Power conversion device, motor drive device, and apparatus using refrigeration cycle

Abstract

A power conversion device (1) comprises a converter (100), a capacitor (200), an inverter (300), and a control device (500) that performs drive control of the inverter (300). The control device (500) has: a capacitor current suppression control unit (502) that calculates a current pulsation command that causes the current that flows through a motor (401) to pulse to reduce the amount of capacitor current that flows into and out of the capacitor (200); and an output upper limit value control unit (503) that controls a current pulsation command upper limit value that is an output upper limit value for the current pulsation command. The output upper limit value control unit (503) controls the current pulsation command upper limit value such that the pulsation amplitude of the capacitor current coincides with a capacitor current target value. The capacitor current suppression control unit (502) limits the current pulsation command on the basis of the current pulsation command upper limit value controlled by the output upper limit value control unit (503).

Description

Power conversion devices, motor drive devices, and refrigeration cycle application equipment

[0001] The present disclosure relates to a power conversion device, a motor drive device, and a refrigeration cycle applied device.

[0002] Conventionally, power conversion devices are known that convert AC power supplied from an AC power source into desired AC power and supply it to a load, such as a motor used in a compressor of an air conditioner. In this type of power conversion device, the AC power supplied from the AC power source is rectified by a converter, smoothed by a capacitor, and then converted into the desired AC power by an inverter consisting of multiple switching elements and output to the load, i.e., the motor. For example, in the power conversion device disclosed in Patent Document 1, the inverter is controlled to reduce pulsation in the motor current flowing through the motor in response to a decrease in the motor load.

[0003] JP 2012-151962 A

[0004] However, reducing the pulsation amplitude of the motor current, as in the technology disclosed in Patent Document 1, may increase the capacitor current flowing through the capacitor. Capacitors have a set upper limit for the allowable current, and if a current exceeding this limit continues to flow, the capacitor will heat up and deteriorate or fail. Meanwhile, reducing the capacitor current flowing in and out of the capacitor increases the pulsation of the motor current, which increases motor loss and reduces motor efficiency.

[0005] The present disclosure has been made in consideration of the above, and aims to provide a power conversion device that can control the capacitor current so that it is within the allowable range of the capacitor while suppressing an increase in pulsation of the motor current.

[0006] To solve the above-mentioned problems and achieve the object, the present disclosure provides a power conversion device for driving a motor provided in a mechanical load, the power conversion device including: a converter that converts first AC power supplied from a commercial power source into DC power; a capacitor connected to the output terminal of the converter; an inverter connected across the capacitor that converts the DC power into second AC power and outputs the second AC power to the motor; and a control device that drives and controls the inverter. The control device includes a capacitor current suppression control unit that calculates a current pulsation command that pulsates the current flowing through the motor to reduce the amount of capacitor current flowing into or out of the capacitor; and an output upper limit control unit that controls a current pulsation command upper limit, which is an output upper limit of the current pulsation command. The output upper limit control unit controls the current pulsation command upper limit so that the pulsation amplitude of the capacitor current matches a capacitor current target value. The capacitor current suppression control unit limits the current pulsation command based on the current pulsation command upper limit controlled by the output upper limit control unit.

[0007] The power conversion device according to the present disclosure has the advantage that it is possible to control the capacitor current so that it falls within the allowable range of the capacitor while suppressing an increase in pulsation of the motor current.

[0008] FIG. 1 is an explanatory diagram showing an example of the configuration of a power conversion device and a motor drive device according to a first embodiment. FIG. 2 is an explanatory diagram showing an example of the configuration of a control device included in the power conversion device according to the first embodiment. FIG. 3 is an explanatory diagram showing an example of the configuration of a capacitor current suppression control unit included in the control device included in the power conversion device according to the first embodiment. FIG. 4 is an explanatory diagram showing the operation of an amplitude limiting unit of a capacitor current suppression control unit included in the control device included in the power conversion device according to the first embodiment. FIG. 5 is an explanatory diagram showing the operation of an output upper limit value control unit included in the control device included in the power conversion device according to the first embodiment. FIG. 1 is an explanatory diagram showing an example of the operation waveforms of the motor speed, capacitor current, and motor current when control by an upper limit value control unit is performed; FIG. 2 is an explanatory diagram showing an example of the configuration of a power conversion device and a motor drive device according to a second embodiment; FIG. 3 is an explanatory diagram showing an example of the configuration of a control device included in the power conversion device according to the second embodiment; FIG. 4 is an explanatory diagram showing an example of the configuration of an output upper limit value control unit included in the control device included in the power conversion device according to the second embodiment;and an explanatory diagram showing an example of the operating waveform of a motor current. An explanatory diagram showing an example of the configuration of a control device included in a power conversion device according to a fourth embodiment. An explanatory diagram showing an example of the configuration of an output upper limit value control unit of a control device included in a power conversion device according to a fourth embodiment. An explanatory diagram showing an example of the configuration of a control device included in a power conversion device according to a fifth embodiment. A refrigerant circuit diagram showing an example of the configuration of a refrigeration cycle application device according to a sixth embodiment.

[0009] Hereinafter, a power conversion device, a motor drive device, and a refrigeration cycle applied device according to embodiments of the present disclosure will be described in detail with reference to the drawings.

[0010] First Embodiment. Fig. 1 is an explanatory diagram showing an example configuration of a power conversion device and a motor drive device according to a first embodiment. The power conversion device 1 drives, for example, a motor 401 built into a compressor 400. Note that the power conversion device 1 can also be applied to motors provided in mechanical devices other than compressors. The compressor 400 includes a motor 401 and a mechanical load 402. The motor 401 is connected to the mechanical load 402 and performs mechanical work. As an example, the mechanical load 402 is a compression mechanism that compresses a refrigerant. The load torque of the compressor 400 changes when it draws, compresses, and discharges the refrigerant. When the speed of the motor 401 is approximately constant, the load torque has a periodic pulsating waveform.

[0011] There are no particular limitations on the mechanical structure for compressing the refrigerant in the compressor 400. The compressor 400 may be a rotary compressor, a reciprocating compressor, a scroll compressor, a screw compressor, or any other compressor.

[0012] The power conversion device 1 is connected to a commercial power supply 110 and a compressor 400. The commercial power supply 110 may be single-phase or three-phase. In the following description, a single-phase commercial power supply 110 will be described. The power conversion device 1 converts first AC power supplied from the commercial power supply 110 into second AC power having a desired amplitude and phase, and supplies the second AC power to the compressor 400. The power conversion device 1 includes a converter 100, a capacitor 200, an inverter 300, current detection units 301a and 301b, a DC bus voltage detection unit 201, and a control device 500.

[0013] The motor drive device 2 includes the power conversion device 1 and a motor 401 provided in the compressor 400 .

[0014] Converter 100 is connected between commercial power supply 110 and capacitor 200, and rectifies and outputs first AC power supplied from commercial power supply 110. Capacitor 200, DC bus voltage detection unit 201, and inverter 300 are connected to the output terminal of converter 100. As shown in FIG. 1 , converter 100 is exemplified as a circuit using reactor 120 and diode rectifier 130, but other circuit configurations may also be used.

[0015] Capacitor 200 is, for example, an electrolytic capacitor or a film capacitor. Capacitor 200 has a capacity that can smooth the power rectified by converter 100 to a certain extent. The waveform of the voltage across capacitor 200 is not the same as the full-wave rectification of commercial power supply 110, but rather has a shape in which a voltage ripple corresponding to the frequency of commercial power supply 110 is superimposed on the DC component due to the smoothing effect of capacitor 200. The magnitude of this voltage ripple varies depending on the capacitor capacitance, but is generally not very large, being less than several tens of percent of the average value of the DC bus voltage.

[0016] Inverter 300 is connected to capacitor 200 and motor 401. Inverter 300 switches an internal power conversion element to convert the DC power stored in capacitor 200 into second AC power having a desired amplitude and phase, and outputs the second AC power to motor 401. Motor 401 rotates in accordance with the amplitude and phase of the second AC power supplied from inverter 300.

[0017] Each of the current detection units 301a and 301b detects the current value of one phase of the three-phase current output from the inverter 300 and outputs the detected current value to the control device 500. When the motor 401 is a three-phase Y-connection, if the current values ​​of two phases of the three-phase current values ​​output from the inverter 300 are obtained, the current value of the remaining phase can be calculated using Kirchhoff's law. For this reason, currents for two phases are obtained here, but current detection units may be provided for all three phases. Alternatively, the three-phase current values ​​may be obtained using a known technique for reconstructing the three-phase current flowing through the motor from the current in the DC bus of the inverter 300.

[0018] The control device 500 receives the current detection values ​​detected by the current detection units 301a and 301b and the voltage detection value detected by the DC bus voltage detection unit 201 as inputs, performs control calculations described below, and outputs each switching signal for the inverter 300. Although not shown, the control device 500 is configured to include electronic circuits such as a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), and various interfaces. The control device 500 reads out programs stored in the ROM and loads them into the RAM, and the CPU executes various processes.

[0019] When the motor 401 is driven, a capacitor current Ic flows through the capacitor 200. The capacitor 200 has an internal resistance component. Therefore, the capacitor 200 generates heat due to the capacitor current Ic. Generally, the capacitor 200 has a set allowable upper limit for the current, and if a current exceeding this limit continues to flow, the capacitor 200 will heat up and deteriorate or fail. Generally, when the capacitor current Ic exceeds the allowable upper limit, the allowable upper limit itself is often increased by using a large-capacity capacitor or connecting multiple capacitors. However, these methods have problems such as increased costs for the capacitor 200 and increased size of the circuits constituting the power conversion device 1 and the motor drive device 2.

[0020] A control method is known that suppresses capacitor current Ic by pulsating the current flowing through motor 401 (hereinafter referred to as motor current) in synchronization with the voltage ripple of capacitor 200. To reduce capacitor current Ic, the motor current is pulsated so as to reduce the difference between rectified current Iin1 flowing from converter 100 and rectified current Iin2 flowing into inverter 300. In this embodiment, this control is referred to as "capacitor current suppression control." Utilizing capacitor current suppression control allows motor drive device 2 to be configured using inexpensive capacitors.

