Program for control of load distribution in compressors of the 3rd West-to-East Gas Pipeline

Upon joint construction of gas compressor stations in western section of the 3rd West-to-East Gas Pipeline and the 2nd West-to-East Gas Pipeline, compressors in these stations are required to perform relevant operations both jointly and independently. Accordingly, control programs for load distribution in the 3rd West-to-East Gas Pipeline have been proposed. The program is based on closed-looped control over outlet pressures load distribution with PLC as controller to combine control algorithms for load control with load distribution to adjust rotation speeds of parallel compressors and apertures of the anti-surge valve. In this way, working points of all compressors can be maintained at equal distance with the surging line. In addition to satisfying requirements related to outlet pressures, total loads can be allocated in accordance with capacities of different compressors. In accordance with calculation formula, the load distribution controller may acquire data related to inlet and outlet pressures, temperatures, pressure differences and other signals of compressors to determine the DEV of working points and the surging line. Upon completion of PID calculation, weighted average of relevant results can be obtained by using relevant software before transmission of performance controller of compressors to control their rotation speeds. In addition, introduction of closed-loop PI control, open-loop RT response and feedforward anti-surge control may help to achieve load distribution objectives. Test results show the program can maintain all compressors within designed working extent to control backflows in these compressors and to reduce energy losses induced by blowdown. In addition to minimizing risks related to surging, the system can be deployed to share impacts of disturbance.