JP6710339B2 - Electric motor drive - Google Patents

Description

The present invention relates to a motor drive equipment. The invention for example relates from the inverter, the motor drive equipment for the variable speed operation to the permanent magnet type synchronous motor by supplying an alternating current voltage variable in frequency variable.
The present invention particularly relates to a drive device of an electric motor suitable for driving a compressor of a refrigeration cycle application device such as an air conditioner or a refrigerator.

Electric power consumption is achieved by changing the rotation speed of the electric motor using a variable frequency and variable voltage inverter and switching the stator winding connection state to star connection (Y connection) or delta connection (Δ connection) according to the load. There is known an electric motor drive device that reduces the number of charges and improves the efficiency.

For example, an electric motor for a compressor of an air conditioner may be driven by a Y connection under intermediate conditions (low load conditions) that contribute to the annual power consumption, and by a Δ connection under rated conditions (high load conditions). Be done. By doing so, it is possible to improve efficiency under intermediate conditions and to achieve high output under rated conditions.

When driving a permanent magnet motor, a method of detecting the position of the rotor and switching the energization to the winding of each phase is often used during normal operation. As a method for detecting the rotor position, a sensorless system that detects the position based on an induced voltage generated in a winding as the rotor rotates is often used in a motor for driving a compressor.

However, driving the permanent magnet motor by the sensorless method has the following problems. That is, the induced voltage is not generated when the rotor is stopped, and immediately after the start, the induced voltage is low and unstable. Therefore, the position of the rotor cannot be accurately detected.
Therefore, at the time of starting, the winding is energized under a predetermined starting condition, and after the rotation of the rotor is stabilized, the driving is switched to the sensorless system.
When the permanent magnet motor is started by such a method, there is a possibility that an overcurrent may flow in the winding or the start may fail and step out may occur.

In order to solve the above problem, Patent Document 1 discloses that a current flowing in a winding of an electric motor is detected, a resistance value of the winding is detected from the detection result, and a starting voltage is determined based on the detected resistance value. Is proposed.

Further, in Patent Document 2, the current flowing in the stator winding of the permanent magnet synchronous motor and the voltage applied to the stator winding are detected, and the position of the rotor is calculated based on these detected values. The rotation speed is detected based on the detected rotor position, the start voltage instruction value in the start mode is determined by PI control or the like based on the detected current, and the start voltage in the start mode is determined based on the detected rotation speed. A motor control device that determines a phase indication value is disclosed.

Further, Patent Document 3 discloses a winding switching device for an electric motor, in which a winding is Y-connected at the time of starting and is switched to a Δ-connection when a predetermined number of rotations is reached. In this device, a reverse blocking semiconductor switch having a breakdown voltage in both forward and reverse directions is used as a connection switching switch. Further, it is also described that the frequency of the gate drive signal of the inverter that supplies AC power to the electric motor is made lower than usual at the time of startup to suppress the surge current (paragraph 0062).

JP, 2007-336626, A JP 2012-228127 A JP, 2011-87399, A

In the drive device shown in Patent Document 1, calculation accuracy can be secured to some extent in the case of an electric motor having a large winding resistance value. However, when an electric motor having a small winding resistance is used, the resistance cannot be calculated with sufficient accuracy, and thus the starting voltage cannot be adjusted accurately. Further, Patent Document 1 does not consider connection switching, and if the connection states are different, it becomes more difficult to secure calculation accuracy.

Patent Document 2 describes that the disclosed electric motor control device can be applied not only to a Y-connected electric motor but also to a Δ-connected electric motor (0011). However, when the connection switching is performed, the detected line voltage or phase current varies depending on the connection state. Therefore, depending on the gain setting of the control, the start convergence may be different depending on the connection state, which may cause start failure.

In the device disclosed in Patent Document 3, the semiconductor switch having a withstand voltage in both forward and reverse directions used as a changeover switch is expensive, and there is a problem that the cost of the device increases. In addition, the frequency of the gate drive signal of the inverter that supplies AC power to the electric motor is set lower than normal at startup to suppress the surge current, but such measures may be appropriate depending on the situation. Not always.

The case where the connection switching is performed between the Y connection and the Δ connection has been described above, but the same applies when the connection switching is performed in another mode, for example, between the serial connection and the parallel connection. There is a problem.

The present invention has been made to solve the above problems, and an object of the present invention is to provide an electric motor drive device that can be surely started in a short time regardless of the connection state.

An electric motor drive device according to one aspect of the present invention is
A connection switching device that switches the connection state of the winding of the electric motor to star connection or delta connection,
An inverter that applies an alternating voltage whose frequency and voltage are variable to the electric motor to control the speed of the electric motor,
Having a start condition memory for storing a plurality of start conditions, having a control device for controlling the inverter and the connection switching device,
The control device is
Among the plurality of starting conditions stored in the starting condition memory, a starting condition corresponding to the wire connection state of the electric motor is selected, and the inverter is controlled using the selected starting condition, whereby the electric motor is Start with the selected start condition,
Each of the plurality of starting conditions, the change pattern of the speed command value for controlling the speed of the electric motor, the relationship between the speed command value and the voltage command value for controlling the amplitude of the drive voltage of the electric motor. Including specified parameters,
The change pattern of the speed command value is to gradually increase the speed command value with the passage of time from the start of activation.
The parameter is to increase the voltage command value as the speed command value increases,
When starting the electric motor,
Based on the change pattern of the speed command value included in the selected start condition, while gradually increasing the speed command value,
Gradually increasing the voltage command value based on the speed command value and the parameter,
Of the plurality of starting conditions, the starting condition corresponding to the star connection causes the voltage command value to rise more rapidly than the starting condition corresponding to the delta connection.
An electric motor drive device according to another aspect of the present invention is
A connection switching device that switches the connection state of the winding of the electric motor to star connection or delta connection,
An inverter that applies an alternating voltage whose frequency and voltage are variable to the electric motor to control the speed of the electric motor,
Having a start condition memory for storing a plurality of start conditions, having a control device for controlling the inverter and the connection switching device,
The control device is
Among the plurality of starting conditions stored in the starting condition memory, a starting condition corresponding to the wire connection state of the electric motor is selected, and the inverter is controlled using the selected starting condition, whereby the electric motor is Start with the selected start condition,
Each of the plurality of starting conditions includes a change pattern of a speed command value for controlling the speed of the electric motor and a change pattern of a voltage command value for controlling the amplitude of the drive voltage of the electric motor,
The change pattern of the speed command value is to gradually increase the speed command value with the passage of time from the start of activation.
The change pattern of the voltage command value is to gradually increase the voltage command value with the passage of time from the start of activation,
When starting the electric motor,
Based on the change pattern of the speed command value included in the selected start condition, while gradually increasing the speed command value,
Based on the change pattern of the voltage command value included in the selected starting condition, gradually increase the voltage command value,
Of the plurality of starting conditions, the starting condition corresponding to the star connection causes the voltage command value to rise more rapidly than the starting condition corresponding to the delta connection.
An electric motor drive device according to still another aspect of the present invention is
A connection switching device that switches the connection state of the winding of the electric motor to star connection or delta connection,
An inverter that applies an alternating voltage whose frequency and voltage are variable to the electric motor to control the speed of the electric motor,
Having a start condition memory for storing a plurality of start conditions, having a control device for controlling the inverter and the connection switching device,
The control device is
Among the plurality of starting conditions stored in the starting condition memory, a starting condition corresponding to the wire connection state of the electric motor is selected, and the inverter is controlled using the selected starting condition, whereby the electric motor is Start with the selected start condition,
When it is determined whether the electric current of the electric motor is excessive during start-up and whether the electric motor is out of step, and when it is determined that the electric current of the electric motor is excessive, or when the electric motor is disconnected. When it is determined that the adjustment is in progress, the activation is stopped, the selected activation condition is changed, and then the activation is performed again.

