JP2016152706A - Motor drive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a synchronous motor drive capable of estimating an input AC current with better accuracy than conventional, with a simple configuration.SOLUTION: In a motor drive MD1, a control section A1 calculates an effective power P consumed by a motor 4, on the basis of three-phase AC currents Iu(t), Iv(t), Iw(t) outputted from an inverter circuit 3, and a DC voltage Vdc outputted from a converter circuit 2. The control section A1 estimates an AC voltage effective value Vac inputted to the converter circuit 2, on the basis of the effective power P thus calculated and the DC voltage Vdc. Furthermore, the control section A1 estimates the power factor cos(θ) of the AC power inputted to the converter circuit 2, on the basis of the effective power P thus calculated and the AC voltage effective value Vac thus estimated. The control section A1 estimates an AC current effective value Iac inputted to the converter circuit 2, by dividing the calculated effective power P by the estimated AC voltage effective value Vac and the estimated power factor cos(θ).SELECTED DRAWING: Figure 1

Description

  The present invention relates to a motor drive device, and is suitably used for, for example, a motor drive device that drives a synchronous motor for a compressor provided in a refrigerator, an air conditioner, or the like.

  In an apparatus such as an air conditioner, an overcurrent breaker for protecting the apparatus is provided at a terminal for connection with a commercial power source. Since overcurrent breaker operation during operation of this type of equipment is problematic in terms of comfort, etc., usually overload suppression such as reducing the compressor speed before the overcurrent breaker operates Control is performed. In order to perform this control, generally, a current transformer (CT: Current Transformer) for detecting an input AC current is required. However, since a current transformer is expensive, a method of performing the above control without using a current transformer has been proposed.

  For example, in a synchronous motor driving device described in Japanese Patent No. 4505932 (Patent Document 1), a shunt resistor for detecting a direct current that has been conventionally provided is used. Specifically, the shunt resistor is provided in the DC wiring between the rectifier and the inverter circuit. In the method of this document, the current flowing through the shunt resistor is integrated, and the input alternating current is estimated from the integration result.

  In order to avoid unnecessary load suppression control, it is desirable to estimate the input AC current as accurately as possible. The technique described in Japanese Patent Application Laid-Open No. 2013-132131 (Patent Document 2) has been previously proposed by the inventor of the present application, and is intended to accurately estimate the input AC current. Specifically, in the method of this document, first, the active power consumed by the synchronous motor is calculated from the three-phase AC current output from the inverter circuit and the DC voltage output from the converter circuit (rectifier circuit). Next, based on the calculated active power, the active power consumed by the motor driving device, the effective value of the input AC voltage of the motor driving device, and the power factor are estimated, and the input AC current is calculated based on these estimation results. The effective value of is calculated.

Japanese Patent No. 4505932 JP 2013-132131 A JP-A-8-19263

  As a result of further study of the technique described in Japanese Patent No. 2013-132131 (Patent Document 2), the inventor of the present case has found that an error occurs when estimating the power factor in the method of Patent Document 2. It was. Specifically, in the method of Patent Document 2, a table representing the relationship between the power consumption (or rotational speed) of the synchronous motor and the power factor is experimentally obtained in advance, and the current power consumption (or rotational speed) of the synchronous motor is obtained. Is applied to this table to estimate the power factor. However, in this case, the magnitude of the power factor can be changed by shifting the effective value of the input AC voltage from the rated value. For this reason, an error occurs in the estimated value of the input AC current finally obtained.

  The present invention has been made in consideration of the above-described problems, and an object of the present invention is to provide a motor drive device that can estimate an input AC current with a simple configuration and with higher accuracy than conventional ones.

  In one aspect, the present invention is a motor driving device that converts AC power into DC power and outputs the converted power, and converts DC power output from the converter circuit into three-phase AC power and outputs the same to a motor. An inverter circuit and a control unit that controls the inverter circuit are provided. The control unit calculates active power consumed by the motor based on the three-phase alternating current output from the inverter circuit and the direct-current voltage output from the converter circuit. The control unit estimates the AC voltage effective value input to the converter circuit based on the calculated active power and DC voltage. Further, the control unit estimates the power factor of the AC power input to the converter circuit based on the calculated active power and the estimated AC voltage effective value. The control unit estimates the AC current effective value input to the converter circuit by dividing the calculated active power by the estimated AC voltage effective value and the estimated power factor. Then, the control unit controls the inverter circuit so that the estimated AC voltage effective value does not exceed the reference value.

  Preferably, the control unit multiplies the provisional estimated value of the power factor corresponding to the calculated active power by a correction coefficient corresponding to the estimated AC voltage effective value, thereby finally determining the power factor of the AC power. Calculate the value.

  More preferably, the control unit is a temporary estimated value of the power factor corresponding to the calculated active power based on the relationship between the active power measured in advance at a predetermined AC voltage effective value and the power factor of the AC power. To decide. The control unit determines the correction coefficient corresponding to the estimated AC voltage effective value based on the relationship between the AC voltage effective value measured in advance at a predetermined motor rotation speed and the power factor of AC power.

  Preferably, the control unit corrects the value of the active power by multiplying the calculated active power by a coefficient based on the heat loss of the inverter circuit, and uses the corrected active power to determine the AC voltage effective value and the AC power. Estimate the power factor and effective value of alternating current.

  In another aspect, the present invention is a motor driving device, which converts AC power into DC power and outputs the converter circuit, and converts DC power output from the converter circuit into three-phase AC power and outputs it to the motor. And an inverter circuit for controlling the inverter circuit. The control unit calculates active power consumed by the motor based on the three-phase alternating current output from the inverter circuit and the direct-current voltage output from the converter circuit. The control unit estimates the AC voltage effective value input to the converter circuit based on the calculated active power and DC voltage. Furthermore, the power factor of the AC power input to the converter circuit is estimated based on the rotational speed of the motor and the estimated AC voltage effective value. The control unit estimates the AC current effective value input to the converter circuit by dividing the calculated active power by the estimated AC voltage effective value and the estimated power factor. Then, the control unit controls the inverter circuit so that the estimated AC voltage effective value does not exceed the reference value.

  ADVANTAGE OF THE INVENTION According to this invention, the synchronous motor drive device which can estimate an input alternating current with a simple structure and more accurate than before can be provided.

It is a circuit diagram which shows the structure of synchronous motor drive device MD1 which concerns on Embodiment 1 of this invention. FIG. 3 is a circuit diagram illustrating a specific configuration of a converter circuit in the synchronous motor driving device according to each embodiment of the present invention. It is a circuit diagram which shows the structure of microcomputer A1 which concerns on Embodiment 1 of this invention. It is a schematic diagram which shows the waveform of the three-phase alternating current which an inverter circuit outputs in the synchronous motor drive device which concerns on each embodiment of this invention. It is a figure which shows the relationship between the active electric power of the synchronous motor in each embodiment of this invention, and a fall DC voltage. It is a graph which shows the relationship between total effective electric power P_md1 and power factor cos ((theta)) when the voltage effective value Vac of the commercial alternating current power supply 1 is made into a parameter. It is a graph which shows the relationship between voltage effective value Vac and power factor cos ((theta)) when using total effective electric power P_md1 as a parameter. It is a figure which shows an example of the table showing the relationship between total effective electric power P_md1 of synchronous motor drive device MD1, and a power factor. It is a figure which shows an example of the table showing the relationship between the voltage effective value Vac and the correction factor of a power factor. It is a flowchart which shows the control procedure of microcomputer A1 of FIG. It is a figure which shows step S120 of FIG. 10 in detail. It is a circuit block diagram which shows the structure of the synchronous motor drive device MD11 which concerns on Embodiment 2 of this invention. It is a circuit diagram which shows the structure of microcomputer A21 which concerns on Embodiment 2 of this invention. It is a circuit diagram which shows the structure of synchronous motor drive device MD2 which concerns on Embodiment 3 of this invention. It is a circuit diagram which shows the structure of microcomputer A3 which concerns on Embodiment 3 of this invention. FIG. 9 is a circuit diagram showing a configuration of a microcomputer A in which a current detection circuit 5A is incorporated in a synchronous motor driving device according to Embodiment 4 of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the description of the embodiments, when the number, amount, or the like is referred to, the scope of the present invention is not necessarily limited to the number, amount, or the like unless otherwise specified. In the drawings of the embodiments, the same reference numerals and reference numerals represent the same or corresponding parts. Further, in the description of the embodiments, the overlapping description may not be repeated for the portions with the same reference numerals and the like.

