Power conversion system and air conditioner

Abstract

This power conversion system comprises: a plurality of substrates on which respective power conversion circuits electrically connected to an AC power supply line at a branch point are mounted; a detection unit that collectively detects common mode noise generated by the plurality of power conversion circuits; and generation units that generate a cancel signal to be output to the power supply line or a ground line on the basis of a level of the common mode noise detected by the detection unit. The number of the generation units is smaller than the number of the substrates.

Description

Power Conversion System and Air Conditioning Apparatus

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

[0002] Conventionally, a noise reduction device in a power conversion device that converts power based on on / off of a switching element is known. This noise reduction device includes noise detection means for detecting a common mode noise current, and a noise compensation current supply circuit that forms a noise compensation current in the opposite direction to the noise current in response to the noise current detected by the noise detection means and supplies this noise compensation current to a line through which the noise current of the power conversion device flows.

[0003] Japanese Patent Application Laid-Open No. 9-266677

[0004] However, in the conventional technology, in the case of a power conversion system including a plurality of power conversion circuits that convert power, the same number of noise compensation current supply circuits as the number of power conversion circuits is required, so it is difficult to miniaturize the power conversion system.

[0005] An object of the present disclosure is to miniaturize a power conversion system.

[0006] A first aspect includes: a plurality of substrates each mounting a power conversion circuit electrically connected at a branch point to an AC power line; a detection unit that collectively detects common mode noise generated by the plurality of power conversion circuits; and a generation unit that generates a cancellation signal output to the power line or the ground line based on the level of the common mode noise detected by the detection unit, and the generation unit is a power conversion system having fewer substrates than the number of the substrates.

[0007] According to the first aspect, since the common mode noise generated by the power conversion circuits respectively mounted on the plurality of substrates is collectively detected, it is possible to generate a cancellation signal for reducing the common mode noise by the generation unit having fewer substrates than the number of the substrates. Since the generation unit has fewer substrates than the number of the substrates, the power conversion system can be miniaturized.

[0008] A second embodiment is a power conversion system according to the first embodiment, wherein the power conversion circuit may include a circuit for driving a motor.

[0009] According to the second embodiment, common-mode noise generated by the circuit for driving the motor can be reduced.

[0010] A third embodiment is a power conversion system comprising a circuit board equipped with a plurality of power conversion circuits electrically connected to an AC power line at a branching point, wherein the power conversion circuits include circuits for driving motors, and the system comprises a detection unit that collectively detects common-mode noise generated by the plurality of power conversion circuits, and a generation unit that generates a cancellation signal to be output to the power line or ground line based on the level of the common-mode noise detected by the detection unit, wherein the generation unit is less than the number of power conversion circuits.

[0011] According to the third embodiment, since the common-mode noise generated by each of the multiple power conversion circuits mounted on the substrate is detected together, it becomes possible to generate a cancellation signal that reduces the common-mode noise using fewer generation units than the number of power conversion circuits. Since the generation units are fewer than the number of power conversion circuits, the power conversion system can be miniaturized. Furthermore, since the power conversion circuits include circuits for driving motors, it is possible to reduce the common-mode noise generated by the circuits for driving motors.

[0012] A fourth embodiment is a power conversion system according to any one of the first to third embodiments, wherein the detection unit includes an annular magnetic core through which the power line passes on the power supply side of the branching point, and an auxiliary winding wound around the magnetic core, and outputs a voltage corresponding to the level from the auxiliary winding.

[0013] According to the fourth embodiment, the detection unit can detect the magnitude of the common-mode noise current (common-mode current) flowing through the power line penetrating the magnetic core as a voltage corresponding to the level of the common-mode noise. The generation unit can then generate a cancellation signal to reduce the common-mode noise based on the voltage corresponding to the level of the common-mode noise.

[0014] A fifth embodiment is a power conversion system according to the fourth embodiment, wherein the generating unit outputs the cancellation signal to the power line on the power conversion circuit side of the position of the magnetic core.

[0015] According to the fifth embodiment, the common-mode noise can be reduced by the cancellation signal output to the power line on the power conversion circuit side rather than at the position of the magnetic core.

[0016] The sixth embodiment is a power conversion system according to the fourth embodiment, wherein the generating unit is connected to the power line on the power conversion circuit side of the position of the magnetic core, and outputs the cancellation signal to the ground wire.

