Under Voltage Load Shedding Scheme in the Presence of DGs

Nowadays, distributed generation (DG) is widely used in power systems. However, the use of DGs has caused new challenges in different aspects of power system operation, one of which is the effect of DGs on the optimal load shedding. Load shedding is a remedial action triggered after disturbances such line tripping. In fact, due to the line outage, the power flowing through other lines will increase which may cause protection systems to operate to trip the overloaded lines and in severe cases result in the system collapse. In this paper, a general load shedding method is proposed to prohibit the system from moving toward collapsing and helping the system to restore in the presence of DGs. In the proposed method, firstly the most critical line whose outage leads to the minimum values of stability indices is determined. Then, after putting this line out of service, harmony search algorithm is used to find the minimum amount of load shedding as well as the optimal location of DGs so that the loadability of the system is maximized preventing the system to collapse. The efficacy of the proposed methodology is demonstrated through applying it on IEEE 14 and 30-bus systems using various scenarios.