[0021] The effect of capacitor current suppression control allows the motor drive device 2 to be configured with inexpensive capacitors. However, on the other hand, there is a trade-off: increased motor current pulsation reduces the efficiency of the motor 401 and increases vibration and noise in the mechanical load 402. Furthermore, the margin of the capacitor current Ic relative to the allowable upper limit varies depending on the operating states of the motor 401 and the mechanical load 402. Therefore, with conventional motor drive devices, it is difficult to balance this trade-off, and excessive capacitor current suppression control can result in an unnecessarily increased loss in the motor 401, or conversely, excessive capacitor current suppression control can result in an increase in the capacitor current. As a result, with conventional motor drive devices, it is difficult to achieve both improved energy-saving performance and reduced device size and cost.

[0022] In order to solve this problem, in the power conversion device 1 according to the first embodiment, an arbitrary capacitor current target value Ic ＊ is input to the control device 500, and the control device 500 minimizes the increase in the pulsation of the motor current while controlling the pulsation amplitude of the capacitor current Ic to the capacitor current target value Ic ＊ The control was carried out so that it coincided with

[0023] The control calculation of the control device 500 included in the power conversion device 1 according to the first embodiment will be described in detail below.

[0024] FIG. 2 is an explanatory diagram illustrating an example of the configuration of a control device included in the power conversion apparatus according to the first embodiment. The control device 500 includes a speed control unit 501, a capacitor current suppression control unit 502, an output upper limit control unit 503, an adder 504, a current control unit 505, a position estimation unit 506, and a PWM (Pulse Width Modulation) signal generation unit 507. Here, a case where control is performed on a dq rotating coordinate system synchronized with the rotor position of the motor 401 is described. However, this is merely an example, and control may be performed on other coordinate systems. Control on the dq rotating coordinate system requires the rotor position of the motor 401. The rotor position of the motor 401 may be detected by a position sensor (not shown). Alternatively, the position estimation unit 506 may calculate a speed electromotive force from the output voltage of the inverter 300 and the current flowing through the motor 401, and estimate the rotor position from the speed electromotive force. There are various methods for position sensorless control of AC motors. For example, sensorless vector control using an adaptive observer is well known.

[0025] The speed control unit 501 calculates the estimated speed ω of the motor 401 estimated by the position estimation unit 506. ＿ Average value ωDC of est and speed command ω ＊ and the first q-axis current command IqDC ＊ As a method of controlling the average speed, PID (Proportional Integral Differential) control is well known. ＊ and the three-phase current detection value Iuvw, the rotor position of the motor 401 is estimated. When the motor speed ω is in a steady state, the first q-axis current command IqDC ＊ The motor speed ω is a rotation speed of the motor 401. The speed control unit 501 also receives the estimated speed ω ＿ Instead of inputting est, a speed detection value detected by using a speed detector that detects the speed of the motor 401 or a position detector that detects the position of the rotor may be input.

[0026] The capacitor current suppression control unit 502 detects the bus voltage Vdc detected by the DC bus voltage detection unit 201 and the current ripple command upper limit value IqrC ＊ max is input, the second q-axis current command IqrC ＊ Alternatively, the detected value of the capacitor current Ic itself may be input to the capacitor current suppression control unit 502. Since the capacitor current Ic and the bus voltage Vdc have a differential and integral relationship, it is sufficient to input either one of them. When the rotation speed ω of the motor 401 is in a steady state, the second q-axis current command IqrC ＊ has a waveform synchronized with the voltage pulsation of the capacitor 200.

[0027] The output upper limit control unit 503 determines the capacitor current target value Ic ＊ is input, and the current pulsation command upper limit IqrC ＊ max is output. Here, the capacitor current target value Ic ＊ The values ​​may be input from outside the control device 500 or may be stored in the ROM of the control device 500 in advance.

[0028] The adder 504 calculates the first q-axis current command IqDC ＊ and the second q-axis current command IqrC ＊ and are added together to obtain the final q-axis current command Iq ＊ Calculate the following.

[0029] The current control unit 505 outputs the final q-axis current command Iq ＊ and the three-phase current detection value Iuvw, and current control is performed based on the three-phase voltage command Vuvw. ＊ As a method of current control, PID control is well known, as is average speed control.

[0030] The position estimation unit 506 calculates the three-phase current detection value Iuvw and the three-phase voltage command Vuvw ＊ and the estimated motor speed ω ＿ est and the estimated position θ ＿ As described above, the three-phase current detection value Iuvw of the AC motor and the three-phase voltage command Vuvw are output. ＊ From this, the estimated motor speed ω ＿ est and the estimated position θ ＿There are various methods for calculating est, and for example, sensorless vector control using an adaptive observer is well known.

[0031] The PWM signal generator 507 generates a three-phase voltage command Vuvw ＊ Based on this, a switching signal is generated for the inverter 300. Carrier comparison modulation is a well-known method for generating a switching signal, but other methods may also be used.

[0032] Next, the control of the capacitor current suppression control unit 502 and the output upper limit value control unit 503 will be specifically described.

[0033] As shown in FIG. 1, it is generally known that the voltage rectified from the single-phase commercial power supply 110 via the diode rectifier 130 has a pulsating component with a frequency 2N times the power supply frequency of the commercial power supply 110. Here, N is a natural number. In the first embodiment, the capacitor current suppression control unit 502 operates to suppress the capacitor current Ic having a component twice the power supply frequency to a capacitor current target value Ic ＊ Hereinafter, the power supply frequency will be referred to as a 1f component, and the component twice the power supply frequency will be referred to as 2f. Furthermore, a frequency twice the power supply frequency will be referred to as power 2f.

[0034] 3 is an explanatory diagram showing an example of the configuration of a capacitor current suppression control unit of the control device of the power conversion apparatus according to the first embodiment. The capacitor current suppression control unit 502 is configured as a feedback controller with a command value of 0. Typically, a feedback controller has a lower control response than a feedforward controller and is not suitable for suppressing high-frequency pulsation. However, various high-frequency pulsation suppression means have been proposed for feedback controllers in the past, and a well-known method is one that uses Fourier coefficient calculation and a PID controller. The capacitor current suppression control unit 502 includes a subtraction unit 521, Fourier coefficient calculation units 522 and 523, PID control units 524 and 525, an amplitude limiting unit 526, and an AC restoration unit 527.

[0035] The subtractor 521 calculates the deviation between the command value = 0 and the bus voltage Vdc. Using the theory of Fourier series expansion, it is possible to extract the amplitudes of the sine signal component and cosine signal component of a specific frequency contained in the deviation. The Fourier coefficient calculators 522 and 523 calculate the amplitudes of the sin2f component and cos2f component contained in the deviation. The detection signals multiplied by the Fourier coefficient calculators 522 and 523 are sin2ωint and cos2ωint, respectively. The amplitudes of the sin2f component and cos2f component contained in the deviation are doubled by the average value of the product of the input signal and the detection signal. In other words, the Fourier coefficient calculators 522 and 523 calculate the amplitude of the component corresponding to the power frequency of the commercial power source 110, which is contained in the deviation between the detection value and the command value. If the bus voltage Vdc has a periodic waveform, the output signals of the Fourier coefficient calculators 522 and 523 will be approximately constant.

[0036] The PID control units 524 and 525 perform proportional-integral-derivative control, i.e., PID control, so that specific frequency components of the deviation become zero, and output second q-axis current commands IqrC ＊ The sin component of IqrCs ＊ and cos component IqrCc ＊ The proportional gain and differential gain may be zero, but the integral gain value must be non-zero in order to converge the deviation to zero. Therefore, the PID control units 524 and 525 mainly perform integral operation. Normally, the output of integral control changes gradually. Therefore, the output of the PID control units 524 and 525 can also be considered to be roughly constant.

[0037] The amplitude limiting unit 526 outputs the second q-axis current command IqrC ＊ The sin component of IqrCs ＊ , cos component IqrCc ＊ , and the current pulsation command upper limit value IqrC ＊ max is input, and the second q-axis current command IqrC after amplitude limitation is ＊ The sin and cos components of the signal are output.

[0038] 4 is an explanatory diagram illustrating the operation of the amplitude limiting unit of the capacitor current suppression control unit of the control device provided in the power conversion device according to the first embodiment. In FIG. 4, the sine component IqrCs of the current ripple command ＊ and cos component IqrCc ＊ is the second q-axis current command IqrC ＊ The ratio of the sine component and the cosine component of the second q-axis current command IqrC ＊ Without changing the phase of the second q-axis current command IqrC ＊ The amplitude of the current pulsation command upper limit IqrC ＊ This amplitude limiting method is performed by adjusting the second q-axis current command IqrC ＊ The sin component of IqrCs ＊ and cos component IqrCc ＊ Current pulsation command upper limit IqrC for the square root of the sum of squares ＊ The ratio of the second q-axis current command IqrC ＊ The sin component of IqrCs ＊ and cos component IqrCc ＊ By multiplying this by , the second q-axis current command IqrC after amplitude limitation is obtained. ＊ The sine and cosine components of can be calculated.

[0039] In order to restore the output of the amplitude limiting unit 526 to an AC component, the AC restoration unit 527 restores the output of the amplitude limiting unit 526 to an AC component by subtracting sin(2ωint+θ ＿ ofst) and cos(2ωint+θ ＿ ofst) and then summed to obtain the second q-axis current command IqrC ＊ That is, the AC restoration unit 527 determines the second q-axis current command IqrC, which is a command for the pulsation component for suppressing the capacitor current Ic. ＊ where the offset phase θ ＿ Since the capacitor current Ic and the bus voltage Vdc have a differential and integral relationship and there is a phase difference of 90 degrees, the ofst takes this phase difference into account. ＿ofst=π / 2 [rad]. In addition, the bus voltage Vdc is used as the input to the capacitor current suppression control unit 502, but as described above, the capacitor current Ic and the bus voltage Vdc have a differential and integral relationship. Therefore, even when the capacitor current Ic is used as the input to the capacitor current suppression control unit 502, the power conversion device 1 of the first embodiment can be realized. In this case, since it is not necessary to take into account the phase difference, the offset phase θ ＿ ofst becomes 0.

[0040] The output upper limit control unit 503 determines whether the amplitude value of the power supply 2f component, which is the pulsation amplitude of the capacitor current Ic, is the capacitor current target value Ic ＊ The current pulsation command upper limit IqrC ＊ As a specific method, for example, the capacitor current target value Ic ＊ Current pulsation command upper limit IqrC ＊ max are stored in advance in the control device 500, and the current pulsation command upper limit value IqrC is calculated by referring to the stored relationship. ＊ It is advisable to determine the max.

