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Modular multilevel converter (MMC) is one of the most promising topologies for medium to high-voltage high-power applications. The main features of MMC are modularity, voltage and power scalability, fault tolerant and transformer-less operation, and high-quality output waveforms. Over the past few years, several research studies are conducted to address the technical challenges associated with the...
Buck and buck-boost ac-ac converter topologies with a center-point-clamped circuit configuration have been recently reported in literature. These converter circuits reduce the voltage stress on the bidirectional switches employed in corresponding direct ac-ac converters. This new topological structure enables access to the mid-point of voltage terminals. This paper introduces a family of such ac-ac...
This paper presents two predictive control methods with reduced number of calculations for five-level AC/DC rectifier. The first method is the simpler and required to calculate the value of cost function for only three converter voltage vectors. The second method is using two steps prediction horizon and required to calculate cost function for seven vectors in first step and for three vectors for...
This paper describes three modern predictive control methods of three-level AC/DC rectifier. Additionally, it presents a comparison of the methods both in static and dynamic states. Simulation and experimental results confirm that all presented control algorithms ensure a good control quality (low THD) in static states and excellent dynamic properties.
Modular Multilevel Converter (MMC) topology is an interesting solution for number of medium and high voltage applications. Key advantages over another multilevel topologies include flexibility of scaling in voltage and simple implementation of redundancy. In this publication control of DC-DC MMC is discussed. Analyzed converter consists of six branches connected in double wye structure. It enables...
Ensuring that the DC voltage remains within an acceptable range is a major concern for HVDC systems. In DC systems, the capacitance is the dominant factor that determines the volatility of the DC voltage against sudden disturbances in analogy to inertia of the AC system characterizing the rate of change of the frequency. As a solution to this problem, the authors of this paper previously proposed...
This paper introduces seven-level Active Neutral-point-clamped (ANPC-7L) inverter first. Then, the paper decouples the two problems of floating capacitors voltage controlling and neutral-point potential balancing by using the concept of average state, proposes a novel neutral-point potential balancing model based on zero-sequence voltage injection. After that, two neutral-point potential balancing...
This paper introduces the fault behavior of full bridge modular multilevel converters (MMCs) considering a non-simultaneous blocking of the two half bridges in each sub-module. In order to protect IGBTs in the full bridge sub-module, both sides of a full bridge sub-module are not blocked at same time point. It is assumed that the first blocking of both sides is random in each sub-module, so there...
In this paper we study the modeling and control of an interleaved DC-DC multilevel topology that exhibits a high-voltage gain and a minimum ripple point design. In this configuration, the current ripple cancelation point can be arbitrarily defined according to a desired specification, which represents an advantage with respect to classical topologies whose minimum ripple point is constrained (e.g...
This paper introduces a efficient design a the grid side inverter for railway applications in cascaded multilevel hybrid technology. It is shown how to balance the capacitor voltages and how to dimension the capacitor size for different control strategies. Additionally the calculated power losses for this topology are determined and compared with two-level converter.
Multi-level flying-capacitor converters are a promising topology for low-power applications. Conventional buck, 3- and 4-level converters have been modeled as a geometric program and optimized for loss and volume. Results show that 3- and 4-level converters are both smaller and more efficient over a wide range of design parameters.
This paper presents a modular multilevel Chain-link converter with reduced energy storage requirement by utilizing an active filter storage method at the converter cell level. The active filter circuit and control are analyzed in detail. A comparison with the conventional cell proves the effectiveness of the reactive energy storage reduction.
In this paper, branch energy balancing as part of a generalised control concept for modular multilevel converter topologies is investigated. A way to derive an optimal branch energy balancing regarding current stress is introduced. Afterwards, this generalised approach is applied to the Modular Multilevel Converter as an example topology. The approach is tested via simulation and verified with a low-voltage...
The modular multilevel converter (MMC) has become a very attractive solution for interfacing high voltages hybrid networks. The MMC enables scalability to different power levels, full controllability provided by IGBTs and can achieve very high efficiencies by using a low switching frequency method as the nearest level modulation (NLM). However, in order to limit failures of the power modules, the...
MULTILEVEL converters compare with the conventional two-level converters provide noticeable advantages such as lower harmonic distortion, lower switching frequency, lower switching losses, and lower stress across the semiconductor switches. To improve the output quality of multilevel converters, different modulation techniques have been suggested in the literature. The most suitable modulation technique...
Multilevel converters are attractive solution for high-power high-voltage applications such as motor drive systems, active filters, and flexible AC transmission systems (FACTS). Several modulation techniques are proposed for multilevel converters. Among them, selective harmonic elimination (SHE) offers high quality voltage waveform with low switching frequency which is especially suitable for high-power...
The growing use of wind energy conversion systems around the world is pushing the individual power of wind turbines to higher values. Especially in offshore farms, where installation and maintenance have higher costs, high power wind turbines and their reliability become critical issues to make investments economically viable. In this context, multilevel converters, widely used in high power drive...
This paper proposes a control scheme based on predictive control for an Asymmetric Multilevel Converter, composed of a two-level inverter and two floating cells per phase. Main cell is handled by using a simple modulation that selects the sector of the reference vector and floating capacitor voltages are controlled to maintain an optimal asymmetry to maximize the number of load voltage levels with...
We present a method for designing a stabilizing reference circulating current for modular multilevel converters. To this end, an optimization problem is formulated. This optimization problem takes into account conflicting control requirements such as reducing the oscillating component of the circulating current as well as the oscillating component of the arm voltages. Tracking of the obtained reference...
Multilevel inverter topologies are an alternative for a wide range of low voltage electrical drives. They can reduce power semiconductor losses, voltage transients at the motor windings, harmonic losses in the cables and common mode disturbance currents. In the voltage range below 1000 V highly optimized switches with lower losses are available. The paper compares the component losses (power semiconductor...
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