Design of Automatic Soil Humidity Control using Maximum Power Point Tracking Controller

1 Design of Automa tic Soil Humidi ty Control using Maxim um Power Point Tracking Controller Choo Kian Hoe 1 , Aravind Ch okalingam Vaithlingam 2 , Rozita T eymourzadeh 3 Rajparthiban Rajk umar 4 1,2 Energy & Power Research Cluster UCSI Uni versity,Kuala Lumpur, Malaysia 2,3 Faculty of Engineering, Arc hitecture & Built Enviro nment UCSI University,Kuala Lumpur, Malaysia 4 Taylors Universit y College, Mala ysia 2 aravind_147@yahoo. com Abstract- The photovoltaic system uses the photovoltaic array as a source of electri cal po wer for the direct conver sion of the sun ’s radiation to direct current without an y en vironmental hazards . T he main purpose of this research i s to design of a converter with Maximu m Po wer Point Tracker (MP PT ) algorithm for an y typical application of so il humidity control. Using this setup the major energy from the solar panel is used for the control of soil h umidity. The design of t he converter w ith MP PT together with the s oil humidity control logic is presented in this paper. Experimental testing o f the d esi gn controller is implemented and evaluated for performance under laboratory environment . Keywords: MPPT; solar ener gy, sustainable future I. INTRODUCT ION Water and energy resources are the m ost essential elements for s ustaining hum an needs, maintaining he alth and food p roduction, as well as for social and economic d evelop ment. B ased on previous resear ch work, the capital city in the text is endea vouring hard to ascertain ways a nd means to keep the w ater level at the optimum le vel by finding an alternative water supply to m aintain the high rising demand for water [1]. The actual ca use o f this high de mand for wa ter is due to the improper usage a nd handling of t he clean water. In order to sustain the rising demand o f energy, some alternative energy reso urces have been proposed in recent years s uch as solar energy, wind and tidal resources. Solar energy i s prevale nt popular choice of clea n, recyclable renewable energy as they are m ore environment al friendly. Unfortunately, the opti mal utilisation o f t he photovoltaic [5 -7] energy is a major drawback with the co nversion efficiency bei ng in the range of 8 to 16 percent. This percentage is eve n lower with lesser radiation from the sun due to the improper weather conditio ns. I n ord er to overcome these proble ms, the conver ter is designed with Maximum Po wer Point Trac king (MPPT) system. This pap er p resents a simple p hotovoltaic rai nwater pumping syste m which is tak en as a n application to demonstrate the soil humidit y control with t he MPPT -based converter. The soil hu midity co ntroller acts automaticall y when the humidit y o f the syste m drops thereby pu mping t he rain water that is collected underneath in the reser voir. The humidity le vel can be adjusted by the users using a set p oint value. II . SYSTEM OVERVIEW The system configuration is divided into two parts, buck co nverter with MP PT algorith m and soil humidity controller. Figure 1 indicates the overall block diagram repr esentation o f the system. Solar Panel Converter with MPPT Soil Humidity Controller Battery Backup Figure 1: Overvie w of the Complete S ystem The b uck converter is d esigned b ased on explications given in ref [3 ]. The MPPT algorit hm is generated using the PWM where the M OSFET driver activate s the corresponding s witch operations . 2 Figure 2 sho ws t he block d iagram f or the buc k converter with MPPT algorit hm . Unregulated DC Voltage Buck Converter MPPT Controller (Changing PWM based on voltage) Regulated DC Voltage Figure 2: Buck Co nverter with MP PT algorithm The soil humidit y co ntroller uses a microcontroller to control th e soil humidity. Using a hu midity sensor such as capacitive se nso r, the status of the humidit y level is measured and displayed on the LCD scree n. The co ntroller ac tivates the ex ternal water pump once the h umidity leve l dr ops to the pre -set val ue. Figure 4 shows the b lock diagram for the so il humidity controller. Fi gure 5 shows the co mplete schematic for the de signed syste m. Soil Humidity Capacitive Sensor Microcontroller External Pump Soil humidity below the set value Display Figure 4: Soil hu midity control PV Panel PWM Controller Humidity Sensor External Water Reservoir Converter with MPPT Control Load Controller Battery Figure 5: Schematic d iagram o f the proposed system III . CONTROLLER DESIGN (a) DC Chopper d esign The DC chopper sho wn in figure 5 is designed based on the explanatio ns found in r eference [3 ]. V in L C out Cin D Figure 5: DC -DC co nverter The various equations involved in the design are as follows; The output voltage is give n by The design values for L and C are where D :duty cycle f : switching frequenc y L : inductor value C: capacitor value The r equired capacito r value must be greater than this minimum value when desi gning the converter [8 ]. 