EP3243270A1

EP3243270A1 - Power-conversion method and device and vehicle comprising such a device

Info

Publication number: EP3243270A1
Application number: EP16702170.8A
Authority: EP
Inventors: Khalil El Khamlichi Drissi; Abbas DEHGHANIKIADEHI; Christophe PASQUIER
Original assignee: Centre National de la Recherche Scientifique CNRS; Universite Clermont Auvergne
Current assignee: Centre National de la Recherche Scientifique CNRS; Universite Clermont Auvergne
Priority date: 2015-01-06
Filing date: 2016-01-06
Publication date: 2017-11-15
Also published as: KR20180020941A; JP2018506253A; FR3031423B1; AU2016205951A1; FR3031423A1; RU2017127568A; US20180026567A1; CA2972945A1; WO2016110643A1; CN108124501A

Abstract

The present invention relates to a power-conversion method (10) for a vehicle comprising: a three-phase electric motor, - two three-phase inverters, each inverter being controlled via modulation of at least six spatial vectors, the output voltage of each inverter being given by a spatial vector referred to as "reference spatial vector". Said method comprises the following steps: - applying (11) an activation sequence to the spatial vectors of one inverter, - applying (12) an activation sequence to the spatial vectors of the other inverter, - subtracting (13) the reference spatial vector of one inverter from the reference spatial vector of the other inverter and - supplying (14) the electric motor with electric power, the voltage inducing the electric power being relative to the vector resulting from the subtraction.

Description

METHOD AND DEVICE FOR CURRENT CONVERSION AND VEHICLE COMPRISING SUCH A DEVICE

Field of the invention

The present invention relates to a method and a device for converting current and a vehicle comprising such a device.

The present invention applies to the field of electronics.

More particularly, the present invention applies to the field of DC conversion for powering an engine of an at least partially electric powered vehicle.

State of the art

Increasing the range and performance of electric and hybrid vehicles, in electric traction such as trains and trams, for example, but also in portable variable speed drives while limiting costs are major objectives in the sector of power conversion. electrical energy.

The DC power supply devices of current hybrid or electric vehicle engines comprise autonomous or non-autonomous electrical power sources whose output voltage must be increased so that the voltage at the terminals of a three-phase inverter supplying a current electric motor is sufficient.

However, the means used, such as voltage choppers, for example, are expensive, take a considerable volume and have a significant weight which directly affects the performance of the vehicle. The means used are intended to attenuate the ripples of the electric currents at the output of the autonomous power supply source to deliver to the inverter an electric current close to a direct current. The effectiveness of the device is about eighty-one percent.

Also, as conventional means have more losses, it is necessary to have enough heat sinks to cool the equipment.

Finally, the depth of discharge (or DOD acronym of "Depth Of Discharge" in English terminology) decreases exponentially with the number of discharges of the autonomous power supply. The efficiency of the means currently used directly affects the speed of discharge and therefore the life of the autonomous power source.

There are also devices comprising inverters having several stages. However, these devices have yield losses induced by a large number of switching, zero voltages also called "ZeroSequence Voltage", acronym ZSV, in English terminology, and a common mode voltage also called "Common Mode Voltage ", acronym CMV, in English terminology. Object of the invention

The present invention aims to remedy all or part of these disadvantages. For this purpose, the present invention aims a current conversion method for a vehicle comprising:

- a three-phase electric motor,

- Two three-phase inverters, each inverter being controlled by a modulation of at least six spatial vectors (or SVM acronym for "SpaceVector Modulation" in English terminology), the output voltage of each inverter being given by a space vector said " reference spatial vector »

which has the following steps:

- application of an activation sequence to the spatial vectors of an inverter,

- application of an activation sequence to the spatial vectors of the other inverter,

subtraction of the reference spatial vector of one inverter from the reference spatial vector of another inverter and

supply of the electric motor with electric current, the voltage which induces the electric current being relative to the vector resulting from the subtraction.

Thanks to the active modulation of six spatial vectors, the number of switches of the inverter switches is thirty-three percent, and thus the power loss is decreased. Also, the device which is the subject of the present invention makes it possible to reduce the common mode current in peak and in rms value. So the control of an engine is improved and the life of the engine is increased. In addition, there is a decrease in electromagnetic interference.