[0041] The magnitude of the capacitor current Ic depends on the power consumption of the load. This is because the rectified current Iin1 of the diode rectifier 130 increases as the power consumption of the load increases. In the first embodiment, the load refers to the inverter 300 and the motor 401. The active power Pmot consumed by the motor 401 is expressed by the dq-axis voltages and dq-axis currents as shown in Equation (1).

[0042]

[0043] Here, when the steady-state voltage equation of the permanent magnet synchronous motor is considered and substituted into equation (1), equation (2) is obtained.

[0044]

[0045] In equation (2), Ra represents the armature resistance. Ld and Lq represent d- and q-axis inductances. Φa represents the number of d- and q-axis interlinkage magnetic fluxes. ωe represents the electrical angular velocity. In cases where the voltage drop due to the armature resistance Ra can be ignored and the d-axis current id can be considered to be almost zero, equation (3) holds.

[0046]

[0047] Here, the capacitor current suppression control unit 502 performs control so that the current pulsation of the power supply 2f component is matched between the rectified current Iin1 of the diode rectifier 130 and the rectified current Iin2 shared by the load. That is, the second q-axis current command IqrC ＊ is controlled.

[0048]

[0049] Therefore, the second q-axis current command IqrC ＊ By manipulating the above, it is possible to control the power supply 2f component of the capacitor current Ic to be any value. Here, equation (4) is a relational expression when the capacitor current Ic is 0, and it can be seen that the electrical angular velocity ωe of the motor has an effect.

[0050] 5 is an explanatory diagram illustrating the operation of the output upper limit value control unit of the control device included in the power conversion device according to the first embodiment. In FIG. 5, the capacitor current target value Ic ＊ The current pulsation command upper limit IqrC ＊ The output upper limit control unit 503 refers to the relationship table shown in FIG. 5 to determine the current pulsation command upper limit value IqrC ＊ max is determined. The relationship table may be determined based on the theoretical formula as described above, or may be determined from experimentally measured results. Also, instead of the relationship table as shown in FIG. 5, it may be determined based on a function. Also, as shown in equation (4), it is known that the electrical angular velocity ωe affects the capacitor current Ic and the q-axis current iq of the motor 401. Therefore, the output upper limit value control unit 503 determines the speed command ωe based on the multiple speed commands ωe shown in FIG. ＊or the estimated speed ω ＿ est may have a relational table according to the est.

[0051] As described above, in the control device 500 of the power conversion device 1 according to the first embodiment, the capacitor current suppression control unit 502 suppresses the current pulsation command upper limit value IqrC ＊ max, the second q-axis current command IqrC ＊ By manipulating the above, the amplitude value of the power supply 2f component of the capacitor current Ic is adjusted to the capacitor current target value Ic ＊ In addition, when the amplitude of the power supply 2f component of the capacitor current Ic is non-zero, the capacitor current target value Ic ＊ The second q-axis current command IqrC ＊ Among them, the amplitude value of the current pulsation command shown in the capacitor current suppression control unit 502 and the output upper limit value control unit 503 of the first embodiment is set as the current pulsation command upper limit value IqrC ＊ Second q-axis current command IqrC ＊ This method of determining the current amplitude of the power supply 2f component flowing through the motor 401 can be minimized. Therefore, this method has the advantage of being able to minimize the deterioration of the efficiency of the motor 401 due to the capacitor current suppression control, as well as the deterioration of the vibration and noise of the mechanical load 402.

[0052] Although the capacitor current suppression control unit 502 and the output upper limit value control unit 503 shown in the first embodiment are applied to a component twice the power supply frequency, they can also be applied to other frequency components, for example, a component four times or six times the power supply frequency. Alternatively, the capacitor current suppression control unit 502 and the output upper limit value control unit 503 may be configured in parallel for a plurality of frequency components.

[0053] Next, the effects of the power conversion device 1 and the motor drive device 2 according to the first embodiment will be described with reference to FIGS.

[0054] FIG. 6 is an explanatory diagram showing an example of the motor speed, capacitor current, and motor current operating waveforms when the capacitor current suppression control unit and the output upper limit control unit are not performing control in the power conversion device according to the first embodiment. However, the waveform of the capacitor current Ic is obtained by extracting only the frequency component identical to the motor speed and the frequency component twice the frequency of the commercial power supply 110. When the capacitor current suppression control unit 502 and the output upper limit control unit 503 are not performing control, the motor current has a sinusoidal waveform. In this case, there is no increase in loss in the motor 401 due to the capacitor current suppression control, and therefore the energy efficiency of the motor drive device 2 is the highest. Furthermore, the capacitor 200 must absorb ripples in the power flowing in and out of the power conversion device 1. Therefore, the capacitor current Ic pulsates sinusoidally at the power source 2f.

[0055] FIG. 7 is an explanatory diagram showing an example of the motor speed, capacitor current, and motor current operating waveforms in the power conversion device according to the first embodiment when the output upper limit control unit is not performing control and only the capacitor current suppression control unit is performing control. The analyzed waveform of the capacitor current Ic is obtained by extracting a frequency component twice the frequency of the commercial power supply 110. The capacitor current suppression control suppresses the pulsation of the capacitor current Ic by pulsating the motor current. Compared to FIG. 6 , the pulsation amplitude of the capacitor current Ic is suppressed to nearly zero. However, the motor current is no longer a sine wave and contains two frequency components. The peak value of the motor current increases, deteriorating the energy efficiency of the motor drive device 2. At this time, the motor speed waveform is also no longer a sine wave and contains two frequency components. The motor speed waveform is such a waveform because the motor current is pulsated at a frequency different from the pulsation frequency of the load torque. Basically, the more one tries to reduce the capacitor current Ic, the more the speed pulsation of the motor 401 or the loss of the motor 401 worsens in the double frequency component of the commercial power supply 110. In conventional motor drive devices, it is difficult to adjust the effectiveness of the capacitor current suppression control, and there are cases where the capacitor current suppression control is performed excessively, increasing the loss of the motor 401 more than necessary.

[0056] 8 is an explanatory diagram showing an example of the motor speed, the capacitor current, and the operating waveforms of the motor current when the control of the capacitor current suppression control unit and the output upper limit value control unit is performed in the power conversion device according to the first embodiment. Note that the analyzed waveform of the capacitor current Ic is obtained by extracting the double frequency component of the frequency of the commercial power supply 110. The output upper limit value control unit 503 controls the capacitor current target value Ic ＊ The capacitor current suppression control unit 502 controls the upper limit of the pulsation amplitude of the motor current by the capacitor current suppression control based on the upper limit of the current pulsation command. ＊ Therefore, in comparison with FIGS. 6 and 7, the pulsation amplitude of the capacitor current Ic in FIG. 8 is smaller than that in FIG. 6 and larger than that in FIG. 7, and the capacitor current target value Ic ＊ 6 and 7. On the other hand, the motor speed and motor current are greater than those in FIG. 6 and smaller than those in FIG. 7. Therefore, the capacitor current Ic is set to the capacitor current target value Ic within the allowable range of the capacitor 200 while minimizing the deterioration of the efficiency of the motor 401 and the deterioration of the vibration and noise of the mechanical load 402. ＊ can be matched with

[0057] As described above, the control device 500 controls the operation of the inverter 300 based on the detection values ​​acquired from the respective detectors. At this time, the current output from the inverter 300 is pulsated to suppress the capacitor current Ic flowing in and out of the capacitor 200. At this time, the output upper limit of the capacitor current suppression control is variably controlled. That is, by performing the output upper limit control and the capacitor current suppression control, the power conversion device 1 and the motor drive device 2 according to the first embodiment can control the capacitor current Ic to be within the allowable range of the capacitor 200 while suppressing an increase in the pulsation of the motor current. This makes it possible to improve the efficiency of the motor 401, reduce vibration and noise of the mechanical load 402, and prevent deterioration or failure of the capacitor 200.

[0058] Embodiment 2 In the first embodiment, the second q-axis current command IqrC＊ and the capacitor current Ic, the current pulsation command upper limit IqrC ＊ max is determined, and the capacitor current Ic is set to the capacitor current target value Ic ＊ However, the method in the first embodiment controls the current pulsation command upper limit IqrC in a feedforward manner. ＊ max is determined, which results in low robustness against parameter fluctuations of the components of the power conversion device 1 and the motor 401. However, there is always variation in the parameters of the components of the power conversion device 1 and the motor 401 due to individual differences, and some parameters change over time.

[0059] Therefore, in the second embodiment, in the power conversion device 1a, the capacitor current Ic flowing through the capacitor 200 is estimated, and the peak value of the capacitor current Ic or the amplitude value of a specific frequency component included in the capacitor current Ic is set to the capacitor current target value Ic ＊ The current pulsation command upper limit IqrC of the motor 401 is set to coincide with ＊ Max is automatically searched for.

[0060] Although the hill-climbing method is a well-known example of an automatic search method, any method may be used as long as it is an automatic search method. For example, in a broad sense, feedback control can also be considered a type of automatic search method, so feedback control may also be used. The control method of embodiment 2 requires a means for estimating the capacitor current Ic, but because an appropriate operating point is automatically searched for, the capacitor current Ic can be robustly controlled even if constant fluctuations occur in the motor 401.

[0061] Specifically, feedback control is utilized to adjust the amplitude value of a specific frequency component contained in the capacitor current Ic to the capacitor current target value Ic ＊ The control method described here is a method for controlling the amplitude value of a specific frequency component contained in the capacitor current Ic to match the capacitor current target value Ic ＊ The current pulsation command upper limit IqrC ＊ Max is automatically searched for.

[0062] Fig. 9 is an explanatory diagram showing an example of the configuration of a power conversion device and a motor drive device according to the second embodiment. The power conversion device 1a is configured by using a control device 500a instead of the control device 500 of the power conversion device 1 of the first embodiment shown in Fig. 1. The motor drive device 2a includes the power conversion device 1a and the motor 401 of the compressor 400.

