Power conversion device and air-conditioning device

Abstract

A power conversion device (100) comprises a converter (2) that rectifies alternating-current power, a first inverter (5a) and a second inverter (5b), a first voltage detection circuit (8a) that filters a detection value for the input voltage to the first inverter and outputs the detection value as a first voltage detection value, a second voltage detection circuit (8b) that filters a detection value for the input voltage to the second inverter and outputs the 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 for the second inverter on the basis of the second voltage detection value. At least one of a time constant for a filter circuit that performs filtering and a threshold value used for abnormality detection processing is set on the basis of the wiring impedance between the converter and each of the first inverter and the second inverter.

Description

Power conversion device and air conditioning device

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

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

[0003] For example, Patent Document 1 discloses a power conversion device (motor drive circuit) in which two inverters, a first inverter and a second inverter, are connected to a rectifier circuit that rectifies the AC voltage of an AC power supply, and the inverters generate drive voltages that drive a fan motor and a compressor motor, respectively.

[0004] Japanese Patent Application Laid-Open No. 2020-61913

[0005] In the circuit configuration disclosed in Patent Document 1, the two inverters are connected to a common bus, so ideally, the input voltages of the two inverters are the same. However, if there is a difference in the distance between the input bus and each inverter, the wiring impedance to each inverter will also differ. This becomes particularly true when the bus distance from the converter (rectifier circuit) to the inverter is long due to layout constraints within the device. Furthermore, the difference in wiring impedance becomes greater when the distance to one inverter is longer than the distance to the other inverter. For example, when a motor drive circuit, which is a power conversion device as described in Patent Document 1, is applied to an air conditioner, the difference in wiring impedance between the electrical path supplying power to the compressor motor in the outdoor unit and the electrical path supplying power to the fan motor in the indoor unit may become large.

[0006] High wiring impedance can cause bus voltage fluctuations, such as transient surges caused by sudden changes in power supply voltage or current due to sudden changes in motor load on one side. The higher the wiring impedance, the greater the transient voltage fluctuations and the higher the risk of overvoltage. Therefore, to protect the inverter, high overvoltage detection responsiveness is required. That is, early detection of overvoltage occurrences and prompt activation of the protection circuit (protection function) are required. On the other hand, when wiring impedance is low, the influence of surrounding noise is greater than the influence of bus voltage fluctuations due to wiring impedance. This can lead to concerns about false voltage detection due to noise affecting motor control and false overvoltage detection. Therefore, when there is a large difference in wiring impedance between the converter and each inverter, attempting to improve overvoltage detection responsiveness without considering the difference in wiring impedance increases the risk of malfunction due to noise on the side with lower wiring impedance, such as the activation of the protection function, causing an operation shutdown. Furthermore, if attempts are made to suppress malfunctions due to noise without taking differences in wiring impedance into consideration, the response to overvoltage detection will decrease, and on the side with high wiring impedance where protection against overvoltage is important, the protection function will be delayed, increasing the risk of device failure.

[0007] It is necessary to reduce the influence of differences in wiring impedance caused by differences in the distance from the converter to each inverter, which arises due to restrictions on the layout within the device.

[0008] The present disclosure has been made in consideration of the above, and aims to obtain a power conversion device that can achieve highly reliable operation by suppressing the influence of the difference in wiring impedance between the converter and each of the two inverters.

[0009] In order to solve the above-mentioned problems and achieve the object, the power conversion device according to the present disclosure includes 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 that smoothes DC power output by the converter, a first voltage detection circuit that detects an input voltage to the first inverter, filters the detected value, and outputs it as a first voltage detection value, a second voltage detection circuit that detects an input voltage to the second inverter, filters the detected value, and outputs it as a second voltage detection value, and a drive signal generation operation for the first inverter based on the first voltage detection value, and The converter includes a first drive signal generating unit that performs a protective operation for the first inverter when an abnormality occurs, and a second drive signal generating unit that performs a drive signal generating operation for the second inverter and a protective operation for the second inverter when an abnormality occurs based on a second voltage detection value, and at least one of the time constants of the filter circuits that perform filtering in each of the first voltage detection circuit and the second voltage detection circuit, and the threshold values ​​used in the abnormality detection processing in 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.

[0010] The power conversion device according to the present disclosure has an advantage in that it is possible to suppress the influence of the difference in wiring impedance between the converter and each of the two inverters, thereby realizing highly reliable operation.

