Active Frequency with a Positive Feedback Anti-Islanding Method Based on a Robust PLL Algorithm for Grid-Connected PV PCS

Jong-Pil Lee; Byung-Duk Min; Tae-Jin Kim; Dong-Wook Yoo; Ji-Yoon Yoo

Active Frequency with a Positive Feedback Anti-Islanding Method Based on a Robust PLL Algorithm for Grid-Connected PV PCS

Vol. 11, No. 3, pp. 360-368, May 2011

10.6113/JPE.2011.11.3.360

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Abstract

This paper proposes an active frequency with a positive feedback in the d-q frame anti-islanding method suitable for a robust phase-locked loop (PLL) algorithm using the FFT concept. In general, PLL algorithms for grid-connected PV PCS use d-q transformation and controllers to make zero an imaginary part of the transformed voltage vector. In a real grid system, the grid voltage is not ideal. It may be unbalanced, noisy and have many harmonics. For these reasons, the d-q transformed components do not have a pure DC component. The controller tuning of a PLL algorithm is difficult. The proposed PLL algorithm using the FFT concept can use the strong noise cancelation characteristics of a FFT algorithm without a PI controller. Therefore, the proposed PLL algorithm has no gain-tuning of a PI controller, and it is hardly influenced by voltage drops, phase step changes and harmonics. Islanding prediction is a necessary feature of inverter-based photovoltaic (PV) systems in order to meet the stringent standard requirements for interconnection with an electrical grid. Both passive and active anti-islanding methods exist. Typically, active methods modify a given parameter, which also affects the shape and quality of the grid injected current. In this paper, the active anti-islanding algorithm for a grid-connected PV PCS uses positive feedback control in the d-q frame. The proposed PLL and anti-islanding algorithm are implemented for a 250kW PV PCS. This system has four DC/DC converters each with a 25kW power rating. This is only one-third of the total system power. The experimental results show that the proposed PLL, anti-islanding method and topology demonstrate good performance in a 250kW PV PCS.

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Cite this article

[IEEE Style]

J. Lee, B. Min, T. Kim, D. Yoo, J. Yoo, "Active Frequency with a Positive Feedback Anti-Islanding Method Based on a Robust PLL Algorithm for Grid-Connected PV PCS," Journal of Power Electronics, vol. 11, no. 3, pp. 360-368, 2011. DOI: 10.6113/JPE.2011.11.3.360.

[ACM Style]

Jong-Pil Lee, Byung-Duk Min, Tae-Jin Kim, Dong-Wook Yoo, and Ji-Yoon Yoo. 2011. Active Frequency with a Positive Feedback Anti-Islanding Method Based on a Robust PLL Algorithm for Grid-Connected PV PCS. Journal of Power Electronics, 11, 3, (2011), 360-368. DOI: 10.6113/JPE.2011.11.3.360.