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Harmonic cancellation PWM generation method

A technology of harmonic elimination and modulation wave, applied in the field of harmonic elimination PWM generation, can solve the problems of large harmonic content, inaccurate switching, slow response of SHEPWM speed regulation, etc., to achieve smooth motor torque output, improve control accuracy, and easy The effect of harmonic cancellation

Active Publication Date: 2016-11-16
SHENZHEN INVT TRANSPORTATION TECH CO LTD
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AI Technical Summary

Problems solved by technology

[0005] The purpose of the present invention is to solve the above technical problems, provide a harmonic elimination PWM generation method, solve the problem of large harmonic content, slow response of SHEPWM speed regulation and switching between PWM modes in the past wide frequency conversion speed regulation range inaccurate question

Method used

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Embodiment Construction

[0034] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0035] In this embodiment, the control system is realized by DSP plus programmable logic controller. The motor control algorithm and PWM operation are all completed by DSP, and then transmitted to the programmable logic controller through bus communication, and the programmable logic controller accurately sends out control pulses Wave. The programmable logic controller can be FPGA or CPLD, etc. In this embodiment, FPGA is selected for illustration.

[0036] Such as figure 1 As shown, a harmonic elimination PWM generation method, within the range of variable frequency speed regulation, the modulation frequency is divided into three stages by the control system: the first stage 1 of low frequency operation, the second stage 2 of low frequency operation, and the stage 3 of medium and high frequency operation part;

[0037] In the firs...

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Abstract

The invention discloses a harmonic cancellation PWM generation method, and the method comprises the steps: dividing the modulation frequency into three parts in a variable frequency speed regulation range: first and second low-frequency operation stages and a middle-high frequency operation stage; respectively an SVPWM asynchronous modulation mode and an SVPWM synchronous modulation mode, which are fixed through employing carrier frequency, at the first and second low-frequency operation stages; carrying out the frequency point control of the above two modulation modes when the synchronous carrier frequency and the set asynchronous carrier frequency are consistent; enabling the second low-frequency operation stage to be carried out at a plurality of different synchronization multiples; employing a mode of dividing each cyclic wave into a plurality of executed harmonic waves equally to eliminate an SHEPWM mode at the middle-high frequency operation stage; reading a current angle before switching, and calculating the time delay when operating to 90 degrees or 270 degrees so as to achieve the switching between the synchronous modulation mode and a harmonic cancellation mode. The method is easier to implement a specific harmonic cancellation algorithm, and increases the response speed and precision.

Description

technical field [0001] The invention relates to the field of AC drive systems, in particular to a method for generating harmonic wave elimination PWM. Background technique [0002] In high-power AC electric drive systems such as rail transit traction and metallurgical rolling mills, high-power semiconductor devices such as IGBT (Insulated Gate Bipolar Transistor) and IGCT (Insulated Gate Commutated Thyristors) are usually used. Low. In addition, due to the wide range of speed regulation of the drive motor, the use of ordinary asynchronous modulation and synchronous modulation can no longer meet the needs. The existing methods basically use overmodulation to square wave output at high speeds, which leads to a large amount of power input and output. harmonics, the system needs to increase the filter reactor, which increases the cost, volume and energy consumption. [0003] Selective Harmonic Elimination Pulse Width Modulation (SHEPWM for short) is based on the characteristic...

Claims

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Application Information

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IPC IPC(8): H02P27/08H02P29/50
CPCH02P27/08
Inventor 王辉华杨北辉
Owner SHENZHEN INVT TRANSPORTATION TECH CO LTD
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