Network disconnection protection strategy of modular multilevel converter distributed control system
A modular multi-level, distributed control technology, applied in electrical components, output power conversion devices, etc., can solve problems such as capacitor voltage soaring, overall system instability, and inability to receive control data, reducing impact, The effect of reasonable protection
Active Publication Date: 2020-01-17
SOUTHWEST JIAOTONG UNIV
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[0005] When a sub-controller has a network disconnection fault, it cannot receive the above five control data, and it can only obtain its capacitance voltage value by sampling the capacitance voltage of the controlled sub-module
At this time, regardless of whether the sub-controller continues the original control program, it will generate a modulation signal lacking the fundamental frequency AC component, which will eventually lead to a surge in the capacitor voltage of the disconnected sub-module corresponding to its control and instability of the overall system.
[0006] At present, no results have been published on the sub-controller disconnection problem in the distributed control system of modular multilevel converters, so it is necessary to conduct research on this issue
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[0024] The present invention will be described in further detail below in conjunction with the accompanying drawings and specific embodiments. In the present invention, by storing the target output current phase sent by the main control, the sub-controller after disconnection can still continue to generate the modulation signal with the fundamental frequency AC component with basically correct phase; The capacitor voltage of the network sub-module is effectively controlled; a complete network disconnection protection strategy is proposed, and reasonable solutions are given for long-term and short-term network disconnection faults.
[0025] After the sub-controller is disconnected from the network, it cannot receive the control information from the main controller, and can only detect the capacitor voltage of the controlled sub-module through the voltage sensor.
[0026] The network disconnection protection strategy proposed in this patent is as follows: under normal circumstan...
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The invention discloses a network disconnection protection strategy of a modular multilevel converter distributed control system. Each sub-controller creates an array to store and refresh a target output current phase or a target output voltage phase sent by a main controller; after a network disconnection fault occurs, each sub-controller uses the stored phase signal as a fundamental frequency component in the modulation wave and continues to generate a modulation signal containing a direct current component and a fundamental frequency alternating current component; and meanwhile, a capacitorvoltage balancing ring is adopted to adjust the modulation ratio Mbreak in the modulation signal after network disconnection, so that the capacitor voltage of the network disconnection sub-module iscontrolled. According to the invention, the influence of the disconnection fault of the sub-controller on the whole modular multilevel converter is effectively reduced; the whole system can be kept stable in the process of a network disconnection fault; therefore, the whole system has a fault ride-through capability for a short-time network disconnection fault, and the system is reasonably protected for a long-time network disconnection fault.
Description
technical field [0001] The invention relates to the technical field of power system control, in particular to a network disconnection protection strategy for a distributed control system of a modular multilevel converter. Background technique [0002] Modular multilevel converter (MMC) is a new power electronic topology, which is suitable for high-voltage and high-power applications, especially in the field of high-voltage direct current transmission (HVDC). [0003] However, due to the limitation of withstand voltage of power electronic devices, when the modular multilevel converter is applied in the field of HVDC transmission, it often requires a large number of sub-modules. At this time, if a centralized control structure is adopted, that is, a central controller is used to control all sub-modules, the system requires a large number of optical fibers and the central controller needs to have strong control capabilities. Therefore, a modular multilevel converter with a lar...
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Login to View More IPC IPC(8): H02M1/32
CPCH02M1/32
Inventor 杨顺风陈海宇王海宇熊成林
Owner SOUTHWEST JIAOTONG UNIV