MMC sub-module topological structure with DC fault blocking capability equivalent to that of full-bridge sub-module
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A full-bridge sub-module and DC fault technology, applied in the direction of converting AC power input to DC power output, power transmission AC network, output power conversion device, etc., can solve the problems of increased equipment cost, high cost, and large number of transistors , to achieve the effect of suppressing fault current and reducing economic cost
Inactive Publication Date: 2020-05-26
XI AN JIAOTONG UNIV
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The MMC module topology formed by cascading half-bridge sub-modules cannot effectively block DC faults. Once a DC fault occurs, power devices such as transistors and diodes will be burned due to the flow of fault current; full-bridge sub-modules can block DC faults, but the required More transistors, higher cost
At present, many scholars have proposed improved sub-module topologies, most of which have the problem of weak DC fault blocking capability, or require transistors to withstand higher voltages during DC faults, which brings difficulties to the selection of transistors and increases cost of equipment
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Embodiment 1
[0053] Build a flexible DC transmission system simulation model in MATLAB / Simulink, such as Figure 5 As shown, the MMC converter station topology is as follows Figure 6 As shown, each bridge arm contains sub-modules n=6, the sub-modules adopt the topology proposed by the present invention, and the parameters of the flexible straight system simulation model are shown in Table 2 below.
[0054] Table 2
[0055]
[0056] When the system is working normally, the active and reactive power waveforms transmitted by the system are as follows: Figure 7 As shown, the DC side current is as Figure 8 As shown, the bridge arm voltage is as Figure 9 As shown, the sub-module current is as Figure 10 shown. It can be seen that the system runs smoothly, the fluctuation of active power and reactive power is small, the fluctuation of DC side current is small, the voltage of the bridge arm is close to sinusoidal, and the sinusoidal and symmetry of the sub-module current is good, indic...
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Abstract
The invention discloses an MMC sub-module topological structure with DC fault blocking capability equivalent to that of a full-bridge sub-module. The MMC sub-module topological structure comprises a first output end, a second output end, a first transistor, a second transistor, a third transistor, a fourth transistor, a fifth transistor, a sixth transistor, a first diode, a second diode, a third diode, a fourth diode, a fifth diode, a sixth diode, a seventh diode, an eighth diode, a first voltage stabilizing capacitor and a second voltage stabilizing capacitor, wherein the first voltage stabilizing capacitor, the first transistor, the second transistor, the first diode and the second diode form a first half-bridge sub-module; and the second voltage stabilizing capacitor, the third transistor, the fourth transistor, the third diode and the fourth diode form a second half-bridge sub-module. The structure has the DC fault blocking capacity equal to that of the full-bridge sub-module, caneffectively block fault current when a direct current fault occurs, and is low in cost.
Description
technical field [0001] The invention belongs to the technical field of flexible direct current transmission, and relates to an MMC submodule topology structure of a full bridge submodule equivalent to a direct current fault blocking capability. Background technique [0002] In recent years, flexible direct current transmission technology has become a research hotspot in the field of power transmission. It has a significant role in promoting the development of new technologies such as large-scale wind power grid integration, urban power supply and island power supply, meeting the continuously growing energy demand and promoting clean and efficient utilization of energy. role. At present, there are mainly three types of voltage source converters used in flexible DC transmission projects: two-level voltage source converters, three-level voltage source converters, and modular multilevel converters (MMC). Both two-level and three-level voltage source converters have problems of ...
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