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

Abstract

A power conversion device (1) comprises: a capacitor (210) connected to the output end of a rectifier unit (130) that rectifies a first AC power supplied from a commercial power supply (110); and an inverter (310) connected to both ends of the capacitor (210) and generating a second AC power to output the second AC power to a motor (314). A control unit (400) for controlling the operation of the inverter (310) performs allocation so that a load ripple compensation control torque current command for suppressing the vibration of the motor (314) and a power supply ripple compensation control torque current command for suppressing capacitor current can be each set properly while prioritizing a constant current load control torque current command for controlling the drive frequency of the motor (314) within a settable torque current range, detects or calculates a physical quantity that has the same characteristics as the capacitor current, and performs control for reducing the drive frequency of the motor (314) or stopping the drive of the motor (314) when the physical quantity exceeds a protection threshold.

Description

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

[0001] The present disclosure relates to a power conversion device that converts AC power into desired power, a motor drive device, and a refrigeration cycle device.

[0002] Conventionally, there have been power conversion devices that convert AC power supplied from a commercial power source into desired AC power and supply it to a load such as an air conditioner. Patent Document 1 below describes a power conversion device that prioritizes constant current load control, which controls the rotation speed of a motor, while also performing load pulsation compensation control, which reduces motor vibration, and power supply pulsation compensation control, which suppresses the charge / discharge current of a capacitor. Power supply pulsation compensation control can suppress ripple voltage contained in the capacitor voltage, allowing the use of a capacitor with a small capacity. Therefore, by using the technology described in Patent Document 1, it is possible to suppress capacitor degradation while also preventing the device from becoming larger.

[0003] International Publication No. 2022 / 149213

[0004] However, the above-mentioned conventional technology only takes into account cases where the power supply pulsation compensation control is operating as expected. Therefore, if the power supply pulsation compensation control is not operating as expected, a large pulsating current flows through the capacitor, which causes deterioration of the capacitor and makes it impossible to guarantee the designed life of the capacitor. Therefore, there is a need for technology that can suppress capacitor deterioration even when the power supply pulsation compensation control is not operating as expected.

[0005] The present disclosure has been made in view of the above, and aims to provide a power conversion device that can suppress capacitor degradation even when power supply pulsation compensation control does not operate as expected.

[0006] To solve the above-mentioned problems and achieve the object, the present disclosure provides a power conversion device including a rectifier that rectifies first AC power supplied from a commercial power source, a capacitor connected to an output terminal of the rectifier, an inverter connected across the capacitor to generate second AC power and output it to a motor, and a control unit that controls the operation of the inverter. The control unit distributes the torque current commands so that they are appropriately set, while prioritizing a torque current command for constant current load control that controls the motor's drive frequency within a settable torque current range. The control unit also detects or calculates a physical quantity having characteristics similar to the capacitor current, and controls the motor's drive frequency or stops driving if the physical quantity exceeds a protection threshold.

[0007] The power conversion device according to the present disclosure has the advantage of being able to suppress capacitor degradation even when power supply pulsation compensation control does not operate as expected.

[0008] FIG. 1 is a diagram showing a configuration example of a power conversion device according to embodiment 1; FIG. 2 is a block diagram showing a configuration example of a control unit provided in the power conversion device according to embodiment 1; FIG. 3 is a diagram used to explain the operation of the main part of the control unit according to embodiment 1; FIG. 4 is a block diagram showing a configuration example of a first protection threshold generation unit provided in the control unit according to embodiment 1; FIG. 5 is a diagram used to explain the operation of the main part of the control unit according to embodiment 1; FIG. 6 is a block diagram showing a configuration example of a capacitor voltage processing unit provided in the control unit according to embodiment 1;

[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 accompanying drawings.

[0010] 1 is a diagram showing a configuration example of a power conversion device 1 according to a first embodiment. The power conversion device 1 is connected to a commercial power supply 110 and a compressor 315. The power conversion device 1 converts a power supply voltage V ｓ The power conversion device 1 converts the first AC power into second AC power having a desired amplitude and frequency and supplies the second AC power to the compressor 315. The commercial power source 110 is an example of an AC power source, and the compressor 315 is an example of a device connected to the power conversion device 1. The compressor 315 is equipped with a motor 314. The power conversion device 1 and the motor 314 included in the compressor 315 constitute a motor drive device 2.

[0011] The power conversion device 1 includes a reactor 120 , a rectifying unit 130 , a smoothing unit 200 , a first voltage detecting unit 500 , a second voltage detecting unit 501 , an inverter 310 , current detecting units 313 a and 313 b , and a control unit 400 .

[0012] Reactor 120 is connected between commercial power supply 110 and rectifier 130. Rectifier 130 has a bridge circuit configured with rectifier elements 131 to 134, and rectifies and outputs the first AC power supplied from commercial power supply 110. Rectifier 130 performs full-wave rectification.

[0013] Smoothing unit 200 is connected to the output terminal of rectifying unit 130. Smoothing unit 200 has capacitor 210 as a smoothing element, and smooths the power rectified by rectifying unit 130. Capacitor 210 is, for example, an electrolytic capacitor or a film capacitor. Capacitor 210 is connected to the output terminal of rectifying unit 130 and has a capacitance that smooths the power rectified by rectifying unit 130. The voltage generated in capacitor 210 by the smoothing does not have the same full-wave rectified waveform as commercial power supply 110, but rather has a waveform in which a voltage ripple corresponding to the frequency of commercial power supply 110 is superimposed on a DC component.

[0014] The inverter 310 is connected to the smoothing unit 200, i.e., both ends of the capacitor 210. The inverter 310 has switching elements 311a to 311f and freewheeling diodes 312a to 312f. The control unit 400 controls the on / off of the switching elements 311a to 311f of the inverter 310. Through this control, the power output from the rectifying unit 130 and the smoothing unit 200 is converted into second AC power having a desired amplitude and frequency. That is, the inverter 310 generates the second AC power by turning on and off the switching elements 311a to 311f, and outputs it to the motor 314.

[0015] The frequency of the voltage ripple generated in the capacitor 210 is the power supply voltage V ｓ When the commercial power supply 110 is three-phase, the power supply voltage V ｓ The main component is a six-fold component of the frequency of the voltage ripple. Furthermore, when the first AC power supplied from commercial power supply 110 and the second AC power output from inverter 310 do not change, the amplitude of the voltage ripple is determined by the capacitance of capacitor 210. For this reason, the capacitance of capacitor 210 is set, for example, so that the maximum value of the voltage generated in capacitor 210 is less than twice the minimum value.

