Method for controlling an electrical machine driven by an inverter equipped with a plurality of switching arms

Abstract

The present invention relates to a method for controlling an electrical machine (EMF) driven by an inverter (OU) equipped with switching arms. The control is performed at a switching frequency. For this method, a regulation frequency is determined, and at this regulation frequency, a vector of N duty cycles for each switching arm is determined (PWM VECT). This vector is then demultiplexed (DMX) to determine a duty cycle for each switching arm at the switching frequency. The inverter (OU) is then controlled (MOD) by applying the demultiplexed duty cycles at the switching frequency. Figure 4 to be published

Description

Title of the invention: Method for controlling an electrical machine driven by an inverter provided with a plurality of switching arms Technical field

[0001] The present invention relates to a method for controlling a rotating electrical machine, preferably a synchronous electrical machine, for example of the synchro-reluctant or permanent magnet synchronous type.

[0002] The invention also relates to a control system implementing such a method.

[0003] It is known to use rotating electrical machines such as permanent magnet synchronous electrical machines or synchro-reluctant machines, in particular synchro-reluctant machines assisted by permanent magnets. Such electrical machines are, for example, used in the field of propulsion, for example for the generation of engine torques on board a vehicle such as a motor vehicle.

[0004] Document FR 3 051 296 A1 describes, for example, a synchro-reluctant machine assisted by permanent magnets.

[0005] In order to increase the power density of synchronous electrical machines in the field of transport, these operate at increasingly higher electrical frequencies and rotation frequencies. This increase in electrical frequency of the motors, controlled by power electronics whose microprocessors are subject to significant cost constraints and therefore computing power constraints, can lead to the appearance of limitations to the increase in "switching" frequency.

[0006] Indeed, the so-called "chopping" method (or Pulse Width Modulation, PWM) is based on the idea that a sinusoid (in this case the control voltage of an electrical machine) can be "chopped" into a series of constant values, as illustrated in [Fig.l]. [Fig.l] is a curve of the voltage Vc in V as a function of time T in ms. The curve Vref is the optimal sinusoidal voltage curve, and the curve Vrec is a voltage curve obtained by a chopping method that approximates the reference curve. It can be seen that the approximation of the reference curve depends on the chopping period.

[0007] Obviously, if the electrical frequency of an electrical machine increases, the number of values ​​per electrical period is reduced, which ultimately leads to obtaining currents in the motors which are strongly non-sinusoidal. generally considers that a factor of around 10 between the switching frequency and the electrical frequency of the motor is at least necessary for its control. Furthermore, the emergence of "wide band gap" power modules (or WBG, which can be translated as wide band semiconductor), which generate significantly fewer losses at each switching period, pushes to consider using even higher factors, of the order of 20 to 30. Finally, the targeted switching frequency can easily reach 30 to 50 kHz, which represents a challenge for microprocessors conventionally used, for example, in automobiles, which cannot normally cope with such a calculation frequency.

[0008] [Fig.2] illustrates an example of current labc in phases ab and c of an electrical machine at A as a function of time T in ms. [Fig.2] concerns a three-phase electrical machine operating at an electrical frequency of 1.5 kHz in the case of a switching frequency of 10 kHz. The curve Iaref corresponds to the reference sinusoidal curve for the current in phase a, and the curve Iarec corresponds to the sinusoidal curve obtained by a switching frequency for the current in phase a. The curve Ibref corresponds to the reference sinusoidal curve for the current in phase b, and the curve Frec corresponds to the sinusoidal curve obtained by a switching frequency for the current in phase b. The curve Lref corresponds to the reference sinusoidal curve for the current in phase c, and the curve Icrec corresponds to the sinusoidal curve obtained by a switching frequency for the current in phase c.

