JP2018182975A - Compressor motor drive device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compressor motor drive circuit capable of preventing an increase in the size of a smoothing capacitor of a direct current unit while keeping a power supply current in a state with less harmonics.SOLUTION: In a voltage control system of a smoothing capacitor 2, control means that adjusts the input current amplitude such that the input current amplitude becomes a desired DC voltage (Vdc*) and PWM-controls a semiconductor switch 152 so as to adjust the amplitude of an AC power supply current (Iac*) even with information of the product of the rotation number (ω*) and a current (Iq*) corresponding to a magnet torque of a compressor motor 4. As a result, in a low speed range, the output power to the load is substantially balanced with the input power, and in a high speed range, the pulsation is reduced, and the output power to the load is balanced with the input power by a DC voltage control system, and the voltage fluctuation of a smoothing capacitor 2 can be reduced.SELECTED DRAWING: Figure 1

Description

  The present invention rectifies a commercial single-phase AC power supply into a substantially direct current, and converts the obtained direct current into an alternating current of an arbitrary frequency and an arbitrary voltage by an electric power conversion circuit, and is used as an air conditioner or the like. Power source harmonics included in the current from a commercial AC power source, having a compression mechanism that drives the compressor motor at variable speed, and the torque required for each rotational phase of the motor fluctuates significantly. The present invention relates to highly efficient drive control of technology that reduces the load on the transmission system by reducing the power factor and improving the power factor.

  Conventionally, as a compressor motor drive circuit of this type, a method shown in Patent Document 1 has been proposed. Here, means for storing the speed for each motor rotation phase is provided, and the drive voltage or the drive current is adjusted and controlled in order to converge the speed detected for each same rotation phase to a desired value. As a result, it is possible to reduce the instantaneous rotational fluctuation.

  Furthermore, the drive of the motor is described by two axes in accordance with the phase of the magnet incorporated in the rotor, and the load torque fluctuates based on the so-called vector control that controls the current component according to those axes. Patent Document 2 and the like introduce a method of making it correspond to.

  In addition, as a power source for driving a motor, a commercial AC power source is usually used. In that case, a commercial AC power supply is once rectified and converted to DC, and the DC is converted to a pseudo AC of any frequency by the inverter circuit to drive the motor, but conversion from commercial AC to a pseudo AC for motor drive is performed. It is desirable to realize it efficiently. Furthermore, it is desirable that the current flowing from the commercial AC power source has less harmonic distortion and a high power factor. To this end, it is important to keep the intermediate DC voltage as low as possible, and to minimize the on / off of the semiconductor switch in the rectifier circuit as much as possible. As a method for this purpose, a method shown in Patent Document 3 has been proposed.

  According to Patent Document 3, the rectification circuit section is realized by adjusting a DC voltage so as to set a period in which the semiconductor switch is turned on or off, that is, a period in which the semiconductor switch is turned off, to a desired value.

  These prior art techniques are premised to be realized independently of each other, and the method for simultaneously fulfilling is to instantaneously input energy to the motor, which is the product of the rotational speed and torque, and energy flowing from the commercial power source. The details are described in Patent Document 4.

JP-A-61-173690 JP, 2010-259133, A International Publication No. 2014/034003 JP, 2016-154434, A

However, in the above-described conventional configuration, information on the torque of the motor is required, and instead of directly detecting the torque, or by using the proportional relationship between the torque and the motor current at the time of high efficiency driving, torque is replaced. The motor current information is used.

  However, in the closed type refrigerant compressor of the refrigeration air conditioning equipment, since the inside including the motor is in a high temperature and high pressure atmosphere, it is very expensive and difficult to directly detect the rotational phase of the motor. For this reason, there has been adopted a method of estimating the rotational phase of the motor using motor drive information such as voltage and current and motor parameters. However, since the motor drive information and the motor parameters may contain errors, the estimation of the rotational phase may also contain errors. An error in the estimated rotational phase will disturb the proportionality constant between the torque and the motor current.