In addition, the ripple of the current consumed by an independent power source is reduced which contributes to extending the life of the autonomous power source and to limit the filtering capacity of a continuous bus.

The harmonics, as far as the motorization is concerned, are also limited by up to three percent compared to the fundamental frequency, which does not degrade the motor used by overheating.

In addition, the yield is about eighty-six percent with such a process. The control of each inverter independently by pulse width modulation (PWM or PWM) means only the instantaneous values of the voltages of each phase and makes it possible to reduce the losses due to the ZSVs and CMV.

In embodiments, the activation sequences are configured so that the reference vectors are out of phase.

The advantage of these embodiments is to decrease the amplitude of CMV and ZSV.

In embodiments, each activation sequence of an inverter is configured so that two spatial vectors of the inverter, V and V _{i +} i, with i an integer of between one and six, are activated consecutively by the sequence of activation.

These embodiments make it possible to limit the disturbances due to

ZSV and CMV at one third of the direct current input of the inverters.

In embodiments, for an inverter O _n controlled according to a conventional modulation of eight spatial vectors Vi with i an integer between zero and seven, with n an integer between one and two:

the conventional cyclic ratio, ° c " _CS yM _> of a vector V, activated by the

activated consecutively by the activation sequence is given by the formula:

where, i is an integer between one and six, θ _η is the phase of the conventional reference vector, and V _r " _pu is the ratio of the norm of the conventional reference vector of the inverter n to the norm of the spatial vector V ,,

the conventional reference spatial vector, V ^ _{ef csVM} of the inverter activated by the activation sequence is given by the following formula:

These embodiments have the advantage of controlling the inverters according to a conventional spatial vector modulation.

In embodiments, for an inverter O _n , where n is an integer between one and two:

the modified cyclic ratio, <x, of a vector V, activated by the activation sequence (260, 265) is given by the following formula:

= I _ ^ SVM- ^ SVM ₌ i _ _y n fcn _sin ( _fn _ _(i _ _f) 2) _(a) - the modified cyclic ratio, oc ₊₁ , of the vector V _{i +} i activated consecutively by the sequence d activation is given by the formula:

+ _{i =} i ₊ ^ SVM- ^ SVM ₌ i ₊ yn fp _sin _ ₍ . _, _} ) _(b) where, i is an integer between one and six, θ _η is the phase of the conventional reference vector, and V? _efiPU is the ratio between the conventional reference vector standard of the inverter n and the norm of the spatial vector V ,,

the modified reference spatial vector, of the inverter activated by the activation sequence, is given by the following formula:

Ttn _ ^v i + ^v i + i, fn _ "n Λ ^v i + i ~ ^v i _ ny," ny "\ ^v ref - ₂ ^† V -i + l, CSVM ° ^ i, CSVM) ₂ ~ ^v i ^v i + l *)

The advantage of these embodiments is to increase the maximum standard of the total spatial vector and therefore the voltage and the supply current of the electric motor.

In embodiments, the activation sequences are independent.

These embodiments have the advantage of being able to choose a phase shift between the reference spatial vectors of each inverter to maximize the voltage of the electrical power supply of the electric motor. For example, the value of the voltage that induces the electrical power supply of the electric motor can be doubled with a phase shift between the reference voltages between zero and one hundred and eighty degrees.

According to a second aspect, the present invention aims a current conversion device which comprises:

means for applying an activation sequence to the spatial vectors of an inverter,

means for applying an activation sequence to the spatial vectors of the other inverter,

means for subtracting the reference spatial vector of one inverter from the reference spatial vector of another inverter and

- Connection means to a power source.

The advantages, aims and particular characteristics of the device object of the present invention being similar to those of the method object of the present invention, they are not recalled here.

According to a third aspect, the present invention relates to a vehicle which comprises a device object of the present invention and a three-phase electric motor.

The advantages, aims and particular characteristics of the vehicle object of the present invention being similar to those of the device object of the present invention, they are not recalled here.

Brief description of the figures

Other advantages, aims and particular characteristics of the invention will emerge from the following nonlimiting description of at least one particular embodiment of a method and a device for converting current and a vehicle comprising such a device, with reference to the appended drawings, in which: FIG. 1 represents, schematically, a first particular embodiment of a method that is the subject of the present invention,

FIG. 2 represents, schematically, a first particular embodiment of a device that is the subject of the present invention; FIGS. 3a and 3b show, schematically, reference vectors in an orthonormal frame (α, β) in the context of FIG. of the present invention,

FIG. 4 represents a vector representative of the input voltage of a three-phase electric motor in an orthonormal reference frame (α, β) in the context of the present invention and

- Figure 5 shows a particular embodiment of a vehicle object of the present invention.

