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This study aims to ameliorate the contribution capability of doubly-fed induction generator (DFIG) to participate in standalone microgrid operation. The islanded microgrid consists of a solar photovoltaic array for solar energy conversion and battery energy storage in addition to DFIG-based wind energy conversion system. Using a simplified control approach, the study describes multi-mode operation of a DFIG-based AC/DC microgrid using a stator-side solid-state transition switch (SSTS). Using SSTS operation, the DFIG stator can be seamlessly disconnected and reconnected from the point of common coupling without interrupting power to the loads in the microgrid. Additionally, non-ideal AC loads can be handled efficiently without the need for computationally exhaustive approaches to enhance stator voltages and currents. [ABSTRACT FROM AUTHOR]

Summary: Problems like intermittent photovoltaic (PV) power, disconnected PV arrays, etc. are brought on by the extensive integration of PV generation. In this article, a single‐stage PV‐integrated grid‐tethered system is controlled using a reconfigurative multiple random features kernel mean p‐power (MRFKMP) control algorithm. The algorithm circumvents the dependence of kernel parameter in the classic random Fourier features mapping and lower the computing complexity in the traditional multiple kernel learning adaptive filter. MRFKMP algorithm with a linear filter structure can reduce both the computational and storage cost. This is the novel application of MRFKMP algorithm to extract fundamental component of nonlinear load currents in PV‐integrated grid‐tied system. Furthermore, to increase the reliability of the system, a reconfigurable control is developed, which adaptive regulates DC link voltage from PV mode (PVM) during PV hours to active power filtering mode (AFM) during PV nonavailability/PV disconnection. On a created laboratory testbed, the applied control's practical feasibility for numerous scenarios is evaluated. Comparison with existing control algorithms reveals that the MRFKMP controller outperforms the LMF based PV system by 79% less peak‐to‐peak load current ripple and 60% less than the best performing SRF control algorithm. The grid current THD is 2.60%, which is 30% low than that presented by SRF technique. [ABSTRACT FROM AUTHOR]

The paper presents a normalized, varying step size-based least mean square-based control for a standalone microgrid and Ant Lion optimization-based maximum power point tracking. This modified version of the incremental conductance algorithm addresses issues like slow dynamic response, fixed step size issues, and steady state oscillations. Comparative analysis with well-known techniques shows that Ant Lion optimizes the tracking of maximum power points more accurately, with fewer oscillations and increased efficiency. Power management and power quality are maintained through proposed adaptive voltage source converter control. The proposed voltage control shows better performance under various dynamic and steady conditions. [ABSTRACT FROM AUTHOR]

Summary: This paper presents the performance of a single‐phase utility‐tied distribution static compensator (DSTATCOM) with nonlinear load operating under weak grid conditions. The DSTATCOM is controlled by a complex kernel risk‐sensitive p‐power (CKRSP) algorithm. Ever‐increasing nonlinearity of the load, rapidly increasing renewable energy system installed capacity, and rising heating loads, especially during the winter season, lead to various power quality issues that worsen during weak grid conditions. An advanced adaptive control scheme, that is, CKRSP, enforces the system to perform various multifaceted operations, including harmonics suppression, handling rapid load variations, voltage sag and swell, and active and reactive power control at the point of common coupling (PCC) during weak grid conditions. The proposed CKRSP algorithm outperforms conventional control algorithms regarding steady‐state error, convergence speed, and accuracy. During weak grid conditions, the proposed system ensures stable DC bus voltage with a reduced second harmonic component. This further assists the CKRSP control in better extracting the fundamental load current component using a smoother loss component of current iloss. The proposed system can handle various power quality issues during weak grid conditions while ensuring the overall system's stability. The laboratory prototype results show that the presented system performs satisfactorily under weak grid conditions per IEEE 519‐2014 standards. [ABSTRACT FROM AUTHOR]

In view of the stochastic nature of wind and solar energy, maintaining quality power in grid-connected hybrid energy system is crucial for efficient energy utilization, especially in the presence of non-linear loads. This paper deals with the control and performance assessment of grid-integrated hybrid energy system that comprises of doubly fed induction generator (DFIG) and photovoltaic (PV) system including battery energy storage (BES) as a stand-by supply to meet utility and load demand. In order to maintain power balance and address various power quality issues encountered with hybrid renewable integration along the source and the grid/load end, a dual-layer variable-step size adaptive control is implemented for the grid-interfaced converter of the proposed system. The variable step-size based dual-layer least mean square (LMS) adaptive control functions by extracting weights of various control signals (stator and load current) where the step-size parameter adjusts according to the conditions that limit the maladjustment error and increase the rate of convergence. The DC-link voltage control realized by bidirectional BES control reduces the steady-state error and fluctuations in the voltage. An artificial bee colony (ABC) optimization is adopted for optimal gain tuning of the DC-link voltage controller as a result of which the battery performance and grid-side converter performance is enhanced with the increased power exchange to the grid. The system model is developed in MATLAB/Simulink and controller performance is evaluated for diverse operating conditions including steady-state, unbalanced non-linear load conditions, wind-speed and solar irradiation variation and specified grid power modes. [ABSTRACT FROM AUTHOR]

