Three-phase three-wire converter power oscillation suppression method based on Fermat point

A three-phase three-wire, power oscillation technology, applied in the direction of reducing/preventing power oscillation, converting AC power input to DC power output, output power conversion devices, etc., to prevent over-limit risks, good oscillation suppression effect, and simplified control. degree of effect

Active Publication Date: 2019-12-13
TIANJIN UNIV
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Problems solved by technology

[0004] In order to overcome the deficiencies of the traditional grid-connected control method in terms of system power oscillation suppression control comp

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  • Three-phase three-wire converter power oscillation suppression method based on Fermat point
  • Three-phase three-wire converter power oscillation suppression method based on Fermat point
  • Three-phase three-wire converter power oscillation suppression method based on Fermat point

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Embodiment Construction

[0041] The present invention will be described in further detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

[0042] The control method of the present invention is based on the topology of cascaded H-bridge converters, such as figure 1 shown. When an asymmetric fault occurs in the power grid, the three-phase three-wire system is usually accompanied by voltage amplitude drop and phase angle deviation. At this time, the three-phase phase voltages under the neutral point in the traditional sense no longer meet the conditions of equal amplitude and 120-degree phase difference. Therefore, for the convenience of analysis, define the equiangular center of the fault system’s off-line voltage triangle satisfying that the angles between the three vertices differ by 120 degrees (the phase angles of th...

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Abstract

The invention discloses a three-phase three-wire converter power oscillation suppression method based on a Fermat point. A triangular equiangular center (Fermat point) of a fault line voltage is defined as a new neutral point, and a novel power oscillation suppression method is presented according to a new rule, which is obtained through mathematical derivation, that 'the system does not have active power oscillation when the power generated by positive and negative sequence voltages of a three-phase three-wire system is uniformly distributed in the three phases'. The method comprises the following steps: S1, calculating a phase voltage under a Fermat point coordinate system according to a grid-side fault line voltage; S2, obtaining a three-phase reference current vector for realizing power oscillation suppression according to the obtained new rule of power distribution and power oscillation, and carrying out current tracking control; and S3, realizing system closed-loop control by using a signal obtained through current tracking control as a PWM reference signal. The asymmetric fault problem is simplified by establishing a new neutral point. The method breaks away from complex coordinate transformation and sequence component calculation of a traditional method, and greatly reduces the control complexity.

Description

technical field [0001] The invention relates to the field of grid-connected control of a three-phase three-wire system, in particular to a new method for suppressing power oscillation of a three-phase three-wire converter applied to an asymmetric fault of a power grid. Background technique [0002] As the penetration rate of new energy loads such as photovoltaics increases, while providing clean and convenient energy for people, it also greatly increases the hidden dangers of system load imbalance and short-circuit faults, which has brought a huge impact on the structure and control of modern distribution networks. [0003] When a voltage asymmetry fault occurs in the power grid, the grid-side power will generate double frequency oscillation, which is caused by the product of the positive sequence current and negative sequence voltage components and the positive sequence voltage and negative sequence current components. Power fluctuations will cause severe fluctuations in th...

Claims

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Application Information

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IPC IPC(8): H02J3/24H02M7/483
CPCH02J3/24H02M7/483H02M7/4835
Inventor 李晓涵何晋伟杜李扬王秀瑞
Owner TIANJIN UNIV
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