[0016] The first voltage detection unit 500 detects the capacitor voltage V ｄｃ The second voltage detection unit 501 detects the power supply voltage V, which is the voltage of the commercial power supply 110, and converts the detected voltage value into a value that can be input to the control unit 400 and outputs it. ｓ The control unit 400 converts the voltage values ​​input from the first and second voltage detection units 500 and 501 into values ​​that can be input to the control unit 400 and outputs the converted values. ｄｃ and power supply voltage V ｓ From this point on, the output voltages of the first and second voltage detection units 500 and 501 are used as the capacitor voltage V ｄｃ and power supply voltage V ｓ The same applies to the other detection units.

[0017] Each of the current detection units 313a and 313b detects the current value of one phase of the three-phase current output from the inverter 310 and outputs the detected current value to the control unit 400. Note that the control unit 400 can calculate the current value of the remaining one phase output from the inverter 310 by acquiring the current values ​​of two phases of the three-phase current values ​​output from the inverter 310. Also, while FIG. 1 shows a configuration in which the phase currents are directly detected, a configuration in which the inverter input current I2 is detected and the three-phase current values ​​are calculated from the detected current values ​​may also be used.

[0018] The motor 314 mounted on the compressor 315 rotates in accordance with the amplitude and frequency of the AC power supplied from the inverter 310 to perform a compression operation. Examples of the compressor 315 include a single rotary compressor and a twin rotary compressor. When the compressor 315 is a single rotary compressor, the main component frequency of the load pulsation of the motor 314 is a component that is one time the mechanical angle drive frequency of the motor 314. When the compressor 315 is a twin rotary compressor, the main component frequency of the load pulsation of the motor 314 is a component that is two times the mechanical angle drive frequency of the motor 314.

[0019] 1 shows a case where the motor windings of the motor 314 are Y-connected, but this is not limiting. The motor windings of the motor 314 may be Delta-connected, or may be configured to be switchable between Y-connection and Delta-connection.

[0020] Furthermore, in the power conversion device 1, the arrangement of each component shown in FIG. 1 is one example, and the arrangement of each component is not limited to the example shown in FIG. 1. For example, the reactor 120 may be arranged after the rectifier 130. Furthermore, the power conversion device 1 may include a booster unit, or the rectifier 130 may be configured to have the function of a booster unit. In the following description, the current detection units 313a, 313b and the first and second voltage detection units 500, 501 may each be simply referred to as a "detection unit." Furthermore, the current values ​​detected by the current detection units 313a, 313b and the voltage values ​​detected by the first and second voltage detection units 500, 501 may each be simply referred to as a "detection value."

[0021] The control unit 400 detects the capacitor voltage V ｄｃ and the power supply voltage V ｓ The control unit 400 also acquires the detection values ​​of the motor currents detected by the current detection units 313a and 313b. The control unit 400 uses the detection values ​​detected by each detection unit to control the operation of the inverter 310, specifically, to control the on / off of the switching elements 311a to 311f of the inverter 310.

[0022] Furthermore, the control unit 400 controls the operation of the inverter 310 so that the inverter 310 outputs to the compressor 315 a second AC power including pulsation corresponding to the pulsation of the power flowing from the rectifier 130 to the capacitor 210 of the smoothing unit 200. The pulsation corresponding to the pulsation of the power flowing into the capacitor 210 of the smoothing unit 200 is, for example, pulsation that varies depending on the frequency of the pulsation of the power flowing into the capacitor 210 of the smoothing unit 200. As a result, the control unit 400 suppresses the capacitor current I3, which is the charging / discharging current of the capacitor 210. The control unit 400 controls the speed, voltage, or current of the motor 314 so that any one of them is in a desired state. Note that the control unit 400 does not need to use all of the detection values ​​acquired from each detection unit, and can perform control using only some of the detection values.

[0023] Note that when the motor 314 is used to drive the compressor 315 and the compressor 315 is a hermetic compressor, it is often difficult to attach a position sensor to the motor 314 to detect the rotor position, both structurally and cost-wise. For this reason, the control unit 400 controls the motor 314 without a position sensor. There are two types of position sensorless control methods for the motor 314: constant primary magnetic flux control and sensorless vector control. In the first embodiment, the sensorless vector control will be described as an example. Note that the control methods described below can also be applied to constant primary magnetic flux control with minor modifications.

[0024] Next, a characteristic operation of the control unit 400 in the first embodiment will be described. First, the rectified current I1 flowing out from the rectifier unit 130 is affected by the power supply phase of the commercial power supply 110, the characteristics of the elements installed before and after the rectifier unit 130, and the like. As a result, the rectified current I1 has characteristics including a current component of the power supply frequency and a harmonic current component of the power supply frequency. The harmonic current component of the power supply frequency is a current component with a frequency that is an integer multiple of the power supply frequency by two or more. Furthermore, in the capacitor 210, if the capacitor current I3 is large, the deterioration of the capacitor 210 over time will be accelerated. In particular, when an electrolytic capacitor is used as the capacitor 210, the degree of acceleration of the deterioration over time will be greater.

[0025] Therefore, the control unit 400 controls the inverter 310 so that the inverter input current I2 is equal to the rectified current I1, thereby controlling the capacitor current I3 to approach zero. This suppresses deterioration of the capacitor 210. However, a ripple component caused by PWM (Pulse Width Modulation) is superimposed on the inverter input current I2. Therefore, the control unit 400 needs to control the inverter 310 taking this ripple component into account.

[0026] In addition, in order to suppress deterioration of the capacitor 210, the control unit 400 monitors the power state of the smoothing unit 200, i.e., the capacitor 210, and applies an appropriate pulsation to the motor 314 so that the capacitor current I3 decreases. Here, the power state of the capacitor 210 refers to the rectified current I1, the inverter input current I2, the capacitor current I3, and the capacitor voltage V, which is the voltage of the capacitor 210. ｄｃ In the control unit 400, at least one of the power states of the capacitor 210 becomes information necessary for degradation suppression control.

[0027] In the power conversion device 1, the control unit 400 detects the capacitor voltage V ｄｃ and the capacitor voltage V ｄｃ Then, the control unit 400 further extracts the ripple value by removing the DC component from the power supply voltage V ｓThe inverter 310 is controlled so that the extracted specific frequency component approaches zero, and a pulsation is added to the power output to the motor 314. Here, when the commercial power supply 110 is a single-phase power supply, the specific frequency component is ｓ When the commercial power supply 110 is a three-phase power supply, the specific frequency component is twice the frequency of the power supply voltage V ｓ The control unit 400 controls the operation of the inverter 310 so that the pulsation according to the power state of the capacitor 210 is superimposed on the drive pattern of the motor 314. This suppresses the capacitor current I3. This control is called "power supply pulsation compensation control."

