Direct-current bus inter-phase voltage balancing control method for chained type triangular connection STATCOM (Static Synchronous Compensator)

Abstract

The invention discloses a direct-current bus inter-phase voltage balancing control method for a chained type triangular connection STATCOM (Static Synchronous Compensator). The chained type STATCOM is connected between a three-phase power source and a non-linear load. A main circuit of the chained type STATCOM is in a triangular connection manner. A zero-sequence component instruction is output through three phases of a triangular connection, so that voltage on three-phase direct-current bus voltage is balanced through three-phase additional zero sequence circular current of the triangular connection, and no negative-sequence current is additionally injected to a power grid.

Description

technical field [0001] The invention belongs to the field of reactive power compensation for power grids, and in particular relates to a chained delta-connected STATCOM direct current bus phase-to-phase voltage equalization control method for reactive power negative-sequence suppression of the power grid. Background technique [0002] With the rapid development of my country's modern industry, reactive power compensation has become a hot spot of common concern for the power sector and power users. The reactive power compensation device in the power system has developed from the earliest capacitor to today, and has gone through capacitors, synchronous condensers, static var compensators (SVC), and static var generators (STATCOM). Compared with the traditional SVC device represented by TCR, STATCOM has a faster adjustment speed and a wider operating range, and can reduce the content of harmonics in the compensation current after taking measures such as multiplexing, multilevel...

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Problems solved by technology

[0006] Yidan Li (Yidan Li, Bin Wu. A Novel DC Voltage Detection Technique in the CHB Inverter-Based STATCOM [J]. IEEE Trans. on Industry Electronics, 2008, 23(3): 1613-1619.) adopts the output AC voltage phase The fine-tuning method adjusts the active power absorbed by the three phases. This method requires three voltage loops to control the three-phase DC bus voltage respectively. This method has the following problems: when the three-phase DC bus voltage is seriously unbalanced, the three-phase output current The amplitudes are not equal, contain negative sequence components and the phases are no longer 120° in sequence. The realization of DC bus voltage balance is at the cost of injecting negative sequence current into the grid; when the grid requires compensation of negative sequence current, in order to maintain the DC bus Voltage equalization, the power quality controller will inject negative sequence current into the grid, so the ability to compensate negative sequence power is very poor

Laxman Maharjan, Shigenori Inoue, Hirofumi Akagi. A Transformerless Energy Storage System Based on a Cascade Multilevel PWM Converter With Star Configuration [J]. IEEE Trans. on Industry Electronics, 2008, 44(5): 1621-1630. The control method and the above The methods are similar, and the two methods also have shortcomings: when the three-phase voltage is seriously unbalanced, after the fine-tuning of the three-phase balance control, the amplitude of the AC output voltage of the three-phase converter has a large difference, which contains a large negative sequence This part of the negative-sequence voltage will generate negative-sequence current and inject it into the grid. Therefore, this method achieves the balance of the three-phase DC bus voltage at the expense of power quality.

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