Showing papers on "Maximum power point tracking published in 2012"
TL;DR: In this article, the authors proposed an improved maximum power point tracking (MPPT) method for the photovoltaic (PV) system using a modified particle swarm optimization (PSO) algorithm.
Abstract: This paper proposes an improved maximum power point tracking (MPPT) method for the photovoltaic (PV) system using a modified particle swarm optimization (PSO) algorithm. The main advantage of the method is the reduction of the steady- state oscillation (to practically zero) once the maximum power point (MPP) is located. Furthermore, the proposed method has the ability to track the MPP for the extreme environmental condition, e.g., large fluctuations of insolation and partial shading condition. The algorithm is simple and can be computed very rapidly; thus, its implementation using a low-cost microcontroller is possible. To evaluate the effectiveness of the proposed method, MATLAB simulations are carried out under very challenging conditions, namely step changes in irradiance, step changes in load, and partial shading of the PV array. Its performance is compared with the conventional Hill Climbing (HC) method. Finally, an experimental rig that comprises of a buck-boost converter fed by a custom-designed solar array simulator is set up to emulate the simulation. The soft- ware development is carried out in the Dspace 1104 environment using a TMS320F240 digital signal processor. The superiority of the proposed method over the HC in terms of tracking speed and steady-state oscillations is highlighted by simulation and experimental results.
851 citations
TL;DR: In this article, a detailed theoretical and experimental comparison of the two perturb and observe (P&O) implementation techniques on the basis of system stability, performance characteristics, and energy utilization for standalone PV pumping systems is presented.
Abstract: The energy utilization efficiency of commercial photovoltaic (PV) pumping systems can be significantly improved by employing simple perturb and observe (P&O) maximum power point tracking algorithms. Two such P&O implementation techniques, reference voltage perturbation and direct duty ratio perturbation, are commonly utilized in the literature but no clear criteria for the suitable choice of method or algorithm parameters have been presented. This paper presents a detailed theoretical and experimental comparison of the two P&O implementation techniques on the basis of system stability, performance characteristics, and energy utilization for standalone PV pumping systems. The influence of algorithm parameters on system behavior is investigated and the various advantages and drawbacks of each technique are identified for different weather conditions. Practical results obtained using a 1080-Wp PV array connected to a 1-kW permanent magnet dc motor-centrifugal pump set show very good agreement with the theoretical analysis and numerical simulations.
646 citations
TL;DR: In this article, a comparison of the performance of different MPPT algorithms on the basis of various speed responses and ability to achieve the maximum energy yield is made, and the optimal torque control (OTC) is found to be the best MPPT method for wind energy systems due to its simplicity.
Abstract: This paper reviews state of the art maximum power point tracking (MPPT) algorithms for wind energy systems. Due to the instantaneous changing nature of the wind, it is desirable to determine the one optimal generator speed that ensures maximum energy yield. Therefore, it is essential to include a controller that can track the maximum peak regardless of wind speed. The available MPPT algorithms can be classified as either with or without sensors, as well as according to the techniques used to locate the maximum peak. A comparison has been made between the performance of different MPPT algorithms on the basis of various speed responses and ability to achieve the maximum energy yield. Based on simulation results available in the literature, the optimal torque control (OTC) has been found to be the best MPPT method for wind energy systems due to its simplicity. On the other hand, the perturbation and observation (P&O) method is flexible and simple in implementation, but is less efficient and has difficulties determining the optimum step-size.
645 citations
TL;DR: In this paper, a one-day-ahead PV power output forecasting model for a single station is derived based on the weather forecasting data, actual historical power output data, and the principle of SVM.
Abstract: Due to the growing demand on renewable energy, photovoltaic (PV) generation systems have increased considerably in recent years. However, the power output of PV systems is affected by different weather conditions. Accurate forecasting of PV power output is important for system reliability and promoting large-scale PV deployment. This paper proposes algorithms to forecast power output of PV systems based upon weather classification and support vector machines (SVM). In the process, the weather conditions are divided into four types which are clear sky, cloudy day, foggy day, and rainy day. In this paper, a one-day-ahead PV power output forecasting model for a single station is derived based on the weather forecasting data, actual historical power output data, and the principle of SVM. After applying it into a PV station in China (the capability is 20 kW), results show the proposed forecasting model for grid-connected PV systems is effective and promising.