[0009] [Fig.3] illustrates an example of current labc in the phases of an electrical machine at A as a function of time T in ms for an electrical machine operating at an electrical frequency of 1.5 kHz in the case of a switching frequency of 50 kHz. The curve Iaref corresponds to the reference sinusoidal curve for the current in phase a, and the curve Iarec corresponds to the sinusoidal curve obtained by a switching frequency for the current in phase a. The curve Ibref corresponds to the reference sinusoidal curve for the current in phase b, and the curve Ibrec corresponds to the sinusoidal curve obtained by a switching frequency for the current in phase b. The curve Icref corresponds to the reference sinusoidal curve for the current in phase c, and the curve Icrec corresponds to the sinusoidal curve obtained by a switching frequency for the current in phase c.

[0010] It is noted that the sinusoid is better reconstructed with a high switching frequency. The distortions of the sinusoidal signal for lower switching frequencies generate an increase in losses in the electrical machine, or even a loss of control of the system. Prior art

[0011] In order to be able to operate at high switching frequencies, one solution could be to change the microprocessor to use a more efficient one, capable of executing all the control calculations at a frequency of 50 kHz. However, this replacement of the microprocessor involves a significant increase in cost.

[0012] Patent application DE102015214839 describes a method for discrete-time regulation of an electrical machine, in which a regulation frequency is set separately from the switching frequency, and in which a pulse model is determined for several time steps. However, this patent application remains theoretical and does not describe the concrete implementation of such a method within a control method. Summary of the invention

[0013] The aim of the invention is to concretely control an electrical machine while reducing the losses of an electrical machine, and in an inexpensive manner. For this purpose, the present invention relates to a method for controlling an electrical machine driven by an inverter provided with switching arms. The control is carried out at a switching frequency. For this method, a regulation frequency is determined, and at this regulation frequency, a vector of N duty cycles of each switching arm is determined, then a demultiplexing of this vector is carried out to determine a duty cycle of each switching arm at the switching frequency. The inverter is then controlled by applying the demultiplexed duty cycles to the switching frequency.The use of a regulation frequency lower than the switching frequency makes it possible to carry out regulation at a suitable frequency without changing the microprocessor, and the determination of the vector of N duty cycles then the demultiplexing step carried out at the switching frequency makes it possible to concretely determine the control of the inverter at high frequency, which makes it possible to reduce the losses of the electrical machine.

[0014] Furthermore, the invention relates to a control system implementing such a control method.

[0015] The invention relates to a method for controlling an electrical machine driven by an inverter provided with a plurality of switching arms, said control method being designed to drive said inverter at a switching frequency. For this method, the following steps are implemented: a. A regulation frequency is determined such that said switching frequency is proportional to the regulation frequency, a coefficient of proportionality between said switching frequency and said regulation frequency being an integer; b. At said regulation frequency, N duty cycles of each switching arm of said inverter are determined by a pulse width modulation method, said number N of duty cycles being equal to said proportionality coefficient; c. A demultiplexing of said N determined duty cycles is carried out to determine a duty cycle of each switching arm of said inverter at said switching frequency; and d. Each switching arm of said inverter is controlled by applying to said switching frequency said duty cycle determined by said demultiplexing.

[0016] Advantageously, said coefficient of proportionality is variable.

[0017] According to one embodiment, said N duty cycles of each switching arm are determined from voltage setpoints.

[0018] Advantageously, said voltage setpoints are determined from current setpoints at said regulation frequency.

[0019] Preferably, said current setpoints are determined from at least one torque setpoint and / or one rotation speed setpoint.

[0020] According to one aspect, the currents in each phase of said electrical machine are measured, and a Park transform is applied to said currents measured in each phase of said electrical machine, and said voltage setpoints are determined as a function of the measured currents expressed in the Park frame.

[0021] According to one implementation, the mechanical rotation speed of said electrical machine is measured by means of an angular position sensor or a rotation speed sensor, and said N cyclic ratios are determined by taking into account said angular position of the rotor of said electrical machine.

[0022] According to one embodiment, for the determination of each of the N determined duty cycles, an inverse Park transform is implemented for which the position of the rotor is determined by means of the following formula:

[0023] With k the number of the duty cycle concerned: k is between 0 and Nl, the position of the rotor, / / ( / ) the position of the rotor of the electrical machine measured or estimated at the start of the regulation period, a) the electrical rotation speed of the rotor of the electrical machine, Tpwm the switching period determined by means of the switching frequency.

