Investigation On Active Control Mechanism For Interconnected Distributed Combined Cooling,Heating And Power Systems

Distributed combined cooling heating and power systems are beneficial to energy conservation and emission reduction.As continuous improvement of information and communication technology as well as the integration with various fields,distributed combined cooling,heating and power systems are becoming more networked and intelligent.This work mainly focuses on the control and operation of interconnected distributed combined cooling,heating and power systems.The active control mechanism and operation strategy are studied for the optimal control of interconnected operating distributed combined cooling,heating and power systems.An interdisciplinary exploratory research is carried out for the explanation of the mechanism for feed back control of systems with uncertain macroscopic states based on thermodynimics and information theory.This work established system off-design model in order to investigate the overall performance during operation period of a combined cooling heating and power system.The design and operation models of individual operation system and system with energy storage are established based on the off-desing model.The operation parameters can be analyzed with the operation model.In following electricity load mode,the electricity supply efficiency decreases and the heat-to-power ratio increases with the use of electricity storage.Thus relative energy saving ratio can be increased by the use of electricity storage when the system waste heat is insufficient without electricity storage.A case study shows that the relative energy saving ratio can be increased from 10.2% to 15.9%.In following thermal load mode,the electricity supply efficiency and system cooling and heat outputs are increased by the use of cooling and heat storages which increases the relative energy saving ratio.A case study shows that the relative energy saving ratio can be increased from 19.3% to 23.8%.The interconnected combined cooling heating and power system model is established and the energy efficiency of interconnected combined cooling heating and power system is studied.Under interconnected operation control,the energy demands can be shifted from peak users to off peak users,thus the matching degree between the system capacity and energy demand can be improved.A case study results show that,the system load ratio and energy outputs are increased and systems operation more hours under interconnected operation compared with individual operation.With the relative energy saving ratio analysis it can be seen that the cooling-to-power ratio and heat-to-power ratio of system output energy are closer to that of the energy demand after the deduction of transportation energy,and energy transportation between systems can achieve peak load shifting.The overall energy utilization ratio and relative energy saving ratio for individual operation are 68.1% and 10.7%,respectively.The overall energy utilization ratio and relative energy saving ratio for interconnected operation are 71% and 15.6%,respectively.A distributed controlled interconnected operation strategy based on exergoeconomic analysis is proposed and an interconnected operation model based on exergoeconomic analysis is established.The energy cost of energy productions are determined by exergoeconomic analysis in this model.The systems can exchange cooling,heating and power energy with each other according to the energy cost.A case including three interconnected operating systems is studied and the system energy production cost,load ratio and energy losses are investigated.The results show that the relative energy saving ratio is increased from 11.1% to 16% under interconnected operation.The study can provide control method for combined cooling,heating and power system network operation.The systems with uncertain macroscopic states are selected as the study object and the feedback control processes of nonequilibrium macroscopic systems considering both the information entropy of microscopic states and macroscopic states are studied.First,the concept of system set is proposed to represent the study object and the information entropy of a system set is demonstrated to be equal to the sum of the average thermodynamic entropy of the systems and the information entropy of macroscopic states of the systems.Then,the thermodynamic model of feedback control of small systems is extended to macroscopic systems to derive the expression of the average maximum net work obtained through feedback control,and the relation among the net work,the free energy of systems and energy consumption of measurement and erasure processes is identified.Finally,the influences of measurement error,mutual information,free energy and information entropy of macroscopic states on the net work are discussed through an example.This work may serve the thermodynamics of nonequilibrium systems with energy and information exchanges with their surroundings.