Description of embodiments of the invention

It is already noted that the figures are not to scale.

This description is given in a nonlimiting manner, each feature of an embodiment being able to be combined with any other feature of any other embodiment in an advantageous manner.

FIG. 1 shows a particular embodiment of a method that is the subject of the present invention for a vehicle 50 comprising:

a three-phase electric motor 245,

- Two three-phase inverters, each inverter being controlled by a modulation of at least six spatial vectors (or SVM acronym for "SpaceVector Modulation" in English terminology), the output voltage of each inverter being given by a space vector said " reference spatial vector ".

which has the following steps:

application 1 1 of an activation sequence 260 to the spatial vectors of an inverter called "inverter 01",

application 12 of an activation sequence 265 to the spatial vectors of the other inverter known as "inverter 02",

subtraction 13 of the reference spatial vector of one inverter from the reference spatial vector of another inverter and supply of the electric motor with electric current, the voltage which induces the electric current being relative to the vector resulting from the subtraction.

We define the six spatial vectors of each inverter, V _; V ₂ , V ₃ , V ₄ , V ₅ , V ₆ , as having the same standard and such as the angle between the direction of a vector V, and the direction of a vector V _{i +} i, with i an integer between one and six, is sixty degrees. By defining the origin of the six spatial vectors Vi, V ₂ , V ₃ , V ₄ , V ₅ , V ₆ , at the same determined point of an orthonormal coordinate system (α, β), the ends of the spatial vectors V _; V ₂ , V ₃ , V ₄ , V ₅ , V ₆ , define a regular hexagon. The vector V is defined as being parallel to the axis a of the orthonormal coordinate system (a, β). The construction of spatial vectors is visible in Figure 3a.

The two vectors V ₀ and V ₇ correspond to zero vectors and are positioned at the center of the regular hexagon defined by the spatial vectors V _; V ₂ , V ₃ , V ₄ , V ₅ , V ₆ .

The inverter, 01 or 02, comprises six power switches which are controlled by the application means of an activation sequence, 260 or 265. Three pairs of power switches are mounted in parallel. The power switches have two states, the open state or the closed state. For the activation of a power switch by torque, in open or closed state, the other power switch is controlled in the other state. Spatial vectors V _; V ₂ , V ₃ , V ₄ , V ₅ , V ₆ , each correspond to a combination of activation of the six switches of different power. The activation sequence of the spatial vectors corresponds to an activation sequence of the power switches. The vector V ₀ corresponds to the closing of the first switches receiving current for each pair of switches. The vector V ₇ corresponds to the opening of the first switches receiving current for each pair of switches.

The electric motor has three phases pa, pb and pc.

Each activation sequence, 260 or 265, of an inverter, 01 or 02, is configured so that two space vectors of the inverter, V, and V _{i +} , with i an integer between one and six, are activated consecutively. by the activation sequence, 260 or 265.

The activation sequence 260 of the inverter 01 comprises six sub-sequences implementing the first subsequence at the sixth subsequence. In the first sub-sequence, the vector V1 of the inverter 01 is activated for a duration t1 + t2, then the vector V2 is activated for a duration Ts - (t1 + t2). The duration Ts corresponds to a period of a clock signal. The duration Ts can be defined as the period of a subsequence.

In the second subsequence, the vector V2 of the inverter 01 is activated for a duration t1 + t2, then the vector V3 is activated for a duration Ts - (t1 + t2).

In the third subsequence, the vector V3 of the inverter 01 is activated for a duration t1 + t2, then the vector V4 is activated for a duration Ts - (t1 + t2).

In the fourth subsequence, the vector V4 of the inverter 01 is activated for a duration t1 + t2, then the vector V5 is activated for a duration Ts - (t1 + t2).

In the fifth subsequence, the vector V5 of the inverter 01 is activated for a duration t1 + t2, then the vector V6 is activated for a duration Ts - (t1 + t2).

The activation sequence 265 of the inverter 02 comprises six sub-sequences implementing the first subsequence at the sixth subsequence.