[0063] 10 is an explanatory diagram illustrating a configuration example of a control device included in a power conversion device according to embodiment 2. The control device 500a includes an output upper limit value control unit 503a and a capacitor current detection unit 508 instead of the output upper limit value control unit 503 of the control device 500 according to embodiment 1 shown in FIG.

[0064] Next, the control of the control device 500a of the power conversion device 1a according to the second embodiment will be specifically described. The only differences from the power conversion device 1 according to the first embodiment are the capacitor current detection unit 508 and the output upper limit value control unit 503a. The other components are the same as those in the first embodiment, and therefore their description will be omitted. Therefore, the control of the capacitor current detection unit 508 and the output upper limit value control unit 503a will be specifically described.

[0065] The capacitor current detection unit 508 detects or estimates the amount of the capacitor current Ic flowing in and out of the capacitor 200. Specifically, the capacitor current detection unit 508 receives the bus voltage Vdc and detects or estimates the capacitor current estimated value Ic ＿ Here, the estimated current value of the capacitor 200 is calculated as Ic ＿ Although the estimated capacitor current Ic is expressed by the symbol est, the capacitor current Ic flowing through the capacitor 200 may be directly measured using a current detector. ＿ est can be calculated by, for example, multiplying the differential value of the bus voltage Vdc by the capacitance C of the capacitor. ＿ n and the previous detection value Vdc ＿ n-1, it is possible to calculate the differential value of the bus voltage Vdc by backward differentiation. Note that other known techniques may also be used to calculate the differential value of the bus voltage Vdc.

[0066] 11 is an explanatory diagram illustrating a configuration example of an output upper limit value control unit of a control device included in a power conversion device according to the second embodiment. The output upper limit value control unit 503a of the second embodiment calculates the output of the capacitor current detection unit 508 and the capacitor current target value Ic ＊ The amplitude value of a specific frequency component contained in the capacitor current Ic, i.e., the pulsation amplitude of the capacitor current Ic, is compared with the capacitor current target value Ic ＊ The current pulsation command upper limit IqrC of the motor 401 is set to coincide with ＊ max is automatically searched for. As in the first embodiment, an example of the specific frequency component is shown here, in which the amplitude value of the component of the capacitor current Ic that is twice the power supply frequency of the commercial power supply 110 is targeted. The output upper limit value control unit 503a includes Fourier coefficient calculation units 531 and 532, an amplitude calculation unit 533, a subtraction unit 534, a PID control unit 535, and a limiting unit 536.

[0067] The Fourier coefficient calculation units 531 and 532 calculate the capacitor current estimate Ic ＿ The amplitudes of the sin2f component and the cos2f component included in the deviation are calculated. The detection signals multiplied by the Fourier coefficient calculation units 531 and 532 are sin2ωint and cos2ωint, respectively. The amplitudes of the sin2f component and the cos2f component included in the deviation are doubled. That is, the Fourier coefficient calculation units 531 and 532 calculate the capacitor current estimation value Ic ＿ The amplitude of the component corresponding to the power supply frequency of the commercial power supply 110, which is included in the estimated capacitor current Ic, is calculated. ＿ If est is a periodic waveform, the output signals of the Fourier coefficient calculation units 531 and 532 are approximately constant.

[0068] The amplitude calculation unit 533 calculates the capacitor current estimate value Ic ＿ The square root of the sum of the squares of the amplitudes of the estsin2f component and cos2f component is calculated to obtain the amplitude value Ic of the power supply 2f component of the capacitor current Ic. ＿ est ＿Here, as described above, if the capacitor current Ic has a periodic waveform, the output signal of the amplitude calculation unit 533 will be approximately constant.

[0069] The subtractor 534 subtracts the capacitor current estimate Ic ＿ The amplitude value Ic of the power supply 2f component of est ＿ est ＿ amp and capacitor current target value Ic ＊ The deviation from the target capacitor current Ic ＊ It is possible to calculate the tracking error for

[0070] The PID control unit 535 performs proportional-integral-derivative control, i.e., PID control, so that the deviation becomes zero, and calculates the current pulsation command upper limit value IqrC ＊ max is calculated. The proportional gain and differential gain may be zero, but the integral gain value must be non-zero in order to converge the deviation to zero. Therefore, the integral action is the main function of the PID control unit 535. Normally, the output of integral control changes slowly, so the output of the PID control unit 535 can also be considered to be roughly constant.

[0071] The limiting unit 536 limits the current pulsation command upper limit value IqrC calculated by the PID control unit 535. ＊ When max becomes an unexpected value, the current pulsation command upper limit value IqrC ＊ The upper limit value limited by the limiting unit 536 is set to, for example, the first q-axis current command IqDC max by referring to the allowable current of the motor 401. ＊ and the second q-axis current command IqrC ＊ The final q-axis current command Iq is the sum of ＊ is determined so as to secure a margin for the allowable current of the motor 401. As a result, the current pulsation command upper limit value IqrC calculated by the PID control unit 535 ＊ max becomes excessively large relative to the allowable current of the motor 401, the power conversion device 1a and the motor drive device 2a can be prevented from malfunctioning. The lower limit value limited by the limiting unit 536 is set to 0. This is because the capacitor current suppression control unit 502＊ The maximum limit is the current command IqrC ＊ The sin component of IqrCs ＊ , cos component IqrCc ＊ , that is, the "amplitude value," and is always a value equal to or greater than 0. Note that, if other protective measures against overcurrent are taken in a location other than the output upper limit value control unit 503a of the power conversion device 1a, the limiting unit 536 may be omitted.

[0072] Next, the effects of the power conversion device 1a and the motor drive device 2a according to the second embodiment will be described with reference to Fig. 12. Fig. 12 is an explanatory diagram showing an example of the operation of the power conversion device and the motor drive device according to the second embodiment. Fig. 12 shows, from top to bottom, the capacitor current Ic, the final q-axis current command Iq, ＊ , the estimated capacitor current Ic ＿ The amplitude value Ic of the power supply 2f component of est ＿ est ＿ amp, and current pulsation command upper limit IqrC ＊ 12 shows the time history response of the capacitor current Ic. Note that the capacitor current Ic is a value obtained by extracting only the power supply 2f component. Fig. 12 shows a state in which the capacitor current suppression control unit 502 and the output upper limit control unit 503a are changed from the control OFF state to the control ON state at time t0 while the power conversion device 1a and the motor drive device 2a are in operation.

[0073] In the control OFF state (t<t0) in FIG. 12, the capacitor current Ic pulsates with an amplitude Ic0. ＊ is the current command IqrC ＊ is 0, the first q-axis current command IqDC ＊ The estimated capacitor current Ic ＿ The amplitude value Ic of the power supply 2f component of est ＿ est ＿ amp has no estimation error, and Ic = Ic ＿ When the current pulsation command upper limit IqrC is equal to the amplitude Ic0 of the capacitor current Ic, the current pulsation command upper limit IqrC is equal to the amplitude Ic0 of the capacitor current Ic. ＊ When the control is OFF, max is equal to 0.

[0074] When the control is ON (t≧t0) in FIG. 12, the pulsation amplitude of the capacitor current Ic gradually decreases from amplitude Ic0 to amplitude Ic ＊ The final q-axis current command Iq ＊ is the current command IqrC ＊ The amplitude value of the current pulsation command upper limit value IqrC ＊ The estimated capacitor current Ic gradually increases following the maximum amplitude value Ic max, and finally the amplitude value becomes constant. ＿ The amplitude value Ic of the power supply 2f component of est ＿ est ＿ amp gradually decreases and finally reaches the capacitor current target value Ic ＊ Current ripple command upper limit IqrC ＊ max gradually increases from 0 and finally converges to a non-zero constant value.

[0075] The reason for the above operation will be explained step by step. First, at time t0 in FIG. ＿ est ＿ amp>Ic ＊ Therefore, the output of the subtractor 534 of the output upper limit control unit 503a at this time is a positive value. Therefore, the current pulsation command upper limit value IqrC ＊ max also becomes a positive value and gradually increases as time passes after time t0. Next, after time t0, the capacitor current suppression control unit 502 generates a current command IqrC ＊ At this time, the current command IqrC ＊ The amplitude of the current pulsation command upper limit IqrC ＊ max, so there is no sudden increase and the current pulsation command upper limit IqrC ＊ The current command IqrC ＊ As the amplitude of the current Ic increases, the amount of current flowing through the motor 401 increases and the current flowing into and out of the capacitor 200 decreases. Therefore, the pulsation of the capacitor current Ic gradually decreases after time t0.

[0076] By continuously performing the above operations, Ic ＿ est＿ amp = Ic ＊ Therefore, the output of the subtractor 534 becomes 0. Therefore, the current pulsation command upper limit value IqrC ＊ max is a constant value and does not change. Therefore, the current command IqrC ＊ The amplitude of the pulsation of the capacitor current Ic also becomes a constant value. ＊ This corresponds to the estimated capacitor current Ic ＿ The amplitude value Ic of the power supply 2f component of est ＿ est ＿ amp is the capacitor current target value Ic ＊ The current pulsation command upper limit IqrC ＊ This is due to the determination of max.

[0077] The above-described operation is the effect of the power conversion device 1a and the motor drive device 2a according to the second embodiment. That is, when the amplitude value of a specific frequency component contained in the capacitor current Ic is equal to or greater than the capacitor current target value Ic ＊ The current pulsation command upper limit IqrC of the motor 401 is set to coincide with ＊ By automatically searching for max, the capacitor current Ic can be controlled arbitrarily.

[0078] 12 illustrates a case in which the capacitor current suppression control unit 502 and the output upper limit control unit 503a are changed from a control-off state to a control-on state at time t0 during operation of the power conversion device 1a and the motor drive device 2a, in order to explain the effects of the power conversion device 1a and the motor drive device 2a according to the second embodiment. However, the use of the power conversion device 1a and the motor drive device 2a according to the second embodiment is not limited to this. For example, there is no problem even if the capacitor current suppression control unit 502 and the output upper limit control unit 503a are always in a control-on state from the start of the power conversion device 1a and the motor drive device 2a.

[0079] As described above, the control device 500a according to the second embodiment controls the operation of the inverter 300 based on the detection values ​​acquired from the respective detectors. At this time, the current output from the inverter 300 is pulsated to suppress the capacitor current Ic flowing in and out of the capacitor 200. At this time, an output upper limit value for the capacitor current suppression control is automatically searched for. As a result, the power conversion device 1a and the motor drive device 2a according to the second embodiment can simultaneously improve the efficiency of the motor 401, reduce vibration and noise of the mechanical load 402, and prevent deterioration or failure of the capacitor, while improving robustness against constant fluctuations.

