Method for limiting the electrical power regenerated by a synchronous electric motor

Abstract

A method for controlling an electric motor (12) comprising at least: a first determination step (E1) in which an intermediate value of a direct axis current (Idstat) and an intermediate value of a quadrature axis current (Iqstat) of the alternating current supplying the motor (12) are determined; a second determination step (E2) in which a target value of the direct axis current (Idcible) and a target value of the quadrature axis current (Iqcible) are determined; a control step (EP) in which at least one inverter is controlled by the microcontroller (20) based on the target value of the direct axis current (Idcible) and the target value of the quadrature axis current (Iqcible). Figure 2

Description

Description of the invention: Method for limiting the electrical power regenerated by a synchronous type electric motor The invention relates to the field of electric motors and more particularly a method for limiting the electrical power regenerated by a synchronous type electric motor. The invention relates to an electric motor, and more particularly to a rotary synchronous electric motor with at least three phases. This electric motor receives an alternating current supply driven by an inverter via vector control, the inverter being supplied with a direct current supply. Vector control, also known as flux-oriented control, is a known method of controlling electric motors in which the alternating current supplying the motor is transformed into two orthogonal components: one along an axis q, hereafter referred to as the quadrature axis current, denoted Iq, and the other along an axis d, called the direct axis current, denoted Id. The quadrature axis current Iq and the direct axis current Id are spatial currents along the magnetization axis, denoted d, and the quadrature axis, denoted q.The quadrature axis current Iq and the direct axis current Id correspond to a spatial projection of the three-phase current system onto a rotating frame of reference linked to a rotor of the electric motor. The quadrature axis current Iq and the direct axis current Id are therefore functions of the phase shift of the three-phase current system with respect to the direct axis d and the amplitude of the three-phase system. For low-reluctance motors, the direct axis current Id generally allows a reduction of perceived magnetic flux to optimize high-speed operation, while the quadrature axis current Iq controls a torque exerted by the motor, hereafter referred to as motor torque. The direct axis current Id and the quadrature axis current Iq are, for example, determined as a function of a motor operating point characterized by at least one parameter among: a setpoint torque, a motor rotational speed, a motor temperature, or a motor supply voltage. Based on the direct axis current Id, and quadrature axis Iq, the motor is powered by the alternating current supplied by the inverter. By convention, in the following description, when the inverter's DC supply current is positive, the motor-inverter assembly consumes energy, meaning current flows from the inverter to the motor, while when the inverter's DC supply current is negative, the motor-inverter assembly generates energy, meaning the inverter feeds back negative energy. current to its DC power supply. Similarly, it is considered that when electrical power is positive, the motor-inverter assembly consumes energy, while when electrical power is negative, the motor-inverter assembly generates energy. During motor operation, the inverter's DC power supply is usually positive, but it can become negative in certain situations. When negative, this DC power supply to the inverter is also called regenerative current. For example, in a vehicle's power steering motor, regenerative current is produced during transient situations such as a sudden change in the steering wheel's direction of rotation. A system upstream of the inverter that is responsible for supplying or receiving direct current from the inverter is subsequently referred to as a DC power supply system. For example, this upstream system could be a battery or a DC-DC converter. When the amount of regenerative current is significant, the DC power supply system may include recovery elements to recover this current. However, when the amount of regenerative current is low, it is not economically advantageous to implement these recovery elements. Thus, the regenerative current degrades the DC power supply system. Therefore, there is a need to limit the amount of regenerative current produced by the motor-inverter assembly. In other words, there is a need to ensure that the motor-inverter assembly remains an energy consumer regardless of the situation. There is a solution for reducing regenerative current by using passive elements such as, for example, a resistive element. However, passive elements can be bulky and expensive. There are also solutions in which the inverter's DC power supply is limited primarily over the required motor torque. These solutions are therefore intrusive because they alter the motor torque supplied, which then no longer corresponds to the required torque. When the engine is a power steering engine, a difference between the engine torque and the set torque results in a change in the driving experience for a driver. The invention aims to remedy all or part of the aforementioned drawbacks by proposing a method of controlling a synchronous type motor which limits the regenerative current while maintaining the motor torque substantially equal to the setpoint torque and which does not require additional components. The invention relates to a method for controlling a synchronous electric motor, powered by an alternating current from at least one inverter, the inverter being controlled by at least one microcontroller using a vector control method, the method being executed by the microcontroller and comprising at least: a first determination stage in which an intermediate value of a direct axis current and an intermediate value of a direct axis current The quadrature of the alternating current supplying the motor is determined by function of at least: a reference setpoint pair or a reference value of the quadrature axis current, a rotational speed of said motor, an inverter supply voltage, a static regeneration threshold and, a reference value for the direct axis current, a second determination step in which a target value of the direct axis current and a target value for the quadrature axis current are determined based on at least: the intermediate value of the direct axis current, the intermediate value of the quadrature axis current, a dynamic regeneration threshold, a piloting stage in which at least one inverter is controlled by the microcontroller based on the target value of the direct axis current and the target value of the quadrature axis current. In this description, the terms reference value of XX, XX denoting direct axis current or quadrature axis current, and reference XX, or intermediate value of XX and intermediate XX, or target value of XX and target XX, refer to the same current. The reference torque is the torque that the motor must exert. The reference torque is generally received as software information, processed within the microcontroller, and used as input data