The demand for renewable energy-based Electric Vehicle (EV) charging infrastructure is increasing in recent years. Solar PV based EV charging method is preferred as it has simple energy harvesting ...technique. The PV system is an uncertain power source, where the power generation is varied with respect to the availability of sunlight. So, that the charging station requires a backup power supply for the uninterrupted charging. For the integrated power sources, the charging station requires a simple and efficient conversion unit for the DC/AC/DC conversion. In this work, a modified Z-source inverter (MZSI) is developed for the multiport EV charger using PV and grid. The proposed MZSI is connected between the input and output sides to boost the voltage as per the demand at the battery side. In order to connect many battery units with the charger, the capacitors used in the MZSI are split as per the required number of charging ports. This developed converter topology operates the systems in four different modes like PV-Grid, PV-battery, grid-battery, and battery-grid. The performance of this proposed work has been validated in MATLAB/Simulink® and in the experimental setup. The experimental setup has been developed with two charging ports for obtaining 250W at each charger end which cumulatively produces 500W output across both chargers with an efficiency of 90.18%.
Power systems networks are traditionally structured and engineered to effectively accommodate the effects of uncertainty and variability as regards energy demand and availability of resources. In ...order to transform the present carbon-intensive electricity generation system to one driven largely by clean energy sources, the inclusion of variable renewable energy sources (vRES) is becoming predominant. However, the inclusion of large vRES in the power plant mix increases the uncertainty, variability and consequently flexibility requirements on the power system network. The inclusion of cost effective and environment friendly flexible generators that can cancel the effects of uncertainty and variability is essential on power system networks with high levels of vRES. This study highlights flexibility as it relates to energy transition. It also provides direction for future research on the issues of flexibility in power systems planning.
► We implement particle swarm optimization (PSO) algorithm as a C-Mex S-function. ► We apply the PSO algorithm to optimize a 9-rule fuzzy logic controller for MPPT in grid-connected inverter. ► ...S-function based PSO algorithm can be easily applied for on-line controller tuning in real-time systems.
This paper presents implementation of particle swarm optimization (PSO) algorithm as a C-Mex S-function. The algorithm is used to optimize a 9-rule fuzzy logic controller (FLC) for maximum power point tracking (MPPT) in a grid-connected photovoltaic (PV) inverter. The FLC generates DC bus voltage reference for MPPT. A digital PI current control scheme in rotating dq-reference frame is used to regulate the DC bus voltage and reactive power. The proposed technique simplifies optimal controller design and ensures fast simulation speeds due to seamless integration with the simulation platform. Validity of the proposed method was verified using co-simulation in PSIM and MATLAB/Simulink. Simulation results show that the optimized FLC gives a better performance compared to fixed-step MPPT.
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•An improved Analytical SVPWM model to reducing CMV developed in this paper.•1st, the partial elimination of CMV with more voltage gain is achieved.•2nd, full elimination of CMV with ...more voltage gain with zero CMV is achieved.•The Proposed algorithms does not require any additional calculations to operate the inverter in the OVM.•The FPGA based hardware corroboration have shown the superiority of the proposed technique over the existing SVPWM schemes.
Multilevel inverters (MLIs) have an essential portion in industrial applications. Eventhough there are various elementary developments in MLI and its pulse width modulation (PWM) control strategies, unfortunately those strategies are least bothered about the common mode voltage (CMV). The CMV appears at the neutral point of the motor’s star connected stator windings with respect to the source ground. This study proposes PWM schemes for three level diode clamped multilevel inverter (DC-MLI) which use an unpretentious switching sequence to determine the triangle for maximum output voltage and minimum CMV in entire modulation range. Here two types of approaches are proposed: (i) Partial elimination SVPWM (PE-SVPWM) and (ii) Full elimination (FE-SVPWM). The proposed strategies suggest switching selection by using the control degree of freedom available in SVPWM without affecting the inverter output voltage. As a result, CMV reduction and elimination with maximum output voltage and better THD is achieved. The proposed PWM approaches can be extended for any number of levels. The theoretical study, the MATLAB/Simulink software based computer simulation and Field Programmable Gate Array (FPGA) SPARTAN-III-3AN-XC3S400 processor supported hardware corroboration have shown the superiority of the proposed technique over the existing SVPWM schemes.
► We evaluate capacity factor of some commercially available wind turbines. ► Wind speed in the sites studied can best be modelled using Weibull distribution. ► Site WM05 has the highest wind power ...potential while site WM02 has the lowest. ► More wind power can be harnessed during the day period compared to the night. ► Turbine K seems to be the best turbine for the coastal region of South Africa.
The operating curve parameters of a wind turbine should match the local wind regime optimally to ensure maximum exploitation of available energy in a mass of moving air. This paper provides estimates of the capacity factor of 20 commercially available wind turbines, based on the local wind characteristics of ten different sites located in the Western Cape region of South Africa. Ten-min average time series wind-speed data for a period of 1 year are used for the study. First, the wind distribution that best models the local wind regime of the sites is determined. This is based on root mean square error (RMSE) and coefficient of determination (R2) which are used to test goodness of fit. First, annual, seasonal, diurnal and peak period-capacity factor are estimated analytically. Then, the influence of turbine power curve parameters on the capacity factor is investigated. Some of the key results show that the wind distribution of the entire site can best be modelled statistically using the Weibull distribution. Site WM05 (Napier) presents the highest capacity factor for all the turbines. This indicates that this site has the highest wind power potential of all the available sites. Site WM02 (Calvinia) has the lowest capacity factor i.e. lowest wind power potential. This paper can assist in the planning and development of large-scale wind power-generating sites in South Africa.
