CN112104283B - Open-winding motor drives and refrigeration cycles - Google Patents

Abstract

An open-winding motor driving device and a refrigeration cycle device, the open-winding motor driving device comprises: primary and secondary inverters connected to the 3 winding terminals, respectively, in a motor having an open winding structure in which the 3-phase windings are independent and each has 6 winding terminals; a converter for supplying a DC power supply, which is obtained by converting a voltage of an AC power supply into a DC, to the primary-side and secondary-side inverters; a phase current detection unit for detecting each phase current flowing through the motor; a zero-phase current detection unit that detects zero-phase current flowing between the primary-side and secondary-side inverters; a speed detecting unit for detecting a rotational speed of the motor; and a control unit that performs PWM control of the primary-side and secondary-side inverters based on the detected phase currents and zero-phase currents, and adjusts the amount of zero-phase current while driving the motor, wherein the control unit includes a phase lead compensation unit that calculates the phase of the detected zero-phase current so as to lead the phase of the detected zero-phase current in accordance with the rotational speed of the motor.

Description

Open-winding motor drives and refrigeration cycles

Technical field

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

Background technique

Regarding a system that drives a motor with an open winding structure, as a technique for improving efficiency, for example, as shown in Japanese Patent No. 3352182, it is known to suppress zero current flowing between two inverters that drive the motor. Phase current to achieve efficiency improvement technology.

A motor that generates a high induced voltage like an open-winding structure can generate the same torque with less current, so it is possible to reduce current consumption and improve efficiency. On the other hand, in the motor having a common DC bus, a zero-phase current is generated that flows in the same direction in the three phases of the motor, causing problems such as reduced efficiency and heating of components.

Furthermore, the frequency of the zero-phase current is three times that of the U, V, and W phase currents that flow to drive the motor, and the detection delay of the zero-phase current becomes large in the high rotation speed range. Therefore, in order to suppress the zero-phase current, it is necessary to shorten the cycle of controlling the motor. This causes problems such as heating of components due to an increase in switching frequency, or an increase in the cost of control arithmetic devices such as microcomputers.

Contents of the invention

According to the following embodiments, there are provided an open-winding motor drive device that can suppress zero-phase current even in a high rotation speed range without shortening the motor control cycle, and a refrigeration cycle device including the same.

The open winding motor driving device of the embodiment includes:

The primary-side inverter is connected to three of the above-mentioned six winding terminals of an open winding structure with independent three-phase windings and six winding terminals;

The secondary side inverter is connected to the remaining 3 winding terminals of the above motor;

A converter that supplies DC power obtained by converting the voltage of the AC power supply into DC to the above-mentioned primary-side inverter and the above-mentioned secondary-side inverter;

A phase current detection unit detects each phase current flowing in the motor;

a zero-phase current detection unit that detects the zero-phase current flowing between the primary-side inverter and the secondary-side inverter;

a speed detection unit that detects the rotation speed of the above-mentioned motor; and

The control unit performs PWM (Pulse Width Modulation) on the primary-side inverter and the secondary-side inverter based on the respective phase currents detected by the phase current detection unit and the zero-phase current detected by the zero-phase current detection unit. , pulse width modulation) control, thereby adjusting the above-mentioned zero-phase current amount while driving the above-mentioned motor,

The control unit includes a phase lead compensation unit that calculates a phase of the detected zero-phase current to advance according to the rotation speed of the motor, and performs the PWM control based on a result of the calculation and the current of each phase.

Furthermore, the refrigeration cycle device of the embodiment includes:

A motor with an open winding structure, the three phase windings are independent and have 6 winding terminals; and

The open winding motor drive device of the embodiment.

Description of the drawings

FIG. 1 shows one embodiment and is a diagram showing the circuit structure of a motor drive system.

FIG. 2 is a functional block diagram showing the internal structure of the control device.

3 is a functional block diagram showing the detailed structure of the zero-phase current control unit.

FIG. 4 is a diagram showing a plate diagram corresponding to the characteristics of the phase advance element part.

FIG. 5 is a diagram showing the phase relationship between the actual zero-phase current and the zero-phase current detected during control.

6 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 phase advance compensation unit is not operated and the rotation speed is 40 rps.

Fig. 7 is a diagram equivalent to Fig. 6 when the rotation speed is 50 rps.

FIG. 8 is a current waveform diagram in a state where the phase advance compensation unit 61 is operated and the zero-phase current suppression unit is not operated when the rotation speed is 50 rps.

FIG. 9 is a current waveform diagram in a state in which the zero-phase current suppressing unit is operated from the state in FIG. 8 .

