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.

This paper presents a wind turbine generation system based on the Z-source inverter with maximum boost control. The proposed system can boost and generate the desired output voltage efficiently when the low voltage of the generator is introduced according to the low wind speed. Moreover, when the wind speed is high, providing higher voltage, the system can also work like the traditional inverter without the boost condition. The proposed system has high performance, minimal component count, increased efficiency and reduced cost. These outstanding performance attributes make the proposed system suitable for the wind turbine distributed generation systems.

Intentional islanding describes the condition in which a microgrid, 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 (or constant power) control mode in order to provide a pre-set 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 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 to implement intentional islanding operation of microgrids. The described method proposes two control algorithms, one for gridconnected operation and the other for intentional islanding operation.

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