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This article presents an enhanced power quality solar photovoltaic (PV) inverter enabling common-mode leakage current elimination. A three-phase transformerless solar energy conversion system is considered here, which, along with peak active-power production from PV array, ensures different power quality improvement capabilities such as grid current harmonics mitigation, grid currents balancing while also offering the grid reactive power support. Unlike conventional power quality inverters, this strategy is robust with respect to abnormalities in grid voltages at far radial ends, and does not compromise with the leakage currents caused by parasitic capacitance of PV array with ground. Common practice in the PV inverter power quality control is to neglect the PV leakage currents; however, they considerably affect the system performance by deteriorating the power quality and causing the safety issues of operating personnel. The standards VDE-00126 and NB/T-32004, therefore, compel the transformerless PV systems to operate with leakage current under 300 mA range. Various simulation and test results show the satisfactory performance of the presented strategy, even under various grid-side abnormalities. The comparative analysis with the state-of-the-art techniques shows the effectiveness of the strategy. Under all test conditions, the harmonics in grid currents are observed within limits as per the IEEE-519 and IEC-61727 standards, whereas the PV leakage currents are maintained well within the range recommended by VDE-00126 standard. [ABSTRACT FROM AUTHOR]

DC microgrids (DCMGs) are evolving into cyber-physical systems with advanced communication networks and computational methodologies, making them sensitive to cyber-attacks. These attacks can threaten the safe operation of a system. In this article, a virtual sensor-based framework is proposed for continuously monitoring and detecting malicious activities at the hardware level of a DCMG system. An adaptive state observer with a low computational burden is designed to estimate the voltage and current of a dc–dc converter. The proposed method considers the effects of cyber-attacks by injecting false data (FD) at targeted nodes in an attempt to affect the voltage regulation and current sharing by modifying the onboard voltage and current sensors. In the presented strategy, first, a DCMG is operated and controlled without any false data injecting attacks with different load conditions. Next, the DCMG is exposed to various cyber-attacks, and the output voltages and currents of dc–dc converters are estimated. Based on the error between the estimated and actual sensed signals, the cyber-attack is detected and corrected with the proposed framework. The proposed scheme is simple in design, efficient in operation, and easily implemented in a distributed control system. The effectiveness and robustness of the proposed method are illustrated by implementing it in real-time hardware using the LabView test bench by considering four dc systems (including a solar photovoltaic system) connected in a ringlike manner communicated via an ethernet-based local area network. [ABSTRACT FROM AUTHOR]

This study proposes a modified decentralised droop controller for inverter‐based autonomous photovoltaics (PV) microgrids to address the problem of instability and slower power sharing between PV inverters. The proposed controller modifies the conventional droop mechanism in transient as well as in steady state by adding an auxiliary control signal in the power control loop of the inverters. The proposed approach offers three key benefits, i.e. improves active power sharing, enhances system stability and performs the secondary control action by nullifying the frequency deviation by using only one auxiliary signal in the control loop. The accuracy of the proposed modified droop controller is verified with the help of time‐domain simulations in MATLAB/SIMULINK. The results obtained show that the controller is able to improve the power sharing and stability of the microgrid as well as to restore frequency. The performance of the proposed control scheme is also validated by experimental results and small‐signal analysis. [ABSTRACT FROM AUTHOR]

This work deals with an implementation of a unique control approach for the power quality enhancement in solar photovoltaic (PV) based grid interfaced system. In this work, a robust control technique with strong filtering capabilities is implemented. A single‐phase two‐stage grid interacted solar PV topology is considered with a second‐order sequence filter as a test system for the validation of the power quality enhancement features. The system constitutes a PV array, a boost converter, a DC link capacitance, a voltage source converter (VSC), an interfacing inductor and a ripple filter. A boost converter is used at a primary stage of proposed topology, which supports the extraction of maximum power from the solar PV array. In addition, the VSC feeds the solar PV power into the grid. It also provides harmonics elimination and power factor correction. A new maximum power point tracking technique avoiding a drift feature is adopted for the fast dynamic performance. The implementation of the solar PV system is performed and the harmonic profile of grid current is observed in compliance to the IEEE‐519 standard. [ABSTRACT FROM AUTHOR]

Partial shading is one of the certain conditions in photovoltaic (PV) power plants. Often the panels get partially shaded due to soiling, clouds, and trees. The effect of shading is of high concern and importance especially in applications such as water pumps due to agricultural environments in which they are employed in. However, the research focus on PV fed pumps till date has been restricted to only uniform shading conditions. Unlike uniform shading conditions during maximum power tracking, where the panel voltage remains almost constant for an entire range of irradiance, partial shading offer conditions such as highly variable panel voltage and transitions of intermediate DC–DC power converter from continuous conduction mode to discontinuous conduction mode. These effects severely affect the performance of the power converter and, therefore, the power output of the pump. This paper presents a study on the effects caused by partial shading conditions on pumps through simulations and verified by experimentations. The simulation and experimental results are found to be in good agreement with each other. This research thus helps in understanding the detrimental effects caused by partial shading conditions and thus serves as a reference tool for practitioners who wish to study PV fed pumps. [ABSTRACT FROM AUTHOR]

