Method for limiting power regenerated by synchronous electric motor

Abstract

To recover a regenerative current without requiring an additional component.SOLUTION: A method includes a first determination step (E1) of determining a d-axis current intermediate value Idstat and a q-axis current intermediate value Iqstat of an AC supply current of a motor, a second determination step (E2) of determining a d-axis current target value Idcible and a q-axis current target value Iqcible, and a drive step (EP) of driving the at least one inverter by a microcontroller on the basis of the d-axis current target value Idcible and the q-axis current target value Iqcible.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to the field of electric motors, and more particularly to a method for limiting the power regenerated by a synchronous electric motor. [Background technology]

[0002] The present invention applies to electric motors, more particularly rotary synchronous electric motors, having at least three phases, receiving an AC supply current driven by a vector-controlled inverter, the inverter being supplied with a DC supply current.

[0003] Vector control, also known as field-oriented control, is a known control method for electric motors in which the motor's AC supply current is converted into two orthogonal components: one along the q-axis (hereinafter referred to as the quadrature axis current and denoted Iq) and the other along the d-axis (hereinafter referred to as the direct axis current and denoted Id). The q-axis current Iq and the d-axis current Id are so-called spatial currents, with the excitation direct axis denoted d and the quadrature axis denoted q. The q-axis current Iq and the d-axis current Id correspond to the spatial projection of the three-phase current system on the rotating coordinate system relative to the rotor of the electric motor. Therefore, the q-axis current Iq and the d-axis current Id are functions of the phase of the three-phase current system relative to the direct axis d and the amplitude of the three-phase current system. For low-reluctance motors, the d-axis current Id generally allows for a reduction in the detected magnetic flux to optimize high-speed operation, while the q-axis current Iq controls the torque exerted by the motor (hereinafter referred to as motor torque). The d-axis current Id and the q-axis current Iq are determined as a function of the motor operating point characterized by at least one parameter, for example, the setpoint torque, the motor rotational speed, the motor temperature, and the motor supply voltage.

[0004] Based on the d-axis current Id and the q-axis current Iq, the motor is supplied with an AC supply current provided by an inverter.

[0005] By convention, in the following description, when the DC supply current of the inverter is positive, the motor-inverter assembly is considered to consume energy, i.e., current flows from the inverter to the motor, while when the DC supply current is negative, the motor-inverter assembly is considered to produce energy, i.e., the inverter returns current to the DC power source.

[0006] Similarly, when the power is positive, the motor-inverter assembly is considered to consume power, while when the power is negative, the motor-inverter assembly is considered to produce power.

[0007] While the motor is running, the inverter's DC supply current is generally positive, but can be negative in some cases. When the inverter's DC supply current is negative, it is also called regenerative current. For example, if the motor is a vehicle power steering motor, regenerative current is generated during transient situations, such as when the steering wheel suddenly changes direction.

[0008] In the following, by DC supply system it is to be understood that a system upstream of the inverter is responsible for supplying or recovering continuous energy from the inverter, for example said upstream system can be a battery or a DC-DC converter.

[0009] When the amount of regenerative current is high, the DC supply system may be equipped with a recovery element that allows this current to be recovered.

[0010] However, when the amount of regenerative current is small, providing said recovery element is not economically viable, as the regenerative current will degrade the DC supply system.

[0011] It is therefore necessary to limit the amount of regenerative current generated by the motor-inverter assembly, in other words to ensure that the motor-inverter assembly remains an energy consumer regardless of the circumstances.

[0012] There are solutions for reducing regenerative current using passive elements, such as resistor elements, however passive elements can be bulky and expensive.

[0013] There are also solutions that limit the inverter's DC supply current in preference to the setpoint torque required by the motor, and these solutions are therefore intrusive because they modify the supplied motor torque so that it no longer corresponds to the required setpoint torque.

[0014] When the motor is a power steering motor, deviations between the motor torque and the setpoint torque lead to changes in the driver's driving experience. Summary of the Invention [Problem to be solved by the invention]

[0015] The present invention aims to overcome all or part of the above drawbacks by proposing a method for controlling a synchronous motor that allows limiting the regenerative current while maintaining the motor torque substantially equal to the setpoint torque, without requiring additional components. [Means for solving the problem]

[0016] The subject of the present invention is a method for controlling a synchronous electric motor supplied with an AC supply current from at least one inverter, the inverter being driven by at least one microcontroller using a vector control method, the method being executed by the microcontroller, The method comprises at least The d-axis current median value and the q-axis current median value of the AC supply current of the motor are at least Reference set value torque or q-axis current reference value, Motor rotation speed, inverter supply voltage, Static regeneration threshold, and d-axis current reference value, a first decision step, determined as a function of The d-axis current target value and the q-axis current target value are at least d-axis current median value, q-axis current intermediate value, Dynamic regeneration threshold, a second decision step, determined as a function of A driving step is provided in which the at least one inverter is driven by a microcontroller based on a d-axis current target value and a q-axis current target value.

[0017] In this specification, the terms reference value of XX, XX referring to the d-axis current or the q-axis current, and reference value XX, or intermediate value XX and intermediate XX, or target value of XX and target XX refer to the same current.

[0018] The reference setpoint torque is the torque that the motor should exert, and is typically received in the form of software information, processed within the microcontroller, and used as input data for software functions that are also executed within the microcontroller itself.

[0019] Motor torque is the torque actually exerted by the motor. Motor torque depends on the AC supply current of the motor. Motor users want to ensure that the motor torque is close to or equal to the nominal setpoint torque.