<Embodiment 1>
With reference to FIG. 1, the configuration and operation of synchronous motor drive device MD1 according to Embodiment 1 of the present invention will be described.

  The synchronous motor driving device MD1 includes a converter circuit 2, an inverter circuit 3, a current detection resistor (shunt resistor) R1, a resistor Rdc1, a resistor Rdc2, a current detection circuit 5, and a microcomputer A1 as a control unit.

  Converter circuit 2 converts AC power supplied from commercial AC power supply 1 having voltage effective value Vac and current effective value Iac into DC power having DC voltage Vdc, and converts DC voltage Vdc to positive DC line PL1 and negative DC. Output between line PL2.

  A specific example of the converter circuit 2 is shown in FIG. FIG. 2A shows a converter circuit that outputs a maximum DC voltage Vdc of 200 V × √2 from an AC voltage of 200 V, for example, (where √2 represents the square root of 2). The actual value of the DC voltage Vdc is less than 200 V × √2 depending on the current consumption of the synchronous motor. The AC voltage is rectified and smoothed by the diode bridge DB and the capacitor C, and output as a maximum DC voltage Vdc of 200 V × √2.

  FIG. 2B is a converter circuit that outputs a DC voltage Vdc having a maximum effective voltage Vac of, for example, 200 V × √2 from an AC voltage of 100 V. The AC voltage is converted into a DC voltage Vdc boosted up to 200 V × √2 by a voltage doubler circuit composed of a diode bridge DB, a capacitor C1, and a capacitor C2. A converter circuit having a necessary configuration is selected according to the value of the effective voltage value Vac supplied to the synchronous motor drive device MD1.

  Referring to FIG. 1 again, the inverter circuit 3 is a three-phase (U-phase, V-phase, W-phase) inverter circuit connected between the positive DC line PL1 and the negative DC line PL2, and is a U-phase switching circuit. Elements Qu and Qx (U-phase arm), V-phase switching elements Qv and Qy (V-phase arm), and W-phase switching elements Qw and Qz (W-phase arm) are included. The inverter circuit 3 generates a three-phase AC current (U phase, V phase, W phase) from the DC voltage Vdc (that is, converts DC power into three-phase AC power), and synchronizes the generated three-phase AC current. Supply to the motor 4.

  In FIG. 1, power bipolar transistors are shown as switching elements Qu, Qx, Qv, Qy, Qw, and Qz. However, other types of semiconductor switching elements such as IGBTs (Insulated Gate Bipolar Transistors) and power MOS transistors are shown. May be used.

  The microcomputer A1 generates a PWM (Pulse Width Modulation) signal as a control signal for controlling the switching of each switching element Qu, Qx, Qv, Qy, Qw, Qz, and the generated PWM signal is converted to the inverter circuit 3 (specifically, Is output to the control electrode of each switching element. By this switching control, the inverter circuit 3 generates a three-phase AC current from the DC voltage Vdc.

  The output side of the converter circuit 2 and the input side of the inverter circuit 3 are connected by a positive DC line PL1 and a negative DC line PL2, and a current detection resistor R1 is provided on the negative DC line PL2 between the two circuits. . The current detection circuit 5 detects the DC current Idc flowing through the inverter circuit 3 based on the voltage generated across the current detection resistor R1, amplifies it, and outputs it to the microcomputer A1 as the DC current monitor signal Idc_sig.

  The resistors Rdc1 and Rdc2 are connected in series between the positive DC line PL1 and the negative DC line PL2, and constitute a DC voltage monitor circuit (voltage dividing circuit). A DC voltage monitor signal Vdc_sig1 obtained by dividing the DC voltage Vdc by both resistances is output to the microcomputer A1 from the connection point between the resistors Rdc1 and Rdc2.

  With reference to FIG. 3, the functional configuration and operation of microcomputer A1 according to the first embodiment of the present invention will be described. Each functional block in FIG. 3 is realized by executing a program in the processor of the microcomputer A1.

(Constitution)
The microcomputer A1 includes a PWM signal generation unit 7 and an input current estimation unit 6. The PWM signal generator 7 generates a PWM signal based on the instantaneous currents Iu (t), Iv (t), Iw (t) output from the inverter circuit 3, the DC voltage monitor signal Vdc_sig, and the rotational speed command value ωd. Generate a signal. The PWM signal generation unit 7 outputs the generated PWM signal to the inverter circuit 3 for switching control of each switching element. As a result, the synchronous motor rotates at a rotation speed corresponding to the rotation speed command value ωd. In this specification, the number of rotations per unit time, that is, the rotation speed may be simply referred to as the number of rotations.

  The input current estimation unit 6 is driven by a synchronous motor from the commercial AC power source 1 based on the DC current monitor signal Idc_sig output from the current detection circuit 5, the PWM signal output from the PWM signal generation unit 7, and the DC voltage monitor signal Vdc_sig1. The estimated effective current value Iac_est of the input alternating current supplied to the device MD1 is calculated and output to the PWM signal generator 7.

  The PWM signal generation unit 7 controls the inverter circuit 3 so that the estimated effective value Ias_est of the input alternating current does not exceed the reference value, that is, avoids an overload state. For example, the rotational speed of the synchronous motor is limited.

  The input current estimation unit 6 includes an instantaneous current distribution unit 61, an instantaneous power calculation unit 62, an active power calculation unit 63, and an input current calculation unit 64. The input current estimation unit 6 further includes a synchronous motor pole number storage unit 612 that stores the number of poles of the synchronous motor 4 driven by the synchronous motor driving device MD1, and a detection cycle storage that stores a detection cycle of the DC current Idc of the inverter circuit 3. 613 and a detection electrical angle setting unit 611 that sets the pitch of the electrical angle of the motor that detects the direct current Idc. These storage unit and setting unit correspond to the memory of the microcomputer A1. Input current estimation unit 6 further includes an instantaneous DC voltage detection unit 621 that detects the value of DC voltage Vdc output from converter circuit 2 at the time when DC current Idc is detected.

(Detection of instantaneous currents Iu (t), Iv (t), Iw (t))
The instantaneous current distribution unit 61 uses a technique described in Japanese Patent Application Laid-Open No. 8-19263 (Patent Document 3) to generate three-phase instantaneous currents Iu (t), Iv (t), Id_tig from the DC current monitor signal Idc_sig. Iw (t) is determined. Specifically, the instantaneous current distribution unit 61 converts the DC current Idc flowing through the inverter circuit 3 at time t into three phases (U phase, V phase, W phase) based on the DC current monitor signal Idc_sig detected at a predetermined time t. ) Instantaneous currents Iu (t), Iv (t), and Iw (t).

  More specifically, the direct current Idc flowing through the negative direct current line PL2 is the sum of the three-phase alternating currents Iu (t), Iv (t), and Iw (t) flowing from the synchronous motor to the inverter circuit 3. The magnitudes of the three-phase alternating currents Iu (t), Iv (t), and Iw (t) are controlled by the PWM signal output from the PWM signal generation unit 7. Therefore, the instantaneous current distribution unit 61 obtains a change in the DC current monitor signal Idc_sig at timings immediately before and immediately after switching of each switching element of the inverter circuit 3 based on switching information of the PWM signal. The instantaneous current distribution unit 61 distributes the change amount to each of the U, V, and W phases based on the switching information of the PWM signal, so that the three-phase alternating currents Iu (t), Iv (t), and Iw (t )

  The instantaneous DC voltage detection unit 621 detects the value of the DC voltage Vdc output from the converter circuit 2 at a set time based on the input DC voltage monitor signal Vdc_sig1 (output of the voltage dividing circuit). The instantaneous DC voltage detection unit 621 outputs the detected value of the DC voltage Vdc to the instantaneous power calculation unit 62 and the voltage effective value calculation unit 641.

