106 research outputs found

    Solar Power Generation Capability and Three-Port Converters for PV-Battery Powered Applications

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    University of Technology Sydney. Faculty of Engineering and Information Technology.Solar energy is one of the most useful sources of sustainable energy. Intermittency negatively affects the efficiency and reliability of solar power. To mitigate such a problem, a power electronic converter is used to enhance the solar power generation capability, such as detecting faulty solar photovoltaic (PV) cells to be eliminated from the solar system or tracking the maximum power point (MPPT). Other advantages of power converters are integrating energy storage systems (ESS) with the solar energy system and managing power flow. Solar cell power performance is greatly affected by two critical factors, aging and cracks. In order to mitigate their negative effects on the solar system, these cells are to be substituted by new cells; therefore, replacing the solar panels. In this research, an active crack detection method is proposed that can detect the cracked cells within a solar string by using AC parameter characterization without a need to have a physical inspection. In this research, an analog voltage-based MPPT algorithm for individual PV module is proposed and experimentally verified. The maximum power points of solar cell can be joined by an approximately linear line. The slope of this line varies depending on the type and characteristic of the panels. Utilizing this characteristic, a bipolar junction transistor (BJT) is used to implement a variable voltage reference as the DC load line of the BJT can be designed to match the MPP line of the PV panel. This improves the accuracy of the maximum power point reference voltage without the need for a digital controller or PID controller. This research also proposes two novel compact three-port converters. The proposed converters are used to interface a PV module, battery and load. The proposed converters are able to achieve MPPT, battery power management and output voltage regulation simultaneously. The first converter can be used for a stand-alone system or in a microgrid structure. The second converter is useful when bidirectional power flow is needed at the output port for some applications, such as grid-connected solar system and electric vehicle where regenerative braking is used. Each converter combines three converters to form one integrated converter by sharing some components such as switches, inductors and capacitors. Thus, the converters have a high power density and fewer components compared to the traditional DC-DC converters. The integrated PV-battery system is the promised solution for both intermittency and the unpredictable load demand

    Parametric estimation in photovoltaic modules using the crow search algorithm

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    The problem of parametric estimation in photovoltaic (PV) modules considering manufacturer information is addressed in this research from the perspective of combinatorial optimization. With the data sheet provided by the PV manufacturer, a non-linear non-convex optimization problem is formulated that contains information regarding maximum power, open-circuit, and short-circuit points. To estimate the three parameters of the PV model (i.e., the ideality diode factor (a) and the parallel and series resistances (Rp and Rs)), the crow search algorithm (CSA) is employed, which is a metaheuristic optimization technique inspired by the behavior of the crows searching food deposits. The CSA allows the exploration and exploitation of the solution space through a simple evolution rule derived from the classical PSO method. Numerical simulations reveal the effectiveness and robustness of the CSA to estimate these parameters with objective function values lower than 1 × 10−28 and processing times less than 2 s. All the numerical simulations were developed in MATLAB 2020a and compared with the sine-cosine and vortex search algorithms recently reported in the literature

    A framework of L-HC and AM-MKF for accurate harmonic supportive control schemes

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    In this paper, an enhanced optimal control technique based on adaptive Maximize-M Kalman filter (AM-MKF) is used. To maximize power extraction from solar PV (Photovoltaic) panel, a learning-based hill climbing (L-HC) algorithm is implemented for a grid integrated solar PV system. For the testing, a three-phase system configuration based on 2-stage topology, and the deployed load on a common connection point (CCP) are considered. The L-HC MPPT algorithm is the modified version of HC (Hill Climbing) algorithm, where issues like, oscillation in steady-state condition and, slow response during dynamic change condition are mitigated. The AM-MKF is an advanced version of KF (Kalman Filter), where for optimal estimation in KF, an AM-M (Adaptive Maximize-M) concept is integrated. The key objective of the novel control strategy is to extract maximum power from the solar panel and to meet the demand of the load. After satisfying the load demand, the rest power is transferred to the grid. However, in the nighttime, the system is used for reactive power support, which mode of operation is known as a DSTATCOM (Distribution Static Compensator). The capability of developed control strategies, is proven through testing on a prototype. During experimentation, different adverse grid conditions, unbalanced load situation and variable solar insolation are considered. In these situations, the satisfactory performances of control techniques prove the effectiveness of the developed control strategy

    PV inverters for module level applications

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    Dissertação para obtenção do Grau de Mestre em Energias Renováveis – Conversão Eléctrica e Utilização SustentáveisNowadays, the photovoltaic (PV) energy is presented as one of the most promising source of clean energy, and so a good way for greenhouse gas emissions mitigation and reduce the fossil fuel dependence. Within it, the photovoltaic energy has caused a huge interest in the electronic converters, and the need to improve their efficiency and reducing their cost. With this work I present a solution for a module scale grid-connected single-phase inverter. The solution consists in a two-stage inverter insolated with a grid line transformer. The two-stage inverter is composed by a DC-DC converter and a DC-AC converter connected through a DC-link capacitor. The DC-DC converter in case is a boost converter used to elevate the voltage from the PV module to a higher level. For the DC-AC converter it is used a full-bridge inverter, and both the DC-DC and the DC-AC converters use the IGBTs form an integrated module with its respective drivers. To the boost control it is implemented a Maximum Power Point Tracking algorithm that can optimize the power extraction from the PV source and for the inverter it is used a sliding mode hysteretic control. Once this inverter is conceived to work connected to the grid, a single-phase PLL system is used to synchronize the injected current to grid voltage. All the control part is made digitally using an Arduino Uno board, which uses an Atmel microcontroller