In the first subsequence, the vector V3 of the inverter 01 is activated for a duration t1, then the vector V4 is activated for a duration Ts - 11.

In the second subsequence, the vector V4 of the inverter 01 is activated for a duration t1, then the vector V5 is activated for a duration Ts - 11.

In the third subsequence, the vector V5 of the inverter 01 is activated for a duration t1, then the vector V6 is activated for a duration Ts - 11.

In the fourth subsequence, the vector V6 of the inverter 01 is activated for a duration t1, then the vector V1 is activated for a duration Ts - t1.

In the fifth subsequence, the vector V1 of the inverter 01 is activated for a duration t1, then the vector V2 is activated for a duration Ts - t1.

In the sixth subsequence, the vector V2 of the inverter 01 is activated for a duration t1, then the vector V3 is activated for a duration Ts - 11. The activation sequences 260 of the inverter 01 and 265 of the inverter 02 are activated consecutively, starting with the first subsequence of each activation sequence in steps 11 and 12. Then the activation sequences 260 and 265, are repeated until the end of the command to start the electric motor. In embodiments, the activation sequence of the inverter 01 begins with a subsequence of the activation sequence and the activation sequence of the inverter 02 begins with a subsequence of the sequence of activation such that the vectors activated in the subsequence are different from the activated vectors of the start subsequence of the activation sequence of the inverter 01.

The duration Ts is a predetermined period which is of the order of 100 με depending on the performance of the digital device used to control the inverters 01 and 02, for example. The more efficient the device, the weaker Ts is. The arithmetic operations of the determination of the activation sequences, 260 and 265, are executable during the control period Ts.

The durations t1 and t2 are defined according to the formula e.

tl = T _s min (<x _i ¹ , <x _i ² )

tl = TsmaxCoCi ¹ , ^ ² )

The cyclic ratio is defined in formula (a) and relating to the inverter 01. The duty ratio o ² is defined in the formula (a) and relating to the inverter 02.

In embodiments in which conventional modulation of spatial vectors is implemented, the durations t1 and t2 are defined according to the formula e _C svM-

(SCSVM)

The two reference vectors V ^ _{ef vu} and V ² _{ef vu} , inverters 01 and 02 respectively, may be equal.

In embodiments, the activation sequences, 260 and 265, are independent. The inverters are therefore independently controlled.

The activation sequences, 260 and 265, are configured so that the reference vectors are out of phase. The three-phase electric motor is powered by three phases. If the currents of each phase of the electric motor are in phase, the electric motor does not work. A phase shift of reference vectors implies a phase shift between the phases of the electric motor that operates.

The cyclic ratios of each active vector V, and the vector activated consecutively V _{i +} obtained by a conventional modulation of spatial vectors (or CSVM acronym for "ConventionnaISpaceVector Modulation" in English terminology) are defined in formulas f and g. A duty cycle can be defined as the activation time of a vector divided by the duration Ts. The following formulas are defined for an inverter O _n controlled according to a conventional modulation of eight spatial vectors V, with i an integer between zero and seven, with n an integer between one and two.

The conventional duty cycle, _α1CSVM , of a vector V, activated by the activation sequence (260, 265) is given by the following formula:

sin i ~ 9 _n j \

sin (-) / ^

The conventional cyclic ratio, <x- _{+ ltC} svM _> of the vector V _{i +} activated consecutively by the activation sequence is given by the formula:

where, i is an integer between one and six, θ _η is the phase of the conventional reference vector, and V _r " _pu is the ratio of the norm of the conventional reference vector of the inverter n to the norm of the spatial vector V ,.

The conventional reference spatial vector, V ^ _{ef csVM,} the inverter activated by the activation sequence is given by the following formula:

In these embodiments, step 1 3 is performed according to the formula dcsvM considering that each inverter, 01 and 02, is connected to the same power supply source. If the standards of the reference vectors of the inverters, 01 and 02, are equal, the formula d is simplified and leads to the formula h CSVM-

^ enteredemotor ⁼ V-ref.CSVM ^~ ^ ref.CSVM (dcSVIVl)

V inputmotor 2 || V _re f SVM \\ (hcSVM)

With θι and θ ₂ the phase of the conventional reference vector of the inverter 01 and of the inverter 02 respectively, the motor input the vector representative of the input voltage of three-phase electric motor 245 and || _re / _<C svM || ^the standard of the reference vectors of the inverters 01 and 02, considered equal.