  The instantaneous DC voltage detector 621 further detects and outputs a ripple frequency f_rpl (reciprocal of the ripple cycle T_rpl) of the DC voltage Vdc based on the DC voltage monitor signal Vdc_sig1. The converter circuit 2 full-wave rectifies the AC voltage with a diode bridge, further reduces the ripple voltage with a smoothing circuit, and outputs a DC voltage Vdc. However, a ripple (pulsation) having a frequency twice that of the commercial AC power supply 1 remains in the DC voltage Vdc as a result of full-wave rectification. This ripple (pulsation) is reflected in the ripple frequency f_rpl of the DC voltage monitor signal Vdc_sig1 generated by resistance-dividing the DC voltage Vdc.

  The ripple period T_rpl is obtained by averaging the value of the DC voltage monitor signal Vdc_sig1 detected in a predetermined detection period. The detection cycle is set to, for example, several microseconds in consideration of noise cancellation. When the frequency of the input AC voltage is 50 Hz or 60 Hz, the ripple period T_rpl is ½ of the period corresponding to the frequency 50 Hz or 60 Hz, respectively, and thus becomes 10 milliseconds and 8.33 milliseconds, respectively.

  Therefore, in order to detect the cycle of the AC voltage (that is, the commercial AC power supply 1) from the DC voltage monitor signal Vdc_sig1, the value of the DC voltage monitor signal Vdc_sig1 is at least about 1 millisecond (preferably with a shorter detection cycle). Need to be detected. This detection cycle is desirably set to a time from several microseconds to several hundred microseconds in consideration of the processing performance of the microcomputer A1 and the relationship with other arithmetic processing.

  The input current estimation unit 6 further includes a voltage effective value calculation unit 641 that calculates the voltage effective value Vac of the commercial AC power supply 1, a power factor table 642 that stores the power factor value of the input AC power, and a power factor correction coefficient. A correction coefficient table 643 to be stored and a proportionality constant storage unit 644 for converting the heat loss energy of the synchronous motor driving device MD1 into power consumption are provided.

  Based on the value of the DC voltage Vdc and the ripple frequency f_rpl output from the instantaneous DC voltage detection unit 621 and the value of the active power P output from the active power calculation unit 63, the voltage effective value calculation unit 641 is calculated by a calculation formula described later. The voltage effective value Vac is calculated.

(Calculation of instantaneous power p (t))
The instantaneous power calculator 62 calculates the instantaneous power p (t) at a predetermined time t based on the three-phase instantaneous currents Iu (t), Iv (t), and Iw (t). Instantaneous DC voltage detection unit 621 detects and outputs the value of DC voltage Vdc at time t output from converter circuit 2. The instantaneous power p (t) is calculated by the following equation based on the instantaneous currents Iu (t), Iv (t), and Iw (t) and the DC voltage Vdc output from the instantaneous DC voltage detector 621. In the following expressions, the symbol “*” means a multiplication symbol, and the symbol “/” means a division symbol.

p (t) = pu (t) + pv (t) + pw (t)
Here, pu (t), pv (t), and pw (t) are instantaneous powers of the U phase, the V phase, and the W phase, respectively, and are obtained by the following equations.
pu (t) = Vdc * U-phase PWM duty ratio * Iu (t)
pv (t) = Vdc * V-phase PWM duty ratio * Iv (t)
pw (t) = Vdc * W-phase PWM duty ratio * Iw (t)
The PWM duty ratio is a duty ratio of the PWM waveform (that is, on time / (on time + off time)).

(Instantaneous power detection times t1 to tn)
With reference to FIG. 4, the detection times t1 to tn of the instantaneous electric power p (t) set in the period T of one mechanical rotation of the synchronous motor 4 will be described. FIG. 4 is a schematic diagram showing a waveform of a three-phase alternating current output from the inverter circuit 3 in the synchronous motor driving device MD1 according to the embodiment of the present invention. The horizontal axis indicates a range corresponding to one mechanical rotation of the synchronous motor 4, that is, a mechanical angle of 360 °. The vertical axis schematically shows the output current waveform of the inverter 3 by phase (U phase, V phase, W phase).

  In the case of a synchronous motor having a four-pole three-phase structure, it makes two electrical revolutions during one mechanical revolution. That is, the mechanical angle 360 ° corresponds to the electrical angle 720 °. In FIG. 4, in the period T of one mechanical rotation of the synchronous motor, the time at the electrical angle of 30 ° is t1, and thereafter, the detection time is set for every electrical angle of 60 ° (pitch at the electrical angle of 60 °). The last detection time tn in the cycle T is a time corresponding to an electrical angle of 690 °, and the total number of detections is 12 (n = 12).

  In the first embodiment, the detection of the instantaneous power has been described by setting the electrical angle 60 ° as the cycle. The calculation accuracy of the active power can be improved by setting the instantaneous power detection time (the pitch of the electrical angle to be set) smaller. In practice, the pitch of the electrical angle for detecting the instantaneous power p (t) is 1 °, 10 °, 30 °, or 60 ° in consideration of the processing performance of the microcomputer A1 and the relationship with other arithmetic processing. It is preferable to select from these periods. However, if the pitch of the electrical angle to be selected is too large, the accuracy of the calculation result output by the active power calculation unit is reduced. Therefore, the pitch of the electrical angle to be set is preferably 60 ° or less.

  Returning to FIG. 3, operations of the detected electrical angle setting unit 611, the synchronous motor pole number storage unit 612, the detection cycle storage unit 613, and the active power calculation unit 63 included in the input current estimation unit 6 will be described.

  The synchronous motor pole number storage unit 612 stores the pole number of the synchronous motor 4 driven by the inverter circuit 3. In the present embodiment, a synchronous motor having a four-pole three-phase structure is described as an example. In this case, the synchronous motor pole number storage unit 612 stores information indicating that the synchronous motor has four poles. The synchronous motor driving device MD1 according to the present embodiment can easily control a synchronous motor having another structure by changing information to be written in the synchronous motor pole number storage unit 612.

  The detection cycle storage unit 613 stores the pitch of the electrical angle for detecting the instantaneous power p (t) in the cycle T of one mechanical rotation of the synchronous motor 4. The synchronous motor driving device MD1 according to the present embodiment can change the pitch of the electrical angle, and can calculate the effective power with the accuracy required by the user.

  The detected electrical angle setting unit 611 outputs the time t at which the DC current monitor signal Idc_sig output from the current detection circuit 5 is detected to the instantaneous current distribution unit 61. The instantaneous current distribution unit 61 calculates three-phase instantaneous currents Iu (t), Iv (t), and Iw (t) to be supplied from the inverter circuit 3 to the synchronous motor at a designated time t.

  Based on the information output from the synchronous motor pole number storage unit 612 and the detection cycle storage unit 613, the detection electrical angle setting unit 611 detects the DC current Idc flowing through the inverter circuit 3 relative to the instantaneous current distribution unit 61 at the detection time t1. ~ Tn is notified.

(Calculation of active power P)
The active power calculation unit 63 integrates the instantaneous power p (t) output from the instantaneous power calculation unit 62 over a predetermined period T, and divides the integration result by the period T to calculate the active power P. In the case of a motor, first, the time for which the motor makes one mechanical rotation is defined as a period T, and a plurality of times t1 to tn are set over the period T. The active power P consumed by the synchronous motor 4 is obtained by the following formula 1 obtained by dividing the sum of the instantaneous powers p (t1) to p (tn) at each time by the period T.
P = (p (t1) + p (t2) +... + P (tn)) / T.
The active power calculation unit 63 calculates the effective power P consumed by the synchronous motor 4 by dividing the sum of the instantaneous powers p (t1) to p (tn) at each time by the period T as described in Equation 1. And output to the input current calculation unit 64 and the voltage effective value calculation unit 641. In the following, a formula for calculating the effective power P will be described, taking as an example the specific number of poles of the synchronous motor 4 and the pitch of the detected electrical angle.

When the synchronous motor 4 has a four-pole three-phase structure, one mechanical rotation corresponds to two electrical rotations. Therefore, when the instantaneous power p (t) of the inverter circuit 3 is detected at an electrical angle of 60 °, the number of detections is 12. Therefore, the active power P is calculated as follows.
P = (p (t1) +... + P (t12)) / 12
The effective power P of the four-pole three-phase synchronous motor is obtained by the above formula.

