Modular multilevel converter control method based on current hysteresis principle
A modular multi-level, converter control technology, applied in the direction of converting AC power input to DC power output, output power conversion devices, electrical components, etc., can solve power quality degradation, harmonics and current distortion, and step approximation Problems such as modulation error and voltage step increase, to achieve the effect of reducing harmonics, simple and effective control, and reducing controller cost
Pending Publication Date: 2020-09-15
XIANGTAN UNIV
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Problems solved by technology
However, for the application of medium-voltage DC distribution network, due to the small number of modules, the error and voltage step size of the ladder approximation modulation will increase greatly
It leads to obvious low-order voltage harmonics and current distortion, which degrades the power quality and makes it difficult to meet the requirements of the distribution network
Although voltage harmonics and current distortion can be reduced by using CPS-PWM, since each sub-module is independently modulated, voltage balance and current average control becomes more complicated
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[0032] In order to describe the present invention in more detail, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.
[0033] The present invention relates to a control method of a modular multilevel converter based on the principle of current hysteresis, and the topology of the MMC main circuit adopted is as follows figure 1 shown. It consists of three phases and six bridge arms. The sub-module of each bridge arm adopts a half-bridge structure. Each phase bridge arm is composed of a commutation inductor and 2N sub-modules of a half-bridge structure. Each sub-module includes two IGBTs, An energy storage capacitor and a freewheeling diode can output a stable waveform at the output terminal by controlling the on and off of the sub-module.
[0034] figure 2 It is the control block diagram of the principle of current hysteresis, and the phase A of the three phases is taken as an example to illu...
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The invention discloses a modular multilevel converter control method based on a current hysteresis principle. When an upper bridge arm and a lower bridge arm of the MMC increase or decrease one sub-module SM at the same time, the amplitude of the output voltage is not changed. In this way, current hysteresis control is introduced into the nearest level approximation modulation strategy of the MMC, the number of sub-modules calculated through nearest level approximation modulation is rapidly adjusted through the current hysteresis controller, and therefore rapid tracking of reference current is achieved, and optimization of output waveform quality is achieved. Compared with a traditional control method of the modular multilevel converter, the control method does not need a PI controller, the number of controllers is reduced, control is simple and effective, the cost of the controllers is reduced, and the control method is suitable for being applied to actual engineering. In addition, on the premise of controlling the capacitor voltage balance of the sub-modules, the output voltage harmonic and the current distortion rate can be significantly reduced.
Description
technical field [0001] The invention relates to the technical field of power electronic converters, in particular to a control method for modular multilevel converters based on the current hysteresis principle. Background technique [0002] With the application of power electronic technologies such as flexible DC transmission and large-scale new energy power generation in the field of power systems, higher requirements are placed on the voltage level and transmission capacity of power converters. The emergence of cascaded devices and multi-level converter structures effectively solve the above-mentioned requirements. However, most of these multi-level topologies have disadvantages such as unbalanced capacitor voltage, poor static and dynamic voltage equalization effects, and large device volume, which limit their application scope to a large extent. In order to effectively solve the problems in these multilevel topologies, a modular multilevel converter (MMC) was proposed i...
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Login to View More IPC IPC(8): H02M7/483H02M7/5387H02M1/12
CPCH02M7/483H02M7/53871H02M1/12
Inventor 易灵芝刘罗陈才学陈智勇邓成范朝冬胡毕华
Owner XIANGTAN UNIV