Current fluctuation suppression method for converter station based on high-precision general-purpose controller
A current fluctuation and controller technology, applied in the output power conversion device, the conversion of AC power input to DC power output, electrical components, etc. Running ability, the effect of ensuring symmetry
Active Publication Date: 2018-12-21
NORTHEAST DIANLI UNIVERSITY
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Problems solved by technology
[0003] Although MMC has many advantages, its dynamic performance will also be affected by changes in the operating status of the AC system connected to it. When there is a three-phase load imbalance or asymmetrical fault in the AC system, the overcurrent caused by the three-phase current imbalance may be Block or stop the operation of the MMC converter station connected to the AC system, and at the same time cause fluctuations in the active and reactive power of the AC side of the converter station
Under this working condition, the complexity of the internal current components of the MMC system increases, and the sudden change of the bridge arm current in the converter station may cause damage to the valve group components, which in turn endangers the High Voltage Direct Current Transmission Based On Modular Multilevel High Voltage Direct Current Transmission Based On Modular Multilevel Converter, MMC-HVDC) system operation safety
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[0058] The technical scheme adopted by the present invention to solve its technical problems is as follows (as figure 1 shown):
[0059] MMC consists of three-phase six bridge arms, where L 0 is the bridge arm series inductance, R 0 is the equivalent resistance of the bridge arm, U dc is the DC bus voltage, u j and i j Respectively, the AC voltage and current on the MMC valve side (j=a, b, c), u pj and u nj is the output voltage of the bridge arm (p stands for the upper bridge arm, n stands for the lower bridge arm), i pj and i nj is the current flowing through the upper and lower bridge arms.
[0060] Thus, the AC and DC equivalent circuits of MMC can be obtained as figure 2 shown. according to figure 2 (a) and (b), the mathematical model of MMC can be expressed as
[0061]
[0062]
[0063] In the formula, e j is the j-phase output voltage of the converter, which can be expressed as
[0064]
[0065] u diffj is the unbalanced voltage inside the MMC, c...
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The invention relates to a current fluctuation suppression method of a converter station based on a high-precision universal controller, belonging to the technical field of electric power control. Inorder to suppress MMC AC-DC side current fluctuation caused by AC three-phase asymmetry, , By analyzing the mathematic model of MMC under the condition of asymmetrical alternating current, a current fluctuation suppression strategy based on general controller is provided. By comparing the control effect of the proposed general controller with that of the second-order resonant controller, the theory proves that the MMC closed-loop system using UC as current controller has the advantages of high control accuracy, good stability and simple structure. by Using RT-LAB Simulation Platform, a Dual-Terminal 31-Level MMC HVDC transmission system model is established, As a result of validating the effectiveness of the proposed control strategy, it is shown that under the asymmetric condition of theAC system, the proposed control strategy can effectively suppress the current fluctuation of the AC and DC sides of the MMC, ensures the symmetry of the AC current of the valve side and the stabilityof the DC system, and improves the operation capability of the MMC system under this condition.
Description
technical field [0001] The invention belongs to the technical field of electric power control, and mainly relates to a method for suppressing current fluctuations in an MMC-HVDC converter station based on a high-precision general controller. Background technique [0002] Modular Multilevel Converter (MMC) is a new type of Voltage Source Converter (Voltage Source Converter, VSC), which has the advantages of high modularity, weak electromagnetic interference, low harmonic content and high waveform quality. High advantages, and it has obvious engineering advantages in modular design and capacity upgrade, so it has gradually become the main development trend of flexible direct current transmission engineering technology. [0003] Although MMC has many advantages, its dynamic performance will also be affected by changes in the operating status of the AC system connected to it. When there is a three-phase load imbalance or asymmetrical fault in the AC system, the overcurrent cause...
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Login to View More IPC IPC(8): H02M7/483H02J3/26
CPCH02J3/26H02M7/483H02M7/4835Y02E40/50
Inventor 陈继开张程王振浩李国庆辛业春董飞飞
Owner NORTHEAST DIANLI UNIVERSITY