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In recent years, the Modular Multilevel Converter (MMC) has gained a lot of interest in industry due to its modularity and scalability for different power and voltage levels. However, the control of a MMC consisting of several submodules is often implemented in a central control system, so that the whole MMC system cannot be considered as modular. The thought to distribute control tasks to each submodule...
Modular multilevel converters (MMC) are used in the applications such as medium voltage multi-megawatt drives and in HVDC power transmission. The converter has several sub-modules connected in series that are switched appropriately to regulate the pole voltage. Besides regulation of output voltage, it is also essential to regulate the individual sub-module capacitor voltages. In this paper, a novel...
Modular multilevel converter (MMC) is being considered as the next generation converter among multilevel topologies and by introduction of MMC, a new era has opened to the field of medium- and high-voltage, high-power converters. Sizing the passive elements and design of the converter and its performance evaluation is thus of great importance for researchers in this area. The present paper performs...
Various high power applications require power converters with large voltage step ratios, easily achieved by inclusion of a single or multiple transformers, which provide galvanic isolation at the same time. This paper presents, in a systematic manner, the necessary steps for the integration of a Low Frequency Transformer (LFT) into the Modular Multilevel Converter (MMC). Unlike the classical MMC that...
The Modular Multilevel Converter (M2LC) is a well-known modular multilevel topology. This paper proposes a novel branch inductor coupling and compares it to the center-tapped inductor and the standard non-coupled inductor topology. The proposed coupling has a significant influence on the inductor and converter dimensioning. Its properties make it especially well-suited for use in M2LC single-to-three-phase...
This paper presents a new control method for a Modular Multilevel Converter (MMC) fed by a push-pull converter via a medium frequency (MF) transformer. Application of this topology is a universal high-precision 3AC voltage source for a Power Hardware-in-the-Loop Emulator with a frequency range from DC up to almost the medium frequency. Advantages are high efficiency, very low harmonic distortion and...
This paper focuses on the determination of suitable carrier based pulse width modulation (PWM) switching and control methods for grid connected modular multilevel converters (MMCs). Characterization of various level-shifted and phase-shifted carrier based PWM methods are provided in terms of output voltage waveforms both for N+1 and 2N+1 level output phase voltages. Carrier based PWM method based...
The modular multilevel converter (MMC), eliminating the expensive and bulky multi-winding phase-shifting transformer compared with the cascaded H-bridge converter, is shown to be of great potential in the field of medium-voltage motor drive applications. However, special care needs to be taken for MMC driving motor at low speeds, since the voltage fluctuation of the submodule capacitors increases...
The AC side Single Line to Ground (SLG) fault is one of the most frequent faults in power systems. And, in an HVDC system based on modular multilevel converter it calls for the fault ride through strategy to transmit maximum possible electricity during the fault to secure power system stability. It presents different characteristics of SLG faults at the voltage regulator side and the power dispatcher...
Small-signal state-space analysis of power system stability relies on linearized models where steady state operation corresponds to constant values of all state variables. Such models are available and commonly used for analysis of configurations with three-phase 2- or 3-level Voltage Source Converters (VSC). However, the Modular Multilevel Converter (MMC), which is emerging as a preferred topology...
A new ultracapacitor-battery HESS based on bidirectional Z-Source topology is proposed in previous research for better energy and space utilization. By controlling the power of UCs and machine, the steady average battery current get controlled indirectly. However, for safety consideration, the dynamic performance of proposed HESS should be considered, so small signal model based on state-space average...
This paper investigates design procedure of modular multilevel converter (MMC) in active front-end (AFE) mode of operation. The design in performed trying to minimize the amount of passive elements including arm inductances and submodule capacitances. This has been done using basic controllers needed for operation of MMC in AFE mode, without employing any additional controller in the circuit. In other...
Modular Multilevel Converter (MMC) has recently become a popular multilevel topology for high-power applications. Conventionally, the circulating current between the legs of an MMC is an unwanted current that must be minimized in order to reduce the converter loading. In this paper the impacts of the circulating current in the MMC to the current ratings of power semiconductor devices are comprehensively...
Alternate Arm Converter (AAC) is considered as a new breed of hybrid multilevel voltage source converters. In this paper, modeling, design and control of the Alternate Arm Converter (AAC) are presented and operation principles of the AAC is discussed. One of the issues regarding to the AAC is the switching between the upper and lower arms which provides hard switching of the so called Director Switches...
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