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A novel Medium Voltage Direct Current (MVDC) circuit breaker consisting of a High-Speed Switch(HSS) and a bridge-type commutation branch, which is based on current injection, is proposed and analyzed in this paper. The commutation branch of this design adopts bridge type, which can break bidirectional fault current rapidly by controlling thyristors. Meanwhile, after fault current is commutated to...
The paper presents the results of an analysis of the inter-turn fault effects on the voltage and current waveform of the capacitor discharge through transformer winding. The research was done within the FAIR project for which a measuring and diagnostic system for testing the condition of electrical circuits of superconducting electromagnets system is being developed. Appropriate measurements and simulations...
Conventional three-phase MMC consists of six-arms, each arm is controlled to generate unipolar voltage ranging from zero to Vdc where Vdc is the input DC voltage. Each arm voltage has two components (DC and AC components). In this work, the operation of MMC with reduced number of arms (four arms only), correspondingly reduced cost is presented. This mode can be also used with the conventional three-phase...
Aiming at the problem of short-circuit protection, a novel bridge-type topology of fault current limiting (FCL) is established based on resonant characteristics. It is equivalent to a piece of wire during the normal operating state. When short-circuit fault occurs, the dc limiting reactor inserts automatically and rapidly under the joint action of the capacitor, limiting the increasing speed and amplitude...
This paper presents a transformer-less, single stage, doubly grounded, buck-boost single phase inverter. The inverter is derived from SEPIC converter by replacing its output side inductor with a coupled inductor. Stand-alone operation of the inverter is discussed with resistive and inductive load. Simulation results are given to validate the operational ability of proposed inverter.
This paper first introduces the principle of the Modular Multilevel Converter and then describes the mathematic model. Secondly, the proportional resonant controller is studied and used in the modular multilevel converter. The control strategy diagram is presented. After that, the 71-level model of modular multilevel converter is set up in the PSCAD/EMTDC. By the model simulation the proportional...
In this paper, an analysis results for the protection of a DC micro-grid is described. The 400V DC micro-grid consists of a wind power system (Permanent Magnet Synchronous Generator, PMSG), a photo-voltaic system, a fuel cell system and energy storages. Abnormal operating conditions during various faults are studied. According to a series of studies, a protection scheme for a DC micro-grid is suggested...
This paper describes two distinctive functions of the arm inductor in the modular multilevel converters (MMC): suppressing the circulating current and limiting the fault current rise rate. Based on the equality of the instantaneous power, the characteristics of the circulating current are analyzed and demonstrated that it flows through the three phase of the converter in negative sequence at double-fundamental...
With technology scaling, vulnerability to soft errors in random logic is increasing. There is a need for on-line error detection and protection for logic gates even at sea level. The error checker is the key element for an on-line detection mechanism. We compare three different checkers for error detection from the point of view of area, power and false error detection rates. We find that the double...
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