Matlab simulation of Off grid Solar PV Battery system
- lms editor
- 18 hours ago
- 4 min read
Off-grid solar systems are designed to operate independently of the utility grid, and they are ideal for remote locations where grid access is unavailable. The system in focus includes solar panels, a battery storage system, a bi-directional converter, an inverter, and a backup generator, with an intelligent power management strategy in place.
Key Components of the Off-Grid Solar PV System
An off-grid solar PV system consists of several critical components:
Solar Panels: In this simulation, the system uses solar panels rated at 250 watts each, with a total output of 2000 watts when combined. The panels operate at a voltage of 30.9 V at maximum power point (MPP), and the system consists of 4 panels in series per string, with two strings in parallel.
Battery Storage: The battery in this system has a capacity of 200 Ah at 40V. It plays an essential role in storing excess solar power for later use, ensuring the availability of power even when the sun isn’t shining.
Inverter: The single-phase inverter is used to convert DC (direct current) power from the solar panels and battery into AC (alternating current) power for use in home appliances. Voltage and current control are applied to regulate the inverter’s output.
Bi-Directional Converter: This component allows power to flow from the solar panels to charge the battery, as well as from the battery to the AC load when the solar power is insufficient.
Maximum Power Point Tracking (MPPT)
The system employs a Maximum Power Point Tracking (MPPT) algorithm to ensure that the solar panels operate at their most efficient point. As solar irradiance changes, the system dynamically adjusts the panel's operating conditions to extract the maximum power possible. This is achieved through a Particle Swarm Optimization (PSO)-based MPPT algorithm, which helps in optimizing the battery charging process.
Power Flow and Energy Management
The off-grid system operates by first using the solar PV power to supply the AC load (e.g., home appliances). Any excess power that the solar panels generate is used to charge the battery. In the case of insufficient solar power (such as during cloudy weather or nighttime), the battery begins to supply power to the AC load. If both the solar power and battery power are low, the system can switch to a backup generator or AC grid input to maintain the power supply.
Backup Power and Battery Charging
To ensure the system remains operational even in periods of low solar generation or a depleted battery, the system can connect to a backup generator or an AC grid input. When the battery voltage becomes too low, the generator kicks in to provide power, both to the AC load and to recharge the battery. The rectifier and LC filter convert AC power into DC, which is used to charge the battery. The system also uses a bi-directional converter to facilitate power flow between the battery and the inverter.
The Role of the Inverter
The inverter plays a crucial role in converting the DC power from both the solar panels and the battery into AC power for household use. The inverter’s output is controlled by voltage and current regulation, which ensures stable and efficient energy conversion. The DQ form reference method is used to control the inverter voltage, which enables precise power output management.
The inverter’s current is also compared to a reference value to generate modulation signals that control the power conversion process. This approach ensures that the inverter functions efficiently, converting DC to AC with minimal losses.
Simulating the System in MATLAB
The simulation begins with a solar panel irradiation set to 1000 W/m². At this level of irradiation, the solar panels generate approximately 1700 watts of power. During this period, excess power is directed to charge the battery, and the AC load is continuously supplied with power from the solar panels.
As the solar irradiation is reduced to zero (e.g., during cloudy weather or nighttime), the system switches to the battery for power. The battery starts supplying power to the AC load, and its current shifts from a negative to a positive value, indicating that it is discharging.
The Importance of Backup Generation
In the event that the battery is also depleted, the system can incorporate a generator set to supply power to both the AC load and recharge the battery. When the generator is activated, both the voltage and current levels of the system rise, ensuring that power remains available for the AC load. This backup system is critical for ensuring the continuous operation of off-grid systems in remote locations.
Adjusting for Changing Irradiation Levels
As irradiation levels fluctuate, the power output from the solar panels changes accordingly. If the irradiation increases, the solar panels generate more power, which reduces the reliance on the backup generator and allows the battery to charge. Conversely, when irradiation levels drop, the system relies more heavily on the battery and, if necessary, the backup generator.
Conclusion
The off-grid solar PV system with battery storage offers a sustainable, efficient, and flexible solution for energy independence. With the integration of solar panels, batteries, inverters, and backup generators, this system can ensure a continuous supply of power in remote locations. The intelligent MPPT and battery charging control algorithms optimize energy generation and storage, allowing for reliable operation regardless of weather conditions. By simulating this system in MATLAB, we can understand how these components interact and manage energy flows, ensuring efficient power management for off-grid applications.
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