Grid-tied Photovoltaic System Research Articles

Experimental outdoor performance assessment and energy efficiency of 11.28 kWp grid tied PV systems with sun tracker installed in saharan climate: A case study in Ghardaia, Algeria

In recent years, the demand for grid tied solar photovoltaic systems has been rising fleetly, due to the low cost of solar panels, storage systems, and inverter equipment. The expertise of the grid related photovoltaic solar system attached sun trackers doesn't depend on the following factors, the amount of sunshine, angular travel, positioning frequency, and the region where they are installed. To comprehend how they perform in the whole world, we require assessing and comparing their performance in several parts of the country. This work details the experimental PV system setup and the analytics based on the measurements from the system in Algeria (Ghardaia City).This work exhibits detailed simulation data based on PVSYST software and compared with experimental results of an 11.28 kWp grid-connected solar system with sun tracking systems, after one year of operation at Applied Research Unit of Renewable Energy (URAER) in southern Algeria. The PV system consists of three identical 3.76 kWp solar trackers systems with the same module and inverter. This study also investigates during the real outdoor PV system operation, the yearly, monthly, and daily PV array and inverter behavior based on the performance metrics indicators, meteorological data (temperature and solar irradiation), DC and AC energy produced reference yield (YF), array yield (YA), final yield (YF), PV array and system efficiency, performance ratio (PR), PV array and system losses, and capacity factor (CF) of the whole solar photovoltaic system with sun tracker and likewise the three sub-PV systems with sun tracker following to the IEC 61,724 guidance. The electricity produced for the grid was also verified using the sunny portal application. The outcomes indicate that the binary-axis solar tracker shows a preferable performance, which collects about 20.89% further energy compared to that of the steady axis, and the one-axis tracker generates about 12.91% more energy compared to the fixed PV tracker. The energy generated (EDC) over the monitored period (2021) was 6917.50 kWh, 7810.58 kWh, and 8362.68 kWh for the steady PV system, one axis PV system, and twin axis tracking PV system, respectively. The yearly energy fed into the conventional network (EAC) over the period is 7537.4 kWh, 9962.1 kWh, and 10273.5 kWh for the stationary PV system, one axis PV system, and binary axis tracking PV system, respectively. The amount of CO2 emissions avoided over the monitored period (2021) is 4.84 tons, 5.46 tons, and 5.85 tons for the stationary PV system, one axis PV system, and twin axis tracking PV system, respectively, which can significantly contribute to cleaning the environment from pollution. The analysis shows PV module and overall system efficiency varies from (10.66%/10.26%), 10.77%/10.35%, and 10.79%/10.36% noted in July to (12.18%/11.74%, 12.34%/11.9%, and 12.41%/11.95%) noted in January for twin axis solar trackers PV systems, one axis solar trackers PV systems, and PV fixed PV systems, respectively. The analysis shows that the performance ratio (PR) varies from (72.3%, 72.4% and 71.8%) in July to (83.6%, 83.2% and 82.1%) in January and the annual average value reaches (77.95%, 77.80%, and 76.95%) for twin axis solar trackers PV systems, one axis solar trackers PV systems, and PV fixed PV systems, respectively. These performance indicators have the practical value of guiding and providing good feedback for engineers, system designers, contractors, and investors to boost the growing applications of grid-tied PV systems with a sun tracker in the same or similar location and climate conditions (Sahara environment).

An Enhanced Control Strategy to Mitigate Grid Current Harmonics and Power Ripples of Grid-Tied PV System Without PLL Under Distorted Grid Voltages

This article proposes an enhanced integrated control strategy to mitigate grid current harmonics and power ripples for a three-phase grid-tied photovoltaic (GTPV) system without a phase-locked loop (PLL) unit. The proposed control strategy consists of an enhanced proportional resonant (EPR) current controller, which suppresses the harmonics of grid injected current under distorted grid voltage conditions. A phase compensated reference current generator (PCRCG) is integrated with the proposed EPR controller and used to eliminate active and reactive power oscillations under grid voltage sags and swells. The proposed integrated control strategy is implemented in the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\alpha \beta $ </tex-math></inline-formula> stationary reference frame. The synchronization task is included in the PCRCG and making the system PLL-less. Thus, the associated computational burden and implementation complexity are reduced. Furthermore, the frequency adaptability of the GTPV system is enhanced as compared with the PLL-based control strategy in the presence of grid frequency variations using the proposed control strategy. To ensure the fast maximum power point (MPP) tracking, a modified incremental conductance MPP tracking algorithm is implemented in integration with the proposed control strategy. The effectiveness of the proposed control strategy is validated using OPAL-RT real-time digital simulator and compared with the conventional PLL-based control strategy.

