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

Aravind Chellachi Kathiresan,Md Rabiul Islam,Asokan Sivaprakash,Jeyaraj Pandiarajan,Thanikanti Sudhakar Babu

doi:10.3390/su12177048

Aravind Chellachi Kathiresan, Md Rabiul Islam + Show 3 more

Open Access

https://doi.org/10.3390/su12177048

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Abstract

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.

Highlights

Renewable energy systems, such as solar photovoltaic and wind energy conversion systems, use power electronic converters to inject the generated power to the grid
Despite various synchronization techniques that have been enforced in the literature [3,4], the well-known and widely used control technique for three-phase power systems is synchronous reference frame phase-locked loop (PLL) (SRF-PLL) [5]
Phase information is obtained through the abc-to-dq transformation, and the system dynamics are determined by a loop filter

Summary

Introduction

Renewable energy systems, such as solar photovoltaic and wind energy conversion systems, use power electronic converters to inject the generated power to the grid. Major modification introduced by the enhanced PLL [19] in the phase detector section is used in power system applications for frequency measurements In most of these methods [12,13,14,15,16,17,18], the nominal frequency correction is provided by the loop filter. The phase detector generates an error signal with reference to the difference between input and feedbaTchkespighnaasle, danetdecthtoerlgoeonpefiraltteers iasngeernreorraslliygnaaPl Iwciothntrreoflelerernthceattofilttheersdtihffeereernrocer sbiegtnwael.enThinepcuent atenrd frfeeqeudebnaccky soifgVnaCl,Oanisdfitxheedloaotpafnilotemr iinsaglefnreeqraulelyncayP(Ifeceodn-tfroorllwerarthdactofnilstetarns tt)h,eanerdrothr esifgunnacl.tiTohneocfetnhteer VfCreOquisentocygeonf eVraCtOe aissifgixneadl oaft farenqoumenincayl (f∆reωq)uaetntchye(pfeoeidn-tfworhweanrdthceoinnsptuant tf)r,eaqnudentchye vfueenrcstiooffn forfomthe thVeCnOomisintoalgferneqeruaetnecay.sWignhaelnoaf sfruepqpuleynfcryeq(uΔeωn)caythtahseapsoiignntiwfichaennt dtheeviiantpiount ffrreoqmuethnecynovmeeirnsaol fvfaflruoem, tfhrttehheqeeluonleoconkcmckinyii,ngntgahtiletmfimrfereeqeiqnuiucneerncenrcaecysay.esWseerscrhoocenornsniisasdiesedauresapriblapylblyyle.ylfSi.rmiSenqiicnnuecaee∆tneω∆dcyω,

Small Signal Modeling

Performance Analysis of FPLL

Evaluation of System Performance under Voltage Sag

Harmonics