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This article presents a multiobjective control scheme for a bidirectional interlinking converter (ILC) of renewable energy based ac–dc hybrid microgrid. The prime focus of the power management algorithm is to feed the ac loads, and dc loads from ac source, and photovoltaic battery energy storage (BES), respectively. The second objective is to utilize the solar power to maximum capacity, by feeding it to dc load, BES, and ac load, in the given order of priority. The ac and dc subgrids operate independently, while supporting each other in case of overloading/underloading, thus reducing the amount of power reserve required in each, and eliminating the need of dump loads. The ANFIS-MN-based power quality control is integrated in order to ensure the total harmonics distortion of ac source current remains below 5% as per IEEE 519 standard, irrespective of the nature of load connected. In addition, the ILC control prevents any negative sequence currents from entering the ac source, even if there is any open circuit fault leading to unbalanced loading on the three phases. The performance of ANFIS-MN-based ILC control is demonstrated to be superior when compared with the conventional and contemporary techniques under different scenarios. [ABSTRACT FROM AUTHOR]

With increased penetration of renewable power and the nonlinear loads in the distributed generation (DG) systems, increased power quality concerns are exhibited in the active distribution networks, especially the challenges associated with the current and voltage harmonics in the system. Various conventional harmonic compensation techniques are developed for voltage-controlled DG inverters in past, majority involve either multiple proportional-integral (PI) or proportional-resonant (PR) controllers in eliminating grid current harmonics. The current-controlled inverters, on the other hand, are not preferred in industrial applications, accounting to their wide variations in the switching frequency. A novel and adaptive harmonic voltage control is developed here, for voltage-controlled DG inverters, which neither uses any PI regulators nor imposes stability issues associated with nonideal implementation of infinite gains of PR controllers. Interestingly, the developed control logic can be used for DG inverters, both in grid-connected and off-grid operational modes. Furthermore, this strategy allows a network operator to use this as an additional supplement that can be enabled/disabled as per the network requirement. The control logic exploits the property of an optimal-switching-vector controller, i.e., accurate output voltage tracking. Simulations results demonstrate the effectiveness of the controller, to suppress grid current harmonics and load voltage harmonics in grid-interfaced (GI) and off-grid modes, respectively, ultimately satisfying the mandatory IEEE standard-1547. Experimental results verify the viability of the controller for practical applications. [ABSTRACT FROM AUTHOR]

This article aims to develop a solar- battery energy storage (BES) based system, which ensures an uninterruptable supply to loads irrespective of availability of the grid. This system comprises of a solar photovoltaic (PV) array, a BES, the grid and local residential loads. A new control is implemented such that the active power demand of residential loads, is fed from the PV array, a BES unit and the utility grid. In this system, the power control operates in different power modes, which delivers the benefits to the end users with an integration of BES and an excess of PV array power, which is sold back to the grid. For this, an effective control logic is developed for the grid tied voltage source converter. Moreover, this system deals with the issue of an integrating power quality enhancement along with the power generation from the solar PV source. The cascaded delayed signal cancellation based phase locked loop is implemented for grid synchronization during the grid voltage distortion. The developed control is easily implemented in a real time controller (dSPACE-1202). Test results validate the performance of the implemented control in different operating conditions such as varying solar power generation, load variations and unavailability of the grid. [ABSTRACT FROM AUTHOR]

The dual active bridge (DAB) converters have the capability of handling high power in compact form and it is one of the key elements for interconnecting different dc microgrid clusters. A DAB also offers bidirectional power transfer with galvanic isolation between two power buses of similar or different voltage levels, i.e., low voltage and high voltage buses. In microgrid applications, bus voltage regulation is necessary for an uninterrupted power flow and reliable operation of dc microgrids. Due to the galvanic isolation and modularity nature of a DAB, the output can be easily interconnected for efficient and reliable power sharing. In this article, taking the advantage of modularity property of the DAB, an efficient and improved power sharing scheme is developed to stabilize the bus voltage in microgrid applications. A robust bidirectional power sharing control strategy is developed between DABs from different high voltage buses to low voltage buses that improves the voltage stability. An advanced supervisory controller is designed by considering the nonlinearity and uncertainty that ensures stable dc bus voltage and reliable power sharing among DABs under different operating conditions. The controller is validated theoretically and a small-scale laboratory prototype is developed. The concept is verified experimentally at different possible scenarios. From theoretical and experimental results, it is found that the proposed DAB control provides excellent performance in terms of power sharing, dc-bus voltage regulation and power quality. [ABSTRACT FROM AUTHOR]

This article proposes a standalone single stage photovoltaic (PV) fed reduced switch inverter (RSI) based permanent magnet synchronous motor (PMSM) drive for water pumping application. The proposed system aims at reducing the switching losses and overall cost by using reduced switch inverter. The proposed system comprises a PMSM drive, fed by PV source through an inverter employing reduced number of switches. The inverter uses only four switches whereas the conventional voltage source inverter utilizes six switches. Field oriented control scheme is employed to control the PMSM drive. Perturb and observe maximum power point tracking technique is used to generate a speed reference to PMSM drive. The proposed system is simulated using MATLAB/Simulink platform, and it is also experimentally verified with field programmable gate array (FPGA) controller based 400 W laboratory prototype PMSM drive. The simulation and experimental results demonstrate the efficacy of the proposed system. [ABSTRACT FROM AUTHOR]

