MATLAB Implementation of Load Frequency Control of Single Area Power System

Introduction: The Hybrid Grid-Solar System for Water Pumping

The model discussed in this post combines both grid and solar power systems to operate an induction motor for water pumping. The goal is to show how solar energy can drive such a system, while the grid can act as a backup source. Using MATLAB, we simulate how the system dynamically switches between power sources, ensuring that the motor operates efficiently under varying conditions.

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Understanding the Grid System Setup

The grid setup uses a standard single-phase AC supply with a voltage of 230V RMS. To convert this AC voltage into DC, we use a diode rectifier. This is followed by an LC filter to remove any ripple from the rectified signal. A boost converter is then used to correct the power factor of the system.

Since the diode rectifier introduces non-linearity into the system (distorting the source current), the boost converter compensates for this by ensuring that the current drawn from the grid is sinusoidal, which improves the overall efficiency of the system.

Power Factor Correction and Control

One of the challenges in grid-connected systems is managing the power factor. When the diode rectifier is used, the current drawn from the grid becomes non-sinusoidal, which can degrade system performance. To address this, we incorporate a power factor correction (PFC) converter.

The PFC converter adjusts the reference current to make the grid current sinusoidal. A control loop continuously measures the source voltage and current, and uses this data to generate a sinusoidal reference current. This ensures that the grid current is in phase with the voltage, improving the overall power factor of the system and optimizing energy use.

Solar PV System Setup

The solar PV system consists of panels with a rating of 210W per panel. The panels operate at a maximum power point voltage of 28.7V and a current of 1.32A, producing around 2300W of power under standard test conditions. A boost converter is used here to extract the maximum possible power from the solar panels using the incremental conductance method.

This solar power is then combined with the grid power to drive the induction motor. When solar power is available, it reduces the amount of grid power needed, making the system more sustainable and energy-efficient.

Induction Motor for Water Pumping

The induction motor used in this system is rated at 2.2 kV and 23,500 RPM, and it is tasked with driving the water pump. The speed of the motor is carefully controlled to simulate the operation of a water pump.

In a typical water pump setup, the torque is directly related to the square of the motor speed. This relationship is modeled in MATLAB to simulate the pump’s real-world performance, allowing for accurate control of the motor’s speed and torque.

Modes of Operation

The system operates in three distinct modes depending on the availability of power from the grid and solar panels:

1. Mode 1: Solar-Only OperationIn this mode, the system operates fully on solar power. When the grid power is unavailable or turned off, the induction motor is powered exclusively by the energy generated by the solar panels. This mode demonstrates how a standalone solar system can drive a water pump when solar energy is abundant.

2. Mode 2: Grid-Only OperationWhen there is no solar power (e.g., during the night or cloudy days), the system switches to grid power. The induction motor continues to operate at a constant speed, and the grid supplies the necessary power. This mode shows how the system ensures uninterrupted operation by relying on the grid.

3. Mode 3: Hybrid Grid and Solar OperationIn Mode 3, both the grid and solar power are used based on availability. If solar power generation is high, it will primarily drive the motor, and the grid will supply power only as needed. This mode ensures that the motor continues to operate optimally, regardless of solar power fluctuations.

Simulation of Mode 1: Solar-Only Operation

In the solar-only mode (Mode 1), the system operates without any power from the grid. The solar panels supply power to the induction motor, and we observe the motor running at a speed of around 600 RPM, with a torque of 2 Newton-Meters. The motor’s current and speed are controlled based on the solar power available, demonstrating the capability of the system to function entirely off solar energy.

Simulation of Mode 2: Grid-Only Operation

When the solar panels are not producing power (such as during low sunlight), the system switches to grid power. In this mode, the induction motor operates at a reference speed of 1,430 RPM. The motor’s speed and current remain stable, and the grid ensures that the motor continues to run without interruption. The power factor of the system improves as the current drawn from the grid becomes sinusoidal, ensuring efficient operation.

Simulation of Mode 3: Hybrid Operation

Mode 3 allows both solar and grid power to be used simultaneously. When the solar power is sufficient, the motor is driven primarily by solar energy. However, if the solar output drops (due to changing sunlight conditions), the grid provides the additional power needed to maintain the motor’s performance. This mode ensures that the water pump continues to operate efficiently, regardless of solar energy fluctuations.

Impact of Solar Irradiation Changes on System Performance

The system’s performance is sensitive to changes in solar irradiation. For example, when the solar radiation decreases, the power output from the PV system drops, and the grid compensates by supplying more power. When the solar radiation increases, the PV system can generate more power, reducing the need for grid support.

By adjusting the solar radiation in the simulation, we can see how the system adapts to varying conditions. When the radiation drops, the motor continues to operate at its rated speed, with the grid supplying the additional power needed. Conversely, when solar radiation increases, the reliance on grid power decreases, and the system operates more sustainably.

Conclusion: A Sustainable Water Pumping Solution

This MATLAB-based simulation demonstrates the effectiveness of a hybrid grid-solar PV system for water pumping. By switching between solar power and grid power as needed, the system ensures continuous operation while optimizing energy use. This approach not only reduces dependence on the grid but also promotes the use of renewable solar energy for sustainable water pumping applications.

As solar technology advances and grid integration improves, such hybrid systems will become more efficient and cost-effective, paving the way for more sustainable agricultural and water management practices.