FIG. 10 is a current waveform diagram in which the horizontal axis of FIG. 8 is reduced five times.

FIG. 11 is a current waveform diagram in which the horizontal axis of FIG. 9 is reduced five times.

Fig. 12 is a diagram corresponding to Fig. 10 when the rotation speed is 70 rps.

Fig. 13 is a diagram corresponding to Fig. 11 when the rotation speed is 70 rps.

Fig. 14 is a diagram schematically showing the structure of the air conditioner.

Detailed ways

Hereinafter, one embodiment will be described with reference to the drawings. In FIG. 14 , the compressor 2 constituting the heat pump refrigeration cycle device 1 has the compression mechanism unit 3 and the motor 4 housed in the same iron sealed container 5 , and the rotor shaft of the motor 4 is connected to the compression mechanism unit 3 . As a result, the compression mechanism unit 3 is driven by driving the motor 4, and compression operation is performed. Furthermore, the compressor 2, the four-way valve 6, the indoor heat exchanger 7, the pressure reducing device 8, and the outdoor heat exchanger 9 are connected by a pipe as a heat transfer medium flow path to form a closed loop.

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 amount of discharged refrigerant from the compression mechanism unit 3 changes according to changes in the rotational speed of the motor 4, thereby changing the output of the compressor 2, thereby changing the capacity of the refrigeration cycle. The air conditioner E includes 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 shown by the solid line, and the high-temperature refrigerant compressed by the compression mechanism unit 3 of the compressor 2 is supplied from the four-way valve 6 to the indoor heat exchanger 7 The condensed air is decompressed in the pressure reducing device 8 , becomes low temperature, and flows toward the outdoor heat exchanger 9 , where it is evaporated and returned to the compressor 2 . On the other hand, during the cooling operation, the four-way valve 6 is switched to the state shown by the dotted line. Therefore, the high-temperature refrigerant compressed by the compression section 3 of the compressor 2 is supplied from the four-way valve 6 to the outdoor heat exchanger 9 and is condensed. Then, the high-temperature refrigerant is decompressed in the decompression device 8, becomes low temperature, and is heat-exchanged indoors. It flows through the retort 7, where it evaporates and returns to the compressor 2.

The outdoor heat exchanger 9 functions as an evaporator (heat absorber) during the heating operation and functions as a condenser (radiator) during the cooling operation. In contrast, the indoor heat exchanger 7 functions as a condensator during the heating operation. The evaporator functions as an evaporator during cooling operation. Furthermore, fans 10 and 11 are used to blow air to the heat exchangers 7 and 9 on the indoor side and the outdoor side, respectively. This air blowing is configured to efficiently communicate between the heat exchangers 7 and 9 and the indoor air and outdoor air. heat exchange.

The 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 . The fan 10 that supplies air to the indoor heat exchanger 7 is a cross flow fan and is driven by a fan motor 13 . It is also preferable to use a brushless DC motor as the fan motor 13 .

FIG. 1 is a diagram showing the circuit structure of a motor drive system connected to a commercial three-phase AC power supply 27 . The three-phase windings of the motor 4 that drives the compression mechanism unit 3 are formed in an open winding structure in which the two terminals are not connected to each other and are in an open state. The motor 4 has six winding terminals Ua, Va, Wa, and Ub. , Vb, 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 a three-phase bridge connection of IGBTs 23 as switching elements, and a freewheeling current is connected to each IGBT 23 in antiparallel. Diode 24. For example, each of the inverters 21 and 22 can use a module in which six IGBTs 23 and six freewheeling diodes 24 are all built in the same package. In addition, each IGBT 23 may be composed of a high-efficiency wide-bandgap semiconductor such as SiC or GaN. Each phase output terminal of the inverter 21 is connected to the winding terminals Ua, Va, and Wa of the motor 4 respectively, and each phase output terminal of the inverter 22 is connected to the winding terminals Ub, Vb, and Wb of the motor 4 respectively.

Inverters 21 and 22 and converter 25 are connected in parallel. The converter 25 is a three-phase full-wave rectification circuit in which six diodes are bridge-connected, and its three-phase AC input terminal is connected to the three-phase AC power supply 27 via the noise filter 26 . A DC reactor 28 for improving the power factor is inserted into the positive side power line between the converter 25 and the inverter 21 . Furthermore, a smoothing capacitor 29 for smoothing a direct current is connected between the positive side power supply line and the negative side power supply line.