[0011] FIG. 1 is a diagram showing a configuration example of a power conversion device according to a first embodiment; FIG. 2 is a diagram showing a schematic diagram of wiring impedance of the power conversion device according to the first embodiment; FIG. 3 is a diagram showing a configuration example of a first voltage detection circuit and a second voltage detection circuit that constitute the power conversion device according to the first embodiment;

[0012] A power conversion device and an air conditioner according to an embodiment of the present disclosure will be described in detail below with reference to the drawings.

[0013] 1 is a diagram showing an example of the configuration 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 generator 7a, a second drive signal generator 7b, a first voltage detection circuit 8a, and a second voltage detection circuit 8b.

[0014] The converter 2 is connected to the AC power source 1 and rectifies and outputs three-phase AC power supplied from the AC power source 1. The converter 2 may be a passive converter using a diode bridge, or may be 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. 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 terminal of the first inverter 5a, and a second motor 6b is connected to the output terminal of the second inverter 5b.

[0015] The reactor 3 and the main circuit capacitor 4 suppress harmonics and smooth the DC power output from the converter 2. The voltage across the main circuit capacitor 4 is V dc0 The first inverter 5a converts 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 DC-to-AC power conversion operation in accordance with a drive signal input from a first drive signal generator 7a (described later). The second inverter 5b converts 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 DC-to-AC power conversion operation in accordance with a drive signal input from a second drive signal generator 7b (described later).

[0016] The first drive signal generator 7a detects the input voltage V to the first inverter 5a detected by the first voltage detector 8a.dc1 The second drive signal generator 7b generates a drive signal for controlling the power conversion operation of the first inverter 5a based on the input voltage V to the second inverter 5b detected by the second voltage detector 8b and an external voltage command (not shown) and outputs the drive signal to the first inverter 5a. dc2 and an externally input voltage command (not shown), the first drive signal generator 7a generates a drive signal for controlling the power conversion operation of the second inverter 5b and outputs it to the second inverter 5b. The drive signals are generated by the first drive signal generator 7a and the second drive signal generator 7b using a known general drive signal generation method. The first drive signal generator 7a and the second drive signal generator 7b are realized by, for example, a microcontroller. The first drive signal generator 7a and the second drive signal generator 7b may be realized by a single microcontroller, or each may be realized by a separate microcontroller.

[0017] The first voltage detection circuit 8a detects the voltage at the input of the first inverter 5a and converts the detected input voltage V dc1 The second voltage detection circuit 8b detects the voltage at the input of the second inverter 5b and outputs the detected input voltage V dc2 The second drive signal generator 7b transmits a signal according to the received signal to the second drive signal generator 7b.

[0018] Furthermore, the first drive signal generating unit 7a and the second drive signal generating unit 7b have a function of stopping the power conversion operation by the first inverter 5a and the second inverter 5b when the power conversion device 100 fails or is in a state where a failure is likely to occur. For example, the first drive signal generating unit 7a detects the input voltage V dc1 is greater than the predetermined threshold, the second drive signal generator 7b determines that an excessive voltage is being applied to the first inverter 5a, and stops the power conversion operation of the first inverter 5a. dc2is greater than a predetermined threshold, it is determined that an overvoltage abnormality has occurred, that is, an excessive voltage is being applied to the second inverter 5b, and the power conversion operation by the second inverter 5b is stopped.

[0019] Here, wiring impedances as shown in FIG. 2 exist between the converter 2 and the first inverter 5a of the power conversion device 100, and between the converter 2 and the second inverter 5b. FIG. 2 is a diagram schematically illustrating the wiring impedances of the power conversion device 100 according to the first embodiment. In FIG. 2, the wiring impedance from the main circuit capacitor 4 to the positive input terminal of the first inverter 5a is represented by Z1, the wiring impedance from the main circuit capacitor 4 to the negative input terminal of the first inverter 5a is represented by Z2, the wiring impedance from the main circuit capacitor 4 to the positive input terminal of the second inverter 5b is represented by Z3, and the wiring impedance from the main circuit capacitor 4 to the negative input terminal of the second inverter 5b is represented by Z4. The wiring impedances Z1 to Z4 are made up of minute resistance components and reactance components present on the wiring. The wiring impedances Z1 to Z4 are expressed by V dc0 and V dc1 The cause of the potential difference between dc0 and V dc2 This causes a potential difference between the first and second voltage detection circuits 8a and 8b, and voltage fluctuations during transients. Note that 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 are not shown in FIG.

