Control device of synchronous motor

Abstract

To provide a control device for realizing torque-free control in which runaway is avoided when a synchronous motor is stopped.SOLUTION: A control device 1 of a synchronous motor, includes current conversion means 11, current feedback control calculation means 12, and voltage command value conversion means 13, and outputs an output from an inverter to a synchronous motor 2 based on a three-phase voltage command value. The control device has current command intermediate value calculation means 14 for calculating a d-axis current command intermediate value from a motor speed, and current command value calculation means 15 for calculating a d-axis current command value and a q-axis current command value from the d-axis current command intermediate value. When the synchronous motor 2 is stopped, the d-axis current command value and the q-axis current command value obtained by the current command value calculation means 15 are input to the current feedback control calculation means 12, and the output torque of the synchronous motor 2 is made zero to stop the operation of the synchronous motor 2.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a control device for a synchronous motor that operates by vector control, and in particular to a control device that realizes torque-free control to prevent the motor from running out of control when the motor is stopped in a torque-free state (output torque is set to zero) by fail-safe operation upon detection of a fault or by a command from a higher-level controller while the synchronous motor is being driven or generating electricity. [Background technology]

[0002] A synchronous motor is an electric motor that rotates in synchronization with an input AC voltage. The rotor is attracted to the rotating magnetic field formed by the input AC current, and rotates by following the magnetic field. Generally, a synchronous motor is driven and controlled by a control system using a control device connected to it.

[0003] An example of a conventional motor control system is shown in Figure 4. In this system, the three-phase current (i U ,i V ,i W ) is expressed as the d-axis current (i d ),q-axis current(i q )

[0004] This d-axis current (i d ),q-axis current(i q ) are the d-axis current command values ​​(i dref ),q-axis current command value (i qref ) is obtained by using current feedback control to obtain the d-axis voltage command value (v dref ), d-axis voltage command value (v qref ) is calculated. This voltage is used as the motor's three-phase voltage command value (v Uref ,v Vref ,v Wref ) and output to the motor.

[0005] Here, to realize torque-free control, the q-axis current command value (i dref) to zero, as disclosed in, for example, Japanese Patent Laid-Open Publication No. 2014-233109 (Patent Document 1).

[0006] On the other hand, the d-axis current command value (i dref ) requires a negative current corresponding to the rotation speed to flow even under torque-free control in order to prevent the control device from being damaged by the induced voltage of the motor.

[0007] The problems with conventional motor control systems will be explained using Figure 5. Normally, the d-axis current (i d ),q-axis current(i q ) flows, but if this motor position is shifted by Δθ from the actual motor magnetic axis, the q-axis current command value (i dref ) is zero, the q-axis current (i qreal ) current flows through it.

[0008] As a result, if torque in the accelerating direction is output, the motor rotation speed will increase further. Furthermore, if the d-axis current increases as the rotation speed increases, the output torque will also increase, leading to runaway. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-233109 Summary of the Invention [Problem to be solved by the invention]

[0010] An object of the present invention is to provide a control device for realizing torque-free control that prevents runaway when a synchronous motor is stopped. [Means for solving the problem]

[0011] The present invention, which has been made to solve the above problems, provides a synchronous motor having a rotor using a permanent magnet, an inverter that drives the synchronous motor, current conversion means that converts three-phase currents of the synchronous motor into d-axis currents and q-axis currents, current feedback control calculation means that calculates d-axis voltage command values ​​and q-axis voltage command values ​​from the d-axis currents and q-axis currents using current feedback control, and voltage command value conversion means that converts the d-axis voltage command value and q-axis voltage command value into three-phase voltage command values, a control device for a synchronous motor that outputs from the inverter to the synchronous motor based on the three-phase voltage command value, a current command intermediate value calculation means for calculating a d-axis current command intermediate value from a motor speed, and a current command value calculation means for calculating a d-axis current command value and a q-axis current command value from the d-axis current command intermediate value, When stopping the synchronous motor, the d-axis current command value and the q-axis current command value obtained by the current command value calculation means are input to the current feedback control calculation means, thereby making the output torque of the synchronous motor zero and stopping the operation of the synchronous motor.