The current sensor 30 (U, V, W) is a sensor that detects the respective phase currents I _u , I _v , and I _w of the motor 4 , and is provided between the three-phase output lines of the inverter 21 and the winding terminals of the motor 4 . In addition, 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 . The voltage sensor 31 detects the DC power supply voltage V _DC which is the terminal voltage of the smoothing capacitor 29 .

The control device 33 is given a speed command value ω _ref as the target rotation speed of the compression mechanism unit 3 from a higher-level control device in the system that drives the motor, such as the air conditioning control unit of the air conditioner E, so that the detected motor speed ω Control is performed in a manner consistent with the speed command value ω _ref . The control device 33 generates a voltage applied to the gate of each IGBT 23 constituting the inverters 21 and 22 based on the phase currents I _u , I _v , and I _w detected by the current sensor 30 and the DC voltage V _DC detected by the voltage sensor 31 . switch signal. The control device 33 corresponds to a control unit.

FIG. 2 is a functional block diagram showing the internal structure of the control device 33 . The 3-phase/dq0 conversion unit 34 converts the currents I _u , I _v , and I _w of each phase detected via the current sensor 30 into the currents I _d and I _q of each axis coordinate of d, q, and 0 used for vector control. , I ₀ . The zero-phase current I ₀ can be calculated by summing the respective phase currents I _u , I _v , and I _w . That is, I ₀ =I _u +I _v +I _w is multiplied by 1/(√2) times in the second half (not shown) and output. In the following, regarding the zero-phase current I ₀ , the coefficient 1/(√2) is omitted. The timing at which the 3-phase/dq0 conversion unit 34 performs current detection is set, for example, to be synchronized with the carrier cycle in PWM control. Similarly, the current sensor 30 and the 3-phase/dq0 conversion unit 34 correspond to the phase current detection unit. Furthermore, the 3-phase/dq0 conversion unit 34 corresponds to the zero-phase current detection unit.

The speed and position estimation unit 35 which is an example of the speed detection unit estimates the speed ω, the motor current frequency ω _e and the rotational position θ based on the voltage and current of the motor 4 . The rotational position θ is input to the 3-phase/dq0 converting unit 34 and the dq0/3-phase converting unit 36. The speed control unit 37 generates and outputs the q-axis current command I _qref by performing a PI operation on the difference between the input speed command ω _ref and the estimated speed ω, for example. The d-axis current command generation unit 38 generates and outputs a d-axis current command value I _dref by similarly performing a PI operation on the difference between the DC voltage V _DC and the dq-axis voltage amplitude V _dq .

The current control unit 39 generates the q-axis voltage command V _q based on the difference between the q-axis current command I _qref and the q-axis current I _q , and generates the d-axis voltage command based on the difference between the d-axis current command I _dref and the d-axis current I _{d Vd} . The zero-phase current control unit 40 generates and outputs a zero-phase based on the zero-phase current command I _0ref , the zero-phase current I ₀ input from the 3-phase/dq0 conversion unit 34 , and the motor current frequency ω _e input from the speed and position estimation unit 35 Voltage command V ₀ .

The dq0/3-phase conversion unit 36 converts the voltage commands V _q , V _d , and V ₀ of each axis into the three-phase voltage command values V _u1 , V _v1 , V _w1 , and V _u2 , V _v2 , V _w2 .

The modulation unit 42 generates and outputs switching signals and PWM signals U1, V1, W1, X1, Y1, Z1, U2, V2, W2, X2, Y2, Z2. The DC voltage V _DC is input to the modulation unit 42 .

FIG. 3 is a functional block diagram showing the detailed structure of the zero-phase current control unit 40 . The subtractor 43 obtains the difference between the zero-phase current command I _0ref and the zero-phase current I ₀ , and outputs the difference to the phase lead compensation unit 61 . In addition, in this embodiment, the zero-phase current command I _0ref is set to zero under normal conditions, thereby realizing the suppression of the zero-phase current I ₀ . The phase advance compensation unit 61 includes a phase advance element unit 62 and an amplifier 63 . The phase advance element unit 62 performs calculations as shown below. First, if the carrier frequency in PWM control is set to f _c , the frequency corresponding to the rotation speed of the motor is set to ω _e , and the signal delay of the circuit system is set to δ,

Then the detection delay φ of the zero-phase current is calculated by equation (2).

Furthermore, the coefficients α and T are determined using equations (3) and (4) respectively.

Furthermore, if s=jω, the phase leading element unit 62 multiplies the input zero-phase current signal by equation (5).

