FR3075517A1 - METHOD FOR CONTROLLING A ROTATING ELECTRIC MACHINE - Google Patents

Abstract

 The invention relates mainly to a method for controlling a rotary electrical machine (10) electrically connected to an energy storage device (11), characterized in that it comprises:  a step of generating a first excitation duty cycle (R1) from a difference (Ev) between a reference voltage value (Vref) and an actual voltage value (Vs) at the output of the machine rotating electric,  a step of generating a second excitation duty cycle (R2) from a difference (Ei) between a reference current value (Iref) and an actual current value (Is) at the output of the machine rotating electric,  a step of selecting the smallest excitation duty cycle between the first excitation duty cycle (R1) and the second excitation duty cycle (R2), and  - A step of applying to a wound rotor (12) of the rotary electrical machine (10) a control signal having the smallest selected excitation duty cycle.

Description

The present invention relates to a method for controlling a rotary electrical machine.

In the automotive field, rotary excitation electric machines are known, used as an alternator or alternator-starter, which include a rotary inductor provided with an excitation coil as well as a polyphase stator.

When the machine operates as an alternator and the rotor is rotating, the stator windings provide alternating voltages which are rectified in order to obtain continuous current and voltage. This DC voltage is regulated so as to provide the vehicle's on-board power supply network with a constant DC voltage for charging the battery and supplying the consumers connected to the network. The alternator then operates as a generator with a fixed voltage output.

Regulation of the alternator output voltage is carried out in a conventional manner by adjusting the excitation current flowing in the inductor coil.

At rotational speed and at constant load, the alternator's response to a variation of the excitation current is limited by the intrinsic bandwidth of the system which depends on the electromechanical characteristics of the alternator.

For automotive applications, the output voltage must be regulated so as to remain constant within operating ranges (ranges of speed and electrical charge represented by the battery and consumers) which are defined by the manufacturers. of the vehicle.

To this end, the output voltage is continuously measured and compared to a reference value by a regulating device which controls the excitation current so as to minimize or cancel the error between the measured output voltage and the reference value. .

The alternator used as a voltage generator thus makes it possible to fix the voltage of the on-board network of the vehicle at a given class voltage, for example 12V, 24V, or 48V, so that the vehicle battery, generally lead, is almost always in charge.

However, with the evolution of the architectures of motor vehicles which integrate more and more often batteries of the Lithium-Ion type, there is the need to be able to control the intensity of the current on the on-board network in order to avoid the deterioration of such batteries sensitive to variations in current during charging. In addition, it could be useful to limit the alternator's throughput in order to adapt its class and performance to the demand of the car manufacturer.

The invention aims to fill this need by proposing a method for controlling a rotary electric machine electrically connected to an energy storage device, characterized in that it comprises:

a step of generating a first excitation duty cycle from a difference between a reference voltage value and a real voltage value at the output of the rotary electric machine,

a step of generating a second excitation duty cycle from a difference between a reference current value and an actual current value at the output of the rotary electrical machine,

a step of selecting the smallest excitation duty cycle between the first excitation duty cycle and the second excitation duty cycle, and

a step of applying to a wound rotor of the rotary electrical machine a control signal having the smallest selected excitation duty cycle.

The invention thus makes it possible to operate in parallel and permanently the voltage regulation loop generating the first excitation duty cycle and the current regulation loop generating the second excitation duty cycle. Thanks to the selection step, the most restrictive loop is naturally activated, and thus the correct operating mode is applied immediately. For example, when the current limitation is taken into account by the regulator, the voltage is no longer regulated. The invention thus makes it possible to precisely control the current when recharging the battery which is protected therefrom. In addition, due to the current loop, the current is slaved to a value which does not depend on external physical variables, such as the temperature of the electric machine, the temperature of the electronics, and the speed of rotation of the rotor. . This results in better machine control and therefore better performance. The efficiency of the machine is therefore improved.

According to one implementation, to generate the first excitation duty cycle, the method comprises a step of correcting the voltage difference and a step of converting the corrected voltage difference into an excitation duty ratio.

According to one implementation, to generate the second excitation duty cycle, the method comprises a step of correcting the current deviation and a step of converting the corrected current deviation into a duty excitation duty ratio.

According to one implementation, a correction of the voltage difference and / or of the current difference is carried out by means of a proportional or Proportional-integral or Proportional-Integral-Derivative type corrector.

According to one implementation, the actual current value at the output of the rotary electrical machine is measured or estimated.

According to one implementation, the actual current value is estimated from the following parameters: a rotation speed of the wound rotor, an excitation current of the wound rotor, and the voltage value at the output of the rotary electric machine. This avoids having to use a dedicated sensor, which reduces the size of the electronics and saves costs.

