JP7237746B2 - Open winding motor drive device and refrigeration cycle device - Google Patents

Description

Embodiments of the present invention relate to a device for driving a motor with an open winding structure and a refrigeration cycle apparatus including the device.

As a technique for improving the efficiency of a system that drives a motor with an open winding structure, a technique for improving efficiency by suppressing the zero-phase current flowing between two inverters that drive the motor is known. .

Japanese Patent No. 3352182

A motor that generates a high induced voltage, such as an open winding structure, can generate the same torque with less current, so current consumption can be reduced and efficiency can be improved. On the other hand, in the DC-link-sharing type motor, zero-phase currents are generated that flow in the same direction in the three phases of the motor.

Further, the frequency of the zero-phase current is three times that of each of the U, V, and W phase currents to drive the motor, and the detection delay of the zero-phase current increases in the high rotation region. Therefore, in order to suppress the zero-phase current, it is necessary to shorten the cycle of controlling the motor, which causes the problem of heat generation of the elements due to the increase in the switching frequency, and increases the cost of the control operation device such as the microcomputer. leads to

Therefore, an open-winding motor drive device capable of suppressing the zero-phase current even in a high-speed region without shortening the motor control cycle, and a refrigeration cycle apparatus including the device are provided.

In the open-winding motor drive device of the embodiment, each of the three-phase windings is independent and connected to three of the six winding terminals of an open-winding structure having six winding terminals. a primary inverter;
a secondary inverter connected to the remaining three winding terminals of the motor;
a converter that converts the voltage of an AC power source into a DC power source and supplies the DC power source to the primary side inverter and the secondary side inverter;
a phase current detection unit that detects each phase current flowing in the motor;
a zero-phase current detection unit that detects a zero-phase current flowing between the primary and secondary inverters;
a speed detection unit that detects the rotation speed of the motor;
PWM (Pulse Width Modulation) control of the primary-side and secondary-side inverters based on each phase current detected by the phase current detection unit and the zero-phase current detected by the zero-phase current detection unit , a control unit that adjusts the amount of zero-phase current while driving the motor,
The control unit includes a phase advance compensating unit that calculates to advance the phase of the detected zero-phase current according to the rotation speed of the motor, and based on the result of the calculation and the phase currents The PWM control is performed.

In addition, the refrigeration cycle apparatus of the embodiment includes a motor having an open winding structure in which three-phase windings are independent of each other and provided with six winding terminals;
and the open winding motor drive device of the embodiment.

1 is a diagram showing a circuit configuration of a motor drive system according to an embodiment; FIG. Functional block diagram showing the internal configuration of the control device Functional block diagram showing the detailed configuration of the zero-phase current controller The figure which shows the Bode plot corresponding to the characteristic of a phase advance element part. A diagram showing the phase relationship between the actual zero-phase current and the zero-phase current detected by control FIG. 10 is a diagram showing the suppression state of the zero-phase current before and after the zero-phase current suppression control unit is operated when the rotation speed is 40 rps without operating the phase lead compensation unit; Equivalent to Fig. 6 when the rotation speed is 50 rps Current waveform diagram in a state where the phase lead compensator 61 is operated and the zero-phase current suppressor is not operated when the rotation speed is 50 rps. Current waveform diagram in a state in which the zero-phase current suppression unit is operated from the state in FIG. A current waveform diagram showing the horizontal axis of FIG. 8 shrunk to 5 times A current waveform diagram showing the horizontal axis of FIG. 9 shrunk 5 times Equivalent to Fig. 10 when the rotation speed is 70 rps Fig. 11 equivalent diagram in case of rotation speed 70rps A diagram schematically showing the configuration of an air conditioner

An embodiment will be described below with reference to the drawings. In FIG. 14, a compressor 2 that constitutes a heat pump refrigeration cycle apparatus 1 is configured by housing a compression mechanism portion 3 and a motor 4 in the same closed iron container 5 , and the rotor shaft of the motor 4 is connected to the compression mechanism portion 3 . connected to As a result, the motor 4 is driven to drive the compression mechanism 3 to perform the compression operation. The compressor 2, the four-way valve 6, the indoor heat exchanger 7, the decompression device 8, and the outdoor heat exchanger 9 are connected to form a closed loop by pipes serving as heat transfer medium flow paths.

The compressor 2 is, for example, a rotary compressor, and the motor 4 is, for example, a three-phase IPM (Interior Permanent Magnet) motor or a brushless DC motor. The output of the compressor 2 is changed by changing the amount of refrigerant discharged from the compression mechanism portion 3 in accordance with the change in the rotation speed of the motor 4, and the capacity of the refrigeration cycle can be varied. The air conditioner E has the heat pump refrigeration cycle device 1 described above.

