Adjust the motor deceleration according to the average rectified voltage

Abstract

The present invention relates to a method for adjusting the deceleration of an electric motor powered by a variable speed drive, the variable speed drive comprising a plurality of at least N low-voltage power cells connected in series, N being greater than or equal to 1, the method comprising performing the following operations during a period of deceleration of the electric motor: determining (507) at least one average motor voltage within a given period based on motor voltage values ​​measured at the terminals of the electric motor within the given period; determining (508) an average rectified voltage value based on the determined average motor voltage, wherein the rectified voltage corresponds to the voltage obtained at the output of the rectifier of each power cell; and adjusting the deceleration of the electric device (509) based on the average rectified voltage value.

Description

Technical Field

[0001] The present invention relates to the control of the power supply to an apparatus such as an electric motor, and in particular to the control of the control voltage to a variable speed drive of an electric motor. Background Art

[0002] According to the power topology of the variable speed drive, the high voltage is provided by connecting a certain number of low voltage converters (called "power cells") in series in the variable speed drive. The control of these power cells makes it possible to provide a voltage with several levels or multiple levels, each power cell adding the voltage so that a continuous voltage level can be achieved.

[0003] According to European standards, low voltage is understood to mean a voltage between 0 and 1000 V in the case of AC voltage and between 0 and 1500 V in the case of DC voltage. High voltage is understood to mean a voltage greater than 1000 V in the case of AC voltage and greater than 1500 V in the case of DC voltage.

[0004] A low voltage variable drive may have a similar structure but with a single power cell.

[0005] Speed ​​reduction involves the transfer of energy from the mechanical system (the motor's rotor shaft and the driven load) to the electrical system (the variable speed drive's capacitors). Therefore, the sum of the time differentials of the electrical and mechanical energies of the system (and therefore the corresponding power) is equal to the inverse of the power lost by the system.

[0006] When the motor is the actuator driving a load or inertial load, during the deceleration phase, one of the following situations will occur:

[0007] - The mechanical power supplied is greater than the total electrical losses and it is necessary to dissipate the excess energy. The electrical energy can then be returned to the grid, the variable speed drive or, alternatively, a brake resistor can be used to dissipate the energy thermally. At low voltages, the brake resistor can be placed in series outside the variable speed drive, between the variable speed drive and the motor. At medium / high voltages, such a resistor cannot be used because it is too bulky;

[0008] -The mechanical power provided is less than the total electrical losses (motor operation);

[0009] -The mechanical power supplied is equal to the electrical losses (zero total losses). Therefore, the motor provides braking power without dissipating energy.

[0010] To manage the deceleration phase, there are several strategies. During the deceleration phase, the electric motor can switch to generator mode and return electrical energy to the variable drive. As a result, the voltage on each power cell increases and needs to be controlled in order to avoid damaging or even destroying the capacitors of the power cell.

[0011] Therefore, most strategies are based on the measurement of the DC bus voltages. These voltages correspond to the rectified voltages at the input of each power unit of the variable speed drive. According to these solutions, the rectified voltages are interlocked and the control variable of the variable speed drive becomes the output torque of the motor. For example, by setting the maximum DC bus voltage to 800 volts, the motor is decelerated until it approaches this value, and then the rectified voltage is adjusted below this value by reducing the motor torque.

[0012] However, measuring this rectified voltage on each power cell is cumbersome and costly. Then, without access to these voltages, a solution provides to set the deceleration time to a very high value so as not to induce overvoltages on the capacitors of the power cells, thus avoiding damaging them. However, the deceleration of the motor is very slow, which is unacceptable in the context of certain applications.

[0013] Therefore, there is a need to quickly decelerate an electric motor without an energy dissipation system while protecting the capacitors of the power unit of the variable speed drive.

[0014] The present invention solves the above-mentioned disadvantages. Summary of the invention

[0015] A first aspect of the invention relates to a method for regulating deceleration of an electric motor powered by a variable speed drive, the variable speed drive comprising a plurality of at least N low voltage power cells linked in series, N being greater than or equal to 1, the method comprising the following operations during deceleration of the electric motor:

[0016] determining at least one average motor voltage for a given period based on motor voltage values ​​measured at motor terminals during the given period;

[0017] determining an average rectified voltage value based on the determined average motor voltage, wherein the rectified voltage corresponds to the voltage obtained at the output of the rectifier of each power unit;

[0018] The deceleration of the electrical equipment is adjusted according to the average rectified voltage value.