547 citations
TL;DR: In this article, a dual-path architecture for energy harvesting is employed that has a peak efficiency improvement of 11-13% over the traditional two-stage approach, which is achieved by combining energy from solar, thermal, and vibration sources.
Abstract: A platform architecture combining energy from solar, thermal, and vibration sources is presented. A dual-path architecture for energy harvesting is employed that has a peak efficiency improvement of 11%-13% over the traditional two-stage approach. The system implemented consists of a reconfigurable multi-input, multi-output switch matrix that combines energy from three distinct energy-harvesting sources-photovoltaic, thermoelectric, and piezoelectric. The system can handle input voltages from 20 mV to 5 V and is capable of extracting maximum power from individual harvesters all at the same time utilizing a single inductor. A proposed time-based power monitor is used for achieving maximum power point tracking for the photovoltaic harvester. This has a peak tracking efficiency of 96%. The peak efficiencies achieved with inductor sharing are 83%, 58%, and 79% for photovoltaic boost, thermoelectric boost, and piezoelectric buck-boost converters, respectively. The switch matrix and the control circuits are implemented on a 0.35-μm CMOS process.
446 citations
TL;DR: In this article, a particle swarm optimization (PSO)-based MPPT algorithm for PGS operating under PSC is proposed, where the standard version of PSO is modified to meet the practical consideration of the P-V curve.
Abstract: A photovoltaic (PV) generation system (PGS) is becoming increasingly important as renewable energy sources due to its advantages such as absence of fuel cost, low maintenance requirement, and environmental friendliness. For large PGS, the probability for partially shaded condition (PSC) to occur is also high. Under PSC, the P-V curve of PGS exhibits multiple peaks, which reduces the effectiveness of conventional maximum power point tracking (MPPT) methods. In this paper, a particle swarm optimization (PSO)-based MPPT algorithm for PGS operating under PSC is proposed. The standard version of PSO is modified to meet the practical consideration of PGS operating under PSC. The problem formulation, design procedure, and parameter setting method which takes the hardware limitation into account are described and explained in detail. The proposed method boasts the advantages such as easy to implement, system-independent, and high tracking efficiency. To validate the correctness of the proposed method, simulation, and experimental results of a 500-W PGS will also be provided to demonstrate the effectiveness of the proposed technique.
437 citations
TL;DR: A survey of the proposed approaches in each category of modified MPPT techniques that properly detect the global MPP is surveyed and a brief discussion of their characteristics is provided.
Abstract: Partial shading in photovoltaic (PV) arrays renders conventional maximum power point tracking (MPPT) techniques ineffective. The reduced efficiency of shaded PV arrays is a significant obstacle in the rapid growth of the solar power systems. Thus, addressing the output power mismatch and partial shading effects is of paramount value. Extracting the maximum power of partially shaded PV arrays has been widely investigated in the literature. The proposed solutions can be categorized into four main groups. The first group includes modified MPPT techniques that properly detect the global MPP. They include power curve slope, load-line MPPT, dividing rectangles techniques, the power increment technique, instantaneous operating power optimization, Fibonacci search, neural networks, and particle swarm optimization. The second category includes different array configurations for interconnecting PV modules, namely series-parallel, total-cross-tie, and bridge-link configurations. The third category includes different PV system architectures, namely centralized architecture, series-connected microconverters, parallel-connected microconverters, and microinverters. The fourth category includes different converter topologies, namely multilevel converters, voltage injection circuits, generation control circuits, module-integrated converters, and multiple-input converters. This paper surveys the proposed approaches in each category and provides a brief discussion of their characteristics.
433 citations
TL;DR: A new method to track the global MPP is presented, which is based on controlling a dc/dc converter connected at the PV array output, such that it behaves as a constant input-power load.
