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This paper presents discontinuous pulse width modulation (DPWM) scheme for a modular multilevel converter (MMC) to achieve an advanced switching losses reduction. The MMC is considered to be one of the most attractive multilevel topology for high-power applications because of the features of its high power quality, modularity, and availability. However, the MMC has large switching losses because of...
Modulation techniques for the modular multilevel converter consider that the total number of sub-modules in the phase-leg is, either instantaneously or on average, equal to N balancing the capacitor voltages to a constant reference. This paper proposes an offset PWM technique that utilises the total number of the SMs in the arms of the MMC, particularly under low modulation indices. The result is...
In this paper, a modulation strategy based on zero-sequence voltage injection is proposed for module multilevel converter (MMC). By the proposed method, the remaining capacitor voltages not vary and the line-to-line voltages are balanced. This method is easy to be implemented by adjusting the voltage injection coefficient when SM fault occurs. The coefficient of injected zero-sequence voltage is designed...
Conventional three-phase MMC consists of six-arms, each arm is controlled to generate unipolar voltage ranging from zero to Vdc where Vdc is the input DC voltage. Each arm voltage has two components (DC and AC components). In this work, the operation of MMC with reduced number of arms (four arms only), correspondingly reduced cost is presented. This mode can be also used with the conventional three-phase...
The internal dynamics governing the modular multilevel converter can be described by considering the total capacitor's voltages of each arm and the circulating currents. In this study, dynamics of the total capacitor voltage of the modular multilevel converter (MMC) is analyzed. Depending on the internal control approach adopted which ensure a symmetrical energy distribution in the arms of the converter,...
Modular multilevel converters (M2Cs) consist of a high number of cells per phase complicating system analysis and simulation. The present paper introduces a suitable two-terminal network for the series connection of the submodules in an arm. Furthermore, an averaged model for an M2C intended for the use with three-phase AC-loads is derived.
This paper first introduces the principle of the Modular Multilevel Converter and then describes the mathematic model. Secondly, the proportional resonant controller is studied and used in the modular multilevel converter. The control strategy diagram is presented. After that, the 71-level model of modular multilevel converter is set up in the PSCAD/EMTDC. By the model simulation the proportional...
This paper describes two distinctive functions of the arm inductor in the modular multilevel converters (MMC): suppressing the circulating current and limiting the fault current rise rate. Based on the equality of the instantaneous power, the characteristics of the circulating current are analyzed and demonstrated that it flows through the three phase of the converter in negative sequence at double-fundamental...
This paper deals with the scalable and transformerless Modular Multilevel Converter (MMC). A new modulation algorithm for this converter is presented, together with a Matlab-Simulink simulation based validation, of eight sub-module single phase MMC. In addition, the capacity of the proposed modulation to operate at high power applications with high number of sub-modules is demonstrated, by means of...
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