The voltage which induces the electric current is given by the formula I _C in which V _dc is the value of the voltage at the output of the power supply source.

He (Q - Θ \ ίθ - Q \

^ enteremotor || ⁼ 2 ||| re /, Sl ^ M || ^s ï ⁿ (^) - 2V ^ _c sin - ^ J

The duty ratios ° ^ Î, CSVM ® T ° ^ i + I, CSVM defined in formulas f and g are modified to obtain the duty ratios <x _£ and _<£ x _{+ 1.} The cyclic ratios, <x _t and oc _{i + 1 J} are such that the time during which the vector V is active is equal to the time during which the vector V _{i +} i is inactive in the same sub-sequence and vice versa. With the active modulation of six spatial vectors, the number of inverter switching is reduced and the maximum value of the modified reference vector of the inverter is increased. In addition, two phases of the electric motor among the three phases pa, pb and pc, are supplied with positive or negative electric current, a single phase undergoes changes.

For an inverter O _n , where n is an integer between one and two, the modified cyclic ratios are given by the formulas a and b.

The modified cyclic ratio, <x ₊₁ , of the vector V _{i +} i activated consecutively by the activation sequence is given by the formula:

+ _{I =} i ₊ ^ ^ SVM SVM yn ₌ i ₊ _{f sin could} _ _(. _ £ ^ _(b) wherein, i is an integer between one and six, _θ η is the phase of conventional reference vector, and V? _EfiPU is the ratio between the conventional reference vector standard of the inverter n and the norm of the spatial vector V ,.

And the modified reference spatial vector, ¾ / of the inverter activated by the activation sequence is given by the following formula:

Ttn _ ^v i + ^v i + i, fn _ "n Λ ^v i + i ^{~ v} i _ ny _m," ny _m / "\ ^v ref - ₂ ^† V -i + l, CSVM ° ^ i, CSVM) ₂ ^{~ v} i ^v i + l *)

Step 13 is performed according to the formula d considering that each inverter, 01 and 02, is connected to the same power supply source. Yes the standards of the reference vectors of the inverters, 01 and 02, are equal, the formula d is simplified and leads to the formula h.

entréemoteur ^ ~ ^ ~ ^ ref ref (^ ^ entréemoteur ⁼ 2 || V _re / 1 | Sin - J e V 2; (h) With Θ1 and θ ₂ the phase of the conventional reference vector of the inverter

01 and the inverter 02 respectively, V _{motor input} \ e vector representative of the input voltage of the three-phase electric motor 245 and || _re / || the standard of the reference vectors of the inverters 01 and 02, considered equal.

The voltage which induces the electric current is given by the formula i in which V _dc is the value of the voltage at the output of the power supply.

HT? Il- HT? M ■ ί ^θ ί ^{~ θ} 2 \ ^ ⁶ ^ _T ■ fs ₁ -e ₂ ...

\ enteredemotor \ \ ~ ^ \ \ ^V ref \\ ^sm ~) ≤ ~ ^v dc ^sm ~) V)

Preferably, the angle between the reference vectors of the inverters 01 and 02 is greater than sixty degrees.

The activation sequences are such that for the first subsequence, for example:

for the duration t1, the phase pa is supplied by the positive voltage at the output of the power supply source divided by two and the phase pb is supplied by the negative voltage at the output of the power supply source; duration t2, the phase pa is powered by the positive voltage at the output of the power supply source, the phase pb is supplied by the negative voltage at the output of the power supply and the phase pc is supplied by the negative voltage at the output of the power source and

for the duration Ts - (t1 + t2), the phase pa is supplied by the positive voltage at the output of the power supply source and the phase pc is powered by the negative voltage at the output of the power supply source.

The method 10 object of the present invention allows to calculate a ZSV for each inverter. The ZSV of the device according to the invention is the subtraction of the ZSV from the inverter 01 by the ZSV of the inverter 02. The CMV of the device according to the invention is calculated by averaging the ZSV of the inverters 01 and 02 .

Table 1: ZSV values of the device object of the present invention for each activation sub-sequence

Table 1 shows the ZSV values of method 10 and device 20 of the present invention for each activation subsequence. These values are the positive voltage value at the output of the power supply divided by three, zero or the negative voltage value at the output of the power supply divided by three, the value of the output voltage of the power supply. electric power source being.

