CN107947667B

CN107947667B - Rotation position estimation device for synchronous motor, air conditioner, and washing machine

Info

Publication number: CN107947667B
Application number: CN201710790477.8A
Authority: CN
Inventors: 前川佐理
Original assignee: Toshiba Corp
Current assignee: Toshiba Corp
Priority date: 2016-09-06
Filing date: 2017-09-05
Publication date: 2020-03-24
Anticipated expiration: 2037-09-05
Also published as: CN107947667A; KR101934647B1; JP6514164B2; JP2018042336A; KR20180027348A

Abstract

The invention relates to a rotation position estimating device of a synchronous motor, an air conditioner and a washing machine. A rotational position estimation device for a synchronous motor is provided with: a current detection unit for detecting a phase current of the synchronous motor; a PWM generating unit for generating a three-phase PWM signal pattern so as to follow the rotational position of the synchronous motor; a detection timing signal generation unit that generates a detection timing signal based on a carrier of the PWM signal; a current change amount detection unit that obtains a change amount of the phase current detected by the current detection unit based on the detection timing signal; and a rotational position estimating unit that estimates a rotational position of the synchronous motor based on the amount of change in the phase current. The PWM generating section generates a three-phase PWM signal pattern so that the current change amount detecting section can detect the amount of phase current change corresponding to the 3 kinds of voltage vector periods, based on the fixed 6-point detection timing signal generated by the detection timing signal generating section in 1 cycle of the carrier wave.

Description

Rotation position estimation device for synchronous motor, air conditioner, and washing machine

Technical Field

Embodiments of the present invention relate to a device for estimating a rotational position of a synchronous motor, and an air conditioner and a washing machine including the same.

Background

Conventionally, as a method of estimating the rotational position of a synchronous motor, for example, the following methods are widely used: an induced voltage proportional to the speed of the synchronous motor is calculated from the voltage and current input to the synchronous motor, and estimation is performed based on the induced voltage. However, this method has the following problems: although sufficient accuracy can be obtained in a region where the synchronous motor operates at high speed, accurate estimation cannot be performed in a region where the synchronous motor operates at extremely low speed where the induced voltage information is reduced.

Further, the following methods are proposed: an alternating current signal for sensing irrespective of the driving frequency is applied to the synchronous motor, and the rotational position is inferred from the relation of the voltage and the current. However, when the frequency of the ac signal is about several 100Hz to several kHz which is equal to or lower than the carrier frequency, the current ripple frequency of the motor enters the audible range of a human, and thus the driving noise of the motor deteriorates. In contrast, japanese patent No. 3454212 proposes the following method: the pulse width of each phase PWM signal is controlled for each half cycle of the carrier cycle, thereby generating a high frequency current having the same frequency as the carrier frequency, suppressing noise, and estimating the rotational position.

Further, in japanese patent No. 4670045, the following method is proposed: three-phase PWM signals are generated by using 3 kinds of triangular carriers whose phases are shifted by 120 degrees from each other with reference to 1 cycle of the carrier, thereby equivalently generating a high-frequency current having the same frequency as the carrier frequency as in patent document 1, and estimating the rotational position by differentiating the current.

In the method of estimating the rotational position using the high-frequency current of the high-frequency component and the carrier frequency component included in the inverter output, although the high-frequency current flowing in accordance with the high-frequency voltage interferes with the voltage of the fundamental wave component output from the inverter, the carrier frequency is sufficiently high with respect to the rotational speed of the synchronous motor, and therefore does not interfere with the torque. This method also has an advantage that it is not necessary to add a low-pass filter or the like to the current feedback value in the rotational position estimation, and the responsiveness as a control system becomes good.

However, this method is not generally applicable to various systems because the magnitude of the high-frequency current corresponding to the carrier frequency depends on the parameters of the synchronous motor from the viewpoint of practical use, and the influence thereof differs depending on the synchronous motor used. Specifically, in a motor having a small saliency or a large inductance, there is a problem that a current ripple component of a carrier frequency is small and an SN ratio estimated as a rotational position is lowered. Further, when the pulse width of the PWM signal is controlled in accordance with the half cycle of the carrier wave, there is a problem that noise cannot be sufficiently suppressed under the condition that the carrier frequency is low.