According to the present invention, since the activation is performed under different activation conditions depending on the connection state, it is possible to perform the activation reliably and in a short time regardless of the connection state.

It is a schematic diagram showing an example of a refrigerating cycle of an air harmony machine. It is a figure which shows the electric motor drive device of Embodiment 1 of this invention. It is a figure which shows the structure of the inverter of FIG. It is a wiring diagram which shows in detail the winding and connection switching device of the electric motor of FIG. FIG. 3 is a functional block diagram showing an example of a control device used in the first embodiment. (A) And (b) is a figure which shows the change pattern of the speed command value used for starting in Embodiment 1, and the change of the voltage command value accompanying the change of the speed command value. 6 is a functional block diagram showing a configuration example of a PWM waveform generation unit in FIG. 5. FIG. 6 is a flowchart showing a procedure of a startup process of the control device of FIG. 5. (A) And (b) is a figure which shows the example of the change pattern of the speed command value and the change pattern of the voltage command value used for starting in Embodiment 3 of this invention.

An electric motor drive device according to an embodiment of the present invention will be described below with reference to the accompanying drawings.
The motor drive device of the present invention is suitable for driving a compressor of a refrigeration cycle application device. An example of a refrigeration cycle application device is an air conditioner, and the following embodiments apply the present invention to a drive device for an electric motor that drives a compressor of an air conditioner.

First, a refrigeration cycle in an example of an air conditioner will be described with reference to FIG.
The refrigeration cycle 900 of FIG. 1 can perform heating operation or cooling operation by switching operation of the four-way valve 902.

During the heating operation, as indicated by the solid arrow, the refrigerant is pressurized and sent out by the compressor 904, passes through the four-way valve 902, the indoor heat exchanger 906, the expansion valve 908, the outdoor heat exchanger 910, and the four-way valve 902. Return to compressor 904.
During the cooling operation, the refrigerant is pressurized and sent out by the compressor 904 as indicated by the broken line arrow, and passes through the four-way valve 902, the outdoor heat exchanger 910, the expansion valve 908, the indoor heat exchanger 906, and the four-way valve 902. Return to compressor 904.
During the heating operation, the indoor heat exchanger 906 acts as a condenser to release heat, and the outdoor heat exchanger 910 acts as an evaporator to absorb heat. During the cooling operation, the outdoor heat exchanger 910 acts as a condenser to release heat, and the indoor heat exchanger 906 acts as an evaporator to absorb heat. The expansion valve 908 decompresses and expands the refrigerant.
The compressor 904 is driven by the electric motor 7 whose variable speed is controlled.

Embodiment 1.
FIG. 2 is a schematic wiring diagram showing the electric motor drive device 2 of the first embodiment of the present invention together with the electric motor 7.
The illustrated electric motor drive device 2 is for driving the electric motor 7, and includes AC power supply input terminals 2a and 2b, a reactor 8, a rectifier circuit 10, a capacitor 20, an inverter 30, and a connection switching device 60. The busbar current detection unit 85, the busbar voltage detection unit 87, and the control device 100.

The control device 100 may be configured by, for example, a microcomputer (microcomputer) including a CPU (Central Processing Unit), a DSP (Digital Signal Processor), or the like, or may be configured by dedicated hardware.
In the following, description will be made assuming that it is configured by a microcomputer.

The AC power supply input terminals 2a and 2b are connected to an external AC power supply 4, and an AC voltage is applied from the AC power supply 4 to the AC power supply input terminals 2a and 2b.

The rectifier circuit 10 receives AC power from the AC power supply 4 via the input terminals 2 a and 2 b and the reactor 8 and rectifies the AC power. The rectifier circuit 10 is a full-wave rectifier circuit formed by bridge-connecting the rectifier elements 11 to 14 such as diodes.

The capacitor 20 smoothes the DC voltage rectified by the rectifier circuit 10 and outputs the DC voltage Vdc.

As shown in FIG. 3, the inverter 30 has an inverter main circuit 310 and a drive circuit 350, and the input terminal of the inverter main circuit 310 is connected to the electrode of the capacitor 20.
A line connecting the output of the rectifier circuit 10, the electrode of the capacitor 20, and the input terminal of the inverter main circuit 310 is called a DC bus.

The inverter 30 is controlled by the control device 100 so that the switching elements 311 to 316 of the six arms of the inverter main circuit 310 are turned on and off to generate a frequency-variable and voltage-variable three-phase alternating current. Supply. Rectification elements 321 to 326 for reflux are connected in parallel to the switching elements 311 to 316.

