Control for Grid-Connected and
Intentional Islanding
Operations of Distributed Power
Generation
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
BLOCK
DIAGRAM:
Fig. 1. Schematic diagram of the
grid-connected inverter system.
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.
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TRANSACTIONS ON INDUSTRIAL ELECTRONICS, VOL. 58, NO. 1, JANUARY 2011
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