[0020] 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 becomes large, a difference will occur in the response time until the start of protective operation to stop the power conversion operation of the inverters (first inverter 5a, second inverter 5b) when an overvoltage occurs, increasing the possibility that the protection on one inverter side will be delayed and the elements will be destroyed.In addition, the difference in the amount of voltage fluctuation due to the influence of noise will become large, increasing the possibility that an overvoltage abnormality will be falsely detected and unnecessary operation will be stopped.

[0021] To suppress the influence of such a difference in wiring impedance, in the power conversion device 100 according to this 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 individually. In other words, by setting the filter time constants of the respective filter circuits to different values, the influence of the difference between 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 is reduced.

[0022] FIG. 3 is a diagram illustrating an example of the configuration of the first voltage detection circuit 8a and the second voltage detection circuit 8b that constitute the power conversion device 100 according to the first embodiment.

[0023] The first voltage detection circuit 8a and the second voltage detection circuit 8b each include a resistive voltage divider circuit 81 for detecting the input voltage to the inverters (first inverter 5a, second inverter 5b) and an RC circuit 82 serving as a filter circuit. The RC circuit 82 is connected in parallel with the resistor having a resistance value R2, one of the two resistors constituting the resistive voltage divider circuit 81. The filter time constants of the RC circuits 82 constituting the first voltage detection circuit 8a and the second voltage detection circuit 8b are set based on the wiring impedances Z1, Z2, Z3, and Z4 shown in FIG. 2 to values ​​that minimize the difference in response time between the first drive signal generation unit 7a and the second drive signal generation unit 7b when an abnormality occurs and the time it takes them to detect the abnormality. Since the time constant T [sec] of the RC circuit 82 is determined by the product of the resistance value R [Ω] of the circuit and the capacitance value C [F] of the capacitor that constitutes the circuit, the influence of differences in wiring impedance is suppressed by making the time constant T of the first voltage detection circuit 8a and the second voltage detection circuit 8b different. Specifically, by making the time constant T on the side with lower wiring impedance larger than that on the side with higher wiring impedance, a decrease in the detection response of an overvoltage anomaly on the side with higher wiring impedance is prevented, while making it more difficult to determine an overvoltage anomaly when a voltage fluctuation due to noise occurs on the side with lower wiring impedance, thereby preventing malfunction.

[0024] The first voltage detection circuit 8a and the second voltage detection circuit 8b may have a configuration in which the resistive voltage divider circuit 81 shown in FIG. 3 is replaced with a known voltage sensor, and the voltage sensor is combined with an RC circuit 82.

[0025] The first drive signal generator 7a and the second drive signal generator 7b generate an input voltage V dc1 and the input voltage V to the second inverter 5b dc2 The device may further include a function for determining whether or not there is a malfunction based on both of the above.

[0026] The first drive signal generator 7a and the second drive signal generator 7b generate an input voltage V dc1 and the input voltage V to the second inverter 5b dc2 The operation of the first drive signal generator 7a and the second drive signal generator 7b is similar to that of the first drive signal generator 7a, and therefore the operation of the first drive signal generator 7a will be described here.

[0027] FIG. 4 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, specifically showing an example of the operation of detecting a fault in the power conversion device 100 and stopping the power conversion operation by the first inverter 5a.

[0028] The first drive signal generator 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 generator 7a first receives the first voltage detection value V dc1 (Step S12). The first drive signal generator 7a also obtains the first detected voltage value V dc1 The first voltage detection value V obtained in step S12 is output to the second drive signal generator 7b (step S13). dc1 is also used in the process of generating the drive signal for the first inverter 5a.

[0029] Next, the first drive signal generator 7a receives the second voltage detection value V detected by the second voltage detection circuit 8b from the second drive signal generator 7b. dc2 (Step S14). The order of the processing in Step S13 and the processing in Step S14 may be reversed.

[0030] Next, the first drive signal generator 7a calculates the first detected voltage value V dc1 and the second voltage detection value V dc2 The absolute value of the difference between lim Whether it is greater than "V lim < | V dc1 -V dc2 It is checked whether the condition "|" holds (step S15). 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, if a failure occurs in one of the first inverter 5a and the second inverter 5b, the input voltage to the inverter on the side where the abnormality occurs changes suddenly, and the first voltage detection value V dc1 and the second voltage detection value V dc2 Therefore, in step S15, the first voltage detection value V dc1 and the second voltage detection value V dc2 The absolute value of the difference between lim By comparing with this, it is possible to determine whether or not there is a fault.

