Power converters, motor drive systems, and refrigeration cycle application equipment

Abstract

This electric power conversion device (1A) is provided with: a rectification / step-up circuit unit (130) that rectifies and steps up AC power supplied from a commercial power supply (110); a capacitor (210) that is connected to an output end of the rectification / step-up circuit unit; an inverter circuit unit (310) that is connected to both ends of the capacitor and converts power output from the rectification and step-up circuit unit and the capacitor and outputs the inverted power to a load; a current detection unit that detects the current value of a current output from the inverter circuit unit and fed to the load; a power detection unit that detects the power state of the capacitor; and a control unit (400) that controls the rectification / step-up circuit unit and the inverter circuit unit and performs an abnormal stop of the step-up operation when at least one of the detection value detected by the current detection unit and the detection value detected by the power detection unit is a current value indicating an abnormality and controls the inverter circuit unit such that the detection value detected by the power detection unit is smaller than a first reference value.

Description

Technical Field

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

Background Art

[0002] There is a power conversion device that converts AC power supplied from an AC power source into desired AC power and supplies it to a load such as an air conditioner. This power conversion device rectifies the AC power supplied from the AC power source with a converter, smoothes it with a smoothing capacitor, converts it into desired AC power with an inverter, and outputs it to the load. In such a power conversion device, when a large current flows through the smoothing capacitor, the aging deterioration of the smoothing capacitor is accelerated. As a method for suppressing the aging deterioration of the smoothing capacitor, a method of increasing the capacitance of the smoothing capacitor or a method of increasing the current ripple tolerance of the smoothing capacitor can be considered, but the cost of the smoothing capacitor increases and the device becomes larger.

[0003] The power conversion device of Patent Document 1 controls the inverter of the compressor so that a large current does not flow through the smoothing capacitor, and controls the charge and discharge current of the smoothing capacitor, thereby realizing suppression of the deterioration of the smoothing capacitor and suppression of the enlargement of the device.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, with the conventional technology described above, if the converter uses a boost converter method, and the boost operation stops due to a malfunction in the power conversion device, the current ripple flowing through the smoothing capacitor increases rapidly, placing an excessive load on the smoothing capacitor and causing it to deteriorate.

[0006] This disclosure has been made in view of the above, and aims to provide a power conversion device that can suppress the deterioration of a smoothing capacitor even when a boost converter stops its boosting operation. [Means for solving the problem]

[0007] To solve the above-mentioned problems and achieve the objective, the power conversion device of this disclosure comprises a rectifier-boost circuit section that rectifies and boosts a first AC power supplied from a commercial power source, and a capacitor connected to the output terminal of the rectifier-boost circuit section. Furthermore, the power conversion device of this disclosure comprises an inverter circuit section connected to both ends of the capacitor, which converts the power output from the rectifier-boost circuit section and the capacitor into a second AC power and outputs it to a load, and a detection of the current value of the current output from the inverter circuit section and sent to the load. First Current detection unit and capacitor Current between the negative electrode and the rectifier / boost circuit Detect Second current It comprises a detection unit. Furthermore, the power conversion device of this disclosure controls the rectifier boost circuit unit and the inverter circuit unit, First The detected value and Second current If at least one of the detected values ​​detected by the detection unit is an abnormal current value, the boosting operation by the rectifier boosting circuit unit will be abnormally stopped. Second current If the detected value detected by the detection unit is equal to or greater than the first reference value, Second current The system includes a control unit that controls the inverter circuit so that the detected value detected by the detection unit becomes smaller than a first reference value. When the boosting operation has abnormally stopped, the control unit controls the rectifier boosting circuit to resume the boosting operation as it was before the abnormal stop if the restart conditions for restarting the boosting operation are met. After the boosting operation has resumed, if the boosting operation abnormally stops again, the control unit determines whether to restart or prohibit the boosting operation as it was before the abnormal stop, based on the restart operation period, which is the period from the previous restart of the boosting operation to the most recent abnormal stop of the boosting operation. [Effects of the Invention]

[0008] The power conversion device described herein has the effect of suppressing the deterioration of the smoothing capacitor even when the boost converter stops its boosting operation. [Brief explanation of the drawing]

[0009] [Figure 1] This figure shows an example configuration of a motor drive device having a power conversion device according to Embodiment 1. [Figure 2] Flowchart showing the operation of the control unit of the power converter according to Embodiment 1 [Figure 3] Flowchart showing the operation of the control unit of the power converter according to Embodiment 2 [Figure 4] Flowchart showing the operation of the control unit of the power converter according to Embodiment 3 [Figure 5] This figure shows an example configuration of a motor drive device having a power conversion device according to Embodiment 4. [Figure 6] This figure shows an example configuration of a motor drive device having a power conversion device according to Embodiment 5. [Figure 7] This figure shows an example configuration of a motor drive device having a power conversion device according to Embodiment 6. [Figure 8] This figure shows an example of the configuration of a refrigeration cycle application device according to Embodiment 7. [Figure 9] This figure shows an example of the configuration of a processing circuit when the processing circuit included in the control unit of the power converter according to Embodiment 1 is implemented using a processor and memory. [Figure 10] This figure shows an example of a processing circuit when the processing circuit of the control unit of the power converter according to Embodiment 1 is implemented using dedicated hardware. [Modes for carrying out the invention]

[0010] The power conversion device, motor drive device, and refrigeration cycle application equipment according to embodiments of this disclosure will be described in detail below with reference to the drawings.

