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This paper presents a state‐space average model of a three‐level photovoltaic (PV) inverter to understand short‐circuit currents transient characteristics. Analytical solution of the model is also derived. The proposed model is validated with PV system controller hardware in‐loop (HIL) test method. The errors between simulation and HIL tests results under various conditions are evaluated, testifying the validity of the proposed model. With the model and analytical solution, the decaying time constants of sub‐transient and transient processes are derived, which shows that the time constants of a three‐level PV inverter are not fixed and they vary with voltage dips. The analytical expression of short‐circuit currents is also formulated. The findings from this study are essential to short‐circuit current calculations of a power grid with large‐scale PV plants, coordination of power system protections, and grid planning. [ABSTRACT FROM AUTHOR]

This paper introduces a Multi-Level Cascade Inverter (MLI) based on Enhanced Quasi-Z Source Inverter (MQZSI) to connect photovoltaic (PV) systems based on the proposed method. Usually the interface among PV power supply and load is completed with MQZS-CMLI. In this paper, the proposed control scheme is comprehensive implementation of Recalling Enhanced Recurrent Neural Network (RERNN) and Quasi-Opposite Chemical Reaction Optimization (QOCRO) named as RENCO. The main objective of proposed method is to decide the efficiency of the PV system by the maximal power extraction. Here, MQZS-CMLI's modeling design contains suitable number of components, other than their capacitors and semiconductors comply with low-voltage stress. It is improved for providing that maximum power of the PV power generation system. At first, the goal function is described according to the parameters and limitations of controller (like voltage, current, power, modulation index, so on). These parameters apply to recommend RENCO technology input. The proposed RENCO technology improves voltage distribution, power transmission, and minimizes power fluctuations while sharing power with load. The proposed MPPT-based technology ensures that the maximum power is provided to load. The proposed method adjust the duty cycle of MQZS-CMLI and reduces the modulation load. Finally, the proposed technology is executed on the MATLAB/Simulink platform, and its output efficiency is compared to existing systems under dissimilar load circumstances. [ABSTRACT FROM AUTHOR]

The grid connected inverter is the core component of the photovoltaic grid connected power generation system, which mainly converts the direct current of the photovoltaic matrix into alternating current that meets the grid connected requirements, playing a key role in the efficient and stable operation of the photovoltaic grid connected power generation system.This paper uses fuzzy PI control model which to improve the performance of intelligent photovoltaic grid-connected inverter to simulate the intelligent photovoltaic inverter system, using mathematical analysis and reasoning methods for model analysis,adopts two-stage three-phase LCL grid-connected inverter, establishes mathematical models in two-phase synchronous rotating and two-phase static coordinate systems, and adopts an active damping strategy based on grid-connected current. Based on existing research and empirical analysis,aiming at the disadvantage of poor dynamic response of repetitive control, an improved repetitive control strategy is adopted, and the controller is analyzed from two aspects of stability and dynamic performance, and the simulation model of photovoltaic grid-connected power generation system is built. Use experimental analysis method to verify the effectiveness of the model in this article,The experimental results show that the simulation system of intelligent photovoltaic grid-connected inverter considering fuzzy PI control proposed in this paper has certain effects. [ABSTRACT FROM AUTHOR]

Photovoltaic (PV) systems are becoming essential to our energy landscape as renewable energy sources become more widely integrated into power networks. Preserving grid stability, especially during voltage sags, is one of the significant difficulties confronting the implementation of these technologies. This attribute is referred to as low-voltage ride-through (LVRT). To overcome this issue, adopting a Proportional-Integral (PI) controller, a control system standard, is proving to be an efficient solution. This paper provides a unique algorithm-based approach of the Marine Predator Algorithm (MPA) for optimized tuning of the used PI controller, mainly focusing on inverter control, to improve the LVRT of the grid, leading to improvements in the overshoot, undershoot, settling time, and steady-state response of the system. The fitness function is optimized using the MPA to determine the settings of the PI controller. This process helps to optimally design the controllers optimally, thus improving the inverter control and performance and enhancing the system's LVRT capability. The methodology is tested in case of a 3L-G fault. To test its validity, the proposed approach is compared with rival standard optimization-based PI controllers, namely Grey Wolf Optimization and Particle Swarm Optimization. The comparison shows that the used algorithm provides better results with a higher convergence rate with overshoot ranging from 14% to 40% less in the case of DC-Link Voltage and active power and also settling times in the case of MPA being less than PSO and GWO by 0.76 to 0.95 s. [ABSTRACT FROM AUTHOR]

This paper introduces a hybrid multilevel inverter (MLI) with reduced switch count, which can generate higher output voltage level with minimum number of DC input sources. The operation of this proposed MLI is carried out with unequal DC sources to achieve the desired output voltage level. The reduced MLI output voltage is set to minimal total harmonic distortion (THD) with the help of modified JAYA (MJAYA) algorithm. A JAYA algorithm with improved steps by adopting an accelerating parameter has been proposed in this research work to obtain a faster convergence of the objective function. The MJAYA algorithm has provided the suitable switching angles for the proposed three-phase 15-level MLI and reduced the output voltage THD to 2.23%, which satisfies the standard set by IEEE-519. To prove the efficiency of this proposed modified algorithm, the comparative analysis is carried out through MATLAB program and Simulink tool using common JAYA and modified particle swarm optimisation algorithms. The performance and productivity of the proposed MLI have been investigated through simulation and experimental setups. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The main aim of the research work presented in this paper consists of proposing an effective control scheme for a grid-connected single-phase photovoltaic (PV) system to enhance not only the power quality at the point of common coupling (PCC) but also to operate with a maximum power point tracking (MPPT) controller. Moreover, an orthogonal signal generator (OSG) module for effective grid synchronization, a current reference generation controller, and a PWM generating block have also been designed and included in this paper. The proposed control strategy allows the MPPT controller to switch to faulty mode and maintains the voltage according to network requirements using an adaptive neuro-fuzzy inference system (ANFIS)-based control whenever a fault occurs at the PCC. The performance of the analyzed control strategy, which is based on the static compensation of the DC-link voltage fluctuations in a grid-connected inverter powered by PV, is further explored through simulations in MATLAB, and the results are included in this paper. Moreover, the control scheme is implemented experimentally using a dSPACE DS 1104 control board and then assessed on a small laboratory-scale single-phase PV system that is subjected to some fault scenarios. The simulation and experimental results have shown improved power quality and robustness against grid fluctuations, resulting in better dynamic performance. [ABSTRACT FROM AUTHOR]