[0024] According to one configuration, said method comprises a step of injecting voltage harmonics.

[0025] Furthermore, the invention relates to a control system for an electrical machine comprising an inverter provided with switching arms, a computer and a memory configured to implement the steps of the control method according to one of the preceding claims, preferably said electrical machine is a synchronous-reluctant machine assisted by permanent magnets or a synchronous machine with permanent magnets.

[0026] According to one implementation, each switching arm of said inverter comprises at least one wideband WBG semiconductor.

[0027] Other characteristics and advantages of the method according to the invention will appear on reading the following description of non-limiting examples of embodiments, with reference to the appended figures described below. List of figures

[0028] [Fig.l]

[0029] [Fig.l], already described, illustrates sinusoidal voltage curves respectively of reference and obtained by a cutting method.

[0030] [Fig.2]

[0031] [Fig.2], already described, illustrates sinusoidal current curves in the reference phases and those obtained by a cutting method.

[0032] [Fig.3]

[0033] [Fig. 3], already described, illustrates sinusoidal current curves in the reference phases respectively and obtained by a cutting method.

[0034] [Fig.4]

[0035] [Fig.4] illustrates a control system for implementing the control method according to the invention.

[0036] [Fig.5]

[0037] [Fig.5] illustrates a control system for implementing the method according to one embodiment of the invention.

[0038] [Fig.6]

[0039] [Fig.6] illustrates the step of determining N duty cycles.

[0040] [Fig.7]

[0041] [Fig.7] illustrates the demultiplexing step for determining the duty cycles.

[0042] [Fig. 8]

[0043] [Fig.8] illustrates the step of opening and closing the switches of the switching arms. Description of the embodiments

[0044] In [Fig.4] is shown, schematically and in a non-limiting manner, an installation comprising an associated rotating electrical machine MEL, for its control, to a COM control system according to the invention (the COM control system implementing the control method according to the invention). The installation also comprises a DC source of electrical energy, such as a direct voltage bus.

[0045] The rotating electrical machine MEL is a rotating machine with several phases, preferably three phases (alternatively the electrical machine may comprise a number of phases that is a multiple of three, for example six, nine or twelve, or else four or five phases). Advantageously, the rotating electrical machine MEL may be a synchronous electrical machine. Preferably, the synchronous electrical machine MEL may be a permanent magnet or synchro-reluctant synchronous electrical machine, in particular a three-phase synchro-reluctant rotating machine assisted by permanent magnets.

[0046] For the illustrated example (non-limiting), the synchronous electric machine MEL has three inputs. Each input corresponds to a phase of a stator (not shown) of the rotating electric machine MEL.

[0047] The control system COM is intended to control, over time, the power supply of the rotating machine MEL as a function of target values ​​and / or measured values ​​of predetermined quantities. These target values ​​and / or measured values ​​are referred to in the remainder of the description as operating variables of the electrical machine. For the method and the system according to the invention, the control system COM takes into account a torque setpoint Cem* (which can conventionally come from a request from the user of the electrical machine, alternatively this torque setpoint can be calculated by speed regulation), and / or at least one other operating variable VAF which can be a measurement or a setpoint.An operating variable of the electric machine is a quantity that characterizes the operation of the electric machine. This may include an electrical variable, such as the voltage, current, or power of the electric machine, a mechanical variable such as the position, speed, or acceleration of the rotor of the electric machine, etc. The operating variables may, for example, be the electrical rotation speed coe of the rotor (not shown) of the electric machine (alternatively, this variable may also be the norm of the magnetic flux in the phases), the voltage amplitude of the electric machine, the current amplitude of the electric machine, a temperature of the electric machine, etc. It is recalled that the electrical rotation speed coe of the rotor corresponds to the multiplication of the mechanical rotation speed com of the rotor by the number of pairs of poles of the synchronous electric machine MEL.In other words, we can write: coe=p.com with p the number of pairs of poles of the synchronous electric machine MEL. This electrical rotation speed makes it possible to determine the frequency. electric of the electric machine.

