Configurations, coordinated controller design and applications of various off-grid systems with distributed energy resources (DERs) for an uninterrupted supply, are presented in this paper. The ...performances for the optimal operation of a diesel generator (DG) in the presence of nonlinear loads, fuel-savings, voltage and frequency regulation, a soft and secure transition among different operating modes, an optimization, and power management control, are validated through simulated results and test results on the prototype to demonstrate the suitability of these configurations with natural energy resources (NERs) for continuous development in remote as well as in isolated locations.
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This paper presents a novel single-phase grid-tied neutral-point-clamped (NPC) five-level converter (SPFLC). Unlike the literature on five-level NPC topologies, the proposed one is capable of ...inherently balancing the voltage of the DC-link split capacitors. For this purpose, a simple Multicarrier Phase Disposition (MPD) Pulse Width Modulation (PWM) technique is used, thus avoiding both complex modifications to the Space Vector Modulation (SVM) and offset voltage injections into the carrier based (CB) PWM, as commonly done in most conventional balancing algorithms. Bearing in mind that the proposed balancing strategy only requires measuring the capacitors’ voltages and the sign of the converter output current, it has a very low complexity. The developed strategy is not only straightforwardly implemented but is also very effective for obtaining symmetrical and undistorted voltage levels from the proposed multilevel converter, as well as for significantly improving the power quality of the SPFLC output voltage and, in turn, of the grid current. The simulation results obtained with MATLAB-SimPowerSystems as well as the experimental results obtained with the prototype built in the laboratory validate the topology of the proposed NPC five-level converter and the voltage balancing strategy, by showing a good performance under step-changes and exhaustive operating test conditions.
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Considering the poor power quality performance of a two-level capacitor-based electric spring (ES1), this article presents a high-power density multilevel ES1 configuration based on a seven-level ...modified packed U-cell converter (MPUC7-ES1). A novel control strategy based on finite control-set model predictive current control (FCS-MPCC) is also proposed for MPUC7-ES1 application. This algorithm is designed to predict the system behavior for all the conceivable switching vectors based on the discrete models of MPUC7-ES1 that is developed for the first time. To guarantee a desirable operation, the main control objectives are the MPUC7-ES1 current, auxiliary capacitors' voltages, and switching frequency reduction. Compared with the conventional ES1 control methods, the proposed strategy has key merits including considering the dynamic models of ES1 converter, not requiring a modulator, and lower switching frequency. The operation and robustness of MPUC7-ES1 and the introduced nonlinear FCS-MPCC technique are also illustrated through extensive simulation and experimental results.
This paper investigates the performance of two novel half-switching frequency signal injection (HSFSI) demodulation algorithms for encoderless field-oriented control (FOC) of permanent magnet ...synchronous machines (PMSMs) intended for electric vehicle (EV) propulsion. The proposed rotating and pulsating HSFSI demodulation algorithms do not require voltage measurements or approximations for estimating the rotor position angle. The proposed HSFSI algorithms have been quantitatively and qualitatively compared by MATLAB-SimPowerSystems simulations, as well as experimentally against the two equivalent classical high-frequency signal injection (HFSI) approaches. A 2.5 kW PMSM with radially inset rotor magnets has been used for experimentally evaluating and validating the performance analysis and the comparison of the four algorithms fully implemented to work in real-time on a TI C2000 digital signal processor (DSP). The results obtained with an 80 kW interior (I)-PMSM intended for EV propulsion also show that the proposed algorithms allow a better machine control performance in terms of a smaller torque ripple generation and a faster current control loop.
A hybrid system combines two or more energy sources as an integrated unit to generate electricity. The nature of the sources associated varies between renewable and/or non-renewable energies. Such ...systems are becoming popular as stand-alone power systems to provide electricity, especially in off grid remote areas where diesel generators act as primary energy source. Wind–diesel systems are among the preferred solutions for new installations, as well as the upgrade of existing ones. However, efforts to address technical challenges towards energy transformation for sustainable development are multiple. The use of energy storage systems is a solution to reduce energy costs and environmental impacts. Indeed, efficient and distributed storage not only allows the electricity grid greater flexibility in the face of demand variations and greater robustness thanks to the decentralization of energy sources, it also offers a solution to increase the use of intermittent renewables in the energy mix. Among different technologies for electrical energy storage, compressed air energy storage is proven to achieve high wind energy penetration and optimal operation of diesel generators. This paper presents a computer model for performance evaluation of a wind–diesel hybrid system with compressed air energy storage. The model has been validated by comparing the results of a wind–diesel case study against those obtained using HOMER software (National Renewable Energy Laboratory, Golden, CO, United States). Different operation modes of the hybrid system are then explored. The impact of hybridization on time and frequency of operation for each power source, fuel consumption and energy dissipation has been determined. Recommendations are made on the choice of key parameters for system optimization.
