Method and drive system with a device for sensorless determination of the angular frequency and / or position of a permanent magnet rotor of a brushless electric machine

Abstract

Method for sensorless determination of the angular frequency (ωe) and / or position (φe) of a permanent magnet rotor of a brushless electric machine (1), in particular a linear or rotary machine, wherein a d-voltage (ud) and a q-voltage (uq) are provided to the electric machine (1), wherein a high-frequency d-test signal voltage (ud_inj) with a predetermined carrier frequency is applied to the d-voltage (ud) within the framework of an injection method, wherein several phase currents (i1, i2) of the machine (1) are measured and a demodulated current (iq_dem) is determined on the basis of the measured phase currents (i1, i2), wherein a d-voltage deviation (Δud) and a q-voltage deviation (Δuq) are determined on the basis of a motor model (9), in particular a mathematical one.wherein in a fusion device (6) the angular frequency (ωe) and / or position (φe) of the permanent magnet rotor is determined on the basis of the demodulated current (iq_dem) and the d-voltage deviation (Δud) and the q-voltage deviation (Δuq), wherein the fusion device (6) has a controller (22) with an integral component, in particular an integral controller, to which a sum signal is supplied which depends on the demodulated current (iq_dem) and the d-voltage deviation (Δud) and the q-voltage deviation (Δuq) and a feedback of the determined angular frequency (ωe) and / or position (φe) of the permanent magnet rotor, characterized in that the demodulated current (iq_dem) is supplied to a controller with a proportional component, in particular a proportional controller, and an output of the controller with a proportional component is used to generate the sum signal becomes.,

Description

The invention relates to a method for sensorless determination of the angular frequency and / or position of a permanent magnet rotor of a brushless electric machine. Furthermore, the invention relates to a drive system with a device for sensorless determination of the angular frequency and / or position of a permanent magnet rotor of a brushless electric machine. Brushless electric machines with a permanent magnet rotor are also known as permanent magnet electric machines and are increasingly used in the automotive industry, particularly in the form of permanent magnet synchronous motors. Controlling such electric machines requires knowledge of the permanent magnet rotor's position. Conventionally, this position is determined using a position sensor, but this involves additional costs and installation space. Therefore, there is a need for sensorless alternatives for controlling these types of machines. An exemplary method for the sensorless determination of the position and angular frequency of a permanent magnet rotor is known from EP 2 019 482 A1. This method is used within the framework of field-oriented control (vector control) and enables the determination of the rotor's angular frequency based on multiphase current measurements at the machine. A mathematical machine model is used for estimating the angular frequency and position. EP 2 144 362 A1 discloses a method and an arrangement for observing the drive speed of a permagnetic rotor in a drive control loop. Another method for determining the angular frequency and / or position of a permanent magnet rotor of a brushless electric machine without a sensor is described in EP 2 023 479 A1. In this method, a mathematical machine model provides an angular frequency and position estimate in the higher angular frequency range. At lower angular frequencies and when the machine is stationary, an injection method is used in which periodic test signals of a predetermined carrier frequency are injected into a manipulated variable, in this case the so-called d-voltage. The phase currents of the machine are measured and evaluated for position-dependent anisotropy in the magnetic structure of the electric machine, from which the angular frequency and / or position of the permanent magnet rotor is deduced. Figure 1 shows a block diagram of a drive system that implements the method disclosed in EP 2 023 479 A1. To enable a transition between the angular frequency and position estimation by the machine model and by the injection method, a fusion device is provided, the setup of which is shown in Fig. 2. The fusion device comprises a model tracking controller 30, an injection tracking controller 31, and a combination device 50, which combines the estimated values ​​provided by the two tracking controllers. The outputs of the model tracking controller 30 and the injection tracking controller 31 are added together. Both the model tracking controller 30 and the injection tracking controller 31 have controllers with an integrating component, an I-component. It has been found that in situations where the electric machine rotates slowly, the outputs 23, 49 of the model tracking controller 30 and the injection tracking controller 31 can drift in different directions and increase in magnitude in an uncontrollable manner.Due to the weighting factor F being high or close to 1 in the range of low angular frequencies ωe, such an uncontrollable effect on the determined angular frequency ωe. In the region of higher angular frequencies ωe, the weighting factor F is zero. Therefore, the output 49 of the injection-tracking controller 31 has no effect on the estimated angular frequency ωe. Noise at the input 47 of the injection-tracking controller 31 can be integrated into it and lead to an undesirably high value at the output 49 of the injection-tracking controller 31. As soon as the angular frequency of the electric machine decreases and the weighting factor F increases, a high value at the output 49 of the injection-tracking controller 31 can also lead to an uncontrolled increase in the determined angular frequency ωe. This behavior can result in instability or even a crash of the control procedure. Against this background, the task arises to increase the stability of the sensorless control of a brushless electric