[0011] Embodiment 1. FIG. 1 is a diagram showing a configuration example of a motor drive device having a power conversion device according to Embodiment 1. The motor drive device 2A includes a power conversion device 1A and a compressor 315. The power conversion device 1A is connected to a commercial power supply 110 and the compressor 315. The commercial power supply 110 is an example of an AC power supply, and the compressor 315 is an example of a drive device driven by the power conversion device 1A. The power conversion device 1A includes a reactor 120, a rectifier boost circuit section 130, a smoothing section 200, an inverter circuit section 310, compressor current detection sections 313a and 313b, a control section 400, and a bus current detection section 501.

[0012] The compressor 315 includes a motor (compressor motor) 314. The compressor 315 is an example of a load to which the power conversion device 1A supplies AC power.

[0013] The reactor 120 is connected between the commercial power supply 110 and the rectifier boost circuit section 130. That is, the reactor 120 is disposed on one of the connection lines connecting the commercial power supply 110 and the rectifier boost circuit section 130. The reactor 120 realizes power factor improvement, harmonic suppression, power supply coordination, and the like.

[0014] The rectifier boost circuit section 130 is a boost-type converter. The rectifier boost circuit section 130 has a function of rectifying the AC power (first AC power) of the power supply voltage supplied from the commercial power supply 110 and a function of boosting the voltage of the rectified AC power. That is, the rectifier boost circuit section 130 is a boost-type rectifier circuit. The rectifier boost circuit section 130 has an input terminal connected to the commercial power supply 110 and an output terminal connected to the inverter circuit section 310. The rectifier boost circuit section 130 outputs the rectified and boosted first AC power.

[0015] The rectifying and boosting circuit section 130 is connected to the positive electrode side bus Q1 which is one of the buses and the negative electrode side bus Q2 which is the other bus. Also, the inverter circuit section 310 is connected to the positive electrode side bus Q1 and the negative electrode side bus Q2. That is, the positive electrode side bus Q1 is connected to one output terminal of the rectifying and boosting circuit section 130 and one input terminal of the inverter circuit section 310, and the negative electrode side bus Q2 is connected to the other output terminal of the rectifying and boosting circuit section 130 and the other input terminal of the inverter circuit section 310. And the smoothing section 200 is connected to the connection point P1 on the positive electrode side bus Q1 and the connection point P2 on the negative electrode side bus Q2.

[0016] Thus, the smoothing section 200 is connected to the output terminal of the rectifying and boosting circuit section 130 and the input terminal of the inverter circuit section 310. The smoothing section 200 has a capacitor (smoothing capacitor) 210 as a smoothing element, and smoothes the power rectified by the rectifying and boosting circuit section 130. The capacitor 210 is, for example, an electrolytic capacitor, a film capacitor, or the like. The capacitor 210 is connected to the output terminal of the rectifying and boosting circuit section 130 and the input terminal of the inverter circuit section 310. The capacitor 210 has a capacity to smooth the power rectified by the rectifying and boosting circuit section 130. By the smoothing by the capacitor 210, the voltage generated in the capacitor 210 has a waveform in which a voltage ripple corresponding to the frequency of the commercial power supply 110 is superimposed on the DC component, rather than the full-wave rectified wave shape of the commercial power supply 110. Note that the commercial power supply 110 may be single-phase or three-phase.

[0017] The bus current detection section 501 detects the rectified current I1 flowing out from the rectifying and boosting circuit section 130, and outputs the detected value of the detected rectified current I1 to the control section 400. Thus, the bus current detection section 501 detects the current rectified by the rectifying and boosting circuit section 130 and flowing from the rectifying and boosting circuit section 130 into the smoothing section 200, that is, the input current to the smoothing section 200, and outputs the detected current value to the control section 400. The bus current detection section 501 can be used as a power detection section for detecting the power state of the capacitor 210.

[0018] The inverter circuit 310 is connected to both ends of the smoothing unit 200. The inverter circuit 310 includes switching elements 311a to 311f and freewheeling diodes 312a to 312f. The inverter circuit 310 is controlled by the control unit 400 to turn the switching elements 311a to 311f on and off. Through this control, the power output from the rectifier boost circuit 130 and the smoothing unit 200 is converted into AC power (second AC power) having a desired amplitude and phase. That is, the inverter circuit 310 generates second AC power by turning the switching elements 311a to 311f on and off and outputs it to the motor 314.

