Analysis On Thermal Economy Of Thermal Power Unit With Thermal Energy Stored High-backpressure Additional Thermodynamic Cycle

At present,peaking units in China are still dominated by thermal power units,but with the increasing proportion of renewable energy generation,thermal power units must strictly comply with the scheduling scheme to provide space for renewable energy grid connection.However,due to the intermittent and uncertain characteristics of renewable energy,in order to maintain the stability of the power grid,on the one hand,the existing thermal power units are required to have more flexibility,on the other hand,the thermal power units that originally bear the base load are forced to participate in the peak load adjustment process.Heat storage technology can be widely used in the flexible transformation of thermal power units.As a heat storage method,thermal storage can be used to deeply explore the peak adjustment space of thermal power units.Based on this understanding,this paper proposes a new integration idea of heat storage and conventional thermal power units,whose function positioning is to transform traditional thermal power units into peak-regulating power supply by adding energy storage type additional cycle.Firstly,this paper gives a detailed explanation of the thermal system of superhigh back pressure energy storage type additional thermal cycle thermal power unit with steam drum as the cold source,and presents the economic calculation model.A complete parametric modeling was carried out for the rated working condition of traditional coal-fired thermal power units,and the influence of the main parameters of the energy-storage additional circulation system on the peaking performance and economic performance of thermal power units was obtained by using Matlab software.Taking a certain 600MW subcritical coal-fired unit as an example,when the initial steam conditions of the additional cycle are 36MPa,700? and the steam mass flow coefficient is 0.35,the additional cycle can provide 6.23%more output power and the round-trip efficiency can reach 44.18%.Secondly,Ebsilon Professional software is also used to model and analyze the energy storage type additional cycle thermal power unit under variable operating condition sliding pressure operation mode and constant pressure operation mode.Verify the depth peak adjustment capability of the thermal power unit after the modification according to this scheme.Based on the energy-storing high-back-pressure additional cycle,the 330MW coal-fired unit improves the energy conversion efficiency from the thermodynamic perspective.When the inlet steam temperature is 720?,the pressure is 34MPa and the flow coefficient is 0.25,the energy conversion efficiency under rated conditions is 48.6%.For the unit with sliding pressure operation mode,the energy conversion efficiency is especially improved in the intermediate load,which can be close to 50%.Finally,two additional configurations are added,a 330MW coal-fired unit based on the energy storage type high back pressure additional cycle,to verify the rationality of this paper.When the additional cycle exhaust steam enters the main steam pipeline,the absolute electrical efficiency of the additional cycle unit can reach 45.92%when the steam pressure of the additional cycle is 26Mpa,the temperature is 720? and the flow coefficient is 0.4.When the additional cycle exhaust steam is used as the no.0 high heating heat source steam,the inlet steam temperature of the additional cycle turbine is 720?,the pressure is 34MPa,the additional cycle exhaust steam pressure is 8.8MPa,the energy storage type additional cycle unit absolute electrical efficiency can reach 49.2%,the round-trip efficiency can reach 57.87%,and the flow coefficient is only 0.0778.