Photovoltaic Energy Conversion Research Articles

Comprehensive review and analysis of photovoltaic energy conversion topologies

Energy conversion is a pivotal process with widespread applications, spanning renewable energy systems, electric vehicles, and industrial power grids. Selecting the right energy conversion topology is critical for optimizing system performance, efficiency, and reliability. This comprehensive review paper provides a thorough overview of energy conversion topologies used in photovoltaic (PV) panel systems, as well as their applicability in diverse domains. Furthermore, the paper conducts a detailed analysis of commonly employed energy conversion topologies. Each topology is meticulously examined based on its operating principles, advantages, drawbacks, and typical use cases. This comprehensive review serves as an invaluable resource for researchers, engineers, and practitioners engaged in the dynamic field of energy conversion, offering insights into both wind energy and photovoltaic panel systems.

Excitons at the interface of 2D TMDs and molecular semiconductors.

Van der Waals heterostructures (vdWHs) of vertically stacked two-dimensional (2D) atomic crystals have been used to elicit intriguing phenomena stemming from strong electronic correlations, magnetic textures, and interlayer excitons spawned at the heterointerface. However, vdWHs comprised of heterointerfaces between these 2D atomic crystal lattices and molecular assemblies are emerging as equally intriguing platforms supporting properties to be harnessed for photovoltaic energy conversion, photodetection, spin-selective charge injection, and quantum emission. In this perspective, we summarize recent research examining exciton dynamics in heterostructures between semiconducting 2D transition metal dichalcogenides and molecular organic semiconductors. We discuss methods for assembly of these heterostructures, the nature of interlayer or charge-transfer excitons at transition-metal dichalcogenide (TMD)-molecule interfaces, explicit exciton transfer between organics and TMDs, and other interfacial phenomena driven by the merger of these two material classes. We also suggest key new research directions extending the remit of these 2D atomic-molecular lattice heterointerfaces into the domains of condensed matter physics, quantum sensing, and energy conversion.

Robust power control for PV and battery systems: integrating sliding mode MPPT with dual buck converters

This paper presents a comprehensive exploration of an integrated Buck-Boost converter and Sliding Mode Control (SMC) Maximum Power Point Tracking (MPPT) system for optimizing photovoltaic energy conversion. The study focuses on enhancing solar energy extraction efficiency, regulating output currents, and ensuring effective battery utilization. Through a systematic analysis of converter component sizing and operational modes, the paper delves into the intricacies of the Buck-Boost converter. The unique contribution lies in the innovative integration of SMC with the traditional Perturb and Observe (P&O) algorithm, providing robust and adaptive MPPT under varying environmental conditions. Additionally, the paper introduces a battery management system with three distinct modes, namely, Charging, Direct, and Discharging, offering intelligent control over critical scenarios. Simulation results underscore the robustness of the proposed system under diverse conditions, demonstrating its effectiveness in managing power distribution based on battery charge levels, even in scenarios of insufficient solar power. Overall, this research significantly contributes to advancing the understanding of PV/battery systems and offers a practical, sustainable solution for optimizing energy production, distribution, and storage, marking a substantial stride towards a more efficient and sustainable energy future.

Harmonic Elimination Using Grid Integrated Hybrid Renewable Energy System with Optimized Control for Nano Scale Based 31-Level MLI

