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Three-Resistor Current Sampling Method of Inverter Based on Current Prediction

A current prediction and current sampling technology, which is applied in the field of electrical engineering, can solve the problems of insufficient zero-voltage vector duration and the inability to accurately sample three-phase current, and achieve the effects of low cost, increased load capacity, and improved modulation ratio

Active Publication Date: 2018-08-31
SHANGHAI JIAOTONG UNIV
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  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0005] The present invention aims at the problems existing in the traditional three-resistor sampling technology of three-phase frequency converters, that is, the problem that the duration of zero-voltage vectors is insufficient under high modulation ratios, resulting in the inability to accurately sample three-phase currents, and provides a three-resistance frequency converter based on current prediction Current sampling method to realize wide-area current closed-loop vector control of some equipment such as asynchronous motors under low-cost requirements

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  • Three-Resistor Current Sampling Method of Inverter Based on Current Prediction
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  • Three-Resistor Current Sampling Method of Inverter Based on Current Prediction

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Embodiment Construction

[0028] The present invention will be described in detail below with reference to specific embodiments. The following examples will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that, for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0029]In an embodiment of the present invention: based on a general two-level inverter three-resistor sampling circuit (such as figure 1 shown), to provide a three-resistor current sampling method based on current prediction, the control process is as follows figure 2 shown:

[0030] In each PWM cycle, after current closed-loop PID control and SVGEN modulation, A, B, C three-phase PWM comparison value T is obtained 1 , T 2 and T 3 , the three comparison values ​​represent the conductio...

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Abstract

The invention provides a frequency converter three-resistance current sampling method based on current prediction. In each PWM (Pulse-Width Modulation) period, current closed loop PID (Proportion Integration Differentiation) control and SVGEN modulation are performed, and PWM comparison values T<1>, T<2> and T<3> of three phases A, B and C are obtained; the sizes of the T<1>, the T<2> and the T<3> and the shortest time T<min> required by complete sampling are compared in real time; and different current obtaining modes are used according to different size relationships. The method provided by the invention solves the problem that the three-phase current cannot be accurately sampled due to zero-voltage vector duration insufficiency at a high modulation ratio of the conventional three-resistance sampling technology of a three-phase frequency converter. The wide region current closed loop control under the three-resistance sampling can be realized; the modulation ratio is improved; the motor load capability is improved; the cost is low; and the sampling is simple and reliable.

Description

technical field [0001] The invention relates to the technical field of electrical engineering, in particular, to a current sampling method for a three-resistor frequency converter based on current prediction. Background technique [0002] In 1971, the German scholar F. Blaschke proposed the principle of vector control of AC motors. Vector control was quickly used in engineering applications with its own advantages. An important indicator that affects motor vector control is the motor phase current. Using the Hall sensor to sample the three-phase current of the motor is simple to use, but its cost is high; in order to reduce the cost, scholars use the single-resistor sampling of the DC bus current to reconstruct the motor phase current, the method is complicated, and there is a non-observation area; Three resistors are sampled in series under the bridge arm of the three-phase inverter, but there is a problem that some phases cannot be sampled under high modulation ratio. [...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H02P21/22
CPCH02P21/0003
Inventor 李子义高强
Owner SHANGHAI JIAOTONG UNIV
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