[0048] The COM control system comprises an OND inverter and a CAL computer. The COM control system can use, if necessary, a CAP sensor for the angular position and / or angular rotation speed of the rotor of the MEL electrical machine. Such a sensor makes it possible to determine the angular rotation speed com of the electrical machine either directly (in the case of a speed sensor) or by derivation (in the case of the position sensor). In addition, the COM control system can comprise means for measuring the currents (not shown) in the phases of the electrical machine, for example current sensors.

[0049] The inverter OND is configured to route electrical energy between the DC source and the synchronous electric machine MEL. More specifically, the inverter OND is configured to route electrical energy between the DC source and each phase of the stator of the synchronous electric machine MEL. The DC source (for example a battery) provides a DC bus voltage, denoted VDc-

[0050] The OND inverter comprises a first input connected to the DC source, and three outputs, each connected to a corresponding phase of the stator of the synchronous electrical machine MEL. The OND inverter further comprises a second input electrically connected to an output of the CAL computer, such that the OND inverter is configured to route electrical energy between the DC source and the synchronous electrical machine MEL according to a switching control signal applied by the CAL computer to the second input of the OND inverter.

[0051] Preferably, the switching control signal may be such that the inverter OND conveys electrical energy from the DC source to the synchronous electrical machine MEL so that the synchronous electrical machine MEL has an operation commonly called a "motor" and / or an operation commonly called a "generator". Conventionally, the inverter OND comprises several switching arms (not shown), preferably at least one switching arm for each phase of the electrical machine, to transform the DC signal from the DC source into an AC signal for the phases of the electrical machine MEL. Each switching arm comprises at least one controlled switch. Conventionally, each switch of the switching arms can be controlled by means of a pulse width modulation known by the acronym MLI (or PWM for Pulse Width Modulation).

[0052] The optional angular position or angular rotation speed sensor CAP can be configured to measure the angular mechanical position of a rotor (not shown) of the synchronous electrical machine relative to the stator (not shown), and to deliver an angular position signal (respectively angular rotation speed) representative of the measured value of the angular position (respectively of the angular rotation speed) of the rotor of the synchronous electric machine.

[0053] Furthermore, the optional CAP angular position or angular rotation speed sensor can be configured to apply the angular position (respectively angular rotation speed) signal to a corresponding input of the CAL computer.

[0054] The method for controlling an electrical machine according to the invention is designed to control an inverter at a predefined switching frequency (constant or variable, for example depending on the rotational speed of the rotor of the electrical machine), the inverter comprising a plurality of switching arms. It is recalled that a frequency is defined by the number of periods per unit of time, and the period is the smallest duration during which a phenomenon is reproduced. The method for controlling an electrical machine comprises the following steps in real time: - Determining a regulation frequency, such that the switching frequency is proportional to the regulation frequency, a coefficient of proportionality between the switching frequency and the regulation frequency being an integer, - Determination, at the regulation frequency, of a regulation for N duty cycles of each switching arm of the inverter by a PWM pulse width modulation method, the number N of duty cycles determined being equal to the proportionality coefficient, - Carrying out a demultiplexing of the N determined duty cycles to determine a duty cycle of each switching arm of the inverter at the switching frequency, and - Control of each switching arm of the inverter by applying the demultiplexed duty cycle to the switching frequency.

[0055] Thus, the regulation of the currents of the electrical machine is implemented at a regulation frequency which is lower than the switching frequency. The use of a regulation frequency lower than the switching frequency makes it possible to carry out the regulation at a suitable frequency without changing the microprocessor, and the determination of the vector of N duty cycles then the demultiplexing step carried out at the switching frequency makes it possible to concretely determine the control of the inverter at high frequency, which makes it possible to reduce the losses of the electrical machine.

[0056] These steps can be implemented in particular by a computer and a computer memory dedicated to real times. These steps are detailed in the rest of the description.

