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The impedance modeling of modular multilevel converters (MMCs) is a prerequisite for applying the impedance-based stability analysis method to an MMC-based high-voltage direct current (MMC-HVDC) transmission system. The objective of this paper is to develop impedance models of a three-phase MMC in order to assess its stability. The analytical ac-side and dc-side impedance models of the three-phase...
Control of the circulating current in the modular multilevel converter (MMC) is one of the major tasks for the proper operation of the converter topology. This paper develops a controller for the circulating current of the MMC that utilises the redundant voltage levels in 2N+1 modulated MMCs in order to regulate the current to its reference. The main advantages of the approach are the elimination...
The Modular Multilevel Converter (MMC) is a relatively new converter topology which has been favoured for high voltage DC transmission due to its performance, flexibility in control and its modular and scalable design which allow it to be used over a wide variety of system voltage levels and power ratings. The converter consists of a number of cascaded half bridge cells with isolated capacitors to...
The modular multilevel converter (MMC) is one of the most promising converter topologies for medium/high-power applications. One of the technical challenges associated with the control of an MMC is the capacitor voltage balancing among arm capacitors. This paper presents a novel capacitor voltage balancing method combined with the carrier-phase-shifted pulse-width modulation (CPS-PWM) for MMC without...
This paper analyses the behaviour of grid connected modular multilevel converter, under pulsed load at the DC side. The goal is to achieve minimum AC power fluctuation despite high power fluctuation on the DC side. Pulsed load causes imbalances of cell capacitor voltages, and this effect is analytically described. The control methodology, together with an algorithm for capacitor voltage balancing...
In this paper, a new approach to the discontinuous modulation technique for the operation of the modular multilevel converter (MMC) is presented. Discontinuous modulation is based on adding a zero-sequence to the original modulation signals so that each MMC arm is clamped to the upper or lower terminals of the dc-link bus during some intervals. In combination with a circulating current control, the...
The topology of modular multilevel converters (MMC) is investigated in this paper. First, single phase half bridge inverter with split wound coupled inductors was studied, it was found that more voltage levels can be generated by using split wound coupled inductors. Therefore, new MMC topology was proposed by the analysis result, therein, two more diodes were used for each arm, and split wound coupled...
Current source modular multilevel converter (CSMMC) is a potential topology for the high-power applications with low-voltage and high-current requirements. One of the most challenging issues associated with the CSMMC is the submodule inductor currents imbalance if it is not properly controlled. This paper presents a control method for submodule inductor currents balancing in a CSMMC. The control method...
This paper presents a simple core loss modeling approach for an inductor of three-phase voltage source converter (VSC) under pulse width modulation (PWM) technique. The inductor core loss calculation in PWM VSCs is challenging since the current ripple and its duty cycle are varying in each switching cycle. To calculate the core loss, however, generating the loss map as a common method is complicated...
This paper presents a 25kW six-level Modular Multilevel Converter prototype. The designed prototype is an industrial power converter that can be used by the industry. The converter is shown together with a high-performance hardware platform control designed for large multilevel converters. The hardware platform is a custom platform based on Zynq-7000 System-On-Chip that provides high processing performance...
The modulation technique chosen for use in the power converter largely defines the harmonics generated, consequently it is a fundamental part that must be studied. In this paper it's shown a comparative between different modulations techniques applied to a modular multilevel converter. Sinusoidal Pulse Width Modulation, Space-Vector Modulation and Nearest Level Modulation are studied. The whole techniques...
The modular multilevel converter (MMC) is the state-of-the-art voltage-source converter (VSC) topology used for various power-conversion applications. In the MMC, submodule failures can occur due to various reasons. Therefore, additional submodules called the redundant submodules are included in the arms of the MMC to fulfill the fault-safe operation requirement. The performance of the MMC with redundant...
Rapid development of Distributed Energy Resources (DERs) and DC-powered loads entails the possibility of DC micro-grids to revenge conventional AC distribution networks. In addition, a continuous evolution of the power electronic technology allowing the highest possible power of DER production also makes the DC micro-grids more feasible in the near future. Although energy efficiency and steady state...
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