[0019] The compressor current detection units 313a and 313b each detect the current value of one of the three phases of current output from the inverter circuit unit 310 and output the detected current value to the control unit 400. The control unit 400 can calculate the current value of the remaining one phase output from the inverter circuit unit 310 by obtaining the current values ​​of two of the three phases of current output from the inverter circuit unit 310.

[0020] The motor 314 mounted on the compressor 315 rotates in accordance with the amplitude and phase of the AC power (second AC power) supplied from the inverter circuit 310, and performs compression.

[0021] Note that Figure 1 shows the case where the motor windings of motor 314 are Y-connected, but the motor is not limited to this example. The motor windings of motor 314 may be delta-connected, or they may be designed to be switchable between Y-connection and delta-connection.

[0022] Furthermore, in the power converter 1A, the arrangement of each component shown in Figure 1 is just one example, and the arrangement of each component is not limited to the example shown in Figure 1. For example, the reactor 120 may be placed after the rectifier boost circuit section 130. In the following description, the compressor current detection sections 313a, 313b and the bus current detection section 501 may each be simply referred to as the "detection section". Also, the current value detected by at least one of the compressor current detection sections 313a, 313b and the bus current detection section 501 may be simply referred to as the "detected value".

[0023] The control unit 400 acquires the detected value of the rectified current I1 detected by the bus current detection unit 501, and the detected value of the inverter input current I2 detected by the compressor current detection units 313a and 313b. In other words, the control unit 400 acquires the current value of the input current of the smoothing unit 200 and the current value of the second AC power converted by the inverter circuit unit 310.

[0024] Furthermore, the control unit 400 uses the detected values ​​detected by each detection unit to control the operation of the inverter circuit unit 310, specifically the on / off switching of the switching elements 311a to 311f in the inverter circuit unit 310.

[0025] Furthermore, the control unit 400 controls the operation of the inverter circuit unit 310 so that a second AC power, which includes pulsations corresponding to the pulsations of the power flowing from the rectifier boost circuit unit 130 to the capacitor 210 of the smoothing unit 200, is output from the inverter circuit unit 310 to the compressor 315. The pulsations corresponding to the pulsations of the power flowing into the capacitor 210 of the smoothing unit 200 are, for example, pulsations that fluctuate depending on the frequency of the pulsations 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 and discharging current of the capacitor 210. The control unit 400 controls the motor 314 so that the speed, voltage, or current is in a desired state. Note that the control unit 400 does not need to use all the detection values ​​obtained from each detection unit, and may use only some of the detection values ​​to perform the control.

[0026] Next, the characteristic operation of the control unit 400 in Embodiment 1 will be described. The control unit 400 controls the rectifier boost circuit unit 130 and the inverter circuit unit 310 based on the detected current values ​​detected by at least one of the compressor current detection units 313a, 313b and the bus current detection unit 501.

[0027] The control unit 400 stops the boosting operation of the rectifier boosting circuit unit 130 if at least one of the compressor current detection units 313a, 313b, and the bus current detection unit 501 detects a current value indicating an abnormality in the motor drive unit 2A while the rectifier boosting circuit unit 130 is performing the boosting operation. The current value indicating an abnormality in the motor drive unit 2A is a current value outside the allowable range.

[0028] Furthermore, if the current value detected by the bus current detection unit 501 (the input current value to the smoothing unit 200) is greater than or equal to a first reference value predetermined by the control unit 400, the control unit 400 controls the inverter circuit unit 310 so that the input current value becomes less than the first reference value. If the input current value detected by the bus current detection unit 501 is less than the first reference value, the control unit 400 maintains the inverter control as it was before the boost operation stopped.

[0029] Here, the operation of the control unit 400 will be explained using a flowchart. Figure 2 is a flowchart showing the operation of the control unit of the power converter according to Embodiment 1. When the power converter 1A starts operation, the control unit 400 controls the rectifier boost circuit unit 130 to start the boost operation (step S10). The compressor current detection units 313a, 313b and the bus current detection unit 501 detect the current value and send the detected value, which is the detection result, to the control unit 400.

[0030] If, during the boosting operation, at least one of the compressor current detection units 313a, 313b, and the busbar current detection unit 501 detects a current value indicating an abnormality in the motor drive unit 2A, the control unit 400 controls the rectifier boosting circuit unit 130 to cause the rectifier boosting circuit unit 130 to abnormally stop the boosting operation (step S20).

[0031] The control unit 400 determines whether the input current value to the smoothing unit 200 (the current value detected by the bus current detection unit 501) when the boost operation is abnormally stopped is equal to or greater than a predetermined first reference value (step S30).

[0032] If the input current value to the smoothing unit 200 when the boost operation is abnormally stopped is greater than or equal to a predetermined first reference value (step S30, Yes), the control unit 400 controls the inverter circuit unit 310 so that the input current value becomes less than the first reference value (step S40). For example, the control unit 400 controls the inverter circuit unit 310 so that the peak value of the input current value becomes less than the first reference value.