    Modeling and Control of a Battery Connected Standalone Photovoltaic System

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    Nowadays, due to the decrease of conventional energy sources and growing problem of environmental pollution, renewable energy sources are playing a big role in producing electricity. Among them solar and wind are popular renewable energy sources, that have concerned with more and more attention. Solar energy has become a promising, popular and alternative source because of its advantages such as abundance, pollution free, renewability and maintenance free. This work is based on a standalone photovoltaic (PV) system in which a storage device is used as a backup source. The remote areas, which are isolated from utility grid,standalone operation of PV system is the best option. But due to diurnal cycle of the earth and weather condition, solar energy in not constant throughout the day and also sometimes the PV generation is not sucient to full the power demand of the varying local load. Hence PV system cannot give a steady power to the load connected in standalone PV system, which makes the system unstable. So the use of dedicated energy storage systems needs to be taken into account to make this intermittent PV power more dispatchable and stable. Here, the storage device is mainly taken as a lead-acid battery, as it is more convenient to use in high power applications such as solar and wind systems because of its low cost and availability in large size. For controlling the standalone PV system, its mathematical modelling is very much necessary. So the modelling of PV system and lead-acid battery by using the corresponding equivalent circuits are discussed. As we know, to increase the eciency of PV array maximum power should be extracted from it. Here an analog MPPT controller is used for extracting the optimal power available at PV module,by controlling the duty cycle of a boost converter. This analog MPPT control technique shows fast and robust behavior even in changing environmental and load condition compared to conventional MPPT control techniques. For charging and discharging of the lead-acid battery, a bidirectional buck-boost converter is used, which is capable of transferring power in both the direction with appropriate voltage level. To provide electrical power to any load or appliances, the inverter converts the DC bus voltage to a single phase AC voltage with appropriate amplitude and frequency. In this work a current-controlled single phase VSI with bipolar pulse width modulation is used to maintain the stable voltage and current at local load. Thus here three independent control loops are used to control the whole standalone system. Those are MPPT control loop for extracting maximum power from PV module, battery control loop for bidirectional power ow between battery and DC-link through bidirectional buck-boost converter and inverter control loop for maintaining stable voltage and current at local load. The stability analysis is performed by using bode plots for both the inverter control loop and buck-boost converter control loop and these control loops are stable for our tuned controller parameters. The system is simulated in MATLAB/SIMULINK and simulation results shown to full the objectives of the standalone PV system. The simulation results prove the e ectiveness of the proposed controllers

    Simple and Fast Dynamic Photovoltaic Emulator based on a Physical Equivalent PV‐cell Model

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    Photovoltaic emulators are a specific type of power electronics system to mimic the behaviour of a photovoltaic (PV) panel or array and facilitate the testing of energy systems. Existing solutions usually require sophisticated hardware design and fast computing. This paper presents a simple, reliable, and effective circuit-based photovoltaic (PV) emulator based on the equivalent PV stacked cells. The PV emulator can be used for solar system testing and analysis, such as maximum power point tracking (MPPT) and partial shading effect. The – and – characteristic curves of the emulator have been generated by using an LTspice simulator. It is experimentally investigated and compared with a real PV panel and existing emulator products. The experiment results show good agreement with the mimicked actual PV panel. The proposed PV emulator shows a better dynamic response and shorter settling time than several benchmarked commercial products. The enhancement in the time response is due to the simplicity of the emulator, where a few power diodes and some resisters are used. In addition to simplicity, the PV emulator is very cost-effective

    Off-Grid Inverter with Regulated Output Voltage Amplitude

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    The paper discusses the design, simulation, and implementation of a 60W, 115VAC, 60Hz off-grid power inverter. The off-grid inverter creates a mains-level voltage from a 12V lead-acid battery input without connection to a conventional electric grid. The inverter includes a low-voltage H-Bridge circuit that is controlled with 3-level Pulse Width Modulation (PWM), and uses a low frequency step up transformer from 12V to 115V. A feedback system based on IQ sampling and a Proportional, Integral, Derivative controller (PID) is implemented to maintain a constant output voltage amplitude over an input range of 10 to 15VDC. A microcontroller is used to generate PWM and implement the feedback loop. The inverter successfully powers small household loads such as a desktop fan and laptop

    Stargrazer One: A New Architecture for Distributed Maximum Power Point Tracking of Solar Photovoltaic Sources

