Method for determining the angular position of an electric machine rotor

Abstract

The present invention relates to a method for determining an angular position of a rotor of a three-phase synchronous electrical machine, in which the following steps are implemented: a) the instantaneous voltages (U) and currents (I) of each phase are measured (Mes); b) a first rotational speed (ωest) and a first angular position (θest) of a voltage vector are estimated (Est1) from at least the voltages measured in step a); c) said angular position of the rotor (θrotor) is determined (Det1) from said first rotational speed (ωest) and said first angular position (θest) of the voltage vector, the measured currents (I) and from an optimization method based on the search for the maximum power of the electrical machine. The invention also relates to a control method, an electrical machine, a computer program product and a storage medium readable by computer means. Figure 1 to be published

Description

Title of the invention: Method for determining the angular position of an electric machine rotor Technical field

[0001] The invention relates to the determination of the angular position of a rotor of a synchronous electrical machine, in particular in order to control the electrical machine. More particularly, the invention is aimed at applications where the rotational speed of the electrical machine is high (up to 200,000 revolutions per minute in particular). Indeed, the higher the rotational speed, the more the inaccuracy in the angular position of the rotor becomes troublesome, in particular for controlling the electrical machine.

[0002] Furthermore, it is sought to determine the angular position of the rotor of the electric machine without using a position sensor. Indeed, for the high rotation speed applications targeted, the installation of a position sensor proves difficult. Prior art

[0003] Several methods are known for determining the angular position of an electric machine rotor, known as "sensorless", i.e. not using a position sensor.

[0004] Some of these methods are based on the calculation of electromotive forces (known by the abbreviation FEM) and their phase, in steady state. The calculation of the angular position can then be deduced for example using an observer as described in B. NAHID-MOBARAKEH, "Mechanical sensorless vector control of synchronous magnet machines: methods, convergence, robustness, "online" identification of parameters," Doctoral thesis, Institut National Polytechnique de Lorraine, 2001.

[0005] This type of method is simple and easy to implement but the simplified model of the machine introduces significant position calculation errors.

[0006] Other methods use an observer such as the Kalman filter, for example described in the following publications: - Z. Zheng, Y. Li, M. Fadel, “Sensorless control of PMSM based on extended kalman filter,” 2007 European Conference on Power Electronics and Applications, Sep 2007, Aalborg, Denmark. 8 p., ffl0.1109 / EPE.2007.4417275ff. ffhal-03540901. - J. Dilys, V. Stankevic, K. Luksza, “Implementation of Extended Kalman Filter with Optimized Execution Time for Sensorless Control of a PMSM Using ARM Cortex-M3 Microcontroller”, Energies 2021, 14, 3491. https: / / doi.org / 10.3390 / enl4123491 - W. van Meijl, G. Muisers, A. Borisavljevic, M. Brands and E. Lomonova, "Sensorless observation of a very-high-speed permanent magnet synchronous machine," 2013 IEEE International Symposium on Sensorless Control for Electrical Drives and Predictive Control of Electrical Drives and Power Electronics (SLED / PRECEDE), 2013, pp. 1-8, doi: 10.1109 / SLED-PRECEDE.2013.6684502.

[0007] This type of method has two major drawbacks. The first is the dependence of the system of equations and the modeling solely on Gaussian white noise. The second drawback is the high computation time, requiring the use of high-performance processors. For high rotation speeds, it is generally necessary to increase the switching frequency of the speed variators and therefore the computation frequency.

[0008] Methods using a sliding mode observer are also known. The document M. Fadel, R. Ruelland, G Gateau, JC Hapiot, P. Brodeau, JP Carayon, “Control without mechanical sensor of embedded actuators”, 2004 days of the electrotechnical section of the EEA club; March 2004, Cergy Pontoise, France, DO - 10.1051 / bib-j3ea:2005609, describes such a method. The principle of these observers can be divided into two stages. The first stage consists of converging the dynamics of a system of order n into a manifold of order nm, m being the number of measurable outputs. This manifold is then called the “sliding surface”. This involves determining a part of the matrix in order to converge, in a first step, the estimated quantities of the model which are measurable. When this step is completed, a system with dynamics of order nm is obtained.The second step is to impose the dynamics of this system using the remaining gains. This can be calculated by the Fillipov method or by a similar method called the equivalent control method. The goal is to cancel the remaining observation error which corresponds to the estimated non-measurable quantities.

[0009] The disadvantage of this method is that it is highly discontinuous and generates more or less significant noise on the observed quantities (a phenomenon known by the Anglo-Saxon term "chattering"). It is then often necessary to filter these quantities in order to be able to reconstruct a usable high-resolution position. The use of filters generates delays which are more troublesome at very high rotation speeds where the slightest delay can turn into a significant delay angle and thus destabilize the control loop.

[0010] Some methods also seek to minimize the rotor position error, taking into account iron losses. For example, the paper J. Kim, I. Jeong, K. Nam, J. Yang and T. Hwang, "Sensorless Control of PMSM in a High-Speed ​​Region Considering Iron Loss," in IEEE Transactions on Industrial Electronics, vol. 62, no. 10, pp. 6151-6159, Oct. 2015, doi: 10.1109 / TIE.2015.2432104 uses finite element modeling to determine iron losses. However, this method requires accurate modeling of the electrical machine and iron losses. Indeed, iron losses Pf consist of hysteresis losses P h and eddy current losses Pe. Pf = ph + pe = + keB2^

[0011] With Æ the Steinmetz constant, kh and ke the hysteresis and eddy current constants, and B the magnetic field and(!) the rotation speed.

