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

Abstract

A power conversion device (1A) is provided with: a rectifying / boosting circuit unit (130) that rectifies and boosts AC power supplied from a commercial power source (110); a capacitor (210) connected to the output end of the rectification booster circuit unit; an inverter circuit unit (310) which is connected to both ends of the capacitor, converts the power output from the rectifying / boosting circuit unit and the capacitor, and outputs the converted power to a load; a current detection unit that detects a current value of a current output from the inverter circuit unit and transmitted to a load; a power detection unit that detects the power state of the capacitor; and a control unit (400) that controls the rectifying and boosting circuit unit and the inverter circuit unit, and that abnormally stops the boosting operation when at least one of a detection value detected by the current detection unit and a detection value detected by the power detection unit is a current value indicating an abnormality. The inverter circuit unit is controlled such that the detection value detected by the power detection unit is less than the first reference value.

Description

Technical Field

[0001] This disclosure relates to power conversion devices, motor drive devices, and refrigeration cycle application equipment for converting alternating current into desired power. Background Technology

[0002] There exists a power conversion device that converts AC power supplied from an AC power source into desired AC power and supplies it to loads such as air conditioners. This power conversion device, for example, uses a converter to rectify the AC power supplied from the AC power source, then uses a smoothing capacitor to smooth it, and finally uses an inverter to convert it into the desired AC power and output it to the load. In such a power conversion device, if a large current flows in the smoothing capacitor, it will accelerate the deterioration of the smoothing capacitor over time. Although increasing the capacitance of the smoothing capacitor or increasing its current ripple tolerance can be considered as methods to suppress the deterioration of the smoothing capacitor, this increases the cost of the smoothing capacitor and leads to a larger device size.

[0003] The power conversion device in Patent Document 1 controls the inverter of the compressor by controlling the charging and discharging current of the smoothing capacitor in a way that prevents large current from flowing in the smoothing capacitor, thereby suppressing the degradation of the smoothing capacitor and the scaling up of the device.

[0004] Patent Document 1: International Publication No. 2022 / 149210

[0005] However, according to the aforementioned existing technology, if the boost converter stops due to an abnormality in the power conversion device, there is a problem that the current pulsation flowing in the capacitor increases sharply, putting an excessive load on the smoothing capacitor and causing it to deteriorate. Summary of the Invention

[0006] This disclosure is made in view of the above, and its object is to provide a power conversion device that can suppress the deterioration of the smoothing capacitor even when the boost converter stops boosting.

[0007] To address the aforementioned issues and achieve the objectives, the power conversion device of this disclosure includes: a rectifier-boost circuit section for rectifying and boosting 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 includes: an inverter circuit section connected to both ends of the capacitor for converting the power output from the rectifier-boost circuit section and the capacitor into a second AC power, which is then output to a load; a current detection section for detecting the current value of the current output from the inverter circuit section and sent to the load; and a power detection section for detecting the electrical state of the capacitor. Furthermore, the power conversion device disclosed herein includes a control unit that controls the rectifier boost circuit unit and the inverter circuit unit. If at least one of the detection values ​​detected by the current detection unit and the detection value detected by the power detection unit is an abnormal current value, the boost operation based on the rectifier boost circuit unit is abnormally stopped. If the detection value detected by the power detection unit when the boost operation is abnormally stopped is greater than or equal to a first reference value, the inverter circuit unit is controlled to make the detection value detected by the power detection unit less than the first reference value.

[0008] The power conversion device disclosed herein can suppress the deterioration of the smoothing capacitor even when the boost converter stops its boost operation. Attached Figure Description

[0009] Figure 1 This is a diagram illustrating a configuration example of a motor drive device having the power conversion device according to Embodiment 1.

[0010] Figure 2 This is a flowchart illustrating the operation of the control unit included in the power conversion device according to Embodiment 1.

[0011] Figure 3 This is a flowchart illustrating the operation of the control unit included in the power conversion device according to Embodiment 2.

[0012] Figure 4 This is a flowchart illustrating the operation of the control unit included in the power conversion device according to Embodiment 3.

[0013] Figure 5 This is a diagram illustrating a configuration example of a motor drive device having the power conversion device according to Embodiment 4.

[0014] Figure 6 This is a diagram illustrating a configuration example of a motor drive device having the power conversion device according to Embodiment 5.

[0015] Figure 7 This is a diagram illustrating a configuration example of a motor drive device having the power conversion device according to Embodiment 6.

