Research On Power Supply Capability For Distribution Network Based On Reliability Considering Distributed Generation

As a contact link between the customer and the bulk power system, distribution system plays an important role in ensuring the continuous and reliable power supply for customers. With the research and the development of future intelligent distribution network, the load transfer among networks will become very fast. In this context, the research on power supply capability for distribution network has become a hot spot, and how to tap the potential of power supply capability in distribution system with new energy resources is particularly important. At present, many scholars studying on power supply capacity for distribution network have achieved some results. However, most research didn’t involve the distributed generation(DG), especially DGs connected to substation’s low voltage bus in the form of special feeders have not yet been considered. In this paper, based on the existing research results about the concepts, models and methods of power supply capability for distribution network, the power supply capability models of distribution network including DGs are established through N-1 security guidelines and probabilistic reliability analysis respectively, and the factors affecting power supply capability are also analyzed.First, DGs are classified according to their characteristics, the interconnection point and the interconnection types are also determined, and then the equivalent reliability models of DG are established.Second, the total supply capability(TSC) model for distribution network is established based on the N-1 security guidelines and the definition of TSC. The model takes account of the N-1 security check of main-transformers, feeders and DGs and the transfer capacity constraint of feeders. The method of topology simplification is presented based on the feeder interconnecting mode. The index of DG’s effective degree is defined to reflect DG’s contribution to the enhancement of power supply capability. The optimization software Lingo is applied to solve the multi-constraint, multi-variable optimization problem mentioned above. At last, the correctness of the model and algorithm is verified and the results are checked and analyzed.Then the concept of reliable supply capability(RSC) and corresponding indexes for distribution network are defined according to the probabilistic reliability analysis method. The components’ reliability models in the study area and the maximum power supply capability(MPSC) calculation model at a certain state are also set up. The system status and occurrence probability are enumerated, and MPSC is calculated under every certain system state. Eventually RSC is calculated in accordance with the requirements of reliable supply risk level index. The RSC model is improved when DG’s accession to distribution system, and the DG’s effect on the RSC is also analyzed.Finally, two kinds of factors, substation inner factors and load transfer factors, which affect power supply capability for distribution network, are analyzed. The sensitivity indexes, as a quantitative indicator of influencing degree, are defined, and the solving process of all factors’ sensitivity indexes are illustrated.