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    The yield from a solar photovoltaic (PV) source is dependent on factors such as light and temperature. A control system called a maximum power point tracker (MPPT) ensures that the yield from a solar PV source is maximized in spite of these factors. This thesis presents a novel implementation of a perturb and observe (PO) MPPT. The implementation uses a switched capacitor step down converter and a custom digital circuit implementation of the PO algorithm. Working in tandem, the switched capacitor step down converter and the custom digital circuit implementation were able to successfully track the maximum power point of a simulated solar PV source. This implementation is free of the overhead encountered with general purpose processor based MPPT implementations. This makes this MPPT system a valid candidate for applications where general purpose processors are undesirable. This document will begin by discussing the current state of MPPT research. Afterward, this thesis will present studies done to be able to use the chosen switched capacitor step down converter. Then the digital circuit PO implementation will be discussed in detail. Simulations of the architecture will be presented. Finally, experimental validation using a hardware prototype will be shown

    Analysis and Design of High-Speed A/D Converters in SiGe Technology

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    Mixed-signal systems play a key role in modern communications and electronics. The quality of A/D and D/A conversions deeply affects what we see and what we hear in the real world video and radio. This dissertation deals with high-speed ADCs: a 5-bit 500-MSPS ADC and an 8-bit 2-GSPS ADC. These units can be applied in flat panel display, image enhancement and in high-speed data link. To achieve the state-of-the-art performance, we employed a 0.13-μm/2.5-V 210-GHz (unity-gain frequency) BiCMOS SiGe process for all the implementations. The circuit building blocks, such as the Track-and-Hold circuit (T/H) and the comparator, required by an ADC not only benefit from SiGe's superior ultra-high frequency properties but also by its power drive capability. The T/H described here achieved a dynamic performance of 8-bit accuracy at 2-GHz Nyquist rate with an input full scale range of 1 Vp-p. The T/H consumed 13 mW of power. The unique 4-in/2-out comparator was made of fully differential emitter couple pairs in order to operate at such a high frequency. Cascaded cross-coupled amplifier core was employed to reduce Miller effect and to avoid collector-emitter breakdown of the HBTs. We utilized the comparator interpolation technique between the preamplifer stages and the latches to reduce the total power dissipated by the comparator array. In addition, we developed an innovative D/A conversion and analog subtraction approach necessary for two-step conversion by using a bipolar pre-distortion technique. This innovation enabled us to decrease the design complexity in the subranging process of a two-step ADC. The 5-bit interpolating ADC operated at 2-GSPS achieved a differential nonlinearity (DNL) of 0.114 LSB and an integral nonlinearity (INL) of 0.076 LSB. The effective number of bits (ENOBs) are 4.3 bits at low frequency and 4.1 bits near Nyquist rate. The power dissipation was reduced more than half to 66.14 mW, with comparator interpolation. The 8-bit two-step interpolating ADC operated at 500-MSPS. It achieved a DNL of 0.33 LSB and an INL of 0.40 LSB with a power consumption of 172 mW. The ENOBs are 7.5 bits at low frequency and 6.9 bits near Nyquist rate

    In Situ Automatic Analog Circuit Calibration and Optimization

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    As semiconductor technology scales down, the variations of active/passive device characteristics after fabrication are getting more and more significant. As a result, many circuits need more accuracy margin to meet minimum accuracy specifications over huge process-voltage-temperature (PVT) variations. Although, overdesigning a circuit is sometimes not a feasible option because of excessive accuracy margin that requires high power consumption and large area. Consequently, calibration/tuning circuits that can automatically detect and compensate the variations have been researched for analog circuits to make better trade-offs among accuracy, power consumption, and area. The first part of this dissertation shows that a newly proposed in situ calibration circuit for a current reference can relax the sharp trade-off between the temperature coefficient accuracy and the power consumption of the current reference. Prototype chips fabricated in a 180 nm CMOS technology generate 1 nA and achieve an average temperature coefficient of 289 ppm/°C and an average line sensitivity of 1.4 %/V with no help from a multiple-temperature trimming. Compared with other state-of-the-art current references that do not need a multiple-temperature trimming, the proposed circuit consumes at least 74% less power, while maintaining similar or higher accuracy. The second part of this dissertation proves that a newly proposed multidimensional in situ analog circuit optimization platform can optimize a Tow-Thomas bandpass biquad. Unlike conventional calibration/tuning approaches, which only handle one or two frequency-domain characteristics, the proposed platform optimizes the power consumption, frequency-, and time-domain characteristics of the biquad to make a better trade-off between the accuracy and the power consumption of the biquad. Simulation results show that this platform reduces the gain-bandwidth product of op-amps in the biquad by 80% while reducing the standard deviations of frequency- and time-domain characteristics by 82%. Measurement results of a prototype chip fabricated in a 180 nm CMOS technology also show that this platform can save maximum 71% of the power consumption of the biquad while the biquad maintains its frequency-domain characteristics: Q, ωO and the gain at ωO
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