A new hybrid global maximum power point (MPP) tracking (MPPT) method is introduced in this study by using an improved 0.8 V_OC model-based algorithm containing a smart power scanning procedure which is based on the sign of a change of photovoltaic (PV) module power. By courtesy of this procedure, the global MPP is determined effectively and within a small scanning time interval. The effectiveness of the proposed global MPPT algorithm has been validated by experimental studies. One of the buck-boost converter types, a single-ended primary inductance converter was implemented in this context. Experimental results show that tracking efficiency in the proposed algorithm is very satisfactory since blind scanning is prevented. Furthermore, it is presented in the experimental results that tracking efficiency is bigger in the proposed shading detection approach by up to 11.29% than the other technique which monitors voltage and current variations. In addition, there are no high software and hardware burdens which make this MPPT algorithm applicable especially in the smart alternating current module, module-integrated converters, PV power optimisers, and module level distributed MPPT applications.

Hybrid renewable energy systems (HRES) should be designed appropriately with an adequate combination of different renewable sources and various energy storage methods to overcome the problem of intermittency of renewable energy resources. A multi-criteria approach is proposed in this study to design an HRES including wind turbine, photovoltaic panels, fuel cell, electrolyser, hydrogen tank, and battery storage unit with an intermittent load. Three design criteria including loss of power supply probability, total energy loss (TEL), and the power difference between generation and storing capacity (as TELSUB) are taken into account in minimising the total cost of the system considering the interest rate and lifetime. The justifications and advantages of using these criteria are thoroughly discussed along with appropriate presentation of the results. The purpose of considering TEL and TELSUB is discussed thoroughly. The ɛ-constraint method is used to handle practical constraints of the proposed multi-criteria problem to construct a multi-objective fitness function. Shuffled frog leaping algorithm is implemented to achieve better optimal results. The proposed approach is implemented using real wind speed and solar irradiance data for a specific location with an intermittent load demand. The results verify performance of the proposed multi-criteria design procedure.

Increasing the wind energy penetration in a power system presents some technical challenges to the transmission expansion planning (TEP). In the first stage of TEP, the transmission bottlenecks should be determined and ranked via security assessment. The high penetration of wind energy means a large number of wind farms exist in various geographic areas. It is found that there is a correlation between the wind speed series of different farms. Therefore, integration of the correlated wind farms into security assessment is addressed in this study. Hence, a new model of wind speed prediction is presented based on the correlated autoregressive moving average time series. The copula functions are used to make the predefined correlation among wind speed series. Here a linear correlation using a Gaussian copula is implemented. Then, the risk-based security assessment is performed using the proposed sequential time simulation. The proposed process is applied to the modified IEEE 39-bus test system which comprises 15 wind farms. Then, the transmission bottlenecks are identified and ranked regarding their overload risks. Finally, the impacts of the wind farms correlation on the risk index are investigated and those contingencies which impose the highest influence on this risk are identified.

A model for calculation of the economic cross sections of cables within the internal network of a wind farm is presented. The economic cross sections of the internal wind farm cables provide maximisation of the profit generated by the wind farm within its life-span through an optimisation of the balance between the investment and operating costs. This study presents a practical mathematical model for determining the optimal cable cross section based on: the wind statistics at the wind turbine location, wind turbine power curve, price of the electric energy, price of the cable, and interest rate. By using the developed model in the planning phase of a wind farm project each of the connection feeders within the internal cable network can be optimised. The proposed model is demonstrated by the example of a perspective wind farm with a rated power of 25 MW located in the region of Banat, Serbia. The calculations done for the observed wind farm show that the optimisation of the interconnecting cable cross sections makes profit increase of nearly 1 million Euro, compared to the model for the calculation of cable cross sections based only on technical limitations.

The unpredictable nature of renewable power, coupled with the influx of prosumers has made accurate power forecasts in microgrids (MGs) more difficult to obtain. A direct consequence of this is the need for additional spinning reserve (SR) capacity to compensate for resulting power imbalances. Due to the economic and environmental concerns, increasing conventional generation to meet this additional SR capacity is undesirable. The aggregation of prosumer behind-the-meter resources for the provision of SR is proposed in this study, and a mathematical model for the proposed scheme is developed. This scheme is formulated as a constrained optimisation problem, whose solution maintains power supply and demand balance whilst reserving a virtual spinning capacity. The formulation is linearised and solved using the CPLEX 12.6.3 solver in the Advanced Interactive Multidimensional Modelling System environment. A 14-bus MG test system is used to validate the proposed scheme, and results show the benefits of using prosumer behind-the-meter resources to provide ancillary services like SR.

This study proposes a single-stage solar photovoltaic energy conversion system (PV-ECS) integrated to a three-phase four-wire (3P4W) distribution grid with dual-function capabilities, i.e. active power transfer and power quality (PQ) enhancement at the point of interaction (PoI). The PV-ECS system comprises of a solar photovoltaic array and a voltage source inverter (VSI), supplying active power (during daytime) to the distribution grid and connected single-phase and three-phase loads. Apart from transfer of power, the system also improves the PQ at the PoI by compensating reactive power and neutral current, attenuating harmonics, correcting power factor and balancing grid currents. During night, the VSI acts as a shunt active power filter mitigating PQ issues, thereby increasing the device utilisation factor. A three-phase magnitude-phase locked loop (3M-PLL) method is utilised to extract and estimate fundamental term of load currents and an incremental conductance algorithm is applied for maximum power point tracking. To demonstrate its effectiveness, the system is modelled and its performance is simulated on MATLAB and experiments are performed on a developed prototype in the laboratory.