[0019] The invention thus makes it possible to obtain the rectified voltage (average value) without requiring sensors on each power cell.

[0020] According to one embodiment, the determination of the average rectified voltage value is a function of the average motor voltage, a reference motor voltage and a reference rectified voltage, the reference motor voltage being obtained from a command received at the input of the variable speed drive, and the reference rectified voltage being a default value.

[0021] This embodiment allows the average rectified voltage value to be quickly acquired.

[0022] As a variant, the method may include determining at least one reference motor voltage, the reference motor voltage being interlocked with an average motor voltage measured by generating a corrective motor voltage, the control motor voltage being obtained from the reference motor voltage and from the corrective motor voltage, and the average rectified voltage being obtained from the average motor voltage, the control motor voltage and the reference rectified voltage, the reference rectified voltage being a default value.

[0023] This embodiment makes it possible to obtain an average rectified voltage value while interlocking the reference motor voltage.

[0024] According to one embodiment, the regulation of the deceleration comprises comparing the average rectified voltage with at least one predefined threshold value and modifying the torque applied to the electric motor as a function of the comparison result.

[0025] Therefore, the control of the deceleration of the electric motor is optimized.

[0026] Furthermore, the threshold value may be predefined according to the maximum voltage of a capacitor of the power unit of the variable speed drive.

[0027] This embodiment therefore makes it possible to ensure the protection of the power unit.

[0028] According to one embodiment, the adjustment of the speed reduction may include replacing a reference rectified voltage with an average rectified voltage in subsequent cycles in order to determine a control order for a power unit of the variable speed drive, the reference rectified voltage being a default value.

[0029] Thus, the control of the power unit is optimized when achieving the motor voltage.

[0030] According to one embodiment, the given period may be equal to a sampling period of the reference motor voltage at the input of the variable speed drive.

[0031] This synchronization makes it possible to facilitate the determination of the average rectified voltage.

[0032] According to one embodiment, the variable speed drive may include 3×N power cells, wherein the three phases each include N power cells connected in series, and the respective output of each phase may be connected to the motor in a star configuration or a delta configuration.

[0033] Furthermore, the control command of the power unit may be determined from the reference motor voltage and from an additional strategy voltage common to the three phases, the additional strategy voltage being determined so as to minimize the number of switching times of the switches of the power unit.

[0034] Therefore, without changing the voltage applied to the motor, the number of switching times of the switch of the power unit can be minimized.

[0035] A second aspect of the invention relates to a computer program executable by a processor and comprising instructions for implementing the steps of the method according to the first aspect of the invention when executed by the processor.

[0036] A third aspect of the invention relates to a control device for regulating the deceleration of an electric motor powered by a variable speed drive, the variable speed drive comprising N low voltage power cells linked in series, N being greater than or equal to 2. The control device comprises:

[0037] a unit configured to determine at least one average motor voltage within a given cycle from motor voltage values ​​measured at the motor terminals within the given cycle during a period of deceleration of the motor;

[0038] a unit configured to determine an average rectified voltage value based on the determined average motor voltage, wherein the rectified voltage corresponds to a voltage obtained at an output of a rectifier of each power unit;

[0039] A unit configured to adjust a speed reduction of the electrical device based on the average rectified voltage value. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Purely by way of example, embodiments of the invention will now be described with reference to the accompanying drawings, in which:

[0041] Figure 1 A system for controlling power supply to a motor according to an embodiment of the present invention is shown;

[0042] Figure 2 shows the structure of a control device according to an embodiment of the present invention;

[0043] Figure 3 shows the structure of a unit of a control device according to an embodiment of the present invention;

[0044] Figure 4 shows synchronization between realization of the motor voltage and calculation of the average rectified voltage of the variable speed drive according to an embodiment of the present invention;

[0045] Figure 5 is a diagram illustrating steps of a method according to an embodiment of the present invention. DETAILED DESCRIPTION

[0046] Figure 1 A power supply system for an electric motor 100, such as an induction motor, powered by a three-phase variable power supply is presented.

