阅读说明：本技术 用于启动同步马达的方法 (Method for starting a synchronous motor ) 是由 A·卡利金 C·施图尔茨 于 2020-10-15 设计创作，主要内容包括：本发明涉及用于启动同步马达的方法。同步马达包括产生第一磁场的转子和具有连接到将电源电压转换成定子电压的电能转换器的定子绕组的定子。方法包括以下步骤：将参考定子电压施加到定子绕组；测量定子绕组中的定子电流；根据施加的定子电压和测量定子电流计算转子的估计转子速度和估计转子位置；通过从参考转子速度减去估计转子速度计算速度误差；根据速度误差确定参考转矩产生电流分量并用参考转矩产生电流分量修改参考电流矢量；通过从参考转子位置减去估计转子位置计算位置误差；通过将参考电流矢量通过位置误差变换成校正的参考电流矢量校正参考电流矢量；根据参考定子电压确定针对电能转换器的开关信号并将开关信号施加到电能转换器。(The invention relates to a method for starting a synchronous motor. The synchronous motor includes a rotor that generates a first magnetic field and a stator having stator windings connected to an electrical energy converter that converts a supply voltage to 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 the 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; a switching signal for the power converter is determined from the reference stator voltage and applied to the power converter.)

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 a power converter (104), the power converter (104) being adapted to convert a supply voltage (V)_cc) Into stator voltage (V)_sx,V_sy,V_sz) Said stator voltage (V)_sx,V_sy,V_sz) To be applied to the stator winding (110) to generate a rotating second magnetic field interacting with the first magnetic field,

the method (600) comprises:

reference stator voltageApplying (610) to the stator winding (110), wherein the reference stator voltageAccording to reference current vectorAnd reference rotor speedTo determine;

measuring (620) a stator current (i) in the stator winding (110)_sx,i_sy)；

According to the applied stator voltage (V)_sx,V_sy,V_sz) And the measuring stator current (i)_sx,i_sy) To calculate (630) an estimated rotor speed of the rotor (112)And estimating rotor position

By deriving from said reference rotor speedSubtracting the estimated rotor speedTo calculate (640) a speed error (omega)_e)；

According to the speed error (omega)_e) To determine (650) a reference torque producing current componentAnd generating a current component using the reference torqueTo modify the reference current vector

By referencing rotor positionSubtracting the estimated rotor positionTo calculate (660) a position error (theta)_e) Wherein the reference rotor positionAccording to the reference rotor speedAnd referenceRotor speed correction (omega)_c) Is determined, wherein the reference rotor speed correction (ω)_c) Following the position error (θ)_e) But increases and decreases;

wherein the reference rotor speed is determined from the reference rotor speedSubtracting the reference rotor speed correction (ω)_c) To determine a corrected reference rotor speed

Wherein the correction is made by correcting the reference rotor speedIntegrating to determine the reference rotor position

By applying said reference current vectorBy said position error (theta)_e) Conversion into a corrected reference current vectorTo correct (670) said reference current vectorWherein the corrected reference current vectorAnd said estimated rotor position (d) and a rotating coordinate system (dq)Aligning;

according to the reference stator voltageTo determine (680) a switching signal(s) for the power converter (104)₁,s₂,s₃) And the switching signal(s)₁,s₂,s₃) To the power converter (104).

2. The method (600) of claim 1, further comprising:

according to the position error (theta)_e) To determine the estimated rotor positionWhether it is accepted as correct;

when the estimated rotor positionWhen accepted as correct: using the estimated rotor positionAs the reference rotor positionAnd applying the reference current vectorMagnitude of (2)Changing to an initial value for normal operation of an electric drive system comprising the synchronous motor (102); and/or

When the estimated rotor positionWhen not accepted as correct: changing the reference current vector according to a predefined magnitude distribution (300)Magnitude of (2)And/or varying the reference rotor speed according to a predefined rotor speed profile (400)

3. The method (600) of claim 2,

characterized in that said position error (θ)_e) Is compared with a predefined threshold;

wherein when the position error (θ)_e) Remains below the threshold value for a predefined period of time, the estimated rotor positionIs accepted as correct.