This research focuses integration of grid integrated hybrid renewable energy system (HRES) with optimized control techniques for harmonic elimination using Nano Scale Based 31-Level Multi-Level Inverter (MLI). The proposed system combines Renewable Energy Sources (RES), such as Solar Photovoltaic (PV) and Wind Energy Conversion System (WECS) assisted with Doubly Fed Induction Generator (DFIG) to generate power for grid integration. Interleaved KY converter with novel Rain Optimized Algorithm assisted Artificial Neural Network (ROA-ANN) based Maximum Power Point Tracking (MPPT) is established, which is a hybridized approach extracting maximum PV power and optimizes power output for utilization. Excess energy generated from hybrid power sources is utilized to charge battery. The DC supply from hybrid sources is transferred to silicon carbide switches of 31 MLI for elimination of harmonics using Selective Harmonic Elimination Pulse Width Modulation (SHE-PWM). The 31-Level MLI facilitates conversion of DC voltage to AC with assistance of Particle Swarm Optimized Proportional Integral (PSO-PI) controller. Finally, controlled AC supply is transferred to LC filter, resulting in effective grid synchronization with reduced harmonics. The proposed system’s performance is validated using MATLAB Simulink, and obtained results demonstrate effectiveness with reduced total harmonic distortion (THD) of 0.66% in contrast to state-of-art approaches

CHTS/Zn2P3-based solar cells with enhanced efficiency through ETL engineering: A numerical study

Copper Mercury Tin Sulfide (CHTS) solar cells have shown a promising performance in the field of photovoltaic energy conversion with a bandgap range between 1.0 eV and 1.5 eV. However, further improvement is required to enhance the efficiency of CHTS SCs. In our study, we conducted Numerical simulation of the investigation of the effect of different buffer layers and a Zn2P3 back-surface field (BSF) layer on the effectiveness of CHTS SCs using the SCAPS-1D Programming. Initially, we optimized the basic structure of a CHTS SC without a BSF layer. We evaluated three different buffer layers (GaN, In0.4Ga0.6N, and In0.65Ga0.35N) as potential insulating layers. GaN was found to be the optimal buffer strata, with a power conversion efficiency (PCE) of 19.89%. Next, we proposed a new device structure with a Zn2P3 BSF layer. The BSF layer was found to have a positive effect on cell effectiveness, increasing the PCE to 21.16%. We further investigated the effect of different input variables, such as carrier concentration, fault density, and thickness of the absorbed strata on the achievement of both apparatus structures, with and without the BSF layer. Our results showed that the device structure with the Zn2P3 BSF layer achieved a maximum PCE of 23.79%, which is significantly higher than the PCE of the apparatus structure in case of the absence of the BSF strata. This improvement in PCE is due to the reduced reassemble of the charge transporters behind the interface and the improved light absorption in the CHTS layer. Overall, our numeral conclusion suggests that the use of CHTS/GaN-based solar photovoltaic cell design with a Zn2P3. The BSF layer is considered an ideal choice for high-performance solar cells (SCs).

Development of energy conversion and lightning strike protection simulation for photovoltaic-wind turbine on grid

Photovoltaic (PV) installations and wind turbines that are installed on the rooftops of buildings need to be protected because the layout is in a high position and there is a risk of being struck by lightning. Therefore, a more effective protection system is designed to anticipate electronic damage and fire on all materials in the distribution network, especially the addition of PV and wind turbine installations on building roofs. The purpose of this study is to simulate a lightning protection system on the distribution network and the results of on-grid PV energy conversion using electrical transient analyzer program (ETAP) software. Feeder relay delay times and cascade coordination patterns between outgoing and incoming relays do not overlap. the delay time of the relay working on the feeder is 0.31 s and the coordination pattern of the outgoing relay and incoming relay does not touch each other, so the delay time for the incoming relay is 2.73 s. Then testing the results of PV energy conversion connected to the grid using MATLAB Simulink monitoring obtained data reaching 1.600 Wp at peak power with sun conditions parallel to the PV installation layout.