When the synchronous motor 4 has a six-pole three-phase structure, one mechanical rotation corresponds to three electrical rotations. Therefore, when the instantaneous electric power p (t) of the inverter circuit 3 is detected at an electrical angle of 60 °, the number of detections is 18. The active power P is calculated as follows.
P = (p (t1) +... + P (t18)) / 18
The effective power P of the 6-pole 3-phase synchronous motor is obtained by the above formula.

(Total effective power P_md1 of the synchronous motor driving device)
In FIG. 1, the effective values of the AC voltage and the AC current supplied from the commercial AC power supply 1 to the synchronous motor driving device MD1 are Vac and Iac, respectively. When the phase difference between the AC voltage and the AC current is “θ”, the effective power is Vac * Iac * cos (θ). Here, assuming that the total active power consumed by the synchronous motor driving device MD1 is P_md1,
Vac * Iac * cos (θ) = P_md1
The relationship is established.

  In the synchronous motor driving device MD1 shown in FIG. 1, it is considered that the effective power supplied from the commercial AC power source 1 to the converter circuit 2 constituted by a diode bridge or the like and the output power of the converter circuit 2 are substantially equal. The output power of the converter circuit 2 is mainly consumed by the synchronous motor 4 driven by the inverter circuit 3. The active power consumed by the synchronous motor 4 is obtained as the active power P output from the active power calculator 63 shown in FIG. A formula for calculating the effective power P of the synchronous motor 4 is as shown in Formula 1.

Further, the output power of the converter circuit 2 is not only the effective power P of the synchronous motor 4 but also the power consumption due to the heat loss of the switching elements Qu, Qx, Qv, Qy, Qw, Qz, etc. constituting the inverter circuit 3. Sometimes it cannot be ignored. The power for the heat loss of the inverter circuit 3 is assumed to be P_ipm1. This P_ipm1 is proportional to the effective power P of the synchronous motor 4 driven by the inverter circuit 3. If the proportionality constant is k1, the following relationship is established.
P_ipm1 = k1 * P
The proportionality constant k1 is a value obtained by experiments or the like and is stored in the microcomputer A1.

From the above, the total effective power P_md1 consumed by the synchronous motor driving device MD1 is the sum of the effective power P of the synchronous motor 4 and the power P_ipm1 corresponding to the heat loss of the switching elements constituting the IPM. The relationship between the active power supplied from the commercial AC power supply 1 to the converter circuit 2 and the total active power P_md1 consumed by the synchronous motor driving device MD1 is shown below.
Vac * Iac * cos (θ) = P_md1 Equation 2
P_md1 = P + P_ipm1 = (1 + k1) * P Equation 3
From Equation 1, Equation 2, and Equation 3, the effective current value Iac of the input AC power supply, the effective power P of the synchronous motor 4, the effective value Vac of the AC voltage, and the power factor cos (θ) are expressed by the following Equation 4. Have.
Iac = (1 + k1) * P / (Vac * cos (θ)) Equation 4
If the AC voltage effective value Vac and the power factor cos (θ) are known from the above equation, the AC current effective value Iac can be estimated. Below, the calculation method of the effective value Vac and power factor cos ((theta)) of an alternating voltage is demonstrated.

(Calculation of effective value Vac of AC voltage)
A method for calculating the voltage effective value Vac of the commercial AC power supply 1 shown in FIG. 1 will be described. Since the output current of the converter circuit 2 increases as the rotational speed of the synchronous motor 4 increases, the DC voltage Vdc of the converter circuit 2 decreases. That is, the DC voltage Vdc of the converter circuit 2 that supplies the effective power P to the synchronous motor 4 is lower than when the converter circuit 2 does not output the active power P (that is, when there is no load). The drop of the DC voltage Vdc is defined as a dropped DC voltage ΔVdc. The drop DC voltage ΔVdc has a negative value, and is a drop voltage value using the DC voltage Vdc as a reference value when the converter circuit 2 is not supplying the active power P to the synchronous motor 4.

When converter circuit 2 shown in FIG. 2A outputs active power P, voltage effective value Vac, DC voltage Vdc, and drop DC voltage ΔVdc have the following relationship.
Vac = (Vdc−ΔVdc) / √2
= (Vdc + abs (ΔVdc)) / √2 Equation 5
Here, √2 is the square root of 2, and abs (ΔVdc) is the absolute value of ΔVdc.

When the converter circuit 2 is the voltage doubler circuit shown in FIG. 2B, the voltage effective value Vac, the DC voltage Vdc, and the dropped DC voltage ΔVdc have the following relationship.
Vac = (Vdc−ΔVdc) / 2 / √2
= (Vdc + abs (ΔVdc)) / 2 / √2 Equation 51
One of the equations is selected based on the circuit configuration of the converter circuit 2.

With reference to FIG. 5, a method of calculating the drop DC voltage ΔVdc will be described.
FIG. 5 is six graphs showing changes in the drop DC voltage ΔVdc (vertical axis) with respect to the active power P (horizontal axis) of the synchronous motor 4. The six graphs can be broadly divided into a group with a commercial AC voltage frequency of 50 Hz and a group with 60 Hz. Each group is further configured by a graph when the effective value of the AC voltage is 90V, 100V, and 110V. As shown in the six graphs, when the active power P of the synchronous motor 4 increases, the drop DC voltage ΔVdc decreases (the absolute value of ΔVdc increases). That is, the DC voltage Vdc output from the converter circuit 2 decreases.

  As shown in FIG. 5, it can be seen that the active power P and the dropped DC voltage ΔVdc have a nearly inverse relationship, and the relationship further changes with the frequency of the input AC voltage. Therefore, for each frequency of the commercial AC voltage, a data table of the active power P and the drop DC voltage ΔVdc (hereinafter also simply referred to as a data table) is stored in the memory of the microcomputer A1, and the active power P and the commercial AC are stored. By specifying the frequency of the voltage, the drop DC voltage ΔVdc can be obtained.

  The voltage effective value calculation unit 641 shown in FIG. 3 calculates the voltage effective value Vac based on the ripple frequency f_rpl, the DC voltage Vdc, the active power P, and a data table (not shown). The frequency of the commercial AC power supply 1 is determined from the ripple frequency f_rpl output from the instantaneous DC voltage detector 621, and the data group of the determined frequency is selected from the two data groups stored in the data table. As described above, the drop DC voltage ΔVdc corresponding to the active power P of the synchronous motor 4 is determined. Furthermore, based on the active power P output from the active power calculation unit 63, the drop DC voltage ΔVdc is determined with reference to the data table.

  The voltage effective value calculation unit 641 applies the determined drop DC voltage ΔVdc and the DC voltage Vdc output from the instantaneous DC voltage detection unit 621 to Formula 5 or Formula 51, calculates the voltage effective value Vac, and inputs it to the input current calculation unit 64. Output.

  Instead of storing the relationship between the active power P and the drop DC voltage ΔVdc in the form of a data table in the microcomputer A1, the relationship between the two may be set as an approximate expression for each frequency of each AC voltage, and the arithmetic processing may be performed. The approximate expression may be a quadratic expression, or the range of the active power P may be divided as appropriate, and the divided power section may be approximated by a primary expression.

  The DC voltage drop ΔVdc may be calculated according to the frequency with which the rotation speed of the synchronous motor 4 changes. For example, the DC voltage drop ΔVdc may be calculated when the synchronous motor 4 continues to rotate at the same rotational speed for T seconds or longer. When the effective power P does not change over a certain period, the voltage effective value Vac with less error can be estimated by this calculation method. The time T set as the duration is set in the microcomputer A1 in advance.

  With the above configuration, the effective voltage value Vac of the commercial AC power supply 1 during the operation period of the synchronous motor 4 can be detected corresponding to the frequency of the commercial AC power supply 1 and the circuit configuration of the converter circuit 2. Even if the AC voltage varies during the operation period, the effective voltage value Vac can be detected.

