Method for starting a synchronous motor

Abstract

The present invention relates to a method for starting a synchronous motor. The synchronous motor comprises a rotor generating a first magnetic field and a stator having a stator winding connected to an electric energy converter converting a power supply voltage into a stator voltage. The method comprises the following steps: applying a reference stator voltage to the stator winding; measuring a stator current in the stator winding; calculating an estimated rotor speed and an estimated rotor position of the rotor based on the applied stator voltage and the measured stator current; calculating a speed error by subtracting the estimated rotor speed from the reference rotor speed; determining a reference torque generating current component based on the speed error and modifying a reference current vector with the reference torque generating current component; calculating a position error by subtracting the estimated rotor position from the reference rotor position; correcting the reference current vector by transforming the reference current vector into a corrected reference current vector through the position error; determining a switching signal for the electric energy converter based on the reference stator voltage and applying the switching signal to the electric energy converter.

Description

Technical Field

[0001] The present invention relates to the control of electric drives. In particular, the present invention relates to a method, a computer program and a computer-readable medium for starting a synchronous machine, and a synchronous machine having a controller suitable for carrying out such a method. Background Art

[0002] The rotor position and speed of a synchronous motor, such as a permanent magnet synchronous motor (PMSM), can be detected without using any sensors or encoders.

[0003] To start a synchronous motor from a standstill, a rotating stator current vector is applied. This generates an electromagnetic torque that forces the rotor to follow the stator current vector. Since synchronous motors are naturally very weakly damped, this type of start-up can cause rotor speed oscillations. Such oscillations should be avoided.

[0004] Typically, additional damping of the rotor can be achieved by modifying the stator current vector in an appropriate manner. Control of the stator current is typically implemented in an orthogonal coordinate system that rotates with the rotor. Accordingly, the stator current vector can be modified by varying at least one of its components or by varying the frequency at which the coordinate system rotates (e.g., with a predefined frequency distribution).

[0005] Furthermore, the starting procedure of the synchronous motor should be as short as possible. A typical algorithm may be able to start the synchronous motor in at least 3 seconds.

[0006] For example, US Pat. No. 9,998,044 B2 describes a starting method for a three-phase sensorless permanent magnet synchronous motor in which the rotor flux projection onto the d-axis or q-axis of a rotating coordinate system is used to determine whether the stator current reference applied during startup is sufficient to spin the motor. The method can also determine an initial value for the stator torque current reference based on the angular difference between the reference and estimated rotor angles to be used at the start of a closed-loop field-oriented control mode.

[0007] US 2010 / 0264861 A1 describes a method for determining the position of the flux vector of an electric motor. Figure 1 As shown in the figure, by starting from the reference rotor speed ω ref Subtract the estimated rotor speed ω r To calculate the speed error, and determine the current vector I according to the speed error qref . Figure 1 It is also shown that the stator speed ω is estimated by s The integration is performed to determine the angle θ corresponding to the estimated position of the rotor flux vector s The motor is controlled so that the estimated position θ of the rotor flux vector s and the true position θ RMinimize the difference between them.

[0008] CN 106208865 B describes a method for controlling a plurality of permanent magnet synchronous motors. Figure 1 A control scheme is shown in which the speed error and position error are calculated and used to control the motor.

[0009] CN 103270691 B describes a sensorless AC motor controller that uses feed-forward torque control (FFTC) to measure the angular position of the rotor. Figure 3 The following control scheme is shown: the applied rotor speed ω' is determined using the load model 22, and the applied rotor position θ' is determined by integrating the applied rotor speed ω'. The applied rotor position θ' is used by block 31 from the applied current component i' d 、i' q Generates stator voltage v' for motor 11 u 、v' v 、v' w , and is used by block 14 to determine the current component i from the measured stator current of motor 11 d 、i q The applied torque generates a current component i' q and the current component i q The difference between the measured values ​​Δi q can be calculated and used to correct the load model 22 .

[0010] Another example for a sensorless vector control system is described by Xiao Xi et al. in: “A Sensorless Control Based on MRAS Method in Interior Permanent-Magnet Machine Drive,” International Conference on Power Electronics and Drive Systems, Kuala Lumpur, Malaysia, November 28-December 1, 2005, Vol. 1, pp. 734-738. Summary of the Invention

[0011] The object of the present invention is to reduce speed oscillations during start-up of a synchronous motor to a minimum, to reduce the start-up time and to provide a smooth transition to normal operating mode.

[0012] This object is achieved by the subject-matter of the independent claims. Further exemplary embodiments are evident from the dependent claims and the following description.