for a software function also executed within the microcontroller. Motor torque is the actual torque exerted by the motor. Motor torque depends on the alternating current supplying the motor. A motor user aims for the motor torque to be close to or equal to the reference torque setting. The term "motor system" refers to all the components that control the electric motor. The motor system includes, in particular, the motor-inverter assembly and the microcontroller. The electric motor according to the invention is powered by an alternating current supplied by the inverter. The inverter itself is electrically powered by a direct current supply. The alternating current supplying the motor is determined in two main successive steps so that the alternating current supplying the motor is obtained by applying the target values ​​of the direct axis current and the quadrature axis current to the motor, on the one hand, that the motor exerts the reference setpoint torque, and on the other hand, that the direct current supplying the inverter is above an overall regeneration threshold. The overall regeneration threshold corresponds to the maximum regenerative current level that can be generated by the motor-inverter assembly, regardless of the motor's operating conditions. In other words, the inverter's DC power supply current will be greater than or equal to the overall regeneration threshold. The overall regeneration threshold is the minimum value imposed on the inverter's DC power supply current. Thus, the process makes it possible to limit the level of regenerative current produced by the motor-inverter assembly while maintaining a motor torque approximately equal to the reference setpoint torque, and without requiring additional components. According to one embodiment, a global regeneration threshold corresponding to a sum of the static regeneration threshold and the dynamic regeneration threshold. The overall regeneration threshold is logically chosen to be less than or equal to OA in order to control the amount of regenerative current produced without inducing forced motor consumption, which would then correspond to a positive value. However, this scenario is also technically feasible. Thus, an overall regeneration threshold less than or equal to OA corresponds to little or no regenerative current. The static regeneration threshold is chosen by a user of the process. It corresponds to a minimum acceptable value for the inverter's DC power supply current when the motor is in a static virtual state, that is, an imaginary situation in which there is a balance of forces. In other words, in the static virtual state, the motor-inverter system exhibits no dynamic movement; the currents within the motor are constant in terms of phase and amplitude. In the static virtual situation, we can write: [Math.1] Petat # Ptoss + Pimec F Ync-{DCstat With Ps: the electrical power in static mode of the motor-inverter assembly, expressed in Watts. The electrical power is positive when the motor- The inverter consumes energy, and the output is negative when the motor-inverter assembly generates energy. Pioss: the power dissipated by Joule effect in electrical conductors of the motor-inverter assembly, such as a motor winding, a PCB trace, a MOSFET... The power dissipated by Joule effect is always positive, it is expressed in Watts. Prec: the mechanical power of the motor system, expressed in Watts. The mechanical power is positive when the reference motor torque and the rotational speed have the same sign, i.e. positive or negative, and the mechanical power is negative when the reference motor torque and the rotational speed have opposite signs, i.e. one positive and the other negative. Thus, when the reference motor torque and the rotational speed have opposite signs, it is possible that the electrical power of the motor system may be negative. Vbc: the inverter supply voltage, expressed in Volts. The inverter supply voltage is always positive. Ipesu: : 1e Direct current supplying the inverter in a static virtual situation, expressed in Amperes. The direct current supply is negative when the electrical power is negative, and positive when the electrical power is positive. The static regeneration threshold corresponds to the minimum value that is allowed for the inverter's DC power supply current in a static virtual situation. According to one embodiment, the static regeneration threshold is chosen to be positive, zero, or negative depending on the margins chosen. For a 12V DC power supply with a current draw of -8A, this threshold can, for example, be set to -4A, leaving a margin of 48W. For a 48V DC power supply with a current draw of -2A, this threshold can, for example, be set to -1A, also leaving a margin of 48W. The static regeneration threshold is determined such that: [Math.2] Ploss + Pmec Z Vho-!DCstarmin With : Pioss: the power dissipated by Joule effect in electrical conductors of the motor-inverter assembly. Prec: the mechanical power of the motor system, expressed in Watts. Vpc: the inverter's supply voltage, expressed in volts. Ipesramin: the static regeneration threshold corresponding to the minimum value of the inverter's DC power supply current, expressed in Amperes. The dynamic regeneration threshold is chosen by the process user. It corresponds to a minimum acceptable value of the DC power supply current. the inverter when the motor is in a virtual dynamic situation, that is to say an imaginary situation in which only an evolution of the alternating current supplying the motor is taken into account. In the dynamic virtual situation, we can write: [Math.3] P dyn 7 Ype-! DCdyn With Payn: the magnetizing power of the motor stator, expressed in Watts. The magnetizing power is positive when the magnetic energy of the stator increases, i.e., during magnetization, and negative when the magnetic energy of the stator decreases, i.e., during demagnetization. Vpc: the inverter's supply voltage, expressed in volts. The supply voltage is always positive. Ipcayn: 1st direct current supplying the inverter, expressed in Amperes. The direct current supply is negative when the power is negative, and positive when the power is positive. The dynamic regeneration threshold corresponds to the minimum value that is allowed for stator demagnetization in a virtual dynamic situation, that is: [Math.4] Payn? VDe-}Dcdynmin With Pan: the magnetization power of the motor's stator, expressed in Watts, Vbpc: the inverter's supply voltage, expressed in volts. Ipcaynmin: the dynamic regeneration threshold corresponding to the minimum value of the inverter's DC power supply current, expressed in Amperes. According to one embodiment, the dynamic regeneration threshold is chosen to be negative. According to one embodiment, the intermediate value of the quadrature axis current becomes the target value of the quadrature axis current. The general principle of the method is to determine, in the first determination step, the alternating current supplying the motor in a static virtual state such that the direct current supplying the inverter in a static virtual state is greater than or equal to the static regeneration threshold, and then to modify, only and if necessary, the direct axis current of the alternating current supplying the motor in a static virtual state so that the direct current supplying the inverter in