5,547 research outputs found
Adaptive Vectorial Filter for Grid Synchronization of Power Converters Under Unbalanced and/or Distorted Grid Conditions
This paper presents a new synchronization scheme for detecting multiple positive-/negative-sequence frequency harmonics in three-phase systems for grid-connected power converters. The proposed technique is called MAVF-FLL because it is based on the use of multiple adaptive vectorial filters (AVFs) working together inside a harmonic decoupling network, resting on a frequency-locked loop (FLL) which makes the system frequency adaptive. The method uses the vectorial properties of the three-phase input signal in the αÎČ reference frame in order to obtain the different harmonic components. The MAVF-FLL is fully designed and analyzed, addressing the tuning procedure in order to obtain the desired and predefined performance. The proposed algorithm is evaluated by both simulation and experimental results, demonstrating its ability to perform as required for detecting different harmonic components under a highly unbalanced and distorted input grid voltage
Design of a High-Performance High-Pass Generalized Integrator Based Single-Phase PLL
Grid-interactive power converters are normally synchronized to the grid using
phase-locked loops (PLLs). The performance of the PLLs is affected by the
non-ideal conditions in the sensed grid voltage such as harmonics, frequency
deviations and dc offsets in single-phase systems. In this paper, a
single-phase PLL is presented to mitigate the effects of these non-idealities.
This PLL is based on the popular second order generalized integrator (SOGI)
structure. The SOGI structure is modified to eliminate of the effects of input
dc offsets. The resulting SOGI structure has a high-pass filtering property.
Hence, this PLL is termed as high-pass generalized integrator based PLL
(HGI-PLL). It has fixed parameters which reduces the implementation complexity
and aids in the implementation in low-end digital controllers. The HGI-PLL is
shown to have least resource utilization among the SOGI based PLLs with dc
cancelling capability. Systematic design methods are evolved leading to the
design that limits the unit vector THD to within 1% for given non-ideal input
conditions in terms of frequency deviation and harmonic distortion. The
proposed designs achieve the fastest transient response. The performance of
this PLL has been verified experimentally. The results are found to agree with
the theoretical prediction.Comment: 22 pages, 13 figures and 2 table
Quasi Type-1 PLL With Tunable Phase Detector for Unbalanced and Distorted Three-Phase Grid
International audienc
Fuzzy gain scheduling based grid synchronization system responsive to the electrical network conditions
In power conversion applications grid synchronization systems should face very different network operating conditions such as: generic grid connection, faulty or distorted scenarios or islanded conditions among others. However, all the existing synchronization systems have issues operating in all these scenarios if the control tuning parameters cannot be adapted to the grid conditions. This paper proposes a Fuzzy Gain Scheduling PLL (FGS-PLL) to be used for grid synchronization, which has a robust performance in case of severe voltage sag, where there is even a null value of voltage, and phase jump conditions. Moreover, the proposed method employs a fuzzy gain scheduling technique to adjust the proportional and integral gains of the proposed PLL during amplitude, phase and frequency variations in the grid voltage waveform to build a flexible PLL in case of severe grid conditions. This PLL structure permits to adjust the performance in different conditions as well as to provide a voltage reference, even in case of 100% voltage sag.Peer ReviewedPostprint (author's final draft
Hybrid Estimator-Based Harmonic Robust Grid Synchronization Technique
International audienc
Comparison of two three-phase pll systems for more electric aircraft
The More Electric Aircraft power system is characterized by variable supply frequency, in general between 360Hz and 900Hz. All equipment on board the aircraft have to operate delivering high performance under this variable frequency condition. In particular, power electronic converters need accurate control algorithms able to track the fundamental phase and frequency in real time, both in normal and unusual conditions. Phase Locked Loop (PLL) based algorithms are commonly used in traditional single and three phase power systems to provide phase and frequency estimations of the supply. Despite the simplicity of those algorithms, large estimation errors can arise when power supply voltage has variable frequency or amplitude, presents unbalances or is polluted with harmonics. To improve the quality of the phase and frequency real-time estimations, a robust PLL algorithm, based on a prediction-correction filter, is presented in this paper and compared with a Discrete Fourier Transform (DFT) based procedure. The performances of the two algorithms, implemented in a floating-point DSP, have been compared through an experimental validation obtained on a laboratory power converter prototype
A Quasi open-loop robust three-phase grid-synchronization technique for non-ideal grid
Abstract Development of advanced gridâsynchronization technique for unbalanced and distorted grid is considered in this paper. In this context, selfâtuning filter (STF) is considered to extract the fundamental component from the measured unbalanced and distorted voltages. Standard STF considers balanced grid voltages which is not always possible to ensure in the actual power grid. To mitigate this issue, an extended STF is proposed by analyzing the standard STF in the stateâspace framework. To make the proposed ESTF gridâfollowing, a robust openâloop frequency estimator is also applied. The closedâloop system enjoys excellent filtering benefit from the extended STF side while taking advantage of the fast convergence speed property of the openâloop frequency estimation technique. Numerical simulation and experimental results with double secondâorder generalized integrator phaseâlocked loop are provided to validate the theoretical developments
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