[0080] In the first and second embodiments, the pulsation amplitude of the capacitor current Ic is set to the capacitor current target value Ic ＊ As described above, there is a trade-off between the capacitor current Ic and the speed pulsation of the motor 401. Therefore, when the capacitor current suppression control is activated, the speed pulsation of the motor 401 increases.

[0081] In the third embodiment, when the mechanical load 402 driven by the motor drive device 2b has periodic load torque pulsation, the speed pulsation of the motor 401 caused by the periodic load torque pulsation is controlled to an arbitrary magnitude. In this embodiment, this control method is called "speed pulsation suppression control." At the same time, the pulsation amplitude of the capacitor current Ic is controlled to a desired value Ic by the method described in the first or second embodiment. ＊ As an effect of this, it is possible to reduce the total speed pulsation of the motor 401 while controlling the capacitor current Ic to an arbitrary value, which makes it possible to simultaneously reduce the vibration and noise of the mechanical load 402 and prevent the deterioration or failure of the capacitor 200.

[0082] 13 is an explanatory diagram showing an example of the configuration of a power conversion device and a motor drive device according to a third embodiment. The power conversion device 1b is configured by using a control device 500b instead of the control device 500 of the power conversion device 1 according to the first embodiment shown in FIG. 1. The power conversion device 1b also uses a speed pulsation amplitude target value ωrip as an input to the control device 500b. ＊ The motor drive device 2b is different from the power conversion device 1 of the first embodiment in that a motor 401 included in the compressor 400 is added to the power conversion device 1b.

[0083] Fig. 14 is an explanatory diagram showing a configuration example of a control device included in a power conversion device according to embodiment 3. The control device 500b includes an output upper limit value control unit 503b, a speed pulsation suppression control unit 509, and an adder 504b instead of the output upper limit value control unit 503 and the adder 504 of the control device 500 according to embodiment 1 shown in Fig. 2.

[0084] Next, the control of the control device 500b of the power conversion device 1b according to the third embodiment will be specifically described. The only differences from the power conversion device 1 according to the first embodiment are an output upper limit value control unit 503b, a speed pulsation suppression control unit 509, and an adder 504b. The other components are the same as those in the first embodiment, and therefore will not be described.

[0085] The output upper limit control unit 503b determines the capacitor current target value Ic ＊ and the speed pulsation amplitude target value ωrip ＊ is used as an input, and the current ripple command upper limit value IqrC ＊ max and the current pulsation command upper limit Iqrω for speed pulsation suppression control ＊ Here, the output upper limit control unit 503b outputs the capacitor current target value Ic max. ＊ and the speed pulsation amplitude is equal to the speed pulsation amplitude target value ωrip ＊ The current pulsation command upper limit IqrC ＊ max and current pulsation command upper limit Iqrω ＊ Determine the capacitor current target value Ic max. ＊ and the speed pulsation amplitude target value ωrip ＊The values ​​may be input from outside the control device 500b, or may be stored in advance in the ROM of the control device 500b.

[0086] The speed pulsation suppression control unit 509 calculates a current pulsation command that pulsates the motor current flowing through the motor 401 in order to suppress periodic pulsation of the motor speed ω that occurs due to load torque pulsation, and outputs a third q-axis current command IqrV ＊ The speed pulsation suppression control unit 509 outputs the estimated speed ω ＿ est and current pulsation command upper limit value Iqrω ＊ The speed pulsation suppression control unit 509 receives the estimated speed ω ＿ est, as well as the current pulsation command upper limit Iqrω ＊ The third q-axis current command IqrV is calculated taking into account max. ＊ When the motor speed ω is in a steady state, the third q-axis current command IqrV ＊ is a sinusoidal waveform synchronized with the load torque pulsation.

[0087] The adder 504b calculates the first q-axis current command IqDC ＊ , second q-axis current command IqrC ＊ and the third q-axis current command IqrV ＊ and the final q-axis current command Iq ＊ The adder 504b outputs a third q-axis current command IqrV ＊ The difference is that it adds

[0088] In the output upper limit value control unit 503b, the capacitor current target value Ic ＊ The current pulsation command upper limit IqrC for the capacitor current suppression control is ＊ The method for determining max may be the same as that shown in the first or second embodiment. ＊ The current pulsation command upper limit Iqrω of the speed pulsation suppression control is ＊ A method for determining max will now be described.

[0089] The equation of motion for the rotational motion of the motor 401 is expressed by equation (5): where J is the moment of inertia of the motor 401, ω is the rotational speed of the motor 401, τm is the motor torque, and τL is the load torque.

[0090]

[0091] The load torque τL is expressed by the DC component τL as shown in equation (6). ＿ In addition to DC, amplitude τL ＿ rip, and a periodic pulsation component of frequency ωL, where θL is the phase of the load torque pulsation.

[0092]

[0093] Here, consider the case where the motor 401 is in a steady state and is operating at an average speed ωDC. At this time, the motor torque τm is the DC component τL of the load torque τL. ＿ It is assumed that the frequency is equal to DC and does not have a pulsating component. ＿ Substituting DC and equation (6) into equation (5), integrating both sides of equation (5), and rearranging the equation with respect to the rotational speed ω, equation (7) is obtained.

[0094]

[0095] From equation (7), if the motor torque τm does not have a pulsating component, the amplitude is τL due to the influence of the load torque pulsation. ＿ A speed pulsation of AC / (J×ωL) occurs. In order to make this speed pulsation zero, the pulsation component τm of the motor torque τm that coincides with the periodic pulsation component of the load torque must be adjusted. ＿ You need to give it a rip.

[0096] The motor torque τm is expressed by equation (8). In cases where the d-axis current id can be considered to be almost zero, it is expressed by equation (9). Therefore, from equations (5), (6), and (9), it is possible to make the speed pulsation zero by manipulating the pulsation component Iqrω of the q-axis current iq as in equation (10).

[0097]

[0098]

[0099]

[0100] Furthermore, the speed pulsation component ωrip of the motor 401 that occurs when the amplitude of the pulsation component Iqrω of iq is Iqrωamp and the frequency and phase match the frequency ωL and phase θL of the load torque pulsation is given by equation (11).

[0101]

[0102] In equation (11), the target value of the amplitude of the speed pulsation component ωrip is expressed as the speed pulsation amplitude target value ωrip ＊ and solving for the amplitude Iqrωamp of the pulsating component Iqrω of iq, we obtain equation (12).

[0103]

[0104] Therefore, as shown in equation (12), the current pulsation command upper limit Iqrω of the speed pulsation suppression control ＊ max and limit the output of the speed pulsation suppression control unit 509, the speed pulsation amplitude generated by the load torque pulsation is reduced to the speed pulsation amplitude target value ωrip ＊ It is possible to control it so that it coincides with

[0105] In the output upper limit control unit 503b, the speed pulsation amplitude target value ωrip ＊ With reference to the function of equation (12), the current pulsation command upper limit value Iqrω of the speed pulsation suppression control is calculated. ＊ Alternatively, the current pulsation command upper limit value IqrC for the capacitor current suppression control may be determined by referring to a table calculated in advance by experiment or analysis in relation to the equation (12). ＊ A relationship table such as that shown in FIG. 5, which shows a method for calculating max, may be stored in the ROM of the control device 500b, and the max value may be determined by referring to the table.

[0106] Next, the third q-axis current command IqrV in the speed pulsation suppression control unit 509 ＊The current command for reducing the speed pulsation of the motor 401 caused by the load torque pulsation to zero can be calculated by referring to the above-mentioned equation (10). However, in order to determine the current command by referring to the equation (10), the amplitude τL of the load torque pulsation must be ＿ It is necessary that the ripple, frequency ωL, and phase θL are all known. It is difficult to observe all of these without using a torque detector, and these values ​​may change depending on the operating state of the mechanical load 402. Therefore, it is difficult to make the speed pulsation of the motor 401 zero using the current command calculated from equation (10). Therefore, in the third embodiment, the speed pulsation suppression control unit 509 calculates the estimated speed ω ＿ est to automatically search for a current pulsation command that suppresses the speed pulsation.

[0107] 15 is an explanatory diagram showing a configuration example of a speed pulsation suppression control unit of the control device provided in the power conversion device according to embodiment 3. The speed pulsation suppression control unit 509 is configured as a feedback controller with a command value set to 0. The speed pulsation suppression control unit 509 has a subtraction unit 551, Fourier coefficient calculation units 552 and 553, PID control units 554 and 555, an amplitude limiting unit 556, and an AC restoration unit 557.

[0108] The subtractor 551 subtracts the command value from the estimated speed ω ＿est is calculated. Using the theory of Fourier series expansion, it is possible to extract the amplitudes of the sin signal component and cos signal component of a specific frequency contained in the deviation. Fourier coefficient calculation units 552 and 553 calculate the amplitudes of the sin ωL component and the cos ωL component contained in the deviation, respectively. The detection signals multiplied by Fourier coefficient calculation units 552 and 553 are sin ωLt and cos ωLt, respectively. The amplitudes of the sin ωL component and the cos ωL component contained in the deviation are twice the average value of the product of the input signal and the detection signal. In other words, Fourier coefficient calculation units 552 and 553 calculate the amplitude of the component corresponding to the frequency ωL of the load torque pulsation, which is contained in the deviation between the detection value and the command value. It is generally known that when the mechanical load 402 is part of the compressor 400 and the compressor is a single rotary compressor, a load torque pulsation occurs in which the frequency ωL of the load torque pulsation matches the average speed ωDC of the motor 401 and the mechanical load 402. Therefore, in this case, the frequencies of the sine wave and cosine wave of the detection signal should be matched to the average speed ωDC. If the average speed ωDC is constant and the load torque pulsation is periodic, the output signals of the Fourier coefficient calculation units 552 and 553 will be approximately constant.