During the heating operation of the air conditioner E, the four-way valve 6 is in the state indicated by the solid line, and the high-temperature refrigerant compressed by the compression mechanism 3 of the compressor 2 is supplied from the four-way valve 6 to the indoor heat exchanger 7 and condensed. After that, the air is decompressed by the decompressor 8, becomes low temperature, flows to the outdoor heat exchanger 9, evaporates there, and returns to the compressor 2. On the other hand, during cooling operation, the four-way valve 6 is switched to the state indicated by the dashed line. For this reason, the high-temperature refrigerant compressed in the compression section 3 of the compressor 2 is supplied from the four-way valve 6 to the outdoor heat exchanger 9 and condensed, and then decompressed by the decompression device 8 to become low temperature and indoor heat exchange. It flows to vessel 7 where it evaporates and returns to compressor 2 .

The outdoor heat exchanger 9 functions as an evaporator (heat absorber) during heating operation and as a condenser (radiator) during cooling operation. Conversely, the indoor heat exchanger 7 functions as a condenser during heating operation and as a cooling operation. It is sometimes designed to function as an evaporator. Fans 10 and 11 blow air to the heat exchangers 7 and 9 on the indoor side and the outdoor side, respectively. It is designed to do well.

A fan 11 that blows air to the outdoor heat exchanger 9 is a propeller fan and is driven by a fan motor 12 . The fan motor 12 is, for example, a highly efficient brushless DC motor like the motor 4 . A fan 10 that blows air to the indoor heat exchanger 7 is a cross-flow fan and is driven by a fan motor 13 . Fan motor 13 is also desirably a brushless DC motor.

FIG. 1 is a diagram showing the circuit configuration of a motor drive system connected to a commercial three-phase AC power supply 27. As shown in FIG. The three-phase windings of the motor 4 that drives the compression mechanism 3 have an open winding structure in which the terminals are not connected to each other and both terminals are open. It has Wa, Ub, Vb and Wb.

The primary side inverter 21 and the secondary side inverter 22 (hereinafter referred to as inverters 21 and 22, respectively) are each configured by connecting IGBTs 23, which are switching elements, in a three-phase bridge connection. A diode 24 is connected in anti-parallel. For example, each of the inverters 21 and 22 can use a module product in which six IGBTs 23 and six freewheel diodes 24 are all built in the same package. Furthermore, each IGBT 23 may be composed of a highly efficient wide bandgap semiconductor such as SiC or GaN. Each phase output terminal of inverter 21 is connected to winding terminals Ua, Va, Wa of motor 4, and each phase output terminal of inverter 22 is connected to winding terminals Ub, Vb, Wb of motor 4, respectively.

Inverters 21 and 22 are connected in parallel to converter 25 . The converter 25 consists of a three-phase full-wave rectifier circuit in which six diodes are bridge-connected. A DC reactor 28 for improving the power factor is inserted in the positive power line between the converter 25 and the inverter 21 . A smoothing capacitor 29 for smoothing direct current is connected between the positive power line and the negative power line.

Current sensors 30 (U, V, W) are sensors for detecting phase currents Iu, Iv, Iw of motor 4, and are provided between three-phase output lines of inverter 21 and winding terminals of motor 4. ing. Note that the current sensors 30 (U, V, W) may be provided between the three-phase output lines of the inverter 22 and the winding terminals of the motor 4 . A voltage sensor 31 detects a DC power supply voltage _VDC , which is the terminal voltage of the smoothing capacitor 29 .

A control device 33 is provided with a speed command value ω _ref as a target rotation speed of the compression mechanism 3 from a higher-level control device in a system that drives the motor, for example, an air conditioning control unit of the air conditioner E. Control is performed so that the detected motor speed ω coincides with ω _ref . Based on the phase currents Iu, Iv, and Iw detected by the current sensor 30 and the _DC voltage VDC detected by the voltage sensor 31, the control device 33 provides a switching signal to the gates of the IGBTs 23 forming the inverters 21 and 22. to generate The control device 33 corresponds to a control section.