(1+αTs)/(1+Ts)…(5)

The amplifier 63 corresponding to the gain correction unit multiplies the current signal input from the phase lead element unit 62 by the gain G of the following expression. In addition, "＾" means power multiplication.

The input terminal of the zero-phase current suppressing unit 64 is connected to the output terminal of the amplifier 63 . The amplifier 44 outputs a result obtained by multiplying the input current signal by the proportional control gain Kp to the adder 46 , and the amplifier 45 outputs a result obtained by 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 the multiplier 49 .

The square of three times the motor current frequency ωe is input to the multiplier 49, and the frequency (3ωe) ² is multiplied by the integration result of the integrator 48. The third high-frequency component of the motor current frequency is equivalent to the zero-phase current I ₀ . The multiplication result of the multiplier 49 is input to the subtractor 47 via the integrator 50 .

The subtractor 47 subtracts the integration result of the integrator 50 from the output signal of the amplifier 45 and outputs it to the integrator 48 . In the above configuration, parts other than the amplifier 44 and the adder 46 constitute the resonance control unit 51 that controls to improve the responsiveness of the third-order high frequency with respect to the current frequency. The addition result of the adder 46 becomes the zero-phase voltage V ₀ and is output.

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

The specific contents of the motor control calculation are: (1) current coordinate conversion processing by the 3-phase/dq0 conversion unit 34, (2) speed and position estimation processing by the speed and position estimation unit 35, (3) speed control speed control by the section 37, (4) current control by the current control section 39. The duty ratio in PWM control is updated based on the voltage commands V _q and V _d generated by the current control of (4) and the zero-phase voltage V ₀ generated by the zero-phase current suppression control operation, and PWM signals U1, V1, W1, X1, Y1, Z1, U2, V2, W2, X2, Y2, Z2 and output.

Here, as shown in FIG. 5 , a delay of one carrier cycle occurs in the detection of the zero-phase current, so 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 rotational speed of the motor, the proportion of the detection delay relative to the zero-phase current increases in the high rotational speed region and the phase difference increases. This increases the phase difference between the zero-phase voltage command V ₀ that suppresses the zero-phase current and the actual zero-phase current. When the phase lead compensation unit 61 is not used, for example, in the case of a 6-pole motor and a carrier frequency of 5 kHz, the zero-phase current can be suppressed when the rotation speed is 40 rps as shown in FIG. 6 , but as shown in FIG. 7 It shows that the zero-phase current increases when the rotation speed is 50rps.

Therefore, in this embodiment, the phase advance compensation unit 61 is caused to function to suppress the zero-phase current. FIG. 4 is a plate diagram of the phase advance element unit 62 . Based on this figure, use equation (7) to find the angular frequency ω _m at which the phase reaches the maximum value.

Furthermore, the maximum value φ _m of the phase is obtained using equation (8). Furthermore, the coefficient α is derived from the equation (8) in the same manner as the equation (3). Furthermore, the coefficient T is derived from equations (7) and (3) as in equation (4). Furthermore, the current gain Gi [dB] of the phase leading element section 62 is expressed in equation (9), so the ratio (output current)/(input current) is expressed in equation (10).

Furthermore, based on the plate diagram, the current gain Gi with respect to the angular frequency ω _m is:

Gi＝10log ₁₀ α…(11)

. Therefore, the ratio (output current)/(input current) is expressed by equation (12).

Regarding equation (12), the current output from the phase leading element unit 62 is a right-hand numerical multiple of the input current. Therefore, the amplifier 63 performs correction by multiplying the gain G of the equation (6). The amplifier 63 is an example of a gain correction unit.

If the control of this embodiment is applied to a 6-pole motor as an example of a conventional structure when the carrier frequency is 5 kHz, as shown in FIG. 8 , when the rotation speed is 50 rps, the phase advance compensation unit 61 can be used to make the detected The phase of the obtained zero-phase current leads to the phase of the actual zero-phase current. In addition, the zero-phase current suppressing unit 64 is in a non-operating state. FIG. 9 shows a state in which the zero-phase current suppressing unit 64 is operated relative to the state shown in FIG. 8 , and it is understood that the zero-phase current is suppressed. Furthermore, FIGS. 10 and 11 show the time axis, which is the horizontal axis of the waveforms shown in FIGS. 8 and 9 , reduced by five times.

Figures 12 and 13 are diagrams corresponding to Figures 10 and 11 when the rotational speed is 70 rps, and it can be seen that the zero-phase current is suppressed. From this, it can be seen that the effect of zero-phase current suppression control extends to the high rotation speed range.

