研究目的
To develop a low-cost microcontroller-based PV source emulator for testing the static and dynamic performance of PV systems under variable operating and environmental conditions.
研究成果
The proposed PV source emulator faithfully reproduces the characteristic of the simulated photovoltaic module with an average and maximum error of, respectively ±1% and ±5%. The fast dynamic response of the system (150 ms) allows the testing of very fast MPPTs algorithms, thus overcoming the main limitations of state-of-art PV source emulator that is unable to respond to the quick variation of the load.
研究不足
The heat dissipation over the transistor used in linear region reduces the efficiency of the system. However, for the purpose of this work, such drawback is considered acceptable, allowing the reduction of the Bill of Material of the board cost to less than 20 dollars and providing, at the same time, an accurate yet simple method for emulating photovoltaic sources.
1:Experimental Design and Method Selection:
The methodology involves using a low-cost current generator and a single MOSFET converter to reproduce the exact amount of current predicted by the PV model for the actual load conditions. The I–V characteristic is calculated in real-time using a single diode exponential model under variable and user-selectable operating conditions.
2:Sample Selection and Data Sources:
The Simulink model of the photovoltaic module is based on the single diode circuit model of the Solarex MSX-60 photovoltaic module.
3:List of Experimental Equipment and Materials:
The control logic and the mathematical model of the photovoltaic module have been implemented on an STM32F401RE microcontroller (STMicroelectronics), mounted on the STM32 Nucleo board. A specifically made shield board attached on the Nucleo board implements the necessary hardware that allows to control the MOSFET and sense current and voltage.
4:Experimental Procedures and Operational Workflow:
The microcontroller firmware configures and initializes the microcontroller peripherals needed to interact with the PV source emulator hardware, and implements the photovoltaic emulator code. The internal 12-bit ADC is used to measure the voltage on the load through a voltage divider, and the current through a shunt resistor of 10 m? and a current sense amplifier INA283 (Texas Instruments, Dallas, TX, USA) with a gain of 200 V/V.
5:Data Analysis Methods:
The absolute deviation value between the simulated I–V characteristic and the one reproduced by the photovoltaic emulator has been calculated to validate the accuracy of the system.
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Agilent U1272A digital multimeter
U1272A
Agilent
Used to monitor and acquire the signals.
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LeCroy WaveSurfer 343 oscilloscope
WaveSurfer 343
LeCroy
Used to monitor and acquire the signals.
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STM32F401RE microcontroller
STM32F401RE
STMicroelectronics
Implements the control logic and the mathematical model of the photovoltaic module.
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STM32 Nucleo board
Nucleo
STMicroelectronics
Mounts the STM32F401RE microcontroller.
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TC4424A driver
TC4424A
Microchip
Produces a PWM signal between 0 V and 8 V.
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IRF820 MOSFET
IRF820
International Rectifier Semiconductors
Used in linear mode to control the current.
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INA283 current sense amplifier
INA283
Texas Instruments
Measures the current through a shunt resistor.
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Jolight KL824-04 power supply
KL824-04
Jolight
Delivers 700 mA with a voltage range up to 30 V.
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Bias Power BPSX 1-08-50
BPSX 1-08-50
Bias Power
Converts 230 V AC main voltage to 8 V and 5 V DC voltage.
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