[0016] Figure 8 This is a diagram illustrating an example of the configuration of the refrigeration cycle application equipment according to Embodiment 7.

[0017] Figure 9 This diagram illustrates an example of the configuration of a processing circuit in which the processing circuit of the control unit of the power conversion device according to Embodiment 1 is implemented by a processor and a memory.

[0018] Figure 10 This diagram illustrates an example of a processing circuit in which the processing circuit of the control unit of the power conversion device according to Embodiment 1 is implemented using dedicated hardware. Detailed Implementation

[0019] Hereinafter, the power conversion device, motor drive device, and refrigeration cycle application equipment involved in the embodiments of this disclosure will be described in detail based on the accompanying drawings.

[0020] Implementation method 1.

[0021] Figure 1 This diagram illustrates a configuration example of a motor drive unit having the power conversion device according to Embodiment 1. The motor drive unit 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 130, a smoothing unit 200, an inverter circuit 310, compressor current detection units 313a and 313b, a control unit 400, and a bus current detection unit 501.

[0022] The compressor 315 includes a motor (compressor motor) 314. The compressor 315 is an example of a load supplied with alternating current by the power conversion device 1A.

[0023] The reactor 120 is connected between the commercial power supply 110 and the rectifier-boost circuit section 130. That is, the reactor 120 is positioned on one of the connection lines that connect the commercial power supply 110 and the rectifier-boost circuit section 130. The reactor 120 achieves power factor improvement, suppression of higher harmonics, and power supply coordination.

[0024] The rectifier-boost circuit section 130 is a boost converter. It has the functions of rectifying the AC power (first AC power) supplied by the commercial power supply 110 and boosting the voltage of the rectified AC power. In other words, the rectifier-boost circuit section 130 is a boost-mode rectifier circuit. The input terminal of the rectifier-boost circuit section 130 is connected to the commercial power supply 110, and the output terminal is connected to the inverter circuit section 310. The rectifier-boost circuit section 130 outputs the rectified and boosted first AC power.

[0025] The rectifier-boost circuit section 130 is connected to the positive side bus Q1 (one side) and the negative side bus Q2 (the other side). Similarly, the inverter circuit section 310 is connected to both the positive side bus Q1 and the negative side bus Q2. Specifically, the positive side bus Q1 is connected to one output terminal of the rectifier-boost circuit section 130 and one input terminal of the inverter circuit section 310, while the negative side bus Q2 is connected to the other output terminal of the rectifier-boost circuit section 130 and the other input terminal of the inverter circuit section 310. Furthermore, the smoothing section 200 is connected to connection point P1 on the positive side bus Q1 and connection point P2 on the negative side bus Q2.

[0026] Thus, the smoothing section 200 is connected to the output terminal of the rectifier-boost 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 to smooth the power rectified by the rectifier-boost circuit section 130. The capacitor 210 is, for example, an electrolytic capacitor or a film capacitor. The capacitor 210 is connected to the output terminal of the rectifier-boost circuit section 130 and the input terminal of the inverter circuit section 310. The capacitor 210 has the capacity to smooth the power rectified by the rectifier-boost circuit section 130. Through the smoothing effect of the capacitor 210, the voltage generated by the capacitor 210 becomes a waveform with voltage pulsations corresponding to the frequency of the commercial power supply 110 superimposed on the DC component, rather than the full-wave rectified waveform of the commercial power supply 110. The commercial power supply 110 can be single-phase or three-phase.

[0027] The bus current detection unit 501 detects the rectified current I1 flowing from the rectifier boost circuit unit 130 and outputs the detected value of the rectified current I1 to the control unit 400. In this way, the bus current detection unit 501 detects the current rectified by the rectifier boost circuit unit 130 and flowing from the rectifier boost circuit unit 130 into the smoothing unit 200, i.e., the input current to the smoothing unit 200, and outputs the detected current value to the control unit 400. The bus current detection unit 501 can be used as a power detection unit to detect the electrical state of the capacitor 210.

[0028] The inverter circuit section 310 is connected to both ends of the smoothing section 200. The inverter circuit section 310 includes switching elements 311a to 311f and circulating diodes 312a to 312f. The inverter circuit section 310 controls the switching elements 311a to 311f to be switched on / off according to the control unit 400. Through this control, the power output from the rectifier boost circuit section 130 and the smoothing section 200 is converted into alternating current (second AC power) with the desired amplitude and phase. That is, the inverter circuit section 310 generates the second AC power and outputs it to the motor 314 by switching the switching elements 311a to 311f on / off.