[0013] A first aspect of the present invention relates to a method for starting a synchronous motor fed by an electric energy converter. The synchronous motor may include a rotor for generating a first magnetic field and a stator having stator windings connected to an electric energy converter. The electric energy converter is configured to convert a supply voltage into a stator voltage, which is applied to the stator windings to generate a rotating second magnetic field that interacts with the first magnetic field. The rotor may have permanent magnets and / or rotor windings to generate the first magnetic field. The rotor may be rotatably mounted in the stator. The electric energy converter may include a three-phase inverter for providing a three-phase stator voltage from a DC link of the electric energy converter. The stator voltage may be calculated by a controller for sensorless field-oriented control of the synchronous motor. The synchronous motor (i.e., an AC motor in which, in steady state, the rotation of the rotor is synchronized with the frequency of the supply current) may be part of an electric drive system that includes the electric energy converter and a controller for controlling the synchronous motor depending on the load.

[0014] The method can be automatically executed by a controller. Using this method, a synchronous motor can be started in eight steps.

[0015] According to an embodiment of the present invention, the first step of the method comprises applying a reference stator voltage to the stator winding, wherein the reference stator voltage is determined based on a reference current vector and a reference rotor speed. The reference current vector may be determined based on a reference current magnitude during startup. The reference current vector may be provided in an orthogonal coordinate system. The reference rotor speed may be the angular velocity at which the rotor should spin. The rotating coordinate system may be an orthogonal coordinate system and may rotate with the rotor. The reference current vector may have two components related to the rotor flux and the rotor torque. The reference current magnitude and the reference rotor speed may vary during startup, for example, according to a predefined profile, which may be a ramp or step function or any other suitable function. The profile may also include a constant portion.

[0016] According to an embodiment of the present invention, the second step of the method includes measuring the stator current in the stator winding. The stator current can be measured by the control system of the power converter (e.g., using a low-inductance shunt resistor built into the current sensing and fault generation circuitry of the three-phase inverter of the power converter). For example, the measured stator current can be used to estimate the rotor flux. Because the measured stator current can be provided in a fixed three-phase coordinate system, the measured stator current can be transformed into an orthogonal rotating coordinate system before estimating the rotor flux. The measured stator current can also be used to calculate a reference voltage for controlling the speed or torque of the synchronous motor in a closed-loop control mode.

[0017] According to an embodiment of the present invention, the third step of the method includes calculating an estimated rotor speed and an estimated rotor position of the rotor based on the applied stator voltage and the measured stator current. The estimated rotor speed and estimated rotor position may be calculated in a phase-locked loop based on the estimated rotor flux. The stator voltage may be provided in a rotating coordinate system and transformed into a fixed three-phase coordinate system before estimating the rotor speed and rotor position.

[0018] According to an embodiment of the invention, the fourth step of the method comprises calculating a speed error by subtracting the estimated rotor speed from the reference rotor speed. The speed error may be an error signal generated by the difference between the estimated rotor speed and the reference rotor speed.

[0019] According to an embodiment of the present invention, the fifth step of the method includes determining a reference torque-generating current component based on the speed error, and using the reference torque-generating current component to modify the reference current vector. The speed error may be input to a PI controller, which may output a reference current accordingly. Therefore, the reference torque-generating current component may be considered the output of the PI controller for correcting the reference torque-generating current component of the reference current vector. Furthermore, the reference torque-generating current component may be input to a limit controller to verify that the reference torque-generating current component does not exceed an upper and / or lower current limit. For example, the current limit may be provided based on the reference current magnitude.

[0020] According to an embodiment of the present invention, the sixth step of the method includes calculating the position error by subtracting the estimated rotor position from a reference rotor position, wherein the reference rotor position is determined based on a reference rotor speed and a reference rotor speed correction, wherein the reference rotor speed correction increases and decreases with the position error, wherein the reference rotor speed correction is subtracted from the reference rotor speed to determine a corrected reference rotor speed, and wherein the reference rotor position is determined by integrating the corrected reference rotor speed. In other words, as the position error increases, the reference rotor speed correction may increase, and vice versa. For example, the increase in the reference rotor speed correction may be proportional to the increase in the position error, and vice versa.

[0021] According to an embodiment of the present invention, the seventh step of the method includes correcting the reference current vector by transforming the reference current vector into a corrected reference current vector through the position error, wherein the rotating coordinate system of the corrected reference current vector is aligned with the estimated rotor position. When the position error drops below a predefined threshold, the position error may be set to zero. In this case, the reference rotor position may be set to the same as the estimated rotor position.

[0022] According to an embodiment of the present invention, the eighth step of the method includes determining a switching signal for the power converter based on the reference stator voltage and applying the switching signal to the power converter. The switching signal may be a signal generated by pulse-width modulating the phase voltage provided in a three-phase coordinate system. Such pulse-width modulation may be controlled using a space vector modulation algorithm implemented as hardware and / or software in a controller. For example, the switching signals may each be generated as a low-power input signal for a gate driver of the power converter. Alternatively, the switching signals may each be generated as a high-current output signal of such a gate driver. Such output signals may then be applied to the gates of transistors of a three-phase inverter connected to the DC link of the power converter.

