This paper proposed a positive sequence detector (PSD) based on cascaded delayed quadrature signal cancellation (CDQSC). The delayed quadrature signal cancellation (DQSC) operator based on two orthogonal signals in dq...
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ISBN:
(纸本)9781467371520
This paper proposed a positive sequence detector (PSD) based on cascaded delayed quadrature signal cancellation (CDQSC). The delayed quadrature signal cancellation (DQSC) operator based on two orthogonal signals in dq-frame or αβ-frame can be tailored to eliminate any specified harmonic. The proposed DQSC operator can be further cascaded to stepwise reject all undesired harmonics. Then the conditioned voltage signal can be used in phase locked loop (PLL) to obtain the positivesequence component accurately and fast. When the frequency of the three-phase signal is variable, the detector also realizes frequency adaptability by introducing a frequency feedback loop (FFL). Experimental results show that the proposed PSD is effective and feasible.
Synchronization is of concern in AC power systems. Existing synchronization algorithms are hardware intensive. A single phase synchronization scheme referred to as a multi-rate phase locked loop (MPLL) has been report...
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ISBN:
(纸本)9781424400379
Synchronization is of concern in AC power systems. Existing synchronization algorithms are hardware intensive. A single phase synchronization scheme referred to as a multi-rate phase locked loop (MPLL) has been reported The stability of the MPLL is influenced by amplitude variations. An amplitude estimation module based on a fast Fourier transform (FFT) algorithm and an automatic gain control (AGC) are employed to decouple amplitude variations from phase variations. The implementation of the FFT-based amplitude-estimator is complex and hardware intensive. A peak detector module that utilizes only two multiplexers and one comparator is proposed to replace the FFT-based amplitude-estimator. A real-time positive sequence detector is also combined with the MPLL in order to allow process of the three-phase signals. The overall system is implemented and compared for both FFT-based and peak detector approaches and indicates a 60 dB immunity to impulse noise and harmonic contamination and a 20 dB dynamic range.
In a distributed generation (DG) system, several renewable agents are connected to the low-voltage 3-phase utility grid through an inverter which is used as power condition and must guarantee the higher efficiency of ...
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In a distributed generation (DG) system, several renewable agents are connected to the low-voltage 3-phase utility grid through an inverter which is used as power condition and must guarantee the higher efficiency of the renewable agent. To attain this level of efficiency, a unitary power factor (FP) between the inverter currents and the utility grid voltages is necessary, and a synchronization algorithm is needed for the perfect synchronization between the renewable agent and the 3-phase utility grid. Within this context, this paper gives a performance study of the positive sequence detector plus a Synchronous Reference Frame Phase-Locked Loop (PSD+ dqPLL) as the synchronization algorithm, evaluating its accuracy under different conditions and studying their advantages and drawbacks. A grid-connected photovoltaic system with a nominal power of 6 kW is used so as to evaluate the behavior of the synchronization algorithm when the 3-phase utility grid is affected by some disturbances such as voltage unbalances, frequency variations and harmonic distortions. Firstly, several simulations with a disturbed 3-phase utility grid using MATLAB/SIMULINK from The MathWorks, Inc. are shown, and secondly, the previous tests are run in a Real-Time Digital Simulation (RTDS) platform in order to validate the obtained results with simulations. (c) 2014 Elsevier B.V. All rights reserved.
Effects of three different positive sequence detector structures including qPLL, EPLL, and SOGI-PLL on performance of a 10KVA shunt active filter are investigated in this paper. The evaluation is performed through sim...
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ISBN:
(纸本)9781479934799
Effects of three different positive sequence detector structures including qPLL, EPLL, and SOGI-PLL on performance of a 10KVA shunt active filter are investigated in this paper. The evaluation is performed through simulation of practical test conditions including balanced and unbalanced grid voltage, frequency variation, and harmonic polluted grid voltage. These studies lead to recognizing the SOGI-PLL as a proper method for grid-connected power applications, especially for the ones with digital control systems.
Open-loop synchronization techniques OLSs can be classified into True (TOLS) and Pseudo or Quasi-OLSs (POLS/QOLS). The TOLS means a system that has no feedback in its structures which results in unconditional stabilit...
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ISBN:
(纸本)9781665435543
Open-loop synchronization techniques OLSs can be classified into True (TOLS) and Pseudo or Quasi-OLSs (POLS/QOLS). The TOLS means a system that has no feedback in its structures which results in unconditional stability. Roughly speaking the advanced TOLSs suffers from two main drawbakcks:1) compromising performances under off-nominal frequencies in faulty conditions, 2) inefficiency under large frequency drifts and high computation time. To tackle the problem of frequency adaptivity, the POLS uses a frequency estimator. This technique works efficiently under large frequency drifts even in faulty conditions and benefits from low computation time. However, one of the main challenges in OLS techniques is how to improve dynamic performance without compromising the ability to reject disturbances. In this paper, an enhancement is made to the standard POLS to tackle this problem. The use of a cascade positive fundamental components estimator (PFCE) will allow us to enhance the response time while keeping the phase and magnitude error at their lowest. The mathematical model is presented then simulated. The simulation results validate this proposal.
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