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Remote and isolated communities in Canada experience gaps in access to stable energy sources and must rely on diesel generators for heat and electricity. However, the cost and environmental impact ...resulting from the use of fossil fuels, especially in local energy production, heating, industrial processes and transportation are compelling reasons to support the development and deployment of renewable energy hybrid systems. This paper presents a computer model for economic analysis and risk assessment of a wind–diesel hybrid system with compressed air energy storage. The proposed model is developed from the point of view of the project investor and it includes technical, financial, risk and environmental analysis. Robustness is evaluated through sensitivity analysis. The model has been validated by comparing the results of a wind–diesel case study against those obtained using HOMER (National Renewable Energy Laboratory, Golden, CO, United States) and RETScreen (Natural Resources Canada, Government of Canada, Canada) software. The impact on economic performance of adding energy storage system in a wind–diesel hybrid system has been discussed. The obtained results demonstrate the feasibility of such hybrid system as a suitable power generator in terms of high net present value and internal rate of return, low cost of energy, as well as low risk assessment. In addition, the environmental impact is positive since less fuel is used.
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This paper presents the performance evaluation of a proposed single-phase bidirectional active neutral-point-clamped (ANPC) five-level converter (5LC) for active filtering in grid-to-vehicle (G2V), ...vehicle-to-grid (V2G) and vehicle-to-home (V2H) applications. In the system, the 5LC is series-connected with an electric vehicle battery charger based on a dual active half-bridge DC-DC converter (DAHBC). A cascaded strategy with a proportional-resonant compensator controls the 5LC whereas the DAHBC is controlled by a single phase-shift technique. A performance comparison is carried out for the proposed topology versus three NPC/ANPC 5L converters found in literature with similar topologies. The simulation results obtained in MATLAB-SimPowerSystems along with the experimental results obtained from a laboratory prototype validate the following: a) the first two literature topologies have the highest efficiencies, but they are incapable of balancing the voltage of the split-capacitors what increases the total harmonic distortion of both the grid current in the G2V/V2G modes and the 5LC output voltage in the V2H mode while producing a sluggish transient response, b) the 3rd literature topology like the proposed one properly balance the capacitors voltage and achieve a faster dynamics, but at the expense of an efficiency reduction, and c) unlike the former topology that continuously applies a natural but wasting unfedback voltage balancing strategy, the proposed one that includes a closed-loop control allows achieving an ANPC 5LC with a superior performance featured by a higher efficiency, a reduced switches stress, a flatter power losses distribution and a better power quality improving under the three modes of operation.
Massive penetration of plug-in electric vehicles (EVs) may create challenges in the near future for the distribution network. Moreover, this may lead to an increase of the transformers' aging rate ...and a reduction of the financial profits. In this paper, a novel approach is proposed, in which the operational margin of the transformer is optimized based on the transformer's internal characteristics, its loss of life, and the variation of the ambient temperature. This operational power limit should not be exceeded to guarantee that the loss of life of the transformer is equal to or less than the one provided by the manufacturer. For validation purposes, a comparative study between the conventional method and the suggested one is presented. This paper is applied to a parking lot for charging EVs, which is supplied by a distribution transformer. In contrary to the conventional method, the one suggested in this paper can guarantee a predefined transformer loss of life. Simulation results show that the proposed method increases the transformer lifetime, reduces the loss of life, and reduces its depreciation cost by 63% in certain conditions. In addition, it increases the financial profit for the parking lot's owner up to 10% during cold weather.
This article introduces a novel configuration of electric spring (ES) based on the modified five-level packed u-cell (MPUC5) inverter for mitigating harmonics and voltage fluctuations at various ...points of a grid with unstable generated power from distributed renewable energy sources. Immanent merits of the proposed configuration include, but are not limited to, halved dc-links voltages, boost mode operation, the possibility of higher power applications, smooth five-level voltage waveform with low total harmonic distortion (THD) index, the smaller size of output low-pass filter, and low switching frequency. The operation principles, design procedure, and configuration of the MPUC5-based ES (MPUC5-ES) are also presented. Besides, a simple and yet efficient controller without any extra control loop for regulating dc bus voltages has been proposed. Finally, the introduced multilevel ES is tested through extensive simulation and experimental studies to confirm its dynamic and steady-state performances in various operation modes in a weak grid fed by both conventional and intermittent renewable energy sources.
This paper presents a maximum power point tracking (MPPT) method for photovoltaic (PV) systems with reduced hardware setup. It is realized by calculating the instantaneous conductance and the ...junction conductance of the array. The first one is done using the array voltage and current, whereas the second one, which is a function of the array junction current, is estimated using an adaptive neuro-fuzzy (ANFIS) solar cell model. Knowing the difficulties of measuring solar radiation and cell temperature, since those require two extra sensors that will increase the hardware circuitry and measurement noise, an analytical model is proposed to estimate them with a denoising-based wavelet algorithm. The proposed MPPT technique helps to reduce the hardware setup using only one voltage sensor, while increases the array power efficiency and MPPT response time. The simulation and experimental results are provided to validate the MPPT algorithm operation as well as the climatic parameters estimation capabilities.
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