With the continuous expansion of the scale of large and medium-sized cities and the continuous improvement of urban appearance, the number of lighting street lamps is increasing, and its electricity consumption accounts for an increasing proportion of the total electricity consumption of cities. In the past, street lamps mostly used direct power supply, as well as manual power supply and manual shutdown. This method has many disadvantages: the voltage of power supply system fluctuates at different times, the peak period is lower than the rated value, and the low period is higher than the rated value. When the voltage is high, it will not only affect the service life of the lighting equipment, but also greatly increase the power consumption (if the power supply voltage is increased by 20%, the power consumption will increase by 44%). When the voltage is low, the lighting equipment cannot work normally. Manual power transmission increases personnel input, and sometimes it can't be opened and closed in time, which affects normal lighting and wastes electric energy. Therefore, it is necessary to develop a convenient and energy-saving device for the above problems, which should have the following functions.
BCY67
(1) voltage stabilizing control: the power supply voltage can always be stabilized within the rated value, no matter in the peak or trough of power consumption; SL5020P
MM58248V
(2) Display function: input voltage, output voltage, three-phase current, power factor, active power and reactive power can be displayed; FSDL0365R
(3) Timing start and stop: The alternating time of day and night is different in different regions and seasons, and the system can automatically adjust the switching time of street lamps according to regions and seasons;
LM487 1A
(4) Adjust the start-stop time according to the weather conditions: In the timed start-stop function, the street lamps can be turned on and off according to the weather conditions;
HMC3 16MS8
(5) Automatic power factor compensation: With the continuous upgrading of lighting equipment, the system should have power factor compensation function;
SMDJ33A
(6) High efficiency, undistorted waveform, stable voltage, wide load adaptability, capability of withstanding instantaneous overload, long-term continuous operation, random manual control and automatic switching, and automatic protection function for overvoltage and undervoltage.
7386 1-4
Working principle of 1 system
KM4 16V 1200BT-L5
There are many ways of AC voltage regulation, such as autotransformer voltage regulation, phase modulation and magnetic saturation voltage regulation. None of these methods can meet the functional requirements of street lamp energy-saving devices, and the autotransformer method can not meet the requirements due to the limitation of its carbon brush when supplying power at high current. However, the phase modulation method has waveform distortion, that is, it interferes with the power grid and some new lighting equipment, which can not meet the requirements; The magnetic saturation mode can not meet the requirements of high power because of its huge volume. 6MCX0297923
The voltage regulating transformer is a dual-contact output, and each contact can move in the whole range. When contact A is above and contact B is below, the phase of output voltage Ub of compensation transformer is the same as Ui; When the A contact is down and the B contact is up, the phase of the voltage Ub output by the compensation transformer is opposite to that of the Ui. When the input voltage Ui increases Δ UI, the control circuit adjusts the movements of contacts A and B, so that contact B moves to the upper end and A moves to the lower end, and the compensation voltage Ub changes Δ UB, Δ UB =-Δ UI and δUb =-δUi-Δ UB accordingly, so that the output voltage UO remains unchanged; When the input voltage Ui decreases by δUi, the control circuit moves the contact A to the upper end and B to the lower end. At this time, δUb =δUi and Uo = Ui+δUb keep the output voltage Uo unchanged.
The primary winding of the voltage regulating transformer TUV is connected in a Y-shape and connected to the output end of the voltage regulator, and the secondary winding is connected to the primary winding of the compensation transformer TB connected in series in the main circuit.
The voltage stabilizing process is: the voltage detecting unit samples, detects and outputs signals according to the change of output voltage, controls the servo motor to rotate, and drives the brush on the transformer TUV to adjust the secondary voltage of the transformer, thus changing the polarity and magnitude of the compensation voltage, realizing the automatic stabilization of the output voltage within the allowable range of the voltage stabilizing setting precision, and thus achieving the purpose of automatic voltage stabilizing.
The compensation transformer mode has the characteristics of small volume, flexible control, minimum power and output current of the voltage regulating transformer, continuous operation and strong overload capacity.
Hardware design of control circuit
The hardware circuit of the control system consists of single chip microcomputer, A/D converter, LCD, clock circuit and servo driver.
2. 1 single chip microcomputer
Single-chip microcomputer adopts P89C5 1RD2, and P89C5 1RD2 single-chip microcomputer has 64K parallel programmable nonvolatile FLASH program memory, which can realize serial programming ISP in the system and IAP in the application. In the system programming ISP (in system programming), there are 1KB RAM inside, the parallel programmer selects 6-clock/12 clock mode (the default clock mode after chip erasure is 12 clock), 4 interrupt priorities, dual DPTR registers, programmable counter array PCA, PWM output and other functions. The system adopts P89C501RD2 single chip microcomputer, without expanding program memory and data memory. All I/O ports of single chip microcomputer work in normal I/O mode. In order to save port lines, peripheral devices choose chips with serial data communication. In order to prevent interference, all signal lines dealing with strong signals are photoelectric isolated. After level conversion, the serial port can play the role of ISP on the one hand and communicate with the host on the other.