FIG. 2 is a functional block diagram showing the internal configuration of the control device 33. As shown in FIG. A three-phase/dq0 conversion unit 34 converts the phase currents Iu, Iv, and Iw detected via the current sensor 30 into currents Id, Iq, and I0 on the axes of d, q, and 0 used for vector control. do. The zero-phase current I0 is calculated by summing the phase currents Iu, Iv, and Iw. That is, I0=Iu+Iv+Iw, and is output after being multiplied by 1/(√2) in a later stage (not shown). Hereinafter, the coefficient 1/(√2) will be omitted for the zero-phase current I0. The timing at which the 3-phase/dq0 converter 34 detects the current is set, for example, to synchronize with the carrier cycle in PWM control. Similarly, the current sensor 30 and the 3-phase/dq0 converter 34 correspond to the phase current detector. Also, the 3-phase/dq0 conversion section 34 corresponds to a zero-phase current detection section.

A speed/position estimator 35 , which is an example of a speed detector, estimates a speed ω, a motor current frequency ωe, and a rotational position θ from the voltage/current of the motor 4 . The rotational position θ is input to the 3-phase/dq0 conversion section 34 and the dq0/3-phase conversion section 36 . The speed control unit 37 generates and outputs a q-axis current command I _qref by, for example, performing a PI operation on the difference between the input speed command ω _ref and the estimated speed ω. The d-axis current command generator 38 generates and outputs a d-axis current command value I _dref from the DC voltage _VDC and the voltage amplitude V _dq of the dq-axis, for example, by PI-calculating the difference between the two.

Current control unit 39 generates q-axis voltage command Vq according to the difference between q-axis current command _Iqref and _q -axis current Iq, and generates d A shaft voltage command Vd is generated. The zero-phase current control unit 40 determines the zero-phase current from the zero-phase current command _I0ref and the zero-phase current I0 input from the three-phase/dq0 conversion unit 34, and the motor current frequency ωe input from the speed/position estimation unit 35. Generates and outputs a voltage command V0.

The dq0/three-phase converter 36 converts the respective axis voltage commands Vq, Vd, V0 into the three-phase voltage command values Vu1, Vv1, Vw1, Vu2, Vv2, Vw2 of the two inverters 21 and 22 according to equation (1). do.

The modulating unit 42 generates switching signals, PWM signals U1, V1, W1, X1, Y1, Z1, U2, V2, W2, X2, Y2 and Z2 are generated and output. A DC voltage V _DC is input to the modulating section 42 .

そして、係数α及びＴを、それぞれ（３），（４）式で定める。

そして、位相進み要素部６２は、ｓ＝ｊωとすると、入力される零相電流信号に対して（５）式を乗じる。
（１＋αＴｓ）／（１＋Ｔｓ） …（５）
ゲイン補正部に相当する増幅器６３は、位相進み要素部６２より入力される電流信号に対して、次式のゲインＧを乗じる。尚、「＾」はべき乗を示す。

FIG. 3 is a functional block diagram showing the detailed configuration of the zero-phase current controller 40. As shown in FIG. The subtractor 43 finds the difference between the zero-phase current command _I0ref and the zero-phase current I0, and outputs the difference to the phase lead compensator 61. FIG. In this embodiment, the zero-phase current I0 is suppressed by always setting the zero-phase current command _I0ref to zero. The phase lead compensation section 61 includes a phase lead element section 62 and an amplifier 63 . The phase advance element section 62 performs the following calculations. First, let fc be the carrier wave frequency in PWM control, ωe be the frequency corresponding to the rotation speed of the motor, and δ be the signal delay of the circuit system.
A detection delay φ of the zero-phase current is calculated by the equation (2).

Then, coefficients α and T are determined by equations (3) and (4), respectively.

Then, when s=jω, the phase lead element unit 62 multiplies the input zero-phase current signal by the formula (5).
(1+αTs)/(1+Ts) (5)
The amplifier 63 corresponding to the gain correction section multiplies the current signal input from the phase lead element section 62 by the gain G of the following equation. Note that "^" indicates exponentiation.

An input terminal of the zero-phase current suppressor 64 is connected to the output terminal of the amplifier 63 . The amplifier 44 outputs the result of multiplying the input current signal by the proportional control gain Kp to the adder 46 , and the amplifier 45 outputs the result of multiplying the current signal by the resonance control gain Kr to the subtractor 47 . The output signal of the subtractor 47 is integrated by the integrator 48 and output to the adder 46 and multiplier 49 .

The multiplier 49 receives the square of the tripled value of the motor current frequency ωe, and multiplies the frequency ( 3ωe ) ² by the integration result of the integrator 48 . The third harmonic component of the motor current frequency corresponds to the zero-phase current I0. The multiplication result of multiplier 49 is input to subtractor 47 via integrator 50 .