Multistage inverters containing DC-DC converters are more common in grid-tied photovoltaic (PV) systems, because of the low DC voltage value provided by the PV generator, which requires a two-stage topology. The challenge in the latter case is to control the DC-link voltage with an accurate estimation of the current injected into the grid by PV system. In this paper, a two-stage grid-tied PV design based on a high-gain DC-DC converter and a 7 level packed U cells (7L-PUC) inverter, controlled by Finite-Control-Set Model Predictive Control (FCS-MPC) is presented, with the proposal of a novel model for controlling the DC-link voltage by considering system losses. The simulation and experimental results demonstrate the high effectiveness of the proposed control strategy in terms of power quality as well as response time and accuracy under changes in weather conditions and demonstrate the feasibility of the proposed system. [ABSTRACT FROM AUTHOR]

Green energy from Solar PV is getting increased attention in the industries due to the falling price of solar panels in the world market. A grid-tied inverter is one of the major components in such a system, where the DC energy from PV is converted to AC and synchronized with the grid to obtain power sharing between the PV and the grid for the industrial drives. In this paper, a DC link has been proposed instead of an AC link for interconnection between the solar PV system and the grid to run those industrial drives. In most modern industrial applications, induction motors are driven by VVVF (Variable Voltage and Variable Frequency) inverters to achieve efficient speed control. The inverters commonly have a rectifier section at the front end that rectifies the input AC to DC and the DC is then used in PWM mode to generate the required voltage and frequency for the induction motor operating under variable speed and load conditions. Such an inverter can use both AC or DC as the input so long the supply voltage has the right value for the inverter to operate. In our proposition, we eliminate the grid-tied inverter and use a DC link, created from the rectified AC and the regular Solar PV, to obtain the power-sharing between the PV output and the grid. Using the DC link output directly to energize the VVVF inverter has an impact on the performance of the inverter. In the proposed system, the solar PV array is designed in such a way that the grid remains as the supplementary power source only to supplement any shortfall in the PV output due to variable sunshine conditions. The control circuit used in this novel technique is inexpensive, efficient, and simple in design when compared to the grid-tied inverters. The proposed system has been implemented at Niagara Textiles in Gazipur, Bangladesh. The experimental/practical results are presented to validate the basic concept. Around a 20% reduction in the cost of energy has been reported in this paper, with a more than 90% efficient system. This will definitely make solar PV energy more competitive with regular energy and attractive to industries for its simplicity. [ABSTRACT FROM AUTHOR]

In traditional grid-tied photovoltaic (PV) installations, when partial shadowing occurs between different PV modules in a string, bypass diodes short-circuit the output terminals of shadowed modules, and the whole system forgoes their potential energy production. This loss can be recovered if a dc-dc converter (micro-converter) is coupled to every PV module, and operated at the maximum power point (MPP). In this scenario, without communication links between the distributed micro-converter and the grid-tied inverter, a start-up procedure must be carefully designed to seamlessly allow the system to transfer PV power to the grid. During this phase, potentially damaging over-voltages and abrupt transients occurring at the micro-converters/inverter interface must be avoided. In this paper, the control algorithm of each micro-converter is enhanced to provide a smooth start-up operation so that PV units can safely start transferring power to the inverter and the grid. Improving from previous works, the proposed control technique is simple and removes the need for current sensors at the output of each micro-converter and at the inverter dc-link, with an economical advantage. Simulation results demonstrate the successful system start-up behavior, whilst confirming the benefits of the proposed control technique. First, the dc-link is energized from the rectified grid voltage. Then, the micro-converters raise the dc-link voltage so that the available PV power is transferred to the grid, with this sequence of operations not causing any abrupt electrical transient. The results also demonstrate the robust behavior of the PV system under non-uniform solar irradiation conditions. [ABSTRACT FROM AUTHOR]

This article presents a comprehensive review of reduced device count multilevel inverter (RDC MLI) topologies for PV systems. Multilevel inverters are widely used in medium-voltage and high-power applications such as wireless power transform applications, flexible AC transmission (FACT), active filters, AC motor drives, high-voltage DC transmission (HVDC), and renewable energy sources due to their high modularity and high-power quality output. Multilevel inverters have the ability to diminish the harmonics content in the output voltage by applying various modulation techniques. The literature in this field showed that the high-power quality and high modularity of the output demand an undeniable need for multilevel inverter topology. Research in this field has identified various multilevel inverter topologies, each possessing their own merits and demerits. The ubiquitous availability of multilevel inverter topologies illustrates the complexity of their accurate selection. To avoid such complexity, this review shows the state of the art of various reduced device count (RDC) multilevel inverter (MLI) topologies. Details of the various RDC MLIs, along with their comparisons, are provided in this paper. This review will be an important reference tool for future work on RDC MLI for photovoltaic (PV) systems. [ABSTRACT FROM AUTHOR]

Photovoltaic (PV) energy systems have found diverse applications in fulfilling the increasing energy demand worldwide. Transformer-less PV inverters convert the DC energy from PV systems to AC energy and deliver it to the grid through a non-isolated connection. This paper proposes a new transformer-less grid-connected PV inverter. A closed-loop control scheme is presented for the proposed transformer-less inverter to connect it with the power grid. The proposed transformer-less inverter reduces extra leakage current and holds the common-mode voltage at a constant point. To eliminate extra leakage current, as well as achieve constant common-mode voltage, a midpoint clamping method is utilized to operate the inverter. The proposed transformer-less inverter is formed of seven insulated gate bipolar transistors (IGBTs) employing a unipolar sinusoidal pulse width modulation (SPWM) technique for switching purposes. An LCL filter is employed to reshape the two-level inverter output voltage and current to obtain closer sinusoidal waveforms. The output voltage and current total harmonic distortion (THD) of the proposed transformer-less inverter were found to be 1.25% and 0.94%, respectively, in the grid-connected mode. The leakage current elimination mechanism with the proposed transformer-less inverter is deeply analyzed in this paper. The performances of the proposed transformer-less inverter were evaluated with MATLAB/Simulink simulation and validated in a laboratory scale experiment. [ABSTRACT FROM AUTHOR]

According to the traditional voltage and current double closed-loop control mode, the inverter management strategy for photovoltaic grid connection has insufficient anti-interference ability and slow response. This paper proposes a control strategy that applies adaptive-linear active disturbance rejection control (A–LADRC) to the outer loop control to achieve the purpose of anti-interference. The control strategy uses the linear extended state observer (LESO) to evaluate external interference caused by the change of external conditions and the internal disturbance caused by parameter uncertainty. PD controller compensates the disturbances and adds adaptive control to simplify parameter adjustment. Finally, this paper takes advantage of Lyapunov theory to conduct stability analysis. Compared with the traditional linear active disturbance rejection control (LADRC), the superiority of this control strategy is verified. The experimental results show that the system has better control performance and anti-interference ability in the face of various disturbances. [ABSTRACT FROM AUTHOR]

