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Abstract Frequency‐adaptive prefilters are widely used in the phase‐locked loop (PLL) to suppress input disturbances. However, the parameters of the PLL and prefilters are often designed separately or based on an inaccurate model. The positive feedback effect introduced by the frequency adaption (FA) is usually ignored, leading to non‐optimal performance. Based on the accurate small‐signal model with a particular focus on the FA, this paper proposes an optimal design method for these advanced PLLs. The PLL based on dual second‐order generalized integrator (DSOGI) is taken as an example to demonstrate the principle. With different gain margins, the optimal damping factors of DSOGI and PLL, as well as the natural frequency of PLL, are obtained using the proposed method. Then the global optimal parameters are obtained by evaluating the settling time and overshoot. The analysis shows that the truly optimal parameters are quite different with those provided in the literature, and the dynamic performance is significantly enhanced without degrading the steady‐state performance. Experimental results are presented to verify the theoretical analysis.

Frequency‐adaptive prefilters are widely used in the phase‐locked loop (PLL) to suppress input disturbances. However, the parameters of the PLL and prefilters are often designed separately or based on an inaccurate model. The positive feedback effect introduced by the frequency adaption (FA) is usually ignored, leading to non‐optimal performance. Based on the accurate small‐signal model with a particular focus on the FA, this paper proposes an optimal design method for these advanced PLLs. The PLL based on dual second‐order generalized integrator (DSOGI) is taken as an example to demonstrate the principle. With different gain margins, the optimal damping factors of DSOGI and PLL, as well as the natural frequency of PLL, are obtained using the proposed method. Then the global optimal parameters are obtained by evaluating the settling time and overshoot. The analysis shows that the truly optimal parameters are quite different with those provided in the literature, and the dynamic performance is significantly enhanced without degrading the steady‐state performance. Experimental results are presented to verify the theoretical analysis. [ABSTRACT FROM AUTHOR]

The phase-locked loop (PLL) is an essential synchronization technique to ensure stable operation and control of grid-connected converters. Nevertheless, under actual conditions, the grid voltage is often influenced by harmonics and frequency variation, resulting in unsatisfactory steady-state precision and dynamic performance of the PLL. Therefore, in this paper, an improved digital PLL (ID-PLL) including harmonics elimination module and angular frequency reference calculation module is proposed. The proposed ID-PLL can maintain steady-state precision and dynamic performance in the condition of voltage unbalance, voltage harmonics and voltage frequency variation. The influence of adverse grid voltage on PLL performance is analyzed in detail. The parameters design and discretization approach is presented accordingly. The effectiveness of the proposed approach is confirmed by compared experiments with DSOGI-PLL.

This brief presents a conductance-based neuron that is capable of operating under ultra-low-voltage supplies. The proposed neuron employs a variable-gain low-pass filter to linearly integrate the input spikes onto the membrane capacitance. A positive feedback topology is used to generate output spikes and implement a frequency adaption mechanism. A differential amplifier is as well employed as a comparator to reset the membrane potential and set a threshold voltage to control the spike generator circuit. The mathematical analyses result in a first-order linear equation for membrane current of the neuron. The designed neuron was fabricated in TSMC 0.18 $\mu \text{m}$ CMOS technology with an area of 993 $\mu \text{m}^{2}$ that consumes 135 fJ/spike under a 0.3-V supply voltage. The experimental results show frequency adaption mechanism and intrinsic chattering, while regular and fast-firing behaviors are achieved by adjusting control parameters. [ABSTRACT FROM AUTHOR]

This paper proposed an efficient phase-locked loop (PLL) that features zero steady-state error of phase and frequency under voltage sag, phase jump, harmonics, DC offsets and step-and ramp-changed frequency. The PLL includes the sliding Goertzel discrete Fourier transform (SGDFT) filter-based fundamental positive sequence component separator (FPSCS), the synchronous-reference-frame PLL (SRF-PLL) and the secondary control path (SCP). In order to obtain an accurate fundamental positive sequence component, SGDFT filter is introduced as it features better filtering ability at the frequencies that are integer times of fundamental frequency. Meanwhile, the second order Lagrange-interpolation method is employed to approximate the actual sampling number including both integer and fractional parts as grid frequency may deviate from the rated value. Moreover, an improved SCP with single-step comparison filtering algorithm is employed as it updates reference angular frequency according to the FPSC, which promises a zero steady-state error of phase and improves the frequency tracking speed. In this paper, the mathematical model of the proposed PLL is constructed, its stability is analyzed. Also, design procedure of the control parameters is presented. The effectiveness of the proposed PLL is confirmed by experimental results and comparison with advanced pre-filtering PLLs. [ABSTRACT FROM AUTHOR]

We present an electromechanically coupled computational model for the investigation of a thin cardiac tissue construct consisting of human-induced pluripotent stem cell-derived atrial, ventricular and sinoatrial cardiomyocytes. The mechanical and electrophysiological parts of the finite element model, as well as their coupling are explained in detail. The model is implemented in the open source finite element code Code _ Aster and is employed for the simulation of a thin circular membrane deflected by a monolayer of autonomously beating, circular, thin cardiac tissue. Two cardio-active drugs, S-Bay K8644 and veratridine, are applied in experiments and simulations and are investigated with respect to their chronotropic effects on the tissue. These results demonstrate the potential of coupled micro- and macroscopic electromechanical models of cardiac tissue to be adapted to experimental results at the cellular level. Further model improvements are discussed taking into account experimentally measurable quantities that can easily be extracted from the obtained experimental results. The goal is to estimate the potential to adapt the presented model to sample specific cell cultures. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a synchronization technique to accurately track the phase and frequency of the input signal under large frequency deviations. The hybrid FPLL structure consists of a conventional SRF PLL feedback loop along with a feed forward frequency estimator loop. The advantage of this technique is that the feedback controller has to reduce only the phase error and the frequency error is eliminated by the feed forward controller. This increases the dynamic response of the system under frequency deviations. The performance of the hybrid structure is compared with the conventional SRF PLL and the former shows improved performance over the SRF PLL in terms of filtering characteristics and transient response for wide range of frequency deviations. The steady state error analysis is carried out and the necessary condition for stability is also derived. Simulations are carried out in MATLAB/Simulink and implemented in real time using an ALTERA cyclone II FPGA board. The results obtained for various grid conditions such as unbalance, harmonics, phase jump and frequency deviation demonstrate the phase-tracking ability of the technique. [Copyright &y& Elsevier]