[0033] On the other hand, if the input current value to the smoothing unit 200 when the boost operation is abnormally stopped is smaller than a predetermined first reference value (step S30, No), the control unit 400 maintains the inverter control as it was before the boost operation was stopped (step S50).

[0034] As described above, in the first embodiment, the control unit 400 controls the inverter circuit unit 310 so that the input current value to the smoothing unit 200 becomes smaller than the first reference value when the boost operation is abnormally stopped and the input current value to the smoothing unit 200 is greater than or equal to the first reference value. As a result, the power converter 1A can suppress the capacitor current I3, and even when the rectifier boost circuit unit 130, which is a boost converter, stops the boost operation, it can suppress a rapid increase in the current ripple flowing through the capacitor 210. Therefore, the power converter 1A can suppress excessive load on the capacitor 210 when the rectifier boost circuit unit 130 stops the boost operation, and can suppress deterioration and failure of the capacitor 210.

[0035] Embodiment 2. Next, Embodiment 2 will be described using Figure 3. In Embodiment 2, the control unit 400 restarts the boosting operation if it satisfies the conditions for restarting the boosting operation (restart conditions) after abnormally stopping the boosting operation. Note that the motor drive device 2A in Embodiment 2 has the same configuration as the motor drive device 2A in Embodiment 1, so the description of the configuration of the motor drive device 2A will be omitted.

[0036] Figure 3 is a flowchart showing the operation of the control unit of the power converter according to Embodiment 2. When the power converter 1A starts operation, the control unit 400 controls the rectifier boost circuit unit 130 to start the boosting operation (step S110). The compressor current detection units 313a, 313b and the bus current detection unit 501 detect the current value and send the detected value, which is the detection result, to the control unit 400.

[0037] If, during the boosting operation, at least one of the compressor current detection units 313a, 313b, and the busbar current detection unit 501 detects a current value indicating an abnormality in the motor drive unit 2A, the control unit 400 controls the rectifier boost circuit unit 130 to cause the rectifier boost circuit unit 130 to abnormally stop the boosting operation (step S120).

[0038] The control unit 400 determines whether or not to restart the boosting operation (return to the boosting operation state) when the boosting operation has been abnormally stopped. The control unit 400 determines whether or not to restart the boosting operation based on whether or not the conditions for restarting the boosting operation are met (step S130).

[0039] If the conditions for restarting the boost operation are not met (step S130, No), the control unit 400 returns to the process of step S120 and maintains the state in which the boost operation of the rectifier boost circuit unit 130 has been abnormally stopped.

[0040] If the conditions for restarting the boost operation are met (step S130, Yes), the control unit 400 instructs the rectifier boost circuit unit 130 to restart the boost operation so that it returns to the state of boost operation before the abnormal stop (step S140).

[0041] Thus, in the second embodiment, the control unit 400 restarts the boosting operation if the conditions for restarting the boosting operation are met after the boosting operation has abnormally stopped. Therefore, the power converter 1A can quickly return to its state before the abnormal stop even after the boosting operation has abnormally stopped.

[0042] Embodiment 3. Next, Embodiment 3 will be described using Figure 4. In Embodiment 2, the operation of the control unit 400 when an abnormal stop occurs once was described, but in Embodiment 3, the operation of the control unit 400 when abnormal stops occur consecutively will be described. Note that the motor drive device 2A in Embodiment 3 has the same configuration as the motor drive device 2A in Embodiment 1, so the description of the configuration of the motor drive device 2A will be omitted.

[0043] Figure 4 is a flowchart showing the operation of the control unit of the power converter according to Embodiment 3. When the power converter 1A starts operation, the control unit 400 controls the rectifier boost circuit unit 130 to start the boosting operation (step S210). The compressor current detection units 313a, 313b and the bus current detection unit 501 detect the current value and send the detected value, which is the detection result, to the control unit 400.

[0044] If, during the boosting operation, at least one of the compressor current detection units 313a, 313b, and the bus current detection unit 501 detects a current value indicating an abnormality in the motor drive unit 2A, the control unit 400 controls the rectifier boost circuit unit 130 to cause the rectifier boost circuit unit 130 to abnormally stop the boosting operation. In other words, the control unit 400 performs the first abnormal stop of the boosting operation (step S220).

[0045] The control unit 400 restarts the boosting operation after an abnormal stop has occurred if certain conditions are met (step S230). After this, if at least one of the compressor current detection units 313a, 313b and the busbar current detection unit 501 detects a current value indicating an abnormality in the motor drive unit 2A during the boosting operation, the control unit 400 controls the rectifier boost circuit unit 130 to cause the rectifier boost circuit unit 130 to abnormally stop the boosting operation. In other words, the control unit 400 performs a second abnormal stop of the boosting operation (step S240). Then, the control unit 400 decides whether to restart the boosting operation or prohibit it. Specifically, the control unit 400 decides whether to restart the boosting operation or prohibit it based on the time from the previous restart of the boosting operation to the latest abnormal stop of the boosting operation. In other words, the control unit 400 determines whether the period from the restart of the boosting operation to the second abnormal shutdown is within the standard time (step S250). Hereinafter, the period from the restart of the boosting operation to the second abnormal shutdown may be referred to as the restart operation period.