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

This work proposes a hydrological cycle-based optimisation technique for performance enhancement of a non-negative least mean mixed norm (NNLMMN) based voltage source control (VSC) for a three-phase grid integrated wind/photovoltaic (PV) system. Water cycle algorithm (WCA) is employed to tune the proportional–integral (PI) controller parameters of VSC to regulate voltage variations at DC link generated during dynamic load and wind conditions. This results in generation of a specific loss component (Iloss) of current to boost the performance of VSC. The NNLMMN control deals with system identification troubles with a non-negativity limitation in varied Gaussian noise conditions. It generates accurate Iloss to upgrade the ability of VSC to accurately extricate weight signals and the fundamental load current component in terms of improvement in DC link voltage (vdc) and total harmonic distortion. The proposed algorithm mitigates problems like voltage fluctuations besides performing operations like reactive power compensation, enhancement of power quality, load and power balancing at the point of coupling during steady-state and dynamic conditions. In conjunction with the NNLMMN algorithm, the proposed technique reduces the surplus mean square error iteratively, resulting in a compact expression of step size. The proposed topology stands out with an improved performance of vdc under wind gusts and the well-known bell-shaped irradiance curve. For relative evaluations, the performance of non-optimised PI and particle swarm optimised PI has been added to analyse the improved response of vdc and Iloss. Extensive simulation results obtained in MATLAB/Simulink are exhibited to corroborate the efficacy of the suggested system. [ABSTRACT FROM AUTHOR]

The paper presents a grid-connected microgrid with a photovoltaic system and a battery as a storage element. The optimal design and control of storage elements and power quality improvement are enhanced using sigmoid-function-based variable step size (SFB-VSS) adaptive LMS control. The DC-link voltage and battery current are enhanced using an ILA-optimization-based PI controller. Comparative analysis shows that an ILA-optimized PI controller improves battery stress and DC-link voltage fluctuations, enhancing overall system stability. The relative percentage error of Vdc is only 0.5714% for ILA-optimized values as compared to GA, PSO, and manually tuned PI gains which are 0.857%, 1.14285%, and 0.86%, respectively. ILA-optimized parameters also enhance battery current, reducing stress on the battery. The system was studied under various dynamic conditions, achieving power balance in all conditions. The system has the capability of seamless transfer of control from GC mode to SA mode when the grid is disconnected. The proposed VSC control shows better performance in steady-state and dynamic conditions, maintaining a THD under 5%, which follows IEEE standard 519, and providing better DC offset rejection, fewer oscillations in the weight component of the load, and better convergence. The proposed control also enhances the frequency of the grid, ensuring a smooth transition between modes. The system is simulated in the MATLAB Simulink environment, and all the optimization techniques were carried out offline. [ABSTRACT FROM AUTHOR]

Summary: In this study, an optimal double frequency second order generalized integrator (DFSOGI) based grid side converter control (GSC) is used for monitoring active power injection from the DFIG wind energy system as well as improving power quality at utility grid terminals. The reference DC voltage is adapted to variations in voltage at the point of common coupling (PCC) that reduces the burden on the converter switches and switching losses. In addition, an intelligent control technique based on white shark optimization algorithm (WSO) is endorsed, where an objective problem is formulated to obtain the desired parameters of the controller. Finally, time‐domain simulations are conducted in MATLAB environment that demonstrate the validity of the implemented control over various operating conditions. To affirm the adequacy of the proposed control strategy, the response of DC link voltage obtained through optimal tuning is compared to the conventional one. The proposed WSO tuning outperforms traditional manual tuning pertaining to enhancing the overall performance of the DFIG system. The designed WSO gains exhibit better steady‐state and transient performance including settling time, steady‐state error, and peak of over amplitude and harmonic distortion. The grid currents' total harmonic distortion (THD) is within 5% that meets specified IEEE‐519 standard. [ABSTRACT FROM AUTHOR]

This paper presents a path-finder algorithm (PFA) of meta-heuristic optimization for the performance enhancement of the bias compensated normalized maximum correntropy criteria (BCNMCC) based voltage source converter (VSC) control for a three-phase three-wire grid-tied dual-stage PV system. The DC link voltage ( V DC ) variations during induced dynamic conditions are minimized by PFA optimized PI controller which also generates an accurate loss component of current ( I d1 ) for enhancing the VSC control performance. The BCNMCC algorithm effectively performs the system identification and echo cancellation in the presence of Gaussian noises. An accurate I d1 improves the VSC ability to accurately extract the fundamental load current component and to produce precise weight signals. The BCNMCC performs multifunctional operations, i.e., reactive power compensation, harmonics elimination, load balancing, and power balancing at point of common coupling during steady-state and various dynamic conditions, i.e., grid-islanding & re-synchronization, irradiation variation, unbalanced load and fixed power mode. The proposed system is capable of operating under grid-tied and isolated mode due to the seamless transition of a VSC control from grid current control (GCC) to voltage control. The seamless transition of VSC control does not induce any major transients at the source and on the load side of the system. The hybrid energy storage system (HESS) with a battery, fuel-cell and ultra-capacitor further improves the reliability of the PV system and the stability of the overall system during both grid-tied and isolated operations. The proposed system performs satisfactorily under steady-state and diverse dynamic states as per IEEE519 standards. [ABSTRACT FROM AUTHOR]