[0109] The PID control units 554 and 555 perform proportional-integral-derivative control, i.e., PID control, so that specific frequency components of the deviation become zero, and respectively control the sine component Iqrωs of the current pulsation command. ＊ and cos component Iqrωc ＊ The proportional gain and differential gain may be zero, but the integral gain value must be non-zero in order to converge the deviation to zero. Therefore, the integral action is the main function of the PID control units 554 and 555. Normally, the output of integral control changes gradually. Therefore, the output of the PID control units 554 and 555 can also be considered to be roughly constant.

[0110] The amplitude limiting unit 556 limits the sine component Iqrωs of the current pulsation command. ＊ , cos component Iqrωc ＊ , and the current pulsation command upper limit value Iqrω ＊max is input, and the sine and cosine components of the current pulsation command after amplitude limitation are output.

[0111] 16 is an explanatory diagram illustrating the operation of the amplitude limiting unit of the speed pulsation suppression control unit of the control device provided in the power conversion device according to the third embodiment. In FIG. 16, the sine component Iqrωs of the current pulsation command ＊ , cos component Iqrωc ＊ is the ratio of the sine component and the cosine component of the current pulsation command, that is, the amplitude of the current pulsation command is increased to the current pulsation command upper limit value Iqrω without changing the phase of the current pulsation command. ＊ This amplitude limiting method is performed by adjusting the sine component Iqrωs of the current pulsation command. ＊ and cos component Iqrωc ＊ Current pulsation command upper limit Iqrω for the square root of the sum of squares ＊ The ratio of Iqrωs to max is calculated, and the sin component of the current pulsation command Iqrωs is calculated. ＊ , and the cos component Iqrωc ＊ By multiplying this by , the sine component and cosine component of the current pulsation command after amplitude limitation can be calculated.

[0112] The AC restoration unit 557 restores the output of the amplitude limiting unit 556 to an AC component by using sin(ωLt+θ ＿ ofst) and cos(ωLt+θ ＿ ofst) and then summed to obtain the third q-axis current command IqrV ＊ That is, the AC restoration unit 557 determines the third q-axis current command IqrV which is a command for the pulsation component for suppressing the speed pulsation of the motor 401. ＊ where the offset phase θ ＿ Since the motor speed ω and the motor torque τm have a differential and integral relationship and there is a phase difference of 90 degrees, the value of θst takes this phase difference into consideration. ＿ ofst=π / 2 [rad].

[0113] Through the above processing, the third q-axis current command IqrV ＊ By automatically searching for the speed pulsation of the motor 401, the speed pulsation amplitude target value ωrip＊ In the third embodiment, the estimated speed ω ＿ est as an input, and the third q-axis current command IqrV ＊ For example, instead of inputting the estimated speed ω_est, a speed detection value detected using a speed detector that detects the speed of the motor 401 or a position detector that detects the position of the rotor may be input to calculate the third q-axis current command IqrV ＊ In this case, the speed pulsation of the motor 401 may be calculated by the speed pulsation amplitude target value ωrip, except that the subtractor 551 of the speed pulsation suppression control unit 509 calculates the deviation between the command value = 0 and the speed detection value. ＊ Alternatively, instead of inputting the estimated speed ω_est, an estimated acceleration of the motor 401 can be input to obtain the third q-axis current command IqrV ＊ Since the speed and acceleration have a differential and integral relationship, reducing the speed pulsation to 0 is equivalent to reducing the acceleration pulsation to 0. Therefore, the speed pulsation of the motor 401 is reduced to the speed pulsation amplitude target value ωrip by the operation of each part of the speed pulsation suppression control unit 509. ＊ However, when the estimated acceleration is input, since the acceleration and the torque are in the same time dimension, the offset phase θ ＿ ofst is θ ＿ This differs from the case where an estimated speed is input in that ofst=0 [rad].

[0114] Next, the effects of the power conversion device 1b and the motor drive device 2b according to the third embodiment will be described with reference to Fig. 17. Fig. 17 is an explanatory diagram showing an example of the operating waveforms of the motor speed, capacitor current, and motor current when the capacitor current suppression control unit, the speed pulsation suppression control unit, and the output upper limit value control unit are controlled in the power conversion device according to the third embodiment.

[0115] In the first embodiment, FIG. 8 shows an example of the operating waveforms of the motor speed, capacitor current, and motor current when capacitor current suppression control and output upper limit control are implemented. In comparison, FIG. 17 shows an example of the operating waveforms of the motor speed, capacitor current, and motor current when capacitor current suppression control, speed pulsation suppression control, and output upper limit control are implemented. In each waveform shown in FIG. 17, the solid lines indicate the operating waveforms when capacitor current suppression control, speed pulsation suppression control, and output upper limit control are implemented. In each waveform shown in FIG. 17, the dashed lines indicate the operating waveforms when only capacitor current suppression control and output upper limit control, as in the first embodiment, are implemented. Note that, as in FIGS. 6 to 8 shown in the first embodiment, the motor speed ω and capacitor current Ic are obtained by extracting the double frequency component of the frequency of the commercial power supply 110 and the load torque pulsation frequency component.

[0116] As described in the first embodiment, the capacitor current suppression control suppresses the pulsation of the capacitor current Ic by pulsating the motor current. Therefore, when only the capacitor current suppression control and the output upper limit control are implemented, the capacitor current Ic decreases, while the speed pulsation of the motor 401 and the motor current pulsation at the double frequency component of the commercial power supply 110 increase. Therefore, the peak value of the speed pulsation of the motor 401 increases due to the superposition of the speed pulsation of the motor 401 caused by the load torque pulsation and the speed pulsation caused by the capacitor current suppression control. This increases the vibration and noise of the mechanical load 402, and in some cases may damage the motor drive device 2b. In contrast, when the capacitor current suppression control, the speed pulsation suppression control, and the output upper limit control described in the third embodiment are implemented, the amplitude of the speed pulsation of the motor 401 caused by the load torque pulsation can be reduced. Therefore, the peak value of the speed pulsation of the motor 401 can be reduced, improving the vibration and noise of the mechanical load 402 and preventing damage to the motor drive device 2b.

[0117] Note that the speed pulsation suppression control is a control that suppresses speed pulsation due to load torque pulsation by pulsating the motor current, similar to the capacitor current suppression control. Therefore, when the speed pulsation suppression control is performed, the motor current and the capacitor current Ic increase in the frequency component of the load torque pulsation. This may lead to a deterioration in the efficiency of the power conversion device 1b and the motor drive device 2b, and to deterioration or failure of the capacitor 200. Therefore, the speed pulsation amplitude target value ωrip described in the third embodiment is set to ωrip ＊ By appropriately setting the speed pulsation suppression control, it is possible to perform the speed pulsation suppression control to the minimum extent necessary, and it is possible to minimize the deterioration of the efficiency of the power conversion device 1b and the deterioration of the capacitor 200.

[0118] In this way, in the power conversion device 1b and the motor drive device 2b according to the third embodiment, by simultaneously performing the speed pulsation suppression control in addition to the output upper limit value control and the capacitor current suppression control, it is possible to simultaneously reduce the vibration and noise of the mechanical load 402 and prevent the deterioration or failure of the capacitor 200. ＊ and the speed pulsation amplitude target value ωrip ＊ By providing this as a command value, it becomes possible to manipulate the capacitor current Ic, the speed pulsation of the motor 401 due to the load torque pulsation, and the efficiency of the motor 401. Therefore, in the power conversion device 1b and the motor drive device 2b according to the third embodiment, it is easy to adjust the trade-off between these.

[0119] As described above, the control device 500b according to the third embodiment controls the operation of the inverter 300 based on the detection values ​​acquired from the respective detectors. At this time, the current output from the inverter 300 is pulsated to suppress the capacitor current Ic flowing in and out of the capacitor 200 and to suppress speed pulsation of the motor 401 due to load torque pulsation. At this time, the output upper limit values ​​of the capacitor current suppression control and the speed pulsation suppression control are variably controlled. That is, the power conversion device 1b and the motor drive device 2b according to the third embodiment can control the capacitor current Ic to be within the allowable range of the capacitor 200 while suppressing an increase in motor current pulsation. This makes it possible to improve the efficiency of the motor 401, reduce vibration and noise of the mechanical load 402, and prevent deterioration or failure of the capacitor 200.

[0120] Embodiment 4 In the embodiment 3, the third q-axis current command IqrV ＊ and the current pulsation command upper limit Iqrω for the speed pulsation suppression control from the relationship with the speed pulsation of the motor 401. ＊ max is determined, and the speed pulsation amplitude is set to the speed pulsation amplitude target value ωrip ＊ The method shown in the third embodiment uses a relational expression to control the current pulsation command upper limit Iqrω in a feedforward manner. ＊ max is determined. Therefore, the robustness against parameter fluctuations of the components of the power conversion device 1b and the motor 401 is low. However, there is always variation in the parameters of the components of the power conversion device 1b and the motor 401 due to individual differences, and some parameters change over time.

[0121] In the fourth embodiment, the estimated speed ω ＿ The speed pulsation amplitude is detected from est, and the speed pulsation amplitude is set to the speed pulsation amplitude target value ωrip ＊ The current pulsation command upper limit Iqrω is set to coincide with ＊ In the fourth embodiment, the current pulsation command upper limit Iqrω for the speed pulsation suppression control is automatically searched for. ＊ The method for automatically searching for max is to use the current pulsation command upper limit IqrC of the capacitor current suppression control described in the second embodiment. ＊This is similar to the method of automatically searching for max.

[0122] 18 is an explanatory diagram showing a configuration example of a control device included in a power conversion device according to embodiment 4. A control device 500c according to embodiment 4 is configured by adding a capacitor current detection unit 508 and an output upper limit control unit 503c instead of the output upper limit control unit 503b of the control device 500b according to embodiment 3. Here, the capacitor current detection unit 508 included in the control device 500c according to embodiment 4 is similar to the capacitor current detection unit 508 included in the control device 500a described in embodiment 2.

[0123] The capacitor current detector 508 receives the bus voltage Vdc and calculates the estimated capacitor current Ic ＿ est. The capacitor current estimate Ic ＿ The method for calculating est may be the method described in the second embodiment, or other known techniques may be used.