In the air conditioner, the compressor motor is rotated at a high speed to provide a large cooling and heating capacity in the period until the room temperature approaches the desired value at the start of the cooling and heating operation, or in the heating operation at low outside air temperature. Sometimes. In order to rotate the motor at high speed, a high drive voltage is required, which may be difficult to apply in practice. However, at the expense of efficiency, high-speed rotational drive at low voltage by field weakening becomes possible. In this case, the d-axis current, which is a current for weakening the magnetic flux, increases to drive the motor with a larger current than usual.
However, in the estimation of the rotational phase of the motor, if the current becomes large, it becomes susceptible to variations in motor parameters, which contributes to an increase in estimation error. Further, in a motor that also uses reluctance torque, the utilization factor of reluctance torque is increased during field-weakening driving, and accurate rotation phase estimation based on the use of reluctance torque is required. FIG. 3 is a characteristic diagram showing this relationship. That is, in the low rotation speed region, the magnet torque is mainly driven, but in the high speed rotation region, as a result, the utilization rate of the reluctance torque is increased, and as described above, the motor is driven with a large current And contribute to an increase in estimation error.

  That is, due to these errors associated with rotational phase estimation, the method of Patent Document 4 causes not only insufficient modulation of the input current but also excessive modulation such as performing input current modulation exceeding the amount equivalent to the energy input to the motor. In some cases, there is a problem that the voltage fluctuation of the direct current portion may not be sufficiently suppressed.

  An object of the present invention is to solve the above-mentioned conventional problems, and to provide a compressor motor drive circuit which is not affected by an error related to rotational phase estimation and has a small voltage fluctuation in a direct current portion.

  In order to solve the above-mentioned conventional problems, the compressor motor drive device of the present invention controls the alternating current power supply using a semiconductor switch and a reactor while reducing harmonic components of the inflowing current. A compressor motor including a magnet is driven at an arbitrary rotation speed by converting the obtained direct current into a direct current of a desired voltage by adjusting the current amplitude and reconverting the obtained direct current into a pseudo alternating current of an arbitrary frequency and voltage. The compressor motor drive device estimates the instantaneous rotational phase of the compressor motor from the characteristic value and the driving state of the compressor motor, and drives the compressor motor at an arbitrary rotational speed based on the estimated rotational phase. In addition, according to the product of the estimated information of the magnet torque and the rotational speed of the compressor motor, there is provided means for further adjusting the amplitude of the current flowing from the AC power supply.

  Here, the relationship between the torque of the motor and the current will be described on the assumption of rotational phase estimation or speed estimation. Of the motor torque, a current proportional to the magnet torque is called a q-axis current, and the axis rotates in accordance with the rotation of the magnet. The proportional constant is called the power generation constant, and becomes constant when the source of the motor is determined.

  Assuming that the phase estimation deviation is Δ, the estimated value of the q-axis current is deviated by the ratio of cos (Δ). That is, the estimated value of the magnet torque is also shifted by the ratio of cos (Δ).

On the other hand, since the reluctance torque estimated value is proportional to the product of the q-axis current and the d-axis current which is an axis rotating 90 degrees out of phase, assuming that the phase estimation deviation is Δ, the reluctance torque estimated value is
cos (Δ) × sin (Δ) = 0.5 × sin (2 · Δ)
Shift at the rate of Assuming that the estimated deviation Δ is not a large value, each change is cos (Δ) ≒ 1
0.5 × sin (2 · Δ) ≒ Δ
Therefore, the magnet torque estimated value is less susceptible to the phase estimation deviation Δ. Therefore, under driving conditions where the reluctance torque is small, the influence of phase estimation is small, and the power supplied to the motor and the power supplied from the AC power supply substantially match, so the voltage fluctuation in the intermediate DC portion becomes small. It is possible to reduce the withstand voltage of the smoothing capacitor that temporarily accumulates electric power and to reduce the electrostatic capacity, and the drive device can be miniaturized.

  Further, in the compressor to which the present invention is applied, at high speed rotation, the pulsation of the rotational speed is reduced due to the inertia moment of the compression mechanism and the motor, and it is necessary to fluctuate the instantaneous torque to keep the instantaneous rotational speed constant. It disappears. For this reason, the reluctance torque may also be constant, and the difference between the product of the magnet torque and the rotational speed and the compressor motor output becomes a constant value without pulsation. The deviation of the constant value is easily eliminated by integral compensation included in DC voltage feedback control of the rectifier circuit unit.

