Short-circuit Current Prediction Research Articles

STC Short-Circuit Current Prediction and I–V Simulation of Colored BIPV Modules With Machine Learning and One-Diode Equivalent Circuit Models

Colored photovoltaic (PV) modules offer improved aesthetics at the cost of electrical performance loss. Here, we demonstrate a hybrid approach combining experiments, machine learning, and equivalent-circuit model to predict and simulate <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I–V</i> parameters of colored crystalline-silicon PV modules. First, to predict the short-circuit current for different colors and opacity levels, three models—multiple linear regression (MLR), optimized support vector regression (SVR), and optimized Gaussian process regression (GPR)—are trained and evaluated with a ten-fold cross validation. The MLR model shows an MAE = 3.58 and an RMSE = 5.17. The accuracy could be further improved with the more advanced models, i.e., an optimized SVR (MAE = 0.22, RMSE = 0.24) or an optimized GPR (MAE = 0.13, RMSE = 0.17). Following, by taking the predicted short-circuit current values as inputs into a one-diode equivalent circuit model, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I–V</i> curves of two multicolored modules are simulated; and information such as module power <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">P</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mpp</sub> and current mismatch loss are extracted. There is a twofold advantage of implementing our approach: first, it serves as an efficient design space exploration methodology for a wide parameter space (e.g., colors), i.e., evaluating the PV performance for new colors without samples fabrication, thus saving time and resources; and second, it guides architects, designs, and engineers in color/design selection to achieve a balance between aesthetics and engineering considerations.

A Novel Machine Learning-Based Short-Circuit Current Prediction Method for Active Distribution Networks

The traditional mechanism models used in short-circuit current calculations have shortcomings in terms of accuracy and speed for distribution systems with inverter-interfaced distributed generators (IIDGs). Faced with this issue, this paper proposes a novel data-driven short-circuit current prediction method for active distribution systems. This method can be used to accurately predict the short-circuit current flowing through a specified measurement point when a fault occurs at any position in the distribution network. By analyzing the features related to the short-circuit current in active distribution networks, feature combination is introduced to reflect the short-circuit current. Specifically, the short-circuit current where IIDGs are not connected into the system is treated as the key feature. The accuracy and efficiency of the proposed method are verified using the IEEE 34-node test system. The requirement of the sample sizes for distribution systems of different scale is further analyzed by using the additional IEEE 13-node and 69-node test systems. The applicability of the proposed method in large-scale distribution network with high penetration of IIDGs is verified as well.

Subcell Modeling of Partially Shaded Photovoltaic Modules

Increased photovoltaic installations in densely built-up areas give rise to non-uniform irradiation causing partial shading. Non-uniform irradiation further leads to non-uniform temperature, leading to a reduction in output and the formation of deteriorating hotspots. A detailed model involving subcell level behavior is pivotal in understanding the impact of partial shading. In this paper, such a model is developed that analyzes the output of photovoltaic (PV) modules under different translucent and opaque shades while incorporating the diffused light effects. This model further includes the temperature variation of the module and also captures the bypass diode characteristics. The proposed model is experimentally validated for horizontal, vertical, slant, and patch shading patterns with varying shading intensities. This subcell model is shown to perform better than four existing methods of partial shading output prediction. It improves the output open-circuit voltage and short-circuit current prediction accuracy by more than 10% when compared with the average irradiance-based modeling approach, which is the best among the existing methods. Overall, an output prediction accuracy of more than 93% is achieved for opaque shading and more than 95% for translucent shading. As this paper provides the output of PV modules under partial shading, it finds direct application in partial shading detection, prevention of hotspots, and global maximum power point tracking, thereby enhancing their life and efficiency.