[0017] According to the sixth embodiment, the common-mode noise can be reduced by the cancellation signal output to the ground wire.

[0018] A seventh embodiment is a power conversion system according to any one of the first to third embodiments, wherein the power line includes a plurality of branch lines that branch from the branching point to a plurality of power conversion circuits, and the detection unit includes an annular magnetic core through which the plurality of branch lines pass on the power conversion circuit side of the branching point, and an auxiliary winding wound around the magnetic core, and outputs a voltage corresponding to the level from the auxiliary winding.

[0019] According to the seventh embodiment, the detection unit can detect the magnitude of the common-mode noise current (common-mode current) flowing through the plurality of branch lines penetrating the magnetic core as a voltage corresponding to the level of the common-mode noise. The generation unit can then generate a cancellation signal to reduce the common-mode noise based on the voltage corresponding to the level of the common-mode noise.

[0020] The eighth embodiment is a power conversion system according to the seventh embodiment, wherein the generation unit outputs the cancellation signal to the branch line on the power conversion circuit side of the position of the magnetic core.

[0021] According to the eighth aspect, the common-mode noise can be reduced by the cancellation signal output to the branch line on the power conversion circuit side rather than at the position of the magnetic core.

[0022] The ninth embodiment is a power conversion system according to the seventh embodiment, wherein the generating unit is connected to the branch line on the power conversion circuit side of the position of the magnetic core, and outputs the cancellation signal to the ground wire.

[0023] According to the ninth embodiment, the common-mode noise can be reduced by the cancellation signal output to the ground wire.

[0024] The tenth embodiment is a power conversion system according to any one of the first to third embodiments, wherein the detection unit includes an impedance element connected between the power line and the ground line, and outputs a voltage corresponding to the level by voltage division by the impedance element.

[0025] According to the tenth embodiment, the detection unit can detect the magnitude of the common-mode noise voltage (common-mode voltage) generated in the impedance element as a voltage corresponding to the level of the common-mode noise. The generation unit can then generate a cancellation signal to reduce the common-mode noise based on the voltage corresponding to the level of the common-mode noise.

[0026] The eleventh embodiment is a power conversion system according to the tenth embodiment, wherein the generation unit outputs the cancellation signal to the power line on the power conversion circuit side of the detection unit.

[0027] According to the eleventh embodiment, the common-mode noise can be reduced by the cancellation signal output to the power line on the power conversion circuit side rather than at the position of the detection unit.

[0028] The twelfth embodiment is an air conditioning system comprising a power conversion system according to any one embodiment of the first to eleventh embodiments.

[0029] According to the twelfth embodiment, the air conditioning system is equipped with a power conversion system according to any one of the first to eleventh embodiments, so the air conditioning system can be miniaturized by miniaturizing the power conversion system.

[0030] This is a block diagram showing a first configuration example of the power conversion system according to the first embodiment. This is a block diagram showing a second configuration example of the power conversion system according to the first embodiment. This is a block diagram showing a third configuration example of the power conversion system according to the first embodiment. This is a block diagram showing a fourth configuration example of the power conversion system according to the first embodiment. This is a block diagram showing a fifth configuration example of the power conversion system according to the first embodiment. This is a diagram showing a first detailed configuration example of the detection unit and generation unit according to the first embodiment. This is a diagram showing a second detailed configuration example of the detection unit and generation unit according to the first embodiment. This is a block diagram showing a first configuration example of the power conversion system according to the second embodiment. This is a diagram showing a first detailed configuration example of the detection unit and generation unit according to the second embodiment. This is a block diagram showing a first configuration example of the power conversion system according to the third embodiment. This is a block diagram showing a second configuration example of the power conversion system according to the third embodiment. This is a block diagram showing a first detailed configuration example of the detection unit and generation unit according to the third embodiment. This is a block diagram showing a first configuration example of the power conversion system according to the fourth embodiment. This is a block diagram showing a second configuration example of the power conversion system according to the fourth embodiment. This is a block diagram showing a first configuration example of the power conversion system according to the fifth embodiment. This is a block diagram showing a second configuration example of the power conversion system according to the fifth embodiment. This is a block diagram showing a third configuration example of the power conversion system according to the fifth embodiment. This is a block diagram showing a first configuration example of the power conversion system according to the sixth embodiment. This is a block diagram showing a second configuration example of the power conversion system according to the sixth embodiment. This is a block diagram showing a third configuration example of the power conversion system according to the sixth embodiment. This is a diagram showing a first detailed configuration example of the detection unit and generation unit according to the sixth embodiment. This is a diagram showing a second detailed configuration example of the detection unit and generation unit according to the sixth embodiment. This is a block diagram showing a first modified example of the power conversion system. This is a diagram showing an example of the configuration of the detection unit according to the first modified example of the power conversion system. This is a block diagram showing a second modified example of the power conversion system. This is a block diagram showing a third modified example of the power conversion system. This is a diagram showing an example of the configuration of a power conversion circuit.

