جستجوی مقالات مرتبط با کلیدواژه « کلیدزنی نرم » در نشریات گروه « برق »

In this paper, a new two-input converter with zero voltage switching for green energy hybrid systems is presented. In the proposed converter, a new auxiliary circuit is used to create zero voltage switching with the least number of auxiliary elements. The auxiliary circuit not only provides zero voltageswitching conditions, but also absorbs the energy of the leakage inductance and prevents voltage spikesacross the main switches. On the other hand, the use of coupled-inductors also increases the gain of the converter and greatly reduces the voltage stress on the switches. The proposed converter has been designed with a 120 watts power and simulated in PSICE software, and also a prototype has been made to prove the theoretical analysis of the circuit.

In this paper, an interleaved fly-back-forward boost converter with a new auxiliary circuit was presented. An auxiliary circuit with a low number of elements provided zero voltage switching conditions to turn the switches on and off; besides, the energy of the transformer leakage inductance was properly absorbed by the auxiliary circuit and prevented voltage spikes on the switch. Furthermore, the third winding in the auxiliary circuit not only transfered the energy of the auxiliary circuit to the output but also caused a complete discharge of the snubber capacitors of the main switches in the resonance process. This auxiliary circuit could be expanded, and the number of auxiliary switches did not increase with the addition of converter branches. The performance of the proposed converter was fully analyzed, and a 120 W laboratory prototype was implemented to demonstrate its correct operation. The results showed a 6.5% increase in the efficiency compared with the converter without an auxiliary circuit.

In this paper, a non-isolated current-fed high step-up soft-switching converter, is presented. In proposed converter are used of 2-stge switched capacitor and a soft switching active cell. Compared to its high step-up counterpart, the proposed converter has a higher voltage gain. In this converter, an active clamp circuit is used to absorb the energy of leakage inductor, therefore, the ZVS for switches. Also, voltage stresses on the switches are low. In this paper, the operational principle and characteristics of proposed converter are presented, and in order to verify the proposed converter, a 20-400V, 200W prototype converter is simulated and implemented and experimental results are provided.

In this paper, a non-isolated high step-up soft-switching converter is proposed. The proposed converter is a boost converter combined with two voltage multiplier cells for boosting output voltage. Also, extend voltage gain of the proposed converter is achieved by using a coupled-inductor. Compare with other similar high step-up topologies with the same number of components, the proposed converter has a higher voltage gain and higher efficiency. An active clamp circuit is used so, the zero-voltage switching (ZVS) is achieved. Also, in the proposed converter, the voltage stresses on the switches are low. As the voltage stress decreases on the switch, Ron</sub> of the MOSFET is deceased and as a result conduction loss of the switch is decreased. So, the efficiency of this converter increased. In this paper, operational principle of the converter is described and the analytical, simulated results and prototype converters are validated using a 20V input and 400V </strong>output converter at 200W load.

A high step-up two-inputs DC-DC converter is presented in this paper. The soft switching condition is provided for switch in turn on instant, so the converter efficiency is high. Due to the fact that only the capacitor is used to increase the voltage gain and there are no coupled inductors in the converter, the input current of the converter is continuous. The technique used to increase gain can be used with more stages to achieve higher voltage gain. The converter can also be used as a single input intertwined instead of two inputs, which in this case the input current ripple is reduced. The voltage stress on the switches is lower than the output voltage, so lower voltage switches can be used, which reduces the converter cost. The proposed converter is completely analyzed and in order to prove the theoretical results, a simulation is performed on the converter at 500 watts. The results of the simulation at full load show an efficiency of about 95.5%.

In this paper, a new Countinous Current Mode (CCM) nonisolated DC-DC interleaved converter is proposed that uses an auxiliary circuit to create soft switching conditions. The auxiliary circuit used in this converter has no switch and provides soft switching conditions for all switching elements from only one resonance path. Also, the designed auxiliary circuit is not located in the power transmission path from input to output. Due to the use of interleaved structure, the current stress on the switches in the proposed converter is low. This converter has a very simple structure and operation compared to similar structures. The converter control method is also simple and pulse width modulation (PWM) is used to command the switch. Due to soft switching technique, the switching frequency of the converter has increased, this way leads reduced the size and overall volume of the converter, especially the passive elements in the structure, switching and conduction losses and also increased the efficiency of the converter compared to similar structures. Also, the proposed converter with 48V input voltage, 155V output voltage with 100 kHz switching frequency at 900 watts was simulated in PSPICE software. The results of simulation and theoretical and computational analysis confirm the performance of the converter.