Disclosure of Invention

Therefore, a rotational position estimating device for a synchronous motor capable of estimating a rotational position at low cost while suppressing driving noise, and an air conditioner and a washing machine provided with the same are provided.

A rotational position estimation device for a synchronous motor according to an embodiment includes: a current detection unit for detecting a phase current of the synchronous motor; a PWM generating unit that generates a three-phase PWM signal pattern so as to follow a rotational position of the synchronous motor; a detection timing signal generation unit that generates a detection timing signal based on the carrier of the PWM signal; a current change amount detection unit that obtains a change amount of the phase current detected by the current detection unit based on the detection timing signal; and a rotational position estimating unit that estimates a rotational position of the synchronous motor based on an amount of change in the phase current.

The PWM generating unit generates a three-phase PWM signal pattern so that the current variation detecting unit can detect the amount of phase current variation corresponding to 3 voltage vector periods, based on the fixed 6-point detection timing signals generated by the detection timing signal generating unit in 1 cycle of the carrier.

Drawings

Fig. 1 is a functional block diagram showing a configuration of a motor control device according to embodiment 1.

Fig. 2 is a diagram showing the on state of the switching element constituting the inverter circuit by a space vector.

Fig. 3 is a diagram showing a relationship between the amount of change in current and the rotational position of each phase.

Fig. 4 is a functional block diagram showing a configuration of the rotational position estimating unit.

Fig. 5 is a diagram showing PWM carrier waves and pulse signals of the respective phases and current detection timing.

Fig. 6 is a diagram showing PWM carrier waves and pulse signals of the respective phases and current detection timing in embodiment 2.

Fig. 7 is a diagram showing a case where the motor control device according to embodiment 3 is applied to a compressor motor of an air conditioner.

Fig. 8 is a diagram illustrating a case where the motor control device is applied to a drum motor and/or a compressor motor of a washing and drying machine according to embodiment 4.

Fig. 9 is a diagram showing a configuration of a heat pump used in the washing and drying machine.

Detailed Description

(embodiment 1)

Hereinafter, embodiment 1 will be described with reference to fig. 1 to 5. Fig. 1 is a functional block diagram showing a configuration of a motor control device. The dc power supply 1 is a power source for driving a permanent magnet synchronous motor (hereinafter, simply referred to as a motor) 2 having a rotor provided with a permanent magnet. The dc power supply 1 may convert ac power into dc power. The inverter circuit 3 is configured by three-phase bridging of 6 switching elements, for example, N-channel MOSFETs 4U +, 4Y +, 4W +, 4U-, 4Y-, and 4W-, and generates a voltage for driving the motor 2 based on 6 switching signals for three phases generated by a PWM generating unit 5 described later.

The voltage detection unit 6 detects the voltage VDC of the dc power supply 1. The current detection unit 7 is connected between the negative power supply line of the inverter circuit 3 and the negative terminal of the dc power supply 1. The current detection unit 7 is generally configured by a current sensor using a shunt resistor, a hall CT, or the like, and a signal processing circuit, and detects the dc current Idc flowing through the motor 2.

The current change amount detector 8 detects the dc current Idc 6 times based on detection timing signals t1 to t6 input from a detection timing signal generator 9 described later, and calculates the difference values between the detection values 2 times as change amounts dIu _ V1, dIv _ V3, and dIw _ V5. The rotational position calculation unit 10 calculates the detected rotational position value θ c of the motor 2 from the variations dIu _ V1, dIv _ V3, and dIw _ V5. The three-phase voltage command value generation unit 11 generates a voltage amplitude command value Vamp and a voltage phase command value, which are command values

Three-phase voltage command values Vu, Vv, Vw are generated.

The load generation unit 12 calculates modulation commands Du, Dv, and Dw for the respective phases by dividing the three-phase voltage command values Vu, Vv, and Vw by the dc voltage VDC. PWM generating unit 5 compares three-phase modulation commands Du, Dv, and Dw with the PWM carrier wave and the carrier wave to generate PWM signal pulses for each phase. The pulse of each phase is added with dead time to generate switching signals U +, U-, V +, V-, W +, and W-, which are output to the three-phase upper and lower N-channel MOSFETs 4, respectively.

