Improved Design of PLL Controller for <i>LCL</i>-Type Grid-Connected Converter in Weak Grid

Zhu, Donghai; Zhou, Shiying; Zou, Xudong; Kang, Yong

doi:10.1109/tpel.2019.2943634

Cited by 143 publications

(94 citation statements)

References 41 publications

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“…In the literature [18][19][20][21], the impact of PLL on the harmonic stability and impedance modeling of the grid-connected converter under a weak grid has been reported. Literature [18] introduced the double second-order generalized integrator (DSOGI-PLL) to increase the phase margin and improve the stability of the three-phase grid-connected converter.…”

Section: Introductionmentioning

confidence: 99%

“…The harmonic stability improvement, taking the frequency coupling characteristics of the PLL, has been studied in [19] for a single-phase grid-connected converter. The authors in [20] have conducted the study revealing the grid-connected converter with modified PLL parameters to augment the stability analysis. [21] investigated the impact of PLL and current controller on the impedance modeling of the grid-connected converter in αβ stationary frame.…”

Section: Introductionmentioning

confidence: 99%

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Impact of Phase Locked Loop with Different Types and Control Dynamics on Resonance of DFIG System

et al. 2020

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In recent years, the doubly fed induction generator (DFIG) operates in a weak grid, rather than a strong grid due to the high proportion of wind energy into the power grid. The impedance interaction between the DFIG system and series and parallel compensated weak grid might cause the subsynchronous resonance (SSR) and high frequency resonance (HFR) in the DFIG system, respectively. Phase locked loop (PLL) is a popular grid synchronization technique, and the high bandwidth PLL can cause resonance at middle frequencies in the DFIG system. However, the impact of PLL types and their controller dynamics on the resonance in the DFIG system are not adequately researched. The impact of the PLL controller with different types, such as synchronous reference frame (SRF) and Lead/Lag PLL, is studied in this paper to fill this gap. Additionally, an improved PLL is proposed, which can guarantee the high phase margin and decrease the likelihood of the resonance at middle frequencies in the DFIG system under a weak grid. Moreover, the phase margin of the DFIG system impedance with an improved PLL is less sensitive to its controller parameters. Simulation and experimental results verify the effectiveness of the proposed method.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Impact of Phase Locked Loop with Different Types and Control Dynamics on Resonance of DFIG System

et al. 2020

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“…Making revisions to the PLLs is an alternative way for enhancing the stability for the large grid impedance. In [28], [29], the robust design of the three-phase PLL in the weak grid has been discussed. The analysis in [30] recommends the sharp reduction of the PLL bandwidth, which causes the slow transient.…”

Section: Introductionmentioning

confidence: 99%

Robustness Improvement of Single-Phase Inverters Under Weak Grid Cases by Adding Grid Current Feedforward in Delay-Based Phase-Locked Loop

Bian

Qian

et al. 2020

IEEE Access

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For inverters, a phase-locked loop (PLL) is usually needed for the grid synchronization. Typically, for the single-phase inverters, the orthogonal-signal-generators based PLLs (e.g., delay-based PLL) can be used. However, if the grid at the point of common coupling (PCC) exhibits a large grid impedance, the inverter may not work well or even be unstable. In order to work satisfactorily in the very weak grid, this study aims to formulate a robust PLL. At first, by modeling the inverter output impedance and considering the frequency coupling effect, the stability of the typical delay-based PLL has been analyzed and the reason for the performance degradation has been explained. Then, based on analyzing the differences of PLL blocks under different PCC conditions, the robust PLL with the grid current feedforward is discussed. Compared with the typical PLL, the improvement of the system behaviors in the weak grid cases is mainly attributed to the extra term on the numerator of output impedance, which is introduced by the current feedforward of the proposed PLL. The selection of control parameters has been emphasized for maintaining the high robustness. At last, selected comparative waveforms have verified that the single-phase inverter can perform well even with the large grid impedance, without the grid impedance estimation.

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“…Obtaining zero steady-state error under dynamic conditions is a challenging task while developing PLLs for grid applications. To eradicate this problem, the authors in [9][10][11] have proposed the distinct combinations of filtering techniques into the PLL structure.…”

Section: Introductionmentioning

confidence: 99%

An Adaptive Feed-Forward Phase Locked Loop for Grid Synchronization of Renewable Energy Systems under Wide Frequency Deviations

Kathiresan¹,

Jeyaraj²,

Sivaprakash³

et al. 2020

Sustainability

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Synchronization is a crucial problem in the grid-connected inverter’s control and operation. A phase-locked loop (PLL) is a typical grid synchronization strategy, which ought to have a high resistance to power system uncertainties since its sensitivity influences the generated reference signal. The traditional PLL catches the phase and frequency of the input signal via the feedback loop filter (LF). In general, to enhance the steady-state capability during distorted grid conditions generally, a filter tuned for nominal frequency is used. This PLL corrects large frequency deviations around the nominal frequency, which increases the PLL’s locking time. Therefore, this paper presents an adaptive feed-forward PLL, where the input signal frequency and phase under large frequency deviations are tracked precisely, which overcomes the above-mentioned limitations. The proposed adaptive PLL consists of a feedback loop that reduces the phase error. The feed-forward loop predicts the frequency and phase error, and the frequency adaptive FIR filter reduces the ripples in output, which is due to input distortions. The adaptive mechanism adjusts the gain of the filter in accordance with the supply frequency. This reduces the phase and frequency error and also decreases the locking time under wide frequency deviations. To verify the effectiveness of the proposed adaptive feed-forward PLL, the system was tested under different grid abnormal conditions. Further, the stability analysis has been carried out via a developed prototype test platform in the laboratory. To bring the proposed simulations into real-time implementations and for control strategies, an Altera Cyclone II field-programmable gate array (FPGA) board has been used. The obtained results of the proposed PLL via simulations and hardware are compared with conventional techniques, and it indicates the superiority of the proposed method. The proposed PLL effectively able to tackle the different grid uncertainties, which can be observed from the results presented in the result section.

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Improved Design of PLL Controller for LCL-Type Grid-Connected Converter in Weak Grid

Cited by 143 publications

References 41 publications

Impact of Phase Locked Loop with Different Types and Control Dynamics on Resonance of DFIG System

Impact of Phase Locked Loop with Different Types and Control Dynamics on Resonance of DFIG System

Robustness Improvement of Single-Phase Inverters Under Weak Grid Cases by Adding Grid Current Feedforward in Delay-Based Phase-Locked Loop

An Adaptive Feed-Forward Phase Locked Loop for Grid Synchronization of Renewable Energy Systems under Wide Frequency Deviations

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