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In this paper, the short-circuit fault in three-phase quasi-Z-source inverter (q-ZSI) is analyzed and a linear model is proposed for the short-circuit analysis. The proposed model is based on the state space equations of the system. By using this model, the most critical situation during short-circuit fault is recognized; the maximum reaction time for the protection system could be estimated and elements...
In this paper an LCLL tank is presented for application in Load Resonant Converters (LRCs) with the constant current output. Design method is based on the output current independence from load variation and minimization of kVA/kW ratio of the LC tank. A 150kHz 70W LRC is presented as an experimental prototype of the design procedure. This converter has a robust load regulation, minimum reactive power...
Photo voltaic (PV) power sources are new, prominent types of power supplies. Due to unreliability of these kinds of sources, it is required to use an Energy Storage device (ES) in conjugation to make a reliable power supply system for loads. This paper proposes a new multi-port DC-DC converter for PV/ES power supply systems in which, due to application of PV/ES power supply systems in urban places,...
Stand-alone application of PhotoVoltaic (PV) systems have been more considered in recent years. To achieve desired characteristics in power conditioning systems, double input DC-DC converters have been proposed. In this paper a new high step-up current-fed double-input DC-DC converter is proposed based on full-bridge converter. Asymmetrical switching strategy has been used to achieve high voltage...
Photovoltaics are important kinds of renewable energies. In this paper a new high step-up DC-DC converter is proposed based on coupled inductor as a voltage booster. The secondary side of coupled inductor is connected to the switches to increase voltage gain and improve soft switching operation. Due to Special structure of the converter, smaller diodes and capacitors can be used. The operation modes...
Grid-connected photovoltaic (GPV) using module-integrated-inverters is a well known method to use PVs in power networks. This paper proposes a novel structure of module-integrated GPV based on double input DC-DC converters. Special structure and switching strategy of the proposed converter result in high efficient power conditioning system for GPVs. The proposed structure of module-integrated GPV...
Performance optimization is usually an important issue in the design of industrial electric machines. In this paper, a 150 HP induction motor utilized in an industrial floating pump is analyzed and optimized for an enhanced efficiency, a higher power factor, reduced losses and an increased power to weight ratio. Also, two-dimensional time-stepping finite element method (2-D TSFEM) is employed in the...
Various DG technologies are being integrated into power systems as alternative energy sources to improve reliability. Voltage Source Inverters (VSIs) are used as the interfaces between the DGs and the network. These inverters are controlled based on conventional droop method. This method satisfies power sharing between the inverters in steady state. Besides, it enrolls as the frequency and voltage...
This paper presents a new method for islanding detection in Microgrids with multiple distributed generations. The proposed method is based on feature extraction from power system current that is measured after distribution system circuit breaker. Comparing with traditional methods, because of changing in measuring point of current signal and using its transient data, this new method detects the islanding...
As the secondary signal of the Current transformers (CTs) is used in measuring and protection schemes, the accuracy of their operation is so important. In this paper, a real current transformer is modeled using three dimensional (3D) finite element method (FEM). Then its operation is analyzed under normal current of the primary conductor. First, the primary is positioned at the center of the current...
A new method for the power sharing in parallel inverters is proposed in this paper. The power calculation unit of the conventional droop is improved to obtain fast transient response. The reduction of the circulating current between inverters during system dynamics is one of the advantages of this method. Also, the proposed control method has a good dynamic performance and power sharing. The simulation...
With the increasing application of Induction Heating (IH) systems in various industries such as metallurgy, concerns about the harmonic effects and power quality of the power grid have been involved in the problems facing network operation engineers. This paper presents two methods to improve the power quality of three phase current source induction system. The two methods are active and passive solutions...
An analytical method of calculating an optimal resistance for crowbar of doubly fed induction generator (DFIG) under single phase fault is proposed by taking into account the impact of crowbar on reactive power, rotor current, voltage and electrical torque respectively. Finding the optimal resistance value for the crowbar is based on Analytic Hierarchy Process (AHP) in this paper, of the DFIG during...
Nowadays doubly fed induction generators (DFIG) are the most popular generator used in wind turbine plants because of their cost effective partly rated power converter and variable speeds. The main drawback of DFIG is their sensitivity to gird perturbation especially voltage dips since the stator is directly connected to the grid. Rapidly increasing contribution of wind energy in power generation...
Cascaded H-bridge multilevel inverter topology is one of the most popular topologies in high voltage applications. This topology uses multiple units of H-bridge power cells connected in series chain to produce AC voltage. Multilevel inverters have other topologies that can be used according to condition and demand. Pulse width modulation is a popular method to control Cascaded H-bridge inverters....
A novel isolated bi-directional dc- dc converter is proposed in this paper which implements zero current switching (ZCS) for current-fed inverter of the low voltage (LV) side of the converter and zero voltage switching(ZVS) for voltage-fed inverter of the high voltage (HV) side of the converter. Applying the ZCS technique, circulating current of the transformer is limited by the current of input current-sources,...
In this paper a single phase Active Power Filter (APF) based on least compensation current control method is presented. Despite it's simple implementation this technique shows quicker dynamic, better stability and higher reliability compared with existing control methods. Simulation results using MATLAB are presented to verify theoretical predictions and demonstrate effectiveness of the proposed control...
This paper presents a new control method for induction heating applications. In this method the coil current (coil flux) is used in feedback loop. The proposed control scheme is based on current-fed parallel resonant push-pull inverter. The operating frequency is automatically adjusted to maintain approximately zero phase under load parameter variation. Coil current control method is implemented by...
In this paper, a new switching technique for the three-phase multilevel inverter has been presented. The proposed switching technique has been applied to asymmetrical eleven-level inverter. The switching angles have been calculated by using the optimal minimization of total harmonic distortion (OMTHD) technique. The comparison of results with the ordinary switching technique verifies the effectiveness...
Electro-Mechanical Batteries have important advantages compared with chemical batteries, especially in Low Earth Orbit satellites applications. High speed, slotless, external rotor, halbach array permanent magnet machines are used in these systems as Motor/Generator. In this paper proper material and structure for space applications are introduced and a simplified analytic design method is given for...
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