Modified single phase energy meter for rural domestic energy management supplied from solar panel based small grid system

Transcription

1 Modified single phase energy meter for rural domestic energy management supplied from solar panel based small grid system 1 Piyali Das, 2 Mousam Ghosh and 3 Dr. Saswati Mazumdar Abstract 1 Assistant Professor, Dibrugarh University, Assam, India piyali_d2000@yahoo.co.in 2 Trainee Officer, West Bengal Financial Corporation, West Bengal, India ghosh_mousam@yahoo.co.in 3 Professor, Jadavpur University, Kolkata, India saswati.mazumdar@gmail.com In this paper the energy limiting is explored by the use of modified single phase energy meter using PIC16F877A [1]. This paper contains the method which is used to control a predefined domestic load and through out the day the total consumption. It also contains the advantage of using this energy saving energy meter and the method of using this energy meter in domestic use. Key words Energy meter, load control, multistage load control I. Introduction The main principle of this single phase energy meter is to control the wastage. For example a conventional non electrified small rural locality if electrified by solar panel based small grid system then the locality will face a problem which can be minimized by this proposed modified energy meter. Since those houses in this locality are electrified by solar panel and the power is stored in battery, so through out the day they can use limited amount of energy. If some of the houses consumed maximum amount of energy in a certain time through out the day then other houses get hampered. So a device is required which can limit the consumption through out the day. Also if some of the houses consume the total energy within their specified limit but at a certain time they may exceed the maximum power limit which is specified for them. This will again hamper the grid voltage and due to that, the other houses get hampered. So to get better reliability and to minimize these two unwanted situations this modified energy meter has been proposed. 55

2 II. Model Description Fig.-1: Solar Panel based Rural Electrification with small grid system Fig 2: Block diagram of Modified Energy Meter with the help of µcontroller. 56

3 The main principle of this single phase energy meter is to control the wastage of domestic load. Fig.-2 shows the block diagram of modified energy meter with the help of a micro controller. A new modified single phase energy meter system is being implemented with the help of a µcontroller PIC16F877A. To develop this modified energy meter a 3200 pulse per kw-hr electronic energy meter was selected i.e. if a one kw load is connected for a period of one hour then the energy meter gives 3200 nos. of pulses. To modify this energy meter, this pulse signal is manipulated by the microcontroller. Depending upon the following two principles this modified energy meter is developed.[2][3][4][5] i. Firstly, to limit the energy consumption in a day, the microcontroller counts the pulse throughout the day. If for a rural house the limit of energy consumption to 1kW-hr per day is set, that microcontroller counts the pulse throughout the day. If the limit is crossed i.e is counted, the microcontroller trips the power for the house for that day. In the next day it will be reset by the controller and power will be delivered to the house and like this the process will go on. ii. Secondly stop high power demand beyond the specified limit given to each house, the microcontroller checks the time span between two consecutive positive edges of the pulse signal. If any house powered on higher load than specified, this modified energy meter trips the circuit for that instance and there is a provision for user to reset after disconnection of the extra load. For example if it is required to limit a load of 500W for a rural house then a time of 2.25 sec is to be set to microcontroller. In any time during the day the load increases beyond 500W, the time span between two consecutive pulses will be reduced below that 2.25 sec and controller trips the power for that instance. III. Features: Trips the power if energy consumption is more than the specified limit through out a day. There are provisions to set different settings (1/2/3 kw-hr per day) at the time of installation by changing corresponding jumpers. At 80% of specified energy consumption limit through out a day, this modified energy meter shows a warning signal by a LED. There are further provisions for buzzer also. In any day if one of the house in that rural locality exceeds their energy consumption limit then they are not able to power on their lights for that day. But in the next day they will get power automatically. 57

4 Trips power for an instant if any house switches to more load at a time which crosses their specified power limit. But user can reset by pressing reset switch after disconnection of some of the loads. IV.. Instrument I Details Fig 3: A prototype of the Modified energy meter circuit Here in this project Anchor Electricals (P) Ltd. made energy meter is used, which is of 240V & 50 Hz rating. It gives 3200 pulse/kw-hr. Fig4: Circuit diagram of Energy meter controller by using Microcontroller 58