[0047] The variable speed drive 102 comprises a transformer 111 that receives a three-phase variable power supply from a power transmission mains 110. The secondary of the transformer 111 is linked to the power stage of the variable speed drive 102. The transformer 111 may be a multi-winding transformer in order to deliver voltage to several power units described below.

[0048] The power stage of the variable speed drive 102 may include one or more low voltage power cells 101. In the case where the motor receives a three-phase power supply, the variable speed drive 102 includes 3×N power cells, where N power cells are dedicated to each phase, and N is greater than or equal to one.

[0049] In the case where N is equal to 1, the variable speed drive 102 is a low voltage variable speed drive.

[0050] Each power unit 101 receives a three-phase power supply as input from the secondary of the transformer 111 and may include a rectifier ( Figure 1 The rectifier is capable of rectifying the received three-phase variable power supply to provide a DC voltage. The rectified voltage obtained for each power unit 101 is also referred to as a DC bus voltage or bus voltage. The rectifier may include a diode bridge, a thyristor bridge or any other known system for rectifying a three-phase variable voltage. Therefore, the rectifier at the input end is an AC / DC converter.

[0051] Each power cell then comprises a capacitor capable of implementing an intermediate capacitive filtering.

[0052] At the output of the rectifier, each power cell 101 may include an inverter for generating a pulse width modulated PWM signal. Such an inverter may include an H-bridge, which includes four switches controlled in pairs. For each phase, a power electronics system using such a chopped voltage principle applies a voltage proportional to one or more rectified voltages to the motor 120. On average, the applied ratio corresponds to the ratio between the control voltage and the reference rectified voltage (defined below). The operation of the H-bridge is well known and will not be described in detail in this application.

[0053] The switches of the power unit 101 are controlled by a control unit 103 of the power unit 101 .

[0054] The system also comprises a control device 120 capable of controlling the power supply of the electric motor 100. To this end, the control device 120 can control the control unit 103 of the power unit 101. The control device 120 can also control the switches 105 so that for each phase a subset of N power units can be connected in series. As a variant, these switches are controlled by the control device 120 via the control unit 103.

[0055] The control unit 103 may receive control commands from the control device 120, and the control unit 103 may apply a ratio or duty cycle to the rectified voltage from the control device 120 by controlling the switches of the H-bridge. The switches of the H-bridge may be transistors of the insulated gate bipolar transistor IGBT type. The advantage of the IGBT type transistor is that it has a fast switching speed.

[0056] Therefore, by summing up the PWM output voltage of the power unit 101 when the switch 105 is closed, a three-phase voltage for supplying power to the motor 100 is obtained.

[0057] Other functions of the control device will refer to Figures 2 to 4 Provide detailed explanation.

[0058] Figure 2 A control device 120 according to some embodiments of the present invention is presented.

[0059] To this end, the control device 120 includes a plurality of units dedicated to the additional functions according to the present invention. Each unit can be implemented by software involving at least a processor and a memory, or by a monolithic set of electronic components (e.g., such as a microprocessor or an ASIC) programmed for a given function. As a variant, a single processor or a single monolithic set is configured to implement all the additional functions of the control device 120 according to the present invention.

[0060] The control device 120 receives as input a speed command (particularly a deceleration command in the context of the present invention), which is processed by a reference motor voltage calculation unit 201 configured to calculate a reference motor voltage based on the speed command. The reference motor voltage can be represented by a vector V123REF having three voltages, denoted V1REF, V2REF and V3REF (one for each phase).

[0061] According to the reference motor voltage V123REF, the control motor voltage calculation unit 202 is configured to calculate the control motor voltage. The control motor voltage can be represented by a vector V123CONTROL, which has three voltages, denoted as V1CONTROL, V2CONTROL, and V3CONTROL.

[0062] Furthermore, according to the invention, unit 202 can receive the average motor voltage from unit 205 described below. The average motor voltage can be represented by a vector V123MEAS having three voltages, denoted V1MEAS, V2MEAS and V3MEAS.