This paper presents a mathematical model of 255 kW grid-connected solar photovoltaic (SPV) system. To study the performance characteristics of the grid-connected SPV system, a new hybrid adaptive grasshopper optimization algorithm with the recurrent neural network (AGO-RNN) control technique was implemented. Furthermore, the power quality at the point of common coupling (PCC) has been studied using the conventional (PSO) and proposed AGO-RNN controllers. The characteristics of the PV system were analyzed under varying environmental (variable irradiance and temperature) conditions considering 3 different cases such as (i) standard test conditions (STC), (ii) variable radiation with constant temperature, and (iii) variable radiation with variable temperature. For each case, the total harmonic distortion (THD) has been calculated using the proposed AGO-RNN control technique, and the results were compared with particle swarm optimization (PSO) technique. The 255 kW PV model is initially developed and connected to a three-level NPC inverter, an MPPT-based perturbation and observation algorithm. Later, the PV model is controlled by an AGO-RNN pulse width modulation (PWM) controller and is then integrated to the main grid at PCC. The main advantage of this technique is exploiting the separate DC-DC converter between the SPV module and the inverter. Finally, the proposed grid-connected SPV system was simulated on MATLAB for analyzing the performance of the system based on its I-V and P-V characteristics, inverter voltage, grid power, gird voltage, grid current, power factor, and THD under different environmental conditions. The simulation results demonstrate that the current magnitude and THD of the SPVGC system are improved with the cutting-edge AGO-RNN controller compared to PSO in all three different scenarios, and this value is less than 1.6%, which is within the permitted limits of IEC 61727 standards. [ABSTRACT FROM AUTHOR]

Grid integration of solar photovoltaic (PV) systems is becoming popular recently due to the merits of stable support to conventional grid, limiting global warming and reduced emissions. However, maintaining capacitor voltage balancing, unity power factor, sinusoidal grid current and harmonic profile improvement are the challenging tasks owing to change in irradiation conditions. Multi-level inverters in grid connected systems will enhance the power quality of the system in terms of voltage and current total harmonic distortion. This paper proposes a highly reliable, robust and modular single phase solar PV fed fault tolerant hybrid cascaded H-bridge inverter with individual voltage/current control strategy for grid integration. Higher reliability and modularity, power factor correction, able to with stand without degrading the performance of the topology even under faulted conditions and harmonic profile improvement are the main objectives of the proposed system. The proposed system has been simulated and validated with experimental results on the developed prototype for different irradiation conditions and tested the performance of the topology with creation of faults on different modules at different times. [ABSTRACT FROM AUTHOR]

Grid‐connected Single‐Stage Boost Inverters (SSBI) are extensively being researched in the area of photovoltaic energy conversion systems. Owing to their single‐stage boosting capability, this class of power converters results in higher efficiency and reliability. This power circuit configuration is constituted by two mutually dependent sub‐converters, in that a front‐end quasi‐Z‐source (qZS) part is integrated to a back‐end multilevel inverter (MLI). The MLI provides the shoot‐through state to the qZS, while the qZS provides the pulsating DC input to the MLI. In general, solar photovoltaic inverters suffer from the disadvantage of leakage current that flows from solar panels to the grid/load. This paper introduces a dual quasi‐Z‐source based multilevel inverter, which achieves the following benefits: (a) five‐level output voltage, (b) reactive power capability, (c) shoot‐through immunity, (d) continuous input current, and (e) reduced leakage current based on VDE 0126‐1‐1 standards. In this paper, a modified modulation scheme, which is based on the employment of phase‐disposed and level‐shifted carrier signals, has been used to reduce the leakage current. To reduce the leakage current further, a passive filter is employed to eliminate high frequency variations across the parasitic capacitance. The working principle of the proposed power converter and the effectiveness of the modulation scheme have been validated with simulation studies in both standalone and the grid‐connected mode. Finally, the simulation studies are verified through an experimental prototype of 500 W rating. [ABSTRACT FROM AUTHOR]

In photovoltaic (PV) systems, inverters have an essential role in providing an energy supply to meet the demand with power quality. Inverters inject energy into the grid considering that a renewable source is available; however, during intermittent periods or in the absence of power generation, the inverter remains inactive, which decreases the performance of the PV system. One way to increase the operation of inverters is to operate them as Volt-Amps Reactive (VAR) compensators to generate reactive power in the absence of renewable sources. The paper presents the development of a control scheme that allows the PV system's inverter to improve the power factor in the electrical system with or without PV power generation. The proposed control is based on using a sliding mode controller (SMC) current control loop and PI-based voltage control loop. The control scheme is developed in MATLAB/SIMULINK, and for real evaluation, a PV prototype is implemented. The control strategy efficiency is confirmed by the obtained results. The control scheme increases the practical utility of PV systems. Additionally, it improves the power factor in all cases during the injection of active power to the grid operating under intermittent conditions and/or in the absence of power generation. [ABSTRACT FROM AUTHOR]

The voltage rise problem due to the reverse power flow is one of the main obstacles to expanding the photovoltaic systems (PVSs) in distribution networks. In this paper, a decentralized control method for coordinated control of on-load tap changer (OLTC) transformers and PV inverters, is proposed for the voltage regulation of radial distribution networks. In this method, the allowable voltage range is divided into several zones, and appropriate corrective actions are adaptively taken according to each zone. To reduce the tension on the OLTC, first, the reactive power capability of the PV inverters is employed for the voltage regulation, and if it is insufficient, OLTC is used as the last solution. In this regard, the unused capacity of PV inverters is utilized for the reactive power compensation, considering the grid codes reactive power requirements. Furthermore, decentralized control based on a signaling method is used for coordination between OLTC and PVSs, which eliminates the need for communication links. Finally, the effectiveness of the proposed method is validated by the simulation results for the IEEE 33-bus distribution network, and the impact of different reactive power control methods on the number of OLTC operation is investigated. [ABSTRACT FROM AUTHOR]

Integration of multilevel inverters with renewable energy sources have been the subject of many research projects. Numerous topologies of multilevel inverters have been investigated for stand-alone and grid-connected PV systems. The high number of switching devices, complexity, large size, voltage imbalance, and high cost are main drawbacks of the conventional topologies. This paper presents a new three-phase, three-port, five-level inverter based on a switched-capacitor circuit for PV applications. Compared to the conventional topologies, the proposed inverter has voltage boosting capability and multilevel operation without using clamping diodes or flying capacitors, simplifying the control algorithms and improving the reliability, efficiency, and lifetime. The presented multilevel inverter offers 25% reduction in power devices counts and 50% reduction in flying capacitors. The proposed inverter solves the capacitor voltage balancing issue of the conventional topologies and achieves the lowest voltage stress, making it suitable for high voltage applications. Additionally, the new topology harnesses the superior features of silicon-carbide devices; hence, a fast-switching speed can be employed to reduce size of the storage elements and output filter requirements. Furthermore, the soft-switching operation is realized to regulate the charging current of the capacitor. The operating principle of the proposed topology is investigated, and its properties are compared to the traditional multilevel inverters. A laboratory prototype was built to validate the effectiveness of the proposed circuit, simulation and experimental results for the proposed inverter are provided. [ABSTRACT FROM AUTHOR]

