Power Plant Control Systems

By Wayne Salo

Over the past 40+ years I have been involved with the design, specification, installation, maintenance and tuning of boiler/turbine combustion control systems and plant auxiliary systems. Over the years I have observed that companies have not been hiring or replacing control engineers in a timely fashion to provide the time to allow appropriate mentoring on the operation of the plant or of the specific equipment. The control engineer is the last check or line of defense to the proper operation of the equipment. It is important that this last check result in the proper implementation of a control scheme that reflects the appropriate operation and interface of this equipment within the overall design of the plant.

Depending on the particular plant, the design of individual control elements may be more or less sophisticated. Some plants and processes may have been designed for cyclic operation while others may have been designed only for base or steady-state loading.

In this document I will attempt to discuss the control loop/system control implementation from the basic to the most extensive. The actual implementation you may actually need will be determined by the original design criteria for the overall unit and individual components within the generation unit. It must be remembered that the control system is an overlay of the actual plant system and process. The fundamentals of the process must be known and the control system needs to reflect and complement these processes.

Additional associated systems are discussed that may not use control systems through the Computer System, but are important enough to warrant some understanding. These systems may affect the operation of the other controlled systems discussed in other sections of this document.

As the requirements of the processes become more constrained, I have found that it is important to model the process and anticipate and appropriately pre-position the manipulated variables before errors occur in the process that require feedback control.

Since I am now semi-retired, I also wanted to document some of knowledge I have gleaned in these past 40 years. In working with customers I have realized that many of the end users responsible for maintaining this equipment do not understand some of the fundamentals associated with the equipment and processes being controlled.

This document was not created as a research project nor an extensively documented paper but is a summation and monolog of my working experience.

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Please contact Patrick Mahoney at patrick.mahoney@exceleng.net with questions.


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