Power conversion device and air conditioning device

Abstract

A power conversion device (100) is provided with: a converter (2) that rectifies AC power; a first inverter (5a) and a second inverter (5b); a first voltage detection circuit (8a) that filters a detection value of the voltage input to the first inverter and outputs the filtered detection value as a first voltage detection value; a second voltage detection circuit (8b) that filters a detection value of the voltage input to the second inverter and outputs the filtered detection value as a second voltage detection value; a first drive signal generation unit (7a) that performs a drive signal generation operation and a protection operation for the first inverter on the basis of the first voltage detection value; and a second drive signal generation unit (7b) that performs a drive signal generation operation and a protection operation of the second inverter on the basis of the second voltage detection value, and that performs at least one of a time constant of a filter circuit that performs filtering, and a threshold value used in an abnormality detection process. The control unit is set on the basis of the wiring impedance between the converter and each of the first inverter and the second inverter.

Description

Technical Field

[0001] The present disclosure relates to a power conversion device and an air conditioning device. Background Art

[0002] A conventional power conversion device includes a plurality of power conversion circuits for converting power supplied from a common power source into desired AC power, and each power conversion circuit generates and supplies power required by each of a plurality of connected devices.

[0003] For example, Patent Document 1 discloses a power conversion device (motor drive circuit) in which a rectifier circuit for rectifying the AC voltage of an AC power supply is connected to two inverters, namely a first inverter and a second inverter, and each inverter generates a drive voltage for driving a fan motor and a compressor motor.

[0004] Patent Document 1: Japanese Patent Application Publication No. 2020-61913

[0005] In the case of the circuit structure disclosed in Patent Document 1, two inverters are connected to a common bus, so ideally the voltages on the input sides of the two inverters are the same. However, when there is a difference in the distance between the input bus and each inverter, the wiring impedance to each inverter will also be different, especially when the distance from the converter (rectifier circuit) to the inverter bus is longer due to the limitation of the configuration in the device, the wiring impedance is greater. In addition, when the distance from one inverter is longer than the distance from the other inverter, the difference in wiring impedance becomes larger. For example, when a motor drive circuit as a power conversion device is applied to an air conditioning device as described in Patent Document 1, it can be considered that the difference between the wiring impedance of the circuit that supplies power to the motor of the compressor provided in the outdoor unit and the wiring impedance of the circuit that supplies power to the motor of the fan provided in the indoor unit becomes larger.

[0006] Here, if the wiring impedance becomes larger, bus voltage fluctuations such as transient surges caused by sudden changes in current accompanying sudden changes in power supply voltage and sudden changes in motor load on one side will occur. The larger the wiring impedance, the larger the transient voltage fluctuations, and the higher the risk of overvoltage. Therefore, for the purpose of protecting the inverter, high overvoltage detection responsiveness is required. That is, it is required to detect the overvoltage at an early stage when it occurs so that the protection action (protection function) performed by the protection circuit can work quickly. In contrast, when the wiring impedance is small, the influence of noise received from the surrounding is greater than the influence of bus voltage fluctuations caused by the wiring impedance. Due to voltage misdetection caused by noise, there is a concern about the influence on motor control or misdetection of overvoltage abnormalities. Therefore, when the wiring impedance difference from the converter to each inverter is large, if the overvoltage detection responsiveness is to be improved without considering the wiring impedance difference, a misoperation caused by noise will occur on the side with small wiring impedance, for example, the risk of the protection function working and stopping the action increases. Furthermore, if the occurrence of malfunctions caused by noise is suppressed without considering the difference in wiring impedance, the overvoltage detection responsiveness decreases, and the protection function is delayed on the side with larger wiring impedance where overvoltage protection becomes important, thereby increasing the risk of device failure.

[0007] It is necessary to reduce the influence of the difference in wiring impedance caused by the difference in distance from the converter to each inverter due to the limitation of the arrangement within the device. Summary of the invention

[0008] The present disclosure has been made in view of the above circumstances, and an object of the present disclosure is to obtain a power conversion device capable of suppressing the influence of the difference in wiring impedance between the converter and each of the two inverters and realizing highly reliable operation.

