Energy Management in PV, Fuel Cell, and Battery System Using MATLAB
- lms editor
- 1 day ago
- 3 min read
In modern renewable energy systems, integrating multiple energy sources such as solar PV, fuel cells, and batteries is crucial for reliable and uninterrupted power supply. This blog post explains the modeling and control of a hybrid energy management system using MATLAB/Simulink. The system includes a PV array, a battery bank, and a fuel cell unit, all connected to a DC bus and an AC load via a single-phase inverter.
1. PV Panel Configuration and MPPT Control
The system uses eight 250 W PV panels, connected in series to produce a total of 2000 W. Each panel operates at around 30.7 V, leading to a combined voltage of approximately 245.6 V. The PV array connects to the DC bus through a boost converter.
To extract maximum power from the solar panels under varying irradiance, an Incremental Conductance (INC) Maximum Power Point Tracking (MPPT) algorithm is employed. It takes voltage and current as inputs, calculates the duty cycle, and adjusts the switching of the boost converter to ensure optimal PV output.
2. Battery Integration and Bidirectional Power Flow
The battery is connected to the DC bus using a bidirectional DC–DC converter. The battery system is rated at 300 V and 48 Ah. The converter is controlled by a voltage-current loop:
The DC bus voltage is sensed and compared with a reference voltage (400 V).
A PI controller processes this error to generate a battery reference current.
This reference current is compared with the actual battery current.
A second PI controller then generates the gating pulses for the converter.
This structure supports both battery charging and discharging, helping to maintain constant DC bus voltage and supply power during solar shortages.
3. Fuel Cell Backup System and Control Strategy
The fuel cell in the system serves as a backup power source. Its nominal power rating is 4 kW (with a maximum of 7 kW). It typically operates at 220 V and 20 A, and under full load at 200 V and 35 A.
The fuel cell is connected to the DC bus through a boost converter controlled by a current control method. Importantly, the fuel cell only activates under the following two conditions:
The PV power falls below 600 W.
The battery's state of charge (SOC) drops below 30%.
Once these criteria are met, the fuel cell starts supplying power to both DC and AC loads and may also charge the battery if excess energy is available.
4. AC Load Supply via Single-Phase Inverter
An inverter converts DC power to AC to feed an AC load. This inverter is connected through an LC filter to smooth the waveform. The control strategy involves:
Measuring the inverter current and load voltage.
Generating a reference voltage in D–Q (direct-quadrature) coordinates.
Converting actual AC load values to D–Q form and comparing them with reference DQ values.
Using voltage PI controllers to generate the current reference.
The current reference is compared with actual inverter current.
A current PI controller processes this and generates a modulating signal, which is passed to a sine generator.
The generator outputs four PWM pulses to control the inverter switches.
This ensures stable AC voltage and current delivery to the load.
5. System Testing Under Variable Irradiance
The model simulates solar irradiance variations using scaling factors like 1, 0.8, 0.5, and 0.3, corresponding to 1000 W/m², 800 W/m², etc. As irradiance changes, the PV output power adjusts accordingly:
At full irradiance (1000 W/m²), PV generates around 2000 W.
PV voltage remains around 245 V, and current varies with irradiance.
Battery current becomes negative during charging, indicating energy storage.
Fuel cell remains inactive when PV and battery supply sufficient power.
When PV drops below 600 W and SOC falls below 30%, the fuel cell activates.
It then powers the DC and AC loads and charges the battery if surplus energy exists.
6. Summary and Observations
This MATLAB/Simulink model demonstrates efficient hybrid energy management using a solar PV system, battery storage, and fuel cell backup. Key highlights include:
Intelligent source switching based on load demands and resource availability.
Reliable power delivery to both AC and DC loads.
Stable DC bus and AC load voltage regulation.
Dynamic energy routing during fluctuations in solar energy input.
Such hybrid systems are pivotal for off-grid or grid-assisted clean energy solutions, ensuring power reliability even during low-sunlight conditions.
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