An Intelligent Fault Diagnosis Scheme For PV Array Using Machine Learning Techniques

Photovoltaic (PV) systems have recieved a lot of attention in recent decades due to their accessibility and advancements in PV technology. The protection of PV systems from faults such as String to String (SS), String to Ground (SG), Open circuit (OC), and partial shading are the key challenges to the realization of cost-effective and environmentally friendly PV systems. Such unusual circumstances reduce the maximum available PV power. Partial shading and breakdowns in a PV array must therefore be noticed quickly for enhanced system efficiency and reliability. The significant fault current in PV systems can be detected using the existing safety devices in PV systems, such as fuses and residual current detectors. The flowing fault current being of low order is not significant enough for current protection devices to detect if the solar and/or fault mismatch is modest and the fault resistance is high. As a result, under cloudy and low irradiance conditions, the traditional protection devices fail to identify problems, resulting in reliability concerns and photovoltaic fire threats. In this context, a fault diagnosis scheme for PV systems is presented in this paper, which includes feature extraction using the Discrete wavelet transform, and classification of various defects on the PV system using Decision tree.

Partial shading conditions (PSCs) can significantly reduce the output energy produced by photovoltaic (PV) systems. Moreover, when such conditions occur, conventional and advanced maximum power point tracking (MPPT) systems fail to operate the PV system at its peak because the bypassing diodes may cause the PV system to become trapped at a low power point when they are in conduction mode. The PV system can be operated at the global maximum power point (MPP) with the help of global peak searching tools. However, the frequent use of these tools will reduce the output of PV systems since they force the PV system to operate outside its power region while scanning the I-V curve in order to determine the global MPP. Thus, the global peak searching tools should be deployed only when a PSC occurs. In this paper, a simple and accurate method is proposed for detecting PSCs by means of monitoring the sign of voltage changes (positive or negative). The method predicts a PSC if the sign of successive voltage changes is the same for a certain number of successive changes. The proposed method was tested on two types of PV array configurations (series and series–parallel) with several shading patterns emulated on-site. The proposed method correctly and timely identified all emulated shading patterns. It can be used to trigger the global MPP searching techniques for improving the PV system’s output under PSCs; furthermore, it can be used to notify the PV system’s operator of the occurrence of PSCs.

The local shadow can easily make the photovoltaic (PV)array appear hot spot phenomenon, reduce the output power and affects the security and the reliability of the PV power generation system; At the same time, the P-V characteristic of PV array is changed from single peak curve to multi peak curve, which makes the MTTP controller unable to achieve maximum power tracking. In order to solve the problem that the output power is affected by the partial shading, in this paper, a global optimization method for PV array reconfiguration is adopted. By changing the connection mode of the PV array, shadow localized PV array by optimization algorithm can achieve optimal distribution of shadows, maximally achieve the output power of PV array smoothly under the condition of shadow, improve the output power of the whole PV array to some extent. It also eliminate the local peak value, improve the multi peak phenomenon and verify the effectiveness of the optimization strategy by PSCAD/EMTDC simulation.

The expanding use of photovoltaic (PV) systems as an alternative green source for electricity presents many challenges, one of which is the timely diagnosis of faults to maintain the quality and high productivity of such systems. In recent years, various studies have been conducted on the fault diagnosis of PV systems. However, very few instances of fault diagnostic techniques could be implemented on integrated circuits, and these techniques require costly and complex hardware. This work presents a novel and effective, yet small and implementable, fault diagnosis algorithm based on an artificial intelligent nonlinear autoregressive exogenous (NARX) neural network and Sugeno fuzzy inference. The algorithm uses Sugeno fuzzy inference to isolate and classify faults that may occur in a PV system. The fuzzy inference requires the actual sensed PV system output power, the predicted PV system output power, and the sensed surrounding conditions. An artificial intelligent NARX-based neural network is used to obtain the predicted PV system output power. The actual output power of the PV system and the surrounding conditions are obtained in real-time using sensors. The algorithm is proven to be implementable on a low-cost microcontroller. The obtained results indicate that the fault diagnosis algorithm can detect multiple faults such as open and short circuit degradation, faulty maximum power point tracking (MPPT), and conditions of partial shading (PS) that may affect the PV system. Moreover, radiation and temperature, among other non-linear associations of patterns between predictors, can be captured by the proposed algorithm to determine the accurate point of the maximum power for the PV system.