[0009] In order to solve the above-mentioned problems and achieve the purpose, the power conversion device of the present disclosure includes: a converter that rectifies AC power supplied from an AC power source; a first inverter and a second inverter that are connected to both ends of a main circuit capacitor that smoothes the DC power output by the converter; a first voltage detection circuit that detects a voltage input to the first inverter, filters the detection value, and outputs it as a first voltage detection value; a second voltage detection circuit that detects a voltage input to the second inverter, filters the detection value, and outputs it as a second voltage detection value; a first drive signal generation unit that performs a drive signal generation operation for the first inverter and a protection operation for the first inverter when an abnormality occurs based on the first voltage detection value; and a second drive signal generation unit that performs a drive signal generation operation for the second inverter and a protection operation for the second inverter when an abnormality occurs based on the second voltage detection value, and at least one of a time constant of a filter circuit that performs filtering in each of the first voltage detection circuit and the second voltage detection circuit and a threshold used in each of the abnormality detection processing of the first drive signal generation unit and the second drive signal generation unit is set based on the wiring impedance between the converter and each of the first inverter and the second inverter.

[0010] The power conversion device of the present disclosure has an effect of being able to suppress the influence of the difference in wiring impedance between the converter and each of the two inverters, thereby achieving highly reliable operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a diagram showing a configuration example of a power conversion device according to the first embodiment.

[0012] Figure 2 This is a diagram schematically showing the wiring impedance of the power conversion device according to the first embodiment.

[0013] Figure 3 This is a diagram showing a configuration example of a first voltage detection circuit and a second voltage detection circuit constituting the power conversion device according to the first embodiment.

[0014] Figure 4 This is a flowchart showing an example of the operation of the first drive signal generating unit constituting the power conversion device according to the first embodiment.

[0015] Figure 5 It is a diagram showing a configuration example of a power conversion device according to the second embodiment.

[0016] Figure 6 This is a diagram showing a configuration example of an air-conditioning apparatus according to Embodiment 3. DETAILED DESCRIPTION

[0017] Hereinafter, a power conversion device and an air conditioning device according to an embodiment of the present disclosure will be described in detail based on the drawings.

[0018] Implementation method 1.

[0019] Figure 1 1 is a diagram showing a configuration example of a power conversion device 100 according to Embodiment 1. The power conversion device 100 includes a converter 2, a reactor 3, a main circuit capacitor 4, a first inverter 5a, a second inverter 5b, a first drive signal generating unit 7a, a second drive signal generating unit 7b, a first voltage detection circuit 8a, and a second voltage detection circuit 8b.

[0020] The converter 2 is connected to the AC power supply 1, and rectifies and outputs the three-phase AC power supplied from the AC power supply 1. The converter 2 can be a passive converter using a diode bridge, or a boost converter capable of boosting the output voltage. One end of the reactor 3 is connected to the positive output terminal of the converter 2, and the other end is connected to one end of the main circuit capacitor 4. The other end of the main circuit capacitor 4 is connected to the negative output terminal of the converter 2. That is, the main circuit capacitor 4 is connected between the other end of the reactor 3 and the negative output terminal of the converter 2. In addition, a first inverter 5a and a second inverter 5b are connected to both ends of the main circuit capacitor 4. A first motor 6a is connected to the output end of the first inverter 5a, and a second motor 6b is connected to the output end of the second inverter 5b.

[0021] The reactor 3 and the main circuit capacitor 4 suppress and smooth the harmonics of the DC power output by the converter 2. The voltage across the main circuit capacitor 4 is V dc0 . The first inverter 5a converts the DC power input from the converter 2 via the reactor 3 and the main circuit capacitor 4 into AC power and supplies it to the first motor 6a. The first inverter 5a performs a power conversion operation from DC to AC based on a drive signal input from a first drive signal generating unit 7a described later. The second inverter 5b converts the DC power input from the converter 2 via the reactor 3 and the main circuit capacitor 4 into AC power and supplies it to the second motor 6b. The second inverter 5b performs a power conversion operation from DC to AC based on a drive signal input from a second drive signal generating unit 7b described later.

