Addressing DC Component in PLL and Notch Filter Algorithms Karimi-Ghartemani, M.; Khajehoddin, S. A.; Jain, P. K. ...
IEEE transactions on power electronics,
2012-Jan., 2012, 2012-01-00, 20120101, Letnik:
27, Številka:
1
Journal Article
Recenzirano
This paper presents a method for addressing the dc component in the input signal of the phase-locked loop (PLL) and notch filter algorithms applied to filtering and synchronization applications. The ...dc component may be intrinsically present in the input signal or may be generated due to temporary system faults or due to the structure and limitations of the measurement/conversion processes. Such a component creates low-frequency oscillations in the loop that cannot be removed using filters because such filters will significantly degrade the dynamic response of the system. The proposed method is based on adding a new loop inside the PLL structure. It is structurally simple and, unlike an existing method discussed in this paper, does not compromise the high-frequency filtering level of the concerned algorithm. The method is formulated for three-phase and single-phase systems, its design aspects are discussed, and simulations/experimental results are presented.
This paper introduces an approach for the real-time extraction of the frequency, phase angle, and symmetrical components of the grid signal, which is of great importance for many applications in ...power systems such as power quality and protection. The proposed method is based on the concept of the adaptive notch filter that provides a fast and accurate estimation of the symmetrical components in the presence of frequency and amplitude variations. In addition, the system offers a high degree of immunity and insensitivity to power system disturbances, harmonics, and other types of pollutions that exist in the grid signal. The simplicity of the structure makes the method suitable for both software and hardware implementations. Moreover, this very simple and very powerful tool can be used as a synchronization technique, which further simplifies the control issues currently challenging the integration of distributed energy technologies into the electricity grid. Mathematical derivations are presented to describe the principles of operation, and experimental results confirm the validity of the analytical work.
Purpose: Osteoporosis is especially prevalent in the older population and in women. Fractures lead to many health complications, placing an enormous burden on the health system. Improved knowledge ...will encourage healthy practices that prevent osteoporosis and help community members avoid unhealthy lifestyles and habits. The goal of this study was to evaluate the knowledge, attitudes, and practices relating to osteoporosis among male and female students of the Jazan community. Methods: The Jazan region has 13 governorates and a population of more than 1.5 million. For this study, 440 participants were selected from seven different governorates, and the osteoporosis knowledge assessment tool (OKAT) was used together with five background variables and some questions on attitude and practice. A Chi-squared test was implemented to identify any significant relationships between the background variables and the knowledge and practice scores. A P value of less than 0.05 was considered significant. Results: Of the 440 participants, 53% were men and 47% women. Thirty-three percent of them held government jobs, 73% had completed university, and 50% had a monthly income of less than 5,000 riyals. Regarding the risk factors for osteoporosis, 62 (14%) smoked, 37 (8.4%) used steroids, 184 (41.8%) had a family history of osteoporosis, and 393 (89.3%) had not attended an education campaign on osteoporosis. The highest number of correct answers in the OKAT was to the question "osteoporosis increases the risk of fractures" (423, 96.1%), and the lowest number of correct answers was to the question "osteoporosis is more common in men" (60, 13.6%). Regarding protective behaviors against osteoporosis, namely physical activity, daily intake of dairy products, attending an education campaign, and background characteristics, attending an education campaign was statistically significant, with a P value of 0.003, but marital status, education level, body mass index (BMI), and occupation were not statistically significant. For the risk factors, sex was statistically significant, along with the daily soft drink intake and smoking but not with the use of steroids. Other background characteristics, such as education level and BMI, were not statistically significant as osteoporosis risk factors. Conclusions: The participants' level of knowledge was high, and the risk factors for osteoporosis were still present together with a low level of achievement for protective measures. It is highly recommended that education campaigns be implemented to increase knowledge and encourage improved attitudes and practices.
An algorithm based on the concept of adaptive notch filter (ANF) is proposed for estimation of power system frequency. The ANF is a second-order notch filter that is further furnished with a ...nonlinear differential equation to update the frequency. The method permits direct estimation of frequency and its rate of change for a power system signal. The performance of the algorithm is compared with that of a newly introduced algorithm, which is based on using an enhanced phase-locked loop (PLL) system. Unlike the PLL-based frequency estimator, the proposed algorithm does not employ a voltage-controlled oscillator. This makes its structure much simpler for implementation. The transient response of the proposed estimator is faster than that of the PLL-based estimator. Computer simulations are presented to highlight the usefulness of this approach in estimating near-nominal and off-nominal power system frequencies.