[0063] Based on the comparison between the reference motor voltage V123REF and the average motor voltage V123MEAS, the unit 202 may determine a corrected motor voltage represented by a vector V123CORRECTION having three correction values ​​V1CORRECTION, V2CORRECTION and V3CORRECTION.

[0064] The control device 120 further comprises a calculation unit 203 for calculating control commands for the chopping topology.

[0065] Unit 203 first determines a command voltage represented by a vector V123COMMAND based on the control voltage V123CONTROL, V123COMMAND having three voltages, denoted as V1COMMAND, V2COMMAND, and V3COMMAND.

[0066] When determining the command voltage, unit 203 may also take into account the motor strategy voltage VSTRATEGY, which is a voltage value corresponding to the electrical neutral point of the motor, allowing different switching PWM strategies to be implemented.

[0067] Applying the same VSTRATEGY value to all phases of the variable speed drive does not affect the voltage applied to the motor. In fact, each phase of the variable speed drive 102 provides a potential Vi, i being the phase index, and the voltage applied to the motor is constructed according to the potential Vi.

[0068] In the case of a star configuration (whose architecture is known and will not be described further), by using Ui to represent one of the voltages applied to the motor, the following results are obtained:

[0069] Ui=Vi–(V1+V2+V3) / 3;

[0070] Therefore, the Ui value does not vary with the VSTRATEGY value to be added to the three output values ​​V1, V2 and V3.

[0071] In the case of a delta configuration, by using Ui to represent one of the voltages applied to the motor, the following results are obtained:

[0072] Ui=Vi-Vj, j is a phase index different from i.

[0073] Likewise, the Ui value does not vary with the VSTRATEGY value which will be added to the three output values ​​V1, V2 and V3.

[0074] Therefore, in both the star and delta configuration cases, the addition of the VSTRATEGY value provides a degree of freedom to apply specialized strategies to different objectives, such as maximizing coil voltage amplitude (the voltage formed at the variable driver output), minimizing switching, etc.

[0075] The unit 203 then calculates the control commands as a function of the rectified voltage of each power cell 101, which is the voltage that is then chopped by the H-bridge of the power cell 101. However, as previously mentioned, in the context of the present invention, such rectified voltage is not directly measured and the reference rectified voltage VBUSDRIVE obtained from the reference voltage determination unit 204 is initially used in order to calculate the control commands.

[0076] For example, from the command voltage V123COMMAND and from the reference rectified voltage VBUSDRIVE as a default value, the unit 203 determines a modulation ratio in the form of a vector m123 including the values ​​m1, m2 and m3. This modulation ratio is compared with the triangular carrier to determine the following switching command. Each modulation ratio m1, m2 and m3 can change value N times within a carrier period.

[0077] According to the modulation ratio, the unit 203 also determines the switching commands for the switches of the H bridge of the power cell 101, which are represented by the vector T123, which includes the commands T1, T2 and T3 for each of the three phases respectively. The command Ti is a switching vector, each component of the vector corresponds to a power cell of the branch i.

[0078] Each of the N components of the switching vector Ti can be obtained by comparing the modulation ratio mi with the triangular carrier corresponding to phase i.

[0079] The control commands may also include activation / deactivation commands for the switches 105 of the power cells.

[0080] The unit 203 is also configured to transmit control commands for controlling the switches 105 in order to activate or deactivate some power cells previously deactivated / activated and / or command the command unit 103 of the active power cells 101 in order to generate a PWM output voltage of the power cells.

[0081] The voltage is then realized in practice by the active power unit 101 of the variable speed drive 102 and the realized voltage is represented by a vector V123REALIZED comprising the voltages V1REALIZED, V2REALIZED and V3REALIZED corresponding to the three respective phases.

[0082] The control device 120 also includes an average motor voltage calculation unit 205. The unit 205 is capable of receiving continuous or discrete measurements of the voltage applied to the motor at a given frequency. Based on the motor voltage measurements received within a given period, the unit 205 determines the average motor voltage represented by the vector V123MEAS within the given period, the vector V123MEAS including the voltages V1MEAS, V2MEAS and V3MEAS of the three corresponding phases. Such a period can be set or variable. For example, the period for averaging the motor voltage can be calculated based on the sampling period of the reference motor voltage V123REF, which is technically easier to implement than the measurement of the motor voltage sampled according to the characteristic time of the power stage (the calculation of the reference motor voltage and the realization of the voltage of each power stage are synchronized).