Background: Recent advancements in solar power generation technology have paved the way for a vast number of photovoltaic (PV) systems integration into the grid network. The global installed capacity of rooftop PV systems has already surpassed a 50 GW mark in 2020, while the total installed capacity of all types of PV systems is reaching beyond 500 GW. The influx of distributed PV‐generators must be equipped with sophisticated control to ensure grid stability, especially during grid faults. A devastating grid outage may occur if the grid‐tied PV inverters are not equipped with the "fault‐ride‐through" mechanism. Many countries have already enforced a mandatory grid code which includes a low‐voltage‐ride through requirements for PV‐generators. Aim and Objective: This paper reviews the design of a rooftop PV inverters in the light of low‐voltage‐ride‐through requirements. Materials and Methods: For the implementation of low‐voltage‐ride‐through (LVRT), the design of low‐voltage‐sag detection, grid‐synchronization, filter‐selection, and power‐controllers are examined through simulations and literature survey. LVRT implementation issues are highlighted with an emphasis on the current controller performance during grid sags. Results and Discussion: From the review and analysis conducted in this study, this paper concludes that ensuring a stable DC‐link and appropriate control‐reference‐signals during the grid faults are the keys to the LVRT implementation. Conclusion: In addition to robust power control, an autonomous PV generator should promptly detect the grid conditions and fulfils the ancillary services like LVRT, anti‐islanding and flicker compensation. The recommendations and the future trends in the LVRT research conclude the review article. [ABSTRACT FROM AUTHOR]

This paper proposes a new modified buck–boost converter entitled the basic Z‐H8 topology. The modified configuration is composed by adding two dc decoupling and non‐ideal compensation blocks across the dc‐input side of the conventional Z‐H buck converter. These blocks create some benefits such as buck–boost ability and lower stresses and ripples for passive and active elements by up to 50% compared to the traditional Z‐H structure. Moreover, the proposed topology can be used as a dc/dc, dc/ac, or ac/dc converter. Hence, various control techniques based on unipolar PWM and SPWM are proposed for the basic Z‐H8 configuration to act as an inverter. Other valuable advantages are providing galvanic isolation and reducing leakage current by two blocks, which can be extremely useful for photovoltaic (PV) applications. Thus, a grid‐connected single‐stage PV system with a proper model predictive control algorithm is proposed. Despite a continuous voltage on the Z‐H8 inverter output, other benefits of the proposed PV system are tracking the maximum power point, adjusting the injected powers to the grid, and increasing security and reliability. The operating principle of the proposed topologies and control methods are explained in detail with the relevant equations and are confirmed by the simulation and experimental results. [ABSTRACT FROM AUTHOR]

• Fault-tolerant operation for 15LCHB with a solar photovoltaic system (SPV). • Fault-tolerant (FT) operations have detection and identification. • Differential Annealing Dynamic Optimization and Radial Basis Function Neural Network. • DDAO-RBFNN is separated into fault detection with lessening of SPV. This paper proposes a hybrid approach for fault-tolerant operation in fifteen-level cascaded H-Bridge (15LCHB) inverter with solar photovoltaic system (SPV). Fault-tolerant operation performs two tasks: detection (classification of normal or abnormal) and identification (identification of faults). The proposed intelligent controller is the combination of Differential Annealing Dynamic Optimization (DDAO) and Radial Basis Function Neural Network (RBFNN) named DDAO-RBFNN approach. The major intention of the DDAO-RBFNN approach is separated into fault detection with lessening of complete photovoltaic solar energy conversion system. The proposed system takes into account the failure of the entire autonomous photovoltaic solar conversion process and manages the output voltage (OV) owing to the conditions of partial shading (PS). The collected data set (normal, abnormal) is stored at workstation. RBFNN is utilized to compute the CMI switching pattern that changes the PWM carrier signal. DDAO get the voltage values from RBFNN and evaluates them with the data set, if there is a rate of change of voltage. Any deviation find in the rate of voltage change, it makes a decision based on standard or fault conditions. The proposed system is activated on MATLAB/Simulink working platform, then the efficiency is compared with existing approaches. [ABSTRACT FROM AUTHOR]

In this paper, the hybrid synchronization based grid forming (HS-GFM) control and coordination strategy are proposed for the inverter and boost converter to provide frequency support. As the main contribution, the inertia power and damping power are designed with HS-GFM based coordination strategy between inverter and boost converter. The inertia power can be obtained from DC capacitor and photovoltaic system in deloading mode independently. Besides, the damping power can be realized from the PV inverter in deloading mode. After that, the small signal models of inverter and boost converter considering grid frequency coupling are constructed with simplified single input single output (SISO) model to guide the parameter selection. Further, the grid synchronization stability, synchronization bandwidth and grid strength influence on the frequency response of the PV inverter can be analyzed with SISO model. Compared with conventional DC voltage based GFM, HS-GFM can improve stability especially in strong grid with slight reduction of synchronization bandwidth while it has the risk of instability in weak grid if parameters are not proper. Compared with phase locked loop (PLL) based control, the proposed HS-GFM control achieves a fast response under frequency excursion with better stability in weak grid. Finally, realtime and offline simulations are carried out to verify the proposed strategy and analysis. • Inertia and damping power are designed with hybrid synchronization based GFM control. • The DC side thevenin equivalence of boost converter is obtained for SISO analysis. • SISO model of PV inverter is built for stability analysis and parameter selection. • Comparisons with conventional GFM and phase locked loop based control are presented. [ABSTRACT FROM AUTHOR]

• Study of PV power plant with quasi-Z-source cascaded H-bridge multilevel inverter under failure. • Control system to provide a suitable DC voltage at the input of the VSI and ensure the grid power delivery. • Control tested from simulation results under different operating conditions and HIL experimental results. • Correct response of the developed control strategy with failure in qZSI module. At the present time, quasi-Z-source cascaded H-bridge multilevel inverters (qZS-CHBMLI) have gained attention in photovoltaic (PV) applications, due to their advantages over traditional multilevel inverters. They allow single-stage power conversion of a PV power plant by independently adjusting the DC voltage in each module; thus, each PV array operates at the maximum power. This advantage permits dispensing with a DC/DC boost converter and reduces the number of modules required. This paper develops a novel control strategy for a qZS-CHBMLI connected to a single-phase system that guarantees proper operation when a fault occurs in a quasi-impedance source inverter (qZSI). The control strategy is employed in a grid-connected qZS-CHBMLI with three modules, each one with a quasi-impedance network, a 4.8 kW PV array and a voltage source inverter (VSI), with H-bridge topology. The purpose of the control system is to deliver a suitable DC voltage at the input of the VSI and ensure the grid power requirements after a fault in a module. The proposed control system is evaluated through a 40 s simulation in MATLAB/Simulink® in two cases: A) analysis of the system behaviour when there is a variation in the operation limit equation; and B) evaluation of the control strategy under dissimilar operating conditions. In addition, an experimental setup based on an OPAL RT-4510 unit and a dSPACE MicroLabBox prototyping unit is employed to validate the results. The results confirmed the correct response of the applied strategy with the failure of a single module. [ABSTRACT FROM AUTHOR]