[0028] Furthermore, as described above, when a single rotary compressor is used as the compressor 315, the motor 314 generates a load torque pulsation that is one time the mechanical angle drive frequency of the motor 314, and when a twin rotary compressor is used as the compressor 315, the motor 314 generates a load torque pulsation that is twice the mechanical angle drive frequency of the motor 314. For this reason, when the compressor 315 is driven with a constant output current from the inverter 310, i.e., with a constant torque output, speed fluctuations occur due to the torque difference. The motor drive device 2 has the characteristic that the speed fluctuations occur significantly in the low-speed range and become smaller as the operating point moves to the high-speed range.

[0029] Furthermore, in the motor drive device 2, the speed fluctuation component leaks out and is observed externally as vibration. Therefore, when constructing the motor drive device 2, it is necessary to add vibration-suppressing components. Therefore, in the power conversion device 1, a method is often adopted in which a pulsating current component that provides pulsating torque is passed to the compressor 315, separate from the constant torque output current, which is a constant current component output from the inverter 310. By passing the pulsating current component to the compressor 315, the torque difference can be made closer to zero. This reduces the speed fluctuation of the motor 314 that drives the compressor 315, thereby suppressing vibration of the compressor 315. This control is called "load pulsation compensation control."

[0030] As described above, in the first embodiment, the control unit 400 performs power supply pulsation compensation control to compensate for power supply pulsation and load pulsation compensation control to compensate for load pulsation. However, in the power conversion device 1, it is essential that the driven motor 314 follows the speed command. For this reason, the power supply pulsation compensation control and the load pulsation compensation control are performed together with the constant current load control that controls the drive frequency of the motor 314. In addition, although the details will be described later, the control unit 400 controls the capacitor voltage V ｄｃ If the ripple value, which is the magnitude of the ripple in the output voltage, exceeds a protection threshold, the drive frequency of the motor 314 is reduced or the drive of the motor 314 is stopped.

[0031] Next, the detailed configuration and operation of the control unit 400 according to the first embodiment will be described with reference to the drawings of Figs. 2 to 6. Fig. 2 is a block diagram showing an example configuration of the control unit 400 provided in the power conversion device 1 according to the first embodiment. Fig. 3 is a first diagram used to explain the operation of the main parts of the control unit 400 according to the first embodiment. Fig. 4 is a block diagram showing an example configuration of a first protection threshold generation unit 416 provided in the control unit 400 according to the first embodiment. Fig. 5 is a second diagram used to explain the operation of the main parts of the control unit 400 according to the first embodiment. Fig. 6 is a block diagram showing an example configuration of a capacitor voltage processing unit 417 provided in the control unit 400 according to the first embodiment.

[0032] 2 , the control unit 400 includes a rotor position estimation unit 401, a speed control unit 402, a flux-weakening control unit 403, a current control unit 404, coordinate conversion units 405 and 406, a PWM signal generation unit 407, a subtraction unit 408, a distribution ratio multiplication unit 409, a load pulsation compensation control unit 410, an addition unit 411, a subtraction unit 412, a power supply pulsation compensation control unit 413, an addition unit 414, a first protection threshold generation unit 416, and a capacitor voltage processing unit 417. The addition units 411 and 414 configure a q-axis current command generation unit 415.

[0033] The rotor position estimation unit 401 estimates the d- and q-axis voltage command vector V ｄｑ ＊ and dq axis current vector i ｄｑUsing the above, an estimated phase angle θ, which is the direction of the rotor magnetic poles on the dq axes, is calculated for the rotor (not shown) of the motor 314. ｅｓｔ , and the estimated rotor speed ω ｅｓｔ In addition, the q-axis current command I for load pulsation compensation control, which will be described later, is estimated. ｑａｖｓ The correction torque command τ ＊ ｒｉｐ is output to the load pulsation compensation control unit 410. ＊ ｒｉｐ can be generated using the means or techniques described in Japanese Patent No. 7012901, for example.

[0034] The speed control unit 402 receives a speed command ω ＊ and estimated speed ω ｅｓｔ so that the q-axis current command I ｑｓｐ The q-axis current command I ｑｓｐ is a torque current command for constant current load control. Also, the speed command ω ＊ When the power conversion device 1 is used as a refrigeration cycle device such as an air conditioner, the temperature control value is based on, for example, detected temperature information detected by a temperature sensor (not shown), set temperature information indicating a set temperature instructed from a remote control (not shown) which is an operation unit, operation mode selection information, and instruction information for starting and stopping operation, etc. The operation modes are, for example, heating, cooling, dehumidification, etc.

[0035] However, when the stall request output from the capacitor voltage processing unit 417 (described later) is "1: Present", the stall request takes priority over the temperature information, instruction information, and selection information described above, and the speed command ω ＊ Here, even if the stall request changes from "1: Yes" to "0: No", the speed command ω ＊ To prevent hunting of the speed command ω ＊In this case, an example of "for a while" is "about 10 minutes." If the stall request changes from "0: absent" to "1: present" multiple times within a specified time, the control unit 400 determines that power supply pulsation compensation control is not being performed appropriately, and performs control to stop the motor 314. An example of "multiple times" is "three times," and an example of the specified time is "one hour."

[0036] Here, the control unit 400 can use the stall request as a stop request when performing control to stop the motor 314. Specifically, the control unit 400 inputs information about the stop request to the PWM signal generation unit 407, and when the stop request becomes "1: Present", the control unit 400 can request a stall by generating a PWM signal to the inverter 310 to stop driving the motor 314.

[0037] The flux-weakening control unit 403 calculates the d- and q-axis voltage command vector V ｄｑ ＊ The absolute value of is the voltage limit value V ｌｉｍ ＊ The d-axis current command i ｄ ＊ The weakening magnetic field control is roughly divided into the following two cases: ｄ ＊ and the voltage limit value V ｌｉｍ ＊ and the dq axis voltage command vector V ｄｑ ＊ The d-axis current command i ｄ ＊ There are two methods for calculating the above, and either method may be used.

[0038] The current control unit 404 controls the dq-axis current vector i ｄｑ is the d-axis current command i ｄ ＊ and q-axis current command i ｑ ＊ The dq-axis voltage command vector V ｄｑ ＊ Here, even if the flux-weakening control is not performed, the dq-axis voltage command vector V ｄｑ ＊The absolute value of is the voltage limit value V ｌｉｍ ＊ If it is within the limit value of , the d-axis current command i ｄ ＊ The q-axis current command i ｑ ＊ For example, the d-axis current command i ｄ ＊ The q-axis current command i ｑ ＊ Examples of control that sets the torque according to the current include a maximum torque / current control method that generates the maximum torque at a certain current.

[0039] The coordinate conversion unit 405 converts the estimated phase angle θ ｅｓｔ In response to this, the dq axis voltage command vector V ｄｑ ＊ The AC voltage command V is calculated from the dq coordinates. ｕｖｗ ＊ Transform the coordinates to

[0040] The coordinate conversion unit 406 converts the estimated phase angle θ ｅｓｔ The current I flowing through the motor 314 depends on ｕｖｗ From the AC amount, the dq axis current vector i ｄｑ As described above, the control unit 400 converts the current I ｕｖｗ Regarding the current values ​​of the three phases output from the inverter 310, the current values ​​of two phases detected by the current detection units 313a and 313b can be obtained by calculating the current value of the remaining one phase using the current values ​​of the two phases.

