Modular multilevel-based STATCOM device for inhibiting ripples of capacitive voltage

Abstract

The invention provides a modular multilevel-based STATCOM device for inhibiting ripples of capacitive voltage. The STATCOM device comprises an STATCOM system which is directly connected to a common node through a connection inductor in parallel, wherein the STATCOM system comprises a bridge arm phase A, a bridge arm phase B, a bridge arm phase C and a bridge arm phase D. On the basis of an MMC topology, the DC bus voltage of the MMC is eliminated, the hidden danger of a short circuit of a common bus of a DC side is eliminated and the security of the device is improved; the low-frequency ripples of capacitive voltage of an upper bridge arm and a lower bridge arm of each bridge arm phase are inhibited by using a low-voltage and low-capacity capacitor, so that use of lower capacitance of a sub-module is facilitated, the cost of a system is reduced and the volume of the device is reduced. The bride arm phases of switching devices are replaced with buffer inductors, the quantities of the capacitors and the switching devices are reduced to 3 / 4 of those of a conventional structure, so that the cost and the volume of the device are significantly reduced and the loss of the system is reduced. The application of the bridge arm phase is not limited to the application scene of reactive power compensation and an existing bridge arm phase adopting cascaded H-bridge multilevel topological devices can be replaced.

Description

technical field [0001] The invention relates to the technical field of power electronics flexible power transmission equipment, in particular to a STATCOM device based on modular multi-level suppression of capacitor voltage fluctuations. Background technique [0002] The existence of a large number of unbalanced industrial loads and single-phase large-capacity loads such as industrial AC electric arc furnaces and electrified railways, as well as the widespread use of power electronic devices, have brought a large amount of reactive current and negative sequence current to the power system, which not only increases the loss , and endanger electrical equipment. In this context, since power electronic technology can participate in maintaining the stable operation of the power system and the distribution of power flow, it has increasingly become an important technical means for power system compensation and regulation. [0003] Static Synchronous Compensator (STATCOM) is one of...

AI Technical Summary

Problems solved by technology

However, there are still some inherent problems in the STATCOM based on modular multi-level, which need to be paid attention to and solved by the industry. First, the common DC bus in the MMC-based STATCOM has a grid-level high voltage. Once the DC side is short-circuited, it will cause a huge short-circuit current. , burn the device; secondly, engineering experience shows that a large number of sub-module capacitors in the MMC occupy a large amount of space in the device, thereby increasing the volume of the device and increasing the system cost. Reducing the capacitance value of the sub-module capacitor can greatly reduce the capacitance of the capacitor. Capacitance, thereby significantly reducing the size of the device and reducing the cost of the device; in addition, when STATCOM is used in an unbalanced system with a neutral point system and needs to compensate for unbalanced current, the extra zero-sequence channel adds a bridge arm to the MMC, The cost and volume of the device also increase proportionally

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