Optoelectrical Modeling of Perovskite/Perovskite/Silicon Triple‐Junction Solar Cells: Toward the Practical Efficiency Potential

Perovskite‐based triple‐junction solar cells offer the potential for highly efficient and cost‐effective photovoltaic energy conversion. This article aims to provide a roadmap for the optical properties of perovskite/perovskite/silicon triple‐junction cells. A comprehensive optoelectrical model for the perovskite/perovskite/silicon structure is developed in Sentaurus TCAD. The optical part of the model is validated by measurements of a triple‐junction solar cell. As the electrical characterization is an ongoing process, the electrical properties are assumed to be nonlimiting, which enables us to translate the optical improvement steps into efficiency potentials. A first improvement step lies in adjusting the thicknesses of the perovskite layers to achieve current matching between both perovskite subcells. Using perovskites with bandgaps optimized for planar surfaces, it would be possible to increase the photocurrent density to 13.3 mA cm−2 and the efficiency to 41.9%. It is shown that by implementing a fully textured structure and using the best available materials, a short‐circuit current of 14.1 mA cm−2 and an open‐circuit voltage of 3.48 V with an efficiency of 44.3% are possible assuming idealized electrical properties. This can be regarded as a practical efficiency potential for this kind of triple‐junction technology.

Ultra-broadband absorber based on photonic topological transition with large-[formula omitted] metals

We propose and experimentally demonstrate an ultra-broadband metamaterial absorber based on photonic topological transition by using metals with large real part of permittivity (ε′). The simulation results show that the absorptivity is larger than 0.9 in the wavelength range from 400 nm to 2832 nm. The simulation results also show that the absorption effect is insensitive to the incident angle and polarization. According to the effective medium theory, the ultra-broad bandwidth is originated from the photonic topological transition. In addition, the analyses reveal that the absorption bandwidths can be extended by manipulating the wavelengths of photonic topological transition (PTT) points with large-ε′ metals. Furthermore, an ultra-broadband metamaterial absorber with multilayer films is fabricated by using standard film deposition techniques. The measured results show that the absorptivity is larger than 0.9 under normal incidence over the measured wavelength range of 400–2500 nm. This metamaterial absorber is expected to be potential candidate for various applications, such as thermal photovoltaic energy conversion, detectors, and solar cells.

Switched Z-Source Boost Converter in Hybrid Renewable Energy System for Grid-Tied Applications

The world's focus is shifting toward Renewable Energy Sources (RES) as a result of the sharp rise in energy demand and the depletion of conventional energy sources. Distributed generation (DG) units developed on RES are easily and reliably integrated into grid due to microgrid technology. Inverters are typically used to integrate DGs into microgrid. At present, the fastestgrowing renewable sources of electricity in the world is photovoltaic (PV) and wind energy conversion system (WECS), which evolved in response to growing environmental concerns about the risks of climate change connected with power generation. Recent technological developments have made it a top priority for researchers to find ways to enhance the efficiency of hybrid systems and the power converter stage. In order to achieve transmission losses and ensure energy savings, a new 13-bus system is developed in this work for regulating the output voltage in distribution networks. Switched Z-source Boost converter along with Proportional Integral (PI) controller is employed to boost the voltage obtained from PV system. A battery converter along with a bi-directional battery is connected to the DC link, to store energy generated by Hybrid Renewable Energy System (HRES) in excess amount. The obtained DC link voltage is transferred to three-phase voltage source inverter (VSI) for the conversion of DC to AC voltage. Effective harmonic reduction is attained with the aid of LC filter coupled to Three phase grid, and the PI controller associated to the grid supports in achieving effective grid synchronization. The proposed research is validated using MATLAB Simulink by considering the 13-bus system and an efficiency of 96.8 % is obtained with 0.93% Total Harmonic Distortion (THD).

Assimilation of a novel thermal collector and phase change material in photovoltaic/thermal system - An energy and exergy based comparative study

