A parallel, fault-tolerant control and diagnostics system for nuclear power plants

A new integrated fault-tolerant control and diagnostics system was developed and applied to the feedwater flow regulation system of a pressurized water reactor (PWR). Control, signal and command validation, monitoring and diagnostic tasks were integrated into one large-scale system.; The control module of the Fault-Tolerant Control and Diagnostics System (FCDS) includes two nonlinear control algorithms, in addition to conventional controllers. A software-based parallelism was implemented in the design of the control module. The parallel control includes a model-based adaptive controller, two fuzzy logic controllers, and proportional-integral (PI) controller. Each algorithm was designed to handle the same control task using different strategies and different sets of plant measurements.; Using family of control solutions requires a systematic approach to select the most suitable control action for the present demand. A new concept, called Command Validation, was developed as part of the Fault-Tolerant Control and Diagnostics System. Command validation is a prediction scheme in which the objective is to provide an estimate of the expected control action using relevant plant variables. The prediction is then used to cross-examine the output of the control algorithm before the final decision is made by the Decision-Making module. This approach enables the control system to detect anomalies in the sensors, actuators and in the control actions.; A Signal Validation module was also developed for validating the plant measurements before they were utilized by the control algorithms. A software-based parallelism was also included in the signal validation and command validation modules by incorporating two different modeling techniques: process empirical models and artificial neural network models.; The FCDS was tested using an application to the feedwater flow regulation system of a typical four-loop Westinghouse type PWR. In order to test the system, a nonlinear feedwater flow system was modeled with 96 state equations. The model includes four steam generators, two main feed pumps, piping and their control systems. There are two control systems in the feedwater flow regulation of a PWR: the steam generator water level controller and the main feed pump speed controller. Both of these controllers were included in the model.