The interleaved boost converters are the power circuits that provide high-voltage, high-power with regulated output voltage for renewable energy systems which are generally suffer from low-voltage and unregulated output voltages. The soft switching methods reduce electromagnetic noises and switching losses in these converters. In this paper, a ZVT interleaved boost converter with a simple auxiliary circuit is proposed. The proposed converter has a simple structure with low size and cost. In the proposed converter, soft switching condition is provided without any extra voltage and current stress on the main switches. The auxiliary circuit comprises two diodes and one auxiliary switch. The leakage inductance of the utilized coupled inductors is used as resonant inductor. The auxiliary switches benefit from significantly reduced voltage stress without requiring floating gate driver. The proposed converter can achieve zero voltage switching operation for the main switches and zero current switching for diodes and auxiliary switches, which causes to alleviate the reverse recovery problems of all diodes.

In this paper, a new soft switched non-isolated high step-up DC-DC converter is proposed. An auxiliary circuit with minimum number of elements is added to the converter to provide the soft switching conditions for all the semiconductors solving the reverse recovery problem of the diodes, and reducing the conduction and the switching losses of the power switches. Moreover, there is only one magnetic core used in the converter decreasing the copper resistance; thus, the power losses and the electromagnetic interference of the converter is reduced so the efficiency of the proposed converter compared to the conventional hard switched boost converter, is improved. Further, in order to adjust the output voltage of the proposed converter to the desired value under the load variations, a PI controller has been applied to the output of the proposed converter and its operation is simulated by MATLAB. In order to verify the theoretical analysis of the soft switching operations, a 250W prototype is implemented and its experimental results are provided.

One of the main limitations of using renewable energies for electricity generation is the low output voltage of power plants with renewable energies. Therefore, the design of a converter with higher gain voltage and higher efficiency is important in the use of renewable energies. In this paper, a new topology that simultaneously has the structure of a boost converter can minimize switching losses by conventional soft switching methods and is also able to reduce voltage stress on diodes and switches Keep to an acceptable level. A simple boost converter can Increase the output voltage significantly by adding a parallel branch by generating a series resonance and enables zero voltage switching at the same time. Suggested converter without adding active element to converter with simple non-isolated structure at 500 watts and 385 volts it has a voltage gain factor of about 10.8 and efficiency of over 93%. The results show the performance simulation of the proposed converter for different performance modes.

In this paper, a ZVS interleaved flyback converter with two transformers is presented, which consists of two active clamp flyback converters and the main switch of one converter acts as an auxiliary switch of another converter. This converter has less auxiliary elements and less voltage and current stress compared to similar soft switching interleaved flyback converters. The introduction of a new auxiliary circuit for soft switching, in addition to increasing efficiency, minimizes the number of added semiconductors. Also, another advantage of this structure is the applicability of the provided auxiliary circuit to other isolated converters. The soft switching conditions in this converter are created by the auxiliary circuit in such a way that the converter switches turn on and off under ZVS conditions and the converter diodes turn on and off under ZCS conditions. The efficiency of the proposed ZVS interleaved flyback converter at full load is increased by 5%. Another advantage of the proposed converter is that the Q2 switch, in addition to providing zero voltage switching conditions for the Q1 switch, it also transmits energy and increases the density of the converter power and reduces the current stress. The converter is thoroughly analyzed and a 300W laboratory prototype is made to confirm its correct operation and practical results are presented.