•Optimization of Photovoltaic/micro-wind turbine energy systems with hydrogen and battery.•Techno-economic assessment of various Solar Photovoltaic sun tracking configurations.•Battery autonomy and ...hydrogen tank autonomy is considered.•Sensitivity evaluation of the feasible systems is considered.
The residential application of renewable energy is on the rise in sub-Saharan Africa with many of these systems using battery storage systems as back-ups; however, the adoption of hydrogen storage systems in household energy system applications has attracted few research attentions. Since the environmental impact attributed to hydrogen storage devices is small, it can serve as a complementary or alternative storage device. Using the hybrid optimisation model for electric renewables software, this study presents a techno-economic and sensitivity modelling of a solar photovoltaic (PV)/micro wind turbine/ fuel cell (FC) energy system backed up with both battery and hydrogen storage devices, under seven solar photovoltaic tracking orientations. Because of their strategic status in sub-Saharan Africa, one location each in South Africa and Nigeria were selected for the implementation of the study. The results show that the optimal energy system for the Nigerian scenario is a PV/FC/electrolyzer/battery/hydrogen storage system operated in the daily adjusted horizontal axis mode; the total net present cost and the cost of energy for this system is $9421 and $0.754/kWh respectively. As for the South African scenario, the optimal system is also a PV/FC/electrolyzer/battery/hydrogen storage system operated in the dual axis mode; its total net present cost and the cost of energy for the system is $8771 and $0.701/kWh respectively. Overall, the results show that the addition of a hydrogen storage system is technically feasible for most of the sun tracking configurations in both locations of study. Finally, the economic viability of hydrogen storage systems will be increased if the capital costs associated with the hydrogen sub-system is reduced.
•We simulated a power system with real life data from a power utility company in South Africa.•We used stationary wavelet transform (SWT) in filtering decaying DC offset in post fault measurements in ...power transmission line.•We extracted fault type and location information based on a determinant fault features (DFF) algorithm from a 1/4 cycle post fault record.•We used support vector regression (SVR) in estimating fault location on power transmission line.•The result shows that fault location can be estimated correctly irrespective of fault impedance.
This paper proposes a novel transmission line fault location scheme, combining stationary wavelet transform (SWT), determinant function feature (DFF), support vector machine (SVM) and support vector regression (SVR). Various types of faults at different locations, fault impedance and fault inception angles on a 400kV, 361.297km transmission line are investigated. The system only utilizes single-end measurements. DFF is used to extract distinctive fault features from 1/4 cycle of post fault signals after noise and the decaying DC offset have been eliminated by a filtering scheme based on SWT. A classifier (SVM) and regression (SVR) schemes are subsequently trained with features obtained from DFF. The scheme is then used in precise location of fault on the transmission line. The result shows that fault location on transmission lines can be determined rapidly and correctly irrespective of fault impedance.
Various techniques of fault diagnostics in oil-filled electrical equipment have been used in many years and are well documented in literature. The common techniques include; IEEE key gas, IEC 60599 ...gas ratios, Rodgers ratios, Doernenburg ratios and the Duval triangle. Among all the available techniques, Duval triangle remains the most accurate to date. This paper presents a new fault diagnostic method which combines fuzzy trapezoidal membership functions derived empirically after analyzing faults documented in literature and the evidential reasoning techniques. Like in Duval triangle, three gases; methane, acetylene and ethylene are used. First these gases are normalized against their sum. The normalized values are transformed into fuzzy trapezoidal membership functions whose outcome are synthesized into a particular fault type by the evidential reasoning technique. One hundred and seventeen fault cases visually inspected by experts and documented in IEC TC 10 databases are used for verification. This new technique is easy to understand, uses simple standard mathematical expressions and can easily identify simultaneous faults. Unlike Duval triangle where two or more faults lying at the same spot are not easily recognizable, the new technique identifies faults based on numerical values hence it does not have this drawback.
► We modelled a series compensated power transmission line. ► We instantiated all short circuit faults at various fault inception angle and fault resistance. ► We extracted fault signatures from the ...phase current and voltages using the energy of Wavelet Packet Decomposition at level 3. ► We used Support vector regression for fault location based on a half cycle post fault data.
This paper proposes a novel transmission line fault location scheme, combining wavelet packet decomposition (WPD) and support vector regression (SVR). Various types of faults at different locations, fault resistance and fault inception angles on a series compensated 400
kV–285.65
km power system transmission line are investigated. The system only utilizes a single-end measurements. WPD is used to extract distinctive fault features from 1/2 cycle of post fault signals after noises have been eliminated by a low pass filter, and SVR is trained with features obtained from WPD. After training, SVR was then used in precise location of fault on the transmission line. The result shows that fault location on transmission line can be determined rapidly and correctly irrespective of fault impedance.
Advancement in electrochemical micro-machining Bhattacharyya, B.; Munda, J.; Malapati, M.
International journal of machine tools & manufacture,
12/2004, Volume:
44, Issue:
15
Journal Article
Peer reviewed
Electrochemical micro-machining (EMM) appears to be very promising as a future micro-machining technique, since in many areas of applications it offers several advantages, which include higher ...machining rate, better precision and control, and a wide range of materials that can be machined. In this paper, a review is presented on current research, development and industrial practice in micro-ECM. This paper highlights the influence of various predominant factors of EMM such as controlled material removal, machining accuracy, power supply, design and development of microtool, role of inter-electrode gap and electrolyte, etc. EMM can be effectively used for high precision machining operations, that is, for accuracies of the order of ±1 μm on 50 μm. Some industrial applications of EMM have also been reported. Further research into EMM will open up many challenging opportunities of improvement towards greater machining accuracy, new materials machining and generation of complex shapes for effective utilization of ECM in the micro-machining domain.
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