[0057] [Fig. 5] illustrates, schematically and in a non-limiting manner, an installation comprising a rotating electrical machine MEL associated, for its control, with a COM control system according to one embodiment of the invention (the COM control system implementing the control method according to the invention). [Fig. 5] is an exemplary embodiment of the control system of [Fig. 4]. Other implementations of the system of [Fig. 4] can be carried out without departing from the scope of the invention (for example the embodiments described in patent applications WO2021 / 259662 and WO2022 / 078778 or in patent applications bearing the filing numbers FR21 / 13962 and FR22 / 00475). Elements identical to [Fig. 4] are not redescribed.

[0058] The CAL calculator uses current measurements ia, ib, ic in the phases of the electrical machine MEL. In addition, the CAL calculator comprises: - Means for determining CONS the current setpoints idsP and iqsP, in particular from the torque setpoint Cem* and the setpoint of the operating variable VAF, - REG regulation means implemented at the regulation frequency with: • PARK transformation means in the Park reference frame of the measured currents, to determine measured currents expressed in direct current idmes and the quadrature current iqmes (as a reminder: the so-called “direct” and “quadrature” currents and voltages, also called “quadratic(s)”, are currents and voltages expressed in a rotating reference frame linked to the rotor), the PARK transformation means can also depend on a measurement of the angular position 0 of the rotor of the electrical machine, which can be obtained by a CAP sensor, • Means for determining FOC the voltage setpoints v / p and vq sp, in particular from the current setpoints i / p and iqsP, and the measured currents expressed in the Park reference system idmes and iqmes, • Means for vectorizing the PWM pulse width modulation VECT as a function of the voltage setpoints v / p and vqsP, the means for vectorizing the pulse width modulation determine N duty cycles Ta(k), Tb(k), Tc(k) for each switching arm (with k being from 0 to Nl), the means for vectorizing the PWM pulse width modulation VECT can also depend on a measurement of the angular position 0 of the rotor of the electrical machine, which can be obtained by a CAP sensor, these means implement step 2 described below, - DMX demultiplexing means of the N cyclic ratios determined by the means for vectorizing the PWM pulse width modulation VECT, to determine a duty cycle of each switching arm T abc at the switching frequency, these means implement step 3 described below, - Means for controlling MOD of the switches of the switching arms of the OND inverter at the switching frequency, to determine the states of the switches ga, gb, gc from the duty cycle of each switching arm Tabc- 1) Determination of the regulation frequency

[0059] During this step, a regulation frequency is determined, such that the switching frequency is proportional to the regulation frequency. For this proportionality, the proportionality coefficient (i.e. the ratio between the switching frequency and the regulation frequency) is an integer. The regulation frequency is the frequency at which the regulation steps are implemented: for example the Park transform steps, the voltage setpoint determination steps, etc. Thus, these regulation steps are not carried out at the switching frequency. It is therefore possible to increase the switching frequency to limit losses, without implementing a specific computer with a specific microprocessor.

[0060] We can write the following formula:

[0061] f,k, = K^frv

[0062] With fdec the switching frequency, K the coefficient of proportionality with K integer, and freg the regulation frequency.

[0063] According to an implementation of the invention, the coefficient of proportionality can be variable. Thus, it is possible to have the maximum amplitude of variation of the effective cutting.

[0064] According to one embodiment, when it is variable, K can vary between 1 and 10, preferably between 2 and 5. When it is constant, K can be chosen between 2 and 10, preferably between 2 and 5.

[0065] By way of non-limiting example, the regulation frequency may be between 5 and 15 kHz, and the switching frequency between 5 and 60 kHz.

[0066] 2) Determination of the vector of N cyclic ratios

[0067] In this step, N duty cycles of each switching arm are determined at each period of the regulation frequency by a pulse width modulation method. A duty cycle is the ratio of the closing time of a switch of the switching arm to the switching period. Each duty cycle is determined by the pulse width method to form a sinusoidal signal. The number N of duty cycles is equal to the coefficient of proportionality between the switching frequency and the regulation frequency. Thus, in this step, a vector is determined which contains N consecutive values ​​of the duty cycles for each switching arm. In this way, all the consecutive duty cycles of the switches in the regulation period are determined. In other words, the vector includes a number of values ​​that corresponds to the multiplication of N by the number of switching arms of the inverter (which corresponds to the number of phases of the electrical machine). Within this vector, each value is identified with the switching arm concerned as well as the switching period concerned within the regulation period.

