Control loop performance-monitoring software can help to improve loop performance at electric power plants by automatically collecting data, assessing several aspects of loop performance, and providing the results in reports and user interfaces.
Power plant control systems must perform well to obtain maximum efficiency, reliability, regulatory compliance, and safety from a plant. Poorly performing controls can cause operational difficulties such as boiler oscillations, increased heat rate, accelerated equipment wear, increased emissions, slower load ramp rates, reduced generation capacity, steam temperature excursions, and unit trips following upsets.
To maintain optimum plant performance, control loop performance should always be tuned for maximum performance. This can be achieved only by monitoring loop performance and taking the appropriate corrective actions when poor performance is detected. However, the diagnosis and resolution of control loop problems are difficult, particularly in large and complex process facilities such as power plants.
Several control loop performance-monitoring (CLPM) software products have become commercially available over the past decade. These products automatically monitor the performance of control loops. They potentially identify several aspects of poor control and can generate a prioritized list of problem loops with diagnoses of the individual problems so that these can be corrected.
CLPM Software
Control loop monitoring solutions are available from distributed control system (DCS) vendors and third-party software companies, including ABB, AspenTech, Capstone Technology, Control Arts, ControlSoft, Control Station, Emerson, ExperTune, Honeywell/Matrikon, PAS, and RoviSys. The products vary in the range of analyses they perform, presentation of results, reporting features, and data collection methods, but they all aim to identify and report on poorly performing control loops. One such software product, PAS PSS Loop Analysis, was tested by the Electric Power Research Institute (EPRI) and Southern Company on Alabama Power’s Plant Gaston Unit 3.
Although there are differences in the features and presentation methods from one CLPM product to another, most provide the following core functions:
- Automatically collect process data for analysis.
- Assess the dynamic performance of control loops.
- Diagnose loop performance problems.
- Represent loop performance with a set of metrics.
- Aggregate loop performance metrics into high-level key performance indicators (KPIs).
- Present loop performance in user interfaces and/or reports.
The first requirement for monitoring the performance of control loops is access to uncompressed process data sampled sufficiently fast to capture the loop dynamics (Figure 1). A good way of collecting process data for loop monitoring is through object linking and embedding for process control (OPC) with real-time data access (DA) because it is supported by all modern control systems, and it gives the loop-monitoring software the most control over sampling rate and data resolution. Careful consideration should be given to the rate at which loop performance assessment software acquires data from the data server to avoid overloading it.
 |
| 1. Keeping things under control. The basic steps in control loop performance monitoring are shown. Courtesy: OptiControls Inc. |
To improve network security, most plants segregate process control computer systems and regular users into individual networks separated by firewalls. Process data has to flow from the process control network to the application servers, and client computers must have access to connect to these software applications. Software vendors provide various data connectivity solutions to get process data to their application servers and application data to their users.
Because CLPM software will likely have multiple users, a client-server architecture is essential. The server is responsible for collecting data, running the analyses, historicizing the results, sending out scheduled reports, and delivering performance results on request from client applications. The client applications can be used by engineers, technicians, and managers distributed throughout the enterprise. Some plants require web browser access for viewing plant data and reports to minimize the need for software installations and upgrades on client machines.
Email
Comments
Print
Reuse
