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Grid Connected and Islanded Mode Operation of Microgrid

Grid Connected and Islanded Mode Operation of Microgrid

Welcome to LMS Solution! In today's discussion, we'll explore the operation of microgrids in both grid-connected and islanded modes. Our Simulink model is designed to test the microgrid's functionality, incorporating elements such as wind energy systems, PV power generation, battery storage, inverters, AC and DC loads, and grid connections.


Wind Energy System Details

The wind energy system consists of a wind turbine, a permanent magnet synchronous generator (PMSG), a rectifier, and a boost converter for maximum power point tracking (MPPT). The wind generator's output is connected to a DC bus, maintaining a voltage of 400 volts.


Solar PV System Details

The solar PV system, with a capacity of 2 kilowatts, employs a boost converter controlled by incremental conductance MPPT. The DC load is set at 1000 watts, maintaining the DC bus voltage at 400 volts.


Battery Storage System Details

A 22-volt battery with a 48 Ah rating is employed and connected to the DC bus through a bidirectional converter. The voltage controller maintains the DC bus voltage at 400 volts.


Grid Inverter Details

A single-phase inverter with an LCL filter is used, along with two loads totaling 2400 watts. The grid system operates at 230 volts and 50 Hz.


Microgrid Operation Modes

Island Mode Operations

In islanded mode, the inverter is controlled based on measured load voltage, generating a reference sine wave and cosine wave. The actual load voltage and current are converted to a DQ form for comparison. The PI controller generates modulating signals for inverter control.


Grid Connected Mode Control

In grid-connected mode, the inverter control depends on agreements between the microgrid and the grid, considering PV current and battery state of charge. The control logic determines whether power is drawn from the grid or supplied to it.


Simulation Results

Grid Connected Mode

  • PV power varies with irradiation, influencing battery charging.

  • Wind power and battery charging changes with load variations.

  • AC load increases from 1000 to 2400 watts after 2 seconds.

  • Power is shared between microgrid and grid based on agreements.


Islanded Mode

  • Transient occurs during the mode switch from grid-connected to island.

  • Wind and PV power supply microgrid loads in the absence of the grid.

  • The battery continues charging as the microgrid supplies power to both AC and DC loads.

Conclusion

Understanding microgrid operations in grid-connected and islanded modes is crucial for efficient energy management. The flexibility of microgrids allows them to adapt to varying conditions, providing a sustainable and reliable power supply.

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