JP2001327186A - Current detecting device for three-phase synchronous motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a current detecting device capable of accurately detecting phase currents of a three-phase synchronous motor. SOLUTION: The current detecting device detects the phase currents of the three-phase synchronous motor, corrects and outputs a gain. The detecting device comprises (a) a current detector for detecting the phase current flowing to an armature winding for an arbitrary one phase of the motor, (b) a pulse voltage applying unit for applying a pulse voltage between the phase for detecting the phase current and the other arbitrary one phase, (c) a positioning controller for outputting a positioning pulse to the applying unit to stop the rotor in the motor at a predetermined electric angel, and (d) a gain correcting unit for calculating a gain from a current value detected via the current detector by outputting a gain measuring pulse to the applying unit in a state in which the rotor is stopped and an inductance value of the winding and correcting the gain of the phase current when the motor is rotated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a current detecting device for detecting a phase current of a three-phase synchronous motor, and more particularly to a current detecting device for accurately correcting a gain of a detected phase current and outputting the corrected current.

[0002]

2. Description of the Related Art In general, in order to control an inverter of a three-phase synchronous motor, an electrical angle position of a rotor is detected by a phase current flowing through an armature. Conventionally, a Hall element type current sensor has been mainly used for a current detection device for detecting a phase current, and a current detected by the sensor is output after performing offset correction and gain correction. However, when a current detection device is configured using sensors such as a Hall element type current sensor, an offset tolerance due to a variation in an offset current value of a current detection system, and a correlation (= gain) between a measured current value and an output current value. The gain tolerance is large due to the variation in the temperature, and the temperature of the electronic components in the detecting device changes according to the temperature, thereby causing a temperature drift in which the output fluctuates.

In order to suppress such a problem and improve the current detection accuracy, Japanese Patent Application Laid-Open No. Hei 5-297033 discloses
There has been proposed a current detector in which a current detection circuit for a phase current is constituted by a digital circuit instead of an analog circuit, and the offset amount and the gain are automatically corrected when rotation is stopped.

In a current detector proposed in Japanese Patent Application Laid-Open No. Hei 5-297033, an offset amount is measured when the motor stops rotating, and the current when the motor starts next is theoretically estimated and detected. The gain is calculated by comparing with the current value. Thereby, the offset correction and the gain correction corresponding to the temperature change are performed, and the temperature drift is suppressed.

[0005]

However, in the above-described conventional current detector, the gain is calculated assuming that the armature inductance L is a constant value regardless of the rotor electrical angle of the three-phase synchronous motor. Therefore, there is a problem that it is difficult to accurately detect current when the inductance L of the armature changes according to the electrical angle of the rotor. For example, when the rotor is a salient pole type three-phase synchronous motor having a salient pole structure, the inductance L of the armature greatly varies depending on the electrical angle of the rotor, and the gain calculated based on the rotor stop position at that time greatly varies. Cannot perform accurate gain correction. In addition, non salient pole type 3
Also in the case of the phase synchronous motor, it is difficult to realize high current detection accuracy because the inductance L of the armature slightly changes depending on the rotor position.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems. In any three-phase synchronous motor, the detection current can be accurately gain-corrected by a simple system configuration at a low cost. An object of the present invention is to provide a highly reliable current detector.

[0007]

In order to achieve the above object, a current detecting device according to the present invention detects a phase current of a three-phase synchronous motor, corrects the gain, and outputs the corrected current. A) a current detector for detecting a phase current flowing through an armature winding for any one phase of the three-phase synchronous motor;
(B) a pulse voltage applying unit that applies a pulse voltage between the phase for detecting the phase current and another arbitrary phase; and (c) causing the pulse voltage applying unit to output a positioning pulse.
A positioning control unit for stopping a rotor in the three-phase synchronous motor at a predetermined electrical angle; and (d) outputting a gain measuring pulse to the pulse voltage applying unit in a state where the rotor is stopped. Current value detected through the section,
A gain correction unit that calculates a gain from an estimated current value derived based on the inductance value of the armature winding and performs a gain correction of a phase current during rotation of the three-phase synchronous motor based on the gain; It is characterized by having.

According to the current detection device of the present invention, the rotor is fixed at a predetermined electrical angle position and the gain is measured, so that the influence of inductance fluctuation due to the rotor position is eliminated and accurate current measurement is performed. Can be.

While the pulse voltage applying section outputs the positioning pulse and the gain measuring pulse, the phase to which no voltage is applied is preferably set to the open potential.

Further, the estimated current value includes an inductance value of the armature winding, a winding resistance value of the armature winding, a peak value of the gain measuring pulse, and a pulse application of the gain measuring pulse. From the time, it can be calculated based on the three-phase voltage-current equation.

