The present invention relates to the field of control of rotating electric machines.
An electric machine may be used in all industrial fields. For example, some electric machines having a high torque, a low inertia and rapid responses are advantageously used in the motorization of actuators, in particular in on-board systems of an aircraft.
In general, an electric machine, for example an electric motor, is equipped with a control or piloting device intended to adjust the voltage at its terminals according to the feedback electrical data and especially of an accurate piece of data on the angular position θ of the rotor. This information usually originates from a resolver or position sensor often mounted on the shaft of the electric machine in order to measure the mechanical angle θmeca (in rad) of the rotor, also called the mechanical position.
The mechanical position measured by the resolver forms a primary input piece of data for piloting the electric machine. Indeed, the electrical position which is derived therefrom is used to perform reference frame transformations (for example, Park and inverse Park transforms) associated with piloting of the electric machine.
Furthermore, this information on the mechanical position is used to estimate the mechanical rotational speed and to perform the reference frame changes at the control level. Usually, a derivative is used to estimate the mechanical speed from the measurement of the mechanical position of the rotor. The electrical speed deduced from the mechanical speed can be used at the control level of the machine to ensure the decoupling between the axes d and q in a rotating synchronous reference frame (d,q).
Nonetheless, the position signal generated by the resolver is not clean in the sense that it contains harmonics which might have a vibratory origin on the shaft of the electric machine and which could possibly superpose with signals derived from a Resolver-to-Digital Converter (RDC) converter.
Furthermore, the conventional calculation of the mechanical speed based on the calculation of a derivative of the mechanical position θ contains the same harmonics. Any frequency harmonic that superposes with these two quantities, the position and the speed, could generate torque vibrations on the shaft and additional iron and copper losses in the electric machine.
A state-of-the-art solution consists in using digital low-pass filters to attenuate the harmonic content of these two speed and position signals. However, the information on the speed might be attenuated because quite often the considered harmonics in question are of a low frequency nature. Indeed, in order to be effective, the cut-off frequency selected for the low-pass filter should be close to the continuous signal, at zero frequency. Furthermore, the information on the angle might be delayed because of the delay generated by the phase shift of the digital low-pass filter. Both these consequences could jeopardize the stability and feasibility of the control of the electric machine.
Consequently, an object of the present invention is to propose a method and a system for determining the control parameters (position and speed), overcoming the aforementioned drawbacks, allowing for a high accuracy in determining an electrical position with no harmonics and with no phase shift with respect to the mechanical position, thereby enabling an electric machine to be piloted with great stability and great reliability.
The present invention relates to a method for determining control parameters of a rotating electric machine, including the following steps:
This method allows determining the electrical angular position with great accuracy, with no harmonics and with no phase shift with respect to the measured position of the axis of the rotor of the rotating machine.
The mechanical position may be measured by a position sensor mounted on the shaft of the electric machine.
Advantageously, the construction of said two imaginary two-phase signals includes the following steps:
Advantageously, the determination of the estimated electrical speed ωestflt includes the following steps:
Advantageously, the determination of said two pulse signals includes the following steps:
Advantageously, the generation by said phase-locked loop of the actual electrical position θ of the rotating machine includes the following steps:
Advantageously, according to a first embodiment, the method includes determining an actual electrical speed ω of the electric machine by applying low-pass active filtering to the phase-locked electrical speed ωPLL.
Advantageously, according to a second embodiment, the method includes determining an actual electrical speed ω of the electric machine by applying a selective band-pass active filtering on the continuous component of the imaginary signal according to the axis d of the rotating synchronous reference frame, the actual electrical speed then ω corresponding to the phase-locked electrical speed ωPLL.
Advantageously, according to a third embodiment, the method includes determining an actual electrical speed ω of the electric machine by applying a speed observer to the actual electrical position of the electric machine, the actual electrical speed ω then corresponding to an image of the filtered electrical speed obtained by said speed observer.
The invention also relates to a method for controlling a rotating machine comprising determining control parameters according to the preceding aspect.
The invention also relates to a system for determining control parameters of a rotating electric machine, including:
The invention also relates to a device for piloting a rotating electric machine including the system for determining electrical parameters according to the features hereinabove.
The invention also relates to a rotating electric machine including the piloting device according to the features hereinabove.
Other features and advantages of the invention will appear upon reading preferred embodiments of the invention made with reference to the appended figures, wherein:
The concept of the invention is to perform a digital processing on the measurement signal of the mechanical position of the axis of the rotor of an electric machine by creating an imaginary two-phase reference frame and using this two-phase reference frame as input data of a phase-locked loop to generate a harmonic-free resultant position. Furthermore, this locked loop is also used to calculate the speed.
The rotating electric machine 1 (in motor mode or in generator mode) usually includes stator windings 3 and a rotor 5 with p pole pairs (only one pair is illustrated, i.e. p=1).
A resolver or a position sensor 9 (for example, a Hall-effect sensor) is mounted on the shaft of the electric machine 1 to measure the mechanical position of the axis of the rotor 5.