a dynamic virtual state is less than or equal to the dynamic regeneration threshold. Indeed, since the motor torque is primarily controlled by the quadrature axis current, it is not possible to modify the value of this current without changing the motor torque. It is, however, possible to at least partially counterbalance the regenerative current produced by reducing the quadrature axis current is achieved by simultaneously increasing the direct axis current to contain the sum of the two. Ultimately, this ensures that the inverter's DC power supply current in real-world conditions is greater than or equal to the overall regeneration threshold, i.e.: [Math.5] {pe > Ipcmin = Ibestatmin + pc dynmin With: Inc: the inverter's direct current supply, expressed in Amperes; Ipcäynmia: the dynamic regeneration threshold corresponding to the minimum value of the inverter's DC power supply current, expressed in Amperes. Ipcstarmin! the static regeneration threshold corresponding to the minimum value of the inverter's DC supply current, expressed in Amperes. Ipemin: the overall regeneration threshold, expressed in Amperes. More specifically, in the method according to the invention, the first determination step defines a first value, called the intermediate value, for each component of the alternating current supplying the motor, namely the direct axis current and the quadrature axis current, when the motor-inverter assembly is considered in the static virtual state. In other words, the method determines the intermediate value of the alternating current supplying the motor in the static virtual state so as to guarantee that the motor exerts the set torque, and to solve equation Math 1 with the assumption that: [Math.6] Incstat? !DCsatmin With: Iposea: the direct current supplying the inverter, expressed in Amperes, in a static virtual situation; Ipostatmin: 1st static regeneration threshold, expressed in Amperes. Thus, the intermediate value of the motor's AC supply current, determined under static conditions, ensures that the inverter's DC supply current remains above the static regeneration threshold. In other words, this intermediate value is determined based on parameters that guarantee, firstly, that the motor exerts the specified torque, and secondly, that the inverter's DC supply current exceeds the static regeneration threshold. In the method according to the invention, the second determination step makes it possible to define a second value, called the target value, for each component of the alternating current supplying the motor as a function of at least the intermediate value of the direct axis current, the intermediate value of the quadrature axis current, and the dynamic regeneration threshold. In other words, the method determines the target value of the alternating current supplying the motor that will be applied to the motor such that the the motor exerts the set torque, and the inverter's DC power supply current is greater than or equal to the overall regeneration threshold, ensuring in particular that: [Math.7] Ûhcdyn z fhcaynmin With: Inca: the direct current supplying the inverter, expressed in Amperes, in a dynamic virtual situation; Ipcaynmin: the dynamic regeneration threshold, expressed in Amperes. Finally, the process includes a step of controlling the motor based on the target value of the direct axis current and the target value of the quadrature axis current. The invention may also have one or more of the following features taken alone or in combination. According to one embodiment, the electric motor is a power steering motor of a vehicle. According to one embodiment, the method includes a preliminary determination step in which the reference value of the direct axis current and the reference value of the quadrature axis current are determined as a function of at least: the reference setpoint pair, the rotational speed of said motor, the inverter's supply voltage The preliminary determination step aims to define, for the downstream vector control, the reference value of the direct axis current and the reference value of the quadrature axis current among all the pairs of direct axis current and quadrature axis current that ensure the reference setpoint torque. According to one embodiment, the first determination step and / or the second determination step receives as input at least one system parameter chosen from: A total equivalent resistance on the alternating current side, A direct axis and / or quadrature axis inductor of the electric motor, A magnetic flux from the electric motor, An even number of poles of the electric motor, The maximum permissible alternating current power supply to the motor. According to one embodiment, the microcontroller, to perform the first determination step, implements in real time a specific algorithm, and / or uses a solution table of intermediate values ​​stored in memory. The solution table lists, for example as a function of at least the rotational speed and the reference setpoint torque, the intermediate values ​​of each pair of direct axis current and quadrature axis current such that the motor torque is approximately equal to the reference setpoint torque and the DC current inverter power supply in static virtual situation is greater than the static regeneration threshold. Indeed, there are infinitely many pairs of direct axis and quadrature axis currents that can ensure the motor torque is approximately equal to the reference setpoint torque. Thus, it is possible to predict, using an algorithm (for example, an iterative one), for each setpoint torque and rotational speed value, a pair of direct axis and quadrature axis currents that will ensure, in a static virtual environment, the motor torque is approximately equal to the setpoint torque and the inverter's DC supply current is above the static regeneration threshold. For example, the solution table or specific real-time algorithm must solve the system of equations below, for which only the solution offering the current intermediate value with a negative direct axis is to be considered: [Math.8] Cf = Kpi cat ( + (La " L,) assat ) | Vhc \ Rue: \ l'dssar # lastat} + pl rar (?+ (La 7 Le) dasras) ) > lrcssannin With: This: reference setpoint torque, expressed in Nm; Lost: the intermediate value of the quadrature axis current; List: the current intermediate value of the direct axis; W: the magnetic flux of the electric motor, expressed in Wb; Le: the direct axis or quadrature axis inductances of the electric motor (H); Vpc: the inverter supply voltage, expressed in Volts; Rac: the total equivalent resistance on the AC side of the motor system (2); p: the number of pole pairs of the electric motor; © : motor rotation speed, expressed in rad.s! k: transformation factor uvm & dq (3 / 2 or 1 for example depending on the convention chosen) Ipostatmin: 1st static regeneration threshold According to one embodiment, the solution table or the specific algorithm in constant time is a function of a parameter chosen from: unc supply voltage of the inverter, and a temperature of the electric motor. The intermediate values ​​of the direct axis current and the quadrature axis current are highly dependent on the inverter supply voltage and / or the motor temperature. Therefore, the solution table or the specific real-time algorithm may also take these parameters into