[0012] In the present invention, the current command value calculation means a d-axis current command value calculation step of comparing the d-axis current command intermediate value with a previous d-axis current command value to determine a d-axis current command value; and a q-axis current command value calculation step of multiplying the d-axis current command value by a predetermined coefficient to obtain a q-axis current command value, When the d-axis current command value calculation step calculates the d-axis current command value according to the following conditions A and B, there is an advantage that the absolute value of the d-axis current command value does not increase during torque-free control. Condition A: If the d-axis current command intermediate value is equal to or greater than the previous d-axis current command value, the previous d-axis current command value is set as the d-axis current command value. Condition B: If the condition A is not satisfied, the d-axis current command intermediate value is set as the d-axis current command value.

[0013] In the present invention, the predetermined coefficient is a positive value smaller than 1, and if the rotor is rotating forward, a positive sign is assigned to the predetermined coefficient, and if the rotor is rotating backward, a negative sign is assigned to the predetermined coefficient. This makes it easier to output torque in the deceleration direction even if the motor position is misaligned, thereby preventing runaway. [Effects of the Invention]

[0014] According to the present invention, torque-free control can be achieved that prevents runaway when the synchronous motor is stopped. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a functional block diagram showing an outline of a control system in a synchronous motor control device according to the present invention; [Figure 2] FIG. 3 is an explanatory diagram showing current vectors of a d-axis current and a q-axis current in the present invention. [Figure 3] 4 is a flowchart showing the processing performed by a current command value calculation means in the present invention. [Figure 4] FIG. 1 is a functional block diagram showing an outline of a control system in a conventional synchronous motor control device. [Figure 5] FIG. 10 is an explanatory diagram showing current vectors of a d-axis current and a q-axis current in a conventional control system. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0017] In the following description, "torque-free control" refers to control that makes the output torque of a synchronous motor zero, and "torque-free state" refers to a state in which the output torque of a synchronous motor is zero.

[0018] FIG. 1 is a block diagram showing the configuration of a synchronous motor control device according to the present invention. The synchronous motor control device includes a control device 1 that controls the drive of a synchronous motor 2, and a three-phase current (i U ,i V ,i W ) or by expressing it as an axis synchronized with the estimated motor position, the current conversion means 11 converts the d-axis current (i d ),q-axis current(i q )

[0019] The d-axis current (i d ), q-axis current (i q ) is the input d-axis current command value (i dref ), q-axis current command value (i qref ) by the current feedback control calculation means 12. dref ), q-axis voltage command value (V qref ) is calculated.

[0020] This voltage is converted into a three-phase voltage command value (V Uref ,V Vref ,V Wref ), and controls the on / off of the switching elements of the inverter to output a three-phase voltage command value to the synchronous motor 2. The control device 1 can be, for example, a computer such as an in-vehicle ECU.

[0021] In this embodiment, when the synchronous motor 2 is driven or generating power, and the torque-free control is performed in response to a fail-safe operation at the time of fault detection or a command from a higher-level controller to stop the synchronous motor, the d-axis current command value (i dref ) and q-axis current command value (i qref ) is characterized by having a current command intermediate value calculation means 14 and a current command value calculation means 15.

[0022] Specifically, in this embodiment, the current command intermediate value calculation means 14 calculates the d-axis current command calculation result in the conventional example as a q-axis current command intermediate value (i qref1 ), and then the current command value calculation means 15 calculates the d-axis current command value (i dref ) and q-axis current command value (i qref ) is calculated.

[0023] FIG. 2 is an explanatory diagram showing current vectors of the d-axis current and the q-axis current in the present invention.

[0024] In the torque-free control of the conventional example, the q-axis current command is set to zero, but in the present invention, the d-axis current (i d ) is calculated based on

[0025] Actual q-axis current value in the acceleration direction (i qreal ) occurs (becomes a value greater than zero), the system will go out of control. To avoid this, qref ) is negative if rotating forward and positive if rotating backward.

[0026] The q-axis current command value (i qref ) is the d-axis current (i d ) multiplied by a coefficient (K).

