Showing papers on "Grid-connected photovoltaic power system published in 2020"

Advanced Control Strategy with Voltage Sag Classification for Single-Phase Grid-Connected Photovoltaic System

Abstract: This paper develops a fault ride-through (FRT) control strategy for achieving low voltage ride through (LVRT) in single-phase grid-connected photovoltaic (PV) systems (GCPVS). The proposed control system adapts a neural network (NN) classifier for islanding classification and model predictive control (MPC) for achieving the control of the two-stage PV system. This control scheme takes advantage of the nonlinear nature of the power converters and develops a cost function-based approach to achieve fast and efficient control. Besides, the proposed controller provides voltage support to the grid during voltage sags by injecting minimum reactive current within the threshold. The operation of the proposed control strategy is verified by performing simulation tests on a 4 kW GCPVS by creating a sag type of fault in the utility. Further, laboratory experiments were carried out with the developed controller. The results ensure that the proposed control system adheres to the grid requirements by enabling voltage support during grid faults.

Highly Efficient and Robust Grid Connected Photovoltaic System Based Model Predictive Control with Kalman Filtering Capability

Abstract: Renewable energy sources, especially photovoltaic (PV) ones, are gaining more and more interest due to the predicted lack of conventional sources over the coming years. That shortage is not the only concern, as environmental issues add to this concern also. Thus, this study proposes two-stage PV grid connected system, which is supported with extended Kalman filter (EKF) for parameter estimation. In the first stage, maximum power point tracking (MPPT) for the boost converter is accomplished using new MPPT method in which the switching state of the converter is directly generated after the measurement stage, so it is called direct switching MPPT technique. This technique is compared with the conventional finite control set model predictive control (FCS-MPC) method, where the design of the cost function is based on minimizing the error between the reference and the actual current. The reference current is obtained by employing perturb and observe (P&O) method. In the second stage, the two-level inverter is controlled by means of model predictive control (MPC) with reduced computation burden. Further, to overcome the parameter variations, which is a very common problem in MPC applications, an extended Kalman filter is utilized to eliminate the control algorithm’s dependency on the parameters by providing an efficient estimation. After the inverter, an RL filter is inserted to guarantee the quality of the currents injected into the grid. Finally, the system is validated using Matlab under different operating conditions of atmospheric variation and parameter changes.

Effect of partially shaded conditions on photovoltaic array's maximum power point tracking

Abstract: Maximum power point tracking algorithm is widely implemented in photovoltaic system to maximize the PV array output power. In general, Perturb and Observe (P&O) is simple thus being selected to continuously track the array maximum power point (MPP). Under uniform solar irradiance, PV array characteristic is non-linear and consisting only one MPP along the functional operating voltage. However, when the PV array is partially shaded, the P-V characteristic becomes more complex with multiple MPPs. The occurrence of multiple MPP might cause the PV array to be trapped at the local MPP. At this operating condition of local MPP, PV array will generate lesser output power. In this study, the performance of PV array is explored especially when each PV module is at 30% and 70% shaded conditions. Simulation results show that PV array at absolute MPP can generate greater output power with the largest increased by 74.6% hence achieving higher power efficiency.

Automatic Voltage Regulation of Grid Connected Photovoltaic System Using Lyapunov Based Sliding Mode Controller: A Finite — Time Approach

Abstract: Importance of PV based energy systems cannot be denied with quickly increase in renewable energy demand. Due to inherent uncertainties and non-linear behaviour of grid tied PV system, conventional control strategies are unable to provide satisfactory performance. Therefore, key purpose of this paper is to design non linear controller for the control of grid tied PV system. A novel control strategy is devised by utilizing Lyapunov base finite time non-linear reactive power and dc link voltage control. This strategy employes Lyapunov approach to ensure stability and guarantees robustness. With this control strategy, better and superior performance is observed in comparison to proportional integral controller. Furthermore, simulation results are provided to illustrate the effectiveness of proposed algorithm. Various disturbances of system such as change in solar insolation level, change in reference parameters, faults on buses are considered. With this control strategy, settling time and oscillations are found significantly less than PI controller.

