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A fully distributed hierarchical control strategy for multiple inverters‐based AC microgrid is proposed. The developed controller provides real‐time economic dispatch along with the network frequency and average voltage restoration. The controllers cooperate with neighbours using sparse communication network and perform local computations to achieve the assigned objectives. The economic dispatch control unit is embedded with the frequency restoration at the secondary level controller to change the active power supply from the inverter. The voltage controller along with reactive power controller ensures the proportional reactive power sharing as well as network average voltage regulation. The average voltage regulation aids the individual inverter to provide required reactive power demand, with a small, comprise at the terminal output voltages from the nominal values. The convergence of the proposed controller is proved using the Lyapunov stability criteria. The maximum allowable communication delay that obligate stable microgrid operation is derived. The simulation results verify the efficacy of the proposed controller. Experimental validation is also presented, and the controller ability to ride through communication failure and load perturbation condition is demonstrated. [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]

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]

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]

This study proposes a grid supportive control scheme for a single‐phase photo‐voltaic (PV)‐based inverter to mimic the behaviour of a synchronous generator during grid voltage/frequency variations. The converter embedded with the proposed controller, termed as a 'single‐phase synchronverter', transforms a large segment of rooftop PV, which is, in general, single phase, to an ancillary service provider in compliance with the grid code (i.e. if the grid code allows rooftop PV to provide inertial/primary frequency/voltage response). Owing to fluctuations in incident solar irradiation, a battery has been connected at the dc link to take care of the variability in PV output power. The challenges involved in extending the three‐phase synchronverter philosophy to a single‐phase converter have been discussed and the performance of the resultant single‐phase synchronverter to different values of virtual inertia and droop/regulation has been analysed. An experimental setup is developed and the system behaviour for different operating conditions has also been studied. [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]