Abstract
System reliability enhancement of distributed generations (DGs) without aid of fast switches (FSs) is not possible. FSs are responsible for disconnecting unfaulted islands from faulty network to reduce energy not supplied (ENS). Directional overcurrent relays (DOCRs) are employed to send trip signals to FSs. In most of the DGs optimal allocation studies, the switches are assumed to operate correctly. This assumption might not be correct due to the delayed operation of the DOCRs. Few studies offer restricting minimum allowable size of DGs or allowable location of DOCRs to guarantee correct operation of DOCRs. These additional constraints limit the search space which causes nonoptimal answers. Here, the impact of actual operation of DOCRs is considered directly in calculation of ENS and hence in the final objective function. Also, a modified formulation for ENS in order to include cases where DGs capacity is not sufficient for supplying island loads is developed. Simultaneous allocation of DGs, FSs, and DOCRs to minimize cost of energy losses, ENS, and environmental costs are proposed. A multistate model that combines all possible operating conditions of DGs and load levels is utilized. Different cases are simulated in 33-bus, 69-bus, and 118-bus systems to evaluate the proposed method.
Published Version
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