[0012] When iron losses are modeled by a resistance, only eddy current losses are modeled and are proportional to w2. Thus, the finite element calculation consisting of calculating iron losses provides an imprecise result.

[0013] Furthermore, the models used generally do not take into account the evolution of stator resistance with temperature, which negatively impacts their reliability. Summary of the invention

[0014] The aim of the invention is to propose a method for determining the angular position of the rotor, in a precise manner, in particular for high rotation speed applications, without using a position sensor to be implemented in the electrical machine.

[0015] The method of the invention may in particular be insensitive to parametric variations of a model used in the method, to improve the precision of the angular position of the rotor.

[0016] The invention relates to a method for determining an angular position of a rotor of a three-phase synchronous electrical machine, in particular an electrical machine with smooth poles or salient poles, according to which at least the following steps are implemented: a) the instantaneous voltages and currents of each phase of the electrical machine are measured; b) a first rotational speed and a first angular position of a voltage vector of the electrical machine are estimated from at least the voltages measured in step a); c) said angular position of the rotor is determined from said first rotational speed and said first angular position of the voltage vector, from the instantaneous currents measured in step a) and from a method for finding the maximum power of the electrical machine.

[0017] Preferably, no rotor position sensor or torque sensor is used.

[0018] According to a configuration of the invention, an acquisition filter is used generating a time delay between the physical voltage or current signal measured in step a and the corresponding digital signal) and the time delay generated by the acquisition filter is compensated.

[0019] Advantageously, in step b), a phase-locked loop method is applied.

[0020] Preferably, in step b), at least the following sub-steps are carried out: 1) a Park transformation is applied to the measured voltages to determine the direct voltage and the quadrature voltage, said voltage vector corresponding to the vector defined by the direct voltage and the quadrature voltage, 2) a proportional-integral controller is used to determine a comparative rotation speed from the direct voltage, 3) then we estimate a comparative position of the tension vector by integrating (Int) said comparative rotation speed over time, 4) sub-steps 1) to 3) are repeated, taking into account, in sub-step 1), the last estimated comparative position of the voltage vector, until the direct voltage is lower than a predetermined threshold, 5) said first rotational speed and said first angular position are determined as corresponding respectively to the last comparative rotational speed and to the last comparative position of the tension vector.

[0021] Advantageously, in step c), a first estimate of the angular offset between the angular position of the voltage vector and the angular position of the rotor is made, from parameters of the electrical machine, then the angular offset of the rotor is modified from the first estimate of the angular offset and the instantaneous electrical power of the electrical machine to maximize the electrical power, and the angular position of the rotor is determined from the modified angular offset.

[0022] Preferably, in step c), to modify the angular offset of the rotor, at least the following sub-steps are carried out: i) the instantaneous power of the electrical machine is calculated from the measured currents and voltages and the first estimate of the angular offset; ii) we determine (Var) a temporal variation of instantaneous power; iii) depending on the time variation of instantaneous power, a comparative timing angle is determined; iv) the instantaneous power is recalculated from the currents and voltages, taking into account the comparative setting angle; v) preferably, sub-steps i) to iv) are repeated at least once by replacing in step i) the first estimate of the angular offset by the angle of comparative setting determined and the setting angle is determined as the last of the comparative setting angles determined.

[0023] According to an implementation of the invention, in sub-step iii), when the temporal variation is negative, the comparative setting angle is determined by the following formula:

[0024] ®cal_comp = ' PW-P

[0025] and when the time variation is positive, the comparative setting angle is determined by the following formula:

[0026] $ p^ff P

[0027] with Kl, K2, K3 and K4 predefined parameters, s the Laplace operator and Diff_P the temporal variation of power.

[0028] The invention also relates to a method for controlling a synchronous electrical machine in which the angular position of the rotor of said electrical machine is determined according to the method for determining the angular position of the rotor of the electrical machine according to one of the variants or combinations of variants described above and the electrical machine is controlled from the determined angular position of the rotor.

[0029] Preferably, the synchronous electrical machine is a variable reluctance machine, a smooth pole electrical machine or a salient pole electrical machine, the electrical machine comprising or not permanent magnets.

[0030] Advantageously, when the electrical machine has salient poles, a defluxing angle is determined to control the electrical machine.

[0031] The invention also relates to a synchronous electrical machine in which the control method described is implemented according to one of the variants or combinations of variants described previously or in which the angular position of the rotor is determined from the method for determining the angular position of the rotor of the electrical machine according to one of the variants or combinations of variants described previously.

[0032] The invention also relates to a computer program product downloadable from a communication network and / or recorded on a medium readable by a computer means, such as a computer or a calculator, and / or executable by a processor, comprising program code instructions for implementing the method for determining the angular position of the rotor according to one of the variants or combinations of variants described above or the control method according to one of the variants or combinations of variants described above, when said program is executed on a computer means.

[0033] The invention also relates to a storage medium readable by a computer means, such as a computer or a calculator, and storing instructions, which, when executed by a computer means, imply that the computer means implements the method of determining the angular position of the rotor according to one of the variants or combinations of variants described previously or the control method according to one of the variants or combinations of variants described previously. List of figures

[0034] Other characteristics and advantages of the methods and systems according to the invention will appear on reading the following description of non-limiting examples of embodiment, with reference to the appended figures described below. [Fig 1]

[0035] [Fig. 1] represents a block diagram of the method for determining the angular position of the rotor of a synchronous electrical machine according to the invention. [Fig 2]

[0036] The figure represents a block diagram representative of an example of step b) of the method for determining the angular position of the rotor of an electrical machine according to the invention. [Fig 3]

[0037] [Fig.3] illustrates the angular offset between the angular position of the voltage vector and the angular position of the rotor, in a Park frame, for the application of the method for determining the angular position of the rotor of an electrical machine according to the invention. [Fig 4]

