Calculation Of Transient Currents Research Articles

Analytical Calculation of Transient Current From an Inverter-Interfaced Renewable Energy

Short-circuit current analysis, especially transient current calculation, provides a basis for protection design. Because the control systems of inverter-interfaced renewable energy sources have a high degree of nonlinearity, it is difficult to analyze the transient current. To address this issue, in this work, a nonlinear differential equation of transient current of symmetrical fault is derived while considering the saturation characteristics of the current loop. Aiming at the solution of this nonlinear differential equation, an analysis method based on the phase plane is proposed, which makes use of the linear relationship between the current deviation and its derivative to simplify the direct determination of the nonlinear working state in the time domain. The analytical expression of the transient current can then be obtained by the inverse transform from the phase plane to the time domain. The proposed calculation method is verified by both simulations and field tests.

Development of accelerated methods for calculating the pattern of current spreading over the surface of spacecraft

High-energy charged plasma particles pose a danger to space technology. The accumulation of charged particles on the body of the spacecraft generates discharges. Electrostatic discharge is a source of powerful electromagnetic interference that adversely affects the functioning of individual parts and entire systems. According to statistics, in about 30% of cases, the loss of satellites is the consequence of discharges. Before the operation of spacecraft, it is necessary to calculate the spreading of currents, which requires large machine and time costs. The article proposes original approaches for quickly constructing a picture of the spreading of currents over the surface of a spacecraft due to electrification. The key point of the first approach is the construction of a limited area for calculating the flow spreading. The calculation of transient currents will only take place in the electromagnetic compatibility area specified by the user without affecting the rest of it. The paper also developed new simplified computational schemes for a system of differential equations based on the Euler methods. With the help of new computational schemes, the time for calculating unknown quantities in a local area specified by the user has been reduced by several orders of magnitude compared to the calculation of unknown full models. The article presents conclusions on new computational schemes, indicating the complexity of their construction. The adequacy and accuracy of the new computational scheme are confirmed by a practical example.

Fast algorithm for transient current through open quantum systems

Transient current calculation is essential to study the response time and capture the peak transient current for preventing meltdown of nanochips in nanoelectronics. Its calculation is known to be extremely time consuming with the best scaling $T{N}^{3}$ where $N$ is the dimension of the device and $T$ is the number of time steps. The dynamical response of the system is usually probed by sending a steplike pulse and monitoring its transient behavior. Here, we provide a fast algorithm to study the transient behavior due to the steplike pulse. This algorithm consists of two parts: algorithm I reduces the computational complexity to ${T}^{0}{N}^{3}$ for large systems as long as $T<N$; algorithm II employs the fast multipole technique and achieves scaling ${T}^{0}{N}^{3}$ whenever $T<{N}^{2}$ beyond which it becomes $T{log}_{2}N$ for even longer time. Hence it is of order $O(1)$ if $T<{N}^{2}$. Benchmark calculation has been done on graphene nanoribbons with $N={10}^{4}$ and $T={10}^{8}$. This algorithm allows us to tackle many large scale transient problems including magnetic tunneling junctions and ferroelectric tunneling junctions.

Avalanche multiplication properties of GaAs calculated from spatially transient ionisation coefficients

In this paper the high field phenomenon of avalanche multiplication in a GaAs p- i- n infrared detector is studied using a Monte-Carlo simulation. The Lucky-Drift model of impact ionization is used to give the characteristic lengths for transport through the device. The transport is then modelled by generating motion consistent with the probability functions derived from the mean free paths. This produces a spatially transient ionization coefficient for each carrier and allows the realistic statistical simulation of avalanche multiplication. Properties such as mean gain, multiplication noise and the transient response to a photonic pulse have been calculated and explained for a length of i-GaAs, with an emphasis on short active region phenomena. The effect on the ionization coefficients of a periodic field change has been investigated. It has been found that the effective carrier deadspace is approx. 1.35 times the absolute deadspace. The transient current calculations indicate the narrow bandwidth of this type of device. The presence of a periodic field change, caused by periodic δ-doping, was found to increase both electron and hole ionization coefficients by different proportions.

Calculation of transient currents at the neutral of three-phase power lines

A mathematical model appropriate for the calculation of transient neutral currents, when a single circuit three-phase transmission line is switched on, is presented. The practical condition or sequential pole switching of multi-switch circuit breakers is considered. The analysts is based on the Laplace transform concept, while the convolution theorem is used for the determination of original and deduced Laplace transforms. The earth return effect is accounted for which makes the line parameters frequency dependent. The proposed concept is applied successfully to the calculation of transient neutral currents at the sending end of a typical 500 kV, 500 km transmission line. The results obtained indicate that, in such cases, special protection should be considered.

Transient performance of D-C machinery — I

PREVIOUS STUDIES HAVE STRESSED the need for more accuracy in the calculation of transient currents than is provided by present methods. For the design of shipboard power systems, these methods are not sufficiently accurate and do not adequately reflect the influence of initial conditions of load, voltage, and speed on peak currents. There was also a disappointing lack of experimental verification of the important assumptions upon which the theoreticians were proceeding. Before developing a new approach or following a published calculation, it becomes evident that the limitations of any relations are determined by the validity and accuracy of the assumptions employed. It is concluded from this work that a more fundamental knowledge of the internal phenomena of rotating machinery is required before developing relations describing transient response of a d-c machine within design accuracy. Flux variations are fundamental to machine behavior in that they govern generated voltage, leakage fluxes, commutation, coefficients of induction, and eddy currents.