Table 2: CMV values of the device that is the subject of the present invention for each activation sub-sequence

Table 2 shows the CMV values of method 10 and device 20 of the present invention for each activation subsequence. These values are the positive voltage value at the output of the power supply divided by three, zero or the negative voltage value at the output of the power supply divided by three, the value of the output voltage of the power supply. power source being - ^ν .

The method 10 and the device 20 objects of the present invention allows to delete the amplification means currently used, such as voltage boosters output from the power source, for example.

FIG. 2 shows a particular embodiment of a device which is the subject of the present invention and which comprises:

two three-phase inverters 225 and 235, each inverter 225 or 235 being controlled by a modulation of at least six spatial vectors, the output voltage of each inverter being given by a spatial vector called a "reference spatial vector"

means 255 for applying an activation sequence 260 to the spatial vectors of an inverter 225,

means for applying 255 of an activation sequence 265 to the spatial vectors of the other inverter 230,

means for subtracting the reference spatial vector of an inverter 225 from the reference spatial vector of another inverter 235 and

connection means, 205 and 210, to a power supply source 200.

The inverter 225 comprises six power switches 230 which are controlled by the application means 255 of an activation sequence 260. Three pairs of power switches 230 are connected in parallel. The power switches 230 have two states, open or closed. For the activation of a power switch 230 by torque, in the open or closed position, the other power switch 230 is controlled in the other position. The spatial vectors V ₀ , Vi, V ₂ , V ₃ , V ₄ , V ₅ , V ₆ and V ₇ each correspond to an activation combination of the six switches 235 of different power. The activation sequence 260 of the spatial vectors corresponds to an activation sequence of the power switches 230. The vector V ₀ corresponds to the closing of the first switches 230 receiving current for each pair of switches 230. The vector V ₇ corresponds to the opening of the first switches 230 receiving current for each pair of switches 230.

The inverter 235 comprises six power switches 240 which are controlled by the application means 255 of an activation sequence 265. Three pairs of power switches 240 are connected in parallel. The 240 power switches have two states, open or closed. For the activation of a switch 240 of power per pair, in open or closed state, the other power switch 240 is controlled in the other state.

The spatial vectors V ₀ , Vi, V ₂ , V ₃ , V ₄ , V ₅ , V ₆ , V ₇ each correspond to a different activation combination of the six power switches 240. The activation sequence 265 of the spatial vectors corresponds to an activation sequence of the power switches 240. The vector V ₀ corresponds to the closing of the first switches 240 receiving current for each pair of switches 240. The vector V ₇ corresponds to the opening of the first switches 240 receiving current for each pair of switches 240.

A switch, 230 or 240, power may be a diode and a transistor connected in parallel. Preferably, the switches, 230 or 240, power are MOSFET transistors (acronym for "Metal Oxide Semiconductor Field Effect Transistor" in English terminology) or IGBT transistors (acronym for "InsulatedGateBipolar Transistor" in English terminology).

The power supply means 200 to a DC power source may be an autonomous power source or a source of electricity connected to the national grid.

The connection means 205 and 210 may be electrical conductors. The connection means may comprise capacitors 215 and 220 filtering the ripples of the current of a continuous bus. The capacitance value of the capacitors 215 and 220 depends on the ripple rate of the bus current keep on going. The DC bus is the electric current at the output of the supply means 200.

Preferably, the inverters 225 and 235 are identical.

The inverter 225 is preferably the inverter 01 described in the description of Figure 1 and the inverter 235 is preferably the inverter 02 described in the description of Figure 1.

Each activation sequence, 260 or 265, is preferentially a successive, periodic activation of each switch, 230 or 240, of power. The activation sequences 260 and 265 are preferably the activation sequences described in the description of FIG.

Each inverter, 225 or 235, has three electrical conductors at its output and three currents are available at the output of each inverter, 225 or 230. Preferably, the signals at the output of each conductor are similar but out of phase with each other by 2π / 3 radiants. The electric motor 245 comprises three phases 250 called pa, pb or pc according to the description of FIG. Each electrical conductor is connected to a phase, pa, pb or pc, of the electric motor 245.

Preferably, the electric motor 245 is a three-phase asynchronous motor.

