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.

On applying a minimization technique to the harmonic elimination PWM control: the bipolar waveform

Abstract: The well-known harmonic elimination pulse-width modulation (HE-PWM) method for inverter control is revisited. The HE-PWM waveform presents many challenges. It has multiple solutions that not only need to be found as easily and as fast as possible, but must also be evaluated in order to identify the best technique when overall harmonic performance is concerned. Algorithms presented so far rely on starting values that are close to the exact solutions to ensure convergence. A new method based on resultant theory promises limited success since it can only work when a small number of harmonics is to be eliminated. In this paper, it is shown that a minimization technique in combination with a random search results in a relatively simple approach that finds all possible sets of solutions. It is confirmed that numerous independent sets of solutions exist and the ones that offer better harmonic performance are identified. Three cases are reported in detail, including when two, four and six nontriplen odd harmonics are to be eliminated.

Recurrent Neural Networks Trained With Backpropagation Through Time Algorithm to Estimate Nonlinear Load Harmonic Currents

Abstract: Generation of harmonics and the existence of waveform pollution in power system networks are important problems facing the power utilities. The determination of harmonic currents injected into a power network by a nonlinear load is complicated when the supply voltage waveform to the load is distorted by other loads and not a pure sinusoid. This paper proposes a neural network solution to this problem. A recurrent neural network trained with the backpropagation through time training algorithm is used to find a way of distinguishing between the so-called load harmonics and supply harmonics, without disconnecting the load from the network. The advantage of this method is that only waveforms of voltages and currents have to be measured. This method is applicable for both single and three phase loads and could be fabricated into a commercial instrument that could be installed in substations of large customer loads, or used as a hand-held clip on instrument. This paper is particularly useful in determining whether the utility or the customer side has a higher contribution to harmonic pollution in a network. Hence, this method would be helpful in settling utility-customer disputes over who is responsible for harmonic pollution.

A harmonic bandwidth extension method for audio codecs

Abstract: Today's efficient audio codecs for low bitrate application scenarios often rely on parametric coding of the upper frequency band portion of a signal while the lower frequency band portion of the same is conveyed by a waveform preserving coding method. At the decoder, the upper frequency signal is approximated from the lower frequency data using the upper frequency band parameters. However, commonly used methods of bandwidth extension almost inevitably suffer from a sensation of unpleasant roughness, which is especially present for tonal music items. In this paper we expose the origin of the roughness and propose a bandwidth extension method, which does not introduce roughness into the reconstructed audio signal. A listening test demonstrates the advantage of the proposed method compared to a standard bandwidth extension.

Design and implementation of a modified Fourier analysis harmonic current computation technique for power active filters using DSPs

Abstract: The design and implementation of a harmonic current computation technique based on a modified Fourier analysis, suitable for active power filters incorporating DSPs is presented. The proposed technique is suitable for the monitoring and control of load current harmonics for real-time applications. The derivation of the basic equations based on the proposed technique and the system implementation using the Analogue Devices SHARC processor are presented. The steady state and dynamic performance of the system are evaluated for a range of loading conditions.