Abstract
This paper presents a water-level control system in a drum boiler. The system was equipped with a fault tolerant control–type diagnostic system. The paper presents the results of tests conducted on the fault tolerant control system implemented in the water-level control system in a boiler drum. The diagnostics of the measurement circuits was carried out online. To that end, the appropriate partial models were developed and tested. This allowed for the application of analytical redundancy for the measurement circuits. The paper also identifies the influence of diagnostics and fault tolerance on the values of reliability indices and operating safety of a power unit. Fault tolerant control systems increase the safety of a power unit operation, and the studies described in the paper directly contribute to them. These kinds of systems have not been used so far in power unit automation. Site tests confirmed the validity of the acquired concept for the diagnostic system. Fault tolerant control systems have not been commonly applied in power engineering yet. Studies of the water-level control system in a steam drum using the fault tolerant control system for the measurement circuits as presented in the paper are original ideas, providing a new solution. All control systems made for the study fulfil their role in a satisfactory way, which results in a minor deviation in the water-level adjustment in the boiler drum. The tests confirmed the efficiency of the fault detection algorithm. The created models of the water level and flows proved to be successful. Under a no-fault condition of the facility, there were no errors in the diagnoses and the values of all residua were below the detection thresholds. This was achieved despite a high value of measurement noises. The residua helped detect minor faults.
Highlights
From the point of view of automation, power boilers are very complex control systems
The feed water control system is intended to maintain balance between the stream of water getting to the boiler and the stream of steam taken by the turbine
Under abrupt changes in the volume of water flowing to the boiler, a significant delay caused by insufficient heating of the feed water can be observed
Summary
From the point of view of automation, power boilers are very complex control systems. Its characteristic feature is that it uses both equipment redundancy (if available) and analytical redundancy.9 It helps such systems tolerate the types of faults not predicted at the system design stage. An example of such a fault is presented in Blesa et al.5 This type of control systems is characterized by applying analytical redundancy, using methods of fault detection and identifying its location, and accepting capacity reduction during the fault.. Errors caused by poor thermal insulation that is supposed to ensure correct operation of the reference vessels This is a reason for using the reliability and detected minor faults’ method of control of measuring tracks. Studies of the water-level control system in a steam drum using the FTC system for the measurement circuits as presented in the paper are original ideas, providing a new solution. The results of the studies are presented in Pawlak and colleagues.
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