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This paper presents a Fast On-Load Tap Changing Regulator used to correct unbalanced voltages. This regulator uses the semi natural commutation in order to improve the response. The proposed topology injects the voltage in only phase in order to balance the three phase system.
In this paper, a comparison of six representative topologies for the implementation of Solid State Transformers (SST) is performed. The objective is to help identify the most suitable topology capable of supporting additional functionalities as compared to a regular transformer, e.g. on-demand reactive power support to grid, voltage regulation, and current limiting. The comparison is based on switch...
In IGBT PWM inverter-induction motor system, the high dv/dt and di/dt due to the fast swishing of IGBT could bring serious EMI issues and common-mode voltage is a major source of adverse effects. This paper presents a technique for modeling and analysis of the conducted EMI noise. The noise model is investigated to get a full understanding of the EMI mechanism. The analysis and results proposed here...
A novel active gate drive method for high power IGBTs is proposed in this paper. It makes use of 2 simple capacitors and several Transient Voltage Suppressors (TVS) to gain different feedback gains in different turn-off transient period, in order to suppress the turn-off over voltage and control turn-off voltage rise slope. Comprehensive study among several application oriented methods is carried...
In this paper a matrix converter with a special circuit is presented. It works so that no overvoltage can be produced by an interruption of an input phase when operating with inductive load current. Also a switching off of one or more semiconductors of the inverter matrix can not produce the high voltage spikes by using the overvoltage protection circuit. This matrix converter works without any complicated...
To the affections of series IGBTs operation, the working process and characteristics of two kinds of simple, reliable voltage-balancing circuits are analyzed and compared. In the case of non-synchronous of gate signal, RCD snubber can not suppress the dynamic over-voltage during the switch transients observed from the experiments. The RCD active gate control is discussed in detail includes signal...
This paper proposes to apply an AC/AC direct converter topology for servo systems. In the conventional AC/AC converter which consists of a PWM rectifier and a PWM inverter, the p-n junction temperature becomes high at the low output frequency or the servo-lock operation because the output current concentrates at the specific switching devices in the inverter. On the other hands, the AC/AC direct converter...
In this paper, a 20 kVA Solid State Transformer (SST) based on 6.5 kV IGBT is proposed for interface with 7.2 kV distribution system voltage. The proposed SST consists of a cascaded multilevel AC/DC rectifier stage, a Dual Active Bridge (DAB) converter stage with high frequency transformers and a DC/AC inverter stage. Based on the single phase d-q vector control, a novel control strategy is proposed...
In this work, the IGBT turn-on and turn-off waveforms are normalized in order to analyze the closed-loop gate drive switching losses. The relationships of energy losses and controlled switching speed, voltage overshoot, current overshoot are derived. Theoretical analysis results show good agreement with experimental results. The proposed analysis methodology and results can provide guidelines for...
Lightweight power supply systems using soft-switched high frequency dc-dc converter for rolling stock is proposed in this paper. The system consists of hard switched boost chopper, soft switched high frequency inverter, high frequency transformer and rectifier. This system features a boost chopper to control the input current and to set up a controlled DC link. And A soft switched full bridge inverter...
Turn-on performance of a reverse blocking insulated gate bipolar transistor (RB IGBT) is discussed in this paper. The RB IGBT is a specially designed IGBT having ability to sustain blocking voltage of both the polarities. Such a switch shows superior conduction but much worst switching (turn- on) performances compared to a combination of an ordinary IGBT and blocking diode. Because of that, optimization...
Present day power networks have become very complex with integration of various kinds of loads and distributed generations such as wind power, mini hydro, dendro and solar. Hence, research activities in the area of control strategies on sophisticated operation of complex power systems are abundant. These studies require sound mathematical and theoretical analysis, advanced simulation packages and...
This paper presents analysis of time-ratio-controlled autotransformer as a mitigating device for voltage sag disturbance. Control circuit based on load RMS and voltage sag sensing circuit based on peak detection are employed. Commonly dynamic voltage restorer and STATCOM are employed for mitigation of voltage sag. The proposed system has less number of switching devices in comparison to commonly used...
This paper proposes an alternative connection topology for tap changers. Power electronic switches are implemented instead of conventional mechanical tap changers. This topology has the advantage of using less taps than the latter conventional method. The main focus is on improving the response time to sudden voltage changes. A practical implementation is presented to prove the feasibility of the...
Summary form only given. This paper extends previous approaches that use electromagnetic transient simulation to estimate the switching and conduction losses of insulated-gate bipolar transistor-based voltage-sourced converters embedded in large electrical networks. In contrast to earlier approaches, which merely estimate and report the device loss, the proposed new model also reflects this loss back...
The solid state transformer (SST) is one of the key elements proposed in the National Science Foundation (NSF) Generation-III Engineering Research Center (ERC) ldquoFuture Renewable Electric Energy Delivery and Managementrdquo (FREEDM) Systems Center established in 2008. The SST is used to enable active management of distributed renewable energy resources, energy storage devices and loads. In this...
Pulse power supply is widely used in areas of industrial production. A high efficiency high power power supply is badly needed in mass production. And the parameter of a power supply such as: efficiency, power volume , power factor ,and reliability is very important. In this paper a 20 kW pulse power supply is proposed, designed ,and implemented. The system is made up of two stages. First stage is...
To overcome the drawbacks of the conventional gate drive, in this paper a closed-loop gate control method is proposed. In this novel method, the switching speed, specifically di/dt, is measured from the voltage across the parasitic inductance of the IGBT module and a closed-loop control is employed to adaptively adjust the gate drive voltage to control the switching speed according to a preset control...
An active fault protection method is proposed to prevent the IGBTs from being damaged should they be under over-current and short circuit fault conditions. A closed-loop gate drive method is used to effectively control the IGBT turn-off switching speed independent of the fault type or resultant over-current level. Compared with conventional solutions, the proposed method can limit fault current level,...
In this paper, a direct control of a flying capacitor inverter is proposed. This control allows to limit the number of commutations in a switching period with the use of a pre-calculated output voltage profile. A predictive control is made for the 3 phases 4 levels inverter in a active filtering operation. The advantages of this direct control is to reduce the switching frequency of the IGBTs, to...
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