Optimal Scheduling Of Power System And Integrated Energy System Considering Aggregation Flexibilty Of Thermostatically Controlled Loads

The high penetration of renewable energy enlarges uncertainty and fluctuation in the power system,which leads to a flexibility shortage.The massive increase of thermostatically controlled loads,as well as the rapid development of demand response technology,provides the power system with significant potential of flexibility.Additionally,benefiting from the interconnection of electricity and natural gas pipelines,the integrated demand response based on multi-energy complementarity also shows considerable flexibility.Therefore,this paper focuses on the system flexibility enhancement by the thermostatically controlled loads in the optimal scheduling of the power system and the integrated energy system.The contribution of this paper mainly lies in the proposal of reliable and efficient demand response modeling,aggregation and scheduling methods for three kinds of thermostatically controlled loads: fixed-frequency air conditioning load and multi-chiller HVAC(Heating,ventilation,and air conditioning)load in the power system,and gas/electricity switching heating load in the integrated power and gas system,and further lies on the continuous-time optimization to explore the intra-hour flexibility of thermostatically controlled loads.The specific contents and results of the study are as follows:(1)For fixed-frequency air conditioning loads with discrete adjustable electric power,the traditional aggregation and regulation strategies designed for a single function cannot make full use of its flexibility.To eliminate the gap,a refined model of the individual and aggregation characteristics of the fixed-frequency air conditioning load is established.Furthermore,a multi-functional demand response model with time-shifting and capacityreserve is designed under different regulation strategies.On this basis,a stochastic optimal scheduling problem of the power system incorporating multi-function demand response is constructed,considering the uncertainty of wind power distribution probability.Also,an accelerating decomposition solution algorithm is designed to improve computation efficiency.Case studies based on the IEEE standard system and the practical grid show that the proposed multi-function demand response for fixed-frequency air conditioning loads can enhance the system flexibility,and demonstrate the effectiveness and applicability of the proposed accelerating solution algorithm.(2)For multi-chiller HVAC loads with continuous adjustable electric power,the traditional energy conversion model considering load sharing strategy of multi chillers cannot apply to power system optimal scheduling.To eliminate the gap,a linearized modeling method for energy conversion characteristic model is proposed.By introducing unified dispatching signals,aggregation and regulation strategies for massive loads are designed.On this basis,an aggregated reserve demand response model of multiple HVAC loads is constructed.By effectively reducing the dimension of integer variables and constraints,the complexity of the proposed model in applying to power system optimization is reduced.Case studies show that the proposed modeling and aggregation method can improve the solution efficiency while ensuring the flexibility and energy efficiency of multichiller loads in demand response.(3)For gas/electricity switching heating loads with multi-energy conversion properties,the refined model considering practical physical characteristics is absent in the traditional integrated demand response.To eliminate the gap,the advanced Flex Gas technology which allows users to switch between natural gas and electricity to produce heat is analyzed,and a demand response model for gas/electricity switching heat load is further constructed.By modulating integer control variables to continuous output power,aggregation and regulation strategies of massive loads are designed.On this basis,a stochastic optimal scheduling method for the integrated power and gas system that takes into account the demand response of aggregated gas/electricity switching heating loads is proposed.Case studies verify that the proposed scheduling method is effective to enhance the flexibility of the integrated power and gas system and the proposed aggregation method can reduce the computational complexity of the optimization problem caused by large-scale integer variables.(4)For the coordinated scheduling of multiple kinds of thermostatically controlled loads,the traditional discrete-time modelling method cannot characterize the intra-hour flexibility of the loads.To eliminate the gap,continuous-time modeling methods are proposed for the time-shifted demand response,the reserve demand response,and the demand response of gas/electric switching heating loads,respectively.On this basis,a continuous-time stochastic optimal scheduling problem of integrated power and gas systems is constructed.A spatial mapping method based on Bernstein’s differential and integral operators is then designed to transform the difficult functional optimization problem into a solvable algebraic optimization problem.Case studies show that the proposed continuoustime demand response can effectively exploit the intra-hour flexibility of thermostatically controlled loads,and sufficiently accommodate the fluctuation of renewable energy.