[0083] to this end, Figure 4 The synchronization between the calculation of the average motor voltage and the realization of the voltage of the power stage is shown.

[0084] Figure 4 The case where a phase of a variable speed drive has five power cells is presented.

[0085] The curves 401.1 to 401.5 represent the basic triangular signals used by the unit 203 to generate the switching command T123 by comparing the modulation ratio mi (m1, m2 or m3) with the triangular signal. Each triangular signal corresponds to a power cell of the phase. Such comparisons made to determine the switching command T123 of the H-bridge of the power cell are well known and will not be described again. The triangular signal is a voltage value that evolves over time (on the x-axis).

[0086] Successive periods Tk to Tk+5 are shown, corresponding to one fifth of the period 402 of the triangular signal. Such a period may correspond to a time during which, on average, the same active power is obtained from each of the three arms of the variable speed drive. During period Tk+1:

[0087] - the reference voltage V123REF, the control voltage V123CONTROL and the command voltage V123COMMAND as well as the control command T123 are calculated based on the average motor voltage and the average rectified voltage obtained from the period Tk;

[0088] - the control command T123 calculated in the previous step Tk is applied to the power unit in order to achieve the voltage;

[0089] - Calculate the average motor voltage and the average rectifier voltage over all steps Tk+1 for use in the next step Tk+2.

[0090] Therefore, the sampling frequency of the reference motor voltage V123REF may correspond to the frequency of the implementation of the PWM voltage (the frequency of the triangular signal enables PWM modulation to be implemented in the power unit 101). Such a frequency may be set or may be varied. For example, factors affecting the sampling frequency may be:

[0091] - Thermal protection of the power stage according to the thermal state of the variable speed drive 102;

[0092] - protecting the H-bridge including the IGBT switch of the power unit 101, the PWM frequency is adjusted according to the junction temperature of the IGBT switch;

[0093] - when switching from three-phase control to two-phase control; and / or

[0094] -Applies a random component to the PWM frequency to reduce noise.

[0095] The control device 120 further comprises an average rectified voltage calculation unit 206, which is capable of calculating an average rectified voltage value VBUS from the average motor voltage. As an illustration, two embodiments of calculating the average rectified voltage are given below.

[0096] First embodiment:

[0097] According to a first embodiment, the reference motor voltage V123REF is applied without correction associated with the measured average voltage V123MEAS. The correction voltage V123CORRECTION is therefore not taken into account. According to this first embodiment, the average rectified voltage VBUS is also calculated from the reference motor voltage and the reference rectified voltage, which is derived from the calculation described in detail below.

[0098] The balance relationship between the different voltages of the system according to the first embodiment is:

[0099] V123CONTROL=V123REF (correction voltage V123CORRECTION is not applied);

[0100] V123CORRECTION=V123REF-V123MEAS (this calculation is optional because the correction voltage v123CORRECTION is not used);

[0101] V123COMMAND=V123CONTROL+(V123COMPENSATION+VSTRATEGY);

[0102] V123COMPENSATION is a compensation vector comprising the three components V1COMPENSATION, V2COMPENSATION and V3COMPENSATION; such a vector makes it possible to compensate for the inherent drops of the power components, denoted below as VDROP. Such drops occur in the IGBT switches, the diodes and also due to the introduction of dead times to avoid short circuits in the inverter. Alternatively, the compensation values ​​are of low magnitude and they can be neglected at medium and high voltages (at medium and high speeds).

[0103] V123COMMAND / VBUSDRIVE=m123;

[0104] m123*VBUS–V123DROP=v 123REALIZED;

[0105] (VBUS is the average rectified voltage to be determined, V123DROP is a vector having three components V1DROP, V2DROP and V3DROP representing the voltage drop in the power stage for each of the three phases);

[0106] V123MEAS=V123 REALIZED–VNO;

[0107] VNO is the voltage value corresponding to the neutral point of the measuring unit. Such a value may be known in advance, for example, by calibration.