machine. This problem is solved by a method having the features of claim 1 and a drive system having the features of claim 5. The problem is thus solved by a method for sensorless determination of the angular frequency and / or position of a permanent magnet rotor of a brushless electric machine, in particular a linear or rotary machine, wherein a d-voltage and a q-voltage are provided to the electric machine, wherein a high-frequency d-test signal voltage with a predetermined carrier frequency is superimposed on the d-voltage within the framework of an injection method, wherein several phase currents of the machine are measured and a demodulated current is determined on the basis of the measured phase currents, wherein a d-voltage deviation and a q-voltage deviation are determined on the basis of a motor model, in particular a mathematical one, wherein the angular frequency and / or position of the permanent magnet rotor is determined in a fusion device on the basis of the demodulated current and the d-voltage deviation and the q-voltage deviation, wherein the fusion device includes a controller with an integral component.in particular an I-controller, to which a sum signal is supplied which depends on the demodulated current and the d-voltage deviation and the q-voltage deviation and a feedback of the determined angular frequency and / or position of the permanent magnet rotor. For the purposes of this invention, a controller with an integral component is understood to be a controller with an integrating component. Accordingly, an integral controller is an integrating controller. Since the controller with an integral component receives the sum signal, which depends on the demodulated current, the d-voltage deviation, and the q-voltage deviation, no further controllers with an integral component are required to determine the angular frequency and / or position of the permanent magnet rotor. Because the sum signal fed to the controller with an integral component also depends on the feedback of the determined angular frequency and / or position of the permanent magnet rotor, the controller with an integral component is thus arranged in a closed control loop. This measure reduces the risk of the fusion device becoming unstable due to an uncontrollable increase or overflow of the output of the controller with an integral component. Consequently, the stability of the sensorless control of a brushless electric machine can be increased. According to an advantageous embodiment of the invention, the demodulated current is weighted with a weighting factor that depends on the determined angular frequency. Such an embodiment represents a further contrast to the prior art, in which not the demodulated current, but rather an output of an injection tracking controller is weighted with a weighting factor. According to an advantageous embodiment of the invention, the weighting factor is maximal for a determined angular frequency of 0 and decreases for a larger determined angular frequency. Such a characteristic allows the influence of the injection method on the low angular frequency range of the electric machine to be limited. According to the invention, the demodulated current is fed to a controller with a proportional component, in particular a proportional (P) controller, and an output of the controller with a proportional component is used to generate the summed signal. For the purposes of this invention, a controller with a proportional component is understood to be a controller with a proportional component. A P controller is accordingly a proportional controller. This approach prevents the outputs of several controllers with integral (I) components from being added together and leading to an uncontrollable increase in the determined angular frequency. According to an advantageous embodiment of the invention, the demodulated current is supplied to the controller with a proportional (P) component, in particular the P-controller, and the output of the controller with a P component is summed with an output of the controller with an integral (I) component to obtain the determined angular frequency. This summation allows for an angular frequency estimate that depends on both the demodulated current and the d-voltage deviation and the q-voltage deviation. To solve the aforementioned problem, a drive system is further proposed with a device for sensorless determination of the angular frequency and / or position of a permanent magnet rotor of a brushless electric machine, in particular a linear or rotary machine, which is configured to provide the electric machine with a d-voltage and a q-voltage, to impose a high-frequency d-test signal voltage with a predetermined carrier frequency on the d-voltage within the framework of an injection method, to measure several phase currents of the machine and to determine a demodulated current based on the measured phase currents, and to determine a d-voltage deviation and a q-voltage deviation based on a motor model, in particular a mathematical one, wherein the device comprises a fusion device.by which the angular frequency and / or position of the permanent magnet rotor can be determined based on the demodulated current and the d-voltage deviation and the q-voltage deviation, wherein the fusion device has a controller with an integral component, in particular an integral controller, to which a sum signal can be supplied which depends on the demodulated current and the d-voltage deviation and the q-voltage deviation and a feedback of the determined angular frequency and / or position of the permanent magnet rotor. The drive system according to the invention can achieve the same technical effects and advantages that have already been explained in connection with the method according to the invention. According to an advantageous embodiment of the invention, the demodulated current is weighted with a weighting factor that depends on the determined angular frequency. This embodiment contrasts with the prior art, in which not the demodulated current, but rather an output of an injection tracking controller is weighted with a weighting