  In the compressor motor drive circuit according to the present invention, the influence of the phase estimation error is small, and the power supplied to the motor and the power supplied from the AC power source substantially match, so the voltage fluctuation in the intermediate DC portion becomes small. It is possible to reduce the withstand voltage of the smoothing capacitor that temporarily accumulates electric power and to reduce the electrostatic capacity, and the drive device can be miniaturized.

The circuit block diagram of the compressor motor drive unit according to the first embodiment of the present invention The relationship characteristic figure between the number of revolutions, the load torque generating means and the torque ripple rate in the first embodiment of the present invention Relation characteristic figure of the number of revolutions and load torque generating means in compressor motor The whole circuit block diagram in another embodiment of the present invention The whole circuit block diagram in another embodiment of the present invention The whole circuit block diagram in another embodiment of the present invention The whole circuit block diagram in another embodiment of the present invention The whole circuit block diagram in another embodiment of the present invention

According to the first aspect of the present invention, conversion to a direct current of a desired voltage is performed by adjusting the current amplitude while controlling the alternating current power supply to reduce harmonic components of the inflowing current using a semiconductor switch and a reactor. A compressor motor drive device for driving a compressor motor including a magnet at an arbitrary rotational speed by reconverting the obtained direct current into a pseudo alternating current of an arbitrary frequency and voltage, and the characteristics of the compressor motor Based on the estimated rotational phase, the compressor motor is driven at an arbitrary rotational speed based on the estimated rotational phase, and the estimated information on the magnet torque and the rotational speed of the compressor motor And means for further adjusting the amplitude of the current flowing from the AC power supply according to the product of As the estimation information of the magnet torque, it is possible to use the q-axis current multiplied by a proportional constant. Further, while comparing the desired DC voltage value with the actual DC voltage and adjusting the input current amplitude based on the error, it is made to include one that uses the integral information of the error.

  As a result, since the torque of the compressor motor is mostly the magnet torque in the low speed rotation range, the input power and the motor output substantially match, and the torque of the compressor motor may be constant in the high speed rotation range. The reluctance torque used can also be rubbed against a constant value without pulsation. Then, the deviation of the fixed value can be easily eliminated by the integral compensation included in the DC voltage feedback control of the rectifier circuit unit.

  Therefore, in both rotation ranges, the withstand voltage of the smoothing capacitor for temporarily storing DC power can be lowered and the capacitance can be reduced, and the drive device can be miniaturized.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited by the embodiment.

Embodiment 1
FIG. 1 shows an entire circuit configuration diagram of a compressor motor drive device according to a first embodiment of the present invention. AC power is converted into DC power by smoothing with a smoothing capacitor 2 through a rectifier circuit including a diode bridge 151, a reactor 153, a semiconductor switch 152, and a diode 154. The obtained DC power is converted again into AC power by the motor drive circuit (inverter circuit) 3 to drive the compressor motor 4. The torque or speed of the compressor motor 4 is not detected directly.

  A current detection means 155 is attached to the connection between the compressor motor 4 and the motor drive circuit (inverter circuit) 3 so that the current flowing through the motor 4 can be detected. The detected current is converted to rotational coordinate information by the dq conversion means 156, and the converted current is called d-axis current (Id) or q-axis current (Iq), and the q-axis current is a current proportional to the magnet torque And the d-axis current is a current that is orthogonal to the q-axis current. The two types of currents are input to the position estimation means 157. The position estimation means 157 estimates the rotational speed (ω ^) and the rotational phase (θ ^) of the compressor motor 4 using not only the current information but also the inductance information of the compressor motor 4 or the like.

  The estimated rotational speed (ω ^) is compared with the desired value (ω *) of the rotational speed in the comparison means 9 and the error information is sent to the speed PI compensation means 15 for speed control stabilization. The result obtained by the speed PI compensation means 15 is an information value indicating how to increase or decrease the torque with respect to the desired speed as a motor current command (Im *). The motor current command (Im *) is distributed by the dq distributing means 170 into the d-axis current command (Id *) and the q-axis current command (Iq *). The two distributed current commands are sent to the comparing means 158 to be compared with the actual motor current (Id and Iq). As a result of comparison, the obtained current error is sent to the current PI compensation means 159 for stabilizing the current control, passes through the inverse dq conversion means 160, is converted into fixed coordinates of the motor, and is converted by the PWM conversion means 161. The pulse width signal is converted to drive a motor drive circuit (inverter circuit) 3 to configure a speed control system of the motor. That is, the speed control system adjusts the desired current (Id *, Iq *) of the motor to make the speed constant, but as the inner loop, the motor is controlled so that the actual current (Id, Iq) approaches the desired current. It has a current control system that regulates the voltage applied to it. The operation of the current control system causes the motor current (Id, Iq) to substantially match the desired current (Id *, Iq *), and the operation of the speed control system causes the rotational speed (ω ^) to It substantially matches the rotational speed desired value (ω *).