3 (b) MPPT Controller The energy harvested through th e photovoltaic arra y has an optimum point, which is called th e Maximu m Power Po int T racking (MPPT) . T his maximum power point cannot be achieved when the v oltage or the current o f the operating system is in compatible with the s olar array [2]. Meanwhile, the maximu m power point is also d ependent on t he temperature and the d egree of the solar radiation striking b y the panel . Therefore, the Maxi mum Power Point T rac ker method is used to ensure that the s olar module to extract t he maximu m po wer fro m the solar panel for rapidly cha nging co nditions to char ge the batter y. For generating the pulse width, the TL494CN is used instead o f PIC or m icroco ntroller since all the functions needed to construct a pulse widt h modulation is i ncorporated in this chip. T he more flexible TL494 is specially d esigned for po wer supply con trol.. The MPPT algorithm can be achieved b y using the internal function of the chip. Internally, it has t wo err or amplifiers, an o n-chip adjustable o scillator, a Dead Time Co ntrol (DT C) comparator, a pulse -steering control flip -flop, a 5V precision regu lator an d output control circuits. The TL494 achieved the MPPT by u sing the erro r amplifiers that measures the o utput signal and t he sets the value to automatically c hange t he PW M of the converter to achieve the maximum p oint o f t he po wer supplied to the con verter [4] . (c) Soil Humidity Controlle r A microcontroller PIC1 6F887 is used for the soil humidity sensin g and controller ap plication . I t has the feature of sensing b y mean s of the soil hu midity sensor and disp lays the humidit y level on the LC D screen. The controller activates the e xternal water pump once the humidity level drops to the set value. The built-in ADC is suitable t o read the soil humidity since the output signal from the humidity sensor is in analog. The humidity senso r is supplied with 5V DC voltage and the o utput signal is based on the capacitance value o f t he sensor. Fi gure 6 s hows the ADC value progra mmed into the controller . Figure 6 : ADC measurements versus Humidity IV. HARDWARE OVE RVIEW Figure 7 shows the protot ype for the experimental setup operating by extracting the maximised energy from the solar p anel. The solar panel can be adjusted based on the geograp hic coordinate of the place, sinc e different place has different coordinate of sun ra diation that strikes it at a different angle on the plane of the solar p anel. Once the ener gy i s generated, the buck converter with Maximum Power Point Trac ker (MPPT) extracts the most energy from the solar panel to use in t he soil humidity controller and store some o f the e nergy in t he batter y for back-up operation. From this, the system performs autonomously with s ufficient/adequate sun radiatio n and rainwater. Figure 7: Pr ototype experimental setup 4 V. RESULTS AND DI SCUSSION Figure 8 shows t he three different radiation levels on the solar panel at vario us tim es of the day to derive the so lar characteristics . Figure 9 shows the three different solar radiations o n t he so lar panel based o n the power and voltage curves of the solar panel . The PV graph is plotted to show the maximum power point of t he solar panel for op timal co ntrol. Figure 10 shows the ti me and volta ge characteristics o f the converter. T he c harging point of t he converter based on the time o f day indicated can be determined fro m this plo t. Figure 8: Solar p anel radiation characteristics Figure 9: P-V Cur ve of the Solar P anel Figure 10 : Converter voltage c haracteristics Figure 11 shows the ti me an d current value for t he converter. Fro m this value, the Current-T ime Curve graph is plotted to obtain the charging current of the converter at different ti me. Figure 12 shows the Power-Ti me C urve graph t o show the maximum power of the converter Figure 11 : Converter curre nt characteristics Figure 12: P ower-Time Curve o f the Converter VI. CONCLUSIONS The converter with MPPT algorithm is desig ned constructed, bui lt and validated for performance. T his power output i s able to be used in soil h umidity controller w ith batter y backup. The external source is able to supply water to the soil when the humidity level is d ropped to the desired humidity le vel. This research has a co ntributor y significa nce to the c urrent endeavours for sa fe, renewab le and e nvironmental friendly alternati ve source of energ y in the face of countering the adverse human intervention effects on the global climatic change e nvironment. 5 VII. REFERENCE S [1] www.arc sa.org/docs/ Articles/mala ysia.pdf [2] Yi -Hwa Liu, Rong -Ceng Leou and Jeng - Shiung Che ng “ Design and Imple mentation of a Maxi mum Po wer Point T racking Battery Charging S yste m for P hotovoltaic Applications”, IEEE Confere nce on Power Tech , 2005 P g. 1 – 5 . [3] Muha mmad H. Rashid “ Po wer E lectronics, Circuits, Devices & A pplications ” P rentice Hall 2005 [4] R epo rt. “ Designing S witching Voltage Regulators with the T L494 ”, Applicatio n Report , February 2005 [5] Chu n-Wei Lin; Jian-Min Wa ng; Huang -Jen Chiu; Y u-Kang Lo; T ing-Peng Lee; Qing Su Chen; W en Long Y u; J ian-Xing Lee; Shih, F. 2009. A battery charger with maxi mum power point tracking function for lo w-po wer photovoltaic syste m applicatio ns . Internationa l Conference on Power Electronics and Drive Systems. pp 204 -209. [6] Ga mboa, G.; Elmes, J.; Hamilto n, C.; Baker, J.; Pepper, M.; Batarseh, I. 2010. A unity power factor, maximum po wer point tracking batter y charger for low power wind turbines . Twenty-Fifth Ann ual IEEE of Applied Power Electronics Conference and Exposition (APEC). p p. 143 -148. [7] Giustin iani, A.; P etrone, G.; Spagnuolo, G.; Vitelli, M. 2010. Low-Frequency C urrent Oscillations and Maximum Power Point Tracking in Grid-Connec ted Fuel-Cell - Based Systems . IEEE T ransaction s on Industrial Electron ics. vol 57 ( 6 ):2042- 2053.