factor. According to an advantageous embodiment of the invention, the weighting factor is provided that it is maximal for a determined angular frequency of 0 and decreases for a determined angular frequency that is larger in absolute value. According to the invention, the fusion device comprises a controller with a proportional (P) component, in particular a proportional (P) controller, to which the demodulated current can be supplied, with an output of the controller with the P component being used to generate the sum signal. Such a characteristic allows the influence of the injection method on the low angular frequency range of the electric machine to be limited. According to an advantageous embodiment of the invention, the fusion device comprises the controller with a proportional component, in particular the proportional controller, to which the demodulated current is supplied, wherein the fusion device has a summing element for summing an output of the controller with a proportional component with an output of the controller with an integral component in order to obtain the determined angular frequency. Further details and advantages of the invention will be explained below with reference to the embodiment shown in the drawings. Herein: Fig. 1 shows a block diagram of a drive system according to the prior art; Fig. 2 shows a block diagram of a fusion device of the drive system according to Fig. 1; and Fig. 3 shows a block diagram of a fusion device according to an embodiment of the method and drive system according to the invention. Figure 1 shows a drive system that can be used, for example, in the automotive industry. The drive system comprises an electric machine 1 with a stator and a permanent magnet rotor, such as a brushless synchronous machine. A control device implementing field-oriented control (vector control) is provided to regulate the position and angular frequency of the rotor of the electric machine 1. The control unit 100 comprises two controllers 111 and 112, which provide a d-voltage ud and a q-voltage uq in the rotor-related dq coordinate system. These voltages ud and uq are fed to a transformation unit 7, in which a transformation from the rotor-related dq coordinate system to the stator-related a-β coordinate system is performed. The stator-related voltages uα and uβ obtained at the output of the transformation unit 7 are fed to a space vector modulation (SVM) unit 8, which controls a converter 2 by means of pulse width modulation (PWM). This converter 2 provides several, here two, phase currents for the winding of the stator of the electric machine 1. Two phase currents i1 and i2 of the stator are measured by current sensors 41 and 42 and fed to further transformation units 3 and 4, which transform the phase currents into the rotor-related dq coordinate system. This yields the actual currents id and iq. These actual currents id and iq are fed to a notch filter 4a, which has a blocking frequency ωc corresponding to a carrier frequency used in an injection method that will be explained below. The filter 4a filters out high-frequency components in the actual currents id and iq generated by the injection method, preventing them from interfering with the control. The filtered actual currents id and iq are then fed to the controllers 111 and 112 as actual values. Further input signals of the controllers 111, 112 are the setpoint values, the setpoint currents id_soll, iq_soll. For sensorless determination of the angular frequency and position of the permanent magnet rotor, the drive system, according to the prior art, employs two complementary mechanisms. At standstill and in the low angular frequency range, an injection method (blocks 36, 32) is used, while at higher angular frequencies, a mathematical motor model 9 is employed. The values ​​obtained via both mechanisms, in particular angular frequency and / or position values, are fused in a fusion device 6 to determine the angular frequency ωe and the position φ of each rotor of the electric machine 1. A low-pass filtered angular frequency ωef is also provided. The mathematical motor model 9 is supplied with the filtered angular frequency ωfund and the filtered angular frequency ωef. Furthermore, the mathematical motor model 9 is supplied with the filtered actual currents id_fund and iq_fund, as well as the manipulated variables d-voltage ud and q-voltage uq. The mathematical motor model 9 determines a d-voltage deviation Δud and a q-voltage deviation Δuq, which are output to a model tracking controller 30. The model tracking controller 30 determines an angular frequency, also referred to here as the model angular frequency, which is provided at output 23. To implement the injection process, the drive system comprises an injection block 36, a demodulation block 32 and an injection tracking controller 31. In the injection block 36, a high-frequency d-test signal voltage u0sin(ωct) with a predefined carrier frequency ω is generated and superimposed onto the d-voltage ud. This superimposition is achieved via a multiplier 38, in which the d-test signal voltage is multiplied by an output of a hysteresis switching element 39. The switching element 39 is driven by the filtered angular frequency ωefan. If the magnitude of the filtered angular frequency ωe lies within a window defined by the cutoff frequencies of the switching element 39, the switching element 39 outputs the value "1" and the high-frequency d-test signal voltage is switched on for superimposition onto the d-voltage. If, on the other hand, the filtered angular frequency ωef lies outside the window, the switching element 39 outputs the value “0” and the imprinting of the d-test signal voltage onto the d-voltage is interrupted. The demodulation block 32 receives the unfiltered actual currents id and iq as input signals and determines a demodulated current iq_dem. The demodulated current iq_dem is fed to the injection tracking controller 31. The injection tracking controller 31 is implemented as a proportional-integral controller (PI controller), and an injection angular frequency is output via its output 49. In the combination device 