Through the analysis of the main components of the solar street lamp lighting system, this paper introduces a wind-solar complementary street lamp control system based on single-chip technology, LED as light source and ZigBee wireless sensor network for data transmission. The system transmits by installing ZigBee wireless sensor network in the controller of each street lamp. The wireless network is constructed to collect the working state of street lamp, and on this basis, the collected data are analyzed manually or intelligently, so as to realize the intelligent monitoring and management of the wind-solar complementary street lamp system. Nowadays, solar energy and wind energy are more and more widely used as a clean and pollution-free renewable energy.
Solar street lamp is one of the applications of solar energy. At present, solar photovoltaic power generation has the following characteristics: in the past, the installation and construction of ordinary street lamp took a long time, which not only increased the construction cost, but also greatly increased the maintenance cost of facilities and equipment. On the contrary, the application of solar LED street lamp, without laying a large number of power supply cables, saves a lot of manpower and material resources, and is not limited by the application occasions, solar LED street lamp has become a new star in the lighting industry.
However, there are some problems in the current research of solar power generation: because of the rainy weather, the solar street lamp can not be charged normally during the day, thus obtaining enough electricity for lighting at night. Therefore, this system has made the following improvements on the basis of the existing solar street lamps: adding wind turbines, Zigbee wireless sensor network nodes and other components needed to configure. The Zigbee wireless sensor network node is constructed into a wireless sensor network, which connects the management organization with each street lamp, and finally realizes the omni-directional distributed automatic/manual monitoring and control of the working condition of each street lamp, thus realizing the intelligent optimization management of the working state of the street lamp with complementary wind and light. The wind-solar complementary LED street lamp lighting control system is based on micro-processor and Zigbee wireless sensor network technology. It consists of solar panels, wind turbines, controllers, lithium batteries, Zigbee wireless sensor network nodes, auxiliary systems (including light acquisition sensors, GPS modules, temperature and humidity sensors). It includes wind speed, wind direction sensor, etc.) and other components needed for street lamps. On the one hand, the controller controls the output state of the load, on the other hand, it also sends excess energy to the lithium battery bank for storage; when the power generation can not meet the demand of the load, it also controls the power of the lithium battery to the load; under the control of the controller, the energy storage module controls the opening and closing of the discharge path to prevent the battery from passing and discharging, so as to ensure the whole system work. Continuity and stability. Among them, the main task of wind power generation control is to track the change of wind speed. Through variable pitch control or double feedback control, small wind turbines mostly use the control of Boost converter to achieve maximum output power of wind turbines. The main task of photovoltaic power generation control is to track the change of output power and use MPPT algorithm to keep the maximum output power of photovoltaic cells. ZigBee/GPRS gateway mainly receives data transmitted by ZigBee wireless network, and uploads relevant data to remote monitoring center through network to complete real-time monitoring function; or broadcasts remote control data to each street lamp controller node through ZigBee network to complete the corresponding control function [1]. Auxiliary system is used to ensure that temperature and humidity sensors can work steadily, and then the collected temperature data is transmitted to the main control chip, which controls the data transmission to the ZigBee wireless network node. Finally, the collected data is transmitted to the network center by the ZigBee wireless network, and sent by the network center according to the current status. Directives are sent to the ZigBee wireless node to adjust the working state of the control street lamp. The intelligent solar street lamp controller designed in this paper is based on MSP430 series chips.
The controller can monitor the whole system in real time, charge lithium batteries with maximum output power, charge solar photovoltaic panels as energy storage components by sensing sunlight in the daytime, and monitor ambient temperature and temperature. The combination of light and wind speed with MPPT arithmetic module improves the conversion efficiency of solar energy and wind energy and maximizes its charge; automatically opens the street lamp after dark and intelligently adjusts and controls the brightness of the LED street lamp according to the external light intensity; under the control of the controller, the energy storage module controls the opening and closing of the discharge path to prevent the battery from passing. The function of the controller is to make all parts of the whole system work in harmony. It is the control and coordination center of the whole system. It plays a vital role in the stable, reliable and efficient operation of the whole system. In the traditional power disturbance algorithm, the disturbance step D is a fixed value. When MPPT is steady-state, the small step D reduces the power consumption of the controller. When calculating the instantaneous MPPT value, the large step D will quickly get a new MPP, but at the same time it will increase the disturbance range. Therefore, for the traditional power disturbance algorithm, it is obviously a difficult problem to choose the appropriate step size. So this paper designs an adaptive step disturbance MPPT control algorithm, which is used to balance the tracking efficiency and tracking accuracy. Its working principle is to adjust the disturbance value and observe the current of the load curve. Then according to the load current, the disturbance value Delta D is determined adaptively. After the value of Delta D is obtained, the power duty cycle of solar photovoltaic panels will be modified by the value of Delta D. After waiting time T, the MPPT controller will start the next disturbance.