[0020] By motor system is to be understood in the following all elements that allow the control of an electric motor, including in particular a motor-inverter assembly and a microcontroller.

[0021] The electric motor according to the invention is supplied with an AC supply current provided by an inverter, which itself is electrically supplied with a DC supply current.

[0022] The AC supply current of the motor is determined in two successive main steps such that the AC supply current obtained when applying the d-axis current target and the q-axis current target to the motor allows, on the one hand, the motor to develop a nominal setpoint torque and, on the other hand, the DC supply current of the inverter to be greater than the global regeneration threshold.

[0023] The global regeneration threshold corresponds to the maximum level of regenerative current that can be generated by the motor-inverter assembly, regardless of the operating state of the motor. In other words, the inverter's DC supply current will be equal to or greater than the global regeneration threshold. The global regeneration threshold is the minimum value imposed on the inverter's DC supply current. Thus, this method allows for limiting the level of regenerative current generated by the motor-inverter assembly without requiring additional components, while maintaining the motor torque substantially equal to the reference setpoint torque.

[0024] According to one embodiment, the global regeneration threshold corresponds to the sum of the static regeneration threshold and the dynamic regeneration threshold.

[0025] The global regeneration threshold is logically selected to be less than or equal to 0 A so as to control the amount of regeneration current generated without inducing forced consumption of the motor, which corresponds to a positive value. However, this scenario is technically feasible. Thus, a global regeneration threshold less than or equal to 0 A corresponds to little or no regeneration current.

[0026] The static regeneration threshold is selected by the user of the method. It corresponds to the minimum allowable value of the inverter's DC supply current when the motor is at virtual rest, i.e., in a virtual state of balance of forces. In other words, in a virtual rest state, the motor-inverter assembly has no dynamics. The current in the motor is constant in both phase and amplitude.

[0027] In a virtual stationary state, it can be written as follows: [Number 1] TIFF2023181094000002.tif571

[0028] P stat is the power of the motor-inverter assembly in quiescent mode, expressed in watts. This power is positive when the motor-inverter assembly consumes energy and negative when the motor-inverter assembly produces energy.

[0029] P loss is the power loss due to the Joule effect in the conductors of the motor-inverter assembly, for example, the motor windings, the traces on the printed circuit board, and the MOSFETs. This power loss due to the Joule effect is always positive and is expressed in watts.

[0030] P mec is the mechanical power of the motor system, expressed in watts. This mechanical power is positive when the reference motor torque and rotational speed have the same sign (i.e., positive or negative), and negative when the reference motor torque and rotational speed have opposite signs (i.e., one positive and the other negative).

[0031] Thus, when the reference motor torque and rotational speed have opposite signs, the power of the motor system can become negative.

[0032] V DC is the inverter supply voltage, expressed in volts. The inverter supply voltage is always positive.

[0033] I DCstat is the inverter's DC supply current in amperes at rest. This DC supply current is negative when the power is negative and positive when the power is positive.

[0034] The static regeneration threshold corresponds to the lowest DC supply current allowed by the inverter in a virtual quiescent state.

[0035] According to one embodiment, the static regeneration threshold is selected to be positive, zero, or negative depending on the selected margin.

[0036] For a 12VDC supply system with a -8A absorption capacity, this threshold may be set to, for example, -4A, leaving a margin of 48W. For a 48VDC supply system with a -2A absorption capacity, this threshold may be set to, for example, -1A, also leaving a margin of 48W.

[0037] The static regeneration threshold is calculated as follows: [Number 2] TIFF2023181094000003.tif561

[0038] P loss is the power loss due to the Joule effect in the conductors of the motor-inverter assembly, P mec is the mechanical power of the motor system, expressed in watts, V DC is the inverter supply voltage, expressed in volts, I DCstatmin is the static regeneration threshold, which corresponds to the minimum DC supply current of the inverter, expressed in amperes.

[0039] The dynamic regeneration threshold is selected by the user of the method and corresponds to the minimum allowable value of the inverter's DC supply current when the motor is in a virtual dynamic state, i.e., a virtual state in which only changes in the motor's AC supply current are considered.

[0040] In the virtual dynamic state, it can be written as follows: [Number 3] TIFF2023181094000004.tif539

[0041] P dynis the excitation power of the motor stator, expressed in watts. This excitation power is positive when the stator magnetic energy is increasing, i.e., while it is energized, and negative when the stator magnetic energy is decreasing, i.e., while it is demagnetized.

[0042] V DC is the inverter supply voltage, expressed in volts. This supply voltage is always positive.

[0043] I DCdyn is the inverter's DC supply current, expressed in amperes. This DC supply current is negative when the power is negative and positive when the power is positive.

[0044] The dynamic regeneration threshold corresponds to the minimum value allowed for stator demagnetization in a hypothetical dynamic state, i.e., [Number 4] TIFF2023181094000005.tif646

[0045] P dyn is the excitation power of the motor stator, expressed in watts, V DC is the inverter supply voltage, expressed in volts, I DCdynmin is the dynamic regeneration threshold corresponding to the minimum DC supply current of the inverter, expressed in amperes.

[0046] According to one embodiment, the dynamic regeneration threshold is selected to be negative.

[0047] According to one embodiment, the q-axis current intermediate value is the q-axis current target value.