[0031] Several embodiments will be described below.

[0032] Figure 1 is a block diagram showing a first configuration example of a power conversion system according to the first embodiment. The power conversion system 1A shown in Figure 1 converts the AC input from the power source 10 either forward or frequency, and supplies the DC after forward conversion or the AC after frequency conversion to multiple loads (in this example, loads 21 and 22).

[0033] Power supply 10 is an AC power source that provides AC power. If power supply 10 is a three-phase AC power source, three-phase AC power is supplied from power supply 10 to the power conversion system 1A. Power supply 10 is, for example, a commercial power source.

[0034] If load 21 or load 22 is a DC load, the power conversion system 1A has a converter function that forward-converts the AC power supplied from the power source 10 into DC power supplied to load 21 or load 22. In this case, load 21 or load 22 operates on the DC power supplied from the power conversion system 1A. Examples of DC loads include electronic circuits. Electronic circuits include, for example, control circuits that control power conversion circuit 31 or power conversion circuit 32.

[0035] If load 21 or load 22 is an AC load, the power conversion system 1A has an inverter function that converts the frequency of the AC power supplied from the power source 10 to AC power supplied to load 21 or load 22. In this case, load 21 or load 22 operates on the AC power supplied from the power conversion system 1A. An example of an AC load is a motor.

[0036] Any of the multiple loads may be a DC load or an AC load. Alternatively, one or more of the multiple loads may be a DC load and the remaining one or more loads may be AC ​​loads. For example, load 21 may be an AC load and load 22 may be a DC load, or load 21 may be a DC load and load 22 may be an AC load.

[0037] The power conversion system 1A is provided, for example, in a refrigeration system 200 equipped with loads 21 and 22. The refrigeration system 200 is a refrigeration cycle device equipped with a compressor driven by an AC motor, which is an example of load 21 or load 22. An example of the refrigeration system 200 is an air conditioning system that harmonizes the air in a target space. Note that the device to which the power conversion system 1A is provided is not limited to the refrigeration system 200, but may be other equipment that requires a power conversion function.

[0038] Load 21 or load 22 may be a three-phase AC motor. A three-phase AC motor is used as an electric motor to drive a compressor in the refrigerant circuit of the refrigeration system 200. The three-phase AC motor is, for example, a concentrated winding motor such as a 4-pole 6-slot or 6-pole 9-slot motor.

[0039] The power conversion system 1A comprises a plurality of substrates 41, 42, a detection unit 50, and a generation unit 60.

[0040] Multiple circuit boards 41 and 42 each mount a power conversion circuit that is electrically connected to the AC power line 70 at a branching point 80. Circuit boards 41 and 42 are circuit boards such as printed circuit boards. Circuit board 41 mounts a power conversion circuit 31. Circuit board 42 mounts a power conversion circuit 32. Multiple power conversion circuits 31 and 32 are electrically connected to the power supply 10 via the power line 70.

[0041] The power line 70 is a path that supplies single-phase or three-phase AC power generated by the power supply 10. When supplying three-phase AC power, the power line 70 includes three-phase (S phase, R phase, and T phase) power lines. The power line 70 includes multiple branch lines that branch off from the branching point 80 to multiple power conversion circuits 31, 32. Branch line 71 electrically connects the branching point 80 and the power conversion circuit 31. Branch line 72 electrically connects the branching point 80 and the power conversion circuit 32.

[0042] The plurality of power conversion circuits 31 and 32 are circuits that perform forward conversion or frequency conversion on the alternating current input via the power line 70. The power conversion circuit 31 is an inverter circuit that frequency-converts the alternating current power input via the branch line 71 into alternating current power supplied to the load 21 or a converter circuit that forward-converts it into direct current power supplied to the load 21. The power conversion circuit 32 is an inverter circuit that frequency-converts the alternating current power input via the branch line 72 into alternating current power supplied to the load 22 or a converter circuit that forward-converts it into direct current power supplied to the load 22.