Further, the current detection device according to the present invention may further include an offset correction section for performing offset correction of the current value detected via the current detection section and outputting the current value to the gain correction section. The offset correction unit may output the voltage of 0 V to the pulse voltage application unit and use the current value detected via the current detection unit as an offset value.

It is preferable that the positioning control section causes the pulse voltage applying section to output a positioning pulse for a predetermined period and then output 0 V for a predetermined period.
Thus, even if the rotor has a pendulum phenomenon after the application of the positioning pulse, the rotor can be stopped using the brake current of the three-phase synchronous motor.

Further, while the pulse voltage applying unit outputs 0 V, by setting the phase to which no voltage is applied to the ground potential, the brake current can be further increased and the rotor can be stopped more reliably.

Further, the present invention is also an air conditioning system comprising the current detecting device according to the present invention, and a refrigerating device connected to the current detecting device for compressing a refrigerant in a refrigeration cycle system.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram illustrating an example of a current detection device according to the present invention. The current detection device according to the present embodiment includes a pulse voltage application unit 2 that supplies a pulse voltage between arbitrary two phases of the three-phase synchronous motor 5, and a positioning command that sends a positioning command to the pulse voltage application unit 2 to rotate the rotor in the three-phase synchronous motor 5. A position control unit 1 that performs control to stop the motor at a predetermined electrical angle, a current detection unit 4 that detects a phase current flowing through the armature winding for one phase to which a pulse voltage is applied,
It comprises a current correction unit 3 for correcting the current detected by the current detection unit 4. The current correction unit 3 further includes:
An offset correction unit 10 that performs offset correction of the current detected by the current detection unit 4 and a gain correction unit 11 that further performs gain correction on the offset-corrected current.

The current detection device according to the present invention detects the phase current detected via the current detection unit 4 while the three-phase synchronous motor 5 is rotating normally, similarly to a general current detection device. After the offset correction and the gain correction are performed by the current correction unit 3, the current is output as a correction current. Then, at the start of operation of the three-phase synchronous motor 5 or during the rotation stop period during operation,
The correction parameters used for the offset correction and the gain correction are updated.

When the correction parameters are updated, the positioning control unit 1 outputs a positioning command to the pulse voltage application unit 2 to fix the rotor at a predetermined electrical angle, and the current correction unit 3 outputs a gain measurement pulse application command. Is output to the pulse voltage application unit 2 to measure and store an offset value and a gain, which are correction parameters. By fixing the rotor at a predetermined electrical angle position, it is possible to eliminate the influence of the armature winding inductance value variation due to the electrical angle position of the rotor and to accurately update the correction parameter.

FIG. 2 is an operation flow chart of the current detection device, showing the operation of updating the correction parameters performed during the start of operation of the three-phase synchronous motor 5 or during the rotation stop period during operation.
In the first half of the flow, the operation of fixing the rotor in the three-phase synchronous motor 5 at a predetermined electrical angle position is performed under the control of the positioning control unit 1 (steps 1 and 2), and in the second half of the flow, the voltage correction unit By the control of 3, the operation of measuring and storing the correction parameter is performed (steps S3 to S8). In the present embodiment,
For convenience of explanation, a case where the U-phase current of the three-phase synchronous motor 5 is detected by the current detection unit 4 will be described.

First, the positioning operation in the first half of the flow will be described. In step S <b> 1, based on a command from the positioning control unit 1, the pulse voltage applying unit 2 outputs a positioning pulse V <b> ₁ between the U-V terminals of the three-phase synchronous motor 5. Pulse voltage application unit 2 outputs a positioning pulse V ₁ on the basis of the following control conditions. Control conditions: V _u = V _pp , V _v = 0, W-phase open (V _u : U-phase terminal potential, V _v : V-phase terminal potential)

That is, as schematically shown in FIG.
The potential V _u phase terminal 22 to the peak value V _pp of pulses V _1, the potential V _v of the V-phase terminal 23 is fixed to 0V, W-phase terminal 24 is opened. The phase current I _u flowing in the U-phase and the phase current I _v flowing in the V-phase are equal in magnitude with the opposite signs, and the phase current I _w flowing in the W-phase is zero. When the rotor in the electric motor 5 is deviated from the electrical angle position determined by the magnetic field generated at this time, the rotor receives rotational torque and rotates to a predetermined electrical angle position. When the rotor is stopped, each U, V, W
The field of phase磁誘electromotive voltage E _u, E _v, E _w is zero.

