Interharmonics from grid-connected PV systems: Mechanism and mitigation

Due to the Randomness and fluctuation of the photovoltaic (PV) system, Maximum Power Point Tracking (MPPT) algorithm is employed to ensure the maximum power extraction from PV arrays, when it is connected to the grid. The previous studies have indicated that the MPPT algorithm is one of the main causes of interharmonics emission in PV systems. The MPPT algorithm parameters such as perturbation step size inevitably have a strong impact on the interharmonics in the current injected to the grid. In general, a smaller MPPT perturbation step size will reduce the interharmonics emission level, but it will result in poor tracking performance of the MPPT algorithm. Thus, there is a trade-off between the MPPT efficiency and the interharmonics emission in PV system. In this paper, an interharmonics suppression scheme with variable step size MPPT algorithm was proposed. In the suppression scheme, two voltage values near by the MPPT voltage and two tracking step size are preset. When the dc-link voltage of PV is between the two preset voltage values, it means that the PV power near its MPP and the smaller perturbation step size implemented in the MPPT algorithm. Otherwise, the bigger perturbation step size is employed. It can greatly reduce interharmonics emission level and maintain the MPPT efficiency. Simulations have been carried out to verify the effectiveness of the suppression scheme.

This work presents an improved perturb and observe (P&O) algorithm based MPPT (Maximum Power Point Tracking) for a single stage solar photovoltaic (PV) array integrated with a three phase grid. Due to simple implementation and efficient tracking, the P&O approach of extracting maximum power from a PV array is very popular and efficient tracking technique among all MPPT techniques. However, the major pitfalls of this technique are that P&O MPPT is affected from drift, the outcome of drift occurring is much disapproving when there is a quick rate of increment in insolation. Drift takes place because of erroneous judgments taken by traditional P&O technique at the initial step alteration in voltage reference throughout the rise in insolation. An improved P&O algorithm is proposed here to improve the drift issue by deploying the details of variation in PV current (ΔDLI <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">pv</inf> ) to make the judgment in extension to the variation in PV power (ΔDLP <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">pv</inf> ) and variation in PV voltage (ΔDLV <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">pv</inf> ). In this PV system, a VSI (Voltage Source Inverter) and three phase grid are used. In a three phase distribution feeder network for indemnify, the quality of power as per an IEEE-519 standard on harmonics, it satisfies the power quality norms. So, for availing the real power feeding to the grid and to sustain the terminal voltage constant at the PCC (Point of Common Coupling) with sinusoidal grid voltages and grid currents, this system works well simultaneously with improved performance of P&O technique. The Matlab/Simulink is used for simulation and modelling of proposed system and the behavior of proposed MPPT algorithm has been examined for various insolation levels and different environmental situations on an experimental system which is established in the laboratory

An automotive photovoltaic (PV) system is fabricated for an electric vehicle. The PV panel for the PV system prototype comprises modules, each of which is equipped with a converter for maintaining the maximum power point tracking (MPPT) operation. The MPPT operation can be performed individually for each PV module using this configuration. In this study, the MPPT operation performance during driving is verified. The PV system prototype can maintain power generation during driving using the MPPT operation, and it is found that in situations wherein the solar radiation varies frequently, the range of the MPPT voltage search influences the tracking achievement ratio. In addition, the ratio could be 97% and over by optimizing the range of the MPPT voltage search.

This paper deals with the adaptive estimation of frequency observation (AEFO) based technique for compensating the harmonics component of two-stage grid-connected solar photovoltaic (PV) system. The maximum PV power is extracted using maximum power point tracking (MPPT) algorithm. Moreover, the input DC voltage of the voltage source converter (VSC) is maintained at desired level using a proportional integral (PI) controller. The AEFO control injects the required reactive component, which shapes the balanced grid currents. Moreover, the active power is injected in to the grid, which eliminates the harmonics in the grid currents. Using this controller, the fundamental reference currents are estimated using nonlinear load currents. This system maintains the grid current total harmonic distortion (THD) in accordance to the IEEE 519 standard. The dynamic response is improved by adding the PV feed-forward term with the estimated magnitude of i eα and i eβ current quantities. This control improves the dynamic response when insolation is changed and also provided a good response when switched from PV array to DSTATCOM and vice versa. Moreover, the power quality issues such as load unbalancing, power factor correction and reduced the grid side currents harmonics. Test results has shown the reactive power compensation of balanced and unbalanced nonlinear loads and the steady-state and dynamic performances of the system and PV array to DSTATCOM and vice-versa.