[0038] [Fig.4] represents an example of step c) of the method for determining the angular position of the rotor of an electrical machine according to the invention. [Fig 5]

[0039] [Fig.5] represents the comparison between the theoretical rotor angular position and the rotor angular position obtained from the method of determining the angular position according to the invention. [Fig 6]

[0040] [Fig.6] illustrates the comparison between the actual direct current and the direct current resulting from the method of determining the angular position of the rotor of an electrical machine according to the invention. [Fig 7]

[0041] [Fig.7] illustrates the comparison between the actual quadrature current and the quadrature current resulting from the method for determining the angular position of the rotor of an electrical machine according to the invention. Description of the embodiments

[0042] The following annotations are used in this description and / or in the figures:

[0043] d: direct direction of a reference frame (notably a Park reference frame)

[0044] q: direction in quadrature of a reference frame (notably a Park reference frame)

[0045] estimated: direct direction of the Park reference frame estimated from the tension vector

[0046] estimated: quadrature direction of the estimated Park frame of the tension vector

[0047] dréei: direct direction of the Park frame of the real current vector in the rotor

[0048] qréei: quadrature direction of the Park frame of the real current vector in the rotor

[0049] <hcai_comp : angle de calage comparatif

[0050] dLir modified angular offset when the temporal variation of power is positive

[0051] 3>cai2: angular offset modified when the temporal variation of power is negative

[0052] <hcaiage: décalage angulaire entre le repère défini par (dréei, qréei) et le repère défini par (^estimé, Qestimé)

[0053] Kl, K2, K3, K4: predefined parameters

[0054] k: filter parameter

[0055] alternating voltages measured at each phase a, b, c respectively of the electrical machine

[0056] Vmax: maximum voltage

[0057] 0V: real angular position of the voltage vector

[0058] 0est: first estimated angular position of the tension vector

[0059] Oest_rotor* first estimated angular position value of the rotor

[0060] 0rotor: determined angular position of the rotor

[0061] vdq_PLL\ estimated voltage vector composed of vd PLL and vq_PLL

[0062] Vj pll ; forward voltage estimated in step b)

[0063] vq_PLL: quadrature voltage estimated in step b)

[0064] P(-0esti)C23: Park transformation to move from the three-phase reference frame to the Park reference frame

[0065] rs: equivalent resistance of a stator phase

[0066] U: voltage measurements

[0067] I: current measurements

[0068] Id: direct voltage

[0069] Idreab real direct voltage

[0070] Iqreai: real quadrature voltage

[0071] Idcontrob direct voltage coming out of optimization

[0072] Iqcontrob quadrature voltage coming out of optimization

[0073] Iq: quadrature voltage

[0074] Iref: reference voltage

[0075] co: electrical rotation speed

[0076] coest: estimated electrical rotation speed

[0077] <pd : flux magnétique dans la direction directe

[0078] cpq: magnetic flux in the quadrature direction

[0079] Ld: inductance in the direct direction

[0080] Lq: inductance in the quadrature direction

[0081] rpf: flux of permanent magnets seen through the stator windings

[0082] vd: direct voltage

[0083] Vq .quadrature voltage

[0084] p: number of pairs of poles of the electric machine

[0085] PDC: continuous input power (from the inverter for example)

[0086] Diff_P: temporal variation of power

[0087] The invention relates to a method for determining the angular position (and its evolution over time) of a rotor of a three-phase synchronous electrical machine (i.e. with three phases).

[0088] The electric machine may be an electric machine with smooth poles or salient poles. It may also be a variable reluctance machine, for example comprising permanent magnets, or made of a material capable of generating an electromotive force in a vacuum.

[0089] An electrical machine generally comprises a rotor and a stator. The stator is generally a fixed part while the rotor rotates around a longitudinal axis relative to the stator. The rotor may comprise permanent magnets but there are also rotors that do not comprise permanent magnets. Furthermore, the stator comprises one or more pairs of magnetic poles and generally comprises windings (also called electric coils) in each magnetic pole. Thus, when a voltage is applied to the windings of the magnetic poles of the stator, the poles are magnetically activated and drive the rotor into rotation (operation as a motor of the electrical machine). Induced currents are therefore applied to the rotor. Conversely, the electrical machine can operate as a generator.In this case, the rotor is driven into rotation (e.g. by a belt or a set of gears) and the rotation of the rotor causes an induced current in the windings, which can thus generate electric current.

[0090] The electrical machine is said to be “synchronous” when the rotor rotates in synchronization with the rotating field of the stator.

[0091] For this method, at least the following steps are implemented: a) the instantaneous voltages and currents of each phase of the electrical machine are measured; b) estimating a first rotational speed and a first angular position of a voltage vector of the electrical machine from at least said voltages measured in step a); c) the angular position of the rotor is determined from said first rotational speed and said first angular position of the voltage vector, from the instantaneous currents measured in step a) and from a method for finding the maximum power of the electrical machine (for example an optimization method based on finding the maximum power of the electrical machine, where the aim is to optimize the precision of the angular position of the rotor to achieve the maximum power of the electrical machine).

[0092] Preferably, no rotor position sensor or torque sensor may be used. Thus, it is not necessary to install this type of sensor in the electric machine. The construction of the electric machine is therefore simple, and the method allows good precision in determining the angular position of the rotor, in particular for controlling the electric machine.

[0093] The method thus allows the calibration of the angular position of the rotor, without a priori knowledge of the parameters of the electric machine (and therefore without needing to integrate a drift over time of these parameters).