[0048] The general principle of the method is to determine the AC supply current of the motor in a virtual stationary state in a first determination step, so that the DC supply current of the inverter in the virtual stationary state is equal to or greater than the static regeneration threshold. Then, if necessary, the d-axis current of the AC supply current of the motor in the virtual stationary state is changed so that the DC supply current of the inverter in the virtual dynamic state is equal to or less than the dynamic regeneration threshold. In practice, since the motor torque is primarily controlled by the q-axis current, it is not possible to change the value of this q-axis current without changing the motor torque. However, it is possible to at least partially offset the regeneration current generated by a decrease in the q-axis current by a simultaneous increase in the d-axis current, thus including the sum of these two. Finally, it is possible to ensure that the DC supply current of the inverter in the actual state is equal to or greater than the global regeneration threshold, i.e., [Number 5] TIFF2023181094000006.tif683

[0049] I DC is the inverter's DC supply current, expressed in amperes, I DCdynmin is the dynamic regeneration threshold corresponding to the minimum inverter DC supply current, expressed in amperes, I DCstatmin is the static regeneration threshold corresponding to the minimum DC supply current of the inverter, expressed in amperes, I DCmin is the global regeneration threshold, expressed in amperes.

[0050] More specifically, in the method according to the invention, the first determination step makes it possible to assume first values, called median values, for each component of the AC supply current of the motor, i.e., the d-axis current and the q-axis current, when the motor-inverter assembly is considered to be in a virtual rest state. In other words, the method ensures that the motor develops a set torque and determines the median value of the AC supply current of the motor in the virtual rest state by solving the following equation (1) under the assumption that: [Number 6] TIFF2023181094000007.tif541

[0051] I DCstat is the DC supply current of the inverter at virtual quiescent condition, expressed in amperes, I DCstatmin is the static regeneration threshold, expressed in amperes.

[0052] Thus, the intermediate value of the AC supply current of the motor determined in the stationary state allows the DC supply current of the inverter to be greater than the static regeneration threshold, in other words, this intermediate value is determined as a function of parameters that make it possible to ensure, on the one hand, that the motor develops the set torque and, on the other hand, that the DC supply current of the inverter is greater than the static regeneration threshold.

[0053] In the method according to the invention, a second determination step makes it possible to assume, for each component of the AC supply current of the motor, a second value, called a target value, as a function of the d-axis current median value, the q-axis current median value and the dynamic regeneration threshold. In other words, the method determines the AC supply current target value of the motor to be applied to the motor so that the motor develops a setpoint torque and the DC supply current of the inverter is equal to or greater than the global regeneration threshold, in particular by ensuring that: [Number 7] TIFF2023181094000008.tif641

[0054] I DCdyn is the DC supply current of the inverter in the virtual dynamic state, expressed in amperes, I DCdynmin is the dynamic regeneration threshold, expressed in amperes.

[0055] Finally, the method includes driving the motor based on the d-axis current target value and the q-axis current target value.

[0056] The present invention may have one or more of the following features, either alone or in combination:

[0057] According to an embodiment, the electric motor is a power steering motor of a vehicle.

[0058] According to one embodiment, the method comprises the steps of: determining the d-axis current reference value and the q-axis current reference value as at least Reference torque setting the rotational speed of the motor, and inverter supply voltage, A preliminary determination step is performed as a function of

[0059] The purpose of the pre-determination step is to determine the d-axis current reference value and the q-axis current reference value among all pairs of d-axis current and q-axis current that can ensure the reference setpoint torque for downstream vector control.

[0060] According to one embodiment, the first determining step and / or the second determining step comprises: Total equivalent resistance on the AC side, the d-axis inductance and / or the q-axis inductance of the electric motor; magnetic flux in electric motors, the number of pole pairs of the electric motor, and Maximum allowable AC supply current for the motor, The system receives as input at least one system parameter selected from:

[0061] According to one embodiment, the microcontroller executes a specific algorithm in real time and / or uses a solution table of intermediate values ​​stored in memory to perform the first determination step.

[0062] The solution table lists the midpoint of each pair of d-axis and q-axis currents, e.g., as a function of at least rotational speed and reference setpoint torque, such that the motor torque is substantially equal to the reference setpoint torque and the inverter DC supply current at a virtual standstill is greater than the static regeneration threshold.

[0063] In fact, there are an infinite number of pairs of d-axis and q-axis currents that can ensure that the motor torque is substantially equal to the reference setpoint torque. Therefore, for each value of setpoint torque and rotational speed, it is possible to predict, by an algorithm, for example iteratively, a pair of d-axis and q-axis currents that can ensure that, in a virtual stationary state, the motor torque is substantially equal to the setpoint torque and the inverter DC supply current is greater than the static regeneration threshold.

[0064] For example, a solution table or a specific real-time algorithm needs to solve the following simultaneous equations, where only solutions that provide negative d-axis current intermediate values ​​are considered: [Number 8] TIFF2023181094000009.tif19157

[0065] C ref is the reference setpoint torque, expressed in N m, I qstat is the q-axis current intermediate value, I dstat is the d-axis current median value, Ψ is the magnetic flux of the electric motor, denoted as Wb, L d , L q is the d-axis inductance (H) or q-axis inductance (H) of the electric motor, V DC is the inverter supply voltage, expressed in volts, R ac is the total equivalent resistance (Ω) of the AC side of the motor system, P is the number of pole pairs of the electric motor, Ω is the motor rotation speed, rad·s -1 is expressed as k is the coefficient that converts between uvm and dq (for example, 3 / 2 or 1, depending on the chosen convention).