Solar photovoltaic (PV) technology has the versatility and flexibility for developing off-grid electricity system for different regions, especially in remote rural areas. While conventionally straight forward designs were used to set up off-grid PV-based system in many areas for wide range of applications, it is now possible to adapt a smart design approach for the off-grid solar PV hybrid system. A range of off-grid system configurations are possible, depending upon load requirements and their electrical properties as well as on site-specific available energy resources. The overall goal of the off-gird system design should be such that it should provide maximum efficiency, reliability and flexibility at an affordable price. In this chapter, three basic PV systems, i.e. stand-alone, grid-connected and hybrid systems, are briefly described. These systems consider different load profiles and available solar radiations. A systematic approach has then been presented regarding sizing and designing of these systems. Guidelines for selection of PV components and system sizing are provided. Battery energy storage is the important component in the off-grid solar PV system. Due to load and PV output variations, battery energy storage is going to have frequent charging and discharging. So the type of battery used in a PV system is not the same as in an automobile application. Detailed guidelines for selection of battery are therefore also provided. At present, most of the world-wide PV systems are operating at maximum power points and not contributing effectively towards the energy management in the network. Unless properly managed and controlled, large-scale deployment of PV generators in off-grid system may create problems such as voltage fluctuations, frequency deviations, power quality problems in the network, changes in fault currents and protections settings, and congestion in the network. A possible solution to these problems is the concept of active generator. The active generator will be very flexible and able to manage the power delivery as in a conventional generator system. This active generator includes the PV array with combination of energy storage technologies with proper power conditioning devices. The PV array output is weather dependent, and therefore the PV power output predictability is important for operational planning of the off-grid system. Many manufacturers of PV system power condition devices are designing and developing new type of inverters, which can work for delivering the power from PV system in coordination with energy storage batteries as conventional power plant.

Improving the efficiency of photovoltaic (PV) systems has gained priority in current research due to the large volumes of PV panels installed. Moreover, the remarkable efforts made to investigate different methods of diagnosing PV failures have multiplied, giving additional impetus to research on the efficiency of PV systems. However, most of these methods are limited in the number of faults that can be identified; some are expensive and complex, and others require huge amounts of data to train. In this paper, a simple and robust multivariate statistical analysis method is proposed for the diagnosis and identification of faults in a PV system. From the multitude of data that can be collected on a PV system in operation or available on most new inverters on the market, the method used here is based on kernel principal component analysis, which looks at and analyses the variance between these data. Combined with the Hotelling statistic ( T 2 ) and Squared Prediction Error (SPE) index associated with Rolle’s theorem, this analysis identifies six operating states of the PV system: normal operation, short-circuited panels, open-circuit panels, partially shaded panels, serial resistance degradation, and MPPT error. 200 samples of different faults at different irradiance have been generated between an irradiance from 50 to 500 w/m2. The accuracy rate was 64% for the degradation of series resistance, 91.11% for partial shading, 100% for open circuit, 100% for short circuit, and 100% for MPPT error. The various results obtained first from a Matlab-Simulink model, and then from a real system of 18 modules, demonstrate the efficiency and performance of the proposed algorithms.

Energy crises and the growth of the energy demand have increased the interest in utilizing unconventional power sources. Thus, renewable energy sources have become a topic of interest to mitigate rising energy concerns and cope with increased electricity demand. With remarkable merits including cleanness and abundance, photovoltaic (PV) solar energy systems are a key to solving these issues. The employed inverters should effectively utilize the maximum available power from the PV solar system and transfer this power to the utility grid without posing any further limitations. However, the unequal power generation of different PV systems caused by partial shading (PS) and other PV panel degradation factors leads to a reduction in generation capacity. One of the relatively new solutions to mitigate the mismatch concerns between the PV modules and sub-modules is to extract the maximum power of each sub-module individually. The main objective of this paper is to present a comprehensive review of such PV grid-connected inverters topologies associated with sub-module connection and control. It will classify the PV grid-tied inverters in accordance with the level where the maximum power point tracking (MPPT) system is implemented. A special focus has been placed on sub-module microinverters (MI) in terms of circuit topologies, conversion efficiency, and controller design. This paper provides a comprehensive analysis of employing the distributed MPPT (DMPPT) approach to maximize the power generation of PV systems by mitigating the mismatch issues inside the PV module. The circuit topology, PV system configuration, and MPPT algorithms used for applying DMPPT solutions in PV SMs are discussed in detail in this study.

In this paper, detailed studying of the effect of partial shade on Photovoltaic (PV) arrays, which represent one of the most well-known problem that affect this field of renewable energy, because of that matter, this paper discuss this issue and make a detailed discussion for different connection topologies that used to increase the efficiency of the PV system under Partial Shade. This paper using MATLAB/Simulink to analyze three different connection topologies of PV modules under partial shade conditions (PSC), these topologies are the Series-Parallel connection (SP), Total-Cross-Tie (TCT), and Bridge-Linked (BL).The results in the study help the workers in this field to choose the best connection topology for PV power system and reach to that; the Total-Cross-Tie (TCT) topology is the best.

