Automatically shedding loads for lighting systems in corridors and public areas in high-rise apartment buildings

Currently, the lighting system for corridors and public areas in high-rise apartment buildings uses LED systems to replace Sodium lamps, halogen lamps... Although LED lights have been put into use, there are economic benefits such as lower power consumption and longer durability (life expectancy) according to the manufacturer's explanation. But in practice, the LEDs are used with pulse sources with operating voltages from 170VAC to 240VAC and continuous operation time without rest, often resulting in power loss due to overload or the life of the capacitor is reduced. Therefore, in order to improve the life span and efficiently use the energy source, the researches have studied the switching process control such as [1], [2], [3], [5]. This paper presents a new research direction Automatically shedding loads for lighting systems in corridors and public areas in high-rise apartment buildings for greater efficiency.


Introduction
In the process of use, the power supply only provides a fixed and continuous voltage, leading to continuous lighting at maximum power, causing the LED elements in the lamp to age quickly, affecting the intensity of the lamp brightness during use, LED power supplies are designed with a fairly wide voltage range, but use in areas with unstable voltages has not really brought high efficiency. For example: At the beginning of the evening from 5pm to 8pm due to the low voltage in areas with poor power quality, the power supply does not meet the maximum power for LED, the lights will be darker compared with the time from 11 am to 3 am when there are few people using electricity or few people walking in public areas and corridors. The automatic load shedding system for LED public lighting will solve the energy compensation in the early evening hours thanks to the design of the pressure compensation and load shedding mechanism, reducing the power consumption. at a time of little use. The system is used Microcontroller Atmega [2], [4], [6], [7] in controlling and monitoring the power supply process for LED lighting.

Working principle of the system
Technical solution for automatic load shedding for public lighting LEDs using real-time combined with light sensors to automatically power on, automatically shed loads, automatically Real-time power-off action brings more efficiency on light source, saving useless power consumption.

Structure, principle
Connect the circuit block to the lighting system.
In figure 1, the load shedding automatic coupling diagram for LED public lighting uses real-time auto power on, auto load shedding, real time auto power off.  Figure 1, the real-time control block and light sensor (1) are designed with real-time IC Realtime Clock DS1307 -M021 with power supply using 3v Lithium rechargeable battery to maintain system time. (Time may vary from 3-7 minutes per year). The real-time block can be designed to allow the user to set the hour and time of load shedding and the time to turn on and off the lighting system or design to allow the default setting of the on, off, and off time. load and set operating hours with a default key. The control signal from block (1) will send a signal to block (2) Pulse source block (220VAC/72VDC-80VDC-160-200VDC)/5VDC/3.3VDC to regulate output voltage supplied to LED elements lighting (3), block 2 also has the function of supplying 3.3v and 5v DC power to block (1). Block (3) LED lighting block.
-Algorithm diagram of the program Step 1. Initialization (starting program) Step 2. Confirm data, state Step 3. Provide power on signal to LED Step 4. Determine the auxiliary shedding time load (low power supply) + If false go back to step 2 + If true, go to step 5 Step 5. Maintain load shedding time (counting load shedding time) + If false go back to step 2 + If correct go to step 6 Step 6. Maintain LED power supply high Step 7. Finish -Circuit diagram a. Power supply circuit using IC LM1117 b. Circuit diagram of LED power supply with load shedding control  In Figure 4, the 220VAC voltage source is converted to DC voltage by the rectifier bridge and input filter capacitor, then DC voltage is applied to the voltage converter IC from DC to pulse form coupled with pulse transformer to get 72v-80v-160v voltage and diode combined filter capacitor to produce lower DC voltage. In order to derive voltages at different levels, the circuit uses resistor values coupled by controlled electronic switching. These switches are controlled by signals generated from the real-time circuit programmed on the computer or manually set on the circuit.  Shedding circuit In Figure 6, a 20W LED lamp is fitted with an automatic load shedding circuit. In fact, LEDs with a capacity of 20W, 50W, 100W and 200W are used with the included source circuit with only one power level (single luminous intensity). Therefore, the power consumption depends on the input power and the lighting power is only fixed at a fixed level from when the power is powered up until the power is turned off.

Figure 7
The printed circuit board is designed to integrate the voltage converter block, light sensor, real time and automatic load shedding power block In Figure 7, the circuit board is designed to integrate functional blocks. , shown in Figure 1. The circuit uses a common source with the pulse source circuit of the LED but different output voltage.

Experimental results
- + Apply to the road lighting system between villages, communes and townships in Thanh Hoa.

Conclusion
The automatic load shedding system for LED public lighting will bring benefits such as saving electricity, increasing and reducing the light source during the required hours. The switching time is pre-programmed or user-configured for user convenience.
Necessary conditions to apply the initiative: + The solution is suitable and applicable to the existing public lighting system but the efficiency is not high.
+ The system operates in a normal temperature environment, the device is isolated from the water source and is radiated by the LED light housing.
+ Used for public light extraction systems, street lights at different levels in apartments, schools, offices, public houses, roads, etc.