[0094] This method is particularly suitable for electrical machines with high rotational speeds (i.e., for example, rotational speeds greater than 30,000 revolutions per minute).

[0095] [Fig.l] illustrates, in a schematic and non-limiting manner, a first variant of a method for determining the angular position of the rotor according to the invention.

[0096] The diagram illustrates a first step of measuring Mes of the instantaneous voltages U and currents I of each phase of the electrical machine.

[0097] We can then estimate Estl the first rotation speed coest and the first angular position 0est of a voltage vector representative of the measured voltages U. Indeed, the electrical machine being a synchronous machine, the voltage vector is directly linked to the rotation of the rotor of the electrical machine.

[0098] From these estimates, Detl is then determined the angular position 0rotor of the rotor using a search method (in particular optimization based on the search) of maximum power of the electric machine.

[0099] The rotor angular position 0rotor can then be used to command / control Cont the electric machine. This command / control step Cont is framed in dotted lines to represent its optional nature. When this step is implemented, the method can then be considered as an electric machine control method.

[0100] The method according to the invention can in particular be implemented by computer means, such as a computer, a server, or a tablet, in particular by computer means in direct communication (wired or wifi for example) with the electrical machine (in particular with the means for measuring instantaneous voltages and currents of the electrical machine) in order to work in real time. Step a)

[0101] The step of measuring a) the instantaneous voltages and currents of each phase makes it possible to identify, at each instant, the current of each phase and the voltage of each phase.

[0102] According to one implementation of the invention, an acquisition filter can be used. The acquisition filter generates a time delay between the physical voltage or current signal measured in step a) and the corresponding digital signal and the time delay can be compensated. Indeed, the acquisition of a signal generally involves a delay between the real physical signal and the digital signal resulting from the acquisition. This delay can in particular be due to the hardware itself, and / or to the processing of this signal. When the rotation speed is high, even a small delay can have a significant impact on the angular position error and consequently on the control of the electrical machine.When the time delay is known or can be determined sufficiently precisely, the time delay generated by the acquisition filter can be compensated to shift the digital signal by the equivalent of the time delay, in order to make it correspond to the real instant of the real physical signal. Using the time delay compensation of the acquisition filter makes it easier to carry out the following steps since it reduces an initial inaccuracy. For example, by knowing the measurement chain and its filters, it is possible to calculate this delay which can be of the form -k*w in the case of first-order cascaded filters. Step b)

[0103] During this step, we seek to determine the angular position of a vector representative of the voltage in the different phases. Indeed, as it is a synchronous electrical machine, the electrical pulsation of the voltages is equal to the electrical speed of the rotor. As the rotor rotates, the direction of a voltage vector representative of these different phases evolves over time and as a function of the

[0104]

[0105] angular position of the rotor. Thus, from the measured voltages, the angular position of the voltage vector can be determined. Step b) corresponds to an estimation because it allows to identify the angular position of the voltage vector, which does not correspond entirely to the angular position of the rotor. Indeed, there is a slight time lag between the current signal and the voltage signal. Given the rotation speed, this time lag (generally called "power factor") induces an angular shift of the rotor and, of course, the higher the rotation speed, the greater this angular shift. This time lag also depends on the parameters of the electrical machine, for example the inductance, the stator resistance and the flux of the magnets. Control of the electrical machine is then erroneous, or even difficult to achieve. The measured (and possibly filtered) stator voltages vabc are presented in the following equation where is the angular position of the voltage vector. Vabc — ^max sin(ov-?f)

[0106]

[0107] The three phases of the electrical machine are each offset by radians, hence the offsets of 2^ and in the previous expression. Knowing these currents and / or voltages measured for each phase allows, for example, to arrive, via a Park transformation, at a voltage vector and / or a current vector respectively. The Park transformation is a change of reference frame between the fixed stator reference frame and the rotating reference frame considered (for example, the rotor reference frame rotating around the rotor axis relative to the stator), called the Park reference frame. The Park transformation allows a three-phase problem to be modeled as a two-phase model, which is simpler to model and solve. The Park reference frame (each reference frame considered) is defined by two axes, a direct axis d and a quadrature axis q, orthogonal to the direct axis d, the direct axes d and quadrature axes q being orthogonal to a third axis (generally called the zero sequence axis "h") around which the Park reference frame rotates (for example, the rotor axis).The Park transformation of three-phase voltages and / or currents thus makes it possible to obtain respectively a voltage vector composed of the direct voltage (voltage along the direct axis d) and the quadrature voltage (voltage along the quadrature axis q) and / or a current vector composed of the direct current (current along the direct axis d) and the quadrature current (current along the quadrature axis q). The Park reference frame is directly linked to the angular position of the rotating part, for example the rotor (relative to the electrical machine and more precisely the stator). Therefore, in step b), the first rotational speed and the first angular position of the voltage vector (for example the vector resulting from the Park transformation of the voltages of each phase) can be estimated from the measured voltages (and / or measured currents). For example, the voltages measured in each phase at each instant can be transformed into a voltage vector composed of the direct voltage and the quadrature voltage in the Park frame and the first rotational speed and the first angular position are sought so that the direct voltage is zero. Indeed, the aim is to regulate the zero direct voltage so as to regulate the sine function of the difference between the estimated angular position and the zero actual angular position, which corresponds to an estimated angular position of the voltage vector substantially equal to the actual angular position of the voltage vector.

[0108] Preferably, in step b), a phase-locked loop method, known as PLL for “Phase-locked loop” in English, can be applied. This loop makes it possible to control the phase to the three-phase voltages to precisely determine the first angular position of the voltage vector. Indeed, thanks to the use of the phase-locked loop, the first angular position can gradually converge towards its real value.