[0041] The PWM signal generating unit 407 converts the voltage command V ｕｖｗ ＊ The control unit 400 applies a voltage to the motor 314 by outputting the PWM signal generated by the PWM signal generating unit 407 to the switching elements 311a to 311f of the inverter 310.

[0042] The subtractor 408 subtracts the q-axis current limit value I ｑｌｉｍ and the q-axis current command I ｑｓｐ The q-axis current margin I ｑｍａｒｇｉｎ The q-axis current command I ｑｓｐIf the value of is positive, it is not necessary to calculate the absolute value. ｑｌｉｍ is the q-axis current command i input to the current control unit 404 ｑ ＊ This is the limit value for the torque current, and means the upper limit of the torque current range that can be set. ｑｍａｒｇｉｎ is the q-axis current limit value I ｑｌｉｍ The q-axis current command I required for constant current load control is ｑｓｐ This is the remainder after subtracting the current component of the q-axis current limit value I ｑｌｉｍ Among them, the q-axis current command I for constant current load control ｑｓｐ is given priority because the motor 314 is ＊ The control unit 400 is configured to prioritize constant current load control. ｑｍａｒｇｉｎ Since is affected by speed pulsation, bus voltage pulsation, etc., it may be smoothed using a low-pass filter.

[0043] Next, the q-axis current margin I ｑｍａｒｇｉｎ is distributed to the load pulsation compensation control and the power supply pulsation compensation control. Specifically, the distribution ratio multiplier 409 multiplies the q-axis current margin I ｑｍａｒｇｉｎ , the distribution ratio K for each compensation control of the load pulsation compensation control for suppressing the vibration of the motor 314 and the power supply pulsation compensation control for suppressing the capacitor current I3 of the capacitor 210. ｍａｒｇｉｎ and the multiplication result is used as the current limit value I for load pulsation compensation control. ｑｌｉｍＡＶＳ In this way, the current limit value I ｑｌｉｍＡＶＳ is the q-axis current margin I ｑｍａｒｇｉｎ It is set using

[0044] Here, the distribution ratio K ｍａｒｇｉｎ is the q-axis current margin I ｑｍａｒｇｉｎ is a variable between 0 and 1, and is set so as to suppress the vibration of the compressor 315 and the charge / discharge current of the capacitor 210 within their respective allowable ranges. ｍａｒｇｉｎBy appropriately setting the capacitance of the capacitor 210 and the specifications of the compressor 315, it is possible to obtain a power conversion device 1 that is excellent in cost performance.

[0045] However, when the average load torque of the motor 314 is low, the distribution ratio K ｍａｒｇｉｎ In other words, the current limit value I for load pulsation compensation control is increased. ｑｌｉｍＡＶＳ When the distribution of is increased, as shown in FIG. 3, the capacitor voltage V ｄｃ It has been confirmed that the ripple in

[0046] The horizontal axis of FIG. 3 represents the average load torque applied to the motor 314, and the vertical axis of FIG. 3 represents the effective value V of the capacitor voltage ripple. ｄｃ-ｒｐｌ-ｒｍｓ 3 shows the average load torque applied to the motor 314 and the effective value V of the capacitor voltage ripple. ｄｃ-ｒｐｌ-ｒｍｓ The capacitor voltage ripple is expressed as the capacitor voltage V ｄｃ The solid line shows the effective value V of the capacitor voltage ripple when the load proportional compensation limit is not implemented. ｄｃ-ｒｐｌ-ｒｍｓ The dashed line represents the effective value V of the capacitor voltage ripple when the load proportional compensation limit is implemented. ｄｃ-ｒｐｌ-ｒｍｓ As shown by the solid line in FIG. 3, when the load proportional compensation limit is not implemented, the effective value V of the capacitor voltage ripple is ｄｃ-ｒｐｌ-ｒｍｓ It has been confirmed that the phenomenon in which the capacitor voltage V ｄｃ Although this varies depending on the specifications of the motor 314, as an example, in a configuration in which the power conversion device 1 is connected to the compressor 315, it has been confirmed that the speed is between 50 and 60 [rps].

[0047] In Figure 3, the arrows on the horizontal and vertical axes indicate that the values ​​increase in the direction of the arrow. On the horizontal axis, the average load torques T1, T2, and T3 have the relationship "T1 < T2 < T3." Here, T3 represents the maximum expected average load torque, and is appropriately referred to as "MAX load T3."

[0048] Also, in FIG. 3, the first protection threshold is the effective value V ｄｃ-ｒｐｌ-ｒｍｓ , and is set by measuring or simulating in advance a value that can ensure the life of the capacitor 210. Specifically, the first protection threshold is set to "V ｄｃ-ｒｐｌ-ｒｍｓ <First protection threshold value" and the power supply voltage V ｓ Taking into account the magnitude of the power supply voltage effective value V ｒｍｓ The control unit 400 sets the effective value V of the capacitor voltage ripple. ｄｃ-ｒｐｌ-ｒｍｓ exceeds the first protection threshold, the drive frequency of the motor 314 is reduced or the drive of the motor 314 is stopped.

[0049] Here, if the load proportional compensation limit is not implemented, when the average load torque decreases from T2 to T1, it will move along the solid line in FIG. 3, so the effective value V of the capacitor voltage ripple will ｄｃ-ｒｐｌ-ｒｍｓ will exceed the first protection threshold before the average load torque reaches T1, and the power conversion device 1 will take protective action to reduce the drive frequency of the motor 314 or stop the drive of the motor 314. To avoid this, in the first embodiment, a load proportional correction limit is performed as shown by the broken line in FIG. 3. In the load proportional correction limit, the average load torque of the motor 314 and the effective value V of the capacitor voltage ripple are ｄｃ-ｒｐｌ-ｒｍｓ The relationship between the average load torque and the effective value V of the capacitor voltage ripple is directly proportional. ｄｃ-ｒｐｌ-ｒｍｓ The distribution ratio K ｍａｒｇｉｎ When the average load torque of the motor 314 becomes smaller, the distribution ratio K ｍａｒｇｉｎ The distribution ratio K ｍａｒｇｉｎ Reducing the value of τ means limiting the torque current for load pulsation compensation control.