In accordance with the invention, the electric machine 1 is equipped with a system 11 for determining control parameters. This system 11 receives the signal of the mechanical position measured by the position sensor 9 to filter the low-frequency harmonics that might be present in this signal without introducing a phase shift.
Thus, the control parameter determination system 11 transmits to a control device 13 useful signals on the θ position of the rotor and possibly on the rotational speed with no harmonics.
The control device 13 uses the clean signals received from the control parameter determination system 11 as well as usual feedback electrical data to control or pilot the operating point of the electric machine 1 according to the actual position θ of the rotor 5.
The control parameter determination system 11 includes an electronic circuit 15 configured to carry out a filtering digital processing on the signal of the mechanical position measured by the position sensor 9. The angular position resulting from this processing is then harmonic-free. The electronic circuit 15 is also configured to calculate the resulting mechanical speed without repercuting the harmonics and without attenuating the signal.
According to an embodiment of the invention, the electronic circuit 15 includes a two-phase imaginary reference frame module 17, an open-loop module 19, and a phase-locked loop module 21.
The two-phase imaginary reference frame module 17 is configured to construct two imaginary two-phase signals (xα, xβ) based on the measurement of the mechanical position .
The open-loop module 19 is configured to determine an estimate of the electrical speed, so-called open-loop estimated electrical speed ωest
The two imaginary two-phase signals (xα, xβ) and the open-loop estimated electrical speed ωest
It should be noted that the modules 17, 19, 21 may be hardware and/or software modules. The digital processing could then be carried out by a microprocessor comprised in the electronic circuit 15. Furthermore, the electronic circuit 15 may be comprised in the control device 13.
Like in
The two-phase imaginary reference frame module 17 includes a multiplier element 171 and an ortho-normalization element 172. The multiplier element 171 multiplies the mechanical position signal derived from the position sensor 9 by the number of p pole pairs of the electric machine 1. At the output of this multiplier element 171, an estimate of an electrical position, so-called the estimated electrical position in radians, of the angular position of the rotor is obtained:
The ortho-normalization element 172 then calculates, from the estimated electrical position two sinusoidal signals normalized and shifted from each other by 90° thereby forming two imaginary two-phase signals (xα, xβ):
The two imaginary two-phase signals (xα, xβ) form a two-phase imaginary reference frame forming input data for the open-loop 19, and phase-locked loop 21 modules.
The open-loop module (symbolized “flt”) 19 includes three units: a pulse generation unit 191, an average value generation unit 192 and a selective filter unit 193.
The pulse generation unit 191 is configured to generate two pulse signals at the zero crossings of the imaginary two-phase signals (xα, xβ). More particularly, this pulse generation unit 191 includes first 194 and second 195 detection elements and an addition element 196.
The first 194 and second 195 detection elements are configured to generate, at the zero crossings of their respective input signals xα and xα, pulses whose duration is inversely proportional to a maximum useful electrical frequency fmax associated with a maximum rotational speed of the electric machine 1.
Each zero crossing detection is encoded so that, at the output of the first 194 and second 195 detection elements, first and second pulse signals are obtained edgesx
An example of encoding is given hereinbelow for the case of the first pulse signal edgesx
At the beginning, the sinusoidal signal at the input xα is transformed into a square wave signal varying between 0 and 2, such that the maximum value 2 indicates a positive alternation of the sinusoidal signal xα and the minimum value 0 of the square wave signal indicates a negative alternation of xα, as follows:
Afterwards, the changes in the rising and falling edges of the square signal are detected and interpreted by pulses with a period Δt, equal to:
More particularly, each of the first 194 and second 195 detection elements includes two rising-edge and falling-edge monostable circuits (not illustrated) so that the square signals are injected into these two monostable circuits.
For example, the rising-edge monostable circuit is defined in relation with a sampling period Te, as follows:
where y=k−Te and where the value k is defined according to the value of a binary variable u, as follows:
Furthermore, the following truth table (Tab 1) allows deducing the value of the binary variableu:
It should be noted that the logic of the falling-edge monostable circuit is equivalent to the rising-edge monostable circuit. The only difference lies in the calculation of the binary parameter “b” which becomes as follows:
The addition element 196 of the generation unit 191 is configured to add the two pulse signals together edgesx
Moreover, the average value generation unit 192 is configured to determine a preliminary estimate of an electrical speed, so-called the preliminary electrical speed ωest. This preliminary electrical speed ωest is calculated from the superposition signal ZC and the maximum useful electrical frequency fmax. More particularly, the superposition signal ZC is multiplied by 2πfmax and divided by 2, according to the following formula:
Furthermore, the selective filter unit 193 of the open-loop module 19 is configured to apply a selective band-pass filter on the preliminary electrical speed ωest. At the output of this selective filter 193 and therefore at the output of the open-loop module 19, an estimate of the electrical speed, so-called the open-loop estimated electrical speed, is obtained ωestflt.
