Current non-equalizing control method of converter multi-unit parallel system

Abstract

The invention provides a current non-equalizing control method of a converter multi-unit parallel system. The phenomenon of current non-equalizing during converter multi-unit parallel connection is avoided by delaying a falling edge of a control pulse, namely delaying switch-off. When a certain phase of current of a certain converter is low, the aim of increasing the phase of current is fulfilled by delaying the falling edge of the phase of control pulse. When n three-phase pulse width modulation (PWM) converters are connected in parallel, corresponding phases of (n-1) three-phase PWM converters are required to be compensated. The delay time of the falling edge of the control pulse is a current function. In order to achieve an online real-time dynamic compensation effect, a fixed delay time compensation method is employed, a current compensation effect is observed, and compensation time is continuously modified, so a relation curve of the compensation time and current is determined.

Description

technical field [0001] The invention relates to a control method of a converter, in particular to a method for controlling uneven current in a multi-unit parallel system of a converter used in the technical field of power electronics. Background technique [0002] Energy is a major issue facing mankind today. Due to the rapid development of information technology, power electronics technology is a key link in energy conversion and information control. With the continuous development of power electronics technology in the fields of electrical energy saving, new energy power generation, power transmission, electric traction, large-scale oil and gas transmission, and smart grid, the capacity of a single unit continues to increase, and high-power power electronics is facing many problems and challenges. Due to the limitations of the current manufacturing process of power electronic devices, a single converter can no longer meet the requirements of high-power transmission, so the...

AI Technical Summary

Problems solved by technology

The uneven current problem of the system will make the current stress of the power device unbalanced

[0005] For example, the Chinese invention patent application with the publication number CN101521454A proposes that the power supply device determined as the master in advance samples its output current, and receives output current signals from other power supply devices as slaves, and performs current equalization processing. Obtain the target output current, and send the current-balancing adjustment signal to each slave through the broadcast command of the field bus, and then realize parallel current sharing. Although this method can realize parallel current sharing, due to the voltage difference between the parallel units, at the same time Circulation will be generated, and there are master-slave machines between parallel units, and the master-slave machines need to communicate, which is not conducive to system redundancy and reliability design

[0006] Another example is the document (Ollila Jaakko. Parallel connection of inverters: European, 1906518[P]. 2008-02-04.) proposed to use serial communication to synchronize the modulation wave counters of each parallel unit to ensure that the parallel connection of inverters The unit controls the consistency of the pulse, but this method cannot solve the uneven current problem caused by the inconsistency of the impedance, and the method contains communication lines, so that the distance between the parallel units is limited, and it is susceptible to electromagnetic interference. In addition, due to the parallel unit There is a distinction between master and slave, which makes the system redundant

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