c-mmc static voltage equalization control method based on energy source control

Abstract

The invention discloses a C-MMC static voltage equalization control method based on energy-taking power supply control. Firstly, the capacitance voltage of each C-MMC sub-module is collected, and the average value thereof is obtained, and by comparing the voltage of the C-MMC sub-module with the target voltage size, to obtain the modulation signal of the energy harvesting power supply that satisfies the voltage balance between the sub-modules. Then, taking the average value of the voltages of the two capacitors in the sub-module as the target of the balance of the voltages of the two capacitors in the sub-module, by comparing the value of the capacitor voltage with the target value, the modulation of the energy harvesting power supply that satisfies the voltage balance of the two capacitors in the sub-module is given. Signal. The modulation signal is compared with the triangular carrier wave to obtain the control signal of the flyback circuit in the energy harvesting power supply. Depending on the control signal, the input current of the energy harvesting power supply will be adjusted, and the capacitor voltage of the power module will also be indirectly adjusted. No additional additional circuits are required, and the control method is simple, which is of great significance for reducing system loss and ensuring normal startup of the system.

Description

technical field [0001] The invention belongs to static voltage equalization control, in particular to a C-MMC static voltage equalization control method based on energy harvesting power source control. Background technique [0002] In recent years, the flexible DC transmission technology with modular multilevel converter (MMC) as the core topology has been more and more widely used in my country's power grid system. The power module of the converter adopts fully controlled power electronic devices, and the system adopts sub-module (SM, sub-module) cascading form, which is easy to expand, improves the system voltage level, and reduces the switching frequency of switching devices, thereby reducing switching losses , the output voltage waveform is closer to a sine wave to reduce harmonic content. Different from the traditional DC transmission technology, the MMC-based flexible DC transmission technology can supply power to the passive network, realize independent decoupling co...

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Problems solved by technology

[0003] At present, the research on the MMC composed of CDSM mainly focuses on its ability to isolate DC side faults, and there are relatively few studies on its voltage balance, and the system voltage imbalance poses a great threat to the normal operation of the system.

Different from the half-bridge sub-module and the full-bridge sub-module, the clamping twin sub-module contains two capacitors, not only the problem of voltage imbalance between the sub-modules, but also the voltage balance between the two capacitors inside the sub-module, especially in MMC In the stage of uncontrolled pre-charging, since all the IGBTs are in a blocked state, the system capacitor voltage cannot be balanced by controlling the IGBT, and the unbalance of the capacitor voltage is more significant, which will seriously affect the normal startup and operation of the system

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