Drive system of a liquid compression device and associated power supply method

Description

TECHNICAL FIELD

[0001] The present invention relates to a drive system comprising an inverter, an electrical rotating machine and a control device, the inverter comprising a first input, a second input, N arms connected in parallel between the first input and the second input, N being a natural number greater than or equal to 2, each arm comprising an upper half-arm and a lower half-arm in series, the upper half-arm being connected to the first input, the lower half-arm being connected to the second input, the upper half-arm and the lower half-arm of each arm being connected together at a corresponding output of the inverter, each upper half-arm and each lower half-arm comprising at least one switching module capable of switching between an on state and a off state, each of the first input and the second input being intended to be connected to a respective terminal of a direct current source,each output being associated with a respective electrical phase, the rotating machine comprising a stator and a rotor mobile in rotation, relative to the stator, around an axis of rotation, the stator comprising N windings, each winding having an input and an output, the input of each winding being connected to a corresponding output of the inverter, the outputs of the stator windings being connected to a common point.,

[0002] The invention also relates to a feeding method implemented by such a system, as well as a compression assembly comprising such a system.

[0003] The invention applies to the field of electrical rotating machines, in particular for an application to turbomachines, in particular to a compressor or turbocharger for an on-board application on board a vehicle. STATE OF THE PRIOR ART

[0004] A conventional method of manufacturing a rotating machine involves attaching already magnetized permanent magnets to a rotor body, with the rotor then being placed in a cavity of a corresponding stator.

[0005] However, such a method has many disadvantages. In particular, during the step of assembling the rotor with the stator, the rotor (which includes the already magnetized permanent magnets) generates magnetic forces that can lead to difficulties in assembling with the stator, as well as an increased risk of rotor / stator shocks leading to damage.

[0006] To overcome such inconveniences, it has been proposed to produce an electric rotating machine by arranging, in a cavity of a stator, a rotor comprising elements (called "magnetic elements") made of a non-magnetized magnetic material. In the absence of magnetization, the assembly process of the electric machine is simplified. Once this assembly is completed, a magnetic field is generated in the cavity, by means of dedicated windings mounted in the stator, to magnetize the magnetic elements of the rotor.

[0007] However, such a manufacturing process is not entirely satisfactory.

[0008] Indeed, such a manufacturing process requires a structure dedicated to the magnetization of the magnetic elements of the rotor, which has a negative impact on the size and manufacturing cost of the rotating machine.

[0009] Furthermore, the rotating machine obtained by such a manufacturing method is not optimal for use in driving a turbomachine, in particular a turbocharger for a vehicle. Indeed, in such an on-board application, the rotating machine is only used occasionally. In this case, when it is not powered, the rotating machine generates a torque resisting rotation, which leads to no-load losses.

[0010] One aim of the invention is therefore to propose a drive system which is simpler and more economical to produce, while generating fewer losses when the rotating machine it comprises is not in use.

[0011] Known from document EP2048772 is a variable flux motor drive system comprising an inverter for driving a variable flux motor which uses a fixed magnet and a variable magnet, comprising: a torque command generation unit for generating a torque command for the variable flux motor; a variable flux control unit for changing the flux according to a magnetizing current from the inverter and magnetizing the variable magnet; a switch for transmitting D-axis and Q-axis current references based on the torque command from the torque command generation unit or the D-axis and Q-axis magnetizing current commands from the variable flux control unit; a magnetization request generation unit for generating, if predetermined conditions are met, a request to the variable flux control unit to magnetize the variable magnet;and a gate command generation unit for generating a gate command for controlling the inverter according to the torque command-based D- and Q-axis current references or the D- and Q-axis magnetizing current commands from the commutator. ;

[0012] It is also known from JP2008-043172 a variable magnetic flux drive system includes a permanent magnet motor that uses a permanent magnet, an inverter that drives a permanent magnet motor, and a magnetizing means that circulates magnetizing currents to control the magnetic flux of the permanent magnet. The permanent magnet is variable, its magnetic flux density being able to vary depending on the magnetizing current from the inverter. The magnetizing means circulates the magnetizing current that is equal to or greater than a magnetizing saturation region of the magnetic body of the variable magnet. STATEMENT OF THE INVENTION

[0013] To this end, the invention relates to a drive system of the aforementioned type, in which the rotor comprises at least one magnetic element made from a material with adjustable magnetization, the control device being configured to, during a step of magnetization of each magnetic element of the rotor, control the inverter so as to, simultaneously, during a predetermined magnetization time interval: for each of m arms of the inverter, each forming a current injection arm, m being a natural integer between 1 and N-1, controlling each switching module of the corresponding upper half-arm so that it is in the on state, and controlling each switching module of the corresponding lower half-arm so that it is in the off state; for each of k arms of the inverter, taken from the Nm other arms of the inverter, and each forming a current output arm, controlling each switching module of the corresponding upper half-arm so that it is in the off state, and controlling each switching module of the corresponding lower half-arm so that it is in the on state; and for each of the Nmk other arms, controlling each corresponding switching module so that it is in the off state.