Abstract: The power-voltage characteristic of photovoltaic (PV) arrays operating under partial-shading conditions exhibits multiple local maximum power points (MPPs). In this paper, a new method to track the global MPP is presented, which is based on controlling a dc/dc converter connected at the PV array output, such that it behaves as a constant input-power load. The proposed method has the advantage that it can be applied in either stand-alone or grid-connected PV systems comprising PV arrays with unknown electrical characteristics and does not require knowledge about the PV modules configuration within the PV array. The experimental results verify that the proposed global MPP method guarantees convergence to the global MPP under any partial-shading conditions. Compared with past-proposed methods, the global MPP tracking process is accomplished after far fewer PV array power perturbation steps.
426 citations
TL;DR: In this paper, an adaptive control algorithm is proposed to balance the need for power quality (voltage regulation) with the desire to minimize power loss in a radial distribution circuit with a high penetration of photovoltaic cells.
Abstract: We show how an adaptive control algorithm can improve the performance of distributed reactive power control in a radial distribution circuit with a high penetration of photovoltaic (PV) cells. The adaptive algorithm is designed to balance the need for power quality (voltage regulation) with the desire to minimize power loss. The adaptation law determines whether the objective function minimizes power losses or voltage regulation based on whether the voltage at each node remains close enough to the voltage at the substation. The reactive power is controlled through the inverter on the PV cells. The control signals are determined based on local instantaneous measurements of the real and reactive power at each node. We use the example of a single branch radial distribution circuit to demonstrate the ability of the adaptive scheme to effectively reduce voltage variations while simultaneously minimizing the power loss in the studied cases. Simulations verify that the adaptive schemes compares favorably with local and global schemes previously reported in the literature.
390 citations
22 Jul 2012
TL;DR: This paper will illustrate how, depending on the circuit topology and its loading condition, the inverter's optimal reactive power injection is not necessarily monotone with respect to their real power output.
Abstract: The intent of the study detailed in this paper is to demonstrate the benefits of inverter var control on a fast timescale to mitigate rapid and large voltage fluctuations due to the high penetration of photovoltaic generation and the resulting reverse power flow. Our approach is to formulate the volt/var control as a radial optimal power flow (OPF) problem to minimize line losses and energy consumption, subject to constraints on voltage magnitudes. An efficient solution to the radial OPF problem is presented and used to study the structure of optimal inverter var injection and the net benefits, taking into account the additional cost of inverter losses when operating at non-unity power factor. This paper will illustrate how, depending on the circuit topology and its loading condition, the inverter's optimal reactive power injection is not necessarily monotone with respect to their real power output. The results are demonstrated on a distribution feeder on the Southern California Edison system that has a very light load and a 5 MW photovoltaic (PV) system installed away from the substation.
376 citations
TL;DR: In this paper, a three-input dc-dc boost converter is proposed for hybridizing alternative energy sources such as photovoltaic (PV) source, fuel cell (FC) source and battery.
Abstract: A new three-input dc-dc boost converter is proposed in this paper. The proposed converter interfaces two unidirectional input power ports and a bidirectional port for a storage element in a unified structure. This converter is interesting for hybridizing alternative energy sources such as photovoltaic (PV) source, fuel cell (FC) source, and battery. Supplying the output load, charging or discharging the battery can be made by the PV and the FC power sources individually or simultaneously. The proposed structure utilizes only four power switches that are independently controlled with four different duty ratios. Utilizing these duty ratios, tracking the maximum power of the PV source, setting the FC power, controlling the battery power, and regulating the output voltage are provided. Depending on utilization state of the battery, three different power operation modes are defined for the converter. In order to design the converter control system, small-signal model is obtained in each operation mode. Due to interactions of converter control loops, decoupling network is used to design separate closed-loop controllers. The validity of the proposed converter and its control performance are verified by simulation and experimental results for different operation conditions.
TL;DR: The proposed control scheme achieves stable operation in the entire region of the PV panel and eliminates therefore the resulting oscillations around the maximum power operating point.