[0022] The first drive signal generating unit 7a generates a signal based on the input voltage V to the first inverter 5a detected by the first voltage detecting circuit 8a. dc1 The second drive signal generating unit 7b generates a drive signal for controlling the power conversion operation performed by the first inverter 5a based on a voltage command (not shown) input from the outside and inputs the drive signal to the first inverter 5a. ... dc2The first drive signal generating unit 7a and the second drive signal generating unit 7b are used to generate a drive signal for controlling the power conversion operation performed by the second inverter 5b, and output the drive signal to the second inverter 5b. In addition, the generation of the drive signal by the first drive signal generating unit 7a and the second drive signal generating unit 7b is performed using a known general drive signal generation method. The first drive signal generating unit 7a and the second drive signal generating unit 7b are implemented by a microcontroller, for example. The first drive signal generating unit 7a and the second drive signal generating unit 7b can be implemented by one microcontroller, or they can be implemented by separate microcontrollers.

[0023] The first voltage detection circuit 8a detects the voltage of the input portion of the first inverter 5a and compares the detected input voltage V dc1 The corresponding signal is sent to the first drive signal generating unit 7a. The second voltage detection circuit 8b detects the voltage of the input unit of the second inverter 5b and compares the detected input voltage V to the second inverter 5b. dc2 The corresponding signal is sent to the second drive signal generating unit 7b.

[0024] In addition, the first drive signal generating unit 7a and the second drive signal generating unit 7b have a function of stopping the power conversion operation based on the first inverter 5a and the second inverter 5b when a failure occurs in the power conversion device 100 or when there is a concern about the occurrence of a failure. For example, the first drive signal generating unit 7a stops the power conversion operation based on the first inverter 5a and the second inverter 5b when the input voltage V detected by the first voltage detection circuit 8a is dc1 When the input voltage V detected by the second voltage detection circuit 8b is greater than a predetermined threshold, it is determined that an overvoltage abnormality is applied to the first inverter 5a, and the power conversion operation based on the first inverter 5a is stopped. dc2 When the voltage is larger than a predetermined threshold value, it is determined that an overvoltage abnormality occurs in which an excessive voltage is applied to the second inverter 5b, and the power conversion operation by the second inverter 5b is stopped.

[0025] Here, there are the following connections between the converter 2 and the first inverter 5a and between the converter 2 and the second inverter 5b of the power conversion device 100: Figure 2 The wiring impedance is as shown. Figure 2 This is a diagram schematically showing wiring impedance of the power conversion device 100 according to the first embodiment. Figure 2In the example, Z1 represents the wiring impedance from the main circuit capacitor 4 to the positive input terminal of the first inverter 5a, Z2 represents the wiring impedance from the main circuit capacitor 4 to the negative input terminal of the first inverter 5a, Z3 represents the wiring impedance from the main circuit capacitor 4 to the positive input terminal of the second inverter 5b, and Z4 represents the wiring impedance from the main circuit capacitor 4 to the negative input terminal of the second inverter 5b. The wiring impedances Z1 to Z4 are composed of tiny resistance components and reactance components existing in the wiring. The wiring impedances Z1 to Z4 are dc0 With V dc1 The reason for the potential difference between V dc0 With V dc2 The causes of potential differences between the two and the causes of transient voltage fluctuations. Figure 2 In the embodiment, description of the first voltage detection circuit 8a, the second voltage detection circuit 8b, the first drive signal generation unit 7a, and the second drive signal generation unit 7b is omitted.

[0026] If the difference between the wiring impedance (Z1, Z2) between the converter 2 and the first inverter 5a and the wiring impedance (Z3, Z4) between the converter 2 and the second inverter 5b increases, the response time before the protection action that stops the power conversion action performed by the inverter (the first inverter 5a, the second inverter 5b) when an overvoltage occurs will be different, and the possibility of damage to the components due to the protection delay on the inverter side of one side will increase. In addition, the difference in the voltage fluctuation amount caused by the influence of noise will increase, and the possibility of erroneous detection of overvoltage abnormality and unnecessary operation stop will increase.

