Dynamic modeling and frequency regulation performance evaluation of a combined heat and power unit supplying industrial steam

To establish a sustainable energy system, renewables, such as wind and solar energy, have been developed rapidly. However, renewable power has strong time-varying characteristics, which undoubtedly affects the safe and stable operation of the power grid. Combined heat and power plants (CHP) have higher energy efficiency than the condensing power plants that only generate power, but have restricted operational flexibility. The primary frequency regulation capacity of the CHP unit is normally smaller that the condensing power unit. To evaluate the frequency regulation performance of the CHP plants, the dynamic model of a CHP unit was developed based on the GSE software and validated with a 660 MW CHP plant as the reference case. Then, variations of the power grid frequency of the CHP unit were obtained with the step disturbances of power unit's power load in different degrees. Besides, the frequency regulation performances of the CHP unit assisted by the heat storage of heat network pipelines were evaluated. Results show the use of combined valve regulation can shorten the primary frequency regulation time, and improve the primary frequency regulation efficiency. Under the step disturbance of 5 MW and 10 MW power loads, the combined use of heating extraction valve and high-pressure regulation valve can improve the efficiency of primary frequency regulation by 8.5% and 18.8% compared with that using the high-pressure regulation valve alone.