Abstract
With the rapid development of industrialization, the proportion of electric arc furnaces (EAF) in distribution networks is getting higher and higher. Aiming at the problem that grid voltage is distorted by a large number of arc furnace nonlinear loads accessing to distribution networks, it is crucial to make dynamic analysis of distribution network voltage and adopt a control strategy of grid-connected converter based on the new phase-locked loop (PLL) technology. As a result, the harmonic distortion rate is reduced and the quality of grid-connected current and voltage is improved. In this paper, photovoltaic (PV) system model and the typical dynamic model of the EAF are established. By analyzing the influence of the EAF model on the PV grid-connected converter with the traditional phase-locked loop while connected to distribution network, a control strategy of the PV grid-connected converter with the self-adjusting double SOGI (MAF-SASOGI) phase-locked loop with the ideal low-pass filter is proposed. Through the simulation analysis, it is verified that precise phase locked can be realized and harmonic content of the system can be reduced by the PLL strategy proposed in this paper. Therefore, the quality of PV grid-connected voltage and current is improved.
Highlights
With the depletion of fossil fuel reserves, renewable energy (RES) will become an increasingly important part of power generation
When the PV adopts the MAF-SASOGI phase-locked strategy proposed in this paper, because the MAF in the phase-locked loop (PLL) can filter out the high-order harmonics, and the difference node can filter out the DC component and the low-order harmonics, the accuracy of the phase-locked strategy is significantly improved compared with the previous two scenarios
In order to solve the problem that the grid voltage is seriously distorted when the distribution network contains a high proportion of electric arc furnaces (EAF) load, and the PV grid-connected converter can still be safely and effectively connected to the grid, this paper proposes a self-adjusting double SOGI phase-locked strategy with an ideal low-pass filter, which is effectively applied to the PV grid with high harmonic content
Summary
With the depletion of fossil fuel reserves, renewable energy (RES) will become an increasingly important part of power generation. When the voltage distortion of distribution network is serious, using the above lock-in techniques increases the calculation burden, and consumes a lot of resources Various control strategy such as a phase-locked strategy based on second-order generalized integral [21], [22], a high-resolution SOGI-PLL phaselocked strategy [23], an improved control strategy based on negative sequence component compensation [24] etc. In order to effectively connect the PV system to the grid even when the distribution network voltage is seriously distorted, this paper proposes a self-adjusting dual SOGI phase-locked strategy based on the ideal low-pass filter
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