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Leg-Balancing Control of the DC-link Voltage for Modular Multilevel Converters
Du, Sixing,Liu, Jinjun,Lin, Jiliang The Korean Institute of Power Electronics 2012 JOURNAL OF POWER ELECTRONICS Vol.12 No.5
This paper applies carrier phase shifted pulse-width modulation (CPS-PWM) to transformerless modular multilevel converters (MMC) to improve the output spectrum. Because the MMC topology is characterized by the double-star connection of six legs consisting of cascaded modular chopper cells with floating capacitors, the balance control of the DC-link capacitor voltage is essential for safe operation. This paper presents a leg-balancing control strategy to achieve DC-link voltage balance under all operating conditions. This strategy based on circulating current decoupling control focused on DC-link balancing between the upper and lower legs in each phase pair by considering the six legs as three independent phase-pairs. Experiments are implemented on a 100-V 3-kVA downscaled prototype. The experimental results show that the proposed leg-balancing control is both effective and practical.
A PDPWM Based DC Capacitor Voltage Control Method for Modular Multilevel Converters
Du, Sixing,Liu, Jinjun,Liu, Teng The Korean Institute of Power Electronics 2015 JOURNAL OF POWER ELECTRONICS Vol.15 No.3
This paper presents a control scheme with a focus on the combination of phase disposition pulse width modulation (PDPWM) and DC capacitor voltage control for a chopper-cell based modular multilevel converter (MMC) for the purpose of eliminating the time-consuming voltage sorting algorithm and complex voltage balancing regulators. In this paper, the convergence of the DC capacitor voltages within one arm is realized by charging the minimum voltage module and discharging the maximum voltage module during each switching cycle with the assistances of MAX/MIN capacitor voltage detection and PDPWM signals exchanging. The process of voltage balancing control introduces no extra switching commutation, which is helpful in reducing power loss and improving system efficiency. Additionally, the proposed control scheme also possess the merit of a simple executing procedure in application. Simulation and experimental results indicates that the MMC circuit together with the proposed method functions very well in balancing the DC capacitor voltage and improving system efficiency even under transient states.
Leg-Balancing Control of the DC-link Voltage for Modular Multilevel Converters
Sixing Du,Jinjun Liu,Jiliang Lin 전력전자학회 2012 JOURNAL OF POWER ELECTRONICS Vol.12 No.5
This paper applies carrier phase shifted pulse-width modulation (CPS-PWM) to transformerless modular multilevel converters (MMC) to improve the output spectrum. Because the MMC topology is characterized by the double-star connection of six legs consisting of cascaded modular chopper cells with floating capacitors, the balance control of the DC-link capacitor voltage is essential for safe operation. This paper presents a leg-balancing control strategy to achieve DC-link voltage balance under all operating conditions. This strategy based on circulating current decoupling control focused on DC-link balancing between the upper and lower legs in each phase pair by considering the six legs as three independent phase-pairs. Experiments are implemented on a 100-V 3-kVA downscaled prototype. The experimental results show that the proposed leg-balancing control is both effective and practical.
A PDPWM Based DC Capacitor Voltage Control Method for Modular Multilevel Converters
Sixing Du,Jinjun Liu,Teng Liu 전력전자학회 2015 JOURNAL OF POWER ELECTRONICS Vol.15 No.3
This paper presents a control scheme with a focus on the combination of phase disposition pulse width modulation (PDPWM) and DC capacitor voltage control for a chopper-cell based modular multilevel converter (MMC) for the purpose of eliminating the time-consuming voltage sorting algorithm and complex voltage balancing regulators. In this paper, the convergence of the DC capacitor voltages within one arm is realized by charging the minimum voltage module and discharging the maximum voltage module during each switching cycle with the assistances of MAX/MIN capacitor voltage detection and PDPWM signals exchanging. The process of voltage balancing control introduces no extra switching commutation, which is helpful in reducing power loss and improving system efficiency. Additionally, the proposed control scheme also possess the merit of a simple executing procedure in application. Simulation and experimental results indicates that the MMC circuit together with the proposed method functions very well in balancing the DC capacitor voltage and improving system efficiency even under transient states.
A novel medium voltage five-level converter with minimized volume
Deng, Zhifeng,Liu, Jinjun,Du, Sixing The Korean Institute of Power Electronics 2022 JOURNAL OF POWER ELECTRONICS Vol.22 No.10
In applications such as ship propulsion and of-shore wind power generation, it is important to minimize the volume of medium voltage power converters. To make this possible, a novel five-level converter topology is proposed in this paper. This converter is realized by connecting two half-bridge (HB) cells with a three-level neutral point clamped (3L-NPC) unit. In each HB cell, the switches are directly clamped to DC side capacitors where the larger volume high-voltage flying capacitors are avoided. By adopting the 3L-NPC unit, the volume of the proposed converter is further reduced. A comprehensive comparison result shows that the volume of the proposed converter is more than 7% less than existing five-level converters. The operation principle and modulation method of this converter are also introduced. Based on the phase-shift pulse width modulation (PS-PWM) method, the capacitor voltages of the proposed converter can be self-balanced. Simulation and experiment results are shown to verify the performance of this converter and the validity of the theoretical analysis.
Hui Chen,Jinjun Liu,Sixing Du,Cong Li,Zhifeng Deng 전력전자학회 2023 ICPE(ISPE)논문집 Vol.2023 No.-
It is well-known issue that dc bias and oscillations will be introduced into phase current and dc current when the transmission power and control variables of three phase dual active bridge (3ph-DAB) converter have the abrupt changes. It will cause the magnetic saturation problem and degrade the dynamic response seriously. To solve this issue, this paper proposes a novel fast transient current control scheme with asymmetrical three phase (APS) control. By choosing suitable transient phase shift angles, the proposed method can greatly suppress the dc bias and overshoot of phase current and improve the transient performance significantly. It is presented to make 3ph-DAB transit from initial steady state to target steady state within one step through the proposed method and space-vector theory. The simulation results verify the effectiveness of proposed scheme.