4. The method (600) according to one of the preceding claims, further comprising:

generating a current component from the reference torqueAnd said reference current vectorReference value ofTo determine a reference magnetizationComponent of currentAnd using said reference magnetizing current componentTo modify the reference current vector

5. The method (600) of claim 4,

characterized in that said reference magnetizing current componentCalculated using the following equation:

6. the method (600) of one of the preceding claims,

characterized in that said reference rotor speed correction (ω)_c) As the position error (theta)_e) Is determined as a function of (c).

7. The method (600) of one of the preceding claims,

characterized in that said reference torque generates a current componentDependent on the reference current vectorReference value ofTo be determined.

8. The method (600) according to one of the preceding claims, further comprising:

reference current vector according to said correctionAnd the measuring stator current (i)_sd,i_sq) To determine a reference voltage vector

Vector the reference voltageTransforming into a fixed three-phase coordinate system (xyz);

by pulse width modulating the transformed reference voltage vectorPhase voltage (V) of_sx,V_sy,V_sz) To determine the switching signal(s)₁,s₂,s₃)。

9. A computer program for starting a synchronous motor (102), which, when being executed on a processor, is adapted to carry out the method (600) according to one of claims 1 to 8.

10. A computer-readable medium, in which a computer program according to claim 9 is stored.

11. A controller (106) for a power converter (104),

wherein the controller (106) is adapted to perform the method (600) according to one of claims 1 to 8.

12. 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 stator windings (110);

an electrical energy converter (104) connected to the stator winding (110) and adapted to convert a supply voltage (V)_cc) Into stator voltage (V)_sx,V_sy,V_sz) Said stator voltage (V)_sx,V_sy,V_sz) To be applied to the stator winding (110) to generate a rotating second magnetic field interacting with the first magnetic field;

the controller (106) of claim 11.

Technical Field

The present invention relates to control of electric drives. In particular, the 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 adapted to perform such a method.

Background

The rotor position and speed of a synchronous motor, such as a Permanent Magnet Synchronous Motor (PMSM), can be detected without the use of any sensors or encoders.

To start the synchronous motor from a stopped state, a rotating stator current vector may be applied, which generates an electromagnetic torque that forces the rotor to follow the stator current vector. This start-up may cause a speed oscillation of the rotor, since the natural damping of the synchronous motor is very weak. Such oscillations should be avoided.

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

Also, the start-up procedure of the synchronous motor should be as short as possible. A typical algorithm may be able to start the synchronous motor for at least 3 seconds.

For example, US 9998044B 2 describes a starting method for a three-phase sensorless permanent magnet synchronous motor, in which the rotor flux projection on the d-axis or q-axis of a rotating coordinate system is used to determine whether the stator current reference applied during starting is sufficient to spin the motor. The method may also determine an initial value for the stator torque current reference to use at the start of the closed loop field oriented control mode based on an angular difference between the reference angle and the estimated angle of the rotor.

US 2010/0264861 a1 describes a method for determining the position of a flux vector of an electric motor. As shown in fig. 1, by referencing the rotor speed ω from the reference_refSubtracting the estimated rotor speed ω_rTo calculate the speedDegree error, and determining a current vector I based on the speed error_qref. FIG. 1 also shows the stator velocity ω estimated by the pair_sIntegrating to determine an angle θ corresponding to an estimated position of a rotor flux vector_s. The motor is controlled such that the estimated position theta of the rotor flux vector_sAnd true position θ_RThe difference between them is minimized.

CN 106208865B describes a method for controlling a plurality of permanent magnet synchronous motors. Fig. 1 shows a control scheme where a speed error and a position error are calculated and used to control the motor.

CN 103270691B describes a sensorless AC motor controller that uses Feed Forward Torque Control (FFTC) in order to measure the angular position of the rotor. Fig. 3 shows the following control scheme: 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 '. Applied rotor position θ 'is used by block 31 to be derived from applied current component i'_d、i’_qGenerating a stator voltage v 'for the motor 11'_u、v’_v、v’_wAnd is used by the block 14 to determine the current component i from the measured stator current of the motor 11_d、i_qIs measured. Applied torque generating current component i'_qAnd a current component i_qIs measured by the difference Δ i between the measured values_qMay be calculated and used to correct the load model 22.

