Faculty Publications
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Item A Transformerless Photovoltaic Microinverter using High-gain Z-Source Boost Converter for Single-phase Grid connected Applications(Institute of Electrical and Electronics Engineers Inc., 2020) Prabhu, N.S.; Damodaran, R.; Balasubramanian, B.; Mishra, S.Microinverters are the latest advancements in the area of photovoltaic (PV) technology due to their compact design. They improve energy efficiency of PV systems due to the reduced effect of non-uniform operating conditions caused primarily by shading. However due to the low output voltage rating of PV modules, high output to input voltage gain ratio is required for microinverters integrated to the utility grid. Several of the existing techniques use transformers or coupled inductors to achieve high gain ratios. These often require precise design and increase the size and cost of the PV system. The Z-source network based high-gain converters can offer superior performance with reduced components, size and cost. However their operation in a microinverter for grid connected applications have not yet been studied. Therefore this paper presents a novel microinverter utilizing a high-gain Z-source boost converter followed by an H-bridge inverter. The principle of operation of the microinverter is detailed and the overall gain ratio is obtained. The operating region in the I-V characteristics of PV module is determined and the control strategies implemented are discussed in detail. Simulations are performed in MATLAB/Simulink platform to validate the performance of the proposed microinverter under possible operating condition. © 2020 IEEE.Item Performance analysis of automated QFT robust controller for long-term grid tied PV simulations(Institute of Electrical and Electronics Engineers Inc., 2020) Gudimindla, H.; Krishnamurthy, M.S.; Sandhya, S.Long-term simulations are significant to understand the real-time operation of grid-tied renewable energy system configurations. Grid-tied photovoltaic system (GPV) is highly non-linear due to the dependency of real-time meteorological conditions. The non-linear behavior of the photovoltaic (PV) system with the power electronic converter makes the long-term simulation inefficient and slow. This paper presents an efficient and simple modelling approach for GPV modelling suitable for long-term simulations. The recent advancements in control strategies and system configurations, sub-module level controller operation gained much interest but the simulation of such systems can be very challenging due to a large number of power electronic components and their control, non-linear behavior of PV system. This paper proposed a genetic algorithm based robust controller design in the quantitative feedback theory (QFT) framework to extract the maximum power from GPV at the sub-module level to extradict the power losses due to partial shading conditions. The performance of the proposed controller at the PV sub-module level is evaluated through comparison with the Q-parameterization based controller. The proposed QFT methodology based robust controller is shown to have advantages over Q-parameterization approach to simulate long-term GPV operation. © 2020 IEEE.Item A novel AC module with high gain Z-Source converter and pseudo DC-link inverter(Institute of Electrical and Electronics Engineers Inc., 2020) Damodaran, R.; Dastagiri Reddy, B.D.; Balasubramanian, B.The effects of partial shading in low power PV systems can be considerably reduced by using a single PV module of appropriate rating. Such a system is termed as the AC module in the literature and consists of a PV module along with the required power electronic circuitry, known as module integrated converter (MIC). The AC module integrated with the grid is required to operate at high efficiency and provide an output voltage of the expected magnitude and frequency. In this paper an efficient MIC with pseudo DC-link (pDC-l) for grid integration of AC module is proposed. The proposed MIC is claimed to be high efficient due to the fundamental frequency operation of the inverter. To obtain a pDC-l of required magnitude from single photovoltaic (PV) module, a high gain Z-source buck-boost converter (ZBBC) is used. It is followed by an unfolding circuit which operates at fundamental frequency to convert the pDC-l to sinusoidal output. The fundamental frequency operation reduces the switching losses without affecting the total harmonic distortion (THD). The operation of the ZBBC, when used to obtain a pDC-l output is analysed and a simple closed loop control is developed. The control ensures a pseudo DC-link voltage at the input of the H-bridge that acts as an unfolding circuit. The control also ensures power balance by controlling the current injected to the grid. Simulations of the