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Grid connected and Islanded mode operation of Microgrid

Grid connected and Islanded mode operation of Microgrid

Simulink Model Overview

In this video, we showcase a Simulink model developed to test microgrid operations in both grid-connected and islanded modes. The microgrid consists of several components:

  • Wind Energy Systems

  • PV Power Generation

  • Battery Storage

  • Inverter

  • AC Load

  • DC Load

  • Grid System

Wind Conversion System Details

The wind energy system includes:

  • Wind Turbine

  • Permanent Magnet Synchronous Generator (PMSG)

  • Rectifier

  • Boost Converter

The boost converter is used to extract maximum power from the wind energy conversion system using Maximum Power Point Tracking (MPPT). We employ a Perturb and Observe (P&O) method for MPPT. The output of the boost converter is connected to the DC bus, maintaining a voltage of 400V. The wind turbine generator can generate up to 2.78 kW at rated conditions.

Solar PV System Details

The solar PV system is rated at 2 kW under standard irradiation and temperature conditions. It is connected to the DC bus through a boost converter controlled by an incremental conductance MPPT. The DC load is set to 1000W, with the DC bus voltage maintained at 400V.

Battery Storage System Details

The battery system consists of a 12V to 22V battery with a 48 Ah rating. The charge state is set at 50%. A bi-directional converter, controlled by a voltage controller, maintains the DC bus voltage at 400V.

Grid Inverter Details

The grid inverter is a single-phase inverter with an LCL filter. There are two loads: one 1000W and another 1400W, totaling 2400W. Initially, only the 1000W load is connected, and the grid operates at 230V with a 50Hz frequency.

Islanded Mode Control

In islanded mode, the inverter control system maintains the load voltage. A reference sine wave and cosine wave are generated, and the actual load voltage and current are measured. These are converted to DQ form, and reference currents are generated. The control output, after processing through a PI controller, is used to generate pulses for the inverter.

Grid Connected Mode Control

In grid-connected mode, control is based on the PV current and state of charge (SOC) of the battery. Power is exchanged with the grid based on these parameters. The system measures grid voltage, converts it using a Phase-Locked Loop (PLL), and generates modulating signals to control the inverter.

Simulation Results

Grid Connected Mode

During grid-connected mode, the PV power varies according to irradiation. This affects the battery charging current. Initially, the AC load is 1000W, and power is drawn from both the grid and the microgrid. After 2 seconds, the AC load increases to 2400W, and wind power generation changes, resulting in power adjustment from the grid.

Islanded Mode

Switching to islanded mode disconnects the grid, and the microgrid independently supplies power to the loads. Transient behavior is observed, and the system stabilizes within 0.3 seconds. The battery switches to charging mode to compensate for the lack of grid power.

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