[0050] Returning to the explanation of Fig. 2, the load pulsation compensation control unit 410 calculates the current limit value I for load pulsation compensation control generated by the distribution ratio multiplication unit 409. ｑｌｉｍＡＶＳ and the q-axis current command I ｑａｖｓThe q-axis current command I for load pulsation compensation control is generated. ｑａｖｓ is the correction torque command τ from the rotor position estimation unit 401. ＊ ｒｉｐ is converted into a torque current command, and its amplitude I ｑａｖｓ-ａｍｐ is the current limit value I ｑｌｉｍＡＶＳ If it exceeds the amplitude I ｑａｖｓ-ａｍｐ current limit value I ｑｌｉｍＡＶＳ The q-axis current margin I ｑｍａｒｇｉｎ , a current limit value I for load pulsation compensation control ｑｌｉｍＡＶＳ , and the q-axis current command I for load pulsation compensation control ｑａｖｓ The magnitude relationship between I ｑｍａｒｇｉｎ ≧I ｑｌｉｍＡＶＳ ≧I ｑａｖｓ The q-axis current command I for load pulsation compensation control is ｑａｖｓ is a torque current command for load pulsation compensation control.

[0051] The subtractor 412 calculates the q-axis current margin I ｑｍａｒｇｉｎ to the amplitude I of the q-axis current command for load pulsation compensation control ｑａｖｓ-ａｍｐ The result of the subtraction is used as the limit value I for power supply pulsation compensation control. ｑｌｉｍｄ２ｖ In this way, the limit value I for power supply pulsation compensation control is ｑｌｉｍｄ２ｖ is the q-axis current margin I ｑｍａｒｇｉｎ It is set using

[0052] The power supply pulsation compensation control unit 413 sets a limit value I ｑｌｉｍｄ２ｖ The power supply pulsation compensation control is performed within the range of ｑｄ２ｖ The q-axis current command I for power supply pulsation compensation control is generated. ｑｄ２ｖ is the specific frequency component extracted value V of the capacitor voltage ripple described later. ｄｃ-ｒｐｌ-ｎｆｓ This specific frequency component extracted value V ｄｃ-ｒｐｌ-ｎｆｓ is a q-axis current command value calculated by, for example, PI control. The power supply pulsation compensation control unit 413 calculates the q-axis current command I ｑｄ２ｖ The amplitude of I ｑｄ２ｖ-ａｍｐ is the limit value I ｑｌｉｍｄ２ｖ If it exceeds the amplitude I ｑｄ２ｖ-ａｍｐ limit value I ｑｌｉｍｄ２ｖThe q-axis current command I for power supply pulsation compensation control is limited to ｑｄ２ｖ is a torque current command for power supply pulsation compensation control.

[0053] In FIG. 2, the q-axis current command I ｑａｖｓ After calculating the q-axis current command I ｑｄ２ｖ However, the present invention is not limited to this configuration. ｍａｒｇｉｎ If is set appropriately, the q-axis current command I for power supply pulsation compensation control is ｑｄ２ｖ After calculating the q-axis current command I for load pulsation compensation control, ｑａｖｓ It may be configured to obtain the following.

[0054] The q-axis current command generator 415 generates a q-axis current command I ｑｓｐ , q-axis current command I for load pulsation compensation control ｑａｖｓ , and the q-axis current command I for power supply pulsation compensation control ｑｄ２ｖ Using this, the q-axis current command i ｑ ＊ Specifically, in the q-axis current command generating unit 415, the adder 411 generates a q-axis current command I for constant current load control. ｑｓｐ and the q-axis current command I for load pulsation compensation control. ｑａｖｓ The adder 414 adds the q-axis current command I for constant current load control, which is the addition result of the adder 411. ｑｓｐ + q-axis current command I for load pulsation compensation control ｑａｖｓ and the q-axis current command I for power supply pulsation compensation control. ｑｄ２ｖ The q-axis current command generating unit 415 adds the addition result of the adding unit 414 to the q-axis current command i ｑ ＊ to the current control unit 404.

[0055] The first protection threshold generator 416 generates a protection threshold value based on the power supply voltage V detected by the second voltage detector 501. ｓ and outputs a first protection threshold value to be input to a comparison unit 424 described later. ｓ The magnitude of the capacitor voltage V ｄｃ Since the magnitude of the ripple in the power supply voltage V fluctuates, the first protection threshold generator 416 ｓAn appropriate protection threshold value is set to protect the capacitor 210 depending on the magnitude of the voltage.

[0056] 4 shows a detailed configuration example of the first protection threshold generator 416. As shown in FIG. 4, the first protection threshold generator 416 includes an effective value calculator (denoted as "rms" in FIG. 4) 418 and a table 419. The effective value calculator 418 calculates the power supply voltage V ｓ Enter the effective power supply voltage V ｓ-ｒｍｓ The table 419 calculates and outputs the effective power supply voltage V ｓ-ｒｍｓ Enter the effective power supply voltage V ｓ-ｒｍｓ and outputs a first protection threshold value corresponding to the input value of

[0057] FIG. 5 shows the effective value of the power supply voltage V ｓ-ｒｍｓ The table data of the table 419 holds data on the relationship shown in FIG. 5. Based on this table data, the table 419 stores the power supply voltage effective value V ｓ-ｒｍｓ It is possible to set a first protection threshold value that can appropriately protect the capacitor 210 against the power supply voltage effective value V ｓ-ｒｍｓ However, V shown by black dots in FIG. ｓ１ , V ｓ２ , V ｓ３ It is also possible to store only the protection thresholds for these three points, and calculate the protection thresholds for the other points by linear interpolation. In this way, the amount of data stored in the table data can be reduced. Note that the content described here is just an example, and the number of table data stored may be other than three, and the interpolation process may be other than linear interpolation.

[0058] Returning to the explanation of FIG. 2, the capacitor voltage processing unit 417 converts the capacitor voltage V detected by the first voltage detection unit 500 into ｄｃ and the first protection threshold value that is the output of the first protection threshold value generation unit 416, the specific frequency component extracted value V of the capacitor voltage ripple is calculated. ｄｃ-ｒｐｌ-ｎｆｓ and a stall request (0: no, 1: yes). The specific frequency component extracted value V of the capacitor voltage ripple ｄｃ-ｒｐｌ-ｎｆｓ is the capacitor voltage V ｄｃ From the ripple value of the power supply voltage V ｓAs described above, when the commercial power supply 110 is a single-phase power supply, the specific frequency component is a value extracted when the power supply voltage V ｓ When the commercial power supply 110 is a three-phase power supply, the power supply voltage V ｓ It is a frequency component six times the frequency of

[0059] Fig. 6 shows a detailed configuration example of capacitor voltage processing unit 417. As shown in Fig. 6, capacitor voltage processing unit 417 includes an LPF (Low Pass Filter) 420, a subtraction unit 421, a BPF (Band Pass Filter) 422, an effective value calculation unit (denoted as "rms" in Fig. 6) 423, and a comparison unit 424.