Investigation of irreversible demagnetisation in switched flux permanent magnet machines under short‐circuit conditions

The irreversible magnet demagnetization phenomena are investigated in this paper , under both healthy and short - circuit conditions for a switched flux permanent magnet (SFPM) machine. The temperature effects on permanent magnet material are taken into account and the influence of short - circuit current over demagnetization is evaluated. In order to calculate the short - circuit current (mainly inter - turn short - circuit), the MATLAB/Simulink model has been employed. The aforementioned short - circuit current is then fed to the finite element model, so the demagnetization analysis can be carried out. Variou s fault scenarios are investigated, including high speeds and high fault severity. It is found that the short - circuit current has li mited effect on the magnet demagnetization due to particular features of the SFPM machines. The mechanism of demagnetization has been revealed and found out to be mainly due to temperature rise and poor PM materials utilization . Experiments have been carried out to validate the MATLAB/Simulink model for short - circuit current predictions.

Comparative Study of Fault-Tolerant Switched-Flux Permanent-Magnet Machines

The fault-tolerant capabilities are compared in this paper for the conventional double-layer switched-flux permanent-magnet machine and its single-layer counterparts, i.e., C-core, E-core, and modular. The comparison includes the interturn short-circuit and irreversible demagnetization faults. A combination of Simulink and finite element models is used in the study. Based on the predictions, it is found that the modular topology produces the lowest short-circuit current and also has the best demagnetization withstand capability while the conventional one produces the highest short-circuit current and has the worst demagnetization withstand capability. The frozen permeability method is employed to separate the flux produced by armature current and magnets, and the results showed that, besides the influence of short-circuit current, the available magnet volume and magnetic circuit configuration play an important role in the demagnetization process. It is also found that removing half of the magnets, such as using C-core, E-core, and modular topologies, generally improves the demagnetization withstand capability and also increases the torque per magnet volume. Measured results are also presented to validate the short-circuit current predictions and magnet demagnetization.

Influence of Third Harmonic Back EMF on Modeling and Remediation of Winding Short Circuit in a Multiphase PM Machine With FSCWs

For multiphase open-winding permanent-magnet (PM) machines, both back electromotive force (EMF) and short-circuit current (SCC) contain third harmonic components that interact with each other and produce even-harmonic torque pulsation. This paper investigates the impact of the third harmonic component on SCC prediction, torque pulsation and postfault remediation method in case of a winding short-circuit fault. Analytical modeling of SCC is developed, which shows that the third harmonic SCC increases the maximum value of SCC. It is found that the transient SCC is heavily influenced by the initial phase angle of winding axis and exciting current when the fault is incepted. The braking torque due to the negative q -axis SCC component is investigated, which peaks at low speed as winding inductive impedance goes down. The comparison of two postfault remediation methods for single-phase short-circuit faults shows the importance of considering the third harmonics of SCC and back EMF in terms of torque performance. Finally, the theoretical results of SCC, braking torque, and remediation methods are verified and evaluated with experimental results.

Efficient output waveform evaluation of a CMOS inverter based on short‐circuit current prediction

AbstractA novel approach for obtaining the output waveform, the propagation delay and the short‐circuit power dissipation of a CMOS inverter is introduced. The output voltage is calculated by solving the circuit differential equation only for the conducting transistor while the effect of the short‐circuit current is considered as an additional charge, which has to be discharged through the conducting transistor causing a shift to the output waveform. The short‐circuit current as well as the corresponding discharging current are accurately predicted as functions of the required time shift of the output waveform. A program has been developed that implements the proposed method and the results prove that a significant speed improvement can be gained with a minor penalty in accuracy. Copyright © 2002 John Wiley &amp; Sons, Ltd.

Evaluation of Solar Cells by Means of Spectral Analysis

An approach toward testing of solar cells is outlined, and a test set and evaluation procedure of test results are described. Outer space short-circuit current is calculated from spectral response measurements performed on the cells. From this and additional measurements that determine the forward diode characteristic, the maximum obtainable power and the voltage at which maximum power is delivered are computed. The accuracy of outer space short-circuit current predictions is ±2 to 3 per cent when suitable standards are employed.