The efficiency of the photovoltaic (PV) panel's solar energy conversion into usable power is significantly influenced by the elevated temperature of the PV cell. The hybrid photovoltaic/thermal (PV/T) system, on the other hand, is not very efficient overall because the collector profile was not chosen correctly and the PV module temperature changes too quickly, limiting its useful life. This research improved the performance of a PV/T hybrid system by employing a novel butterfly-shaped serpentine flow collector and Hydrated Salt (HS36) Phase Change Materials (PCM). The energy and exergy performances of the PV/T, PV/T-PCM systems are evaluated at diverse volume flow rates of water and compared with orthodox uncooled PV modules. The maximum average overall efficiency of the PV/T and PV/T-PCM systems is chronicled as 79.36 % and 94.05 % at 2 lpm water flow rate, respectively. The suggested PV/T and PV/T-PCM systems outclass the reference PV system in terms of total average exergy efficiency by 13.90 % and 23.54 %, respectively. The PV/T system integrated with a novel BSF profile and HS36 PCM showed more efficiency in capturing solar energy. It provides more opportunities for exploring and developing PV/T systems compared to the orthodox PV system.

Bypassing the Single Junction Limit with Advanced Photovoltaic Architectures.

Multijunction devices and photon up- and down-conversion are prominent concepts aimed at increasing photovoltaic efficiencies beyond the single junction limit. Integrating these concepts into advanced architectures may address long-standing issues such as processing complexity, microstructure control, and resilience against spectral changes of the incoming radiation. However, so far, no models have been established to predict the performance of such integrated architectures. Here, a simulation environment based on Bayesian optimization is presented, that can predict and virtually optimize the electrical performance of multi-junction architectures, both vertical and lateral, in combination with up- and down-conversion materials. Microstructure effects on performance are explicitly considered using machine-learned predictive models from high throughput experimentation on simpler architectures. Two architectures that would surpass the single junction limit of photovoltaic energy conversion at reasonable complexity are identified: a vertical "staggered half octave system," where selective absorption allows the use of 6 different bandgaps, and the lateral "overlapping rainbow system" where selective irradiation allows the use of a narrowband energy acceptor with reduced voltage losses, according to the energy gap law. Both architectures would be highly resilient against spectral changes, in contrast with two terminal multi-junction architectures which are limited by Kirchhoff's law.

(Invited) Development of Perovskite Photovoltaic Devices Using Electrodeposition

Photovoltaic energy is considered today as the most useful natural energy source. To date, different types of solar technologies are industrially available, and the attempts in research and development to improve their potential are continuing. While a number of different materials with different efficiencies can achieve photovoltaic solar energy conversion, so far, no particular material or combination is cheap enough to compete with large-scale fossil fuel-generated electricity. Nowadays, Si-based cells are the most marketed, and they produce high solar conversion efficiencies. However, expensive high temperature and high vacuum processes are adopted in order to elaborate pure Si. Another active material, called perovskite, newly emerged in the solar community. It has attracted major attention worldwide because of its outstanding photovoltaic performance, easy fabrication process, adaptable band-gap, high extinction coefficient, and high carrier mobility. As perovskite is capable of generating a power conversion efficiency approaching that of the leading silicon and that the solar devices fabrication cost is lower, perovskite solar cells tend to be considered as the future of the photovoltaic technology.However, the most used method to deposit perovskite active layer is spin coating, which presents many constraints such as limited surface coverage, non-homogeneity, undefined perovskite crystallinity, and poor stability. Perovskite obtained by spin-coating requires working in inert environment (glove box) and adding some toxic additives to maintain the stability of the perovskite. This increases its cost and enables the deposition only on small surfaces. There is thus a need to look up for alternative deposition methods, more ecofriendly, at lower costs, applicable for large-scale production of perovskite solar cells.Electrodeposition recently started to be explored as an efficient alternative for perovskite fabrication. There have been several attempts over the past years to optimize the electrodeposited perovskite layer and adjust its crystallization on dissimilar layers. All sub-techniques started by electrodepositing an initial layer (PbO, PbO2 or PbI2) followed by one or several conversions of the as-deposited layer. In the presented work, we were able to develop different types of perovskites using electrodeposition, understand the impact of the different deposition parameters on their structure, and improve their stability comparing to the spin-coated ones. Along with the simple MAPbI3 perovskite, the electrodeposition of mixed MAPbI3-xClx and MA1-yFAyPbI3-xBrx perovskites will be presented. The present study is one of its kind, since these mixed perovskite were never developed using electrodeposition before. It was observed that using electrodeposition afford enhanced stability compared to spin-coating process, and the different fabricated perovskites were also proved to experience a positive maturation phenomenon during their first 500 hours of life.The electrodeposition process is easy to manipulate, and the electrodeposited films could grow on surfaces as large as desired, inside an electrolyte, allowing its application in ambient atmosphere, with no need of a glove box. It is also eco-friendly in terms of solvent engineering, since no toxic solvents are needed to stabilize or enhance the morphology of the obtained films. The main solvents used are deionized water, ethanol and isopropanol.

