This work deals with the frequency regulation, voltage regulation, power management and load levelling of solar photovoltaic (PV)-battery-hydro based microgrid (MG). In this MG, the battery capacity is reduced as compared to a system, where the battery is directly connected to the DC bus of the voltage source converter (VSC). A bidirectional DC–DC converter connects the battery to the DC bus and it controls the charging and discharging current of the battery. It also regulates the DC bus voltage of VSC, frequency and voltage of MG. The proposed system manages the power flow of different sources like hydro and solar PV array. However, the load levelling is managed through the battery. The battery with VSC absorbs the sudden load changes, resulting in rapid regulation of DC link voltage, frequency and voltage of MG. Therefore, the system voltage and frequency regulation allows the active power balance along with the auxiliary services such as reactive power support, source current harmonics mitigation and voltage harmonics reduction at the point of common interconnection. The experimental results under various steady state and dynamic conditions, exhibit the excellent performance of the proposed system and validate the design and control of proposed MG.

Renewable energy (RnE) is a key element for the national energy strategies in the world especially for emerging and developing countries. Morocco, which has no conventional energy resources, depends almost entirely on the international primary energy market, to satisfy its growing demand inherent to its economic growth and its demographic progression, the country import the majority for its supply of energy sources. Morocco has implemented an important energy strategy that supports the country's transition to RnE and energy efficiency that generalises across all consumer sectors of the economy (housing, transport, industry). However, the integration of renewables into power systems and the development of adequate reserve capacity are seem to be significant for these strategies in particular in the wind power case. This study presents the impact of the smoothing effect on reserve capacity and energy savings available through the net balancing between different climate zones to achieve fuel cost savings and reduce CO₂ emissions.

This study describes a novel strategy for microgrid operation and control, which enables a seamless transition from grid connected mode to islanded mode, and restoration of utility supply, without loss or disruption to loads sensitive to frequency or phase angle dynamics. A simulation study is conducted on a microgrid featuring inverter connected renewable generation, and power electronic interfaced loads. Therefore, the microgrid inherently has low inertia, which would subsequently affect the dynamic characteristics of the microgrid, in particular during mode transition. The microgrid is controlled by means of synchrophasor data to achieve synchronous island operation, enabling the microgrid to track the utility frequency and phase angle. The simulation includes synchrophasor acquisition and telecoms delays, allowing for detailed investigation of the microgrid dynamics under various mode transition scenarios, including the risk of commutation failure of the inverter sources. The proposed method is demonstrated to successfully maintain a microgrid in synchronism with the main utility grid after the transition to islanded mode without significant impact on various equipment connected to the microgrid. Thus, synchronous island operation of low inertia microgrids is feasible. This study also showed that utility supply could be seamlessly restored if the microgrid is operated as a synchronous island.

This study deals with a fault-tolerant control (FTC) strategy for a marine current energy conversion system based on a five-phase permanent magnet synchronous generator. First, a finite control set-model predictive control is adopted to highlight the advantages of this kind of generator in normal mode. The speed tracking performance is evaluated when the system operates under swell effect. Second, its fault tolerance is evaluated under various open-circuit fault conditions. In this case, the reference currents are reconfigured online to achieve the reference torque while minimising the copper losses. Extensive simulations, based on real-tidal speed data measured at the Raz-de-Sein site in Bretagne, France, are carried out for the validation of the proposed FTC strategy.

Based on the Z-source inverter (ZSI), a unified control strategy of grid-connected photovoltaic (PV) system is investigated. It can both compensate the reactive power and restrain the current harmonics. At first, the principle of the proposed unified control is analysed. Then, the space vector pulse width modulation (SVPWM) is improved for inserting the shoot-through time into the modulation period. Simulation results show that the proposed unified control strategy is feasible and effective. Besides, a hardware controller is designed based on the digital signal processor (DSP). The corresponding approach for applying the improved SVPWM with the DSP and the driver circuit is illustrated in detail. Eventually, an experiment apparatus is implemented. Experiment results reveal that the proposed unified control strategy can effectively regulate active and reactive power generated by the grid-connected PV system. Besides, the fifth current harmonic of grid can be restrained effectively, the total harmonic distortion of the grid current decreases from 20.9 to 8.1%, which indicates that the restraint of the current harmonics is feasible for the proposed unified control strategy.