Xiao Xi et al describe further examples for sensorless vector control systems in the following documents: "Sensorless Control Based on MRAS Method in driving of internal Permanent Magnet motor-Magnet Machine Drive", international conference of power electronics and Drive system, Jilong Hill of Malaysia, 11/28/12/1/2005, Vol. 1, 734-.

Disclosure of Invention

It is an object of the present invention to reduce the 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 a normal operation mode.

This object is achieved by the subject matter of the independent claims. Further exemplary embodiments are apparent from the dependent claims and the following description.

A first aspect of the invention relates to a method for starting a synchronous motor fed by a power converter. The synchronous motor may comprise a rotor for generating a first magnetic field and a stator having stator windings connected to an electrical energy converter for converting a supply voltage into a stator voltage to be applied to the stator windings for generating a rotating second magnetic field interacting with the first magnetic field. The rotor may have permanent magnets and/or rotor windings to generate a first magnetic field. The rotor may be rotatably mounted in the stator. The power converter may include a three-phase inverter for providing a three-phase stator voltage from a DC link of the power converter. The stator voltage may be calculated by a controller for sensorless field-oriented control of the synchronous motor. A synchronous motor (i.e. an AC motor, wherein 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 comprising a power converter and a controller for controlling the synchronous motor in dependence of the load.

The method may be performed automatically by the controller. With this method, the synchronous motor can be started in eight steps.

According to an embodiment of the invention, the first step of the method comprises: a reference stator voltage is applied to the stator windings, wherein the reference stator voltage is determined from the reference current vector and the reference rotor speed. The reference current vector may be determined based on a value of the reference current during start-up. The reference current vector may be provided in an orthogonal coordinate system. The reference rotor speed may be an angular speed 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 relating to rotor flux and rotor torque. The reference current magnitude and the reference rotor speed may vary during start-up, for example according to a predefined profile, which may be a ramp or step function or any other kind of suitable function. The distribution may also include a constant portion.

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

According to an embodiment of the invention, the third step of the method comprises: an estimated rotor speed and an estimated rotor position of the rotor are calculated from the applied stator voltage and the measured stator current. The estimated rotor speed and the estimated rotor position may be calculated in a phase-locked loop from the estimated rotor flux. The stator voltage may be provided in a rotating coordinate system and transformed in a fixed three-phase coordinate system prior to estimating rotor speed and rotor position.

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

According to an embodiment of the invention, the fifth step of the method comprises: a reference torque producing current component is determined from the speed error, and the reference torque producing current component is utilized to modify the reference current vector. The speed error may be input to a PI controller, which may output a reference current accordingly. Thus, the reference torque producing current component may be considered as the output of the PI controller for correcting the reference torque producing current component of the reference current vector. Additionally, the reference torque producing current component may be input to a limit controller to verify that the reference torque producing current component does not exceed the current upper and/or lower limits. For example, the current limit may be provided depending on a reference current magnitude.

According to an embodiment of the invention, the sixth step of the method comprises: calculating a position error by subtracting the estimated rotor position from a reference rotor position, wherein the reference rotor position is determined from 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, the reference rotor speed correction may increase when the position error increases, and vice versa. For example, an increase in the reference rotor speed correction may be proportional to an increase in the position error, and vice versa.

According to an embodiment of the invention, the seventh step of the method comprises: the reference current vector is corrected by transforming the reference current vector into a corrected reference current vector by means of the position error, wherein the rotational coordinate system of the corrected reference current vector is aligned with the estimated rotor position. The position error may be set to zero when the position error falls below a predefined threshold. In this case, the reference rotor position may be set to be the same as the estimated rotor position.

According to an embodiment of the invention, the eighth step of the method comprises: a switching signal for the power converter is determined from the reference stator voltage and applied to the power converter. The switching signal may be a signal generated by pulse width modulating the phase voltages provided in a three-phase coordinate system. Such pulse width modulation may be controlled using a space vector modulation algorithm implemented in the controller as hardware and/or software. 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 the transistors of a three-phase inverter connected to the DC link of the power converter.