[0068] According to one embodiment, the angular position of the rotor of the electrical machine can be measured by means of an angular position sensor or a rotation speed sensor. Alternatively, the angular position of the rotor of the electrical machine can be estimated by means of an estimator; such an estimator can depend in particular on the voltage and / or current setpoints and / or measured voltages and / or currents.

[0069] For either of the implementations described above, the N duty cycles can be determined by taking into account said angular position of the rotor of said electrical machine. Thus, the position of the rotor can be determined at each switching period within the regulation period, and the determination of the N duty cycles can then be adjusted to the angular position of the rotor.

[0070] According to an implementation of the invention, for the determination of each of the N determined duty cycles, N inverse Park transforms can be implemented to determine the rotating reference frame linked to the rotor (the Park reference frame). In this way, the duty cycles adapted to each of the N duty cycles can be applied. In this case, the position of the rotor of the electrical machine can be determined by means of the following formula:

[0071] 9k=0(t)+ür^Tpwm

[0072] With k the number of the duty cycle concerned: k is between 0 and Nl, 0 the position of the rotor, 0( / ) the position of the rotor of the electrical machine measured or estimated at the start of the regulation period, M the electrical rotation speed of the rotor of the electrical machine, Tpwm the switching period determined by means of the switching frequency.

[0073] [Fig. 6] illustrates, schematically and in a non-limiting manner, the duty cycles determined at the regulation frequency for an example of application of the method according to the invention. The duty cycles are indicated Ti / Tpwm, with i representing one of the phases of the electrical machine. For the example, i can be chosen by the three phases a, b and c of the electrical machine (corresponding to the arms of the inverter). For this example, the proportionality coefficient, and a fortiori the number N, are equal to 5. Thus, the regulation period Treg is equal to 5 switching periods Tpwm. For better readability of the figure, the regulation period Treg starts at 0.1 ms. At this time, a vector of the N duty cycles of each phase is determined. This vector includes the duty cycles of phase a for the N switching periods of the regulation period, these duty cycles are noted Ta(0) to Ta(4) and the values ​​are represented by continuous segments. This vector also includes the duty cycles of phase b for the N switching periods of the regulation period, these duty cycles are noted Tb(0) to Tb(4) and the values ​​are represented by dotted segments.This vector also includes the cyclic ratios of phase c for the N cutting periods of the regulation period, these cyclic ratios are noted Tc(0) to Tc(4) and the values ​​are represented by discontinuous segments having an alternation of dashes and dots.

[0074] According to one implementation, the pulse width modulation function may comprise the injection of voltage harmonics to compensate for current or torque harmonics. For this implementation, a criterion may be to predict, in particular in open loop, at the time horizon of the regulation period, the desired harmonic compensation. 3) Demultiplexing

[0075] During this step, a demultiplexing of the N duty cycles determined in step 2 is carried out, to determine at the switching frequency a duty cycle of each switching arm of the inverter. The demultiplexing consists of distributing on a channel successively in time signals (here each switching arm) having previously been grouped (in this case within a vector of N duty cycles). In other words, for each period of the switching frequency (within the regulation frequency) and for each switching arm, a duty cycle is determined from the vector of the N duty cycles. This step is implemented at the switching frequency, consequently at a frequency higher than the regulation frequency.In other words, at each cutting period and for each switching arm, we identify within the vector of N duty cycles the duty cycle which corresponds to the cutting period considered and to the switching arm considered.

