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In this work, an adaptive control of a three phase ac/dc converter is investigated. The classical vector control method has been extensively used for the control of the ac/dc converter in different applications but the design gains are highly dependent on the system parameters. We employed an adaptive PI control method to cope with the system uncertainties. The method relies on a third order model...
This paper presents a new middle-stage current-fed high-frequency link inverter (MSCF-HFLI). The proposed inverter only contains one passive buffering energy element comparing with conventional resonant type HFLI, which at least has two passive buffering energy elements. The topology of the proposed inverter is given and the operational principle in a line-frequency cycle is analyzed, which is similar...
This article presents the analysis of a single-phase Back-to-Back converter with a generalized parallel structure, in order to manage bidirectional active power flow between two AC systems. The considered topology is formed by single-phase cells coupled magnetically through a power transformer. The main strategy to operate the converter is to distribute the active power flow symmetrically between...
Modern civilization depends heavily on the consumption of electrical energy for industrial, commercial, agricultural, domestic and social purposes. However, for the current HVDC system, proper protection devices and logic are not yet as mature as the AC counterpart. This paper presents the fault analysis for the protection of the HVDC (65–765 kV range) grid, using PSCAD. Faults in the DC transmission...
This paper describes the use of the Auxiliary Resonant Commutated Pole (ARCP) converter topology for the cells of a Modular Multilevel Converter. The workings of the ARCP topology are explained as well as the calculation method used to compare the efficiency to a conventional solution. Comparison is done for an HVDC as well as for a STATCOM application. In both cases, use of the ARCP topology can...
The effective efficiency of a photovoltaic system is strongly affected by varying factors such as partial shading. The centralized power conversion has limitations to mitigate that problem. As a possible solution the benefits of the distributed power conversion are explored and as an integral part of distributed power conversion an intra-module DC-DC converter is presented here to implement at substring...
The power handling capability of the state-of-the-art semiconductor devices is limited. Therefore, the Voltage Source Converters (VSCs) are often connected in parallel to realize high power converter. The switching frequency semiconductor devices, used in the high power VSCs, is also limited. Therefore, large filter components are often required in order to meet the stringent grid code requirements...
Fault protection aspects are very crucial for the realization of multi-terminal dc (MTdc) networks. This paper investigates the impact of power flow control strategies on the response of MTdc networks to a dc fault. The successful ride-through of a dc fault is defined by two factors: first, a fast fault isolation and second, a fast post-fault system recovery. According to these criteria, two control...
One of the main issues accompanied with the high penetration of PV distributed generation (DG) systems in low voltage (LV) networks is the overvoltage challenge. The amount of injected power to the grid is directly related to the voltage at the point of common coupling (PCC), which necessitates limiting the amount of injected power to the grid to conservative values compared to the available capacity...
This paper presents a novel switching scheme named as Switched Rectifier Inverter (SRI) modulation scheme for three phase to single phase (3×1) Matrix converter based isolated AC-DC converter. The proposed SRI modulation scheme incorporates symmetrical Space Vector Modulation (SVM) with inverter logic for switching the twelve switches of Matrix based AC-DC converter. The operation of proposed SRI...
Increasing global interest in clean and distributed energy systems emphasizes the importance of power electronics technologies in grid integration of renewable energy resources. High penetration of renewables such as wind turbines introduces new challenges for the grid stability seeking appropriate solutions. From a technical and economic point of view any application and testing of new management...
Cascaded power conversion system was used in battery energy storage system. It can be connected to medium-voltage grid directly and expanded to larger capacity easily. Without 50Hz booster transformer, medium voltage cascaded power conversion system can reduce power loss. In 2011, the China Southern Power Grid launched the project of 2MW/10kV battery energy storage system. In this paper, the design...
An approach for three-phase AC to DC conversion is proposed, which consists of a single-stage while offering galvanic isolation, soft-switching, bi-directional power flow and a significant reduction of inductive and capacitive energy storage. Two elements enable this approach, namely a neutral voltage-lift capacitor and a Quad Active Bridge (QAB) converter. Moreover, a control strategy is described...
The growing availability of high power semiconductor devices and the increasing necessity of high power converters in power systems and industry applications demand the use of multilevel converters topologies, such as the 3-level neutral point clamped voltage source converter. The tradeoff in designing this kind of converter is between switching losses and fast dynamic control. The size and cost of...
In this paper a gain scheduling control scheme is presented for a three-level three-phase voltage source converter for high-voltage direct-current transmission system (VSC-HVDC), based on two neutral point clamped (NPC) converters in Back-to-Back configuration. The proposed model in dq0 is developed in detail and it has the advantage over other solutions of facilitating the mathematical analysis....
Low Voltage Ride Through (LVRT) is an important grid requirement for Voltage Source Converter (VSC) based HVDC links. This paper studies the performance of the modular multilevel converter (MMC) VSC based HVDC systems during faults or voltage dips and proposes a new control strategy to improve the LVRT performance. The proposed algorithm controls the system to generate the required active and reactive...
This paper deals with the regulation of the three-level neutral-point-clamped (NPC) converter operating as synchronous rectifier connected to the ac mains. The regulation of the rectifier, whose primary application is to derive dc power from the utility grid, is based on a dynamic model of the system. This model includes the dynamics of the instantaneous powers as well as those of the total dc-link...
One of the main challenges of voltage source converter based HVDC systems is DC faults. In this paper, two different modified half-bridge modular multilevel converter topologies are proposed. The proposed converters offer a fault tolerant against the most severe pole-to-pole DC faults. The converter comprises three switches or two switches and 4 diodes in each cell, which can result in less cost and...
Modular multilevel converters (MMCs) are widely used in different applications such as high voltage direct current (HVDC) applications. The HVDC station loss is highly related to the converter switching pulse pattern which is generated by modulation algorithm and cell selection methods. This paper formulates the switching pulse pattern generation, as a versatile optimisation problem. The problem constraints...
This paper presents a methodology to deal with the control design for PWM converters in dc-to-dc power conversion systems. The concept of uncoupled dc-to-dc converter is established, which allows dc-to-dc converters to be designed independently from the source and load impedances. The control design strategy of the uncoupled dc-to-dc converters is formulated to offer good and robust closed-loop performance...
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