• The original contribution of the paper is a dq-real domain admittance transfer matrix model of PV-qZ systems. • The study presents some of the the two main origins of instability in multi-terminal AC grid-connected PV-qZ systems. • The study also illustrates the weakness of GNC related to stability assessment and grid partition points. Photovoltaic (PV) power systems are becoming one of the most popular green power systems. Power converters are used in these systems. Among them, quasi-Z-source inverters (qZSIs) are currently on the rise. However, instabilities can appear in multi-terminal AC grid-connected power electronics, such as PV power systems, due to the interaction between power electronic controls and the grid. Modeling of qZSI-based PV power systems is lacking in the literature and stability assessment of grid-connected qZSI-based PV power systems is not yet well understood. Accordingly, the present paper contributes with an s -domain dq -real admittance transfer matrix model of qZSI-based PV power systems derived from their small-signal state-space averaged model. The paper also describes a systematic procedure to study multi-terminal AC grid-connected qZSI-based PV power systems by the nodal admittance method, where the proposed qZSI-based PV power system model is incorporated into the nodal admittance matrix to study stability concerns. Thus, AC grid dynamics in the presence of qZSI-based PV power systems can be investigated using impedance-based stability criteria. The proposed model and the procedure are applied in a stability study of two applications where solutions for improving stability issues are presented. In these applications, the two main causes of instabilities in AC-grid connected PV-qZ systems are analyzed in detail. The study is validated by PSCAD/EMTDC simulation.. [ABSTRACT FROM AUTHOR]

Grid integration of solar photovoltaic (PV) systems is becoming popular recently due to the merits of stable support to conventional grid, limiting global warming and reduced emissions. However, maintaining capacitor voltage balancing, unity power factor, sinusoidal grid current, and harmonic profile improvement are challenging tasks owing to change in irradiation conditions. Multilevel inverters (MLI) in grid‐connected systems will enhance the system's power quality in terms of voltage and current total harmonic distortion (THD). One of the most promising multilevel topologies for renewable energy applications is the cascaded H‐bridge (CHB) inverter. Since CHB inverters include many components, they have a higher risk of failure, lowering system reliability. Due to the change in irradiation condition, the voltage across the corresponding DC link capacitor may vary. Therefore, the DC‐link capacitor balancing is mandatory and done by an individual control scheme. This paper presents a highly reliable, robust, and modular solar PV‐fed fault‐tolerant CHB inverter with an individual voltage/current control strategy for grid integration. Higher reliability and modularity, power factor correction, and harmonic profile improvement are the main objectives of the proposed system. The proposed system has been simulated in MATLAB/Simulink and validated with experimental results on the developed prototype for different irradiation conditions. [ABSTRACT FROM AUTHOR]

Nowadays all-metal induction heating (IH) cooktops have become popular for heating various pots quickly and safely. A load adaptive modulation (LAM) method was proposed to improve the IH power delivery capability and the cost-effectiveness of an all-metal IH system. However, this method shows poor power conversion efficiency under light-load conditions since a high switching loss is induced using the pulse frequency modulation (PFM) method in the series resonant inverters for IH applications. In this paper, a multi-mode control strategy for an IH system employing the LAM method is proposed to improve light-load efficiency when compared with the conventional LAM method. The proposed multi-mode control algorithm automatically changes its modulation according to the pots' material-dependent resistance. The modulation method is selected to improve the light-load efficiency using the proposed control strategy. Experimental results demonstrate the validity and performance of the proposed multi-mode control algorithm with a 2-kW prototype IH series resonant inverter and various-material pots. [ABSTRACT FROM AUTHOR]

The paper presents the results of an experimental study of 26 brand new photovoltaic (PV) inverters widely available for sale on the EU market; the study was conducted in 2021 by researchers at the AGH University of Science and Technology and Tauron Dystrybucja (Polish DSO). The purpose of the study was to compare and assess PV inverter performances in terms of their DC/AC conversion efficiencies, MPPT efficiencies, and harmonic current emissions. To examine the PV inverters, a laboratory test stand was prepared according to the standard EN 50530 and the technical report IEC/TR 61000-3-15. It was composed of a photovoltaic array simulator, a programmable regenerative AC voltage source, and a power analyzer. Each PV inverter was tested in various operating states determined by the DC voltage levels and the volume of active power generation. The results allowed for a benchmark assessment of PV inverters available on the market. The results showed how various energy efficiency indicators of individual PV inverters changed depending on their operating points. The results also revealed that, based on the performed harmonic emission tests, individual harmonics were within the normative requirements; however, in the case of several PV inverters, attention was drawn to the presence of relatively high switching frequency-related components exceeding permissible levels. [ABSTRACT FROM AUTHOR]

This paper investigates the performance of the current model predictive control (CMPC) for controlling a two-stage transformerless grid-connected photovoltaic (PV) system under grid fault conditions. A maximum power point tracking (MPPT) controller was used to extract the maximum power of the PV panel. To stabilize the DC link and generate the reference current values, a proportionalintegral (PI) controller was used. The CMPC strategy was implemented to control the output current of the inverter that connects the PV system to the utility grid. The system and control strategy were simulated via a MATLAB/Simulink environment. The performance of the proposed control strategy was investigated under fault conditions between the three-phase two-level inverter and the grid. Moreover, to validate the capability of the CMPC, comparative case studies were conducted between CMPC, PI, and sliding mode control (SMC) under grid fault. Case studies' results showed that under grid fault, CMPC did not introduce any overshoot or undershoot in the PV output DC current and power. However, PI and SMC produced undershoots of almost 15 kW for the output power and 45 A for the output current. Under the fault conditions, the active output power and three-phase current recovery time of the inverter was 50 ms using CMPC, compared to PI and SMC with recovery times of 80 ms and 60 ms, respectively. Moreover, a voltage dip of 75 V at the DC link voltage was recorded with CMPC under faulty conditions, while the voltage dips for PI and SMC were around 180 V. [ABSTRACT FROM AUTHOR]

