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This paper is about the design for the control of a cascaded hybrid converter for railway applications. It shows, how to control the converter with considerations of special aspects for the use in rail vehicles. It considers several aspects of reducing THD of the current and reduction of switching losses.
The impact of capacitor voltage changes during the modulation period is examined in order to improve the arm voltage of a modular multilevel converter. Different methods are used to predict and compensate for the capacitor voltage change and the resulting arm voltage error, whereby two of the improvements provide a possibility to easily upgrade existing modulation algorithms. Simulation and measurement...
The paper discusses an issue of the voltage balancing in the intermediate DC circuit of a three-level converter system for a smart grid application. A combination of two methods of the voltage balancing is presented in the paper. The voltages of DC-link capacitors, depending on the operating mode, are controlled by the three-level grid connected AC/DC converter or by the two level DC/DC converter...
The accurate control of the line current, robust and dynamic behaviour even under distorted grids and the behaviour on other faults are important requirements for grid connected inverter systems. This paper presents a sensorless grid voltage determination system in combination with an direct current control method optimized for multilevel inverters.
In the frame of a collaboration project within Swiss Competence Centre for Energy Research, a Multi Terminal DC pilot has been implemented. For the interaction with the medium voltage AC grid, a Modular Multilevel Converter has been designed for its features in low harmonic content, scalability, and flexibility. The control of converters in the MTDC network implements a non-dead band voltage control...
This paper concerns the application of three-level neutral point clamped (NPC) voltage source inverter (VSI) to electrical energy conversion of the photovoltaic (PV) power plant. The grid-connected 3-phase NPC inverter is powered via the split DC-link composed of the capacitive divider (Fig. 1). It enables the usage of two DC-buses independently which can be supplied by the separated boost-type DC-DC...
The multilevel converters have advantages of low voltage stresses of the switches and possible reduction of size of the passive components. Input-series output-series (ISOS) configuration of the converter enable the utilization of low voltage rating switches in converters with high input voltage and high output voltage in applications that requires galvanic isolation. While multilevel topology offers...
The increasing number of renewable energy sources and their integration into the medium voltage grid leads to an increasing interest in multilevel structures for the interfacing power electronic converters. A feasible topology for MV applications is the Stacked Multicell Converter (SMC) offering a modular structure and several voltage levels. A robust control, current limiting strategies under grid...
Recently, modular multilevel conterters (MMC) are also considered for medium voltage (MV) applications, where the number of modules and the switching frequency are relatively low compared to high voltage (HV) applications. In this context, standard modulation methods can cause relatively large output voltage errors. This effect is amplified even more, if the value of the module capacitances is decreased...
A multi-terminnal hybrid UHVDC is planned by China Southern Power Grid. The UHVDC system consists of one LCC-based sending end and two VSC-based receiving ends, rated at ±800kV. In this paper, steady-state control strategy is designed to coordinate LCC and VSCs at both sides. Smooth start-up, shutdown and reduced DC voltage operation are achieved.
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...
This paper investigates the dynamic extension of the controllability range of Modular Multilevel Converters for High Voltage Direct Current applications by a injecting minimum zero-sequence voltage. The performance of the claimed features is supported by experimental results obtained from a Small-Scale Prototype for steady-state and under AC side voltage disturbances.
The voltage balancing of the dc-link capacitors in an electric drive system with five-level neutral-point-clamped converters is investigated in this paper. A properly modified space-vector-modulation technique is utilized in combination with a multilevel dc/dc converter for controlling the capacitor voltages. An advanced algorithm has been developed for reducing the losses of the electric drive system...
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 presents a boost switched-capacitor nine-level single-phase inverter, which utilizes flying capacitors and an H-bridge. Besides the boosting ability, the inverter is capable of producing redundant switching states that are used as a degree of freedom in controlling the voltage of DC link capacitor. A comprehensive study of the theoretical aspects of the proposed structure and its practical...
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...
With the rapid development of voltage source converter (VSC) based high voltage direct current (HVDC) transmission technology, the HVDC grid will be an effective solution for large-scale renewable energy generations integration. The modular multilevel converter (MMC) is one the most promising topology for HVDC and DC grid presently. The precharge of the MMCs and start-up of DC grid are essential problems...
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