Method for starting permanent magnet-excited synchronous machine without position sensor

Abstract

The invention relates to a method for starting a synchronous machine fed by a frequency converter having a voltage intermediate circuit without a position sensor and without closed-loop speed regulation, the synchronous machine having a permanent magnet rotor and a stator, for an open-loop-controlled starting operation of the synchronous machine, the vector current regulating device sets a reference current space vector rotating according to a predetermined rising rotational speed curve by means of at least one first current regulator setting a first current component of the stator current. The current regulator has a value predetermined at least by a theoretical value of the first current regulator and a defined angular position in a coordinate system rotating with a reference system fixed with respect to the position of the stator with a reference current space vector. During the start-up operation, an intermediate circuit voltage of the voltage intermediate circuit is determined and the intermediate circuit voltage or a variable derived from the intermediate circuit voltage is compared with a reference value. When the intermediate circuit voltage exceeds the reference value, a rotational speed correction value is added to the rotational speed change curve.

Description

Technical Field

[0001] The invention relates to a method for starting a synchronous motor fed by a frequency converter with a voltage intermediate circuit without position sensors and without closed-loop speed control, the synchronous motor having a permanent-magnet rotor and a stator, wherein, for an open-loop controlled starting operation of the synchronous motor, a vector current control device sets a reference current space vector of the vector current rotating according to a predetermined, increasing speed profile using at least one first controller for setting a first current component of the stator current, the reference current space vector having a value predetermined at least by a setpoint value of the first current controller and a defined angular position in a coordinate system rotating with a reference system in which the position of the reference current space vector is fixed relative to the stator. Background Art

[0002] Field-oriented regulation (FOR) is often used to regulate permanent magnet synchronous motors (PMSM). This method allows the torque of a PMSM to be regulated very accurately. However, for this regulation, it is necessary to know the rotor position, that is to say the angular position of the rotor relative to the stator.

[0003] The rotor position can be determined by a position sensor or by a so-called sensorless method. Since the position sensor increases the cost of the system, a sensorless method is used in many applications, which evaluates the voltage induced by the rotor magnetic field in the stator coil, the so-called Back-EMF (Electromagnetic Force). Methods based on back-electromagnetic force are widely used and can be implemented relatively simply and cost-effectively. However, they only work above a certain minimum speed because they are based on the observation of the induced voltage, which is proportional to the speed. For lower speeds, there are methods with an externally applied carrier signal, for example, which should detect asymmetries in the rotor and thus determine the rotor position. These methods are significantly more complicated to implement and are not suitable for all PMSMs. Therefore, the rotor position can only be determined with difficulty during the starting operation of the synchronous motor and is therefore unknown in many cases.

[0004] Therefore, for synchronous motors as drive devices for loads with load characteristic curves, a method that is simply controlled by open loop is usually used for starting operation, and the load characteristic curve only requires a small torque at low speed and is also only rarely operated at low speed, such as in the case of blowers and centrifugal pumps. In other words, the control of the synchronous motor is not carried out in a closed loop but in an open loop in terms of control technology during the starting operation. This means that the starting operation is not carried out using the actual position and / or actual speed of the rotor that is fed back to the regulator input of the speed regulator. Instead, the theoretical position or angular position of the rotor is completely predetermined. In this way, the area of ​​low speed is passed through in a simple open loop control before changing from a defined target speed to the field-oriented regulation area, that is, before using the field-oriented regulation. The theoretical position or angular position of the rotor is usually predetermined using a current or voltage space vector according to a defined trajectory, for example, a constant current is set for a constant acceleration, so that the rotor occupies a predetermined theoretical position or angular position corresponding to the trajectory.

[0005] The problem with purely open-loop controlled start-up operation is that the torque cannot be adjusted. This is due to the initial position of the load to be driven, the frequency setting and the load characteristics. More precisely, the torque M is determined by the angle between the current space vector I and the interconnected magnetic flux ψ (hereinafter also referred to as flux linkage). and the value of the current space vector is, that is, the height of the stator current is, as expressed by the following torque equation 1 and Figure 1 As shown,

[0006] Equation 1:

[0007] Where p is the number of pole pairs of the rotor. Figure 1 A stator 2 of a synchronous machine 1 is shown in cross section, with three stator windings spatially offset by 120°, and a permanent magnet rotor 3, each of which is assigned to one of the axes A, B and C offset by 120° to one another. The rotor 3 has two permanent magnets 4 (p=1) here, which form a north pole (N) and a south pole (S). The spatial vector of the flux linkage ψ of the rotor 3 lies by definition on the north-south axis of the magnets 4, so that the flux linkage ψ can also be equated with the rotor field. The rotor field / flux linkage ψ has an angular position θ relative to the stator 2 or to a Cartesian αβ coordinate system (stator reference system) arranged in the stator 2 and having stator-fixed coordinate axes α and β, which corresponds to the rotor position relative to the stator 2. Figure 1 The current space vector I of the stator current is plotted by way of example in FIG. 1 , which has an angle with respect to the space vector of the rotor field / flux linkage ψ. and the angle in the αβ coordinate system The αβ coordinate system with fixed coordinate axes α and β is used separately for reasons of clarity. Figure 2 It is shown in, where Figure 2 The coordinate axis α in corresponds to Figure 1 The spatial axis A is fixed in position.

[0008] Figure 2 Also shown is a Cartesian dq coordinate system for field-oriented control and rotating with an estimated or open-loop controlled rotor angle, and a δγ coordinate system that describes the actual angular position of the rotor with respect to the αβ coordinate system. The coordinate axes d, q are shown with dashed lines. Here, the δ axis points in the direction of the flux linkage ψ by definition. When the rotor position / angular position of the rotor is known exactly, the two coordinate systems dq, δγ are precisely superimposed on each other.

[0009] The current applied to the stator 2, or the current space vector I that can be shown in the αβ coordinate system for this purpose, can be decomposed into a first current component id and a second current component iq by projection onto the coordinate axes d and q. This is done mathematically with the help of the so-called Park Transformation. Here, graphically observed, the first current component id is located on the d axis and the second current component iq is located on the q axis, wherein the current space vector I is obtained by the vector addition of the first and second current components id, iq. These two current components id, iq are usually also referred to as d current and q current in language use. When the rotor position is known, the q current iq is the current component that produces torque, while the d current id produces magnetic flux. The two current components id, iq are orthogonal and can therefore be adjusted independently of each other.

[0010] In the diagram selected here, the actual torque is generated by the current iγ. The current components id, iq can be determined by the rotation angle is converted into current components iδ and iγ.

[0011] If the stator current I is applied in such a way that it has only a component on the d-axis in the dq coordinate system, as in Figure 2 As in the case of the dq current, i.e. as a pure d current, no torque is applied to the rotor 3 when the dq coordinate system coincides with the δγ coordinate system (viewed at rest). The rotor 3 therefore remains in the existing angular position. However, this is different when the actual angular position of the rotor 3 deviates from the angular position or direction of the applied current space vector. In this case, the rotor rotates until the coordinate systems (dq and δγ) coincide.

[0012] As in Figure 2 As shown in FIG, it is assumed that the rotor 3 is at an angle to the d-axis. There is then a torque-forming current iγ>0, and the rotor 3 is oriented so that the δ-axis coincides with the d-axis. In other words, the δγ coordinate system is rotated toward the dq coordinate system so that they coincide in the final state. Therefore, in this case the δγ coordinate system describes the unknown actual position or actual angular position of the rotor, while the dq coordinate system describes the theoretical position or theoretical angular position. In the final state, the projection of the d current onto the γ-axis is equal to zero, so that no torque M acts on the rotor 3. Therefore, it applies that: iδ=id and iγ=iq=0. Therefore, in the torque equation for torque M, according to equation 1, it is obtained:

[0013] Equation 2:

[0014] As already mentioned, the start-up operation of a sensorless synchronous machine with a permanent magnet rotor (PMSM) is usually carried out purely in open-loop control by repeatedly setting the current space vector at a predetermined angle. The angle of the respectively set current space vector increases, or more precisely increases faster over time. This can be referred to as the "open-loop phase".