This study presents an optimal control operation of a photovoltaic‐battery based standalone microgrid, feeding non‐linear 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 study presents the fuzzy logic integrator gain-tuned improved second-order generalized integrator (GI) for a double-stage grid-interfaced photovoltaic (PV) system. The proposed system includes the functionalities of feeding active power to the grid, power factor correction, grid currents balancing and system isolation under grid side faults. Moreover, the smooth system operation is ensured under weak distribution grids where grid voltage is subject to huge diversions. Furthermore, automatic protection scheme for the system under grid-side faults is also established with the proposed algorithm for increased reliability. The fuzzy-tuned GI provides advantages of efficient and effective extraction of load current fundamental component under steady-state and dynamic grid conditions. The non-linear frequency error variation is compensated here using fuzzy logic-based self-tuning integrator gain of the controller. The controller is improved to mitigate the possible DC component in the load current. The neutral current in the loads is nullified by using a four wire system. The adaptive DC bus voltage helps to minimize the switching losses and prevents unexpected tripping of the PV inverter. The system is experimentally verified using a prototype built in the laboratory. [ABSTRACT FROM AUTHOR]

This study presents a novel handshaking approach to reduce transformer and line overloading using plug‐in electric vehicles (PEVs) connected to a photovoltaic (PV) assisted charging station (CS) via vehicle‐to‐grid (V2G) control strategy. The discharging behaviour of PEVs on receiving an aggregator command is carried out using a priority index function under two variant of customer command: (i) normal charging; and (ii) fast charging. Moreover, it is carried out to maximise aggregator profit in an optimal fashion by broadcasting to each CS and scheduling their dispatch based on the available power feedback from each CS. The energy command compliance for handshaking is ensured in a sturdy manner using a (N−1) contingency approach considering the uncertain mobile behaviour of PEVs. Owing to the highly unlikely travelling behaviour of PEVs, a novel distributed consensus‐based power restoration between a fleet of CSs is proposed to endure handshaking using average power contribution from the rest of the CS if (N−1) contingency fails for any CS. The proposed strategy has been tested on a 1 kVA FPGA‐based experimental setup to validate the proposed control scheme under different scenarios. [ABSTRACT FROM AUTHOR]

Eigenvalue analysis is a very essential technique for power system small‐signal stability (SSS) determination. Uncertainties in load/generation forecast are very common in power systems due to its geographical spread, size and complexity. These uncertainties can be divided into two types: (a) statistical (b) non‐statistical. It is observed from the literature that the effects of non‐statistical uncertainties in eigenvalue analysis are discussed comparatively less. In this study, a boundary eigenvalue analysis is developed based on boundary power flow to handle the non‐statistical uncertainties in loads and solar photovoltaic generation (SPVG) forecasts. First, mathematical model for evaluation of boundary of the critical eigenvalues for SSS analysis of dynamic power system (DPS) is developed. Then, the upper/lower boundary of a particular eigenvalue for a given range of uncertainties in load/SPVG at various buses is investigated. The boundary eigenvalue analysis predicts the worst‐case scenario for a given range of uncertainty in forecasted data which may help for secure operation of DPS. Second, Hopf bifurcations which may lead in highly stressed DPS is evaluated with increasing load/generation in the system in the presence of non‐statistical uncertainties. Results for two standard test systems are taken to demonstrate the potential of the proposed approach. [ABSTRACT FROM AUTHOR]

Unity power factor injection from single‐phase photovoltaics (PVs) located towards the end of a residential feeder leads to voltage rise problems. Also, unbalanced current injection due to variable solar insolation results in voltage unbalancing and makes the situation worst. A decoupled controller for a single‐phase PV inverter is proposed to improve the voltage profile of the distribution feeders. The proposed controller consists of the following components: voltage regulator (to control the amount of reactive power injection), outer voltage control loop (slow controller to set the reference for the inner current loop), inner current control loop (to control the PV inverters) and modified second‐order generalised integrator (to generate fundamental frequency). A sample distribution systems consisting of several PVs located in all three phases and a three‐phase induction motor load is considered. The real‐time hardware‐in‐the‐loop simulations are performed to test the efficacy of the proposed controller scheme. Results show the improvement in voltage regulation of different buses. [ABSTRACT FROM AUTHOR]

A control strategy is formulated for photovoltaic generators (PVG) operating in parallel in a Microgrid. A radial microgrid is considered and when it is isolated from the utility grid, the PVG's must operate in the voltage‐frequency control mode in the absence of a storage or a diesel generator unit. It is observed that the conventional P‐f and Q‐v droop control method fails to deliver correct power references for inverters operating in parallel when network impedance is unequal, and therefore an active power‐reactive power‐frequency‐derivative (PQFD) droop control is proposed to achieve an error free power sharing. Seamless operation from the grid connected mode to isolated mode and vice‐versa is achieved with the help of the aforementioned control, which in addition assists in the alleviation of sluggish response in the presence of Induction motor (IM) loads by providing appropriate damping. For a transient free transfer from isolated mode to grid connected mode, a synchronisation control is formulated which helps in the proper reconnection. The controller designed is tested in both Microgrid and the grid connected mode and during transition. The controller gains used in the paper have been obtained with the help of a small signal analysis of the system considered. [ABSTRACT FROM AUTHOR]

