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Positive- and negative-sequence combined control method for three-phase PWM current transformer when power grid is imbalanced

A power grid imbalance and joint control technology, applied in the direction of irreversible AC power input conversion to DC power output, AC power input conversion to DC power output, electrical components, etc., can solve the problem of reducing the reliability of the control system and unfavorable controller value implementation, complex control methods, etc.

Active Publication Date: 2015-08-12
新源智储能源发展(北京)有限公司
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Problems solved by technology

However, the above-mentioned control method is relatively complicated, which is not conducive to the numerical realization of the controller, and can reduce the reliability of the control system.

Method used

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  • Positive- and negative-sequence combined control method for three-phase PWM current transformer when power grid is imbalanced
  • Positive- and negative-sequence combined control method for three-phase PWM current transformer when power grid is imbalanced
  • Positive- and negative-sequence combined control method for three-phase PWM current transformer when power grid is imbalanced

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Embodiment Construction

[0041] Such as figure 1 Shown is a block diagram of a three-phase PWM converter. The three-phase PWM converter is composed of three power switch arms, the AC side is connected to the power grid through the filter inductor L, and the DC side is connected to the post-stage load through the DC capacitor C. The three-phase grid voltage is u a , u b , u c , the three-phase grid current is i ca i cb i cc .

[0042]In industrial sites, there are actually a large number of unbalanced three-phase loads such as electric arc furnaces and single-phase motors. The electrical operating environment of PWM rectifiers is harsh, and the grid voltage is generally unbalanced. For the three-phase Y-type system without neutral line, since there is no zero-sequence current loop, the influence of the zero-sequence component can be ignored when analyzing the unbalanced control operation of the three-phase PWM rectifier. For the convenience of analysis, only the operation of the fundamental wav...

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Abstract

The invention discloses a positive- and negative-sequence combined control method for a three-phase PWM current transformer when a power grid is imbalanced. The combined control of positive-sequence and negative-sequence currents is realized in a positive-sequence dq synchronous rotating reference frame, the control system is simplified, and the normal and stable operation of the PWM current transformer is ensured when the voltage of the power grid is imbalanced. To solve the problem of separation of positive-sequence and negative-sequence vectors of the power grid voltage, a novel positive-sequence and negative-sequence vector separation method in the positive-sequence dq synchronous rotating reference frame is provided such that only a primary positive- and negative-sequence voltage extraction module is needed, and a positive- and negative-sequence extraction module is omitted. For the inner-loop control of current, a PI+R type composite controller method is provided, and a resonant frequency of a resonance controller is configured to be 2[omega], so that zero steady-state error control for the negative-sequence component in the dq synchronous rotating reference frame is realized. Besides, in order to increase the response speed of the control system, a voltage feedforward control method is adopted according an output voltage and current vector model of the PWM current transformer, so that the dynamic performance of the control system is improved.

Description

technical field [0001] The invention relates to the field of output current control of a three-phase PWM converter, in particular to a method for combined positive and negative sequence control of a three-phase PWM converter when the grid is unbalanced. Background technique [0002] Electric energy is one of the key factors affecting the development of my country's industry, and electric energy conservation will occupy an increasingly important position in the process of building a conservation-oriented society in my country. In recent years, due to the power quality problems such as harmonics and reactive power caused by the nonlinear load of the distribution network, the operation of electrical equipment is disordered, the power factor of transformers and other equipment is low, and the line loss is large, causing problems for power supply and power consumption enterprises. Thanks to the development of power electronics, power conversion and other technologies, the active ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H02M7/12
CPCH02M7/2173H02M1/0022
Inventor 马伏军毕然何志兴岳雨霏
Owner 新源智储能源发展(北京)有限公司
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