[0014] Indeed, in such a drive system, during the magnetization step, the inverter is controlled so that the magnetic field intended to magnetize the magnetic elements is generated by the stator windings which are usually used to set the rotor in motion. The magnetization of the magnetic elements is therefore made possible without an additional dedicated structure, which gives an advantage in weight and manufacturing cost compared to systems of the state of the art.

[0015] Furthermore, no connection is required between the inverter and the neutral point of the rotating machine. This is advantageous, as the neutral point is likely to be inaccessible.

[0016] Furthermore, such a drive system provides the ability to modify the amplitude and / or direction of the magnetization of the magnetic elements of the rotor depending on the operating conditions. More specifically, in the drive system according to the invention, the direction and amplitude of the magnetic field generated by the stator depend on the choice of the magnetization outputs of the inverter. However, such a stator magnetic field has an influence on the magnetization of the magnetic elements of the rotor.

[0017] In particular, when the operation of the electrical rotating machine is no longer required to drive the fluid compression device, the drive system according to the invention advantageously allows, thanks to a judicious choice of the magnetization outputs, the application to the magnetic elements of a magnetic field having the effect of modifying, in particular significantly reducing, or even canceling, the magnetization of said magnetic elements. Such magnetic elements are thus said to have “modulatable magnetization”.

[0018] As a result, the rotating machine, which is mechanically coupled to the fluid compression device and is driven by it even when not electrically stressed, generates a much lower braking force than with a state-of-the-art drive system without an inverter configured to modify the magnetization of the magnetic elements depending on the operational conditions.

[0019] Modulable magnetization is relevant on an electrified turbocharger, whose operation and electrical power demands in motor and generator modes are transient (pulse operating mode). The rotor, rendered magnetically inert when the operation of the rotating electrical machine is no longer required, therefore limits the losses of the drive system when the latter is not in use, compared to a conventional drive system.

[0020] According to other advantageous aspects of the invention, the drive system comprises one or more of the following characteristics, taken in isolation or in all technically possible combinations: the control device comprises a member for detecting a magnetic field generated by the rotor, the control device being, in addition, configured to, during the magnetization step: detect the magnetic field generated by the rotor; choose each of the m current injection arms and the k current output arms as a function of the detected magnetic field;the drive system further comprises a first switching member, a second switching member and a load, the first switching member being connected in series between each arm and the second input of the inverter, the second switching member and the load being connected in series, and connected in parallel with the first switching member, the control device being configured to, during the magnetization step, control the first switching member so that it is in a blocked state, and control the second switching member so that it is in a conducting state;the control device is, furthermore, configured to implement a step of exciting the rotating machine, subsequent to the magnetization step, the control device being configured to, during the excitation step, control the inverter according to a predetermined inverter control law to connect, successively over time, each output of the inverter to the first input and / or the second input of the inverter in order to drive the rotor in rotation around a corresponding axis of rotation; the duration of the magnetization time interval depends on the material with modulatable magnetization and / or the m current injection arms and the k current output arms; the duration of the magnetization time interval depends, furthermore, on an impedance of the load. ;