[0015] Here again, it is mentioned that in the open-loop phase, the torque of the drive is only open-loop controlled, that is, not closed-loop controlled, because the actual rotor position is unknown. For this reason, it may happen during the start-up operation that the rotor 3 rotates faster than the current space vector is further switched. This means that the rotor 3 briefly leads the set current space vector or stator field, that is, exceeds the current space vector or stator field. This causes the torque to become negative and the rotor 3 is pulled back in the direction of the set current space vector. The rotor 3 is braked and energy is fed back into the intermediate circuit. As a result, the intermediate circuit voltage increases. This may lead to overcurrent and / or overvoltage in the intermediate circuit and in the worst case - when the intermediate circuit does not have sufficient intermediate circuit capacitance - the intermediate circuit may be destroyed, which is the case in so-called "slender (schlank)" intermediate circuits, that is, in intermediate circuits with small capacitance. Usually, an emergency cut-off is initiated to protect the frequency converter. It goes without saying that this situation must be avoided in practice. This is possible by using a sufficiently large intermediate circuit capacitance in the frequency converter of the synchronous motor. However, a large intermediate circuit capacitance results in a correspondingly large construction volume, leading to higher costs and a greater weight of the frequency converter. Summary of the invention

[0016] According to a first aspect, the object of the present invention is therefore to optimize the open-loop controlled starting operation, or "open-loop phase", of a synchronous machine with a permanent-magnet rotor in such a way that negative torques are avoided during the starting operation and thus a small or minimal intermediate circuit capacitance can be used in the frequency converter.

[0017] This object is achieved by a method according to claim 1. Advantageous further developments are specified in the dependent claims and are explained below.

[0018] According to the invention, a method is proposed for starting a synchronous machine fed by a frequency converter with a voltage intermediate circuit without position sensors and without closed-loop speed control, the synchronous machine having a permanent magnet rotor and a stator, wherein for an open-loop controlled starting operation of the synchronous machine, a vector current control device sets a reference current space vector rotating according to a predetermined, increasing speed profile by means of at least one first controller which sets a first current component of the stator current, the reference current space vector having a value predetermined at least by a setpoint value of the first current controller and a defined angular position in a coordinate system rotating with the reference current space vector relative to a fixed reference system of the stator. The fixed reference system of the stator corresponds to the αβ coordinate system described above in the introduction. In the method, an intermediate circuit voltage of the voltage intermediate circuit is determined during the starting operation. The intermediate circuit voltage or a variable derived therefrom is then compared with a reference value, in particular a limit value, and a speed correction value is added to the speed profile if the intermediate circuit voltage exceeds the reference value.

[0019] By adding the speed correction value, it is achieved that the current space vector or the stator field is accelerated more strongly or rotated forward when viewed in the αβ coordinate system in order to catch up with the mechanically preceding rotor. As a result, any negative torque is minimized or even overcompensated, so that a positive torque is achieved again. The core of the invention is therefore to dynamically adapt a predetermined speed curve as a function of the intermediate circuit voltage. For the starting operation, the speed curve is a monotonically increasing function, the slope of which is at least temporarily increased by the speed correction value relative to the initially predetermined curve. This adaptation of the speed curve can also be referred to as compensation control or, in view of the purpose achieved thereby, as current angle control or intermediate circuit voltage control.

[0020] Negative torques cannot be completely avoided, since their presence leads to the compensation reaction according to the invention for preventing an overload of the intermediate circuit. Negative torques are detected by means of the feedback of energy into the voltage intermediate circuit, and thus by means of a rising intermediate circuit voltage. When the intermediate circuit voltage exceeds a reference value, a speed correction value can be added to the speed curve.

[0021] As a reference value, for example, the value of the intermediate circuit voltage before the start-up operation begins or a value which is 1% to 10% above it can be used.

[0022] Alternatively, the rotational speed correction value can be added when the intermediate circuit voltage increases. Thus, the variable derived from the intermediate circuit voltage can be the time derivative of the intermediate circuit voltage, which is positive when the intermediate circuit voltage increases. In this case, the reference value can be 0 V / ms or a slightly positive value, for example 1 V / ms or 10 V / ms.

[0023] In one embodiment variant, it can be provided that the two criteria mentioned above are fulfilled cumulatively. In this case, a first query is made as before: whether the intermediate circuit voltage exceeds the reference value. However, the rotational speed correction value is only added if the intermediate circuit voltage increases at the same time or increases to a certain extent. In this case, a second query is additionally made, namely, for example: whether the time derivative of the intermediate circuit voltage is positive.

[0024] According to an advantageous further development, it can be provided that the greater the deviation of the intermediate circuit voltage from the reference value, the greater the rotational speed correction value or is determined to be greater. This corresponds to proportional control or control with a P component. In this case, the deviation is first determined by calculation. Subsequently, the size of the rotational speed correction value is determined as a function of the size of the ascertained deviation, for example by multiplying the rotational speed correction value by the deviation or a first correction factor derived therefrom and adding the rotational speed correction value determined in this way to the rotational speed curve.

[0025] Alternatively or additionally, it can be provided that the deviation of the intermediate circuit voltage from a reference value is determined and that the rotational speed correction value is greater or is determined to be greater the longer the deviation exists. This corresponds to an integral control or a control with an I component. In this case, the determined deviation is integrated over time. Subsequently, the size of the rotational speed correction value is determined as a function of the size of the integral value obtained by the integration, for example by multiplying the rotational speed correction value by the integral value or a second correction factor derived therefrom and adding the rotational speed correction value determined in this way to the rotational speed curve. If the deviation has already been determined within the scope of the proportional control, then this deviation naturally does not need to be determined again for the integral control.

[0026] It can further alternatively or additionally be provided that the faster the intermediate circuit voltage or the deviation rises, the greater the speed correction value is, or is determined to be greater. This corresponds to a differential control, or a control with a D component. In this case, the intermediate circuit voltage or the deviation is differentiated. Subsequently, the size of the speed correction value is determined according to the size of the differential value obtained by differentiation, for example, in that the speed correction value is multiplied by the differential value or by a third correction factor derived therefrom, and the speed correction value thus determined is added to the speed curve. If the deviation has already been determined within the scope of proportional control or integral control, this deviation naturally does not need to be re-determined for the differential control. Otherwise, the deviation of the intermediate circuit voltage from the reference value is first determined.

[0027] It is particularly advantageous to orient the rotor to a target position before the start-up operation in that the vector current control device sets at least one static reference current space vector with a defined angular position as a starting position for the start-up operation relative to a stationary reference system, at least with a first current regulator. In other words, the rotor is parked in the target position so that its angular position is known at the beginning of the start-up operation. This orientation of the rotor to the target position can be carried out independently of the adaptation of the speed curve according to the invention by means of a speed correction value.

[0028] For orientation, one or more current space vectors can also be set within a certain time. In the case of multiple current space vectors, the last current space vector set determines the target position of the rotor. The rotor is then always oriented in the direction of the static current space vector or the stator field, because the current space vector defines the direction of the stator field in the αβ coordinate system. Preferably, at least two different current space vectors are set, because in addition to the desired stable equilibrium position (the dq coordinate system is consistent with the δ, γ coordinate system), there is always an unstable equilibrium position offset by 180° (the dq coordinate system and the δ, γ coordinate system are offset by 180° from each other, that is, the externally applied d current is unfavorably accidentally opposite to the δ axis), so that the machine does not generate torque. If the rotor is accidentally in this position before starting, the rotor will not be aligned.