[0021] FIG. 5 is a schematic diagram showing a waveform of a positioning pulse V _1. The peak value of the pulse V ₁ is V _pp , the pulse width is ΔT ₁ , and the pulse interval is ΔT _OFF . The pulse V ₁ is
It is applied during the time 0 to T _1. Pulse application time T ₁
Is a time sufficient for the rotor to rotate to a predetermined electrical angle position and stop according to the type and use state of the three-phase synchronous motor 5. Further, the duty ratio of the pulse width ΔT ₁ and the pulse interval width ΔT _OFF is set such that a sufficient rotation torque for rotating the rotor can be obtained in a range in which an overcurrent does not flow through the motor 5. The magnitude of V _pp is not particularly limited. For example, when a pulse voltage is formed from a 200 V commercial power supply through a voltage doubler rectifier circuit, the magnitude of V _pp is 2 V.
80V.

Next, in step S2, the pulse voltage application unit 2, after the output finish positioning pulses V _1, and outputs a 0V between the 3-phase synchronous motor 5 U phase terminal -V phase terminal. Application of 0V is performed during the time T ₁ through T _2. In this way, by fixing the U-phase terminal and the V-phase terminal to 0 V, the regenerative current (brake current) of the electric motor 5 can be used even if the rotor in the electric motor 5 has a pendulum phenomenon. Thus, the rotor can be completely stopped. Time T ₂ are the phase current detected by the current detector 4 is set sufficient time to zero. At this time, the W-phase terminal may be fixed to 0 V in order to further increase the brake current and to speed up the stop of the rotor.

FIG. 7 is a schematic diagram showing the positional relationship between the armature winding UVW and the rotor. As shown in FIG. 7A, the rotor electrical angle θ is an angle formed between the d-axis and the U-phase armature winding 37. The d-axis is an axis passing through the center of the rotor 35 and the centers of the N and S poles and passing through the centers of the U-phase winding 37, the V-phase winding 38, and the W-phase winding 39. In FIG. 7, N of the rotor 35 represents the N pole of the magnet, and S represents the S pole of the magnet.

FIGS. 7B and 7C show the rotor position after the completion of the positioning operation. 7B, the rotor electrical angle θ is −30 °, and in FIG. 7C, the rotor electrical angle θ is 150 °. After the completion of the positioning operation, the rotor is stationary in one of these two positions.
If the rotor tries to stop at any other point,
Negative feedback torque that converges to the position shown in FIG. 7B or 7C is generated. Therefore, in steps S1 and S2, if the pulse voltage V ₁ , time T ₁ , T _{2, and the} like are appropriately set according to the characteristics of the three-phase synchronous motor 5, the rotor can be stopped at any of the above points. .

FIG. 4 shows the relationship between the rotor electrical angle θ and the inductance L _uv between the U and V phases (= L _u −L _v , _Lu and L _v are the inductance values of the U and V phase armature windings). It is a graph shown. FIG. 4 shows a graph when the motor 5 is a reverse salient pole type three-phase synchronous motor. Inductance L
_uv periodically vary depending on θ the electrical angle position of the rotor, the minimum value of d-axis (= magnetic field axis) inductance L _d 2
Times, the maximum value is twice the q-axis inductance L _q. The position shown in FIG. 7B corresponds to point A in FIG. 4, and the position shown in FIG. 7C corresponds to point B in FIG.

As shown in FIG. 4, at point A or point B where the rotor is stationary, the inductance L _uv between the U and V phases has a minimum value of 2 · L _d . The motor 5 is a salient pole type 3
In the case of a phase synchronous motor, the minimum value of the inductance L _uv is 2 · L _q and the maximum value is 2 · L _d , but since the rotor is stationary at the position where the inductance is the maximum, the rotor at the stationary position of the rotor is L _uv is 2.
The L _d.

Next, the operation of measuring the correction parameters in the latter half of the flow will be described. In step S3, the current detection unit 4 detects a phase current flowing through the U-phase armature winding. At this time, since the rotor is stopped and no pulse voltage is applied, the phase current itself is zero, but the constant current I ₀ is detected by an internal offset inherent to the current detection system. The detected offset current I ₀ is
The offset value is stored in the offset correction unit 10.

Next, in step S4, based on a command from the gain correction unit 11, the pulse voltage application unit 2
The gain measurement pulse V ₂ is applied between the U-phase terminal -W phase terminal. Gain measurement pulse V ₂ is applied over the time T ₂ through T _3. Then, in step S5, the current detector 4 detects the phase current I _s of the armature winding of the U-phase at time T _3.