[0031] The first drive signal generator 7a generates a first detected voltage value V dc1 and the second voltage detection value V dc2 The absolute value of the difference between lim In the following cases (step S15: No), the process returns to step S12, and the processes of steps S12 to S15 are repeated, and the operation of generating the drive signal for the first inverter 5a is continued.

[0032] The first drive signal generator 7a also generates a first detected voltage value V dc1 and the second voltage detection value V dc2 The absolute value of the difference betweenlim (Step S15: Yes), the first drive signal generator 7a stops generating the drive signal for the first inverter 5a (Step S16), thereby stopping the power conversion operation of the first inverter 5a. At this time, the first drive signal generator 7a controls all switching elements of the first inverter 5a to be in the OFF state.

[0033] In step S14 of the example shown in FIG. 4, the first drive signal generator 7a receives the second detected voltage value V dc2 However, the second voltage detection value V dc2 Alternatively, the voltage detection circuit 8b may be configured to directly acquire the voltage.

[0034] As described above, the second drive signal generating unit 7b detects a fault by performing the same operation as the first drive signal generating unit 7a and stops the power conversion operation of the second inverter 5b, but 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, if only the first drive signal generating unit 7a detects a fault, step S13 shown in FIG. 4 is omitted, and the first drive signal generating unit 7a, upon detecting a fault in step S15, stops the first voltage detection value V dc1 and the second voltage detection value V dc2 The absolute value of the difference between lim If it is determined that the difference is greater than 1, the second drive signal generator 7b notifies the second drive signal generator 7b of the detection of a fault and executes step S16. Upon receiving the notification of the detection of a fault from the first drive signal generator 7a, the second drive signal generator 7b stops generating the drive signal for the second inverter 5b, thereby stopping the power conversion operation by the second inverter 5b.

[0035] As described above, the power conversion device 100 according to this embodiment includes the converter 2 that rectifies AC power, the first inverter 5 a and the second inverter 5 b that convert the DC power output from the converter 2 into AC power for driving a load connected thereto, and the first voltage detection value V dc1 a first voltage detection circuit 8a that acquires a first voltage detection value V dc1a first drive signal generator 7a that generates a drive signal for the first inverter 5a based on the detected voltage V and stops the operation of the first inverter 5a when a voltage abnormality is detected; and a second voltage detection value V dc2 a second voltage detection circuit 8b that acquires a second voltage detection value V dc2 and a second drive signal generator 7b that generates a drive signal for the second inverter 5b based on the first voltage detection value V and stops the operation of the second inverter 5b when a voltage abnormality is detected. dc1 is greater than a predetermined threshold, the second voltage detection circuit 8b determines that a voltage abnormality has occurred, and the second voltage detection value V dc2 is greater than a predetermined threshold, a voltage abnormality is determined. The first voltage detection circuit 8a and the second voltage detection circuit 8b each include a filter circuit that filters the detected voltage value, and each filter circuit has a different time constant. The time constant of the filter circuit in the first voltage detection circuit 8a and the time constant of the filter circuit in 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.

[0036] The power conversion device 100 according to this embodiment can achieve highly reliable operation by suppressing the influence of the difference in wiring impedance between the converter 2 and each of the first inverter 5a and the second inverter 5b, by setting the time constants of the filter circuits of the first voltage detection circuit 8a and the second voltage detection circuit 8b to different values.

[0037] 1, the AC power supply 1 to which the power conversion device 100 is connected is a three-phase AC power supply, but it may also be a single-phase AC power supply. Also, although the configuration 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 may also be provided on the power supply wiring connecting the AC power supply 1 and the converter 2. Also, although the example in which the main circuit capacitor 4 is an electrolytic capacitor has been described, the main circuit capacitor 4 may also be a film capacitor.

[0038] 5 is a diagram showing a configuration example of a power conversion device 100a according to embodiment 2. Like the power conversion device 100 according to embodiment 1, 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 generation unit 7a, a second drive signal generation unit 7b, a first voltage detection circuit 8a, and a second voltage detection circuit 8b, and converts three-phase AC power output from an AC power supply 1 to generate three-phase AC power for driving a first motor 6a and a second motor 6b.

[0039] The power conversion device 100a according to the second embodiment differs from the power conversion device 100 according to the first embodiment 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 mounted 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 mounted on a second substrate 10b separate from the first substrate 10a.