Summary: An advanced topology comprising a wind‐turbine driven synchronous generator (SG) and solar photovoltaic (PV) array to address the power quality (PQ) concerns and the uncertainty in renewable energy generation is proposed in this paper. The fluctuations in wind speed and insolation are soaked up by utilizing successively interfaced power electronic converters (PECs), namely, SG side converter (SGC) and utility grid side converter (UGC) integrated with a DC link capacitor and a PV array. SGC is controlled by estimating the rotor position from the stator voltage and current measurement data and maintains unity power factor (UPF) at stator terminals. UGC is controlled by employing filtered X least mean fourth (FXLMF) control, which ensures superior convergence performance and reduced computational complexity. Besides, it performs operations like reactive power compensation, enhancement of PQ, load and power balancing during steady‐state and dynamic conditions. The notion of optimal fuzzy reasoning is instilled which generates a fuzzy scheme with inherent optimal‐tuning characteristics to bring about considerable improvement in system performance. A water cycle algorithm (WCA) tuned fuzzy logic controller (FLC) is employed for dynamic stability enhancement leading to the generation of accurate loss component, iloss, which bolsters the ability of VSC to accurately extricate weight signals and the fundamental load current component. This improves regulation of DC link voltage during dynamic load, insolation and wind conditions. The veracity of the proposed model is verified under wind gusts and the bell‐shaped irradiance curve. Extensive simulation results obtained in MATLAB corroborate the efficacy of the system. [ABSTRACT FROM AUTHOR]

As the wind energy is progressively pursued to supplement conventional power generation, the stochastic wind behavior considerably deteriorates power quality (PQ) and stability of the connected grid. This article is attributed to the comprehensive control design of the grid-integrated doubly fed induction generator (DFIG) wind energy system that aims to address encountered wind variability and PQ intricacies. Battery energy storage with bidirectional dc–dc converter control is assimilated at the dc-link of the DFIG that regulates the dc-link voltage to mitigate the wind power fluctuations in specified grid power modes. A higher order adaptive control for grid-interfaced converter accurately computes desired weights of various components to exercise accurate power balance and PQ control. Moreover, a novel Jaya particle swarm optimization algorithm is adopted for the optimal tuning of wind maximum power point tracking and the dc-link voltage PI controller parameters that significantly improves steady-state and dynamic responses of both the controllers. The rotor speed converges faster with precise reference tracking that leads to almost zero steady-state error using optimized PI controller gains. Along with the attenuated initial overshoot and fast settling time during sudden large step wind speed change, the dc-link voltage also characterizes superior response with optimal tuning during load unbalance and abnormal grid voltage conditions. The presented control strategy analyzes the capability of DFIG system under variable wind-speed changes, specified grid power modes, load changes, and other grid disturbances. The satisfactory system response is endorsed through experimental results conducted on a laboratory prototype. [ABSTRACT FROM AUTHOR]

This article presents a photovoltaic (PV)–battery energy storage (BES) system functioning in both grid-tied and standalone modes while performing multifunctional operations, including reactive power compensation, power balancing, and power quality enhancement. The PV–BES system ensures uninterrupted power supply to the critical loads even during seamless transitions from grid-tied mode to islanded mode, and vice versa. The incremental conductance technique controls the boost converter and confirms maximum PV power extraction. The bidirectional converter connects BES to the dc bus. The dc bus voltage $({{V}_{dc}})$ is regulated by a slime mold optimized proportional-integral controller to limit the dynamic state variation and improve stability. The voltage-source converter (VSC) is controlled by a minimum kernel-risk-sensitive mean p-power loss algorithm during the grid-synchronization mode. In contrast, the voltage control algorithm executes islanded control of VSC. The VSC control transition is achieved seamlessly without any significant disturbance at the point of common coupling. The hardware test results demonstrate that the present system remains stable during dynamic conditions and performs adequately as per the IEEE 519-2014 standard. [ABSTRACT FROM AUTHOR]

The presented system is a three-phase three-wire (3P–3W), seamless, capable, dual-stage PV power generation system without battery storage for rural residential loads to ensure a continuous power supply during the daytime. This system effortlessly shifts from the grid-connected (GC) mode to the standalone (SA) mode when the grid utility is unavailable. During the GC mode, a voltage source converter (VSC) is regulated by the polynomial zero-attracting least mean square (PZA-LMS) algorithm-based current control scheme. During the GC mode, the power balance is achieved at the point of common coupling (PCC) by exchanging active power with the grid, whereas the VSC delivers reactive power. Considering the low efficiency of PV power generation systems, an incremental conductance (InC)-based maximum power point tracking (MPPT) algorithm is necessary for the maximum power extraction out of a PV array. During the unavailability of the grid, the presented system operates in the SA mode, when the load is delivered with PV power only via VSC. Considering the high cost of the battery storage system (BSS), bi-directional converter, and charge control circuitry incurred by rural consumers, they were omitted from the system. Without a BSS, the InC-based MPPT is executed in the derated mode, extracting the PV power to exactly match the load demand. Without derated PV power generation operation, the load may be damaged due to excess PV power flow to the load end or the load may remain underpowered, leading to load shedding or complete disconnection. A synchronous reference frame (SRF)-based voltage control scheme is responsible for the VSC control during the SA operation of the system. The presented system performance was observed and found satisfactory during the irradiation variation, load balancing, islanding, and re-synchronization of the grid. The presented system was found to carry out harmonics suppression and active and reactive power balance at the PCC during both the GC and SA modes. The grid's total harmonics distortion (THD) levels were shown to be kept below 5% as per the IEEE 519 standard in the GC mode. [ABSTRACT FROM AUTHOR]