  Instead of the above active power P, the total active power P_md1 considering the heat loss in the power module may be used. This makes it possible to estimate the voltage effective value Vac more accurately.

(Calculation of power factor cos (θ))
A method for calculating the power factor cos (θ) between the alternating voltage and the alternating current will be described with reference to FIGS. 6 and 7.

  FIG. 6 is a graph showing the relationship between the total effective power P_md1 and the power factor cos (θ) when the voltage effective value Vac of the commercial AC power supply 1 is used as a parameter. The graph of FIG. 6 is obtained by experiment. As shown in FIG. 6, the power factor cos (θ) increases as the total effective power P_md1 increases. When the value of the total effective power P_md1 is fixed to a constant value, the power factor cos (θ) decreases as the voltage effective value Vac increases.

  FIG. 7 is a graph showing the relationship between the effective voltage value Vac and the power factor cos (θ) when the total active power P_md1 is used as a parameter. The graph of FIG. 7 is a rewrite of the graph of FIG. The horizontal axis of FIG. 7 indicates the ratio of the actual voltage effective value Vac to the rated voltage effective value as a percentage. The vertical axis in FIG. 7 indicates the ratio (power factor change rate) between the power factor (denominator) in the case of the rated voltage effective value and the power factor (numerator) in the case of the actual voltage effective value Vac. As shown in FIG. 7, the relationship between the voltage effective value Vac and the power factor change rate hardly depends on the total effective power P_md1.

  Therefore, based on the experimental results of FIGS. 6 and 7, the power factor cos (θ) can be estimated by the following procedure. First, the relationship between the total effective power P_md1 and the power factor cos (θ) is obtained by experimenting in advance in the case of the rated AC voltage effective value Vac by changing the rotational speed of the synchronous motor. FIG. 8 is a diagram illustrating an example of a table representing the relationship between the total effective power P_md1 and the power factor of the synchronous motor driving device MD1. The table in FIG. 8 is stored as a power factor table 642 in the memory of the microcomputer A1.

  Next, when the rotational speed of the synchronous motor is fixed to a certain value by experiment in advance (in this case, the magnitude of the total effective power P_md1 is also substantially fixed), the voltage effective value when the voltage effective value Vac is changed. The relationship between Vac and power factor cos (θ) is obtained. The value of the power factor cos (θ) is obtained as the rate of change with respect to the power factor in the case of the rated voltage effective value. This power factor change rate corresponds to a power factor correction coefficient. FIG. 9 is a diagram illustrating an example of a table representing the relationship between the voltage effective value Vac and the power factor correction coefficient. The table of FIG. 9 is stored as a correction coefficient table 643 in the memory of the microcomputer A1.

After preparing the above table in advance, the input current calculation unit 64 (the processor of the microcomputer A1) uses the power factor table 642 to calculate the total active power P_md1 calculated according to Equation 3 when the synchronous motor is actually driven. By applying (FIG. 8), the power factor (provisional estimated value) corresponding to the rated voltage effective value is obtained. Next, the input current calculation unit 64 obtains a power factor correction coefficient by applying the voltage effective value Vac calculated according to Expression 5 or 51 to the correction coefficient table 643 (FIG. 9). The final power factor estimate is
Power factor = Power factor at rated voltage × Power factor correction coefficient Equation 6
It can be obtained according to the relationship. This makes it possible to estimate the power factor value more accurately than in the past.

  Instead of obtaining the power factor at the rated voltage using the table (power factor table 642) representing the relationship between the total active power P_md1 and the power factor cos (θ) of the synchronous motor drive device MD1, an approximation representing the relationship between the two The power factor at the rated voltage may be obtained by calculation processing according to the equation. Similarly, instead of determining a power factor correction coefficient using a table (correction coefficient table 643) representing the relationship between the voltage effective value Vac and the power factor correction coefficient, an arithmetic process according to an approximate expression representing the relationship between the two. The power factor correction coefficient may be obtained by

  Instead of the above method, the total effective power P_md1, the voltage effective value Vac, and the force are measured by measuring in advance the power factor value when the rotational speed of the synchronous motor and the value of the voltage effective value are changed in a matrix. It is also possible to create a table group representing the relationship with the rate. For example, a table representing the relationship between the total active power P_md1 and the power factor is generated for each value of the voltage effective value Vac. In this case, the input current calculation unit 64 (the processor of the microcomputer A1) applies the total effective power P_md1 calculated according to Equation 3 and the voltage effective value Vac calculated according to Equation 5 or 51 to the above table group. To find the power factor. However, this method requires a large number of preliminary experiments to create the above table group. Moreover, the table created for each synchronous motor drive device is different. Compared to this, the method using the tables shown in FIGS. 8 and 9 has an advantage that the number of preliminary experiments is reduced.

  Since the rotation speed (rpm) per unit time of the synchronous motor 4, that is, the rotation speed is substantially proportional to the total effective power P_md1, the rotation speed and the power factor of the synchronization motor 4 are replaced with the table of FIG. A table indicating the relationship may be created. In this case, the input current calculation unit 64 (the processor of the microcomputer A1) obtains the power factor in the case of the rated voltage by applying the rotation speed command value ωd to this table.

  When the heat loss in the power module can be ignored, for example, when a large heat sink is attached to the semiconductor switching element, the effective power consumed by the synchronous motor 4 in place of the total effective power P_md1 described above. Electric power P may be used.

(Calculation of estimated current effective value Iac_est)
A method of calculating the estimated current effective value Iac_est by the input current calculation unit 64 will be described with reference to FIG.

  The input current calculation unit 64 estimates the current effective value Iac of the AC power supplied from the commercial AC power supply 1 based on the active power P of the synchronous motor 4 output from the active power calculation unit 63, and estimates the current effective value Iac_est. Output as.

The calculation of the estimated current effective value Iac_est includes the voltage effective value Vac output from the voltage effective value calculation unit 641, the power factor value stored in the power factor table 642, and the power factor correction coefficient stored in the correction coefficient table. The value and the proportional constant k1 stored in the proportional constant storage unit 644 are cited. The value of the power factor cos (θ) is corrected according to Equation 6. Finally, the calculation formula of the estimated current effective value Iac_est is as follows.
Iac_est = (1 + k1) * P / (Vac * cos (θ))
The calculation formula of the estimated current effective value Iac_est corresponds to the above formula 4.

  When the input estimated current effective value Iac_est exceeds a predetermined value, the PWM signal generation unit 7 changes the duty of the PWM signal output to the inverter circuit 3 to reduce the rotational speed of the synchronous motor 4. By this rotation speed control, the synchronous motor driving device MD1 can maintain the continuous operation of the refrigeration / air conditioning device.

(Computer control procedure)
FIG. 10 is a flowchart showing a control procedure of the microcomputer A1 of FIG. FIG. 11 is a diagram showing step S120 of FIG. 10 in more detail. Hereinafter, with reference to FIG. 1, FIG. 3, FIG. 10, FIG. 11, the control procedure of the inverter circuit 3 by the processor of the microcomputer A1 will be summarized. 10 and 11 are repeated every control cycle (for example, electrical angle 60 °).

  Referring to FIGS. 1, 3, and 10, first, the processor determines the three-phase AC current supplied from the inverter circuit 3 to the synchronous motor based on the DC current detected by the shunt resistor R1 and the PWM signal. Instantaneous values Iu (t), Iv (t), and Iw (t) are obtained (step S100). Further, the processor detects the DC voltage Vdc output from the converter circuit 2 based on the detection value of the voltage dividing circuit configured by the resistors Rdc1 and Rdc2 (step S110).

  Next, the processor calculates the alternating current effective value Iac input to the converter circuit 2 based on the instantaneous values Iu (t), Iv (t), Iw (t) of the three-phase alternating current and the detected value Vdc of the direct current. (The specific procedure will be described with reference to FIG. 11). As a result, when the estimated AC current effective value Vac is smaller than the reference value (YES in step S130), the processor generates a PWM signal so that the synchronous motor rotates at the input rotation speed command value. And output to the inverter circuit 3 (step S150).