account. According to one embodiment, the solution table is established by considering the voltage minimum inverter power supply and minimum electric motor temperature. The minimum inverter supply voltage is the lowest possible inverter supply voltage. The minimum engine temperature is the lowest possible temperature of the engine system under consideration. According to one embodiment, the intermediate value of the direct axis current and the intermediate value of the quadrature axis current are determined by interpolation of the solution table or calculated by the specific algorithm in real time. In the case of a motor exhibiting low or zero reluctance (Ld = La), the system is solved very simply, so a real-time implementation will be chosen in preference to interpolation by solution table. According to one embodiment, the second determination step receives as input an equivalent amplitude from the motor current system, independent of its phase, achieved during a previous and / or ongoing evaluation. The equivalent amplitude of the three-phase current system, regardless of its phase, is used, for example, in square form. The second step focuses on controlling the magnetization / demagnetization power of the stator winding, hence its dynamic nature, as it assumes a change in currents. For example, the intermediate value of the direct axis current is modified in the second determination step as a function of a maximum dynamic direct axis current comprising the target value of the motor supply AC current achieved in the previous evaluation, the dynamic regeneration threshold, a characteristic quantity of the magnetic behavior, such as the motor inductance, and a time since the previous evaluation. The maximum dynamic direct axis current corresponds to the maximum permissible direct axis current value in order to control the decay of the alternating current supplying the motor without interfering with the target quadrature axis current. The maximum dynamic direct axis current is defined as less than or equal to 0. For example, the maximum dynamic direct axis current can be expressed by the equation below: [Math.9] cp Ê 4 PV Of pcasmir!e cor 7 7 \Eciblepre ” *gstat KL With : Ceor: the maximum dynamic direct axis current; Ipcaynmin: the dynamic regeneration threshold; Pa cri lE a vals e ur in te: rmé éd: jai re duco ui ra n td' ax: e de e qu: ladre at ui re Péibiepre: the target value of the alternating current supplying the motor achieved during a previous evaluation; YVpc: the inverter's supply voltage expressed in Volts; t.: a duration since the previous evaluation; L: an inductance of the motor; k: transformation factor uvw © dq (3 / 2 or | for example, depending on the chosen convention) Note that a negative value below the root means a maximum dynamic direct axis current of zero. According to one embodiment, the first determination step includes an appraisal phase in which a comparison of the theoretical regenerative current is made with respect to the overall regeneration threshold. This comparison is carried out, for example by means of the equation below math 10, from the rotational speed of the motor, the supply voltage of the inverter, the reference value of the direct axis current, and optionally, the reference setpoint torque or the reference value of the quadrature axis current, one being directly derived from the other as soon as the reference value of the direct axis current is fixed. If the comparison of the appreciation phase is respected, then the reference value of the direct axis current becomes the intermediate value of the direct axis current and the reference value of the quadrature axis current becomes the intermediate value of the quadrature axis current. If the criterion of the assessment phase is not met, then the reference value of the direct axis current and the reference value of the quadrature axis current are modified in accordance with the continuation of step 1. [Math.10] Var (Rae: (yes *TGyes ) * PA aae (F + (La-Lg)-éreg )) ? Tests With: k: transformation factor uvw « dq (3 / 2 or | for example depending on the convention chosen); Vopc: the inverter's supply voltage expressed in Volts; Rs: the total equivalent resistance on the AC side of the motor system (82); p: the number of pole pairs of the electric motor; © : motor rotation speed, expressed in rad.s-! Losta: the intermediate value of the quadrature axis current; W: the magnetic flux of the electric motor, expressed in Wb; La, L: the direct-axis or quadrature-axis inductances of the electric motor (H); Iposeamin: the static regeneration threshold Lars: the reference value of the direct axis current, expressed in Amperes; Lyer: the reference value of the quadrature axis current, expressed in Amperes. The invention also relates to a power steering system comprising at least one motor controlled by the method according to the invention. The invention will be better understood from the following description, which relates to several embodiments of the present invention, given by way of non-limiting examples and explained with reference to the accompanying schematic drawings, in which: [Fig.1] is a schematic representation of a power steering system comprising a method according to the invention, [Fig.2] is a diagram of the process according to the invention. A steering system 1 of a vehicle 2 is designed to allow a driver to control the vehicle's trajectory by changing the steering angle of the vehicle's wheels 10, 11 using a steering wheel 3. The steering angle is specifically linked to an angle 03 of the steering wheel 3. The driver changes the angle 03 of the steering wheel 3 by applying a force T3 to the steering wheel, hereinafter referred to as "steering wheel torque". The force T3 applied to the steering wheel can be measured using a torque sensor 23. Generally, a steering system comprises several elements, including a steering wheel 3, a rack 6, and two wheels 10, 11, each connected to a tie rod 8, 9. The rack 6 is the component that allows the wheels 10, 11 to be maneuvered, that is, it allows the steering angle of the wheels 10, 11 to be changed via the tie rods 8, 9. The rack 6 transforms a change in the angle of the steering wheel 3 into a change in the steering angle of the vehicle's wheels 10, 11. An electric power steering system 1 includes at least one microcontroller 20, which notably determines a reference torque setpoint C,+ to be applied by an electric motor 12. The motor 12 exerts a motor torque T12 on the rack 6 based on the reference torque setpoint C,.The said reference setpoint torque C,: is determined according to various parameters, notably from the force T3 exerted on the flywheel 3, received by the microcontroller 20 in a manner known to a person skilled in the art. The electric motor 12 will preferably be an electric motor, with two directions of operation, and preferably a rotary electric motor, of brush or brushless type, of synchronous type. The invention applies, for example, to an electric motor 12 of a mechanical power steering system, that is to say, one in which there is a mechanical link. actually achieved by a steering column 4 which engages, by means of a steering pinion 5, on the rack 6, which is itself guided in translation in a casing 7 fixed to the vehicle 2, or an electric power steering system without mechanical link, called "steer-by-wire" in