[0027] In order to suppress the influence of such a difference in wiring impedance, in the power conversion device 100 of the present embodiment, the first voltage detection circuit 8a and the second voltage detection circuit 8b are provided with filter circuits, and the time constants of the respective filter circuits (hereinafter referred to as filter time constants) are set separately. That is, by setting the filter time constants of the respective filter circuits to different values, the influence of the difference in wiring impedance between the converter 2 and the first inverter 5a and the wiring impedance between the converter 2 and the second inverter 5b is reduced.

[0028] Figure 3 1 is a diagram showing a configuration example of the first voltage detection circuit 8 a and the second voltage detection circuit 8 b constituting the power conversion device 100 according to the first embodiment.

[0029] The first voltage detection circuit 8a and the second voltage detection circuit 8b include: a resistor voltage divider circuit 81 for detecting the input voltage to the inverter (the first inverter 5a, the second inverter 5b); and an RC circuit 82 as a filter circuit. The RC circuit 82 is connected in parallel with the resistor with the resistance value R2 of the two resistors constituting the resistor voltage divider circuit 81. Figure 2 The wiring impedances Z1, Z2, Z3, and Z4 shown, the filtering time constant of the RC circuit 82 constituting the first voltage detection circuit 8a, and the filtering time constant of the RC circuit 82 constituting the second voltage detection circuit 8b are set to values ​​such that the difference in response time before the first drive signal generating unit 7a and the second drive signal generating unit 7b detect the abnormality when the abnormality occurs becomes small. The time constant T [sec] of the RC circuit 82 is determined by the product of the value R [Ω] of the resistor constituting the circuit and the value C [F] of the electrostatic capacitance of the capacitor constituting the circuit, so that the values ​​of the time constant T of each of the first voltage detection circuit 8a and the second voltage detection circuit 8b are different, thereby suppressing the influence of the difference in wiring impedance. Specifically, by setting the time constant T on the side with small wiring impedance to a value larger than that on the side with large wiring impedance, the detection responsiveness of the voltage abnormality on the side with large wiring impedance is suppressed from being reduced, and when the voltage change caused by noise occurs on the side with small wiring impedance, it is difficult to determine it as an overvoltage abnormality, thereby preventing malfunction.

[0030] In addition, the first voltage detection circuit 8a and the second voltage detection circuit 8b may also Figure 3 The resistor voltage divider circuit 81 shown is replaced with a known voltage sensor, and a voltage sensor and an RC circuit 82 are combined.

[0031] The first drive signal generating unit 7a and the second drive signal generating unit 7b may further include a voltage generator based on the input voltage V to the first inverter 5a. dc1 and the input voltage V to the second inverter 5b dc2 Both parties come to determine whether there is a fault function.

[0032] The following operation is described: The first drive signal generating unit 7a and the second drive signal generating unit 7b generate a signal based on the input voltage V dc1 and the input voltage V to the second inverter 5b dc2 Failures are detected by both, and the power conversion operation by the first inverter 5a and the second inverter 5b is stopped. Since the operation of the first drive signal generating unit 7a and the second drive signal generating unit 7b is the same, the operation of the first drive signal generating unit 7a will be described here.

[0033] Figure 4 This is a flowchart showing an example of the operation of the first drive signal generating unit 7a constituting the power conversion device 100 according to the first embodiment, and specifically shows an example of the operation of detecting a failure of the power conversion device 100 and stopping the power conversion operation by the first inverter 5a.

[0034] The first drive signal generating unit 7a starts generating a drive signal for the first inverter 5a (step S11), and outputs the generated drive signal to the first inverter 5a. After starting to generate the drive signal, the first drive signal generating unit 7a first obtains the first voltage detection value V from the first voltage detection circuit 8a. dc1 (Step 12). In addition, the first drive signal generating unit 7a generates the first voltage detection value V obtained in step S12. dc1 The first voltage detection value V obtained in step S12 is output to the second drive signal generating unit 7b (step S13). dc1 It is also used for the drive signal generation process of the first inverter 5a.

[0035] Next, the first drive signal generating unit 7a obtains the second voltage detection value V detected by the second voltage detecting circuit 8b from the second drive signal generating unit 7b. dc2 (Step S14) In addition, the processing of step S13 and the processing of step S14 may be switched in order.