[0124] The output upper limit control unit 503c determines the capacitor current target value Ic ＊ , speed pulsation amplitude target value ωrip ＊ , the estimated capacitor current Ic ＿ est and estimated speed ω ＿ est is input, and the current pulsation command upper limit value IqrC of the capacitor current suppression control is ＊ max and the current pulsation command upper limit Iqrω for speed pulsation suppression control ＊ Here, the output upper limit value control unit 503c outputs the capacitor current estimated value Ic ＿ The amplitude value of the specific frequency component of est is the capacitor current target value Ic ＊ The current pulsation command upper limit IqrC of the capacitor current suppression control is set to coincide with ＊ max is automatically searched for by feedback control. ＿ The amplitude value of a specific frequency component of est, i.e., the speed pulsation amplitude, is detected, and the speed pulsation amplitude and the speed pulsation amplitude target value ωrip ＊ The error is compared with the speed pulsation amplitude target value ωrip ＊ The current pulsation command upper limit Iqrω for the speed pulsation suppression control is set to coincide with＊ The maximum is automatically searched for by feedback control.

[0125] 19 is an explanatory diagram illustrating a configuration example of an output upper limit control unit of the control device included in the power conversion device according to embodiment 4. The output upper limit control unit 503c includes Fourier coefficient calculation units 531, 532, 537, and 538, amplitude calculation units 533 and 539, subtraction units 534 and 540, PID control units 535 and 541, and limiting units 536 and 542.

[0126] The Fourier coefficient calculation units 531 and 532 calculate the capacitor current estimate Ic ＿ The amplitudes of the sin2f component and cos2f component included in the deviation are calculated. The detection signals multiplied by the Fourier coefficient calculation units 531 and 532 are sin2ωint and cos2ωint, respectively. The amplitudes of the sin2f component and cos2f component included in the deviation are doubled. Similarly, the Fourier coefficient calculation units 537 and 538 calculate the amplitudes of the sin2f component and cos2f component included in the deviation by multiplying the average value of the product of the input signal and the detection signal. ＿ The amplitudes of the sin ωL component and cos ωL component included in est are calculated. The detection signals multiplied in Fourier coefficient calculation units 537 and 538 are sin ωLt and cos ωLt, respectively. The amplitudes of the sin ωL component and cos ωL component included in the deviation are twice the average value of the product of the input signal and the detection signal.

[0127] The amplitude calculation unit 533 calculates the capacitor current estimate Ic ＿ The capacitor current estimate Ic is calculated by calculating the square root of the sum of the squares of the amplitudes of the sin2f and cos2f components included in est. ＿ The amplitude value Ic of the power supply 2f component of est ＿ est ＿ Similarly, the amplitude calculation unit 539 calculates the estimated speed ω ＿ The estimated speed ω is calculated by calculating the square root of the sum of the squares of the amplitudes of the sinωL component and cosωL component included in est. ＿ Amplitude ω of the load torque pulsation frequency component of est ＿ est ＿ Calculate amp.

[0128] The subtractor 534 subtracts the capacitor current estimate Ic＿ The amplitude value Ic of the power supply 2f component of est ＿ est ＿ amp and capacitor current target value Ic ＊ The subtractor 540 calculates the deviation between the estimated speed ω ＿ Amplitude ω of the load torque pulsation frequency component of est ＿ est ＿ amp and speed pulsation amplitude target value ωrip ＊ Calculate the deviation.

[0129] The PID control unit 535 performs proportional-integral-derivative control, i.e., PID control, so that the deviation becomes zero, and calculates the current pulsation command upper limit value IqrC ＊ The PID control unit 541 performs PID control and calculates the current pulsation command upper limit value Iqrω. ＊ The control gains of the PID control units 535 and 541 may be a common value or may be individually set.

[0130] The limiting unit 536 limits the current pulsation command upper limit value IqrC calculated by the PID control unit 535. ＊ When max becomes an unexpected value, the current pulsation command upper limit value IqrC ＊ The limiting unit 542 limits the current pulsation command upper limit value Iqrω calculated by the PID control unit 541. ＊ When max becomes an unexpected value, in order to prevent the power conversion device 1b and the motor drive device 2b from performing unintended operations, the current pulsation command upper limit value Iqrω is set to ＊ Limit max.

[0131] The upper limit value limited by the limiting units 536 and 542 is set by, for example, referring to the allowable current of the motor 401, and calculating the first q-axis current command IqDC ＊ , second q-axis current command IqrC ＊ and the third q-axis current command IqrV ＊ The final q-axis current command Iq is ＊ is determined so as to secure a margin for the allowable current of the motor 401. As a result, the current pulsation command upper limit value IqrC calculated by the PID control units 535 and 541＊ max or Iqrω ＊ max becomes excessively large relative to the allowable current of the motor 401, the power conversion device 1b and the motor drive device 2b can be prevented from being broken down. The lower limit value limited by the limiting unit 536 is set to 0. This is because the capacitor current suppression control unit 502 and the speed pulsation suppression control unit 509 suppress the current pulsation command upper limit value IqrC ＊ max and Iqrω ＊ This is because what is limited by max is the "amplitude value" of the current pulsation command, and it is always a value equal to or greater than 0. Note that if other protective measures against overcurrent are taken in a location other than the output upper limit value control unit 503c of the power conversion device 1b, the limiting units 536 and 542 may be omitted.

[0132] According to the above configuration, the amplitude value of the specific frequency component contained in the capacitor current Ic is set to the capacitor current target value Ic ＊ and the amplitude value of the characteristic frequency component included in the motor speed ω is equal to the speed pulsation amplitude target value ωrip ＊ The current pulsation command upper limit IqrC of the capacitor current suppression control is set to coincide with ＊ max and the current pulsation command upper limit Iqrω for speed pulsation suppression control ＊ By automatically searching for max, the capacitor current Ic and the speed pulsation of the motor 401 can be controlled arbitrarily.

[0133] In the fourth embodiment, the speed pulsation suppression control unit 509 calculates the estimated speed ω ＿ est as an input, and the third q-axis current command IqrV ＊ For example, instead of inputting the estimated speed ω_est as supplemented in the third embodiment, a speed detection value detected using a speed detector that detects the speed of the motor 401 or a position detector that detects the position of the rotor may be input to calculate the third q-axis current command IqrV ＊ Alternatively, the estimated acceleration of the motor 401 may be input to calculate the third q-axis current command IqrV ＊ may be calculated.

[0134] Also, in the output upper limit value control unit 503c, instead of inputting the estimated speed ω_est, a speed detection value detected using a speed detector that detects the speed of the motor 401 or a position detector that detects the position of the rotor may be input to calculate the current pulsation command upper limit value Iqrω*max. ＿ Instead of inputting est, an estimated acceleration may be input. As described above, the frequency of the speed pulsation generated by the load torque pulsation coincides with the average speed ωDC. Therefore, since the speed and acceleration have a differential and integral relationship, if the average speed ωDC is constant and the load torque pulsation is a periodic pulsation, the speed pulsation amplitude ω_rip and the acceleration pulsation amplitude a_rip have the relationship ω_rip = a_rip / ωDC. By taking this relationship into consideration, the speed pulsation of the motor 401 is adjusted to the speed pulsation amplitude target value ωrip by operating each part of the output upper limit control unit 503c. ＊ It is possible to converge to

[0135] In this way, the control device 500c in the fourth embodiment controls the operation of the inverter 300 based on the detection values ​​acquired from the respective detection units. At this time, the current output from the inverter 300 is pulsated in order to suppress the capacitor current Ic flowing in and out of the capacitor 200 and to suppress the speed pulsation of the motor 401 due to the load torque pulsation. At this time, the output upper limit value of each control is automatically searched for, thereby controlling the capacitor current Ic and the capacitor current target value Ic. ＊ and the speed pulsation amplitude and the speed pulsation amplitude target value ωrip ＊ This makes it possible to match the parameters of the motor 401 and the capacitor 200. Even if the parameters change due to individual differences or changes over time in the parameters of the components of the power conversion device 1b and the motor 401, it is possible to improve the efficiency of the motor 401, reduce vibration and noise of the mechanical load 402, and prevent deterioration or failure of the capacitor 200. Furthermore, since it is possible to manipulate the capacitor current Ic, the speed pulsation of the motor 401 due to load torque pulsation, and the efficiency of the motor 401, it is easy to adjust the trade-off between them.

[0136] Fifth Embodiment A control device 500d according to a fifth embodiment controls a capacitor current target value Ic ＊ and the speed pulsation amplitude target value ωrip ＊ is changed depending on the operating state of the motor 401.

[0137] 20 is an explanatory diagram illustrating a configuration example of a control device included in a power conversion device according to embodiment 5. A control device 500d according to embodiment 5 is obtained by adding a target value determination unit 510 to the control device 500b according to embodiment 3.

[0138] The target value determination unit 510 determines the capacitor current target value Ic in accordance with the operating state of the motor 401 by the power conversion device 1b and the motor drive device 2b shown in the third embodiment. ＊ and the speed pulsation amplitude target value ωrip ＊ The operating state of the motor 401 is, for example, the rotation speed of the motor, the motor current, or the load torque.

[0139] Next, a specific target value determination method performed by the target value determination unit 510 will be described. As described in the first embodiment, the magnitude of the capacitor current Ic depends on the load, i.e., the power consumption of the motor 401. This is because, as the power consumption of the load increases, the rectified current Iin1 of the diode rectifier 130 increases. A case in which the power consumption of the load is large occurs when the rotation speed of the motor 401 is high or when the load torque is large. Therefore, when the rotation speed of the motor 401 is low and the load torque is small, the magnitude of the capacitor current Ic is small even when the capacitor current suppression control is not performed. Therefore, the capacitor current Ic has a margin with respect to the allowable current value of the capacitor 200. In such a case, the target value determination unit 510 determines that the capacitor current target value Ic is larger than the capacitor current Ic when the capacitor current suppression control is not performed. ＊ This makes it possible to equivalently turn off the capacitor current suppression control, enabling operation that prioritizes the efficiency of the motor 401. Conversely, when the rotation speed of the motor 401 is high, the capacitor current Ic increases. Therefore, the capacitor current target value Ic is set to a large value so as to ensure a margin with respect to the allowable current value of the capacitor 200.＊ This makes it possible to prevent breakdown or deterioration of the capacitor 200 and to improve the efficiency of the power conversion device 1b and the motor drive device 2b, depending on the operating state of the motor 401.

