WO2008139087A2 - Power supply system for a plasma pollution control device to be mounted on an automobile - Google Patents

Abstract

The invention relates to a power supply system for a plasma pollution control device (10) to be mounted on an automobile comprising a DC voltage source (2) supplying the onboard network of the vehicle. It is characterised in that it comprises an assembly of at least two resonance converters (20, 21, 22), all the converters being connected at the input to the voltage source (2) of the vehicle onboard network, while the outputs of the converters (20, 21, 22) are connected in series or in parallel between them to the terminals of the pollution control device (10), and in that the control instruction of the resonance converters are synchronised.

Description

 ELECTRIC POWER SUPPLY SYSTEM OF A PLASMA DEPOLLUTION DEVICE FOR MOUNTING ON A MOTOR VEHICLE

Technical area

The present invention relates to a power supply system for certain devices fitted to motor vehicles, and requiring the formation of plasma, and therefore the generation of particularly high electrical voltages. By way of example, these types of devices can be used for depollution functions, typically for the decontamination of the gaseous effluents, or the deodorization of the passenger compartment of the vehicle, or even for the reforming of hydrocarbons in the case of use of fuel cells.

The invention relates more specifically to the architecture of the power system for generating such voltages.

Previous techniques

In general, the generation of very high voltages, of the order of several thousand volts, requires the use of particular converters, insofar as the power source forming the on-board electrical system available on a vehicle is fed from a storage battery, whose voltage is generally of the order of 12 or 24 volts. Such converters therefore generally include a resonant converter structure, combined with a step-up transformer, and possibly capacitive voltage multiplier arrangements. Examples of these supply systems are in particular described in documents FR-2 861 802 and EP-0 519 882, or US-6 777 881.

These systems, although satisfactory, however, have a number of disadvantages. Indeed, insofar as they are intended to generate high voltages, of the order of several tens of kilovolts, to provide powers of the order of one kilowatt hour, they generate current stresses relatively components on the input stages of the resonance converter. These currents can indeed reach peaks of the order of 200 amperes for an onboard network in 12 volts, and consumptions of the order of a kilowatt for example. Similarly, the very high voltages required by plasma devices, generate significant tension stress on the components located at the output stages of the resonant converters, and in particular at the level of the step-up transformers, the capacitors at the level of the multipliers voltage, as well as for neighboring semiconductor components.

One of the objectives of the invention is to reduce the electrical and thermal stresses on the components of the supply systems, so as to allow more economical sizing, and increase the operating efficiencies.

Presentation of the invention

The invention thus relates to a power supply system for a plasma pollution control device, intended to be mounted on a motor vehicle equipped with a DC voltage source supplying the electrical vehicle electrical network.

According to the invention, this power supply system is characterized in that it comprises a set of at least two resonant converters, all of the converters being all input connected to the voltage source of the onboard electrical system. vehicle. The outputs of these converters are connected in series or in parallel with each other and at the terminals of the plasma pollution control device. Additionally, the control commands of the resonant converters are synchronized.

In other words, the invention consists in using several resonant converters simultaneously supplying the same load, so as to reduce the electrical and thermal stresses at the level of the electrical components forming the converter. Indeed, the various converters in accordance with the invention having their input stages connected in parallel on their edge network, they only see a fraction of the current required to produce the overall power, thus with less current stresses. . The gains in thermal stress are also significant, since they are generally proportional to the square of the current.

Thanks to this modular design of the power system, it is thus possible to use low volume components, and advantageously made in CMS technology thus allowing automated assembly, and a particularly reduced overall volume.

The combination of the operation of several resonant converters has multiple advantages, and this depending on the way in which each of the converters operates, whether it is a continuous mode operation, alternating or even pulse.

Thus, in a first case, the control commands of the resonant converters can be synchronized and out of phase, so that the output voltages of the resonant converters are themselves also out of phase by an angle of 2π / N. , where N is the number of operational converters. In other words, the system operates in a polyphase mode, in which each converter provides a substantially equivalent output energy, but consuming as input a current whose AC component is out of phase from one converter to another. In this way, the filter installed at the input of the power supply upstream of the converters can be dimensioned in a reduced way, because of the decrease in the ripple of the overall current consumed.