  On the other hand, when the estimated alternating current effective value Vac is equal to or greater than the reference value (NO in step S130), the processor limits the rotational speed command value to a predetermined upper limit value (step S140). The processor generates a PWM signal and outputs it to the inverter circuit 3 so that the synchronous motor rotates at the limited rotational speed command value (that is, so as to reduce the rotational speed of the synchronous motor 4) (step S150). .

  Next, the procedure of step S120 in FIG. 10 will be described. First, based on the detected values of the instantaneous values Iu (t), Iv (t), Iw (t) of the three-phase alternating current from the current time to one cycle before the mechanical angle, and the detected value of the DC voltage Vdc, The active power P consumed by the synchronous motor is calculated (step S200). The specific calculation is based on Equation 1. The processor calculates the total active power P_md1 by multiplying the calculated active power P by a coefficient (1 + k1) representing the heat loss of the power module (step S210). The specific calculation is based on Equation 2.

  Next, the processor obtains a drop DC voltage ΔVdc corresponding to the calculated total active power P_md1 by referring to a table representing the relationship between the total active power P_md1 and the drop DC voltage ΔVac measured in advance. The processor calculates an estimated value of the AC voltage effective value Vac in accordance with Equation 5 or Equation 51 from the obtained drop DC voltage ΔVdc and the detected value of the DC voltage Vdc (step S220).

  Next, the processor refers to a table (power factor table 642) representing the relationship between the pre-measured total active power P_md1 and the power factor in the case of the rated voltage, and thereby the power factor corresponding to the calculated total active power P_md1. cos (θ) is obtained (step S230). Further, the processor reads the correction coefficient corresponding to the estimated value of the AC voltage effective value Vac obtained in step S220 by referring to the correction coefficient table 643, and multiplies the correction coefficient to obtain the force obtained in step S230. The value of the rate cos (θ) is corrected (step S240).

  Next, the processor calculates an estimated value of the AC current effective value Iac by dividing the total effective power P_md1 by the estimated AC voltage effective value Vac and the corrected power factor cos (θ) (step S250). .

  As described above, the synchronous motor driving device MD1 according to the first embodiment uses a general-purpose arithmetic processing function provided in the microcomputer A1, and thus does not add complicated circuit components and has a refrigeration cycle. Continuous operation can be maintained. Further, the input current effective value can be estimated more accurately by adding the power corresponding to the heat loss of the switching element to the effective power of the synchronous motor drive device MD1, and further by increasing the accuracy of estimating the power factor. .

<Embodiment 2>
With reference to FIG. 12, the configuration and operation of synchronous motor drive device MD11 according to Embodiment 2 of the present invention will be described. The second embodiment is a modification of the first embodiment.

  Synchronous motor drive device MD11 shown in FIG. 12 converts AC power supplied from commercial AC power supply 1 having voltage effective value Vac and current effective value Iac into DC voltage Vdc, and is connected between positive DC line PL1 and negative DC line PL2. It has the converter circuit 2 which outputs. Unlike synchronous motor drive device MD1 shown in FIG. 1, synchronous motor drive device MD11 has inverter circuit 31 and inverter circuit 32 connected in parallel to positive DC line PL1 and negative DC line PL2.

  The converter circuit 2 shown in FIG. 2A or 2B is appropriately selected according to the value of the voltage effective value Vac of the AC power supplied to the synchronous motor driving device MD11.

  The inverter circuit 31 and the inverter circuit 32 generate a three-phase alternating current from the direct-current voltage Vdc, and supply the three-phase alternating current to the compressor synchronous motor 41 of the refrigeration / air conditioner and the fan synchronous motor 42 of the outdoor unit, respectively. The microcomputer A21 generates the PWM signal 1 and the PWM signal 2, and controls the switching operations of the inverter circuit 31 and the inverter circuit 32, respectively.

  On the negative DC line PL21 connecting the converter circuit 2 and the inverter circuit 31, a current detection resistor R11 is provided. On the negative DC line PL22 connecting the converter circuit 2 and the inverter circuit 32, a current detection resistor R21 is provided. Based on the voltages generated at both ends of the current detection resistor R11 and the resistor R21, the current detection circuit 1 (51) and the current detection circuit 2 (52) respectively generate DC currents Idc1 and Idc2 flowing through the inverter circuit 31 and the inverter circuit 32, respectively. It detects, amplifies, and outputs DC current monitor signal Idc1_sig and DC current monitor signal Idc2_sig to microcomputer A21.

  Synchronous motor drive device MD11 further includes a DC voltage monitor circuit (voltage dividing circuit) configured by resistors Rdc1 and Rdc2 connected in series between positive DC line PL1 and negative DC line PL2. A DC voltage monitor signal Vdc_sig11 obtained by dividing the DC voltage Vdc by both resistors is output to the microcomputer A21 from a connection point between the resistors Rdc1 and Rdc2.

  The configuration and operation of the microcomputer A21 will be described with reference to FIG. The microcomputer A21 includes a first input current estimation unit 6M, a second input current estimation unit 6FM, a first PWM signal generation unit 7M, and a second PWM signal generation unit 7FM. First PWM signal generation unit 7M and second PWM signal generation unit 7FM generate PWM signal 1 and PWM signal 2, respectively, and output them to inverter circuit 31 and inverter circuit 32.

  The first input current estimation unit 6M is supplied from the commercial AC power supply 1 to the compressor synchronous motor 41 based on the DC current monitor signal Idc1_sig and the PWM signal 1 output from the first PWM signal generation unit 7M. An estimated current effective value Iac1_est of the alternating current is calculated and output to the first PWM signal generation unit 7M. The second input current estimation unit 6FM is based on the DC current monitor signal Idc2_sig and the PWM signal 2 output from the second PWM signal generation unit 7FM, and the input AC supplied from the commercial AC power supply 1 to the fan synchronous motor 42. The estimated current effective value Iac2_est of the current is calculated and output to the second PWM signal generation unit 7FM.

  The first input current estimation unit 6M shown in FIG. 13 has the same configuration as the input current estimation unit 6 according to Embodiment 1 shown in FIG. 3 except for the following points. 3 detects the value of the DC voltage Vdc output from the converter circuit 2 at the set time based on the DC voltage monitor signal Vdc_sig1, and the instantaneous power calculator 62 and the voltage effective value calculator 641 is output. On the other hand, the instantaneous DC voltage detection unit 621 (not shown) included in the first input current estimation unit 6M shown in FIG. 13 detects the value of the DC voltage Vdc based on the DC voltage monitor signal Vdc_sig11.

  A first input current estimation unit 6M shown in FIG. 13 is a first synchronous motor pole number storage unit 612M that stores the number of motor poles of the compressor synchronous motor 41, and a first electrical angle that detects an instantaneous power. Detection cycle storage unit 613M and a first proportionality constant storage unit 644M that stores the proportionality constant k1.

  The second input current estimation unit 6FM shown in FIG. 13 has the same configuration as the input current estimation unit 6 according to Embodiment 1 shown in FIG. 3 except for the following points. The instantaneous DC voltage detection unit 621 in FIG. 3 detects the ripple frequency f_rpl and the DC voltage Vdc of the DC voltage Vdc based on the DC voltage monitor signal Vdc_sig1.

  On the other hand, the second input current estimation unit 6FM does not include the instantaneous DC voltage detection unit 621 in FIG. The instantaneous power calculation unit 62 and the voltage effective value calculation unit 641 calculate the instantaneous power p (t) and the voltage effective value Vac based on the data output from the instantaneous DC voltage detection unit 621 of the first input current estimation unit 6M. calculate. That is, only the first input current estimation unit 6M has a function of detecting the ripple frequency f_rpl of the DC voltage Vdc and the DC voltage Vdc from the DC voltage monitor signal Vdc_sig11.

  If necessary, the first input current estimation unit 6M and the second input current estimation unit 6FM may have a function of detecting the ripple frequency f_rpl of the DC voltage Vdc and the DC voltage Vdc from the DC voltage monitor signal Vdc_sig11. The detection function may be provided in the second input current estimation unit 6FM.

  The second input current estimation unit 6FM includes a second synchronous motor pole number storage unit 612FM that stores the motor pole number of the fan synchronous motor 42, and a second detection cycle storage unit that stores an electrical angle for detecting instantaneous power. 613FM and a second proportional constant storage unit 644FM for storing the proportional constant k2.