[0066] I DCstatmin is the static regeneration threshold.

[0067] According to one embodiment, the solution table or specific real-time algorithm is a function of parameters selected from the supply voltage of the inverter and the temperature of the electric motor.

[0068] The d-axis current median value and the q-axis current median value are highly dependent on the inverter supply voltage and / or the motor temperature, so the solution table or specific real-time algorithms may also take these parameters into account.

[0069] According to one embodiment, the solution table is set by considering the minimum supply voltage of the inverter and the minimum temperature of the motor.

[0070] The minimum inverter supply voltage is the lowest possible inverter supply voltage of the inverter.

[0071] The minimum motor temperature is the lowest possible temperature for the motor system under consideration.

[0072] According to one embodiment, the d-axis current median value and the q-axis current median value are determined by interpolation of a solution table or by calculation of a specific real-time algorithm.

[0073] Low or zero reluctance (L d =L q ), this system is so simple to solve that real-time implementation is chosen over interpolation with a solution table.

[0074] According to one embodiment, the second determination step receives as input the equivalent amplitude of the motor's current system achieved during the previous evaluation and / or the current evaluation, regardless of its phase.

[0075] The equivalent amplitude of the three-phase current system is, for example, squared, regardless of its phase. The second step focuses on the dynamic aspects, such as controlling the magnetizing / demagnetizing forces of the stator windings and therefore on the assumption of current variations.

[0076] For example, the d-axis current intermediate value is modified in the second determination step as a function of the motor AC supply current target value achieved during the previous evaluation, the dynamic regeneration threshold, a characteristic quantity of the magnetic behavior, e.g., the inductance of the motor, and the dynamic d-axis current maximum value, including the time elapsed since the previous evaluation.

[0077] The dynamic d-axis current maximum corresponds to the maximum value of the d-axis current allowed to control the decay of the AC supply current of the motor without disturbing the q-axis current target value.

[0078] The dynamic d-axis current maximum value is set to 0 or less.

[0079] For example, the dynamic d-axis current maximum value can be expressed by the following equation: [Number 9] TIFF2023181094000010.tif1197

[0080] C corr is the maximum dynamic d-axis current value, I DCdynmin is the dynamic regeneration threshold, I 2 qstat is the q-axis current intermediate value, I 2 ciblepre is the motor AC supply current target achieved during the previous evaluation, V DC is the inverter supply voltage, expressed in volts, t e is the time since the last evaluation, L is the inductance of the motor.

[0081] k is the coefficient that converts between uvm and dq (for example, 3 / 2 or 1, depending on the chosen convention).

[0082] It should be noted that a negative value in the root means that the maximum dynamic d-axis current is zero.

[0083] According to one embodiment, the first determination step comprises an evaluation phase in which a comparison of the logical regeneration current is performed against a global regeneration threshold.

[0084] This comparison is performed from the motor rotational speed, inverter supply voltage, d-axis current reference value, and optionally a reference setpoint torque or q-axis current reference value, one of which is derived directly from the other once the d-axis current reference value is set, for example, according to the following equation (Equation 10):

[0085] If the comparison in the evaluation phase satisfies the condition, the d-axis current reference value becomes the d-axis current median value, and the q-axis current reference value becomes the q-axis current median value.

[0086] If the conditions of the evaluation phase are not met, the d-axis current reference and the q-axis current reference are modified as per step 1 continuation. [Number 10] TIFF2023181094000011.tif12155

[0087] k is the coefficient that converts between uvm and dq (e.g., 3 / 2 or 1, depending on the chosen convention); V DC is the inverter supply voltage, expressed in volts, R ac is the total equivalent resistance (Ω) of the AC side of the motor system, P is the number of pole pairs of the electric motor, Ω is the motor rotation speed, rad·s -1 is expressed as I qstat is the q-axis current intermediate value, Ψ is the magnetic flux of the electric motor, denoted as Wb, L d , L q is the d-axis inductance (H) or q-axis inductance (H) of the electric motor, I DCstatmin is the static regeneration threshold, I dref is the d-axis current reference value, expressed in amperes, I qrefis the q-axis current reference value, expressed in amperes.

[0088] The invention also relates to a power steering system comprising at least one motor controlled by the method according to the invention. [Brief explanation of the drawings]

[0089] The invention will be better understood from the following description of some embodiments according to the invention, given as non-limiting examples and illustrated with reference to the attached schematic drawings, in which: FIG. [Figure 1] FIG. 1 is a schematic diagram of a power steering system equipped with the method according to the invention. [Figure 2] FIG. 2 is a diagram of the method according to the invention. DETAILED DESCRIPTION OF THE INVENTION

[0090] The object of the steering system 1 of the vehicle 2 is to enable the driver to control the path of the vehicle by changing the steering angle of the vehicle's wheels 10, 11 via the steering wheel 3. The steering angle of the wheels is particularly related to the angle θ3 of the steering wheel 3. The driver changes the angle θ3 of the steering wheel 3 by applying a force T3 to the steering wheel (hereinafter referred to as "steering wheel torque"). This force T3 applied to the steering wheel can be measured by a torque sensor 23.

[0091] In general, the steering system 1 comprises several elements, including the steering wheel 3, a rack 6, and two wheels 10, 11 connected to tie rods 8, 9, respectively. The rack 6 is a part that allows the wheels 10, 11 to be manipulated, i.e., the angle of the wheels 10, 11 to be changed via the tie rods 8, 9. The rack 6 converts variations in the angle of the steering wheel 3 into variations in the angle of the wheels 10, 11 of the vehicle.