At present the multi-stage transformation topology are more used in photovoltaic (PV) grid-connected system, although the control of this structure is relatively simple but the conversion efficiency is difficult to improve due to increase in transformation series. The single stage topology has a simple topology with high reliability and efficiency because of low power consumption, but control algorithm is more complex because of its power convert main circuit without DC-DC. This paper describes a method for maximum power point tracking (MPPT) in the single-stage and single-phase PV grid-connected system. In the paper, the nonlinear output characteristics of the PV including I-V &amp; P-V are obtained in changed solar insulations or temperature based on MATLAB, and the MPPT algorithm which is based on the particle swarm optimization (PSO) method is also described. The simulation model of the single-stage and single-phase PV grid-connected system is built , and simulation results show the MPPT algorithm has excellent dynamic and static performances ,which verifies the PSO method is effective for MPPT in the single-stage and single-phase PV grid-connected system.

-The rapid integration of photovoltaic (PV) systems into modern power networks has intensified the need for efficient control strategies to ensure maximum power extraction, grid stability, and power quality. Variations in solar irradiance, temperature, and grid conditions significantly affect PV system performance, necessitating advanced Maximum Power Point Tracking (MPPT) and inverter control methods. This paper presents a comprehensive review of conventional, intelligent, and optimization-based control techniques employed in grid-connected PV and hybrid microgrid systems. Various MPPT algorithms, including classical methods, soft computing approaches, and metaheuristic optimization techniques, are critically analyzed with respect to tracking accuracy, convergence speed, computational complexity, and robustness under dynamic conditions. Furthermore, inverter control strategies, synchronization methods, and hierarchical control architectures for microgrids are discussed. A generalized control block diagram is presented to illustrate system integration. Finally, key challenges, research gaps, and future directions are highlighted to guide researchers toward next-generation intelligent and resilient PV-based energy systems. Key Words: Photovoltaic System; Maximum Power Point Tracking (MPPT); Grid-Connected Inverter; Microgrid Control; DC–DC Converter; Intelligent Control; Renewable Energy

The main purpose of this paper is to model, study and analyze the effect of shading with different Photovoltaic (PV) array configurations on a three-phase two-stage grid connected PV system. The first stage is a boost converter, which serves the purpose of MPPT (maximum power point tracking) and feeding the extracted solar energy, whereas the second stage is a two-level VSC (voltage source converter) serving as PV inverter which feeds power from a boost converter into the grid. The Incremental Conductance technique was used to track the Maximum Power Point (MPP). The two PV configurations used through this paper are Series-Parallel (SP) and Total Cross Tied (TCT) configurations, which showed best performance among other configurations (Series, Parallel, Bridge-linked and Honey-Comb configurations) [1]. The results showed that TCT configuration PV array Grid connected PV system has better efficiency under partial shading effect than SP, and that validated by simulation in the Matlab-Simulink environment.

The industry of solar photovoltaic (PV) energy and its application is still booming to enhance the sustainability of the society. When PV systems are connected to the grid, challenging issues should be addressed. One of the challenges is related to interharmonics in PV systems, especially with a large-scale adoption of PV systems. However, the origins of interharmonics remain unclear, although the impact of interhamonics has been reported in the literature. Thus, this paper explores the generation mechanisms of interharmonics in PV systems and the characteristics. The exploration reveals that the perturbation from the maximum power point tracking (MPPT) algorithm is one of the origins of interharmonics appearing in the grid current. Accordingly, the MPPT controller parameters such as the perturbation step size and the sampling rate have an inevitable impact on the interharmonic characteristics. Furthermore, an approach to characterize the interharmonics in the grid current is proposed. With the proposed model, interharmonics can be predicted according to the designed controller parameters in terms of frequencies and amplitudes. Experimental tests are performed on a single-phase grid-connected PV system. The results are in a close agreement with the analysis and, thus, validate the effectiveness of the proposed model.

Photovoltaic (PV) grid-connected system is the development trend of photovoltaic systems. According to the PV grid-connected system characteristics, analyzes the maximum power point tracking(MPPT) control strategy based on two-stage power conversion architecture, proposed a novel MPPT control algorithm, it can achieve the maximum power point tracking by only detect one parameter-the inverter output current. In the Matlab/Simulink simulation environment, building the system model and simulation based on the control scheme, the system can find the maximum power point quickly and steadily, compared with the widely used MPPT algorithm simulation result, proved the correctness and feasibility of control scheme, has practical value.

This paper introduces the simulation and analysis of a three-phase large-scale grid-connected solar Photovoltaic (PV) system in order to assess the effect of integrated PV grid-connected mode on the power quality of the utility grid. The study takes into account the effect of solar system power variation as well as the PV inverter's introduction of penetrating harmonics into the system. The simulation of the system is done in MATLAB software using the SIMULINK environment and is tested by the Pysyst program. Where it is done in real-time with an actual case study on a 1620-kW PV array connected to an 11-kV grid via a three-level Voltage Source Converter (VSC). The technical data was recorded, and the system's power quality was examined. The grid-connected PV system's Performance Ratio (PR) is assessed to determine the PV system's reliability and grid connectivity.

