Optimised operation mode for the Hexverter topology based on adjacent compensating power

Karwatzki, Dennis; Baruschka, Lennart; Hofen, Malte von; Mertens, Axel

doi:10.1109/ecce.2014.6954141

Cited by 16 publications

(6 citation statements)

References 18 publications

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“…The hexverter contains three control schemes for operation, i.e., an inner loop for current control, an outer loop for voltage control, and a circulating current control loop, as shown in Figures 4-6. All of these control loops can be easily derived from Equations (13)- (18). Figure 6.…”

Section: Hexverter Modeling and Its Control Strategymentioning

confidence: 99%

“…Researchers have proposed different strategies for the hexverter optimization, such as active power control, branch voltage control, inductance influence and control [15,16], but no one has addressed the control strategy for zero-sequence current. Furthermore, a lot of work has also been done on offshore wind farm integration with LFAC and FFT systems interim of inverter control, converter control for the resonance contingency of long transmission lines and harmonics problem in inverters [17][18][19][20].…”

Section: Introductionmentioning

confidence: 99%

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Low-Frequency AC Power Transmission and Distribution for Subsea Application Using Hexverter

et al. 2020

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Environmental goals set by world leaders to normalize climate changes are quite difficult to achieve without renewable power generation and suitable transmission technologies like low-frequency AC transmission (LFAC). The LFAC is nowadays becoming a popular choice for long-distance power transmission due to its high efficiency and low losses. This research work investigates the feasibility of employing the LFAC system for subsea transmission and distribution of 58 MW power. In this paper, the simulation model of the LFAC-based subsea transmission and distribution system is presented. This model is composed of several parts such as hexverter as a frequency converter, where a novel control strategy to optimize its zero-sequence circulating current is employed. Detailed mathematical modeling based on active, reactive power constraints and DQ transformation is performed to achieve the control strategy for zero-sequence current optimization. An offshore wind farm is proposed to be integrated with the LFAC subsea system to fulfill the compatibility requirements of the system. The control system of both the grid side and the machine-side inverter of the wind farm is designed to eliminate the real-time disturbances such as wind speed fluctuations and harmonics due to heavy inductive load operating at 16 Hz. To drive the subsea pump, a vector control-based variable-speed drive is employed for the heavy induction motor. A 5 MW, 16 Hz RL load is also added in the model to analyze the effect of general-purpose load. Each component of this system is carefully designed to make it as close to real-time as possible. The whole system is designed for 16 Hz and is compared with the standard 50 Hz system to validate this design.

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Section: Hexverter Modeling and Its Control Strategymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Low-Frequency AC Power Transmission and Distribution for Subsea Application Using Hexverter

et al. 2020

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“…It is also shown in [20] that the Hexverter system offers superior performance for low-frequency wind turbines. Other research on Hexverter mainly focuses on its branch energy control based on adjacent compensating power [21][22][23]. Compared with M3C, only six branches are required for Hexverter to achieve AC/AC conversion, so equipment volume and cost is greatly reduced.…”

Section: Introductionmentioning

confidence: 99%

Modeling and Control of Modular Multilevel AC/AC Converter in Y Configuration for Fractional Frequency Transmission System

Meng

Shang

et al. 2020

IEEJ Transactions Elec Engng

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The modular multilevel AC/AC converter topology in Y configuration, which is called Y‐MMC, suitable for fractional frequency transmission system is proposed in this paper. Y‐MMC can directly connect two three‐phase AC systems of different frequencies and voltage amplitudes with only six equivalent branches, and it has satisfying performance in power quality and characteristics. Y‐MMC enjoys a simple and symmetrical structure with no circulating current problem. The detailed topology and operating principle of Y‐MMC are addressed in this paper. The frequency‐decoupled mathematical model of the Y‐MMC system is deduced. Corresponding control scheme is thoroughly designed, including the inner loop current control, the outer loop control, the individual‐balancing control, and frequency leakage suppression control. The paper also lays emphasis on the optimization of reactive power distribution between the main branches and the assistant branches of Y‐MMC. The validity of the Y‐MMC topology and the effectiveness of the proposed control scheme are verified by the simulation results in MATLAB/Simulink. © 2020 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

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“…Unlike the control schemes presented in [17], a new circulating current optimization method is proposed as follows to minimize I cir .…”

Section: Circulating Current Optimization Controlmentioning

confidence: 99%

“…Subsequent studies on the Hexverter mainly focus on its branch energy control based on adjacent compensating power [16][17][18]. Reference [19] presents a simplified qualitative comparison of previously presented cascaded multilevel converter topologies for AC/AC conversion, with particular emphasis on motor drive applications.…”

Section: Introductionmentioning

confidence: 99%

Control scheme of hexagonal modular multilevel direct converter for offshore wind power integration via fractional frequency transmission system

Meng

Liu²,

Luo³

et al. 2017

J. Mod. Power Syst. Clean Energy

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A fractional frequency transmission system (FFTS) is a promising solution to offshore wind power integration, for which the hexagonal modular multilevel converter (Hexverter) is an attractive choice for power conversion. The Hexverter has recently been proposed to directly connect two three-phase systems of different frequencies and voltage amplitudes, with only six branches in the FFTS in that case. This paper examines for the first time the control scheme of the Hexverter when applied to offshore wind power integration via a FFTS. Firstly, the frequency-decoupled mathematical model of the Hexverter is deduced by introducing the double dq transformation. Then the branch energy of the Hexverter is analyzed in detail and the reactive power constraint equation is obtained. The corresponding control scheme is thoroughly discussed, including the inner loop current control, the outer loop voltage control in both grid-connected mode and passive mode, and a novel optimization method to minimize the circulating current in the Hexverter. Finally, a simulation model of offshore wind power integration via a 4-terminal FFTS based on the Hexverter is built in MATALB/Simulink to verify the feasibility of Hexverter and the effectiveness of the control scheme proposed in this paper.

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Optimised operation mode for the Hexverter topology based on adjacent compensating power

Cited by 16 publications

References 18 publications

Low-Frequency AC Power Transmission and Distribution for Subsea Application Using Hexverter

Low-Frequency AC Power Transmission and Distribution for Subsea Application Using Hexverter

Modeling and Control of Modular Multilevel AC/AC Converter in Y Configuration for Fractional Frequency Transmission System

Control scheme of hexagonal modular multilevel direct converter for offshore wind power integration via fractional frequency transmission system

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