In the outside environment, the partial shading on the photovoltaic (PV) arrays occurs frequently and the generated power of PV arrays is far lower than the rated power of inverters, thereby it will cause the total output power of PV system decline sharply. In this study, a flexible topology structure of PV power generation network, connecting PV arrays and inverters by the switching matrix is presented. Then, it introduces the working principle of topology structure and puts forward the corresponding multi-population genetic algorithm to realise the group management of the multi-objective control, so as to achieve the power matching optimisation between PV arrays and inverters during partial shading. Finally, the simulation and experiment show that the conversion efficiency of PV system used by the control strategy is much better than that of conventional distributed structure of PV power for the shade of PV arrays, and provide a new way for the effective use of solar energy.

One of the most promising forms of renewable energy is solar photovoltaic (PV) energy, which directly generates electric power from sun irradiation. Since the solar photovoltaic system has non-linear nature, therefore despite the benefits, partial shading presents a significant barrier to photovoltaic (PV) systems’ efficient utilization. Partial shading may be due to nearby buildings, trees, electric poles, etc. Partial shading reduces the maximum power output of photovoltaic arrays, and arrays have a few peaks in their PV characteristics. The output power reduction depends on the shading pattern, array structure, and physical placement of the array’s modules rather than being exactly proportional to the shading area. There are numerous techniques that can be used to mitigate partial shading problems in a photovoltaic (PV) array. One of the most productive methods to avoid this barrier is by adopting a reconfiguration strategy. In this article, to reduce the consequences of partial shadowing, a strategy of PV array reconfiguration is implemented. There are several other topologies that can be implemented to reduce the impact of partial shading, among them the five topologies described here: Total Cross Tied (TCT), Honey-Comb (HC), Series Parallel (SP), Bridge-Link (BL), and Su-Do-Ku. In this article, numerous performance parameters such as short circuit current, global maximum output power, and open circuit voltage are taken to examine the effectiveness of each topology. In furthermore, the fill effect is taken into account in order to conduct a fair comparative analysis under various shading patterns. The responses of each pattern are carried out in Matlab/Simulink.

Photovoltaic module is very susceptible to partial shading problem. In a photovoltaic power system, large number of photovoltaic modules are connected in series to provide required voltage and power. Due to large number of photovoltaic modules, the chances of every photovoltaic module to receive uniform solar irradiance become lower. Therefore, a photovoltaic system consists of large number of photovoltaic modules is even more susceptible to partial shading problem. This paper presents the investigation of the energy yield of a photovoltaic system under partial shading conditions. The investigation results shows that the energy yield of a photovoltaic system decreases as the shading heaviness increases. However, the effect is not constant. The effect is especially significant when the photovoltaic system is under lightly partial shaded conditions. In worst case, the energy yield of the photovoltaic system can drops up to 17.65 % as the shading heaviness increases by 20 %. Therefore, the partial shading need to be address in order to minimize the losses of the photovoltaic system under partial shading conditions.

Photovoltaic (PV) system output power greatly depends on environmental operating conditions. Partial shaded condition (PSC) operates PV string under mismatch. PV module mismatch has been one of the major causes for reduced amount of output power. Maximizing the amount of energy extraction from PV system under mismatch greatly influenced by conversion efficiency as well as the mismatch mitigation topology used. Differential power processing (DPP) is one of the advanced techniques to deal with mismatch conditions and enhance power output from a PV system. In this paper hybrid modular DPP topology is presented. The proposed technique mitigates the effect of mismatches at submodule and enhance power extraction from PV string. Since in majority shading on a PV module is nonuniform. The conversion efficiency of module level DPP shading mitigation techniques enhanced using submodule level DPP architecture. To demonstrate its applicability simulation study is carried out in MATLAB Simulink and results are compared with traditional bypass method and module level DPP. Simulation results showed the reduction in mismatch loss and improvement in efficiency and power output.

Solar ship, which integrates the solar photovoltaic (PV) system into its own ship power system, is becoming one kinds of most promising and fastest developing green ship. Since the electric energy transformed by PV system is provided to the power load through the ship's distribution system, the output power of synchronous generator will be reduced in proportion. Especially, if the matching relationship among solar PV system, energy storage system and the power load requirement is precisely analyzed and the operation characteristics and reliability of solar inverter have already meet the strict test standards for marine equipment, the design capacity of synchronous generators could also be reduced. The off-grid mode and grid mode are the main way of integrated application of solar power photovoltaic system of ship. And the solar PV system is a kind of inverter power supply, which is essentially based on the electronic inverted technology, so PV system can be regarded as a ‘fragile power source’ with ‘zero inertia’. Therefore, the influence of solar photovoltaic grid-connected system to the power flow and power quality of the ship power system cannot be ignored. And the effect of photovoltaic system on the power quality of transient and steady-state and flow calculation remains to be studied. This paper mainly research the changes of power load flow calculation(PLFC) on the system, using the toolbox PSAT of MATLAB Simulink. This paper research the PLFC on the system of different solar photovoltaic systems access points, and analysis the experimental results. The results show that, under the premise of the normal operation of the ship electric power system, the improvement of the capacity of solar photovoltaic system in ship , and different access modes of photovoltaic grid-connected system, have slight impact on the power flow of power system, indicating that the photovoltaic grid-connected system in ship is stable, an appropriate increase in the capacity of PV system is feasible. The results is of certain significance of secure application of grid connected photovoltaic system in this paper.