Design of Super Twisting Sliding Mode Controller for a Three-Phase Grid-connected Photovoltaic System under Normal and Abnormal Conditions

Abstract: The novelty behind the research in this paper is to investigate the Super Twisting Sliding Mode Controller (ST-SMC) for efficiently injecting both active and reactive power under normal and abnormal operating conditions for a three-phase grid-connected photovoltaic (PV) system. The ST-SMC is aimed to inject sinusoidal current to the grid with low Total Harmonic Distortion (THD), to avoid chattering with easy real implementation, and to enhance the quality of disturbance rejection and sensitivity to parameter variation. The test under normal conditions includes initialization, steady state behavior, dynamic behavior, and interrupting the injection of acting and reactive power while the abnormal conditions consists of voltage sag, voltage swell, frequency variation, DC-link variation, and inclusion of 5th harmonics, etc. The phase lock loop used for synchronization is based on a synchronous reference frame that works well under distorted grids and nonideal. Automatic code is generated in PSIM 9.1 for hardware implementation in the DSP board TMS32F28335 from Texas Instruments while code composer studio 6.2.0 is used for debugging. The real time testing is executed using Typhoon Hardware in Loop (HIL) 402 device on the DSP board. The results authenticate the fastness, effectiveness, and robustness for both steady state and dynamic behavior under various scenarios of the designed controller.

A Highly-Efficient Fuzzy-Based Controller With High Reduction Inputs and Membership Functions for a Grid-Connected Photovoltaic System

Abstract: Most conventional Fuzzy Logic Controller (FLC) rules are based on the knowledge and experience of expert operators: given a specific input, FLCs produce the same output. However, FLCs do not perform very well when dealing with complex problems that comprise several input variables. Hence, an optimization tool is highly desirable to reduce the number of inputs and consequently maximize the controller performance, leading to easier maintenance and implementation. This paper, presents an enhanced fuzzy logic controller applied to a photovoltaic system. Specifically, both inputs and membership functions are reduced, resulting in a Highly Reduced Fuzzy Logic Controller (HRFLC), to model a 100kW gridconnected Photovoltaic Panel (PV) as part of a Maximum Power Point Tracking (MPPT) scheme. A DC to DC boost converter is included to transfer the total energy to the grid over a three-level Voltage Source Converter (VSC), which is controlled by varying its duty cycle. FLC generates control parameters to simulate different weather conditions. In this study, only one input representing the current variation (ΔI) of the FLC is used to provide an effective and accurate solution. This reduction in simulation inputs results in a novel HRFLC which simplifies the solar electric system design with output Membership Functions (MFs). Both are achieved by grouping two rules instead of using an existing state-of-the-art method with twenty-five MFs. To the best of our knowledge, this is the first FLC able to provide such rules compression. Finally, a comparison with different techniques such as Perturb and Observe (PandO) shows that HRFLC can improve the dynamic and the steady state performance of the PV system. Notably, experimental results report a steady state error of 0.119%, a transient time of 0.28s and an MPPT tracking accuracy of 0.009s.

Impact of Power Quality Issues in Grid Connected Photovoltaic System

Abstract: Power quality in the recent decade becomes one of the key components, which impacts the economy of a country. A huge increase in the population matters the large consumption of energy, in turn, leads to equivalent power generation. To control the greenhouse emissions and the worldwide warming up due to the utilization of conventional sources, substitution can be made with the support from the alternate green energy source. Also, the performance of the electrical utility can be improved by exploiting renewable resources since conventional energy is decaying day by day. Solar energy becomes the most prominent among the renewable resources, having enormous potential across the country. Power electronic interfaces like DC-DC converter, DC-AC inverter incorporated between the source and utility provides a stable power output. This proposed paper portrays the difficulties and concerns in the deployment of solar power towards the utility/public grid integration. The permissible level of penetration, optimal planning and sizing, voltage fluctuations, associated harmonics and appropriate filters are reviewed precisely.