In FIG. 12, when the phase difference between the AC voltage and the AC current of the commercial AC power supply 1 is “θ”, the effective power is Vac * Iac * cos (θ). Assuming that the total active power consumed by the synchronous motor driving device MD11 is P_md11, the value of the effective power of both is
Vac * Iac * cos (θ) = P_md11
The relationship is established. As in the first embodiment, Vac and Iac are the effective voltage value and the effective current value of the commercial AC power supply 1.

  In FIG. 13, the effective power of the compressor synchronous motor 41 obtained by the first input current estimation unit 6M is P_comp, and the effective power of the fan synchronous motor 42 obtained by the second input current estimation unit 6FM is P_fan. To do.

The calculation formula of the electric power P_ipm21 for the heat loss of the IPM (microcomputer A21) resulting from the chopping operation control of the inverter circuit 31 and the inverter circuit 32 is
P_ipm21 = k1 * P_comp + k2 * P_fan
It becomes.

Therefore, the total effective power P_md11 of the synchronous motor driving device MD11 is
Vac * Iac * cos (θ) = P_md11
P_md11 = (1 + k1) * P_comp + (1 + k2) * P_fan
It becomes.

  The voltage effective value Vac of the commercial AC power supply 1 is obtained by Equation 5 or Equation 51 in the first embodiment. In Equation 5 or 51, the DC voltage Vdc and the drop DC voltage ΔVdc are the same as in Embodiment 1 except that the instantaneous DC voltage detector 621 and the active power calculator 63 provided in the first input current estimator 6M in FIG. Calculate based on the output of. The drop DC voltage ΔVdc is obtained based on a data table (not shown) provided in the microcomputer A21 shown in FIG.

The first estimated current effective value Iac1_est output from the first input current estimation unit 6M and the second estimated current effective value Iac2_est output from the second input current estimation unit 6FM in FIG. Become.
Iac1_est = (1 + k1) * P_comp / (Vac * cos (θ))
Iac2_est = (1 + k2) * P_fan / (Vac * cos (θ))
The voltage effective value Vac and the power factor cos (θ) are obtained in the same manner as in the first embodiment.

  When the sum of Iac1_est and Iac2_est exceeds a predetermined value, the microcomputer A21 controls the inverter circuit 31 and the inverter circuit 32 as appropriate so that the rotation speed of the compressor synchronous motor 41 and the fan synchronous motor 42 is increased. Reduce. By this rotation speed control, the synchronous motor driving device MD11 can maintain the continuous operation of the refrigeration / air conditioning device.

  As described above, the synchronous motor drive device MD11 according to the second embodiment calculates the total effective power of the synchronous motor for the compressor and the synchronous motor for the fan, including the power for the heat loss of the switching elements and the like. Is possible.

<Embodiment 3>
Referring to FIG. 14, the configuration and operation of synchronous motor drive device MD2 according to Embodiment 3 of the present invention will be described.

  A synchronous motor driving device MD2 shown in FIG. 14 includes a converter circuit 2, an inverter circuit 3, a shunt resistor R1, a resistor Rdc1, a resistor Rdc2, a current detection circuit 53, and a microcomputer A3.

  Converter circuit 2 converts AC power supplied from commercial AC power supply 1 having voltage effective value Vac and current effective value Iac into DC voltage Vdc, and outputs the DC voltage Vdc between positive DC line PL1 and negative DC line PL2. The converter circuit 2 is appropriately selected from those shown in FIG. 2A or FIG. 2B according to the value of the voltage effective value Vac of the AC power supplied to the synchronous motor driving device MD2.

  The inverter circuit 3 includes three-phase (U-phase, V-phase, W-phase) inverters (Qu, Qx, Qv, Qy, Qw, Qz) connected between the positive DC line PL1 and the negative DC line PL2. Each of the three-phase inverters converts the DC voltage Vdc into a three-phase AC current (U phase, V phase, W phase) and supplies the same to the synchronous motor 4.

  The microcomputer A3 generates a PWM (Pulse Width Modulation) signal and controls switching of each of the three-phase inverters. By this switching control, the inverter circuit 3 generates a three-phase AC current from the DC voltage Vdc.

  The output side of the converter circuit 2 and the input side of the inverter circuit 3 are connected by a positive DC line PL1 and a negative DC line PL2, and a shunt resistor R1 is provided on the negative DC line PL2 between the two circuits.

  The resistors Rdc1 and Rdc2 are connected in series between the positive DC line PL1 and the negative DC line PL2, and constitute a DC voltage monitor circuit (voltage dividing circuit). A DC voltage monitor signal Vdc_sig2 obtained by dividing the DC voltage Vdc by both resistors is output to the microcomputer A3 from the connection point between the resistors Rdc1 and Rdc2.

  In FIG. 14, the third embodiment of the present invention is different from the first and second embodiments as follows. That is, a current detection resistor (shunt resistor) Ru is provided between the switching elements Qx, Qy, Qz for the three phases (U phase, V phase, W layer) constituting the inverter circuit 3 and the negative DC line PL2. , Rv, Rw are arranged. In the first embodiment and the second embodiment, the three-phase alternating current output from the inverter circuit 3 is obtained based on the direct current Idc detected by the shunt resistor R1. In the third embodiment, the shunt resistor R1 is used to detect an overcurrent of the inverter circuit 3, and the shunt resistors Ru, Rv, and Rw are used to detect a three-phase alternating current.

  The potential at the connection point between the three-phase switching elements Qx, Qy, Qz and the current detection resistors Ru, Rv, Rw is input to the current detection circuit 53. The current detection circuit 53 converts the value of the potential of each phase into alternating current signals Iru, Irv, and Irw for each phase, and outputs them to the microcomputer A3.

  With reference to FIG. 15, the configuration of a microcomputer A3 according to Embodiment 3 of the present invention will be described.

  The microcomputer A3 includes an input current estimation unit 6A and a PWM signal generation unit 7. The PWM signal generation unit 7 generates a PWM signal and outputs it to the inverter circuit 3. The input current estimator 6A is based on the AC current signals Iru, Irv, Irw output from the current detection circuit 53, the PWM signal output from the PWM signal generator 7, and the DC voltage monitor signal Vdc_sig1. 1 to calculate the estimated current effective value Iac_est of the input AC current supplied from 1 to the synchronous motor drive device MD2, and outputs it to the PWM signal generator 7.

  The instantaneous current detector 61A of the input current estimator 6A has a three-phase instantaneous current Iu (t) generated by the inverter circuit 3 at the time t based on the alternating current signals Iru, Irv, Irw detected at the predetermined time t. , Iv (t), and Iw (t) are output. Unlike the first embodiment, the instantaneous current detection unit 61A need not distribute the detection value of the current detection resistor R1 to the three-phase instantaneous current based on the PWM signal.

  The instantaneous power calculator 62A outputs the three-phase instantaneous currents Iu (t), Iv (t), and Iw (t), the PWM signal output from the PWM signal generator 7, and the instantaneous DC voltage detector 621. The instantaneous power p (t) at a predetermined time t is calculated based on the DC voltage Vdc to be performed. Since a specific calculation method is the same as that described in the first embodiment, description thereof will not be repeated.

  Since the other configuration of input current estimating unit 6A is the same as that of the first embodiment described in FIG. 3, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated. According to the third embodiment described above, the same effects as those of the first embodiment are obtained.

  In the above description, the shunt resistors Ru, Rv, and Rw are provided for each phase. However, since the sum of the instantaneous currents Iu (t), Iv (t), and Iw (t) is 0, any two phases It is also possible to provide a shunt resistor only for the AC current of the remaining phase by calculation.

<Embodiment 4>
With reference to FIG. 16, Embodiment 4 is demonstrated as a modification common to each embodiment of this invention.

  A microcomputer A shown in FIG. 16 has a configuration in which the current detection circuits 5, 51, 52, and 53 included in each embodiment are incorporated in the microcomputer A as a current detection circuit 5A. The current detection circuit has a function of converting a voltage generated by a current flowing through the current detection resistor into a current value. The current detection circuit 5A, which is a voltage-current conversion circuit, is composed of an operational amplifier built in the microcomputer.