[0076] [Fig.7] illustrates, schematically and in a non-limiting manner, the duty cycles Ti / Tpwm of each switching arm as a function of time T in ms. [Fig.7] corresponds to the example of [Fig.6]. The duty cycles are indicated Ti / Tpwm, with i representing one of the phases of the electrical machine. For the example, phase i can be chosen from the three phases a, b and c. For this example, the co efficient proportionality, and a fortiori the number N, are worth 5. Thus, the regulation period Treg is worth 5 cutting periods Tpwm. For better readability of the figure, the regulation period Treg starts at 0.1 ms. At this moment, a demultiplexing step of the vector of N duty cycles is applied. The demultiplexing step makes it possible to generate the duty cycles of phase a for the N cutting periods of the regulation period, these duty cycles are noted Ta(0) to Ta(4), and the values ​​are represented by continuous segments. This demultiplexing step also makes it possible to generate the duty cycles of phase b for the N cutting periods of the regulation period, these duty cycles are noted Tb(0) to Tb(4), and the values ​​are represented by dotted segments.This step also makes it possible to generate the cyclic ratios of phase c for the N cutting periods of the regulation period, these cyclic ratios are noted Tc(0) to Tc(4), and the values ​​are represented by discontinuous segments having an alternation of dashes and dots. 4) Inverter control

[0077] During this step, each switching arm of the inverter is controlled by applying to the switching frequency the duty cycle determined in step 3. This step is implemented at the switching frequency. In other words, an opening and / or closing instruction is applied to each switch of the switching arms so as to correspond to the determined duty cycle. In this way, the inverter generates a machine control current signal close to a sinusoidal signal.

[0078] According to one embodiment option, the control can be symmetrical (which corresponds to the conventional pulse width modulation method) or asymmetrical. Such an asymmetrical method allows two controls of the switches of the switching arms in a single switching period. An example of asymmetrical control is described in particular in paragraph 3.6 of the following document:

[0079] Holmes, Grahame. (2003). Draw Width Modulation for Power Converters: Principles and Practice.

[0080] The invention makes it possible to apply asymmetric control without increasing the regulation frequency.

[0081] [Fig.8] illustrates schematically and in a non-limiting manner, the opening and closing states gabc of the switches of phases a, b and c as a function of time T in ms for the examples of figures 6 and 7. For better readability, the states of the switches of the different phases are illustrated at different values. For phase a (curve ga), the switch is closed at the value 1.5 and open at the value 0.5. The closing time Ta corresponds to the duty cycle determined in the previous step multiplied by the switching period Tpwm. For phase b (curve gb), the switch is closed at the value 0.5 and opened at the value -0.5. The closing time Tb corresponds to the duty cycle determined in the previous step multiplied by the switching period Tpwm. For phase c (curve gc), the switch is closed at the value -0.5 and opened at the value -1.5. The closing time Tc corresponds to the duty cycle determined in the previous step multiplied by the switching period Tpwm.

[0082] Furthermore, the method according to the invention can implement the following steps (illustrated in particular in Figures 4 and 5, or in patent applications WO2021 / 259662 and WO2022 / 078778, or in patent applications bearing filing numbers FR21 / 13962 and FR22 / 00475), in real time: a. Current setpoints are determined by means of the calculator as a function of at least one torque setpoint and / or one rotation speed setpoint and / or one operating variable; b. Voltage setpoints are determined using the calculator from the determined current setpoints, at the regulation frequency; c. A vector of N duty cycles of the switching arms is determined at the regulation frequency as a function of the determined voltage setpoints; d. Demultiplexing is carried out at the switching frequency to generate the duty cycles of each switching arm, e. A switching control signal for the inverter is generated by means of the computer from the determined duty cycles, at the switching frequency; and f. The inverter is controlled by means of the generated switching signal.

[0083] Thus, the inverter can be controlled with a high switching frequency which limits losses, while maintaining the regulation steps at a lower regulation frequency, which limits the computing capacity requirements of the computer (in particular of the computer's microprocessor).

[0084] According to one embodiment of the invention, the currents in each phase of the electrical machine can be measured, and a Park transform can be applied to the measured currents. This Park transform can be implemented at the regulation frequency. This Park transform makes it possible to define the currents measured in the Park frame, which is a rotating frame linked to the rotor.

[0085] For this embodiment, the voltage setpoints can be determined as a function of the measured currents expressed in the Park frame. Thus, the step of determining the voltage setpoints can depend on the current setpoints and the measured currents.

