Turbomachinery control optimized for industrial power generation

Very often, steam turbines are used to produce electricity and, at the same time, provide steam for plant operations. That is why they have one, and sometimes two, extraction and/or admission steam headers to manage intermediate and low-pressure steam. When the electrical load changes, controllers manipulate the main steam valve to stabilize the grid frequency. However, this means they add or decrease the amount of steam going through the turbine, which can have a severe effect on the steam pressure in the steam headers. CCC has developed robust algorithms to coordinate the control of the main steam valve and extraction valves simultaneously, ensuring very stable steam header pressure while maintaining high precision of the grid frequency.

The turbine controller operates in coordination with the generator controller to ensure stable performance across all modes. During startups or idle periods, when the generator breaker is open, the turbine controller manages turbine speed. If the generator breaker is closed and the utility breaker is open, either Isochronous or Droop Control is applied:

• Isochronous Control: Maintains the unit’s nominal synchronous speed and frequency via a dedicated speed control loop.
• Droop Control: Utilizes a generator loop with distinct PID settings and a set point from the generator controller.

When both breakers are closed, Droop Control remains active. If the utility breaker opens while the local bus is exchanging power with the grid, logic controllers adjust outputs and set points, switching one of the local units to Isochronous Control to minimize local bus impact. In cases of sudden, significant load changes, Droop Control stabilizes grid frequency at a defined offset, and generator controls can automatically reduce power set points if limits are exceeded.

Some standards are key to obtaining certification or negotiating the best insurance conditions. Honeywell | CCC offers solutions that make control systems compliant with both API-612 (Steam Turbines) and API-670 (Machinery Protection Systems). Necessary components include dual and triple-redundant speed pick-ups, segregation of safety and overspeed systems, and others.