| Distributed generation, as a kind of flexible power supply, has played an important role in saving the investment and reducing the line loss of distribution network by the coordination of the existing distribution network. However, due to the distributed power supply through the power electronic devices, especially the wind power, photovoltaic power generation output is vulnerable to weather, temperature and other meteorological conditions, which will give a great impact on the safe operation of the distribution network. In this paper, the distribution of harmonic voltage and current in distribution network is studied from the point of view of the harmonic problem caused by distributed generation.According to the structure of distributed generation and distribution network, the equivalent circuit of distributed generation is established. The relationship between distributed power output voltage, current and grid position, distributed power supply capacity can be obtained by equivalent circuit analysis. The model of distributed power distribution network is built by Matlab/Simulink simulation platform. Through simulation, the harmonic problem caused by the grid connected distributed power supply is analyzed:The relation between the access position of the distributed power supply and its output voltage, and the relationship between the network voltage and current harmonic distortion rate and the grid connected position, the relationship between the capacity of distributed generation and the network voltage harmonics and the influence of the access mode of distributed power supply on harmonics. Through the analysis of simulation results, summarized the distribution of distributed generations voltage and current harmonics.In order to quantitatively analyze the harmonic problem of distribution network with distributed generation, the maximum penetrating power of distributed generation is calculated under various conditions. According to the simulation example, the calculation value of the penetrating power of each node is obtained. Through the analysis of the penetrating power of each node, the relevant theory of harmonic distribution is verified. For multiple distributed power problems, the’at least penetrating power’ is calculated. The at least penetrating power is the calculation result of the system in the worst case. According to the results of the access power, this paper proposes some measures to improve the penetrating power, such as adjusting the network voltage, reduce distributed power supply output harmonic, which is validated by simulation.Finally, this paper studies the problem of the distribution network which may be caused by the access of distributed power supply, the modal analysis method can be very good to adapt to the change of the network operating parameters of the distributed power supply, and the frequency domain of the resonance can be relatively wide. In view of harmonic and harmonic vibration in distribution network with distributed generation, this paper summarizes and classifies the harmonic suppression measures and the principle and method of resonance, and the relevant conclusions can be used as a guide for practical engineering. |
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