This study investigates the impact of shading on the performance of photovoltaic (PV) systems, a critical consideration for optimizing solar energy generation. Shading can occur due to various environmental factors, including nearby structures, vegetation, and atmospheric conditions, leading to significant reductions in energy output and overall system efficiency. Through a combination of experimental measurements and simulation modeling, we assessed how different shading scenarios affect the electrical performance of PV arrays. The findings reveal that even partial shading can cause substantial decreases in power generation, with shaded cells experiencing reverse biasing and increased thermal stress, resulting in potential hot spot formation. The analysis also highlights the importance of PV module configuration and orientation in mitigating shading effects. Additionally, the study highlights the functionality of bypass diodes in PV systems. By allowing current to bypass shaded or malfunctioning cells, these diodes help maintain optimal performance levels even when some cells are compromised. The analysis includes comparative assessments of PV systems with and without bypass diodes under identical shading conditions. Results demonstrate that systems equipped with bypass diodes exhibit significantly improved performance, including higher voltage and current outputs, thereby enhancing overall energy yield. This research underscores the necessity for site-specific evaluations during the design phase of PV installations to ensure maximum efficiency. The insights gained from this study contribute to a deeper understanding of shading dynamics in PV systems and provide practical recommendations for improving solar energy utilization. Ultimately, addressing shading challenges is essential for advancing the reliability and effectiveness of solar power as a sustainable energy solution. The findings deduce the importance of integrating bypass diodes in PV systems to mitigate the detrimental effects of shading, ultimately contributing to more effective utilization of solar energy resources.

Long term supporting schemes for photovoltaic (PV) system installation have led to accommodating large numbers of PV systems within load pockets in distribution grids. High penetrations of PV systems can cause new technical challenges, such as voltage rise due to reverse power flow during light load and high PV generation conditions. Therefore, new strategies are required to address the associated challenges. Moreover, due to these changes in distribution grids, a different response behavior of the distribution grid on the transmission side can be expected. Hence, a new equivalent model of distribution grids with high penetration of PV systems is needed to be addressed for future power system studies. The thesis contributions lie in three parts. The first part of the thesis copes with the PV modelling. A non-proprietary PV model of a three-phase, single stage PV system is developed in PSCAD/EMTDC and PowerFactory. Three different reactive power regulation strategies are incorporated into the models and their behavior are investigated in both simulation platforms using a distribution system with PV systems. In the second part of the thesis, the voltage rise problem is remedied by use of reactive power. On the other hand, considering large numbers of PV systems in grids, unnecessary reactive power consumption by PV systems first increases total line losses, and second it may also jeopardize the stability of the network in the case of contingencies in conventional power plants, which supply reactive power. Thus, this thesis investigates and develops the novel schemes to reduce reactive power flows while still keeping voltage within designated limits via three different approaches: 1. decentralized voltage control to the pre-defined set-points 2. developing a coordinated active power dependent (APD) voltage regulation Q(P) using local signals 3. developing a multi-objective coordinated droop-based voltage (DBV) regulation Q(V) using local signals In the third part of the thesis, furthermore, a gray-box load modeling is used to develop a new static equivalent model of a complex distribution grid with large numbers of PV systems embedded with voltage support schemes. In the proposed model, variations of voltage at the connection point simulate variations of the model’s active and reactive power. This model can simply be integrated into load-flow programs and replace the complex distribution grid, while still keeping the overall accuracy high. The thesis results, in conclusion, demonstrate: i) using rms-based simulations in PowerFactory can provide us with quite similar results using the time domain instantaneous values in PSCAD platform; ii) decentralized voltage control to specific setpoints through the PV systems in the distribution grid is fundamentally impossible due to the high level voltage control interaction and directionality among the PV systems; iii) the proposed APD method can regulate the voltage under the steady-state voltage limit and consume less total reactive power in contrast to the standard characteristic Cosf (P) proposed by German Grid Codes; iv) the proposed optimized DBV method can directly address voltage and successfully regulate it to the upper steady-state voltage limit by causing minimum reactive power consumption as well as line losses; v) it is beneficial to address PV systems as a separate entity in the equivalencing of distribution grids with high density of PV systems.