In the above configuration, the portion other than the motor 2 and the inverter circuit 3 constitutes the rotational position detecting device 13. The portion of the rotational position detecting device 13 after the inverter circuit 3 is added constitutes a motor control device 14.

Here, the principle of the rotational position detection method of the present embodiment will be explained. (1) The formula represents the three-phase inductance of the synchronous motor having saliency.

[ equation 1 ]

As shown in expression (1), the inductances Lu, Lv, Lw of the respective phases change in accordance with the rotational position θ. By utilizing the dependence of the inductance on the rotational position, the rotational position can be estimated even under the condition that the speed of the motor is near zero.

Fig. 2 is a diagram showing the on states of the switching elements constituting the inverter circuit by a method called space vector. For example, (1, 0) indicates a state in which the switching element on the upper side of the U-phase is turned on and the switching elements on the upper sides of the V-phase and W-phase are turned off, and the voltage vector has 8 patterns of V0 to V7.

Here, expression (2) represents an equation of inter-phase voltage of the motor when the voltage vector V1(1, 0) is applied. The UV line voltage, VW line voltage, and WU line voltage are shown from above.

[ equation 2 ]

Where Vdc is a direct-current voltage, Eu, Ev, and Ew are induced voltages of respective phases, R is a winding resistance, and Iu _ V1, Iv _ V1, and Iw _ V1 are three-phase current values when voltage vector V1 is applied. Here, when the motor rotation speed is extremely low and the voltage drop due to the winding resistance and the induced voltage are extremely small compared to the dc voltage Vdc, the current differential value of each phase in equation (2) can be approximated to equation (4) by equation (3).

[ equation 3 ]

Here, when the inductance values L0, L1 and the dc voltage Vdc are replaced with a as in expression (5), expression (4) can be modified to expression (6).

[ equation 4 ]

Similarly, a V-phase current differential value dIv _ V3/dt during application of the voltage vector V3 and a W-phase current differential value dIw _ V5/dt during application of the voltage vector V5 are expressed by expression (7). The current differential values of U, V, W phases in the process of applying the voltage vectors V1, V3, and V5 are multiplied by the differential time dt to obtain a current change amount, and the current change amount is summarized as expression (8).

[ equation 5 ]

These 3 current change amounts are ac signals having a dc offset amount of 2dt/a and changing with a phase difference of 2 pi/3 according to the rotational position 2 θ at an amplitude of L1dt/(AL0) as shown in fig. 3. These are ac signals, but the offset 2dt/a and the amplitude L1dt/(AL0) include parameters of the motor. Therefore, in order to perform a simple rotational position calculation without using a parameter, a zero-cross signal of the difference values of the 3 signals is generated, and the estimated rotational position θ c is obtained based on the zero-cross signal. (8) The rotational positions at which the amounts of current change of the three phases shown in the formula intersect are as shown in formula (9).

[ equation 6 ]

The reason why each intersection position represents 2 kinds of rotational positions θ is that the amount of change in current in equation (8) changes by 2 θ.

Further, based on these intersection positions, the phases can be divided into 6 segments according to the magnitude relationship of the phases.

[ equation 7 ]

Here, if the resolution of the rotational position is set to "12", the rotational position in the above-described segment can be represented as in () as an angle obtained by averaging the intersection angles of the amounts of change in the respective phase currents.

Next, an algorithm for determining which of the 2 rotational positions is selected for each segment will be described. When the motor rotates, the above section changes from 1 to 6 again after changing from 1 to 6 in 1 cycle of the electrical angle. Therefore, the first segments 1 to 6 are set as the 1 st cycle of the segment, and the next 2 nd cycle is considered as another segment. That is, as described below, the number of segments is set to "12" and the rotational positions are assigned to the segments. This is easily achieved by using a counter whose counting ends after the section changes from 1 to 6.

[ number 8 ]

As another implementation method, a method may be used in which the intersection angle of the current change amount of each phase shown in equation (9) is used, and the rotational position is updated to the intersection angle when the current change amounts intersect.