[0027] Here, the d-axis current command value (i dref ) is always a negative value, the coefficient (K) is set to a small positive value of about 0.1, and the sign assigned to the coefficient (K) is adjusted to be positive or negative so that a large current does not flow.

[0028] This makes it easier to output torque in the deceleration direction even if the motor position is misaligned, preventing runaway.

[0029] Furthermore, if the rotation speed increases even though torque-free control is in progress, the d-axis current command value is normally increased, but if the d-axis current command value is larger than the previous value, the previous value is output as is.

[0030] 3 is a flowchart showing the processing performed by the current command value calculation means of the present invention. The current command value calculation means has a d-axis current command value calculation step of comparing the d-axis current command intermediate value with the previous d-axis current command value to determine the d-axis current command value, and a q-axis current command value calculation step of multiplying the d-axis current command value by a predetermined coefficient to obtain the q-axis current command value.

[0031] The d-axis current command value calculation step calculates the d-axis current command value under the following conditions A and B. Condition A: If the d-axis current command intermediate value is equal to or greater than the previous d-axis current command value, the previous d-axis current command value is set as the d-axis current command value. Condition B: If the condition A is not satisfied, the d-axis current command intermediate value is set as the d-axis current command value. This process prevents the absolute value of the d-axis current command value from increasing during torque-free control.

[0032] Then, the q-axis current command value is calculated by multiplying the d-axis current and the rotation direction of the motor by a predetermined coefficient. The predetermined coefficient is a positive value smaller than 1, and in this embodiment is set to about 0.1.

[0033] When the rotor is rotating in the forward direction, a positive sign is assigned to the predetermined coefficient, and when the rotor is rotating in the reverse direction, a negative sign is assigned to the predetermined coefficient.

[0034] This makes it possible to prevent the motor from running out of control in a torque-free state even if the motor position is misaligned. [Explanation of symbols]

[0035] 1 control device, 2 synchronous motor, 11 current conversion means, 12 current feedback control calculation means, 13 voltage command value conversion means, 14 current command intermediate value calculation means, 15 current command value calculation means

Claims

1. a synchronous motor having a rotor using a permanent magnet; an inverter that drives the synchronous motor; a current conversion means for converting the three-phase current of the synchronous motor into a d-axis current and a q-axis current; a current feedback control calculation means for calculating a d-axis voltage command value and a q-axis voltage command value from the d-axis current and the q-axis current using current feedback control; a voltage command value conversion means for converting the d-axis voltage command value and the q-axis voltage command value into three-phase voltage command values, a control device for a synchronous motor that outputs from the inverter to the synchronous motor based on the three-phase voltage command value, a current command intermediate value calculation means for calculating a d-axis current command intermediate value from the motor speed; a current command value calculation means for calculating a d-axis current command value and a q-axis current command value from the d-axis current command intermediate value, When stopping the synchronous motor, The d-axis current command value and the q-axis current command value obtained by the current command value calculation means are input to the current feedback control calculation means, reducing the output torque of the synchronous motor to zero to stop the operation of the synchronous motor; A synchronous motor control device characterized by:

2. The current command value calculation means a d-axis current command value calculation step of comparing the d-axis current command intermediate value with a previous d-axis current command value to determine a d-axis current command value; a q-axis current command value calculation step of multiplying the d-axis current command value by a predetermined coefficient to obtain a q-axis current command value, the d-axis current command value calculation step calculates the d-axis current command value under the following conditions A and B: Condition A: If the d-axis current command intermediate value is equal to or greater than the previous d-axis current command value, the previous d-axis current command value is set as the d-axis current command value. Condition B: If the condition A is not satisfied, the d-axis current command intermediate value is set as the d-axis current command value.

2. The synchronous motor control device according to claim 1.

3. The predetermined coefficient is a positive value less than 1, If the rotor is rotating in the forward direction, a positive sign is assigned to the predetermined coefficient; If the rotor is rotating in the reverse direction, a negative sign is assigned to the predetermined coefficient.

3. The synchronous motor control device according to claim 2.

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