Abstract: This paper presents a new digital control scheme for a standalone photovoltaic (PV) system using fuzzy-logic and a dual maximum power point tracking (MPPT) controller. The first MPPT controller is an astronomical two-axis sun tracker, which is designed to track the sun over both the azimuth and elevation angles and obtain maximum solar radiation at all times. The second MPPT algorithm controls the power converter between the PV panel and the load and implements a new fuzzy-logic (FLC)-based perturb and observe (P&O) scheme to keep the system power operating point at its maximum. The FLC-MPPT is based on a voltage control approach of the power converter with a discrete PI controller to adapt the duty cycle. The input reference voltage is adaptively perturbed with variable steps until the maximum power is reached. The proposed control scheme achieves stable operation in the entire region of the PV panel and eliminates therefore the resulting oscillations around the maximum power operating point. A 150-Watt prototype system is used with two TMS320F28335 eZdsp boards to validate the proposed control scheme performance.
TL;DR: In this paper, a modified current-voltage relationship for the single-diode model is presented, based on the well-known equivalent circuit for a single photovoltaic (PV) cell.
Book•
18 Dec 2012TL;DR: In this article, a review of methods for modeling a photovoltaic array working in uniform and mismatched conditions is presented, as well as several ways to achieve the best maximum power point tracking (MPPT) performance.
Abstract: Incentives provided by European governments have resulted in the rapid growth of the photovoltaic (PV) market. Many PV modules are now commercially available, and there are a number of power electronic systems for processing the electrical power produced by PV systems, especially for grid-connected applications. Filling a gap in the literature, Power Electronics and Control Techniques for Maximum Energy Harvesting in Photovoltaic Systems brings together research on control circuits, systems, and techniques dedicated to the maximization of the electrical power produced by a photovoltaic (PV) source.
Tools to Help You Improve the Efficiency of Photovoltaic Systems
The book supplies an overview of recent improvements in connecting PV systems to the grid and highlights various solutions that can be used as a starting point for further research and development. It begins with a review of methods for modeling a PV array working in uniform and mismatched conditions. The book then discusses several ways to achieve the best maximum power point tracking (MPPT) performance. A chapter focuses on MPPT efficiency, examining the design of the parameters that affect algorithm performance. The authors also address the maximization of the energy harvested in mismatched conditions, in terms of both power architecture and control algorithms, and discuss the distributed MPPT approach. The final chapter details the design of DC/DC converters, which usually perform the MPPT function, with special emphasis on their energy efficiency.
Get Insights from the Experts on How to Effectively Implement MPPT
Written by well-known researchers in the field of photovoltaic systems, this book tackles state-of-the-art issues related to how to extract the maximum electrical power from photovoltaic arrays under any weather condition. Featuring a wealth of examples and illustrations, it offers practical guidance for researchers and industry professionals who want to implement MPPT in photovoltaic systems.
TL;DR: This paper aims at reviewing part of these topics (MPPT, current and voltage control) leaving to a future paper to complete the scenario.
Abstract: Photovoltaic Systems (PVS) can be easily integrated in residential buildings hence they will be the main responsible of making low-voltage grid power flow bidirectional. Control issues on both the PV side and on the grid side have received much attention from manufacturers, competing for efficiency and low distortion and academia proposing new ideas soon become state-of-the-art. This paper aims at reviewing part of these topics (MPPT, current and voltage control) leaving to a future paper to complete the scenario. Implementation issues on Digital Signal Processor (DSP), the mandatory choice in this market segment, are discussed.
TL;DR: In this article, a novel frequency regulation by DIFG-based wind turbines to coordinate inertial control, rotor speed control and pitch angle control, under low, medium or high wind speed mode is presented.
Abstract: The increasing penetration of wind power impacts the frequency stability of power systems. A doubly fed induction generator (DFIG)-based wind power plant naturally does not provide frequency response because of the decoupling between the output power and the grid frequency. DFIGs also lack power reserve margin because of the maximum power point tracking (MPPT) operation. Therefore this study presents a novel frequency regulation by DFIG-based wind turbines to coordinate inertial control, rotor speed control and pitch angle control, under low, medium or high wind speed mode. Inertial control emulates the inertia of wind generators and supports frequency control during transient. The gain of inertial control is calculated from a creative viewpoint of protecting the wind turbine from stalling. Rotor speed control and pitch angle control enable DFIGs to reserve sufficient active power for a steady-state frequency adjustment. The numerical simulations demonstrate that the coordinated control enhances the frequency regulation capability and damps the frequency oscillations effectively.
TL;DR: In this article, a second-order sliding mode is proposed to control the wind turbine DIF according to references given by an MPPT, which can directly track the DFIG torque leading to maximum power extraction.
