2010 IEEE International Conference on Power and Energy (PECon2010), Nov 29 - Dec 1, 2010, Kuala Lumpur, Malaysia
Proteus Based Simulation of a Charge Controller Ahmad Shukri Bin Fazil Rahman* and Abdul Rahim Bin Abdul Razak** Power Electronics Cluster, Department of Electrical System, Universiti Malaysia Perlis, Tingkat 1, Blok A, Jalan Satu, Taman Seberang Jaya 3, 02000 Kuala Perlis, Perlis, Malaysia. *Email:
[email protected] **Email:
[email protected]
Abstract- This paper provides the simulation aspect of a newly design charge controller in Proteus Isis environment. The system function by to managing battery (for two batteries) charging scheme by regulating incoming source. The sensing method only employs voltage reading from source. Since the research is at initial stage, it is therefore conducted in an adequate manner by completing each stage at fundamental basis. Keywords-Charge controller, Proteus Mikroelektronika, microcontroller, voltage divider.
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METHODOLOGY
Isis,
I. INTRODUCTION Charge controller has been regarded as one of the important devices in stand-alone photovoltaic systems to prevent the battery from damage due to overcharging and over-discharging [1]. The charge controller regulates the supply power and thus prevents overcharging. This can be achieved by limiting the input current at a predefined charge regulation voltage [2]. Microcontroller is the common choice of implementing digital charge controller as in [1]. The proposed microcontroller used in this system is PIC16F877A from Microchip. The selection was made due to certain factors, such as cost effective, reliable and etc. The microcontroller was loaded with a series of algorithm (see Methodology) to perform voltage regulation. Charging is accomplished by connecting and disconnecting battery from source through a series of a common relay. Relay was chosen because of its ability to withstand high input current and cost effective. Sensing method incorporates a common potential reading from source. As precaution a standard voltage divider circuit was built to drop the incoming voltage. A display unit consists of LCD (Liquid Crystal Display) attached to the existing system. Actions such as charging and reading will be displayed on the LCD. The proposed system may be suitable for typical electrical application usage such as laptop, radio and etc.
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Figure 1. Proposed Charge controller block diagram
The proposed system was design as shown in figure 1, with rechargeable batteries, relays, microcontroller and a LCD display. Source (ie generator or photovoltaic array) received, will be sensed by a PIC16F877A microcontroller. The voltage divider drops the incoming source to a tolerable level. Other sensed method may be considered as in [3,4,5]. The PIC16F877A microcontroller read the value and determined a series of actions set to be as default condition: • If voltage source is greater than the threshold value, charge battery 1. • If battery 1 is fully charged, then charge battery 2. • If battery 2 is fully charged, then ‘on’ dummy load. • If voltage source is lower than the threshold value, keep sensing. III. RESULTS The Proteus Isis’ circuit was implemented as in figure 2. Several modifications have been conducted for the purpose of optimizing the system performance. The rechargeable batteries were replaced by voltage divider circuits while LEDs (Light Emitting Doides) were used to indicate selection progress. Relays were chosen since it is cheaper (actual hardware
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implementation), provide better isolation (protection) and able to tolerate high current.
Figure 2. Proteus Isis’ circuit
The initial stage requires the PIC16F877A to be loaded with a HEX (hexadecimal or machine language) file, which was accomplished by using MikroC software from Mikroelektronika. Upon completion, several tests have been conducted to verify the actions of PIC16F877A (see methodology). A. Voltage source greater than threshold value. A supply source, Vgen (Voltage generator) greater than threshold value (>12V) is supplied via generator. This can be achieved by increasing the variable resistor value at RV1. If source is greater than threshold value, the controller (PIC16F877A) will measured potential from Vb1 (Voltage battery 1) and Vb2 (Voltage battery 2). When both batteries are high (greater than 11.5V), the dummy load will be ‘on’ as shown in figure 3. The LED (D3) will turn ‘on’ to indicate the working process of the dummy load.
Figure 3. Voltage source greater than threshold value
B. Charging of Vb1. Vb1 is set to low by lowering the variable resistor at RV3. The controller will starts charging Vb1 and
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disconnect dummy load as shown in figure 4. When Vb1 is fully charge, the controller will proceed to charge Vb2, since Vb2 already fully charge the dummy load is set to ‘on’ again. The ‘low’ part of Vgen represent the sampling period of the controller at 5second interval.
Lower source Figure 6. Lower source
1) Display The proposed circuit in figure 2 also included an LCD to show important parameters, when charging to Vb1 a series of texts will be displayed as in figure 7. Other parameters such as ‘reading from Vb1’, ‘reading from Vb2’, ‘dummy load on’ and ‘generator low’ as per figure.
Figure 4. charging of Vb1
C. Charging of Vb2. Vb1 is set to high by increasing the variable resistor at RV3 and lowering Vb2. The controller will starts charging Vb2 and disconnect dummy load as shown in figure 5. When Vb2 is fully charge, the controller will proceed to charge Vb1, since Vb1 already fully charge the dummy load is set to ‘on’ again.
Figure 7. Text indicating charging to Vb1 is in progress.
Figure 5. charging of Vb2
D. Lower source. The source, Vgen is set again to be less than 12V, by decreasing RV1. The controller will keep on sampling until Vgen starts to increase and greater than threshold value as shown in figure 6.
Figure 8. Text indicating reading voltage from Vb1.
Figure 9. Text indicating reading voltage from Vb2.
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without spending too much time on hardware. Through simulation, adjustment can be made and finalized design could be accomplished through hardware circuit. Preliminary results show that the proposed circuit is functioning as expected by performing series of action such charging, reading and etc. Future works might consist of hardware implementation and non-contact sensor (i.e. hall sensor). The source voltage might be suitable if increase to higher than existing value (12V). Additional controller may be considered as in [6,7]. REFERENCES Figure 10. Text indicating dummy load is ‘on’. [1]
[2] [3]
[4]
[5]
Figure 11. Text indicating Vgen is low.
[6]
[7]
IV. CONCLUSION With the implementation of Proteus software, the realization of a charge controller circuit is possible
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Muthukumaran, M.B., “Micro controller Based Charge Controller For Photo Voltaic System”, IEEE Power Systems Conference and Exposition (PSCE), pp. 1454-1457, Oct. 2006. http://en.wikipedia.org/wiki/Charge_controller James P. Dunlop, P.E., Batteries and Charge Control in StandAlone Photovoltaic Systems, Clearlake Road, FL: Florida Solar Energy Center/University of Central Florida, 1997. Amin, Nowshad; Azim, Md. Anwarul; Sopian, Kamaruzzaman; “Development of cost effective charge controller with data acquisition options for PV powered sensor nodes,” 33rd IEEE Photovolatic Specialists Conference (PVSC), pp. 1 – 4, May 2008. Amin, N.; Lam Zi Yi; Sopian, K.; “based smart charge controller for standalone solar photovoltaic power systems,” 34th IEEE Photovoltaic Specialists Conference (PVSC), pp. 001094 – 001097, 2009. Ullah, Z.; Burford, B.; Dillip, S.; “Fast intelligent battery charging: neural-fuzzy approach,” IEEE Aerospace and Electronic Systems Magazine, Vol. 11, pp. 26-34, June 1996. Singh, P.; Rajagopalan, J.; LaFollette, R.; Fennie, C., Jr.; Reisner, D.E.; “Fuzzy logic-based solar charge controller for microbatteries,” Conference Record of the Twenty-Eighth IEEE Photovoltaic Specialists Conference, pp. 1726 – 1729, Sept. 2000.
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