The electric motor 7 is a three-phase permanent magnet synchronous electric motor, the lead wire of the stator winding is drawn out of the electric motor 7, and is switched to either star connection (Y connection) or delta connection (Δ connection). Is possible. This switching is performed by the connection switching device 60.
The switching by the connection switching device 60 is controlled by the switching signal Sc output from the control device 100.

FIG. 4 shows the stator winding and connection switching device 60 of the electric motor 7 in more detail.
As shown in the drawing, the first ends 71a, 72a, 73a of the windings 71, 72, 73 of the U-phase, V-phase, and W-phase of the electric motor 7 are connected to the external terminals 71c, 72c, 73c, respectively. And the second ends 71b, 72b, 73b of the U-phase, V-phase, W-phase windings 71, 72, 73 are connected to external terminals 71d, 72d, 73d, respectively. Connection is possible. The U-phase, V-phase, and W-phase output lines 331, 332, 333 of the inverter 30 are connected to the external terminals 71c, 72c, 73c.

The connection switching device 60 is composed of switching devices 61, 62, 63 in the illustrated example. As the switches 61, 62, 63, electromagnetic contactors whose contacts are opened and closed electromagnetically are used. Such electromagnetic contactors are also called relays, contactors and the like.

The common contact 61c of the switch 61 is connected to the terminal 71d via the lead wire 61e, the normally closed contact 61b is connected to the neutral point node 64, and the normally open contact 61a is the V phase output line of the inverter 30. 332 is connected.
The common contact 62c of the switch 62 is connected to the terminal 72d through the lead wire 62e, the normally closed contact 62b is connected to the neutral point node 64, and the normally open contact 62a is the W-phase output line of the inverter 30. It is connected to 333.
The common contact 63c of the switch 63 is connected to the terminal 73d via the lead wire 63e, the normally closed contact 63b is connected to the neutral point node 64, and the normally open contact 63a is the U-phase output line of the inverter 30. It is connected to 331.

When the switching devices 61, 62 and 63 are switched to the normally closed contacts side as shown in the figure, that is, when the common contacts 61c, 62c and 63c are connected to the normally closed contacts 61b, 62b and 63b, respectively. The electric motor 7 is in a Y connection state.
Contrary to the switching devices 61, 62 and 63, when they are switched to the normally open contact side, that is, when the common contacts 61c, 62c and 63c are connected to the normally open contacts 61a, 62a and 63a. Indicates that the electric motor 7 is in the Δ connection state.

The bus-bar current detector 85 detects the bus-bar current, that is, the input current Idc of the inverter 30.
The bus current detector 85 includes a shunt resistor inserted in the DC bus and supplies an analog signal indicating the detection result to the control device 100. This signal (detection signal) Idc is converted into a digital signal by an A/D converter (not shown) in the control device 100 and used for processing inside the control device 100.

The bus voltage detector 87 detects the voltage Vdc between both electrodes of the capacitor 20 as a bus voltage. The bus bar voltage detector 87 includes, for example, a circuit that divides the bus bar voltage Vdc by a series-connected resistor, and converts the bus bar voltage Vdc into a signal having a voltage suitable for processing by the microcomputer in the control device 100, for example, a voltage of 5 V or less. Output. This signal (detection signal) Vdc is also converted into a digital signal by an A/D conversion unit (not shown) in the control device 100 and used for processing inside the control device 100.

As described above, the control device 100 controls the switching of the connection state by the connection switching device 60 and the operation of the inverter 30. The control device 100 supplies the switching signal Sc to the connection switching device 60 for controlling the switching of the connection state by the connection switching device 60. For controlling the inverter 30, the control device 100 generates the PWM signals Sm1 to Sm6 and supplies the PWM signals Sm1 to Sm6 to the inverter 30.

As described above, the inverter 30 includes the drive circuit 350 in addition to the inverter main circuit 310, and the drive circuit 350 generates the drive signals Sr1 to Sr6 based on the PWM signals Sm1 to Sm6 to generate the drive signals. The switching elements 311 to 316 are controlled to be turned on and off by Sr1 to Sr6, so that the frequency-variable and voltage-variable three-phase AC voltage is applied to the electric motor 7.

The PWM signals Sm1 to Sm6 are of the signal level of the logic circuit (0 to 5V), whereas the drive signals Sr1 to Sr6 are the voltage levels required to control the switching elements, for example, +15V to −. This is a signal having a magnitude of 15V. Further, while the PWM signals Sm1 to Sm6 use the ground potential of the control device 100 as a reference potential, the drive signals Sr1 to Sr6 each have a potential on the negative side terminal (emitter terminal) of the corresponding switching element. Is the reference potential.

The control of the inverter 30 and the connection switching device 60 by the control device 100 includes control at the time of starting the electric motor 7 as well as control at the normal operation of the electric motor 7.
In the control at the time of starting, control device 100 starts electric motor 7 under a predetermined starting condition. This starting condition differs depending on whether the electric motor 7 is in the Y connection state or in the Δ connection state.

As shown in FIG. 5, the control device 100 has a start condition memory 101, an operation control unit 102, and an inverter control unit 110.

The activation condition memory 101 stores a plurality of activation conditions. The start condition includes, for example, a change pattern of the speed command value ω ^* at the time of start, and a parameter that defines the relationship between the speed command value ω ^* and the voltage command value V ^* .
Change pattern of the velocity command value omega ^* is to be specified with respect to time elapsed from the start of activation, how to increase the speed command value of the motor 7 omega ^*. Here, the speed is represented by an angular speed (angular frequency) at the electric angle of the electric motor 7. The inverter 30 is controlled so as to output a voltage having a frequency that matches the speed command value ω ^* .
The above parameters represent how the voltage command value V ^* is changed in accordance with the change of the speed command value ω ^* , and therefore indirectly determine the change pattern of the voltage command value V ^*. is there.
The voltage command value V ^* is a command value for the drive voltage of the electric motor 7. In the present embodiment, a value representing the amplitude of the drive voltage in the dq coordinate system is used as the drive voltage command value.

FIGS. 6A and 6B show examples of a change pattern of the speed command value ω ^* and a change pattern of the voltage command value V ^{* with} the change of the speed command value ω ^* for the Y connection and the Δ connection, respectively. Has been done. 6A and 6B, the horizontal axis represents the elapsed time from the start of activation, and the vertical axis represents the speed command value ω ^* and the voltage command value V ^* .

