Browsing by Author "Ranaweera, A.L.A.K."

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Analysis of Impedance Matching Technique for Novel Supercapacitor Assisted PV Systems
(IEEE Computer Society, 2020-10) Piyumal, P.L.A.K.; Ranaweera, A.L.A.K.; Kalingamudali, S.R.D.; Kularatna, N.
To extract the maximum power from a photovoltaic (PV) system, the maximum power point (MPP) of the PV array must be tracked continuously. A directly coupled load with the PV array does not track the MPP of the PV array because the load has a constant resistive value. Therefore, to track the MPP of the PV array, a technique called impedance matching is used. This is done by continuously matching the load impedance to the instantaneous impedance of the PV array. Switch mode DC-DC converters are widely used for this purpose which also helps to interface the DC output of the PV array with power distribution systems in order to deliver the power to the consumer end. However, the efficiency of these converters lies around 90% which degrade the end to end efficiency of the PV system. In this context, novel supercapacitor (SC) assisted PV systems have been introduced, which were able to enhance the end to end efficiency of PV systems. However, existing impedance matching technique is no longer valid for SC assisted PV systems. Therefore, still it is a challenge for these systems to track MPP of the PV array continuously while in operation. This paper presents a study on impedance matching technique for the novel SC assisted PV systems. Previously, it has been experimentally shown that a series connected SC bank between PV array and DC-DC buck converter of a PV system could deliver higher end to end efficiency than typical systems. This study validates the impedance matching technique for SC assisted PV systems by connecting a SC bank in series with buck, boost, and buck-boost converters. Simulation results indicate that this can be achieved by carefully designing the system with given parameters. © 2020 IEEE. https://ieeexplore.ieee.org/document/9254315
Design and characterization of a parametric speaker using Pulse Width Modulation method
(Faculty of Science, University of Kelaniya, Sri Lanka, 2020) Jayawardana, D.G.D.D.,; Ranaweera, A.L.A.K.; Kalingamudali, S.R.D.
This study focuses on designing and characterization of a parametric speaker. It is used to convert sound waves that spread out in all directions emitted from a sound source into a narrow sound beam to reduce noise pollution. The designed parametric speaker consisted of a parametric acoustic array. The operation of the device is based on nonlinear acoustic characteristics of sound in air. An ultrasound wave that can be modulated by any audio signal is radiated from a transducer array into the air. As a result, an audio signal is produced by the self-demodulation effect of the modulated sound in the air due to the nonlinearity of the air. Typical parametric speakers use different amplitude modulation methods to produce the parametric acoustic array. There is a high cost to produce parametric speakers using those methods. In this work, a method is proposed to produce the parametric acoustic array using the pulse width modulation method (PWM). PWM techniques were used for modulating the input signal. Mainly TL494 IC was used to realize the modulate system. In that process, input audible sound waves were converted to digital high frequency sound (ultrasound) waves which contains information of the audible sound. The proposed design consists of an array of ultrasound transducers each with 8 mm radius that produces ultrasound wave of 40 kHz frequency as the carrier frequency and a class D power amplifier to amplify the sound level of the modulated output sound. The operation of the proposed parametric speaker was tested by changing the carrier frequency and audio signal and measuring the sound pressure level of the parametric speaker for the different distances. It is identified that this method will be a suitable and cost effective method to produce the parametric speaker. Further the directness of the parametric sound beam depends on the carrier frequency and slightly on the input signal. Hence, the parametric sound beam can be more narrowed by using the (30 kHz – 80 kHz) high-frequency range ultrasound emitters and carrier frequencies for the parametric speaker array. It is concluded that the pulse width modulation method based parametric array used for this research is cost effective method and has a great potential to be further developed for designing commercial scale parametric speakers.
Design and Implementation of Smart Standalone Gas Fire Security System for Domestic Usage
(19th Conference on Postgraduate Research, International Postgraduate Research Conference 2018, Faculty of Graduate Studies,University of Kelaniya, Sri Lanka, 2018) Rajapaksha, R.M.I.U.; Perera, P.S.H.; Nandasena, P.K.D.M.; Gunarathna, E.P.G.T.K.; Pieris, T.P.D.; Kanishka, G.; Ranaweera, A.L.A.K.; Kalingamudali, S.R.D.
