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Tracker system working principle and hardware design

2022-02-09 14:45:38

The light intensity of the sun is changing in real time with the weather, when the light intensity is good, the photoelectric sensor is more sensitive to light, then choose automatic tracking mode (i.e. photoelectric tracking); when the weather is bad, the light intensity is weak, the diffuse reflection of the aggravation of the photoelectric sensor produces great interference, in this case choose fixed tracking mode. The sensor signal is processed through a specific circuit and input into the microcontroller, after the processing of the internal program of the microcontroller to get the sun position deviation angle, and then drive the motor to achieve accurate tracking of the sun.

Selection of the main control chip

The AT89C51 microcontroller is used as the core of the system. The main function of this unit is to receive the signal issued by the photoelectric detection circuit, according to which the signal is used to control the motor drive circuit, thus realizing the control of the motor and thus the tracking of the sun. The following is a brief introduction to the AT89C51 type microcontroller.

The AT89C51 microcontroller is widely used for its powerful functions, which are as follows:

①4KB rewritable program Flash memory.

②All static operation: 0~24Hz.

③3-level program memory secrecy.

④128X8-bit internal RAM.

⑤32 programmable I/O lines.

⑥Two 16-bit timers/counters.

⑦5 interrupt sources.

⑧Programmable serial channels.

Tracker system working principle and hardware design 1

Design of power controller

An important part of the overall system is the controller, whose performance directly affects the life of the system, especially the life of the storage pool. There are two basic types of controllers in PV systems: split controllers and series controllers. A split controller is used to change or split the battery charging current and has a large heat sink to dissipate the heat generated by the excess current. Most tap controllers are designed for systems with less than 30A of current. Series controllers disconnect the charging current by disconnecting the PV array. There are many different types of split and series controllers, but in general both types of controllers can be designed for single or multi-stage operation. Single-stage controllers disconnect the array only when the voltage reaches its maximum level; while multi-stage controllers allow charging at different currents as the battery approaches full charge, which is an efficient charging method. As the battery approaches the full charge state, its internal resistance increases and it is charged with a low current, which reduces energy loss.

When the system works, the controller realizes the main functions such as management of system working status, management of remaining battery capacity, MPPT (maximum photovoltaic power tracking) charging control of the battery, switching control of main power and backup power and temperature compensation of the battery. The controller uses industrial-grade (microcontroller) MCU as the main controller, through the measurement of the ambient temperature, the battery and solar cell module voltage, current and other parameters of the detection judgment, control MOSFET devices (metal oxide semiconductor effect tube) to turn on and off, to achieve a variety of control and protection functions, and the battery to play a role in overcharge protection, over discharge protection. Other additional functions such as light control switch, time control switch should be the controller's auxiliary functions. The controller is the key component of the whole system acting as a manager, and its biggest function is the overall management of the battery. As the battery has voltage self-recovery characteristics, when the battery is in the over-discharge state, the controller cut off the load, and then the battery voltage recovery, so as to play a role in the protection of the battery.

The design control section circuit contains: DC-DC converter circuit, data acquisition circuit, A/D converter circuit, microcontroller control circuit and status display section. The design of the ATMEL series AT89C51 microcontroller as the control center of the combination of hardware and software, the use of two series resistors connected in parallel at both ends of the battery, the battery, solar cell voltage sampling in the form of voltage division, sent to the A/D converter to get a digital signal voltage value, and then the signal is sent to the microcontroller for processing. Microcontroller output through the optocoupler circuit to control the MOSFET tube. Control MOSFET tube conduction is pulse width modulation (PWM), according to the programmed load changes to modulate the bias of the MOSFET tube gate to achieve the switching function. According to the program design when the detected battery voltage is lower than 12V, the charging mode is even charging, MOSFET tube Q1 is fully on state, that is, the pulse duty cycle of on is maximum; when the detected battery voltage is 12~14.5V, the charging mode is floating charging, MOSFET tube Q1 on and off duty cycle becomes smaller; when the detected battery voltage is equal to 15V, MOSFET tube Q1 cutoff charging stop. MOSFET tube Q1 cutoff charging stop. When the detected battery voltage is lower than 10.8V, MOSFET tube Q2 closes to stop the discharge.

Tracker system working principle and hardware design 2

Program control part

The whole program design includes photoelectric detection tracking mode, sun fixed track tracking mode, clock part, display part. That is, after power on, power on reset, the system enters the enable interrupt handler and enters the waiting mode; if it is daytime, the system will judge whether it is sunny or cloudy through the photo diode, when it is sunny, the system enters the photoelectric tracking mode, when it is cloudy, the system enters the sun fixed track tracking mode.

The detection of day or night is judged by INT0. As long as INT0 detects a low potential, the system enters the interrupt service program, i.e. the waiting state. And detecting sunny or cloudy is achieved by I/O port query, although the I/O port query method needs to constantly detect the I/O level change, the microcontroller runs fast enough to achieve the desired effect.

In the phototracking mode:The system first detects whether the photodiode located in the center of the disk is exposed to light, which is determined by detecting the high and low potentials of the pins of the microcontroller corresponding to the photodiode. If the system detects that the sensor is illuminated, the software control system delays for 15 min. if the system detects that the sensor is not illuminated, then the system detects each of the four photodiodes around it, and if it detects that the pin of the microcontroller corresponding to the photodiode is low, it means that the photodiode is illuminated, and then the system commands the motor corresponding to this photodiode to move in the specified direction. The system then commands the motor corresponding to this photodiode to rotate in the specified direction until the sensor is illuminated, thus completing the purpose of tracking the sun.

Tracker system working principle and hardware design 3

In the sun fixed track tracking mode, when it is cloudy, the photoelectric tracking mode cannot track accurately, so the sun fixed track tracking mode is enabled for tracking. This mode is only related to the time and location, and is not affected by the sunlight intensity, which exactly makes up for the defect that the photoelectric tracking mode cannot track properly on cloudy days.

The interrupt service program is used in the system. When INT0 detects a low potential in the blackout state, the system enters the interrupt handler and commands the motor to stop rotating.

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