[0023] According to an embodiment of the present invention, the method further includes: determining whether the estimated rotor position is accepted as correct based on the position error; when the estimated rotor position is accepted as correct: using the estimated rotor position as the reference rotor position and changing the magnitude of the reference current vector to an initial value for normal operation of the electric drive system; and / or when the estimated rotor position is not accepted as correct: changing the magnitude of the reference current vector according to a predefined magnitude distribution and / or changing the reference rotor speed according to a predefined rotor speed distribution. For example, the estimated rotor position may be determined to be correct when the estimated rotor position reaches a desired minimum value, and may be determined to be incorrect as long as the desired minimum value has not been reached. In the former case, the value of the reference rotor position may be set to the value of the estimated rotor position, i.e., the position error may be set to zero. During normal operation of the electric drive system, the electric energy converter may be controlled based on an external speed and / or torque reference signal via closed-loop sensorless field-oriented control, which may also be referred to as a speed and / or torque control scheme. The initial value of the reference torque-producing current component may be selected to ensure a smooth transition from a startup procedure to a speed or torque control scheme. For example, the initial value may be the most recent value of the reference torque-generating current component calculated during the startup procedure. Once the estimated rotor position is determined to be correct, the magnitude of the reference current vector may be set to the initial value using a ramp or step function. In this way, a smooth transition to the normal operating mode of the electric drive system can be achieved. Additionally or alternatively, the predefined magnitude profile may be an ascending curve or a curve having an ascending portion and a constant portion. The ascending curve may be a linear or nonlinear continuous curve. The constant portion may be a horizontal line of the curve.

[0024] According to an embodiment of the present invention, the absolute value of the position error is compared with a predefined threshold value, wherein the estimated rotor position is accepted as correct when the absolute value of the position error remains below the threshold value for a predefined period of time. The threshold value may be calculated or determined experimentally.

[0025] According to an embodiment of the present invention, the method further includes determining a reference magnetizing current component based on the reference torque generating component and a reference magnitude of the reference current vector, and modifying the reference current vector using the reference magnetizing current component. The reference magnetizing current component can be considered as one of two components of the reference current vector that affects the motor magnetizing (main) flux.

[0026] According to an embodiment of the present invention, the reference magnetizing current component is calculated using the following formula:

[0027]

[0028] According to an embodiment of the invention, the reference rotor speed correction is determined as a function of the product of the position error and a gain factor.For example, the gain factor may be set to zero when the position error remains below a threshold for a predefined amount of time.

[0029] According to an embodiment of the invention, the reference torque generating component is determined in dependence on a reference magnitude of the reference current vector.For example, the reference magnitude may be used to set positive and / or negative limits of a limit controller for the reference torque generating current component.

[0030] According to an embodiment of the present invention, the method further includes: determining a reference voltage vector based on the corrected reference current vector and the measured stator current; transforming the reference voltage vector into a fixed three-phase coordinate system; and determining a switching signal by pulse-width modulating a phase voltage of the transformed reference voltage vector. For example, each of the components of the reference voltage vector may be an output signal of a PI controller. The output signal may be generated by amplifying an error signal generated by comparing the components of the reference current vector with the measured stator current. The reference voltage vector may be provided in a rotating orthogonal coordinate system.

[0031] A further aspect of the invention relates to a computer program which, when executed on a processor, is adapted to perform the method as described above and below.

[0032] Another aspect of the present invention relates to a computer-readable medium having such a computer program stored therein. The computer-readable medium may be a floppy disk, a hard disk, a USB (Universal Serial Bus) storage device, a RAM (Random Access Memory), a ROM (Read Only Memory), an EPROM (Erasable Programmable Read Only Memory), or a flash memory. The computer-readable medium may also be a data communication network, such as the Internet, that allows downloading program code. In general, the computer-readable medium may be a non-transitory or transient medium.

[0033] Another aspect of the present invention relates to a controller for an electric energy converter. The controller is adapted to perform the method described above and below. For example, the controller may include a processor and a memory for storing a computer program. However, the method may also be implemented partially or completely in hardware.

[0034] Another aspect of the present invention relates to an electric drive system comprising a synchronous motor having a rotor for generating a first magnetic field and a stator having a stator winding. Furthermore, the electric drive system includes an electric energy converter connected to the stator winding and adapted to convert a supply voltage into a stator voltage, which is applied to the stator winding to generate a rotating second magnetic field that interacts with the first magnetic field. The electric drive system also includes a controller for controlling the electric energy converter. The controller is adapted to perform the method described above and below.