According to an embodiment of the invention, the method further comprises: 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 a 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: the magnitude of the reference current vector is varied according to a predefined magnitude distribution and/or the reference rotor speed is varied 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 power converter may be controlled based on the external speed and/or torque reference signal by closed loop sensorless magnetic field orientation 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 such that a smooth transition from the start-up procedure to the speed or torque control scheme is ensured. For example, the initial value may be the most recent value of the reference torque generating current component calculated during the start-up procedure. Once the estimated rotor position is determined to be correct, the magnitude of the reference current vector may be set to an initial value using a ramp or step function. In this way, a smooth switching to the normal operating mode of the electric drive system may be achieved. Additionally or alternatively, the predefined magnitude distribution may be an ascending curve or a curve having an ascending portion and a constant portion. The ascending curve may be a linear or non-linear continuous curve. The constant portion may be a horizontal line of the curve.

According to an embodiment of the 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.

According to an embodiment of the invention, the method further comprises: the reference magnetizing current component is determined from the reference torque producing component and the reference magnitude of the reference current vector, and the reference magnetizing current component is utilized to modify the reference current vector. The reference magnetizing current component can be seen as one of the two components of the reference current vector, which affects the motor magnetizing (main) flux.

According to an embodiment of the invention, the reference magnetizing current component is calculated using the following equation:

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

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

According to an embodiment of the invention, the method further comprises: determining a reference voltage vector from the corrected reference current vector and the measured stator current; transforming the reference voltage vector into a fixed three-phase coordinate system; the switching signal is determined by pulse width modulating the phase voltages of the transformed reference voltage vectors. 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 resulting from a comparison of a component of the reference current vector to the measured stator current. The reference voltage vector may be provided in a rotating orthogonal coordinate system.

Further aspects of the invention relate to a computer program which, when executed on a processor, is adapted to perform the method as described above and below.

A further aspect of the invention relates to a computer-readable medium in which such a computer program is stored. The computer readable medium may be a floppy disk, a hard disk, a USB (universal serial bus) memory 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, allowing downloading of the program code. Generally, computer readable media may be non-transitory or transitory media.

Further aspects of the invention relate to a controller for a power converter. The controller is adapted to perform the method as described above and below. For example, the controller may include a processor and a memory for storing computer programs. However, the method may also be implemented partially or completely in hardware.

Further aspects of the invention relate to an electric drive system comprising a synchronous motor having a rotor for generating a first magnetic field and a stator having stator windings. Furthermore, the electric drive system comprises an electric energy converter connected to the stator windings and adapted to convert a supply voltage into a stator voltage to be applied to the stator windings for generating a rotating second magnetic field interacting with the first magnetic field. The electric drive system also has a controller for controlling the power converter. The controller is adapted to perform the method as described above and below.

It must be understood that the features of the method as described above and below may be features of the electric drive system as described above and below.

These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.

Drawings

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.

FIG. 1 schematically illustrates an electric drive system according to an embodiment of the present invention.

Fig. 2 schematically shows the transformation means from fig. 1 in more detail.

FIG. 3 shows a diagram of a predefined magnitude distribution that may be used with the electric drive system from FIG. 1.

FIG. 4 shows a diagram of a predefined rotor speed profile that may be used with the electric drive system from FIG. 1.

Fig. 5 schematically shows the current controller from fig. 1 in more detail.

FIG. 6 shows a flow chart of a method for starting a synchronous motor according to an embodiment of the invention.

FIG. 7 shows a graph of different drive signals with reference rotor speed correction disabled according to an embodiment of the invention.

FIG. 8 shows a graph of different drive signals with reference rotor speed correction enabled according to an embodiment of the invention.

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 figures.

