Capacitor voltage fluctuation suppression method for modular multilevel converter at low frequency and low voltage

A modular multi-level, capacitive voltage technology, applied in the direction of converting AC power input to DC power output, electrical components, output power conversion devices, etc., can solve the problem of increasing converter cost, converter design problems, and affecting motor insulation Design and other issues to achieve the effect of improving work performance, solving control problems, and strong practicability

Inactive Publication Date: 2019-03-12
JIMEI UNIV
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Problems solved by technology

The main problem with this method is that the injection of high-frequency components will affect the insulation design of the motor. At the same time, to completely offset the voltage fluctuations of the upper and lower bridge arms, the injected common-mode voltage must reach the DC bus voltage, and the injected current must be When the load current is large, it will obviously bring difficulties in the design of the converter, which makes the converter need to increase the voltage and current level and increase the cost of the converter

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  • Capacitor voltage fluctuation suppression method for modular multilevel converter at low frequency and low voltage
  • Capacitor voltage fluctuation suppression method for modular multilevel converter at low frequency and low voltage
  • Capacitor voltage fluctuation suppression method for modular multilevel converter at low frequency and low voltage

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Embodiment Construction

[0021] The technical solution of the present invention will be specifically described below in conjunction with the accompanying drawings.

[0022] Such as figure 1 As shown, it is a modular multilevel converter structure. In conventional modular multilevel converter control, in order to share the output power with the upper and lower bridge arms, the upper and lower bridge arms adopt a symmetrical operation mode, and the output voltage of the upper and lower bridge arms is

[0023]

[0024]

[0025] where U dc is the DC side voltage, U o It is the maximum value of AC voltage on the output side. Similarly, the output current of the upper and lower bridge arms is,

[0026]

[0027]

[0028] where I cir is the circulation flow. Therefore, when the converter is running, the power of the upper and lower bridge arms is respectively,

[0029]

[0030]

[0031] It can be seen from the above that when the motor is driven at low speed, U O ≈0, there are large ...

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Abstract

The invention relates to a method for suppressing fluctuations in capacitor voltage of a modular multilevel converter at low frequency and low voltage. Through unbalanced control, the upper and lower bridge arms are rotated. One of the bridge arms mainly outputs AC voltage and AC current, while the other bridge arm mainly outputs DC voltage without outputting AC current. After switching in turn, the difference in capacitor voltage between the upper and lower bridge arm modules of the three phases is well suppressed. The method is used to solve the problem of excessive voltage fluctuation of the module capacitor in the low frequency band when the modular multilevel converter is used for motor driving, and avoids the negative impact on the load caused by the high frequency injection method. The method does not need to modify the hardware circuit, greatly improves the low-frequency working performance of the modularized multilevel converter, and has a wide range of industrial applications and strong practicability.

Description

technical field [0001] The invention relates to a low-frequency low-voltage driving technology of a modular multilevel converter, in particular to a control method for reducing capacitor voltage fluctuations in the low-frequency and low-voltage section of a modular multilevel converter. Background technique [0002] The modular multilevel converter obtains high voltage output by cascading (voltage superposition) and using conventional grade power modules. Since its appearance, modular multilevel converters have been applied in many fields, such as high-voltage direct current transmission, medium-voltage DC / DC converters, and medium-voltage motor drives. Theoretical analysis proves that the harmonic performance of the output voltage of the modular multilevel converter is better than that of the conventional H-bridge cascaded multilevel converter using a phase-shifting transformer structure. At present, some manufacturers have launched corresponding modular multilevel frequen...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H02M7/483
CPCH02M7/483H02M1/0038
Inventor 杨荣峰王国玲俞万能廖卫强李晓英
Owner JIMEI UNIV
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