of heat exchanger

The invention discloses an online diagnosis and selective control method and device for leakage current unusual service conditions of a heat exchanger. The online diagnosis method for leakage current unusual service conditions of the heat exchanger comprises the following steps: establishing a dynamic mathematical model of the leakage current unusual service conditions of the heat exchanger; identifying the model gain of the dynamic mathematical model on line by adopting a least squares recursive algorithm; and performing online diagnosis on the leakage current unusual service conditions of the heat exchanger according to the symbol change of the model gain. The selective control method for leakage current unusual service conditions of the heat exchanger comprises the following steps: respectively establishing a normal controller which operates under normal service conditions of the heat exchanger and an abnormal controller which operates under leakage current unusual service conditions of the heat exchanger according to the dynamic mathematical model; setting a selector between the normal controller and the abnormal controller, wherein the selector is switched between the normal controller and the abnormal controller according to the diagnosis result of the online diagnosis method. The method is high in calculation real-time property, small in time delay, convenient to implement and low in total cost.