IEEE Paper review

Review on IEEE paper

Subject: Comb filter for noise reduction

Topic: Improving Dynamic Response of Active Harmonic Compensator using Digital Comb Filter

Harmonic extraction and control is one of the main elements in active power filter design.To improve the dynamic response of the active harmonic controller, a comb-filter is the solution, which can be implemented on a DSP platform. Performance evaluation results for the load transient show a substantial improvement in the dynamic performance of the harmonic compensator compared with the conventional low pass filter-based approaches. The whole system mainly includes voltage source converter and harmonic and reactive power compensator. Resonant current control has also been used widely for reducing the current harmonic distortion in many different distributed generation applications. A resonant harmonic compensator attenuates the current harmonics and is capable of achieving zero steady-state error. The proposed solution in this paper used for improving the dynamic response of a system by using a limited bandwidth compensator with selective unwanted frequency components.

PAPER LINK : http://ieeexplore.ieee.org/document/6872521/

Patent review

PATENT REVIEW

PATENT: United States Patent, SIGNAL PROCESSING SYSTEM AND METHOD FOR
               ENHANCED CASCADED INTEGRATOR-COMB INTERPOLATION FILTER
               STABILIZATION

PATENT NUMBER: US5880973

In this patent, overflow detection circuit monitors the output of the CIC (Cascaded Integrated Comb)interpolation filter for an overflow condition which is indicative of filter instability. When an Overflow Condition is detected, the reset circuitry automatically resets the filter, thereby eliminating the instability. CIC interpolation filters are constructed as a series of ‘N’comb filter circuits (subtractors), followed by a Zero pad circuit, followed by a series of “N” integrator circuits(adders). The comb section of the filter operates at a low sample rate, Whereas the integrator section of the filter operates at a high sampling rate. Typically, the interpolation factor (R) is set between 2 and 10,000. The number of stages of filter increases accuracy. Implementing a CIC interpolation filter generally involves the three requirements that the filter must be reset before use, addition and subtractions must be performed using modulo arithmetic and the Word size in the subtracters, adders, and storage elements must be large enough to accommodate the arithmetic gain of the filter. This circuit checks whether overflow is there or not,if no then it will proceed further and if yes then it will reset filter. This invention detects instabilities in the CIC interpolation filter by continuously monitoring the output samples of the filter.

PATENT LINK: https://www.google.ch/patents/US5880973

DSP PROCESSOR

DSPs are processors or microcomputer whose hardware, software and instruction set are optimised for high-speed numeric processing application. It is capable of handling large mathematical operations easily while using real-time signals for the manipulations of the data. In this experiment, we performed with basic operations of the DSP processor C2000 such as addition, subtraction, bit manipulation, etc. The coding platform used was Code Composer Studio.

FIR filter design using FSM

In this experiment, we have done FIR filter design using Frequency Sampling Method. In this method, impulse response h(n) is obtained using desired frequency response. The given frequency response is sampled at a set of equally spaced frequencies to obtain N samples. Sampling the continuous frequency response Hd(w) at N points essentially gives the N-point DFT of Hd(wk). A Set of samples determined from Hd(w) are identified as Discrete Fourier Transform Coefficients. It is denoted by H(k). The filter coefficients are obtained by IDFT.

Linear phase FIR filter designing using Windowing method

In this experiment, we have designed linear phase FIR filter using windowing method. Different types of windows are used to design FIR filter, which includes Hamming window, Hanning window, Bartlett window, Blackman window and Kaiser window. Here, we used Hanning window for designing of filter. The parameters used for designing the FIR filters are attenuation in stop band(As),attenuation in pass band (Ap),pass band frequency, stop band frequency and sampling frequency. We have written scilab code with reference of designing method done in class. Advantage of the windowing method is it requires minimum amount of computational effort, so window method is simple to implement.