[0029] Compressor current detection units 313a and 313b respectively detect the current value of one phase of the three-phase current output from inverter circuit unit 310 and output the detected current value to control unit 400. Control unit 400 can calculate the remaining current value output from inverter circuit unit 310 by obtaining the current values ​​of two phases of the three-phase current output from inverter circuit unit 310.

[0030] The motor 314 mounted on the compressor 315 rotates according to the amplitude and phase of the AC power (second AC power) supplied from the inverter circuit section 310, and performs compression operation.

[0031] In addition, although Figure 1 The illustration shows a motor winding in motor 314 with a Y-connection, but it is not limited to this example. The motor winding of motor 314 can be delta-connected, or it can be configured to switch between Y-connection and delta connection.

[0032] In addition, in the power conversion device 1A, Figure 1 The configuration of each component shown is an example, and the configuration of each component is not limited to... Figure 1 The example shown. For example, reactor 120 can also be configured after rectifier boost circuit section 130. In the following description, compressor current detection sections 313a, 313b and bus current detection section 501 are sometimes simply referred to as "detection sections". In addition, the current value detected by at least one of compressor current detection sections 313a, 313b and bus current detection section 501 is sometimes simply referred to as "detection value".

[0033] The control unit 400 acquires the detection value of the rectified current I1 detected by the bus current detection unit 501 and the detection value of the inverter input current I2 detected by the compressor current detection units 313a and 313b. That is, 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.

[0034] In addition, the control unit 400 uses the detection values ​​detected by each detection unit to control the operation of the inverter circuit unit 310. Specifically, it controls the switching elements 311a to 311f of the inverter circuit unit 310 to be turned on / off.

[0035] Furthermore, the control unit 400 controls the operation of the inverter circuit unit 310 to output a second AC power, which includes a pulsation corresponding to the pulsation of the power flowing from the rectifier boost circuit unit 130 into the capacitor 210 of the smoothing unit 200, to the compressor 315. The pulsation corresponding to the pulsation of the power flowing into the smoothing unit 200 into the capacitor 210 is, for example, a pulsation that varies according to the frequency of the pulsation of the power flowing into the smoothing unit 200 into the capacitor 210. Thus, the control unit 400 suppresses the capacitor current I3, which is the charging and discharging current of the capacitor 210. The control unit 400 performs control to make any one of the speed, voltage, and current of the motor 314 reach a desired state. The control unit 400 may not use all the detection values ​​obtained from each detection unit, or it may use only a portion of the detection values ​​for control.

[0036] 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 values ​​of the current detected by at least one of the compressor current detection units 313a, 313b and the bus current detection unit 501.

[0037] During the boost operation of the rectifier boost circuit 130, if at least one of the compressor current detection units 313a, 313b and the bus current detection unit 501 detects an abnormal current value indicating an abnormality in the motor drive unit 2A, the control unit 400 stops the boost operation of the rectifier boost circuit 130. The abnormal current value indicating an abnormality in the motor drive unit 2A is a current value outside the allowable range.

[0038] 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 to make the input current value 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 before the boost operation stopped.

[0039] Here, a flowchart is used to explain the operation of the control unit 400. Figure 2This is a flowchart illustrating the operation of the control unit included in the power conversion device according to Embodiment 1. When the power conversion device 1A starts operating, the control unit 400 controls the rectifier boost circuit unit 130 to start boosting operation (step S10). The compressor current detection units 313a and 313b and the bus current detection unit 501 detect current values ​​and send the detected values ​​as detection results to the control unit 400.

[0040] During the boost operation, if at least one of the compressor current detection units 313a, 313b and the bus current detection unit 501 detects an abnormal current value indicating an abnormal motor drive unit 2A, the control unit 400 controls the rectifier boost circuit unit 130 to abnormally stop the boost operation (step S20).

[0041] 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 above a predetermined first reference value (step S30).

[0042] If the input current to the smoothing unit 200 is greater than or equal to a predetermined first reference value when the boost operation is abnormally stopped (step S30, Yes), the control unit 400 controls the inverter circuit unit 310 to make the input current value less than the first reference value (step S40). For example, the control unit 400 controls the inverter circuit unit 310 to make the peak value of the input current value less than the first reference value.

[0043] On the other hand, if the input current value to the smoothing unit 200 is less than the predetermined first reference value when the boost operation stops abnormally (step S30, no), the control unit 400 maintains the inverter control before the boost operation stopped (step S50).