A Novel Asymmetric Multilevel Inverter with Reduced Number of Switches for Grid-tied Solar PV System

Background &amp; Objective: In single-phase solar PV applications, the module voltage level is limited; therefore, a coupled step up transformer is mandatory portion to interconnect into the grid. However, due to presence of transformer, the overall cost and size of the single-phase grid tied solar PV system is higher. Multilevel inverter is an alternative solution to solve these issues, but it requires more number of switches. Methods: In order to overcome this drawback, this particular paper proposes a novel asymmetric multilevel inverter (AMLI) with reduced number of switches for solar PV grid-tied system. The operational details of the proposed converter are explained in this paper. In addition, the MPPT control has been implemented in the proposed novel AMLI and presented in this paper. The hysteresis current control mechanism is applied to the proposed converter and corresponding control blocks are reported in this paper. Results: Finally, to validate the proposed system, the simulation results are performed and correlated with theoretical approach Furthermore, to verify the feasibility of proposed converter for solar PV grid-tied system, the experimental setup was made and experimental results have been measured and presented in this paper. Conclusion: From the measured results, it is concluded that the proposed asymmetric MLI can be most promising converter for solar PV grid connected system.

The Energy Storage System Integration Into Photovoltaic Systems: A Case Study of Energy Management at UTFPR

Energy storage system integration can reduce electricity costs and provide desirable flexibility and reliability for photovoltaic (PV) systems, decreasing renewable energy fluctuations and technical constraints. In this sense, this study aimed to propose energy management strategies through this integration, aiming to improve the demand profile of a university commercial consumer for compensation during peak hours. To achieve the objectives of this research, a pilot project was installed which included a 10 kWp grid-tie PV system (GTPVS), bidirectional inverters, and battery bank, as part of a research and development (R&amp;amp;D) project implemented in the Federal University of Technology–Paraná (UTFPR) Curitiba campus at Neoville headquarters. The methodology consisted of the analysis of variables that interfere with the operation of this system, such as a detailed university profile of demand and consumption, local energy pricing, PV generation profile as well as the interaction between PV generator and the energy storage system, and the variation in power fluctuations throughout the year. Additionally, a technical feasibility study was carried out aimed to determine this consumer’s optimal size through the Homer Grid software. The detailed demand profile allowed us to know in depth the peak values were above 80 kW, for university working days. Furthermore, the daily analysis of the PV generation profile confirmed that although the PV source is quite variable, the scheduled dispatch operation is not interfered by the variability and intermittency of the solar source, as the system was designed and programmed to operate in parallel with the electrical network. Regarding the energy consumed at the university, very significant values were obtained, in which the month of July presented the highest consumption for the base year 2019, with a total monthly value of 48,670 kWh. The established operating strategy for the battery bank with a 10% discharge depth resulted in a life cycle of 2,500 cycles which can extend its useful life by approximately 9.5 years. The results obtained by the simulation show different levels of energy contribution with percentages of 60.0, 33.6, and 2.7%, respectively.

