A three-phase modular multilevel converter parallel system and its control method
A three-phase module and conversion system technology, applied in the direction of converting AC power input to DC power output, irreversible DC power input to AC power output, electrical components, etc., can solve the problem of limited output current and output current limitation And other issues
Active Publication Date: 2017-12-22
SHANDONG UNIV
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Problems solved by technology
[0004] Although the modular multilevel converter realizes the problem of wide-range voltage application, its output current is still limited by the switching tube, and the output current is still limited
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specific Embodiment approach
[0058] In the step (2), the phase angle is obtained by phase-locking the grid voltage, so that the current and the grid voltage can be in phase through the phase angle, so that the system can obtain the maximum power factor at all times. The specific implementation is as follows:
[0059] First, the three-phase grid voltage u a , u b , u c Transform it from the three-dimensional coordinate system to the two-dimensional αβ coordinate system by 3-2 transformation, and get
[0060] where u a , u b , u c is the grid voltage, u α , u β is the value of the grid voltage in the two-dimensional αβ coordinate system.
[0061] pass where u α , u β is the value of the grid voltage in the two-dimensional αβ coordinate system, ωt is the phase angle of the grid voltage, and the phase angle of the grid voltage is obtained.
[0062] In the step (3), firstly, the current of each three-phase modular converter is transformed from the three-dimensional coordinate system to the αβ co...
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The invention discloses a three-phase modular multi-level power conversion system and a control method thereof, comprising an input power supply connected in parallel with N sets of three-phase modular converters connected in parallel, each three-phase modular The converter includes three-phase bridge arms, each phase bridge arm includes an upper bridge arm and a lower bridge arm, and the structure of the upper bridge arm and the lower bridge arm is symmetrical, and each includes n sub-modules in series and an inductor close to the neutral point, where each Each sub-module includes two series-connected switching tubes and a capacitor connected in parallel with the two series-connected switching tubes, the neutral point of each phase bridge arm is connected to the grid after being connected by a filter, and each sub-module is connected to the controller; The control strategy proposed by the present invention effectively solves the problem of circulating current among multiple converters, and solves the problem of circulating current between multiple converters by controlling the zero-sequence current of N-1 converters.
Description
technical field [0001] The invention relates to a three-phase modular multilevel converter parallel system and a control method thereof. Background technique [0002] With the country's increasing emphasis on new energy, the photovoltaic industry has developed very rapidly in recent years. Improving power quality, reducing harmonic pollution, and improving the efficiency and power of power generation systems are important parameters for various converters. In recent years, high-voltage power transmission technology has become more and more popular, and high-voltage power transmission has become a general trend. The traditional method to improve the system withstand voltage is to select a high-voltage resistant device as the switch tube of the converter. Although this can increase the system withstand voltage, the improvement space is limited, and it is easy to cause system instability. Therefore, other methods are selected to increase the system withstand voltage abnormally....
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IPC IPC(8): H02M7/493H02M7/49
Inventor 张承慧张桐盛杜春水邢相洋
Owner SHANDONG UNIV