Global synchronous pulse width modulation self-synchronization method in communication failure state

Abstract

The invention discloses a global synchronous pulse width modulation self-synchronization method in the communication failure state, and by means of the method, grid-connected inverters can still maintain the global synchronous operation state under the circumstance of communication failure, the states of all the grid-connected inverters are not needed to be changed, and the advantages of the global synchronous pulse width modulation method are given full play. The method comprises the steps that a global synchronization unit sends a synchronizing signal to the grid-connected inverter M and sends the synchronizing signal transmission frequency fsyn to the grid-connected inverter M, and the grid-connected inverter M calculates out the crystal oscillator error between the grid-connected inverter M and the grid-connected inverter 1 according to the synchronizing signal; the grid-connected inverter M sets self-synchronization parameters according to the calculation result; the grid-connected inverter M predicts the moment when the synchronizing signal appears next time according to received delta Tsyn, if the synchronizing signal appears, a communication system works normally, self-synchronization is not needed to be conducted, if the synchronizing signal does not appear, communication system failure occurs, and the grid-connected inverter M conducts self-synchronization.

Description

technical field [0001] The invention relates to a global synchronous pulse width modulation self-synchronization method under communication failure state. Background technique [0002] In recent years, with the continuous deterioration of the environment, renewable energy power generation technology and distributed power generation technology have attracted the attention of all parties. The grid-connected inverter can connect distributed power sources to the AC grid, and is a key device for connecting distributed power sources to the AC grid. Due to the existence of power electronic devices, the output current of the grid-connected inverter contains a large number of high-order harmonics. Various methods for reducing high-order harmonics have been mentioned in existing patents and literature, including increasing switching frequency, filter parameters, filter order, adopting interleaved parallel structure, multi-level structure, etc., but these methods will increase inverte...

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Problems solved by technology

Although this patent mentions the countermeasures under the failure of communication facilities, the global synchronous pulse width modulation method still cannot work normally at this time, the switching frequency of the inverter increases, and the loss increases, so the advantages of the global synchronous pulse width modulation method cannot be fully utilized.

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