Toward an intelligent community microgrid energy management system based on optimal control schemes

This article investigates a modelization of the energy management strategy of a grid-tied photovoltaic (PV), wind generator, and battery system. The model uses a smart metering system to collect data from various electrical components of a microgrid. The power optimization strategy is modeled under demand response, including time-of-use pricing to create a home's energy flow more efficiently. Two optimal control strategies are developed to coordinate energy expenses, expressed as the cost of minimizing electricity supplied by the utility grid and maximizing the opportunity for energy to sell to the grid. A nonlinear open-loop control and quadratic programming using model predictive control (MPC) are compared to assess the performance of the developed model. The design model takes into consideration the operational cost of batteries and degradation. The importance of the energy storage system is demonstrated in the context of energy conservation and gain on the demand side. MPC's capacity to specify the proper control and forecast future system reaction enables the proposed method to ensure significant daily energy and cost savings from 70.44 to 24.74 $ day−1 in the first scenario (without disturbances) and from 70.44 to 18.24 $ day−1 in the second case (with disturbances). In both methods, the net savings of greenhouse gas are approximately 288.10 (kgCO2-eq) and 338.87 (kgCO2-eq). These show better performance of the MPC compared to the linear model. Highlights Investigate the dynamic performance of an intelligent home energy management scheme. Implement a grid-tied photovoltaic, wind turbine, and energy storage system. Use intelligent metering to collect data from various electrical components of a smart home. Compare the energy saving from an open-loop algorithm and a model predictive control. Assess the topmost benefits of the optimal control method of grid-tied distributed energy resources.

Use of Hybrid Photovoltaic Systems with a Storage Battery for the Remote Objects of Railway Transport Infrastructure

The use of a grid-tied photovoltaic system with a storage battery to increase the power of objects of railway transport infrastructure above the limit on consumption from the grid with the possibility of energy saving is considered. The methods of analysis of energy processes in photovoltaic systems with a storage battery are used. They are added via the processing of archival data of power generation of a photovoltaic battery and computer modeling results. A technique of system parameter calculation to increase the power according to the given load schedule of the object at constant and maximum possible degree of power increasing is developed. The values of the average monthly generation of a photovoltaic battery at the location point of the object based on archival data are used. The principle of the control of power, consumed from the grid, according to the given values of the added and total load is developed. Using the basic schedule of added load power in connection with the graph of photovoltaic battery generation allows reducing the installed power of the storage battery. The additional reduction in the installed power of the photovoltaic and storage batteries is possible at the corresponding choice of the degree of power load increasing. The joint formation of current schedules with reference to the added power value and state of charge of the battery according to the short-term forecast of the generation of a photovoltaic battery is proposed. The value of added power at certain intervals of time is set according to the graph of actual generation of the photovoltaic battery, which contributes to the maximum use of its energy. With the average monthly generation of a photovoltaic battery in the spring–autumn period, the discharge of the battery during the hours of the morning load peak is not used. This reduces the number of deep discharge cycles and extends the battery life. The description of energy processes in steady-state conditions for the daily cycle of system functioning is formalized. On this basis, a mathematical model is developed in MATLAB with an estimation of the costs of electricity consumed from the grid. When modeling, archival data are used for days when the generation of a photovoltaic battery over time intervals is close to average monthly values. This makes it possible to evaluate the effectiveness of system management under conditions close to real during the year.

Comparative Analysis Different Topologies of Grid-tied Transformer Less Inverters for Photovoltaic system.

Transformer less inverters are widely used in grid-tied photovoltaic (PV) generation systems, due to the benefits of achieving high efficiency and low cost. Various transformer less inverter topologies have been proposed to meet the safety requirement of leakage currents. In this paper, a family of H6 transformer less inverter topologies with low leakage currents is proposed, and the intrinsic relationship between H5 topology, highly efficient and reliable inverter concept (HERIC) topology, and the proposed H6 topology has been discussed as well. One of the proposed H6 inverter topologies is taken as an example for detail analysis with operation modes and modulation strategy. The power losses and power device costs are compared among the H5, the HERIC, and the proposed H6 topologies. A universal prototype is built for these three topologies mentioned for evaluating their performances in terms of power efficiency and leakage currents characteristics. Experimental results show that the proposed H6 topology and the HERIC achieve similar performance in leakage currents, which is slightly worse than that of the H5 topology, but it features higher efficiency than that of H5 topology.