[0108] From the previous equilibrium relationship, the following relationship can be obtained:

[0109] V123CORRECTION=V123REF–V123MEAS;

[0110] V123COMMAND=V123REF+(V123COMPENSATION+VSTRATEGY);

[0111] m123=V123REF / VBUSDRIVE+(V123COMPENSATION+VSTRATEGY) / VBUSDRIVE;

[0112] V123REALIZED=V123REF*gV+(V123COMPENSATION+VSTRATEGY)*gV–V123DROP;

[0113] V123MEAS=V123REF*gV+(V123COMPENSATION+VSTRATEGY)*gV–V123DROP–VNO;

[0114] (gV is the VBUS / VBUSDRIVE ratio determined at the end of the method according to the invention).

[0115] By defining oV = (V123COMPENSATION + VSTRATEGY) * gV - V123DROP - VNO, the above relationship can be simplified to:

[0116] V123MEAS = V123REF * gV + oV;

[0117] V123CONTROL=V123REF (operation of unit 202 according to the first embodiment);

[0118] V123CORRECTION=(1-gV)*V123REF–oV.

[0119] oV can be thought of as an offset that represents an imperfection in the power stage. If the imperfection is compensated, oV approaches 0.

[0120] In this case, gV=V123MEAS / V123REF, so the VBUS value can be determined.

[0121] The ratio presented above and which enables acquisition of gV corresponds to the ratio of the magnitude of the vector V123MEAS to the magnitude of the vector V123REF.

[0122] For example, a Clarke-type transformation may be considered, such that a three-phase vector may be transformed into a two-phase vector (usually denoted as (alpha, beta)).

[0123] Therefore, a three-phase vector with the following components can be converted into a two-phase system:

[0124] V1=V cos(wt-phi)+VN;

[0125] V2=V cos(wt-phi–2pi / 3)+VN;

[0126] V3=V cos(wt-phi–4pi / 3)+VN.

[0127] The converted two-phase system is as follows:

[0128] Valpha=V cos(wt–phi);

[0129] Vbeta = V sin (wt – phi).

[0130] From this two-phase system the polar coordinates can be derived:

[0131] V_amplitude = V (corresponding to the amplitude indicated by the ratio gV);

[0132] V_phase=wt–phi.

[0133] Second embodiment:

[0134] According to the second embodiment, unit 202 adjusts the measured motor voltage V123MEAS to a reference motor voltage V123REF by calculating a correction motor voltage V123CORRECTION, which unit 203 applies when determining control voltage V123CONTROL.

[0135] According to a second embodiment, the calculation of the average rectified voltage VBUS is the same as in the first embodiment (and therefore is calculated based on the measured motor voltage V123MEAS and the reference motor voltage V123REF), or the average rectified voltage VBUS is calculated by replacing the average motor voltage V123MEAS or the reference motor voltage V123REF with the correction motor voltage V123CORRECTION or the command voltage V123COMMAND, as described in detail in the calculation below.

[0136] The equilibrium relationship is as follows:

[0137] V123REF = V123MEAS;

[0138] V123CONTROL=V123REF+V123CORRECTION;

[0139] V123COMMAND=V123CONTROL+V123COMPENSATION+VSTRATEGY;

[0140] V123COMMAND / VBUSDRIVE=m123;

[0141] m123*VBUS–V123DROP=V123REALIZED;

[0142] V123MEAS=V123REALIZED–VNO.

[0143] or:

[0144] V123MEAS = V123REF;

[0145] V123CONTROL=V123REF+V123CORRECTION;

[0146] V123COMMAND=V123REF+V123CORRECTION+V123COMPENSATION+VSTRATEGY;

[0147] m123=V123REF / VBUSDRIVE+(V123CORRECTION+V123COMPENSATION+VSTRATEGY) / VBUSDRIVE;

[0148] V123REALIZED=V123REF*gV+(V123CORRECTION+V123COMPENSATION+VSTRATEGY)*gV–V123DROP-VNO

[0149] By defining oV in the same manner as in the first embodiment, the relationship is simplified to:

[0150] V123CORRECTION=(V123REF*(1-gV)–oV) / gV;

[0151] V123MEAS = V123REF;

[0152] V123CONTROL=V123REF / gV–oV / gV.