[0021] Furthermore, the invention relates to a method for powering an electrical rotating machine by means of an inverter, the inverter comprising a first input, a second input, N arms connected in parallel between the first input and the second input, N being a natural number greater than or equal to 2, each arm comprising an upper half-arm and a lower half-arm in series, the upper half-arm being connected to the first input, the lower half-arm being connected to the second input, the upper half-arm and the lower half-arm of each arm being connected together at a corresponding output of the inverter, each of the upper half-arm and the lower half-arm comprising at least one switching module capable of switching between an on state and a off state, each of the first input and the second input being intended to be connected to a respective terminal of a direct current source, each output being associated with a respective electrical phase, the rotating machine comprising a stator and a rotor mobile in rotation, relative to the stator,around an axis of rotation, the stator comprising N windings, each winding having an input and an output, the input of each winding being connected to a corresponding output of the inverter, the outputs of the stator windings being connected at a common point, the rotor comprises at least one magnetic element made of a material with adjustable magnetization, the power supply method comprising a step of magnetizing each magnetic element of the rotor comprising: connecting each of the first input and the second input to a respective terminal of a direct current source; and simultaneously, during a predetermined magnetization time interval: for each of m arms of the inverter, each forming a current injection arm, m being a natural integer between 1 and N-1, controlling each switching module of the corresponding upper half-arm so that it is in the on state,and controlling each switching module of the corresponding lower half-arm so that it is in the blocked state; for each of k arms, taken from the Nm other arms of the inverter, and each forming a current output arm, controlling each switching module of the corresponding upper half-arm so that it is in a blocked state, and controlling each switching module of the corresponding lower half-arm so that it is in an on state; and for each of the Nmk other arms, controlling each corresponding switching module so that it is in the blocked state, so as to simultaneously inject, into each winding, an electric current to generate, in the stator cavity, a non-zero magnetic field intended to magnetize each magnetic element.

[0022] According to other advantageous aspects of the invention, the feeding method comprises the following characteristic(s), taken in isolation or in combination: the power supply method further comprises, during the magnetization step: the detection of a magnetic field generated by the rotor; and the choice of each of the m current injection arms and the k current output arms as a function of the detected magnetic field; the power supply method further comprises a step of exciting the rotating machine subsequent to the magnetization step, and comprising the control of the inverter according to a predetermined inverter control law to connect, successively over time, each output of the inverter to the first input and / or the second input of the inverter, so as to inject electric current into the windings of the stator to generate, in the cavity of the stator, a rotating magnetic field intended to drive the rotor in rotation around the axis of rotation.

[0023] Furthermore, the invention relates to a compression assembly comprising a fluid compression device and a drive system as defined above, the fluid compression device being coupled to the stator of the rotating machine of the drive system for its drive.

[0024] According to an advantageous aspect of the invention, the drive system comprises the characteristic: the fluid compression device is a turbocharger combining a turbine and a compressor, in particular for an internal combustion engine, or a microturbine. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The invention will be better understood with the aid of the following description, given solely by way of non-limiting example and made with reference to the appended drawings in which: [ Fig. 1 ] there figure 1is a schematic representation of an assembly comprising a drive system according to the invention, associated with a direct current source; [ Fig. 2 ] there figure 2 is a schematic sectional view of a rotating machine of the drive system of the figure 1 , according to a transverse plane of the rotating machine according to an embodiment of the invention; [ Fig. 3 ] there figure 3 is a diagram illustrating the electrical circuit of the entire figure 1 , during a magnetization step during which electric current is injected into a single winding of a stator of the rotating machine of the figure 2 ; [ Fig. 4 ] there figure 4 is a schematic sectional view of the stator of the rotating machine of the figure 2 , according to a transverse plane of the rotating machine, during the magnetization stage of the figure 3 ; And [ Fig. 5 ] there Figure 5 is similar to the figure 4, a total magnetic field prevailing in a stator cavity being represented. DETAILED DESCRIPTION

[0026] An example of a drive system 2 according to the invention is illustrated by the figure 1 . In this figure, a direct current source 4 is connected to the input of the drive system 2.

[0027] The drive system 2 comprises an inverter 6, an electric rotating machine 8 and a control device 12.

[0028] The inverter 6 is configured to route electric current from the source 4 to windings (described later) of the rotating machine 8, and this selectively.

[0029] The rotating machine 8 is intended to drive in rotation an element connected to its output shaft, in particular a fluid compression device, for example a compressor or a turbocharger.

[0030] Furthermore, the control device 12 is configured to control the inverter 6.

[0031] The inverter 6 has a first input 14 and a second input 16, as well as N arms 18. N is a natural integer greater than or equal to 2, for example equal to 3, as illustrated in the figure.

[0032] The inputs 14, 16 of the inverter 6 form the inputs of the drive system 2. Each of the first and second inputs 14, 16 is intended to be connected to a respective terminal 19 of the source 4.

[0033] The N arms 18 are connected in parallel between the first input 14 and the second input 16 of the inverter 6.

[0034] Each arm 18 comprises an upper half-arm 20 and a lower half-arm 21 in series, connected together at a midpoint forming a corresponding output 22 of the inverter 6. Each output 22 is associated with a respective electrical phase, and is connected to a corresponding winding of the rotating machine 8.

