Frequency-locked loop

Abstract: This paper proposes a new technique for grid synchronization under unbalanced and distorted conditions, ie, the dual second order generalised integrator - frequency-locked loop (DSOGI-FLL) This grid synchronization system results from the application of the instantaneous symmetrical components method on the stationary and orthogonal alphabeta reference frame The second order generalized integrator concept (SOGI) is exploited to generate in-quadrature signals used on the alphabeta reference frame The frequency-adaptive characteristic is achieved by a simple control loop, without using either phase-angles or trigonometric functions In this paper, the development of the DSOGI-FLL is plainly exposed and hypothesis and conclusions are verified by simulation and experimental results

Abstract: This paper presents a new frequency-adaptive synchronization method for grid-connected power converters which allows estimating not only the positive- and negative-sequence components of the power signal at the fundamental frequency, but also other sequence components at higher frequencies The proposed system is called the MSOGI-FLL since it is based on a decoupled network consisting of multiple second order generalized integrators (MSOGI) which are frequency-adaptive by using a frequency-locked loop (FLL) In this paper, the MSOGI-FLL is analyzed and its performance is evaluated by both simulations and experiments

Abstract: A method and apparatus is provided for facilitating coherent communication reception. A received reference symbol coded spread-spectrum communication signal is despread with a spreading code to derive a stream of reference samples (152) and a stream of data samples (158). The channel response is estimated by utilizing the stream of reference samples (152). An offset frequency detector (443) determines an offset to be applied to the received signal via a frequency locked loop (456), while a timing control (176) compensates for slow timing drift and fast fading based on power estimates derived from the stream of reference samples (152) and/or the stream of data samples (158). A rate estimator determines the rate at which the information was encoded, and the rate information is used to optimize the timing control (176), frequency offset detector (443) and channel estimator (154). Thus an improved detection of estimated data symbols from the stream of received data samples (158) is provided.

Abstract: Renewable energy sources (RESs) have been extensively employed to replace fossil fuels for reducing carbon footprints. Since RESs are normally coupled to the power grid by fast-response power converters without providing any inertia, the power system inertia generated by synchronous generators continues to decrease, making modern power systems sensitive to frequency events. As a result, undesirable load-shedding, cascading failures, or even large-scale blackouts may occur under severe frequency events. To address the lack of inertia concern, this paper presents a frequency derivative-based inertia enhancement method for battery storage systems. Specifically, the method achieves inertia emulation by proportionally linking the time derivative of the grid frequency and active power references of power converters. The main contribution is to use a frequency-locked-loop to accurately estimate the frequency derivative signal, which avoids the high frequency noises introduced by differential operators. Simulation and experimental results are finally presented to validate the effectiveness of the proposed method.