Combined Economic Dispatching Of Wind-hydro-thermal Power System With Generating And Transmissing Operational Flexible Space

In recent years,with the increase of loads and in the proportion of new energy installed capacity,the security region of power grid operation is gradually reduced,and the operation of power grids is reaching its limits,affecting the safety and stability operation of the power grid.At present,many scholars have carried out related research on key issues such as power grid operation optimization methods,and optimize grid operation in the safe operation domain of the grid to ensure that the grid achieves optimal benefits.However,as the safety domain for grid operation reduces,in order to solve the negative impact of new energy uncertainties and increased power load on the power grid,it is necessary to expand the operation boundary of the power grid and tap the flexible space of the power grid operation to improve the structure of power grid.Therefore,this paper proposes a method of combined economic dispatching of wind-hydro-thermal power system with generating and transmissing operational flexible space.According to the physical nature of the existing power equipment operating constraints,tapping the operational flexible space of the power system to evaluate the economic benefit and the consumption of clean energy.The major contents are summarized as follows:(1)The way is proposed to improve generating operation flexible space and establish corresponding models:1)Considering the flexible adjustment of the minimum output of the thermal power unit,the operational flexible model of thermal power unit with deep peak regulation is established.The generation cost curve of the existing thermal power unit with deep peak regulation model is a non-linear discrete curve.In this paper,the thermal power unit with deep peak regulation is established as a linear mixed integer linear model,which is convenient for commercial solvers to solve.2)Considering the short-term stability characteristics and losses of the restricted operation area of the hydropower unit,an operational flexible model for the operation of the restricted operation area of the hydropower unit is established.The model converts the loss cost of the hydropower restricted operation area into water consumption,and considers that the hydropower unit can be adjusted to the normal operating range in a short time after operating in the limited operation area.(2)The way is proposed to improve transmissing operation flexible space and establish corresponding models:1)Establish the fault short time capacity-increase operational flexible model of transmission lines based on the power transfer distribution factor.By utilizing the time process required for the accumulation of overloaded heat in the line,the transmission capacity of the line is improved in a short time,and the operational flexible space of the transmission line is tapped.In this paper,the transfer distribution factor modeling method of unit output as the optimization variable is used to reduce the number of variables effectively.2)Propose a static equivalent method of the external network for the available capacity of the tie line,establish a tie-line flexibility adjustment operational flexible model,and tap the operational flexible space of the tie line of the interconnected power grid.Compared with the existing static equivalent method of the external network,the model proposed in this paper not only considers the stepped constraints and the constant daily exchange capacity constraints,but also considers the operational constraints of the external network,accurately depicts the available transmission capacity of the tie line,and expands the tie line operational flexible space.(3)Based on the generating and transmissing operational flexible space model,a way of combined economic dispatching of wind-hydro-thermal power system with generating and transmissing operational flexible space is peoposed.This way breaks through the more conservative operation modes of the power system,expands the security region of power grid operation and comprehensively analyzes the impact of power system generation and transmission operational flexible space on power grid.The method of combined economic dispatching of wind-hydro-thermal power system with generating and transmissing operational flexible space in this paper can effectively improve the safe operation domain of the extended power grid and realize optimal resource allocation in a larger space.The benefit of the proposed method is evaluated through the IEEE 30-bus system and a provincial power grid system.The simulation results show that this method can improve the operation cost of power grids and consumption of clean energy such as wind power and hydropower effectively compared with conventional dispatching method.