Energy is one of the most important factors for the economic growth and development of each country. Most of the energy is consumed in the form of electricity. One of the most important ways to generate electricity is to produce electricity through fossil fuels. However, due to their disadvantages such as limitations and concerns about the environment and increased demand for energy, engineers are focusing on renewable energy sources such as Wind turbines, hydro, solar cells, and the use of renewable energies and energy with less pollution is concerned. As we know, the sun is the largest source of energy on Earth, that the energy exported is used in various ways. due to the high cost of the main element of these systems, the use of this type of energy production system alone has no economic justification. Due to the diversification of energy sources and the need to use more than one source of electricity in some applications, it is better to use a multi-input converter instead of a few independent converters because multi-input converters make it easier to reduce the cost and increase efficiency and increase the power conversion capacity due to lower semiconductor elements, lower inductors, and capacitors, and lower control capacities have become. In many applications of multi-input converters, where the terminal output voltage of a specified value should not be greater, non-isolated converters can be used to simultaneously provide high voltage output and high efficiency. Isolation in multi-input converters has advantages and disadvantages that are selected based on the type of system application. Its advantage is the isolation of sources from each other (in multi-input magnetic converters) as well as the load of the sources, which allows the use of different sources with different voltages. Disadvantages of isolation include design problems for transformers with multiple windings, as well as increasing circuit volume. Since energy sources are inherently low voltage, high-step-up techniques are used to increase their voltage gain. In switching converters, to reduce the amount of inductor and capacitor elements, the increase in switching frequency is desirable. But with increasing switching frequency, the switching losses and electromagnetic disturbances increase, which is due to the use of common elements in multi-input transducers, to increase the problems mentioned above than other switching converters. To solve these problems, one of the voltage or current parameters must be limited at the moment of switching so that soft switching can be achieved. In this paper, a high step-up multi-input converter is presented which, using soft switching techniques, the voltage gain of converter can be increased. In this converter, the combination of the inductance coupling method with the voltage multiplier is used to achieve high voltage. Due to the addition of a voltage multiplier cell, the amount of leakage inductor and the ratio of transformer increase and as a result, the circuit volume decreases. To reduce the voltage stress of the main switch, due to leakage inductor energy and also an active clamp circuit is used to provide a soft-switching mode, Switches with low voltage stress and low conductivity can be used by combining these two methods. first, the structure and performance of the proposed converter to design a high step-up multi-input converter, have been thoroughly analyzed and reviewed. To the converter to function properly, the exact converter design method is presented, Finally, the simulation results for different modes show the correctness of the converter operation.

High power density of switched-capacitor converters (SCCs) is due to absent of inductive components. But, this subject leads to output voltage regulation problem and hard switching characteristics due to high current spikes, which increase switching losses and noise and limit the power rating. Although, performances of some SCCs have been improved recently by including some small inductors in their topologies, but, only few of them can regulate output voltage and have soft switching characteristics. Here, by combining an active clamp and a boost SCC, both output voltage regulation and soft switching characteristics are achieved, even when wide input voltage and load variations are applied. So, switching frequency can be increased to reduce inductors and capacitors values, due to low switching losses and noise. It reduces the converter volume and also improves its performance, because small inductors and capacitors have better high-frequency characteristics, practically. Therefore, the modified converter is practically much better than the conventional configuration, especially at high power ratings. Here, the modified converter has been analyzed, mathematically, and to verify the given analyses, it has been simulated and implemented at 200kHz for regulating a 400V output voltage, even when wide input voltage (50-100V) and load (400Ω-8kΩ) variations are applied.

In this paper, a single-stage soft-switching power-factor-correction (PFC) converter is proposed for driving two strings of LEDs. In the proposed driver, a transformer is added to an asymmetric series resonant half bridge converter to shape the input current. Also, zero-current-switching condition (ZCS) and zero-voltage-zero-current-switching (ZVZCS) condition are provided for switches at turn-on and turn-off, respectively, and near-unity power-factor is achieved for the converter. Moreover, the output currents are equal and independent of the output voltages which eliminates the need for current feedback or active current sharing method. Besides, the proposed driver provides minimum voltage for DC-bus capacitor and also switches voltage stress, while attaining low THD. Therefore, low voltage rating semiconductors with low on resistance and lower voltage capacitors with lower volume can be used. To validate the proposed driver features, operating principle of the proposed LED driver is presented, design considerations are discussed and experimental results of a laboratory prototype for supplying two 50 W/70 V strings of LED modules from 220 Vrms/50 Hz ac main is reported in this paper.

