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This paper presents a new application of modular multilevel cascaded converters (MMCC) for combined active harmonic current elimination and reactive power compensation in a power distribution line. A technique for simultaneous extracting harmonic components and reactive element in the load current is presented. A novel voltage control scheme for balancing the module intra-cluster capacitor voltages...
This paper is introducing a new method of operation for a series resonant converter, with intended application in megawatt high voltage DC wind turbines. Compared to a frequency-controlled series resonant converter operated in sub-resonant mode, the new method (entitled pulse removal technique) allows the transformer design to be determined by peak load and maximum switching frequency, while still...
Hybrid Microgrids are currently of great interest and are considered the distribution and transmission systems of the future, because they enable the coexistence of the AC microgrids and DC microgrids. This paper deals with the implementation of a new power management algorithm of the power converters that form part of the hybrid microgrid of Distributed Generation. The hybrid microgrid consists of...
This paper provides conclusions on design and laboratory tests of a hybrid rectifier prototype which employs the newest generation of SiC transistors and diodes. For the presented hardware prototype the AC-DC efficiency is about 98%. Based on simulation analysis and the practical realization pros and cons of this topology were identified. It should be noted that hybrid rectifiers importance is growing...
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...
A linear controller is proposed for dc microgrids with SEPIC, Cuk and Zeta power electronic converters supplying constant power loads. The controller is implemented in two stages. During the first stage, also known as active damping stage, limit cycle oscillations are damped by inserting a virtual resistance in series with the input inductor of each of the converters. In the second stage, an integral...
A simplified method is proposed to investigate potential instabilities originated from dc-side resonances in multi-terminal HVDC systems. The method consists of identifying the resonances from the points to where the converters are connected. The method is applied to a four-terminal HVDC system, and the analysis indicates there are two resonance phenomena and a group of converters have the most significant...
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...
As one type of the interconnected device between HVDC systems, the DC/AC/DC converter is able to achieve high-voltage connection and bulk-power transportation, which makes this device fit the interconnection of LCC-HVDCs. To achieve an efficient interconnected LCC-HVDC system, the DC/AC/DC converter is possible to operate under the condition that one LCC-HVDC runs at normal operation and the other...
This paper presents the modeling and control of a doubly-fed induction generator (DFIG) driven by a wind turbine on a real time digital simulator. Real time digital simulators are widely used in the electric power industry by utilities, equipment manufacturers and research organizations. In this paper, two scenarios are considered, the first with a detailed switching model of the back-to-back Voltage...
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.
In this paper, stability of regenerative brake control system is studied, focusing on the difference in the feeder line circuit model on factory test conditions and actual load conditions. The factory test is always carried out to determine the gain of regenerative brake control system because there are restrictions in the on-track test. However, the influence on the difference of the circuit configurations...
A control concept is presented to include grid supporting schemes into the droop control of grid-supporting and grid-forming power electronic converters. This control scheme adopts advanced power reference strategies used for grid-feeding converters to voltage controlling converters during unbalanced faults. The strategies are evaluated first with respect to the maximum power injection in case of...
This paper proposes the novel generation method of gate signals to control output voltage in a wide range and to achieve synchronous rectification operating in half-bridge LLC resonant converters. The switching frequency modulation is used in half-bridge LLC resonant converters for control strategy of output voltage. The switching timing of secondary MOSFETs is compensated using the gate signal of...
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...
The paper presents a state-feedback current controller with damped oscillatory terms designed for three-phase grid-connected voltage source converters under distorted grid voltage conditions. The paper focuses on a synthesis of an anti-windup strategy for the LQ current controller. This strategy is based on an active clamping method for the proportional-integral part and the adjusting mechanism of...
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