Detailed Description

FIG. 1 shows an electric drive system 100 having a synchronous motor 102, an electric power 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, the stator windings 110 each connected to an output of the power converter 104. The rotor 112 is configured to rotate within the stator 108. To generate the first magnetic field, the rotor 112 includes one or more permanent magnets 114, and the permanent magnets 114 may be mounted on the rotor 112 and/or buried within 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 power converter 104 is connected to provide an AC supply voltage V_ccTo the grid 116. The power converter 104 is configured to be based on a switching signal s generated by the controller 106₁、s₂、s₃(e.g. pulse width modulated or space vector modulated) for supplying the supply voltage V_ccConverted into three stator voltages V_sx、V_sy、V_szA three-phase AC voltage of the form (1). Stator voltage V_sx、V_sy、V_szTo respective terminals of the stator windings 110. Current through stator windings 110 establishes rotation in the air gap between rotor 112 and stator 108Of the second magnetic field. The interaction between the two magnetic fields causes the rotor 112 to rotate, thereby generating torque. The speed and torque of synchronous motor 102 may be controlled by controlling the current through stator windings 110.

The synchronous motor 102 may be controlled using Field Oriented Control (FOC) techniques without any sensors or encoders. In this case, the flux and torque components of the stator current are based on the reference rotor speed by the controller 106Which may be an external speed reference signal, and an estimated rotor position estimated based on a back electromagnetic force (back electromotive force) calculated from the number of stator windings 110To be controlled independently. This means that the synchronous motor 102 must rotate at a minimum speed for a sufficient amount of back EMF to be detected by the controller 106 to accurately calculate the estimated rotor positionThus, the controller 106 is configured to execute a start-up procedure to start the synchronous motor 102 from zero speed.

Fig. 1 depicts a block diagram of an algorithm implemented in the controller 106 for starting the synchronous motor 102 from a stopped state. During start-up, the reference current generator 118 generates a reference current for the magnetic field having a reference magnetization componentAnd a reference torque generation componentReference magnitude of a reference current vectorFor example, the reference current generator 118 may output a reference magnitude value according to a desired distribution as shown in FIG. 3The desired distribution may be a ramp function that references a magnitudeRamp up to a specified value and hold it constant until the rotor position is estimatedIs accepted as correct. The reference current generator 118 may then reference the magnitude valueChanges to a value defined as an initial value for the torque control mode.

Reference speed generator 122 generates a reference rotor speed for rotor 112Reference rotor speedIt may also be generated from a desired distribution, for example ramping up from a specified minimum value to a specified maximum value, as shown in fig. 4.

The flux estimate is active from the start of the start-up procedure. The estimator block 124 includes a block for calculating an estimated rotor fluxAnd a rotor flux estimator 126 for estimating rotor flux based thereonTo calculate an estimated rotor positionAnd estimating rotor speedRotor position estimator128. Estimating rotor positionAnd/or estimating rotor speedCan be calculated in a Phase Locked Loop (PLL).

Estimating rotor fluxBased on applied stator voltage V_sx、V_sy、V_szAnd a stator current i measured in the stator winding 110_sx、i_syTo calculate. In the example illustrated in fig. 1, only two phases i of the stator current are measured_sx、i_sySince it can be based on the other two phases i by the controller 106_sx、i_syTo calculate a third phase.

Measuring stator current i_sx、i_syAnd the applied stator voltage V_sx、V_sy、V_szMay be provided in a fixed three-phase xyz coordinate system. In calculating estimated rotor fluxBefore, the stator current i is measured_sx、i_syAnd an applied stator voltage V_sx、V_sy、V_szMay be transformed into a fixed orthogonal α β coordinate system by the transformation means 130, as illustrated in fig. 2.

To dampen rotor speed oscillations, the rotor speed will be estimated in the speed comparator 132And reference rotor speedFor comparison, the speed comparator 132 compares the reference rotor speedSubtracting the estimated rotor speedTo generate a speed error omega_eAs an error signal. Speed error omega_eAmplified by a torque controller 134 (e.g., a PI controller), the torque controller 134 generates a reference torque producing current componentThe limit controller 136 is based on the reference valueTo limit the reference torque-generating current component

In addition, the rotor position is referencedCalculated by the position reference generator 138, the position reference generator 138 may be for referencing a rotor speedAn integrator for performing the integration. Position comparator 140 derives a reference rotor positionSubtracting the estimated rotor positionTo generate a position error theta_eAs an error signal.