[0040] In this way, by mounting two systems of power conversion circuits consisting of an inverter and related peripheral circuits on separate boards, the same effect as that of the power conversion device 100 of embodiment 1 can be obtained, and further, since there is no interference between the signals on each power conversion circuit, malfunctions of the power conversion circuits mounted on each board can be prevented, further improving operational reliability.

[0041] Embodiment 3 In this embodiment, an apparatus to which the power conversion devices described in Embodiments 1 and 2 are applied will be described. As an example, an air conditioning apparatus realized by applying the power conversion device 100 described in Embodiment 1 will be described.

[0042] 6 is a diagram showing a configuration example of an air conditioning apparatus 200 according to embodiment 3. The air conditioning apparatus 200 according to embodiment 3 includes the power conversion apparatus 100 described in embodiment 1. The power conversion apparatus 100 is connected to an AC power supply 1. Note that the power conversion apparatus 100 may be replaced with the power conversion apparatus 100a described in embodiment 2.

[0043] The air conditioning apparatus 200 also includes a compressor motor 6c and a compression element 61 that constitute the compressor 60, a fan motor 6d that rotates the fan 62, and a four-way valve 121, a heat source-side heat exchanger 122, an expansion device 131, and a load-side heat exchanger 132 that, together with the compression element 61, constitute the refrigeration cycle 110. The power conversion apparatus 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 an outdoor unit 120 of the air conditioning apparatus 200. The expansion device 131 and the load-side heat exchanger 132 are provided in an indoor unit 130 of the air conditioning apparatus 200. For example, the compressor motor 6c corresponds to the first motor 6a shown in FIG. 1 , and the fan motor 6d corresponds to the second motor 6b shown in FIG. 1 . The configuration of the refrigeration cycle 110 is not limited to that shown in FIG. 6 . FIG. 6 illustrates a well-known configuration example.

[0044] In the power conversion device 100 applied to the air conditioning device 200, the time constant of the filter provided in the voltage detection circuit that detects the input voltage of the inverter connected to the fan motor 6d is set to be larger than the time constant of the filter provided in the voltage detection circuit that detects the input voltage of the inverter connected to the compressor motor 6c. Furthermore, the first drive signal generation unit 7a and the second drive signal generation unit 7b detect overvoltage abnormalities using the same threshold value.

[0045] With this configuration, in the air conditioning apparatus 200, if the transient change in the input voltage of each inverter during an abnormality in the power conversion devices 100, 100a is the same, the operation of the first inverter 5a on the compressor 60 side, which has a smaller filter time constant, will stop first. Therefore, even if the overvoltage abnormality protection operation is performed and the operation of the first inverter 5a driving the compressor motor 6c stops, the operation of the second inverter 5b driving the fan motor 6d will continue, and the rotation of the fan motor 6d will also continue. Therefore, even if the compressor 60 stops, the power conversion devices 100, 100a can continue to be cooled by the wind generated by the fan 62, and electronic components such as switching elements that constitute the first inverter 5a can be protected.

[0046] Furthermore, the air conditioning device 200 according to this embodiment can reduce the risk of the air conditioning operation by the air conditioning device 200 abnormally stopping due to a malfunction of the protection operation in the power conversion device 100 or 100a, thereby improving user comfort.

[0047] Fourth Embodiment In the power conversion devices 100 and 100a of the air conditioning device 200 according to the third embodiment, the influence of the difference in wiring impedance between the converter 2 and the first inverter 5a and the second inverter 5b is absorbed by setting the time constants of the filter circuits included in the first voltage detection circuit 8a and the second voltage detection circuit 8b to different values, but other methods may also be used to absorb the influence.

[0048] For example, the first drive signal generator 7 a and the second drive signal generator 7 b may use different threshold values ​​to determine whether an overvoltage abnormality has occurred, thereby absorbing the influence of differences in wiring impedance. In this case, the time constant of the filter circuit included in the first voltage detection circuit 8 a and the time constant of the filter circuit included in the second voltage detection circuit 8 b may be set to the same value or different values. That is, the influence of differences in wiring impedance between the converter 2 and the first inverter 5 a and the second inverter 5 b may be absorbed by setting different values ​​for at least one of the time constants of the filter circuits included in each voltage detection circuit and the threshold values ​​used by each drive signal generator to determine whether an overvoltage abnormality has occurred.