DC bus voltage in islanded DC microgrids (MGs) is prone to power fluctuations of sources and loads. This is due to the lack of generational inertia, which is caused by high penetration of converter-based renewable energy sources (RESs). With the growing penetration of RESs, especially photovoltaic arrays (PVAs), they are required to provide grid support services such as inertial response in a similar way to conventional synchronous generators. Here, a virtual inertia control (VIC) is proposed for PVAs to enhance the inertia of a hybrid PVA-battery DC MG. The proposed VIC employs active power control of PVAs to provide virtual inertial response (VIR) without using any high-power energy storage system such as supercapacitors. An adaptive virtual inertia gain is introduced to achieve dynamic power sharing between the PVAs that provide VIR. Impedance-base stability analysis is utilised to study the impact of the virtual inertia gain on the system stability and to show the impact of the proposed VIC on improving the stability margin of the DC MG in the presence of destabilising constant power loads (CPLs). Finally, simulation results are presented to verify the effectiveness of the proposed method in dynamic performance and damping enhancement of the DC MG and reducing the high-current stress on the battery.

Three-phase seven-level cascaded DC-link converter (CDCLC) is proposed for solar photovoltaic (PV) applications. The proposed configuration is integrated with stepped DC-link module (DCLM) and H-bridge inverter. In CDCLC configuration, the stepped DC-link voltage is attained through DCLMs with reduced inverter voltage stress. Compared with conventional two-level and three-level inverters, power spectral density in the multiples of switching frequency is significantly reduced. Elimination of inverter end filter components emphasises the advantage of CDCLC systems over conventional inverters. A reduction in DC sources, power switches, and gate driver units make the system more cost-effective over conventional cascaded multilevel inverter. To achieve the quality of power output in the proposed converter, carrier level shifted pulse width modulation (CLSPWM) schemes are developed for the DC-link converter switching. Simulated and experimental models of three-phase seven-level CDCLC configuration are developed and its performance is analysed for CLSPWM switching schemes.

The goal of this study is to develop units of a photovoltaic (PV) cooling system and evaluate its performance, aiming at commercial electricity production, once the increase in electricity output is obtained by cooling down the temperature of the PV module. The methodology covers the description of production procedures, control and verification of three different models of the cooling system, of which two are sheet-and-tube types, with different diameters of coil curvature (85 and 140 mm), and one is a multi-channel type model. Results show that the production of the two sheet-and-tube models presented no issues during their construction and operating phases, while the multiple-channel model presented some complications at the construction phase (e.g. the thickness of the sheets hampered the welding process, leading to leakages during the tightness tests). The empirical control tests showed that the temperature of the PV module with a cooling system applied remains lower than the nominal operating cell temperature, whereas the PV modules without a cooling system presented temperatures higher than 68.1°C. Thus, the authors conclude that the most appropriate model for large-scale production applied at PV systems is the coil one, with 85 mm of the diameter of coil curvature.

Accidental disconnection of a live feeder section is a major concern accompanying large distributed solar photovoltaic (PV) generation integration. High localised penetration can alter power flows leading to anomalous occurrences. Load-inverter power balance during grid-side disturbances, for different load models, may cause unique situations that can trigger the interconnection point protective devices. One such phenomenon, identified as a potential cause of unintentional islanding on radial feeder models (a modified IEEE feeder in simulation and verified on a laboratory-hardware network), has been used in this work. A pre-emptive detection strategy has been implemented to identify such islanding initiators among other power system transients. Computational geometry concepts have been utilised to create an optimisation-derived feature extraction methodology for effective training of a classifier module realised in a Raspberry Pi microcomputer. This module predicts the class labels of test data points transmitted from simulations carried on a personal computer for the feeder model. The proposed pre-emptive islanding detection strategy can trigger an appropriate change in a PV inverter's operating mode before a feeder protective device is tripped by such island initiating anomalies. The online classification accuracy and speed indicate a possible integration of the proposed methodology and strategy with the inverter's control circuitry.