Liquid Petroleum Gas (LPG) fire security system for domestic gas cylinders has been designed and prototype is implemented. The proposed system automatically takes preventive measures in case of gas leakage. It includes an electronic circuit designed with 8-bit AVR microcontroller for emergency shut-off of the regulator for domestic gas cylinders, a control circuit for switching off the power nearby area and a transceiver unit for sending SMS to the corresponding people. In order for firing to occur LPG concentration should at least be reached to 200 ppm level. This level of LPG is detected with commercially available LPG sensor (MQ-5). A commercially available gas regulator is modified by attaching a spring and a solenoid valve. The spring is compressed when the regulator is ON in domestically available gas cylinders. Once a gas leakage of appropriate ppm is detected a pulse is send to solenoid valve such that, the attached spring gets rest by removing off the regulator from the cylinder. At the same time warning messages will automatically be sent to relevant consumers via GSM module attached to the circuit. The circuit is operated with battery power so that it will work even in power failure. Additional gas sensors are installed in electrical switches located near to the gas cylinder to cut-off power to prevent any spark. Integrating all these sensors through IOT platform is the subject of an on-going study
Design of an auto disconnecting regulator and a safety switch to prevent domestic gas leakages
(Department of Industrial Management, Faculty of Science, University of Kelaniya, Sri Lanka, 2020) Rajapaksha, R.M. I. U.; Perera, P.S.H.; Nandasena, P.K.D.M.; Gunarathna, P.S.T.K.; Kanishka, P.P.D. Gihan; Ranaweera, A.L.A.K.; Kalingamudali, S.R.D.
There is a growing demand for research in various aspects of smart homes. Automated security systems are an integral part of smart homes. Liquid Petroleum Gas (LPG) is one of the popular fuels used in domestic cooking. Therefore, there is a very high demand for LPG fire security systems. In this study, an automated LPG fire security system for domestic gas leakages has been designed and a prototype model is constructed. The designed system automatically takes preventive measures in case of gas leakage. It includes a newly designed automatically disconnecting regulator from the cylinder which shuts OFF gas supply from commercially available gas cylinders, a control circuit for switching OFF the power supply of nearby area of gas leakage and transceiver unit for sending SMS to the corresponding people. It has been designed to operate automatically when LPG concentration reaches to 200 PPM, a value well below the LPG gas inflammable concentration. LPG concentration is sensed by the MQ-5 gas sensor and fed into the microcontroller. The commercially available gas regulator is modified by attaching a spring and solenoid valve. The spring is compressed when the regulator is ON. Once an LPG leakage of appropriate PPM is detected, a pulse is sent to the solenoid valve such that the attached spring gets rest by removing the regulator from the cylinder. At the same time, a warning message will automatically send to the corresponding users and security personnel through a GSM module attached to the circuit. The circuit is embedded with a rechargeable battery to work even in power outage. Additional gas sensors are installed in electrical switches located near to the gas cylinder and kept in connection with the microcontroller through the Bluetooth module to cutoff electrical power to prevent any spark.
Improving the Energy Storage of Standalone PV Systems while Enhancing the Charging Efficiency using Supercapacitors
(IEEE Xplore Digital Library, 2019) Piyumal, P.L.A.K.; Ranaweera, A.L.A.K.; Kalingamudali, S.R.D.; Kularatna, N.
Usually a battery is used as the energy storage device in typical standalone solar photovoltaic (PV) systems. It is charged by a solar charge controller. The charging efficiency of the system depends on the efficiency of the DC-DC converter of solar charge controller. However, a considerable amount of usable energy is wasted during the charging process. In this work, a method is proposed to utilize this wasted energy and thereby to enhance the charging efficiency. In the case of an empty capacitor being charged by an external source, it stores only half of the energy delivered by the source as compared to that of an electrochemical battery. Therefore, it wastes 50% of useful energy. A portion of this wasted energy can be collected and utilized if a useful resistive load is connected in series to this capacitor charging loop. In this study, a DC-DC converter and battery bank is connected as the useful resistive load in the capacitor charging loop. A supercapacitor (SC) bank is used replacing the conventional capacitor. Therefore, total energy loss in capacitor charging loop can be minimized by storing energy in both battery bank and SC bank. This concept is introduced into a typical PV system for reducing its energy losses. Experimental results show an enhancement in charging efficiency when this new method is employed. The energy stored in the SC bank could be used for driving loads with required electronics.
Novel Approach for Harnessing Maximum Energy from PV Systems using Supercapacitors
(IEEE Xplore, 2018) Piyumal, P.L.A.K.; Ranaweera, A.L.A.K.; Kalingamudali, S.R.D.; Kularatna, N.
Typical standalone solar photovoltaic (PV) systems use battery bank as the energy storage device. The battery bank is charged by using a solar charge controller connected to a solar array. For similar PV systems, charging efficiency mostly depends on the efficiency of DC-DC converter available inside the charge controller. However, considerable amount of usable energy will be wasted during the charging process. In this work, a method is proposed to utilize this wasted energy while enhancing the end to end efficiency of standalone PV systems. When an empty capacitor is charged by an external source, it stores only a half of the energy delivered by the source as compared to the case of an electrochemical battery. As a result, 50% of useful energy is lost in the charging loop of a capacitor. If a useful resistive load is connected to this loop, some amount of energy can be utilized by doing a beneficial work. In this study, a DC-DC converter and battery bank has been chosen as the useful load in the capacitor charging loop, and a supercapacitor (SC) bank is used replacing the conventional capacitor. Therefore, total energy loss can be minimized by storing energy in both battery and SC bank. The energy stored in the SCs could be used for driving loads with required electronics. Consequently, it leads to an improvement of end to end efficiency of the PV system.