[0029] During the orientation process, it becomes clear that the rotor performs a more or less large movement, depending on its initial position, which can extend in the direction of the rotation direction set later (defined here as a positive rotation speed) or in the opposite direction (defined here as a negative rotation speed). The maximum movement corresponds to half an electrical period, i.e. a mechanical angle of π / p (p=pole pair number). In other words, a maximum movement of π / p=180° is possible with a pole pair number of p=1 (two magnets).

[0030] If in position If the rotor 3 is oriented in the middle, then for the angular movement of the rotor 3 from the initial position θ1 to the target position θ2 the following applies for the kinetic energy E:

[0031] Equation 3: That is, under unfavorable conditions, when the initial position θ1 = π / p

[0032] Equation 4:

[0033] The kinetic energy E built up by the angular movement therefore depends on the angular difference θ2 − θ1 between the initial position θ1 and the target position θ2 and on the motor current is and the magnetic flux linkage ψ.

[0034] The kinetic energy builds up until the oriented position is reached. To reach a standstill, this kinetic energy must now be reduced again by friction or by the counter-torque generated by the motor. This also presents problems if the intermediate circuit cannot accommodate this energy, as in the case of an open-loop phase where the rotor overtakes the stator field, which can be the case in so-called "slim" intermediate circuits, i.e., intermediate circuits with relatively low capacitance.

[0035] Furthermore, it should be taken into account that the target position of the rotor 3 is not suddenly occupied. Instead, the rotor exceeds the target position, oscillates back and stabilizes in the target position. This transient response can be compared to the oscillation of a spring-mass system, in which the rotational inertia moment of the rotor corresponds to the mass and the magnetic moment corresponds to the spring force. Therefore, the rotor position follows a slowly decaying, reduced oscillation. Here, the mechanical friction in the bearings of the rotor and the electrical losses (ohmic losses and re-magnetization losses) in the stator play a damping role. If the pump is regarded as a load of the synchronous motor, the friction of the liquid in the impeller is also a damping parameter. However, since the hydraulic pressure is relatively small at low speeds, only a small damping can be generated depending on the rotating mass, that is, the inertia moment of the rotor. The resulting danger is that despite the damping, the system still overshoots strongly. The excess kinetic energy formed due to the overshoot must be reduced again. In extreme cases, the entire kinetic energy E must therefore be fed back into the intermediate circuit. This may lead to overcurrent and / or overvoltage in the intermediate circuit, and in the worst case, if the intermediate circuit does not have sufficient intermediate circuit capacitance, the intermediate circuit may be destroyed. Normally, an emergency shut-off is activated for this purpose to protect the frequency converter.

[0036] Therefore, according to a second aspect of the invention, the object is to design the starting process of a permanent magnet synchronous motor (PMSM), in particular the orientation of the rotor to a target position for a subsequently defined starting operation, in such a way that possible transient oscillation processes are minimized and, if such transient oscillation processes occur, the resulting overcurrents or overvoltages in the intermediate circuit are avoided, wherein at the same time the maximum adjustable torque should be available for accelerating the rotor.

[0037] The object is achieved by a method for sensorless starting of a synchronous machine fed by a frequency converter with a voltage intermediate circuit, the synchronous machine having a permanent magnet rotor and a stator, wherein, in order to orient the rotor to a target position for a subsequent starting operation of the synchronous machine, a vector current control device sets at least one static reference current space vector with at least one first current regulator which sets a first current component of a stator current, the reference current space vector having a value which is predetermined at least by a setpoint value of the first current regulator and a defined angular position in a coordinate system which rotates with a reference system which is fixed relative to the position of the stator, wherein, when setting the static reference current space vector, an actual value of the first current component of the stator current set by the first current regulator is ascertained and compared with a setpoint value of the first current regulator, and, for the first current regulator, a first set of controller parameters is used when the actual value is higher than the setpoint value, and a second set of controller parameters is used when the actual value is lower than the first setpoint value, wherein the first set of controller parameters parameterizes the current regulator in such a way that the current regulator controls faster than if it were parameterized with the second set of controller parameters.

[0038] Therefore, the core of the second aspect of the method according to the invention is to use different regulator parameters for the current regulator depending on whether it exceeds or falls below the theoretical value. This causes the dynamic behavior of the current regulator when the rotor is oriented according to its actual position, thereby minimizing or even avoiding overshoot beyond the target position and the resulting overcurrent and overvoltage in the intermediate circuit. Because this shows that the current regulation also has an impact on the damping of the system. Therefore, it can be seen with the help of equation 4 that the variation curve of is(θ) is also included in the energy. That is, if the current regulator has a "poor" or "soft" interference characteristic, less energy is introduced. In other words, the induced voltage reacts to the cause or movement. At the same time, the theoretical value can correspond to the maximum possible settable current at any time, so that the maximum possible torque can be called according to the initial position of the rotor.

[0039] The first set of controller parameters results in a rigid parameterization or rigid controller behavior due to a relatively small time constant, while the second set of controller parameters results in a soft parameterization or soft controller behavior due to a relatively large time constant. Since the setpoint value should not be exceeded too strongly, the rigid parameterization, i.e. the first set of controller parameters, is used in the case where the actual value exceeds the setpoint value. If the setpoint value falls below the setpoint value, the soft parameterization, i.e. the second set of controller parameters, is used, whereby the back-induced voltage (Back-EMF) can counteract the acceleration of the drive and limit it.

[0040] Studies have shown that, apart from the initial position θ1, the time profile of the current is strongly dependent on the parameters of the current control. If a rigid controller parameterization of the current controller is selected, the current vector in the virtual rotor-related δ, γ coordinate system is almost constant. The disadvantage here is that a large amount of kinetic energy is introduced into the system and the electromechanical system has little damping. Therefore, significant mechanical oscillations occur and the kinetic energy converted here must be buffered in the intermediate circuit, which can lead to high voltages in the intermediate circuit in the case of small capacitances.

[0041] The apparent mechanical oscillation of the rotor Figure 3 In the curve K R1 Visible in. Figure 3 Five curves K for different regulator parameterizations R1 , K R2 , K R3 , K R4 , K R5 The change process of the rotor position over time is shown in FIG. Figure 4 The five corresponding curves K for different controller parameterizations are shown in FIG. I1 , K I2 , K I3 , K I4 , K I5 The stator current changes with time as shown in Fig. I1 It can be seen that the current I is adjusted quickly and well with the parameterization selected here, but the rotor position fluctuates greatly and for a long time, as shown by the curve K R1 As shown.

[0042] If the current regulator is now designed to be less rigid or "slower", the mechanical oscillations of the rotor are reduced. This shows the curves K compared to each other. R2 , K R3 , K R4 and K R5 Curve K R2 and K I2 The following controller parameterization is recorded in which the closed control loop has a transfer function with a time constant of 5 ms. R3 and K I3 In the case of , the controller is parameterized so that the closed control loop has a transfer function with a time constant of 10ms. R4 and K I4 , the time constant is 25ms, and for curve K R5 and K I5 , the time constant is 50ms. Figure 3It can be seen that the mechanical oscillations of the rotor decrease with increasing time constant, more precisely both in terms of the height of the overshoot and in terms of the number of oscillating movements, until the target position is stationary, see curve K R2 , K R3 , K R4 and K R5 Since the induced counter voltage generated by the movement in the case of a current regulator with a lower stiffness can now reduce the current, the torque and acceleration are also reduced and less kinetic energy is introduced into the system. The disadvantage here is that a significant overshoot occurs in the current, as shown in the associated curve K I2 , K I3 , K I4 and K I5 This means that for these parameterizations of the current regulator, the theoretical value for the current must be selected to be smaller, if necessary also significantly smaller, than the maximum permissible current in order to avoid overcurrents. This, however, also reduces the maximum achievable torque that is generated when the rotor is blocked.

