Control.com - Nerds in Control

Hello,

I would like to know how is the normal control architecture of a generation plant.

I am used to see DCS which includes all the control systems and which also communicates with vendor equipments for signals exchange.

Since I am working for a Combined Cycle project, I have seen some power control systems: PMS, AGC, AVR, Load Shedding...

I would like to know their functions and their control level, if they are in the DCS or independent and communicated.

- PMS (Power management system)
- AGC (Automatic governor controller)
- Load Shedding
- AVR (Excitation control of the turbine)
- Pipe Leak system
- ESD (Emergency shut-down system)

For example, the control architecture will be like this:

            -----------------------------------
            |                                 |
            | DCS--> PMS + Load Shedding +ESD |  
            |                                 |
            ----------------------------------- 
              |    |      | 
              |    |      |
             AGC  AVR  Pipe Leak

In this case, the DCS has integrated in its logic programming the PMS, Load shedding screens and ESD. The AVR is communicated with DCS and the AGC will be something different (I do not know if it should be something programmed in DCS). Pipe leak will be some vendor equipment communicated with DCS.

Could the ESD be inside of the DCS, or must be something independent due to the redundancy? What should include? Is it a new PLC or only programmed?

What kind of functions has the PMS? What does normally controls? How is it interconnected with AGC?

What is AGC? Is it some logic programmed in DCS or something different? Is its function to receive the generation set points from the grid and send them to the TCS (turbine control system)?

To be more clear, I want to know what could come with DCS (programmed inside of it) and what must be from another supplier and then communicated with DCS.

Also, I would like to know how PMS and AGC normally work, what do they do and what kind of sub-systems they have inside.

Thank you very much for helping, I apologize if my explanation is not very clear.

Best regards,
Daniel

Hi Daniel,

I can talk about AGC (Automatic Generation Control).

It is an external system that produces generator MW set points, or MW raise/lower controls depending on the generator. Your unit/station will have some interface (for example, an RTU - Remote Terminal Unit) to the remote control center where AGC runs. AGC's function is maintaining generation-load balance within an area. The area can be an electrical island without connection to another area, in which case AGC will send unit MW controls to restore system frequency if it deviates from what it's supposed to be (50 or 60 Hz). If the area is connected to other areas that purposely transfer power between them, those unit MW controls are aimed at keeping both system frequency and the power transfer(s) between areas at their intended values.

Your generator may be base-loaded, meaning it operates at a set power level for long periods of time, or it may participate in so-called regulation. If it is base-loaded, it is usually either set to a certain power output by the unit operator, or it may be maintained at one by controls from AGC. If it can regulate, AGC will send it controls so its output varies up and down as the generation-load balance within the area changes.

I hope this gives you a start!