[0060] The LPF 420 is a capacitor voltage V ｄｃ By applying low-pass filtering to the capacitor voltage V ｄｃ DC component V ｄｃ-ｌｐｆ The subtraction unit 421 extracts the capacitor voltage V ｄｃ DC component V ｄｃ-ｌｐｆ The result of the subtraction is the capacitor voltage V ｄｃ Ripple voltage V ｄｃ-ｒｐｌ The "ripple voltage" here is synonymous with the above-mentioned "capacitor voltage ripple", and the ripple voltage V ｄｃ-ｒｐｌ is the capacitor voltage V ｄｃ The BPF 422 is a ripple voltage V ｄｃ-ｒｐｌ By performing band-pass filtering on the specific frequency component, a specific frequency component extracted value V ｄｃ-ｒｐｌ-ｎｆｓ Output.

[0061] The effective value calculation unit 423 calculates the ripple voltage V ｄｃ-ｒｐｌ and its effective value V ｄｃ-ｒｐｌ-ｒｍｓ The comparator 424 calculates and outputs the first protection threshold value V , which is the output of the first protection threshold generator 416, and the effective value V of the capacitor voltage ripple. ｄｃ-ｒｐｌ-ｒｍｓ First protection threshold ≧ V ｄｃ-ｒｐｌ-ｒｍｓIn this case, the comparison unit 424 outputs "0 (no stall request)". ＊ The output value indicates that it is not necessary to perform control to reduce the first protection threshold value<V ｄｃ-ｒｐｌ-ｒｍｓ In this case, the comparison unit 424 outputs "1 (stall request present)". "1 (stall request present)" indicates that the speed command ω ＊ This is an output value that indicates that control should be performed to reduce the

[0062] In the above determination process, the "effective value V ｄｃ-ｒｐｌ-ｒｍｓ " exceeds the "first protection threshold", "1 (stall request present)" is output. ｄｃ-ｒｐｌ-ｒｍｓ " and the "first protection threshold" may be equal. ｄｃ-ｒｐｌ-ｒｍｓ " may be configured to output "1 (stall required)" when "first protection threshold" is equal to or greater than "first protection threshold".

[0063] In the above description, the ripple voltage V is used as the physical quantity to be compared with the first protection threshold. ｄｃ-ｒｐｌ The effective value V ｄｃ-ｒｐｌ-ｒｍｓ However, the present invention is not limited to this example. The object of comparison with the first protection threshold may be any detected value or calculated value that represents a physical quantity having similar characteristics to the capacitor current I3. Other examples of calculated values ​​that represent a physical quantity having similar characteristics to the capacitor current I3 will be described in the second embodiment.

[0064] Next, a description will be given of a hardware configuration for realizing the functions of the control unit 400 according to embodiment 1. Fig. 7 is a block diagram showing an example of a hardware configuration for realizing the functions of the control unit 400 according to embodiment 1.

[0065] To realize some or all of the functions of the control unit 400, a configuration including a processor 450 that performs calculations and a memory 452 that stores programs read by the processor 450 can be used, as shown in FIG.

[0066] The processor 450 is an example of a computing means. The processor 450 may be a computing means called a microprocessor, a microcomputer, a central processing unit (CPU), or a digital signal processor (DSP). Examples of the memory 452 include non-volatile or volatile semiconductor memory such as random access memory (RAM), read-only memory (ROM), flash memory, erasable programmable read-only memory (EPROM), and electrically programmable programmable read-only memory (EEPROM), a magnetic disk, a flexible disk, an optical disk, a compact disk, a minidisk, and a digital versatile disk (DVD).

[0067] The memory 452 holds a program that executes the functions of the control unit 400. The processor 450 receives and stores necessary information in the memory 452, executes the program held in the memory 452, and refers to the data and tables stored in the memory 452, thereby executing the above-mentioned processing. The results of calculations by the processor 450 can be stored in the memory 452.

[0068] As described above, in the power conversion device according to the first embodiment, the control unit performs control to distribute the torque current command for load pulsation compensation control, which suppresses motor vibration, and the torque current command for power supply pulsation compensation control, which suppresses capacitor charge / discharge current, so that they can be appropriately set, while prioritizing the torque current command for constant current load control, which controls the motor drive frequency within a settable torque current range. This control makes it possible to suppress capacitor degradation while suppressing vibration in the motor and compressor. Furthermore, because capacitor degradation is suppressed, there is no need to use a capacitor with a large capacity, and the use of a capacitor with a high degradation tolerance can be avoided. These advantages result in a power conversion device that can be prevented from becoming larger in size.

[0069] Furthermore, in the power conversion device according to the first embodiment, the control unit detects or calculates a physical quantity having characteristics similar to those of the capacitor current, and when this physical quantity exceeds a first protection threshold, performs control to reduce the drive frequency of the motor or stop driving the motor. An example of the physical quantity is the ripple value of the capacitor voltage. With this power conversion device configured in this manner, it is possible to obtain the effect of suppressing capacitor degradation even when the power supply pulsation compensation control is not operating as expected.

[0070] Furthermore, in the power conversion device according to the first embodiment, the torque current command for load pulsation compensation control may be limited to a range in which the ripple value of the capacitor voltage is proportional to the magnitude of the load on the motor. By limiting the torque current command for load pulsation compensation control from this perspective, it becomes possible to set the first protection threshold value described above while taking into account only the maximum condition of the motor load. This provides the advantages of enabling the first protection threshold value to be set simply and easily, and eliminating the need to set the first protection threshold value depending on the drive frequency and load of the motor.

[0071] Furthermore, according to the power conversion device of embodiment 1, the first protection threshold is set according to the magnitude of the power supply voltage of the commercial power supply, thereby achieving the effect of being able to appropriately protect the capacitor even if there are fluctuations in the power supply voltage.

[0072] Second Embodiment Fig. 8 is a diagram showing an example of the configuration of a power conversion device 1a according to a second embodiment. In the power conversion device 1a shown in Fig. 8, the control unit 400 is replaced with a control unit 400a. In addition, in accordance with this change, the motor drive device 2 is changed to a motor drive device 2a. These changes are the differences from the first embodiment.

[0073] 9 is a block diagram showing an example of the configuration of a control unit 400a included in a power conversion device 1a according to embodiment 2. In the control unit 400a, the capacitor voltage processing unit 417 is replaced with a capacitor voltage processing unit 417a, and the first protection threshold generation unit 416 is deleted. The other configuration is the same as or equivalent to the control unit 400 shown in FIG. 2, and the same or equivalent components are denoted by the same reference numerals, and duplicated explanations will be omitted.

[0074] Fig. 10 is a block diagram showing an example of the configuration of a capacitor voltage processing unit 417a included in a control unit 400a according to embodiment 2. Fig. 11 is a diagram illustrating the operation of the main parts of the capacitor voltage processing unit 417a according to embodiment 2.

