Showing papers on "Voltage-controlled filter published in 2018"

An LCL -Filter Design With Optimum Total Inductance and Capacitance

Abstract: LCL -filter is among the best performing filters for grid-connected voltage source inverters Designing of the filter parameters (grid-side and inverter-side inductors and capacitor), takes an iterative approach due to the coherence between the parameters and design requirements such as IEEE-519 Std for harmonic current limitations, reactive power compensation limit, and maximum allowable voltage drop across the filter to limit the switching losses Most of the proposed LCL -filter optimization strategies emphasize on reducing the total inductance and losses of the filter while meeting the design requirements There is less emphasis given on the capacitor selection and optimizing its value Therefore, this paper proposes a method to compute the optimum capacitance requirement of the LCL -filter based on reactive power compensation of the filter rather than calculating it as a percentage of base capacitance of the filter as found in the literature The proposed design methodology compared to the previously proposed designs is capable of reducing filter capacitance by 50% while meeting the harmonic limitation demanded by IEEE-519 Std and also considers the impact of the total inductance on reactive power compensation Based on the proposed methodology an LCL -filter with minimum total inductance and capacitance is realized Functionality of the proposed LCL -filter is verified and validated through simulations and experimental results

Variable Structure Control in Natural Frame for Three-Phase Grid-Connected Inverters With LCL Filter

Abstract: This paper presents a variable structure control in natural frame for a three-phase gird-connected voltage-source inverter with LCL filter. The proposed control method is based on modifying the converter model in natural reference frame, preserving the low-frequency state-space variables dynamics. Using this model in a Kalman filter (KF), the system state-space variables are estimated allowing us to design three independent current sliding-mode controllers. The main closed-loop features of the proposed method are: first, robustness against grid inductance variations because the proposed model is independent of the grid inductance; second, the power losses are reduced since physical damping resistors are avoided; third, the control bandwidth can be increased due to the combination of a variable hysteresis comparator with the KF; and fourth, the grid-side current is directly controlled providing high robustness against harmonics in the grid. To complete the control scheme, a theoretical stability analysis is developed. Finally, selected experimental results validate the proposed control strategy and permit illustrating all its appealing features.

RF Wide-Band Bandpass Filter With Dynamic In-Band Multi-Interference Suppression Capability

Abstract: A class of RF multi-functional bandpass filter with multiple frequency-reconfigurable rejected bands that are embedded into its broad transmission frequency range is reported. This filter concept exploits an original tunable multi-band quasi-bandstop section as constituent block. In this manner, unprecedented levels of spectral adaptivity are obtained for its in-band notches. Among them: 1) independent control of center frequency and rejection level; 2) notch-combination capability to conform wider rejected bands and make their number dynamically selectable; and 3) generation of dual-band bandpass responses with adjustable bandwidth and inter-band transmission zeros. This results in controllable in-band stopbands with reconfigurable bandwidth, attenuation level, and filtering-profile type. The devised filter architecture, which is appropriate for dynamic multi-interference mitigation in broad-band RF receivers, is scalable to any number of arbitrary-order in-band notches. For proof-of-concept purposes, a UHF-band microstrip prototype with up to two tunable in-band second-order stopbands is manufactured and measured.

Synthesis and Analysis of Electronically Adjustable Fractional-Order Low-Pass Filter

Abstract: A proposal of a fractional (1+α)-order low-pass filter is presented in this paper. The proposed filter operates in the current-mode and it is designed using Multi-Output Current Followers (MO-CFs), Dual-Output Current Follower (DO-CF), Dual-Output Adjustable Current Amplifier (DO-ACA) and Adjustable Current Amplifiers (ACAs) as active elements within the presented topology of the filter. The filter possesses ability to electronically control its order and also the pole frequency by changing the current gain of current amplifiers (ACAs) already present in the structure. Three different values of the order and pole frequency of the proposed low-pass filter were tested as an example. Design of the proposed filter is supported by simulation and experimental results. Simulations of the circuit are carried out in PSPICE simulator with behavioral models of used active elements. The experimental laboratory measurements are performed with the help of available devices forming equivalent circuits. Simulations and experimental results of the electronical control of the order and pole frequency are compared in this contribution.

High-Order Filter Design for High-Power Voltage-Source Converters

Abstract: This paper proposes an analytical design procedure for the LLCL and the LCCL filters for grid integration of high-power voltage-source converters. The low switching frequency and stringent limits on grid-injected harmonics in high-power applications lead to large smoothing filters. In order to reduce the size and weight, high-order filters are already proposed and wise design procedures with the main goal of minimizing the overall filter size are being suggested. In this paper, the parameters of the LLCL and the LCCL filters are designed in the per-unit system to satisfy the requirements on the injected grid current and at the same time minimize the overall filter size through minimizing the total energy stored in the filter components. The experimental results of a downscaled laboratory prototype with a low switching frequency prove the effectiveness of the proposed design procedure.

Performance improvement of shunt active power filter by a new wavelet-based low-pass filter: Theory and implementation:

Abstract: In this paper, a wavelet-based low-pass filter (WBLPF) is proposed to improve the direct current (DC) component separation speed. To this end, three different methods are studied to implement discrete wavelet transform, and then they are compared with each other in term of transient response time, accuracy and computational cost. Afterwards, the conventional low-pass filter is replaced by the new WBLPF in the p-q method. This replacement increases the speed of DC component separation, and consequently the performance of the shunt active power filter is improved. To verify and examine the proposed method, a power system is simulated in MATLAB software and a prototype is implemented in the laboratory. The simulation and experimental results confirm the superiority of the proposed method.

Active bandpass filter circuit with adjustable resistance device and adjustable capacitance device

Abstract: In an illustrative example, a device includes an operational amplifier of an active bandpass filter circuit. The device further includes an adjustable resistance device configured to adjust a center frequency associated with the active bandpass filter circuit. The device further includes an adjustable capacitance device configured to adjust the center frequency and a bandwidth associated with the active bandpass filter circuit.

Fast, Simple Filter Design

Abstract: Filter design by transfer equation can be cumbersome and formidable to an engineer accustomed to the digital, firmware, and FPGA design world. The vast majority of filter applications do not have to be general in scope—a unity gain, Butterworth response is all that is needed. Very quick calculations can design a filter without the need to resort to the more general (and more complex) solutions.