English, in which the steering wheel is mechanically detached from the rack, not illustrated in the figures. In the case of a mechanical power steering system, the electric motor 12 can engage, via a gear reducer, either with the steering column 4 itself, to form a so-called "single pinion" mechanism, or directly with the steering rack 6, by means, for example, of a second pinion 13 distinct from the steering pinion 5 which allows the steering column 4 to mesh with the rack 6, so as to form a so-called "double pinion" mechanism, as illustrated in [Fig.1]. The invention relates more particularly to a method of controlling a synchronous type electric motor 12 which may be an electric motor 12 of the steering system as represented in [Fig.1] or of another application. The electric motor 12 is powered by an alternating current supply from an inverter, the inverter being controlled by the microcontroller 20 using a vector control method. The inverter is electrically powered by a direct current supply voltage Inc, which has a supply voltage Vpc. The inverter supplies the electric motor 12 with an alternating current based on a target value of a direct axis current LA and a target value of a quadrature axis current LA. The motor torque T12 is the actual torque exerted by the motor 12. The motor torque T12 depends on the alternating current supplying the motor 12. A user of the motor 12 seeks to have the motor torque T12 be close to or equal to the reference setpoint torque CE. The motor system is subsequently referred to as the set of elements enabling the control of the electric motor 12. The motor system includes in particular the motor-inverter assembly, and the microcontroller 20. The process is shown in [Fig.2] and includes a preliminary EO determination step in which a reference value for the Taser direct axis current and a reference value for the quadrature axis current Igxss are determined as a function of at least: the reference setpoint pair Cr, a rotational speed @ said motor, the supply voltage Vpc of the inverter. The preliminary step of determining E0 aims to define, without any prior assumptions about the regenerative current, the reference value of the direct axis current Lire and the value of reference of the quadrature axis current Ir for obtaining the reference setpoint torque C,s. For example, it can be carried out in accordance with a so-called “Maximum Torque Per Ampere” MTPA law offering the best efficiency at low speed, and from a demagnetization strategy (“flux weakning”) at high speed when the electromotive force approaches the supply voltage of the inverter’s DC power supply. The microcontroller 20 then performs a first determination step El in which an intermediate value of the direct axis current Is, and an intermediate value of the quadrature axis current I, of the alternating current supplying the motor 12 are determined as a function of: of the reference setpoint couple C, or of the reference current value quadrature axis of the rotational speed © of said motor 12, of the inverter's supply voltage Vpe, of a static regeneration threshold Incsumin Et, of the reference value of the direct axis current. The first determination step El allows us to define a first value, called the intermediate value, for each component of the alternating current supplying the motor, that is to say the direct axis current Lasu and the quadrature axis current Igsturs when the motor-inverter assembly is considered in the static virtual situation. In other words, the process determines the intermediate value of the alternating current supplying the motor in the static virtual situation so as to guarantee that the motor 12 exerts the reference setpoint torque C,s, and to guarantee that: [Math.11] poster Z IDCstetmin With: Ipesa: the direct current supplying the inverter, expressed in Amperes, in a static virtual situation; Ipostatmin: the static regeneration threshold, expressed in Amperes. Thus, the intermediate value of the alternating current supplying motor 12, determined in static conditions, ensures that the direct current supplying inverter Ipc is greater than the static regeneration threshold Ipesumin. In other words, this intermediate value is determined based on parameters that ensure, on the one hand, that motor 12 exerts the reference setpoint torque C, and on the other hand, that the direct current supplying inverter Ipcsua is greater than the static regeneration threshold Ipcstamia. According to one embodiment, the microcontroller 20, to carry out the first determination step El, implements in real time a specific algorithm, and / or uses a solution table of intermediate values ​​stored in a memory. The solution table lists, for example as a function of at least the rotational speed 2 and the reference setpoint torque C, the intermediate values ​​of each pair of direct axis current Toy and quadrature axis current I, so that the motor torque T12 is substantially equal to the reference setpoint torque C, and that the DC supply current of the inverter Ipcsu EN static virtual situation is greater than the static regeneration threshold Ipestamin- Indeed, there are infinitely many pairs of direct axis current and quadrature axis current that can ensure the motor torque T12 is approximately equal to the reference setpoint torque C. Thus, it is possible to predict, using an algorithm (for example, an iterative one), for each value of the reference setpoint torque C and the rotational speed C, a pair of direct axis current and quadrature axis current that will ensure, in a static virtual situation, the motor torque T12 is approximately equal to the reference setpoint torque Cys, and the inverter's DC supply current Ipcsui is greater than the static regeneration threshold Ipcsumin. For example, the solution table or the specific real-time algorithm must solve the system of equations below, for which only the solution offering the intermediate negative direct axis current value is to be considered. [Math.12] Cf = KP stat ( ?+ (a -L, ) asser ) | Vpa' Rae (Lästar + lg ) +p£d 1 car + (La- L, )-Tésat ) ) z IpCstarmin With: This: reference setpoint torque, expressed in Nm; Lost: the intermediate value of the quadrature axis current; Losru: the current intermediate value of the direct axis; W: the (magnetic lux of the electric motor, expressed in Wb; Le, La: the direct axis or quadrature axis inductances of the electric motor (H); Vpc: the inverter supply voltage, expressed in Volts; Rac: the total equivalent resistance on the AC side of the motor system (2); p: the number of pole pairs of the electric motor; L2: motor rotation speed, expressed in rad.s! Ipostatmin: the static regeneration threshold k: transformation factor uvm + dq (3 / 2 or | for example, depending on the chosen convention) According to one embodiment, the solution table or the specific real-time algorithm is a function of a parameter chosen from: the supply voltage Vpc of the inverter, and a temperature of the electric motor 12. The intermediate values ​​of the direct axis current IL. €t of the axis current of Quadrature Isa are highly dependent on the inverter's supply voltage Vpc and / or the motor temperature. Therefore, the solution table or the specific real-time algorithm may also take these parameters into account. According to one embodiment, the solution table is established by considering the