[0035] It has to be understood that features of the method as described above and below may be features of the electric drive system as described above and below.

[0036] These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The subject matter of the invention will be explained in more detail in the following text with reference to exemplary embodiments illustrated in the drawings.

[0038] Figure 1 An electric drive system according to an embodiment of the present invention is schematically shown.

[0039] Figure 2 More detailed schematic diagram of the Figure 1 The transformation component.

[0040] Figure 3 Shows that can be compared with Figure 1 A diagram of a predefined magnitude distribution for use with an electric drive system.

[0041] Figure 4 Shows that can be compared with Figure 1 A diagram of a predefined rotor speed profile for use with an electric drive system.

[0042] Figure 5 More detailed schematic diagram of the Figure 1 Current controller.

[0043] Figure 6 A flow chart of a method for starting a synchronous motor according to an embodiment of the present invention is shown.

[0044] Figure 7Graphs showing different drive signals with reference rotor speed correction disabled according to an embodiment of the invention.

[0045] Figure 8 Graphs showing different drive signals with reference rotor speed correction enabled according to an embodiment of the invention.

[0046] The reference symbols used in the drawings and their meanings are listed in summary form in the list of reference symbols. In principle, identical components are provided with the same reference symbols in the drawings. DETAILED DESCRIPTION

[0047] Figure 1 An electric drive system 100 is shown having a synchronous motor 102, an electric energy converter 104, and a controller 106. The synchronous motor 102, which may be a permanent magnet synchronous machine (PMSM), includes a stator 108 having stator windings 110, each of which is connected to an output of the electric energy converter 104. A rotor 112 is configured to rotate within the stator 108. To generate a first magnetic field, the rotor 112 includes one or more permanent magnets 114, which may be mounted on and / or embedded in the rotor 112. Additionally or alternatively, the rotor 112 may include a number of electrical windings to generate the first magnetic field. The stator windings 110 are arranged around the rotor 112. The electric energy converter 104 is connected to a supply voltage V cc The power converter 104 is configured to convert the power supply voltage V to the power supply voltage V based on the switching signals s1, s2, s3 (eg, pulse width modulation signals or space vector modulation signals) generated by the controller 106. cc Converted into three stator voltages V sx 、V sy 、V sz The three-phase AC voltage in the form of stator voltage V sx 、V sy 、V sz The current flowing through the stator windings 110 creates a rotating second magnetic field within the air gap between the rotor 112 and the stator 108. The interaction between the two magnetic fields causes the rotor 112 to rotate, thereby generating torque. The speed and torque of the synchronous motor 102 can be controlled by controlling the current flowing through the stator windings 110.

[0048] The synchronous motor 102 may be controlled using a field oriented control (FOC) technique without any sensors or encoders. In this case, the flux and torque components of the stator current are controlled by the controller 106 based on a reference rotor speed (which may be an external speed reference signal) and an estimated rotor position based on a back electromagnetic force (back EMF) estimate calculated from the number of stator windings 110 This means that the synchronous motor 102 must rotate at a minimum speed for the controller 106 to detect a sufficient amount of back EMF to accurately calculate the estimated rotor position Therefore, the controller 106 is configured to execute a starting procedure to start the synchronous motor 102 from zero speed.

[0049] Figure 1 A block diagram depicts an algorithm implemented in the controller 106 for starting the synchronous motor 102 from a stopped state. During startup, the reference current generator 118 generates a reference current with a reference magnetizing component and the reference torque generating component The reference value of the reference current vector For example, the reference current generator 118 may be configured as follows: Figure 3 The expected distribution shown in the output reference value The expected distribution may be a ramp function that reduces the reference value Ramp up to the specified value and hold it constant until the rotor position is estimated is accepted as correct. The reference current generator 118 can then Changes to the value defined as the initial value for the torque control mode.

[0050] The reference speed generator 122 generates a reference rotor speed for the rotor 112 Reference rotor speed It can also be generated according to a desired distribution, such as ramping from a specified minimum value to a specified maximum value, such as Figure 4 As shown in .

[0051] The flux estimation is active from the start of the startup procedure. The estimator block 124 includes the functions for calculating the estimated rotor flux The rotor flux estimator 126 and the rotor flux estimator 126 are used to estimate the rotor flux based on the To calculate the estimated rotor position and estimated rotor speed The rotor position estimator 128 estimates the rotor position and / or estimated rotor speed Can be calculated in a phase-locked loop (PLL).

[0052] Estimated rotor flux Based on the applied stator voltage V sx 、V sy 、V sz and the stator current i measured in the stator winding 110 sx 、i sy To calculate. Figure 1In the example shown in FIG, only two phases of the stator current are measured. sx 、i sy , because the controller 106 can be based on the other two phases sx 、i sy The third phase is calculated from the measured values.

