Deep Peak Shaving Optimization Scheme And Performance Analysis Of Combined Heat And Power Units Based On Thermoelectricity

Thermal energy and electricity are the main sources of energy consumption.To simultaneously meet the demand for heat and electricity and improve energy efficiency,combined heat and power(CHP)units are widely applied in the power system.Wind power and photovoltaic power generation are considered the most promising choices for future power energy sources to achieve the goals of carbon peak and carbon neutrality.Consequently,China’s installed capacity and power generation of wind power and PV have increased rapidly.However,the inherent thermal-electric coupling mechanism of CHP units operating in heat-defined electricity mode leads to an increase in the forced power generation under high thermal loads,limiting the unit’s power generation adjustment range.The reduced flexibility of the CHP system’s loadfollowing ability due to its inherent thermal-electric coupling mechanism decreases its capacity for integrating new energy,resulting in severe wind and photovoltaic power curtailment.To address the insufficient load-following capability of CHP units during the heating season and improve the depth of unit load following,five retrofitting technologies,including low-pressure cylinder cutoff modification,high and lowpressure bypass compensation,thermal storage tank,electric boiler,and absorption heat pump,are integrated into the CHP system to enhance its flexibility.From the perspective of safe operation feasible region,the mathematical models of the feasible region and flexibility improvement index of each CHP decoupling retrofit scheme are established.From the perspective of CHP unit operation,the detailed simulation model of the unit is established using EBSILON,and the energy consumption performance of the reference and new systems under the same conditions is compared.Combining the advantages and disadvantages of each retrofitting scheme,a multi-scheme coupling thermal-electric decoupling combination system with an electric boiler,thermal storage tank,and energy storage device is designed.The operation mode of the system during the heating season and wind and photovoltaic power curtailment is described in detail.The variation of the feasible region for safe operation is analyzed and calculated,and the area of the feasible region is taken as the flexibility evaluation index of the system to compare the load-following flexibility of different schemes.The study analyzes the effects of each CHP decoupling retrofitting scheme on the CHP system,using a 330 MW extraction-condensing steam turbine generator unit in a power plant as the research object.The results show that all five retrofitting schemes can expand the feasible region for safe CHP unit operation,and the two-stage bypass retrofitting scheme has the largest increase in the maximum heating capacity of the unit.Except for the low-pressure cylinder cutoff modification,the decoupling ability of the other four schemes is improved to varying degrees.Among them,the electric boiler retrofitting scheme has the strongest decoupling ability.Under the same conditions,the unit’s standard coal consumption of each retrofitting scheme is ranked from high to low as follows:electric boiler,two-stage bypass,low-pressure cylinder cutoff,thermal storage tank,and absorption heat pump.Against the backdrop of carbon neutrality and carbon peak,these research findings can effectively promote the sustainable and healthy development of China’s new energy industry and facilitate the realization of the dual-carbon goals.