[0044] Thus, in Embodiment 1, if the input current value to the smoothing unit 200 is greater than or equal to the first reference value when the boost operation is abnormally stopped, the control unit 400 controls the inverter circuit unit 310 to make the input current value less than the first reference value. Therefore, the power conversion device 1A can suppress the capacitor current I3, and even when the rectifier boost circuit unit 130, which is a boost converter, stops boost operation, it can suppress a sharp increase in current pulsation flowing in the capacitor 210. Therefore, when the rectifier boost circuit unit 130 stops boost operation, the power conversion device 1A can suppress excessive load on the capacitor 210, and can suppress the deterioration and failure of the capacitor 210.

[0045] Implementation method 2.

[0046] Next, use Figure 3Embodiment 2 will be described. In Embodiment 2, after the pressure boosting operation is abnormally stopped, the control unit 400 restarts the pressure boosting operation if the conditions for restarting the pressure boosting operation (restart conditions) are met. The motor drive device 2A in Embodiment 2 has the same configuration as the motor drive device 2A in Embodiment 1, therefore, the description of the configuration of the motor drive device 2A is omitted.

[0047] Figure 3 This is a flowchart illustrating the operation of the control unit included in the power conversion device according to Embodiment 2. When the power conversion device 1A starts operating, the control unit 400 controls the rectifier boost circuit 130 to start boosting operation (step S110). The compressor current detection units 313a and 313b and the bus current detection unit 501 detect current values ​​and send the detected values ​​as detection results to the control unit 400.

[0048] During the boost operation, if at least one of the compressor current detection units 313a, 313b and the bus current detection unit 501 detects an abnormal current value indicating an abnormal motor drive unit 2A, the control unit 400 controls the rectifier boost circuit unit 130 to abnormally stop the boost operation (step S120).

[0049] When the boosting operation is abnormally stopped, the control unit 400 determines whether to restart the boosting operation (restore to the boosting operation state). The control unit 400 determines whether to restart the boosting operation based on whether the conditions for restarting the boosting operation are met (step S130).

[0050] If the conditions for restarting the boost operation are not met (step S130, no), the control unit 400 returns to the processing of step S120, maintaining the state in which the rectifier boost circuit unit 130 abnormally stopped the boost operation.

[0051] If the conditions for restarting the boost operation are met (step S130, yes), the control unit 400 restarts the boost operation of the rectifier boost circuit unit 130 so that the boost operation is in the state before the abnormal stop (step S140).

[0052] Thus, since the control unit 400 of Embodiment 2 restarts the boosting operation if the conditions for restarting the boosting operation are met after the abnormal stop of the boosting operation, the power conversion device 1A can also quickly return to the state before the abnormal stop after the abnormal stop of the boosting operation.

[0053] Implementation method 3.

[0054] Next, use Figure 4Embodiment 3 will be described. In Embodiment 2, the operation of the control unit 400 in the event of a single abnormal stop was described. In Embodiment 3, the operation of the control unit 400 in the event of consecutive abnormal stops will be described. The motor drive device 2A in Embodiment 3 has the same configuration as the motor drive device 2A in Embodiment 1, therefore, the description of the configuration of the motor drive device 2A is omitted.

[0055] Figure 4 This is a flowchart illustrating the operation of the control unit included in the power conversion device according to Embodiment 3. When the power conversion device 1A starts operating, the control unit 400 controls the rectifier boost circuit 130 to start boosting operation (step S210). The compressor current detection units 313a and 313b and the bus current detection unit 501 detect current values ​​and send the detected values ​​as detection results to the control unit 400.

[0056] During the boost operation, if at least one of the compressor current detection units 313a, 313b and the bus current detection unit 501 detects an abnormal current value indicating an abnormality in the motor drive unit 2A, the control unit 400 abnormally stops the boost operation of the rectifier boost circuit unit 130 by controlling the rectifier boost circuit unit 130. That is, the control unit 400 performs the first abnormal stop of the boost operation (step S220).

[0057] After an abnormal stop in the boosting operation, if a specific condition is met, the control unit 400 restarts the boosting operation (step S230). Subsequently, during the boosting operation, 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, the control unit 400 abnormally stops the boosting operation by controlling the rectifier boosting circuit unit 130. That is, the control unit 400 performs a second abnormal stop of the boosting operation (step S240). Then, the control unit 400 determines whether to restart the boosting operation or prohibit it. Specifically, the control unit 400 determines whether to restart the boosting operation or prohibit it based on the time from the last restart of the boosting operation to the latest abnormal stop. That is, the control unit 400 determines whether the period from the restart of the boosting operation to the second abnormal stop is within a reference time (step S250). Hereinafter, the period from the restart of the boosting action to the second abnormal stop is sometimes referred to as the restart action period.

