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Over modulation method and system for three level space vector

A space vector, three-level technology, applied in the field of AC drive, can solve the problems of many system resources, limited algorithm accuracy, and cumbersome implementation steps.

Active Publication Date: 2009-08-12
ZHUZHOU CSR TIMES ELECTRIC CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0016] In the overmodulation algorithm of the prior art, it is necessary to calculate the reference angle or holding angle according to the modulation ratio first, and then correct the amplitude and phase of the reference voltage vector according to the reference angle or holding angle, and also judge and correct the vector action time. The implementation steps are cumbersome and take up a lot of system resources
At the same time, in the prior art, there is a nonlinear relationship between the reference angle, hold angle and modulation ratio that cannot be expressed analytically. In practical applications, the functional relationship between them can only be described by curve fitting or tables, which severely limits the accuracy of the algorithm

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  • Over modulation method and system for three level space vector

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Embodiment Construction

[0089] In order to make the above objects, features and advantages of the present invention more comprehensible, specific implementations of the present invention will be described in detail below in conjunction with the accompanying drawings.

[0090] In order to facilitate those skilled in the art to better implement the present invention, the working principle of the three-level inverter is briefly introduced first. see image 3 , is the main circuit topology diagram of a typical diode neutral point clamped three-level inverter.

[0091] Such as image 3 As shown, each bridge arm of the inverter output of the diode neutral point clamped (NPC: Neutral Point Clamped) three-level inverter is composed of V 1 ~V 4 It consists of four turn-off power devices. By controlling each phase power device V 1 ~V 4 The turn-on and turn-off of each phase, and under the condition that at most two adjacent power devices of each phase are turned on at any time, each phase can obtain thre...

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Abstract

The invention provides a method and a system for over-modulating three-level space vectors. The method comprises the following steps: calculating the modulation ratio and angle of a reference voltage; dividing the modulation ratio into a first setting interval and a second setting interval; positioning the modulation ratio in the first setting interval and calculating the duty cycle of a short vector, a long vector and a medium vector by intervals according to the angle of the reference voltage; correcting the duty cycle of the short vector, the long vector and the medium vector respectively according to the magnitude of the short-vector duty cycle; calculating the N-action duty cycle and the P-action duty cycle of each phase according to the corrected duty cycle; positioning the modulation ratio in the second setting interval and calculating the keeping angle of the reference voltage; calculating the N-action duty cycle and the P-action duty cycle of each phase by intervals according to the resulting of comparing the keeping angle with the angle of the reference voltage; and conversing the N-action duty cycle and the P-action duty cycle of each phase into action time and mapping the action time back to the prior sector. The method and the system have the advantage of ensuring that SVPWM over-modulation is simple in calculation steps and higher in modulation precision.

Description

technical field [0001] The invention relates to the technical field of AC drives, in particular to an overmodulation method and system for a three-level space vector. Background technique [0002] Pulse Width Modulation (PWM: Pulse Width Modulation) is an important part of the AC drive control system. Its function is to adjust the width of the pulse signal that controls the on-off of the main circuit power semiconductor device according to the input reference voltage vector and the current DC bus voltage, so that the fundamental wave voltage output by the main circuit is equal to the input reference voltage vector. [0003] Space Vector Pulse Width Modulation (SVPWM: Space Vector Pulse Width Modulation) is a PWM method based on the control idea of ​​motor flux trajectory tracking. [0004] According to the different modulation ratios, SVPWM can be divided into linear modulation and over modulation. see figure 1 , is a schematic diagram of three-level space vector pulse wi...

Claims

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Application Information

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IPC IPC(8): H02M7/42H02M7/48
Inventor 丁荣军李江红许为陈华国
Owner ZHUZHOU CSR TIMES ELECTRIC CO LTD
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