Regarding the growing need for cheap and unlimited energy sources, renewable energies have been considered. Solar energy is one of the main sources of energy. This article studies the performance of floating solar chimney technology for the manufacturing purpose in Isfahan city. In this purpose, Isfahan city is considered to determine the performance of floating solar chimney power plant (SCPP) to build this type of SCPP. The results have shown that the floating solar chimney power plant can produce 5–200 MW of electrical energy in Isfahan city. Then a study is performed according to return of finance rate, net price value, and finance return period criteria. The results have shown that these power plants are able to be built in large scales of 100 and 200 MW of electricity with an annual capacity of 381 and 712 GW with 44 and 60%, respectively. However, a comparison between the cost analyses of two tested models shows that the 200 MW power plant with a cost of 13,941.52 milliard Rials is more beneficial in Isfahan city.‏

Increasing concern about the shortage of energy resources and harmful outcome of fossil fuel emission has initiated new requirement of reliable and cleaner green power sources. Hence, solar photovoltaic and wind power system are fastest developing sources among different renewable energy sources. In the proposed work, the urgency of the national policy to upgrade the existing coal-based plant as integrated solar, wind and coal-based power plant to reduce the carbon emission and to evaluate the feasibility of developing grid-connected hybrid energy system in Ramapuram Chennai, India has been presented. Moreover, the regression models for estimation of global solar radiation using different metrological parameters are developed and compared with the results of other models. In this work, Ramapuram, Chennai, India area is chosen to install the wind and solar photovoltaic systems to feed three types of load (residential, commercial and industrial). In this study, ENNORE thermal power station, Chennai is considered to reduce the carbon emission as the integration of solar photovoltaic system and wind system to the grid reduce the units generation from this plant. Hence, study shows that 110329.56 kg emission is reduced from ENNORE thermal power station by using this system.

This study proposes a combined control method based on vector control (VC) and virtual flux direct power control (VFDPC) for grid-side converter of doubly fed induction generator (DFIG)-based wind energy conversion systems (WECSs). VC gives lower power ripple with a slower dynamic response, while VFDPC provides a faster dynamic response, but higher power ripple. So, an analogy between VC and VFDPC is proved first and then used to propose a combined control method that takes the advantages of VC and VFDPC in an integrated control system. In the combined control method, the grid currents are directly controlled using hysteresis controllers and optimal switching table. It has several advantages compared to VC including faster power/current dynamic response, robustness to grid filter parameter variation, lower computation, and simple implementation. On the other hand, its advantages compared to VFDPC include less current harmonic distortion, lower power ripple, and robustness to measurement noise. To demonstrate the effectiveness and robustness of the combined control method, simulation results on a 1.5 MW DFIG-based WECS are provided and compared with both VC and VFDPC under different steady-state and transient conditions. The simulation results verify the superiority of the proposed method over either VC or VFDPC.

Harmonics and interharmonics adversely affect power grids. The fast Fourier transform (FFT) algorithm is one of the most commonly used methods for harmonic analysis. However, in practical applications, the accuracy of harmonic analysis can be seriously affected by fence effect and spectral leakage, which are undesired characteristics inherent to discrete Fourier transforms. Moreover, when non-synchronous sampling is carried out, the phase measurement is not accurate enough, and there is a large error in the identification of interharmonics. In order to improve the measurement precision, the method of all-phase spectrum analysis is used, since it has the characteristics of phase invariance and good spectral leakage suppression. A novel method based on improved Nuttall double-window all-phase FFT is proposed by improving the window function and the spectrum correction method for achieving higher precision. Through simulation and experimental verification, the proposed algorithm has proven to perform better than the traditional algorithms both for the detection of harmonics and interharmonics. In addition, the computation burden is not considerably increased when compared to such algorithms, which allows the on-line use of the proposed algorithm.

This study proposes a fractional-order control for a variable speed wind energy system equipped with a doubly-fed induction generator. The control scheme under study, which is applied to the generator-side converter, combines the feedback form of backstepping technique with two Takagi–Sugeno fuzzy systems in the fractional order. The resulting virtual and global control laws improve the system's robustness and tracking performance. Moreover, this allows getting rid of the requirements of the generator parameters knowledge, which is an initial condition to the conventional backstepping controller. This control system, with a fractional Lyapunov function, assures the global system stability, aims to attenuate the effect of external disturbances and the model uncertainties on the power transferred to the grid. The comparison of the simulation results between the proposed control technique and its integer-order counterpart confirms the efficiency of the fractional suggested approach.

This study presents a non-linear tip speed ratio (TSR) cascade controller for high power wind turbines (WTs) considering the effects of the large rotor inertia and torsional behaviour of the shafts. A model-based non-linear rotor speed controller is proposed for the inner loop. The required speed reference is provided by an outer loop. A design procedure for cascade control of WTs is based on a backstepping design. It is shown that the above two-loop control schemes lead to a nice cascade structure for the closed-loop systems. Stability result adapted for analysis of this particular kind of systems is developed. The effectiveness of the proposed control approach is evaluated on a WT by comparing with typical control strategies such as non-linear TSR control, optimal torque control, and sliding mode control. Simulation results show that the proposed two-loop controller exhibits better performance than the above typical control strategies.