Design of Intelligent LED Solar Street Light System

Abstract: A new type of intelligent control LED street light system is proposed. The output voltage of the solar panel passes through the DC/DC boost circuit, and the MPPT control strategy based on the CVT method is introduced. The analog switch 4051 and PIC are used to realize the real-time monitoring and control of the working status of the street light system. The relevant application of Zigbee communication components in the system is briefly introduced.

　　Solar energy is the most direct, common and cleanest energy on earth. As a huge renewable energy, solar energy will be used more and more widely as traditional energy becomes increasingly scarce. In particular, the field of solar power generation has developed into a mature sunrise industry in just a few years.

　　At present, road lighting accounts for 25% to 30% of the total lighting electricity consumption, so there is great potential and space for energy saving in road lighting. At present, the most commonly used light source for road lighting is high-pressure sodium lamps, which have disadvantages such as poor color rendering, long startup time, high power consumption, and high heat generation. It is necessary to develop new and more energy-saving road lighting light sources.

　　High-power and high-efficiency LED is a new light source that has developed rapidly at home and abroad in recent years. It has the advantages of high light efficiency (≥90 lmPW (1W LED)), long life (30000~50000h), vibration resistance, not easy to damage, instant start, and no pollution. White light LED is an ideal light source for general lighting and road lighting. Solar street lights have many advantages: safe and reliable, easy to maintain; no conventional energy is required, no pollution to the environment; can be installed anywhere as needed, without connecting to the public power grid. Therefore, the development of LED street lights has important energy-saving significance. This paper proposes and develops a new type of intelligent LED solar street light system based on the original solar street light system.

　　1 Composition of solar street light system

　　The street light system consists of the following parts: solar panels, boost circuit modules, controller modules, Zigbee communication components, battery packs, and LED light sources.

　　As shown in Figure 1.

　　Figure 1 Effect diagram and composition diagram of street lamp

　　The basic working principle of the system: under the control of the solar controller, the solar panel charges the battery pack through two boost circuits (12V to 42V) during the day, and the battery pack provides power to the LED light load at night. In the control module, real-time control of the boost circuit, battery voltage, temperature, LED light group temperature, and battery panel voltage is achieved, and data is collected through analog switches and fed back to the PIC to realize intelligent control of the street light system. The Zigbee module provides reliable technical support for the networking of the street light system.

　　1.1 Solar Panels

　　Solar panels are the core part of solar street lights and the most valuable part of solar lights. Their function is to convert the sun's radiation energy into electrical energy or send it to batteries for storage. Among the many solar cells, the most common and practical ones are single-crystal silicon solar cells, polycrystalline silicon solar cells and amorphous silicon solar cells. In areas with sufficient sunlight and good sunshine, it is better to use polycrystalline silicon solar cells, because the production process of polycrystalline silicon solar cells is relatively simple and the price is lower than that of single-crystal silicon solar cells. In areas with more rainy days and relatively insufficient sunlight, it is better to use single-crystal silicon solar cells, because the performance parameters of single-crystal silicon solar cells are relatively stable. Amorphous silicon solar cells are better when there is insufficient sunlight outdoors, because amorphous silicon solar cells have relatively low requirements for sunlight conditions. In addition, the development of the second generation of solar cells is about to make a breakthrough, and its core component is a bondable film, that is, a thin film solar cell material.

　　1.2 Boost circuit module and its battery pack

　　In this system, the solar energy collected by the solar panel is used to charge the battery through two DCDC boost circuits. The boost circuit is built with LM5022, and the low-voltage self-locking function of the chip itself is used to cleverly control the circuit charging. Referring to the relationship between the output voltage of the solar cell and the light, it can be seen that in the evening (around 18:00 in summer and around 17:00 in winter), the output voltage of the solar cell will be lower than the self-locking voltage of the chip (about 1.25V), and the control module in the system will stop charging the battery and enter the lighting state.