Abstract: This paper deals with power extraction maximization of a doubly fed induction generator (DFIG)-based wind turbine. These variable speed systems have several advantages over the traditional wind turbine operating methods, such as the reduction of the mechanical stress and an increase in the energy capture. To fully exploit this latest advantage, many control schemes have been developed for maximum power point tracking (MPPT) control schemes. In this context, this paper proposes a second-order sliding mode to control the wind turbine DFIG according to references given by an MPPT. Traditionally, the desired DFIG torque is tracked using control currents. However, the estimations used to define current references drive some inaccuracies mainly leading to nonoptimal power extraction. Therefore, using robust control, such as the second-order sliding mode, will allow one to directly track the DFIG torque leading to maximum power extraction. Moreover, the proposed control strategy presents attractive features such as chattering-free behavior (no extra mechanical stress), finite reaching time, and robustness with respect to external disturbances (grid) and unmodeled dynamics (generator and turbine). Simulations using the wind turbine simulator FAST and experiments on a 7.5-kW real-time simulator are carried out for the validation of the proposed high-order sliding mode control approach.
TL;DR: In this paper, a stand-alone hybrid power system consisting of three power generation systems, photovoltaic (PV) panels, a wind turbine and a proton exchange membrane fuel cell (PEMFC) is presented.
TL;DR: In this article, a lowvoltage ride-through scheme for the permanent magnet synchronous generator (PMSG) wind power system at the grid voltage sag is proposed, where the dc-link voltage is controlled by the generator side converter instead of the grid-side converter (GSC).
Abstract: This paper proposes a low-voltage ride-through scheme for the permanent magnet synchronous generator (PMSG) wind power system at the grid voltage sag. The dc-link voltage is controlled by the generator-side converter instead of the grid-side converter (GSC). Considering the nonlinear relationship between the generator speed ωm and the dc-link voltage Vdc , a dc-link voltage controller is designed using a feedback linearization theory. The GSC controls the grid active power for a maximum power point tracking. The validity of this control algorithm has been verified by simulation and experimental results for a reduced-scale PMSG wind turbine simulator.
TL;DR: In this article, a MATLAB-Simulink-based PV module model is presented, which includes a controlled current source and an S-Function builder. And the model has good predictability in the general behaviors of MPPT under the conditions of both non-uniform and uniform irradiance.
Abstract: The performance of a photovoltaic (PV) module is mostly affected by array configuration, irradiance, and module temperature. It is important to understand the relationship between these effects and the output power of the PV array. This paper presents a MATLAB-Simulink-based PV module model which includes a controlled current source and an S-Function builder. The modeling scheme in S-Function builder is deduced by some predigested functions. Under the conditions of nonuniform irradiance, the model is practically validated by using different array configurations in testing platform. The comparison experiments indicate that I-V and P-V characteristic curves of simulation match the measurements from outdoor experiment well. Under the conditions of nonuniform irradiance, both simulation and experiment show that the output power of a PV array gets more complicated due to multiple peaks. Moreover, the proposed model can also simulate electric circuit and its maximum power point tracking (MPPT) in the environment of MATLAB-Simulink. The experiments show that the proposed model has good predictability in the general behaviors of MPPT under the conditions of both nonuniform and uniform irradiance.
TL;DR: In this paper, the authors discuss the size of the perturbation of the operating conditions for both algorithms, based on the single-diode model, in order not to run away under certain dynamic conditions.
Abstract: Maximum power point tracking (MPPT) is an important function in all photovoltaic (PV) power systems. The classical “hill climbing” and “incremental conductance” MPPT algorithms are widely applied in many papers and applications. Both algorithms perturb the operating conditions of the PV array and detect the changes in generated power. Since the detected change in generated power also could be a result of changes in irradiance, both algorithms are prone to failure in case of large changes in irradiance. This paper starts to discuss the size of the perturbation of the operating conditions for both algorithms, based on the single-diode model. The result is used to select the updating frequency for the two algorithms, in order not to run away under certain dynamic conditions. Both algorithms are implemented in an inverter and tested over 16 days of simultaneous operation. Basic statistical procedures, the paired t-test, have been applied to the data with the conclusion that the two algorithms perform equally good.
