Design and implementation of energy saving control

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Design and implementation of intelligent street lamp energy-saving controller

0 introduction

with the rapid development of China's economy, people's living standards are improving day by day, energy and resources are becoming increasingly tense, and power shortage has become a prominent contradiction restricting the development of the national economy. At present, the electric energy consumed by lighting in China accounts for about 10% - 20% of the total power production, while urban public lighting accounts for 30% of the lighting power consumption. In recent years, with the slogan of making cities light up, the number of street lamps in the country is still growing rapidly. Therefore, the slogan of public street lamp energy saving was put forward. There are usually two ways to save energy: one is to use energy-saving light sources; The second is to adopt a reasonable control circuit. In this paper, under the condition of using energy-saving light source, reasonable control circuit is adopted to realize energy saving of street lamp. In the power supply system, in order to avoid line loss during power transmission and low terminal voltage during peak power consumption, the power supply department adopts higher voltage for transmission. Therefore, the voltage borne by street lamps is mostly higher than the rated voltage of lamps. However, according to the survey, after 21:00 p.m. in small cities in China, the roads in large and medium-sized cities are almost empty after 00:00 p.m. As a result, it is unreasonable that there are fewer people and fewer cars, and the lights are brighter. In order to avoid this situation, most cities and regions have adopted the original street lamp control method of turning off lights every other lamp, which has long been eliminated in developed countries. This method not only leads to the non detection and control of road illumination distribution, which are two different concepts, but also reduces the service life of street lamps. This paper adopts the time-sharing control idea of dividing the whole year into three quarters and one quarter into periods to achieve the purpose of energy saving. Put different power supply voltages into operation in different periods of time, and take into account the energy-saving effect during the power trough period on the premise of ensuring the normal lighting of street lamps. At the same time, the power carrier technology is used to realize the real-time monitoring of the operation status of street lamps

1 design of system hardware circuit

1.1 intelligent street lamp control system

the intelligent street lamp energy-saving system is mainly composed of electric quantity detection circuit, real-time clock, autotransformer circuit, display circuit and carrier communication circuit. The year is roughly divided into three seasons to control the street lights, so that they have different switching times in different seasons. The molding temperature: 300 (3) 30 ℃. From light on to light off, according to the local traffic, it can be roughly divided into three stages (peak, normal and trough) to control the street lights. The current working conditions of street lamps are classified from the real-time clock chip. The output of the single chip microcomputer controls the breaking and closing of the coil of the contactor, and the output of the contact controls the three contacts of the autotransformer respectively, corresponding to four gears, and each gear corresponds to the corresponding street lamp voltage. Due to the power instability caused by harmonic interference in power transmission, it is necessary to detect the power of street lamps at all times. The current or voltage is detected to be too high or too low by the power chip ATT7028, and the obtained information is transmitted to the AT89C51 single chip microcomputer. At the same time, the single chip microcomputer is compared with the information of ferroelectric memory. If the current or voltage is found to be too high or too low, the single chip microcomputer will immediately make adjustments to appropriately reduce or increase the voltage, so as to realize the overload of street lamps Overvoltage and other functions are controlled, and the on-site situation is transmitted to the monitoring room by power carrier communication technology. The principle block diagram is shown in Figure 1

1.2 design of electric quantity detection circuit

the electric quantity acquisition module mainly completes the data acquisition of street lamp current and voltage. The collected signals are converted into analog signals that can be collected and processed by ADC circuit, which are converted into digital signals through electric chip and sent to MCU to detect whether the voltage and current are overloaded, and then the voltage of circuit load is controlled according to this. The design adopts three-phase electric energy special metering chip att7028a, which is suitable for three-phase three wire and three-phase four wire applications. It can measure the active power and active energy of each phase and combined phase. At the same time, it can also measure the current, voltage effective value, power factor, phase angle, frequency and other parameters of each phase, fully meeting the needs of three-phase complex power multi-function watt hour meter. At the same time, the electric quantity signal is stored in the ferroelectric memory at24c24, and the memory data is not easy to lose, so as to query the historical records of active electric energy. Att7028a provides an SPI interface to facilitate the transmission of measurement parameters and calibration parameters with external single-chip computers. In the design, att7028a is used to measure the effective value of current and voltage, and the software is used to calibrate the meter. The measurement parameters are transmitted between SPI interface and external single chip microcomputer, so as to detect the effective value of street lamp voltage and current. In addition, alarm the detected overload, overvoltage and other faults

1.3 street lamp control circuit

street lamp control circuit is composed of decoding circuit, switching circuit and transformer control circuit. In order to make the street lamp branch Airbus will use it for its wide body a350-xwb; Bombardier has achieved excellent energy-saving effect when it applies it to the C series of narrow body aircraft. In addition to starting different gear voltages according to the time period, it also needs to actually consider the voltage fluctuations of the electric voltage in different periods. Therefore, the electric quantity signal detected by the single chip microcomputer and the processed real-time clock chip DS1302 signal are used as the input of the decoding address of the 74ls155 two four decoder. The output of the four ends of the decoder is amplified by the triode and drives the coils of the four contactors respectively, and its four contacts correspond to the three contacts of the autotransformer, that is, the four gears of the street lamp: full voltage (220 V), peak gear (93% of the rated voltage), normal gear (88% of the rated voltage) Low peak period (83% of rated voltage). So as to achieve both the brightness of street lamps and energy-saving effect. Km4 can also turn off street lights when connected to the bus. The principle is shown in Figure 2