minimum inverter supply voltage and the minimum electric motor temperature. The minimum inverter supply voltage is the lowest possible inverter supply voltage Vpc. The minimum engine temperature is the lowest possible temperature of the engine system 12 under consideration. According to one embodiment, the intermediate value of the direct axis current Les and the intermediate value of the quadrature axis current La are determined by interpolation of the solution table or by the specific real-time algorithm. According to one embodiment, the first determination step El includes an appraisal phase in which a comparison of the theoretical regenerative current is performed with respect to an overall regeneration threshold Ipemin- This comparison is carried out, for example by means of the equation below math 13, from the rotation speed © of the motor 12, the supply voltage of the inverter Vpc, the reference value of the direct axis current Let, and optionally, the reference setpoint torque C, Or the reference value of the quadrature axis current Lors one being directly derived from the other as soon as the reference value of the direct axis current I: is fixed. If the comparison of the appreciation phase is respected, then the reference value of the direct axis current Iger becomes the intermediate value of the direct axis current Tasar, and the reference value of the quadrature axis current Igrs becomes the intermediate value of the quadrature axis current I,s1a- If the criterion of the assessment phase is not met, then the reference value of the direct axis current Iares and the reference value of the quadrature axis current Ier are modified in accordance with the continuation of step 1. [Math.13] 2 2 Ver (Roc (ares * Gros ) + PA ggaar (PF + (Ba- Ep) Ares ) | ? Tocstonmin With: k: transformation factor uvw «+ dq (3 / 2 or 1 for example depending on the convention chosen); Vpc: the inverter's supply voltage expressed in Volts; Rec: the total equivalent resistance on the AC side of the motor system (©); p: the number of pole pairs of the electric motor; £2: motor rotation speed, expressed in rad.s-! Lost: the intermediate value of the quadrature axis current; W: the magnetic flux of the electric motor, expressed in Wb; La, L, : the direct axis or quadrature axis inductances of the electric motor (H); Ipostatmin: 1st static regeneration threshold The ! the reference value of the direct axis current, expressed in Amperes; Lrer:1a reference value of quadrature axis current, expressed in Amperes. The microcontroller 20 then performs a second determination step E2 in which the target value of the direct axis current I4ciye and the target value of the quadrature axis current Lopipie are determined as a function of: of the intermediate value of the direct axis current Lis of the intermediate value of the Losux quadrature axis current of a dynamic regeneration threshold Ipcaynmins The second determination step E2 allows for the definition of a second value, called the target value, for each component of the alternating current supplying the motor, based on at least the intermediate value of the direct axis current Ir, the intermediate value of the quadrature axis current Il, and the dynamic regeneration threshold IDCImin. In other words, the process determines the target value of the alternating current supplying the motor that will be applied to motor 12 such that motor 12 exerts the reference setpoint torque Cr, and that the DC supply current Incn of the inverter is greater than or equal to the overall regeneration threshold Incmin; ensuring in particular that: [Math.14] 1 pcdyn = Phcdynmin With: Ipcayn: the direct current supplying the inverter, expressed in Amperes, in a dynamic virtual situation; Ipcaynmin: the dynamic regeneration threshold, expressed in Amperes. According to one embodiment, the second determination step E2 receives as input an equivalent amplitude from the motor current system, independent of its phase, achieved during a previous and / or ongoing evaluation. The equivalent amplitude of the three-phase current system, regardless of its phase, is used, for example, in square form. The second step focuses on controlling the magnetization / demagnetization power of the stator winding, hence its dynamic aspect, as it assumes a change in currents. For example, the intermediate value of the direct current Issu Est is modified in the second determination step E2 as a function of a maximum dynamic direct current Cor, which includes the target value of the alternating current supplying motor 12. In the previous evaluation, the dynamic regeneration threshold Incaynmin: A characteristic quantity of magnetic behavior, such as motor inductance, and a duration since the previous evaluation. The maximum dynamic direct axis current corresponds to the maximum permissible direct axis current value in order to control the decay of the alternating current supplying the motor without interfering with the target quadrature axis current. The maximum dynamic direct axis current is defined as less than or equal to 0. For example, the maximum dynamic direct axis current Ceox can be expressed, for example, by the equation below: [Math.15] 2.Vpethe ft 2 2 *” DC DCdynmin" € Ceorr = - for 7 Pt + KL With: Ceox: the maximum dynamic direct axis current; Ipcaynmin: the dynamic regeneration threshold; Pos: the intermediate value of the quadrature axis current; Peiblepre: the target value of the alternating current supplying the motor achieved during a previous evaluation; Vopc: the inverter's supply voltage expressed in Volts; t.: a duration since the previous evaluation; k: transformation factor uvw & dq (3 / 2 or | for example, depending on the chosen convention) L: an inductance of the motor. Note that a negative value below the root means a maximum dynamic direct axis current of zero. According to one embodiment, the first determination step E1 and / or the second determination step E2 receives as input at least one system parameter chosen from: A total equivalent resistance R, on the alternating current side, A direct axis inductance La and / or quadrature axis inductance L, of the motor electric 12, A magnetic flux W from the electric motor 12, A pair number of poles p of the electric motor 12, The maximum permissible alternating current power supply to the motor. Finally, the microcontroller 20 performs an EP control step in which the inverter is controlled by the vector control method based on the target value of the direct axis current Lacipie and the target value of the quadrature axis current Iccivle. According to the method of the invention, the alternating current supplying the motor is determined in two main successive steps such that the alternating current supply obtained by applying the target values ​​of the direct axis current Iacibie and the quadrature axis current IAU of motor 12 allows, on the one hand, the motor 12 to exert the reference setpoint torque Cf, and on the other hand, the DC supply current Inc of the inverter to be greater than the overall regeneration threshold IDCmin+ The overall regeneration threshold Incmin corresponds to a maximum regenerative current level that can be generated by the motor-inverter assembly regardless of the motor's operating conditions. In other words, the inverter's DC supply current Inc will be greater than or equal to the