Modulation Coordinated Voltage Balance Strategy for a Dual-T-Type Modular Multilevel Converter

With the development of flywheel technology, the speed and the voltage level of flywheel continue to increase. The Z-type self-balancing modular multilevel converter can have a wide frequency range at medium voltage and is suitable for flywheel driving application. However, the voltage and current characteristics of the flywheel and the variable frequency drive still affect capacitor voltage balance in each phase-leg. The new balance of capacitor voltage can be achieved by controlling the circulating current. This paper proposed a control algorithm of the novel Z-type self-balancing modular multilevel converter for flywheel driving applications. Simulation results are presented to validate the theoretical analysis.

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A Novel STATCOM Based on Flying Capacitor Modular Multilevel Converter

International Journal of Emerging Research in Management and Technology ◽

10.23956/ijermt.v6i11.51 ◽

2018 ◽

Vol 6 (11) ◽

pp. 86

Author(s):

T. Sanjeeva Rao ◽

T. Sowjanya

Keyword(s):

Control Method ◽

Modular Multilevel Converter ◽

Multilevel Converter ◽

Static Synchronous Compensator ◽

Current Compensation ◽

Negative Sequence ◽

Capacitor Voltage ◽

Voltage Balance ◽

Capacitor Voltage Balance ◽

Negative Sequence Current

A new static synchronous compensator (STATCOM) based on Flying Capacitor modular multilevel converter (DCM2C) is proposed in this thesis. In this converter topology the capacitor voltage is clamped by using a low power rating diode in each sub-module (SM). The quantity of voltage sensors is significantly reduced and is free from the number of voltage levels. Furthermore the voltage balancing control method becomes very simple and the capacitor voltage balance speed is fast. Based on the structure of MMC the DCM2C-STATCOM has the capability of Var compensation and negative sequence current compensation. The topology characteristics and compensation control method of DCM2C-STATCOM are investigated in this thesis. That the capacitor voltage of the proposed DCM2C-STATCOM can be well balanced and the Var and negative-sequence current compensation are effective.

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Research on the Voltage Balance Strategy of Modular Multilevel Converter

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1055.157 ◽

2014 ◽

Vol 1055 ◽

pp. 157-160

Author(s):

Ji Min Jing ◽

Jing Ze Wang ◽

Yan Chao Ji

Keyword(s):

Control Strategies ◽

Low Frequency ◽

Voltage Divider ◽

Voltage Source ◽

Stable Operation ◽

Modular Multilevel Converter ◽

Multilevel Converter ◽

Factors Affecting ◽

Capacitor Voltage ◽

Voltage Balance

The modular multilevel converter (MMC) does not need clamping devices and multiple independent DC voltage source and has a modular structure which is easy to be extended to any level, share a DC side, easy to direct back to back four-quadrant operation and attracts widespread attention. Due to the use of sub-module MMC suspended on the DC side capacitor voltage divider provides synthetic AC output voltage required voltage level and therefore it is essential to the stable operation of the sub-module capacitor voltage balance of the MMC. In this paper, the factors affecting the MMC sub-module capacitor voltage balancing has been carried out a detailed analysis and this paper focuses on the nominal frequency erupted module capacitor voltage control strategies and the average low frequency sub-module capacitor voltage ripple suppression strategies.

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