The application means 255 of an activation sequence 260 to the spatial vectors of an inverter 225 and application means 255 of an activation sequence 265 to the spatial vectors of the other inverter 230 are preferably a microcontroller generating a digital control signal during the period Ts.

The subtraction means of the reference spatial vector of an inverter

225 to the reference spatial vector of another inverter 235 are preferably made by connecting an inverter 235 to the negative pole of the power supply source 200 and an inverter 225 to the positive pole of the power supply source 200. The voltages delivered in the inverters 225 and 235, being of opposite signs, the subtraction is performed automatically.

Preferably, the device 20 is such that each element of each inverter, 225 or 235, is connected symmetrically with respect to the electric motor 245. The device 20 implements the method 10 described in the description of FIG.

The representations whose results are shown in FIGS. 3a, 3b, 4a and 4b are representations made by means of an embodiment of a device that is the subject of the present invention.

FIGS. 3a and 3b show reference vectors in an orthonormal frame (α, β) within the scope of the present invention,

FIG. 3a represents a graph 30a in the orthonormal reference frame (, β), representative:

points 305 of a curve of values of a reference vector of an inverter O1 or O2,

reference vectors, ¾¾ and V? _and at the output of the inverter 01 and the inverter 02 respectively, during the first subsequence of the activation sequences 260 and 265 and

space vectors V ₀ , Vi, V ₂ , V ₃ , V ₄ , V ₅ , V ₆ , V ₇ , of each inverter, 01 and 02.

We define the six spatial vectors of each inverter, V _; V ₂ , V ₃ , V ₄ , V ₅ , V ₆ , as having the same standard and such as the angle between the direction of a vector V, and the direction of a vector V _{i +} i, with i an integer between one and six, is sixty degrees. By defining the origin of the six spatial vectors Vi, V ₂ , V ₃ , V ₄ , V ₅ , V ₆ , at the same determined point of an orthonormal coordinate system (α, β), the ends of the spatial vectors V _; V ₂ , V ₃ , V ₄ , V ₅ , V ₆ , define a regular hexagon. The vector V is defined as being parallel to the axis a of the orthonormal coordinate system (a, β).

The two vectors V ₀ and V ₇ correspond to null vectors and are positioned at the center of the regular hexagon defined by the spatial vectors V _; V ₂ , V ₃ , V ₄ , V ₅ , V ₆ .

The vector V _ef is in transition between the spatial vector Vi and the spatial vector V ₂ according to the description of the first activation subsequence of the inverter 01 described in the description of FIG.

The vector V? _ef is in transition between the spatial vector V ₃ and the spatial vector V ₄ according to the description of the first activation subsequence of the inverter 01 described in the description of FIG. FIG. 3b shows a comparison of the maximum values of the reference vectors for a conventional modulation of spatial vectors and for a modulation as described in the description of FIG. 1, in an orthonormal frame of reference (α, β). ) for positive values of a and β.

Chart 30b shows:

- 0 31 points of a curve of values of a representative vecteurï¾ _cs ^ _M of a reference voltage for a conventional modulation spatial vectors,

points 305 of a vector value curve / representative of a reference voltage for a modulation as described in the description of FIG. 1,

a curve 300 representative of a reference voltage for a modulation as described in the description of FIG. 1, extrapolated from the points 305,

a vector 320 representative of the spatial vector Vi of the inverter, 01 or 02, and

a vector 31 representative of the spatial vector V ₂ of the inverter, 01 or 02.

It is observed that the maximum values of the reference vectors for a conventional modulation of spatial vectors are lower than the maximum values of the reference vectors for a modulation as described in the description of FIG.

FIG. 4 shows a graph 40 of a vector simulation, for an embodiment of a device 20 of the present invention, in the representative orthonormal referential (, β):

points 31 0 of a curve of values of a vector V ^ _{ef csVM} representative of a reference voltage for a conventional modulation of spatial vectors,

a curve 300 representative of a reference voltage for a modulation as described in the description of FIG. 1, extrapolated from the points 305, reference vectors, ¾, / and V? _ef , at the output of the inverter 01 and the inverter 02 respectively, during the first subsequence of the activation sequences 260 and 265 and

the vector 400 representative of the voltage which induces the electric current available at the input of the electric motor 245.