In photovoltaic (PV) systems, a wide variety of power converter topologies and PV configurations have been developed in order to increase the system efficiency. Traditionally, grid-connected PV systems use one or two conversion stages. The single conversion stage is mainly used for large-scale PV systems working with only a DC-AC converter. Whereas, for small and medium-scale, two conversion stages are used. The advantages working with a DC-stage are mainly the distributed maximum power point tracking (MPPT) algorithm and the elevation capability, but it presents a reduced conversion efficiency compared with the single stage configurations. On the other hand, the single conversion stage presents a reduced overall efficiency produced by partial shading. The proposed work presents a Partial Power DC-DC converter (PPC) which process only a portion of the whole power, reducing the conversion losses. It includes the benefits of two stage configurations so that it performs individual MPPT. Besides, due to the modularity of the architecture, it allows the parallel connection of many strings as required to use in large-scale PV systems. Simulations are performed in order to evaluate the converter performance.

By detection of input signal, Maximum Power Point Tracking (MPPT) algorithms are used to maximize the potential output power. Since Perturbation and Observe (P&O) method was first applied in a Photovoltaic (PV) system, a myriad of MPPT algorithms has been proposed. With the pros and cons of various MPPT algorithms, a detailed analysis of several typical direct search and module-integrated MPPT algorithms is presented in this paper. Directions of future work for implementing new MPPT algorithms are also outlined.

Photovoltaic (PV) systems are increasingly used as a sustainable energy source, but their efficiency is significantly affected by environmental factors such as shading and temperature variations. This study proposes a novel Maximum Power Point Tracking (MPPT) algorithm based on the fusion of Support Vector Regression (SVR) and Incremental Conductance (INC) techniques, designed to enhance the performance of PV systems under partial shading conditions. The SVR model is employed to predict the power output of the PV system based on voltage and current measurements, leveraging its capability to handle non-linear relationships with high accuracy. The INC method is then integrated with the SVR predictions to dynamically adjust the operating point of the PV array, ensuring rapid and precise tracking of the maximum power point (MPP). The algorithm was implemented in MATLAB, and comprehensive simulations were conducted to evaluate its performance. Simulation results demonstrate that the SVR-INC fusion algorithm significantly improves the accuracy and stability of MPPT under varying shading conditions. The algorithm effectively reduces the tracking time to the MPP and minimizes power losses caused by partial shading. Compared to traditional MPPT methods, the proposed algorithm shows enhanced robustness and faster convergence, making it highly suitable for practical applications in real-world PV systems. Furthermore, the integration of SVR with INC provides a robust framework for dealing with the complexities of $P V$ power generation. The algorithm’s ability to adapt to changing environmental conditions ensures that the PV system operates at its maximum efficiency. The study also discusses the optimization of SVR parameters and the importance of datadriven approaches in enhancing MPPT performance. In conclusion, the proposed SVR-INC fusion MPPT algorithm offers a promising solution for improving the efficiency and reliability of PV systems under partial shading. The findings highlight the potential of this approach for future advancements in PV technology, contributing to the development of more efficient and resilient solar energy systems..

Grid-connected photovoltaic (PV) systems with power electronic interfaces can provide both real and reactive power to meet power system needs with appropriate control algorithms. This paper presents the control algorithm design for a three-phase single-stage grid-connected PV inverter to achieve either maximum power point tracking (MPPT) or a certain amount of real power injection, as well as the voltage/var control. The switching between MPPT control mode and a certain amount of real power control mode is automatic and seamless. Without the DC-to-DC booster stage, PV DC voltage stability is an important issue in the control design especially when the PV inverter is operating at maximum power point (MPP) with voltage/var control. The PV DC voltage collapse phenomenon and its reason are discussed. The method based on dynamic correction of the PV inverter output is proposed to ensure PV DC voltage stability. Simulation results of the single-stage PV system during system disturbances and fast solar irradiation changes confirm that the proposed control algorithm for single-stage PV inverters can provide appropriate real and reactive power services and ensure PV DC voltage stability during dynamic system operation and atmospheric conditions.

This paper presents the analysis and operation of a grid connected photovoltaic (PV)energy conversion system with an Adaptive Neuro-Fuzzy Inference System (ANFIS)based maximum power point tracking (MPPT)algorithm. Particle swarm optimization is used to train the membership functions while the least squares algorithm is used to update the consequent parameters of the ANFIS with changing operating condition of PV solar system. The MPPT algorithm maximizes conversion efficiency by adjusting the duty cycle of the buck boost converter to change the output voltage of the solar panel and hence achieving the maximum panel output power for a given set of environmental conditions. The ANFIS is trained by using a hybrid algorithm implementing least squares estimator and particle swarm optimization with data obtained by operating the system using the Perturb and Observe (P&O)MPPT algorithm. The performance of the proposed ANFIS based MPPT algorithm is validated in simulation using MATLAB/Simulink at different operating conditions. It is proven that the designed ANFIS based MPPT scheme achieves a very fast response with little oscillations while transferring maximum power from solar panel to the grid line as compared to the conventional P&O based MPPT scheme.