A Comparative Study of Supercapacitor-Based STATCOM in a Grid-Connected Photovoltaic System for Regulating Power Quality Issues

Abstract: Renewable energy resources (RERs) play a vital role in reducing greenhouse gases, as well as balancing the power generation demand in daily life. Due to the high penetration of RERs and non-linear loads into utility power systems, various power quality issues arise, i.e., voltage drop, harmonic distortion, reactive power demand, etc. In order to handle these power quality issues, there is a need for smart flexible alternating current transmission system (FACTS) devices. In this paper, a super capacitor energy storage system (SCESS)-based static synchronous compensator (STATCOM) is designed in order for the grid-connected photovoltaic (PV) system to overcome the abovementioned power quality issues. A voltage controller and a d-q axis controller are used for the efficient performance of the STATCOM. In order to show the superiority of the supercapacitor, a detailed comparison is made between a battery energy storage system (BESS)-based STATCOM and a SCESS-based STATCOM. Four scenarios are studied to evaluate the performance of the proposed STATCOM design. The proposed SCESS-based STATCOM not only boosts the voltage but also stabilizes it from 368 V to 385 V (Ph-Phrms). The simulated results have confirmed that the proposed design is not only superior to a BESS-based STATCOM but also has the capability to overcome the power quality issues as well.

A novel nonlinear sliding mode controller for a single stage grid-connected photovoltaic system.

Abstract: A nonlinear sliding mode controller is proposed for a single stage grid-connected photovoltaic system with a novel nonlinear sliding surface. The proposed controller is designed to ensure maximum power extraction with unity power factor. There are two main advantages of the proposed sliding surface. The new surface will results in a first order sliding mode controller. The second advantage is that maximum power extraction is achieved by tracking DC-link voltage ( V d c ) of the PV system. The proposed controller is also compared with the existing sliding mode controller in terms of both numerical simulation and experimental results. It is found that, the proposed controller’s performance is better than the existing controller in terms of power extraction and more robust when there are uncertainties and disturbance in PV system.

Data Description Technique-Based Islanding Classification for Single-Phase Grid-Connected Photovoltaic System.

Abstract: This paper develops an islanding classification mechanism to overcome the problems of non-detection zones in conventional islanding detection mechanisms. This process is achieved by adapting the support vector-based data description technique with Gaussian radial basis function kernels for islanding and non-islanding events in single phase grid-connected photovoltaic (PV) systems. To overcome the non-detection zone, excess and deficit power imbalance conditions are considered for different loading conditions. These imbalances are characterized by the voltage dip scenario and were subjected to feature extraction for training with the machine learning technique. This is experimentally realized by training the machine learning classifier with different events on a 5 kW grid-connected system. Using the concept of detection and false alarm rates, the performance of the trained classifier is tested for multiple faults and power imbalance conditions. The results showed the effective operation of the classifier with a detection rate of 99.2% and a false alarm rate of 0.2%.

Analysis of the Power Quality of a Grid-Connected Photovoltaic System

Abstract: The use of Grid-Connected Photovoltaic Systems is increasingly on the rise in Brazil. Faced with this growth, it is necessary to evaluate the impacts of this source in the electric energy systems. Based on this scenario, the present work aims to analyze and quantify the impact of a grid-connected photovoltaic system connection, evaluating the Electric Power Quality indicators based on the levels specified in Module 8 of the Electric Energy Distribution Procedures in the National Electric System. To perform the data collection, an energy analyzer device was installed at the output of the grid-connected system inverter located in the Energy Laboratory of the Federal Rural Semi-Arid University, located in the city of Mossoro-RN. Using the collected data, it was possible to analyze parameters of voltage and current distortion, power factor, active, reactive and apparent power, voltage, frequency variations, and voltage unbalance. It was observed that the criteria analyzed were within the appropriate standards although there were also verified cases that there was an elevation in tension levels. Finally, it is concluded that the impacts caused are relevant within the electric system, and grid connected system performance was satisfactory, although there are still possibilities for improvements.

Energetic-Environmental-Economic Feasibility and Impact Assessment of Grid-Connected Photovoltaic System in Wastewater Treatment Plant: Case Study