[0058] If the restart operation takes longer than the reference time (step S250, no), the control unit 400 returns to the processing of step S230 and restarts the boost operation. That is, if the restarted boost operation is stable but the restart operation takes longer than the reference time, the control unit 400 restarts the boost operation.

[0059] On the other hand, if the restart operation is within the reference time (step S250, Yes), the control unit 400 prohibits the boost operation (step S260). That is, if the restarted boost operation is unstable and the restart operation is within the reference time, the control unit 400 prohibits the boost operation. In this case, even if the restart conditions for the boost operation are met, the control unit 400 will not perform the boost operation.

[0060] If the time between the restart of the last boost operation and the abnormal stop of the latest boost operation (the restart operation period) is extremely short, it can be considered not an occasional malfunction of the motor drive unit 2A, but rather a chronic failure of the motor drive unit 2A. In this state, the rectifier boost circuit 130 repeatedly performs boost operations and abnormal stops, causing the motor drive unit 2A to operate unstably. Therefore, in Embodiment 3, when the restart operation period is within a reference time, the control unit 400 prohibits boost operations.

[0061] Thus, since the control unit 400 of the power conversion device 1A in Embodiment 3 prohibits the boost operation during the restart period within a reference time, unstable operation of the motor drive device 2A can be suppressed. As a result, the power conversion device 1A can suppress overload of the capacitor 210.

[0062] Implementation method 4.

[0063] Next, use Figure 5 Embodiment 4 will be described. In Embodiment 4, when the capacitor current I3 flowing in the smoothing section 200 is greater than or equal to the second reference value when the boost operation stops abnormally, the control section 400 controls the inverter circuit section 310 to make the capacitor current I3 less than the second reference value.

[0064] Figure 5 This is a diagram illustrating a configuration example of a motor drive device having the power conversion device according to Embodiment 4. Figure 5 Among the various constituent elements, the realization and Figure 1 The components of the motor drive device 2A of Embodiment 1 shown have the same function and are labeled with the same reference numerals, and repeated descriptions are omitted.

[0065] Compared to the motor drive device 2A in embodiments 1 to 3, the motor drive device 2B in embodiment 4 includes a power conversion device 1B instead of the power conversion device 1A. The power conversion device 1B includes the components of the power conversion device 1A and a smoothing capacitor current detection unit 502.

[0066] The smoothing capacitor current detection unit 502 is connected to a portion capable of detecting only the capacitor current I3 flowing in the smoothing unit 200. For example, the smoothing capacitor current detection unit 502 is disposed on a connection line connecting the connection point P1 to 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.

[0067] Therefore, the control unit 400 obtains the detection value detected by the smoothing capacitor current detection unit 502. If the detected value of the capacitor current I3 by the smoothing capacitor current detection unit 502 is higher than or equal to a second reference value predetermined by the control unit 400 when the boost operation abnormally stops, the control unit 400 controls the inverter circuit unit 310 to make the capacitor current I3 less than the second reference value. When 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.

[0068] Thus, in Embodiment 4, the smoothing capacitor current detection unit 502 only detects the capacitor current I3 flowing in the smoothing unit 200. If the detected value of the capacitor current I3 is above the second reference value when the boost operation abnormally stops, the control unit 400 controls the inverter circuit unit 310 to make the capacitor current I3 less than the second reference value. As a result, the power conversion device 1B can suppress overload on the capacitor 210 when the boost operation abnormally stops.

[0069] Furthermore, the power conversion device 1B can control the inverter circuit section 310 to ensure that the detected value of the rectified current I1 detected by the bus current detection section 501 is less than the first reference value, and that the detected capacitor current I3 detected by the smoothing capacitor current detection section 502 is less than the second reference value. Therefore, the power conversion device 1B can suppress overload on the capacitor 210 with a higher accuracy than in Embodiment 1.

[0070] Implementation method 5.

[0071] Next, use Figure 6 Embodiment 5 will be described. In Embodiment 5, the control unit 400 estimates the capacitor current I3 based on the voltage trend at both ends of the smoothing unit 200 when the boost operation stops abnormally, and controls the inverter circuit unit 310 to make the estimated capacitor current I3 less than the third reference value.

