Research On Comfort And Energy Saving Control Strategy Of HVAC System Based On MPC Strategy

With the proposal of carbon peak and carbon neutralization strategy in China,it’s becoming more and more important to realize low-carbon production and lifestyle through energy saving and emission reduction.On account of the high energy consumption of building,it’s urgent to improve the control strategy of the main energy consuming equipment in the building and promote the increase of the proportion of green buildings.HVAC usually accounts for more than 55% of the building’s electricity demand,but as an important electrical equipment to maintain the indoor environment,it plays an irreplaceable role.Therefore,how to design advanced control algorithms to improve the energy efficiency of air conditioning has important research significance under the current situation of energy shortage.In this paper,the HVAC control strategy based on MPC algorithm is proposed from the perspective of two important indexes of air conditioning energy efficiency evaluation,namely comfort and energy saving.In terms of comfort,we pay attention to the adjustment of microclimate inside the room,which is the terminal of air conditioning.In terms of energy saving,controlling the working frequency of the compressor in real time according to demand response by connecting HVAC to the smart grid can relieve pressure on the supply side.Firstly,a multi-zone temperature and humidity prediction model is established based on computational fluid dynamics method,and the objective function of temperature and humidity tracking was constructed by using the basic MPC algorithm.The microclimate environment indoor is under control mainly by adjusting the air flow rate.The feasibility of the algorithm can be verified by simulating in the MATLAB platform.In the presence of external disturbance,temperature and humidity can fluctuate in a small range around the reference value.By changing the reference temperature before peak demand hours,the electricity price cost can be reduced by about 34% throughout the day compared with the fixed reference value,and energy saving control can be preliminarily realized.Secondly,considering the thermal dynamic characteristics of buildings,the influence on indoor environment is analyzed.In the process of modeling,the change of convective heat transfer coefficient and thermal conductivity coefficient under different indoor or outdoor environment and different envelope structure are included,then the polytopic liner parameter-varying model can be obtained.Based on Linear Matrix Inequality,an improved Min-Max Robust MPC strategy is proposed.Results show that the improved algorithm can effectively deal with the parametric uncertainty perturbation,and the indoor environment in each zone can maintain stable state.The mean tracking error of temperature and humidity in the working zone are within 0.1℃ and 0.13g/(kg dry air).Respectively,the average PMV index is 0.34.Finally,in order to take account of energy saving and comfort,a MPC strategy is designed which can respond to dynamic power price changes in time and control the working frequency of inverter air conditioning compressor.The performance model of the compressor and the room temperature load model are established respectively,the outdoor weather condition is also taken as the external input to obtain the final control system.In order to save electricity price cost and optimize room temperature,power-price time-varying constraints and comfort constraints are considered.The simulation results show that compared with the traditional PID algorithm,the total energy consumption and the total electricity price cost of the whole day can be reduced by 11.09% and 21.65%,the peak-hour energy consumption and electricity price cost can be reduced by 22.91% and 35.04% under MPC control based on demand response,peak shifting is achieved.At the same time,the average room temperature is close to 24.4℃,the indoor comfort is guaranteed.