However, to achieve a smart control and efficient charging, a good utilization of the power electronic converter is highly required. The next step is changing the coupling factor to a value less than one which represents the leakage inductance in the transformer. According to the graphs, there is a delay between turning off S4 and turning. They are basically used in battery-powered applications and devices that require different levels of voltage. Následn ovit funknost menm nejdleitjch veliin.
1.1: Part of the architecture of an electric vehicle, the investigated DC/DC converter is marked red.4 Method Study relevant equipment, literature and documentation Get familiar with Allegro AMS software, hence build up different DC/DC converter topologies in the software. Vgate1 Vgate2 Vgate3 Vgate4 Voltage V Time us Fig. The secondary side switches behave almost the same as the primary, but in this case, the active leg switches and the passive buck converter design thesis leg upper switch turn on in a hard way as it is seen from the.10. Simulations have been performed in Allegro AMS and calculations carried out in Matlab. The lower switch (S6) is already on at this moment and can carry the free-wheeling current, 22.1. ZVS topology is constituted, when the switch turns on and off at zero voltage. The voltage V in is immediately exerted on the transformer primary side, transferred to the secondary side with transformer s turns ratio. Therefore, it requires some time to reverse the polarity of the current and to start the active power exchange. Zobrazit minimáln záznam visor, palack, Petr cs thor, chalupka, Tomá cs cessioned T09:57:08Z. 3.6, the duty cycle for rectifier switches is more than 50 because they both need to be on, during free-wheeling period, where the upper (S1 S3) or the lower (S2 S4) primary switches are working at the same time.
Consequently, to overcome these unwelcome stresses one may utilize the technique of turning on and off each of the converter switches when either the switch voltage or current is zero. The purpose, which is implied in the project, is referred to quantification of losses and efficiency of both converter topologies as well as verification of DC/DC converter functionalities for a hybrid electric vehicle. There is no energy exchange between the two sides of the transformer in this mode. It will have a transformer for galvanic insulation and fullbridge rectifier on the output with a LC filter to reduce output ripple as much as possible. 4.2 Switching techniques This chapter buck converter design thesis is devoted to the description of the three cases which result in different switching behaviors. This process sustains when running the normal active duty cycle in the circuit.
Indeed, there is always current in these two inductors and these currents will be integrated and flow to the load. The gate voltages of the six switches are shown in Fig V Gate1 V Gate2 V Gate3 V Gate4 V Gate5 V Gate6 Voltage V Time us Fig. ZVS switching buck converter design thesis technique has been successfully implemented that has reduced switching losses significantly, which has improved the efficiency of the converters. It eliminates the body diode conduction and reduces the rectifier conduction loss, hence improves 12.3. The two topologies investigated are the full bridge with full wave rectification and full bridge with current doubler synchronous rectification. 3.2: Full-bridge DC-DC converter with current doubler synchronous rectification.3 Switching pattern There is a big variety of switching patterns utilized in modern switching converters. Consequently, the following discussion and analysis will be devoted to investigate and to quantify several DC/DC converter topologies used for auxiliary purposes inside the hybrid electric vehicles. The transformer secondary voltage is trying to reach to the final value. The idea is that the converter topologies should be implemented in Allegro AMS and a loss calculation script should be written in Matlab. This corresponds to the output inductor discharge, hence leading to inductor current decrease.
4.8: Bipolar hard switching for conventional DC/DC, secondary side switches The overlap that is created during voltage/current transition causes energy loss and it may be minimized by increasing di/dt and dv/dt. Matlab-Projects, the article presents the application of a probabilistic robust control scheme for DC-DC Buck Converter, on the basis of the idea of randomly selected scenarios from an uncertain set. 16 25 4 Analysis.1 Waveforms verification The following chapter is devoted to the description of the operation principles of the full-bridge DC-DC converter with full wave and current doubler synchronous rectification Full wave synchronous rectification The following analysis. SET-UP descriptioate1 V Gate2 V Gate3 V Gate4 V Gate5 V Gate6 Voltage V Time us Fig. 3.5: Bipolar switching pattern in the current doubler converter In the phase shifted pattern, two secondary switches S5 and S6 start conducting together with the switches S1 S3 or. Everything that is happening on the primary is reflected to the secondary sides, but with a certain delay, due to the leakage inductance in the transformer, if it is not perfectly coupled. The research in this particular area has been accelerated in a rapid pace during recent years. The primary side consists of two legs, one active and one passive; where in each leg there are two primary switches and their diodes in anti-parallel to allow freewheeling, when there is no power transfer interval. A deeper study is needed on the zero voltage switching in order to undertand how it is achieved in some conditions and not in the other. 4.13: Hard switching in the primary side switches of the current doubler converter in case of phase shifted switching pattern 29.2. By turning on S3 the current starts flowing through it and it should be considered that this current is negative according to the switch positioning. At this instant after turning off S4, the stored energy in L 1 charges the capacitance of C 4 and discharges C 3 which makes D3 to conduct.