50, the model angular frequency and the injection angular frequency are fused. Thus, the combination device 50 can output (estimated) values ​​of the angular frequency ωe and the position φe. The determined position φe is forwarded to the controller 100, in particular the transformation units 7, 4, and is taken into account there during the transformation from the stator-related to the rotor-related coordinate system or vice versa. A detailed representation of the fusion device 6 of the drive system according to the prior art is shown in Fig. 2. The fusion device 6 receives as input values ​​the d-voltage deviation Δud and the q-voltage deviation Δuq, as well as the demodulated current iq_dem. The fusion device 6 determines the angular frequency ωe and the position φe of the permanent magnet rotor of the electric machine. The angular frequency ωe is filtered by a low-pass filter E to obtain a filtered angular frequency ωef. The position φe of the permanent magnet rotor is derived from the angular frequency ωe by an integrator 24. The fusion device 6 comprises several controllers 22, 31 with an integrating component. Firstly, the model tracking controller 30 includes an integrating controller 22. This controller receives a sum calculated from the q-voltage deviation Δuq19 and an output signal from a proportional controller 20. The proportional controller 20 receives the d-voltage deviation Δud18, weighted by a factor G. The factor G depends on the filtered, determined angular frequency ωef. Specifically, the factor G is equal to 1 for an angular frequency ωef > ωe0 and equal to -1 for an angular frequency ωef < -ωe0. For an angular frequency -ωe0 < ωef < ωe0, the factor G is equal to ωef. Secondly, the injection tracking controller 31 includes an integral component. The fusion device 6 comprises a summing element 51, which adds the output 23 of the model tracking controller 30 and the output 49 of the injection tracking controller 31, weighted by a factor F. The factor F is at its maximum and equals 1 for a filtered angular frequency ωef = 0. For a larger filtered angular frequency ωef, the factor decreases in magnitude and takes on the sign of the angular frequency ωef. For angular frequencies ωef > ωe0 and ωef < -ωe0, the factor F = 0. In the prior art fusion device 6, it has proven disadvantageous that both the model tracking controller 30 and the injection tracking controller 31 have a controller with an integrating component, an I-component. In situations where the electric machine 1 rotates slowly, i.e., the angular frequency ωe is low, the factor F is high. Consequently, the outputs 23, 49 of the model tracking controller 30 and the injection tracking controller 31 can drift in different directions and increase uncontrollably in magnitude. In the region of higher angular frequencies ωe, the weighting factor F is zero. Therefore, the output 49 of the injection-tracking controller 31 has no effect on the estimated angular frequency ωe. However, noise at the input 47 of the injection-tracking controller 31 can lead to high values ​​at the output 49 of the injection-tracking controller 31 due to the integral component. As soon as the angular frequency ωe of the electrical machine 1 decreases again and the weighting factor F subsequently increases, a high value at the output 49 of the injection-tracking controller 31 can also lead to an uncontrolled increase in the determined angular frequency ωe. This behavior can result in instability or even a crash of the control procedure. Fig. 3 shows an embodiment of a fusion device 6 according to the invention, in which measures are taken to enable stable control behavior. The fusion device 6 according to the invention does not generate either a model angular frequency or an injection angular frequency. Rather, the fusion device 6 according to the invention comprises exactly one controller 22 with an integral component, in particular an integral controller, to which a sum signal is supplied that depends on the demodulated current iq_de and the d-voltage deviation Δud and the q-voltage deviation Δuq and a feedback of the determined angular frequency ω of the permanent magnet rotor. In this respect, the controller 22 of the model tracking controller 30 is also used to calculate the integral component of both the model tracking controller and the injection tracking controller. The demodulated current iq_dem is first multiplied by the weighting factor F in a multiplier 52 and then fed to a proportional (P) controller 31. The output 49 of this P controller is connected on one side to the summing element 51 and on the other side, via a transfer element 101, to the summing element 102, which generates the aforementioned summed signal for the controller 22. In this respect, the P controller 31 from Fig. 3 corresponds to the proportional component of the injection-tracking controller 31 from Fig. 2. The gain of this proportional component is denoted by k2. In the embodiment according to the invention shown in Fig. 3, the integral (I) component of the injection tracking controller 31 from Fig. 2 is converted by the I controller 22 by connecting the outputs of blocks 31 and 21 to the summing element 102 via the additional proportional (P) elements 101 and 103. The transfer factors of elements 101 and 103 are set to the values ​​and , respectively, to achieve the desired reset time of the injection tracking controller.the desired integral gain of the model tracking controller according to Fig. 2. The fusion device 6 according to the embodiment of the invention contains neither an addition of the outputs of two independent integrators nor an "open" integration. The single integrator, namely the I-controller 22, is located in a closed loop with feedback. Therefore, there is no risk of instability of the algorithm due to an uncontrollable increase or overflow of the integrator's output. The fusion device shown in Fig. 3 can be used in a drive system with a device 100 for sensorless determination of the angular frequency ωe and / or position φe of a permanent magnet rotor of a brushless electric machine 1, for example as shown in Fig. 1.

