Research on Modeling and Rapid Load Change Control Strategy for High Back- Pressure Extraction-Condensing Combined Heat and Power System

doi:10.12096/j.2096-4528.pgt.24208

Abstract

Abstract:

Objectives Rapid load change capability of combined heat and power units can ensure the consumption capacity of the power grid for renewable energy and play an important role in improving the economic efficiency of thermal power units. Therefore, taking a high back-pressure extraction-condensing combined heat and power system in a power plant as the research object, this study focuses on system modeling, dynamic characteristic analysis, and rapid load change control strategy, leveraging the characteristics of its high back-pressure exhaust steam and heating extraction steam to achieve cascade heating of the return water in the heating network. Methods A dynamic characteristic model of the system is established based on the APROS simulation platform, and the accuracy of the model is verified using on-site operation data. The dynamic response characteristics of the thermal and electrical regulation process of the system under varying operating conditions are investigated, and the relationship between the thermal and electrical loads of the unit and the steam extraction valve (EV) under different operating conditions is established. A rapid load change control strategy coupling the heating steam extraction regulation of the unit is proposed. By implementing feedforward compensation at the EV valve, rapid changes of the unit output are realized, improving its load change response speed. Results Compared to coordinated thermal-electrical control, the rapid load change strategy reduces the response time to automatic generation control (AGC) commands by 150 seconds and shortens the time to reach steady state by 300 seconds. Conclusions The rapid load change control strategy for the dual-unit combined heat and power system significantly enhances the response speed of the system to AGC commands, with reduced oscillations during the transition process and a shorter time to reach steady state.

Key words: combined heat and power system, new energy consumption, steam extraction valve control, rapid load change, coordinated control system, high back-pressure, steam extraction regulation butterfly valve

CLC Number:

TK 32

Zongbo ZHAN, Jiping REN, Liping DING, Zhaolong SUN, Heng DING, Yue CAO. Research on Modeling and Rapid Load Change Control Strategy for High Back- Pressure Extraction-Condensing Combined Heat and Power System[J]. Power Generation Technology, 2025, 46(6): 1074-1084.

Figures/Tables 12

Fig. 1 Diagram of high back-pressure extraction-condensing combined heat and power system

Fig. 2 Overall model of high back-pressure extraction-condensing combined heat and power system

Fig. 3 Input and output variables of heating unit

Fig. 4 Time variation curves of related parameters during EV adjustment under THA condition in high back-pressure unit

Fig. 5 Time variation curves of mechanical power output of turbine cylinders during EV regulation under THA condition

Fig. 6 Time variation curves of electric power and heat supply during EV regulation in extraction-condensing unit

Fig. 7 Relationship between electrical and thermal loads and EV opening under THA condition

Fig. 8 Relationship between variations of relevant parameters and EV opening under different operating conditions

Fig. 9 Fitting surface of relationship between electrical and thermal loads and EV opening in extraction-condensing unit

Fig. 10 Fitting surface of relationship between electrical and thermal loads and EV opening in high back-pressure unit

Tab. 1 Fitting coefficients of heat consumption characteristic surfaces of each unit

系数	高背压抽凝机组拟合值(j=1)	抽凝机组拟合值(j=2)
z₀	-1.619	1.233
a	8.085×10^-3	-1.691×10^-2
b	5.523×10^-3	6.417×10^-3
c	-1.157×10^-5	7.915×10^-5
d	-2.876×10^-5	-7.074×10^-5
e	7.816×10^-6	1.942×10^-5
f	3.877×10^-9	-1.338×10^-7
g	3.911×10^-8	2.008×10^-7
h	-2.269×10^-8	-1.095×10^-7
i	5.054×10^-9	1.952×10^-8

Fig. 11 Comparison of electrical load response curves under three control strategies

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