[0035] For each arm 18, the corresponding upper half-arm 20 is connected to the first input 14, while the corresponding lower half-arm 21 is connected to the second input 16.

[0036] Each upper half-arm 20 and each lower half-arm 21 comprises at least one switching module 26 capable of switching between a blocked state preventing the flow of electric current between its terminals, and a passing state allowing the flow of electric current. For example, on the figure 1, each upper half-arm 20 and each lower half-arm 21 comprises a switching module 26. For example, the switching modules 26 of the inverter 6 are insulated gate bipolar transistors, also called IGBT (from the English " Insulated Gate Bipolar Transistor ") or metal-oxide gate field effect transistors, also called MOSFETs (from the English " Metal Oxide Semiconductor Field Effect Transistor ").

[0037] As illustrated by the figure 2 , schematically and non-limitingly, the rotating machine 8 comprises a stator 30 and a rotor 32 movable in rotation, relative to the stator 30, around an axis of rotation XX.

[0038] More specifically, the stator 30 comprises a cavity 34 in which the rotor 32 is arranged.

[0039] The output shaft 36 of the rotating machine 8, mentioned above, extends along the axis of rotation XX and is integral with the rotor 32 to be driven in rotation around the axis of rotation XX.

[0040] The stator 3 comprises N windings 38, arranged in a known manner to generate a magnetic field in the cavity 34 when an electric current passes through them. For example, the windings 38 are arranged so that the magnetic fields corresponding to two separate windings 38 are images of each other by a rotation of a non-zero angle multiple of 360° / N.

[0041] The magnetic field generated by the windings 38 is, in particular, intended to form an excitation magnetic field to set the rotor 32 rotating around the axis of rotation XX.

[0042] As will be described later, the magnetic field generated by the windings 38 is also intended to form a magnetizing magnetic field to magnetize at least one magnetic element 48 (for example inserts) of the rotor 32 prior to its rotation.

[0043] Each winding 38 has an input 40 and an output 42.

[0044] The input 40 of each winding 38 is connected to a corresponding output 22 of the inverter 6. Furthermore, the outputs 42 of the windings 38 are connected to a common point 44, called the neutral point of the rotating machine 8. The connection of the outputs 42 to the neutral point 44 is carried out, depending on the case, outside or inside the rotating machine 8.

[0045] The rotor 32 comprises at least one magnetic element 48 made from a material with adjustable magnetization.

[0046] For the purposes of the present invention, the term "material with adjustable magnetization" means a ferromagnetic material, preferably a soft ferromagnetic material, or a medium-hard ferromagnetic material.

[0047] A soft ferromagnetic material (in English " soft magnetic material ") is a ferromagnetic material with a coercive field of less than 1000 Am -1< (ampere per meter).

[0048] In addition, a medium-hard ferromagnetic material (in English " semi-hard magnetic material ") is a ferromagnetic material having a coercive field between 1000 Am -1< and 100000 Am -1< , preferably between 1000 Am -1< and 10000 Am -1< .

[0049] Such a material is, for example, an alloy called FeCrCo comprising iron, chromium and cobalt, or an alloy called AlNiCo comprising aluminium, nickel and cobalt.

[0050] For example, each magnetic element 48 is an insert secured to a body 46 of the rotor 32. For example, each magnetic element 48 is integrated into the body 46, or else arranged on the periphery of the body 46. According to one aspect, it can take the form of a ring.

[0051] In this case, the rotor 32 advantageously comprises a plurality of magnetic elements 48 arranged circumferentially around the axis of rotation XX, preferably at regular angular intervals.

[0052] Preferably, each insert 48 extends along the axis of rotation XX.

[0053] According to a variant not shown, the magnetic element 48 forms all or part of the body of the rotor 32.

[0054] As described above, the control device 12 is configured to control the inverter 6. In particular, the control device 12 is configured to control the inverter 6 in order to selectively connect the outputs 22 of the inverter 6 to the first input 14 and / or the second input 16 of the inverter 6.

[0055] More precisely, the control device 12 is configured to, during a step of magnetization of each magnetic element 48 of the rotor 32, control the inverter 6 so as to circulate a direct electric current through the windings 38 of the stator 30 to generate, in the cavity 34, a non-zero magnetic field intended to cause magnetization to appear within each magnetic element 48.

