Estimation Of Short-circuit Current Research Articles

Online Stator Inter-Turn Short Circuit Estimation and Fault Management in Permanent Magnet Motors

This paper presents an online short circuit current amplitude estimation solution for permanent magnet synchronous motors (PMSM) with Inter-Turn Short Circuit (ITSC) fault in their stator winding. Short circuit current estimation amplitude is one of the most critical parameters while making critical decisions for the post-fault operations. Once the fault is detected, it is essential to control it to keep amplitude below rated current to prevent further winding degradation due to overheating. In this paper, a simplified ITSC fault model is developed for permanent magnet motors and integrated into the drive control for all permanent magnet motors. Based on the estimated amplitude of short circuit current, the speed reference is adjusted by an iterative scheme to bring short circuit current amplitude to a safe value. The adjusted speed reference defines the motor's Safe Operating Area (SOA) under ITSC fault. To test the efficacy and validity of the proposed method, experiments are conducted on lab prototype motors that have taps introduced in their stator windings to mimic ITSC faults.

Online Short-Circuit Current Estimation of Permanent Magnet Motors

In this article, online short-circuit estimation of permanent magnet synchronous motors (PMSMs) are presented, which is essential for postfault ac drive operations. For this purpose, initially, the PMSM model with interturn short-circuit fault (ITSC) is extended to cover motors with saliency. By utilizing ITSC model voltage equations and voltage reference equations, the amplitude and phase relationship between short-circuit current and the phase reference voltage is established. In the next step, second harmonics in the reference voltage and feedback current are used to extract the short-circuit current information. In order to efficiently use ac drive microcontroller bandwidth, the proposed short-circuit current estimation method is executed after the ITSC fault is detected, not continuously. Instead of running the proposed short-circuit current estimation continuously, it is reasonable to run it after an ITSC fault detection to efficiently use ac drive microcontroller bandwidth. Therefore, two intermediate steps, a simple ITSC fault detection and severity estimation algorithms are proposed as well. The proposed technique can estimate the fault current and severity without the knowledge of fault location and valid for all PM motors. The findings are experimentally tested using two PMSMs to demonstrate the effectiveness and practicability of the proposed estimation technique.

Online current-sensorless estimator for PV open circuit voltage and short circuit current

The suggested paper presents a new method for the estimation of short circuit current (Isc) and open-circuit voltage (Voc) of the photovoltaic (PV) system. Moreover, a modified relation of reverse saturation current (Is) is used to prevent the wrong estimation of Isc and Voc values at any point of the P-V curve. In addition, a new current-sensorless method of PV current estimation is used to further reduce the cost of the proposed technique. The accuracy of the proposed method is checked by testing on three different PV panels such as Yingli 245C-30b, Sharp NT-180U1, and Risen SYP-110S. Moreover, the fractional short circuit current (FSSC) and fractional open-circuit voltage (FOCV) algorithms are also implemented using the proposed and conventional analytical method and their results are compared with each other. The proposed method is validated in the Matlab/Simulink and hardware experimentation. The results of the proposed method indicate the following advantages: (1) accurate prediction of the Isc and Voc values at any point of the P-V curve, (2) interruption free output power during the Isc and Voc measurement, (3) accurate sensorless estimation of PV current, 4) no overshoot and undershoot in the tracked power of PV module, and 5) significant improvement in tracking efficiency by 38.33% for the FSSC algorithm and 28.2% for the FOCV algorithm, compared to the conventional analytical method.