[0046] If the restart operation period is longer than the reference time (step S250, No), the control unit 400 returns to the process in step S230 and restarts the boost operation. In other words, if the restarted boost operation is stable and the restart operation period is longer than the reference time, the control unit 400 restarts the boost operation.

[0047] On the other hand, if the restart operation period is within the standard time (step S250, Yes), the control unit 400 prohibits the boost operation (step S260). In other words, the control unit 400 prohibits the boost operation if the restarted boost operation is unstable and the restart operation period is within the standard time. In this case, even if the conditions for restarting the boost operation are met, the control unit 400 will not execute the boost operation.

[0048] If the period from the restart of the previous boost operation to the abnormal stop of the latest boost operation (restart operation period) is extremely short, it is possible that the motor drive unit 2A is not just an accidental malfunction, but rather a chronic defect in the motor drive unit 2A. In such a state, the rectifier boost circuit unit 130 will constantly repeat boost operation and abnormal stop, resulting in unstable operation of the motor drive unit 2A. For this reason, in Embodiment 3, if the restart operation period is within the standard time, the control unit 400 will prohibit the boost operation.

[0049] As described above, the control unit 400 of the power converter 1A in Embodiment 3 prohibits the boost operation if the restart operation period is within the reference time, thereby suppressing unstable operation of the motor drive unit 2A. As a result, the power converter 1A can suppress overloading of the capacitor 210.

[0050] Embodiment 4. Next, Embodiment 4 will be described using Figure 5. In Embodiment 4, if the capacitor current I3 flowing through the smoothing unit 200 is greater than or equal to the second reference value when the boost operation has abnormally stopped, the control unit 400 controls the inverter circuit unit 310 so that the capacitor current I3 becomes less than the second reference value.

[0051] Figure 5 shows an example of the configuration of a motor drive device having a power conversion device according to Embodiment 4. Among the components in Figure 5, components that achieve the same function as the motor drive device 2A of Embodiment 1 shown in Figure 1 are denoted by the same reference numerals, and redundant explanations are omitted.

[0052] The motor drive device 2B of Embodiment 4, compared to the motor drive devices 2A of Embodiments 1 to 3, is equipped with a power converter 1B instead of a power converter 1A. The power converter 1B has the components of the power converter 1A and a smoothing capacitor current detection unit 502.

[0053] The smoothing capacitor current detection unit 502 is connected to a location where only the capacitor current I3 flowing through the smoothing unit 200 can be detected. For example, the smoothing capacitor current detection unit 502 is placed on the connection line connecting connection point P1 and the smoothing unit 200. The smoothing capacitor current detection unit 502 sends the detected value of the capacitor current I3 to the control unit 400.

[0054] As a result, the control unit 400 acquires the detected value detected by the smoothing capacitor current detection unit 502. If the detected value of the capacitor current I3 detected by the smoothing capacitor current detection unit 502 when the boost operation has abnormally stopped is greater than or equal to a second reference value predetermined in the control unit 400, the control unit 400 controls the inverter circuit unit 310 so that the capacitor current I3 becomes less than the second reference value. If the detected value of the capacitor current I3 is less than the second reference value, the control unit 400 maintains the inverter control as it was before the boost operation stopped.

[0055] Thus, in Embodiment 4, the smoothing capacitor current detection unit 502 detects only the capacitor current I3 flowing through the smoothing unit 200, and when the detected value of the capacitor current I3 at the time of abnormal shutdown of the boosting operation is greater than or equal to the second reference value, the control unit 400 controls the inverter circuit unit 310 so that the capacitor current I3 becomes less than the second reference value. As a result, the power converter 1B can suppress overload on the capacitor 210 when the boosting operation abnormally shuts down.

[0056] Furthermore, the power converter 1B can control the inverter circuit 310 such that the detected value of the rectified current I1 detected by the bus current detection unit 501 becomes smaller than the first reference value, and the capacitor current I3 detected by the smoothing capacitor current detection unit 502 becomes smaller than the second reference value. As a result, the power converter 1B can suppress overload to the capacitor 210 with higher accuracy than in the first embodiment.

[0057] Embodiment 5. Next, Embodiment 5 will be described using Figure 6. In Embodiment 5, the control unit 400 estimates the capacitor current I3 based on the voltage trend across the smoothing unit 200 when the boost operation abnormally stops, and controls the inverter circuit unit 310 so that the estimated capacitor current I3 becomes smaller than the third reference value.

[0058] Figure 6 shows an example of the configuration of a motor drive device having a power conversion device according to Embodiment 5. Among the components in Figure 6, components that achieve the same function as the motor drive device 2A of Embodiment 1 shown in Figure 1 are denoted by the same reference numerals, and redundant explanations are omitted.