2.2 Analog-to-digital conversion circuit
The analog-to-digital conversion circuit consists of a signal conditioning circuit and an A/D conversion circuit. The main function of signal conditioning circuit is to convert external signals such as voltage, current and ambient light into acceptable signal range of A/D. The A/D conversion chip adopts TLC2543 converter. TLC2543 is a 12-bit ADC with 14 channels. There are three channels inside the chip and 1 1 channels outside. The input voltage is 0~5V(VER-=0, VER+=5V). The interface between TLC2543 and CPU adopts SPI mode, and its pins are converted. TLC2543 can work in 8-bit and 12-bit modes. It can be selected during initialization, and the conversion can be started by sending the corresponding channel number TLC2543 in the command. After the conversion is completed, EOC will send a low-level pulse to the microcontroller. After the MCU responds to the interrupt, it can read the conversion data from TLC2543 and send the next channel start command at the same time.
2.3 stepper motor drive circuit
The stepper motor is driven by the commercially available stepper motor drive module, and only five wires are needed to interface with the single chip microcomputer. The pins of this module include direction control, step pulse, braking signal, GND and VCC. After the three-phase voltage is collected by single chip microcomputer, it is compared with the set value to determine the running direction and the number of stepping pulses. Once the output voltage is within the error range, the stepping motor will stop running.
2.4 Display and keyboard circuit
The display adopts 128×64LCD, and the data can be displayed in separate screens. The interface between the monitor and the single chip microcomputer is 4-wire serial data transmission. The keyboard is a 4×4 matrix keyboard with * * 16 keys. Parameters such as system time, voltage stabilization, latitude and longitude, and street lamp switching time can be set through the keyboard.
2.5 Ambient light detection circuit
The function of ambient light detection circuit is to detect outdoor light. As long as this function is turned on during setting, the equipment can automatically turn on the street lamp when the outdoor light is dark to a certain extent. The circuit is shown in Figure 4.
When the environment is bright, the resistance of photosensitive resistor RS is very small, and the collector voltage of triode is very low. When the ambient light is dim to a certain extent, the output out voltage rises, and when it is higher than the set value, the single chip microcomputer controls the street lamp to turn on.
2.6 Power factor detection circuit
The voltage and current are shaped and sent to INT0 and INT 1 of single chip microcomputer. When INT0 (voltage signal) is interrupted, the timer T0 starts counting, when INT 1 (current signal) is interrupted, the T0 count is read, and when INT0 is interrupted again, the T0 value is read and cleared. The frequency and power factor of the power supply can be calculated from the value of T0 read twice.
3 software design of control circuit
The software program adopts C5 1 language and is modularized. The software consists of main program, A/D sampling program, digital filtering program, display program, key processing program, stepping motor driver program, voltage regulation program and power factor compensation program.
3. 1 main program
After the system starts to work, the main program first initializes the internal and external resources of the single chip microcomputer, and then calls the function module program in turn.
3.2 modulus sampling program
The A/D sampling program is called circularly by the main program, and 10 external analog signals are collected 12 times each time, and then sent to the data buffer for use by other programs after digital filtering.
3.3 voltage regulation program
The voltage regulation program adopts PID algorithm, and its inputs are the set regulation voltage and output voltage, which are converted into the number of pulses output by the stepping motor after PID operation for use by the stepping motor driver program. The driving program of stepping motor is relatively simple. According to the number and direction of pulses calculated by PID, the corresponding pulses are sent to the stepper motor driver through I/O port. Because the voltage stabilizing precision of the system can be set in a certain range through the keyboard, there is no overshoot in the voltage regulating process of the system.
3.4 Display program
The display program displays parameters such as voltage, current, power factor, system time and working state on the LCD screen. Because there is a Chinese character library in the LCD module, the internal code of Chinese characters can be sent directly when displaying Chinese characters, and the dynamic numbers are also displayed in the font inside the LCD, so there is no need to establish fonts in the program.
3.5 Power Factor Compensation Procedure
The power factor is calculated based on the data read back from interrupts INT0 and INT 1. Compared with the set power factor, after calculation, the external relay is controlled to switch the capacitor bank to keep the power factor of the street lamp power supply branch within the set range.
4 conclusion
Intelligent street lamp energy-saving device adopts transformer compensation and voltage stabilization mode, and uses the powerful operation control ability of single chip microcomputer, which has the advantages of small size, reliable work and energy saving. If it can be popularized, the management of urban street lamps will be improved to a new level, which not only saves energy, but also reduces the loss of lighting lamps, so it has broad popularization prospects.