Browsing by Author "Kularatna, N."

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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 However, existing impedance matching technique is no longer valid for SC assisted PV systems.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
Designing and constructing a DC microgrid with uninterrupted power supply capability and optimizing its energy usage by smart controlling system
(2018 IEEE International Conference on Industrial Electronics for Sustainable Energy Systems (IESES), 2018) De Zoysa, H.B.H.; Guruge, P.A; Kalingamudali, S.R.D; Kularatna, N.; Kanishka, G.
Abstract: This paper outlines the methodology of designing and implementation of a solar powered system which can be used to make a human comfort zone during day time without using battery backup but with the use of Supercapacitors. Basically, major converter losses are reduced in this system. In acquiring a highly efficient power supply, the charge controller plays an important role. When a DC microgrid powers DC loads based on a renewable source such as a PV system; energy storage becomes mandatory due to fluctuating nature of the source. Localized DC-energy storage within DC-DC converters could address this requirement. A variation of supercapacitor assisted regulators could provide localized energy storage with low-noise and fast transient response [1]. 12 V LED lights will be powered from this system. LEDs can be powered directly via a supercapacitor bank from the regulated Photovoltaic energy. In the case of Inverter type Air Conditioner, in order to overcome converter losses, the DC Bus inside it should be accessed. Typically, DC Bus voltage inside the Variable Frequency Drive (VFD) is 1–414 times the supply voltage. Hence DC-DC Converters are used to power up the inside circuitry of the Inverter Air Conditioner from the solar panel. In order to optimize the energy usage and reduce electricity consumption, light dimming and air conditioning control systems were added to control the light intensity and switching of the air conditioner.
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.
Maximum Power Point Tracking of an Off-grid Photovoltaic System Consisting of a Series Connected Supercapacitor with a Step-down Converter
(The Electrochemical Society, 2022) Piyumal, P. L. A. K.; Ranaweera, A. L. A. K.; Kalingamudali, S. R. D.; Kularatna, N.
An off-grid photovoltaic (PV) system's PV array is connected with a charge controller as the first power conversion stage. The average efficiency of the power stage of charge controllers is around 90%. Supercapacitor (SC) - battery hybrid PV system is a novel PV system that utilizes some of the wasted energy of a typical system and enhances the system's efficiency up to 98%. However, the feasibility of maximum power point tracking (MPPT) for this system is yet to be validated. This paper presents a comparative study to adapt MPPT for the proposed system consisting of a series- connected SC bank with PV array and step-down DC-DC converter. The step-down converter is used as the impedance matching network. Different solar irradiance profiles were emulated to check the feasibility and efficiency of MPPT. Experimentally, it was shown that the typical MPPT could be adapted to the proposed PV system with very high MPPT efficiency.
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.
Novel slow switching technique for efficient solar energy harnessing for off grid photovoltaic systems
(proceedings of the 4th International Research Symposium on Pure and Applied Sciences 2019, Faculty of Science, University of Kelaniya, Sri Lanka, 2019) Piyumal, P. L. A. K.; Ranaweera, A. L. A. K.; Kalingamudali, S. R. D.; Kularatna, N.
Electricity consumers in remote areas where the grid connection is not available rely on diesel generators or off grid photovoltaic (P V) systems. These PV systems uses battery banks as backup energy storage. Those battery banks are charged by using a battery charge controller connected to a PV array. Because of the recent advances in solar charge controllers, they can reach maximum of 90% charging efficiency, where 10% will be unutilized. Since the efficiency of conventional solar panels lies around 20-25% which is relatively low as compared to other energy generation methods, it is important to utilize as much energy as possible produced by the solar panels. Also, when driving loads, energy stored in the battery bank again goes through a converter or inverter by wasting considerable amount of useful energy. Hence, the purpose of this study is to minimize the energy loss of the charging process of the battery bank while using the energy produced by the PV array in an effective manner. In previous publications, it was introduced a novel way of using supercapacitors (SCs) in an off grid PV system. When charging an empty capacitor in parallel with a source, 50% of energy is wasted irrespective of the value of total loop resistance. In contrast, by connecting a SC bank in series with a typical solar charge controller, it was shown that the energy loss of the combined system is less than the energy loss of parallelly connected SC bank and the battery bank in their individual systems. Experimentally, it has been shown that a 9% increment in overall charging efficiency of the combined system when a charge controller having 80% of efficiency is used to charge the battery bank in typical off grid PV system. The present study introduces a possible method of utilizing the energy stored in SC bank in an effective manner using an intelligent electronic switching scheme. The proposed method uses a second SC bank along with the existing one along with a smart electronic switching circuitry which is able to switch each SC bank between charging or discharging stages when necessary. When one SC bank is in its charging state, the other SC bank will be in its discharging state through a proper load. After that, when the first SC bank is fully charged or the second SC bank is fully discharged, positions of each SC bank is swapped so that the second SC bank will start its charging process while the first SC bank is now discharging through the load. This way both charging and discharging of SC bank can be done efficiently while charging the battery bank in the system by the same manner.