In the case of using these methods, it is necessary to determine which position is correct from the amount of change in current of each phase, because the counter starts counting before the motor rotates, that is, before the initial rotation position. For example, when the magnitude relation of the detected current variation amount is dIv _ V3 > dIu _ V1 > dIw _ V5, the corresponding segment is 1 or 7, and the rotation position is 75 ° or-105 °.

In order to determine which of the above-described states is in the stopped state before the motor is driven, an algorithm for identifying the initial position is required. In this regard, the determination is made by a conventional known technique, that is, a method using the characteristic of magnetic saturation. The known techniques include, for example, the following documents.

Journal of electric society D (journal of industry sector) Vol.125(2005), No.3 "method for estimating initial rotational position of surface magnet synchronous motor using pulse voltage", Shanben Xiu, Shankuan Longyu

With the above algorithm, the rotational position of the synchronous motor can be estimated from the detected amount of current change.

Fig. 4 shows the configuration of the rotational position calculating unit 10. The comparator 21u compares the inputted current change amounts dIu _ V1 and dIv _ V3. The comparator 21V compares the inputted current change amounts dIv _ V3 and dIw _ V5. The comparator 21w compares the inputted current variation dIw _ V5 with dIu _ V1. The output signals of the comparators 21u to 21w are input to the 2 θ c calculation unit 22. The 2 θ c calculation unit 22 calculates the rotational position 2 θ c based on the 6 segments based on the combination of the binary levels of the signals input from the comparator 21, and outputs the calculated position to the counter calculation unit 23. As described above, the counter arithmetic unit 23 is a counter in which counting is completed after the sector changes from 1 to 6, and outputs the rotational position θ c corresponding to the "12" sector.

Next, a method of detecting the amount of current change in the application of the 3 types of voltage vectors represented by the formula (8) will be described. It is necessary to detect the U-phase current during application of the voltage vector V1, the V-phase current during application of the V3, and the W-phase current during application of the V5, respectively. In the present embodiment, as shown in fig. 5, 3 types of carrier waves having different waveforms are used for generating the PWM signals of the respective phases. For example, the U phase is a triangular carrier, the V phase is an inverted sawtooth carrier, and the W phase is a sawtooth carrier. When a PWM signal is generated using such a carrier, when a U-phase triangular carrier is used as a reference, the following are:

u-phase PWM pulse: generated to both sides with the valley of the triangular wave as a reference

V-phase PWM pulse: generated to the left side with respect to the mountain of the triangular wave

W-phase PWM pulse: the triangular wave is generated to the right with respect to the mountain.

Then, as shown in fig. 5, detection timing signals t1 to t6 of the current are given 6 times.

Signals T1 and T2 for detecting the amount of current change dIu _ V1 of the U-phase from the dc current Idc, with the time shifted by Δ T/2 before and after the valley of the triangular wave as a reference being the reference

Signals T3 and T4 for detecting the amount of current change dIv _ V3 of the V phase from the dc current Idc, with the time Δ T before the peak of the triangular wave and the time at the peak of the triangular wave being taken as references

Signals T5 and T6 for detecting the amount of current change dIw _ V5 of the W phase from the dc current Idc are based on the time of the peak of the triangular wave and the time delayed by Δ T from the peak of the triangular wave.

In addition, since noise may have a large influence on the current detection value even immediately after the pulse is actually generated, the detection timing may be shifted by about several μ s from the reference value. The detection timings of t1 to t6 are always constant, i.e., fixed timings at 6 points, regardless of the PWM signal input to the inverter circuit.

In order to set the current values detected at these fixed timings to the U-phase current applied with the vector V1, the V-phase current applied with the vector V3, and the W-phase current applied with the vector V5, it is necessary to set the following constant limits to the pulse width of each phase.

< dIu _ V1 capable of detecting the condition >

U phase load Du > Δ T

The V phase load Dv is less than 50% -delta T/2

W phase load Dw < 50% -delta T/2

< dIv _ V3 capable of detecting the condition >

U phase loading Du < 100% -2. delta. T

The V-phase load Dv > Δ T

W phase load Dw < 100% - Δ T

< dIw _ V5 capable of detecting the condition >

U phase loading Du < 100% -2. delta. T

The V phase load Dv < 100% -delta T

W phase load Dw > Δ T

Therefore, in the case of estimating the rotational position as in the present embodiment, the modulation degree that can be output by the inverter circuit 3 is limited, but in general, the modulation degree is low when the motor is stopped and at low speed, and therefore this is difficult to cause a problem.

