Harmonic Power Flow Research For Distribution System With Distributed Generations

Distributed generation has the advantages of small investment,energy saving and environmental protection,reliable power supply and flexible power generation.However,with the continuous access of distributed generation supplied to the distribution network,the normal operation of the distribution network will be affected.At present,the problem of harmonic distortion caused by more and more distributed generations connected to distribution network has become one of the main concern of the technicians in the field of energy utilization in the power industry.However,the calculation of harmonic power flow is an effective method to ensure the reliable operation of the distribution network and some equipment,and then predict the potential problems caused by the increasing nonlinear load.This paper proposed the backward/forward branch sequence algorithm firstly,and a new PV node processing algorithm was given to overcome the defects and shortcomings of the traditional algorithm for calculating PV nodes,and then presented a backward/forward sweep harmonic power flow algorithm for distribution network with distributed generation.When a distributed generation is connected to the distribution network through an inverter,it will have a harmonic interaction with the distribution network and affect the harmonic distribution in the distribution network.The harmonic interaction is not considered when the distributed generation is used as the constant current source in harmonic power flow calculation.Therefore,this paper established the output impedance model of the grid-connected inverter of the distributed generation,and deduced the corresponding frequency domain model,verified the effectiveness of the output impedance model through simulation,and then applied it to the calculation of harmonic power flow.At the end of the paper,the IEEE33 nodes distribution system was used as an example,from the interconnection location,harmonic level,multiple distribution generation,etc.,to calculate the distributed generation with output impedance model and constant current source model of the system harmonic current distribution and the distribution of each node of the harmonic voltage distortion rate,the result verified the validity and feasibility of the algorithm.