Service Restoration Using Different Types of DGs Considering Dynamic Characteristics

After major outages of distribution system, critical loads on distribution feeders can be locally restored by multiple types of distributed generators (DGs) before the utility power is available. However, due to the low inertia and small capacity of DGs, it may cause large disturbances when conducting switching operations, which may cause failure of restoration. In addition, dynamic characteristics of different types of DGs are different and should be considered in implementation of restoration strategies. This paper proposes a two-step restoration method to determine the sequence of switching operations, including startup of DGs, line switching operations and load pick-up, to mitigate transients caused by the switching operations. First, the operating point of the post-restoration system is identified by formulating the problem as a relaxed mixed-integer second-order conic program. Then, a restoration rule is proposed to determine the sequence of switching operations to reach the operating point. The entropy weight method is used to find the sequence of the startup of DGs considering the dynamic features of each DG. A 32-bus test feeder with several types of DGs is utilized to demonstrate the effectiveness of the proposed method.