Research On Adjustment Strategy Of The Closed Loop Current In Distribution Network With Distributed Generation

Closed-loop operation of distribution network is regarded as a necessary step of power system operation. It significantly improves the reliability of power supply. However, the operation produces the surge current, which severely affects the security and stability of system operation. For this reason, it seems critical to simulate and ensure operation safety before closing loops. In addition, as permeability continually increasing, the distributed generation behaves advantageous in terms of pollution reduction and the energy efficiency utilization. However, it also has a negative impact on the operation security. Hence, it is supposed to develop an effective method for not only secure closed-loop operation, but also the impact to distribution generation.Firstly, this paper establishes a mathematical model of closed-loop operation in the distribution network and presents corresponding calculation process. Besides, compared to traditional method, this paper applies an advanced backward-forward sweep method for distribution power flow calculation. Furthermore, superposition and Thevenin’s theorem are employed to complete calculation of stable current and the surge current respectively. It is assumed that corresponding relationship of these two current is deduced and used to investigate influence of the surge current on other branches.Secondly, this paper analyses the mechanism of the closed-loop stable current and surge current. It is concluded that transformer ratio and compensation capacity are major factors affecting the size of closed-loop current. When the current is excessively large, it is effective to regulate the closed-loop current by the change of transformers’ tap and compensation capacity of reactive power equipment. Moreover, this paper establishes a model for closed-loop current control, which target on the closed-loop surge current. Control variables are both the tap position of transformers and the number of groups of capacitors. Besides, in this paper also considers the influence of distributed generations on closed-loop operation in distribution network. It is proposed corresponding measures to adapt distributed gen- erations for various types. Additionally, the influence of distributed generations is reflected in the constraint equations of the model.Finally, in order to calculate closed-loop current control model of distribution network, this paper proposes the collaborative algorithm, which consists of particle swarm optimization and simulated annealing algorithm. It is relatively superior in fast local search ability of particle swarm algorithm and global convergence of the algorithm simulated annealing algorithm. Based on the collaborative algorithm, this paper utilizes Matlab software to write the program of closed loop current control. It simulates a random closed-loop network for example. The results indicate the algorithm has advantages in fast, stable and accuracy convergence. Therefore, it is proven effective for closed loop current control in distribution network. In addi-tion, this paper also changes capacity and location of distributed generation. The impact and corresponding solutions are analyzed and displayed in the following chapters.