In the change patterns shown in FIGS. 6A and 6B, the speed command value ω ^* and the voltage command value V ^* linearly increase with the passage of time.
6A and 6B, the change patterns of the speed command value ω ^* are the same. That is, the speed command values ω ^* for the same elapsed time are the same.
On the other hand, the change patterns of the voltage command value V ^* are different from each other, and the change pattern of the Y connection has a steeper slope. In other words, the voltage command value V ^* (Y) corresponding to a certain elapsed time in the case of Y connection is larger than the voltage command value V ^* (Δ) in the case of Δ connection corresponding to the same elapsed time.

When the speed command value ω ^* and the voltage command value V ^* are as shown in FIGS. 6A and 6B, the relationship between the speed command value ω ^* and the voltage command value V ^* is expressed by the following equation. To be done.
V ^* =K×ω ^* (1)
In Expression (1), K is a parameter that defines the relationship between ω ^* and V ^* .
The parameter K differs between the Y connection and the Δ connection.
If the parameter K for the Y connection is represented by K(Y) and the parameter K for the Δ connection is represented by K(Δ), the voltage command value V ^* (Y) for the Y connection is
V ^* (Y)=K(Y)×ω ^* (2)
The voltage command value V ^* (Δ) in the case of Δ connection is
V ^* (Δ)=K(Δ)×ω ^* (3)
It is represented by.

The parameter K(Y) for the Y connection is set to a value larger than the parameter K(Δ) for the Δ connection. For example, at the start of operation of the motor drive device, K(Y)=√3×K(Δ) (4)
Is determined. However, the adjustment after the start of operation may not satisfy the relationship of Expression (4).

The activation condition memory 101, for example as a change pattern of the speed command value omega ^*, LUT (lookup table) showing a change in the speed command value omega ^* with respect to the elapsed time may be stored, the speed the elapsed time as a variable A function (or a parameter defining the function) for obtaining the command value ω ^* may be stored.

The operation control unit 102 receives information indicating a room temperature (temperature of the air-conditioned space) from a temperature sensor (not shown), receives an instruction from an operation unit (not shown), and controls the operation of each unit of the air conditioner. The instruction from the operation unit includes information indicating the set temperature, instructions for starting and ending the operation, and the like. The operation unit is composed of, for example, a remote controller.

Before starting the electric motor 7, the operation control unit 102 selects whether the electric motor 7 should be Y-connected or Δ-connected, and outputs a switching signal Sc according to the selection result.
The operation control unit 102, for example, decides to use the Δ connection when the difference between the room temperature and the set temperature is large, sets the target rotation speed to a relatively high value, starts up, and after the start-up, the target rotation speed is set. The velocity command value ω ^* that gradually increases to the angular velocity corresponding to is output.
When the room temperature is close to the set temperature, stop the motor once, switch to Y connection, set the target speed to a relatively low value, restart, and after restarting up to the angular speed corresponding to the above target speed. The speed command value ω ^* that gradually increases is output.

The operation control unit 102 selects an operation mode and causes each unit of the control device 100 to operate in the selected operation mode. In order to perform the operation in the selected operation mode, the operation control unit 102 sets the mode signal Ss to a first value, for example, High at startup, and sets the mode signal Ss to a second value, for example, Low during normal operation. To do.

At the time of startup, the operation control unit 102 sets the mode signal Ss to High and performs the startup process. This activation process is performed by selecting one of the plurality of activation conditions stored in the activation condition memory 101 and using the selected activation condition. In the present embodiment, the starting condition is composed of the change pattern of the speed command value ω ^* and the parameter K.
In this embodiment, different starting conditions are selected for the Y connection and the Δ connection.
As a result, the same change pattern of the speed command value ω ^* is read in the case of the Y connection and the case of the Δ connection, and the parameter K is read in the case of the Y connection and the case of the Δ connection. Different values are read.

When the speed control value ω ^* is increased to a predetermined value according to the read change pattern, the operation control unit 102 switches to the normal operation mode at that time. When switching to the normal operation mode, the mode signal Ss is set to Low.
The mode signal Ss is supplied to the inverter control unit 110.

The inverter control unit 110 includes a current command generation unit 111, a current restoration unit 112, a three-phase/two-phase conversion unit 113, a position/speed estimation unit 114, a speed control unit 115, a voltage command calculation unit 116, and a two-phase/three-phase conversion. It has a unit 117, a PWM waveform generation unit 118, an integration unit 119, and switch groups 121 and 122.

The switch groups 121 and 122 are controlled by the mode signal Ss. When the mode signal Ss is Low, the first switch group 121 is in the closed state (OFF state) and the second switch group 122 is in the open state (ON state) as illustrated. When the mode signal Ss is High, contrary to the figure, the first switch group 121 is in the open state (OFF state) and the second switch group 122 is in the closed state (ON state).
The mode signal Ss is also supplied to the voltage command calculation unit 116, and the voltage command calculation unit 116 performs different processing during normal operation and during startup.

First, the operation during normal operation will be described.
During normal operation, the operation control unit 102 sets the mode signal Ss to Low. Therefore, the switch groups 121 and 122 are in the illustrated state. That is, the switch group 121 is on and the switch group 122 is off.

The current command generation unit 111 generates the current command value Id ^* based on the speed command value ω ^* . The current command generation unit 111 determines the current command value Id ^* so that the torque required to rotate the electric motor 7 is generated at the rotation speed corresponding to the speed command value ω ^* .

The current restoration unit 112 restores the phase currents Iu, Iv, Iw flowing through the electric motor 7 based on the current value Idc detected by the bus current detection unit 85. The current restoration unit 112 restores the phase current by sampling the DC current Idc detected by the bus current detection unit 85 at a timing determined based on the PWM signal from the PWM waveform generation unit 118.

The three-phase/two-phase conversion unit 113, based on the current values Iu, Iv, Iw restored by the current restoration unit 112 and the rotor magnetic pole position (electrical angle phase) θ estimated by the position/speed estimation unit 114 described later, The coordinate conversion generates a current on the dq coordinate axes, that is, a d-axis current Id on the d-axis coordinates and a q-axis current Iq on the q-axis coordinates.