overall regeneration threshold Ipemin. The overall regeneration threshold Ipcmin is the minimum value allowed for the inverter's DC supply current Inc. Thus, the method makes it possible to limit the level of regenerative current produced by the motor-inverter assembly while maintaining a motor torque T12 that is approximately equal to the reference setpoint torque Cyr, and without requiring additional components. The overall regeneration threshold Ipcmin corresponds to the sum of the static regeneration threshold Incswmin and the dynamic regeneration threshold Ipcaynnin. Logically chosen to be less than or equal to OA, this is done to control the amount of regenerative current produced without inducing forced motor consumption, which would then correspond to a positive value. However, this scenario is also technically feasible. Thus, an overall regeneration threshold less than or equal to OA corresponds to little or no regenerative current. The static regeneration threshold Ipesræ €St, chosen by a user of the process, corresponds to a minimum acceptable value of the inverter's DC supply current Incseu when the motor is in a static virtual state, that is, an imaginary situation in which there is a balance of forces. In other words, in the static virtual state, the motor-inverter system exhibits no dynamics; the currents within the motor are constant in terms of phase and amplitude. In the static virtual situation, we can write: [Math.16] Prat # Pross + Prree 7 Vne-IdCstet With Ps: the static electrical power of the motor-inverter assembly, expressed in Watts. The electrical power P is positive when the motor-inverter assembly consumes energy, and negative when the motor-inverter assembly generates energy. Pios: the power dissipated by Joule effect in electrical conductors the motor-inverter assembly, such as a motor winding, a PCB trace, a MOSFET... The power dissipated by Joule effect P,,, is always positive, it is expressed in Watts. Prec: the mechanical power of the motor system, expressed in Watts. The mechanical power P,,, is positive when the reference motor torque and the rotational speed © have the same sign, i.e. positive or negative, and the mechanical power Prec is negative when the reference motor torque and the rotational speed © have opposite signs, i.e. one positive and the other negative. Thus, when the reference motor torque and the rotational speed © have opposite signs, it is possible that the electrical power P,… of the motor system is negative. Vpc: the inverter's supply voltage, expressed in volts. The inverter's supply voltage Vpc is always positive. Iposu: : 1e Direct current supplied to the inverter, expressed in Amperes, in static conditions. The direct current supplied to the inverter Ipcsa is negative when the electrical power is negative, and positive when the electrical power is positive. The static regeneration threshold Incsumin corresponds to the minimum value that is allowed for the continuous supply current Ipcsu of the inverter in a static virtual situation. The static regeneration threshold Ipcsumin €St is chosen to be positive, zero, or negative depending on the margins chosen. For a 12V DC power supply with a current draw of -8A, this threshold can, for example, be set to -4A, leaving a margin of 48W. For a 48V DC power supply with a current draw of -2A, this threshold can, for example, be set to -1A, also leaving a margin of 48W. It is negative for situations where little or no regenerated current is desired. The static regeneration threshold Inestmin €St is determined such that: [Math.17] Pross + Pmec Z Ve TDCstarmin With : Pioss: the power dissipated by Joule effect in electrical conductors of the motor-inverter assembly. Prec: the mechanical power of the motor system, expressed in Watts. Vpc: the inverter's supply voltage, expressed in volts. Ipestatmin: 1st static regeneration threshold, expressed in Amperes. The dynamic regeneration threshold for Ipcayamia €St is chosen by the user of the process. It corresponds to a minimum acceptable value of the DC supply current Ipceyn of the inverter when the motor 12 is in a dynamic virtual situation, that is to say an imaginary situation in which only an evolution of the AC supply current of the motor is taken into account. In the dynamic virtual situation, we can write: [Math.18] P don 7 Ype- DCdyn With Payn: the magnetizing power of the motor stator, expressed in Watts. The magnetizing power Pa is positive when the magnetic energy of the stator increases, i.e., during magnetization, and negative when the magnetic energy of the stator decreases, i.e., during demagnetization. Vpc: the inverter supply voltage, expressed in Volts. Ipcayn: The DC supply current of the inverter, expressed in Amperes, under dynamic conditions. The DC supply current Ipcay is negative when the magnetization power Pa is negative, and positive when the magnetization power Payn is positive. The dynamic regeneration threshold corresponds to the minimum value that is allowed for stator demagnetization in a dynamic virtual situation, that is: [Math.19] Pam} Voe-tpedynmin With Pan: the magnetization power of the motor's stator, expressed in Watts, Vbpc: the inverter's supply voltage, expressed in volts. Ipcaynmin: the dynamic regeneration threshold, expressed in Amperes. The dynamic regeneration threshold for Ipcayamin is chosen to be negative. The general principle of the process is to determine, in the first determination step El, the alternating current supplying the motor in a static virtual situation so that the direct current supplying the inverter Ipes is notably greater than or equal to the static regeneration threshold Incscamins THEN to modify, only and if necessary, the intermediate value of the direct axis current Istar of the alternating current supplying the motor 12 in a static virtual situation so that the direct current supplying the inverter in a dynamic virtual situation is less than or equal to the dynamic regeneration threshold Ipcevamin- Thus, the intermediate value of the quadrature axis current Igsu becomes the target value of the quadrature axis current Iccine Indeed, the motor torque T12 being mainly controlled by the quadrature axis current, it is not possible to modify the value of this current without varying the motor torque T12.However, it is possible to at least partially counterbalance the regenerative current produced by a di- . minification of the quadrature axis current by a simultaneous increase in the direct axis current so as to contain the sum of the two. Finally, it is thus possible to guarantee that the continuous supply current Inc of the inverter in real-world conditions is greater than or equal to the overall regeneration threshold Ipomin. That is: [Math.20] {pe > Ipcmin = Ibestatmin + pc dynmin With: Inc: the inverter's direct current supply, expressed in Amperes; Ipcaynmin: the dynamic regeneration threshold, expressed in Amperes. Ipestarmin: the regeneration threshold, expressed in Amperes. Ipemin: the overall regeneration threshold, expressed in Amperes. Of course, the invention is not limited to the embodiments described and shown in the accompanying figures. Modifications remain possible, particularly with regard to the composition of the various elements or by substitution of technical equivalents, without departing from the scope of protection of the invention.

