Aiming at the complexity of power management in college students' dormitory and the management needs of safe electricity, a smart dormitory management terminal for student dormitory is designed.
Xu Hua 1 Zhou Zhengbo 2 Bibo 3 Zong Shousong 3 Yang Lihai 3
(1. Tsinghua University Architectural Design and Research Institute Co., Ltd., Beijing 100084)
(2. Sichuan Institute of Building Science, Chengdu 610084, China)
(3. Ankerui Electric Co., Ltd., Shanghai, Jiading 201801)
0 Preface
With the development of social economy and the popularity of student apartments, the electricity consumption of student residences has undergone tremendous changes. Scientifically and reasonably managing the electricity consumption of student residences has become a very important issue for the school logistics management department. Comprehensive survey compares the electricity consumption of school dormitory, and summarizes the following requirements for school electricity management:
(1) Commercialization of electricity. The traditional limited-time limited power supply method and the method of charging the average electricity fee from the accommodation fee are not suitable for the increasing demand of the current power-consuming equipment. It is an imperative management method to implement the power commercialization by purchasing power on demand.
(2) Safe use of electricity. In order to avoid fires caused by students using non-safety electrical equipment, the automatic power-off control measures for overload and malicious load identification should be considered.
(3) Control as needed. In order to cultivate students' good living habits and standardize students' work and rest, we should implement timing control on the electricity circuit of student dormitory in combination with school management needs.
This paper designs a smart dormitory management terminal for student dormitory to meet the electricity management needs of the school logistics management department.
1 functional design
Combined with the requirements of metering and billing, intelligent monitoring and identification, and power transmission control management, the design functions of the dormitory security power management terminal are as follows:
(1) Accumulating the total electricity consumption and measuring the remaining electricity;
(2) Real-time detection of power parameters such as voltage, current, active power, reactive power and power factor;
(3) Support independent control of three output circuits (such as lighting, sockets, air conditioners);
(4) Support four kinds of logic control functions such as prepaid control, load identification control, time control, and forced control;
(5) can query various log records.
2 hardware components
The dormitory security power intelligent management terminal is designed with a dedicated Micro Control Unit (MCU). The hardware system implementation of the whole machine is developed according to each functional module, including microprocessor, resistor divider network voltage sampling, current transformer current sampling, three-way magnetic holding relay control output, ferroelectric data storage, liquid crystal display, key input, The active energy pulse indicates the output and so on. The hardware composition is shown in Figure 1.
Figure 1 hardware components
3 software design
3.1 main program flow
The main program is used as a trigger for time slices and events to manage various functional modules. The main program software flow is shown in Figure 2.
Figure 2 main program software flow
3.2 Load Limit and Load Identification Algorithm
When students use illegal electrical appliances (malignant loads) with pure resistive load, they can easily lead to safety accidents such as electrical fires, which have an impact on students' life and property safety. When students use too many conventional electrical appliances, they accumulate electricity load. High, it will also cause a safety accident.
Therefore, the management terminal determines the load control result from the requirements of the maximum power limitation and the malicious load identification to ensure the safety of the dormitory.
The method of maximum power limitation is relatively simple. If all load power exceeds the maximum power, it is judged that the power is out of limits, and the dormitory power supply circuit must be cut off.
For the judgment of the malignant load, if the method of total power judgment is also adopted, it cannot be accurately identified. When testing the operating characteristics of low-power pure resistive malignant loads, it can be found that its power factor is very high. However, if the power factor of the main power supply loop of the dormitory is not high, the design terminal adopts the incremental judgment method, that is, the power factor increment of the power loop is detected in real time as the basis for judging the malicious load. In the case where the total power of the dormitory main power circuit is exceeded, if the power factor increment exceeds the maximum set value, it is judged that the malicious load is connected. Power factor increment is
Where: PN - current active power;
PL - the active power at the previous moment;
ΔP - active power increment;
QN - current reactive power;
QL - last reactive power;
ΔQ - reactive power increment.
3.3 Logic control mode.
3.3.1 Mandatory control
Some dormitory rooms in colleges and universities will be arranged for the relevant management personnel and international students to stay. These dorms are often not powered off and have no load, time constraints, etc. In this case, if the forced control function is turned on, other control functions will not work. In addition, when there are large-scale activities in colleges and universities, it is necessary to make a unified power transmission and discharge processing for each dormitory circuit, and also through the mandatory control function.
3.3.2 Time Control
There are many students in colleges and universities. In order to arrange work and rest in a unified manner, it is necessary to unify the power on/off. For example, from 06:00 to 08:00, the students should wake up in the morning and keep the lighting and socket circuits energized. 08:00~11:00 For the student's class time, the students are generally not in the dormitory, cut off all circuits; 23:00~06:00 for the student's rest time, the lighting should be cut off, but the socket and air conditioning power circuit is guaranteed to supply power; on weekends, 08:00~ At 23:00, the average student does not have to take classes, and most of the time is in the dormitory. At this time, all relevant circuits should be guaranteed.
The terminal provides two sets of independent control timetables for lighting, sockets and air-conditioning circuits, which is convenient for the school management department to control different loops on/off according to actual conditions to meet the requirements of timing control management.
3.3.3 Load Control
The terminal provides load control for the main circuit of the dormitory, which can identify the malicious load and respond quickly.
3.3.4 Prepaid Control
The terminal cooperates with the remote prepaid power sales management system to realize the function of paying the electricity after paying the fee first. Students can recharge their own electricity according to the dormitory's electricity consumption to ensure the normal use of electricity in the dormitory. When the student runs out of recharged power, the terminal will cut off the electricity used by the dormitory. If students recharge in time, they can resume power supply in time.
3.3.5 Combination Control
The above four logic control methods can be used alone or in combination. The terminal can jointly determine the on/off of the power supply output circuit according to the combined control logic and priority of the forced control, time control, load control, and prepaid control.
The combined control logic is shown in Figure 3.
Figure 3 combined control logic
4 test results
The results of the malignant load recognition test are shown in Table 1.
It can be seen from Table 1 that the management terminal can quickly identify the malicious load of the student accessing the dormitory circuit and give a trip command. As shown in Table 2, the combined control logic can realize combined logic control such as time period control, load control, and prepaid control to jointly monitor the power consumption of the dormitory.
5 Conclusion
The electricity management terminal of the student dormitory has the functions of measurement, monitoring and control, which can reduce the difficulty of collecting electricity fees in schools and other management areas, improve work efficiency, realize optimal operation, effectively save energy, and provide data basis for reasonable management of users. A practical user-side power charging management system.
Source: Modern Building Electric, 2015, issue 5.
references:
Wen Tao.Application of safe electricity management system in student apartments[J].电å测试,2013,06(11):64-65 Luo Hui, Qiao Lili, Zhong Donghua. Intelligent and safe electricity energy-saving measurement management system in college energy Application in Management [J]. Intelligent Building and City Letter. 2012 (5): 68-71 Lai Xiaojun. Design and Implementation of Logistics Intelligent Power Management System of Jinhua Vocational and Technical College [D]. Chengdu: University of Electronic Science and Technology, 2010 Hu Xinfeng,Zhou Wei,Sun Yiwen.The Management System of University Dormitory Electricity Based on 51 Single Chip Microcomputer[J].电å制作,2013(11):36-38
Table 1 Malignant load identification test results
Table 2 Combination Control Logic
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