  The other circuits included in the microcomputer A shown in FIG. 16, that is, the configurations and operations of the input current estimating unit 6 and the PWM signal generating unit 7 are the same as those according to the other embodiments, and the description thereof is omitted. .

  As described above, in the synchronous motor driving device of the modification common to the respective embodiments of the present invention, the current detection circuit is built in the microcomputer. Thereby, a synchronous motor drive device can be provided much smaller and cheaper.

<Appendix>
A part of the invention based on the above embodiments will be listed below.

  (1) The motor drive device MD1 according to one aspect converts the AC power into DC power and outputs it, and converts the DC power output from the converter circuit 2 into three-phase AC power and outputs it to the motor 4 And an inverter circuit 3 for controlling the inverter circuit 3. Based on the three-phase AC currents Iu (t), Iv (t), Iw (t) output from the inverter circuit 3 and the DC voltage Vdc output from the converter circuit 2, the control unit A1 The active power P to be consumed is calculated. Control unit A1 estimates AC voltage effective value Vac input to converter circuit 2 based on calculated active power P and DC voltage Vdc. The control unit A1 estimates the power factor cos (θ) of the AC power input to the converter circuit 2 based on the calculated active power P and the estimated AC voltage effective value Vac. The control unit A1 estimates the AC current effective value Iac input to the converter circuit 2 by dividing the calculated active power P by the estimated AC voltage effective value Vac and the estimated power factor cos (θ). Configured. The control unit controls the inverter circuit so that the estimated AC voltage effective value does not exceed the reference value.

  According to the above configuration, the AC current effective value Iac is more accurately estimated based on the calculated active power P, the estimated AC voltage effective value Vac, and the estimated AC power factor cos (θ). be able to. In particular, in estimating the power factor cos (θ) of AC power, in addition to the calculated effective power P, the estimated accuracy of the AC power factor cos (θ) is increased by using the estimated AC voltage effective value Vac. be able to.

  (2) In the above (1), the control unit A1 multiplies the provisional estimated value of the power factor cos (θ) corresponding to the calculated active power P by the correction coefficient corresponding to the estimated AC voltage effective value Vac. By this, it is comprised so that the final estimated value of the power factor of alternating current power may be calculated.

  (3) In the above (2), the control unit A1 corresponds to the calculated active power P based on the relationship between the active power P measured in advance at the predetermined AC voltage effective value Vac and the power factor of the AC power. A temporary estimated value of the power factor cos (θ) is determined, and the estimated alternating current is based on the relationship between the AC voltage effective value Vac measured in advance at a predetermined motor rotational speed and the power factor cos (θ) of the AC power. The correction coefficient corresponding to the voltage effective value Vac is determined.

  By the simple method shown in the above (2) and (3), the estimation accuracy of the power factor cos (θ) of AC power can be increased. In particular, according to the methods (2) and (3) described above, the AC power when the AC voltage effective value Vac and the motor rotation speed are changed in a matrix form in order to estimate the power factor cos (θ) of the AC power. There is no need to conduct a huge preliminary experiment to measure the power factor.

  (4) In the above (1), the control unit A1 corrects the value of the active power P by multiplying the calculated active power P by the coefficient (1 + k1) based on the heat loss of the inverter circuit 3, and after the correction, The effective power P_md1 is used to estimate the AC voltage effective value Vac, the AC power power factor cos (θ), and the AC current effective value Iac.

  According to the above configuration, the input current effective value can be estimated more accurately by adding the power corresponding to the heat loss of the switching element to the effective power of the synchronous motor driving device MD1.

  (5) The motor drive device MD1 according to another aspect converts the AC power into DC power and outputs the converter circuit 2, and converts the DC power output from the converter circuit 2 into three-phase AC power to the motor 4 An inverter circuit 3 for outputting and a control unit A1 for controlling the inverter circuit 3 are provided. Based on the three-phase AC currents Iu (t), Iv (t), Iw (t) output from the inverter circuit 3 and the DC voltage Vdc output from the converter circuit 2, the control unit A1 The active power P to be consumed is calculated. Control unit A1 estimates AC voltage effective value Vac input to converter circuit 2 based on calculated active power P and DC voltage Vdc. The controller A1 estimates the power factor of the AC power input to the converter circuit 2 based on the rotational speed of the motor 4 and the estimated AC voltage effective value Vac, and the AC voltage effective that estimates the calculated effective power P. The AC current effective value Iac input to the converter circuit 2 is estimated by dividing the value Vac by the estimated power factor cos (θ). Control unit A1 controls inverter circuit 3 so that estimated AC voltage effective value Iac does not exceed the reference value.

  Unlike the case of (1) above, the power factor cos (θ) of AC power can be estimated using the rotational speed of the motor 4 instead of the active power P consumed by the motor.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  1 commercial AC power supply, 2 converter circuit, 3, 31, 32 inverter circuit, 4, 41, 42 synchronous motor, 5, 51, 52, 53 current detection circuit, R1, R11, R21, Ru, Rv, Rw current detection resistor , Rdc1, Rdc2 resistance, Vdc_sig1, Vdc_sig11, Vdc_sig2, DC voltage monitor signal, A1, A21, A3 microcomputer, Iac current effective value, Vac voltage effective value, PL1, PL11 positive DC line, PL2, PL22 negative DC line, MD1, MD11, MD2 Synchronous motor driving device, Idc_sig, Idc1_sig, Idc2_sig DC current monitor signal, 6,6M, 6FM, 6A Input current estimation unit, Iac_est, Iac1_est, Iac2_est Estimated current effective value, L coil, DB diode bridge, C, C1 , C2 Capacitor.

Claims (5)

A converter circuit that converts alternating current power into direct current power and outputs,
An inverter circuit that converts the DC power output from the converter circuit into three-phase AC power and outputs it to the motor;
A control unit for controlling the inverter circuit,
The controller is
Based on the three-phase AC current output from the inverter circuit and the DC voltage output from the converter circuit, the active power consumed by the motor is calculated,
Based on the calculated active power and the DC voltage, an AC voltage effective value input to the converter circuit is estimated,
Based on the calculated active power and the estimated AC voltage effective value, the power factor of AC power input to the converter circuit is estimated,
By dividing the calculated active power by the estimated AC voltage effective value and the estimated power factor, the AC current effective value input to the converter circuit is estimated,
The control unit controls the inverter circuit so that the estimated AC voltage effective value does not exceed a reference value.   The control unit multiplies the provisional estimated value of the power factor corresponding to the calculated active power by a correction coefficient corresponding to the estimated AC voltage effective value, thereby obtaining a final power factor of the AC power. The motor drive apparatus of claim 1, configured to calculate an estimated value. The controller is
Based on the relationship between the active power measured in advance at a predetermined AC voltage effective value and the power factor of the AC power, a provisional estimate of the power factor corresponding to the calculated active power is determined,
Based on the relationship between the AC voltage effective value measured in advance at a predetermined motor rotation speed and the power factor of the AC power, the correction coefficient corresponding to the estimated AC voltage effective value is determined. The motor drive device according to claim 2. The controller is
Correcting the value of the active power by multiplying the calculated active power by a coefficient based on the heat loss of the inverter circuit;
The motor driving device according to claim 1, configured to estimate the AC voltage effective value, the power factor of the AC power, and the AC current effective value using the corrected effective power. A converter circuit that converts alternating current power into direct current power and outputs,
An inverter circuit that converts the DC power output from the converter circuit into three-phase AC power and outputs it to the motor;
A control unit for controlling the inverter circuit,
The controller is
Based on the three-phase AC current output from the inverter circuit and the DC voltage output from the converter circuit, the active power consumed by the motor is calculated,
Based on the calculated active power and the DC voltage, an AC voltage effective value input to the converter circuit is estimated,
Based on the rotational speed of the motor and the estimated AC voltage effective value, the power factor of AC power input to the converter circuit is estimated,
By dividing the calculated active power by the estimated AC voltage effective value and the estimated power factor, the AC current effective value input to the converter circuit is estimated,
The control unit controls the inverter circuit so that the estimated AC voltage effective value does not exceed a reference value.

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