The optimal location and penetration level of distributed generation

Modern distribution systems face a problem that the loads are growing continuously, thus the operation of distribution equipments are close to their marginal status, which will inevitably result in voltage instability problem. Meanwhile, with the development of distributed generation (DG) technologies, more and more DGs have been interconnected into distribution network to improve the reliability of power supply, reduce the cost of electricity and lower emissions of air pollutants. The connection of DG can also improve the voltage stability of distribution system. In some urgent situation, therefore, DG can be connected as a kind of reactive compensation equipment to improve voltage stability. This application makes DG units become "mobile reactive compensators". In order to obtain DGs\´ maximum potential benefits, proper location and optimal penetration level need to be calculated. This paper theoretically proves the improvement effect of DG onto the distribution system voltage stability. And a quantitative index is proposed to evaluate the voltage stability of load nodes. This index is calculated by continuation power flow (CPF) and then ranked to decide the optimal DG location. After the selection of best location, the optimal penetration level of DG at selected buses is calculated by primal-dual interior point method. The optimal calculation realizes the highest voltage eligible ratio and minimum power loss by adjusting the reactive output of DG in precondition of system security. At last, taking the American PG&E 69-bus system as an example, this paper shows the simulation results that indicate the best location and penetration level of DG for voltage stability in the test system.