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Summary: This paper presents a novel control scheme on AC/DC ring bus islanded microgrid under unbalanced and non‐linear loads. The DC bus is integrated with the fuel cell, one wind turbine, and two batteries. The DC bus can be divided into two sub‐sections, where the first zone is supported by the fuel cell and battery 1, and the second zone is installed with the wind turbine and battery 2. The AC bus is also able to be sectionalized into two sub‐sections where the diesel generator and the unbalanced load are located on the first section and the non‐linear load with one wind turbine are placed on the other section. The DC bus is connected to the AC bus through two parallel three‐phase lines each one configured by three single‐phase inverters. The proposed control scheme in the ringed and separated modes presents several contributions including balancing the unbalanced loads, compensating the harmonics of non‐linear loads, improving the voltage stability and sag/swells, enabling partial operation under outages, and enhancing resilience. In the ring mode, wind turbine 1 and diesel generator inject balanced and linear P‐Q powers to the system as 39 kW/6 kVAr and 7 kW/9 kVAr, respectively. In the separated mode, the P‐Q powers of wind turbine 1 are 36 kW/9 kVAr and they are 15 kW/9 kVAr for diesel generators. In both modes, the unbalanced and non‐linear powers are supplied by the DC bus. The results verify that the developed control strategy efficiently deals with harmonic components, unbalanced currents and voltage issues. [ABSTRACT FROM AUTHOR]

• Dynamic practical model of DC fast charging station is derived and used. • Steady-state and dynamic operations are studied under healthy-faulty conditions. • Charging station is integrated with distributed energy storage units. • Multi-layer control is designed for connecting charging station to grid. • Power and energy of station and electric vehicles are managed and optimized. In this paper, DC fast charging (DCFC) stations are integrated into the distribution network (DN). The designed DCFC stations are equipped with several charging devices (CDs) at different rated powers, which can charge electric vehicles (EVs) at various power levels through charging points (CPs). A central control system (CCS) is designed for each DCFC, which is applied for managing its local controllers. The CDs also use distributed energy storage (DES) alongside the DC chargers in order to increase the speed of the charging process and utilize the stored energy for improving the DN operation. The DN central controller scheme is as well designed to control the CCS of DCFCs and make positive effects on the upstream distribution grid. The CCS of DN, in addition to managing the CCS of DCFCs, is responsible for controlling the charge level of DCFCs according to four control strategies in each station including improving voltage fluctuations on the DN side, injecting reactive power from DCFCs to DN during a fault on the DN side, increasing DN resiliency by supplying critical loads in the time of upstream network outage, and supplying loads with time-varying active-reactive powers. The nonlinear simulations using MATLAB-SIMULINK demonstrate that the proposed strategies can effectively improve the performance of DN in addition to accurate control of the charging process in the EVs. [Display omitted] [ABSTRACT FROM AUTHOR]

This paper presents an integrated control framework for islanded DC microgrid (MG) with electric vehicle (EV) charging stations, energy storage unit, and AC/DC loads. The proposed DC MG consists of two DC buses with different voltages, photovoltaic (PV) arrays as intermittent power generation sources, energy storage, three EV charging stations, and a three-phase inverter to power time-varying three-phase loads. Control strategies are proposed to select the charge-discharge mode of EVs that does not negatively affect the MG, as well as coordinate the production and demand management. A central control system enables the operation of MG under different working conditions by managing generation, consumption, and energy storage and also monitors the performance of the charging/discharging unit and the issues relevant to commands of different charging/discharging programs. A specific control strategy has also been implemented to provide fault ride-through (FRT). As a result, the MG feeds its loads in any operating condition. Nonlinear simulations are carried out in MATLAB/SIMULINK software to show that the proposed control methods easily and effectively achieve all objectives, including supplying DC/AC loads, managing battery/resources/charging stations, and detecting/dealing with AC faults. [ABSTRACT FROM AUTHOR]

• Integrated system including DFIG, battery storage, TCR and TSC is implemented. • Set of TCR-TSC-DFIG is controlled to compensate voltage sag-swell. • Set of DFIG-battery is controlled to damp out oscillations and power regulation. • Proper control loop is designed to improve DFIG resilience under three-phase fault. • Set of TSC-TCR-battery balances the unbalanced time-varying load. This paper presents a novel control scheme in doubly-fed induction generators (DFIG) wind turbine for operation under time-varying unbalanced loads. The proposed control scheme is implemented on a DFIG connected to the external grid. Additional equipment such as battery, thyristor-controlled reactor (TCR) and thyristor-switched capacitor (TSC) are integrated to the DFIG. These devices are integrated to DC link, grid side and rotor side converters. The developed control scheme aims to achieve several purposes simultaneously including voltage compensation, damping fluctuations, regulating frequency, increasing resilience, and balancing the unbalanced time-varying loads. Each purpose is realized by designing a separated control loop on DFIG, battery and TCR-TSC. All the designated control loops are operated coordinately. The non-linear time-domain modelling and simulations are carried out in MATLAB software and demonstrate that the proposed multi-purpose control plan can optimally utilize set of DFIG/battery/TCR/TSC and achieve all the objectives efficiently. [ABSTRACT FROM AUTHOR]