[0086] Furthermore, the invention relates to a control system for an electrical machine synchronous comprising an inverter provided with switching arms, a computer and a memory configured to implement the steps of the control method according to any one of the preceding variants or according to any one of the combinations of preceding variants, to apply the switching frequency to the inverter, and to apply regulation to the regulation frequency.

[0087] Preferably, the electrical machine may be a permanent magnet-assisted synchronous-reluctant machine or a permanent magnet synchronous machine.

[0088] Advantageously, the switching arms of the inverter may comprise wideband semiconductors of the WBG ("wide band gap") type power modules, which generate significantly fewer losses at each switching period. Indeed, the present invention allows a suitable switching frequency for these switches. Alternatively, the power modules may be of the IGBT or MOSFET type.

[0089] According to one implementation, the control system may in particular conform to the embodiment of Figures 4 and 5. However, the control system may be adapted to other embodiments, for example those described in patent applications WO2021 / 259662 and WO2022 / 078778, or in patent applications bearing filing numbers FR21 / 13962 and FR22 / 00475.

[0090] As goes without saying, the invention is not limited to the embodiments described above as examples; on the contrary, it encompasses all variant embodiments.

Claims

Claims

1. Method for controlling an electrical machine (MEL) driven by an inverter (OND) provided with a plurality of switching arms, said control method being designed to drive said inverter (OND) at a switching frequency, characterized in that the following steps are implemented: a. A regulation frequency is determined such that said switching frequency is proportional to the regulation frequency, a coefficient of proportionality between said switching frequency and said regulation frequency being an integer; b. N duty cycles of each switching arm of said inverter are determined (PWM VECT) at said regulation frequency by a pulse width modulation method, said number N of duty cycles being equal to said coefficient of proportionality; c.A demultiplexing (DMX) of said N determined duty cycles is carried out to determine a duty cycle of each switching arm of said inverter at said switching frequency; and d. Each switching arm of said inverter (OND) is controlled (MOD) by applying to said switching frequency said duty cycle determined by said demultiplexing (DMX).

2. A control method according to claim 1, wherein said proportionality coefficient is variable.

3. Control method according to one of the preceding claims, in which said N duty cycles of each switching arm are determined (PWM VECT) from voltage setpoints.

4. Control method according to claim 3, in which said voltage setpoints (FOC) are determined from current setpoints at said regulation frequency.

5. Control method according to claim 4, in which said current setpoints (CONS) are determined from at least one torque setpoint and / or one rotation speed setpoint.

6. Control method according to one of claims 3 or 4, in which the currents in each phase of said electrical machine are measured, and a Park transform (PARK) is applied to said currents measured in each phase of said electrical machine, and said voltage setpoints are determined as a function of the measured currents expressed in the Park frame.

7. Control method according to one of the preceding claims, in which the mechanical rotation speed of said electrical machine is measured by means of an angular position sensor (CAP) or a rotation speed sensor, and said N cyclic ratios are determined (PWM VECT) by taking into account said angular position of the rotor of said electrical machine.

8. Control method according to one of the preceding claims, in which for the determination of each of the N determined duty cycles, an inverse Park transform is implemented for which the position of the rotor is determined by means of the following formula: 3k = 3 ( t ) + of*k*Tpwm With k the number of the duty cycle concerned: k is between 0 and Nl, G the position of the rotor, 3(t) the position of the rotor of the electrical machine measured or estimated at the start of the regulation period, w the electrical rotation speed of the rotor of the electrical machine, Tpwm the switching period determined by means of the switching frequency.

9. Control method according to one of the preceding claims, wherein said method comprises a step of injecting voltage harmonics.

10. System for controlling an electrical machine (MEL) comprising an inverter (OND) provided with switching arms, a computer (CAL) and a memory configured to implement the steps of the control method according to one of the preceding claims, preferably said electrical machine (MEL) is a synchronous-reluctant machine assisted by permanent magnets or a synchronous machine with permanent magnets.

11. Control system according to claim 10, wherein each switching arm of said inverter (OND) comprises at least one wideband semiconductor WBG.

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