[0092] The electric power steering system 1 is particularly adapted to have a reference setpoint torque C applied by the electric motor 12. ref The motor 12 includes at least one microcontroller 20 that determines the reference setpoint torque C ref Based on the reference set torque C ref is determined as a function of various parameters received by the microcontroller 20 in a manner known to those skilled in the art, in particular the force T3 applied to the handle 3.

[0093] The electric motor 12 is preferably an electric motor with two directions of operation, and is preferably a synchronous rotary electric motor of the brush or brushless type.

[0094] The invention applies, for example, to the electric motor 12 of a mechanical power steering system (i.e., typically with a mechanical link created by a steering column 4 meshing with a rack 6 by means of a steering pinion 5, the rack 6 itself being guided for translational movement in a casing 7 fixed to the vehicle 2), or to an electric power steering system (not shown) without a mechanical link (known as "steer-by-wire", in which the steering wheel is mechanically separated from the rack).

[0095] In the case of mechanical power steering, the electric motor 12 may either mesh directly with the steering column 4 itself, to form a so-called "single pinion" mechanism, or with the steering rack 6 via a gear reducer type reducer, for example, by means of a second pinion 13 separate from the steering pinion 5, which allows the steering column 4 to mesh with the rack 6, to form a so-called "double pinion" mechanism, as shown in FIG. 1.

[0096] More particularly, the present invention relates to a method for controlling a synchronous electric motor 12, which may be an electric motor 12 in a steering system or other application, as shown in FIG.

[0097] The electric motor 12 is fed with AC supply current from an inverter, which is driven by a microcontroller 20 using vector control techniques.

[0098] The inverter operates at a supply voltage V DC DC supply current I of the inverter with DC is electrically supplied. This inverter controls the d-axis current target value I dcible and q-axis current target value I qcible The motor torque T12 is the torque actually provided by the motor 12. The motor torque T12 depends on the AC supply current of the motor 12. The user of the motor 12 may determine whether the motor torque T12 is greater than the reference setpoint torque C ref We try to ensure that the

[0099] In the following, by motor system it should be understood to mean all the elements that allow the control of the electric motor 12. This motor system includes in particular the motor-inverter assembly and the microcontroller 20.

[0100] This method is shown in Figure 2, where the d-axis current reference value I dref and q-axis current reference value I qref But at least, Reference torque setting C ref the rotational speed Ω of the motor, and Inverter supply voltage V DC , A preliminary determination step E0 is determined as a function of

[0101] The purpose of the preliminary determination step E0 is to determine the reference setpoint torque C without the influence of the regenerative current. ref To obtain the d-axis current reference value I dref and q-axis current reference value I qrefFor example, it provides the highest efficiency at low speeds, according to the so-called "Maximum Torque Per Ampere" MTPA method, and at high speeds, where the electromotive force approaches the supply voltage of the inverter's DC supply current, a demagnetization strategy (flux weakening) can be implemented.

[0102] Then, the microcontroller 20 calculates the d-axis current intermediate value I of the AC supply current of the motor 12. dstat and q-axis current intermediate value I qstat but, Reference torque setting C ref or q-axis current reference value I qref , The rotation speed Ω of the motor 12, Inverter supply voltage V DC , Static Regeneration Threshold I DCstatmin , and d-axis current reference value I dref , , and then a first decision step E1 is carried out, which is determined as a function of

[0103] The first determination step E1 is to determine the components of the AC supply current of the motor, i.e., the d-axis current I, when the motor-inverter assembly is considered to be in a virtual rest state. dstat and q-axis current I qstat In other words, this method allows the motor 12 to assume a first value, called the intermediate value, for the reference setpoint torque C ref and find the intermediate value of the AC supply current of the motor in the virtual stationary state so as to guarantee that: [Number 11] TIFF2023181094000012.tif541

[0104] I DCstat is the DC supply current of the inverter at virtual quiescent condition, expressed in amperes, I DCstatmin is the static regeneration threshold, expressed in amperes.

[0105] Therefore, the intermediate value of the AC supply current of the motor 12 determined in the stationary state is the DC supply current I DC is the static regeneration threshold I DCstatmin In other words, this intermediate value allows the motor 12 to operate at a reference setpoint torque C ref On the other hand, the inverter DC supply current I DCstat is the static regeneration threshold I DCstatmin It is calculated as a function of parameters that allow us to guarantee that the

[0106] According to one embodiment, the microcontroller 20 executes a specific algorithm in real time and / or uses a solution table of intermediate values ​​stored in memory to carry out the first decision step E1.

[0107] This solution table shows that the motor torque T12 is essentially the reference set torque C ref and the DC supply current I of the inverter in the virtual stationary state is equal to DCstat is the static regeneration threshold I DCstatmin For example, at least the rotational speed Ω and the reference set torque C ref As a function of , the d-axis current I dstat and q-axis current I qstat The median value of each pair is listed.

[0108] In fact, the motor torque T12 is essentially the reference set torque C ref There are an infinite number of pairs of d-axis current and q-axis current that can be guaranteed to be equal to the set torque C ref and rotation speed Ω, in the virtual stationary state, the motor torque T12 is substantially equal to the reference set value torque C ref and the inverter DC supply current I DCstat is the static regeneration threshold I DCstatmin It is possible to predict by an algorithm, for example iteratively, the d-axis current and q-axis current pair that allows for the guarantee of being greater.