The paper presents a novel approach for low-order harmonic power mitigation in a single-phase, three-level DC/AC inverter. Traditionally, a bulk electrolytic capacitor is used at the DC bus to eliminate the low-frequency ripple. However, owing to the low-frequency components and large capacitor, this technique is not a practical solution. A new active filtering technique using a ripple port without an external circuit or additional switching power devices is proposed. The new technique harnesses the superior features of switched-capacitor circuits to create a topology with a multiport structure. As a result, a small DC-link capacitor can be applied by controlling the modulating reference waveforms between the different ports of the inverter. Additionally, the use of fast wide bandgap devices will allow for smaller passive components, and with high operating temperatures, the heat sink size can be greatly reduced. The theoretical analysis of the ripple reduction technique is explained in detail. The prototype was built in a laboratory, and experimental results are provided. [ABSTRACT FROM AUTHOR]

Summary: In this paper, a three‐phase single‐stage grid‐connected photovoltaic (PV) system with active power filtering capability by means of a three‐level T‐type inverter is presented. The system is intended to fulfill many functions: harmonic mitigation, unity power factor operation, maximum power extraction from PV source, and so on. For the proposed system to achieve these tasks with a good dynamic performance, a new control strategy based on the fuzzy logic controller is developed. Fuzzy control has three main stages and each one requires many settings or selection of parameters. A new approach of setting the scaling factors which considerably affect the system's response is proposed. Furthermore, a methodology to properly set the fuzzy rules is suggested. The electrical power chain of the system comprises a farm of a PV source, three‐level T‐type inverter space vector pulse width modulation controlled, inductor filter, non‐linear load, and the utility grid. To evaluate the performance of the proposed control, a processor‐in‐the‐loop is performed as a hardware verification of the inverter control algorithm using a low‐cost STM32F4 discovery board, while the power circuit plant is modeled in the host computer using Matlab/Simulink. The obtained results are very satisfactory and confirm the role of each component, especially in terms of maximum power tracking, power quality, unity power factor operation, and control robustness. [ABSTRACT FROM AUTHOR]

Summary: An effective peak current‐limiting control strategy is presented in this paper, for improved dynamic performance of a grid‐connected photovoltaic (GCPV) inverter under unbalanced grid voltages. A simple analysis is developed for calculating the rated inverter power under unbalanced grid voltages without tripping the PV inverter for reliable operation. The active power oscillations induced due to the unbalance in the grid voltages are minimized by equating the active power oscillating terms to zero in the reference current generation. The prime focus of this work is on estimating the reference currents and limiting the inverter currents to rated value and providing low‐voltage ride‐through capability by judiciously balancing positive and negative sequence currents. A prototype hardware is developed in the laboratory and the proposed control scheme is implemented using dSPACE 1103 real‐time controller board. A solar simulator has been used to replicate the PV array. The simulation (MATLAB/Simulink) and the experimental results establish that the proposed controller scheme effectively minimizes the oscillation in active power and limits the inverter currents. [ABSTRACT FROM AUTHOR]

In this paper five different flexibility options are analysed from a techno-economic perspective as alternatives to traditional grid expansion for a specific distribution grid in Germany. The options are: two reactive power control strategies with photovoltaic inverters (as a function of the power feed-in, or of the voltage at the connection point), one residential and two large scale battery storage applications (primary control reserve with autonomous reactive power control or self consumption maximisation strategy with autonomous reactive power control). For the pilot grid located in Southern Germany a photovoltaic expansion pathway is determined. The main goal of this work is to quantify the grid expansion actions that can be avoided by applying these five flexibility options for the assumed expansion pathway, focusing on large scale battery storages. It is shown that the five flexibility options increase the hosting capacity for PV systems, compared to a scenario without, by up to 45%. Furthermore, the results of the economic assessment indicate that the analysed flexibility options might be a viable alternative to traditional grid expansion as all of them show a cost reduction potential for the pilot region. These results could encourage DSOs to consider the integration of additional PV and battery storage systems not as a problem which triggers grid expansion, but as part of the solution reducing future grid expansion costs. [ABSTRACT FROM AUTHOR]

Voltage/VAR regulation (VVR) implemented by capacitor banks (CBs), on-load tap changers (OLTCs), and photovoltaic (PV)-associated inverters is effective to enhance voltage stability and reduce power loss. On the other hand, conservation voltage reduction (CVR) has been widely adopted in distribution networks to reduce load demand. Existing works mainly focus on each of them. This paper proposes a VVR method with CVR, forming a multi-objective optimisation problem which minimises (i) voltage collapse proximity indicator (VCPI), (ii) load demand, and (iii) power loss. Besides, PV power generation as uncertainty significantly impairs the VVR results. To deal with the uncertainty issue, this paper proposes a rollinghorizon framework to determine VVR and applies Taguchi's orthogonal array testing (TOAT) to model the uncertain PV power generation, achieving rolling-horizon-based multi-objective robust VVR. The proposed model is tested and demonstrated on the IEEE 33-bus and 69-bus systems, and simulation results verify that the proposed method can support robust solutions of the multi-objective VVR problem for decision-making. [ABSTRACT FROM AUTHOR]

• This research presents and investigates the experimental measurements of power quality parameters in-field on 8 kWp PV system connected to the LV distribution network in Electronics Research Institute, Egypt. Also, This research aims to investigate unity power factor and constant reactive power as two different functions of the PV inverter. • Statistical analysis of each harmonic, power factor and total harmonic distortion are analyzed and presented under different loading conditions and two different functions. • The focus is set on the characterization of relationship between current harmonics of PV inverter and voltage harmonics prevailing in the LV system at unity power factor and constant reactive power. • This paper proposes mathematical models in order to characterize current total harmonic distortion and power factor. The accuracy of proposed empirical models was compared with previous research studies and presented the highest accurate results. Since the penetration of photovoltaic (PV) systems in the Low Voltage (LV) distribution network is increasing, the need to characterize and model the effect of these systems on power quality parameters is an up-to-date issue. Also, the reactive power capability of PV inverter should be defined and discussed. This research presents and investigates the experimental measurements of power quality parameters in-field on 8 kWp PV system connected to the LV distribution network in Electronics Research Institute, Egypt. This research aims to investigate unity power factor and constant reactive power functions as two different operation modes of PV inverter based on the measurements at PV inverter output and the grid point without local loads at off days of the governmental building in order to avoid load effects on the PV inverter parameters. Field measurement data were recorded using the power quality analyzer CA8335. Statistical analysis of each harmonic, power factor and total harmonic distortion are analyzed and presented under different loading conditions and two different functions of the PV inverter. The focus is set on the characterization of the relationship between current harmonics of PV inverter and voltage harmonics prevailing in LV system. It is found that the PV inverter presents high current total harmonic distortion levels at power levels below its rated value. This paper proposes mathematical models in order to characterize the current total harmonic distortion and the power factor at two different operation modes. The accuracy of the proposed empirical models was compared with previous research studies and presented the highest accurate results. The presented results are useful for the manufacturer of the tested PV inverter. [ABSTRACT FROM AUTHOR]