[0043] The method according to the invention overcomes this disadvantage by switching according to the invention between the first controller parameters and the second set of controller parameters, that is, between a rigid or fast and a relatively soft or slow control, wherein the current is increased when the current is above the setpoint value I ref When the current is below the theoretical value I ref When using the voltage intermediate circuit, a softer parameterization, i.e. a parameterization with a higher time constant, is used. Thus, the value of the reference current space vector, in particular the setpoint value of the current regulator, can correspond to the maximum settable current. In addition, due to this conversion, the intermediate circuit can be designed to be "slim", that is to say with only a small capacitance. Preferably, the voltage intermediate circuit can have an intermediate circuit capacitance of less than 0.02 μF per watt.

[0044] The second aspect of the method according to the invention, i.e. the conversion of the controller parameterization, can also be used when setting a reference current space vector that rotates according to a predefined, increasing speed profile according to the first aspect of the method. This also applies to all further developments of the second aspect. However, it should be emphasized that the second aspect of the method is independent of the first aspect of the method and can therefore also be used separately.

[0045] Therefore, the method described in the first aspect is further refined as follows: when setting a reference current space vector that rotates according to a predetermined, increasing speed variation curve, an actual value of a first current component of the stator current set by a first current regulator or a first parameter related to the actual value of the first current component is determined, and the actual value or the first parameter is compared with a theoretical value of the first current regulator or a second parameter related to the theoretical value, and for the first current regulator, when the actual value or the first parameter is higher than the theoretical value or higher than the second parameter, a first set of regulator parameters is used, and when the actual value or the first parameter is lower than the first theoretical value or lower than the second parameter, a second set of regulator parameters is used, wherein the first set of regulator parameters parameterizes the current regulator so that the current regulator is adjusted faster than when it is parameterized using the second set of regulator parameters.

[0046] Therefore, transitions between regulator parameters can be triggered in different ways:

[0047] a) In the simplest case, the actual value of the first current component can be compared with a setpoint value of the first current regulator.

[0048] b) Alternatively, a first variable can be calculated from the actual value of the first current component and compared with a setpoint value of the first current regulator.

[0049] c) According to a further alternative, the actual value of the first current component can be compared with a second variable calculated from a setpoint value.

[0050] d) As a further alternative, a first variable can be calculated from the actual value of the first current component and compared with a second variable calculated from the setpoint value.

[0051] By using the first and / or second variable in variants b), c) and d), the conditions for switching between the first and second sets of controller parameters can be adapted as required. The first variable can be the product of the actual value and a first weighting factor, which can be, for example, between 0.9 and 1.1. The second variable can be the product of the theoretical value and a second weighting factor, which can be, for example, between 0.9 and 1.1. Depending on the result of the respective comparison of a) to d), the first or second set of controller parameters is used for the first current controller.

[0052] The value of the reference current space vector, in particular the setpoint value of the current regulator, can also correspond to the maximum settable current. In addition, the intermediate circuit can be designed to be "slim", ie, have only a small capacitance. Preferably, the voltage intermediate circuit can have an intermediate circuit capacitance of less than 0.02 μF per watt.

[0053] The following embodiments relate both to the first aspect and to the second aspect of the method according to the invention.

[0054] Whether the actual value or the first parameter is lower or higher than the theoretical value or the second parameter can be judged based on the error deviation between the parameters to be compared, that is, the theoretical value and the actual value, the theoretical value and the first parameter, the second parameter and the actual value, or the second parameter and the first parameter, wherein when the error deviation is negative, a first set of regulator parameters is used for the first current regulator, and when the error deviation is positive, a second set of regulator parameters is used.

[0055] The reference current space vector I can be selected for the start-up operation in essentially any way with regard to its position. However, there is a simple case when it is formed or set by only one of the two current components of the reference current space vector. This is meaningfully the id current component, since only this generates the magnetic flux necessary for orienting the rotor. In contrast, the iq current component can therefore be zero. Figure 2 This can be seen from the reference current space vector I plotted there, which has only the current component id lying on the d-axis, while the current component iq, or more precisely the theoretical value for the second current component iq, is zero. The reference current space vector I thus assumed here has the value id and the angle relative to the αβ coordinate system It is therefore advantageous if the reference current space vector is set only by the first current regulator, while the setpoint value for a second current regulator of the vector current control device, which can set the second current component of the reference current space vector, is zero.

[0056] Preferably, the vector current control device has a first current regulator for setting the first current component and a second current regulator for setting the second current component, wherein the first and second current components jointly define a reference current space vector. If the reference current space vector is set only by the first current regulator, the theoretical value of the second current regulator is zero, that is, the second current component is regulated to zero. However, the theoretical value of the second current component can also be different from zero, whereby any reference current space vector can be set.

[0057] The first current regulator is preferably a current regulator which, in a field-oriented control of the permanent-magnet synchronous machine connected to the starting operation, determines in normal operation the id current component for setting the stator current space vector, while the second current regulator determines the iq current component for setting the stator current space vector. This has the advantage that an existing control structure for field-oriented control can be used in order to carry out the starting operation of the synchronous machine according to the first or second aspect. No new regulator needs to be implemented.

[0058] In one embodiment variant, it can be provided that the first set of regulator parameters and the second set of regulator parameters parameterize both the first current regulator and the second current regulator. The switchover from the first set of regulator parameters to the second set of regulator parameters and vice versa preferably takes place simultaneously, for example in that a common switch simultaneously transmits a switchover signal to the first and second current regulators. The switchover can be triggered as described above if the actual value or the first variable rises above the setpoint value or the second variable, in which case the first set of regulator parameters is used, otherwise the second set of regulator parameters is used.

[0059] In one embodiment variant, the conversion can be performed solely as a function of the first current component, more precisely as a function of an error deviation / difference between an actual value of the first current component or a first variable calculated therefrom and a setpoint value thereof or a second variable calculated therefrom.

[0060] Alternatively, the switchover for the two current regulators can be carried out as a function of the first and second current components, in particular as a function of an error deviation / difference between a first variable formed by an actual value of the first current component and an actual value of the second current component and a second variable formed by a theoretical value of the first current component and a theoretical value of the second current component. For example, the first variable can be the sum of the squares of the actual values ​​and the second variable can be the sum of the squares of the theoretical values.

[0061] According to a further development, the first variable can also be the square root of the sum of the squares of the actual values ​​and the second variable can be the square root of the sum of the squares of the setpoint values. The first variable in this case corresponds to the value (amplitude) of the actual current space vector formed by the actual value of the first current component and the actual value of the second current component, and the second variable corresponds to the value (amplitude) of the reference current space vector formed by the setpoint value of the first current component and the setpoint value of the second current component. In other words, the conversion is carried out here according to an error current space vector, which corresponds to the difference between the actual current space vector and the reference current space vector.

[0062] In another embodiment variant, the switch between the first and second set of controller parameters for the second current regulator can be performed independently of the switch of the controller parameter set of the first current regulator. For example, the switch between the first and second set of controller parameters for the second current regulator can be performed only as a function of the second current component, while the switch between the first and second set of controller parameters for the first current regulator can be performed only as a function of the first current component.

[0063] The first set of controller parameters can parameterize the first current controller or the first and second current controller, for example, in such a way that the open control loop including the respective first or second current controller has a transfer function that has a so-called symmetrical optimum (Symmetrische Optimum, SO). In other words, the first current controller or the first and second current controller are then parameterized according to the method of the symmetrical optimum in order to achieve good interference characteristics. Figure 3 and Figure 4 In the curve K R1 and K I1 The parameterization according to the symmetrical optimum is used in the design of a controller according to the "symmetrical optimum" is known per se. In this regard, reference is made to the relevant professional literature, for example "Elektrische Antriebe / Dierk Springer, 2nd edition, 2001, ISBN 3-540-41994-2, Chapter 3.2. "Symmetrical optimum" is an important optimization criterion in electric drive technology, wherein the term refers to the frequency response of an optimized open control loop, whose phase response is symmetrical at the amplitude pass-through point.

