Primary frequency regulation capacity enhancement of CHP units: Control strategy combining high pressure valve adjustment and heating extraction steam adjustment

Abstract

With the increasing penetration of renewable energy in China, the primary frequency regulation (PFR) performance of coal-fired units plays more critical role in sustaining the security and stability of the electrical power system. A case study regarding the 350 MW combined heat and power (CHP) unit is conducted to analyze the response capacity to large frequency disturbances of the grid. Simulation models of PFR are developed to reflect the unit characteristics. The PFR capacity is evaluated for six common operating load points in the heating season, and only some load points could satisfy the power demand when grid frequency deviations are −0.122 Hz to −0.165 Hz. Further, the feasibility of the PFR control strategy combining high pressure valve adjustment and heating extraction steam adjustment is explored, resulting in enhanced response capacity of the unit. The maximum increment of PFR capacity under above large disturbances is 6.03 MW, an improvement of 48.72%. Moreover, large grid frequency deviation disturbances are simulated, results show that the power contribution index increases from 56.2% to 88.9% with the novel PFR control strategy. Above-mentioned results mean that the PFR capacity of CHP units is enhanced in response to large grid frequency disturbances in the heating season.