The Suppression of Modular Multi-Level Converter Circulation Based on the PIR Virtual Impedance Strategy

Abstract

In recent years, with the rise of the electric vehicle industry, there has been significant research on charging and power supply vehicle technologies for electric vehicles. In terms of the corresponding converter usage, modular multi-level converters (MMCs) are also increasingly used in the field of electric vehicle power supply research because of their unique advantages. However, the circulating current problem of MMCs has not been effectively addressed in existing domestic and international studies. In this paper, we propose a proportional-integral resonant (PIR) control method combined with virtual impedance for the optimal suppression of the MMC internal circulating current problem based on the comparison and generalization of the existing methods. Based on the analysis of the working principle of MMCs, this paper proposes and adopts the control strategy of combining virtual impedance and proportional-integral resonance to suppress the circulating current and builds a simulation model in MATLAB to verify that the control strategy proposed in this paper is feasible.

Suppression of Negative Sequence Current on HVDC Modular Multilevel Converters in Offshore Wind Power

“…Applying the Laplace inverse transform to Equation (24) and taking the limit, we can obtain lim ( ) 0 t y t →∞ = . Moreover, as the observer bandwidth 0 ω increases, the rate of decrease in ( ) y t also increases.…”

“…However, due to the structure of MMC itself, the instantaneous voltages of the sub-modules of the upper and lower bridge arms are different, which leads to the internal circulation between the phases in the normal operation of the system. The existence of circulating current not only increases power consumption and energy loss and causes voltage fluctuation and voltage distortion but also shortens the service life of power electronic devices [23,24]. Well-specified circulating current suppressors play an important role in improving power quality, reducing loss and optimizing system performance in HVDC systems.…”

Circulating Current Suppression Strategy Based on Virtual Impedance and Repetitive Controller for Modular Multilevel Converter Upper and Lower Bridge Arm Capacitance Parameter Asymmetry Conditions

“…According to the above analysis, the introduction of the low-pass filter ( ) Q z improves the stability of the system; however, it weakens the gain at high frequencies. The introduction of additional VI can equivalently increase the bridge arm reactance to improve the suppression of high-frequency harmonics and can share the circulating current suppression at low frequencies [27][28][29]. The virtual impedance is improved from the virtual reactance.…”