On the other hand, the estimated rotational phase (θ ^) is sent to the dq conversion means 156 and the inverse dq conversion means 160 and used for coordinate conversion in the drive control of the motor. The processing content in the position estimation means 157 can use what is described, for example in patent document 2 grade | etc.,.

  Next, the configuration of the rectifier circuit will be described. The AC power supply 1 is DC-pulsed by the diode bridge 151, and the output therefrom is supplied to the smoothing capacitor 2 through the reactor 153 and the diode 154. A semiconductor switch 152 is provided between the connection point of the reactor 153 and the diode 154 and the other terminal of the direct current, and the alternating current power source 1 can be short-circuited / opened via the reactor 153. Further, the current flowing in the reactor 153 can be detected by the current detection means 5.

  The operation as a rectifier circuit will be described. The voltage (Vdc) of the smoothing capacitor 2 is detected, compared with a desired value (Vdc *) by the comparison means 20, and the error information is input to the voltage PI compensation means 21 for voltage control stabilization. The output of the voltage PI compensation means 21 is input to the multiplication means 7 through the addition means 22 and multiplied with the AC voltage waveform information 6 to obtain the desired current value (Iac *) of the AC current. The other information input to the addition means 22 will be described later.

  That is, due to excess or deficiency of the voltage (Vdc) of the smoothing capacitor 2 with respect to the desired voltage (Vdc *), the desired current value of the alternating current is adjusted with its waveform maintained. The desired value (Iac *) of the alternating current determined in this way is sent to the comparison means 8 to be compared with the actually detected alternating current (Iac), and its error information is used to stabilize the current control. Current PI compensation means 10 of FIG.

  The output of the current PI compensation means 10 is sent to the PWM conversion means 165 and converted to a pulse width signal to control the semiconductor switch 152 on / off. That is, the control system is configured to bring the alternating current (Iac) close to the desired value (Iac *).

  The other information input to the addition means 22 provided in the control system of the voltage (Vdc) of the smoothing capacitor 2 is information from the motor drive control system. Specifically, command information (Iq *) of the q-axis current, which is a current proportional to the magnet torque of the compressor motor 4, and the rotation speed command (ω *) of the compressor motor are input to the multiplication means 23 as a result It is information.

  Here, as shown in FIG. 3, when the number of revolutions of the compressor motor 4 is low, most of the torque required for the compressor motor 4 is supplied by the magnet torque. Even in the case of driving while estimating the rotational phase of the motor, since the magnet torque is less affected by the estimation error, it is possible to estimate the torque with almost no deterioration.

  That is, in the low rotation range, the torque can be accurately estimated only by using current information proportional to the magnet torque. Then, when it is multiplied by the rotation speed command (ω *) by the multiplication means 23, it becomes the instantaneous power information input to the motor 4. If the desired value (Iac *) is directly adjusted so that the current (Iac) from the AC power supply 1 interlocks by inputting the instantaneous power information of the motor into the adding means 22, the load pulsation of the motor 4 can be obtained. Since the power supply current directly interlocks, the adjustment of the load pulsation of the motor 4 by the smoothing capacitor 2 becomes unnecessary, and the downsizing of the smoothing capacitor 2 such as the low capacity and the low withstand voltage becomes possible. Moreover, no load torque detection means for the motor 4 is required.