[0049] When the influence of the difference in wiring impedance between the converter 2 and the first inverter 5a and the second inverter 5b is absorbed by setting different threshold values ​​used by the first drive signal generating unit 7a and the second drive signal generating unit 7b to determine overvoltage abnormalities, the threshold value used to determine overvoltage abnormalities in the drive signal generating unit that generates the drive signal for the inverter to which the fan motor 6d is connected is set to be larger than the threshold value used to determine overvoltage abnormalities in the drive signal generating unit that generates the drive signal for the inverter to which the compressor motor 6c is connected.

[0050] The threshold value used by each drive signal generating unit (first drive signal generating unit 7a, second drive signal generating unit 7b) to determine overvoltage abnormalities is determined based on the wiring impedance between the converter 2 and the first inverter 5a and second inverter 5b.

[0051] In the present embodiment, it is assumed that the power conversion devices 100 and 100a described in the first and second embodiments are applied to an air conditioner, and the influence of the wiring impedances from the converter 2 to the inputs of the inverters on the operating characteristics is reduced by adjusting at least one of the time constants of the filter circuits in each voltage detection circuit and the thresholds used by each drive signal generation unit to determine whether an overvoltage abnormality has occurred, but this is not limiting. Similarly, when the power conversion devices 100 and 100a are applied to other devices (devices other than air conditioners), the influence of the wiring impedances on the operating characteristics can be reduced by adjusting at least one of the time constants of the filter circuits in each voltage detection circuit and the thresholds used by each drive signal generation unit to determine whether an overvoltage abnormality has occurred.

[0052] The configurations shown in the above embodiments are merely examples, and may be combined with other known technologies, or different embodiments may be combined with each other. It is also possible to omit or modify parts of the configurations as long as they do not deviate from the gist of the invention.

[0053] 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 board, 10b Second board, 60 Compressor, 61 Compression element, 62 Fan, 81 Resistive 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 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 that smoothes the DC power output by the converter; a first voltage detection circuit that detects an input voltage to the first inverter, filters the detected value, and outputs the detected value as a first voltage detection value; a second voltage detection circuit that detects an input voltage to the second inverter, filters the detected value, and outputs the filtered value as a second voltage detection value; a first drive signal generating unit that generates a drive signal for the first inverter based on the first voltage detection value and performs a protection operation for the first inverter when an abnormality occurs; a second drive signal generating unit that generates a drive signal for the second inverter based on the second voltage detection value and performs a protection operation for the second inverter when an abnormality occurs; Equipped with A power conversion device in which at least one of the time constants of filter circuits that perform the filtering in each of the first voltage detection circuit and the second voltage detection circuit, and the threshold values ​​used in the abnormality detection processing in each 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.

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

3. 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; The power conversion device according to claim 1 .

4. When the time constants of the filter circuits included in the first voltage detection circuit and the second voltage detection circuit are set based on the wiring impedance, when a wiring impedance between the converter and the first inverter is larger than a wiring impedance between the converter and the second inverter, a time constant of a filter circuit included in the first voltage detection circuit is set to be smaller than a time constant of a filter circuit included in the second voltage detection circuit, and when a wiring impedance between the converter and the first inverter is smaller than a wiring impedance between the converter and the second inverter, a time constant of the filter circuit included in the first voltage detection circuit is set to be larger than a time constant of a filter circuit included in the second voltage detection circuit. The power conversion device according to claim 1 .

5. In a case where a threshold value used in the abnormality detection process in each of the first drive signal generation unit and the second drive signal generation unit is set based on the wiring impedance, when a wiring impedance between the converter and the first inverter is larger than a wiring impedance between the converter and the second inverter, a threshold value used in the abnormality detection process in the first drive signal generation unit is set to be smaller than a threshold value used in the abnormality detection process in the second drive signal generation unit, and when a wiring impedance between the converter and the first inverter is smaller than a wiring impedance between the converter and the second inverter, a threshold value used in the abnormality detection process in the first drive signal generation unit is set to be larger than a threshold value used in the abnormality detection process in the second drive signal generation unit.

5. The power conversion device according to claim 1.

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

7. An air conditioning apparatus comprising the power conversion device according to any one of claims 1 to 3, An air conditioning apparatus in which the first inverter drives a compressor motor provided in a compressor, the second inverter drives a fan motor that rotates a fan, and a threshold value used in the abnormality detection processing in the second drive signal generation unit is set to be greater than the threshold value used in the abnormality detection processing in the first drive signal generation unit.