Optimal Allocation Of Distributed Generations In Distribution Networks

Distributed generations (DGs) have attracted increasing attention on the background of the gradual failure of the global primary energy and the deregulation of electricity enterprise. DGs have many advantages, for example, reducing environmental pollution and the users' terminal costs, increasing power supply reliability, improving power quality, flexibly tracking the load's changes and meeting the sustainable development and so on. It's a good way for the comprehensive utilization of existing resources and equipments to provide users with reliable and quality power that distributed generations and large power supply electricity complement each other.How to choose reasonably among so many types of DGs in the planning stage of distributed generation system is very important. Reasonable choice of DGs can fully exploit the dispersion power, improve energy efficiency and reduce investment costs. Optimal allocation of DGs is another key issue in the planning stage. Reasonable planning of DGs could improve power quality and increase load ratio, while unreasonable planning may lead to increasing of energy loss, dropping of some nodes' voltage or the over voltage in the power system and even it may change the magnitude, duration and the direction of the fault current. How to determine the DGs' allocation and capacity in order to get the maximal benefits and do not effect the security and stability of the power system is also extremely important. This paper focuses on these two issues and the main research work is as below:Firstly, the characters of different types of DGs are summarized and steady-state models are established. Considering the instability output of many DGs, this paper combines the energy storage device and DGs which can effectively improve the imbalance for the supply and demand between the distributed generation systems and electric power load. This also can improve power quality and the stability of distributed generation systems.Secondly, a cost model of distributed generations is established which considered the environmental benefits of the DGs. We get the optimal combination types through the sensitivity analysis on the factors which have impact on the selection of distributed generations. This further emphasized the importance of selection of DGs' type.Then, this paper gives a review of the optimal allocation of DGs and establishs the optimization model and improve traditional genetic algorithm. In the condition that DGs' type, allocation and capacity are uncertain, the multi-objective function which concerned the cost of DGs and the improvement of net loss is proposed. The improved genetic algorithm is used to find the optimal allocation and capacity of DGs. Moreover, the multi-objective function is changed into single objective function using linear weighting method. This study takes many factors into account and is more realistic which can provide some theoretical basis for the future study of the optimal allocation of distributed generations.Finally, an example of 33-node system is used to test the method proposed. Test results verifies the feasibility of the proposed algorithm.