Claims

Demands

1. Method for controlling a synchronous DC electric motor (12), powered by an alternating current supply from at least one inverter, the inverter being controlled by at least one microcontroller (20) using a vector control method, the process being executed by the microcontroller(20) and comprising at least: a first determination stage (El) in which a intermediate value of a direct axis current (Tasu) and A intermediate value of a quadrature axis current (The) of the alternating current power supply to the motor (12) are de- completed based on at least: a reference setpoint pair (C,r) OR a value quadrature axis current reference (Lyref)s a rotational speed (2) of said motor (12), a supply voltage (Vpc) of the inverter, a static regeneration threshold (Ipcsumin) And, a reference value for the direct axis current (Link), a second determination step (E2) in which a target value of the direct axis current (Lecipie) and a target value of the quadrature axis current (Lcivie) are determined in function of at least: the intermediate value of the direct axis current (Lasur)s the intermediate value of the axis current quadrature (Lystur) a dynamic regeneration threshold (Inceyamin) a pilot stage (PS) in which at least one The inverter is controlled by the microcontroller (20) based on the target value of the direct current (Lecipie) Ct of the target value quadrature axis current (Lreible)-

2. Method according to claim !, wherein the regeneration threshold static (Incsamin) €St chosen positive, zero, or negative.

3. A method according to any one of the preceding claims, in in which the dynamic regeneration threshold (Ipcaynmin) is chosen to be negative.

4. Method according to any one of the preceding claims, in which a global regeneration threshold (Ipemin) corresponds to a sum of the static regeneration threshold (Ipcseimin) and of the regeneration threshold dynamic (Incaynmin)-

5. A method according to any one of the preceding claims, in which is the intermediate value of the quadrature axis current (Iostar) becomes the target value of the quadrature axis current (Lçcivie)-

6. Method according to any one of the preceding claims, including a preliminary determination step (E0) in which the reference value of the direct axis current (L;.s) and the reference value The quadrature axis currents (L,s) are determined as a function of Less : the reference setpoint pair (C,…), the rotational speed {©2) of said motor, the inverter's supply voltage (Vpc)

7. A method according to any one of the preceding claims, in which the first determination step (El) and / or the second step determination (E2) receives at least one system parameter as input chosen from: A total equivalent resistance (R,c) on the alternating current side, A direct axis inductance (L') and / or quadrature axis inductance (L') 4) of the electric motor (12), A magnetic flux (V) from the electric motor (12), A number of pole pairs (p) of the electric motor (12), A maximum alternating current power supply to the motor ad- missible.

8. A method according to any one of the preceding claims, in which the microcontroller (20), to perform the first step of determining- mination (El), implements a specific algorithm in real time, and / or uses a solution table of intermediate values ​​stored in a memory.

9. A method according to any one of the preceding claims, in which the second determination step (E2) receives as input a equivalent amplitude of the motor current system, inde- during its phase, carried out during a previous assessment and / or in progress.

10. Power steering system comprising at least one motor controlled by the method according to any one of claims 1 to 9.