This paper presents a tree growth optimization based control of a grid-tied dual-stage photovoltaic system. The tree growth optimization has been employed for optimizing the proportional and integral controller gains for direct current bus voltage (Vdc) regulation to have minimum variation during dynamic conditions and to generate an accurate loss component of current (iLoss). The accurate i L o s s , further enhance the control's performance by generating the accurate reference currents. The presented system is simulated and analyzed in a MATLAB simulation environment under various dynamic conditions, i.e., irradiation variation, unbalanced and abnormal grid voltage. The overall performance is satisfactory as per IEEE 519 standards. [ABSTRACT FROM AUTHOR]

In this article, the control of a grid-connected, single-phase, dual-stage photovoltaic (PV) residential system with electric vehicle (EV)-charging capability is being presented. A residential system faces a lot of dynamic conditions such as changing atmospheric condition or random patterns of load connection or disconnection as well as power failure. In this regard, this article proposes the optimization of proportional and integral gains selection of the bidirectional DC/DC converter (BDC) PI controller through golden eagle optimization (GEO) algorithm to improve the system performance. The system is subjected to various induced dynamic conditions simulated in MATLAB Simulink environment and the performance is compared with particle swarm optimization, genetic algorithm, and gains obtained through hit and trial. In comparison with other techniques, GEO algorithm provides optimum BDC PI gains, as a result, the DC-link voltage achieves 1.5 times shorter settling time. During the non-linear load changes and voltage swell condition, the settling time is 2 times shorter. Settling time of the EV battery power shows 1.7 times reduction. The transient response of the PV power also shows dramatic improvement with 3 times faster settling time during solar insolation changes. During the sudden non-linear load changes, the momentary transients die 1.5 times faster. Moreover, a seamless control is developed to achieve a seamless transition from islanded mode to grid connected mode and vice versa. The proposed system achieves unity power factor and complies with the IEEE -519 power quality standard. [ABSTRACT FROM AUTHOR]

This paper describes the normalized maximum correntropy criteria (NMCC) based seamless control of three-phase four-wire voltage source converter (VSC) for a grid-tied PV-Hybrid energy storage system (HESS). The micro-grid can operate in both islanded and grid-tied mode with seamless control. The seamless control facilitates the VSC control transition from grid current control (GCC) during grid-tied mode to voltage control during grid-isolated mode and back to GCC control with grid-resynchronized mode. The seamless control ensures the system stability and security of the personnel with reduces transients on the grid and load side of the system during the VSC control transition. The VSC is designed to fulfill the multi-objective including power quality enhancement, reactive power compensation, load balancing during unity power factor (UPF) operation. The VSC maintains the system stability during diverse dynamic conditions, inducing disturbances on grid side, load side and PV side of the system, i.e., Irradiation variation, unbalanced load, abnormal grid voltage, intentional islanding, specified power mode and grid-resynchronization. The hybrid energy storage system (HESS) consisting of lead-acid battery and ultra-capacitor (UC) further enhances the stability and disturbances handling capability of the grid-tied PV system. The functioning of the proposed system is found adequate as per IEEE 519 standards during steady and induced dynamic conditions. [ABSTRACT FROM AUTHOR]

This paper proposes a hybrid learning algorithm based super twisting sliding mode control (STSMC) of a hybrid wind/photovoltaic (PV) power system for grid connected applications. The gating pulses of the voltage source converter (VSC) are generated by employing adaptive reweighted zero attracting least mean square (RZA-LMS) algorithm. The control law acquiring the super-twisting algorithm generates a continuous and saturated control signal to regulate a hybrid system influenced by disturbances. The proposed control injects sinusoidal currents into the grid with low total harmonic distortion (THD) which improves the steady state & dynamic performance of the system by mitigating power system problems like harmonic injections besides giving satisfactory results under dynamic loading, varying wind speeds and solar insolation. It is a chattering free control which enhances the quality of disturbance rejection and sensitivity to parameter variation. It also caters to abnormal conditions like voltage distortions, DC link variations and reduces the latter by a factor of 80 V besides reducing switch stress by a factor of 5 V. This control exhibits robustness against model uncertainties and external disturbances. Also, the loss component is reduced which decreases the unmodelled losses. It also ensures efficient power flow between the grid, hybrid source and the load. The efficacy of the system is verified in MATLAB/Simulink. Improvements are also observed during dynamic conditions in terms of reduced fluctuations, steady state error and peak overshoot. [ABSTRACT FROM AUTHOR]

ABSTRACT This study delves into the advancements, challenges, and opportunities in the solar grid technology, emphasizing its integration into the existing power infrastructure. The proposed ML‐FOGI (multilayer fourth‐order generalized integrator) algorithm presents a promising solution for modern grid synchronization requirements, addressing challenges posed by the integration of renewable energy into the distributed generation. This technology enhances system robustness and dynamic response, particularly in weak distribution grids characterized by voltage distortions and imbalances. This innovative approach enhances system stability and performance, particularly in polluted grid conditions. Through MATLAB/Simulink modelling and experimental validation, the effectiveness of the proposed control strategy is investigated across diverse testing conditions. Emphasizing the significant role of the control strategy in enhancing power quality and grid stability in the solar photovoltaic systems, this research underscores the importance of robust and adaptive control mechanisms for optimizing performance and ensuring grid reliability in modern microgrid. This study delves into this complex issue of working of the grid connected photovoltaic (GCPV) system, emphasizing the importance of balanced unit templates and a stable DC link voltage with unpredictable grid harmonics. This research aims to enhance the resilience of solar PV systems against grid disturbances by drawing inspiration from the adaptable nature of ADALINE filters and adhering to the IEEE519 requirements. This study employs OPAL‐RT's resilient experimental configuration. [ABSTRACT FROM AUTHOR]

