Optimal support method for fault voltage of microgrid with three-phase four-wire inverter

Abstract

The invention discloses a micro-grid fault voltage optimization support method including a three-phase four-wire inverter. The method is to collect the voltage and output current at the common coupling point, obtain the voltage sequence component and the corresponding reactive voltage; obtain the αβ0 coordinate system The voltage sequence component at the lower public coupling point and the corresponding reactive voltage, the output current αβ0 coordinate system component; obtain the amplitude of each phase of the voltage at the common coupling point and compare it with the rated voltage amplitude to determine whether the microgrid is faulty; when it is determined that a fault occurs, Obtain the fault type coefficient, negative-sequence and zero-sequence voltage unbalance, and the phase difference of each sequence voltage; obtain the reference current in the αβ0 coordinate system; compare the reference current in the αβ0 coordinate system with the actual output current to generate a modulated wave voltage, and obtain the abc coordinates through inverse Clark transformation Four groups of half-bridge modules modulate the wave voltage; use the PWM module to generate four groups of half-bridge module driving signals; return and continue to perform the above steps. The method of the invention effectively improves the asymmetrical fault ride-through ability of the microgrid containing the three-phase four-wire inverter.

Description

technical field [0001] The invention belongs to the technical field of grid-connected power generation of distributed power sources, and relates to a micro-grid fault voltage optimization support method including a three-phase four-wire inverter. Background technique [0002] At this stage, as the penetration rate of distributed photovoltaic and wind power grid-connected inverters continues to increase, when common asymmetric faults such as single-phase grounding and two-phase grounding occur in low-voltage microgrids, it is easy to cause serious operational reliability problems. Based on this, relevant countries and institutions have drafted corresponding new energy grid-connected specifications, requiring that when a short-term fault occurs in the grid, the grid-connected inverter must maintain non-off-grid operation, and at the same time provide sufficient support for the fault grid voltage, that is, have fault ride-through ability. However, when the voltage of the low-v...

AI Technical Summary

Problems solved by technology

[0006] The present invention provides a micro-grid fault voltage optimization support method including a three-phase four-wire inverter, which solves the problem that the three-phase three-wire grid-connected inverter in the prior art cannot Output zero-sequence current, so that the zero-sequence voltage at the point of public coupling (PCC) cannot be suppressed when a ground fault occurs in the microgrid, and the fault voltage support effect is limited; and it is impossible to simultaneously realize the optimal support of voltage at the point of public coupling (PCC) and output active power Multi-objective control problems such as oscillation suppression and peak current limitation

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