TL;DR: The main contribution of this paper is the proposal of new modulation techniques for three-phase transformerless neutral point clamped inverters to eliminate leakage currents in photovoltaic systems without requiring any modification on the multilevel inverter or any additional hardware.
Abstract: The main contribution of this paper is the proposal of new modulation techniques for three-phase transformerless neutral point clamped inverters to eliminate leakage currents in photovoltaic systems without requiring any modification on the multilevel inverter or any additional hardware. The modulation techniques are capable of reducing the leakage currents in photovoltaic systems by applying three medium vectors or using only two medium vectors and one specific zero vector to compose the reference vector. In addition, to increase the system utilization, the three-phase neutral point clamped inverter can be designed to also provide functions of active filter using the p-q theory. The proposed system provides maximum power point tracking and compensation of current harmonics and reactive power. To validate the simulation models, an experimental three-phase inverter is used to evaluate leakage currents and the dc link voltage control.
18 May 2012
TL;DR: In this article, a new methodology for optimal design of transformerless photovoltaic (PV) inverters targeting a cost-effective deployment of grid-connected PV systems is presented.
Abstract: This paper presents a new methodology for optimal design of transformerless photovoltaic (PV) inverters targeting a cost-effective deployment of grid-connected PV systems. The optimal switching frequency as well as the optimal values and types of the PV inverter components is calculated such that the PV inverter LCOE generated during the PV system lifetime period is minimized. The LCOE is also calculated considering the failure rates of the components, which affect the reliability performance and lifetime maintenance cost of the PV inverter. A design example is presented, demonstrating that compared to the nonoptimized PV inverter structures, the PV inverters designed using the proposed optimization methodology exhibit lower total manufacturing and lifetime maintenance cost and inject more energy into the electric-grid and by that minimizing LCOE.
TL;DR: In this article, a grid-connected boost-half-bridge photovoltaic (PV) microinverter system and its control implementations are presented, where a plug-in repetitive current controller based on a fourth-order linear-phase IIR filter is proposed to regulate the grid current.
Abstract: This paper presents a novel grid-connected boost-half-bridge photovoltaic (PV) microinverter system and its control implementations. In order to achieve low cost, easy control, high efficiency, and high reliability, a boost-half-bridge dc-dc converter using minimal devices is introduced to interface the low-voltage PV module. A full-bridge pulsewidth-modulated inverter is cascaded and injects synchronized sinusoidal current to the grid. Moreover, a plug-in repetitive current controller based on a fourth-order linear-phase IIR filter is proposed to regulate the grid current. High power factor and very low total harmonic distortions are guaranteed under both heavy load and light load conditions. Dynamic stiffness is achieved when load or solar irradiance is changing rapidly. In addition, the dynamic behavior of the boost-half-bridge dc-dc converter is analyzed; a customized maximum power point tracking (MPPT) method, which generates a ramp-changed PV voltage reference is developed accordingly. Variable step size is adopted such that fast tracking speed and high MPPT efficiency are both obtained. A 210 W prototype was fabricated and tested. Simulation and experimental results are provided to verify the validity and performance of the circuit operations, current control, and MPPT algorithm.
03 Apr 2012
TL;DR: A transformer-based self-starting boost converter architecture with low-power maximum power point tracking (MPPT) control for low-voltage thermoelectric generator applications and an improved MPPT sensing method is proposed to simplify the circuit.
Abstract: While the demand for micro-energy harvesters (μEHs) is increasing (for seamless energy source in applications such as wireless sensor node), two major problems still obstruct versatile use of them. The first problem is the self-startup capability. Because many wireless sensor nodes are likely to be located where human-maintenance is difficult, starting them up manually can be as difficult as replacing the battery. Its realization has been difficult because μEHs must be able to turn itself on without any stored energy. Some previous works have reported such a function: some needed high voltage [1] or vibration [2] and one used a transformer as a starter [3]. The other problem is the maximum power point tracking (MPPT) capability. Because it is known that MPPT algorithms usually require considerable power consumption [4], using them in μEHs is impractical. This paper suggests a new boost converter architecture and MPPT control method which can bring μEH into practical use.