Solvent Annealing Enabling Reconstruction of Cadmium Sulfide Film for Improved Heterojunction Quality and Photovoltaic Performance of Antimony Selenosulfide Solar Cells

AbstractAntimony selenosulfide, Sb2(S,Se)3, has been considered as new‐generation light‐harvesting material for high‐efficiency photovoltaic applications due to its adjustable bandgap, high absorption coefficient, and excellent stability. In terms of device operation, the electron transfer from the electron transporting layer to Sb2(S,Se)3 layer plays a critical role in improving the photovoltaic energy conversion efficiency of solar devices. Intricately manipulating the surface and interface properties has been a great challenge in solar cell fabrications. Herein, an effective approach toward the reconstruction of the CdS interfacial layer, and the following Sb2(S,Se)3 absorber film by utilizing polar ethylenediamine (EDA) solvent annealing at room temperature is developed. It is found that the presence of nitrogen‐containing functional groups of EDA on the CdS surface not only promotes the grain growth and crystallization of CdS, but also induces optimized deposition of Sb2(S,Se)3 films in terms of interfacial contact and defect formation. Finally, the Sb2(S,Se)3 solar cell based on EDA–CdS achieves a top efficiency of 10.10%. This study provides an efficient method and a new understanding of chemically healing inorganic thin films.

Photovoltaic energy conversion in multiferroic perovskite absorber-based devices via experiment and theoretical calculations

Initially, La and Ti-doped BiFeO3 (BLFTO) was prepared through the solid-state method, and the formation of perovskite structure was confirmed through powder X-ray diffraction (XRD) analysis. SEM-EDX analysis confirms the merging of grains for the increasing concentration of Ti ion doping and the presence of all elements in the samples. The bandgap tuning in BLFTO (2.05 eV–2.11 eV) was analyzed through UV–vis spectroscopy and confirming the change in bandgap for Ti-doped BLFO samples. The observed energy bandgap range of the doped BFO absorber suggested its potential applications in solar cell devices. Therefore, we have designed lead-free FTO/TiO2/absorber/Spiro-OMeTAD/Au heterostructure device and achieved a power conversion efficiency (PCE) of ∼5.61% with an open-circuit voltage (VOC) of ∼0.91 V, fill factor (FF) of 55.55%, and current density (JSC) of 10.87 mA/cm2 for lead-free doped Bi0.80La0.20Fe1−xTixO3 (x = 0.0) based perovskite solar cells with proper optimization of thickness of absorber and operating temperature.

Hybrid optimized-ANFIS based MPPT for hybrid microgrid using zebra optimization algorithm and artificial gorilla troops optimizer

