JP3394161B2 - Motor control device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor control device having a PWM type three-phase inverter and performing feedback control by detecting at least two-phase motor current. 2. Description of the Related Art In a conventional motor control device as shown in FIG. 5, which includes a PWM three-phase inverter and detects at least two-phase motor current to perform feedback control, feedback control of the motor current is performed. Since the same feedback gain G is used for both phases for the detected motor current when performing the above, each of the detected current values includes an error due to a variation in elements used in the current detection circuit. For example, even if motor currents of the same magnitude actually flow in these two phases,
In some cases, different current values are detected due to the influence of the error described above. Such an error in the detected current value between the two phases results in an imbalance in the three-phase relationship. An example of a technique for solving this problem is disclosed in Japanese Patent Application Laid-Open No. 7-5206. However, an additional circuit such as a means for generating a three-phase reference signal and a switch means for switching an inverter output is required. And in terms of cost,
Also, it has a large disadvantage in space and is not generally used. As described above, in the conventional motor control device, a three-phase imbalance occurs due to an error in two-phase current detection values caused by variations in current detection circuit elements. Therefore, the feedback control of the motor current cannot be performed accurately. Therefore, if feedback control is performed on the detected motor current using the same feedback gain G for both phases without considering the variation of the elements used in the current detection resistor and the current detection circuit, the current detection value Problems arise when accuracy is required. The present invention has been made to solve the above problems, and has a PWM three-phase inverter.
In a motor control device that performs feedback control by detecting at least two-phase motor current, a motor control device is used for each of the two-phase current detection circuits instead of adding a means for generating a three-phase reference signal and a switch for switching an inverter output. The feedback gain is calibrated in consideration of the variation of the current elements, and the new feedback gain is set independently for each phase. It aims to eliminate imbalances in relationships. SUMMARY OF THE INVENTION The present invention relates to a motor control device having a PWM three-phase inverter and detecting at least two-phase motor current and performing feedback control. The objective is to generate a current command value for giving a motor current having the same magnitude of amplitude and diametrically opposite polarities to the two phases, a current command value generating unit, and the current command and an output from the feedback process based on the current command. A current control unit that controls the currents of the two phases and controls the current of the remaining one phase to be 0; a current detection circuit that detects a value of the motor currents of the two phases;
An average value calculation unit that calculates the respective average values of the current detection value of One phase, is provided and a gain ratio calculator for calculating a gain ratio of said current detecting circuit from said average value, said current finger
The same large magnitude is applied to the two phases by the threshold value generation unit and the current control unit.
The motor current with the opposite polarity to the amplitude of the
This is achieved by controlling the current of one phase to be 0, and independently setting the feedback gains of the two phases based on the gain ratio. According to the motor control device of the present invention, it is possible to eliminate an error in the current detection value caused by the variation of the elements used in the current detection circuits of the two phases. No longer occurs. Therefore,
Feedback control of the motor current can be performed more accurately. FIG. 1 is a block diagram showing an embodiment of a motor control device according to the present invention. U phase, V phase, W
The motor current of each phase is output from the PWM three-phase inverter 1 to the motor 3 under the control of the current control unit 4 based on the output of a feedback process described later and the current command from the current command value generation unit 5. Further, in this example, U-phase and V-phase motor currents among the three phases output to the motor 3 are detected, and current detection resistors 2a and 2b are provided on the U-phase and V-phase power transmission paths. ing. Hereinafter, the main components of the present invention will be described with reference to the flowchart of FIG. 2 showing an example of feedback gain calibration performed in the feedback processing in the motor control device of FIG. First, U
