Strategy Research Of Harmnic Optimal Governance In Active Distribution Network

Along with a large number of distributed generations accessing into grid and the improvement of automatic and intelligent control in distribution network,the traditional passive distribution system is gradually developing to a flexible and controllable active distribution network(ADN).The typical characteristic of the ADN is containing lots of complex and diverse harmonic sources.In addition to electric locomotives,electric arc furnace and other major harmonic sources,there are a large number of inversion type distributed generations,load power electronic equipments and other nonlinear harmonic sources.The harmonic current of these nonlinear harmonic sources is not large.But these nonlinear harmonic sources are widely distributed and have a high degree of intensity in ADN.Their harmonic current in the dissemination process will be superimposed and enlarged,which poses a major challenge to harmonic pollution control in ADN.The traditional harmonic current control method is centralized point-to-point governance aiming at a certain harmonic source.This mode of governance has a passive mode of work,a small range of governance,poor economy,and other shortcomings.So this way of governance is no longer applicable for the distributed harmonic source ADN.Based on analysing the advantages and disadvantages of harmonic control equipments and governance methods,at the system level,this paper proposes a optimization strategy of harmonic in ADN.This method uses the voltage-detection-type SAPF as the control equipment,and takes the total distortion rate of each node in the power grid as the evaluation index.The ADN's harmonic problem can be managed globally by optimizing the harmonic current control of all control equipments.The node importance evaluation method is studied to form the objective function.The fundamental current equation and the harmonic current equation of the grid are constrained to the equality constraints,the APF capacity constraint and the constraint value of the electrical parameters are constrained to the inequality constraints,and the optimization model is established.The improved particle swarm optimization(PSO)algorithm is used to optimize the harmonic current compensation of distributed APFs.And then the harmonic optimization model of active distribution network is formed.Finally,taking the IEEE 33-nodes distribution network as an example structure,and the simulation is carried out in MATLAB.The results show that the harmonic optimization strategy proposed in this paper can allocate the harmonic compensation amount of APFs according to the importance of nodes,so that the ADN's harmonic problem can be managed globally and effectively.The proposed method provides a new solution for the ADN to realize the high quality power supply of the whole network.