High-voltage converter fault-tolerant modulation method for preventing active recharge

Abstract

The invention relates to the technical field of conversion of electrical energy, in particular to a high-voltage converter fault-tolerant modulation method for preventing active recharge. The high-voltage converter fault-tolerant modulation method comprises the following steps: calculating an upper bound u<max> and a lower bound u<min> of a zero-sequence voltage; with u<max> and u<min> as the upper bound and the lower bound respectively, carrying out dynamic amplitude limiting on the zero-sequence voltage u<0, in> to generate a zero-sequence component u<0>; obtaining final modulation wave signals u<ag>, u<bg> and u<cg> according to three-phase command voltage u<an>, u<bn> and u<cn> and the zero-sequence component u<0>; and carrying out normalization and phase-shift PWM modulation on the final modulation wave signals to generate switching signals of various power units. Zero-sequence voltage shaping is carried out through a feedback control; a fundamental component in the zero-sequence voltage is greatly reduced; and active recharge is effectively suppressed. Meanwhile, dynamic amplitude limiting is carried out on the zero-sequence voltage by setting the upper bound and the lower bound, so that the zero-sequence voltage in the entire shaping process is always limited within a reasonable range; even if a command voltage amplitude ascends to the maximal value which can be output by the converter, over-modulation is not caused; and the maximization of output voltage within a linear modulation region ensured.

Description

technical field [0001] The invention relates to the technical field of electric energy conversion, in particular to a high-voltage frequency converter fault-tolerant modulation method for preventing active power recharge. Background technique [0002] High-voltage and high-power frequency conversion speed regulation technology is of great significance for energy saving. The cascaded H-bridge inverter is the mainstream topology for high-voltage inverters. It has the advantages of small output harmonics, fewer devices used when outputting the same level number, and strong fault tolerance. Due to the large number of power units of the cascaded H-bridge inverter, the probability of failure is also very high, so its reliability has become the focus of many studies. On the other hand, when one or several power units fail, these faulty units can be short-circuited through triacs or bypass contactors, and the cascaded H-bridge inverter can continue to operate relying on the remain...

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Problems solved by technology

[0014] However, the above methods all face a common problem when running with load: the injected fundamental zero-sequence voltage will interact with the output current and may generate negative active power

However, these methods do not take into account the zero-sequence voltage requirements for fault-tolerant operation

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