This paper presents an effective hybrid renewable energy system. This system utilizes primary energy sources represented by both photovoltaic (PV) and wind energy conversion system (WECS). In addition, integrating the battery energy storage system (BESS), the hydrogen energy storage system (HESS), and the supercapacitor energy storage system (SESS), as backup sources which providing reliable simultaneous power supply and loading. A new design for a wind energy conversion system based on a hybrid excitation permanent magnet synchronous generator (HEPMSG) is proposed, and then artificial intelligence strategies are utilized to determine the optimal flow of energy when the system is operating immediately. Moreover, new hybrid maximum power point tracking (MPPT) techniques have been proposed including zebra optimization algorithm (ZOA)-ANFIS-based MPPT and gorilla troops optimizer (GTO)-ANFIS-based MPPT to obtain the maximum power of solar panels and wind turbines, which leads to enhancing the performance of these energy sources. The implemented power flow management (PFM) model is designed by MATLAB/Simulink, considering three various operating cases to evaluate the performance and effectiveness of various backup system configurations under different operating scenarios. According to the results, power can be generated, and load requirements can be efficiently met by applying the proposed PFM strategy, and this leads to the system operating at optimal performance. When comparing two optimization techniques, it will become clear that both give robust performance, but ZOA technique significantly outperforms the GTO technique in the computation time (26.17 % reduction) for the photovoltaic system. On the other hand, in the case of the wind energy conversion system, the ZOA technique achieves a significant reduction in calculation time by 35.5 %. The ZOA technique achieves computation times of 1616.80 s and 672.43 s for the photovoltaic and wind energy conversion system, respectively.

Multi-objective control and optimization of a stand-alone photovoltaic power conversion system with battery storage energy management

This paper addresses the problem of controlling a stand-alone photovoltaic (PV) energy conversion system integrated with a battery energy storage system. The study focuses on a series association of PV panels, a DC/AC converter, a Li-ion battery, and a DC load. The intermittent nature of PV power and frequent variations in load demand decrease battery lifetime and its charging performance. To mitigate these issues, an efficient battery charge controller is proposed to instantaneously balance the PV power flow delivered to the DC load and the battery, ensuring optimal utilization of PV power and appropriate battery charging. Based on available solar power, battery state of charge (SOC), and DC load demand The controller adapts to three charging modes, namely, maximum power point tracking (MPPT) charging mode, constant current (CC) charging mode, and constant voltage (CV) charging mode. Additionally, a novel energy management algorithm is designed to ensure battery safety and determine the system’s mode of operation, considering weather conditions and load demand variations. Interestingly, no solar irradiation or battery SOC sensors are required for the implementation of the control system. Nonlinear and robust controllers are developed to provide the necessary control input laws for the management algorithm. The robustness and stability of the system are verified using the Lyapunov theory. Furthermore, the paper quantifies the performance of the proposed strategy through a comparative analysis using integral of absolute error (IAE) indices against two conventional control approaches. Simulation results validate the effectiveness of the proposed controller strategy, demonstrating its high performance and ability to meet the specified objectives. This work presents an innovative approach to enhance the efficiency and reliability of stand-alone PV energy conversion systems with battery storage, offering promising prospects for sustainable energy applications.

Cu2SnS3 based photovoltaic structure with improved open circuit voltage for air stable self-driven enhanced NIR photodetection

Copper tin sulfide (Cu2SnS3) is an environmentally benign and economical semiconductor comprising earth-abundant, non-toxic elements with flexible optoelectronic properties for photovoltaic energy conversion and photodetection. The optimization of sulfurization temperature resulted in significant improvement in structure, morphology, elemental composition, optical and electrical properties. A substantial advancement in photovoltaic performance was achieved by integrating a thin layer of SnS and the same enhancement theoretically predicted using SCAPS-1D simulation. Photovoltaic structure with optimized monoclinic Cu2SnS3 as an absorber layer and thin SnS layer (Glass/FTO/CdS/SnS/Cu2SnS3/Ag) resulted in photovoltaic parameters: Voc = 415 mV, Jsc = 17.2 mA.cm−2, and PCE = 2.12 %. We demonstrate the first self-powered SnS/Cu2SnS3 based photodetector which delivers high detectivity of 1.41 × 1011 Jones under the illumination of an 840 nm laser with rapid rise and decay time of 10.2 and 10.1 ms, respectively. Economic and environmentally benign Cu2SnS3 thin films based photovoltaic structures will be beneficial for harvesting sustainable energy and paving a strong platform for self-powered, air-stable, and spectral selective photodetection.