Position error theta_eIs input to the reference position corrector 142, and the reference position corrector 142 amplifies the position error θ by an appropriate gain factor_eAnd outputs a reference rotor speed correction omega_c. The reference position corrector 142 is configured to correct the position error theta_eSame proportional increase and decrease reference rotor speed correction omega_c. Alternatively, ω is corrected with reference to rotor speed_cAnd position error theta_eMay be modified in different proportions.

Reference rotor speed correction omega_cUsed by the reference speed corrector 144 to calculate a corrected reference rotor speed(e.g., by reference rotor speed as output by reference speed generator 122)Subtracting a reference rotor speed correction omega_c). Corrected reference rotor speedAnd then input to the position reference generator 138 for use in calculating the reference rotor position

Reference rotor speed correction omega_cWill be understood as referring to the rotor positionOrientation estimation rotor positionAdditional rotations of (a). This results inAndfaster convergence and thus better oscillation damping and shorter start-up time.

For providing a reference current vector during start-up, a current component is generated in addition to the reference torqueIn addition, the reference magnetizing current component must be calculatedReference magnetizing current componentBased on a reference magnitude by the magnitude limiter 148And reference torque generating current componentTo calculate. E.g. and componentOrthogonal reference magnetizing current componentCan utilizeCalculated as a reference magnitudeThe square complement of (c). Before entering the current magnitude limiter 148, the reference magnitude is setAnd reference torque generating current componentEach is squared in a squaring component 149. The current magnitude limiter 148 then derives a squared reference magnitude from the squared reference magnitudeSubtracting the squared reference torque produces a current componentSquaring the difference (i.e., squaring the reference magnetizing current component) from the square root component 150) Calculating a reference magnetizing current component

Reference magnetizing current componentReference torque generating current componentAnd position error theta_eAre each input to a reference transformation means 151, the reference transformation means 151 being configured to reference a magnetizing current componentAnd reference torque generating current componentBy the position error theta_eTransformation from a reference rotational orthogonal dq coordinate system to and estimation of rotor positionAligned rotated orthogonal dq coordinate systems. The resulting corrected reference current vector has a corrected reference magnetizing current componentAnd corrected reference torque generation component

The current controller 152 receives the corrected reference torque generation current componentAnd a corrected referenceComponent of magnetizing currentAnd both. The current controller 152 generates a current component from the corrected reference torqueWith measured and transformed stator current i_sqComparing, and correcting the reference magnetizing current componentWith measured and transformed stator current i_sdMaking a comparison to generate a switching signal s₁、s₂、s₃As will be described in more detail in fig. 5.

For example, when the position error θ_eIs kept below a given threshold value for a certain amount of time, the rotor position is estimatedIs accepted as correct by the reference position corrector 142. In this case, the reference current generator 118 may reference the magnitudeRamp up to a value that serves as an initial value for a normal operation control scheme. The initial value may be equal to the reference torque producing current component generated by torque controller 134Thereafter, the startup sequence is deemed to be successfully completed and the controller 106 switches to a closed loop torque or speed control mode based on the FOC. In this case, the orientation angle of the rotating dq coordinate system is from the reference rotor positionChanging to an estimated rotor positionIn addition, the current is referencedAndchanges to the values generated by the torque and flux control loops. In this way, a seamless transition of the synchronous motor 102 from the start-up procedure to normal operation can be achieved.

The various 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 as described above and below.

Fig. 2 schematically shows the transformation member 130 from fig. 1 in more detail. The transforming means 130 comprise a first transforming unit 200 for measuring the stator current i by performing a Clarke transformation_sx、i_syFrom a fixed three-phase xyz coordinate system to a fixed orthogonal α β coordinate system. The resulting stator current i_sα、i_sβThen transformed to a rotational orthogonal dq coordinate system by a second transformation unit 202, the second transformation unit 202 based on the estimated rotor positionTo perform the Park transformation. As a result, the second transformation unit 202 outputs a measured and transformed stator current i_sd、i_sqThe stator current is used by the current controller 152 to generate a switching signal s for controlling the power converter 104₁、s₂、s₃。

The transforming member 130 may be configured to transform the applied stator voltage V in a similar manner_sx、V_sy. The reference transformation member 151 may have only the transformation member 202.