Abstract: Wastewater treatment plants and power generation constitute inseparable parts of present society. So the growth of wastewater treatment plants is accompanied by an increase in the energy consumption, and a sustainable development implies the use of renewable energy sources on a large scale in the power generation. A case study of the synergy between wastewater treatment plants and photovoltaic systems, aiming to improve the energetic, environmental and economic impacts, is presented. Based on data acquisition, the energy consumption analysis of wastewater treatment plant reveals that the highest demand is during April, and the lowest is during November. The placement of photovoltaic modules is designed to maximize the use of free space on the technological area of wastewater treatment plant in order to obtain a power output as high as possible. The peak consumption of wastewater treatment plant occurs in April, however the peak production of the photovoltaic is in July, so electrochemical batteries can partly compensate for this mismatch. The impact of the photovoltaic system connectivity on power grid is assessed by means of the matching-index method and the storage battery significantly improves this parameter. Carbon credit and energy payback time are used to assess the environmental impact. The results prove that the photovoltaic system mitigates 12,118 tons of carbon and, respectively, the embedded energy is compensated by production in 8 ½ years. The economic impact of the photovoltaic system is analyzed by the levelized cost of energy, and the results show that the price of energy from the photovoltaic source is below the current market price of energy.

Dynamic Operation of Grid-Connected Photovoltaic Power System

Abstract: Recently, the market of grid-connected photovoltaic (PV) systems is growing rapidly, and therefore, grid-connected PV inverters are in more demand. Now, various researchers are working on cost optimization and tracking efficiency of PV system and hence increase the power quality of the grid-connected PV system. The main objective of this research paper is to harvest optimal energy from solar which has reduced cost of inverter, and for this, cascaded inverter has been selected for grid integration with improved performance.

Grid-Connected Photovoltaic System

Abstract: As energy needs increase and fossil resources decrease, the development of grid-connected photovoltaic energy is becoming an important part of the energy mix in the majority of countries. In this article, our attention has been concentrated on a strategy to control and interface photovoltaic power injection systems to the grid without batteries in order to make a significant and reliable contribution to sustainable energy supply and further improve the performance and stability of the power system. Different control mechanisms are considered in power flow management, maximum power point tracking (MPPT) for a three-phase photovoltaic inverter connected to the grid, PLL design standards (Phase Locked Loop), the current and voltage regulator VDC are also presented. The simulation results demonstrate the ability of the proposed control systems to control the energy flow, ensuring a good transfer of all maximum power to the grid.

Modeling & Simulation of Photovoltaic System Connected to Grid using Matlab

Abstract: This paper represents PV model which is connected to the grid having maximum power point tracking (MPPT) by the use of MATLAB/Simulink software. It also gives the information about the behaviours of the photovoltaic (PV) model and its characteristics. The PV system connected to Grid comprises a photovoltaic array with MPPT, a distribution network, a control system and a load. The control system part of PV system connected to Grid consists of two operative controls. One of them is the current control which regulates the current at the PCC (point of common coupling). So, it achieves power factor control as well as regulates dc link voltage. The other one is the voltage control which is employed to achieve the PV output voltage, so that maximum power point can be tracked smoothly and quickly of PV array. MPPT improves the efficiency of the solar energy of PV panel effectively. P&O (Perturb and observe) technique is used in this paper to attain the obtained results. The proposed simulation model and obtained results shall provide the depth understanding of grid connected photovoltaic system.

Grid-Connected Photovoltaic System Stability Enhancement Using Ant Lion Optimized Model Reference Adaptive Control Strategy

Abstract: An inductive-capacitive-inductive (LCL) type filters are broadly utilized in grid-connected voltage source inverters (VSIs) since they can give substantially improved attenuation of switching harmonics in currents injected into the grid with lower cost, weight and power losses than their L and LC type counterparts. This paper discusses an improved model reference adaptive control (MRAC) strategy for designing the control parameters to voltage source converter and improves stability of photovoltaic (PV) generation in different grid capabilities. An improved damping strategy is commonly referred to as MRAC, which has been developed using the proportional resonant (PR) controller and its gain parameters are optimized by Ant Lion optimization (ALO) algorithm. The error elimination at steady-state and gain at particular frequency were provided by the PR current controller. The main focus is set on the mathematical modelling of grid-connected PV, LCL filter and PR current controller and its parameters specifically, resonant and proportional gains. Further, the phase margin and gain of the controller transfer function are presented by means of bode plot to evaluate the operating condition of the controller for different gain parameters. Moreover, a large number of control strategies are mandatory for optimizing the controller parameters and to stabilize the system with zero steady-state error. The obtained results of improved MRAC strategy is presented and its effectiveness is compared with some existing controllers.