According to one implementation, the smallest excitation duty cycle is selected via the application of a saturation curve having a maximum value imposed by the second excitation duty cycle. Other implementations are possible.

According to an implementation, the reference voltage value and the reference current value are fixed values, recorded by default in a memory of the regulator and / or adjustable values, generated by a engine ECU and transmitted, via a channel communication, from the engine control unit to the regulator.

According to one implementation, the controlled rotary electric machine is an alternator or an alternator-starter for a motor vehicle.

The subject of the invention is also a rotary electric machine of a motor vehicle provided with a regulator carrying out functions for the implementation of the piloting method as defined above.

The invention will be better understood on reading the description which follows and on examining the figures which accompany it. These figures are given only by way of illustration but in no way limit the invention.

Figure 1 is a schematic representation of a rotary electrical machine provided with a regulator implementing the control method according to the present invention;

FIG. 2 is a schematic representation illustrating an alternative embodiment of the regulator comprising an estimator of the output current of the rotary electrical machine;

FIG. 3 is a graphic representation of a saturation curve that can be implemented to carry out the function of selecting the smallest excitation duty cycle of the rotor coil.

Identical, similar, or analogous items retain the same reference from one figure to another.

FIG. 1 is a schematic representation of an alternator 10 capable of transforming the mechanical energy of the heat engine into electrical energy intended for recharging an energy storage device, such as a battery 11. The battery 11 having for example an operating voltage called 12V, 24V, or 48V could be a lead battery or a Lithium-Ion type battery, or a combination of these two types of batteries.

To this end, a wound rotor 12 carrying an excitation coil is mounted on a shaft comprising a pulley connected to the heat engine via a belt transmission device. A stator 13 is provided with a winding connected to a diode bridge, the outputs of which are electrically connected between the positive terminal and the earth of the battery 11. Loads 14 of the on-board network of the motor vehicle are connected to the terminals of the battery 11.

In addition, a regulator 15 comprises a power stage 16 integrating piloting transistors, typically of the MOS type, making it possible to apply a control signal having a variable duty cycle across the terminals of the excitation coil of the rotor 12. The current mean in the excitation coil is proportional to the excitation duty cycle of the control.

The regulator 15 has functions for implementing the control method according to the invention which is based on the parallel operation of a voltage regulation loop 18 and a current regulation loop 19 of the alternator 10.

More precisely, the voltage regulation loop 18 makes it possible to regulate the output voltage of the alternator 10. To this end, a comparator 18.1 ensures the comparison between an actual voltage value Vs measured at the output of the alternator 10 and a reference voltage value Vref corresponding to the desired voltage across the battery 11 to determine a voltage difference Ev between these two values.

A corrector 18.2 ensures a correction of the voltage difference Ev. The corrector 18.2 is preferably of the Proportional-integral type (PI), but could alternatively be a proportional corrector (P) or a Proportional-Integral-Derivative corrector (PID).

An 18.3 converter, such as a pulse width modulator, transforms the deviation in corrected voltage Ev into an excitation duty cycle

R1. Reference may be made to document WO2011058259 for more details on the operation of the voltage regulation loop 18.

Furthermore, the current regulation loop 19 is integrated in parallel with the voltage regulation loop 18. This loop 19 includes a comparator 19.1 ensuring the comparison between an actual current value Is at the output of the alternator 10 and a value reference current Iref to determine a difference in current Ei between these two values.

The actual current value Is can be measured or estimated. In the embodiment of FIG. 1, the real current value Is is measured for example by means of a sensor 22 for measuring magnetic field, such as a Hall effect sensor, or a low resistance connected in alternator output 10. Any other device suitable for carrying out this current measurement can also be used. It depends on the application.

In the embodiment of FIG. 2, the real current value Is is estimated, by means of the module 21, from the following parameters: a speed of rotation Ω of the rotor 12, an excitation current lex of the rotor 12, and the voltage Vs delivered by the alternator. The speed of rotation Ω is obtained from the derivation, as a function of time, of the measurement of the angular position of the rotor 12 obtained using a device integrated in the alternator 10 comprising, in a manner known per se , a target and a corresponding magnetic field measurement sensor. More simply, the speed can be estimated from the measurement of the phase voltages. The excitation current lex of the rotor 12 as well as the voltage value Vs at the output of the electric machine are for example known state variables of the alternator 10 intended to be transmitted to the engine computer of the motor vehicle.

A corrector 19.2 ensures a correction of the difference in current Ei. The corrector 19.2 is preferably of the Proportional-integral type (PI), but could alternatively be a proportional corrector (P) or a Proportional-Integral-Derivative corrector (PID).

A converter 19.3, such as a pulse width modulator, transforms the deviation in corrected current Ei into an excitation duty cycle R2.