Multi-Objective Spotted Hyena Optimization-Based Control of Grid-Tied PV System

This article describes the multi-objective spotted hyena optimization (MOSHO) based control of a three-phase three-wire grid-tied dual-stage PV system. The MOSHO delivers an optimized step size ( δ ) for the incremental conductance (InC) based maximum power point tracking (MPPT) algorithm, as well as optimizes the PI controller gains for DC bus voltage ( V d c ) regulation. The δ optimized MPPT facilitates the faster and more accurate tracking of maximum power point with fewer fluctuations at steady-state. The MOSHO optimized PI controller regulates the V dc and delivers better stability with reduced V dc variations in DC bus voltage during steady-state and dynamic states, i.e. irradiation variation, abnormal and unbalanced grid voltage. The optimized DC bus generates an accurate loss component of current, which further enhances the voltage source converter (VSC) performance in terms of precise reference currents generation and power quality improvement. The proposed system performs satisfactorily in a MATLAB simulation environment as per IEEE519 standards.

A Reconfigurable Fault-Tolerant PV Inverter via Integrating HERIC and H5 Topologies

Solar energy is prevalent in many applications, therefore, the reliability of solar energy systems has become an important topic for research communities and industry. High reliability and fault-tolerant capability are particularly vital for the solar energy systems that are mission-critical and/or inaccessible to affordable maintenance. In order to enhance the reliability of a grid-tied PV system, a fault-tolerant Photovoltaic (PV) inverter, termed Integrated Fault-Tolerant PV Inverter (IFTPVI), is proposed in this paper. The IFTPVI is based on the Highly Efficient and Reliable Inverter Concept (HERIC) and H5 inverters that are both popular and commercialized transformerless inverters in grid-tied PV applications. The IFTPVI can tolerate both open-circuit (OC) and short-circuit (SC) faults while maintaining the same voltage and current levels. The system description, reliability analysis, simulation in Matlab/Simulink 2018, and experimental results are provided to verify the feasibility and viability of the proposed inverter topology.

A novel combined Fuzzy-M5P model tree control applied to grid-tied PV system with power quality consideration

ABSTRACT A novel control strategy based on an effective combination of the fuzzy logic controller and the M5P decision tree algorithm (Fuzzy-M5P) for a grid-interfaced solar energy system is proposed in this paper. The aim is to benefit from fuzzy logic advantages using its resulting datasets along with the fast model tree functionality. This mixed control has the ability to cope effectively with the large computation time and complexity of fuzzy logic controllers especially when embedded systems or real-time implementation are considered. Using a photovoltaic (PV) inverter with active filtering capability, the primary objective is to provide a grid-solar topology with a maximum PV energy extraction and power quality enhancement. For the inverter control, the M5P model was tested in the indirect current technique. This harmonic generation method is very efficient and its performances are entirely dependent on the chosen dc-link controller. Moreover, a novel maximum power point tracking technique (MPPT) based on the M5P model tree is performed in which data inputs are collected from fuzzy logic-based MPPT. WEKA and MATLAB software are used to translate the model by formulating a simple hierarchical program structure. To validate the effectiveness of the proposed control, simulation, and experimental tests are done under steady and dynamic conditions. The final developed algorithm based on simple IF-ELSE rules shows promising results, it can reduce harmonic distortions to 2.77%, perfectly compensates reactive power with almost unity power factor, and enhances dynamic performances with fast transient response.

Development of Prototype Fractional Order Controller for a Grid-Tied Photovoltaic System

This paper presents design of a robust fractional order proportional-integral (FO-PI) prototype controller for a grid connected photovoltaic (PV) system. The robustness in face of parameter variation is handled by designing a suitable controller considering sensitivity function, gain margin and phase margin for both inner and outer control loops. As FO-PI controller is not yet available in physical form and due to complexity involved in grid-tied PV system, we propose an alternative way of hardware implementation of inner loop FO-PI controller by using fractor through RC ladder network. Firstly, an emulator circuit of the inner current loop comprising the FO-PI controller (including fractor and the proportional gain) along with the transfer function of inverter and filter is developed and the response is verified through a real-time simulator (OPAL-RT). Finally, the FO-PI part of the emulator circuit is interfaced with the PC target to form a hardware-in-loop (HIL) by employing OPAL-RT. The performance of the complete system is verified through OPAL-RT simulator. The result shows the improved robustness by the proposed control design method.

