Harmonic

About: Harmonic is a research topic. Over the lifetime, 44833 publications have been published within this topic receiving 495922 citations. The topic is also known as: overtone & partial.

A comparative study of dynamic analysis methods for structural topology optimization under harmonic force excitations

Abstract: This work is focused on the topology optimization related to harmonic responses for large-scale problems. A comparative study is made among mode displacement method (MDM), mode acceleration method (MAM) and full method (FM) to highlight their effectiveness. It is found that the MDM results in the unsatisfactory convergence due to the low accuracy of harmonic responses, while MAM and FM have a good accuracy and evidently favor the optimization convergence. Especially, the FM is of superiority in both accuracy and efficiency under the excitation at one specific frequency; MAM is preferable due to its balance between the computing efficiency and accuracy when multiple excitation frequencies are taken into account.

An analytical method for calculating harmonic currents of a three-phase diode-bridge rectifier with DC filter

Abstract: Commonly, three-phase diode bridge rectifiers with an LC filter at the DC side are often used to convert AC input into a DC voltage. It is well known that they generate large amounts of harmonic currents. This paper proposes an analytical method for calculating the harmonic currents for both the continuous and discontinuous current conductions. The equations for the harmonic currents are derived, taking into account the effects of the DC and AC side impedances. All the calculations are conducted only by algebraic calculation with high accuracy. The validity of the proposed method is demonstrated by comparison to the results of time simulation. >

Circulating Current Suppression of the Modular Multilevel Converter in a Double-Frequency Rotating Reference Frame

Abstract: The modular multilevel converter (MMC) has attracted significant interest for medium-/high-power energy conversion applications due to its modularity, scalability, and excellent harmonic performance. One of the technical challenges associated with the operation of the MMC is the circulation of double-frequency harmonic currents within its phase legs. This paper proposes a circulating current control strategy in a double-frequency rotating reference frame, which, contrary to the existing solutions that are based on approximate/inaccurate models, relies on an experimentally identified nonparametric model of circulating currents to determine the coefficients of the controller. Minimizing the squared second norm of the error between the open-loop transfer function of the system and a desired one, the coefficients of the controller are determined. To guarantee the stability of the closed-loop system, the minimization problem is subjected to a few constraints. The validity and effectiveness of the proposed control strategy is confirmed, and its dynamic performance is compared with that of an existing solution by experimental results.

A transformer of one-third wavelength in two sections - for a frequency and its first harmonic

Abstract: The quarter-wave transformer transforms in one frequency f/sub 0/, but not its first harmonic 2f/sub 0/. The transform in 2f/sub 0/ is needed in a dual-band operation of GSM and PCS. This requirement can be fulfilled in a two line-sections of 1/6 wavelengths each, adding to 1/3 wavelengths for the total transformer length in the lower band centering at f/sub 0/ (fundamental), or 2/3 wavelengths in the upper band centering at 2f/sub 0/ (1st harmonic). The 1/3-wave transformer is analytically inexact but effectively exact for engineering applications. For example, for impedance transforms of K = 4, the inexactness gives a reflection of |/spl Gamma/| = 0.013.