Voltage-controlled filter

About: Voltage-controlled filter is a research topic. Over the lifetime, 5514 publications have been published within this topic receiving 70872 citations. The topic is also known as: VCF.

New universal filter using two current-feedback amplifiers

Abstract: A new universal voltage-mode second-order filter circuit is presented. The circuit has three inputs and one-low-impedance output and can realize all the standard filter functions; lowpass, highpass, bandpass, notch and allpass, without changing the passive elements. The proposed circuit uses only five passive components and enjoys independent control of the natural frequency and the bandwidth, and orthogonal control of the natural frequency and the quality factor as well as low active and passive sensitivities.

Reconfigurable Fractional-Order Filter with Electronically Controllable Slope of Attenuation, Pole Frequency and Type of Approximation

Abstract: This paper presents design of electronically reconfigurable fractional-order filter that is able to be configured to operate as fractional-order low-pass filter (FLPF) or fractional-order high-pass filter (FHPF). Its slope of attenuation between pass band and stop band, i.e., order of the filter, is electronically adjustable in the range between 1 and 2. Also, pole frequency can be electronically controlled independently with respect to other tuned parameters. Moreover, particular type of approximation can be also controlled electronically. This feature set is available both for FLPF and FHPF-type of response. Presented structure of the filter is based on well-known follow-the-leader feedback (FLF) topology adjusted in our case for utilization with just simple active elements operational transconductance amplifiers (OTAs) and adjustable current amplifiers (ACAs), both providing possibility to control its key parameter electronically. This paper explains how reconfigurable third-order FLF topology is used in order to approximate both FLPF and FHPF in concerned frequency band of interest. Design is supported by PSpice simulations for three particular values of order of the filter (1.25, 1.5, 1.75), for several values of pole frequency and for two particular types of approximation forming the shape of both the magnitude and phase response. Moreover, theoretical presumptions are successfully confirmed by laboratory measurements with prepared prototype based on behavioral modeling.

New hybrid parallel active filter configuration minimising active filter size

Abstract: The authors propose a new topology for a hybrid parallel active filter that can further reduce the active filter (inverter) power rating. The basic idea is to install the active filter in parallel with the passive filter inductor. One advantage of this is that the passive filter can operate by itself if the inverter is in the high-impedance mode. This means that the passive filter can operate without the aid of the active filter. Another advantage is that, because the significant portion of fundamental and harmonic components flows through the passive filter, the current loading to the inverter is reduced greatly. This contributes to reducing the cost of the expensive inverter, and, hence, this makes the application of a hybrid active power filter more feasible. Through computer simulations and experiments, the authors have verified the effectiveness of the proposed topology.

Filter apparatus and frequency converter to which the filter apparatus is connected

Abstract: The invention provides a technique and a product in which for a frequency converter supplying electric power to, for example, a motor, a downsizing, lightening or the like of the frequency converter is realized while providing a filter apparatus reducing electromagnetic noises and the like. The filter apparatus reducing electromagnetic noises and the like is provided near a main circuit terminal board of the frequency converter, and the filter apparatus is connected directly to a main circuit terminal as a wiring drawing portion of the frequency converter. Part of a housing of the frequency converter and part of a filter housing are fitted to each other to fix the filter housing to the frequency converter.

Hybrid filter control system with adaptive filters for selective elimination of harmonics and interharmonics

Abstract: The interharmonics produced by some classes of nonlinear loads limit the effectiveness of classical passive filter compensation and active compensation must be considered. In high-voltage, high-power applications hybrid filter systems are technically justified and cost-effective solutions. Hybrid filter control strategies successfully employed in the compensation of high-power rectifier loads based on the detection of the total current distortion are less effective in the compensation of interharmonics. A frequency selective control system for a voltage controlled active filter connected to the power system through a multistage passive filter is described. A bank of second-order IIR digital filters with interharmonic tracking ability is employed for high-resolution spectral estimation and control. This approach is verified by simulation. It is shown for example that the active filter can compensate for supply interharmonics produced by a cycloconverter load. Different control strategies based on the selective control system are investigated and compared with an earlier strategy based on the detection of the total current distortion. By using individual detection and compensation of critical harmonics and interharmonics, hybrid power filters can be optimised to satisfy the distortion limits with the lowest active filter rating and switching frequency.