[0140] On the other hand, as shown in equation (11) in the third embodiment, the lower the frequency of the load torque pulsation, the larger the amplitude of the speed pulsation. Here, when the compressor 400 is a single rotary compressor, as described above, the frequency ωL of the load torque pulsation matches the average speed ωDC of the motor 401. Therefore, when the rotation speed of the motor 401 is low, the speed pulsation amplitude becomes large, and conversely, when the rotation speed of the motor 401 is high, the speed pulsation amplitude becomes small. Therefore, the target value determination unit 510 determines the speed pulsation amplitude target value ωrip according to the rotation speed of the motor 401. ＊ By setting the above, it is possible to prevent failures in the motor 401 and the mechanical load 402 and to improve the efficiency of the power conversion device 1b and the motor drive device 2b at the same time.

[0141] As another specific example, the capacitor current target value Ic can be calculated from the operating state of the motor drive device 2b and the allowable current value that can be passed through the motor 401. ＊ and the speed pulsation amplitude target value ωrip ＊ When the power consumption of the motor 401 is large, that is, when the load torque is large, or when the rotation speed of the motor 401 is high, the amount of current required for the motor 401 to maintain the rotation speed, that is, the first q-axis current command IqDC ＊ and the d-axis current id become large, and the margin for the allowable current value of the motor 401 becomes small. Therefore, the allowable current value that can be used in the capacitor current suppression control and the speed pulsation suppression control, which is determined by the difference between the allowable current value of the motor 401 and the amount of current required for the motor 401 to maintain its rotation speed, becomes small. In such a case, the target value determination unit 510 determines the capacitor current target value Ic ＊ and the speed pulsation amplitude target value ωrip ＊ and either one of them is set to a value larger than the original value. ＊and the third q-axis current command IqrV ＊ This allows the motor 401 to continue operating within the allowable current value of the motor 401.

[0142] As described above, the control device 500d of the fourth embodiment controls the capacitor current target value Ic in accordance with the operating state of the motor 401 by the power conversion device 1b and the motor drive device 2b. ＊ and the speed pulsation amplitude target value ωrip ＊ This makes it possible to prevent breakdown or deterioration of the capacitor 200, to prevent breakdown of the motor 401 and the mechanical load 402, and to improve the efficiency of the power conversion device 1b and the motor drive device 2b, depending on the operating state of the motor 401.

[0143] Sixth embodiment Fig. 21 is a refrigerant circuit diagram showing a configuration example of a refrigeration cycle-applied device according to a sixth embodiment. A refrigeration cycle-applied device 900 according to the sixth embodiment includes any one of the power conversion devices 1, 1a, and 1b described in the first to fifth embodiments. Note that Fig. 21 shows, as an example, a configuration including the power conversion device 1 described in the first embodiment.

[0144] The refrigeration cycle applied device 900 according to the sixth embodiment is applied to products equipped with a refrigeration cycle, such as an air conditioner, a refrigerator, a freezer, or a heat pump water heater.

[0145] The refrigeration cycle application equipment 900 includes a compressor 400 incorporating a motor 401, a flow path switching mechanism 902, an indoor heat exchanger 906, an expansion valve 908, and an outdoor heat exchanger 910, which are connected via refrigerant piping 912.

[0146] Inside the compressor 400, a compression mechanism 904 that compresses the refrigerant and a motor 401 that operates the compression mechanism 904 are provided.

[0147] The refrigeration cycle device 900 can perform heating or cooling operation by switching the flow path of a flow path switching mechanism 902. The compression mechanism 904 is driven by a variable speed controlled motor 401. Note that although a four-way valve is shown as an example of the flow path switching mechanism 902, it may also be configured with a combination of two-way valves, for example.

[0148] During heating operation, the refrigerant is pressurized by the compression mechanism 904 and sent out, as shown by the solid arrow, and passes through the flow path switching mechanism 902, the indoor heat exchanger 906, the expansion valve 908, the outdoor heat exchanger 910, and the flow path switching mechanism 902 in that order, before returning to the compression mechanism 904.

[0149] During cooling operation, the refrigerant is pressurized by the compression mechanism 904 and sent out, as shown by the dashed arrow, and passes through the flow path switching mechanism 902, the outdoor heat exchanger 910, the expansion valve 908, the indoor heat exchanger 906, and the flow path switching mechanism 902 in that order before returning to the compression mechanism 904.

[0150] During heating operation, the indoor heat exchanger 906 acts as a condenser to release heat, and the outdoor heat exchanger 910 acts as an evaporator to absorb heat. During cooling operation, the outdoor heat exchanger 910 acts as a condenser to release heat, and the indoor heat exchanger 906 acts as an evaporator to absorb heat. The expansion valve 908 reduces the pressure of the refrigerant to expand it.

[0151] The power conversion device 1 controls the operation of the inverter 300 based on the detection values ​​acquired from each detector, and variably controls the upper limit of the current pulsation amplitude when pulsating the current output from the inverter 300 to suppress the capacitor current Ic flowing in and out of the capacitor 200. This makes it possible to realize a refrigeration cycle device that is small, low-cost, and has high energy-saving performance.

[0152] The configurations shown in the above embodiments are merely examples, and may be combined with other known technologies or may be combined with other embodiments. Furthermore, it is also possible to omit or modify part of the configurations without departing from the spirit of the invention.

[0153] 1, 1a, 1b Power conversion device, 2, 2a, 2b Motor drive device, 100 Converter, 110 Commercial power supply, 120 Reactor, 130 Diode rectifier, 200 Capacitor, 201 DC bus voltage detection unit, 300 Inverter, 301a, 301b Current detection unit, 400 Compressor, 401 Motor, 402 Mechanical load, 500, 500a, 500b, 500c, 500d Control device, 501 Speed ​​control unit, 502 Capacitor current suppression control unit, 503, 503a, 503b, 503c Output upper limit value control unit, 504, 504b Addition unit, 505 Current control unit, 506 Position estimation unit, 507 PWM signal generation unit, 508 Capacitor current detection unit, 509 Speed ​​pulsation suppression control unit, 510 Target value determination unit, 521, 534, 540, 551 subtraction unit, 522, 523, 531, 532, 537, 538, 552, 553 Fourier coefficient calculation unit, 524, 525, 535, 541, 554, 555 PID control unit, 526, 556 amplitude limiting unit, 527, 557 AC restoration unit, 533, 539 amplitude calculation unit, 536, 542 limiting unit, 900 refrigeration cycle applied equipment, 902 flow path switching mechanism, 904 compression mechanism, 906 indoor heat exchanger, 908 expansion valve, 910 outdoor heat exchanger, 912 refrigerant piping.

Claims

1. A power conversion device for driving a motor attached to a mechanical load, A converter that converts the first AC power supplied from the commercial power source into DC power, A capacitor connected to the output terminal of the converter, An inverter connected to both ends of the capacitor converts DC power into a second AC power and outputs it to the motor, The system comprises a control device for driving and controlling the inverter, The control device is A capacitor current suppression control unit calculates a current pulsation command to cause the current flowing to the motor to pulsate in order to reduce the amount of capacitor current flowing into and out of the capacitor, The system includes an output limit control unit that controls the current pulsation command upper limit, which is the upper limit of the output of the current pulsation command, The output upper limit control unit controls the current pulsation command upper limit so that the pulsation amplitude of the capacitor current matches the capacitor current target value. The capacitor current suppression control unit limits the current pulsation command based on the current pulsation command upper limit value controlled by the output upper limit control unit. A power conversion device characterized by the following features.

2. The control device further comprises a capacitor current detection unit that detects or estimates the amount of current in the capacitor, The output upper limit control unit compares the error between the output of the capacitor current detection unit and the target capacitor current value, and automatically searches for the current pulsation command upper limit so that the pulsation amplitude of the capacitor current matches the target capacitor current value. The power conversion device according to feature 1.

3. The control device further includes a speed pulsation suppression control unit that calculates a second current pulsation command to cause the motor current flowing through the motor to pulsate in order to suppress the speed pulsation of the motor caused by the load torque pulsation of the mechanical load, The output upper limit control unit controls the second current pulsation command upper limit so that the velocity pulsation amplitude of the velocity pulsation matches the velocity pulsation amplitude target value. The velocity pulsation suppression control unit limits the second current pulsation command based on the second current pulsation command upper limit value controlled by the output upper limit control unit. The power conversion device according to feature 1.

4. The control device further comprises a speed pulsation suppression control unit that calculates a second current pulsation command to cause the motor current flowing through the motor to pulsate in order to suppress the speed pulsation of the motor caused by the load torque pulsation of the mechanical load, The output upper limit control unit controls the second current pulsation command upper limit so that the velocity pulsation amplitude of the velocity pulsation matches the velocity pulsation amplitude target value. The velocity pulsation suppression control unit limits the second current pulsation command based on the second current pulsation command upper limit value controlled by the output upper limit control unit. The power conversion device according to feature 2.

5. The output upper limit control unit detects the velocity pulsation amplitude, compares the error between the detected velocity pulsation amplitude and the target velocity pulsation amplitude, and automatically searches for the second current pulsation command upper limit so that the velocity pulsation amplitude matches the target velocity pulsation amplitude. The power conversion device according to feature 3.

6. The output upper limit control unit detects the velocity pulsation amplitude, compares the error between the detected velocity pulsation amplitude and the velocity pulsation amplitude target value, and automatically searches for the second current pulsation command upper limit value so that the velocity pulsation amplitude matches the velocity pulsation amplitude target value. The power conversion device according to feature 4.

7. The control device further includes a target value determination unit that determines at least one of the speed pulsation amplitude target value and the capacitor current target value according to the operating state of the motor. The power conversion device according to feature 3.

8. The control device further comprises a target value determination unit that determines at least one of the speed pulsation amplitude target value and the capacitor current target value according to the operating state of the motor. The power conversion device according to feature 4.

9. The control device further comprises a target value determination unit that determines at least one of the speed pulsation amplitude target value and the capacitor current target value according to the operating state of the motor. The power conversion device according to feature 5.

10. The control device further comprises a target value determination unit that determines at least one of the speed pulsation amplitude target value and the capacitor current target value according to the operating state of the motor. The power conversion device according to feature 6.

11. A power conversion device according to any one of claims 1 to 10, A motor provided on a mechanical load and driven and controlled by the power conversion device, A motor drive device characterized by the following features.

12. A motor drive device according to claim 11, A refrigeration cycle application device characterized by the following features.