In another mode of operation, it may be advantageous for the control commands of the resonant converters to be synchronized and in phase, so that the voltages at the output of the converters are also in phase. This mode is particularly useful for operation in pulse mode, making it possible to obtain very high voltages, of the order of several tens of kilovolts, and with low rise times. In this case, the outputs of the converters are advantageously connected in series, so as to add the output voltages of each of the converters.

According to another characteristic of the invention, it may be useful in this mode of impulse operation to use a bipolar mode, as described in document US-6 156 162. In fact, in this case, the positive pulse is immediately followed by a negative pulse, which has the effect of reinforcing the electric field at the arrival of the next pulse, of inverse polarity between the electrodes of the plasma reactor.

According to another characteristic of the invention, the system may comprise means for varying the number of operational converters among all available converters, and this as a function of the electrical power consumed by the plasma device.

In other words, only a portion of the converters can be turned on, in the case of low power operation. Indeed, the operation of resonant converters under very low load generally poses problems of stability and efficiency. Thus, by reducing the number of operational converters during low load operation, the power to be supplied is distributed over a small number of converters which thus function correctly. If necessary, the phase shift of the control commands of the resonant converters is thus adapted as a function of the number of operational converters, so as to maintain equi-distributed phase shifts to limit the input ripple.

The modular architecture of the power system according to the invention allows its operation in different modes, whether it is a mode pulsed, or even continuously, in which case each converter comprises at the output a rectifying stage, so as to deliver a DC voltage.

Description of figures

The manner of carrying out the invention as well as the advantages which result therefrom will emerge from the description of the embodiment which follows, in support of the appended figures in which:

FIG. 1 is a diagram showing in a simplified manner the main elements constituting a resonance converter;

FIGS. 2 and 3 are simplified diagrams showing the way in which the different resonant converters constituting the invention are connected;

FIGS. 4a and 4b are two timing diagrams showing the current consumed by two resonant converters operating in a system according to the invention;

FIG. 4c is a timing diagram showing the overall current consumed by a system according to the invention, comprising two resonance converters whose consumed currents are illustrated in FIGS. 4a and 4b; FIG. 5 is a simplified diagram showing a system including three resonance converters operating in a pulse mode;

FIG. 6c is a timing chart showing the output voltage at the load of FIG. 5, when the control commands corresponding to FIGS. 6a and 6b are applied.

Way of realizing the invention

In general, and as illustrated in FIG. 1, a resonant converter 1 is fed at the input by a DC voltage source, typically the vehicle's onboard network, powered by a storage battery 2. At the input, the converter comprises a bridge or a half-switching bridge 3, typically including Mosfet or IGBT transistors operating at a frequency high, of the order of a few tens or a few hundred kHz. This switching bridge 3 delivers in an LC 4 resonant circuit in series. This LC circuit is in series with the primary 6 of a step-up transformer 5.

In the case illustrated in Figure 1, the secondary 7 of the transformer 5 feeds a rectifier assembly 8, typically in the transition from a diode bridge. This voltage is then filtered, for example based on a capacitive filter 9, to then deliver a voltage V ₃ to the load.

By the application of appropriate orders 12 at the switching bridge 20,

22, the power transmitted by the resonant converter can be adjusted.

According to the invention, the power supply system of the plasma device includes a set of resonance converters which, as illustrated in FIG. 2, are all connected in parallel at their input stage on the on-board network. 2 of the vehicle. In the embodiment illustrated in Figure 2, the output stages of each of the converters 20, 21, 22 are connected in series, so as to output the load voltage V ₁₀ equals the sum of the voltages V ₂₀ V ₂₁ V ₂₂ delivered by each of the converters 20, 21, 22.

In a variant illustrated in FIG. 3, the output stages of the different converters 30, 31, 32 may be connected in parallel. This configuration is more suitable when the voltage V ₁₀ required by the load is lower, and on the other hand, the charging current is higher. In this case, the currents I _30, 1˝ _31, I ₃₂ of each of the converters 30, 31, 32 add up to the current I consumed by the load _10.