[0109] Advantageously, for the phase-locked loop method, at least the following sub-steps can be carried out: 1) a Park transformation can be applied to the measured voltages to determine the forward voltage and the quadrature voltage, said voltage vector corresponding to the vector defined by the forward voltage and the quadrature voltage, 2) a proportional-integral controller can be used to determine a comparative rotation speed from the forward voltage: this type of controller is simple to implement, 3) then we can estimate a comparative position of the tension vector by integrating said comparative rotation speed over time, the angular position being directly linked to the rotation speed, 4) sub-steps 1) to 3) can be repeated, taking into account, in sub-step 1), the last estimated comparative position of the voltage vector, until the direct voltage is lower than a predetermined threshold, so as to make the estimated angular position of the voltage vector converge towards the actual angular position of the voltage vector (and therefore the sine function of the difference between these two positions tends towards zero), which implies that the direct voltage tends towards zero, 5) said first rotational speed and said first angular position can be determined as corresponding respectively to the last comparative rotational speed and to the last comparative position of the tension vector, that is to say when the loop has converged.

[0110] These steps make it possible to precisely and quickly define the first rotation speed and the first angular position of the tension vector.

[0111] [Fig.2] illustrates, in a schematic and non-limiting manner, an example of a phase-locked loop for determining the first rotational speed and the first angular position of the speed vector according to the invention.

[0112] In a first step, Mes of the instantaneous voltages U and currents I of each phase of the electrical machine are measured.

[0113] At least the voltage measurements U are used to perform Park transforms and thus determine a voltage vector composed of the direct voltage vd and the quadrature voltage vq. To initialize the control loop, an arbitrary value of the angular position of the rotor can be used (for example equal to zero or to the last known position of the rotor).

[0114] We seek to regulate the zero direct voltage so as to regulate the sine function of the difference between the estimated angular position and the actual angular position so that it is zero, which corresponds to an estimated angular position of the voltage vector substantially equal to the actual angular position of the voltage vector. Thus, we can find the angular position of the voltage vector.

[0115] Thus, we compare CompO with the direct voltage vd to a zero value and then apply a proportional-integral regulator PI to determine the rotation speed coest. By integrating Int then this rotation speed coest, we can estimate the angular position 0est of the voltage vector. This angular position 0est of the voltage vector is then reused at the input of the loop for the Park transformation. When the direct voltage is zero or almost zero, we can then determine the first angular position of the voltage vector and the first rotation speed, as corresponding to the last estimated values ​​respectively of the estimated angular position 0est of the voltage vector and the rotation speed coest.

[0116] For example, the following equation can give the tension vector, in the estimated Park frame dq^, as a function of the estimated angular position Qest of the tension vector, sin(ev-0estï) ' -cos(dv-9est}).

[0118] As we seek to bring vd_PLL back to 0, the estimated position 9est becomes equal to when the phase-locked loop converges. Step c)

[0119] Step c) makes it possible to refine the precision of the angular position of the rotor, from the estimation of the first angular position obtained for the voltage vector. This step may for example comprise a loop to gradually refine the angular position of the rotor. To initialize this loop, one can for example consider, 'vd_PLL Vq_PLL '^est ) max Vdq_PLL ~ initially, that the angular position of the rotor corresponds either to the first angular position of the voltage vector, or to a first estimate value.

[0120] [Fig.3] illustrates, in a schematic and non-limiting manner, the angular phase shift between the currents and the voltages.

[0121] This figure illustrates a first reference frame (Park) defined by the axes dréd and qréei and a second reference frame (Park) defined by the axes destimated and qestimated. The angular phase shift between these two reference frames corresponds to the setting angle 0caiage.

[0122] The first reference frame (dréei, qréei) corresponds to the Park reference frames of the currents in the rotor and the second reference frame (destimated, qestimated) corresponds to the Park reference frame of the voltage vector. Thus, in the first reference frame (dréei, qréei), the current vector is in the qréei direction (in fact, we assume a smooth-pole synchronous machine operating at maximum torque). We therefore have the reference current Iref equal to the quadrature current Iq in the qréei direction and the direct current is zero in the dréei direction.

[0123] In the second frame, the voltage vector V is in the direction qestimated. Taking into account the non-zero calibration angle 0caiage between the two frames (dréei, qréei) and (destimated, qestimated), the voltage vector V is decomposed into a direct voltage Vd = - w -Lq-Iq in the direction dréd of the first frame (dréei, qréei) and into a quadrature voltage Vq-rS'Iq"F (x? * Oans the direction q,ée of the first frame (dæei, qréei)*

[0124] Using a search method (in particular optimization based on the search) of maximum power of the electric machine is advantageous because the input power, in particular at the level of an inverter (the electric machine advantageously comprising this inverter) is an easily determinable quantity. For example, one can measure the direct voltage (by a voltage measuring means such as a voltmeter for example) and the direct current (by an electric current measuring means such as an ammeter for example) at the input of the inverter, and deduce the direct power at the input of the inverter by the product of the direct voltage and the direct current. Generally, the electric machine is used to operate at its maximum torque, which corresponds to a zero direct current and a maximum quadrature current (after Park transformation, in the Park frame).For a smooth pole machine, maximizing the torque of the electric machine is equivalent to maximizing the power. Thus, the search method (search-based optimization) for the maximum power of the electric machine makes it possible to search for the maximum torque, corresponding to the operation of the electric machine.