[0059] The motor drive device 2C of Embodiment 5, compared to the motor drive devices 2A of Embodiments 1 to 3, is equipped with a power converter 1C instead of a power converter 1A. The power converter 1C has the components of the power converter 1A and a smoothing capacitor voltage detection unit 503.

[0060] The smoothing capacitor voltage detection unit 503 is a detection unit that detects the voltage across the smoothing unit 200. The smoothing capacitor voltage detection unit 503 is connected to detect the voltage across the smoothing unit 200. For example, the smoothing capacitor voltage detection unit 503 is connected to the connection line connecting connection point P1 and capacitor 210, and to the connection line connecting connection point P2 and capacitor 210. The smoothing capacitor voltage detection unit 503 sends the detected voltage value to the control unit 400.

[0061] As a result, the control unit 400 acquires the detected value from the smoothing capacitor voltage detection unit 503. The control unit 400 estimates the capacitor current I3 based on the trend of the detected voltage value from the smoothing capacitor voltage detection unit 503.

[0062] The control unit 400 may estimate the capacitor current I3 based on the change in the detected voltage value detected by the smoothing capacitor voltage detection unit 503 during a specific period, or it may estimate the capacitor current I3 based on the detected voltage value at one or more timings. The following describes the case in which the control unit 400 estimates the capacitor current I3 based on the detected voltage value at a specific timing.

[0063] If the control unit 400 determines that the estimated capacitor current I3 is greater than or equal to a third reference value predetermined in the control unit 400, it controls the inverter circuit unit 310 so that the capacitor current I3 becomes less than the third reference value. In other words, if the control unit 400 determines that the estimated capacitor current I3 is greater than or equal to the third reference value, it controls the inverter circuit unit 310 so that the capacitor current I3 estimated based on the voltage detected after this control becomes less than the third reference value. If the capacitor current I3 estimated based on the detected voltage value detected by the smoothing capacitor voltage detection unit 503 is less than the third reference value, the control unit 400 maintains the inverter control as it was before the boost operation stopped.

[0064] Thus, in Embodiment 5, the smoothing capacitor voltage detection unit 503 detects the voltage across the smoothing unit 200, and the control unit 400 estimates the capacitor current I3 based on the detected voltage. If the estimated capacitor current I3 is greater than or equal to a third reference value, the control unit 400 controls the inverter circuit unit 310 so that the capacitor current I3 estimated thereafter is less than the third reference value. As a result, the power converter 1C can suppress overload of the capacitor 210 using the smoothing capacitor voltage detection unit 503, which is used for another purpose, without using a dedicated detection unit to detect the capacitor current I3, thus reducing the number of detection units.

[0065] Furthermore, the power converter 1C can control the inverter circuit 310 such that the detected value of the rectified current I1 detected by the bus current detection unit 501 becomes smaller than the first reference value, and the detected value of the voltage detected by the smoothing capacitor voltage detection unit 503 becomes smaller than the third reference value. As a result, the power converter 1C can suppress overload to the capacitor 210 with higher accuracy than in the first embodiment.

[0066] Embodiment 6. Next, Embodiment 6 will be described using Figure 7. In Embodiment 6, the control unit 400 estimates the capacitor current I3 based on the trend of the input current from the commercial power supply 110 when the boost operation abnormally stops, and controls the inverter circuit 310 so that the estimated capacitor current I3 becomes smaller than the fourth reference value.

[0067] Figure 7 shows an example of the configuration of a motor drive device having a power conversion device according to Embodiment 6. Among the components in Figure 7, components that achieve the same function as the motor drive device 2A of Embodiment 1 shown in Figure 1 are denoted by the same reference numerals, and redundant explanations are omitted.

[0068] The motor drive device 2D of Embodiment 6, compared to the motor drive devices 2A of Embodiments 1 to 3, is equipped with a power converter 1D instead of a power converter 1A. The power converter 1D has the components of the power converter 1A and an input current detection unit 504.

[0069] The input current detection unit 504 is connected between the commercial power supply 110 and the reactor 120. The input current detection unit 504 detects the current value of the input current input to the power converter 1D by the commercial power supply 110. The input current detection unit 504 sends the detected value of the input current to the control unit 400.

[0070] As a result, the control unit 400 acquires the detected value from the input current detection unit 504. The control unit 400 estimates the capacitor current I3 based on the trend of the detected value of the input current detected by the input current detection unit 504.

[0071] The control unit 400 may estimate the capacitor current I3 based on the change in the detected input current value detected by the input current detection unit 504 during a specific period, or it may estimate the capacitor current I3 based on the detected input current value at one or more timings. The following describes the case in which the control unit 400 estimates the capacitor current I3 based on the detected input current value at a specific timing.