[0064] In contrast, the second set (Set2) of controller parameters can parameterize the first current controller or the first current controller and the second current controller in such a way that the closed control loop including the respective first current controller or the second current controller has a transfer function with a time constant between 5 ms and 20 ms. This parameterization is shown in the curve K R2 To K R5 and K I2 To K I5 Used in.

[0065] If the first current regulator is or has a P regulator or a PI regulator and is a gain factor for the proportional component of the P regulator or the proportional component and the integral component of the PI regulator, a simple implementation of the current regulation is achieved. Therefore, each of the two groups of regulator parameters can include only one parameter value, namely the parameter value for the proportional component, or two parameter values, namely the parameter value for the proportional component and the integral component. The same applies to the second current regulator.

[0066] In one embodiment variant, the second current regulator can use the same set of regulator parameters as the first current regulator. However, according to another embodiment variant, it can be provided that each current regulator has its own regulator parameters, so that the regulator parameters can be different. In this case, the first and second sets of regulator parameters can each include two or four regulator parameters, namely one proportional component for each of the first and second current regulators, or one proportional component and an integral component for each of the first and second current regulators. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] Figure 1 A stator of a synchronous machine with three stator windings spatially offset by 120° and a permanent magnet rotor are shown in cross section;

[0068] Figure 2 The αβ coordinate system fixed to the stator, the dq coordinate system for field-oriented control, and the δγ coordinate system indicating the actual angular position of the rotor with respect to the αβ coordinate system are shown;

[0069] Figure 3 The time course of the rotor position is shown in each of five curves for different controller parameterizations;

[0070] Figure 4 The five curves for different controller parameterizations each show the temporal course of the stator current;

[0071] Figure 5 A block circuit diagram showing an implementation of the current regulating device according to the present invention;

[0072] Figure 6 The behavior of two controller parameterizations in comparison with one another is shown in the event of a jump in the setpoint value;

[0073] Figure 7 The behavior of two controller parameterizations in comparison with one another in the event of a disturbance variable jump is shown;

[0074] Figure 8a A block circuit diagram showing a more detailed implementation of the current regulating device according to the present invention;

[0075] Figure 8b A block circuit diagram showing another implementation of the current regulating device according to the present invention;

[0076] Fig. 9 A block diagram showing a third implementation scheme of the current regulating device according to the present invention;

[0077] Fig.10 A block circuit diagram is shown for implementing the method according to the first aspect of the present invention;

[0078] Fig.11 A block circuit diagram shows a more detailed illustration of the execution of the method according to the invention according to the first aspect. DETAILED DESCRIPTION

[0079] Reference is now made again to the drawings which illustrate exemplary embodiments of the present invention.

[0080] If Figure 2 It can be seen that each reference current space vector I of the stator current in the dq coordinate system for the vector current control device consists of the vector addition of two current components iδ and iγ, which point in the direction of the corresponding coordinate axis δ or γ. The δγ coordinate system associated with the rotor is rotated relative to the αβ coordinate system associated with the stator and has an angle θ relative to this coordinate system, as previously referred to Figure 1 As explained. The stator-related variables α, β and the rotating variables d, q for current control can be converted into each other by a d / q transformation, also called Park transformation or inverse d / q transformation or inverse Park transformation. The variables iδ, iγ are unknown. If the actual rotor position is used for current control after the start-up operation, the dq coordinate system corresponds to the rotor-related δγ coordinate system. However, this is not the case during the start-up operation under open-loop control, because the rotor position is unknown, that is, the unknown angle Located between the dq coordinate system and the δγ coordinate system related to the rotor.

[0081] Nevertheless, according to the present invention, a dq coordinate system with current components id, iq is still used for the open-loop controlled starting operation in order to set the reference current space vector I, because the current regulator for setting the current components id, iq already exists due to the vector current control performed after the starting operation, and therefore no additional current regulator is required to set or adjust the current components iδ and iγ.

[0082] Figure 5 The block diagram shows an implementation of the current control device 5 according to the invention during the starting operation, wherein the control of the id current component is shown here, while the iq current component is controlled to zero, that is, the reference current space vector is formed only by the id current component. The current control device 5 comprises a control loop with a current controller 11 (hereinafter referred to as first current controller 11), which has a current actual value id at the controller input. act A negative feedback 6 is provided at the regulator input at which a target current value id for the id current component is also predetermined. ref =I maxThe theoretical value corresponds to the maximum allowed stator current, which can flow continuously. As mentioned, for the iq current component, the theoretical value is equal to zero (iq ref =0), so that the reference current space vector I=id is located on the d-axis of the dq coordinate system, see Figure 2 .

[0083] Actual value of stator current id act Determined from the measurements of the phase currents ia, ib, ic. In a known manner, the three phase currents ia, ib, ic can then be converted into α and β current components in the αβ coordinate system by a Clarke transformation, and these current components are in turn converted into d and q current components in the dq coordinate system by a Park transformation, thereby obtaining the actual value id of the stator current act . This is done in box 9b. The subtractor 7 at the regulator input forms an error deviation e between the theoretical value and the actual value, which is directed to the first current regulator 11. The first current regulator 11 is implemented here as a PI regulator and therefore has a regulator parameter Kp that indicates the gain factor for the proportional component and a regulator parameter Ki that indicates the gain factor for the integral component. Based on the error deviation e, the first current regulator 11 provides a theoretical value of the d component ud of the stator voltage in the dq coordinate system. The q component uq of the stator voltage is regulated similarly. The d component and q component ud, uq of the stator voltage are converted into phase voltages in a known manner by means of an inverse Park transformation and a subsequent inverse Clarke transformation implemented in box 9a, which are then set by the frequency converter. The synchronous motor 1 and the frequency converter together form a Figure 5 An electric drive device is included in the block 1a, which has phase currents ia, ib, ic at the output.

[0084] According to a second aspect of the invention, this known and general structure of the current control is extended by a changeover switch 8 which determines whether the actual value id act Is it lower or higher than the theoretical value id ref To do this, use the theoretical value id ref With the actual value id act For the current regulator 11, the first set of "Set1" regulator parameters Ki, Kp is used when the error deviation e is negative, and the second set of "Set2" regulator parameters Ki2, Kp2 is used when the error deviation e is positive. If the actual value id act Too high, that is, the current id act Exceeds theoretical value id ref(e<0), a stiff controller parameterization which can be set with the first set of controller parameters Ki1, Kp1 is used in order to immediately compensate for overshoot and thus prevent overcurrent and / or overvoltage in the selected elongated intermediate circuit of the frequency converter. act Lower than the theoretical value id ref (e>0), a softer parameterization, ie a second set of controller parameters Ki2 , Kp2 with a higher time constant, is used in order to damp the mechanical oscillations of the rotor 3 .

[0085] The first set of controller parameters “Set1” Ki, Kp can be selected in such a way that the first current regulator 11 meets the optimization criterion of a symmetrical optimum (SO), while the second set of controller parameters “Set2” K I2 , Kp2 can be selected in such a way that the transfer function of the closed control loop including the first current regulator 11 has a time constant of 5 ms to 20 ms for the current control. Good results were obtained in tests by these parameterization studies.

[0086] Figure 6 FIG. 4 shows the behavior of the two controller parameterizations in comparison with one another in the case of a target value jump. FIG. 4 shows the current actual value id of the first current controller 11 for the id current in the case of a target value jump. act The time curves of the controller K with a soft or slow controller parameterization according to the second set of controller parameters at a time constant of 5 ms are shown by the curve K with a solid line. S2 The rigid or fast controller parameterization according to the first set of controller parameters is shown by the dashed curve K S1 , where the current regulator is in the first set of regulator parameters K S1 In the case of , it is optimized according to the symmetric optimal value.