[0053] Measure the stator current i sx 、i sy and the applied stator voltage V sx 、V sy 、V sz Available in a fixed three-phase xyz coordinate system. Before, measure the stator current i sx 、i sy and the applied stator voltage V sx 、V sy 、V sz It can be transformed into a fixed orthogonal αβ coordinate system by the transformation component 130, such as Figure 2 As shown in the figure.

[0054] To damp the rotor speed oscillations, the estimated rotor speed is converted to With reference rotor speed The speed comparator 132 compares the reference rotor speed Subtract estimated rotor speed To generate the speed error ω e As the error signal. Speed ​​error ω e The torque controller 134 (eg, a PI controller) generates a reference torque-producing current component. The limit controller 136 is based on the reference value The given value is used to limit the reference torque generating current component

[0055] In addition, the reference rotor position Calculated by the position reference generator 138, the position reference generator 138 may be used to determine the reference rotor speed The position comparator 140 is an integrator that performs integration. Subtract the estimated rotor position To generate the position error θ e as the error signal.

[0056] Position error θ e is input to the reference position corrector 142, which amplifies the position error θ using an appropriate gain factor. e , and output the reference rotor speed correction ω cThe reference position corrector 142 is configured to e The same ratio increases and decreases the reference rotor speed correction ω c Alternatively, the reference rotor speed correction ω c and position error θ e Can be modified in different proportions.

[0057] Reference rotor speed correction ω c Used by the reference speed corrector 144 to calculate the corrected reference rotor speed (e.g., by obtaining a reference rotor speed as output by reference speed generator 122) Subtract the reference rotor speed correction ω c ). Corrected reference rotor speed It is then input to the position reference generator 138 for calculating the reference rotor position

[0058] Reference rotor speed correction ω c will be understood as the reference rotor position Estimated rotor position towards This results in an additional rotation of and The faster convergence of the oscillations results in better oscillation damping and shorter start-up times.

[0059] In order to provide a reference current vector during startup, in addition to the reference torque generating current component In addition, the reference magnetizing current component must be calculated Reference magnetizing current component The current magnitude limiter 148 is based on the reference magnitude and the reference torque to generate the current component For example, with the component The quadrature reference magnetizing current components Available Calculated as reference value Before entering the current magnitude limiter 148, the reference magnitude and the reference torque to generate the current component Each is squared in squaring means 149. The current magnitude limiter 148 then squares the reference magnitude from Subtracting the squared reference torque yields the current component The square root component 150 takes the difference (ie, the square of the reference magnetizing current component) obtained from the ) Calculate the reference magnetizing current component

[0060] Reference magnetizing current component Reference torque generating current component and position error θ e Each is input to the reference conversion component 151, which is configured to convert the reference magnetizing current component and the reference torque to generate the current component Through the position error θ e Transform from the reference rotating orthogonal dq* coordinate system to the estimated rotor position The resulting corrected reference current vector has a corrected reference magnetizing current component and the corrected reference torque generating component

[0061] The current controller 152 receives the corrected reference torque generating current component and the corrected reference magnetizing current component The current controller 152 generates the current component of the corrected reference torque and the measured and transformed stator current i sq Compare and correct the reference magnetizing current component and the measured and transformed stator current i sd Compare to generate switching signals s1, s2, s3, as will be Figure 5 As described in more detail in .

[0062] For example, when the position error θ e When the absolute value of remains below a given threshold for a certain amount of time, the rotor position is estimated. is accepted as correct by the reference position corrector 142. In this case, the reference current generator 118 may Ramp up to a value used as an initial value for the normal operation control scheme. This initial value may be equal to the reference torque producing current component generated by the torque controller 134. Thereafter, the startup procedure is deemed to be successfully completed and the controller 106 switches to a closed loop torque or speed control mode based on FOC. In this case, the orientation angle of the rotating dq coordinate system is changed from the reference rotor position Change to estimated rotor position In addition, the current reference and is changed to the values ​​generated by the torque and flux control loops. In this way, a seamless transition of the synchronous motor 102 from a start-up procedure to normal operation can be achieved.

[0063] The different components of the controller 106 may be implemented in hardware and / or software. The controller 106 may also include a processor and a memory for storing instructions that, when executed by the processor, may perform the methods described above and below.

[0064] Figure 2 More detailed schematic diagram of the Figure 1 The transformation component 130 includes a first transformation unit 200 for transforming the measured stator current i by performing Clarke transformation. sx 、i sy Transform from the fixed three-phase xyz coordinate system to the fixed orthogonal αβ coordinate system. The resulting stator current i sα 、i sβ Then the second transformation unit 202 transforms the coordinate system into a rotational orthogonal dq coordinate system. The second transformation unit 202 is based on the estimated rotor position. To perform Park transformation. As a result, the second transformation unit 202 outputs the measured and transformed stator current i sd 、i sq , which is used by the current controller 152 to generate switching signals s1 , s2 , s3 for controlling the power converter 104 .