[0036] Next, the first drive signal generating unit 7a confirms the first voltage detection value V dc1 and the second voltage detection value V dc2 Is the absolute value of the difference greater than the threshold V lim , that is, "V lim <|V dc1 -V dc2 |" is established (step S15). Threshold V lim is a threshold value for determining whether a fault has occurred in the power conversion device 100. When both the first inverter 5a and the second inverter 5b are operating normally, the first voltage detection value V dc1 and the second voltage detection value V dc2 However, when a fault occurs in one of the first inverter 5a and the second inverter 5b, the input voltage to the inverter on the abnormality side changes suddenly, and the first voltage detection value V dc1 and the second voltage detection value V dc2 Therefore, in step S15, by dc1 and the second voltage detection value V dc2 The absolute value of the difference between lim Compare to determine whether there is a fault.

[0037] The first drive signal generating unit 7a generates a first voltage detection value V dc1 and the second voltage detection value V dc2 The absolute value of the difference is the threshold V limIn the following case (step S15: No), the process returns to step S12, and the processes of step S12 to step S15 are repeated. In addition, the generation operation of the drive signal of the first inverter 5a is continued.

[0038] In addition, the first drive signal generating unit 7a generates a first voltage detection value V dc1 and the second voltage detection value V dc2 The absolute value of the difference is greater than the threshold V lim In the case of (step S15: Yes), the drive signal generation of the first inverter 5a is stopped (step S16), so that the power conversion operation based on the first inverter 5a is stopped. At this time, the first drive signal generating unit 7a controls so that all the switching elements constituting the first inverter 5a are in the off state.

[0039] In addition, Figure 4 In step S14 of the example shown, the first drive signal generating unit 7a obtains the second voltage detection value V from the second drive signal generating unit 7b. dc2 , but it can also be configured to directly obtain the second voltage detection value V from the second voltage detection circuit 8b dc2 .

[0040] In addition, as described above, the second drive signal generating unit 7b performs the same operation as the first drive signal generating unit 7a and detects a fault, thereby stopping the power conversion operation based on the second inverter 5b. However, the fault detection may be performed only by the first drive signal generating unit 7a or the second drive signal generating unit 7b. For example, when only the first drive signal generating unit 7a detects a fault, the fault detection may be omitted. Figure 4 In step S13 shown in FIG. 1 , when the first drive signal generating unit 7a detects a fault in step S15, that is, when it is determined that the first voltage detection value V dc1 and the second voltage detection value V dc2 The absolute value of the difference is greater than the threshold V lim When the second drive signal generating unit 7b receives the notification of the detection of the fault from the first drive signal generating unit 7a, the drive signal generation of the second inverter 5b is stopped, so that the power conversion operation based on the second inverter 5b is stopped.

[0041] As described above, the power conversion device 100 of the present embodiment includes: a converter 2 for rectifying AC power; a first inverter 5a and a second inverter 5b for converting DC power output from the converter 2 into AC power for driving a connected load; a first voltage detection circuit 8a for obtaining a first voltage detection value V as a voltage value of an input portion of the first inverter 5a. dc1The first drive signal generating unit 7a, based on the first voltage detection value V dc1 , generating a driving signal for the first inverter 5a, and stopping the operation of the first inverter 5a when a voltage abnormality is detected; the second voltage detection circuit 8b obtains the voltage value of the input part of the second inverter 5b, that is, the second voltage detection value V dc2 And a second drive signal generating unit 7b, based on the second voltage detection value V dc2 The first voltage detection circuit 8a generates a driving signal for the second inverter 5b, and stops the operation of the second inverter 5b when a voltage abnormality is detected. dc1 If the voltage is greater than the predetermined threshold, it is determined that the voltage is abnormal, and the second voltage detection circuit 8b determines that the voltage is abnormal. dc2 When the voltage is greater than the determined threshold, it is determined that the voltage is abnormal. In addition, the first voltage detection circuit 8a and the second voltage detection circuit 8b include a filter circuit for filtering the voltage detection value, and the time constants of each filter circuit are different. The time constant of the filter circuit of the first voltage detection circuit 8a and the time constant of the filter circuit of the second voltage detection circuit 8b are determined based on the wiring impedance between the converter 2 and the first inverter 5a and the wiring impedance between the converter 2 and the second inverter 5b.

