Design of energy-saving LED lamp control system for wind-solar hybrid power generation

introduction

With the rapid development of control technology, more and more control technologies are being applied to lighting projects. At present, the control methods for high-rise corridor light switches are mostly "clock control + light control" or "sound control + light control". "Clock control" is not suitable for natural conditions such as sudden weather changes and seasonal changes, while "sound control" is not suitable for quiet places such as hospitals, schools, and libraries. Therefore, neither of them can achieve the rationalization, humanization, and scientific control of light switches. Turning on the lights early and turning off the lights late, or turning on the lights late and turning off the lights early, will cause a lot of waste of electricity. In recent years, due to people's increasing attention to energy and environmental issues, solar energy and wind energy have received more and more attention. Since rainy days are often accompanied by strong winds, using this complementary phenomenon can effectively solve the problem of discontinuous single power generation and improve the reliability of the power generation system. When the battery provides insufficient power to the outside, the system can automatically switch to the mains power supply, ensuring the reliability of the designed circuit power supply system. Combined with "pyroelectric human infrared + light control", it can effectively save energy.

1 Overall design plan

The structure of the LED lamp system is shown in Figure 1, which mainly includes wind and solar power generation modules, control modules (STM32) and load modules (LED lamps). Among them, the control module is divided into a wind-solar complementary control module with STM32 as the core and an LED lamp control module. In addition, a mains backup circuit is designed. When the battery cannot supply power due to special circumstances, or the sum of the power provided by the battery and wind power generation is less than the load power consumption, the system switches to mains power supply.

2 Hardware Circuit Design

2.1 Power Module

The controller design of the power module is based on the STM32 chip, which is used to achieve maximum power tracking control of wind power generation and solar power generation, as well as charge and discharge control of the battery and overcharge and over-discharge protection. The designed mains backup module is used when there is no wind or low wind, continuous rainy days and insufficient battery power storage, and the STM32 chip is used to control the automatic switch to mains power supply.

2.1.1 Overall structure of wind and solar complementarity

The overall wind-solar complementary circuit consists of a DC/DC conversion module and a battery charging and discharging module. The switches V1 to V6 in Figure 2 use IGBT transistors with low driving power and low saturation voltage. The DC/DC conversion module uses a boost circuit with a boost effect. In addition, when the wind is too strong, the speed of the fan increases rapidly, and the mechanical output power also increases rapidly. Due to the limited capacity of the subsequent circuit design and the excessive speed of the fan, the mechanical transmission device of the fan is also greatly damaged. For this reason, a load unloading circuit is added between the rectifier and the boost circuit. The load unloading circuit is composed of V2 and R1, and adopts a continuous power regulation method.

The battery charging and discharging module uses a current reversible chopper circuit:

① Charging process: When the input power provided by wind power generation and solar energy is greater than the load consumption, V4 is turned on and V5 is turned off, forming a Buck circuit to charge the battery.

②Discharge process. When the power provided by wind power generation and solar energy is less than the power consumed by the load, or when neither of them provides energy to the outside, V4 is turned off, V5 is turned on, and the Boost circuit formed by D4 supplies power to the load. To prevent the battery from overcharging, a load unloading circuit is added before the reversible chopper circuit.

2.1.2 Voltage detection module

The battery is an indispensable part of the independent operation of the system. The life of the battery is affected by the depth of discharge and the degree of charge. In addition, its depth of discharge is also affected by environmental factors. In order to improve the stability and reliability of the battery, the system is designed to collect the battery terminal voltage in real time, and the battery charge and discharge degree is judged by the voltage at both ends of the battery. The input voltage range of the STM32 ADC is 0-3.6 V, while the normal operating voltage range of the 12 V battery used in the design is 10.8-14.4 V. To this end, the battery voltage is divided and collected using the resistor voltage division principle, as shown in Figure 3. The collected voltage is converted to 2.7-3.5 V and input to the ADC port of the STM32 through the designed second-order low-pass filter circuit. When the collected voltage exceeds the set range, the battery charge and discharge are controlled by adjusting the PWM pulse.