Subtractor 47 subtracts the integration result of integrator 50 from the output signal of amplifier 45 and outputs the result to integrator 48 . In the above configuration, the part other than the amplifier 44 and the adder 46 constitutes a resonance control section 51 that performs control so as to enhance the response to the third harmonic of the current frequency. The addition result of the adder 46 is output as the zero-phase voltage V0.

Next, the operation of this embodiment will be described with reference to FIGS. 4 to 9. FIG. The control device 33 performs current detection and control calculation in synchronization with the carrier cycle in PWM control. U-phase, V-phase, W-phase, and zero-phase currents are detected at the starting point of the carrier cycle, and motor control calculations and then zero-phase current suppression control calculations are performed based on the detected currents.

The specific contents of the motor control calculation are (1) current coordinate conversion processing by the 3-phase/dq0 conversion unit 34, (2) speed/position estimation processing by the speed/position estimation unit 35, and (3) speed control unit 37. (4) current control by the current control unit 39; The duty in the PWM control is updated based on the voltage commands Vq, Vd generated by the current control in (4) and the zero-phase voltage V0 generated by the zero-phase current suppression control calculation, and the PWM signals U1, V1, W1, X1 , Y1, Z1, U2, V2, W2, X2, Y2, Z2 are generated and output.

Here, as shown in FIG. 5, since the detection of the zero-phase current is delayed by one carrier cycle, a phase difference occurs between the actual zero-phase current and the detected zero-phase current. Since the frequency of the zero-phase current is proportional to the number of revolutions of the motor, the ratio of the detection delay with respect to the zero-phase current increases in the high speed region, increasing the phase difference. This increases the phase difference between the zero-phase voltage command V0 for suppressing the zero-phase current and the actual zero-phase current. When the phase lead compensator 61 is not operated, for example, in the case of a 6-pole motor with a carrier frequency of 5 kHz, the zero-phase current can be suppressed at a rotational speed of 40 rps as shown in FIG. , the zero-phase current increases.

また、位相の最大値φ_ｍは（８）式で求められる。そして、係数αは（８）式から（３）式のように導出される。また、係数Ｔは、（７）式及び（３）式から（４）式のように導出される。また、位相進み要素部６２の電流利得Ｇｉ［ｄＢ］は（９）式となるので、
比（出力電流）／（入力電流）は、（１０）式となる。

そして、角周波数ω_ｍに対する電流利得Ｇｉは、ボード線図から
Ｇｉ＝１０ｌｏｇ_１０α …（１１）
となる。よって、比（出力電流）／（入力電流）は（１２）式で表される。

（１２）式は、位相進み要素部６２より出力される電流が、入力電流の右辺倍になることを示している。そこで、増幅器６３が（６）式のゲインＧを乗じることで補正する。増幅器６３はゲイン補正部の一例である。 Therefore, in this embodiment, the zero-phase current is suppressed by operating the phase lead compensator 61 . FIG. 4 is a Bode plot of the phase lead element portion 62. As shown in FIG. From this figure, the angular frequency ω _m at which the phase reaches the maximum value can be obtained by equation (7).

Also, the maximum value φ _m of the phase is obtained by the equation (8). Then, the coefficient α is derived from Equation (8) as shown in Equation (3). Also, the coefficient T is derived from the equations (7) and (3) as in the equation (4). Also, since the current gain Gi [dB] of the phase lead element section 62 is given by the equation (9),
The ratio (output current)/(input current) is given by equation (10).

Then, the current gain Gi with respect to the angular frequency ω _m is given by Gi=10log ₁₀ α (11) from the Bode diagram
becomes. Therefore, the ratio (output current)/(input current) is represented by equation (12).

Equation (12) indicates that the current output from the phase lead element section 62 is the right side times the input current. Therefore, the amplifier 63 corrects by multiplying the gain G of the equation (6). The amplifier 63 is an example of a gain correction section.

When the control of the present embodiment is applied to a conventional 6-pole motor with a carrier frequency of 5 kHz, as shown in FIG. can be advanced to the phase of the actual zero-phase current. Note that the zero-phase current suppressing unit 64 is in a non-operating state. FIG. 9 shows a case where the zero-phase current suppressing section 64 is operated in the state shown in FIG. 8, and it can be seen that the zero-phase current is suppressed. Also, FIGS. 10 and 11 show the waveforms shown in FIGS. 8 and 9 with the time axis, which is the horizontal axis, reduced by a factor of five.