[0125] For a salient pole machine, the defluxing angle is taken into account to integrate the phase shift induced by this type of machine on the maximum torque. Indeed, for the salient pole machine, the maximum current intensity is not in the quadrature direction q but shifted from this direction by a defluxing angle (which therefore corresponds to the angular offset between the quadrature direction q and the direction of maximum current intensity, after Park transformation). This defluxing angle is generally known elsewhere and depends on the electric machine. It is therefore a predetermined parameter of the salient pole electric machine. Thus, the defluxing angle can be taken into account to define the Park frame linked to the rotor for this type of electric machine and thus control the electric machine in the correct direction of the Park frame for example.

[0126] Determining the angular position of the rotor can in particular be used for controlling the electrical machine.

[0127] According to a configuration of the invention, a first estimate of the angular offset between the angular position of the voltage vector and the angular position of the rotor can be made, from parameters of the electrical machine, then the angular offset of the rotor can be modified from the first estimate of the angular offset and the instantaneous electrical power of the electrical machine to maximize the electrical power. Then, the angular position of the rotor can be determined from the modified angular offset. In other words, the angular offset is initialized by a first value. This first value can be that of the first angular position of the voltage vector or can be determined for example numerically from different parameters of the electrical machine.This first value is imprecise, either because we know that the voltage vector is angularly offset from the rotor, or because the parameters of the electrical machine induce errors.

[0128] For example, when determined numerically, the first value of the angular offset can be determined from the following equation:

[0129] , \ \ v calage “ ~ ^TCtail [ rsl /

[0130] This equation is particularly valid for salient pole machines.

[0131] When the electric machine is a smooth pole machine, we can simplify the previous equation and determine the first value of the angular offset from the following equation, assuming that the direct current is regulated to zero so as to maximize the torque of the electric machine (the stator is assumed to be unsaturated): FOI 371 f vd \ l \ ( -wLalq \ $ shim = U ) = *^11 ( ) « ^Ctail ( )

[0133] The preceding equations for determining the first value of the setting angle are highly dependent on parameters of the electric machine.

[0134] Thus, a parametric error risks inducing an error in the angle which can lead to a loss of performance of the electric machine (the torque at the point of operation is not maximum), or even to a loss of control. This is why the angular offset is then modified to improve its precision.

[0135] For these reasons, we then seek to modify this first value to reduce the error associated with it. To improve the accuracy of the angular position of the rotor, we then seek to modify the angular offset so as to maximize the electrical power, which amounts to maximizing the electrical torque. The (modified) angular offset gradually converges and we can then deduce the angular position of the rotor.

[0136] Advantageously, to modify the angular offset of the rotor, at least the following sub-steps can be carried out: i) the instantaneous power of the electrical machine can be calculated from the measured currents and voltages (which can be the currents and voltages measured in step a) or the DC currents and voltages measured at the inverter) and the first estimate of the angular offset; ii) a temporal variation of instantaneous power can be determined; in fact, as the currents and voltages are measured instantaneously, it is possible, for two successive measurement instants, to determine the power (by the product of the voltage and the current for example) of each instant and consequently the variation of power between these two successive instants; iii) based on the time variation of instantaneous power, a comparative setting angle can be determined; for example, if the power variation is positive, this means that the maximum power has not yet been reached since the power tends to increase. Therefore, the comparative setting angle can be increased. Conversely, if the power variation is negative, this means that the maximum power has been exceeded and the power then tends to decrease. Therefore, the comparative setting angle can be reduced to get closer to the maximum power value. iv) the instantaneous power can be recalculated from the currents and voltages taking into account the comparative setting angle; this allows the power to be re-evaluated with the comparative setting angle to converge towards the maximum power; v) preferably, sub-steps i) to iv) can be repeated at least once by replacing in step i) the first estimate of the angular offset with the determined comparative setting angle and the setting angle can be determined as the last of the determined comparative setting angles. This reiteration allows a gradual convergence towards the setting angle making it possible to define the angular position of the rotor. This also allows good precision.

[0137] According to one configuration, sub-step v) can be implemented continuously: in other words, the loop of step c) runs continuously.

[0138] For example, one may seek to maximize the continuous input power PDC of the inverter of the electric machine. The continuous input power can be determined, for a smooth pole machine, by the following equation: [01391 Pnc*l[P-^ + P'(^-^'h^^^

[0140] Preferably, the angular offset can be adjusted to a reference current I f— + / ' constant ct at constant rotation speed. Therefore, the joule losses corresponding to the term 2^ + j2 and the mechanical losses are constant during the adjustment of the angular offset. Therefore, maximizing power is indeed maximizing the electromagnetic torque.

[0141] When the electrical machine has salient poles, the principle explained previously applies but it is necessary to determine the defluxing angle which corresponds to the torque maximization angle, to generate the references of the currents Id and Iq in the control reference frame (corresponding to the Park reference frame defined by the determined angular position of the rotor).

[0142] Furthermore, if the delays caused by the acquisition filters and the calculation delays are known, they can be compensated separately and added as compensation to the setting angle (for example, to allow its initialization).

[0143] The optimization method based on the search for maximum power of the electrical machine consists of searching for the compensation angle to be added to the first angular position of the voltage vector to compensate for the phase shift angle between voltages and current (and possibly the filter delays). This method can use, for example, measurements of the DC voltage and current (for example that of the power supply bus) to maximize the DC input power PDC.

[0144] [Fig.4] illustrates, in a schematic and non-limiting manner, an example of an optimization method based on the search for the maximum power of the electrical machine according to the invention.

[0145] From the measurements of the instantaneous voltages U and current I of each phase of the electrical machine and a first angular position value 0est_rotor of the rotor, we can determine Power the instantaneous electrical power P of the electrical machine. We can then determine Var the temporal variation of the instantaneous power Diff_P.