Estimation of short-circuit current induced by ELF uniform electric fields in grounded humans with different body shapes based on a semi-ellipsoidal model

It has been reported that when a grounded human is exposed to an electric field at power frequency, a short-circuit current flowing from the feet to the ground is proportional to the square of his or her height. The current, however, should also vary with the body surface area, that is, body shape, even in people with the same height. In the present study, we confirmed this hypothesis using an analytical solution derived from a semi-ellipsoidal model. The short-circuit currents were calculated for various numerical human body models in which the horizontal length of a voxel was varied from 1.8 to 3.0 mm, and the results for different body shapes were compared. Finally, we derived an approximate expression for estimating the short-circuit current from the left-right width (2b), frontal thickness (2c), and height (a) of a human from the analytical solution. The short-circuit currents obtained from the approximate expression are consistent with those obtained from numerical calculations for 48 differently shaped human body models with a correlation coefficient of 0.9942. Hence, we concluded that the short-circuit current can be determined depending on the similarity ratio (a/b) and the ellipticity ratio (c/b) of the human body as well as the height. This finding is consistent with the numerical human body models that have been used previously, in which the similarity and ellipticity ratios were very close. Therefore, we can make the limited conclusion that the short-circuit current is proportional only to the square of the height. Additionally, numerical calculations showed that the short-circuit current is the same whether one foot or both feet are grounded.

An Approximate Short Circuit Strategy for Transient MPPT Performance of Uniformly Irradiated Photovoltaic Modules

This paper presents an improved strategy to provide better maximum power point tracking (MPPT) performance and increase energy yield during transient state of MPPT process. This strategy is based on the estimation of short circuit current (SCC) of the photovoltaic (PV) system without short circuit. Besides that, this strategy aims to decrease convergence time to maximum power point (MPP) by preventing real short circuit of PV source and eliminating the additional switch requirement. To determine performance of the proposed strategy, simulation studies have been performed in MATLAB/Simulink and this strategy has been compared with fractional SCC (FSCC) technique and perturb and observe (P&O) algorithm. In addition, to make validation experimentally, a low powered single ended primary inductance converter (SEPIC) is realized. Both simulation and experimental results show that proposed strategy performs better transient MPPT performance than FSCC technique and P&O algorithm.

A New Maximum Power Point Tracking (MPPT) Algorithm for Thermoelectric Generators with Reduced Voltage Sensors Count Control †

This paper proposes a new maximum power point tracking (MPPT) algorithm for thermoelectric generators (TEG). The new-presented method is based on implementing an indirect open circuit voltage detection and short circuit current estimation methods, which will be used to directly control the TEG interface power converter, resulting in reaching the maximum power point (MPP) in minimal number of steps. Two modes of operation are used in the proposed algorithm, namely the perturb and observe (P&O) method for fine-tuning and the transient mode for coarse tracking of the MPP during fast changes that occur to the temperature gradient across the structure. A novel voltage sensing technique as well is proposed in this work, to reduce the number of voltage sensors used to control and monitor the power converter. The proposed strategy employs a novel approach to sense two different voltages using the same voltage sensor. The input and output voltage information is collected from an intermediate point in the converter. The reconstructed voltages are used in the control loops as well as for monitoring the battery output or load voltages. Simulation and experimental results are provided to validate the effectiveness of the proposed algorithm and the sensing technique.

Design Considerations for Permanent Magnet Direct Drive Generators for Wind Energy Applications

Permanent Magnet Direct Drive (PMDD) generators offer very high force density, high efficiency and low number of components. Due to these advantages, PMDD generators are getting popular in the wind energy industry especially for offshore application. Presence of permanent magnets gives magnetic field for free but there are many design considerations which must be taken into account for a good design. The design considerations presented in this paper are rotor eccentricity, short circuit current estimation, voltage reflection at generator terminals due to high frequency switching and forces during magnet assembly. Simplified analytical methods which give quick results have been developed and then simulations have been performed to validate the analytical models. FEMM 4.0 which is a Finite Element (FE) solver was used for validation of various magnetic force models. MATLAB® Simulink was used for short circuit and voltage reflection validation. It was deduced that the analytical methods give good estimation of these effects and can thus be included at an early design stage.

Short-circuit current estimation from measurements of voltage and current during disturbances

Short-circuit current estimation from measurements of voltage and current during disturbances