[0109] For example, a solution table or a specific real-time algorithm needs to solve the following simultaneous equations, where only solutions that provide negative d-axis current intermediate values ​​are considered: [Number 12] TIFF2023181094000013.tif19157

[0110] C ref is the reference setpoint torque, expressed in N m, I qstat is the q-axis current intermediate value, I dstat is the d-axis current median value, Ψ is the magnetic flux of the electric motor, denoted as Wb, L d , L q is the d-axis inductance (H) or q-axis inductance (H) of the electric motor, V DC is the inverter supply voltage, expressed in volts, R ac is the total equivalent resistance (Ω) of the AC side of the motor system, P is the number of pole pairs of the electric motor, Ω is the motor rotation speed, rad·s -1 is expressed as I DCstatmin is the static regeneration threshold, k is the coefficient that converts between uvm and dq (for example, 3 / 2 or 1, depending on the chosen convention).

[0111] According to one embodiment, the solution table or a specific real-time algorithm calculates the inverter supply voltage V DC , and the temperature of the electric motor 12.

[0112] d-axis current intermediate value I dstat and q-axis current intermediate value I qstat is the inverter supply voltage V DC and / or the temperature of the motor, so the solution table or a specific real-time algorithm may also take these parameters into account.

[0113] According to one embodiment, the solution table is set by considering the minimum supply voltage of the inverter and the minimum temperature of the motor.

[0114] The minimum inverter supply voltage is the lowest possible inverter supply voltage V DC is.

[0115] The minimum motor temperature is the lowest possible temperature of the motor system 12 under consideration.

[0116] According to one embodiment, the d-axis current intermediate value I dstat and q-axis current intermediate value I qstat is found by interpolation of a solution table or by a specific real-time algorithm.

[0117] According to one embodiment, the first decision step E1 is performed by comparing the logical regeneration current with a global regeneration threshold I DCmin It has an evaluation phase that is performed on

[0118] This comparison is based on the rotation speed Ω of the motor 12 and the inverter V DC supply voltage, d-axis current reference value I dref , and optionally, the d-axis current reference value I dref When the reference set torque C is set, one is directly derived from the other. ref or q-axis current reference value I qref Then, for example, it is executed by the following equation (Equation 13).

[0119] If the comparison in the evaluation phase satisfies the condition, the d-axis current reference value I dref is the d-axis current intermediate value I dstat and the q-axis current reference value I qref is the q-axis current intermediate value I qstat This becomes:

[0120] If the evaluation phase condition is not met, the d-axis current reference value I dref and q-axis current reference value I qref is modified as a continuation of step 1. [Number 13] TIFF2023181094000014.tif9154

[0121] k is the coefficient that converts between uvm and dq (e.g., 3 / 2 or 1, depending on the chosen convention); V DC is the inverter supply voltage, expressed in volts, R ac is the total equivalent resistance (Ω) of the AC side of the motor system, P is the number of pole pairs of the electric motor, Ω is the motor rotation speed, rad·s -1 is expressed as I qstat is the q-axis current intermediate value, Ψ is the magnetic flux of the electric motor, denoted as Wb, L d , L q is the d-axis inductance (H) or q-axis inductance (H) of the electric motor, I DCstatmin is the static regeneration threshold, I dref is the d-axis current reference value, expressed in amperes, I qref is the q-axis current reference value, expressed in amperes.

[0122] Thereafter, the microcontroller 20 sets the d-axis current target value I dcible and q-axis current target value I qcible but, d-axis current intermediate value I dstat , q-axis current intermediate value I qstat , and Dynamic Regeneration Threshold I DCdynmin , A second decision step E2 is carried out, in which the value is determined as a function of

[0123] In a second determination step E2, for each component of the AC supply current of the motor, the d-axis current intermediate value I dstat , q-axis current intermediate value I qstat , and dynamic regeneration threshold IDCdynmin In other words, this method allows the motor 12 to assume a second value, called the target value, as a function of the reference setpoint torque C ref and the inverter DC supply current I DC is the global regeneration threshold I DCmin To achieve the above, the target AC supply current value of the motor given to the motor 12 is determined by, in particular, ensuring the following equation: [Number 14] TIFF2023181094000015.tif641

[0124] I DCdyn is the DC supply current of the inverter in the virtual dynamic state, expressed in amperes, I DCdynmin is the dynamic regeneration threshold, expressed in amperes.

[0125] According to one embodiment, the second determination step E2 receives as input the equivalent amplitude of the motor's current system achieved during the previous evaluation and / or the current evaluation, regardless of its phase.

[0126] The equivalent amplitude of the three-phase current system is, for example, squared, regardless of its phase. The second step focuses on the control of the magnetizing / demagnetizing forces of the stator windings, and therefore on the dynamic aspects of current changes. For example, the d-axis current intermediate value I dstat is the AC supply current target value of motor 12 achieved during the previous evaluation, and the dynamic regeneration threshold I DCdynmin , the characteristic quantities of the magnetic behavior, e.g., the inductance of the motor, and the maximum dynamic d-axis current C, including the time elapsed since the previous evaluation corr is modified in a second decision step E2 as a function of

[0127] The dynamic d-axis current maximum corresponds to the maximum value of the d-axis current allowed to control the decay of the AC supply current of the motor without disturbing the q-axis current target value.

[0128] The dynamic d-axis current maximum value is set to 0 or less.