[0146] We can then compare CompP this temporal variation of the instantaneous power Diff_P with respect to zero and define an angular offset according to this comparison. For example here, when the temporal variation of the instantaneous power Diff_P is less than zero Neg, we determine <e>cai2 the angular shift; when the time variation of the instantaneous power Diff_P is greater than zero Pos, we determine <e>can the angular offset. Then, we calculate the impact on the voltage V + AV and on the current I + AI based on the angular offset calculated previously. We can then take into account these impacts on the voltage and on the current at the input of the Power determination step of the instantaneous electrical power P of the electrical machine.

[0147] Advantageously, in step iii), when the time variation is negative, the comparative setting angle can be determined by the following formula: [° 14 81 Æ • Dtff_P

[0149] and when the time variation is positive, the comparative setting angle can be determined by the following formula:

[0150] . Diff _P

[0151] with Kl, K2, K3 and K4 predefined parameters, s the Laplace operator and Diff_P the temporal variation of power. Therefore, the response of the method can be adapted to the dynamics of the slope of the temporal variation of power Diff_P.

[0152] The comparative calibration angle is a filtering term (first order) that can be parameterized to manage the detection dynamics when the Diff_P derivative is positive or negative. We thus have degrees of freedom on the dynamics when the Diff_P derivative is positive or negative.

[0153] K1, K2, K3 and K4 can come from maps of the electrical machine determined beforehand, or from recalibration during the lifetime of the electrical machine. These parameters can also depend on the value of the temporal variation of power Diff_P to make the setting angle converge more quickly.

[0154] The invention also relates to a method for controlling a synchronous electrical machine in which the angular position of the rotor of said electrical machine is determined according to one of the variants or combinations of variants described above and the electrical machine is controlled from the determined angular position of the rotor.

[0155] Preferably, the synchronous electrical machine is a variable reluctance machine, a smooth pole electrical machine or a salient pole electrical machine, the electrical machine comprising or not permanent magnets.

[0156] According to an implementation of the invention, when the electrical machine has salient poles, a defluxing angle can be determined to control the electrical machine.

[0157] The control method according to the invention can in particular be implemented, at least partially by computer means, such as a computer, a server, or a tablet, in particular by computer means in direct communication (wired or wifi for example) with the electrical machine (in particular with the means of measuring instantaneous voltages and currents of the electrical machine) in order to work in real time and to be able to control the electrical machine in real time.

[0158] Furthermore, the invention relates to a synchronous electrical machine in which the control method is implemented according to one of the variants or combinations of variants described above or in which the angular position of the rotor is determined from the method according to one of the variants or combinations of variants described above.

[0159] The invention also relates to a computer program product downloadable from a communication network and / or recorded on a medium readable by a computer means (such as a computer or a calculator) and / or executable by a processor, comprising program code instructions for implementing the method for determining the angular position of the rotor according to one of the variants or combinations of variants described above or the control method according to one of the variants or combinations of variants described above, when said program is executed on the computer means.

[0160] The invention also relates to a storage medium readable by a computer means (such as a computer or a calculator), and storing instructions, which, when executed by the computer means, imply that the computer means implements the method of determining the angular position of the rotor according to one of the variants or combinations of variants described previously or the control method according to one of the variants or combinations of variants described previously. Examples

[0161] The method for determining the angular position of the rotor according to the invention was tested for a smooth-pole synchronous electric machine, and the control of the electric machine was carried out based on the angular position of the rotor determined according to this method of the invention.

[0162] The angular position of the rotor is determined by the method according to the invention at the following operating point: • Rotation speed: 50,000 revolutions per minute • Input current: 50 A in alternating current • Maximum power (when the angular position of the rotor determined by the method according to the invention corresponds to the actual position): 180W

[0163] The model of the electric machine is as follows: • Number of pole pairs: 1 • Ld and Lq inductances: 12pH • Magnetic flux of the magnets through the stator windings: 450 pWb

[0164] For the operating point tested, the speed is imposed by an external system (here a motor coupled to the same shaft as the electric machine but another system could have been used instead). The method for determining the angular position of the rotor according to the invention is implemented from the instant t=0.01s. Figures 6 and 7 respectively represent the evolution of the direct current ([Fig.6]) and the quadrature current ([Fig.7]), in amperes, over time time(s) in seconds. The direct current Idreaicorresponds to the real direct current of the electric machine, while the direct current Idcontroicorresponds to the direct current determined by the method according to the invention.Similarly, the quadrature current Iq reai corresponds to the actual quadrature current of the electric machine, while the quadrature current Iq controi corresponds to the quadrature current determined by the method according to the invention.

[0165] As shown in Figures 6 and 7, at the time when the method of the invention is implemented, i.e. t=0.01s, the actual reference frame of the electric machine (direct and quadrature directions of the actual Park reference frame of the electric machine) is not in phase with the reference frame of the determined angular position of the rotor. Indeed, it is observed that at t=0.01s and just after, the real direct and quadrature currents Idreai and Iqreaisont are very offset from the direct and quadrature currents resulting from the determined angular position of the rotor according to the method of the invention Idcontroi and Iqconnoi- This is due to the fact that the angular offset between acquired voltages and measured currents is not compensated at the beginning of the implementation of the method according to the invention. It can be seen that the method of the invention nevertheless makes it possible to quickly converge the direct and quadrature currents estimated by the method Idcontroi and Iq controi with the real direct and quadrature currents Idreai and Iqreai, respectively, thanks to the phase-locked loop presented in [Fig.2] on the one hand and to the optimization method based on the search for maximum power (which here runs in a loop according to the example presented in [Fig.4]).This demonstrates the quality of the method in determining the angular position of the rotor precisely and quickly, without the need for sensors to be integrated into the electric machine, and without the need for parameters of the electric machine which may change over time and are therefore unreliable.