[0087] Figure 7 Shows the jump in the disturbance parameter The behavior of the two regulator parameterizations in comparison with one another in the case of a disturbance variable jump is shown in FIG. act The time curves of the controller K with a soft or slow controller parameterization according to the second set of controller parameters at a time constant of 5 ms are shown by the curve K with a solid line. N2 The rigid or fast controller parameterization according to the first set of controller parameters is shown by the dashed curve K N1 , where the current regulator is in the first set of regulator parameters K N1 In the case of , it is optimized according to the symmetric optimal value.

[0088] Figure 8a A more detailed implementation of the current regulating device 5 according to the invention is shown with reference to a block diagram. Figure 5 In the diagram, the control structure is supplemented by a second current regulator 12, which is based on a setpoint value iq that is independent of the id current component. ref Regulate the iq component. All features described for the first current regulator 11 apply accordingly to the second current regulator 12, so refer to these explanations. However, the second current regulator 12 regulates the voltage uq to regulate the iq component, for example, to keep it to 0. The changeover switch 8 also acts on the second current regulator 12 in this embodiment variant, more precisely so that the first or second set of regulator parameters is given not only to the first current regulator 11 but also to the second current regulator 12. Therefore, the first and second current regulators 11, 12 use the same regulator parameters here. At the same time, the regulator switches between the various regulator parameter groups, more precisely in this embodiment variant only with the help of error deviations when regulating the id current.

[0089] Figure 8b A further embodiment of the current regulating device 5 according to the invention is shown with reference to a block diagram. Figure 8a The difference of the embodiment variant in the embodiment is that according to the actual value id of the two current components id, iq act 、iq act The calculated first variable is the same as the theoretical value id of the two current components id and iq ref 、iq ref The comparison of the calculated second variables is used to switch between the first and second sets of controller parameters for the two current regulators 11, 12. More precisely, the calculation of the first variable is carried out in such a way that the actual values ​​id of the two current components id, iq act 、iq act are respectively squared in the squarer 20 and the square id thus formed 2 act 、iq 2 act They are then added in adder 14. Analogously, the calculation of the second variable is performed such that the setpoint value id of the two current components id, iq ref 、iq ref are respectively squared in the squarer 20 and the square id thus formed 2 ref 、iq 2 ref The sum is then added in the adder 14, wherein the square sum id thus formed 2 act +iq2 act is the first parameter and the square and id 2 ref +iq 2 ref is the second variable. Subsequently, the first variable is subtracted from the second variable in the subtractor 7, which also corresponds to the error deviation transmitted to the changeover switch 8. As in the previous example, when the error deviation is negative, that is, the first variable is greater than the second variable, the changeover switch 8 selects the first set of regulator parameters, and when the error deviation is positive, that is, the first variable is less than the second variable, the changeover switch selects the second set of regulator parameters.

[0090] Intuitively speaking, according to Figure 8b In a variant of the controller parameter set, the switchover between the controller parameter sets is carried out as a function of the value (amplitude) of the error current space vector, which is described in terms of the setpoint values ​​id for the current components id, iq. ref 、iq ref (iq ref The reference current space vector set by the current components id and iq is also zero. act 、iq act The error deviation between the actual current space vector defined by sqrt(id 2 act +iq 2 act ). It therefore corresponds to the square root of the first variable. The reference current space vector has the value sqrt(id 2 ref +iq 2 ref ) and thus corresponds to the square root of the second variable. Since the square root is always positive and only which of the first and second variables is important for the comparison is which one is greater, the square root formation can be omitted and the square sums can be compared directly with one another. The comparison of the square sums is simplified by means of the subtractor 7, since the first and second variables [(id 2 ref +iq 2 ref )-(id 2 act +iq 2 act )], ie the error deviation, only needs to be checked whether the difference of the sum of squares is positive or negative.

[0091] Therefore, the first and second current regulators 11, 12 are in accordance with Figure 8bIn the variant of , the same controller parameters are also used, and the controller switches between the controller parameter sets simultaneously. However, in this embodiment variant, the error deviation is used as the switching criterion when regulating the id current and the iq current, more precisely the value (amplitude) of the error current space vector.

[0092] Fig. 9 A third embodiment of the current regulating device 5 according to the invention is illustrated by means of a block diagram. Figure 8a and Figure 8b The difference in the implementation scheme is that the current regulators 11, 12 use their own regulator parameter sets respectively. For this reason, there are two changeover switches 8 and each changeover switch 8 has a first and a second set of regulator parameters respectively. Therefore, the changeover switch 8 acting on the first current regulator 11 switches between the first set of "Set1d" regulator parameters and the second set of "Set2d" regulator parameters, and the changeover switch 8 acting on the second current regulator 11 switches between the first set of "Set1q" regulator parameters and the second set of "Set2q" regulator parameters. The two first sets "Set1d", "Set1q" have different regulator parameters. In addition, the two second sets "Set2d", "Set2q" have different regulator parameters.

[0093] also, Fig. 9 The two changeover switches 8 in the first current regulator 11 use different changeover standards, however this is not mandatory. The changeover switch 8 associated with the first current regulator 11 uses the error deviation e of the Id current component, while the changeover switch 8 associated with the second current regulator 12 uses the error deviation e of the Iq current component. In the first current regulator 11, when the actual value id act Higher than the theoretical value id ref The first set of "Set1d" regulator parameters is used, and when the actual value id act Lower than the theoretical value id ref , wherein the first set of “Set1d” controller parameters parameterizes the first current controller 11 so that it regulates faster than if it were parameterized with the second set of “Set2d” controller parameters. Furthermore, in the second current controller 12, when the actual value iq act Higher than the theoretical value IQ ref The first set of "Set1q" regulator parameters is used when the actual value iq act Lower than the theoretical value IQ refThe second set of controller parameters "Set2q" is used when the first set of controller parameters "Set1q" is used, wherein the first set of controller parameters "Set1q" parameterizes the second current controller 12 so that it is regulated faster than if it were parameterized with the second set of controller parameters "Set2q". The different sets of controller parameters [Set1d, Set2d] and [Set1q, Set2q] for the first and second controllers take into account that the inductance Ld in the d-axis direction is not equal to the inductance Lq in the q-axis direction.

[0094] Fig.10 A block circuit diagram for implementing the method according to the first aspect of the invention is shown. Here, too, for the open-loop controlled starting operation of the synchronous machine 1, a vector current control device 5 is provided, which sets the stator current according to a predetermined, increasing speed profile n start The current regulator 5 is not shown in detail here. As mentioned above, the current regulator comprises a first current regulator 11 for setting a first current component of the stator current, namely the id current, and a second current regulator 12 for setting a second current component of the stator current, namely the iq current.

[0095] The vector current control device 5 sets the reference current space vector in the dq coordinate system such that the reference current space vector has a theoretical angle More precisely, it has a theoretical angle of The theoretical perspective The theoretical rotor position is given in advance. This theoretical angle is obtained by the speed curve n start The integral of is determined in the integrator 15, to which the starting position or starting angle is also supplied It can simply be set to zero. Speed ​​curve n start In this example, this is the speed target value ramp.

[0096] According to the invention, the rotational speed correction value n is added by means of an adder 14. add Add to the speed curve n start This causes the reference current space vector to be accelerated, that is, faster than the predetermined speed variation curve n start The measures are carried out when the rotor 3 exceeds the reference current space vector or the stator field, that is, when it leads the reference current space vector or the stator field, which results in a negative torque (braking torque) that feeds energy back into the intermediate circuit. This is done by means of the rising intermediate circuit voltage U dc It can be seen that it is ascertained, in particular measured, at the electric drive 1 a, more precisely at its intermediate circuit. dcis supplied to the current angle regulator 13, which determines the rotational speed correction value n add .