Supercapacitor Assisted Hybrid PV System for Efficient Solar Energy Harnessing
(Electronics 2021, 2021) Piyumal, K.; Ranaweera, A.; Kalingamudali, S.; Kularatna, N.
In photovoltaic (PV) systems, maximum power point (MPP) is tracked by matching the load impedance to the internal impedance of the PV array by adjusting the duty cycle of the associated DC-DC converter. Scientists are trying to improve the efficiency of these converters by improving the performance of the power stage, while limited attention is given to finding alternative methods. This article describes a novel supercapacitor (SC) assisted technique to enhance the efficiency of a PV system without modifying the power stage of the charge controller. The proposed system is an SC—battery hybrid PV system where an SC bank is coupled in series with a PV array to enhance the overall system efficiency. Developed prototype of the proposed system with SC assisted loss circumvention embedded with a DC microgrid application detailed in the article showed that the average efficiency of the PV system is increased by 8%. This article further describes the theoretical and experimental investigation of the impedance matching technique for the proposed PV system, explaining how to adapt typical impedance matching for maximum power transfer.
Supercapacitor based novel approach for efficient solar energy harnessing
(Research Symposium on Pure and Applied Sciences, 2018 Faculty of Science, University of Kelaniya, Sri Lanka, 2018) Piyumal, P. L. A. K.; Ranaweera, A. L. A. K.; Kalingamudali, S. R. D.; Kularatna, N.
Finding greener solutions through renewable energy sources to provide energy demand in 21st century is an important task due to the shortage of world energy sources. From many types of renewable energy sources, photovoltaic cell is the most popular device that can be used to harvest solar energy and produce electricity. Currently, efficiency of conventional solar panels lies between 20-25%. In addition, part of energy is lost during the power conversion process in solar power converters. Standalone photovoltaic systems used in houses and other buildings in remote areas employ solar charge controllers to charge their battery banks in order to store energy. Efficiency of these systems relies mostly on the efficiency of in built DC-DC converter of the charge controller. With the advancement of modern semiconductor technologies and electronics, maximum of 90% efficiency can be achieved by a brand new solar charge controller. Usually this value will be decreased with the years of usage. Hence, the purpose of this work is to minimize the energy wasted during charging process of the battery bank of a standalone photovoltaic system. The initial approach was to connect DC-DC converter and battery bank in series with a capacitor charging loop. When an empty capacitor is charged by delivering Q charge using an external source, it can theoretically be shown that 50% of energy will be lost in the charging loop regardless of the resistance of the loop. If a useful resistive load is attached to the capacitor charging loop in series, this wasted energy can be effectively utilized by doing a treasured work while charging the capacitor too. In this work, this basic concept was used by replacing the conventional capacitor from a supercapacitor and attaching the DC-DC converter and the battery bank as the useful resistive load. Thereby, charging both supercapacitor and battery bank has been done. Theoretical analysis of this novel method shows promising outcomes on achieving high charging efficiency. Experimental results show this technique increases the overall charging efficiency of a standalone photovoltaic system by 9% when 80% efficient DC-DC converter is used to charge the battery bank. Therefore, it can be concluded that the overall charging efficiency of a typical standalone photovoltaic system can be enhanced by adding supercapacitor in series. The energy stored in both devices could be used to drive DC or AC loads using necessary electronics.