The position/velocity estimation unit 114, based on the currents Id and Iq generated by the three-phase/two-phase conversion unit 113, and the voltage command values Vd ^* and Vq ^* generated by the voltage command calculation unit 116 described later, the motor The speed of 7 is estimated, and the estimated speed value ω is generated.

The speed control unit 115 calculates the q-axis current command value Iq ^* based on the speed command value ω ^* given from the operation control unit 102 and the speed estimated value ω generated by the position/speed estimation unit 114. The q-axis current command value Iq ^* is set to a value that matches the estimated speed value ω with the speed command value ω ^* .

The voltage command calculation unit 116 receives the d-axis current Id and the q-axis current Iq from the three-phase/two-phase conversion unit 113, the d-axis current command value Id ^* from the current command generation unit 111, and the speed control unit 115 with q. The axis current command value Iq ^* is received, and the d-axis voltage command value Vd ^* and the q-axis voltage command value Vq ^* are generated based on these.

The voltage command calculation unit 116 performs PI control so that the d-axis current Id matches the d-axis current command value Id ^* and the q-axis current Iq matches the q-axis current command value Iq ^* , and the d-axis voltage command value. Vd ^* and q-axis voltage command value Vq ^* are generated.

For example, the d-axis voltage command value Vd ^* and the q-axis voltage command value Vq ^* are obtained by the following calculation.
Vd ^* =(Kpd+Kid/s)*(Id ^* -Id) (5)
Vq ^* =(Kpq+Kiq/s)*(Iq ^* -Iq) (6)
In equations (5) and (6),
Kpd is the d-axis proportional gain,
Kpq is the q-axis proportional gain,
Kid is the d-axis integral gain,
Kiq is the q-axis integral gain,
s is a Laplace operator.

The two-phase/three-phase converter 117 includes a bus voltage Vdc detected by the bus voltage detector 87, a d-axis voltage command value Vd ^* and a q-axis voltage command value Vq ^* calculated by the voltage command calculator 116, and a position. The U-phase voltage command value Vu ^* , the V-phase voltage command value Vv ^* , the W-phase voltage command value Vw ^*, and the voltage phase θv are generated based on the rotor magnetic pole position θ estimated by the speed estimator 114.
Various methods have been proposed for generating the voltage command values Vu ^* , Vv ^* , Vw ^* , and any method may be used as long as it is a control technique capable of driving the electric motor 7.

The PWM waveform generation unit 118 generates PWM signals Sm1 to Sm6 based on the phase voltage command values Vu ^* , Vv ^* , Vw ^* and the voltage phase θv calculated by the two-phase/three-phase conversion unit 117.

The PWM waveform generation unit 118 has a carrier generation unit 131 and a carrier comparison unit 132, as shown in FIG. 7, for example.
The carrier generation unit 131 generates carriers based on the voltage phase θv.
The carrier comparison unit 132, based on the carrier signal generated by the carrier generation unit 131 and the phase voltage command values Vu ^* , Vv ^* , Vw ^* calculated by the two-phase/three-phase conversion unit 117, the PWM signals Sm1 to Sm6. To generate.

As described above, during normal operation, the inverter control unit 110 estimates the rotor magnetic pole position θ by the operations of the current restoration unit 112, the three-phase/two-phase conversion unit 113, and the position/speed estimation unit 114, and based on the estimation result. The inverter 30 is controlled by generating the phase voltage command value and generating the PWM waveform based on the command voltage value. Since such control does not use a position sensor, it is called a sensorless control.

Next, the operation at startup will be described.
At start-up, during normal operation, the operation control unit 102 sets the mode signal Ss to High. Therefore, the switch groups 121 and 122 are in a state opposite to that shown. That is, the switch group 122 is on and the switch group 121 is off.

The operation control unit 102 selects whether the electric motor 7 should be Y-connected or Δ-connected at the time of startup, and outputs the switching signal Sc according to the selection result.
The operation control unit 102 further reads the start condition from the start condition memory 101. The starting condition includes the change pattern of the speed command value ω ^* and the parameter K.

The operation control unit 102 outputs the speed command value ω ^* that changes according to the change pattern of the speed command value ω ^* included in the read start condition. The speed command value ω ^* is input to the voltage command calculation unit 116 and the integration unit 119.
The operation control unit 102 supplies the parameter K included in the read start condition to the voltage command calculation unit 116.

The voltage command calculation unit 116 generates the d-axis voltage command value Vd ^* and the q-axis voltage command value Vq ^* based on the speed command value ω ^* , the mode signal Ss, and the parameter K.

The voltage command calculation unit 116 generates the voltage command value V ^* based on the speed command value ω ^* and the parameter K output from the operation control unit 102, and further, based on the voltage command value V ^* , the d-axis voltage. The command value Vd ^* and the q-axis voltage command value Vq ^* are generated.
The voltage command value V ^* is generated by ^obtaining the product of the speed command value ω ^* and the parameter K.

Generation of the d-axis voltage command value Vd ^* and the q-axis voltage command value Vq ^* based on the voltage command value V ^* is performed as follows. First, the d-axis voltage command value Vd ^* and the q-axis voltage command value Vq ^* are Vd ^*2 +Vq ^*2 =V ^*2 (7)
To meet the relationship.

In calculating the d-axis voltage command value Vd ^* and the q-axis voltage command value Vq ^* , it is desirable to take the characteristics of the electric motor 7, the moment of inertia of the mechanical system, the environmental temperature, etc. into consideration. Therefore, parameters indicating the characteristics of the electric motor 7 and the moment of inertia of the mechanical system are stored in advance (in a memory (not shown) inside or outside the voltage command calculation unit 116) and the stored parameters are used as the d-axis voltage command value Vd ^*. It is desirable to use it for calculating the q-axis voltage command value Vq ^* . It is also possible to detect the environmental temperature and adjust the parameters used to calculate the d-axis voltage command value Vd ^* and the q-axis voltage command value Vq ^* according to the detection results.

The integrator 119 estimates the rotor magnetic pole position θ by integrating the speed command value ω ^* .

In the two-phase/three-phase converter 117, the voltage command values Vd ^* and Vq ^* generated by the voltage command calculator 116, the bus voltage Vdc detected by the bus voltage detector 87, and the estimation by the integrator 119. The U-phase voltage command value Vu ^* , the V-phase voltage command value Vv ^* , the W-phase voltage command value Vw ^*, and the voltage phase θv are generated based on the rotor magnetic pole position θ.
This process is similar to that in normal operation.