The diesel‐photovoltaic (PV) based hybrid AC microgrid systems with conventional control philosophies deliver very good performance in the grid connected mode. However, once the microgrid is isolated from the main grid the same philosophies which control the PV at its maximum power can make the microgrid unstable. In this connection, this study proposes a novel neuro‐fuzzy controller to ensure the smooth transition of microgrid from grid connected mode to isolated mode, to retain the system stability even in isolated mode and to deliver the superior performance in grid connected mode as well. The considered artificial neural networks is trained with PMPP–Temp against VMPP characteristic, first of its kind. The fuzzy part of the controller derives the reference voltages subjected to the limits provided by the ANN. This study describes how well the data analytics can be utilised to retain the power system stability in emergencies. The proposed controller has been evaluated under different operating conditions and is exhibiting superior performance in achieving the desired control objectives. Results from the numerical simulations are confirmed from the experiments in real‐time environment. [ABSTRACT FROM AUTHOR]

Sluggish tracking for change in solar irradiations is the main demerit of the perturb and observe (P&O) algorithm because of its fixed perturb. To overcome this, an adaptive tracking algorithm based on Takagi–Sugeno fuzzy implications is proposed in this study. Input to the fuzzy controller is the error between conductance and incremental conductance which is otherwise zero at the maximum power point. The P&O algorithm and the proposed algorithm along with the recently published adaptive incremental conductance algorithm are examined for their performance efficacy on a photovoltaic (PV) generating system with fabricated as well as real irradiation data. As a case study, all the considered algorithms are validated under partial shading conditions also. The effectiveness of the proposed algorithm is verified for the tracking of the maximum power point of a PV system in steady as well as changing irradiations and the conclusions are supported through some experimental validations. [ABSTRACT FROM AUTHOR]

This paper uses the recently proposed H∞-learning method, for updating the parameter of the radial basis function neural network (RBFNN) used as a control scheme for the unified power flow controller (UPFC) to improve the transient stability performance of a multimachine power system. The RBFNN uses a single neuron architecture whose input is proportional to the difference in error and the updating of its parameters is carried via a proportional value of the error. Also, the coefficients of the difference of error, error, and auxiliary signal used for improving damping performance are depicted by a genetic algorithm. The performance of the newly designed controller is evaluated in a four-machine power system subjected to different types of disturbances. The newly designed single-neuron RBFNN-based UPFC exhibits better damping performance compared to the conventional PID as well as the extended Kalman filter (EKF) updating-based RBFNN scheme, making the unstable cases stable. Its simple architecture reduces the computational burden, thereby making it attractive for real-time implementation. Also, all the machines are being equipped with the conventional power system stabilizer (PSS) to study the coordinated effect of UPFC and PSS in the system. [ABSTRACT FROM AUTHOR]

This paper proposes a systematic approach to enhance the performance of a 21‐level asymmetrical multilevel inverter (MLI) with less power electronics switches and DC voltage sources. In the first step (Configuration 1), the voltage level is improved at the cost of DC‐link voltage utilization. In the second step (Configuration 2), the ratio of the DC‐link voltages is modified to improve the utilization of DC‐link voltage, with an insignificant reduction of voltage levels as compared to Configuration 1. Finally, another modification of the MLI configuration is proposed (Configuration 3), by incorporating an H‐bridge in place of a T‐type module for further improvement of DC source utilization and increasing the number of voltage levels. Thus, Configuration 3 improves the inverter's total standing voltage (TSV) and efficiency. To reduce the number of DC sources, the output voltage levels are obtained in Configuration 3 by adding and subtracting the input DC sources. Moreover, conducting switches are reduced to minimize conduction loss and maximize efficiency. The DS1103‐based digital controller is used to verify the performance of the proposed configurations, which are compared with the literature‐based MLI models. [ABSTRACT FROM AUTHOR]

Summary: This paper deals with a sixth‐order generalized integrator for single phase grid interlinked solar photovoltaic generation system (PVGS). The objective of the proposed algorithm is to control the power transfer between the photovoltaic (PV) and grid and the load at unity power factor and load current harmonics compensation. The proposed PVGS works in 3 modes: (1) PV‐voltage source converter (VSC), (2) VSC as an active power filter (ie, solar power is zero), and (3) PV‐VSC without the load. The VSC is to inject the available active power from PV array to load and the grid, with auxiliary services such as harmonics compensation with high utilization factor. The sixth‐order generalized integrator structure provides fast response than a single second‐order generalized integrator with same harmonics attenuation. The effectiveness of the control algorithm of PVGS under different modes and environmental conditions is validated by using the simulation and experimental results. [ABSTRACT FROM AUTHOR]