Here, an implementation of three‐phase grid‐tied single‐stage solar photovoltaic (PV) system is done at adverse grid situations of voltage unbalances. The proposed convex combination of least mean square (CCLMS) control approach is adaptive in nature, which extracts the fundamental component of load current (FCI) with fast convergence and provides good performance than conventional controls. The CCLMS algorithm overcomes the compromise of LMS filters between precision and tracking capability due to fixed stepping by providing a combination of two filters for precision and fast tracking. The perturb and observe (P&O)‐based maximum power point tracking (MPPT) is employed for peak power extraction from a PV array. The system is tested in the laboratory on a developed prototype at several adverse conditions like voltages unbalance, load currents unbalances, and irradiation changes. The system performance is acceptable and harmonics distortion is in the limits according to the IEEE‐519 standard while supplying energy to the utility and to the loads. [ABSTRACT FROM AUTHOR]

In this paper, a vector-based synchronization technique is proposed for the synchronization of a solar photovoltaic (PV)-battery system to the grid. In this technique, the three-phase grid and point of common coupling voltages are transformed into two vectors in the α–β plane. Due to the absence of a phase-locked loop and feedback, the proposed technique is simple, and also instantaneous changes in the voltages are considered here. The grid-connected solar PV-battery system operates in the current control mode, while the islanded system operates in a voltage control. Experimental results are obtained on a grid-solar PV-battery system in grid-connected and islanded modes. The two transitions between these operating modes are also studied in detail. All these test results of harmonics in grid voltages and currents are found satisfactory and in accordance to the IEEE-519 and 1547 Standards. [ABSTRACT FROM AUTHOR]

This paper deals with a quadrature oscillator (QO)-based demodulation technique algorithm to improve the power quality of a grid-tied solar photovoltaic (PV) system in the distribution network for power factor correction, load balancing, and harmonics mitigation. The QO algorithm rejects the second harmonic generated by the demodulated load current. The improved incremental conductance-based maximum power point tracking scheme is utilized to extract maximum power from a solar PV array. Simulation results illustrate the effectiveness of QO algorithm for steady state and dynamic conditions to verify the effectiveness of the proposed algorithm. Test results show reliable, robust performance, and accurate estimation under steady state, variable insolation, load unbalancing, PV to distribution static compensator (DSTATCOM) mode and DSTATCOM to PV mode. The total harmonic distortion of grid current and grid voltage lies within the limits of the IEEE 519 standard. [ABSTRACT FROM AUTHOR]

This study presents an optimal control operation of a photovoltaic-battery based standalone microgrid, feeding nonlinear loads. To ensure continuous power supply to the critical loads during low insolation or low battery state of charge, a diesel generator (DG) is used as an auxiliary generator. This cost effective hybrid system with maximum utilisation of the renewable as well as fossil fuel based generators can be employed in hospitals, telecom stations in remote areas. In order to nullify the effect of non-linear loads on the DG, modified enhanced phase-locked loop (EPLL) based power quality conditioner is used. The characteristic equation of conventional EPLL is amplitude dependent, thus, the controller tuning parameters need to be modified if the input signal varies over a large range. The presented controller overcomes this problem making the system more robust in eliminating noise and harmonics and extracting fundamental component of a given signal. This component is drawn from the DG with the help of a voltage source converter, thus, making its current always distortion free. The proposed control scheme is simulated in MATLAB. Furthermore, experimental verification is done on a laboratory prototype of the same. The steady state and dynamic responses of the system validate its satisfactory performance. [ABSTRACT FROM AUTHOR]

This paper proposes an improved second-order generalized integrator with frequency-locked loop (ISOGI-FLL) based control scheme for a grid-connected solar photovoltaic (PV) array fed voltage source converter (VSC) to mitigate the power quality problems. The steepest descent algorithm based maximum power point tracking is used to achieve the crest power from a solar PV array to improve solar power generation (SPG) into the grid as well as to maintain dc bus voltage of the VSC. The ISOGI-FLL-based control scheme is very effective for grid currents balancing and harmonics mitigation, at a variation of SPG and unity power factor operation. Simulated results are demonstrated using MATLAB/Simulink for load unbalancing and variation in solar insolation. The effectiveness of the proposed algorithm is demonstrated based on comparative performance with conventional algorithms. Test results of a developed prototype show satisfactory performance for different operating conditions like grid currents balancing, photovoltaic-distribution static compensator (PV-DSTATCOM) mode, and DSTATCOM-PV mode at variable solar insolation. Moreover, total harmonic distortions of grid voltages–currents are achieved within the limit of the IEEE-519 standard. [ABSTRACT FROM AUTHOR]

In this paper, a Volterra-filter-based control algorithm is developed to generate reference currents for a solar photovoltaic-distribution static compensator (PV-DSTATCOM) system in the distribution network. The developed control is analyzed for being stable under Lyapunov stability criterion; consequently, the error function of the system converges to zero asymptotically. The PV-DSTATCOM system is integrated to the grid to compensate the nonlinear load, while supplying solar PV array active power to the grid. The system is modeled in MATLAB and is executed on a developed prototype in the laboratory, under balanced, unbalanced loading conditions, and variable insolation conditions. Moreover, the harmonic distortion of the grid currents is observed under the IEEE-519 standard. [ABSTRACT FROM AUTHOR]