In the meantime, if the delay time determined is too high, the interval when 31.2. SET-UP description Vgate1 Vgate2 Vgate3 Vgate4 Voltage V Time us Fig. Efficiency has been determined and for the full wave topology it reached a maximum value.4 at the load level of 35 and for the current doubler it has reached.5 at the load level. Then design and realize power unit boost DC/DC converter for photovoltaic panel with the specified parameters and the possibility of microcomputer control system. Type Diplomová práce cs feree Chlebi, Petr cs cepted cs gree-name Ing. Maintaining the output voltage to the desired value in the presence of load variations is formulated as an LPV H-infinity optimization problem. 2.1: Switch mode inductive current switching The area under this trajectory represents the switching loss, hence it must be reduced. 3.6: Phase shifted switching pattern in the current doubler converter mosfet The rated current is calculated using obtained data from the simulations in Allegro AMS with maximum power output and then imported to Matlab, where the relevant calculations have been performed. Moreover, problems like increased switching losses and electromagnetic interference (EMI) occurring due buck converter design thesis to reverse recovery of body diodes arise. Filed in: Matlab Power Electronics Projects, tags: 2014 matlab project, matlab consultant, matlab projects, share This Post. The transformer current starts decreasing, the same as inductors currents which show their discharging behavior and results in supplying the output energy. Dále navrhnout a realizovat vkonovou jednotku zvyujcho DC/DC mnie pro fotovoltaick panel s danmi parametry a s monost zen mikropotaovm systémem.
Abstract, the main objective this thesis is to perform theoretical analysis and description of the basic DC/DC converter suitable for connection to photovoltaic panels. Introduction Compare the ideal and real converters, verify the simulated performance through studying relevant waveforms Determine the appropriate switching technique, among hard- or soft-switching Determine and quantify important parameters,. On the other hand, the output voltage in this particular application is not high and the diode voltage drops will be a high percentage of the output voltage in case 10.3. The most fundamental of the existing high power bi-directional DC/DC converter topologies is depicted in Fig. One method which was used above was changing the switching pattern that was mentioned as the second case at the beginning of this chapter. 4.16: ZVS switching with phase-shifted switching pattern for full wave DC/DC, secondary side switches According to the performed simulations and obtained waveforms ZVS is successfully achieved on the primary as well as on the secondary side switches. However, pollution is not the only vital aspect that must be considered, another fact is that fossil fuels are depleting, hence the road transportation sector has high dependency on it and convenient alternatives must be identified to maintain efficient and reliable performance.
However, these snubbers do not decrease the overall switching power loss, because it is simply shifted from the switch to the snubber circuit. The operation represents zero voltage switching on both sides of the transformer, which was one of the aims in the project. During the whole time of this mode, the rectifier inductors currents are decreasing linearly until t 2 which is the ending point. In this case D4 is conducting first and then S4 turns on under zero voltage condition. This variation in load appears as a linear uncertain parameter, with a known range, in the dynamic model of the converter.
All of them come with rechargeable batteries that can be restored to almost full state of charge by either connecting the vehicle plug to an external power source or by an internal generator on board in the car. This circuit has one additional filter inductor in the output side compared to the conventional topology, but each of those inductors carries only half of the output current. This could be explained by the fact that the direction of the current through S7 is strongly dependant on the operating point (loading) of the converter at that particular time instant and the size of the leakage inductance of the transformer. Concerning the project s application purpose, one may say that there is a vital need to deliver regulated low ripple voltage to the battery, having a big freedom in controlling the output voltage. The secondary side has the same configuration as the primary, but diodes are connected in parallel to the switches, to allow current flow when some switch is not conducting (current commutation interval). It has to be avoided, if there is a need of reducing the switching losses and stress over the semiconductor devices. A lot of development strategies have been elaborated, relevant experiments have been performed and practical models have been built. Therefore, all the following analysis will be oriented on deep investigation, validation and quantification of DC/DC converters, needed for auxiliary purposes in a hybrid electric vehicle. To be able to analyze and compare, two 11.3. Remark The important observation has to be noticed that there is a positive current flowing through S7, which might seem doubtful from the first sight. Extent 3283708 bytes cs rmat. Analysis has been initiated. At t 1 by turning off S1, the stored energy in the leakage and magnetizing inductances charge the capacitance C 1 and discharge C 2 which makes D2 to conduct.
