Coupling harmonic injection method for suppressing overvoltage of MMC capacitor under AC fault
A technology of harmonic injection and overvoltage, applied in the field of coupled harmonic injection to suppress the overvoltage of MMC capacitors under AC single-phase ground faults, and can solve the problems of sub-module capacitor voltage fluctuations, damage to power electronic devices, device overvoltages, etc. Achieve the effect of reducing sub-module overvoltage, reducing capacitor voltage fluctuation, and reducing the possibility of
Pending Publication Date: 2022-07-22
NORTH CHINA ELECTRIC POWER UNIV (BAODING)
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Problems solved by technology
When an AC single-phase ground fault occurs, the dynamic characteristics of the MMC will change greatly, and the voltage fluctuation of the sub-module capacitor will inevitably increase, which may cause device overvoltage and cause damage to power electronic devices
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[0011] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present invention.
[0012] Embodiments of the present invention provide a coupled harmonic injection method for suppressing MMC capacitor overvoltage under AC single-phase ground fault. The flowchart and overall system control block diagram are as follows: Figure 1 to Figure 2 As shown, the method mainly includes the following steps:
[0013] 1. Taking the fundamental frequency and double frequency fluctuation components of the instantaneous power of the three-phase bridge ...
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The invention provides a coupling harmonic injection method for suppressing the overvoltage of a sub-module capacitor of a modular multilevel converter (MMC) under a single-phase earth fault, and relates to a coupling harmonic injection method for suppressing the overvoltage of the sub-module capacitor of the MMC under the single-phase earth fault. According to the method, firstly, a three-phase bridge arm instantaneous power model after the alternating current single-phase earth fault occurs is established, the power model considers coupling injection of double-frequency circulating current and triple-frequency voltage and double-frequency voltage generated by the double-frequency circulating current on a bridge arm, and fundamental frequency and double-frequency fluctuation components of three-phase bridge arm instantaneous power serve as suppression targets; and performing amplitude and phase optimization design on the injected double-frequency circulating current and triple-frequency voltage, and finally injecting the calculated double-frequency circulating current and triple-frequency voltage in three phases by changing a modulation wave signal. According to the method, the fluctuation of the bridge arm power of the converter valve during the fault can be effectively suppressed, so that the capacitor voltage fluctuation of the sub-module during the fault period is reduced, and the possibility of sub-module overvoltage of the MMC during the fault period is reduced.
Description
technical field [0001] The invention relates to the technical field of flexible direct current transmission, in particular to a coupled harmonic injection method for suppressing overvoltage of MMC capacitors under an alternating current single-phase grounding fault. Background technique [0002] Flexible DC transmission (VSC-HVDC) is a new generation of DC transmission technology following AC transmission and conventional DC transmission. Flexible DC transmission technology has the characteristics of independent adjustment of active power and reactive power, strong weak grid access and low voltage ride-through capability, low AC filtering and reactive power compensation requirements. Modular multilevel converter (MMC) has the characteristics of flexible control, modular expansion, low switching frequency, and low harmonic content. At present, the Shanghai Nanhui flexible DC project, the Nan'ao three-terminal flexible DC project, the Zhoushan five-terminal flexible DC projec...
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IPC IPC(8): H02M1/12H02M1/32H02H9/04
CPCH02M1/12H02M1/32H02H9/04
Inventor 王鋆鑫邓伟成许建中
Owner NORTH CHINA ELECTRIC POWER UNIV (BAODING)
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