[0072] If the control unit 400 determines that the estimated capacitor current I3 is greater than or equal to a fourth reference value predetermined in the control unit 400, it controls the inverter circuit unit 310 so that the capacitor current I3 becomes less than the fourth reference value. In other words, if the control unit 400 determines that the estimated capacitor current I3 is greater than or equal to the fourth reference value, it controls the inverter circuit unit 310 so that the capacitor current I3 estimated based on the input current detected after this control becomes less than the fourth reference value. If the capacitor current I3 estimated based on the input current detected by the input current detection unit 504 is less than the fourth reference value, the control unit 400 maintains the inverter control as it was before the boost operation stopped.

[0073] Thus, in Embodiment 6, the input current detection unit 504 detects the input current from the commercial power supply 110, and the control unit 400 estimates the capacitor current I3 based on the detected input current value. If the estimated capacitor current I3 is greater than or equal to the fourth reference value, the control unit 400 controls the inverter circuit unit 310 so that the capacitor current I3 estimated thereafter is less than the fourth reference value. As a result, the power converter 1D does not need to use a dedicated detection unit to detect the capacitor current I3, and can suppress the overload of the capacitor 210 using the input current detection unit 504 which is used for another purpose, thus reducing the number of detection units.

[0074] Furthermore, the power converter 1D can control the inverter circuit 310 such that the detected value of the rectified current I1 detected by the bus current detection unit 501 becomes smaller than the first reference value, and the detected value of the input current detected by the input current detection unit 504 becomes smaller than the fourth reference value. As a result, the power converter 1D can suppress overload to the capacitor 210 with higher accuracy than in the first embodiment.

[0075] Embodiment 7. Next, Embodiment 7 will be described using Figure 8. In Embodiment 7, the power converter is applied to equipment used in a refrigeration cycle. In the following description, the case in which power converter 1A is applied to equipment used in a refrigeration cycle will be described, but power converters 1B to 1D may also be applied to equipment used in a refrigeration cycle.

[0076] Figure 8 shows an example of the configuration of a refrigeration cycle application device according to Embodiment 7. In Figure 8, components having the same function as those in Embodiment 1 are denoted by the same reference numerals as in Embodiment 1.

[0077] The refrigeration cycle application device 900 according to Embodiment 7 includes the power converter 1A described in Embodiment 1. The refrigeration cycle application device 900 according to Embodiment 7 can be applied to products equipped with a refrigeration cycle, such as air conditioners, refrigerators, freezers, and heat pump water heaters.

[0078] The refrigeration cycle application equipment 900 is equipped with 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, all of which are connected via refrigerant piping 912.

[0079] Inside the compressor 315 are a compression mechanism 904 for compressing the refrigerant and a motor 314 for operating the compression mechanism 904.

[0080] The refrigeration cycle equipment 900 can operate in heating or cooling mode by switching the four-way valve 902. The compression mechanism 904 is driven by a variable-speed controlled motor 314.

[0081] During heating operation, as indicated by the solid arrows, the refrigerant is pressurized by the compression mechanism 904 and sent out, then returns to the compression mechanism 904 after passing through the four-way valve 902, indoor heat exchanger 906, expansion valve 908, outdoor heat exchanger 910, and the four-way valve 902.

[0082] During cooling operation, as indicated by the dashed arrows, the refrigerant is pressurized by the compression mechanism 904 and sent out, then returns to the compression mechanism 904 after passing 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.

[0083] 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 and causes it to expand.

[0084] Thus, according to Embodiment 7, the power converter 1A, which suppresses the degradation of the capacitor 210 and is miniaturized, is incorporated into the refrigeration cycle application equipment 900, resulting in a long-life, compact refrigeration cycle application equipment. 900 This can be achieved.

[0085] Here, we will describe the hardware configuration of the control unit 400 provided in power converters 1A to 1D. The control unit 400 provided in power converters 1A to 1D is implemented by a processing circuit. The processing circuit may be a processor and memory that execute a program stored in memory, or it may be dedicated hardware. Since power converters 1A to 1D have similar hardware configurations, the hardware configuration of power converter 1A will be described below.

[0086] Figure 9 is a diagram showing an example of the configuration of a processing circuit when the processing circuit of the control unit of the power converter according to Embodiment 1 is realized with a processor and memory. The processing circuit 90 shown in Figure 9 comprises a processor 91 and a memory 92. When the processing circuit 90 is composed of a processor 91 and a memory 92, each function of the processing circuit 90 is realized by software, firmware, or a combination of software and firmware. The software or firmware is written as a control program and stored in the memory 92. In the processing circuit 90, each function is realized by the processor 91 reading and executing the control program stored in the memory 92. That is, the processing circuit 90 includes a memory 92 for storing a control program that will result in the processing of the control unit 400 being executed. This control program can also be said to be a program that causes the control unit 400 to execute each function realized by the processing circuit 90. This control program may be provided by a storage medium on which the control program is stored, or by other means such as a communication medium.