2.2 LED light control module

The LED light control module is composed of a pyroelectric human infrared sensing control module and a light control module. The LED light will only light up when the two switches work at the same time, otherwise it will go out.

The human body generally has a constant body temperature, so infrared rays of a specific wavelength are emitted from the surface of the human body. The infrared rays radiated by the human body are enhanced by a Fresnel lens and then focused on a pyroelectric infrared sensor, which converts the energy into an electrical signal through subsequent circuits.

The module is based on the BISS0001 sensor signal processor. BISS0001 is a digital-analog hybrid special integrated circuit consisting of a voltage comparator, an operational amplifier, a state controller, a blocking timer, a delay timer, and a reference voltage source, which is very suitable for controlling LED lights. The LED light control module circuit is shown in Figure 4.

① Adjustment of the blocking time T. The blocking time can be changed by changing the resistance value of the resistor R11 connected to the RR2 pin of the chip BISS0001 and the capacitance value of the capacitor C6 connected to the pin RC2:

Ti≈24R11×C6

② Adjustment of output delay time T. The output delay time can be changed by changing the resistance value of resistors RT3 and R12 connected to the RR1 pin of BISS0001 and the capacitance value of capacitor C5 connected to the pin RC1, thereby adjusting the duration of the output action after the human body triggers the signal:

Tx≈49 152×(RT3+R12)×C5

The VC terminal of the chip BISS0001 is the trigger prohibition terminal, and the low level is effective. A light control module is added to this pin design to control whether the chip BISS0001 is allowed to be triggered.

The circuit principle is as follows: When the light intensity exceeds the limit, Q2 is turned on, the level of point a is pulled down, and then the pin 2 of the comparator U1 is pulled down. At the same time, the pin 3 of the comparator U1 is divided by the resistor RT1 to obtain a more appropriate high level. In this way, the input level of the pin 3 of the comparator U1 is greater than the input level of the pin 2, so the comparator U1 outputs a high level, the NPN transistor Q1 is turned on, and the VC pin of the chip BISS0001 is pulled down, and the trigger is prohibited. When the light intensity does not reach the limit, Q2 is not turned on, the pin 2 of U1 is pulled high, and the potential of point a is higher than the input level of the pin 3 of the comparator U1. In this way, after passing through the comparator U1, a low level is output, and the indicator LED1 is lit at this time, the transistor Q1 cannot be turned on, and the pin VC level is pulled high. At this time, the chip BISS0001 allows triggering.

When the light intensity is at the critical limit, that is, the level value at point a is the threshold level, whether it is a slight change in light intensity or external interference, it will cause the level at point a to jump. To solve this problem, a positive feedback link is introduced into the comparison circuit, making the circuit design a hysteresis comparison circuit, thereby avoiding interference caused by the level jump at the threshold point (point a).

2.3 LED lamp driving circuit

The LED lamp driver chip uses AMC7135. AMC7135 is a step-down constant current chip with a power supply range of 2.7 to 6 V and an output constant current of 350mA (current range is optional). In addition, it also has advantages such as output short-circuit protection. Its design circuit diagram is shown in Figure 5.

The lighting power range of LED corridor lights is 2 to 5 W. This design uses three 1 W high-power LEDs in series, and a protective resistor R1 in series. The resistance value of R1 can be referred to the following formula, where VLED is the voltage drop of the LED lamp:

R1=(12 V-3x VLED)/350 mA

Conclusion

This article briefly introduces the hardware circuit and power circuit of energy-saving LED corridor lights. According to the test, the movement of human body can be detected within a range of 5 m, and the effect of "light on when people come, light off when people leave" can be achieved. It can also cope with emergencies such as continuous cloudy days and power outages. The idea of ​​energy saving can be better realized by using wind and solar complementary power generation and long-life, low-power LED lights. This system is not only suitable for high-rise office buildings, teaching buildings, hospitals and other places, but can also be used as street lights, which has high practical promotion value.