TL;DR: A new method for the modeling and simulation study of a photovoltaic grid connected system and its experimental validation is presented and good agreement with experimental data is shown, whether for the I–V characteristics or for the whole operating system.
TL;DR: In this article, the authors proposed a controller for a PV three-phase inverter that ensures minimum peak values in the grid-injected currents, as compared with conventional controllers, from the system analysis, a design method is presented in order to set the parameters of the control scheme.
Abstract: Nowadays, the majority of the photovoltaic (PV) power sources are connected to the public grid. One of the main connection problems occurs when voltage sags appear in the grid due to short circuits, lightning, etc. International standards regulate the grid connection of PV systems, forcing the source to remain connected during short-time grid-voltage faults. As a consequence, during the voltage sag, the source should operate with increasing converter currents to maintain the injection of the generated power. This abnormal operation may result in nondesired system disconnections due to overcurrents. This paper proposes a controller for a PV three-phase inverter that ensures minimum peak values in the grid-injected currents, as compared with conventional controllers. From the system analysis, a design method is presented in order to set the parameters of the control scheme. Selected experimental results are reported in order to validate the effectiveness of the proposed control.
TL;DR: In this article, the IEEE 13 bus system has been modified and extended to explore network stability impacts of variable PV generation, and the results show that a voltage stability issue with PV integration does exist in distribution networks.
Abstract: Several studies on voltage stability analysis of electric systems with high photovoltaic (PV) penetration have been conducted at a power-transmission level, but very few have focused on small-area networks of low voltage. As a distribution system has its special characteristics-high R/X ratio, long tap switching delay, small PV units, and so on-PV integration impacts also need to be investigated thoroughly at a distribution level. In this paper, the IEEE 13 bus system has been modified and extended to explore network stability impacts of variable PV generation, and the results show that a voltage stability issue with PV integration does exist in distribution networks. Simulation comparisons demonstrate that distribution networks are traditionally designed for heavily loaded situations exclusive of PVs, but they can still operate under low PV penetration levels without cloud-induced voltage-stability problems. It is also demonstrated that voltage instability can effectively be solved by PV inverter reactive power support if this scheme is allowed by the standards in the near future.
Patent•
23 Aug 2012TL;DR: In this paper, a wireless power transmission system includes a charging and path controller configured to supply, to a battery module, power generated by a solar cell module, or energy generated by an alternating current-to-direct current (AC/DC) converter, based on a control signal.
Abstract: A wireless power transmission system includes a charging and path controller configured to supply, to a battery module, power generated by a solar cell module, or power generated by an alternating current-to-direct current (AC/DC) converter, based on a control signal; a power converter configured to receive power from the battery module and generate a supply power to be supplied to a target device from power received from the battery module using a resonant frequency; a source resonator configured to receive the supply power from the power converter and transmit the supply power received from the power converter to the target device; and a control/communication unit configured to generate the control signal of the charging and path controller based on an amount of the power generated by the solar cell module and an amount of power that can be output from the battery module.
TL;DR: In this article, a single-phase grid-connected transformerless photovoltaic inverter for residential application is presented, which is derived from a boost cascaded with a buck converter along with a line frequency unfolding circuit.
Abstract: In this paper, a single-phase grid-connected transformerless photovoltaic inverter for residential application is presented. The inverter is derived from a boost cascaded with a buck converter along with a line frequency unfolding circuit. Due to its novel operating modes, high efficiency can be achieved because there is only one switch operating at high frequency at a time, and the converter allows the use of power MOSFET and ultrafast reverse recovery diode. It also features a robust structure because the phase leg does not have a shoot-through issue. This paper begins with theoretical analysis and modeling of this boost-buck converter-based inverter. And the model indicates that small boost inductance will lead to an increase in the resonant pole frequency and a decrease in the peak of Q, which results in easier control and greater stability. Thus, interleaved multiple phases structure is proposed to have small equivalent inductance; meanwhile, the ripple can be decreased, and the inductor size can be reduced as well. A two-phase interleaved inverter is then designed accordingly. Finally, the simulation and experiment results are shown to verify the concept and the tested efficiency under 1-kW power condition is up to 98.5%.