Online frequency estimation of a pure sinusoidal signal is a classical problem that has many practical applications. Recently an ANF with global convergence property has been developed for this ...purpose. There exist some practical applications in which signals are not pure sinusoidal and contain harmonics. Therefore, online frequency estimation of periodic but not necessarily sinusoidal signals espoused by such applications becomes quite important. This note presents an alternative stability analysis for a modified ANF that permits the presence of harmonics in the incoming signal. Also, this stability analysis is simpler and alleviates the problem complexity even in the case of pure sinusoidal signal. Simulation results confirm theoretical issues.
Time-Domain Signal Analysis Using Adaptive Notch Filter Mojiri, M.; Karimi-Ghartemani, M.; Bakhshai, A.
IEEE transactions on signal processing,
2007-Jan., 2007, 2007-01-00, 20070101, Letnik:
55, Številka:
1
Journal Article
Recenzirano
Noise reduction and signal decomposition are among important and practical issues in time-domain signal analysis. This paper presents an adaptive notch filter (ANF) to achieve both these objectives. ...For noise reduction purpose, the proposed adaptive filter successfully extracts a single sinusoid of a possibly time-varying nature from a noise-corrupted signal. The paper proceeds with introducing a chain of filters which is capable of estimating the fundamental frequency of a signal composed of harmonically related sinusoids, and of decomposing it into its constituent components. The order of differential equations governing this algorithm is 2n+1, where n is the number of constituent sinusoids that should be extracted. Stability analysis of the proposed algorithm is carried out based on the application of the local averaging theory under the assumption of slow adaptation. When compared with the conventional Fourier analysis, the proposed method provides instantaneous values of the constituting components. Moreover, it is adaptive with respect to the fundamental frequency of the signal. Simulation results verify the validity of the presented algorithm and confirm its desirable transient and steady-state performances as well as its desirable noise characteristics
This paper presents a new three-phase phase-locked loop (PLL) system that primarily estimates the phase angles, frequency, and magnitudes of the a three-phase input signal and also provides a ...filtered version of the input. It is then extended to the estimation of sequence components, their magnitudes, and phase angles. As compared with the conventional three-phase PLL, this method does not suffer from errors that are caused by signal unbalance and dc offset. It also provides estimate for several other variables which are not included in the conventional three-phase PLL. As compared with the method of using three independent single-phase enhanced PLLs, the proposed method offers a simpler structure. Moreover, the estimated frequency is more accurate and smoother because it uses the information from all three phases to estimate a single value for frequency. The paper also presents a modification that makes the PLL parameters independent from the input signal amplitude. The same modification is applicable to existing methods such as conventional three-phase PLL. Simulation and experimental results are presented to confirm desirable performance of the proposed method.
This paper introduces a new adaptive notch filtering approach to extract the harmonic and reactive current components for power quality purposes in grid-connected converters. The main function of ...this method is to provide synchronized harmonic and reactive current components for control purposes. The theoretical analysis is presented, and the performance of the method is experimentally evaluated. The methodology is applicable for a wide range of equipment such as uninterrupted power supplies, regenerative converters, active power filters, etc., as a basis for generating the reference signals.
Inspired by the extremum seeking (ES) algorithm, new approaches for source localization in global positioning system denied environments are presented using a nonholonomic unicycle. Existing ES-based ...schemes apply an excitation signal that causes difficulties in the analysis and performance of the unicycle. The aim of this brief is to develop schemes without employing any excitation signal. To this end, two control schemes are developed for tuning the forward and angular velocities of the unicycle. The first scheme only tunes the forward velocity and is based on the conventional form of ES. In this form, a high-frequency excitation signal (dither) is employed to find the gradient of an unknown function that is optimized. The proposed scheme benefits from the fact that the dither part already exists in the unicycle model. The second scheme only tunes the angular velocity and is based on the recently developed form of ES. In this form, the function that is optimized appears as the argument of a sine/cosine function. The presented scheme takes the advantage from the fact that the sine/cosine function of this form of ES already exists in the vehicle model. Both schemes are structurally simple and significantly improve the unicycle motion. A stability analysis of the schemes is carried out using the averaging theory and their performances are illustrated through carefully studied simulation examples.