[0065] The transformation member 130 may be configured to transform the applied stator voltage V in a similar manner. sx 、V sy The reference transformation component 151 may only have the transformation component 202 .

[0066] Figure 3 shows that the Figure 1 FIG1 shows a diagram of a predefined magnitude distribution 300 in a reference current generator 118 of FIG1 . According to this example, magnitude distribution 300 includes a first portion 302 in the form of an ascending curve. First portion 302 transitions into a constant second portion 304 in the form of a horizontal line. Alternatively, reference magnitude distribution 300 may include only an ascending curve. The ascending curve may be a linear or nonlinear function.

[0067] Figure 4 shows that the Figure 1 According to this example, the rotor speed profile 400 has the form of an ascending curve, which can be used to convert the reference rotor speed into a predetermined value. A linear or non-linear function that ramps from a predefined minimum value to a predefined maximum value.

[0068] Figure 5 More detailed schematic diagram of the Figure 1 The current controller 152 includes a first current comparator 500 for converting the current generated by the reference conversion component 151 into a current. Subtract i as generated by the transformation component 130 sdTo generate a first error signal 502. The first error signal 502 is amplified by a first PI controller 504 to generate a reference d component voltage

[0069] Furthermore, the current controller 152 comprises a second current comparator 506 for converting the current from the reference current generated by the reference conversion means 151. Subtract i as generated by the transformation component 130 sq To generate a second error signal 508. The second error signal 508 is amplified by a second PI controller 510 to generate a reference q component voltage The voltage conversion component 512 is configured to convert the reference d component voltage and the reference q component voltage Transformed into the fixed three-phase xyz coordinate system. The three reference stator voltages obtained are will be applied to the stator winding 110. To achieve this, the reference stator voltage is input to the modulation component 514, which is configured to modulate the stator voltage V sx 、V sy 、V sz To generate switching signals s1, s2, s3, each of which corresponds to a modulated voltage. sx 、V sy 、V sz The modulation may be performed using a space vector modulation algorithm implemented in the modulation component 514 .

[0070] Figure 6 Shown is a method for starting a circuit without position and speed sensors. Figure 1 Flowchart of a method 600 of synchronous motor 102 .

[0071] In step 610, the stator voltage V sx 、V sy 、V sz applied to the stator winding 110 .

[0072] In step 620, the stator current i is measured in the stator winding 110. sx 、i sy .

[0073] In step 630, the stator current i sx 、i sy and the applied stator voltage V sx 、V sy 、V sz The rotor position is estimated based on the back electromotive force generated by the rotation of the rotor 112 and rotor speed

[0074] In step 640, the rotor speed is estimated With reference rotor speed Compare to determine the speed error ω e .

[0075] In step 650, the velocity error ω is used e To determine the reference torque generating current component

[0076] In step 660, the reference rotor position Subtract the estimated rotor position To determine the position error θ e . Based on the corrected reference rotor speed (For example, by correcting the reference rotor speed Integrate) to determine the reference rotor position By subtracting the position error θ e Calculated reference rotor speed correction ω c , the corrected reference rotor speed Based on the reference rotor speed In optional step 662, the position error θ can be calculated. e The absolute value of the position error θ is compared with the predefined threshold. e When the absolute value of is less than a threshold value for at least a predefined period of time, in optional step 664, the reference rotor position is set to estimate the rotor position This can be achieved by setting the position error θ e and reference rotor speed correction ω c Furthermore, the magnitude of the reference current vector may be changed to an appropriate initial value for normal operation of the synchronous motor 102 to ensure a smooth transition to the closed-loop torque or speed control mode.

[0077] On the other hand, when the position error θ e When the absolute value of is equal to or greater than the threshold, in optional step 666, the position error θ e To calculate the reference rotor speed correction ω c , so that the position error θ e In other words, the position error θ e The larger the reference rotor speed correction ω c In short, by changing the reference rotor speed accordingly The rotor position can be estimated Correct the reference rotor position in the direction

[0078] In step 670, the current component is generated using the reference torque The modified reference current vector is obtained from the reference dq* coordinate system through the position error θ e Transform to the estimated rotor position In other words, once the position error θ e is accepted as correct, i.e. set to zero, the reference rotor position Estimating the rotor position same.

[0079] In step 680, based on the corrected reference current vector component and To generate switching signals s1, s2, s3.

[0080] During the start-up of the synchronous motor 102, the reference value It can be changed from a specified minimum value upward to a specified maximum value and remain constant until the rotor position is estimated. is accepted as correct. Then, the reference value can be changed to a value defined as the initial value for the torque controller. Also during startup, the reference rotor speed Can be changed from a specified minimum value upward to a specified maximum value.