As in the normal operation, the PWM waveform generation unit 118 uses the PWM signals Sm1 to Sm6 based on the phase voltage command values Vu ^* , Vv ^* , Vw ^* and the voltage phase θv calculated by the two-phase/three-phase conversion unit 117. To generate.

The current value Idc detected by the bus current detection unit 85 is transmitted to the operation control unit 102, and the operation control unit 102 determines whether the current flowing in the electric motor 7 is excessive at the time of start based on the current value Idc. Make a decision.

The current restoration unit 112, the three-phase/two-phase conversion unit 113, and the position/speed estimation unit 114 are operating at the time of startup in the same manner as during normal operation, and the speed estimation value output from the position/speed estimation unit 114 is calculated. ω is transmitted to the driving control unit 102, and the driving control unit 102 compares the estimated speed value ω output from the position/speed estimation unit 114 with the speed command value ω ^* generated by the driving control unit 102. Then, it is determined whether or not the step is out of step. For example, if a state where the difference between the two is larger than a predetermined threshold value continues for a predetermined time or more, it is estimated that the step is out of sync.

FIG. 8 shows a procedure of processing for starting the electric motor 7 performed by the electric motor drive device according to the embodiment. This process is performed by the operation control unit 102.

When the electric motor 7 is in the stopped state (ST100), the operation control unit 102 repeatedly determines whether to start it (ST102). For example, when the user gives an instruction to start the operation of the air conditioner using the operation unit (not shown), the operation unit gives a start instruction to the operation control unit 102 of the control device. In that case, the operation control unit 102 determines that it should be started.
Further, when the operation unit gives an instruction to automatically start the operation at the set time (or after the set time elapses), the operation control unit 102 stores that information and is set. When the time comes (or when the set time elapses), it is determined that it should be started.
Further, when the room temperature becomes close to the set temperature, the electric motor may be temporarily stopped. In that case, if the difference between the room temperature and the set temperature becomes large due to a change in the room temperature or a change in the set temperature thereafter, it is determined that the system should be started.
When it is determined that it should be activated for any of the above reasons, the process proceeds to step ST104.

In step ST104, the operation control unit 102 acquires information for selecting the connection state.
The information for selecting the connection state includes information indicating room temperature and information indicating the set temperature. The information indicating the room temperature is given by a temperature sensor (not shown). Information indicating the set temperature is given from the operation unit (not shown).

When the acquisition of the information for selecting the connection state is completed, the process proceeds to step ST106.
In step ST106, the operation control unit 102 selects a connection state.
For example, the connection state to be selected may differ depending on the load of the air conditioner. For example, when the difference between the room temperature (temperature detected by a temperature sensor (not shown)) and the set temperature is large, the Δ connection is selected, and when the difference is small, the Y connection is selected. There is a case. In such a case, the wire connection state is selected based on the set temperature and the room temperature.

After selecting the connection state (ST106), the process proceeds to step ST108.
In step ST108, the operation control unit 102 controls the connection switching device 60 based on the connection state selected in step ST106 (ST108).
That is, if the connection state selected in step ST106 and the actual connection state of the connection switching device 60 are the same, the connection switching device 60 is maintained as it is.
When the connection state selected in step ST106 is different from the actual connection state of the connection switching device 60, the connection switching device 60 is caused to execute the switching operation.
For example, if the connection state selected in step ST106 is Δ connection, but the actual connection state of the connection switching device 60 is Y connection, the connection state is shifted to the Δ connection state.

After step ST108, a startup process is performed (ST110 to ST122).

In the startup process, the operation control unit 102 first selects a startup condition (ST110).
In selecting the starting condition, different starting conditions are selected according to the connection state selected in step ST106. The selection of the start condition includes the selection of the change pattern of the speed command value ω ^* and the selection of the parameter K.

After step ST110, the process proceeds to step ST112. In step ST112, the operation control unit 102 starts the activation process using the selected activation condition. At the start of the startup process, the operation control unit 102 supplies the parameter K to the voltage command calculation unit 116 of the inverter control unit 110.

While performing the activation process, the operation control unit 102, according to the speed command value omega ^* change pattern included in the selected start condition, the speed command value omega ^*, with time, increase gradually.
The voltage command calculation unit 116 calculates the voltage command value V ^* by multiplying the speed command value ω ^* by the parameter K.
The voltage command calculation unit 116 calculates the d-axis voltage command value Vd ^* and the q-axis voltage command value Vq ^* based on the voltage command value V ^* .

The integrator 119 estimates the rotor magnetic pole position θ by integrating the speed command value ω ^* .
The two-phase/three-phase conversion unit 117 calculates the d-axis voltage command value Vd ^* , the q-axis voltage command value Vq*, the rotor magnetic pole position θ to the V-phase voltage command value Vu ^* , the V-phase voltage command value Vv ^* , and the W-phase. The voltage command value Vw ^* and the voltage phase θv are calculated.
The PWM waveform generation unit 118 generates Pm1 to Pm6 based on the phase voltage command values Vu ^* , Vv ^* , Vw ^* , and the voltage phase θv.

As described above, the inverter control unit 110 controls the inverter 30 and tries to start the electric motor 7 by generating the PWM signals Pm1 to Pm6 based on the speed command value ω ^* .

While attempting to start up in this way, the operation control unit 102 repeats the determination of whether or not the start up was successful (ST114, ST116, ST120).
To determine whether or not the start-up has succeeded, it is determined whether or not an overcurrent state has been reached (ST114), whether or not a step-out state has been reached (ST116), and whether or not a predetermined speed has been reached. The determination (ST120) is included.

The overcurrent state in step ST114 is a state in which the electric motor current is excessive.
For example, the operation control unit 102 determines whether or not the electric motor current is excessive based on the current value Idc detected by the bus current detection unit 85.

When the electric motor current is excessive (YES in ST114), the process proceeds to step ST118.
In step ST118, the operation control unit 102 stops the inverter 30 and changes the start condition. In this case, the electric motor current is changed to be smaller.
For example, a smaller value is adopted as the parameter K, and the new condition is used to update the start condition stored in the start condition memory 101. For example, the previously stored value is overwritten with a new value.