[0129] For example, the maximum dynamic d-axis current C corr can be expressed, for example, by the following formula: [Number 15] TIFF2023181094000016.tif1195

[0130] C corr is the maximum dynamic d-axis current value, I DCdynmin is the dynamic regeneration threshold, I 2 qstat is the q-axis current intermediate value, I 2 ciblepre is the motor AC supply current target achieved during the previous evaluation, V DC is the inverter supply voltage, expressed in volts, t e is the time since the last evaluation, k is the coefficient that converts between uvm and dq (e.g., 3 / 2 or 1, depending on the chosen convention); L is the inductance of the motor.

[0131] It should be noted that a negative value in the root means that the maximum dynamic d-axis current is zero.

[0132] According to one embodiment, the first determining step E1 and / or the second determining step E2 comprises: Total equivalent resistance on the AC side R ac , The d-axis inductance L of the electric motor 12 d and / or q-axis inductance L q , the magnetic flux Ψ of the electric motor 12, the number of pole pairs p of the electric motor 12, and Maximum allowable AC supply current for the motor, The method receives as input at least one parameter selected from:

[0133] Finally, the microcontroller 20 controls the inverter to set the d-axis current target value Idcible and q-axis current target value I qcible Based on this, a driving step EP driven by a vector control method is executed.

[0134] According to the method of the present invention, the d-axis current target value I dcible and q-axis current target value I qcible is applied to the motor 12, while the motor 12 is supplied with a reference setpoint torque C ref On the other hand, the inverter DC supply current I DC is the global regeneration threshold I DCmin The AC supply current of the motor is determined in two successive main steps to allow the motor current to be greater than .

[0135] Global Regeneration Threshold I DCmin corresponds to the maximum level of regenerative current that can be generated by the motor-inverter assembly, regardless of the operating state of the motor. In other words, the inverter DC supply current I DC is the global regeneration threshold I DCmin Global Regeneration Threshold I DCmin is the inverter DC supply current I DC Therefore, this method sets the motor torque T12 to the reference set torque C ref This allows for limiting the level of regenerative current generated by the motor-inverter assembly without requiring additional components while maintaining the regenerative current substantially equal to

[0136] Static Regeneration Threshold I DCstatmin and dynamic regeneration threshold I DCdynmin The global regeneration threshold I corresponds to the sum of DCmin is logically chosen to be less than or equal to 0 A so as to control the amount of regenerative current that can be generated without inducing forced consumption of the motor, which would then correspond to a positive value. However, this scenario is also technically feasible. Thus, a global regenerative threshold of less than or equal to 0 A corresponds to little or no regenerative current.

[0137] Static Regeneration Threshold I DCstatmin is selected by the user of the method. This is the inverter DC supply current I when the motor is in a virtual rest state, i.e., in a virtual state of force balance. DCstat In other words, in a virtual rest state, the motor-inverter assembly has no dynamics: the current in the motor is constant in phase and amplitude.

[0138] In a virtual stationary state, it can be written as follows: [Number 16] TIFF2023181094000017.tif571

[0139] P stat is the power of the motor-inverter assembly in quiescent mode, expressed in watts. This power P stat is positive when the motor-inverter assembly consumes energy and is negative when the motor-inverter assembly produces energy.

[0140] P loss is the power loss due to the Joule effect in the conductors of the motor-inverter assembly, such as the motor windings, the traces on the printed circuit board, and the MOSFETs. This Joule effect power loss P loss is always positive and is expressed in watts.

[0141] P mec is the mechanical power of the motor system, expressed in watts. This mechanical power P mec is positive when the reference motor torque and the rotational speed Ω have the same sign (i.e., positive or negative), and is negative when the reference motor torque and the rotational speed Ω have opposite signs (i.e., one positive and the other negative).

[0142] Thus, when the reference motor torque and rotational speed Ω have opposite signs, the power P of the motor system stat can be negative.

[0143] V DC is the inverter supply voltage, expressed in volts. DC is always positive.

[0144] I DCstat is the DC supply current of the inverter in quiescent condition, expressed in amperes. This DC supply current I DCstat is negative when the power is negative and positive when the power is positive.

[0145] Static Regeneration Threshold I DCstatmin is the DC supply current I of the inverter in the virtual stationary state DCstat corresponds to the lowest value allowed as

[0146] Static Regeneration Threshold I DCstatmin is chosen to be positive, zero, or negative depending on the margin chosen.

[0147] For a 12VDC supply system with a -8A absorption capacity, this threshold may be set to, for example, -4A, leaving a margin of 48W. For a 48VDC supply system with a -2A absorption capacity, this threshold may be set to, for example, -1A, also leaving a margin of 48W.

[0148] In situations where little or no regenerative current is required, this is negative.

[0149] Static Regeneration Threshold I DCstatmin is calculated as follows: [Number 17] TIFF2023181094000018.tif561

[0150] P loss is the power loss due to the Joule effect in the conductors of the motor-inverter assembly, P mec is the mechanical power of the motor system, expressed in watts, V DCis the inverter supply voltage, expressed in volts, I DCstatmin is the static regeneration threshold, expressed in amperes.

[0151] Dynamic Regeneration Threshold I DCdynmin is selected by the user of the method. This is the inverter DC supply current I when the motor 12 is in a virtual dynamic state, i.e., a virtual state in which only changes in the motor AC supply current are considered. DCdyn corresponds to the minimum acceptable value of

[0152] In the virtual dynamic state, it can be written as follows: [Number 18] TIFF2023181094000019.tif539

[0153] P dyn is the excitation power of the motor stator, expressed in watts. This excitation power P dyn is positive when the magnetic energy of the stator is increasing, i.e., while it is energized, and is negative when the magnetic energy of the stator is decreasing, i.e., while it is demagnetized.