[0081] Figure 7 A timing diagram is depicted to illustrate the time from when starting from a stop with reference rotor speed correction disabled. Figure 1 The time diagram shows a graph 700 of motor current, a graph 702 of estimated motor speed, a graph 704 of measured motor speed, a graph 706 of measured rotor position, and a graph 708 of estimated rotor position. One can clearly see the rotor speed oscillation during startup, which lasts for approximately 2.3 seconds.

[0082] Figure 8 A time diagram is depicted to illustrate when Figure 1 The effectiveness of oscillation damping of the synchronous motor 102 when starting from a standstill with reference rotor speed correction enabled. The parameters shown are Figure 7 The parameters in are the same. The oscillations are almost completely damped. The startup time is reduced to about 1 second. This may be the point at which the controller 106 switches to normal operating mode (e.g., closed-loop torque or speed control of the synchronous motor 102).

[0083] Although the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments. Other variations to the disclosed embodiments may be understood and effected by those skilled in the art and in practicing the claimed invention through a study of the drawings, the present disclosure and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. A single processor or controller or other unit may perform the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.

[0084] Reference Symbol List

[0085] 100 Electric Drive System

[0086] 102 Synchronous Motor

[0087] 104 Power Converter

[0088] 106 Controller

[0089] 108 stator

[0090] 110 stator winding

[0091] 112 rotor

[0092] 114 permanent magnet

[0093] 116 Power Grid

[0094] 118 Reference Current Generator

[0095] 122 Reference Velocity Generator

[0096] 124 Estimator Block

[0097] 126 Rotor Flux Estimator

[0098] 128 Rotor Position Estimator

[0099] 130 Transformation Components

[0100] 132 Speed ​​Comparator

[0101] 134 Torque Controller

[0102] 136 Limit Controller

[0103] 138 Position Reference Generator

[0104] 140 Position Comparator

[0105] 142 Reference Position Corrector

[0106] 144 Reference Speed ​​Corrector

[0107] 148 Stator current limiter

[0108] 149 Find the square component

[0109] 150 Find the square root component

[0110] 151 Reference Transformation Component

[0111] 152 Current Controller

[0112] 200 First transformation unit

[0113] 202 Second Transformation Unit

[0114] 300 Reference Value Distribution

[0115] 302 rising part

[0116] 304 Constant part

[0117] 400 Reference velocity distribution

[0118] 500 First current comparator

[0119] 502 first error signal

[0120] 504 First PI controller

[0121] 506 Second current comparator

[0122] 508 second error signal

[0123] 510 Second PI controller

[0124] 512 Voltage conversion components

[0125] 514 Modulation Components

[0126] 600 Method for starting a synchronous motor

[0127] 610 Apply stator voltage

[0128] 620 Measuring stator current

[0129] 630 Calculate estimated rotor speed and estimated rotor position

[0130] 640 Calculation speed error

[0131] 650 Determine the reference torque generating current component

[0132] 660 Calculate position error

[0133] 662 Compare position error with threshold

[0134] 664 Use estimated rotor position as reference rotor position

[0135] 666 Change the magnitude of the reference rotor speed and / or reference current vector

[0136] 670 Correction reference current vector

[0137] 680 confirm switch signal

[0138] 700 Motor current curve

[0139] 702 Estimated motor speed curve

[0140] 704 Measured motor speed curve

[0141] 706 Curve for measuring rotor position

[0142] 708 Estimated rotor position curve

[0143] dq Rotation Orthogonal Coordinate System

[0144] i sα Transformed stator current

[0145] i sβ Transformed stator current

[0146] i sd Transformed stator current

[0147] i sq Transformed stator current

[0148] i sx Measuring stator current

[0149] i sy Measuring stator current

[0150] Reference magnetizing current component

[0151] Reference torque generating current component

[0152] Reference current vector

[0153] Corrected reference magnetizing current component

[0154] Corrected reference torque generating current component

[0155] Corrected reference current vector

[0156] The magnitude of the reference current vector

[0157] s1 switch signal

[0158] s2 switch signal

[0159] s3 switch signal

[0160] t time

[0161] V cc Power supply voltage

[0162] Reference d component voltage

[0163] Reference q component voltage

[0164] Reference voltage vector

[0165] Transformed reference voltage vector

[0166] V sx Applied stator voltage

[0167] V sy Applied stator voltage

[0168] V sz Applied stator voltage

[0169] Reference stator voltage, reference phase voltage

[0170] Reference stator voltage, reference phase voltage

[0171] Reference stator voltage, reference phase voltage

[0172] xyz fixed three-phase coordinate system

[0173] αβ fixed orthogonal coordinate system

[0174] Estimated rotor flux

[0175] θ e Position error

[0176] Reference rotor position

[0177] Estimated rotor position

[0178] ω c Reference rotor speed correction

[0179] ω e Speed ​​error

[0180] Corrected reference rotor speed

[0181] Reference rotor speed

[0182] Estimate the rotor speed.