[0072] Figure 6This is a diagram illustrating a configuration example of a motor drive device having the power conversion device according to Embodiment 5. Figure 6 Among the various constituent elements, the realization and Figure 1 The components of the motor drive device 2A of Embodiment 1 shown herein have the same reference numerals, and repeated descriptions are omitted.

[0073] Compared to the motor drive device 2A in embodiments 1 to 3, the motor drive device 2C in embodiment 5 includes a power conversion device 1C instead of the power conversion device 1A. The power conversion device 1C includes the components of the power conversion device 1A and a smoothing capacitor voltage detection unit 503.

[0074] The smoothing capacitor voltage detection unit 503 is a detection unit that detects the voltage across the two ends of the smoothing unit 200. The smoothing capacitor voltage detection unit 503 is connected in a manner that detects the voltage across the two ends of the smoothing unit 200. For example, the smoothing capacitor voltage detection unit 503 is connected to the connecting line that connects connection point P1 to capacitor 210 and the connecting line that connects connection point P2 to capacitor 210. The smoothing capacitor voltage detection unit 503 sends the detected voltage value to the control unit 400.

[0075] Therefore, the control unit 400 obtains the detection value detected by the smoothing capacitor voltage detection unit 503. The control unit 400 infers the capacitor current I3 based on the trend of the detection value of the voltage detected by the smoothing capacitor voltage detection unit 503.

[0076] The control unit 400 can estimate the capacitor current I3 based on the change in the detected voltage value of the smooth capacitor voltage detection unit 503 during a specific period, or it can estimate the capacitor current I3 based on the detected voltage values ​​at one or more times. The following describes the case where the control unit 400 estimates the capacitor current I3 based on the detected voltage values ​​at a specific time.

[0077] When the estimated capacitor current I3 is greater than or equal to a third reference value predetermined by the control unit 400, the control unit 400 controls the inverter circuit unit 310 to make the capacitor current I3 less than the third reference value. That is, the control unit 400 controls the inverter circuit unit 310 when the estimated capacitor current I3 is greater than or equal to the third reference value, so that the capacitor current I3 estimated based on the voltage detected after this control is less than the third reference value. When the capacitor current I3 estimated based on the voltage 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 before the boost operation stopped.

[0078] 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 value. Then, 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 to make the subsequently estimated capacitor current I3 less than the third reference value. Therefore, the power conversion device 1C can suppress overload of the capacitor 210 using the smoothing capacitor voltage detection unit 503, which is used for other purposes, instead of a dedicated detection unit for detecting the capacitor current I3, thus reducing the number of detection units.

[0079] Furthermore, the power conversion device 1C can control the inverter circuit section 310 so that the detected value of the rectified current I1 detected by the bus current detection section 501 is less than the first reference value, and the detected value of the voltage detected by the smoothing capacitor voltage detection section 503 is less than the third reference value. As a result, the power conversion device 1C can suppress overload on the capacitor 210 with higher accuracy than in Embodiment 1.

[0080] Implementation method 6.

[0081] Next, use Figure 7 Embodiment 6 will be described. 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 unit 310 to make the estimated capacitor current I3 less than the fourth reference value.

[0082] Figure 7 This is a diagram illustrating a configuration example of a motor drive unit having the power conversion device according to Embodiment 6. Figure 7 Among the various constituent elements, the realization and Figure 1 The components of the motor drive device 2A of Embodiment 1 shown herein have the same reference numerals, and repeated descriptions are omitted.

[0083] Compared to the motor drive device 2A in embodiments 1 to 3, the motor drive device 2D in embodiment 6 includes a power conversion device 1D instead of the power conversion device 1A. The power conversion device 1D includes the components of the power conversion device 1A and an input current detection unit 504.

[0084] An 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 from the commercial power supply 110 to the power conversion device 1D. The input current detection unit 504 sends the detected input current value to the control unit 400.

[0085] Therefore, the control unit 400 obtains the detection value detected by the input current detection unit 504. The control unit 400 infers the capacitor current I3 based on the trend of the input current detection value detected by the input current detection unit 504.

[0086] The control unit 400 can estimate the capacitor current I3 based on the change in the detected value of the input current detected by the input current detection unit 504 during a specific period, or it can estimate the capacitor current I3 based on the detected values ​​of the input current at one or more times. The following describes the case where the control unit 400 estimates the capacitor current I3 based on the detected value of the input current at a specific time.