A current command value generator 5 generates a current command for providing a motor current having the same magnitude and the opposite polarity to the phase and the V phase. The current control unit 4 appropriately controls the U-phase and V-phase currents based on the command and the output from the feedback processing, and controls the remaining W-phase so that the current is 0 (step S1). . The current waveforms of the respective phases when the current values are controlled as described above are as shown in FIG. 3, and at this time, the currents between the PWM three-phase inverter 1 and the motor 3 are all U-phase and V-phase. Flows through the circuit formed by That is, as shown in FIG. 4, all the current flowing out of the U-phase flows into the V-phase, so that no current flows in the W-phase power transmission path. The current detection circuits 6a and 6b are connected to the U-phase
Current detection resistors 2a and 2b provided on the phase power transmission path
, The value of the motor current of each phase is detected from the potential difference generated in the above, and the value obtained here is used as the current detection value of each phase to calculate the multiplication operation unit 8
And outputs it to the feedback gain calculator 9. The feedback gain calculator 9 includes average value calculators 10a and 10b, a gain ratio calculator 11, and feedback gain holding units 12a and 12b. In the average value calculation units 10a and 10b, the average values I1 and I2 of the U-phase and V-phase current detection values are obtained (Step S).
2), is sent to the gain ratio calculation unit 11. The gain ratio calculator 11 calculates the gain ratio K of the current detection circuits 6a and 6b based on K = I1 / (− I2) (Step S).
3) The feedback gain holding unit 1 sets a predetermined feedback gain G as a U-phase feedback gain G1.
2a, and the V-phase feedback gain G2 obtained according to G2 = G × K is set in the feedback gain holding unit 12b (step S2).
4). The multiplication operation unit 8 reads the U-phase and V-phase current detection values sent from the current detection circuits 6a and 6b from the feedback gain holding units 12a and 12b of the feedback gain calculation unit 9. The feedback gains G1 and G2 are multiplied, and the result is sent to the addition operation unit 7. The addition operation unit 7 includes a current command value generation unit 5
From the current command value and the respective feedback gains after the multiplication are sent to the current control unit 4. In this manner, the predetermined feedback gain G is calibrated in consideration of the variation of the elements used in the U-phase and V-phase current detection circuits, and becomes a new feedback gain G1 and G2 for each phase. It is set independently for each. As described above, according to the motor control device of the present invention, the two-phase motor current detected when performing the feedback control takes into account the dispersion of the respective current detection circuit elements. Since the feedback gain after calibration can be set independently for each phase, the imbalance of the three-phase relationship does not occur, and the feedback control of the motor current can be performed more accurately.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing one embodiment of a motor control device of the present invention. FIG. 2 is a flowchart illustrating a processing example by a motor control device of the present invention. FIG. 3 is a diagram showing a waveform example of a current flowing through each phase in the embodiment of FIG. 1; FIG. 4 is an explanatory diagram showing a current flowing in each phase in the embodiment of FIG. FIG. 5 is a block diagram illustrating an example of a conventional motor control device. [Description of Signs] 1 PWM three-phase inverter 2a, 2b Current detection resistor 3 Motor 4 Current control unit 5 Current command value generation unit 6a, 6b Current detection circuit 7 Addition calculator 8 Multiplication calculator 9 Feedback gain calculation unit 10a 10b Average value calculation unit 11 Gain ratio calculation units 12a, 12b, 13 Feedback gain holding units G, G1, G2 Feedback gain

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H02P 5/408-5/412 H02P 7/628-7/632 H02P 21/00

Claims (1)

(57) [Claim 1] In a motor control device having a PWM type three-phase inverter and detecting at least two-phase motor current and performing feedback control, an amplitude of the same magnitude is applied to two phases. A current command value generating section for generating a current command for giving a motor current having a polarity opposite to that of the current command value, based on the current command and the output from the feedback processing.
The current of one phase is controlled and the current of one
A current control unit that controls the current values of the two phases, a current detection circuit that detects a value of the motor current of the two phases, an average value calculation unit that calculates an average value of the current detection values of the two phases, A gain ratio calculation unit that calculates a gain ratio of the current detection circuit from the average value, wherein the current command value generation unit
And the same magnitude of amplitude in the two phases by the current controller
And the motor current with the opposite polarity
A motor control device that controls the currents of the two phases to be 0 and independently sets the two-phase feedback gains based on the gain ratio.