Claims

1. A method (600) for starting a synchronous motor (102), The synchronous motor (102) comprises a rotor (112) for generating a first magnetic field and a stator (108) having a stator winding (110) connected to an electric energy converter (104) for converting a power supply voltage (V cc ) is converted into stator voltage (V sx ,V sy ,V sz ), the stator voltage (V sx ,V sy ,V sz ) is applied to the stator winding (110) to generate a rotating second magnetic field that interacts with the first magnetic field, The method (600) comprises: The reference stator voltage applied to the stator winding (110), wherein the reference stator voltage According to the reference current vector and the reference rotor speed to determine; Measuring the stator current (i sx ,i sy ); According to the applied stator voltage (V sx ,V sy ,V sz ) and the measured stator current (i sx ,i sy ) to calculate the estimated rotor speed of the rotor (112) and estimated rotor position By taking the reference rotor speed Subtract the estimated rotor speed To calculate the speed error (ω e ); According to the speed error (ω e ) to determine the reference torque generating current component And using the reference torque to generate a current component To modify the reference current vector By taking the reference rotor position Subtract the estimated rotor position To calculate the position error (θ e ), wherein the reference rotor position According to the reference rotor speed and reference rotor speed correction (ω c ) is determined, where the reference rotor speed correction (ω c ) According to the position error (θ e ) and the gain factor; Where, from the reference rotor speed Subtract the reference rotor speed correction (ω c ) to determine the corrected reference rotor speed Wherein, the reference rotor speed of the correction is Integrate to determine the reference rotor position By placing the reference current vector By the position error (θ e ) is transformed into a corrected reference current vector To correct the reference current vector Wherein, the reference current vector of the correction The rotating coordinate system (dq) and the estimated rotor position Alignment; According to the reference stator voltage A switching signal (s1, s2, s3) for the electric energy converter (104) is determined and the switching signal (s1, s2, s3) is applied to the electric energy converter (104).

2. The method (600) according to claim 1, characterized in that: Further including: According to the position error (θ e ) to determine the estimated rotor position whether it is accepted as correct; When the estimated rotor position When accepted as correct: use the estimated rotor position as the reference rotor position And the reference current vector The value of Changing to an initial value for normal operation of an electric drive system including the synchronous motor (102); and / or When the estimated rotor position If not accepted as correct: changing the reference current vector according to a predefined magnitude distribution (300) The value of and / or changing the reference rotor speed according to a predefined rotor speed profile (400) 3. The method (600) according to claim 2, It is characterized in that The position error (θ e ) is compared with a predefined threshold value; Among them, when the position error (θ e ) remains below the threshold for a predefined period of time, the estimated rotor position Accepted as correct.

4. The method (600) according to one of the preceding claims, characterized in that Further including: The current component is generated according to the reference torque and the reference current vector Reference value To determine the reference magnetizing current component And using the reference magnetizing current component To modify the reference current vector 5. The method (600) according to claim 4, It is characterized in that The reference magnetizing current component Use the following formula to calculate:

6. The method (600) according to one of claims 1 to 3, It is characterized in that The reference torque generating current component Depends on the reference current vector Reference value 7. The method (600) according to one of claims 1 to 3, characterized in that Further including: According to the corrected reference current vector and the measured stator current (i sx ,i sy ) to determine the reference voltage vector The reference voltage vector Transform into a fixed three-phase coordinate system (xyz); The reference voltage vector is converted by pulse width modulation The switching signals (s1, s2, s3) are determined based on the phase voltages.

8. A computer program product for starting a synchronous motor (102), comprising a computer program, which, when executed on a processor, is adapted to perform the method (600) according to one of claims 1 to 7.

9. A computer-readable medium in which a computer program is stored, wherein: When executed on a processor, the computer program is adapted to perform the method (600) according to one of claims 1 to 7.

10. A controller (106) for an electric energy converter (104), in, The controller (106) is adapted to perform the method (600) according to one of claims 1 to 7.

11. An electric drive system (100), comprising: A synchronous motor (102) comprising a rotor (112) for generating a first magnetic field and a stator (108) having a stator winding (110); An electric energy converter (104) is connected to the stator winding (110) and is adapted to convert a power supply voltage (V cc ) is converted into stator voltage (V sx ,V sy ,V sz ), the stator voltage (V sx ,V sy ,V sz ) is applied to the stator winding (110) to generate a rotating second magnetic field that interacts with the first magnetic field; The controller (106) of claim 10.

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