[0056] In particular, the control device 12 is configured to, during the magnetization step, control the inverter 6 so as to, simultaneously, during a predetermined magnetization time interval: for each of m arms 18 of the inverter 6, each forming a current injection arm, m being a natural integer between 1 and N-1, controlling each switching module 26 of the corresponding upper half-arm 20 so that it is in the on state, and controlling each switching module 26 of the corresponding lower half-arm 21 so that it is in the off state; for each of k arms 18 within the Nm other arms 18 of the inverter 6, m being a natural integer between 1 and Nm, each forming a current output arm, controlling each switching module 26 of the corresponding upper half-arm 20 so that it is in the off state, and controlling each switching module 26 of the corresponding lower half-arm 21 so that it is in the on state; and for each of the other Nmk arms 18, each forming an inactive arm, control each corresponding switching module 26 so that it is in the blocked state.

[0057] In a preferred embodiment, k is Nm, i.e. there is no inactive arm during the magnetization step.

[0058] The m current injection arms and the k current output arms are, for example, predetermined.

[0059] In this way, during the magnetization step, the electric current from the source 4 is routed to the first input 14, then, through the upper half-arms 20 of the m current injection arms, to the windings 38 connected to said current injection arms. The current then reaches the common point 44, then flows in the opposite direction, i.e. from the common point 44 to the outside of the rotating machine 8, through the k other windings 38 connected to the current output arms. Then, the current is routed to the second input 16 through the lower half-arms 21 of said current output arms. The switching modules 26 of the Nmk other arms 18 being in the off state, no current flows through the windings connected to them.

[0060] Hereinafter, a winding 38 connected to a current injection arm or a current output arm will be called an "active winding".

[0061] The path of the electric current described above corresponds to the situation where the first input 14 is brought to a higher electric potential than the second input 16. In the opposite situation, the electric current follows the opposite path.

[0062] Such current flow in the active windings 38 leads to the generation, by each of them, of a magnetic field in a corresponding direction. By a judicious choice of the m current injection arms and the k current output arms, a non-zero total magnetic field, intended to magnetize each magnetic element 48, is generated in the cavity 34 during the magnetization time interval.

[0063] The windings 38 are arranged to generate magnetic fields in different directions. Furthermore, for a given winding 38, the direction of the magnetic field generated by said winding depends on the direction of the electric current flowing through it (i.e., from its input 40 to the common point 44, or from the common point 44 to its input 40). As a result, the amplitude (as well as the direction and sense) of the total magnetic field in the cavity 34 varies depending on which arms 18 act as current injection arms and which act as current output arms. Consequently, the minimum duration allowing magnetization of each magnetic element 48, i.e., the minimum duration of the magnetization time interval, varies depending on the chosen combination of current injection arms and current output arms.

[0064] Preferably, the duration of the magnetization time interval is also chosen as a function of the material with modulatable magnetization from which each magnetic element 48 is made. Indeed, the magnetization time interval corresponds to the time interval during which each magnetic element 48 is subjected, during the magnetization step, to the magnetic field intended to cause its magnetization. For a given amplitude of such a magnetic field, the duration of the magnetization time interval is chosen to ensure magnetization of each magnetic element 48.

[0065] In the example of the figure 3 , illustrating the operation of the drive system 2 of the figure 1 , the rotating machine 8 is a three-phase machine. The number m is chosen equal to 1, and the number k is chosen equal to 2. Furthermore, the path of the electric current is illustrated by dotted arrows.

[0066] In this example, during the magnetization step, the control device 12 controls the inverter 6 so that, for the single current injection arm, the switching module 26 of the corresponding upper half-arm 20 is in the on state, and the switching module 26 of the corresponding lower half-arm 21 is in the off state. As a result, the winding, denoted 38A, connected to the output 22 of the current injection arm, is crossed by the electric current delivered by the source 4 in a direction going from the first input 14 of the inverter to the common point 44 of the rotating machine 8.

[0067] Simultaneously, the control device 12 controls the inverter 6 so that, for each of the two current output arms, the switching module 26 of the corresponding upper half-arm 20 is in the blocked state, and the switching module 26 of the corresponding lower half-arm 21 is in the conducting state. As a result, the windings, denoted 38B, 38C, connected respectively to the current output arms, are crossed by the electric current in a direction going from the common point 44 of the rotating machine 8 to the second input 16 of the inverter 6.

[0068] The windings 38 being assumed to be identical, it follows from the above that the current flowing through the winding 38A has an intensity im , while the current flowing through each of the windings 38B, 38C has an intensity im / 2.