[0075] First, as shown in FIG. 10 , the capacitor voltage processing unit 417 a includes an LPF 420, a subtraction unit 421, BPFs 425 and 427, a first multiplication unit (denoted as “nfs × coefficient” in FIG. 10 ) 426, a second multiplication unit (denoted as “nfm × coefficient” in FIG. 10 ) 428, an addition unit 429, and a comparison unit 430.

[0076] The LPF 420 is a capacitor voltage V ｄｃ By applying low-pass filtering to the capacitor voltage V ｄｃ DC component V ｄｃ-ｌｐｆ The subtraction unit 421 extracts the capacitor voltage V ｄｃ DC component V ｄｃ-ｌｐｆ The result of the subtraction is the capacitor voltage V ｄｃ Ripple voltage V ｄｃ-ｒｐｌ The BPF 425 outputs the ripple voltage V ｄｃ-ｒｐｌ By performing band-pass filtering on the specific frequency component, a specific frequency component extracted value V ｄｃ-ｒｐｌ-ｎｆｓ and outputs the specific frequency component amplitude value V ｄｃ-ｒｐｌ-ｎｆｓ－ａｍｐ The specific frequency component extracted and output by the BPF 425 is V ｄｃ-ｒｐｌ-ｎｆｓ is the same as the value extracted by the capacitor voltage processing unit 417 in the first embodiment.

[0077] In addition, the BPF 427 reduces the ripple voltage V ｄｃ-ｒｐｌ By performing band-pass filtering on the load pulsation of the motor 314, the main component frequency of the load pulsation of the motor 314 is extracted, and the amplitude value of the load pulsation frequency component amplitude value V ｄｃ-ｒｐｌ-ｎｆｍ－ａｍｐ As described above, the main component frequency of the load pulsation of the motor 314 is a component that is one time the mechanical angle drive frequency when the compressor 315 is a single rotary compressor, and is a component that is two times the mechanical angle drive frequency when the compressor 315 is a twin rotary compressor.

[0078] The first multiplier 426 multiplies the specific frequency component amplitude value V ｄｃ-ｒｐｌ-ｎｆｓ－ａｍｐ The second multiplier 428 multiplies the load pulsation frequency component amplitude value V ｄｃ-ｒｐｌ-ｎｆｍ－ａｍｐ The adder 429 outputs a product obtained by multiplying the extracted principal component frequency nfm by the extracted principal component frequency nfm and a predetermined coefficient. The adder 429 outputs a sum of the multiplied value output from the first multiplier 426 and the multiplied value output from the second multiplier 428.

[0079] The coefficient used in the first multiplication unit 426 and the second multiplication unit 428 is the same fixed value. When the capacitance value of the capacitor 210 is represented by "C," if this coefficient is "C x 2π," the values ​​output from the first multiplication unit 426 and the second multiplication unit 428 correspond to the amplitude value of the component of frequency nfs and the amplitude value of the component of main component frequency nfm, respectively, contained in the capacitor current I3.

[0080] Here, in general, the capacitor voltage V ｃ and the capacitor current I ｃ There is a relationship between them expressed by the following formula (1).

[0081]

[0082] In addition, the ripple voltage V ｄｃ-ｒｐｌ is expressed by the following equation (2).

[0083]

[0084] In the above formula (2), ω １ , ω ２ , ω ３ is the ripple voltage V ｄｃ-ｒｐｌに is the angular frequency of the dominant frequency component in the １ , φ ２ , φ ３ is the angular frequency ω １ , ω ２ , ω ３ are the phases corresponding to each of the above. １ , V ２ , V ３is the angular frequency ω １ , ω ２ , ω ３ are the amplitudes corresponding to each of the

[0085] According to the formulas (1) and (2), the ripple voltage V ｄｃ-ｒｐｌ The ripple current I flowing through the capacitor 210 due to ｃ-ｒｐｌ can be expressed as the following equation (3).

[0086]

[0087] The adder 429 performs the above calculation and outputs the sum. The sum output from the adder 429 is as shown in FIG. 11 relative to the average load torque of the motor 314. FIG. 11 shows the relationship between the average load torque applied to the motor 314 and the sum. The graph is presented in the same manner as in FIG. 3.

[0088] 11, the sum output from the adder 429 can be expressed as a proportional relationship between the average load torques T1 and T2, and between the average load torque T2 and the maximum load T3. Also, in FIG. 11, the second protection threshold is a value determined for the sum, and is set by measuring or simulating in advance a value that can ensure the life of the capacitor 210 under the condition of the maximum load T3. The coefficients used in the first multiplier 426 and the second multiplier 428 may be standardized to "1," and the second protection threshold may be set to correspond to the standardized coefficient.

[0089] The comparator 430 compares the sum output from the adder 429 with the second protection threshold. If the second protection threshold is equal to or greater than the sum, the comparator 430 outputs "0 (no stall request)." As in the first embodiment, "0 (no stall request)" indicates that the speed command ω ＊ This is an output value indicating that it is not necessary to perform control to reduce the speed command ω. Furthermore, when the second protection threshold value is smaller than the total value, the comparison unit 430 outputs "1 (stall request present)." As in the first embodiment, "1 (stall request present)" indicates that the speed command ω ＊ This is an output value that indicates that control should be performed to reduce the

[0090] In the above determination process, "1 (stall required)" is output when the "total value" exceeds the "second protection threshold," but the case where the "total value" is equal to the "second protection threshold" may also be included. In other words, "1 (stall required)" may be output when the "total value" is equal to or greater than the "second protection threshold."

[0091] As described above, in the power conversion device according to the second embodiment, the control unit detects or calculates a physical quantity having characteristics similar to those of the capacitor current, and if this physical quantity exceeds the second protection threshold, controls the motor to reduce the drive frequency or stop driving the motor. An example of the physical quantity is a sum of a dominant frequency component extracted from the ripple value of the capacitor voltage and a value obtained by multiplying the amplitude of the extracted frequency component by a predetermined coefficient. The power conversion device configured in this manner has the effect of suppressing capacitor degradation even when the power supply ripple compensation control is not operating as expected.

[0092] Furthermore, according to the power conversion device of the second embodiment, the threshold determination is performed using the sum calculated as described above, so it is possible to protect the capacitor without implementing the load proportional correction limit as in the first embodiment. This provides the advantage of being able to eliminate the constraint on the torque current command for load pulsation compensation control, which is the implementation of the load proportional correction limit.

[0093] Third Embodiment Fig. 12 is a diagram showing a configuration example of a refrigeration cycle-applied device 900 according to a third embodiment. The refrigeration cycle-applied device 900 according to the third embodiment includes the power conversion device 1 described in the first embodiment. The refrigeration cycle-applied device 900 according to the third embodiment can be applied to products equipped with a refrigeration cycle, such as air conditioners, refrigerators, freezers, and heat pump water heaters. In Fig. 12, components having the same functions as those in the first embodiment are denoted by the same reference numerals as those in the first embodiment.

