Modified centralized ROCOF based load shedding scheme in an islanded distribution network

•Two new centralized adaptive under frequency load shedding methods are proposed.•DG units operation and loads willing to pay (WTP) are considered.•The objective is to minimize the resulting penalties of the load shedding.

This paper presents two centralized adaptive under frequency load shedding (UFLS) methods based on loads willing to pay (WTP) and new objective function. The objective function is considered to minimize load shedding penalties that are paid by distribution network operator (DNO), using optimal algorithm. Maintaining DG units in an islanded distribution system is proposed to prevent system blackout. One of the most important protection schemes to prevent a system blackout is UFLS method. In our proposed UFLS method, amount of load shedding is dependent on loads priority table and intensity of event. Loads priority table is formed, using rate of change of frequency of loads (ROCOFL) indices. Proposed techniques apply the amount of loads active power every few minutes to update loads priority table. These proposed UFLS methods are implemented on the 14-bus Danish distribution system in 3 different load scenarios and are compared with a conventional approach.