As described above, according to the present embodiment, the detection timing signal generator 9 generates the detection timing signals t1 to t6 based on the carrier wave of the PWM signal, and the current change amount detector 8 obtains the amount of change in the phase current detected by the current detector 7 based on the detection timing signals t1 to t 6. The rotational position calculation unit 10 estimates the rotational position of the motor 2 based on the amount of change in the phase current.

Then, the PWM generator 5 generates a three-phase PWM signal pattern based on the fixed 6-point detection timing signals t1 to t6 in 1 cycle of the PWM carrier so that the current change amount detector 8 can detect the phase current change amounts dIu _ V1, dIv _ V3, and dIw _ V5 corresponding to the 3 voltage vector periods V1, V3, and V5.

Specifically, the PWM generator 5 increases and decreases the load Du in both the delay side and the advance side with respect to an arbitrary phase of the PWM carrier period in the U phase of the three-phase PWM signal, increases and decreases the load Dv in one of the delay side and the advance side with respect to the arbitrary phase in the V phase, and increases and decreases the load Dw in the opposite direction with respect to the arbitrary phase in the W phase. Thus, the motor 2 can be stopped or the sensorless drive in the low speed region can be performed by using an inexpensive arithmetic unit based on only a simple algorithm based on the magnitude relation of the detected current change amount without using an expensive arithmetic unit having arithmetic capability.

Further, since the PWM generating unit 5 sets the reference for generating the PWM pulse of each phase based on the phase at which the amplitude of the carrier wave becomes maximum or minimum, the setting of the reference is simple. The PWM generating unit 5 uses a triangular wave as a carrier wave for the U phase, a sawtooth wave having a maximum amplitude and a maximum or minimum amplitude of the triangular wave in the V phase, and a sawtooth wave having an opposite phase to the sawtooth wave in the W phase. In this case, the reference for each phase is set based on the phase in which the maximum value or the minimum value of the amplitude of each carrier completely matches. This makes it possible to easily set the extension direction of the PWM pulse for each phase.

(embodiment 2)

Hereinafter, the same portions as those in embodiment 1 are denoted by the same reference numerals, and the description thereof is omitted, and different portions are described. In embodiment 2, the PWM carrier used for each phase is set as shown in fig. 6. The waveforms of the carrier waves used for the respective phases are the same, but in embodiment 2, the valley of the U-phase triangular wave is made to coincide with the zero point of the V, W-phase sawtooth wave.

In embodiment 2, the pattern of the voltage vector is made different as follows with respect to the amount of current change necessary for estimating the rotational position.

Change amount of W-phase current when voltage vector V2 is applied: dIw _ V2

U-phase current change amount when voltage vector V4 is applied: dIu _ V4

V-phase current change amount when voltage vector V6 is applied: dIv _ V6.

According to embodiment 2 as described above, the same effects as those of embodiment 1 can be obtained.

(embodiment 3)

Fig. 7 shows embodiment 3, in which the motor control device according to

embodiment

1 or 2 is applied to a compressor motor of an air conditioner. The compressor 32 constituting the heat pump system 31 is configured such that a compression unit 33 and a motor 34 are housed in the same iron-made closed container 35, and a rotor shaft of the motor 34 is coupled to the compression unit 33. The compressor 32, the four-way valve 36, the indoor-side heat exchanger 37, the pressure reducer 38, and the outdoor-side heat exchanger 39 are connected by pipes as heat transfer medium flow paths to form a closed loop. The compressor 32 is, for example, a rotary compressor, and the motor 34 is, for example, a three-phase ipm (interior Permanent magnet) motor. Further, the motor 34 is a brushless DC motor. The air conditioner 30 is configured to include the heat pump system 31.