[0029] FIGS. 6 (a) and (b) is a schematic diagram showing a the detected U-phase current I _s and the waveform of the gain measurement pulse V _2. The peak value of the gain measurement pulse V ₂ is V _pp , and the pulse width is ΔT ₂ (= T ₃ −T ₂ ). U-phase current I _s to be detected is equal to the offset current I ₀ is at time T _2, increases in proportion to the pulse application time. Detection current _Is
To improve the measurement accuracy, the detected current I _s is the electric motor 5
It is preferable to set the pulse width ΔT ₂ to be long within a range not exceeding the rated current.

Next, in step S6, the offset correction unit 10 has the formula 1 a current I _s of the current detecting unit 4 detects
And the offset correction current _Is1 . I _s1 = I _s −I ₀ (Equation 1)

Next, in step S7, gain correction unit 11 calculates the estimated current I _s0 for comparison with the offset correction current I _s1. Estimated current I _s0 is a d-axis inductance value L _d of the armature winding of the U-phase of the motor 5, the winding resistance value R ₁ of the armature winding of the U-phase, a peak value V of the gain measurement pulse It can be calculated from _pp and the pulse application time ΔT ₂ of the gain measurement pulse based on Equation 2. Equation 2 is derived based on a three-phase voltage-current equation, and its derivation will be described in detail later.

(Equation 1)

[0032] and d-axis inductance value L _d of the U-phase armature winding to be used in calculating the theoretical current I _s0, winding resistance value R ₁ is measured in advance using a pre-dedicated instrument. As previously mentioned,
d-axis inductance value L _d can be easily determined by measuring the steady state U-V-phase inductance L _uv that shown in FIG. 7 (b) or (c).

Next, in step S8, gain correction unit 11, a gain correction coefficient G _i by calculation based on Equation 3, and stores. _{G i = I s0 / I s1} ( Equation 3)

By performing the above operation, the offset value and the gain can be accurately measured and updated without being affected by the inductance variation due to the rotor position in the electric motor 5. During normal operation of the motor 5, by using the updated offset value I ₀ and the gain G _i, a current I ₁ detected by the current detector 4, be output as a correction current I _1A corrected according to equation 4 it can. I _1A = G _i · (I ₁ −I ₀ ) (Equation 4)

Here, the derivation of Equation 2 from the three-phase voltage-current equation will be described. The three-phase voltage-current equation of the three-phase synchronous motor is expressed by the following equation (5).

(Equation 2)

[0036] In this three-phase voltage current _{equation, E u = E v = E} w = 0, I u = -I v = I s0, I w = 0, θ = -30 ° + (180 °) × n ( n = 0, ± 1, ±
2 ...) Then, the following differential equation 6 is obtained (P
Is the differential operator). _{L d · P (I s0)} + R 1 · I s0 = V pp / 2 ( Equation 6) Solving this equation for _{I s0 I s0 = V pp /} (2R 1) · (1-exp (-R 1 / L _d · t) (Equation 7). Here, if t = ΔT ₂ , Equation 2 is obtained.

In the present embodiment, the U-phase current of the three-phase synchronous motor 5 is detected by the current detector 4; however, the present invention is not limited to this. U
Instead of a phase, a V-phase or W-phase current may be detected. For example, when detecting the W-phase current, the pulse voltage application unit 2
By applying a pulse voltage between the W phase and the U phase or the V phase, the same operation as in the present embodiment can be performed.

In this embodiment, the U-V
Although a configuration has been described in which a pulse voltage is applied between phases to detect a phase current for one phase of the U phase, the present invention is not limited to this. For example, two phase currents of a U phase and a V phase may be detected. As described above, since the absolute value of the U-phase current is equal to the absolute value of the V-phase current, detecting the phase currents of the U-phase and the V-phase is substantially equivalent to detecting the phase currents at two points for the U-phase. Become. By detecting the U-phase current at two points, the detection accuracy can be further improved.

Further, the current detection device of the present invention can be applied to an electric compressor with a refrigerant compression operation of a refrigeration system / air conditioning system. In such a system, the load torque during the rotation of the compressor fluctuates every moment. According to the current detection device of the present invention, since the phase current of the three-phase synchronous motor, which changes in response to the change in the load torque, can be accurately detected, a stable refrigerant compression operation can be performed. Therefore, a highly reliable air conditioning system and refrigeration system suitable for mass production can be easily configured.

[0040]

According to the current detecting device of the present invention, in the current detecting device for a three-phase synchronous motor, the measured current value and the estimated current value of the phase current are measured while the rotor is stopped at a predetermined electrical angle position. Since the gain is calculated from the comparison, the phase current of the three-phase synchronous motor can be detected with high accuracy in any three-phase synchronous motor.

