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1

Modified Dual Second-order Generalized Integrator FLL for Frequency Estimation Under Various Grid Abnormalities

Patil K. R., Patel H. H.

Transactions on Environment and Electrical Engineering

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2016

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Vol. 1, No. 4

10--18

EN

Proper synchronization of Distributed Generator with grid and its performance in grid-connected mode relies on fast and precise estimation of phase and amplitude of the fundamental component of grid voltage. However, the accuracy with which the frequency is estimated is dependent on the type of grid voltage abnormalities and structure of the phase-locked loop or frequency locked loop control schemes. Among various control schemes, second-order generalized integrator based frequency- locked loop (SOGI-FLL) is reported to have the most promising performance. It tracks the frequency of grid voltage accurately even when grid voltage is characterized by sag, swell, harmonics, imbalance, frequency variations etc. However, estimated frequency contains low frequency oscillations in case when sensed grid-voltage has a dc offset. This paper presents a modified dual second-order generalized integrator frequency-locked loop (MDSOGI-FLL) for three-phase systems to cope with the non-ideal three-phase grid voltages having all type of abnormalities including the dc offset. The complexity in control scheme is almost the same as the standard dual SOGI-FLL, but the performance is enhanced. Simulation results show that the proposed MDSOGI-FLL is effective under all abnormal grid voltage conditions. The results are validated experimentally to justify the superior performance of MDSOGI-FLL under adverse conditions.

2

Algorytm sterowania przekształtnikiem DC/AC dla małej elektrowni wiatrowej

Młodzikowski P., Milczarek A., Malinowski M.

Przegląd Elektrotechniczny

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2011

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R. 87, nr 6

67-72

PL

Artykuł omawia zagadnienia sterowania przekształtnikiem DC/AC pośredniczącym w przekazywaniu energii elektrycznej wyprodukowanej przez małą elektrownię wiatrową (MEW) do sieci elektroenergetycznej nn. lub odbiorników lokalnych.

EN

Paper presents control methods for a DC/AC converter working in a grid connected or a stand-alone mode and transferring energy from a small wind turbine to the electrical grid or autonomous local grid.

3

Grid synchronization and symmetrical components extraction with PLL algorithm for grid connected power electronic converters - a review

Bobrowska-Rafał M., Rafał K., Jasiński M., Kaźmierkowski M.

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2011

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Vol. 59, nr 4

485-497

EN

In this paper, a review of Phase Locked Loop (PLL) algorithms and symmetrical component extraction methods intended for grid-connected power electronic converters are presented. Proposed classification is based on voltage representation in three coordinates: natural (abc), stationary (alfa beta) and rotating coordinates (dq). The three selected algorithms are described in details: Dual Second Order Generalized Integrator (DSOGI-PLL), Dual Virtual Flux – both in stationary coordinates. The third one, in rotating dq coordinates, is Dual Synchronous Reference Frame PLL (DSRF-PLL). A comparison of PLL algorithms is presented. Also, selected experimental results are given to verify practical application of discussed algorithms.