Active Power Control for Grid-Connected Photovoltaic System: A Review

Abstract: The penetration of grid-connected photovoltaic systems (PVSs) shows a trend of ever-increasing, which yields potential risk in power system. To further enhance the integration penetration, the power from PVSs is required to obtained advanced functionalities, such as peak power limitation, voltage fluctuation elimination and frequency regulation capacity. Hence, kinds of functional ancillary services are developed and standardized in grid codes. Meanwhile, the approaches should be cost-effective, which is benefit to the competitive strength of solar (a) energy. In this paper, a compressive review on modified MPPT-based active power controls for grid-connected PVSs is giving out. The basic concept of these controls is to move the operation point away from maximum power point, which is suitable to exist PVSs and no extra requirements are needed. Besides, detailed analysis of some key issues in control designs, such as the determination of available power and the selection of operation point, are carried out in this paper.

Grid connected photovoltaic system efficiency and quality improvement using fuzzy-incond MPPT

Abstract: Maximum Power Point Tracking (MPPT) techniques are developed to harvest and supply maximum power to the load. This depends on the power generated and the MPPT accuracy. Under quick-changing weather conditions, Incremental Conductance (InCond) and numerous different algorithms may fail to track the exact Maximum Power Point (MPP) which may result in significant power loss. Fuzzy Logic (FL) based MPPT is quick and accurate in tracking the MPP, but the high complexity and the implementation difficulty are their main disadvantages. A novel FL-InCond MPPT improved technique is developed based on the features of InCond and FL techniques to overcome their drawbacks.The newly developed approach can automatically adjust the variation of the duty cycle for tracking the MPP with accuracy. The obtained results are compared with conventional Perturb and observe (P&O) and InCond MPPTs for grid-connected mode under fast weather conditions. It is demonstrated that the developed method outperforms the aforementioned MPPT techniques in terms of tracking response, efficiency and the delivered current quality.

Modeling and Performance Analysis of a Grid-connected Polycrystalline Silicon Photovoltaic System under the Maritime Climate of El Jadida in Morocco

Abstract: Renewable energy sources (RES) have been extensively deployed as green energy producers for reducing power consumption while diminishing greenhouse emissions Nowadays, Morocco focuses on RES, especially solar energy due to its abundance, in order to reduce its dependence on fossil products (eg, coal, oil, gas) The aim of the work presented in this article is the modeling, the simulation, the experimentation and the assessment of the performance of a 2040 kWp grid-connected photovoltaic (PV) system It is based on polycrystalline silicon technology (pc-Si) and installed on the flat roof of the Physics department building of the Faculty of Sciences El Jadida (Latitude 3322°N, Longitude 848°W, Altitude 24 m, and 21 km away from the Atlantic Ocean) in Morocco Thus, the daily and monthly characteristics of the PV system (eg, power, voltage, current) have been measured, monitored, and analyzed during three years (January 2015-December 2017) Besides, several simulations and experiments have been carried out and the results have been reported and showed that the simulation gives a good approximation of the real-world scenarios Therefore, the monthly average of the produced energy, the efficiency, the final and the reference yields ( Y F and Y R ), the performance ratio ( PR ), and the annual capacity factor ( CF ) of the PV system have been computed, presented and evaluated in order to assess its performance For our pc-Si PV system, the average annual values of the produced energy, the PR and the CF are 1830 kWh/kWp, 79% and 021 respectively

Design of a 7-Level Single-Stage/Phase PUC Grid-Connected PV Inverter with FS-MPC Control

Abstract: Multilevel, transformer-less inverters are becoming more and more a subject of interest in grid connected photovoltaic system due to their low cost and high efficiency features. However, most of the designed grid tied systems show more than one stage conversion process to inject the amount of power generated to the grid. Mainly, a DC-DC conversion stage is always requested between the Photovoltaic (PV) panel and the inverter. In this paper, a single-stage grid connected design based on seven level packed U-cell inverter controlled by a finite-set model predictive algorithm with a maximum power point tracking capability is presented as a competitive single-stage/phase grid-connected topology. The overall design is less complex compared to existing topologies where a maximum power point operation of the PV system is well achieved without the use of a boost converter. A predictive algorithm takes in action of the inverter control. Simulation results in MATLAB/SIMULINK are presented to validate the proposed design in both constant and variable irradiation conditions.