In order to minimize the cost and maximize the profit of cogeneration enterprises

it is necessary to accurately grasp the electric-thermal energy efficiency correlation characteristics of different heating modes

as well as the optimal distribution of heating load among units under the electric-thermal bivariate constraints. Taking the thermal power plant with multi-unit and three heating moded as an example

the energy consumption analysis model of multi-unit multi-heating mode and the plant-level heating load optimization distribution model are established

with the optimization goal of the minimum plant-level total coal consumption under the constraint of total heating load and power generation. Finally

the optimal distribution strategy of heating load under variable total heating load and variable power load is obtained. The results show that

the back pressure of the heating unit with high back pressure always keeps high value. The unit with higher thermoelectric ratio carries the maximum heating load and the rest heat load is supplemented by other units. By optimizing the distribution of heating load at the plant level

the total coal consumption of the whole plant can be reduced by 2.5～5.9 t/h

accounting for 0.60%～1.66% of the total coal consumption.