Intentional Islanding Solution Based on Modified Discrete Particle Swarm Optimization Technique Abstract— Implementation of intentional islanding can prevent the power system blackout by partitioning the system into feasible sets of islands. The main challenge in determining the optimal islanding solution is the selection of transmission lines to be disconnected (cutsets) to form islands. The islanding solution must be the optimal solution and should not destabilize or cause the system to collapse. Therefore, this work developed a Modified Discrete Particle Swarm Optimization (MDPSO) with three- stages mutation technique to determine the optimal intentional islanding solution. An initial solution based heuristic method is used to assists the MDPSO technique to find the optimal islanding solution with minimal power disruption as its objective function. The post- islanding generation-load balance and transmission line power flow analysis are assessed to ensure the steady state stability is maintained in each island. The load shedding algorithm is carried out if generation-load balance criteria are violated. The proposed technique is tested on a modified IEEE 30-bus and IEEE 39-bus system. The results obtained show that the proposed technique produces an optimal intentional islanding solution with lower power flow disruption compared to other existing methods. Keywords—intentional islanding, MDPSO technique, minimal power flow disruption, heuristic method I. I NTRODUCTION Severe disturbances in transmission lines or line outages can cause sequence tripping which could result in partial or total power system blackout. In most cases, the cascading tripping of transmission lines will cause the occurrence of unintentional islanding (known as passive islanding). Unintentional islanding which are usually uncontrollable, always produces unbalanced islands [1]. These unbalanced islands will subsequently lead to catastrophic system blackout due to its inability to maintain stable system operation. Therefore, intentional islanding (also known as network splitting) is preferred in order to prevent passive islanding which can lead to total system blackout. Intentional islanding is performed to partition the system into few standalone islands. The crucial part in implementing intentional islanding is determining the proper set of transmission lines that needs to be disconnected to form the islands. The process becomes more challenging when the system size is increases as the search space of possible islanding solution increases proportionally. The implementation of intentional islanding in transmission lines has drawn a great attention in recent years. Various approaches have been proposed by previous researchers for intentional islanding implementation. One of the earlier method is the graph partitioning approach using ordered binary decision diagrams (OBDD) method introduced in [1]-[2] to find proper islanding strategies. A generator grouping method using slow coherency approach is introduced in [3]. The proposed approach identifies the weakest connection in the network to determine the proper splitting solution. This method is then improved in [4] using minimal flow-minimal strategy determination approach which leads to the islanding solution with less number of transmission line cutsets. A numerical approach (linear programming) using piecewise linear AC power flow is introduced in [5] to find a proper islanding solution. Voltage and reactive power are the main constraints considered in forming the islands and mixed integer linear programming (MILP) [6] is used to find the possible islanding solutions. Other technique such as heuristic technique using ant mechanism is proposed in [7] where the probabilistic search approach is used to find the best islanding solution. Besides, meta-heuristic approach has been proposed by the authors in [8]-[9] to reduce the computational complexity in obtaining the islanding solution. Different from previous work, this paper proposes a Modified Discrete Particle Swarm Optimization (MDPSO) technique to find the optimal islanding solution using minimum power flow disruption as its objective function. Intentional islanding is a discrete problem in nature; therefore discrete optimization approach is more suitable to use in this study. The graph theory approach is utilized in this work to represent the physical connection of power system network during the islanding implementation. In order to narrow down the huge search space of possible islanding solution to the smaller scope, heuristic methods is used to aid the optimization algorithm in finding an optimal islanding solution. Other constraints such as generation- load balance, generators coherency and transmission line capacity. Subsequent to islanding execution, the power imbalance in each island is calculated, network reordering is carried out and load shedding is executed if necessary. The power flow analysis is also performed to ensure the line loading capacity is not violated during islanding solution. proportionally. N.Z. Saharuddin Faculty of Electrical Engineering Universiti Teknikal Malaysia Melaka Melaka, Malaysia Institute of Power Engineering Universiti Tenaga Nasional Selangor, Malaysia nurzawani@utem.edu.my I. Z. Abidin Institute of Power Engineering Universiti Tenaga Nasional Selangor, Malaysia Izham@uniten.edu.my Hazlie bin Mokhlis Department of Electrical Engineering Universiti Malaya Kuala Lumpur, Malaysia hazli@um.edu.my 2018 IEEE 7th International Conference on Power and Energy (PECon) 399