[0087] Here, the processor 91 is, for example, a CPU (Central Processing Unit), processing unit, arithmetic unit, microprocessor, microcomputer, or DSP (Digital Signal Processor). The memory 92 is, for example, a non-volatile or volatile semiconductor memory such as RAM (Random Access Memory), ROM (Read Only Memory), flash memory, EPROM (Erasable Programmable ROM), EEPROM (Registered Trademark) (Electrically EPROM), magnetic disks, flexible disks, optical disks, compact disks, minidiscs, or DVDs (Digital Versatile Discs).

[0088] Figure 10 shows an example of a processing circuit when the processing circuit of the control unit of the power converter according to Embodiment 1 is implemented with dedicated hardware. The processing circuit 93 shown in Figure 10 can be, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or a combination thereof. The processing circuit 93 may be partially implemented with dedicated hardware and partially implemented with software or firmware. In this way, the processing circuit 93 can realize each of the above functions with dedicated hardware, software, firmware, or a combination thereof.

[0089] The configurations shown in the above embodiments are merely examples, and it is possible to combine them with other known technologies, combine different embodiments, and omit or modify parts of the configuration without departing from the gist of the invention. [Explanation of Symbols]

[0090] 1A~1D Power converter, 2A~2D Motor drive unit, 90,93 Processing circuit, 91 Processor, 92 Memory, 110 Commercial power supply, 120 Reactor, 130 Rectifier boost circuit section, 200 Smoothing section, 210 Capacitor, 310 Inverter circuit section, 311a~311f Switching element, 312a~312f Freewheeling diode, 313a,313b Compressor current detection section, 314 Motor, 315 Compressor, 400 Control unit, 501 Bus current detection section, 502 Smoothing capacitor current detection section, 503 Smoothing capacitor voltage detection section, 504 Input current detection section, 900 Refrigeration cycle application equipment, 902 Four-way valve, 904 Compression mechanism, 906 Indoor heat exchanger, 908 Expansion valve, 910 Outdoor heat exchanger, 912 Refrigerant piping, I1 Rectifier current, I2 inverter input current, I3 capacitor current, P1, P2 connection points, Q1 positive busbar, Q2 negative busbar.

Claims

1. A rectifier and boost circuit section that rectifies and boosts the first AC power supplied from the commercial power source, A capacitor connected to the output terminal of the rectifier / boost circuit section, An inverter circuit is connected to both ends of the capacitor and converts the power output from the rectifier boost circuit and the capacitor into a second AC power, which is then output to the load. A first current detection unit detects the current value of the current output from the inverter circuit and sent to the load, A second current detection unit for detecting the current between the negative electrode of the capacitor and the rectifier boost circuit unit, A control unit controls the rectifier boost circuit and the inverter circuit, and if at least one of the detected values ​​among the detected value detected by the first current detection unit and the detected value detected by the second current detection unit is an abnormal current value, it abnormally stops the boost operation by the rectifier boost circuit, and if the detected value detected by the second current detection unit when the boost operation is abnormally stopped is greater than or equal to the first reference value, it controls the inverter circuit so that the detected value detected by the second current detection unit becomes smaller than the first reference value. Equipped with, The control unit, When the aforementioned boosting operation has stopped abnormally, if the restart conditions for restarting the boosting operation are met, the rectifier boosting circuit unit is controlled to restart the boosting operation to the state it was in before the abnormal stop. A power converter that, after restarting the aforementioned boosting operation, if the boosting operation malfunctions, determines whether to restart or prohibit the boosting operation before the malfunction, based on the restart operation period, which is the period from the restart of the previous boosting operation to the malfunction of the most recent boosting operation.

2. The system further includes a capacitor current detection unit that detects the capacitor current flowing through the capacitor, The control unit controls the inverter circuit unit so that the detected value detected by the capacitor current detection unit becomes smaller than the second reference value when the boost operation is abnormally stopped and the detected value detected by the capacitor current detection unit is greater than or equal to the second reference value. The power conversion device according to claim 1.

3. The system further includes a capacitor voltage detection unit that detects the voltage across the capacitor, The control unit estimates the capacitor current flowing through the capacitor based on the detected value detected by the capacitor voltage detection unit when the boost operation abnormally stops, and if the estimated capacitor current is greater than or equal to a third reference value, it controls the inverter circuit unit so that the capacitor current estimated thereafter becomes less than the third reference value. The power conversion device according to claim 1.

4. The system further includes an input current detection unit that detects the input current supplied by the commercial power supply, The control unit estimates the capacitor current flowing through the capacitor based on the detected value detected by the input current detection unit when the boost operation abnormally stops, and if the estimated capacitor current is greater than or equal to a fourth reference value, it controls the inverter circuit unit so that the capacitor current estimated thereafter becomes less than the fourth reference value. The power conversion device according to claim 1.

5. A motor drive device having a power conversion device according to any one of claims 1 to 4.

6. A refrigeration cycle application device comprising a power conversion device according to any one of claims 1 to 4.

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