[0069] Therefore, and as illustrated by the figure 4, the winding 38A generates, along a corresponding axis AA, a magnetic field BA of amplitude B m depending on the intensity im of the current. In addition, each of the windings 38B and 38C generates, along a respective axis BB, CC, a magnetic field, respectively noted BB , BC , of amplitude B m / 2.

[0070] Due to the direction of flow of the electric current in the windings 38 of the rotating machine 8 during the magnetization step, the oriented angle between the magnetic fields BB and BA has a positive value of 60°, and the oriented angle between the magnetic fields BA and BC also has a positive value of 60°. It follows that the total magnetic field B tot , which is the resultant of the magnetic fields BA , BB and BC , is collinear with BA and has an amplitude equal to 3B m / 2, as shown in the Figure 5 .

[0071] For a sufficient amplitude of the total magnetic field and a sufficient duration of the magnetization time interval, a magnetization appears within each magnetic element 48, which persists at the end of the magnetization time interval.

[0072] It should be noted that, on the figures 4 , 5 , the stator 30 comprises a single pole per winding 38. However, a higher number of poles per winding 38 is possible.

[0073] Furthermore, the control device 12 is advantageously configured to implement the magnetization step prior to a step of excitation of the rotating machine 6. Such an excitation step comprises the control of the inverter 6 so as to inject, into the windings 38 of the stator 30, electric current to generate, in the cavity 34, a magnetic excitation field intended to drive the rotation of the rotor 32 around the axis of rotation XX.

[0074] More precisely, the control device 12 is configured to, during the excitation step, control the inverter 6 according to a predetermined inverter control law to connect, successively over time, the first input 14 and the second input 16 of the inverter 6 to each of the outputs 22 of the inverter 6.

[0075] The purpose of such an excitation step is to cause the rotor 32 to rotate around its axis XX. This is made possible by the presence of magnetization within the magnetic elements 48 of the rotor 32, due to the implementation of the magnetization step previously described.

[0076] Optionally, the drive system 2 further comprises a first switching member 50, a second switching member 54 and a load 56.

[0077] As it appears on the figure 1, the first switching member 50 is connected in series between each arm 18 and the second input 16 of the inverter 6. Furthermore, the second switching member 52 and the load 54 are connected in series, and connected in parallel with the first switching member 50.

[0078] Each of the first switching member 50 and the second switching member 52 is capable of switching between a blocked state preventing the flow of electric current, and an on state allowing the flow of an electric current.

[0079] Each switching member 50, 52 is, for example, a MOSFET transistor or a relay.

[0080] According to this variant, the control device 12 is advantageously configured to, during the magnetization step, simultaneously control the first switching member 50 so that it is in the blocked state, and the second switching member 52 so that it is in the on state.

[0081] In this case, during the magnetization step, the load 54 is inserted into the circuit through which the electric current flows between the first input 14 and the second input 16, so that the intensity of the current flowing in the windings 38 during the magnetization step is also a function of the impedance of the load 50.

[0082] The addition of such a load 54 is advantageous, insofar as the intensity of the current during the magnetization step is reduced compared to that of the current which would flow in the absence of load, in particular in the case of rotating electrical machines having low stator inductances (for example of the order of a few microhenries). The components of the inverter 6 and the stator 30 are less likely to be damaged by overcurrents.

[0083] The operation of drive system 2 will now be described.

[0084] During a step of assembly of the rotating machine 8, the magnetic elements 48 of the rotor 32 have no magnetization, and the rotor 32 is arranged in the cavity 34 of the stator 30.

[0085] Furthermore, during an assembly step of the drive system 2, the input 40 of each winding 38 of the stator 30 is connected to a corresponding output 22 of the inverter 6.

[0086] Then, each of the first input 14 and the second input 16 of the inverter 6 is connected to a respective terminal of the direct current source 4.

[0087] Then, during the magnetization step, the control device 12 controls the inverter 6 so that, during the magnetization time interval: for each arm 18 among the m current injection arms, each switching module 26 of its upper half-arm 20 is in the on state, and each switching module 26 of its lower half-arm 21 is in the off state; for each arm 18 among the k current output arms, each switching module 26 of its upper half-arm 20 is in the off state, and each switching module 26 of its lower half-arm 21 so that it is in the on state; and for each arm 18 among the Nmk inactive arms, which are neither current injection arms nor current output arms, each corresponding switching module 26 is in the off state.

[0088] As a result, an electric current flows through each active winding 38, to generate, in the cavity 34 of the stator 30, a magnetic field intended to magnetize each magnetic element 48.