[0153] In the case where the offset oV is zero, that is, the imperfections of the power stage are perfectly compensated, the following results can be obtained:

[0154] gV=V123MEAS / V123CONTROL, so the VBUS value can be determined.

[0155] Once the average rectified voltage VBUS is determined, according to any embodiment of the present invention, the unit 204 can use the average rectified voltage VBUS to replace the reference rectified voltage VBUSDRIVE for the next cycle. For example, the voltage VBUS can replace the reference rectified voltage VBUSDRIVE in the memory of the unit 204.

[0156] According to the average rectified voltage value VBUS, the motor torque can be controlled to control the deceleration. For example, the reference motor voltage V123REF can be controlled by the unit 207. For example, if the average rectified voltage VBUS is less than the first threshold th1, the deceleration of the motor can be increased. If the average rectified voltage is between the first threshold th1 and the second threshold th2, and the second threshold th2 is the acceptable limit voltage of the capacitor of the power unit 101, the deceleration can be gradually reduced to avoid re-injecting energy that can no longer be stored or dissipated. If the average rectified voltage is greater than th2, the variable speed drive 102 stops controlling the motor in order to protect the variable speed drive 102.

[0157] The values ​​th1 and th2 may be predetermined. As a variant or complement, the comparison of the average rectified voltage value VBUS may be compared with threshold values ​​th1 and th2 in order to control the power supply frequency of the electrical device.

[0158] Figure 3 The structure of the unit of the control device according to the embodiment of the present invention is shown.

[0159] Previous reference Figure 2 Each unit presented may include Figure 3 Alternatively, each or some of these units may be in the form of an electronic circuit dedicated to performing a function specific to the unit. Such a dedicated electronic circuit may be a microcontroller or a monolithic ASIC configured for a function specific to the electronic circuit.

[0160] The unit comprises a processor 300 capable of bidirectional communication via a bus with a memory 301, such as a random access memory RAM, a read-only memory ROM, a flash memory, a hard disk and / or any type of storage medium. The processor 300 is capable of executing instructions for performing functions specific to the unit. The unit also comprises an input interface 302 and an output interface 303 in order to communicate with other entities of the control device, receive voltage measurements, transmit / receive commands.

[0161] The unit may also include a database for storing data for performing functions specific to the unit.

[0162] According to a variant, the processor 300 may execute the above-referenced Figure 2 The functions of all units 201 to 207 are described.

[0163] Figure 5 is a diagram illustrating steps of a method according to several embodiments of the present invention.

[0164] Steps 501 to 509 are implemented in a current cycle that is continuous with a previous cycle.

[0165] In step 501, unit 201 receives the average motor voltage obtained from measurements performed during the previous cycle, as referenced Figure 2 Described in detail.

[0166] In parallel, in step 502, unit 201 may calculate a reference motor voltage V123REF, such as reference Figure 2 Described in detail.

[0167] In step 503 , unit 202 determines control voltage V123CONTROL according to the first embodiment of the invention (by copying reference motor voltage V123REF) or according to the second embodiment of the invention (by taking into account correction voltage V123CORRECTION).

[0168] In step 504 , unit 203 may use voltages VSTRATEGY and V123COMPENSATION to determine command voltage V123COMMAND from control voltage V123CONTROL. Such a step is optional, and command voltage V123COMMAND can be directly derived from control voltage V123CONTROL.

[0169] In step 505, unit 203 determines the control command for power stage T123, as described above.

[0170] Then, in step 506 , the control command T123 is transmitted to the three branches of the power stage to achieve the motor voltage V123 REALIZED.

[0171] In step 507, upon receiving the motor voltage measurements, the average motor voltage V123MEAS is determined by unit 205, as described in detail above. The determined average motor voltage V123MEAS may be used during step 501 of a subsequent cycle continuous with the current phase.

[0172] In step 508 , unit 206 may determine an average rectified voltage VBUS, as described in detail above. The average rectified voltage VBUS may replace the reference rectified voltage VBUSDRIVE in unit 204 .