After that, the process returns to step ST112 and restarts. In the case of restarting, the updated parameter K is used. As a result, the voltage command value V ^* rises more slowly (the rate of increase is smaller).

The step-out state in step ST116 is a state in which the electric motor cannot be started due to insufficient torque. For example, a state in which the difference between the estimated speed value ω output from the position/speed estimation unit 114 and the speed command value ω ^* generated in the operation control unit 102 is larger than a predetermined threshold value continues for a predetermined time or more. If so, the operation control unit 102 estimates that the step is out of sync.

When it is determined that the step is out of step (YES in ST120), the process proceeds to step ST122.
In step ST122, the operation control unit 102 stops the inverter 30 and changes the starting condition. In this case, the motor current is changed to be larger (torque is larger).
For example, a larger value is adopted as the parameter K, and the starting condition stored in the starting condition memory 101 is updated using this new value. For example, the previously stored value is overwritten with a new value.

After that, the process returns to step ST112 and restarts. In the case of restarting, the updated parameter K is used. As a result, the voltage command value V ^* rises more rapidly (the rate of increase becomes larger).

When it is determined in step ST120 that the predetermined speed is reached, it is determined that the startup is completed, and the process proceeds to step ST124.
The predetermined speed is, for example, a speed corresponding to a rotational speed slightly lower than the target rotational speed.
The predetermined speed is, for example, a speed slightly higher than the lower limit of the range in which the sensorless control is possible.

In step ST124, the startup mode is changed to the normal operation mode.
The process in the normal operation mode is as described above.

The activation process described with reference to FIG. 8 above can be performed by an arithmetic unit having a relatively low processing capacity. That is, in order to perform the above processing, the control device 100, particularly the operation control unit 102 and the inverter control unit 110 do not need to include a high-performance arithmetic device.
Therefore, the electric motor drive device of the present invention can reliably perform the start-up process with a relatively simple configuration.

In the above example, the phase currents Iu, Iv, and Iw are restored from the DC current Idc on the input side of the inverter 30, but the output lines 331, 332, 333 of the inverter 30 are provided with current detectors. The detector may be configured to detect the phase current, and in that case, the phase current detected by the detector may be used instead of the current restored by the current restoration unit 112.
In that case, instead of the bus current detected by the bus current detector 85, it is determined whether an excessive current is flowing through the motor based on the phase current detected by the above detector. Good as a matter.

Embodiment 2.
In the first embodiment, the change condition of the speed command value ω ^* and the parameter K for obtaining the voltage command value V ^* from the speed command value ω ^* are stored as the start condition, and when the start fails. The value of the parameter K is to be adjusted. On the other hand, in the second embodiment, the change pattern of the speed command value ω ^* can be adjusted, and the change pattern is adjusted when starting fails.

When the change pattern is represented by a function, the change pattern can be adjusted by adjusting the parameters that define the above function. When the change pattern is represented by an LUT, adjustment of the change pattern can be realized by adjusting the data of the LUT. Such processing can also be performed by the operation control unit 102.

Embodiment 3.
In the first embodiment, as the activation condition, and stores a speed command value omega ^* change pattern, the parameter K for obtaining a voltage command value V ^* from the speed command value omega ^*. On the other hand, in the third embodiment, the change pattern of the speed command value ω ^{* and} the change pattern of the voltage command value V ^* are stored as the start condition.
Changing pattern of the voltage command value V ^*, to the time elapsed from the start of activation, prescribes how to raise the voltage command value V ^*. As described in the first embodiment, the voltage command value V ^* is a value representing the amplitude of the drive voltage in the dq coordinate system, and the inverter 30 is a phase generated based on the voltage command value V ^*. It is controlled to output a phase voltage that matches the voltage command values Vu ^* , Vv ^* , Vw ^* .

Changing pattern of the voltage command value V ^*, as shown in FIG. 6 (a) and (b), the voltage command value V ^* with respect to the speed command value omega ^*, maintaining the relationship of the above formula (1) , The speed command value ω ^* may be linearly increased from 0. For example, the speed command value ω ^* may be linearly increased without maintaining the relationship of the above equation (1). On the other hand, the voltage command value V ^* may be set to rise along a polygonal line or in a curved line.

For example, in a low range in which the speed command value ω ^* is close to zero, the width of the PWM pulse for voltage generation becomes narrow, and the arm short circuit prevention time (dead time) of the inverter and the switching delay time cause the electric motor 7 to operate substantially. The drive voltage may be lower than a value proportional to the frequency of the output voltage of the inverter 30 (which matches the speed command value ω ^* ). In consideration of that point, the voltage command value V ^* may be set to a value larger than a value proportional to the speed command value ω ^* .

Examples of such voltage command values are shown in FIGS. 9(a) and 9(b).
In the example shown in FIGS. 9A and 9B, the voltage command value V ^* has certain values V0(Y) and V0(Δ) that are greater than zero at the elapsed time of zero.
That is, the voltage command value V ^* (Y) shown in FIG. 9(a) has a certain value V0(Y) larger than zero at the elapsed time zero, changes along the curve with the passage of time, and K(Y )×ω ^* is asymptotic to the straight line.
Similarly, the voltage command value V ^* (Δ) shown in FIG. 9(b) has a certain value V0(Δ) larger than zero at the elapsed time zero, changes along the curve with the passage of time, and K( Asymptotically approaches a straight line represented by Δ)×ω ^* .

As described above, when the start condition includes the change pattern of the speed command value ω ^{* and} the change pattern of the voltage command value V ^* , the change pattern of the speed command value ω ^* is changed in the adjustment of the start condition. At best, may be configured to change the voltage command value V ^* of the change pattern, it may be changed both the speed command value omega ^* change pattern and the voltage command value V ^* of the change pattern.
Such processing can also be performed by the operation control unit 102.

In the first to third embodiments described above, the value V ^* representing the amplitude of the driving voltage in the dq coordinate system is used as the command value of the driving voltage, and the inverter control unit 110 determines the voltage command value V. The phase voltage command values Vu ^* , Vv ^* , Vw ^* are generated based on ^* , but the present invention is not limited to this, and command values of other drive voltages may be used. In that case, in the first and second embodiments, the starting condition memory 101 stores the parameter K for calculating the other voltage command value, and in the third embodiment, the change pattern of the other voltage command value. May be stored in the activation condition memory 101.

