Intentional islanding describes the condition in which a microgrid or a portion of the power grid, which consists of a load and a distributed generation (DG) system, is isolated from the remainder of the utility system. In this situation, it is important for the microgrid to continue to provide adequate power to the load. Under normal operation, each DG inverter system in the microgrid usually works in constant current control mode in order to provide a preset power to the main grid. When the microgrid is cut off from the main grid, each DG inverter system must detect this islanding situation and must switch to a voltage control mode. In this mode, the microgrid will provide a constant voltage to the local load. This paper describes a control strategy that is used to implement grid-connected and intentional-islanding operations of distributed power generation. This paper proposes an intelligent load-shedding algorithm for intentional islanding and an algorithm of synchronization for grid reconnection.

1. ELECTRICAL PROJECTS USING MATLAB/SIMULINK
Gmail: asokatechnologies@gmail.com, Website: http://www.asokatechnologies.in
0-9347143789/9949240245
Control for Grid-Connected and Intentional Islanding
Operations of Distributed Power Generation
For Simulation Results of the project Contact Us
Gmail: asokatechnologies@gmail.com, Website: http://www.asokatechnologies.in
0-9347143789/9949240245
ABSTRACT:
Intentional islanding describes the condition in which a microgrid or a portion of the power grid,
which consists of a load and a distributed generation (DG) system, is isolated from the remainder
of the utility system. In this situation, it is important for the microgrid to continue to provide
adequate power to the load. Under normal operation, each DG inverter system in the microgrid
usually works in constant current control mode in order to provide a preset power to the main
grid. When the microgrid is cut off from the main grid, each DG inverter system must detect this
islanding situation and must switch to a voltage control mode. In this mode, the microgrid will
provide a constant voltage to the local load. This paper describes a control strategy that is used to
implement grid-connected and intentional-islanding operations of distributed power generation.
This paper proposes an intelligent load-shedding algorithm for intentional islanding and an
algorithm of synchronization for grid reconnection.
KEYWORDS:
1. Distributed generation (DG)
2. Grid-connected operation
3. Intentional-islanding operation
4. Islanding detection
5. Load shedding
6. Synchronization
SOFTWARE: MATLAB/SIMULINK

2. ELECTRICAL PROJECTS USING MATLAB/SIMULINK
Gmail: asokatechnologies@gmail.com, Website: http://www.asokatechnologies.in
0-9347143789/9949240245
For Simulation Results of the project Contact Us
Gmail: asokatechnologies@gmail.com, Website: http://www.asokatechnologies.in
0-9347143789/9949240245
BLOCK DIAGRAM:
Fig. 1. Schematic diagram of the grid-connected inverter system.

3. ELECTRICAL PROJECTS USING MATLAB/SIMULINK
Gmail: asokatechnologies@gmail.com, Website: http://www.asokatechnologies.in
0-9347143789/9949240245
EXPECTED SIMULATION RESULTS:
Fig. 2. From grid-connected to intentional-islanding operation.
Fig. 3. Synchronization for grid reconnection.
For Simulation Results of the project Contact Us
Gmail: asokatechnologies@gmail.com, Website: http://www.asokatechnologies.in
0-9347143789/9949240245

4. ELECTRICAL PROJECTS USING MATLAB/SIMULINK
Gmail: asokatechnologies@gmail.com, Website: http://www.asokatechnologies.in
0-9347143789/9949240245
Fig. 4. Phase voltage (top) without and (bottom) with the synchronization
algorithm.
Fig. 5. Phase voltage Va without the load-shedding algorithm.
For Simulation Results of the project Contact Us
Gmail: asokatechnologies@gmail.com, Website: http://www.asokatechnologies.in
0-9347143789/9949240245

5. ELECTRICAL PROJECTS USING MATLAB/SIMULINK
Gmail: asokatechnologies@gmail.com, Website: http://www.asokatechnologies.in
0-9347143789/9949240245
Fig. 6.Phase voltage Va with the load-shedding algorithm.
For Simulation Results of the project Contact Us
Gmail: asokatechnologies@gmail.com, Website: http://www.asokatechnologies.in
0-9347143789/9949240245
CONCLUSION:
Through this paper, the control, islanding detection, load shedding, and reclosure algorithms
have been proposed for the operation of grid-connected and intentional-islanding DGs. A
controller was designed with two interface controls: one for grid-connected operation and the
other for intentional islanding operation. An islanding-detection algorithm, which was
responsible for the switch between the two controllers, was presented. The simulation results
showed that the detection algorithm can distinguish between islanding events and changes in the
loads and can apply the load-shedding algorithms when needed. The reclosure algorithm causes
the DG to resynchronize itself with the grid. In addition, it is shown that the response of the
proposed control schemes is capable of maintaining the voltages and currents within permissible
levels during grid connected and islanding operation modes. The experimental results showed
that the proposed control schemes are capable of maintaining the voltages within the standard
permissible levels during grid-connected and islanding operation modes. In addition, it was
shown that the reclosure algorithm causes the DG to resynchronize itself with the grid.

6. ELECTRICAL PROJECTS USING MATLAB/SIMULINK
Gmail: asokatechnologies@gmail.com, Website: http://www.asokatechnologies.in
0-9347143789/9949240245
For Simulation Results of the project Contact Us
Gmail: asokatechnologies@gmail.com, Website: http://www.asokatechnologies.in
0-9347143789/9949240245
REFERENCES:
[1] D. Jayaweera, S. Galloway, G. Burt, and J. R. McDonald, “A sampling approach for
intentional islanding of distributed generation,” IEEE Trans. Power Syst., vol. 22, no. 2, pp. 514–
521, May 2007.
[2] J. M. Guerrero, J. C. Vásquez, J. Matas, M. Castilla, and L. García de Vicuña, “Control
strategy for flexible microgrid based on parallel lineinteractive UPS systems,” IEEE Trans. Ind.
Electron., vol. 56, no. 3, pp. 726–736, Mar. 2009.
[3] P. Fuangfoo, T. Meenual,W.-J. Lee, and C. Chompoo-inwai, “PEA guidelines for impact
study and operation of DG for islanding operation,” IEEE Trans. Ind. Appl., vol. 44, no. 5, pp.
1348–1353, Sep./Oct. 2008. 156 IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS,
VOL. 58, NO. 1, JANUARY 2011
[4] E. Carpaneto, G. Chicco, and A. Prunotto, “Reliability of reconfigurable distribution systems
including distributed generation,” in Proc. Int. Conf. PMAPS, 2006, pp. 1–6.
[5] IEEE Recommended Practice for Utility Interface of Photovoltaic (PV) Systems, IEEE Std
929-2000, 2000, p. i.