[0173] In step 509, the control of the motor is adjusted according to the average rectified voltage VBUS. For example, such control may include replacing the reference rectified voltage VBUSDRIVE with the average rectified voltage VBUS and / or modifying the frequency of the motor or the reference motor voltage V123REF by the unit 207 (returning to step 502 in the next cycle), or by modifying the motor torque.

[0174] Although the invention has been described above with reference to specific embodiments, it is by no means limited to the forms described. The invention is limited only by what is defined in the claims and embodiments other than the above described may fall within the scope of the claims.

[0175] Furthermore, although the embodiments have been described above as combinations of components and / or functions, it should be clearly understood that alternative embodiments may be obtained by other combinations of components and / or functions without departing from the scope of the present invention in any way.

Claims

1. A method for regulating the deceleration of an electric motor (100) powered by a variable speed drive (102), the variable speed drive comprising at least N low voltage power cells (101) connected in series, N being greater than or equal to 1, It is characterized in that The method comprises performing the following operations during a period of deceleration of the electric motor: - determining at least one average motor voltage (507) within a given period from the motor voltage values ​​measured at the terminals of the motor within the given period; - determining an average rectified voltage value (508) from the determined average motor voltage, wherein the rectified voltage corresponds to the voltage obtained at the output of the rectifier of each power cell; - adjusting the deceleration of the electric motor according to the average rectified voltage value (509).

2. The method according to claim 1, in, The determination (508) of the average rectified voltage value is a function of the average motor voltage, a reference motor voltage, and a reference rectified voltage, the reference motor voltage being obtained from a command received at an input of the variable speed drive (102), and the reference rectified voltage being a default value.

3. The method according to claim 1, in, The method includes determining at least one reference motor voltage (502), wherein the reference motor voltage is interlocked with the average motor voltage measured by generating a correction motor voltage, a control motor voltage being derived from the reference motor voltage and the correction motor voltage, The average rectified voltage is obtained from the average motor voltage, the control motor voltage and a reference rectified voltage, and the reference rectified voltage is a default value.

4. The method according to any one of claims 1 to 3, in, The adjustment (509) of the deceleration includes comparing the average rectified voltage with at least one predefined threshold value and modifying the torque applied to the electric motor according to the comparison result.

5. The method according to claim 4, in, The threshold value is predefined according to the maximum voltage of a capacitor of a power unit of the variable speed drive (102).

6. The method according to any one of claims 1 to 3, in, The adjustment of the speed reduction comprises replacing a reference rectified voltage with the average rectified voltage in a subsequent cycle in order to determine a control command for the power unit (101) of the variable speed drive (102), The reference rectified voltage is a default value.

7. The method according to any one of claims 1 to 3, in, The given period is equal to a sampling period of a reference motor voltage at an input terminal of the variable speed drive (102).

8. The method according to any one of claims 1 to 3, in, The variable speed drive comprises 3×N power cells, wherein three phases each comprise N power cells connected in series, wherein a respective output terminal of each phase is connected to the motor in a star configuration or a delta configuration.

9. The method according to claim 8, in, A control command for the power unit is determined according to a reference motor voltage and an additional strategy voltage common to three phases, the additional strategy voltage being determined so as to minimize the number of switching times of the switches of the power unit.

10. A computer program product comprising instructions executable by a processor (300) and which, when executed by the processor, cause the implementation of the steps of the method according to any one of claims 1 to 9.

11. A control device for regulating the deceleration of an electric motor (100) powered by a variable speed drive (102), the variable speed drive comprising N low voltage power cells (101) connected in series, N being greater than or equal to 1, It is characterized in that The control device comprises: - a unit (205) configured to determine at least one average motor voltage within a given period from motor voltage values ​​measured at the terminals of the motor within said given period during a period of deceleration of the motor; - a unit (206) configured to determine an average rectified voltage value as a function of the determined average motor voltage, wherein the rectified voltage corresponds to the voltage obtained at the output of the rectifier of each power cell; - a unit (204; 207) configured to adjust the deceleration of the electric motor as a function of the average rectified voltage value.

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