Selective magnetic field localization for safety enhancement in wireless power transfer applications
(Faculty of Science, University of Kelaniya, Sri Lanka, 2016) Ranaweera, A.L.A.K.
During the last decade wireless power transfer (WPT) has been immerged as one of the rapidly growing area of research. Wide range of its commercial applications such as charging pads, are appearing in market today. The operating principle of WPT is based on resonant inductive coupling which use evanescent magnetic field patterns. However, inherent magnetic flux leakage in it makes concerns on human safety. Therefore, there is a higher demand for selective wireless power transfer where only the intended receiver location is powered. To that aim, a mechanism is needed to precisely focus the magnetic field into the receiver location. The currently available WPT applications lack the precise spatial control of magnetic field. Therefore, in this study, novel method of magnetic field localization is proposed to reduce the magnetic flux leakage into the surrounding area other than the intended receiver location. Several methods have been reported recently for light localization in the deep sub wavelength scale using the capabilities of metamaterials. Metamaterials are a kind of artificially designed material which provides unique and exotic electromagnetic properties such as negative refraction, evanescent wave amplification. Metamaterials usually studied under effective medium approach has previously been successfully utilized in several applications including superlensing, sub-wavelength imaging beyond classical diffraction limit and wireless power transfer. Metamaterials shown to exhibit the well known hybridization bandgap above its resonance arising from the Fano type interference between continuum of plane waves and locally resonating unit cells. By creating a local cavity within the hybridization bandgap, it is possible to localize the magnetic field into the cavity location. Using this property, we propose a method to precisely localize the magnetic field on to surface of the metamaterial where the cavity is created. We utilize active metasurface which can be externally controlled to realize a local cavity within the hybridization bandgap. The proposed metasurface is fabricated with standard PCB fabrication process and experimental investigation is carried out to obtain the spatial distribution of magnetic field. To obtain experimental results, we place the fabricated metasurface in between Tx and Rx of WPT system which is connected to two ports of vector network analyzer. We use small loop coil as receiver loop to make the measurements non-invasive. Spatial distribution of magnetic field is extracted from the measured scarring matrix parameters using the Keysight 5063A vector network analyzer. The results indicated that the magnetic field can be precisely localized to the intended location. We believe that this can be used to improve the safety of wireless power transfer applications.
Smart System Using Lora Technology to Connect Rural Areas Underserved By Existing Internet and Telecommunication Technologies
(The Electrochemical Society, 2022) Jayasekaraa, L.D.P.S.; Gurusinghe, T.N.; Wijesooriya, H.E.; Seneviratne, J.A.; Ranaweera, A.L.A.K.; Jayathilaka, K.M.D.C.; Wijesundera, L.B.D.R.P.; Kalingamudali, S.R.D.
LoRa, Sigfox, and Narrowband-Internet of Things (NB-IoT) are some of the long-distance, low-power wireless communication technologies developed in the recent past. The proposed system consists of mainly nodes and a gateway as the fundamental system architecture. Nodes only communicate with the gateway individually and the gateway communicates with all the nodes separately and wirelessly. System in this proposed study, uses long range low power RF wireless communication technique for primary data communication, where an Internet connection will not be required for the communication between the gateway and the nodes. Any number of nodes can be paired with the gateway, and the gateway can individually communicate with each and every node. Furthermore, gateways have the ability of storing real-time data. Due to its unique design, the proposed system in this study, can achieve addressable, bidirectional, and continuous data communication even without the Internet connection. The bidirectional communication design of this proposed system facilitates real time and uninterrupted simultaneous handling of monitoring/sensor devices and controller devices without the need of a separate controlling system. As this system consists of those unique features, it is recommended to use in the rural areas underserved by current internet and telecommunication technologies. Furthermore, with the in-built option to get connected to the Internet, this system can be further expanded to an IoT based addressable data communication, processing, and visualization systems by eliminating the major technical problems in typical IoT systems such as interrupted communication and data losses during an Internet connection failure, power concerns and customization issues. This system is highly customizable, and the nodes and the connected devices can be controlled through the gateway or remote dashboard by assigning automated or user defined custom commands. These features together improve the robustness of the system and facilitates enhanced data recovery in case of a failure in the Internet connectivity.