Research On Wind Power Integration Scale Evaluation And Wind Storage Control Strategy Considering The Electro-thermal Coupling Characteristics Of The Line

With the development of industrial modernization and continuous population growth,energy and environmental issues have become increasingly prominent.Energy crises and environmental pollution have limited the survival and development of humanity.Compared with traditional fossil energy,wind power is economical and environmentally friendly.From the consideration of alleviating energy crisis and environmental protection,vigorously developing wind power is the only way of chinese energy revolution.In China,there is an obvious imbalance and regional difference between the distribution of wind energy resources and the demand for electricity.Large-scale wind farms often transmit electricity to the main grid through long-distance dedicated overhead lines.Therefore,the wind power received by the main power system will be constrained by the transmission capacity of the overhead lines.The transmission capacity of overhead lines is defined as the maximum power or current they can carry.Currently,a conservative set of meteorological parameters is often used to evaluate the transmission capacity of overhead lines,which leads to the underutilization of the transmission capacity of overhead lines and greatly restricts the integration scale of wind power.In addition to meeting the transmission capacity constraint of the lines,wind power integration also needs to meet the volatility constraint.The inherent volatility of wind power will cause significant impacts on the voltage stability,frequency stability,and angle stability of the power grid.How to further meet the volatility constraint of wind power and achieve safe wind power integration while satisfying the transmission capacity constraint of the lines is a pressing problem that needs to be solved.In view of the above problems,this paper uses the theory of electro-thermal coupling as a bridge to introduce the meteorological parameters in the actual operating environment into the transmission capacity analysis of overhead lines,overcoming the conservativeness of traditional methods.The integration scale of wind power is evaluated by considering the electro-thermal coupling of overhead lines.In addition,in order to take into account the volatility constraint of wind power and the transmission capacity constraint of the line,this paper proposes a wind-storage control strategy considering the transmission capacity of the line,which realizes the safe grid connection of wind power.The main research contents of the paper include:(1)In order to calculate the temperature variation law of overhead lines under the action of multiple meteorological parameters,a dynamic simulation method of line operating temperature considering the electro-thermal coupling characteristics is proposed.Firstly,based on the heat balance equation under IEEE-738 standard,the basic process of heat absorption and heat dissipation of overhead lines is introduced.Then,based on the assumption that the line is in thermal equilibrium,the influence of different meteorological parameters on the operating temperature of the line is analyzed.Finally,taking the electrothermal coupling theory as a bridge,the resistance of the overhead line is set as a function of temperature,and the linear change of environmental variables is introduced into the dynamic thermal balance equation,which realizes the rapid calculation of the operating temperature of the overhead line and provides a data basis for the subsequent transmission line transmission capacity analysis.(2)Aiming at the problem that the current evaluation of line transmission capacity is too conservative and thus limits the scale of wind power integration,a wind power integration scale assessment method considering the characteristics of line electro-thermal coupling is proposed.Firstly,the power balance equation of wind power connection is coupled with the dynamic heat balance equation of the transmission line.The transmission power capacity of the line that considers the influence of environmental parameters is calculated by using the operating temperature of the line as the criterion.Then,a wind power output model is established,and based on this,the correlation between wind power output and line current carrying characteristics is analyzed,which theoretically confirms the application value of considering the influence of meteorological parameters on line transmission capacity in improving the scale of wind power integration scale.Finally,an evaluation model of wind power integration scale is established,which analyzes the whole life cycle cost of wind farm integration scale by taking the line transmission capacity under environmental parameters as the wind curtailment standard,which can give the optimal integration scale of wind power under the condition of limited transmission resources,and provide a basis for wind power planning and capacity increase.(3)Aiming at the problem that the volatility and transmission capacity do not meet the grid connection requirements,this paper proposes a wind-storage control strategy that takes into account the transmission capacity of the line by introducing hybrid energy storage on the wind farm side.Firstly,a wind-storage integration model is established,and the basic models of wind power output and hybrid energy storage are introduced.Further analysis of the frequency-domain characteristics of wind power output is conducted to determine the distribution of wind energy in different frequency bands to guide the design of subsequent energy storage control strategies.Then,based on the fluctuation requirements of wind power integration,a hybrid energy storage control strategy is developed using wavelet decomposition.This strategy can adaptively adjust the number of wavelet decomposition layers according to the fluctuation characteristics of wind power,which decomposes wind power into standard grid-connected power and hybrid energy storage power instructions.In terms of the distribution of hybrid energy storage power instructions,the strategy includes two levels of power instruction distribution:the initial allocation based on the response characteristics of hybrid energy storage,and the secondary modification based on fuzzy control of energy storage charge status.the reasonable allocation of power command is realized through the above method.Finally,by combining the transmission capacity calculated in Chapter 3 with the hybrid energy storage control strategy for smoothing wind power fluctuations,a wind-storage control strategy that takes into account the transmission capacity of the line is proposed.This strategy can further satisfy the wind power fluctuation constraints while meeting the transmission capacity requirements,achieving the safe grid connection of wind power.