[0087] When the estimated capacitor current I3 is greater than or equal to a fourth reference value predetermined by the control unit 400, the control unit 400 controls the inverter circuit unit 310 to make the capacitor current I3 less than the fourth reference value. That is, the control unit 400 controls the inverter circuit unit 310 when the estimated capacitor current I3 is greater than or equal to the fourth reference value, so that the capacitor current I3 estimated based on the input current detected after this control is less than the fourth reference value. When 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 before the boost operation stopped.

[0088] 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 value of the input current. Then, if the estimated capacitor current I3 is greater than or equal to a fourth reference value, the control unit 400 controls the inverter circuit unit 310 to make the subsequently estimated capacitor current I3 less than the fourth reference value. As a result, the power conversion device 1D can suppress the overload of the capacitor 210 by using the input current detection unit 504, which is used for other purposes, without using a dedicated detection unit for detecting the capacitor current I3, thereby reducing the number of detection units.

[0089] Furthermore, the power conversion device 1D can control the inverter circuit section 310 so that the detected value of the rectified current I1 detected by the bus current detection section 501 is less than the first reference value, and the detected value of the input current detected by the input current detection section 504 is less than the fourth reference value. As a result, the power conversion device 1D can suppress overload on the capacitor 210 with higher accuracy than in Embodiment 1.

[0090] Implementation method 7.

[0091] Next, use Figure 8Embodiment 7 will be described. In Embodiment 7, the power conversion device is applied to a refrigeration cycle application device. Hereinafter, the case where the power conversion device 1A is applied to the refrigeration cycle application device will be described, but the power conversion devices 1B to 1D can also be applied to the refrigeration cycle application device.

[0092] Figure 8 This is a diagram illustrating a configuration example of the refrigeration cycle application equipment according to Embodiment 7. In this diagram... Figure 8 In the figures, the constituent elements that have the same function as in Embodiment 1 are labeled with the same reference numerals as in Embodiment 1.

[0093] The refrigeration cycle application device 900 according to Embodiment 7 includes the power conversion device 1A described in Embodiment 1. The refrigeration cycle application device 900 according to Embodiment 7 can be applied to products with refrigeration cycles, such as air conditioners, refrigerators, freezers, and heat pump water heaters.

[0094] The refrigeration cycle application equipment 900 is equipped with a compressor 315 with a built-in motor 314, a four-way valve 902, an indoor heat exchanger 906, an expansion valve 908, and an outdoor heat exchanger 910, as described in Embodiment 1, via refrigerant piping 912.

[0095] The compressor 315 contains a compression mechanism 904 for compressing the refrigerant and a motor 314 for actuating the compression mechanism 904.

[0096] The refrigeration cycle application equipment 900 can operate in heating or cooling mode by switching the four-way valve 902. The compressor 904 is driven by a motor 314 with variable speed control.

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

[0098] During refrigeration operation, as shown by the dashed arrow, the refrigerant is pressurized and sent out in the compression mechanism 904, 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, releasing heat, while the outdoor heat exchanger 910 acts as an evaporator, absorbing heat. During cooling operation, the outdoor heat exchanger 910 acts as a condenser, releasing heat, while the indoor heat exchanger 906 acts as an evaporator, absorbing heat. The expansion valve 908 causes the refrigerant to expand due to pressure reduction.

[0100] Thus, according to Embodiment 7, since the power conversion device 1A, which suppresses the deterioration of the capacitor 210 and achieves miniaturization, is assembled in the refrigeration cycle application equipment 900, a long-life and compact refrigeration cycle application equipment can be realized.

[0101] Here, the hardware configuration of the control unit 400 provided in the power conversion devices 1A to 1D will be described. The control unit 400 provided in the power conversion devices 1A to 1D is implemented by a processing circuit. The processing circuit may be a processor that executes a program stored in a memory, or it may be dedicated hardware. Since the power conversion devices 1A to 1D have the same hardware configuration, the hardware configuration of the power conversion device 1A will be described below.

[0102] Figure 9 This diagram illustrates an example of the configuration of a processing circuit in which the processing circuit of the control unit of the power conversion device according to Embodiment 1 is implemented by a processor and a memory. Figure 9 The processing circuit 90 shown includes 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 implemented through software, firmware, or a combination of software and firmware. The software or firmware is described as a control program and is stored in the memory 92. In the processing circuit 90, each function is implemented 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 ultimately executes the processing of the control unit 400. This control program can also be described as a program for causing the control unit 400 to perform the functions implemented by the processing circuit 90. This control program can be provided by a storage medium storing the control program, or by other means such as a communication medium.