[0042] The power conversion device 100 of this embodiment sets the time constants of the filter circuits of the first voltage detection circuit 8a and the second voltage detection circuit 8b to different values, thereby suppressing the influence of the difference in wiring impedance between the converter 2 and the first inverter 5a and the second inverter 5b, thereby achieving highly reliable operation.

[0043] In addition, although Figure 1 In the example shown, the AC power source 1 connected to the power conversion device 100 is set as a three-phase AC power source, but it can also be set as a single-phase AC power source. In addition, although the structure in which the reactor 3 (DC reactor) is provided on the DC bus connecting the converter 2 and the main circuit capacitor 4 is shown, an AC reactor can also be provided on the power supply wiring connecting the AC power source 1 and the converter 2. In addition, although the example in which the main circuit capacitor 4 is set as an electrolytic capacitor is described, the main circuit capacitor 4 can also be composed of a film capacitor.

[0044] Implementation method 2.

[0045] Figure 51 is a diagram showing a configuration example of a power conversion device 100a according to Embodiment 2. The power conversion device 100a includes a converter 2, a reactor 3, a main circuit capacitor 4, a first inverter 5a, a second inverter 5b, a first drive signal generating unit 7a, a second drive signal generating unit 7b, a first voltage detection circuit 8a, and a second voltage detection circuit 8b, similarly to the power conversion device 100 according to Embodiment 1, and converts the three-phase AC power output by the AC power source 1 to generate three-phase AC power for driving each of the first motor 6a and the second motor 6b.

[0046] The power conversion device 100a of embodiment 2 is different from the power conversion device 100 of embodiment 1 in that a first power conversion circuit including a first inverter 5a, a first drive signal generating unit 7a and a first voltage detection circuit 8a is installed on a first substrate 10a, and a second power conversion circuit including a second inverter 5b, a second drive signal generating unit 7b and a second voltage detection circuit 8b is installed on a second substrate 10b separated from the first substrate 10a.

[0047] In this way, by installing the power conversion circuits of two systems composed of peripheral circuits related to the inverter on different substrates respectively, the same effect as the power conversion device 100 of embodiment 1 can be obtained, and since the signals on each power conversion circuit will not interfere with each other, it is possible to prevent malfunction of the power conversion circuits installed on each substrate, thereby further improving the reliability of the operation.

[0048] Implementation method 3.

[0049] In this embodiment, a device to which each power conversion device described in Embodiments 1 and 2 is applied will be described. As an example, an air conditioning device realized by applying the power conversion device 100 described in Embodiment 1 will be described.

[0050] Figure 6 1 is a diagram showing a configuration example of an air conditioner 200 according to Embodiment 3. The air conditioner 200 according to Embodiment 3 includes the power conversion device 100 described in Embodiment 1. The power conversion device 100 is connected to an AC power supply 1. The power conversion device 100 may be replaced with the power conversion device 100a described in Embodiment 2.

[0051] In addition, the air conditioning device 200 includes: a compressor motor 6c and a compression element 61 constituting a compressor 60, a fan motor 6d for rotating a fan 62, a four-way valve 121 constituting a refrigeration cycle 110 together with the compression element 61, a heat source side heat exchanger 122, an expansion device 131, and a load side heat exchanger 132. The power conversion device 100, the compressor 60, the fan motor 6d, the fan 62, the four-way valve 121, and the heat source side heat exchanger 122 are provided in the outdoor unit 120 of the air conditioning device 200. The expansion device 131 and the load side heat exchanger 132 are provided in the indoor unit 130 of the air conditioning device 200. For example, the compressor motor 6c is equivalent to Figure 1 The first motor 6a and the fan motor 6d are shown relative to Figure 1 The second motor 6b shown in FIG. 1 is a schematic diagram of a refrigeration cycle 110. Figure 6 The structure shown. Figure 6 A well-known structural example is shown in FIG.

[0052] In the power conversion device 100 applied to the air conditioner 200, the time constant of the filter included in the voltage detection circuit for detecting the input voltage of the inverter connected to the fan motor 6d is set to be larger than the time constant of the filter included in the voltage detection circuit for detecting the input voltage of the inverter connected to the compressor motor 6c. In addition, the first drive signal generating unit 7a and the second drive signal generating unit 7b use the same threshold value to detect the overvoltage abnormality.