[0166] [Fig.5] illustrates the comparison over time between the angle of the theoretical rotor angular position Ang_th and the angle of the rotor angular position determined by the optimization method based on the search for maximum power according to the invention. It can be seen that thanks to the method according to the invention, the determined angle converges quickly towards the theoretical angle, in a precise manner without the need for sensors to be integrated into the electric machine, and without the need for parameters of the electric machine that may evolve over time and are therefore unreliable. The optimization method based on the search for maximum power allows rapid and reliable convergence to determine the angle of the rotor angular position.< / e> < / e>

Claims

Claims

1. Method for determining an angular position of a rotor of a three-phase synchronous electrical machine, in particular an electrical machine with smooth poles or salient poles, according to which at least the following steps are implemented: a) measuring (Mes) the instantaneous voltages (U) and currents (I) of each phase of the electrical machine; b) estimating (Estl) a first rotational speed (œest) and a first angular position (0est) of a voltage vector of the electrical machine from at least the voltages measured in step a); c) determining (Detl) said angular position of the rotor (0rotor ) from said first rotational speed (œest) and said first angular position (0est) of the voltage vector, the instantaneous currents (I) measured in step a) and from a method for finding the maximum power of the electrical machine.

2. Method for determining an angular position of a rotor of a synchronous electrical machine according to claim 1, in which an acquisition filter is used generating a time delay between the physical voltage or current signal measured in step a and the corresponding digital signal) and the time delay generated by the acquisition filter is compensated.

3. Method for determining an angular position of a rotor of a synchronous electrical machine according to one of the preceding claims, in which in step b), a phase-locked loop method is applied.

4. Method for determining an angular position of a rotor of a synchronous electrical machine according to claim 3, wherein, in step b), at least the following sub-steps are carried out: 1) a Park transformation (Transf) is applied to the measured voltages (U) to determine the direct voltage (vd) and the quadrature voltage (vq), said voltage vector corresponding to the vector defined by the direct voltage (vd) and the quadrature voltage (vq), 2) a proportional-integral (PI) controller is used to determine a comparative rotation speed from the direct voltage, 3) then a comparative position of the voltage vector is estimated by integrating (Int) said comparative rotation speed over time, 4) sub-steps 1) to 3) are repeated, taking into account, in sub-step 1), the last estimated comparative position of the voltage vector, until the direct voltage (vd) is lower than a predetermined threshold, 5) said first rotation speed (coest) and said first angular position (0est) are determined as corresponding respectively to the last comparative rotation speed and to the last comparative position of the voltage vector.

5. Method for determining an angular position of a rotor of a synchronous electrical machine according to one of the preceding claims, in which, in step c), a first estimate of the angular offset between the angular position of the voltage vector and the angular position of the rotor is made, from parameters of the electrical machine, then the angular offset of the rotor is modified from the first estimate of the angular offset and the instantaneous electrical power of the electrical machine to maximize the electrical power, and the angular position of the rotor is determined from the modified angular offset.

6. Method for determining an angular position of a rotor of a synchronous electrical machine according to claim 5, wherein, in step c), to modify the angular offset of the rotor, at least the following sub-steps are carried out: i) calculating (Power) the instantaneous power (P) of the electrical machine from the measured currents (I) and voltages (U) and from the first estimate of the angular offset (0est_rotor); ii) determining (Var) a temporal variation of instantaneous power (Diff_P); iii) as a function of the temporal variation of instantaneous power (Diff_P), a comparative setting angle is determined; iv) recalculating the instantaneous power from the currents and voltages taking into account the comparative setting angle;v) preferably, sub-steps i) to iv) are repeated at least once by replacing in step i) the first estimate of the angular offset with the determined comparative setting angle and determining; the setting angle as the last of the determined comparative setting angles.

7. Method for determining an angular position of a rotor of a synchronous electrical machine according to claim 6, in which, in sub-step iii), when the time variation (Diff_P) is negative (Neg), the comparative setting angle ( <bcai_comp) par la formule suivante : ^cal comp (¾¾ ■ Diff Pet lorsque la variation temporelle est positive (pos), on détermine l’angle de calage comparatif (<bcai_comp) par la formule suivante : ^cal comp - 'Diff Pavec Kl, K2, K3 et K4 des paramètres prédéfinis, s l’opérateur de Laplace et Diff_P la variation temporelle de puissance.

8. Method for controlling a synchronous electrical machine in which the angular position of the rotor of said electrical machine is determined according to the method according to one of claims 1 to 7 and the electrical machine is controlled (Cont) from the determined angular position of the rotor.

9. A control method according to claim 8, wherein the synchronous electric machine is a variable reluctance machine, a smooth pole electric machine or a salient pole electric machine, the electric machine including or not including permanent magnets.

10. Control method according to one of claims 8 or 9, wherein, when the electrical machine has salient poles, a defluxing angle is determined to control the electrical machine.

11. Synchronous electric machine in which the control method according to one of claims 8 to 10 is implemented or in which the angular position of the rotor (0rotor) is determined from the method according to one of claims 1 to 7.

12. Computer program product downloadable from a communication network and / or recorded on a medium readable by computer means, such as a computer or a calculator, and / or executable by a processor, comprising program code instructions for implementing the method for determining the angular position of the rotor according to one of claims 1 to 7 or of the control method according to one of claims 8 to 10, when said program is executed on a computer means.

13. Storage medium readable by a computer means, such as a computer or a calculator, and storing instructions, which, when executed by a computer means, imply that the computer means implements the method of determining the angular position of the rotor according to one of claims 1 to 7 or the control method according to one of claims 8 to 10.

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