Microgrid is defined as the cluster of multiple distributed generators (DGs) such as renewable energy sources that supply electrical energy. The connection of microgrid is in parallel with the main grid. When microgrid is isolated from remainder of the utility system, it is said to be in intentional islanding mode. In this mode, DG inverter system operates in voltage control mode to provide constant voltage to the local load. During grid connected mode, the Microgrid operates in constant current control mode to supply preset power to the main grid. The main contribution of this paper is summarized as
- Design of a network based control scheme for inverter based sources, which provides proper current control during grid connected mode and voltage control during islanding
- Development of an algorithm for intentional islanding detection and synchronization controller required during grid
- Dynamic modeling and simulation are conducted to show system behavior under proposed method using
From the simulation results using Simulink dynamic models, it can be shown that these controllers provide the microgrid with a deterministic and reliable connection to the grid.
- Distributed generation (DG)
- grid connected operation
- intentional islanding operation and islanding detection
Fig.1. Dynamic model of microgrid with controller.
EXPECTED SIMULATION RESULTS:
Fig. 2. Line Current without current controller
Fig.3. Line Voltage without Voltage controller
Fig. 4. Line Voltage with voltage controller
Fig. 5. Phase voltage waveform (a) without re-closure controller (b) with re-closure controller
Fig. 6. Synchronization for grid reconnection (a) without re-closure algorithm (b) with re-closure algorithm
Current and voltage Control techniques have been developed for grid connected and intentional islanding modes of operation using PI controllers. An intentional islanding detection algorithm responsible for switching between current control and voltage control is developed using logical operations and proved to be effective. The reconnection algorithm coupled with the synchronization controller enabled the DG to synchronize itself with the grid during grid reconnection. The performance of the microgrid with the proposed controllers and algorithms has been analyzed by conducting simulation on dynamic model using SIMULINK. The simulation results presented here confirms the effectiveness of the control scheme.
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