1.4 power carrier communication

in order to realize that the control room can easily and timely understand the operation of on-site street lamps, the power line carrier communication technology is used to transmit the detection and operation of on-site street lamps to the control room. Power carrier communication is realized by LM1893 integrated chip, which is a FSK modulation and demodulation chip produced by National Semiconductor Corporation of the United States. It can realize the half duplex power line communication of reliable serial data, has two working modes of sending and receiving data, and is compatible with 51 single chip microcomputer. The LM1893 modulation and demodulation data input terminal datain is connected with the serial output port TXD of AT89C51 single chip microcomputer, and the output terminal dataout is connected with the serial input port RXD of AT89C51. The TX/RX sending and receiving control end of LM1893 is controlled by p1.o end of MCU. The high level is the sending state, and the low level is the receiving state. After receiving the external data information, the street lamp controller must first judge the message header and address of the received data. When the message header is correct and the address is the local address, it will execute the corresponding light control command and enter the sending state after execution

2 software design

the software is mainly completed: according to the comparison results, the hardware is controlled to switch gears to meet the requirements of street lamp timing; Detect the real-time electrical voltage to control whether to change the gear to achieve the purpose of real-time electrical monitoring; Finally, cooperate with the main control room to complete multi machine communication. The whole intelligent street lamp energy-saving control system is divided into time-sharing and segmentation module (mainly completed by the cooperation of clock chip DS1302 and ferroelectric memory chip AT24C02), voltage monitoring and gear adjustment module (realized by software judgment of electrical parameter measurement chip ATT7028), remote communication module (completed by LM1893) and real-time display module. The year is roughly divided into three seasons to control the street lights, and each season has a different light on and off time. From turning on the lights to turning off the lights, according to the local traffic, the street lights can be roughly divided into three stages to control, namely, the traffic peak period, the traffic normal period and the traffic trough period. These three stages, together with the full voltage operation gear to avoid low electric voltage, constitute four working periods of full voltage, peak, normal and trough, which are divided according to the actual situation of the region. The system compares the current light on and off time read out by the calendar clock chip DS1302

with the light on and off time stored in the ferroelectric memory chip AT24C02, switches to the corresponding gear at the time when each gear is turned on, turns off in the off period, and monitors the rest of the period. Ensure sufficient illumination of street lamps during peak traffic hours. Therefore, under normal circumstances, the street lamp should be put into the first gear. At this time, when the electric voltage is too low (lower than 208 V), the street lamp should operate at full voltage; If the electric voltage is too high (higher than 236 V), the street lamp can skip the first gear and directly put into the second gear. In the normal stage of traffic, the illumination and power saving effect should be taken into account. Under normal circumstances, the street lights should be put into the second gear. When the electric voltage is low by 205 V, return to the first gear for operation; When the electric voltage is higher than 242 V, put the third gear into operation. In the traffic trough stage, we should focus on the effect of power saving. Under normal conditions, put the third gear into operation. Only when the electric voltage is too low (lower than 195 V), the street lamp will return to the second gear for operation. However, due to the fluctuation or interference of electricity, the voltage may occasionally be abnormal. If the gear is switched once the voltage exceeds the limit is detected, it is easy to cause misoperation, resulting in frequent switching. The following methods are adopted in the design to avoid frequent gear switching: when the street lamp operates between gear 1 and gear 2, the voltage needs to be maintained between 208 and 236 v. here, count, count are used_ H,COUNT_ L three counters to monitor the voltage. Count starts from 0, increases by 1 every minute, increases to 5, that is, it is cleared after 5 minutes. COUNT_ H starts from 0, and compares the current voltage with the upper limit value of voltage every minute. If it exceeds the upper limit, count_ H plus 1. Before each count reset, if the count H value is equal to 5, it is considered that the voltage exceeds the upper limit for 5 minutes, and the street lamp operation gear is switched to the lower gear accordingly; If count_ If the value of H is less than 5, it is considered as electric fluctuation, and switching is not carried out. The same is true for lower voltage limit monitoring. Clear the three counters at the same time every 5 minutes

obtain the measurement results of the electrical parameters detected by ATT7028 from the SPI bus, and then calibrate the measured values, which can be used for software calibration by assigning values to the calibration registers

the display module mainly displays the current time and the operation of the detected street lights in the control room

the main program and each sub module are connected by timed interruption, which is interrupted every 1 min. during each interruption, four tasks should be completed, that is, reading the real-time time time and sending it to the main control room to decide whether to shift gears, controlling and deciding whether to change gears according to the actual situation of electric fluctuation, and sending the original electric voltage to the monitoring room according to the actual situation. The software flow chart is shown in Figure 3

3 energy saving effect analysis

take 1 kW street lamp as an example. When the street lamp voltage is 205 V, the power consumption per unit time is 0.87 kwh; When the street lamp voltage is 193 V, the power consumption is 0.77 kwh; Under the condition of meeting the operation needs of pedestrians and vehicles, appropriately reducing the terminal voltage of street lamps can save energy by about 20%. When there are few pedestrians at night, the terminal voltage of the street lamp can be reduced to 170 ~ 180 v. within 1 hour of the street lamp, and it is emphasized to build a new friendly political and business relationship. The power consumption is about 0.55 kwh. Excluding other losses, nearly 40% of the power can be saved

4 conclusion

the intelligent street lamp energy-saving device adopts the time-sharing shift method, which takes into account the energy-saving effect in the low power consumption period while ensuring the lighting. Experiments show that the intelligent street lamp energy-saving control system can significantly improve the power efficiency of street lamps and prolong the service life of street lamps. Today, with energy conservation and rational utilization of power resources, the device has a very broad social and commercial prospects

Copyright © 2011 JIN SHI