In grounded photovoltaic (PV) systems, dc leakage to earth is formed by the contribution of the PV modules, inverters, and dc circuitry. Ground faults in such systems occur when there is an unintentional connection between any dc-carrying conductor with a grounded surface or earth. On the occurrence of ground faults, dc leakage will be intensified and will flow through the earth or other conductive paths, before returning back to the source. Thus, it is highly probable that some portion of the dc leakage will attempt to return to the source through any low-resistance paths that exist in the nearby vicinity, for example, through nearby buried pipelines. Therefore, unattended dc leakage may induce stray current corrosion concerns on these pipelines. To this extent, this paper presents a detailed dc interference modeling for assessing the dc leakage activity in PV systems—particularly under undetected fault conditions. First, the modeling carried out embraces the topologically accurate consideration of all sources of dc leakage that are associated with the grounded PV systems. A second feature presented in the paper is the modeling of blind-spot dc faults and their impact on third-party infrastructure. [ABSTRACT FROM AUTHOR]

Increasing penetration of photovoltaic power plants (PVPPs) to the electrical grid leads to continuous evaluation of grid interconnection requirements. For this purpose, Malaysian grid representative from Tenaga Nasional Berhad (TNB) issued technical rules and requirements concerning the connection of photovoltaic system to low and medium voltage networks. The objective of this paper is to design a large-scale PV plant connected to the MV side of the Malaysian grid, taking the compliance of TNB technical regulations into consideration. In this study, the PV plant has been modeled using MATLAB/Simulink with nominal rated peak power of 1.5 MW. The sizing of suggested PV system is achieved in which the simulation results matched the sizing calculation results. The paper focuses on the model’s ability to reflect the important requirements that a PVPP should have based on TNB rules for MV connection. The results show that the proposed PVPP is compatible with TNB requirements. [ABSTRACT FROM AUTHOR]

This paper presents the development of methods and mathematical models to determine the DC/AC average efficiency of inverters that allow to optimize estimates of electricity generation of photovoltaic systems. The adaptive hybrid mathematical model of DC/AC average efficiency of inverters of photovoltaic systems proposed in this paper may be composed of three function settings–Linear, Lognormal, and Polynomial–considering the influence of the relative power, which varies with the sizing factor inverter and the DC input voltage. Determining of the average efficiency with a high degree of accuracy guarantees greater reliability in estimating electricity generation of photovoltaic systems. Depending on the specific behavior of each model and topology of inverter, the adaptive hybrid mathematical model determines the fit functions with highest coefficient R 2 , and estimates with accuracy the DC/AC average efficiency that represents the operation and dynamic behavior of the inverters. [ABSTRACT FROM AUTHOR]

The popularity of multi-level inverters (MLIs) for high power and high voltage applications, is increasing day-by-day. These MLIs are being integrated with the grid for renewable energy extraction like solar photovoltaic (PV) system. The MLI produces a staircase output voltage with low harmonic content and may inject a sinusoidal grid current with improved power factor. Thus, the MLI based grid-tied PV system can operate at the lower switching frequency with reduced filter requirements. This paper presents the various MLIs, their modulation and control techniques for the grid connected applications. A detailed classification of different grid connected Multi-level inverters (GCMLIs) based on the number and arrangement of DC voltage sources is presented. Also, different control techniques and the modulation techniques have been discussed for different MLI based PV systems being interfaced with the utility grid. The thorough comparisons and discussion of different control techniques used in single-phase and three-phase grid-connected MLI is also incorporated in this paper for better understanding and effectiveness of the past-present and future PV system developments. [ABSTRACT FROM AUTHOR]

Summary: Battery energy stored single‐phase quasi‐Z‐source inverter photovoltaic (BES‐qZSI‐PV) power system shows many advantages in comparison with other tri‐port inverter‐based PV power systems. However, the existing BES‐qZSI‐PV power system does not work at night or cloudy day because of its circuit limitation. This paper proposes a 24‐h operational BES‐qZS‐PV system by the following approaches: (1) the main power circuit is proposed for the day and night operation; (2) the detailed circuit models including the DC model and the second‐harmonics ripple model are built by considering scenarios of day and night operations; (3) the design method of quasi‐Z‐source network parameters is proposed to meet the requirement of day and night operations; and (4) the control strategy is proposed to achieve the high‐performance system operation all the time and seamless transition between day and night operation. After theoretical modeling and analysis, the built models are verified by comparing their calculation results with the circuit‐based simulation and experimental results. The proposed single‐phase BES‐qZSI‐PV power system is tested; experimental and simulation results are captured when the system operates in day, night, and transition to validate the proposed 24‐h operational BES‐qZSI‐PV system. [ABSTRACT FROM AUTHOR]

• A comprehensive review of MPPT techniques. • Review of high gain resonant soft-switching dc-dc converters. • Review of high gain current-fed dc-dc converters. • Review of multilevel inverters for high solar power generation. Power generated by PV panels is highly vulnerable to uncertain weather conditions, and impedance connected to its terminals. Therefore, to maximize the energy productivity from panels by controlling output impedance, a power electronic converter capable of adopting maximum power point tracking (MPPT) technique is required. This paper includes a comprehensive review of basic and advanced MPPT techniques proposed to address the variations in temperature, irradiance, partial shading conditions. Power processing equipment such as dc/dc converters and inverters are mandatory in extracting power from PV panels and utilizing either for standalone systems or grid integration. Grid integration is a major focus where access to utility line ranging from domestic micro-inverters (<300 W) to solar generation (>MW). A centralized inverter topology interfaces a MW power rating PV farm consisting several parallel strings of series connected PV panels to the grid. This review article contributes on presenting an overview of the state-of-the-art power electronics systems for integration of PV panels to the grid. Various interfacing power electronic architectures covering micro-inverter, central inverter up to modular inverter approach operating at low switching frequency and high switching frequency with resonant and pulse-width modulated (PWM) soft-switching or hard-switching are reported. Various voltage-fed and current-fed multi-level inverters for such architectures are studied and discussed. [ABSTRACT FROM AUTHOR]

All-metal induction heating (IH) systems have been introduced to heat both ferromagnetic and non-ferromagnetic pots using dual resonant frequencies. They are designed for heating ferromagnetic pots using a first harmonic operation mode (FHOM) and for heating the non-ferromagnetic pots using a third harmonic operation mode (THOM). All-metal IH systems employing dual resonant frequencies consist of an IH inverter and a power factor correction (PFC) circuit to transfer desired power to pots by increasing the input voltage of the IH inverter. In this paper, the input voltage is designed to obtain an efficiency-optimized operating point. To obtain an appropriate input voltage, power loss analyses are conducted using first harmonic approximation (FHA). Based on analysis results, the input voltage of the IH inverter can be selected to improve its power conversion efficiency. A 2-kW half-bridge series resonant inverter prototype is implemented to verify the effectiveness of the proposed design by heating ferromagnetic pots using the FHOM with a 2-kW transfer power and by heating non-ferromagnetic pots using the THOM with a 1-kW transfer power. [ABSTRACT FROM AUTHOR]