[0097] Only when the intermediate circuit voltage U dc Exceeding the limit value U dcmax When the speed correction value n is add Speed ​​variation curve n start The current angle regulator 13 adjusts the intermediate circuit voltage U dc With the limit value U dcmax The comparison is made and when the limit value U is exceeded dcmax When the speed correction value n add In the simplest case, the speed correction value n add It can be a constant value. However, it is also possible to dc With the limit value U dcmax The speed correction value n is selected based on the deviation add In particular, the speed correction value n add Can be connected to the intermediate circuit voltage U dc With the limit value U dcmax This means that the intermediate circuit voltage U dc The further the limit value U is exceeded dcmax , speed correction value n add This corresponds to proportional regulation. In addition, the longer the deviation exists and / or the intermediate circuit voltage U dc The faster it rises, the faster the speed correction value n add To achieve this, the current angle regulator 13 may have the function of a PID regulator.

[0098] Through the speed correction value n add In other words, the resulting forward rotation of the reference current space vector minimizes the negative torque and preferably also changes it back into a positive torque acting on the rotor 3 , thereby preventing a further increase in the intermediate circuit voltage and thus protecting it.

[0099] Fig.11 A more detailed illustration of the implementation of the method according to the invention according to the first aspect is shown in a block circuit diagram. In particular, components of the vector current control device 5 are shown here. In addition, in this exemplary embodiment, the transition from a purely open-loop controlled starting operation "open-loop operation" to a field-oriented controlled "closed-loop operation" (FOR operation) is shown.

[0100] The vector current control device 5 receives the three phase currents ia, ib, ic of the stator phases of the electric drive 1a or the synchronous machine 1 at the input. These three phase currents ia, ib, ic are transformed in block 9b2 by means of a Clarke transformation into current components iα, iβ of a reference system related to the stator, more precisely, of an αβ coordinate system. The current components iα, iβ are used to determine the current rotor position during the operation of the field-oriented control. and the current speed n act In addition, the current components id, iq of the reference system related to the rotor, more precisely the dq coordinate system, are determined from the current components iα, iβ. This is done with the help of the Park transformation in block 9b1. For this purpose, either the current rotor position is used in closed-loop operation Either the actual rotor position is unknown during the start-up operation, so the setpoint position for the rotor is used in the open-loop operation Or theoretical perspective

[0101] If targeted Fig. 9 Described, theoretical perspective The integrator 15 is activated during the start-up operation and calculates the speed profile n start Integrate, where the initial value of the integral is the starting angle This starting angle corresponds to the position of the rotor 3 in which the rotor 3 previously rested. In simple terms, the starting angle can be The rotor is thus oriented or rests on the α axis. Fig. 9 As described above, the adder 14 converts the rotation speed correction value n provided by the current angle regulator 13 into + Add to the speed change curve n start In this example, the starting angle is also provided by the current angle regulator 13 The speed correction value n is adjusted by the current angle regulator 13 + The determination is also as for Fig. 9 Proceed as described in the example in .

[0102] Fig.11 The control structure in the embodiment includes a speed regulator 16, which is however not active during the starting operation and the signal flow involving it can therefore be initially ignored. The starting operation is activated by a corresponding activation signal "starting operation on", which is activated at Fig.11 The activation signal activates and deactivates individual components of the control structure and causes a switch between signal paths. Thus, the current angle regulator 13 and the speed preset value n startis activated and the speed regulator 16 is deactivated. The latter is achieved by means of an inverter 19 which negates the activation signal. Furthermore, the activation signal acts on a first switch 17 which switches to the setpoint value id for the id and iq currents from the speed regulator 16. ref 、iq ref The predetermined values ​​and these theoretical values ​​id used for starting operation ref 、iq ref For the start-up operation, these setpoint values ​​id ref =I max And iq ref =0, as in Figure 5 The activation signal also acts on the second switch 18, which, when the current, ie actual, rotor position used in the field-oriented control operation is known, The theoretical rotor position used during the start-up operation Switches 17 and 18 are switched between Fig.11 , it is shown in the position provided for the starting operation.

[0103] The first current regulator 11 for setting the id current and the second current regulator 12 for setting the iq current are arranged in Fig.11 In the diagram in FIG. 1 , the dq current regulator 11 , 12 is functionally integrated. The dq current regulator 11 , 12 obtains the setpoint values ​​id for the id current and the iq current. ref 、iq ref And on the other hand get the actual value of id current and iq current act 、iq act The dq current regulators 11 , 12 calculate from this the current reference value id in the dq coordinate system in order to set the current reference value id ref 、iq ref The voltage components ud, uq required for the defined reference current space vector are then calculated in block 9a1 using the theoretical angle of the rotor during the starting operation. Or the current rotor position during field-oriented control in normal operation In the case of , the voltage components ud, uq are converted into voltage components uα, uβ in the αβ coordinate system. The voltage components uα, uβ are then converted in block 9a2 by means of a Clarke transformation into phase voltages Ua, Ub, Uc, which must be set on the electric drive 1a in order to set the desired reference current space vector. In normal operation, during field-oriented regulation, the voltage components uα, uβ are also used to determine the current speed n act and the current rotor position This is done in a known manner.

[0104] exist Fig.11 The operating principle of the control structure shown in the figure during start-up operation is similar to that for Fig.10 The operating principle described is the same. If the start-up operation is completed, that is, the predetermined target speed is reached, the switch is made to the normal operation of the field-oriented control. This is achieved by shutting off the start-up operation via a corresponding deactivation signal "start-up operation shut-off". The deactivation signal is an inverted activation signal. The deactivation signal deactivates the current angle regulator 13 and the speed preset value n start The speed regulator 16 is activated, which now regulates the predetermined set speed n ref And for this purpose according to the actual speed n act The setpoint values ​​id for the id current and the iq current are given in advance ref 、iq ref At the same time, the deactivation signal switches the first switch 17 so that the dq current regulators 11 , 12 now receive the setpoint values ​​id for the id current and the iq current from the speed regulator 16 . ref 、iq ref , and on the other hand, switching the second switch 18 so as to deliver the current rotor position to the Park transformation and the inverse Park transformation By activating the speed controller, a switch is made from "open-loop operation" to "closed-loop operation" during the start-up operation.

[0105] Here again, the torque of the drive is not regulated in open-loop operation, since the rotor position is unknown. Instead, the torque is due to the unknown angle between the δγ coordinate system describing the actual position of the rotor and the dq coordinate system Therefore, it is possible that the torque becomes negative and energy is fed back into the intermediate circuit, thereby causing the intermediate circuit voltage U dc Increase.

[0106] In a variant embodiment not shown, a switch between a first and a second set of controller parameters for the first and / or second controller 11, 12 according to the second aspect of the method according to the invention (e.g. for Figure 5 , Figure 8a , Figure 8b and Fig. 9 As described in Fig.10 and Fig.11 In the embodiment variant in , it is supplemented so that the first and second aspects of the method according to the invention can also be used simultaneously.

[0107] It should be pointed out that the above description is merely exemplary for the purpose of explanation and in no way limits the scope of protection of the present invention. Features of the present invention given as "can", "for example", "preferred", "optional", "ideal", "advantageous", "when necessary", "suitable", etc. can be regarded as purely optional and do not limit the scope of protection, which is determined only by the claims. If the elements, components, process steps, values ​​or information listed in the above description have known, similar or predictable equivalents, these equivalents are included in the present invention. The present invention also includes any changes, modifications or modifications of the embodiments, which involve the replacement, addition, change or omission of elements, components, process steps, values ​​or information, as long as the basic idea of ​​the present invention remains unchanged, regardless of whether the changes, modifications or modifications lead to improvements or degradations of the implementation methods.