A module 23 ensures selection of the smallest excitation duty cycle between the first excitation duty cycle R1 and the second excitation duty cycle R2 (see FIG. 3). The smallest excitation duty cycle can be selected for example by applying a saturation curve Csat having a maximum value imposed by the second excitation duty cycle R2. Thus, as illustrated in FIG. 3, the curve Csat selects a duty cycle Rsel corresponding to the duty cycle R1 except in the case where the maximum imposed by the duty cycle R2 is less than the value of R1.

Alternatively, it is possible to use a counter, activated on the rising edge of the signal, capable of selecting the minimum excitation duty cycle R1, R2 having the first falling edge. Any other device suitable for selecting the smallest duty cycle R1, R2 may be used. It depends on the application. The duty cycles are generally synchronous.

The control signal having the smallest selected excitation duty cycle R1, R2 is applied, via a power stage 16, to the wound rotor 12 of the alternator 10.

Thus, when the minimum duty cycle is in favor of the voltage Vs, the duty cycle R1 is applied to the rotor 12. This results in a control of the output voltage Vs of the alternator 10.

When the minimum duty cycle is in favor of the current Is, the duty cycle R2 is applied to the wound rotor 12 of the alternator 10. This results in a control of the output current Is of the alternator 10, the voltage being more enslaved.

The reference voltage value Vref and the reference current value Iref may be fixed. This is the case for example for systems used with multifunction regulators, in particular in the default mode where

Vref and Iref are fixed values saved by default in a memory of the controller.

According to one implementation, the reference current value Iref is fixed to clamp the electric machine 10 and the reference voltage value Vref 5 is adjustable. Alternatively, the reference voltage value Vref is fixed and the reference current value Iref is adjustable.

The reference voltage value Vref and / or the reference current value Iref are adjusted by the engine computer via a communication channel between said engine computer and the alternator 10. An example of application would be to set Vref to 16V , to avoid overvoltages, and to control the machine in current.

Of course, the foregoing description has been given by way of example only and does not limit the scope of the invention from which one would not depart by replacing the various elements with any other equivalent.

Furthermore, the various features, variants, and / or embodiments of the present invention can be combined with one another in various combinations, insofar as they are not incompatible or mutually exclusive of one another.

Claims (10)

1. Method for controlling a rotating electric machine (10) electrically connected to an energy storage device (11), characterized in that it comprises: a step of generating a first excitation duty cycle (R1) from a difference (Ev) between a reference voltage value (Vref) and an actual voltage value (Vs) at the output of the machine rotating electric, a step of generating a second excitation duty cycle (R2) from a difference (Ei) between a reference current value (Iref) and an actual current value (Is) at the output of the machine rotating electric, a step of selecting the smallest excitation duty cycle between the first excitation duty cycle (R1) and the second excitation duty cycle (R2), and - A step of applying to a wound rotor (12) of the rotary electrical machine (10) a control signal having the smallest selected excitation duty cycle. 2. Method according to claim 1, characterized in that to generate the first excitation duty cycle (R1), the method comprises a step of correcting the voltage difference (Ev) and a step of converting the difference in voltage (Ev) corrected to an excitation duty cycle (R1). 3. Method according to claim 1 or 2, characterized in that to generate the second excitation duty cycle (R2), the method comprises a step of correcting the current difference (Ei) and a step of converting the current deviation (Ei) corrected to an excitation duty cycle (R2). 4. Method according to claims 2 and 3, characterized in that a correction of the voltage difference (Ev) and / or the current difference (Ei) is carried out by means of a corrector (18.2, 19.2 ) of the Proportional or Proportional-integral or Proportional-Integral-Derivative type. 5. Method according to any one of claims 1 to 4, characterized in that the actual current value (Is) at the output of the rotary electrical machine (10) is measured or estimated. 6. Method according to claim 5, characterized in that the actual current value (Is) is estimated from the following parameters: a speed of rotation (Cl) of the wound rotor (12), an excitation current (lex) of the wound rotor (12), and the voltage value (Vs) at the output of the rotary electric machine (10). 7. Method according to any one of claims 1 to 6, characterized in that the smallest excitation duty cycle (R1, R2) is selected via the application of a saturation curve (Csat) having a maximum value imposed by the second excitation duty cycle (R2). 8. Method according to any one of claims 1 to 7, characterized in that the reference voltage value (Vref) and the reference current value (Iref) are fixed values, recorded by default in a memory of a regulator (15) and / or adjustable values, generated by an engine computer and transmitted, via a communication channel, by the engine computer to the regulator (15). 9. Method according to any one of claims 1 to 11, characterized in that the rotary electric machine (10) controlled is an alternator or alternator-starter (10) for a motor vehicle. 10. Rotating electric machine (10) of a motor vehicle provided with a regulator (15) embedding functions for the implementation of the piloting method as defined according to any one of the preceding claims.