proposed AC module with ZBBC cascaded with pDC-l inverter have been carried out using MATLAB/Simulink platform and the results are presented to validate the proposed MIC and its closed loop control. © 2020 IEEE.Item Power control of PV/fuel cell/supercapacitor hybrid system for stand-alone applications(International Journal of Renewable Energy Research, 2016) Sabhahit, N.S.; Gaonkar, D.N.; Nempu, P.B.This paper presents modeling and control of photovoltaic/fuel cell/supercapacitor hybrid power system for stand-alone applications. The hybrid power system uses solar photovoltaic array and fuel cell as the main sources. These sources share their power effectively to meet the load demand. The supercapacitor bank is used to supply or absorb the power during load transients. The main control system comprises of controller for maximum power tracking from photovoltaic system, a DC-DC boost converter with controller for fuel cell system for power management and inverter controller to regulate voltage and frequency. The stand-alone hybrid system aims to provide quality power supply to the consumers with a constant voltage and frequency along with proper power management using simple control techniques. The modeling and control strategies of the hybrid system are realized in MATLAB/Simulink.Item A new control method to mitigate power fluctuations for grid integrated PV/wind hybrid power system using ultracapacitors(Walter de Gruyter GmbH info@degruyter.com, 2016) Sabhahit, N.S.; Gaonkar, D.N.The output power obtained from solar-wind hybrid system fluctuates with changes in weather conditions. These power fluctuations cause adverse effects on the voltage, frequency and transient stability of the utility grid. In this paper, a control method is presented for power smoothing of grid integrated PV/wind hybrid system using ultracapacitors in a DC coupled structure. The power fluctuations of hybrid system are mitigated and smoothed power is supplied to the utility grid. In this work both photovoltaic (PV) panels and the wind generator are controlled to operate at their maximum power point. The grid side inverter control strategy presented in this paper maintains DC link voltage constant while injecting power to the grid at unity power factor considering different operating conditions. Actual solar irradiation and wind speed data are used in this study to evaluate the performance of the developed system using MATLAB/Simulink software. The simulation results show that output power fluctuations of solar-wind hybrid system can be significantly mitigated using the ultracapacitor based storage system. © by De Gruyter 2016.Item Megawatt-scale solar variability study: An experience from a 1.2 MWp photovoltaic system in Australia over three years(Institution of Engineering and Technology journals@theiet.org, 2016) Yan, R.; Saha, T.K.; Meredith, P.; Ananth, A.; Hossain, M.I.With more photovoltaic (PV) systems being integrated into distribution networks, power utilities are facing many challenges in both planning and operation. Network operators are concerned with PV variability and associated necessity of voltage regulation, control coordination, reserve adequacy and dispatch constraints. While to address the obligatory connection agreement, it is vital for PV farm owners to accurately estimate PV variability and then provide the most cost-effective compensation method. In the literature, PV variability of different scales has been investigated over the last 20 years. However, little has focused on output fluctuations of PV systems with long-term and high-resolution recorded data at a low-voltage distribution feeder level where voltage regulation has become a serious issue. This is particularly true in Australia, where PV penetration is growing in many states and is expected to grow further in the near future. This study utilises the data of a distributed 1.2 MWp PV system in the University of Queensland recorded over the last three years with 1-min resolution to analyse the statistical characteristics of PV power variability. The results from this study will provide very useful information for both power utilities and solar farm owners regarding network operation and future PV system development. ©The Institution of Engineering and Technology 2016.Item Design and implementation of single phase inverter based on Cuk converter for PV system(International Journal of Renewable Energy Research, 2017) Sabhahit, N.S.; Gaonkar, D.N.; Anandh, N.; Kumar, N.S.In this paper, analysis and hardware implementation of a single phase inverter based on Cuk converter for PV system is presented. The buck-boost characteristic of such a converter promotes flexibility for both grid tied as well as standalone connections where the ac voltage is either higher than or lesser than the dc input voltage. Further Cuk based topologies