[0154] V DC is the inverter supply voltage, expressed in volts.

[0155] I DCdyn is the DC supply current of the inverter in operation, expressed in amperes. This DC supply current I DCdyn is the excitation power P dyn When is negative, the excitation power P dyn is positive when is positive.

[0156] The dynamic regeneration threshold corresponds to the minimum value allowed for stator demagnetization in a hypothetical dynamic state, i.e., [Number 19] TIFF2023181094000020.tif646

[0157] P dynis the excitation power of the motor stator, expressed in watts, V DC is the inverter supply voltage, expressed in volts, I DCdynmin is the dynamic regeneration threshold, expressed in amperes, Dynamic Regeneration Threshold I DCdynmin is chosen to be negative.

[0158] The general principle of the method is that in a first determination step E1, the DC supply current I of the inverter is determined. DCstat In particular, the static regeneration threshold I DCstatmin The AC supply current of the motor in the virtual stationary state is calculated so that the DC supply current I of the inverter in the virtual dynamic state is calculated. DCdyn is the dynamic regeneration threshold I DCdynmin The d-axis current intermediate value I of the AC supply current to the motor 12 in the virtual rest state is dstat is changed only when necessary. Therefore, the q-axis current intermediate value I qstat is the q-axis current target value I qcible In fact, since the motor torque T12 is mainly controlled by the q-axis current, it is not possible to change the value of this q-axis current without changing the motor torque T12. However, it is possible to at least partially offset the regenerative current generated by the decrease in the q-axis current by the simultaneous increase in the d-axis current, which includes the sum of these two. Finally, in this way, the inverter DC supply current I DC is the global regeneration threshold I DCmin This is all that is required, that is, the following formula can be guaranteed. [Number 20] TIFF2023181094000021.tif683

[0159] I DC is the inverter's DC supply current, expressed in amperes, I DCdynmin is the dynamic regeneration threshold, expressed in amperes, I DCstatmin is the regeneration threshold, expressed in amperes, I DCmin is the global regeneration threshold, expressed in amperes.

[0160] Naturally, the invention is not limited to the embodiments described and represented in the attached drawings: modifications are still possible, in particular with regard to the configuration of the various elements or by substitution with technical equivalents, without departing from the scope of protection of the invention.

Claims

1. A method for controlling a synchronous electric motor supplied with AC current from at least one inverter, The inverter is driven by at least one microcontroller (20) using a vector control method. The above method is performed by the microcontroller (20), The above method at least, The intermediate value of the d-axis current of the AC supply current of the motor (12) (I dstat ) and the q-axis current intermediate value (I qstat ) but at least, Reference setting torque (C ref ) or q-axis current reference value (I qref ), The rotational speed (Ω) of the motor (12), The supply voltage (V) of the inverter DC ), Static regenerative threshold (I DCstatmin ), and, d-axis current reference value (I dref ), The first decision step (E1) is obtained as a function of, d-axis current target value (I dcible ), and q-axis current target value (I qcible ), are at least The intermediate value of the d-axis current (I dstat ), The intermediate value of the q-axis current (I qstat ), and, Dynamic regenerative threshold (I DCdynmin ), The second decision step (E2) is obtained as a function of, The at least one inverter sets the d-axis current target value (I dcible ) and the target value of the q-axis current (I qcible A drive step (EP) is driven by a microcontroller (20) based on the following: A method that includes [a certain feature].

2. The static regenerative threshold (I DCstatmin The method according to claim 1, wherein ) is selected to be positive, zero, or negative.

3. The aforementioned dynamic regenerative threshold (I DCdynmin The method according to claim 1, wherein ) is selected to be negative.

4. Global regenerative threshold (I DCmin ) is the static regenerative threshold (I DCstatmin ) and the dynamic regeneration threshold (I DCdynmin The method according to claim 1, which corresponds to the sum of )

5. The intermediate value of the q-axis current (I qstat ) is the q-axis current target value (I qcible The method according to claim 1, wherein the result is as follows.

6. The aforementioned d-axis current reference value (I dref ) and the q-axis current reference value (I qref ) is at least, The aforementioned reference set value torque (C ref ), The rotational speed (Ω) of the motor, and The supply voltage (V) of the inverter DC ), The preliminary decision step (E0) is obtained as a function of The method according to claim 1, comprising:

7. The first decision step (E1) and / or the second decision step (E2) are: The total equivalent resistance (R) on the AC side ac ), The d-axis inductance (L) of the electric motor (12) d ) and / or q-axis inductance (L q ), The magnetic flux (Ψ) of the electric motor (12), The number of pole pairs (p) of the electric motor (12), and The maximum allowable AC supply current of the motor, The method according to claim 1, which receives at least one system parameter selected from as input.

8. The method according to claim 1, wherein the microcontroller (20) executes a specific algorithm in real time and / or uses a resolution table of intermediate values ​​stored in memory to perform the first decision step (E1).

9. The method according to claim 1, wherein the second determination step (E2) is to receive as input the equivalent amplitude of the motor current system achieved between the previous evaluation and / or the current evaluation, regardless of its phase.

10. A power steering system comprising at least one motor (12) controlled by the method described in any one of claims 1 to 9.

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