Control method of three-phase four-leg grid-connected inverter with adaptive current limiting function

Abstract

The invention relates to the field of power system protection and control, and provides a method for determining upper limit values of various sequence output current in view of shortage of corresponding researches on determination of various sequence current limiting values under a dividing-sequence control strategy of a three-phase four-leg inverter. According to the method, development of the maximum voltage balancing ability of the inverter can be ensured. Therefore, according to the adopted technical scheme, a control method of a three-phase four-leg grid-connected inverter with an adaptive current limiting function comprises the steps of calculating the sun of various phases of negative sequence current and zero sequence current under unified two-phase synchronous rotating coordinates and calculating the maximum value of the sequence current according to actual upper limit values of various phases of current, namely the maximum carrying current of a power electronic switching device of the inverter, so that the inverter can develop the maximum voltage balancing ability under the condition that various phases of current do not exceed the maximum value. The control method is mainly used for power system protection and control occasions.

Description

technical field [0001] The present invention relates to the field of power system protection and control, in particular to a three-phase four-leg inverter control strategy and current limiting technology, in particular to a three-phase four-leg inverter control strategy with an adaptive current limiting function. Background technique [0002] The three-phase four-leg inverter can maintain the three-phase symmetry of the output voltage in the case of unbalanced three-phase loads, and can meet the needs of equipment with high voltage quality requirements. When used as grid-connected equipment, it can improve the low-voltage distribution network The three-phase unbalanced situation has significant economic benefits. There are various control strategies for three-phase four-leg inverters, and the common way is to decompose positive and negative zero-sequence for independent control. Due to the limited capacity of the three-phase four-arm inverter type distributed power supply, ...

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Problems solved by technology

[0003] At present, the research on the three-phase four-leg inverter mainly focuses on the control strategy, and lacks attention to the distribution and limitation of each sequence current.

The traditional current limiting idea is to limit the phase current, but due to the existence of negative-sequence and zero-sequence current, the output current of each phase of the three-phase four-leg inverter is not equal, and the current limit cannot only calculate the single-phase current

Moreover, the three-phase four-leg inverter with split-sequence control is more difficult to uniformly limit the current because it decomposes the current into multiple components.

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