[0089] Then, during the excitation step of the rotating machine 8, subsequent to the magnetization step, the control device 12 controls the inverter 6 according to a predetermined inverter control law (control by pulse width modulation, for example) to connect, successively over time, the first input 14 and the second input 16 of the inverter 6 to each of the outputs 22 of the inverter so as to inject excitation currents into each of the windings 38 of the stator 30 in order to generate, in the cavity 34 of the stator 30, a rotating magnetic field intended to drive the rotor 32 in rotation around the axis of rotation XX.

[0090] Alternatively, the control device 12 also comprises a means for detecting a magnetic field generated by the rotor 32, said magnetic field originating from the magnetization of the magnetic elements 48. In this case, the control device 12 is also configured to, in particular after the step of exciting the rotating machine 8, implement an additional magnetization step, which differs from the magnetization step described previously only in that the control device 12 further performs: a detection of the magnetic field generated by the rotor 32; a choice of the m current injection arms and the k current output arms as a function of the detected magnetic field.

[0091] Such a characteristic is advantageous, insofar as a judicious choice of the magnetization outputs leads to the generation, by means of the stator, of a magnetic field intended to modulate, in particular to reduce, or even to cancel, the magnetization of the magnetic elements 48. This has the effect of reducing the losses due to the rotating machine 8 when said rotating machine 8 is no longer required for driving, compared to a situation where such modulation of the magnetization of the magnetic elements would not be implemented.

[0092] The choice of the current injection arms and the current output arms as a function of the detected magnetic field is, for example, made from calibration data pre-recorded in the control device 12. According to another example, such a choice is the result of the implementation, by the control device 12, of an optimization calculation making it possible to best approximate a desired generated magnetic field by the magnetic field likely to be generated by the stator.

Claims

1. Drive system (2) including an inverter (6), an electric rotary machine (8) and a control device (12), the inverter (6) including a first input (14), a second input (16), N arms connected in parallel between the first input (14) and the second input (16), N being a natural number greater than or equal to 2, each arm (18) comprising an upper half-arm (20) and a lower half-arm (21) in series, the upper half-arm (20) being connected to the first input (14), the lower half-arm (21) being connected to the second input (16), the upper half-arm (20) and the lower half-arm (21) of each arm (18) being connected to one another at a corresponding output (22) of the inverter (6), each upper half-arm (20) and each lower half-arm (21) comprising at least one switching module (26) capable of switching between a conducting state and a blocking state, the first input (14) and the second input (16) each being intended to be connected to a respective terminal of a DC source (4), each output (22) being associated with a respective electrical phase, the rotary machine (8) comprising a stator (30) and a rotor (32) that is rotatable, relative to the stator (30), about an axis of rotation (X-X), the stator (30) comprising N windings (38), each winding (38) having an input (40) and an output (42), the input (40) of each winding (38) being connected to a corresponding output (22) of the inverter (6), the outputs (42) of the windings (38) of the stator (30) being connected at a common point (44), the rotor (32) comprising at least one magnetic element (48) made of a tuneable magnetic material, the control device (12) being configured to, during a step of magnetizing each magnetic element (48) of the rotor (32), control the inverter (6) to, simultaneously, during a predetermined magnetization time interval: - for each of m arms (18) of the inverter (6), each forming a current injection arm, m being a natural number between 1 and N-1, control each switching module of the corresponding upper half-arm to be in the conducting state, and control each switching module of the corresponding lower half-arm to be in the blocking state; - for each of k arms (18) of the inverter (6), taken from the N-m other arms (18) of the inverter, and each forming a current output arm, control each switching module of the corresponding upper half-arm (20) to be in the blocking state, and control each switching module of the corresponding lower half-arm (21) to be in the conducting state; and - for each of the N-m-k other arms (18), control each corresponding switching module (26) to be in the blocking state, characterized in that said system further comprises a first switching member (50), a second switching member (52) and a load (54), the first switching member (50) being connected in series between each arm (18) and the second input (16) of the inverter (6), the second switching member (52) and the load (54) being connected in series, and connected in parallel with the first switching member, the control device (12) being configured to, during the magnetizing step, control the first switching member (50) to be in a blocking state and control the second switching member (52) to be in a conducting state.

2. Drive system (2) according to Claim 1, wherein the control device (12) includes a member for detecting a magnetic field generated by the rotor (32), the control device (12) being further configured to, during the magnetizing step: - detect the magnetic field generated by the rotor (32); - choose each of the m current injection arms and k current output arms depending on the detected magnetic field.