As described above, according to this embodiment, the primary-side inverter 21 is connected to the three winding terminals of the open-winding structure motor 4, and the secondary-side inverter 22 is connected to the remaining three winding terminals. The converter 25 supplies the DC power obtained by converting the voltage of the AC power supply 27 into DC to the inverters 21 and 22 . The current sensor 30 detects the respective phase currents I _u , I _v , and I _w flowing through the motor 4 , and the 3-phase/dq0 conversion unit 34 detects the zero-phase current I ₀ flowing between the inverters 21 and 22 .

The control device 33 generates the switching patterns of the inverters 21 and 22 through PWM control based on the respective phase currents I _u , I _v , I _w and the zero-phase current I ₀ , and uses the zero-phase current control unit to drive the motor 4 40 suppresses the current amount of the zero-phase current I ₀ . Specifically, the calculation is performed so that the phase of the zero-phase current I ₀ detected by the leading phase compensation unit 61 leads in accordance with the rotation speed of the motor 4, and PWM control is performed based on the result of the calculation and the above-mentioned respective phase currents. To suppress the current amount of zero-phase current I ₀ .

The leading phase compensation unit 61 includes a phase leading element unit 62 and an amplifier 63. The phase leading element unit 62 sets the detection delay φ of the zero-phase current using equation (2), and determines the coefficients α and T using equations (3) and (4). The calculation of equation (5) is performed for the difference between the input zero-phase current I _0ref and the zero-phase current I ₀ . Furthermore, the amplifier 63 multiplies the current input from the phase leading element unit 62 by the gain G of the equation (6).

This makes it possible to speed up the zero-phase current suppression control without changing the carrier cycle and the motor control cycle, thereby minimizing an increase in the calculation load.

Furthermore, since the compressor 2 constituting the air conditioner E is driven by the motor 4, the air conditioner E can be constructed inexpensively.

(Other embodiments)

The noise filter 26 can be set as needed.

The refrigeration cycle device can also be applied to devices other than air conditioners such as heat pump water heaters and refrigerators.

It can also be applied to devices other than refrigeration cycle devices.

The embodiments of the present invention have been described above. However, the embodiments are merely presented as examples and are not intended to limit the scope of the invention. The above-described new embodiments can be implemented in various other forms, and various omissions, substitutions, and changes can be made without departing from the spirit of the invention. The above-described embodiments and modifications thereof are included in the scope or gist of the invention, and are included in the invention described in the technical claims and their equivalent scope.

Claims (3)

1. An open-winding motor driving device is provided with:

a primary inverter connected to 3 winding terminals among 6 winding terminals in a motor having an open-winding structure in which 3-phase windings are independent and each having the 6 winding terminals;

a secondary-side inverter connected to the remaining 3 winding terminals of the motor;

a converter that supplies a dc power supply obtained by converting a voltage of an ac power supply into a dc power to the primary-side inverter and the secondary-side inverter;

a phase current detection unit configured to detect each phase current flowing through the motor;

a zero-phase current detection unit configured to detect a zero-phase current flowing between the primary-side inverter and the secondary-side inverter;

a speed detecting unit for detecting a rotational speed of the motor; and

a control unit that performs PWM control, that is, pulse width modulation control, on the primary side inverter and the secondary side inverter 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, thereby adjusting the zero phase current amount while driving the motor,

the control unit includes a phase lead compensation unit that calculates a phase of the detected zero-phase current so as to lead the phase of the detected zero-phase current in accordance with a rotational speed of the motor, and performs the PWM control based on a result of the calculation and the respective phase currents.

2. The open-winding motor driving apparatus according to claim 1, wherein,

the phase lead compensation unit includes a phase lead element unit and a gain correction unit,

in the phase advance element unit, when the zero-phase current detection delay is set to be Φ, the carrier frequency in PWM control is set to be fc, the frequency corresponding to the rotation speed of the motor is set to be ωe, and the signal delay of the circuit system is set to be δ

φ＝3ωe/fc+δ，

The coefficient alpha and T are determined by the following equation,

α＝－(sinφ+1)/(sinφ－1)，T＝1/(3ωe√α)

when s=jω, the following operation is performed for the zero-phase current inputted,

(1+αTs)/(1+Ts)

the gain correction unit multiplies the current input from the phase advance element unit by a gain G as follows, wherein, the power is represented by the power,

G＝1/{10＾(log ₁₀ α/2)}。

3. a refrigeration cycle device is provided with:

a motor with an open winding structure, wherein 3-phase windings are independent and provided with 6 winding terminals; and

an open-winding motor drive as claimed in claim 1 or 2.