Optimization of DG Units in Distribution Systems for Voltage Sag Minimization Considering Various Load Types

The optimum installation of distributed generation (DG) units in distribution systems has always been challenging due to the continually increase of electrical energy demands. However, the improper installation of DG units may have negative impact on the power quality of the distribution system. Voltage sag is one of the most important power quality problems, which has the bad effects on the performances of different loads, especially on sensitive and uninterruptible loads. To mitigate the voltage sag problem in distribution systems, a new formulation is proposed for optimal location and sizing of DG units. Particle swarm optimization algorithm is employed to solve the problem. The minimization of the total power losses, total cost of DG units, improvement of the voltage profile, and the reduction in the voltage sag effect are considered as the main objectives. To involve the voltage sag occurrence in distribution system, a penalty is considered for interruption of each type of available load. Different types of load models such as industrial, residential and commercial loads are considered in the system. For the demonstration of the effectiveness of the proposed algorithm, 34-bus test system is considered as the case study. The proposed method results are shown that there is about 72% reduction in total power losses in the optimal configuration of DG units in the distribution system. It is observed that the total number of disturbed buses decreases to 4, which is equal to 12%, as the number of DG units increases. It can be seen that the total cost of the system is reduced from 36.250 to 31.824 M$, when the optimum number of DG units is increased from 1 to 5. The simulation results show the effectiveness of the proposed algorithm.