[0094] The refrigeration cycle application equipment 900 includes a compressor 315 incorporating the motor 314 in embodiment 1, a four-way valve 902, an indoor heat exchanger 906, an expansion valve 908, and an outdoor heat exchanger 910, which are attached via refrigerant piping 912.

[0095] Inside the compressor 315, a compression mechanism 904 that compresses the refrigerant and a motor 314 that operates the compression mechanism 904 are provided.

[0096] The refrigeration cycle device 900 can perform heating or cooling operation by switching the four-way valve 902. The compression mechanism 904 is driven by a motor 314 that is variably controlled in speed.

[0097] During heating operation, as shown by the solid arrow, the refrigerant is pressurized by the compression mechanism 904 and sent out, passes through the four-way valve 902, the indoor heat exchanger 906, the expansion valve 908, the outdoor heat exchanger 910 and the four-way valve 902 and returns to the compression mechanism 904.

[0098] During cooling operation, as shown by the dashed arrow, the refrigerant is pressurized by the compression mechanism 904 and sent out, and returns to the compression mechanism 904 through the four-way valve 902, the outdoor heat exchanger 910, the expansion valve 908, the indoor heat exchanger 906 and the four-way valve 902.

[0099] 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.

[0100] The refrigeration cycle applied equipment 900 according to the third embodiment has been described as including the power conversion device 1 described in the first embodiment, but is not limited to this. It may also be configured to include the power conversion device 1a shown in Fig. 8. Furthermore, any power conversion device other than the power conversion devices 1 and 1a may be used as long as the control methods of the first and second embodiments can be applied.

[0101] According to the refrigeration cycle application equipment of embodiment 3, since it is configured with the power conversion device of embodiment 1 or embodiment 2, it is possible to appropriately control the temperature and suppress the vibration generated from the compressor, while ensuring the product life and providing a product at a low price.

[0102] The configurations shown in the above embodiments are merely examples, and may be combined with other known technologies, or different embodiments may be combined with each other. It is also possible to omit or modify parts of the configurations as long as they do not deviate from the gist of the invention.

[0103] For example, in the above-described first and second embodiments, the capacitor voltage V ｄｃ Ripple voltage V ｄｃ-ｒｐｌ However, a configuration may be adopted in which the capacitor current I3 is directly detected to suppress deterioration of the capacitor 210. Furthermore, since there is a relationship of "I1 = I2 + I3" among the rectified current I1, the inverter input current I2, and the capacitor current I3, a configuration may be adopted in which the capacitor current I3 is found by detecting the rectified current I1 and the inverter input current I2.

[0104] 1, 1a Power conversion device, 2, 2a Motor drive device, 110 Commercial power supply, 120 Reactor, 130 Rectification unit, 131 to 134 Rectification elements, 200 Smoothing unit, 210 Capacitor, 310 Inverter, 311a to 311f Switching elements, 312a to 312f Freewheeling diodes, 313a, 313b Current detection unit, 314 Motor, 315 Compressor, 400, 400a Control unit, 401 Rotor position estimation unit, 402 Speed ​​control unit, 403 Flux weakening control unit, 404 Current control unit, 405, 406 Coordinate conversion unit, 407 PWM signal generation unit, 408, 412, 421 Subtraction unit, 409 Distribution ratio multiplication unit, 410 Load pulsation compensation control unit, 411, 414, 429 Adder, 413: Power supply pulsation compensation control unit, 415: q-axis current command generation unit, 416: First protection threshold generation unit, 417, 417a: Capacitor voltage processing unit, 418, 423: Effective value calculation unit, 419: Table, 420: LPF, 422, 425, 427: BPF, 424, 430: Comparison unit, 426: First multiplication unit, 428: Second multiplication unit, 450: Processor, 452: Memory, 500: First voltage detection unit, 501: Second voltage detection unit, 900: Refrigeration cycle applied equipment, 902: Four-way valve, 904: Compression mechanism, 906: Indoor heat exchanger, 908: Expansion valve, 910: Outdoor heat exchanger, 912: Refrigerant piping.

Claims

1. a rectification unit that rectifies a first AC power supplied from a commercial power source; A capacitor connected to an output terminal of the rectifier unit; an inverter connected across the capacitor to generate a second AC power and output the second AC power to a motor; A control unit that controls an operation of the inverter; Equipped with The control unit prioritizes a torque current command for constant current load control that controls the drive frequency of the motor within a settable torque current range, distributes a torque current command for load pulsation compensation control that suppresses vibration of the motor and a torque current command for power supply pulsation compensation control that suppresses a capacitor current that is a charge / discharge current of the capacitor so that they can be appropriately set, and detects or calculates a physical quantity having the same characteristics as the capacitor current, and when the physical quantity exceeds a protection threshold, performs control to reduce the drive frequency of the motor or stop driving the motor. Power conversion equipment.

2. a first voltage detection unit that detects a capacitor voltage, which is a voltage across the capacitor; A ripple value of the capacitor voltage detected by the first voltage detection unit as the physical quantity is calculated, and when the calculated ripple value exceeds a first protection threshold, a drive frequency of the motor is reduced or the drive of the motor is stopped. The power conversion device according to claim 1 .

3. The torque current command for the load pulsation compensation control is limited within a range in which the ripple value is proportional to the magnitude of the load on the motor. The power conversion device according to claim 2 .

4. a second voltage detection unit that detects a power supply voltage of the commercial power supply; The first protection threshold is set according to the magnitude of the power supply voltage detected by the second voltage detection unit. The power conversion device according to claim 2 .

5. a first voltage detection unit that detects a capacitor voltage, which is a voltage across the capacitor; A ripple value of the capacitor voltage detected by the first voltage detection unit is calculated as the physical quantity, a dominant frequency component is extracted from the ripple value, and a sum value is calculated by multiplying the amplitude of the extracted frequency component by the frequency component and a predetermined coefficient, and when the calculated sum value exceeds a second protection threshold, a drive frequency of the motor is lowered or the drive of the motor is stopped. The power conversion device according to claim 1 .

6. When the commercial power source is a single-phase power source, a frequency component twice the power source voltage of the commercial power source and a main component of the load pulsation of the motor are extracted as the frequency components. The power conversion device according to claim 5 .

7. When the commercial power supply is a three-phase power supply, a frequency component six times the power supply voltage of the commercial power supply and a main component of the load pulsation of the motor are extracted as the frequency components. The power conversion device according to claim 5 .

8. A motor drive device comprising the power conversion device according to any one of claims 1 to 7.

9. A refrigeration cycle application device comprising the power conversion device according to any one of claims 1 to 7.