Fig. 3 shows a diagram of a predefined magnitude distribution 300 as may be stored in the reference current generator 118 of fig. 1. According to this example, the magnitude distribution 300 comprises a first portion 302 in the form of a rising curve. The first portion 302 transitions into a constant second portion 304 in the form of a horizontal line. Alternatively, the reference quantity distribution 300 may include only the rising curve. The ascending curve may be a linear or non-linear function.

Fig. 4 shows a diagram of a predefined rotor speed profile 400 as may be stored in the reference speed generator 122 of fig. 1. According to this example, the rotor speed profile 400 has the form of an ascending curve, which may be used to reference the rotor speedA linear or non-linear function that ramps from a predefined minimum to a predefined maximum.

Fig. 5 schematically shows the current controller 152 from fig. 1 in more detail. The current controller 152 comprises a first current comparator 500 for comparing the current through the reference signal generated from the reference transformation means 151Subtract i as generated by transformation component 130_sdA first error signal 502 is generated. The first error signal 502 is amplified by a first PI controller 504 to generate a reference d-component voltage

Furthermore, the current controller 152 comprises a second current comparator 506 for comparing the current generated by the reference transformation means 151 with a reference currentSubtract i as generated by transformation component 130_sqTo 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 voltageThe voltage transformation means 512 is configured to transform the reference d component voltage by inverse Park and Clarke transformationAnd reference q component voltageTransforming into a fixed three-phase xyz coordinate system. Resulting three reference stator voltagesWill be applied to the stator windings 110. To achieve this, the stator voltage is referencedIs input to a modulating member 514, the modulating member 514 being configured to modulate the stator voltage V by pulse width_sx、V_sy、V_szGenerating a switching signal s₁、s₂、s₃Switching signal s₁、s₂、s₃Each corresponding to a modulated voltage. Stator voltage V_sx、V_sy、V_szMay be modulated using a space vector modulation algorithm implemented in the modulating means 514.

Fig. 6 shows a flow chart of a method 600 for starting the synchronous motor 102 from fig. 1 without position and speed sensors.

In step 610, the stator voltage V is applied_sx、V_sy、V_szTo the stator windings 110.

In step 620, the resulting stator current i is measured in the stator winding 110_sx、i_sy。

In step 630, the measured stator current i is used_sx、i_syAnd the applied stator voltage V_sx、V_sy、V_szEstimating rotor position based on back EMF generated by rotation of rotor 112And rotor speed

In step 640, the rotor speed will be estimatedAnd reference rotor speedMaking a comparison to determine the speed error omega_e。

In step 650, the velocity error ω is used_eTo determine a reference torque generating current component

In step 660, the rotor position is referenced from a reference rotor positionSubtracting the estimated rotor positionTo determine the position error theta_e. According to corrected reference rotor speed(e.g. by correcting for a reference rotor speedIntegrated) to determine a reference rotor positionBy subtracting the error theta based on position_eCalculated reference rotor speed correction omega_cCorrected reference rotor speedBased on reference rotor speedTo calculate. In optional step 662, the position error θ may be determined_eIs compared with a predefined threshold value. When the position error theta_eIs less than a threshold value for at least a predefinedTime period, in optional step 664, reference rotor positionIs arranged to estimate the rotor positionThe value of (c). This can be done by subtracting the position error θ_eAnd reference rotor speed correction omega_cSet to zero. Also, 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.

On the other hand, when the position error θ_eIs equal to or greater than the threshold, in optional step 666, a position error θ can be based on_eTo calculate a reference rotor speed correction omega_cTo make the position error theta in a further correction loop_eAnd (4) minimizing. In other words, the position error θ_eThe larger the reference rotor speed correction ω_cThe larger and vice versa. In short, by varying the reference rotor speed accordinglyCan estimate the rotor positionIn the direction of (1) correct the reference rotor position

In step 670, a current component is generated using the reference torqueThe modified reference current vector passes through the position error theta from the reference dq coordinate system_eTransformation to and estimation of rotor positionAligned dq coordinatesIn the series. In other words, once the position error θ_eAccepted as correct, e.g. set to zero, reference rotor positionEstimate the rotor positionThe same is true.