Further, in the current detection device of the present invention, since the estimated current value is derived from the three-phase voltage-current equation of the three-phase synchronous motor, current correction can be easily performed for all three-phase synchronous motors. This can be performed by calculation.

Further, the current detection device of the present invention includes an offset correction unit for offset-correcting the current value detected via the current detection unit and outputting the current value to the gain correction unit. Thus, it is possible to correct the gain deviation of the current detecting means.

Further, by providing a predetermined length of 0 V application period after outputting the positioning pulse for stopping the rotor, the rotor may have a pendulum phenomenon after the application of the positioning pulse. Also, the rotor can be stopped using the brake current of the three-phase synchronous motor. As a result, the rotor can be securely fixed at a predetermined position, so that an operation inductance value having almost no error can be set as compared with an actual inductance value.
A highly accurate current correction operation can be performed.

Further, by setting the phase to which no voltage is applied to the ground potential during the 0 V application period, the brake current can be further increased and the rotor can be stopped more reliably. Therefore, it is possible to perform the phase current detection with higher accuracy while minimizing the displacement.

Further, by constituting an air conditioner from the current detecting device of the present invention and a refrigerating device connected to the current detecting device and performing refrigerant compression of a refrigeration cycle system,
A stable and reliable refrigerant compression operation can be performed, and an air conditioning system suitable for mass production can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a current detection device according to the present invention.

FIG. 2 is an operation flowchart showing a measurement operation of a correction parameter in the current detection device according to the present invention.

FIG. 3 is a schematic diagram showing an electrical equivalent circuit of a three-phase synchronous motor.

FIG. 4 is a schematic diagram showing the rotor electrical angle θ dependence of the U-V phase inductance L _uv .

Figure 5 is a schematic diagram showing a voltage waveform of a positioning pulse V _1.

[6] FIG. 6 (a) and (b) is a schematic diagram showing the waveforms and voltage waveforms of the gain measurement pulse V ₂ of the detection current I _s.

FIG. 7 is a schematic diagram showing a positional relationship between an armature winding UVW and a rotor position.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 positioning control unit 2 pulse voltage unit 3 current correction unit 4 current detection unit 5 three-phase synchronous motor 10 offset correction unit 11 gain correction unit 22 U-phase terminal 23 V-phase terminal 24 W-phase terminal 35 rotor 37 U-phase winding 38 V Phase winding 39 W phase winding

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H02P 7/63 303

Claims (8)

[Claims] 1. A current detecting device which detects a phase current of a three-phase synchronous motor, corrects a gain, and outputs the corrected phase current, and detects a phase current flowing through an armature winding for an arbitrary phase of the three-phase synchronous motor. A current detection unit that performs a pulse voltage application between a phase that detects the phase current and another arbitrary phase; and a pulse that outputs a positioning pulse to the pulse voltage application unit. A positioning control unit that stops the rotor in the phase synchronous motor at a predetermined electrical angle; and, while the rotor is stopped, a pulse for applying a gain measurement to the pulse voltage application unit and detection via the current detection unit. A gain is calculated from the calculated current value and an estimated current value derived based on the inductance value of the armature winding, and based on the gain, a gain correction of a phase current during rotation of the three-phase synchronous motor is performed. Current detecting device is characterized in that a Cormorant gain correction unit. 2. The current detection device according to claim 1, wherein the pulse voltage application unit sets a phase to which no voltage is applied to an open potential while outputting the positioning pulse and the gain measurement pulse. 3. The method according to claim 1, wherein the gain correction unit includes: an inductance value of the armature winding; a winding resistance value of the armature winding;
The current detection according to claim 1, wherein the estimated current value is derived from a peak value of the gain measurement pulse and a pulse application time of the gain measurement pulse based on a three-phase voltage-current equation. apparatus. 4. The current detection device according to claim 1, further comprising: an offset correction unit that offset-corrects a current value detected via the current detection unit and outputs the current value to the gain correction unit. 5. The current detection device according to claim 4, wherein the offset correction unit outputs 0 V to the pulse voltage application unit and sets a current value detected via the current detection unit as an offset value. apparatus. 6. The current detection device according to claim 1, wherein the positioning control unit causes the pulse voltage application unit to output a positioning pulse for a predetermined period and then output 0 V for a predetermined period. . 7. The current detection device according to claim 6, wherein a phase to which no voltage is applied is set to a ground potential while the pulse voltage application unit outputs 0V. 8. A refrigeration apparatus comprising: the current detection device according to claim 1; and a refrigeration device connected to the current detection device to perform refrigerant compression of a refrigeration cycle system. Air conditioning system.