In this work, a multifunctional control is implemented for a solar photovoltaic (PV) integrated battery energy storage (BES) system (PVBES), which operates both in the grid-connected mode (GCM) and a standalone mode (SAM). This system addresses the major issues of integrating power quality enhancement along with the solar PV generation. Thus, a multifunctional control of voltage source converter (VSC) is implemented to provide the load compensation, harmonics mitigation, unity power factor, and an automated transition between GCM and SAM in PVBES. A single VSC is used to control the active power and to maintain the power quality in this PVBES. Furthermore, due to an automated transition in the system, the local loads have continuous power irrespective of the grid accessibility. The main challenges addressed are the operation of an automated transition between GCM and SAM with the least disturbance to the nonlinear loads. The integration of a BES enables the SAM operation and improves the reliability of the PVBES. The charging and discharging of BES are controlled by using a dc–dc bidirectional converter. The performance of the implemented controls is tested using a real-time processor (dSPACE-1202) and validated through test results for steady state and dynamic conditions. In all operating conditions, the harmonics content of the grid current is maintained less than 5%, which follows the IEEE standard 519-2014. [ABSTRACT FROM AUTHOR]

Amongst the modulation techniques used for grid-tie inverters (GTIs), hysteresis current control (HCC) facilitates simple, stable and rugged control with improved dynamic response. However the variable switching frequency of HCC demands high precision AC current sensors (CS) which introduce noise in the power circuit in addition to measurement noise and delay. Therefore, this brief presents a hysteresis current control without AC current sensor based on switching instant computation for a two-level GTI. The proposed control strategy uses the DC link and instantaneous grid voltages to calculate the switching instants. The conventional methods of calculating switching instant of HCC can result in tracking errors. Hence the computations are modified in the proposed algorithm considering the effects of non-linearity in error current and dynamic variations due to supply and load changes. A single-phase GTI is simulated with the proposed control and the results are verified experimentally. The proposed method is observed to considerably reduce the computational time, DC shift and total harmonic distortion compared to the commonly used sensorless current control. [ABSTRACT FROM AUTHOR]

This article proposes a predictive optimal switching vector controlled virtual synchronous machine (VSM) for three-phase microgrid applications, which inherits self-synchronization and islanding detection technique within the controller. A novel synchronization signal is introduced here, to modify the frequency reference in VSMs. This integrates the synchronization and islanding detection within the control loop, thereby resulting in smooth system responses without causing stability issues associated with phase-locked loops. Moreover, it totally eliminates proportional–integral (PI) regulators in the system. The traditional pulsewidth modulation controllers use cascaded internal control loops, and they demand multiple PI regulators and synchronous coordinate transformations. They are associated with finite dynamic response time by PI regulators and necessitate rigorous tuning for practical implementation purposes. The proposed controller, however, estimates the behavior of output voltages and uses a minimization criterion to produce optimal inverter switching sequences. The voltage vectors that cause the overcurrents in the inverter are inherently avoided by the minimization function within the controller. The effectiveness of the proposed control strategy is verified through simulations and experiments validate the performance under different operating conditions. [ABSTRACT FROM AUTHOR]

This paper presents a step in microlevel photovoltaic (PV) summation technology for combining unsymmetrical PV modules with differences in specification and age, relocation on nonfertile land, or multilocation mounting by designing an add-on modular hardware interface to a multi-input single-output (MISO) dc bus, using an MISO controller employing a suitable maximum power point (MPP) tracker under partial shading/long distance/mismatching PV module conditions along with a sensor-less PV vector control inverter (PV–VCI) driving a three-phase asynchronous squirrel cage induction motor dedicated to irrigation, with the facility of autoconfiguration/autotuning at the beginning. A PV source gets automatically added/removed in a ramp profile in proportion to the load in steps, thus keeping on only when required, enabling high efficiency, minimum heating, and prolonged life as that of a PV module. The contribution includes a reduced PV energy cost per watt by 24.10%, improved return on investment by 27.48%, improved water discharge yield by 11.06%, and improved MPP tracker impact by 14.59% with 90.88% MISO system efficiency compared to a normal scheme. [ABSTRACT FROM AUTHOR]

This paper presents a multi-objective adaptive power management scheme for an autonomous dc microgrid which consists of a novel adaptive gain-based proportionate charging/discharging strategy in order to provide energy balancing between battery energy storage systems (BESSs) of different capacities. As BESSs are a key component to maintain reliability and stability in an autonomous microgrid, control measures for longevity of these units should be properly investigated. Following the recommended way of charging for BESSs, i.e., constant current/constant voltage (CV) charging, the conventional methods undergo mode switching using a floating reference value to control CV charging which does not guarantee zero current when the battery is fully charged. To account for this issue, a novel progressive de-rating control scheme for PV in a seamless fashion to carry out CV charging of BESSs is done using the adaptive mechanism introduced by model reference adaptive control scheme for optimized power management between sources and loads. Furthermore, emergency events such as load shedding and load following operation of PV have also been discussed in detail. The proposed control strategy is simulated in MATLAB/SIMULINK environment and tested on a 1 kVA FPGA-based experimental prototype to validate the control approach under different scenarios. [ABSTRACT FROM AUTHOR]

A robust controller design for the voltage control of an autonomous three-phase voltage source converter (VSC) is proposed. As compared with the conventional proportional plus integral (PI) controllers, fractional order controllers make the VSC system robust due to their fractional characteristics. The fractional PI $\lambda$ controller has an additional degree of freedom $\lambda$ along with $k_p$ and $k_i$ gains of the conventional PI controller. Detailed modeling of a VSC is used in the controller design process so as it include inner current control and filter dynamics. The outer fractional voltage controller is designed such that the VSC system satisfies a required phase margin, with improved robustness in the system and capability to attenuate the noise. The overall system stability is analyzed using both bode plot and step response, and these responses are compared with a conventional PI controller. Further, the dynamic performance of the fractional controller is evaluated by simulating the nonlinear system. A hardware prototype is also developed to demonstrate the practical realization of the controller. [ABSTRACT FROM AUTHOR]