During heating, the four-way valve 36 is in a state shown by solid lines, and the high-temperature refrigerant compressed by the compression section 33 of the compressor 32 is supplied from the four-way valve 36 to the indoor-side heat exchanger 37, condensed, decompressed by the decompression device 38, turned into a low temperature, flows to the outdoor-side heat exchanger 39, evaporated there, and returned to the compressor 32. On the other hand, during cooling, the four-way valve 36 is switched to the state shown by the broken line. Therefore, the high-temperature refrigerant compressed by the compression unit 33 of the compressor 32 is supplied from the four-way valve 6 to the outdoor heat exchanger 39, condensed, decompressed by the decompression device 8, turned into a low temperature, flows into the indoor heat exchanger 37, evaporated there, and returned to the compressor 32. The

fans

40 and 41 blow air to the indoor and

outdoor heat exchangers

37 and 39, respectively, and the heat exchange between the

heat exchangers

37 and 39 and the indoor air and the outdoor air is performed efficiently by the blown air. The motor 34 is driven and controlled by the motor control devices according to embodiments 1 to 3.

According to embodiment 3 configured as described above, the motor control device of the embodiment controls the driving of the motor 34 of the compressor 32 constituting the heat pump system 31 in the air-conditioning apparatus 30, thereby improving the operation efficiency of the air-conditioning apparatus 30.

(embodiment 4)

The 4 th embodiment shown in fig. 8 and 9 shows a case where the motor control device is applied to a drum motor and/or a compressor motor of a washing and drying machine. Fig. 8 is a vertical sectional side view schematically showing an internal structure of drum type washing and drying machine 51. The outer casing 52 forming the outer casing of the drum type washing and drying machine 51 has a laundry entrance 53 opened in a circular shape in the front, and the laundry entrance 53 is opened and closed by a door 54. A bottomed cylindrical water tank 55 having a closed back surface is disposed inside the outer box 52, and a stator of the motor 50 is fixed to a central portion of the back surface of the water tank 55 by screwing. A rear end portion of the rotating shaft 56 of the motor 50 and an end portion on the right side in fig. 8 are fixed to a shaft mounting portion of a rotor of the motor 50, and a front end portion and an end portion on the left side in fig. 8 protrude into the water tank 55.

A bottomed cylindrical drum 57 having a closed back surface is fixed to a distal end portion of the rotary shaft 56 coaxially with the water tank 55, and the drum 57 is rotated integrally with the rotor and the rotary shaft 56 by driving of the motor 50. Further, the drum 57 is provided with a plurality of circulation holes 58 through which air and water can flow, and a plurality of baffles 59 for catching and scattering laundry in the drum 57. A water supply valve 60 is connected to the water tank 55, and when the water supply valve 60 is opened, water is supplied into the water tank 55. A drain pipe 62 having a drain valve 61 is connected to the water tank 55, and when the drain valve 61 is opened, the water in the water tank 55 is discharged.

A ventilation duct 63 extending in the front-rear direction is provided below the water tank 55. The ventilation duct 63 has a front end connected to the inside of the water tank 55 via a front duct 64, and a rear end connected to the inside of the water tank 55 via a rear duct 65. An air blowing fan 66 is provided at the rear end of the ventilation duct 63, and air in the water tub 55 is blown into the ventilation duct 63 from the front duct 64 and returned into the water tub 55 through the rear duct 65 as indicated by arrows by the air blowing action of the air blowing fan 66.

An evaporator 67 is disposed on the front end side and a condenser 68 is disposed on the rear end side in the ventilation duct 63. As shown in fig. 9, the evaporator 67 and the condenser 68 constitute a heat pump 71 together with a compressor 69 and a throttle valve 70, and the air flowing through the ventilation duct 63 is dehumidified by the evaporator 67, heated by the condenser 68, and circulated into the water tank 55. The throttle valve 70 is formed of an expansion valve and has an opening degree adjusting function.

An operation panel 72 is provided on the front surface of the outer box 52 above the door 54, and a plurality of operation switches, not shown, for setting an operation flow and the like are provided on the operation panel 72. The operation panel 72 is connected to a control circuit unit (not shown) configured mainly of a microcomputer and controlling the overall operation of the drum-type washing and drying machine 51, and the control circuit unit controls the driving of the motor 50, the water supply valve 60, the drain valve 61, the compressor 69, the throttle valve 70, and the like and executes various operation flows in accordance with the contents set via the operation panel 72. The motor 50 and/or the compressor motor constituting the compressor 69 are/is driven and controlled by the motor control device according to

embodiment

1 or 2.

