| With the high proportion of wind power,photovoltaics and other intermittent distributed generations,and the impact loads such as electric vehicles being connected to distribution network,the voltage deviation,power fluctuation and line loss of the distribution network may be increased and the power quality of the distribution network declines,which bring challenges to the safe and stable operation of distribution network.In this thesis,the minimum of line loss,voltage deviation,power fluctuation and operation cost of the distribution network are taken as the optimization objective considering user demand response under time-of-use price.Distributed energy storage is explored to improve the operation level of distribution network by using the characteristics of storing electric energy at the low point of power consumption,sending electric energy at the peak of power consumption and flexible charging and discharging.The main work of this thesis is as follows:Firstly,the distributed generator and distributed energy storage connected to the distribution network are modeled,and the impact of distributed generator and distributed energy storage connected to the distribution network on node voltage and line loss is analyzed.Secondly,the operation mechanism of demand response is analyzed,and a price-based demand response model based on load transfer rate is built,which clarifies the mechanism of user demand response changing under time-of-use price.Considering the limitation of demand response under peak-valley power price,starting from the four output modes of distributed energy storage,and utilizing the flexible charging and discharging characteristics of distributed energy storage,the dynamic combination of user demand response caused by price fluctuation and distributed energy storage is made.Considering the constraints of charging and discharging times of energy storage devices in the demand response period,a multi-objective optimal operation model of distributed energy storage is built considering user demand response under time-of-use price.And a distributed energy storage charging and discharging strategy is proposed to ensure the continuous and stable operation of energy storage and improve the operation level of the distribution network.Finally,in view of the slow convergence and large fluctuation in the evolution process of the traditional genetic algorithm,an improved genetic algorithm is proposed and implemented to solve the multi-objective optimal operation model of distributed energy storage considering user demand response under time-of-use price by using the uniform random strategy to generate the initial population and by using the method of multi-crossover,multi-variation and adding the vaccine library.The multi-objective optimal operation model of distributed energy storage considering user demand response under time-of-use price is solved and validated by using the improved genetic algorithm based on the standard IEEE 33-bus system and the actual example of a local 10 k V distribution network in China.The test results show that considering the constraints of charging and discharging times of energy storage devices in the demand response period,the distributed energy storage charging and discharging strategy based on the established model can effectively reduce line loss,voltage deviation,power fluctuation and operation cost of the distribution network,improve power quality,the operation economy of the distribution network and the safe operation level of the distribution network.The continuous and stable operation of the energy storage in the whole demand response operation cycle are ensured,which extends the service life of the energy storage.At the same time,it proves that the improved genetic algorithm proposed for solving the model has the characteristics of rapid convergence and smooth and stable evolution process. |
PDF Full Text Request