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4 Harmonics
Published in C. Sankaran, Power Quality, 2017
Active filters use active conditioning to compensate for harmonic currents in a power system. Figure 4.23 shows an active filter applied in a harmonic environment. The filter samples the distorted current and, using power electronic switching devices, draws a current from the source of such magnitude, frequency composition, and phase shift to cancel the harmonics in the load. The result is that the current drawn from the source is free of harmonics. An advantage of active filters over passive filters is that the active filters can respond to changing load and harmonic conditions, whereas passive filters are fixed in their harmonic response. As we saw earlier, application of passive filters requires careful analysis. Active filters have no serious ill effects associated with them. However, active filters are expensive and not suited for application in small facilities.
Single-Phase Parallel A.C. Circuits
Published in Christopher R Robertson, Further Electrical and Electronic Principles, 2010
A filter is a network designed to pass signals at certain frequencies, and to reject signals at all other frequencies. Ideally, a filter would introduce zero attenuation to selected frequencies, known as the pass band(s), and completely block all others (the stop band). Since a filter has to be frequency sensitive, then it must employ frequency dependent components; i.e. inductors or capacitors, or (usually) a combination of both of these components. There are four basic types of filter, namely, low-pass, high-pass, band-pass and band-stop. In addition, a filter circuit may be classified as being either passive or active. A passive filter is one which contains only a combination of resistors, inductors or capacitors, but no power source within it. An active filter consists of a combination of these components interconnected with an operational amplifier (op amp). The latter would include its own power supply source, independent of the signal to be filtered.
Basic electronics
Published in Raymond F. Gardner, Introduction to Plant Automation and Controls, 2020
Filters are energy-storage devices that smooth out pulsations or ripples in dc-power systems, or filters can be used to block the transmission of particular signal frequencies. Filters are classified as either active or passive. A passive filter uses combinations of resistors, capacitors, and inductors to store or delay the transmission of energy in an R-L-C circuit. Active filters use passive filters in conjunction with amplifying components, such as transistors, operational amplifiers (OPAMPS), or digital signal processors. Active filters require a source of power to function.
Modelling and sizing techniques to mitigate the impacts of wind fluctuations on power networks: a review
Published in International Journal of Ambient Energy, 2022
M. V. Tejeswini, I. Jacob Raglend
The low-pass filter is a filter which permits signals lower than the cut-off frequency and attenuates the signals above the cut-off signal. There are three types of filter: active filter, passive filter and hybrid filter. Passive filters are made up of passive components (resistors, capacitors and inductors). It doesn’t consist of amplifying elements. Always their output will be less than the given input. The low-pass filter rejects and modifies the unwanted signals. The power electronic converter produces the harmonics. A filter circuit is used on the grid side converter to reduce the impact of harmonics on the grid. The converters used in DFIGs are modelled as ideal current source (Surinkaew and Ngamroo 2014). But in practice ideal case will not hold good. An AC filter is used on the grid side converter to remove some of the voltage harmonics of converter. The commonly used filter in grid side is L(inductor) and LCL(inductor capacitor inductor). The model of single-phase LCL filter is shown in (Mulolani, Althobaiti, and Alamoudi 2019). The resonant frequency is calculated using Equation (31)
Artificial Neural Network based Solar Energy Integrated Unified Power Quality Conditioner
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2021
Dheeban S S, Muthu Selvan N B, Umashankar Subramaniam
Flexible AC Transmission Systems devices play an important role in the Power system in compensation as well as power quality. The Unified Power Quality Conditioner operation is similar to the operation of the Unified Power Flow Controller except the UPQC is designed to be operated at the distribution side of the power system. The Active filters are of two types: shunt active power filter and series active power filter. The harmonics induced by the load current can be minimized with the help of a shunt active power filter. The disturbance caused in the voltage like voltage swell/sag is compensated by the series active power filter. The shunt and the series active power filter are connected in a back-to-back configuration and the energy exchange is carried out by coupling with a DC-Link Capacitor. The block diagram of the UPQC system is given in Figure 1. The UPQC has a power circuit and a control circuit. The power circuit includes the Series Injecting Transformer, two Voltage Source Converters coupled with DC-link Capacitor. The Voltage Source Converters are used rather than the Current Source Converter, as the Voltage Source Converters have flexible controllability, easy to implement with a minimum rating, and are cost-effective. The control circuit comprises controllers for both the Series Compensation and Shunt Compensation. The DC-link Capacitor is powered by Renewable energy resources. In general, the power from the Photovoltaic Cells is injected into the DC-Link Capacitor.
Design and analysis of MISO bi-quad active filter
Published in International Journal of Electronics, 2019
Vikash Kumar, Rishab Mehra, Aminul Islam
Filters are considered a vital component in analog signal processing circuits. Filters facilitate diverse applications and are used for noise reduction, demodulation, signal detection, multiplexing, etc., (Dimopoulos, 2012). Analog filters can be classified into passive filters and active filters. Passive filters are made up of passive elements such as resistors, capacitors, inductors, transformers and require no power supplies. On the contrary, active filters consist of active as well as passive elements and need to be externally powered. Each filter type has its own set of advantages and disadvantages. However, for integrated circuit applications, active filters outperform their passive counterparts in terms of cost, die area, tunability, etc.