Claims

Method for sensorless determination of the angular frequency (ωe) and / or position (φe) of a permanent magnet rotor of a brushless electric machine (1), in particular a linear or rotary machine, wherein a d-voltage (ud) and a q-voltage (uq) are provided to the electric machine (1), wherein a high-frequency d-test signal voltage (ud_inj) with a predetermined carrier frequency is applied to the d-voltage (ud) within the framework of an injection method, wherein several phase currents (i1, i2) of the machine (1) are measured and a demodulated current (iq_dem) is determined on the basis of the measured phase currents (i1, i2), wherein a d-voltage deviation (Δud) and a q-voltage deviation (Δuq) are determined on the basis of a motor model (9), in particular a mathematical one.wherein in a fusion device (6) the angular frequency (ωe) and / or position (φe) of the permanent magnet rotor is determined on the basis of the demodulated current (iq_dem) and the d-voltage deviation (Δud) and the q-voltage deviation (Δuq), wherein the fusion device (6) has a controller (22) with an integral component, in particular an integral controller, to which a sum signal is supplied which depends on the demodulated current (iq_dem) and the d-voltage deviation (Δud) and the q-voltage deviation (Δuq) and a feedback of the determined angular frequency (ωe) and / or position (φe) of the permanent magnet rotor, characterized in that the demodulated current (iq_dem) is supplied to a controller with a proportional component, in particular a proportional controller, and an output of the controller with a proportional component is used to generate the sum signal becomes., Method according to claim 1, characterized in that the demodulated current (iq_dem) is weighted with a weighting factor which depends on the determined angular frequency (ωe). Method according to claim 2, characterized in that the weighting factor is maximal for a determined angular frequency (ωe) of 0 and decreases for a determined angular frequency (ωe) of a larger magnitude. Method according to one of the preceding claims, characterized in that the output of the controller with P-component is summed with an output of the controller with I-component to obtain the determined angular frequency (ωe). Drive system with a device (100) for sensorless determination of the angular frequency (ωe) and / or position (φe) of a permanent magnet rotor of a brushless electric machine (1), in particular a linear or rotary machine, which is configured to provide the electric machine (1) with a d-voltage (ud) and a q-voltage (uq), to impose a high-frequency d-test signal voltage (ud_inj) with a predetermined carrier frequency on the d-voltage (ud) within the framework of an injection method, to measure several phase currents (i1, i2) of the machine (1) and to determine a demodulated current (iq_dem) on the basis of the measured phase currents (i1, i2), to determine a d-voltage deviation (Δud) and a q-voltage deviation (Δuq) on the basis of a motor model (9), in particular a mathematical one, wherein the device (100) is a fusion device (6) includes,by which the angular frequency (ωe) and / or position (φe) of the permanent magnet rotor can be determined based on the demodulated current (iq_dem) and the d-voltage deviation (Δud) and the q-voltage deviation (Δuq), wherein the fusion device (6) has a controller (22) with an integral component, in particular an integral controller, to which a sum signal can be supplied which depends on the demodulated current (iq_dem) and the d-voltage deviation (Δud) and the q-voltage deviation (Δuq) and a feedback of the determined angular frequency (ωe) and / or position (φe) of the permanent magnet rotor, characterized in that the fusion device (6) has a controller with a proportional component, in particular a proportional controller, to which the demodulated current (iq_dem) is supplied, wherein an output of the controller with a proportional component is used to form the sum signal is used. Drive system according to claim 5, characterized in that the demodulated current (iq_dem) is weighted with a weighting factor which depends on the determined angular frequency (ωe). Drive system according to claim 6, characterized in that the weighting factor is maximum for a determined angular frequency (ωe) of 0 and decreases for a determined angular frequency (ωe) of a larger magnitude. Drive system according to one of claims 5 to 7, characterized in that the fusion device (6) has a summing element for summing an output of the controller with a P-component with an output of the controller with an I-component in order to obtain the determined angular frequency (ωe).

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