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This paper presents a method for selecting pilot points used in secondary voltage control of active distribution networks. A unique formulation for pilot point selection is presented as a multi-objective stochastic optimization problem solved using differential evolution. The pilot point selection method considers multiple operating cases with different combinations of solar photovoltaic generation, loads, and electric vehicle uncertainties. The proposed methodology is applied to the IEEE 33 bus test system and a large Australian distribution feeder while observability, controllability, and robustness metrics are used to compare the proposed method against existing methods. Compared with the existing pilot point selection approaches, it is found that the proposed method obtains the most observable, controllable, and robust set of pilot points, making the method effective for the optimal selection of pilot points used in secondary voltage control of active distribution networks. [ABSTRACT FROM AUTHOR]

This paper proposes and implements a model-free optimal strategy to regulate the voltage in distribution systems by effective control of Inverter-Interfaced Distributed Energy Resources (I-DERs) output power. In distribution systems, where the ratio of R/X is considerable, reactive power control is not always an optimum solution for voltage regulation. With the aim of improving voltage regulation, this paper proposes an alternative method to optimally coordinate active and reactive power of I-DERs in the grid. The proposed method does not need to have a system model and phase measurement, which are barriers in control and operation of behind-the-meter assets. The paper formulates the problem of voltage regulation in form of equilibrium-map-with-optimum, without any restriction on system configuration, amount of reverse power flow and losses. Using the extremum seeking control technique and without an explicit model of distribution circuit, the ratio of active and reactive power is coordinated in real time. The amount of exchanged apparent power is also adjusted simultaneously. Simulation results for a typical distribution circuit verify the effectiveness of the proposed approach in improving the voltage regulation performance. The experimental results also show a 20 percent reduction in use of system capacity to provide the desired voltage regulation performance. [ABSTRACT FROM AUTHOR]

This paper presents a need-based distributed coordination strategy (NDCS) for multiple electric vehicle (EV) storages in an islanded commercial hybrid alternating-current (AC)/direct-current (DC) microgrid. The control capacity of the interlinking converter is enhanced by incorporating combined power-droop and voltage-droop strategies to leverage the coupling of AC and DC voltages. Therefore, the AC bus voltage can be regulated simultaneously by regulating only the DC bus voltage without affecting the power-sharing capabilities of the converter. The NDCS is proposed to coordinate the EV storages to regulate the DC bus voltage. The main objective of the NDCS is to decide whether the coordination of the available EV storages is to be done in a decentralised or a distributed manner. The mathematical model and the algorithm to deploy NDCS are developed to realise its application to a real system. The effectiveness of the control system is verified in a commercial hybrid AC/DC microgrid comprising one photovoltaic unit and four EV storages directly connected to the DC bus via DC/DC converters and four distributed-generation (DG) units connected to the AC bus using the conventional droop-control scheme. The performance of both controllers is tested under variable irradiation, commercial loading, and various fault conditions. The results of the case studies demonstrate the efficacy of the overall system in terms of robustness for a variable generation-demand scenario, time delay, EV plug-and-play, and fault conditions. [ABSTRACT FROM AUTHOR]

Distributed generation (DG) is one of the key components of the emerging microgrid concept that enables renewable energy integration in a distribution network. In DG unit operation, inverters play a vital role in interfacing energy sources with the grid utility. An effective interfacing can successfully be accomplished by operating inverters with effective control techniques. This paper reviews and categorises different control methods (voltage and primary) for improving microgrid power quality, stability and power sharing approaches. In addition, the specific characteristics of microgrids are summarised to distinguish from distribution network control. Moreover, various control approaches including inner-loop controls and primary controls are compared according to their relative advantages and disadvantages. Finally, future research trends for microgrid control are discussed pointing out the research opportunities. This review paper will be a good basis for researchers working in microgrids and for industry to implement the ongoing research improvement in real systems. [ABSTRACT FROM AUTHOR]

This paper presents a robust control design scheme for a multidistributed energy resource (DER) microgrid for power sharing in both interconnected and islanded modes. The scheme is proposed for micgrogrids consisting of photovoltaic (PV) units and wind turbine driven doubly fed induction generators (DFIGs). A battery is integrated with each of the wind and solar DER units. The control scheme has two levels: 1)one centralized multi-inputmulti-output robust controller for regulating the set reference active and reactive powers and 2)local real and reactive power droop controllers, one on each DER unit. The robust control scheme utilizes multivariable H_\infty control to design controllers that are robust to the changes in the network and system nonlinearities. The effectiveness of the proposed controller is demonstrated through large-disturbance simulations, with complete nonlinear models, on a test microgrid. It is found that the power sharing controllers provide excellent performance against large disturbances and load variations during islanding transients and interconnected operation. [ABSTRACT FROM PUBLISHER]