3. Drive system (2) according to either of Claims 1 and 2, wherein the control device (12) is further configured to implement a step of exciting the rotary machine after the magnetizing step, the control device (12) being configured to, during the excitation step, control the inverter (6) according to a predetermined inverter control law to connect, successively over time, each output (22) of the inverter (6) to the first input (14) and / or the second input (16) of the inverter (6) in order to drive the rotor (32) in rotation about a corresponding axis of rotation (X-X).

4. Drive system (2) according to any one of Claims 1 to 3, wherein the duration of the magnetization time interval is dependent on the tuneable magnetic material and / or the m current injection arms and k current output arms.

5. Drive system (2) according to Claim 4, wherein the duration of the magnetization time interval is further dependent on an impedance of the load (52).

6. Method for supplying power to an electric rotary machine (8) using an inverter (6), the inverter (6) including a first input (14), a second input (16), N arms connected in parallel between the first input (14) and the second input (16), N being a natural number greater than or equal to 2, each arm (18) comprising an upper half-arm and a lower half-arm in series, the upper half-arm being connected to the first input (14), the lower half-arm being connected to the second input (16), the upper half-arm and the lower half-arm of each arm being connected to one another at a corresponding output (22) of the inverter (6), each of the upper half-arm and the lower half-arm comprising at least one switching module capable of switching between a conducting state and a blocking state, the first input (14) and the second input (16) each being intended to be connected to a respective terminal of a DC source (4), each output (22) being associated with a respective electrical phase, the rotary machine (8) comprising a stator (30) and a rotor (32) that is rotatable, relative to the stator (30), about an axis of rotation (X-X), the stator (30) comprising N windings (38), each winding (38) having an input (40) and an output (42), the input (40) of each winding (38) being connected to a corresponding output (22) of the inverter (6), the outputs (42) of the windings (38) of the stator (30) being connected at a common point (44), the rotor (32) comprises at least one magnetic element (48) made of a tuneable magnetic material, the power supply method comprising a step of magnetizing each magnetic element (48) of the rotor (32) including: - connecting each of the first input (14) and the second input (16) to a respective terminal of a DC source (4); and - simultaneously, during a predetermined magnetization time interval: • for each of m arms (18) of the inverter (6), each forming a current injection arm, m being a natural number between 1 and N-1, controlling each switching module of the corresponding upper half-arm to be in the conducting state, and controlling each switching module of the corresponding lower half-arm to be in the blocking state; • for each of k arms (18), taken from the N-m other arms of the inverter (6), and each forming a current output arm, controlling each switching module of the corresponding upper half-arm to be in a blocking state, and controlling each switching module of the corresponding lower half-arm to be in a conducting state; and • for each of the N-m-k other arms (18), controlling each corresponding switching module (26) to be in the blocking state, to simultaneously inject an electric current into each winding (38) to generate a non-zero magnetic field in the cavity (34) of the stator (30) to magnetize each magnetic element (48), said method being characterized by the use of a drive system including the inverter (6), the electric rotary machine (8) and the control device (12) and further comprising a first switching member (50), a second switching member (52) and a load (54), the first switching member (50) being connected in series between each arm (18) and the second input (16) of the inverter (6), the second switching member (52) and the load (54) being connected in series, and connected in parallel with the first switching member, the control device (12) being configured to, during the magnetizing step, control the first switching member (50) to be in a blocking state and control the second switching member (52) to be in a conducting state.

7. Power supply method according to Claim 6, further including, during the magnetizing step: - detecting a magnetic field generated by the rotor (32); and - choosing each of the m current injection arms and k current output arms depending on the detected magnetic field.

8. Power supply method according to Claim 6 or 7, further including a step of exciting the rotary machine after the magnetizing step, and comprising controlling the inverter (6) according to a predetermined inverter control law to connect, successively over time, each output (22) of the inverter (6) to the first input (14) and / or the second input (16) of the inverter (6) in order to inject electric current into the windings (38) of the stator (30) to generate a rotary magnetic field in the cavity (34) of the stator (30) to drive the rotor (32) in rotation about the axis of rotation (X-X).

9. Compression assembly comprising a fluid compression device and a drive system according to any one of Claims 1 to 5, the fluid compression device being coupled to the stator of the rotary machine (8) of the drive system (2) used to drive it.

10. Compression assembly according to Claim 9, wherein said fluid compression device is a turbocompressor that brings together a turbine and a compressor, notably for an internal combustion engine, or a micro-turbine.