5 Fig 4 shows the microcontroller based Energy Meter. In first step the single phase energy meter is supplying pulse to the µcontroller through an isolation circuit, which is made of R1 and optocoupler Opt. By the rising edge of the pulse, the µcontroller is interrupted by the capture pin 17 which is selecting the positive edge of the pulse and feeding this to the µcontroller input pin, this is the second step. In third step three output pins of µcontroller are operating from which one is connected with a relay for tripping at overload condition, and two another output pins are operated to indicate at overload condition and 80% consumption of set point condition respectively. LED1 is the indicator of 80% consumption and LED2 is the indicator of overload condition. ow in fourth step Ph out is going to one of the relay pins and out is going to neutral of the load respectively (as load needs phase and neutral to operate). Load phase is being fed from another relay pin. This relay will operate when the initially set pulse in the µcontroller exceeds and will disconnect the load from the supply. µcontroller gets supply from a 5V supply and the relay gets supply from a 12V supply. The relay can be replaced by 240V contactor. SL. O. LEGET AME VALUE 1 U1 Micro- Controller PIC 16F877A 2 S1 Switch Push on switch 3 R1 Resistor 1KΩ /0.25W 4 R2 Resistor 5.6KΩ /0.25W 5 R3 Resistor 560Ω /0.25W 6 C1, C2, C5 C Capacitor 1µF/63V 7 R4,R8 Resistor 5.6KΩ/0.25W 8 R5,R7 Resistor 330Ω/0.25W 9 C3, C4 Capacitor 15PF/25V 10 XT1 Crystal 4 MHz 11 R6 Resistor 2.2K/0.25W 12 Rel1 Relay 12V 1CO, 10Amp, Table:1 List of Circuit Components 59

6 V. Flow Chart for self explanation START Initialize all the Variables. Configure the Capture Pin as Interrupt Capture at Every Rising Edge of Input Pulse. Configure Parallel I/OUT Ports SET all Variables to default SET all the O/P Port to ZERO Counting Sec, Min, Hr with 4MHz crystal as reference 1 2 Is Pulse Rising Edge Interrupt Occur? Increment the Pulse Counting, Reset the Timer_ConsecutivePulse Is Pulse counting = 80% of Set Point (for a KWh)? 2 Warning SET that bit 1 Is Pulse counting = Set Point (for a KWh)? Power OFF SET that bit 0 60

7 2 Is 24 Hours Completed? Pulse Counting Reset to Zero Power O SET that bit 1 and Reset Warning Bit Is Timer_ConsecutivePulse > Ref time for given Power OFF SET that bit 0 and OL O/P bit 1 SET a Flag Power_OFF_OL= 1 Check IPUT of Over Load Reset Pin Is Flag Power_OFF_OL Is User Reset The OVER LOAD Condition? Power O SET that bit 1 RESET a Flag Power_OFF_OL=

8 VI. Conclusion: In many rural place conventional electricity is yet not supplied and with a solar panel based small grid system is installed to serve the people. In those places the main object is to enlighten them at night. For these places, low wattage CFL or LED based lighting systems are more suitable. These lamps are fed by the stored energy in battery through solar panel (or any other non-conventional source). The stored energy is limited so if one or some of the houses in that locality connected with that grid consumes maximum amount of energy then other houses connected with that grid get hampered. Also if they consume within the limit but at a certain interval draw a high load current, it also hampers the grid voltage as well as other circuits of the arrangement and system stability will be reduced. These reduce the system reliability also. So to overcome these situations for small grid system this modified energy meter, which is basically a small modification of existing electronic energy meter with the use of a microcontroller, will be of great use. References [1] Application ote of PIC 16F877A from [2] A single phase microcontroller based energy meter, Loss, P.A.V., Lamego, M.M., Sousa, G.C.D., Vieira, J.L.F., Instrumentation and Measurement Technology Conference, IMTC/98. Conference Proceedings. IEEE, Date of Conference: May 1998, Volume: 2, Page(s): vol.2, Product Type: Conference Publications [3] United States Patent- Programmable Electrical Energy meter using Multiplexed Analog-to-Digital Converter, Inventor- Rodney C. Hamminger, Mark L. Munday, Assignee- ABB Power T & D Company Inc., Raleigh,. C., Patent number: , Filing date: 7 Jun 1995, Issue date: 6 Aug [4] Programmable electrical energy meter and methods therefore, Inventor- Mark L. Munday Rodney, C. Hamminger, Assignee- ABB Power T & D Company Inc., Raleigh,. C., Patent number: , Filing date: 6 Jun 1996, Issue date: 20 May [5] Power Energy Meter in a Low Cost Hardware/Software, Libano, F., Dept. of Electr. Eng., PUC- RS, Paranhos, I. ; Melchiors, J. ; Mano, O. ; Fehlberg, R. ; Braga, R. ; Muller, S.; Volume: 3,Page(s): ; Industrial Electronics, 2006 IEEE International Symposium on 9-13 July