[0053] With such a configuration, in the air conditioning device 200, when the transient change amounts of the input voltages of the respective inverters are the same when the power conversion devices 100 and 100a are abnormal, the operation of the first inverter 5a on the compressor 60 side having a small filter time constant is stopped first. Therefore, the overvoltage abnormality protection operation is performed, and even if the operation of the first inverter 5a driven by the compressor motor 6c is stopped, the operation of the second inverter 5b driven by the fan motor 6d continues, and the rotation of the fan motor 6d also continues. Therefore, even if the compressor 60 stops, the power conversion devices 100 and 100a are continuously cooled by the wind generated by the fan 62, and the electronic components such as the switching element constituting the first inverter 5a can be protected.

[0054] In addition, the air conditioning device 200 of the present embodiment can reduce the risk of abnormal stop of the air conditioning operation of the air conditioning device 200 due to malfunction of the protection operation in the power conversion device 100 or 100a, and can improve the comfort of the user.

[0055] Implementation method 4.

[0056] In the power conversion devices 100 and 100a of the air-conditioning device 200 of embodiment 3, the influence of the difference in wiring impedance between the converter 2 and the first inverter 5a and the second inverter 5b can be absorbed by setting the time constants of the filter circuits respectively provided in the first voltage detection circuit 8a and the second voltage detection circuit 8b to different values, but other methods can also be used to absorb the influence.

[0057] For example, the threshold values ​​used by the first drive signal generating unit 7a and the second drive signal generating unit 7b for determining the overvoltage anomaly may be set to be different to absorb the influence of the difference in wiring impedance. In this case, the time constant of the filter circuit of the first voltage detection circuit 8a and the time constant of the filter circuit of the second voltage detection circuit 8b may be set to be the same or different. That is, the influence of the difference in wiring impedance between the converter 2 and the first inverter 5a and the second inverter 5b may be absorbed by setting at least one of the time constant of the filter circuit of each voltage detection circuit and the threshold value used by each drive signal generating unit for determining the overvoltage anomaly to be different.

[0058] While absorbing the influence of the difference in wiring impedance between the converter 2 and the first inverter 5a and the second inverter 5b by setting different thresholds for determining overvoltage abnormalities in the first drive signal generating unit 7a and the second drive signal generating unit 7b, the threshold used for determining overvoltage abnormalities in the drive signal generating unit that generates a drive signal for the inverter connected to the fan motor 6d is set to be larger than the threshold used for determining overvoltage abnormalities in the drive signal generating unit that generates a drive signal for the inverter connected to the compressor motor 6c.

[0059] The threshold value used by each drive signal generating unit (first drive signal generating unit 7a, second drive signal generating unit 7b) for determining an overvoltage abnormality is determined based on the wiring impedance between the converter 2 and the first inverter 5a and the second inverter 5b.

[0060] Although the following case is described in the present embodiment: the influence of each wiring impedance from the converter 2 to the input part of each inverter on the operating characteristics is reduced by adjusting at least one of the time constant of the filter circuit of each voltage detection circuit and the threshold value used by each drive signal generation unit for judging the overvoltage abnormality, based on the premise that the power conversion device 100 and 100a described in Embodiments 1 and 2 are applied to the air conditioner, the present invention is not limited to this. Similarly, when the power conversion device 100 and 100a are applied to other devices (devices other than air conditioners), the influence of the wiring impedance on the operating characteristics can be reduced by adjusting at least one of the time constant of the filter circuit of each voltage detection circuit and the threshold value used by each drive signal generation unit for judging the overvoltage abnormality.

[0061] The configuration described in the above embodiment is merely an example, and may be combined with other known techniques, the embodiments may be combined with each other, and a part of the configuration may be omitted or modified without departing from the gist.