For this purpose two transition points have been chosen and are depicted in Fig and.20 by vertical dashed-lines in magenta color. Abstract, hlavnm clem této práce je provést teoretick rozbor a popis základnch DC/DC mni vhodnch pro pipojen k fotovoltaickm panelm. Another point corresponding to the proper circuit operation would be body diode conduction prior to turn-on of the switches Current doubler synchronous rectification - soft switching There are several ways to achieve zero voltage switching. In contrast to ZCS, the 7.3. These rise/fall times may be reduced by introducing dissipative passive snubber circuits, and they are usually implemented in real power devices.
Torbjörn Thiringer for his immense help and relevant advices. 3.3: Bipolar switching pattern, gate drive signals Hard switching implies that power switches must cut off the load current within turn on and turn off time intervals, resulting in severe stress on the semiconductors. We would like to express special gratitude to all the guys who were helping and supporting us throughout the project, especially to Mats Nilsson, Anders Magnusson and Leif Karlsson. These techniques have been developed using resonant switch concept to tackle the switching losses in power devices as well as to suppress electromagnetic interference (EMI) produced, due to large di/dt and dv/dt caused by switch-mode operation. Mode III: (t 2 -t 3 ) As it can be observed, this mode is starting at the time t 2 where the current in D6 reaches zero and the transformer secondary current magnitude is equal. Therefore, the concept is to move to resonant converter operation, incorporating zero voltage (ZVS) or zero current (ZCS) switching with the help of a resonant tank, consisting of inductances and capacitors. The conducted experiments and simulated waveforms are presented in the next section Current doubler synchronous rectification - hard switching As it can be seen in the simulation results in Fig and Fig. Date.available T09:57:08Z sued 2014 cs entifier.
Various topologies are utilized for this particular purpose nowadays. To implement a proper switching transition, the inductor energy stored at the start of the transition must be large enough to completely charge the switch capacitance from the initial to the final voltage. The peak resonant voltage appears across the switch, but the peak switch current remains the same as in its switched-mode counterpart. Analysis but S5 is not turned on yet. In the particular application, where low output voltage and very high output current are required for supplying the auxiliary network of the car, the transformer is required not only for isolation purposes, but to downscale. It is seen that the voltage potential over S7 is changing with respect to the load change, seen from Fig At some load conditions, the direction of the current flow through S7 during freewheeling interval may also change (indicated. 8 17 3 Set-up description This chapter is devoted to the thorough description of the converter circuits being investigated in the thesis work. Fakulta elektrotechniky a informatiky cs partment 430 - Katedra elektroniky cs gree-program Elektrotechnika cs gree-branch Elektronika cs sult vborn cs nder S2724 cs esis cess openAccess Soubory tohoto záznamu Tento záznam se objevuje v následujcch kolekcch Zobrazit minimáln záznam.
In the meantime, DC/DC converters are the devices that change one level of DC voltage to another (either higher or lower) level. Analysis Here it may be observed that during the transient, there is an undershoot of the voltage over the switches in the passive leg, which is due to the reverse recovery of the diodes, connected in parallel. All switching waveforms can be seen in Fig and Fig Fig. The waveforms are depicted in Fig and Fig It should be mentioned again that the upper parts of the each subplot show the gate pulse voltage in different switches and the lower parts show the voltage over the switches. 4.12, all switches are turned on when the voltage over them are not zero. 4.1: Primary and secondary sides currents and voltages in the transformer as well as output inductor current Fig. Analyze and verify the obtained results, maybe suggest possible improvements, if necessary. The coherent analysis is conducted with simulated results and an explicit explanation of the converters performance is carried out through obtained waveforms. The zero-voltage-switching (ZVS) can reduce the total switching losses by more than half, while zero-current-switching (ZCS) reduces them by about 25 when compared to hard switching. The inverter side of this topology is the same as conventional full bridge converter with four switches in two different legs. In this case the leakage inductance is represented by changing the coupling factor of the transformer to Full wave synchronous rectification - hard switching Fig. Those power electronic devices are much more efficient, allow better controlability, safer and more powerful. Analysis the voltage across the switch is zero would be missed, which would lead to the capacitance being repeatedly recharged and the possibility of zero voltage switching would be lost.