It is observed in FIG. 4 that the norm of the vector 400 is greater than the norm of the vectors ¾, and V? _ef . It is also observed that the standard of the vector 400 is greater than the maximum achievable output of a conventionally modulated inverter or as described in Figure 1. The standard of the vector 400 corresponds to the voltage available at the input of the electric motor 245 of the device 20 object of the present invention.

FIG. 5 shows a particular embodiment 50 of a vehicle that is the subject of the present invention.

The vehicle 50 can be any type of electric or hybrid vehicle, such as a car, a train or a tram, for example.

The vehicle 50 includes an embodiment 20 of a device object of the present invention. The embodiment 20 of the device which is the subject of the present invention is preferentially connected to DC power supply means of the vehicle 50 and to a three-phase electric motor of the vehicle 50.

Claims

1. A method (10) for converting current for a vehicle (50) comprising:

a three-phase electric motor (245),

two inverters (01, 02, 225, 235) three-phase, each inverter being controlled by a modulation of at least six spatial vectors (or SVM acronym for "SpaceVector Modulation" in English terminology), the output voltage of each inverter being given by a spatial vector called "reference spatial vector"

characterized in that it comprises the following steps:

- application (1 1) of an activation sequence (260) to the spatial vectors of an inverter (01, 225),

- applying (12) an activation sequence (265) to the spatial vectors of the other inverter (02, 235),

subtraction (13) of the reference spatial vector from one inverter to the reference spatial vector of another inverter and

- Supply (14) of the electric motor in electric current, the voltage which induces the electric current being relative to the vector resulting from the subtraction.

The method (10) of claim 1, wherein the activation sequences (260, 265) are configured so that the reference vectors are out of phase.

The method (10) according to one of claims 1 or 2, wherein each activation sequence (260, 265) of an inverter (01, 02, 225, 235) is configured so that two spatial vectors of the inverter, V, and V _{i +} i, with i an integer between one and six, is activated consecutively by the activation sequence.

4. Method (10) according to claim 3, wherein, for an inverter O _n controlled according to a conventional modulation of eight spatial vectors Vi with i an integer between zero and seven, with n an integer between one and two:

the conventional cyclic ratio, _α1CSVM , of a vector V, activated by the activation sequence (260, 265), is given by the following formula:

.not

OC; = κ n ^"" V 3 'V!

i.CSVM (f)

.not

the conventional cyclic ratio of the vector V _{i +} activeconsecectively by the activation sequence is given by the

where, i is an integer between one and six, 0 _n is the phase of the conventional reference vector, and V _r " _pu is the ratio between the norm of the conventional referential vector of the inverter n and the norm of the spatial vector V ,,

vref, CSVM

5. Method (1 0) according to claim 4, wherein for an inverter O _n , with n an integer between one and two:

the modified cyclic ratio, α, of a vector V, activated by the activation sequence (260, 265), is given by the following formula:

n _ ¹ ^ i + l.CSVM ^ i.CSVM

■ - = ¹ ₂ - V _r ⁿ _ef , _P u Sm

2 2 (e _n - (i - i) i) (a)

the modified cyclic ratio, α ₊₁ , of the vector V _{i +} i activated consecutively by the activation sequence is given by the formula:

+ _{i =} i ₊ ^ SVM- ^ CSVM ₌ i _{+ v} n fn _sin _ ₍ . _ _f) ^ _(b) where, i is an integer between one and six, θ _η is the phase of the conventional reference vector , and V? _efiPU is the ratio between the conventional reference vector standard of the inverter n and the norm of the spatial vector V ,,

yti _ ^v i ^{+ v} i + iif _0, n _

vref - ₂ ^† V -i + l, CSVM

6. Method (1 0) according to one of claims 1 to 4, wherein the activation sequences (260, 265) are independent.

7. Device (20) for converting current characterized in that it comprises:

two inverters three-phase (01, 02, 225, 235), each inverter being controlled by a modulation of at least six space vectors (or SVM acronym for "SpaceVector Modulation" in English terminology), the output voltage of each inverter being given by a spatial vector called "reference spatial vector"

means for applying (255) an activation sequence to the spatial vectors of an inverter,

means for applying (255) an activation sequence to the spatial vectors of the other inverter,

connecting means (205, 210) to a power supply source (200).

8. Vehicle (50) characterized in that it comprises a device (20) according to claim 7 and a three-phase electric motor (245).