[0103] Here, processor 91 is, for example, a CPU (Central Processing Unit), processing device, arithmetic device, microprocessor, microcomputer, or DSP (Digital Signal Processor). Additionally, memory 92 is, for example, non-volatile or volatile semiconductor memory such as RAM (Random Access Memory), ROM (Read-Only Memory), flash memory, EPROM (Erasable Programmable ROM), and EEPROM (Electrically Erasable Programmable ROM), as well as disks, floppy disks, optical disks, compact optical disks, mini-disks, or DVDs (Digital Versatile Discs).

[0104] Figure 10 This diagram illustrates an example of a processing circuit in which the processing circuit of the control unit of the power conversion device according to Embodiment 1 is implemented using dedicated hardware. Figure 10 The processing circuit 93 shown is, for example, equivalent to a single circuit, a composite circuit, a programmable processor, a parallel programmable processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or a combination thereof. The processing circuit 93 can be partially implemented by dedicated hardware, or partially by software or firmware. Thus, the processing circuit 93 can implement the aforementioned functions through dedicated hardware, software, firmware, or a combination thereof.

[0105] The above embodiments illustrate an example and can be combined with other known technologies, or the embodiments can be combined with each other, or a part of the configuration can be omitted or modified without departing from the spirit.

[0106] Explanation of reference numerals in the attached figures

[0107] 1A~1D...Power conversion device; 2A~2D...Motor drive device; 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...Circulating diode; 313a, 313b...Compressor current detection section; 314...Motor; 315...Compressor; 400...Control section; 501...Bus current detection unit; 502...Smoothing capacitor current detection unit; 503...Smoothing capacitor voltage detection unit; 504...Input current detection unit; 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 side busbar; Q2...Negative side busbar.

Claims

1. A power conversion device, characterized in that, have: The rectifier and boost circuit section rectifies and boosts the first AC power supplied from the commercial power source; A capacitor is connected to the output terminal of the rectifier boost circuit. The inverter circuit section, connected to both ends of the capacitor, converts the power output from the rectifier boost circuit section and the capacitor into a second AC power and outputs it to the load; The current detection unit detects the current value of the current output from the inverter circuit section and sent to the load; The power detection unit detects the electrical state of the capacitor; as well as The control unit controls the rectifier boost circuit section and the inverter circuit section, and abnormally stops the boost operation based on the rectifier boost circuit section when at least one of the detection values ​​detected by the current detection section and the detection values ​​detected by the power detection section is an abnormal current value. When the boost operation is abnormally stopped and the detection value detected by the power detection section is greater than or equal to a first reference value, the control unit controls the inverter circuit section to make the detection value detected by the power detection section less than the first reference value.

2. The power conversion device according to claim 1, characterized in that, When the boost operation stops abnormally, if the restart conditions for restarting the boost operation are met, the control unit controls the rectifier boost circuit unit to restart the boost operation that was before the abnormal stop.

3. The power conversion device according to claim 2, characterized in that, When the boosting operation stops abnormally, the control unit determines whether to restart or prohibit the boosting operation based on the period from the resumption of the last boosting operation to the abnormal stop of the latest boosting operation, i.e., the restarting period.

4. The power conversion device according to any one of claims 1 to 3, characterized in that, It also includes a capacitor current detection unit for detecting the capacitor current flowing in the capacitor. If the capacitor current detection unit detects a value greater than or equal to the second reference value when the boost operation abnormally stops, the control unit controls the inverter circuit unit to make the detection value detected by the capacitor current detection unit less than the second reference value.

5. The power conversion device according to any one of claims 1 to 3, characterized in that, It also includes a capacitor voltage detection unit for detecting the voltage across the capacitor. The control unit estimates the capacitor current flowing in the capacitor based on the detection value detected by the capacitor voltage detection unit when the boost operation abnormally stops, and controls the inverter circuit unit to make the subsequently estimated capacitor current less than the third reference value if the estimated capacitor current is greater than or equal to the third reference value.

6. The power conversion device according to any one of claims 1 to 3, characterized in that, It also includes an input current detection unit for detecting the input current supplied by the commercial power supply. The control unit estimates the capacitor current flowing in the capacitor based on the detection value detected by the input current detection unit when the boost operation abnormally stops, and controls the inverter circuit unit to make the subsequently estimated capacitor current less than the fourth reference value if the estimated capacitor current is greater than or equal to the fourth reference value.

7. A motor drive device, characterized in that, The power conversion device having any one of claims 1 to 6.

8. A refrigeration cycle application device, characterized in that, The power conversion device comprising any one of claims 1 to 6.

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