A Cascaded Controller for a Grid-Tied Photovoltaic System With Three-Phase Half-Bridge Interleaved Buck Shunt Active Power Filter: Hybrid Control Strategy and Fuzzy Logic Approach

This paper focuses on the control development of a grid-tied photovoltaic system coupled with a shunt active power filter. The considered power system includes a PV panel, a single-capacitor three half-bridge interleaved buck converter connected to a three-phase power grid and a nonlinear load. This study aims to accomplish simultaneously three objectives: i) to ensure a high compensation level of current harmonics and reactive power consumed by the nonlinear load in order to perform power factor correction at the grid side; ii) to extract the maximum power from the PV panel regardless the climatic conditions; iii) to regulate the dc bus capacitor voltage to its reference provided by the MPPT controller. To this end, a controller using a two-loop cascade strategy is designed. First, the inner loop is developed with the hybrid automaton approach to formulate the switching control signals with the aim of guaranteeing a unitary power factor. Second, the outer loop is designed using fuzzy logic control to ensure the regulation of the photovoltaic voltage, while the perturb and observe algorithm is employed to perform maximum power point tracking. Finally, the system with the developed control scheme is simulated using MATLAB/SimPowerSystems environment. The obtained results confirm that the proposed controller is able to achieve the previous objectives under varying environmental conditions.

Impact of grid-tied photovoltaic systems on voltage stability of tunisian distribution networks using dynamic reactive power control

Analysis of voltage stability of transmission network with high photovoltaic (PV) integration is a challenging problem because of the stochastic generation of a solar system. Stabilization of the output power is an important criterion for determining the degree of penetration of PV in active distribution networks, considering loading capability. This article describes the effective voltage regulation strategy for the transmission system using the STATCOM module to resolve the drop and the effect aspects on the voltage stability in the transmission network. This paper analyzes also the influence of the STATCOM control system on preventing the combination of injection voltage STATCOM with harmonics from achieving pure voltage compensation. The proposed test system under analysis is the 53-Bus Tunisian distribution power network integrating 12 MW solar PV plant. Simulation results are added to demonstrate the efficiency of the proposed control technique for enhancing the power system quality based on the Tunisian grid code. Investigation of voltage stability shows that the dynamic behavior of the voltage depends strongly on the short circuit capacity of the power network at the point of PVs integration.

Modified zeta inverter intended for single-phase grid-tied photovoltaic system

A novel integrated converter structure intended for a single-phase grid-tied photovoltaic (PV) system is proposed in this paper. The proposed topology, named Modified Zeta Inverter (MZI), is deployed using two modified Zeta converters operating in discontinuous conduction mode. The main advantage of the MZI is its capability to step-up the input voltage while injects into the single-phase utility grid the energy produced from photovoltaic arrangements. Besides low total harmonic distortion in the grid-injected current, the proposed MZI topology was conceived to replace the conventional two-stage grid-tied system. A comprehensive study involving both static and dynamic analyses is presented. Furthermore, small-signal modeling is developed to give subsidies for designing the controllers' gains adopted in the voltage and current control loops. After a proper system sizing, it was developed a prototype setup with 432 W. Simulation and experimental results are presented to evaluate and demonstrate the feasibility of the proposed system.

Hardware implementation of an active learning self-organizing neural network to predict the power fluctuation events of a photovoltaic grid-tied system

Power fluctuations happens due to highly stochastic solar irradiance nature and this could cause unwanted power quality issues in photovoltaic (PV) system. First predicting the PV output then mitigating the fluctuation by using energy storage system is one of the most effective power fluctuation mitigation method. Incremental learning algorithm such as incremental self-organizing map can be used to actively learn and predict power output. Although significant improvement in terms of mitigated events can be achieved in this kind of system, it still suffers from prediction accuracy due to the highly fluctuating PV profile. In this paper, a time-series unsupervised learning algorithm namely the Time-Series Self-Organizing Incremental Neural Network (TS-SOINN) is proposed to better predict the highly stochastic PV output. It incorporates a novel weighted memory layer to give higher emphasis to recent observation and improves data overlap issues in the conventional self-organizing map algorithm. In the simulation results, the TS-SOINN achieves prediction rate of 93.81% which outperforms the latest unsupervised incremental learning algorithm, M-SOINN by 33.44% and the TS-SOINN mitigated 89.13% power fluctuation events whereas M-SOINN only mitigated 79.62% events. In addition, the TS-SOINN is implemented in Altera Stratix V GS Field Programmable Gate Array (FPGA) board to run real-time prediction. This hardware architecture is able to increase new node and remove inactive nodes throughout the real-time prediction. The hardware TS-SOINN is integrated with mitigation engine to smoothen out power fluctuation events in PV grid-tied system, the experimental results show that the proposed system mitigated 83.33% of power fluctuation events at the grid and the battery state-of-charge maintains within 30%-100%.