12 and 13 are diagrams corresponding to FIGS. 10 and 11 for the case of a rotational speed of 70 rps, and it can be seen that the zero-phase current is suppressed. From these, it can be seen that the effect of the zero-phase current suppression control can be extended to the high rotation region.

As described above, according to the present embodiment, the primary inverter 21 is connected to the three winding terminals of the motor 4 having the open winding structure, and the secondary inverter 22 is connected to the remaining three winding terminals. . The converter 25 converts the voltage of the AC power supply 27 into DC and supplies the DC power to the inverters 21 and 22 . Current sensor 30 detects phase currents Iu, Iv, and Iw flowing through motor 4 , and three-phase/dq0 converter 34 detects zero-phase current I0 flowing between inverters 21 and 22 .

The control device 33 generates switching patterns for the inverters 21 and 22 by PWM control based on the phase currents Iu, Iv, and Iw and the zero phase current I0, drives the motor 4, and controls the zero phase current control unit 40 to control the zero phase current. The current amount of the phase current I0 is suppressed. Specifically, the phase of the zero-phase current I0 detected by the lead phase compensator 61 is calculated so as to advance according to the rotation speed of the motor 4, and the PWM control is performed based on the result of the calculation and the phase currents. By controlling, the current amount of the zero-phase current I0 is suppressed.

The lead phase compensating unit 61 includes a phase lead element unit 62 and an amplifier 63. The phase lead element unit 62 sets the detection delay φ of the zero-phase current by equation (2), and the coefficients α and T are set to (3). and (4), and the calculation of the equation (5) is performed for the difference between the input zero-phase current I0 _ref and the zero-phase current I0. Then, the amplifier 63 multiplies the current input from the phase lead element section 62 by the gain G of the equation (6).

As a result, the zero-phase current suppression control can be speeded up without changing the carrier period and the motor control period, and an increase in computational load can be minimized.
Since the motor 4 drives the compressor 2 constituting the air conditioner E, the air conditioner E can be constructed at a low cost.

(Other embodiments)
The noise filter 26 may be provided as required.
The refrigerating cycle device may be applied to other than air conditioners such as heat pump water heaters and chillers.
You may apply to things other than a refrigerating-cycle apparatus.

While embodiments of the invention have been described, the embodiments have been presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and modifications can be made without departing from the scope of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are included in the scope of the invention described in the claims and equivalents thereof.

2 is a compressor; 4 is a motor; 21 is a primary inverter; 22 is a secondary inverter; 23 is an IGBT; is a current sensor, 33 is a controller, 34 is a 3-phase/dq0 converter, 40 is a zero-phase current controller, and 42 is a modulator.

Claims (3)

a primary-side inverter connected to three of the six winding terminals in a motor having an open winding structure in which each of the three-phase windings is independent and has six winding terminals;
a secondary inverter connected to the remaining three winding terminals of the motor;
a converter that converts the voltage of an AC power source into a DC power source and supplies the DC power source to the primary side inverter and the secondary side inverter;
a phase current detection unit that detects each phase current flowing in the motor;
a zero-phase current detection unit that detects a zero-phase current flowing between the primary and secondary inverters;
a speed detection unit that detects the rotation speed of the motor;
PWM (Pulse Width Modulation) control of the primary-side and secondary-side inverters based on each phase current detected by the phase current detection unit and the zero-phase current detected by the zero-phase current detection unit , a control unit that adjusts the amount of zero-phase current while driving the motor,
The control unit includes a phase advance compensating unit that calculates to advance the phase of the detected zero-phase current according to the rotation speed of the motor, and based on the result of the calculation and the phase currents An open winding motor drive device that performs the PWM control. The phase lead compensating unit includes a phase lead element unit and a gain correcting unit,
In the phase advance element section, φ is the detection delay of the zero-phase current, fc is the carrier wave frequency in PWM control, ωe is the frequency corresponding to the rotation speed of the motor, and δ is the signal delay of the circuit system.
φ=3ωe/fc+δ
and the coefficient α and T are determined by the following equation,
α=-(sinφ+1)/(sinφ-1), T=1/(3ωe√α)
When s=jω, the following formula is calculated for the input zero-phase current,
(1+αTs)/(1+Ts)
The gain correction section multiplies the current input from the phase lead element section by a gain G of the following equation (^ indicates a power)
G=1/{10̂( _log10α /2)}
2. The open winding motor drive device of claim 1. a motor with an open winding structure in which three-phase windings are independent of each other and provided with six winding terminals;
A refrigeration cycle apparatus comprising the open winding motor drive device according to claim 1 or 2.

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