This paper presents an improved generalized integrator (GI)-based control with a frequency locked loop for multifunctional three-phase single-stage grid interfaced solar energy conversion system for power quality enhancement of the distribution network under abnormal grid conditions. The perturb and observe-based maximum power point tracking technique is utilized to obtain peak power from solar photovoltaic array under varying atmospheric conditions. This control scheme provides unity power factor operation, load balancing, harmonics mitigation, and reactive power compensation. The improved GI control algorithm has an advantage of better dc offset and harmonics rejection capabilities as compared to a conventional second-order GI algorithm. To substantiate the control scheme, tests are performed on a paradigm in the research laboratory for manifold operating conditions. Test results show the satisfactory behavior under steady state and dynamic operating scenario such as unbalanced load, solar irradiations variation, voltage sag, and swell and distorted voltage grid. The total harmonic distortions of the grid voltages–currents are achieved within constraints of grid code compliance of an IEEE 519 and 1564 standards. [ABSTRACT FROM AUTHOR]

A differentiation-based control method for a shunt active power filter is used in this paper for functioning in the presence of grid voltages distortion and imbalances. To enable the fast and accurate estimation of the variables in the presence of unbalancing or distortion in the grid voltages, a prefiltering scheme is considered based on the dual second-order generalized integrator approach. The signal recomposition performed by the prefilter isolates the harmonics from the voltage and current waveforms, and the differentiator frequency locked loop (dFLL) is able to estimate the frequency of the waveforms, which is used as a feedback for the prefilter, thus making the system frequency adaptive. The control algorithm is validated with both simulation studies. The prototype of an active power filter is developed, which carried out current compensation robustly, demonstrating the speed and accuracy of the system even under distorted grid conditions by achieved total harmonic distortions (THDs) of the grid currents within limits (less than 5%) as dictated by IEEE Std. 519-2014. [ABSTRACT FROM AUTHOR]

An integration of renewable sources based distributed generating systems encounters various power quality issues due to uncertain loads at the distribution end. These uncertainties arise due to nonlinearity, disturbances or unbalanced loads. A three-phase grid-integrated solar photovoltaic (PV) system incorporating a control technique based on a modified decorrelation normalized least mean square (DNLMS) algorithm, aiming to enhance its overall performance under adverse conditions, is presented in this work. The three-phase, grid-tied, single-stage solar PV system comprises a solar PV array with a suitable maximum power point tracking method, filters, loads, and a capacitor fed voltage source converter (VSC). The key objective of the solar PV integrated structure with an adaptive law based control algorithm is to attain a unity power factor (UPF) at the grid end ensuring harmonics mitigation from the grid currents. Moreover, this structure effectively transfers active power from the PV array to the local loads and the grid. These aforesaid objectives are achieved through providing controlled switching pulses to the insulated gate bipolar transistor based VSC using the modified DNLMS control algorithm with fast convergence rate. Harmonics-free, sinusoidal reference grid currents, are obtained by using the modified DNLMS algorithm. A simulation model developed in MATLAB/Simulink is used for the validation of the modified DNLMS-based control approach. In the laboratory, an experimental prototype is developed and the proposed algorithm is implemented to verify its performance. [ABSTRACT FROM AUTHOR]

This paper deals with a novel reduced sensor strategy, for two-stage single-phase grid connected solar photovoltaic system with a battery, where the dc-link voltage sensor is not required. Moreover, for maximum power point tracking (MPPT), a new “normal harmonic search” (NHS) algorithm is used, and for voltage source converter (VSC) control, a novel “power normalized kernel least mean square” (PNKLMS) algorithm is proposed. The PNKLMS algorithm is used for active load component extraction from the load current, even when the load current is characterized by linear or nonlinear behavior. Moreover, PNKLMS algorithm is used for reference grid current generation. The NHS algorithm is an improved version of the harmony search, which is inspired to the music composition technique and its searching ability is improved by using the normal probability distribution factor. Therefore, NHS reaches the global maximum power point very quickly and is suitable for online searching on hardware. Moreover, the extracted power is fed into the grid. For control of VSC, the proposed PNKLMS control technique is used, which maintains the power quality. The performances of NHS-based MPPT and PNKLMS-based control technique with reduced sensor approach are tested on a developed prototype. The satisfactory steady-state and dynamic performances of the NHS algorithm are demonstrated under variable irradiance and temperature during partial shaded conditions. Moreover, the performances of the PNKLMS algorithm, without using dc-link voltage sensor are demonstrated during overvoltage, undervoltage, harmonics distortion, and load nonlinearity condition, results of which have satisfied the objective of the proposed system and the IEEE-519 standard. [ABSTRACT FROM AUTHOR]

This paper deals with the use of a distribution static compensator (DSTATCOM) to the system constituted by a nonlinear load fed from a distorted grid. Moreover, an improved proportionate normalized least mean square (i-PNLMS) control algorithm is proposed for the DSTATCOM. The system is first modeled on a MATLAB/Simulink platform and its performance is analyzed under steady state and load increment cases. The frequency response of the compensated system is also obtained. Tests are conducted on a laboratory prototype to analyze the system's performance under steady state and load unbalancing. This algorithm helps in achieving the desired grid currents easily and efficiently, and it shows an inherent tendency to adapt to the system's requirements. The obtained total harmonic distortion of grid currents and point of common coupling voltages are within the limits defined in the IEEE-519 standard. [ABSTRACT FROM AUTHOR]

