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This paper presents the design of a digital controller for a 600 W Boundary-Conduction-Mode (BCM) interleaved boost converter used in an ac-dc Power-Factor-Correction (PFC) power supply. The output voltage of a typical boost PFC rectifier contains a 2nd harmonic ripple. Therefore to achieve good power factor, the output voltage compensator must have a low bandwidth, in order to sufficiently attenuate...
This paper proposes an adaptive DC-bus stabilizer for single-phase grid-connected voltage source converter (VSC) with small-scale renewable energy integration. To enhance converter's power density, the conventional active power decoupling (APD) techniques were adopted to reduce the DC capacitance by compensating the inherent second-order harmonic power ripples in the single-phase VSC. However, it...
This paper presents dynamic analysis of a Modular Multi-Parallel Rectifier (MMR) based on state-space modelling. The proposed topology is suitable for high power motor drive or multi-parallel AC-DC applications, which can reduce line current harmonics emissions significantly. However, a proper controller is required to share and control current through each rectifier. Mathematical analysis and simulations...
Solid state transformers (SSTs) include dc subsystems to enable plug-and-play support of dc loads, generation sources, and energy storage. Dual active bridge (DAB) converters are a suitable topology for both the primary energy conversion and load interface applications in an SST. This study considers an SST that uses DAB converters for both applications, and describes a method of generating a full...
The paper deals with a high efficiency boost rectifier for high rotational speed Gen-Set applications. It is tailored around a permanent magnet synchronous generator (PMSG) featuring an open end winding configuration. According to such a configuration the generator stator windings are connected on one side to a three level T-type unidirectional rectifier, and on the other side, to an auxiliary two-level...
A model predictive control system for delta-connected modular multilevel converter is proposed in this paper. The control system is based on offline computed optimal pulse patterns, which are modified online using model predictive control. Optimized pulse patterns facilitate the shaping of the grid current spectrum at low switching frequencies. Unlike conventional control methods with optimal pulse...
This paper presents a unified selective harmonic compensation strategy using DG-interfacing inverter with LCL filter in the presence of nonlinear local loads for both grid-connected and islanded microgrid. Compared with the existing harmonic compensation methods in the literature, the proposed strategy consists of a triple-control-loop in the grid-connected mode to compensate the grid current harmonics...
The advantages of the Modular Multilevel Converter (MMC) as a Voltage Source Converter (VSC) is well known. These includes scalability, increased reliability, lower Total Harmonic Distortion (THD) in output variables, fault tolerance and so forth. The MMC has found its most application in High Voltage DC (HVDC) systems again because of the stated advantages. In the analysis of such systems, because...
The star-configured modular multilevel converter is a promising topology for grid-connected storage as well as power-quality applications and motor drives. During operation, the ac output power generates substantial current pulsation at twice the output frequency in the modules, which causes additional loss and requires an increase of the module capacitance. This paper presents a common-mode voltage...
A hybrid modulation approach is proposed in this work, which allows to modulate the switches of the five level neutral point clamped inverter (5LANPC) with different switching frequencies. Some of the switches are controlled with a low switching frequency using six-step modulation and Optimized Pulse Patterns (OPPs), whereas the rest are modulated with a high switching frequency using Carrier-Based...
Advent of Modular multilevel converters (MMC) made the voltage sourced high voltage direct current (HVDC) transmission systems a reality mainly due to its modular structure, scalability and reliability. For these converters, minimization of sub-module (SM) capacitor voltage spread without increasing the switching frequency is the biggest challenge as it directly affects the efficiency and cost. Moreover,...
A modular multilevel converter (MMC) with traditional cascaded PI control structure suffers from poor steady state and dynamic performance. This is due to the limited harmonic rejection capability of PI controller thus failing to alleviate even order harmonics in circulating current and due to the slower outer average voltage control loop resulting in significant deviation in submodule capacitor voltages...
The multiobjective allocation optimization of single tuned passive power filters for decreasing the power losses and harmonic mitigation in distribution networks is presented in the paper. The Pareto definition of the multiobjective problems is used in the paper. The two objectives problem consists of the two technical objective functions, the real power losses and the total harmonic distortion, is...
A well-known problem of three-level neutral point clamped (NPC) inverter is the voltage imbalance in the dc-link capacitors. This paper proposes the dc-link capacitor voltage balancing method where a common offset voltage is injected. The offset voltage consists of a harmonic voltage and a magnitude difference between the upper and the lower capacitors. Theoretical analysis is provided to balance...
The active or passive decoupling method has to be utilized to deal with the second-order harmonic existing in the DC-bus of the grid-tied single-phase inverters. Compared with the active decoupling method, the passive decoupling method is simpler, cheaper and more reliable. The electrolytic capacitors are usually used in the DC-bus as typical passive decoupling components. The film capacitors can...
A control strategy to manage the circulating current content in a Modular Multilevel Converter in direct AC-AC topology is proposed in this article. The converter is connected in three-phase YDY configuration which forms a closed delta path for free current circulation while keeping outsider waveforms with low THD content. Circulating current correction becomes necessary face to any kind of unbalance...
AC-DC single-stage converters are widely used in industrial applications because they are cheaper than conventional two-stage converters. In this paper, state of the art low power single-stage converters are reviewed. These converters are classified into several types in the paper, the operation of an example converter of each type is discussed, and the advantages and drawbacks of each type are stated...
This paper presents the application of a modular multilevel cascade converter(MMCC) based on single-delta bridge cells(SDBC) as an active power filter(APF). It is required that the mean value of the DC capacitor voltages is controlled so that the tracking of the source current reference is guaranteed in operation of APF. This paper proposes a DC capacitor voltage regulation method for MMCC-SDBC under...
This paper analyzes ratio and phase displacement errors produced by commercial capacitive voltage transformers (CVT) under non-sinusoidal waveforms, as exist in power networks. As power quality measurements in high voltage systems are performed at the low voltage side, it is relevant to know the incidence of the CVT in the results. Additionally, a preliminary proposal to compensate those errors is...
In this paper, the effect of capacitor voltage ripple on current quality in a cascaded H-bridge (CHB) low-capacitance static compensator (LC-StatCom) with symmetrical I-V characteristics is investigated. Total harmonic distortion of the synthesized ac voltage of an H-bridge converter operating with different capacitor voltage ripples is evaluated for both inductive and capacitive operating modes....
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