On the other hand, in the high rotation range, as shown in FIG. 3, the required torque increases and the load ratio of the reluctance torque also increases. However, as shown in the characteristic diagram showing the relationship with the torque pulsation of the compressor motor 4 in FIG. 2, the torque pulsation rate decreases when the rotational speed becomes high. The principle is that as the compressor rotational speed increases, the rotational fluctuation is reduced due to the moment of inertia of the motor and the compression mechanism, even if the load torque pulsation is not compensated by the motor torque. In this case, since the pulsation of the reluctance torque is also reduced, as a result, the pulsation fluctuation of the DC voltage is not increased. However, as it is, the difference based on the reluctance torque not including pulsation remains between the calculated value determined by the motor's magnet torque and rotation speed and the input value determined by the power supply current and the power supply voltage, and the DC voltage has a desired value. The deviation of the DC voltage from the desired value is actually eliminated by the integral action of the voltage PI compensation means 21 of FIG. That is, the error based on the increased reluctance torque is eliminated at the rectifier circuit side.

  In addition, the circuit configuration method of the rectifier circuit 11 is described below. In FIG. 1, although what was implement | achieved using a reactor, a semiconductor switch, and a diode what was rectified | straightened with the diode bridge was shown, it does not specifically limit. For example, as shown in FIG. 8 of the present application and FIG. 1 of Patent Document 3, a reactor and a bidirectional switch are provided in front of the diode bridge, or as shown in FIG. A semiconductor switch is connected in parallel to the arm, and a reactor is provided between the connection point and the power supply, or, as shown in FIG. 7 of this application or FIG. It is obvious that the same thing can be realized by connecting semiconductor switches in parallel to each other and providing a reactor between the connection point and the power supply.

  Similarly, as shown in FIG. 4 of the present application, providing means for interlocking only the fundamental frequency components, or using information of AC voltage as shown in FIGS. 7, 8 and 9 of the present application. Further, the configuration as disclosed in FIG. 5 of the present application can be similarly realized in order to further improve the accuracy and to perform control to keep the semiconductor switch OFF period of the patent document 3 at a desired value. It is obvious.

  As described above, in the compressor motor drive circuit according to the present invention, the voltage fluctuation in the intermediate DC portion is reduced, and the withstand voltage of the smoothing capacitor for temporarily storing DC power can be reduced and the capacitance can be reduced. The drive device can be miniaturized. It is also possible to increase the number of heat exchangers in the same occupied space, and energy saving of air conditioners and various heat pump devices can be achieved.

1 AC power supply 2 smoothing capacitor 3 motor drive circuit (inverter circuit)
Reference Signs List 4 motor 5, 155 current detection means 6 AC voltage waveform information 7, 23 multiplication means 8, 9, 20, 158, 181 comparison means 10, 159 current PI compensation means 11 rectification circuit 12 speed detection means 15 speed PI compensation means 16 drive Control circuit 17 Drive circuit 21 Voltage PI compensation means 22 Addition means 151 Diode bridge 152 Semiconductor switch 153 Reactor 154 Diode 156 dq conversion means 157 Position estimation means 160 Inverse dq conversion means 161, 165 PWM conversion means

Claims (4)

  A direct current obtained by converting the AC voltage to a desired voltage by adjusting the current amplitude while controlling the alternating current power supply to reduce harmonic components of the inflowing current using the semiconductor switch and the reactor. A compressor motor drive device for driving a compressor motor including a magnet at an arbitrary rotation speed by reconverting into a pseudo-AC of an arbitrary frequency and voltage, and from the characteristic value and the driving state of the compressor motor The instantaneous instantaneous rotational phase of the compressor motor is estimated, and the compressor motor is driven at an arbitrary rotational speed based on the estimated rotational phase, and according to the product of the estimated information of the magnet torque and the rotational speed of the compressor motor A compressor motor drive, comprising: means for further adjusting the amplitude of the current flowing from the AC power supply.   The compressor motor drive device according to claim 1, wherein an estimated value of a current proportional to the magnet torque is used as the estimated information of the magnet torque. As a means for converting into a direct current of a desired voltage by adjusting the current amplitude, the desired voltage value is compared with the actual direct current voltage, and in the operation of adjusting the current amplitude based on the error, The compressor motor drive device according to any one of claims 1 or 2, characterized in that the use of integral information is included. The command information of the estimated value of the current proportional to the magnet torque is used instead of the estimated value of the current proportional to the magnet torque, and the rotational speed command is used instead of the rotational speed. A compressor motor drive according to any one of the preceding claims.

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