Advantageously, this open-loop estimated electrical speed ωestflt is injected into the direct chain of the position servo-control of the phase-locked loop module 21, thereby improving the dynamics of this module 21.
The phase-locked loop module (symbolized “PLL” for Phase-Locked Loop) 21 is a servo-control loop configured to make the signal of the electrical position converge towards a useful signal of an actual electrical position θ of the electric machine 1 free of harmonics. This actual electrical position θ is a filtered image of the position measured by the position sensor 9. The phase-locked loop module 21 is further configured to supply the actual electrical speed ω of the electric machine also harmonic-free.
According to a first embodiment, the phase-locked loop module 21 includes the following units (or sub-modules): a rotation unit 211, a regulation unit 212, a speed addition unit 213, an integration unit 214, a delay compensation unit 215, a position compensation unit 216, and an active filter unit 217.
The rotation unit 211 is configured to apply a rotation matrix with an angle ϑPLL
The regulation unit 212 is a proportional integral type regulator applied to the error according to the axis d of the rotating synchronous reference frame. More particularly, the regulation unit 212 includes a servo-control element 221 and a corrector element 222.
The servo-control element 221 is configured to servo-control the continuous component of the imaginary signal on the axis d at a zero setpoint x*d. The deviation ε between the setpoint x*d and the continuous component is then:
The corrector element 222 is configured to determine a corrector y based on the deviation between the setpoint x*d and the continuous component . This corrector y is of the proportional integral “PI” type which is expressed according to a deactivated or activated state, as follows:
with,
The gains {Kp
The values of these parameters of the phase-locked loop are defined in the following table Tab 2:
The output y of the correction element 222 is a correction (in rad/s) of the electrical speed which is used to obtain more accurate information on the angular position of the shaft 5 of the electric machine 1.
The electrical speed ωestflt estimated by the open-loop module 19 (based on the detection of zero crossings) is injected as a predictive action “FeedForward” into the direct chain. This FeedForward action has the merit of improving the dynamics of the PLL and enabling the convergence of the loop towards the useful value of speed of the shaft 5 especially when activating the PLL at a non-zero shaft speed (for example, 15,000 rpm).
The addition unit 213 is an adder which is configured to add the corrector y derived from the corrector element 222 to the estimated electrical speed ωestflt, injected from the open-loop module 19. Thus, at the output of the addition unit 213, we obtain an estimate of a phase-locked electrical speed ωPLL:
Afterwards, the integration unit 214 is configured to integrate the phase-locked electrical speed ωPLL. At the output of the integration unit 214, an estimate of a preliminary angular position ϑv referenced with respect to the signal is then obtained, as follows:
The delay compensation unit 215 is configured to compensate for a delay on the estimate of the preliminary angular position ϑv. This delay is compensated by taking account of the rotation of the shaft of the electric machine at the scale of the sampling step used to generate the position used in the rotation matrix. Thus, at the output of the delay compensation unit 215, a compensated angular position is obtained ϑPLL
Moreover, the unit for compensating the angular position 216 of the shaft of the electric machine 1 is configured to bring the angle estimated by the phase-locked loop back to the reference . Indeed, the phase-locked loop is based on the resolution of the following equation:
This amounts to solving the following trigonometric equation:
The resolution of this trigonometric equation leads to the following solution (modulo 2π):
This solution gives the actual electric position of the electric machine 1.
Furthermore, the signals derived from this phase-locked loop are canceled when the phase-locked loop is deactivated:
Advantageously, the phase-locked loop module 21 includes an active filter 217 configured to apply a low-pass active filtering to the phase-locked electrical speed ωPLL to determine an actual electrical speed ω of the shaft of the electric machine 1. This filtering is carried out according to the equations hereinbelow:
More particularly,
The electrical speed in this figure relates to a starting profile of a turbine over a wide speed range.
More particularly, the curve C1 shows the signal of the electrical speed obtained according to the prior art with a filtered derivative applied to the position measurement. The curve C2 shows the ideal theoretical signal of the electrical speed if the measured position was harmonic-free. The curve C3 shows the signal of the electrical speed obtained according to the method of the present invention. The appearance of the curve C3 is identical to that of the ideal curve C2 showing the effectiveness of the harmonic filtering. Furthermore, the curve C3 is only very slightly offset from C2 showing the minimization of the attenuation of the electrical speed according to the present invention.
This second embodiment differs from that of
This third embodiment differs from that of
Thus, the present invention allows attenuating, and even eliminating, the harmonics. Furthermore, it allows preserving the accuracy and the integrity of the position measurement by avoiding shifting or attenuating the signals. It does not generate any additional phase shift between the measured position of the axis of the rotor and the digitally processed position. In addition, it allows calculating harmonic-free and attenuation-free position and speed control signals or data. These control data, which is used as input data for the control unit, then enable a very stable and very accurate piloting of the electric machine.
Number | Date | Country | Kind |
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2111101 | Oct 2021 | FR | national |
Filing Document | Filing Date | Country | Kind |
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PCT/FR2022/051966 | 10/18/2022 | WO |