[Objective] Combined heat and power(CHP) technology serves as a pivotal and efficient technical approach to reducing the comprehensive energy consumption of traditional coal-fired generating units in thermal power plants

and the refined and accurate quantitative evaluation of heating energy consumption is extremely crucial for further improving the overall energy utilization efficiency and energy-saving operation level of largescale CHP units. In complex actual operational scenarios of cogeneration units

multiple practical influential factors will inevitably interfere with the internal energy conversion and utilization process of CHP units

resulting in variable additional heating energy consumption that significantly deviates from the ideal design operating state. Typical key influencing factors include the auxiliary power consumption of supporting thermal network equipment

the throttling regulation energy loss caused by variable heating extraction steam

and the dynamic variation of main turbine unit back pressure induced by large-fluctuation extraction steam for industrial and civil heating. [Methods] To systematically clarify the spatial and temporal distribution characteristics and quantitative variation rules of the additional heating energy consumption of CHP units under diverse complex off-design operating conditions

this paper takes a widely applied 330 MW commercial CHP unit as the core research subject and establishes a complete and accurate variable-condition thermodynamic calculation model for the full operating range of the unit. With the mature theoretical benchmark unit comparison method adopted to scientifically and quantitatively determine the additional heating energy consumption

this study precisely quantifies the variable additional energy consumption under various coupled working conditions of different electric generation loads and heating supply loads

and further conducts comprehensive comparative analysis to explore the influence laws of key operational parameters on the heating-related additional energy consumption of the unit. [Results] The research results indicate that the application of steam-driven circulating pumps for thermal networks can reduce the heating energy consumption of CHP units by 0.37～1.74 kg/GJ compared with conventional electric-driven pumps. The throttling effect of the heating butterfly valve brings about obvious positive additional energy consumption ranging from 4.04～8.57 kg/GJ. Moreover

heating steam extraction effectively reduces the condensing flow of the low-pressure cylinder and lowers its exhaust back pressure

thereby generating a beneficial negative additional energy consumption of 0.42～1.17 kg/GJ. [Conclusion] The findings of this study clarify the internal generation mechanism of heating energy consumption variation under variable working conditions

and provide reliable theoretical support and practical engineering guidance for energy-saving optimization

load optimal dispatch and low-energy stable operation of large-scale CHP units.