have the better efficiency and voltage regulation, which is a lacking feature in a basic boost or a buck configuration. The proposed system not only offers continuous input and output current but also controlled voltage over a wider range. Hence this topology can serve as an expedient alternative converter stage for photovoltaic applications. In the proposed bidirectional two-switch Cuk converter, DSPIC30F2010 controller is used for controlling the duty ratio of switching pulses. Also, this controller generates PWM signals for the switches of single phase H-bridge inverter. The hardware results for the developed prototype of a Cuk converter based single phase inverter are presented. The developed scheme can easily be scalable to a much larger rating of the PV system.Item Integrated power flowand voltage regulation of stand-alone PV-fuel cell system with supercapacitors(Acta Press journals@actapress.com, 2017) Sabhahit, J.N.; Gaonkar, D.N.; Nempu, P.B.The output of the solar cell is fluctuating due to intermittency of solar irradiation. Hybridizing the solar photovoltaic (PV) system with other sources and appropriate storage devices is essential to generate electricity continuously. This paper presents the control strategies for a PV-fuel cell hybrid power system with supercapacitor bank for isolated load applications. Supercapacitor bank is controlled using a bidirectional DC/DC converter so as to regulate voltage at a DC link and to keep the system stable under transient load variations. The H-bridge inverter is controlled to regulate voltage and frequency across the load. The PV system is controlled to extract maximum power using the maximum power point tracking algorithm. This paper aims to provide a single-phase supply with constant voltage and frequency to the consumers with proper power sharing among different sources. The hybrid system is realized in Matlab/Simulink environment.Item Effect of Partial Shading on PV Fed Induction Motor Water Pumping Systems(Institute of Electrical and Electronics Engineers Inc., 2019) Mudlapur, M.; Ramana, V.V.; Damodaran, R.; Balasubramanian, B.; Mishra, S.Partial shading is one of the certain conditions in photovoltaic (PV) power plants. Often the panels get partially shaded due to soiling, clouds, and trees. The effect of shading is of high concern and importance especially in applications such as water pumps due to agricultural environments in which they are employed in. However, the research focus on PV fed pumps till date has been restricted to only uniform shading conditions. Unlike uniform shading conditions during maximum power tracking, where the panel voltage remains almost constant for an entire range of irradiance, partial shading offer conditions such as highly variable panel voltage and transitions of intermediate DC-DC power converter from continuous conduction mode to discontinuous conduction mode. These effects severely affect the performance of the power converter and, therefore, the power output of the pump. This paper presents a study on the effects caused by partial shading conditions on pumps through simulations and verified by experimentations. The simulation and experimental results are found to be in good agreement with each other. This research thus helps in understanding the detrimental effects caused by partial shading conditions and thus serves as a reference tool for practitioners who wish to study PV fed pumps. © 1986-2012 IEEE.Item A Hybrid Evolutionary-Based MPPT for Photovoltaic Systems under Partial Shading Conditions(Institute of Electrical and Electronics Engineers Inc., 2020) Joisher, M.; Singh, D.; Taheri, S.; Espinoza-Trejo, D.R.; Pouresmaeil, E.; Taheri, H.Under partial shading conditions (PSCs), photovoltaic (PV) system characteristics vary and may have multiple power peaks. Conventional maximum power point tracking (MPPT) methods are unable to track the global peak. In addition, it takes a considerable time to reach the maximum power point (MPP). To address these issues, this paper proposes an improved hybrid MPPT method using the conventional evolutional algorithms, i.e., Particle Swarm Optimization (PSO) and Differential Evaluation (DE). The main feature of the proposed hybrid MPPT method is the advantage of one method compensates for shortcomings of the other method. Furthermore, the algorithm is simple and rapid. It can be easily implemented on a low-cost microcontroller. To evaluate the performance of the proposed method, MATLAB simulations are carried out under different PSCc. Experimental verifications are conducted using a boost converter setup, an ET-M53695 panel and a TMS320F28335 DSP. Finally, the simulation and hardware results are compared to those from the PSO and DE methods. The superiority of the hybrid method over PSO and DE methods is highlighted through the results. © 2013 IEEE.