Leakage Current Mitigation of Photovoltaic System Using Optimized Predictive Control for Improved Efficiency

This paper proposes an optimized predictive control strategy to mitigate the potential leakage current of grid-tied photovoltaic (PV) systems to improve the lifespans of PV modules. In this work, the PV system is controlled with an optimized predictive control algorithm that selects the switching voltage vectors intelligently to reduce the number of computational burdens. Thus, it improves the dynamic performance of the overall system. This is achieved through a specific cost function that minimizes the change in common-mode voltage generated by the parasitic capacitance of PV modules. The proposed controller does not require any additional modulation schemes. Normalization techniques and weighting factors are incorporated to obtain improved results. The steady state and dynamic performance of the proposed control scheme is validated in this work through simulations and a 600 W experimental laboratory prototype.

A grid-connected single-stage closed-loop controlled five-level boosting inverter for solar PV systems

ABSTRACT Multilevel inverters (MLIs) have gotten a lot of attention recently in the power industry because of their efficiency. The application of MLI in photovoltaic (PV) systems to improve power quality and performance has grown dramatically. An innovative, low-component-count 5-L boosting inverter interfaces a single-stage grid-tied PV system with a closed-loop control method in this research. The proposed MLI is put to the test using a 2.1 kW PV system. This technique guarantees optimum power monitoring, DC link voltage balancing, appropriate MLI operation and injection of clean sinusoidal grid current. The suggested system’s outcome is tested by Matlab/Simulink.

Bode diagram based control system design of three phase grid tied photovoltaic systems with Quasi-Z source inverter

In single-stage power conversion, quasi-Z Source inverter (ZSI) provides buck-boost capability and permits shoot through state to enhance the input dc-link voltage. This article discusses the control system design for quasi-ZSI basedthree-phase grid-tied photovoltaic (PV) systems. The inclusion of a low pass filter in the shoot-through duty ratio control loop eliminates ripples in the calculated duty ratio. For tuning the controller gains, an analysis of bode diagrams for the system under consideration is presented. This theoretical analysis is validatedby simulation studies using MATLAB/SIMULINK. The simulation studies reveal that the proposed control system design results in grid code compliant operation of grid-tied PV systems with sinusoidal currents injected at unity power factor. Moreover, PV operation at maximum power point is achieved with good steady-state and dynamic performance.

Minimization of leakage current in a maximum boost control impedance source transformer-less inverter

The solar energy is utilized the most for a decade and the grid connected inverter is necessary for the distribution systems as the grid connected inverter will performances as in interface between the renewable solar energy source and the distribution end. However, due to the existence of magnetizing current in the transformer, the lower order harmonics in the grid current is high in PV systems. In addition, the efficiency of the system and inverter lifetime is reduced due to the usage of high volume capacitance. To overcome this issue, the transformer-less inverter is used in grid-tied PV system where the size and weight is reduced which results in reduction of cost and improve the efficiency of system. However, the leakage current is a major issue needs to be addressed which is minimized by Galvanic isolation methods in the transformer less photovoltaic (PV) inverters. In this project, the performance of the boosting H5 topology is proposed theoretically and analysed with validated simulation and experimental results. It helps in choosing and providing the best design principles.

Improving Photovoltaic Penetration to a Higher Level in Grid-Tied Pv Systems by Implementing Energy Storage Management

Improving Photovoltaic Penetration to a Higher Level in Grid-Tied Pv Systems by Implementing Energy Storage Management