According to embodiment 4 configured as described above, the motor control device of the embodiment controls the driving of the drum rotation motor 50 and/or the motor of the compressor 69 constituting the heat pump system 71 in the washing and drying machine 51, thereby improving the operation efficiency of the washing and drying machine 51.

(other embodiments)

In order to generate three-phase PWM signals as in the respective embodiments, the use of 3 types of carriers is not limited, and a method of changing the load setting timing of one type of carrier, the comparative polarity of pulse generation, or the like may be used, using a phase shift function, or the like.

The current change amount detection unit 8 may set the timing of detecting the three-phase currents in the carrier cycle based on an arbitrary phase of the carrier within a range in which the three-phase currents can be detected, without necessarily setting the phase in which the level of the carrier shows the minimum value or the maximum value as a reference.

The timing of detecting the current does not need to coincide with the period of the PWM carrier, and may be detected, for example, at a period 2 times or 4 times the period of the carrier. Therefore, the current detection timing signal input to the current change amount detection unit 8 does not need to be a signal obtained from a carrier wave, and may be a signal generated by an independent timer.

The current detection unit may be a shunt resistor or a CT.

The switching element may be a MOSFET, an IGBT, a power transistor, a wide bandgap semiconductor such as SiC or GaN, or the like.

The present invention has been described with reference to several embodiments, which are presented as examples and are not intended to limit the scope of the invention. These new embodiments can be implemented in other various ways, and various omissions, substitutions, and changes can be made without departing from the spirit of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the scope equivalent thereto.

Claims

1. A rotational position estimation device for a synchronous motor includes:

a current detection unit for detecting a phase current of the synchronous motor;

a PWM generating unit that generates a three-phase PWM signal pattern so as to follow a rotational position of the synchronous motor;

a detection timing signal generation unit that generates a detection timing signal based on a carrier of the PWM signal;

a current change amount detection unit that obtains a change amount of the phase current detected by the current detection unit based on the detection timing signal; and

a rotational position estimating unit that estimates a rotational position of the synchronous motor based on a change amount of the phase current,

the PWM generating section generates a three-phase PWM signal pattern so that the current variation detecting section can detect the amount of phase current variation corresponding to 3 voltage vector periods, based on the fixed 6-point detection timing signal generated by the detection timing signal generating section in 1 cycle of the carrier.

2. The rotational position inferring device of a synchronous motor according to claim 1,

the PWM generating unit increases/decreases the ratio of the pulse width to the carrier period in both the delay side and the forward side with respect to an arbitrary phase of the carrier period as a reference for one phase of a three-phase PWM signal,

for the other phase, the ratio of the pulse width to the carrier frequency is increased or decreased in one direction of the delay side and the advance side with reference to an arbitrary phase of the carrier period,

for the remaining one phase, the ratio of the pulse width to the carrier frequency is increased or decreased in a direction opposite to the one direction with reference to an arbitrary phase of the carrier period.

3. The rotational position inferring device of a synchronous motor according to claim 2,

the PWM generating unit sets the reference for each phase based on the phase at which the amplitude of the carrier wave becomes maximum or minimum.

4. The rotational position inferring device of a synchronous motor according to claim 3,

the PWM generating unit uses a triangular wave as a carrier wave for one phase of the three-phase PWM signals,

for the other phase, a sawtooth wave having a maximum amplitude and a maximum or minimum amplitude is used as a carrier wave,

for the remaining one phase, a sawtooth wave which is in an opposite phase to the sawtooth wave is used as a carrier wave,

the reference for each phase is set based on the phase in which the maximum value or the minimum value of the amplitude of each carrier is all matched.

5. An air conditioner is provided with:

a synchronous motor;

an inverter circuit that drives the synchronous motor by converting a direct current into a three-phase alternating current by on-off controlling a plurality of switching elements bridged in three phases in accordance with a predetermined PWM signal pattern; and

the rotational position inferring device according to any one of claims 1 to 4,

the air conditioning operation is performed by the rotational driving force generated by the synchronous motor.

6. A washing machine is provided with:

a synchronous motor;

the rotational position inferring device according to any one of claims 1 to 4,

the washing operation is performed by the rotational driving force generated by the synchronous motor.