This paper presents a novel fourth-order generalized integrator using a frequency locked loop (FOGI-FLL) based control algorithm for a single-stage three-phase grid-interfaced solar energy conversion system (SECS) with the distribution static compensation (DSTATCOM) capabilities. The proposed FOGI-FLL control algorithm suffices multifarious power quality objectives in the distribution network such as harmonics mitigation, reactive power compensation, load balancing, etc. The FOGI-FLL has good frequency tracking performance along with high dc offset rejection and high-order harmonic filtering capabilities. Simulated results demonstrate the satisfactory response of the system under load unbalancing, variable insolation, and system frequency variation. The effectiveness and advantages of the proposed algorithm are shown by comparing it with conventional algorithms. To validate the control algorithm, an experimental prototype is developed and test results depict the performance and behavior of the system under various conditions such as load unbalancing, variable insolation, photovoltaic (PV) to DSTATCOM mode, DSTATCOM to PV mode, and voltage sag and swell. The total harmonics distortions in grid currents and grid voltages are found well within limits according to IEEE-519 and −929 standards. [ABSTRACT FROM AUTHOR]

This paper presents a control of smart photovoltaic (PV)-distribution static compensator (DSTATCOM) grid tied system using an adaptive reweighted zero attracting control algorithm with perturb and observe maximum power point tracking technique for a three phase system to improve power quality and support the three phase ac grid by supplying power both to the grid and the connected loads. The proposed PV grid tied system is capable of working round the clock. During sunshine conditions, the proposed system performs dual functions of improving power quality by working as DSTATCOM and also transfers power to the load and the grid obtained from PV array. However, during night or cloudy conditions, the proposed system works as DSTATCOM improving power quality and the power is transferred from the grid to the load. The system is termed as a smart as it is able to perform both modes automatically sensing the PV power and is capable of multidirectional power flow. The experimental validation is carried out on a developed prototype in the laboratory under varying modes. [ABSTRACT FROM AUTHOR]

A new control approach of integrating a solar photovoltaic (PV) with a battery storage is presented to a single-phase grid for residential and electric vehicle application. The main purpose of the proposed work is to feed a continuous power to the grid, thereby enhancing the viability of the battery energy storage support connected to the system. The charging and discharging of the battery achieve power leveling and load leveling along with increased reliability of the system. The multifunctional voltage-source converter acts as an active power filter and performs the harmonics mitigation along with reactive power compensation. In the proposed system, a unique control is developed for resynchronization of the grid during reconnection of the grid after the mitigation of a failure. The overall control of the system is adaptable under various practically occurring situations such as disconnection of the PV array, the battery, and the grid from the system. The detailed design and control of the proposed system are presented. The validity of the proposed system is performed through a laboratory prototype developed for a power rating of 2.2 kW connected to the utility grid. The performance of the system is found satisfactory under various disturbance, and the recorded results have been demonstrated. [ABSTRACT FROM PUBLISHER]

This paper presents a fuzzy-logic-based fourth-order generalized integrator (FOGI) frequency locked loop (FLL) based control for optimal operation of solar energy conversion system (SECS) having distribution static compensator (DSTATCOM) capabilities along with supplying active power to the distribution network. The proposed SECS is multifunctional having capabilities of power factor correction, load balancing, and harmonics mitigation in a three-phase distribution system. The FOGI-FLL has higher order filtering capabilities compared to conventional algorithms. The frequency tracking capabilities of proposed control technique exhibit better performance as compared to a conventional algorithm. The comparative performance of harmonics filtering and frequency tracking capabilities is demonstrated between FOGI-FLL and various conventional algorithms. Simulation results demonstrate the behavior of the system at various conditions. To validate the proposed algorithm, a prototype is developed and test results demonstrate the reliable performance of the system at various conditions, such as load unbalancing, variable insolation, solar photovoltaic to DSTATCOM mode at abnormal grid conditions, such as distorted grid voltages, unbalanced grid voltages, voltage sag, and swell. The total harmonics distortions of grid voltages and currents are found well within limit of the IEEE 519 standard. [ABSTRACT FROM AUTHOR]

In this work, a simple phase-locked loop -- less control is presented for a single-stage solar photovoltaic (PV) -- battery-grid-tied system. As compared to traditional solar PV systems, the system has reduced losses due to the absence of boost converter and a flexible power flow due to the inclusion of a storage source (battery). The synchronous reference frame theory is used to generate the pulses for switching the voltage-source converter (VSC), while maximum power is extracted from the solar PV array by using perturb and observe-based maximum power point tracking technique. The inherent feature of shunt active filtering by the VSC has also been incorporated in this system. Test results for the system operation under fixed power and variable power mode are studied on a prototype developed in the laboratory. During fixed power mode, a fixed amount of power is fed to the grid, whereas in variable power mode the power fed to the grid varies. Test results obtained are in accordance with the IEEE-519 standard. This work is a basis for the upcoming power market, where solar PV consumers can manage the generated electricity and maximise their profit by selling the power to the grid judiciously. [ABSTRACT FROM AUTHOR]

