Research And Simulation Of Dynamic Performance Of Heating System And Application In Electric Peak Shaving

As an efficient mode of production, CHP(Combined Heat and Power) has been extensively approbated and developed around the world. However, in most CHP units, heat loads following the electric loads during the operation. With the increasing of difference between electric peak and valley, the problem of peak shaving in CHP plant has been valued. It has been an urgent task how to remove the coupling relationgship between heat and electric loads in CHP plant.According to the mass and energy conservation equation, the thermal dynamic models of main equipments in the IDHS(Indirect District Heating System) were developed. The parameters that influenced the thermal characteristics were particularly taken into account. The models were presented under the assumption that the pipe network was in hydraulic balance.Based on the mathematical models, dynamic models of the IDHS were established, which include primary and secondery networks. Focus on the IDHS, the characteristics of thermal inertia and long time delay were simulated and analysed. And a control strategy that the operation of CHP plant as an electric peak shaving plant was designed, which can significantly improve the efficiency and the electrcic peak shaving performance of CHP units.In primary network, the characteristics of time delay and thermal inertia were analysed and quantified by dynamic simulation. It was found that the flow of water affect the time delay heavily. And when the heat input changed, the temperature of pipe wall changed more slowly than the supply water. Due to the characteristic of thermal storage, the pipe wall can slow down the rate by dissipate or regenrate heat and influenced the heat load of customers.The heat exchange between building envelope and internal thermal mass with the inside air were analysed. The results show that both can slow down the change of temperature in the room.Based on the characteristics and the basic control schemes of IDHS, two operation schemes were put forward that can make CHP units take part in electric peak shaving. In the schemes, heat load changed in different period of one day and the heat loads were determined by the characteristics of the heat and electric load and the coupling of CHP units in different period. The simulation results show that the two schemes can improve the electrcic shaving performance of CHP units efficiently. Additionally, by computation, it was proved that the new control schemes can increase the the profits of electric power significantly. The feasibility and validity of the schemes are proved through real-case simulation.