During the disturbance period of the algorithm, thermostatic element the duty cycle of DC-DC converter and its load current are recorded as sum respectively. The duty cycle and load current of the power converter at the previous disturbance time are recorded as sum respectively. The variation of load current and duty cycle from one working cycle to another can be defined as: and. If the signal sum is the same, the duty cycle Delta D will increase, and the variable X will be set to “1” so that the algorithm can remember the direction of the last disturbance of the duty cycle. If the signal sum is opposite, the duty cycle will be reduced and the variable X is set to “0” so that the algorithm can remember the direction of the last disturbance of this duty cycle. The value of variable X is used in time, because the resolution of A/D converter is not high enough, so we can see the result of the change of disturbance load current in the last working cycle. Under such conditions, the perturbation in the duty cycle will take the same direction as the last iteration perturbation, and the current value will not change. This step is equivalent to increasing the disturbance step of duty cycle. But the duty cycle is always compared. Its minimum value is Dmin and its maximum value is Dmax [3].
In the intelligent solar LED street lamp lighting system, the street lamp controller mainly controls the conversion of light radiation energy from solar panels into electric energy, which is stored in lithium batteries, and then the electric load in lithium batteries is supplied. When the photoresistor detects changes in external light, that is, when it enters the night, the driving LED lights become brighter and begin to illuminate. If the voltage of lithium battery is insufficient, it is managed by battery management chip TP4056 to check whether it is charging condition. If it meets the condition, it begins to enter charging mode, otherwise it enters standby mode. Because of the complexity of MPPT algorithm in software design and the improvement of its peripheral hardware circuit according to requirements, the MPPT implemented in this system is designed with a hardware chip, which is a fixed frequency PWM step-up and step-down DC-D converter of XLSEMI Company. Its model is XL6009. The solar street lamp system designed in this paper is a general simulation test subject, so it is not necessary to consider field work. This design is based on STC12C5A602S2 intelligent solar LED street lamp controller, and designed a simple street lamp system with the controller as the core. The brightness of street lamp can be adjusted automatically according to the change of external light.
When SOC is more than 95%, lithium batteries are charged by floating charge; when SOC is less than 95%, lithium batteries are charged by MPPT. When SOC is more than 50%, lithium batteries supply power to the LED load; when SOC is less than 50%, lithium batteries are turned off. Wind mode, same as strong light mode. Wind mode is in the case of weak wind, such as weak illumination mode, while in the case of strong wind, such as strong illumination mode.
The innovation of this system lies in its application and combination of microprocessor, ZigBee wireless sensor network, lithium battery and wind-solar complementary technology [4], which realizes the wind-solar complementary street lighting intelligent system. The system can not only monitor and control the working condition of each street lamp by wireless sensor network, but also can control automatically by single chip computer. Secondly, the output power characteristics of solar photovoltaic panels and the commonly used MPPT algorithm are analyzed, and a new MPPT algorithm is proposed. However, a hardware-based MPPT algorithm is used to implement MPPT algorithm without software design and improvement, that is, the fixed frequency PWM wave in the hardware internal resources is used to control DC/DC converter directly to realize MPPT algorithm. The content of this design involves knowledge of many disciplines, but it has not been studied in depth on many issues, so the shortcomings of the system design are also the next step to continue to improve and improve the content. How to design and optimize MPPT algorithm to improve the output power of solar photovoltaic panels; whether solar photovoltaic panels can be combined with the design of mechanical structure to enable them to move with the change of the direction of the sun’s movement; how to design, revise and improve the energy output model of wind-solar complementary power generation system; and how to adopt appropriate methods The algorithm solves Weibull distribution parameters of wind speed, and then establishes the energy output model of wind power generation according to the power characteristics of wind turbines. These issues will also become the focus of future attention.