[0108] Although the above invention description lists many tangible, intangible or specific method features of one or more specific embodiments, these features can also be used independently from the specific embodiments, at least when they do not require the absolute existence of other features. On the contrary, these features listed in relation to one or more specific embodiments can be combined with each other and with other disclosed or undisclosed features of the illustrated or unillustrated embodiments at will, in any case, as long as these features do not exclude each other or do not lead to technical incompatibility.

Claims

1. A method for starting a synchronous machine (1) fed by a frequency converter with a voltage intermediate circuit without position sensors and without closed-loop speed control, the synchronous machine having a permanent-magnet rotor (3) and a stator (2), wherein: For an open-loop controlled starting operation of the synchronous machine (1), a vector current control device (5) uses at least one first current regulator (11) for setting a first current component (id) of the stator current to set a predetermined, increasing speed profile (n start ) is a reference current space vector (I) which is rotated by the first current regulator (11), the reference current space vector having a setpoint value (id ref ) and an angular position defined in a coordinate system (d, q) rotated about a reference system (α, β) fixed in position with respect to the stator (2) the reference current space vector (I) is characterized in that during the starting operation, the intermediate circuit voltage (U dc ) and compares the intermediate circuit voltage or a variable derived from the intermediate circuit voltage with a reference value (U dcmax ) is compared, wherein when the intermediate circuit voltage (U dc ) exceeds the reference value (U dcmax ), a speed correction value (n+) is added to the speed change curve.

2. The method according to claim 1, characterized in that Only when the intermediate circuit voltage (U dc ) increases or the intermediate circuit voltage increases to a certain extent, the speed correction value (n + ).

3. The method according to claim 1 or 2, characterized in that: Determine the intermediate circuit voltage (U dc ) and the reference value (U dcmax ), and the larger the deviation, the larger the speed correction value (n + ) is bigger.

4. The method according to any one of the preceding claims, characterized in that Determine the intermediate circuit voltage (U dc ) and the reference value (U dcmax ), and the longer the deviation exists, the rotation speed correction value (n + ) is bigger.

5. The method according to any one of the preceding claims, characterized in that The faster the intermediate circuit voltage increases, the faster the rotational speed correction value (n + ) is larger, or the intermediate circuit voltage (U dc ) and the reference value (U dcmax ), and the faster the deviation increases, the faster the speed correction value (n + ) is bigger.

6. The method according to any one of the preceding claims, characterized in that Prior to the start-up operation, the rotor (3) is oriented to a target position by setting the vector current control device (5) at least with the first current regulator (11) to a defined angular position relative to the stationary reference system (α, β) At least one static reference current space vector (I) is used as a starting position for the start operation.

7. The method according to any one of the preceding claims, characterized in that When setting the reference current space vector (I), an actual value (id) of a first current component (id) of the stator current set by the first current regulator (11) is determined. act ) or a first variable related to the actual value of the first current component, and the actual value (id act ) or the first parameter and the theoretical value (id ref ) or with the theoretical value (id ref ) is compared with a second parameter related thereto, and for the first current regulator (11), when the actual value (id act ) or the first parameter is higher than the theoretical value (id ref ) or higher than the second parameter, the first set (Set1) of regulator parameters (Ki1, Kp1) is used, and when the actual value (id act ) or the first parameter is lower than the theoretical value (id ref ) or below the second parameter, using a second set (Set2) of regulator parameters (Ki2, Kp2), wherein the first set (Set1) of regulator parameters (Ki1, Kp1) parameterizes the current regulator (11) so that the current regulator is regulated faster than when it is parameterized with the second set (Set2) of regulator parameters (Ki2, Kp2).

8. A method according to at least claim 7, characterized in that According to the theoretical value (id ref ) and the actual value (id ref )、Theoretical value(id ref ) and the first parameter, the second parameter and the actual value (id act ) or the error deviation (e) between the second parameter and the first parameter to evaluate: the actual value (id act ) or whether the first parameter is lower or higher than the theoretical value (id ref ) or a second parameter, wherein, when the error deviation (e) is negative, a first set (Set1) of regulator parameters (Ki1, Kp1) is used for the first current regulator (11), and when the error deviation (e) is positive, a second set (Set2) of regulator parameters (Ki2, Kp2) is used.

9. The method according to any one of the preceding claims, characterized in that The reference current space vector (I) is set only by the first current regulator (11), while the setpoint value (iq ref ) is zero, the second current regulator can set the second current component (iq) of the reference current space vector (I).

10. The method according to any one of the preceding claims, characterized in that The vector current control device (5) comprises a first current regulator (11) for setting a first current component (id) and a second current regulator (12) for setting a second current component (iq), wherein the first current regulator (11) is a current regulator which, in a field-oriented control of the permanent-magnet synchronous motor connected to a starting operation, determines in normal operation an id current component for setting a stator current space vector, and the second current regulator (12) determines in normal operation an iq current component for setting a stator current space vector.

11. The method according to any one of the preceding claims, characterized in that The value of the reference current space vector (I), in particular the setpoint value (id ref ) corresponds to the maximum settable current (I max ).

12. A method according to at least claim 7, characterized in that The first current regulator (11) is or has a P regulator or a PI regulator, and the regulator parameters (Ki1, Kp1, Ki2, Kp2) are gain coefficients for a proportional component of the P regulator or a proportional component and an integral component of the PI regulator.

13. A method according to at least claim 7, characterized in that The first set (Set1) of controller parameters (Ki1, Kp1) parameterizes the first current controller (11) in such a way that an open control loop including the first current controller (11) has a transfer function having a symmetrical optimum (SO).

14. A method according to at least claim 7, characterized in that The second set (Set2) of controller parameters (Ki2, Kp2) parameterizes the first current controller (11) in such a way that a closed control loop including the first current controller (11) has a transfer function with a time constant between 5 ms and 20 ms.

15. The method according to any one of the preceding claims, characterized in that The voltage intermediate circuit has an intermediate circuit capacitance of the converter of less than 0.02 μF per Watt of rated power.

16. System for starting a synchronous machine (1) fed by a frequency converter with a voltage intermediate circuit without position sensors and without closed-loop speed control, characterized in that The system is designed to carry out the method according to any one of claims 1 to 15 .

17. The system according to claim 16, characterized in that The system comprises: A vector current control device (5) comprising at least one first current regulator (11) for setting a first current component (id) of a stator current, wherein the first current regulator is designed to set a first current component (id) of a stator current according to a predetermined, increasing speed profile (n start ) is a reference current space vector (I) which is rotated by the first current regulator (11), the reference current space vector having a setpoint value (id ref ) and an angular position defined in a coordinate system (d, q) rotated about a reference system (α, β) fixed in position with respect to the stator (2) the reference current space vector (I) a current angle regulator (13) which is designed to determine a rotational speed correction value (n+); and An adder (14) is designed to add a rotational speed correction value (n+) to the rotational speed profile.

18. The system according to claim 17, characterized in that The current angle regulator (13) is designed to adjust the intermediate circuit voltage (U dc ) and the reference value (U dcmax ) is compared, and when the intermediate circuit voltage (U dc ) exceeds the reference value (U dcmax ), set the speed correction value (n+) to a value greater than zero.

19. The system according to claim 17 or 18, characterized in that The current angle regulator (13) has the function of a PID regulator.

20. The system according to any one of claims 17 to 19, characterized in that The vector current control device (5) comprises a changeover switch (8) which is designed to switch between a first set (Set1) of controller parameters (Ki1, Kp1) and a second set (Set2) of controller parameters (Ki2, Kp2) for the first current regulator (11).

21. The system according to any one of claims 17 to 20, characterized in that The vector current control device (5) comprises a second current regulator (12) which is designed to set a second current component (iq) of the reference current space vector (I).

22. A computer program product comprising instructions, characterized in that When the instructions are executed by a processor, the method according to any one of claims 1 to 15 is implemented.

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