Comparison of Control Method System by Using Perturbation and Observation Algorithms and Fuzzy Logic for the Maximum Power Point Control in Photovoltaic Systems

Currently, photovoltaic energy conversion has developed tremendously in the global energy industry. The enormous capacity of solar power plants generates electricity all over the world. Hundreds of gigawatts of electrical energy are supplied to the networks of various countries around the globe. In addition, up to hundreds of gigawatts of installed capacity of solar power plants are commissioned every year in all countries of the world. And this has been the trend for the past few decades. The main problem of solar photovoltaic conversion is the instability of the solar radiation flux associated with the climatic conditions in the regions where photovoltaic plants are operated. This problem can be solved by using highly efficient methods to control the generation of solar power plants, in particular, such as the use of information control systems for a particular PV system to increase the final generation of electrical energy supplied to the consumer. The photovoltaic (PV) conversion of solar radiation flux is an important renewable energy source. Due to the varying intensity of the sun, the electricity generated by PV directly from the radiation flux is not constant. The photovoltaic system currently uses maximum power point (PMP) tracking in perturbation and observation (P&O) mode to increase the final output power of the photovoltaic panels. A step-down DC-DC converter allows PMP to change the PV operating voltage and determine the maximum power output of the PV panel. This study proposes a fuzzy logic implementation. The magnitude of the perturbed voltage is determined by the change in power dq and the change in power relative to the change in voltage dq/dv is fuzzy. The performance of fuzzy logic is investigated in this work in order to optimize MPM. Fuzzy logic can simplify maximum power tracking and reduce voltage instability. According to the simulation results, the MPM method based on fuzzy computation performs better than the traditional P&O method. By using the proposed methods, we can significantly improve electric power generation and increase the efficiency of photovoltaic conversion.

Overview and Perspective for High‐Efficiency Single‐Junction Solar Cells

Photovoltaic energy conversion is expected to contribute to creation of a clean energy society and high‐performance solar cells are very attractive for realizing such a vision. The development of high‐performance solar cells offers a promising pathway toward achieving high power per unit cost for many applications. Although state of the art of some of single‐junction solar cells are approaching the Shockley–Queisser limit of 32–33%, further improvements in efficiencies of solar cell and modules are thought to be possible. Herein, efficiency improvements in various single‐junction solar cells are overviewed in this article and several losses of high‐efficiency single‐junction solar cells are discussed about. Perspective of single‐junction solar cells from the viewpoint of practically feasible efficiency based on scientific and technological arguments is also presented. In addition, problems to be solved for solar cell modules are discussed.

New backstepping controllers with enhanced stability for neutral point clamped converters interfacing photovoltaics and AC microgrids

This work presents a new approach to obtain pulse width modulation (PWM) backstepping controllers with enhanced stability for neutral point clamped (NPC) multilevel converters to deliver energy from photovoltaic (PV) panels into AC microgrids. Stability enhanced backstepping non-linear controllers are obtained from the equations of the dq frame converter model to regulate the PV voltage to track the power point, and to balance the capacitor voltages through DC biasing of the PWM carriers, using a novel dynamic equation of the capacitors incremental unbalance voltage, while controlling the grid injected AC currents. Besides, the proposed controllers can change the PV panels operating point to curtail inject power for AC voltage / frequency regulation. The NPC converter and AC microgrid are simulated in MATLAB / Simulink and implemented in the laboratory to evaluate the performance of the PV energy conversion using the new stability enhanced backstepping PWM control. Simulation and experimental results show that, regarding predictive controllers, the novel stability enhanced backstepping requires lower microprocessor power than predictive controllers while presenting a similar behavior in PV voltage and power point tracking regulation, or for voltage / frequency regulation of the microgrid. AC injected currents show low levels of total harmonic distortion similar to predictive controllers and can operate at near unity power factor.