Further, in the above-described first to third embodiments, the starting condition is selected according to the connection state, but not only the connection state, but also the environmental condition, for example, the difference between the room temperature and the set temperature, the operation mode (whether heating or not). It is also possible to use different starting conditions depending on whether it is cooling or the like. Even in such a case, by applying the present invention, the starting can be appropriately performed.

Although the case where the connection switching is performed between the Y connection and the Δ connection has been described above, the present invention is also applicable when the connection switching is performed in another mode, for example, when the series connection and the parallel connection are performed. The invention can be applied.

As described above, according to the present invention, since the starting condition is changed according to the wire connection state of the electric motor, the start can be appropriately performed regardless of the wire connection state.

Further, according to the present invention, since the starting condition is determined according to the connection state before starting the electric motor, it is possible to reduce the possibility that the electric motor current becomes excessive or the step-out occurs at the time of starting. The processing can be performed in a short time.

Further, according to the present invention, when the startup process is not successful, the startup condition is adjusted and the startup is performed again. Therefore, when the load is larger than expected or the load is smaller than expected. Even in this case, it is possible to minimize the delay in the completion of startup.

In addition, by updating the activation conditions that have been used until then with the adjusted activation conditions, it is possible to increase the probability that the activation will succeed with the activation condition (default value) that is selected first in the subsequent activation processing. it can. Therefore, the time required for activation can be further shortened.

2 motor drive device, 4 AC power supply, 7 motor, 8 reactor, 10 rectifier circuit, 20 capacitor, 30 inverter, 60 connection switching device, 85 bus current detection unit, 87 bus voltage detection unit, 100 control device, 101 start condition memory , 102 operation control unit, 110 inverter control unit, 111 current command generation unit, 112 current restoration unit, 113 three-phase/two-phase conversion unit, 114 position/speed estimation unit, 115 speed control unit, 116 voltage command calculation unit, 117 Two-phase/three-phase converter, 118 PWM generator, 121, 122 switch group, 131 carrier generator, 132 carrier comparator, 900 refrigeration cycle, 902 four-way valve, 904 compressor, 906 indoor heat exchanger, 908 expansion valve , 910 Outdoor heat exchanger.

Claims (6)

A connection switching device that switches the connection state of the winding of the electric motor to star connection or delta connection,
An inverter that applies an alternating voltage whose frequency and voltage are variable to the electric motor to control the speed of the electric motor,
Having a start condition memory for storing a plurality of start conditions, having a control device for controlling the inverter and the connection switching device,
The control device is
Among the plurality of starting conditions stored in the starting condition memory, a starting condition corresponding to the wire connection state of the electric motor is selected, and the inverter is controlled using the selected starting condition, whereby the electric motor is Start with the selected start condition,
Each of the plurality of starting conditions, the change pattern of the speed command value for controlling the speed of the electric motor, the relationship between the speed command value and the voltage command value for controlling the amplitude of the drive voltage of the electric motor. Including specified parameters,
The change pattern of the speed command value is to gradually increase the speed command value with the passage of time from the start of activation.
The parameter is to increase the voltage command value as the speed command value increases,
When starting the electric motor,
Based on the change pattern of the speed command value included in the selected start condition, while gradually increasing the speed command value,
Gradually increasing the voltage command value based on the speed command value and the parameter,
Among the plurality of start conditions, compared to the activation condition corresponding to the delta connection, activation condition corresponding to the star connection is Ru der those that increase the voltage command value more abruptly
Electric motive drive. A connection switching device that switches the connection state of the winding of the electric motor to star connection or delta connection,
An inverter that applies an alternating voltage whose frequency and voltage are variable to the electric motor to control the speed of the electric motor,
Having a start condition memory for storing a plurality of start conditions, having a control device for controlling the inverter and the connection switching device,
The control device is
Among the plurality of starting conditions stored in the starting condition memory, a starting condition corresponding to the wire connection state of the electric motor is selected, and the inverter is controlled using the selected starting condition, whereby the electric motor is Start with the selected start condition,
Each of the plurality of starting conditions includes a change pattern of a speed command value for controlling the speed of the electric motor and a change pattern of a voltage command value for controlling the amplitude of the drive voltage of the electric motor,
The change pattern of the speed command value is to gradually increase the speed command value with the passage of time from the start of activation.
The change pattern of the voltage command value is to gradually increase the voltage command value with the passage of time from the start of activation,
When starting the electric motor,
Based on the change pattern of the speed command value included in the selected start condition, while gradually increasing the speed command value,
Based on the change pattern of the voltage command value included in the selected starting condition, gradually increase the voltage command value,
Of the plurality of starting conditions, the starting condition corresponding to the star connection causes the voltage command value to rise more rapidly than the starting condition corresponding to the delta connection.
Electric motive drive. A connection switching device that switches the connection state of the winding of the electric motor to star connection or delta connection,
An inverter that applies an alternating voltage whose frequency and voltage are variable to the electric motor to control the speed of the electric motor,
Having a start condition memory for storing a plurality of start conditions, having a control device for controlling the inverter and the connection switching device,
The control device is
Among the plurality of starting conditions stored in the starting condition memory, a starting condition corresponding to the wire connection state of the electric motor is selected, and the inverter is controlled using the selected starting condition, whereby the electric motor is Start with the selected start condition,
When it is determined that the current of the electric motor is excessive during start-up and whether the electric motor is out of step, and it is determined that the electric current of the electric motor is excessive, or the electric motor is disconnected. when it is determined that there is a tone, stop the activation, on changing the selected start condition, intends row activation again
Electric motive drive. When it is determined that the electric current of the electric motor is excessive, the selected starting condition is changed so that the electric motor current at the time of starting becomes smaller, and the electric motor is restarted using the changed starting condition. The electric motor drive device according to claim 3 . When it is determined that the electric motor is out of step, the selected starting condition is changed so that the electric motor current at the time of starting becomes larger, and the electric motor is restarted using the changed starting condition. The electric motor drive device according to claim 3 or 4 . The electric motor drive device according to claim 4 or 5 , wherein when the selected starting condition is changed, the selected starting condition among the plurality of starting conditions stored in the starting condition memory is updated.

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