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A High Frequency Oscillation Suppression Method for Flexible DC Transmission System

A power transmission system, flexible DC technology, applied in AC network circuits, reducing/preventing power oscillation, electrical components, etc., can solve problems such as unfavorable power grid economy, increase power loss, and affect control system performance, so as to reduce high-frequency oscillation The effect of the risk

Active Publication Date: 2022-06-17
ZHEJIANG UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

In terms of hardware, a passive filtering device is added at the grid-connected point. This method increases the construction investment cost of the system and the power loss during normal operation, which is not conducive to improving the economy of the power grid; Additional damping control strategy, for example, during the commissioning of the South Channel of the Chongqing-Hubei Project, a 1.82kHz oscillation appeared on the Hubei side, and the oscillation disappeared after a first-order low-pass filter with a bandwidth of 400Hz was used in the voltage feedforward link. To a certain extent, the risk of high-frequency oscillation in the system is reduced, but the high-frequency oscillation of 695 Hz still occurs when the same solution is used on the Chongqing side
In general, most of the current additional control strategies cannot adapt to the changing working conditions of the system, and may affect the performance of the control system

Method used

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  • A High Frequency Oscillation Suppression Method for Flexible DC Transmission System
  • A High Frequency Oscillation Suppression Method for Flexible DC Transmission System
  • A High Frequency Oscillation Suppression Method for Flexible DC Transmission System

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0055] This embodiment is described by taking the flexible direct current power transmission system as an MMC-HVDC power transmission system as an example, and the converter described in this embodiment refers to a modular multi-level converter, ie, MMC.

[0056] figure 1 in, u s , i and i cir are the AC bus voltage, AC current and MMC circulating current in the abc coordinate system sampled by one voltage sensor and two current sensors, respectively, u dq , i dq , i cirdq are the AC voltage, AC current and circulating current of MMC in the dq coordinate system obtained by Park transformation, i dqref is the reference command value of active and reactive current, u cdq and i cirdq are the output of the inner loop fundamental frequency current controller and the circulating current suppression controller, respectively, to obtain the reference voltage of the bridge arm of the MMC, u dc is the DC voltage. This embodiment suppresses the occurrence of high frequency oscilla...

Embodiment 2

[0063] This embodiment is described by taking the flexible direct current power transmission system as a VSC-HVDC power transmission system as an example, and the converter described in this embodiment refers to a voltage source converter, that is, a VSC.

[0064] figure 1 in, u s , i and i cir are the AC bus voltage, AC current and VSC circulating current in the abc coordinate system sampled by one voltage sensor and two current sensors, respectively, u dq , i dq , i cirdq are the AC voltage, AC current and VSC circulating current in the dq coordinate system obtained by Park transformation, i dqref is the reference command value of active and reactive current, u cdq and i cirdq are the output of the inner loop fundamental frequency current controller and the circulating current suppression controller to obtain the reference voltage of the bridge arm of the VSC, u dc is the DC voltage. This embodiment suppresses the occurrence of high frequency oscillation by adding a ...

Embodiment 3

[0071] This embodiment is described by taking the flexible DC power transmission system as an MMC-HVDC power transmission system as an example, and the converter described in this embodiment refers to a modular multi-level converter, ie, MMC.

[0072] figure 1 in, u s , i and i cir are the AC bus voltage, AC current and MMC circulating current in the abc coordinate system sampled by one voltage sensor and two current sensors, respectively, u dq , i dq , i cirdq are the AC voltage, AC current and circulating current of MMC in the dq coordinate system obtained by Park transformation, i dqref is the reference command value of active and reactive current, u cdq and i cirdq are the output of the inner loop fundamental frequency current controller and the circulating current suppression controller, respectively, to obtain the reference voltage of the bridge arm of the MMC, u dc is the DC voltage. This embodiment suppresses the occurrence of high frequency oscillation by addi...

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Abstract

The invention discloses a method for suppressing high-frequency oscillation of a flexible direct current transmission system, comprising: S11, sampling and obtaining the AC side current signal under the dq rotating coordinate system of the converter; S12, comparing active and reactive current reference command values ​​with the converter The current modulation signal is obtained after the difference of the AC side current signal in the dq rotating coordinate system of the current transformer, and the voltage modulation signal u of this cycle is obtained by the PI controller c (s); S13, sampling to obtain the AC side voltage signal u in the dq rotating coordinate system of the converter s , put u s with u c (s) After subtraction, the comprehensive internal potential modulation signal E(s) of this cycle is obtained; S14, Smith predictor takes u c (s) and the compensated comprehensive internal potential modulation signal E(s)′ are added to obtain the estimated voltage modulation signal u s ', u s 'After being processed by the Smith predictor, the voltage incremental signal Δu(s) is obtained; S15, after subtracting Δu(s) from E(s), the compensated integrated internal potential modulation signal E(s)' is input to the pulse modulation device.

Description

technical field [0001] The invention relates to the technical field of flexible direct current transmission, in particular to a method for suppressing high frequency oscillation of a flexible direct current transmission system. Background technique [0002] The flexible DC transmission system has broad application prospects in such occasions as grid connection of renewable energy, interconnection of asynchronous AC systems, passive network power supply, and power supply and distribution of large city load centers. It is one of the important directions of the development of modern power systems. At present, the two mainstream flexible DC transmission systems are two-level and three-level VSC-HVDC (the full name is a high voltage DC transmission system based on voltage source converters) and MMC-HVDC (the full name is based on modular multi-level converters). high-voltage direct current transmission system). The use of a large number of power electronic equipment has caused p...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H02J3/24
CPCH02J3/241
Inventor 胡鹏飞刘思奇梁一桥江道灼
Owner ZHEJIANG UNIV
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