scholarly journals A Novel Z-Type Self-Balancing Modular Multilevel Converter for Flywheel Driving Applications

2021 ◽  
Vol 271 ◽  
pp. 01025
Author(s):  
Shuoqi Cheng ◽  
Tong Zheng ◽  
Congzhe Gao ◽  
Jingliang Lv ◽  
Xinjian Jiang
Keyword(s):  
Wide Frequency Range ◽  
Modular Multilevel Converter ◽  
Multilevel Converter ◽  
Variable Frequency Drive ◽  
Medium Voltage ◽  
Circulating Current ◽  
Capacitor Voltage ◽  
Voltage Balance ◽  
Current Characteristics ◽  
Capacitor Voltage Balance

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.

A Novel STATCOM Based on Flying Capacitor Modular Multilevel Converter

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.

scholarly journals Circulating Current Suppression Control in Surrogate Network of MMC- HVDC System

2020 ◽  
Vol 8 (6S) ◽  
pp. 29-34
Keyword(s):  
Output Voltage ◽  
Electromagnetic Transients ◽  
Modular Multilevel Converter ◽  
Multilevel Converter ◽  
Voltage Balancing ◽  
Hvdc System ◽  
Circulating Current ◽  
Capacitor Voltage ◽  
Circulating Currents ◽  
Three Phases

Modular multilevel converter consists of hundreds of submodules (SMs) like half bridge and full bridge converters etc. These hundreds of SMs and electrical nodes poses challenges while computing electromagnetic transients (EMTs). This problem becomes more complex while computed in real-time. To overcome this, an equivalent topology to model MMC arm/valve called surrogate network is utilized. But, the major ambiguity integrated with surrogate network model is SM capacitor voltage balancing. This leads to variation in voltage among the three phases which are parallel and produces circulating current between the three phases. A control circuitry is proposed in this paper to suppress/minimize circulating currents between the phases. Apart from circulating current suppression, the ‘ac’ output voltage is also enhanced at the converter with this proposed controller. Simulation is carried out in RSCAD software using RTDS simulator.

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