Mode I: (t 0 -t 1 ) This mode starts from t 0 where S4 is turned off and the buck converter design thesis transformer voltages are falling to zero. Losses have been determined and the efficiency plots have been created and presented. It should be mentioned that the current flowing through the switch is considered negative according to the switch positioning. A calculation script for loss determination has been successfully written and losses have been determined, which are included in the results section. Consequently, introducing a resonant LC-tank allows avoiding conduction of the body diode during the switching transitions. Then verify the functionality of measuring the most important variables. 3.3 and Fig During the switching intervals, the power semiconductor device should withstand high voltage and high current at the same time, resulting in substantial stress and switching losses. Mimetype application/pdf cs o cs. This might be done in different ways. So, there is no soft switching in any switches during turn-on duration. Therefore, with the help of the energy released from the resonant tank, the switch junction capacitance is discharged, which allows the power switch to turn on at ZVS Switching pattern of Case II On the full bridge.
Similarly, the magnitude and the direction of the output current can be controlled 2 Full bridge DC-DC converter with current doubler rectification One of the most common alternative topologies for vehicle applications is current doubler. 3.4 Components selection For choosing the appropriate rating for the semiconductor devices, a 200 current margin and 100 voltage margin have been selected, due to the high power application of. The entire ripple created by the inductor is absorbed by the capacitor C 3, allowing the load to have almost pure DC current. Full bridge DC/DC converter, modeling, zero-voltage switching, current doubler, synchronous rectification, switching loss, conduction loss, transformer design, efficiency 4 5 Acknowledgments We are grateful to Volvo Car Corporation, specially to Karl Klang for giving us the opportunity to perform our project at their premises. As it is seen from the circuit, the secondary side is implemented with controlled switches; such a configuration is called synchronous rectification.
4.17: Zero voltage switching in the primary side switches of the current doubler converter in case of phase shifted switching pattern and coupling factor0.99 Fig. Furthermore, turn-on high voltage levels induces a severe switching noise phenomenon known as the Miller effect (increase in the equivalent input capacitance due to amplification of the effect of capacitance between the input and output terminals) which is coupled into. It can be said that at this mode the power exchange period starts and energy is delivered to the load from the source side until t 3 where the next free-wheeling period will be initiated and sequence. They are made by changing the location of switches and inductors on the secondary side and also by choosing diodes or other semiconductors as switches. The next event is turning on S2, so the current of D2 is moved to the anti-parallel switch (S2). For the current doubler, IPW65R080 from Infenion with almost the same ratings was chosen. There are many topologies for DC/DC conversion, such as buck, boost, buck-boost, forward, cuk, flyback, push-pull converters etc. This small time interval corresponds to the transition interval (dead time between the switch operations). However, higher switching frequencies result in an increase of switching losses, which have to be minimized. The decrease of the secondary current continues and crosses zero, then the polar- 23.2. 4.15: ZVS switching with phase-shifted switching pattern for full wave DC/DC, primary side switches 30.2.
To relieve these switch stresses, dissipative snubber circuits may be connected in series or parallel with the buck converter design thesis switches in the switch-mode converters. The topology is shown in Fig. 4.11: Hard switching in the primary side switches of the current doubler converter in case of bipolar switching pattern 28.2. By turning off S4, the stored energy in L 1 charges the capacitance of C 4 and discharges C 3 which makes D3 to conduct. Conduction of S3 and D2 at the same time applies the input voltage on the primary side of transformer inversely, but because of conducting S5 and S6 the voltage over the secondary of the transformer is still zero. 4.8 turn on of the switches in the primary side do not satisfy zero voltage condition, therefore switches are forced to commutate the full load current by the control device, resulting in high voltage stress over the switch while turning on, hence increased switching losses. Formerly, it was the alternator that has been generating power to the internal power network inside the car, but now manufacturers are heading towards utilization of more innovative decisions, those like DC/DC converters. SET-UP description of using diodes which is not reasonable.
The upper parts of the each subplot show the gate pulse voltages in different switches and the lower parts show the voltages over the switches. The same procedure has been conducted for the secondary side, but the ratings are different. Bipolar switching, which means two pairs of diagonal switches work respectively and unipolar switching, when diagonal switches work with a certain delay relative to each other that is also called the phase shift. However, in this particular application, the DC/DC converter serves as a main source of power supply to the inner auxiliary network of the car, which means that if fault happens auxiliary network will be out, which is of course not allowed. Using switches instead of diodes at the rectifier side is preferred in order to achieve synchronous (active) rectification for improving the efficiency. The justification is brought down in Table.1. It is characterized by a traditional full bridge inverter, isolation transformer and high current rectifier with synchronous rectification on buck converter design thesis the low voltage side. Another solution was using transformer leakage inductance. However, there is a time instant when the parasitic body diode unavoidably will carry the load current, which decreases the converter s efficiency because of the higher voltage drop over the body diode than over the switch itself.