This paper analyzes the benefits of the active damping applied to transformerless three-phase grid-connected photovoltaic (PV) inverters using modified LCL (MLCL) filter for leakage current reduction. In comparison with passive damping techniques, the active damping can reduce the MLCL filter resonance peaks, improving the dynamic performance of the control system without addition of power losses. Besides these classical advantages, this paper demonstrates that the active damping also contributes for PV leakage current reduction, preserving the high-frequency attenuation of the MLCL filter. Additionally, an active damping for the inverter common-mode circuit is also proposed, reducing the low-frequency leakage current caused by the common-mode signal used to extend the inverter modulation index. Experimental results are given to demonstrate the leakage current reduction and the grid current control for a 10 kW PV inverter. [ABSTRACT FROM PUBLISHER]

This paper deals with the instability and resonant phenomena in distribution systems with multiple grid-connected inverters with an LCL output filter. The penetration of roof-top and other types of small photovoltaic (PV) grid-connected systems is rapidly increasing in distribution grids due to the attractive incentives set forth by different governments. When the number of such grid-connected inverters increases, their interaction with the distribution grid may cause undesirable effects such as instability and resonance. In this paper, a grid system with several grid-connected inverters is studied. Since proportional-resonant (PR) controllers are becoming more popular, it is assumed that most inverters use this type of controller. An LCL filter is also considered at the inverters output to make the case as realistic as possible. A complete modeling of this system is presented. Consequently, it is shown that such a system is prone to instability due to the interactions of the inverter controllers. A modification of PR controllers is presented where the output capacitor is virtually decreased. As a result, the instability is avoided. Simulation results are presented and show a good agreement with the theoretical studies. Experimental results obtained on a laboratory setup show the validity of the analysis. [ABSTRACT FROM AUTHOR]

The combination of multilevel inverter with renewable energy source power generation is paid more attention among the researchers, because multilevel inverters are widely accepted power converters in for high-power applications. The conventional multilevel inverters are highly implemented in industries, and the success of this has motivated to create newer topologies with the reduced overall power electronics components. In this paper, recent multilevel inverter topologies with reduced number of switches are taken into account and to find a suitable topology for photovoltaic (PV) and wind energy applications. Finally, this paper gives a pathway for the upcoming researchers to consider the design issues and challenges in the development of new multilevel inverter topologies. [ABSTRACT FROM AUTHOR]

This paper addresses the control problem of a PV power generating chain such that the maximum power is provided to the grid connected system without the need of any additional module stages. For this purpose, the proposed control system is directly applied to the power inverter using power-MOS switches, for which, a prediction-based model selects the switch state while minimizing the error between actual and predicted power outputs. Obtained predictions are evaluated using a cost function. Attention is paid in this paper to the validation of the proposed control method using one and two steps future predictions. Finally, simulation results are provided to demonstrate the effectiveness of the proposed control methodology. [ABSTRACT FROM AUTHOR]

This paper proposes and validates model predictive control as an alternative control strategy for H-bridgeneutral-point-clamped (H-NPC) converters for single-phase grid-tied string photovoltaic (PV) systems. The presented control scheme achieves good quality current waveforms with unity power factor, dc-link voltage control, and neutral-point voltage minimization. Furthermore, the predictive controller has been further enhanced by including an average device switching frequency restriction and a $dv/dt$ mitigation. The main contribution of this paper is the avoidance of the potential leakage current due to parasitic capacitance of the PV modules by using a predictive model based control technique instead of modulated schemes and eliminating high-frequency common-mode voltage components. Experimental results during steady state and dynamic operation are presented to illustrate the behavior of the H-NPC converter commanded by the proposed control scheme. [ABSTRACT FROM AUTHOR]

Numerous countries are trying to reach 100% renewable penetration. Variable renewable energy (VRE), for instance wind and PV, will be the main provider of the future grid. Cost reduction of accelerates the large scale VRE deployment around the world. The efforts to decrease the greenhouse gases are promising on the current remarkable growth of grid-connected photovoltaic (PV) capacity. This paper provides an overview of the presented techniques, standards and grid interface of the PV systems in distribution and transmission level. This paper compares the different review studies which has been published recently and provides an extensive survey on technical specifications of grid connected PV systems. Moreover, the adopted topologies of the converters, a thorough control strategies for grid connected inverters, as well as their applications in PV farms has been studied. This study will help researchers and industry users to establish their research based on connection requirements and compare between different existing technologies. [ABSTRACT FROM AUTHOR]

Large-scale grid-connected photovoltaic (PV) systems are facing issues like increment of efficiency, minimization of cost, and robustness of the total system. PV strings should operate at maximum power point in all weather conditions to make an efficient system. Inverter is one of the main components along with PV string in grid-connected PV system. Two-level inverters are normally used for practical implementation; however, multilevel inverters, especially cascaded H-bridge (CHB) inverter is one of the best alternative solutions available for large-scale PV plants keeping cost and efficiency in mind. CHB inverters generate a higher voltage output based on series connection of lower voltage H-bridge cells and also having features like higher modularity in structure. High-quality input current and output voltage can be obtained with lower rating devices in CHB-based system. CHB inverters are successfully used in high-power medium voltage drives, STATCOM, and active filter, but CHB-based PV system is facing great challenges in DC voltage balancing, active and reactive power control. This paper presents a comprehensive review on CHB-based large-scale grid-connected PV system. Different topologies and control techniques are reviewed thoroughly to justify potential of CHB-based PV inverters to replace conventional two-level grid-tied large-scale PV inverter. A list of 88 research papers is appended based on advancement, various topologies, and control technique on this area and classified for reference. [ABSTRACT FROM PUBLISHER]

Soft Computing (SC) methods are emerged as an alternative approach to conventional techniques for Grid connected Photovoltaic (PV) system because of their ability to solve the complex non-linearity problems. Soft Computing (SC) techniques are developed to handle the adverse environmental conditions such as sudden change in temperature and irradiation which are not addressed by conventional methods. The main focus of this paper is to summarize the application of various SC techniques which apply to different stages of a grid connected PV system such as panel reconfiguration, Maximum Power Point Tracking (MPPT) technique in the converter, Harmonic elimination in inverter and islanding detections. Furthermore, the comparison is made on the performance of SC methods based on several conditions, namely convergence, algorithm complexity, real time implementation, System dependency, Periodic tuning and Oscillations around the operating point. It is envisioned that the information provided in this paper is intended to serve as a valuable reference for future research in grid connected PV system. [ABSTRACT FROM AUTHOR]