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This paper investigates the design of robust distributed voltage and frequency control for a self-organized microgrid. A multiagent distributed secondary hierarchy is proposed using control Lyapunov function. Power resources are categorized as controllable and uncontrollable distributed generations (DG). Controllable DGs are exchanging information with neighbor DGs through agents at communication layer. The agents communicate to restore the voltage and frequency to their nominal references. Furthermore, the proposed scheme is robust against the insufficient data from uncontrollable DGs, since it provides an improved and stable operation even when there is no communication with uncontrollable DGs and loads. It can actively compensate for the random unknown demand and generation, by sharing the power mismatch in distributed droop architecture. It is shown that the suggested controller is capable of stabilizing an uncooperative microgrid in which not all DGs are cooperating. Also, the convergence speed of the system is improved using the finite-time controller. The performance and finite-time stability of a microgrid with partially-cooperative DGs is proved using Lyapunov theorem and is validated through numerical simulation. The results show improved transients, accurate steady state values for voltage and frequency control of a microgrid, and robustness against communication architecture variations. The impact of communication delays, the uncertainty in coupling gains of the communication links, and the time-interval between updating the controller and the states through communication are investigated. [ABSTRACT FROM AUTHOR]

Highlights: [•] This paper presents a new algorithm based on combining of the improved QPSO-NM algorithms for solving load flow problem. [•] The modification of both improved QPSO-NM method intends to obtain more accurate convergence and good search performance. [•] The proposed algorithm is tested on different IEEE test systems for a set of normal and critical operating conditions. [•] The test results are compared to the conventional NR algorithm, PSO and different versions of QPSO. [•] The numerical results reveal the superiority of the proposed approach for solving LF problems under different situations. [Copyright &y& Elsevier]

• Introducing a multi-objective model predictive control, with a complex cost function. • Improved control accuracy and added flexibility for load sharing between inverters. • Faster dynamic response (i.e., 12.5% higher) & lower switching frequency (i.e., 15%) compared to fastest in literature. • Minimizing microgrid grid injected current THD to 1.5% with average fs of 3 kHz. • Improved version of MOMPC to compensate the calculational delays. Integration of microgrids may introduce significant power quality challenges to the power distribution networks that may necessitate additional enforcement such as installing new Power Quality Improvement Devices (PQID), which is costly and not always possible option. This paper proposes a control approach that enables the existing power electronics devices within the microgrid to perform multiple functions to address the resultant power quality problems. The proposed method introduces flexibility in harmonic and fundamental power sharing and controlling switching frequency through an improved cost function. Grid connected operation-mode, harmonic compensation capabilities as well as improved dynamic response of controller to fast reference changes have been studied and experimentally verified on a microgrid prototype. Finally, the experimental results of the proposed control method are compared with the results from most recent relevant research activities in the field, evidencing its superiority as compared to the existing control methods presented in the literature. [ABSTRACT FROM AUTHOR]

Highlights • An advanced controller applied to multilevel converter. • An improved active power filter application. • Compensating Harmonics as well as linear load feeding. • Improved dynamic response behavior while having the previous controllers advantages. • Full Experimental results provided. Abstract Multifunctional DGs and active power filters have become a mature technology in recent years, so in this paper, an optimized current control method for a multilevel converter is proposed. The control method will overcome harmonic current tracking inefficiency of previous control methods in online harmonic compensation applications in microgrids. This control method is applicable for grid-connected inverter-based multi-functional Distributed Generation (DG) converters. It could also be used in active power filter applications which need high-speed reference tracking ability. Having the advantages of current control methods like hysteresis band control, proportional-integral (PI) and proportional-resonant (PR) control methods, the proposed approach overcomes disadvantages of these methods especially in harmonic reference tracking as it will be discussed in detail. The main advantages of this method are the simplicity of implementation, calculation delay compensation and its fast response to changes. The power electronic circuit, operating principles, two-horizon predicted switching states of multilevel inverter, experimental results and applications of this control method will be discussed in the paper. For studying the feasibility of the control method, an experimental prototype is tested in a microgrid platform. [ABSTRACT FROM AUTHOR]

• Modeling a residential hybrid energy system composed of various sources, storages and loads. • Dividing the uncertain parameters into two classifications and considering different risk levels. • Using both stochastic programming and robust optimization methods to model the uncertainties. • Analyzing the financial risks of system by robust and conditional value-at-risk approaches. Hybrid energy systems are developed recently due to their applicability in small scales. This paper presents a hybrid approach to optimize the operation and handle the uncertainties of a residential energy system composed of photovoltaic, fuel cell, boiler and storage units. In this regard, the uncertain parameters are divided into two categories including badly-behaved and well-behaved parameters and then, robust optimization and stochastic programming are utilized for modeling, respectively. As well, conditional value-at-risk is implemented to evaluate the risk of well-behaved parameters. According to the simulations, it is proved that badly-behaved uncertainties have higher impacts on system operation. Moreover, changing the control parameters of robust optimization and conditional value-at-risk from 0 to 24 and 0 to 1 increase the total cost by 5.2% and 0.47%, respectively. The comparative results also show that the proposed hybrid method takes less conservative decisions to optimize cost. [ABSTRACT FROM AUTHOR]

Recently, the application of multi-energy infrastructure has been widespread since the emergence of new technologies in this field. Accordingly, modeling and providing energy supply for consumers at an acceptable level of security is vital. It is also important for sustainable development in all directions to develop and support resources and infrastructures against natural disasters. In this study, the preventive maintenance scheduling of multi-energy microgrid is introduced to enhance the resiliency of system in unpredictable circumstances. The proposed formulation intends to make the best use of the profitable levels of freedom related to the maintenance and operational variables by considering the feasible operating region of components. By the use of sequential approach the near-optimal solutions in operation and maintenance schedule is obtained to meet the resiliency requirement. The exact model of electricity and natural gas is adopted to validate the simulation results. Three different cases is examined to prove the effectiveness of the proposed approach in standard multi-energy microgrid. According to the results, the utilization of the proposed method improves the resiliency of system in critical conditions. • This paper reschedule the maintenance program of multi-energy microgrid. • The exact interaction between different energy infrastructures is modeled. • The sequential approach is adopted to tackle with consequences of natural disasters. • Maintenance programming is mixed into the operation of the system. • The resiliency of the multi-energy microgrid is improved by 30% averagely. [ABSTRACT FROM AUTHOR]