SHEPWM-based pulse width modulation system and modulation method

Abstract

The invention provides a SHEPWM-based traction inverter pulse width modulation system and a modulation method. The modulation system comprises a first processor and a second processor; the first processor comprises a SHEPWM modulation unit for generating a SHEPWM modulation signal at a SHEPWM fundamental wave frequency band; the SHEPWM modulation unit comprises a storage unit for storing all switching angle initial values in initial value distribution regions of different carrier wave ratios, and a calculation unit for calculating effective switching angles, initial levels and PWM period values of each section of three phases of different carrier wave ratios; the output end of the first processor is connected with the second processor; the second processor comprises a pulse generator usedfor generating modulation pulse; and the pulse generator generates a pulse modulation signal according to the effective switching angles, initial levels and PWM period values transmitted from the first processor to trigger the first processor to perform interruption processing. The method can realize stable switching among different carrier wave ratios, and is low in impact and torque pulsation.

Description

technical field [0001] The invention relates to the technical field of inverter and related converter control, relates to an inverter modulation control method, in particular to a SHEPWM-based traction inverter pulse width modulation system and modulation method. Background technique [0002] In high-power applications such as modern AC locomotives, the heat dissipation conditions are relatively harsh, and the switching frequency of the power device of the traction inverter is limited to several hundred Hz. The modulation strategy is related to the operating performance of the system. [0003] At present, the mainstream of high-power converters adopts the multi-mode segmental pulse width modulation strategy. The basic strategy is asynchronous modulation-ordinary synchronous modulation-optimized PWM modulation-square wave. Optimal PWM modulation is the technical core of the entire modulation strategy. The characteristic requirements are small current harmonic content, small ...

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Problems solved by technology

[0005] Aiming at the problems of poor modulation accuracy, large torque ripple or large code amount, and difficult realization in existing pulse width modulation methods, the present invention proposes a new SHEPWM-based pulse width modulation system and modulation method. The switching between carrier ratios is stable, the impact is small, the modulation accuracy is high, the torque ripple is small, easy to implement and the amount of code is small

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