Current Ripple Suppression Method for Modular Multilevel Converter DC Side
A modular multi-level, DC side current technology, applied in the direction of electrical components, output power conversion devices, etc., can solve the problems of high-frequency current pulsation, high-frequency current can not cancel each other, to suppress current pulsation, easy to understand and implement and control simple effects
Active Publication Date: 2020-10-02
SOUTHEAST UNIV
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Problems solved by technology
The phase of the pulse voltage on the three-phase bridge arm inductance is arbitrary, and it cannot be guaranteed that the sum is zero at every moment. Therefore, the high-frequency currents generated on the three-phase bridge arms cannot cancel each other out, and then flow into the DC side bus, causing High frequency pulsation of current on DC bus
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[0037] The present invention will be further explained below in conjunction with the accompanying drawings.
[0038] The present invention is applicable to the method for suppressing the current ripple on the DC side of the three-phase MMC, wherein the topological structure of the MMC is as follows figure 1 As shown, the three-phase MMC has a total of 6 bridge arms, and each bridge arm is composed of n sub-module units (Cells) and series inductors. u als , u bls , u cls Respectively A, B, C three-phase upper and lower bridge arm inductance voltage sum. The sub-module unit is a half-bridge topology, and can also be a full-bridge, clamping twin sub-modules and other topologies.
[0039] Such as figure 2 As shown, a current ripple suppression method on the DC side of the MMC adopts the carrier layered pulse width modulation (PD-PWM) method, and adds a control algorithm for suppressing the double frequency circulation of the bridge arm. Regardless of redundant sub-modules, ...
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A DC side current ripple suppression method of a modular multilevel converter (MMC) is disclosed, a three-phase MMC system adopts a carrier stack pulse width modulation method and adds a control algorithm for suppress double-frequency circulating current of bridge arm to divide carrier into two groups, that first group comprises n-phase pulse width modulation and n-phase pulse width modulation. Acarrier wave and a sinusoidal reference wave + / - y (i) j ( / i); The second group consists of one carrier whose phase is variable and is compared with the compensation reference wave y (i) j ( / i) 2 output from the second harmonic circulating current controller. By shifting the phase of the second group of carriers in the three-phase bridge arm respectively in each carrier period, the sum of the pulse voltages on the inductors of the three-phase bridge arm is zero, and the high-frequency currents caused by the pulse voltages in the three-phase bridge arm cancel each other and do not flow into theDC bus bar, thereby suppressing the high-frequency current ripple on the DC bus bar. There is no need to make any topological changes, through the improvement of the traditional PD-PWM control method, the high frequency harmonic current brought by the traditional control method to the MMC DC side is restrained, and the defects of the traditional method are remedied.
Description
technical field [0001] The invention belongs to the technical field of multilevel power electronic converters, and relates to a method for suppressing current ripple on a DC side of a modular multilevel converter (MMC). Background technique [0002] Compared with the traditional two-level and three-level converters, MMC has the characteristics of high efficiency, small output AC voltage harmonics, and high modularity, and is more suitable for high-voltage, high-power applications. has been widely used. [0003] Carrier layered pulse width modulation (PD-PWM) method is a relatively common MMC modulation method. The method is to "stack" n triangular carriers with the same frequency, phase and amplitude and compare them with the modulating wave to obtain the trigger pulse of the switching device. Generally, the phases of the triangular carrier waves of the upper and lower bridge arms of each phase are set to be opposite. If the sinusoidal modulation wave given by the upper a...
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IPC IPC(8): H02M1/15H02M1/32
CPCH02M1/15H02M1/32
Inventor 邓富金喻强王青松程明
Owner SOUTHEAST UNIV