In this paper a quasi z-source DC-DC converter is proposed that provides soft switching condition for all semiconductor devices with only two resonant paths without the use of any auxiliary circuitry, as well as any auxiliary switch. Based on the proposed structure, only one switch is used in the circuit, which greatly simplifies the performance of this converter in comparison with the similar structures. Also, the non-isolated structure and the lack of use of transformers and even coupled inductors to increase the voltage gain have led to the simplicity and high efficiency of the proposed converter. The converter efficiency is 95.8% at full load range. The control technique of the converter is simple and the pulse width modulation (PWM) is used to trigger the switch. Due to use of high switching frequency, the total size and volume of the converter especially for passive elements in its structure has decreased. The converter is completely analyzed and simulated in the software environment. Also, a 40-360V 50W laboratory prototype operating at 100 kHz is implemented. The experimental results confirm the simulation results and theoretical analysis.

In this paper, a novel structure and a control method to improve the performance of inductive heating circuits is proposed. In the presented structure, with the combination of the performance of a half-bridge resonant converter with voltage-boost capability, the reduction in output efficiency at low power and at high power is compensated to an acceptable level. The use of the low number of switches and diodes, the use of the high-quality capacitors with low capacities, good quality of the input current and also high power factor ensures the proper operation of the proposed converter. The switching of high frequency switches in the proposed structure is carried out as soft-switching where resulting in very low switching losses. In this converter, the design of the input filter in order to prevent the effects of electromagnetic interference has been prepared. Finally, to demonstrate the proposed structure operation, the simulation and experimental results are presented.

Renewable energy sources cannot provide load power continuously which is an important challenge in applying these sources. Therefore, usually several renewable sources; such as, solar cells and fuel cells are applied simultaneously. A converter can be applied for each source which results in high implementation cost. Therefore, multi input converters are used to reduce cost and volume of the system. In this paper, a new soft switching multi input converter is proposed. In this converter by applying one additional switch, soft switching is achieved for all main switches. The proposed converter is analyzed and design considerations are discussed.

In this paper a new soft switching boost-flyback converter is introduced to eliminate conventional boost-flyback converter problems in the high voltage applications. The main application of this converter is conction of PV system to the power system. In the proposed converter not only the operating duty cycles proper in high voltage gains but also the switch voltage stress is lower than output voltage. Also, in the proposed converter any auxiliary switch or magnetic core has not been used so the number of converter components has not increased much in comparison with the conventional boost-flyback converter. The operation principles of the proposed converter and its theoretical operation waveforms is presented. In order to justify the theoretical analysis, a prototype of the proposed converter is designed, simulated and experimentally implemented. The simulation and practical results are presented for a 100w boost-flyback converter with input voltage of 40V and output voltage of 400V.

In this paper, a soft switching buck dc/dc converter applicable for fuel cell has been analyzed and the complete details of designing have been presented. Reduction in switching losses and the elimination of voltage/current stresses of the switches are the major advantages of the aforementioned converter. In this converter, the switches are to be ON under zero voltage and zero current conditions, whereas they are to be OFF under zero voltage condition. This converter can be used in high switching frequency. In this paper, the principles of the performance, full details of the analyses of conduction modes, and designing approach have been presented. The performance and correct operation of the converter are validated by the experimental and simulation in PSCAD/EMTDC software.

In this paper a compound boost- sepic converter with soft switching for high voltage application is proposed. One of the advantages of this converter is that, the main switch is turned on under the ZCS condition without need to any auxiliary switch so we have lower switching loss. In order to increase the voltage gain in this topology, a boost converter used in series with the output stage of sepic converter, therefore the output voltage of boost converter added to the output voltage of sepic converter and the voltage gain has been increased. Also a coupled inductor has been used in the boost converter topology which leads to a further increase in the voltage gain of the converter. In order to evaluate the operation of the proposed converter, simulation results and analysis of converter operational modes are presented. In addition, experimental results are presented for a typical boost-sepic converter. These results verify the proper operation of proposed converter.