In this paper, a three-phase grid interfaced solar photovoltaic (PV) system is controlled through a fixed forward prediction (FFP)-based algorithm, which extracts the fundamental current component of load connected at point of common coupling. This voltage-source converter with the FFP-based control algorithm feeds the PV power to the grid along with balancing of loads, reduction of harmonics, stabilization of the grid under voltage sag/swell, and voltage unbalance conditions. Moreover, the rate of convergence of this algorithm is very high. Simulated performance of this system is verified experimentally. The incremental conductance-based maximum power point tracking algorithm is applied on a PV array for the extraction of maximum power from it. The system is tested under different abnormal conditions such as load unbalance, solar PV array connection/disconnection, voltage sag, voltage swell, voltage unbalance, and variable solar insolation. The distortions levels of voltage/current are found to be within limits as defined in an IEEE-519 standard while feeding active power to a distribution network and connected loads. [ABSTRACT FROM AUTHOR]

This paper presents an adaptive control approach based on a novel multilayer fifth-order generalized integrator (MFOGI) and single-input fuzzy-tuned proportional-integral (PI) controller for single-phase two-stage grid-connected partially shaded solar photovoltaic (PV) system, where the global maximum power point (GMPP) is tracked by using a novel human psychology optimization (HPO) algorithm. The MFOGI is used to extract the fundamental component from the grid voltage, even when the grid voltage is characterized by undervoltage, overvoltage, severe harmonics distortion, frequency variations, direct current (dc) offset, etc., on a wide range. Moreover, the single-input fuzzy-tuned PI controller is used for online PI controller gains tuning during different disturbances and dynamic conditions. To ensure a fast dynamic response, a PV feed-forward component is also included in the control algorithm as well as HPO is developed for quick GMPP tracking (GMPPT). The proposed control is modeled and simulated in MATLAB platform, as well as tested on a developed prototype in the laboratory. During simulation and testing, overvoltage, undervoltage, severe harmonics distortion, and dc offset in grid voltage, as well as insolation and temperature variations on PV array are considered. The total harmonic distortions in grid current, during the different complex disturbances and dynamic situations, are found very less, in comparison to the state-of-the-art techniques and IEEE-519 standard, as well as due to the HPO algorithm, the GMPPT time is very less, which shows the superiority over state-of-the-art techniques. [ABSTRACT FROM AUTHOR]

This study proposes a single‐stage solar photovoltaic energy conversion system (PV‐ECS) integrated to a three‐phase four‐wire (3P4W) distribution grid with dual‐function capabilities, i.e. active power transfer and power quality (PQ) enhancement at the point of interaction (PoI). The PV‐ECS system comprises of a solar photovoltaic array and a voltage source inverter (VSI), supplying active power (during daytime) to the distribution grid and connected single‐phase and three‐phase loads. Apart from transfer of power, the system also improves the PQ at the PoI by compensating reactive power and neutral current, attenuating harmonics, correcting power factor and balancing grid currents. During night, the VSI acts as a shunt active power filter mitigating PQ issues, thereby increasing the device utilisation factor. A three‐phase magnitude‐phase locked loop (3M‐PLL) method is utilised to extract and estimate fundamental term of load currents and an incremental conductance algorithm is applied for maximum power point tracking. To demonstrate its effectiveness, the system is modelled and its performance is simulated on MATLAB and experiments are performed on a developed prototype in the laboratory. [ABSTRACT FROM AUTHOR]

In this paper, an adaptable dual-mode single-stage solar photovoltaic (PV) tied to a three-phase voltage-weak distribution network is proposed using a multilayer perceptron (MLP) neural network control structure. The system operates in dual modes: First, it performs as a PV supplying active power with distributed static compensator (DSTATCOM) capability thereby improving power quality simultaneously; and second, it works as a DSTATCOM alone during unavailability of the solar PV generation. The system is adaptable as it continues to operate satisfactorily for voltage-weak distribution grid that has frequent voltage fluctuations and flickers. A single-stage converter based system is utilized here, which incorporates an incremental conductance based approach for maximum power point tracking and MLP neural network structure for the extraction of fundamental components of load currents. The main advantages of MLP are its simplicity, generic nature, and ease of implementation. The system and the control algorithm are validated by using MATLAB-based simulation results and test results are achieved on a laboratory prototype. [ABSTRACT FROM AUTHOR]

This paper deals with a control technique of a three-phase grid connected solar photovoltaic (SPV) system, which is based on the fast zero attracting normalized least mean fourth algorithm. This control algorithm achieves the objectives of mitigation of power quality issues such as harmonics reduction and power factor correction, together with extraction of peak power generated by the PV array. The system uses a PV array, a voltage-source converter (VSC), and linear and nonlinear loads. Here, VSC is connected to a PV array to transfer the active power to the three-phase load and the grid. The dependence on tuning of proportional-integral controller is reduced because of the feedforward term of the PV power. Due to this, the system dynamic response is improved, which makes the system quite robust. The system goals are to mitigate power quality problems and to provide current conditioning while operating in coherence with a weak distribution grid, which has poor quality of power in terms of voltage distortions with imbalances. MATLAB/Simulink is used to develop the model of the proposed system. The validation of proposed control is done at varying linear and nonlinear loads and under different environmental conditions on a prototype developed in the laboratory. [ABSTRACT FROM PUBLISHER]