[0062] Description of Reference Numerals

[0063] 1...AC power supply; 2...converter; 3...reactor; 4...main circuit capacitor; 5a...first inverter; 5b...second inverter; 6a...first motor; 6b...second motor; 6c...compressor motor; 6d...fan motor; 7a...first drive signal generating unit; 7b...second drive signal generating unit; 8a...first voltage detection circuit; 8b...second voltage detection circuit; 10a...first substrate; 10b...second substrate; 60...compressor; 61...compression element; 62...fan; 81...resistance voltage divider circuit; 82...RC circuit; 100, 100a...power conversion device; 110...refrigeration cycle; 120...outdoor unit; 121...four-way valve; 122...heat source side heat exchanger; 130...indoor unit; 131...expansion device; 132...load side heat exchanger; 200...air conditioning device.

Claims

1. A power conversion device, characterized in that: have: a converter that rectifies AC power supplied from an AC power source; a first inverter and a second inverter connected to both ends of a main circuit capacitor for smoothing the DC power output from the converter; a first voltage detection circuit, which detects a voltage input to the first inverter, filters the detection value and outputs it as a first voltage detection value; a second voltage detection circuit, which detects the voltage input to the second inverter, filters the detection value and outputs it as a second voltage detection value; a first drive signal generating unit that generates a drive signal for the first inverter and performs a protection action for the first inverter when an abnormality occurs based on the first voltage detection value; as well as a second drive signal generating unit that generates a drive signal for the second inverter and performs a protection action for the second inverter when an abnormality occurs based on the second voltage detection value; At least one of the time constant of the filter circuit that performs the filtering in each of the first voltage detection circuit and the second voltage detection circuit, and the threshold used in the abnormality detection processing of each of the first drive signal generating unit and the second drive signal generating unit are set based on the wiring impedance between the converter and each of the first inverter and the second inverter.

2. The power conversion device according to claim 1, characterized in that: The first drive signal generating unit and the second drive signal generating unit also have a function of detecting abnormalities of the first inverter and the second inverter based on the difference between the first voltage detection value and the second voltage detection value, and when an abnormality is detected based on the difference, the operation of the first inverter and the second inverter is stopped.

3. The power conversion device according to claim 1 or 2, characterized in that: The first voltage detection circuit, the first drive signal generation unit, and the first inverter are mounted on a first substrate, and the second voltage detection circuit, the second drive signal generation unit, and the second inverter are mounted on a second substrate different from the first substrate.

4. The power conversion device according to any one of claims 1 to 3, characterized in that: When the time constant of the filter circuit included in each of the first voltage detection circuit and the second voltage detection circuit is set based on the wiring impedance, When the wiring impedance between the converter and the first inverter is greater than the wiring impedance between the converter and the second inverter, the time constant of the filter circuit of the first voltage detection circuit is set to be smaller than the time constant of the filter circuit of the second voltage detection circuit; when the wiring impedance between the converter and the first inverter is smaller than the wiring impedance between the converter and the second inverter, the time constant of the filter circuit of the first voltage detection circuit is set to be larger than the time constant of the filter circuit of the second voltage detection circuit.

5. The power conversion device according to any one of claims 1 to 4, characterized in that: When the thresholds used in the abnormality detection process of each of the first drive signal generating unit and the second drive signal generating unit are set based on the wiring impedance, When the wiring impedance between the converter and the first inverter is greater than the wiring impedance between the converter and the second inverter, the threshold used in the abnormality detection processing of the first drive signal generating unit is set to be smaller than the threshold used in the abnormality detection processing of the second drive signal generating unit. When the wiring impedance between the converter and the first inverter is smaller than the wiring impedance between the converter and the second inverter, the threshold used in the abnormality detection processing of the first drive signal generating unit is set to be larger than the threshold used in the abnormality detection processing of the second drive signal generating unit.

6. An air conditioning device comprising the power conversion device according to any one of claims 1 to 3, characterized in that: The first inverter drives a compressor motor provided in the compressor, and the second inverter drives a fan motor for rotating a fan, and the time constant of the filter circuit of the second voltage detection circuit is set to be greater than the time constant of the filter circuit of the first voltage detection circuit.

7. An air conditioning device comprising the power conversion device according to any one of claims 1 to 3, characterized in that: The first inverter drives a compressor motor provided in the compressor, and the second inverter drives a fan motor for rotating the fan, and a threshold used in an abnormality detection process of the second drive signal generating unit is set to be larger than a threshold used in an abnormality detection process of the first drive signal generating unit.

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