According to an important feature of the invention, the control commands of each of the resonant converters can be organized to optimize certain operating parameters of the power system. Thus, as illustrated in FIGS. 4a to 4c, the input current of the supply system may have an optimized waviness factor. More precisely, FIGS. 4a and 4b illustrate the input current, taken from the on-board network for a resonance converter, taken in isolation. This current I ₂₀ , I ₂₁ has a shape based on the rectified sinusoid portion. It can be seen, by comparing FIGS. 4a and 4b, that the waveforms are identical, but out of phase by a half-period, that is to say a phase shift angle of π. FIG. 4c illustrates the sum I ₂ of the two currents of FIGS. 4a and 4b, from which it appears that the current ripple rate is much lower. As a result, the filtering required input of the power system can be dimensioned accordingly, and present equivalent power a smaller footprint.

In the case where the output of the supply system is also continuous, the current delivered to the load has a waveform similar to the input current. The ripple at the load current is therefore also reduced.

Of course, Figures 4a to 4c are given for a power system including two resonant converters, but the invention can be declined using a larger number N converters. In this case, the phase difference between the control commands of each of the converters is

2π / N.

In the embodiment illustrated in FIG. 5, each resonant converter 60, 61, 62 operates in a pulse mode, which can be unipolar or bipolar. The switches Q ₁₁ , Q ₁₂ , Q ₂₁ , Q ₂₂ , Q _{n 1} and Q _{n 2} illustrated in FIG. 6 can be made in different ways, and in particular by thyristors or IGBT transistors, combined with an antiparallel diode. , or even by Mosfet transistors. Two control modes are possible, namely a control of the switches in phase, and a command out of phase. In the latter case, the control of a lower switch Q ₁₂ , Q ₂₂ , Q _n2 makes it possible to generate the output voltage as illustrated in FIG. 7, in which the control of a first converter, according to the operating order of the switch Q ₁₂ shown in FIG. 6a, makes it possible to generate a voltage pulse at the output, and more specifically a sinusoidal pulse 70 of a single period as illustrated in FIG. 6c. Controlling the second converter, in the order illustrated in FIG. 6b, and shifted in the appropriate phase-shift time, also makes it possible to deliver the same type of output voltage 71, with the same time offset. The width of the pulse is determined by the characteristics of the resonant circuit of the converter, namely the inductance L and the capacitor C as well as the characteristics of the step-up transformer. In the case of FIG. 5, a DC-DC converter of the "flyback" type, for example, can be added between the battery and the input of all the converters for raising the voltage (at 500 V for example). .

It follows from the above that the power system according to the invention has the advantage over single converter solutions, to improve the overall performance, in terms of reducing thermal and electrical stresses on the passive components and assets, as well as in terms of overall performance.

Moreover, the operation in polyphase mode makes it possible to improve the dynamic response of the system, and to reduce the size of the input and output filters. In addition, the modularity, that is to say the possibility of using a partial number of converters on the whole available, allows low-load operations, which are generally problematic for resonant converters.

Claims

1 / Power supply system of a plasma pollution control device 10 intended to be mounted on a motor vehicle equipped with a DC voltage source 2 supplying the on-board vehicle network, characterized in that it comprises a set at least two resonant converters 20, 21, 22, all of the converters being all input connected to the voltage source 2 of the vehicle onboard network, the outputs of said converters 20, 21, 22 being connected in series or in parallel with each other across the terminals of the pollution control device 10, and in that the control commands 12 for the resonant converters are synchronized. 2 / System according to claim 1 characterized in that the control commands 12 of the resonant converters 20, 21, 22 are synchronized and out of phase so that the output voltages of the resonant converters are out of phase by an angle of 2π / N, where N is the number of operational converters. 3 / System according to claim 1, characterized in that the control orders of the resonant converters are synchronized and in phase, so that the output voltages of the converters are in phase. 4 / A system according to claim 1, characterized in that it comprises means for varying the number of operational converters among all available converters, depending on the electrical power consumed by the plasma device. 5 / System according to claim 4, characterized in that the phase shift of the control orders of the resonant converters is adapted according to the number of operational converters. 6 / System according to claim 1, characterized in that each converter 60, 61, 62 resonance operates in a pulse mode. 11 System according to claim 1, characterized in that each converter 1 comprises a rectifying stage 8 at the output, so as to deliver a DC voltage.