Here, a hybrid fast damping control strategy based on bang–bang modulation is proposed for doubly fed induction generators (DFIGs) against inter-area oscillations. Since the changes in active power modulation of DFIG may result in its interactive effect with torsional oscillations, this study relies on the modulation of DFIG reactive power to rapidly attenuate the system's critical oscillation mode. In order to overcome the buffeting of the bang–bang modulation, the proposed control strategy is designed as a hybrid scheme consisting of three operating modes which are switched based on the amplitude of the detected critical oscillation mode. The required lead phase for the proposed control strategy is determined using frequency domain analysis using detailed dynamic model of the DFIG. A comprehensive test is carried out by conducting simulation studies on a modified two-area system including an aggregated wind farm. It has been shown that the proposed strategy damps inter-area oscillations much quicker than the conventional continuous damping controller. Simulation results also showed that the control scheme is robust to the operation point variation and identification errors for practical application.

A procedure based on genetic algorithm (GA) has been formulated for the performance predetermination of wind-driven self-excited induction generators (SEIGs) operating in parallel and supplying common loads. Both static and induction motor (IM) loads have been considered. The GA technique has also been applied for the evaluation of the excitation capacitor required for obtaining a desired terminal voltage for a given speed and load. This technique is also used for the predetermination of the upper and lower limits of the rotor speed of any SEIG in the parallel set up, to keep all the machines in the generating mode. The necessity of the terminal voltage equality of all the parallel operating machines serves as one of the factors in the formation and minimisation of the objective function, leading to the solution for the unknown magnetising reactances and core loss resistances of the various induction machines and the common frequency of operation of the set-up. Experimental results obtained on the SEIGs have been furnished and they are shown to be in close agreement with predetermined values using the GA method. The analysis developed herein will be useful in forming AC and DC microgrids, fed by several SEIGs.

Energy storage using electrochemical battery systems has been widely addressed as a key element to enable widespread integration of renewable energy. Here, an updated battery model is investigated in order to allow accurate standalone photovoltaic (PV) systems simulation, for performance assessment and long-term energy prediction. Battery models have been largely described in the literature. However, this study reviews the most commonly used models in PV application such as Shepherd, Manegon, and Coppetti models in order to validate the suitable mathematical model. The updated battery model based on experimental results and parameter extraction procedure is carried out using sealed gelled lead/acid battery during charge and discharge processes. A comparative analysis based on statistical tests and optimisation method confirms the effectiveness of the most accurate model among the three models using new proposed parameters. The simulation results of the model with new coefficients are compared with measured data, recorded from battery charge and discharge test bench to validate the accuracy of the updated model.

One of the main challenges of the microgrid (MG) operation in autonomous mode is the uncertain output due to the fluctuating nature of renewable energy resources (RES). This study investigates the effects of RES uncertainties to the oscillatory stability of a hybrid MG in islanded operation. A comprehensive model of Wind Energy Conversion System (WECS), a two-stage Photovoltaic (PV) and bio--diesel engine (BDE) based distributed generation (DG) units are considered to capture a complete dynamic response of the hybrid MG. Trajectories and distribution of damping ratios and oscillatory frequencies of the critical modes were thoroughly investigated through Monte Carlo simulation considering wind speed and solar irradiance uncertainties. From the probabilistic study, it was observed that the presence of RES variations results in a dynamic change of power-sharing strategies and introduce an adverse effect on small signal stability. Uncertain condition of wind speed brings more deterioration in system damping than solar irradiation variation. From time domain simulation, it was confirmed that at higher wind speed, damping on the critical modes reduced. As a consequence, the hybrid MG experienced more oscillatory conditions and even lead to unstable situation at high wind speed conditions. While with solar irradiance change, the investigated MG system can maintain its stable operation.