In step 680, the reference current vector component based on the correctionAndgenerating a switching signal s₁、s₂、s₃。

Reference magnitude during start-up of synchronous motor 102May be changed from a specified minimum value up to a specified maximum value and held constant until the rotor position is estimatedIs accepted as correct. Then, reference quantity valueMay be changed to a value defined as an initial value for the torque controller. Also during start-up, reference rotor speedMay be changed from a specified minimum value up to a specified maximum value.

Fig. 7 depicts a timing diagram to illustrate the oscillation of rotor speed from the synchronous motor 102 of fig. 1 when starting from a stopped state with reference rotor speed correction disabled. The time diagram shows a plot 700 of motor current, a plot 702 of estimated motor speed, a plot 704 of measured motor speed, a plot 706 of measured rotor position, and a plot 708 of estimated rotor position. One can clearly see the rotor speed oscillation during start-up, which oscillation lasts about 2.3 seconds.

Fig. 8 depicts a time diagram to illustrate the effectiveness of oscillation damping when the synchronous motor 102 from fig. 1 is started from a stopped state with reference rotor speed correction enabled. The parameters shown are the same as in fig. 7. The oscillation is almost completely damped. The start-up time is reduced to about 1 second. This may be the point at which the controller 106 switches to a normal operating mode (e.g., closed loop torque or speed control of the synchronous motor 102).

While 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 can be understood and effected by those skilled in the art and practicing the claimed invention, from a study of the drawings, the 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 fulfill 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 shall not be construed as limiting the scope.

REFERENCE SIGNS LIST

100 electric drive system

102 synchronous motor

104 electric energy converter

106 controller

108 stator

110 stator winding

112 rotor

114 permanent magnet

116 electric network

118 reference current generator

122 reference velocity generator

124 estimator block

126 rotor flux estimator

128 rotor position estimator

130 transformation component

132 speed comparator

134 torque controller

136 limit controller

138 position reference generator

140 position comparator

142 reference position corrector

144 reference velocity corrector

148 stator current value limiter

149 squaring component

150 square root component

151 reference transformation means

152 current controller

200 first conversion unit

202 second conversion unit

300 reference value distribution

302 rising part

304 constant part

400 reference velocity profile

500 first current comparator

502 first error signal

504 first PI controller

506 second current comparator

508 second error signal

510 second PI controller

512 voltage conversion member

514 modulating component

600 method for starting a synchronous motor

610 applying a stator voltage

620 measuring stator current

630 calculating an estimated rotor speed and an estimated rotor position

640 calculate speed error

650 determine a reference torque generating current component

660 calculating position error

662 compares the position error to a threshold

664 using the estimated rotor position as a reference rotor position

666 change the reference rotor speed and/or the magnitude of the reference current vector

670 correcting reference current vector

680 determine the switching signal

700 motor current curve

702 estimating a profile of motor speed

704 profile for measuring motor speed

706 curves for measuring rotor position

708 curves for estimating rotor position

dq rotating orthogonal coordinate system

i_sαAlternating stator current

i_sβAlternating stator current

i_sdAlternating stator current

i_sqAlternating stator current

i_sxMeasuring stator current

i_syMeasuring stator current

Reference magnetizing current component

Reference torque generating current component

Reference current vector

Corrected reference magnetizing current component

Corrected reference torque generating current component

Corrected reference current vector

Magnitude of reference current vector

s₁Switching signal

s₂Switching signal

s₃Switching signal

time t

V_ccSupply voltage

Reference d component voltage

Reference q-component voltage

Reference voltage vector

Transformed reference voltage vector

V_sxApplied stator voltage

V_syApplied stator voltage

V_szApplied stator voltage

Reference stator voltage, reference phase voltage

Reference stator voltage, reference phase voltage

Reference stator voltage, reference phase voltage

xyz stationary three-phase coordinate system

Alpha beta fixed orthogonal coordinate system

Estimating rotor flux

θ_ePosition error

Reference rotor position

Estimating rotor position

ω_cReference rotor speed correction

ω_eError in velocity

Corrected reference rotor speed

Reference rotor speed

The rotor speed is estimated.