[0043] The substrate 41 may further mount one or more power conversion circuits that convert the alternating current input via one or more branch lines further branched from the branch line 71 into direct current or alternating current. The substrate 42 may further mount one or more power conversion circuits that convert the alternating current input via one or more branch lines further branched from the branch line 72 into direct current or alternating current.

[0044] FIG. 29 is a diagram showing a configuration example of a power conversion circuit. The power conversion circuit 30 shown in FIG. 29 includes a circuit for driving the motor M and is an example of the above-described power conversion circuit 31 or power conversion circuit 32. The power conversion circuit 30 is an inverter circuit that frequency-converts the three-phase alternating current power input via the above-described power line 70 into three-phase alternating current power supplied to the motor M, which is an example of the load 21 or load 22. The power conversion circuit 30 includes a converter 102, a DC link 103, and an inverter 104 as a circuit for driving the motor M.

[0045] The converter 102 is a circuit that converts the alternating current input via the power line 70 into direct current, for example, converting three-phase alternating current into direct current. The converter 102 is, for example, a diode bridge circuit in which a plurality (for example, six) of diodes are connected in a bridge shape. These diodes full-wave rectify the alternating voltage input from the power line 70 and convert it into a direct voltage. The converter 102 may be a voltage conversion circuit of a circuit form different from the diode bridge circuit. The converter 102 supplies the converted direct current power to the inverter 104 via the DC link 103.

[0046] The DC link 103 is a part to which DC output from the converter 102 is supplied. The DC link 103 includes, for example, a pair of DC buses 111 and 112 connecting between the converter 102 and the inverter 104, and a capacitor 113 connected between the pair of DC buses 111 and 112. The voltage Vdc of the DC link 103 is the potential difference between the pair of DC buses 111 and 112, and is substantially equal to the DC voltage generated across both ends of the capacitor 113. The DC voltage Vdc is input to the inverter 104.

[0047] The inverter 104 is a circuit that converts DC from the DC link 103 into AC, for example, converting DC into three-phase AC. The inverter 104 supplies the converted AC power to the motor M. The inverter 104 is, for example, a bridge circuit in which a plurality (for example, six) of switching elements 104a are connected in a bridge shape. The inverter 104 converts the DC power from the DC link 103 into AC power to the motor M by turning on or off the plurality of switching elements 104a according to a command S generated by a control unit (not shown).

[0048] In FIG. 1, the detection unit 50 and the generation unit 60 function as an active noise canceller. The active noise canceller detects common-mode noise generated by the power conversion circuit, and outputs a cancellation signal generated based on the level of the detected common-mode noise to the power line or the ground line. By outputting the cancellation signal to the power line or the ground line, the common-mode noise flowing out to the power supply electrically connected to the power line and the ground line is reduced. The cancellation signal is a signal that reduces common-mode noise and is also referred to as a compensation signal.

[0049] The common-mode noise generated by the power conversion circuit 31 is transmitted through the ground line 91 and the branch line 71 through the floating capacitance between the load 21 or the power conversion circuit 31 and the ground line 91. The common-mode noise generated by the power conversion circuit 31 is generated, for example, along with the switching operation of the switching elements of the power conversion circuit 31. The ground line 91 is grounded (connected) to the ground 90 to which the power supply 10 is grounded (connected).

[0050] Common-mode noise generated by the power conversion circuit 32 is transmitted through the ground wire 92 and branch wire 72 via stray capacitance between the load 22 or the power conversion circuit 32 and the ground wire 92. Common-mode noise generated by the power conversion circuit 32 is generated, for example, in conjunction with the switching operation of the switching elements of the power conversion circuit 32. The ground wire 92 is grounded (connected) to the ground 90 to which the power supply 10 is grounded (connected).

[0051] The power conversion system 1A according to the first embodiment includes a detection unit 50 and a generation unit 60 as an active noise canceller according to the first embodiment. The active noise canceller according to the first embodiment detects a common-mode noise current Ic (common-mode current) and outputs a compensation current Io generated based on the level of the detected common-mode current to the power line 70 or the ground line 91. The active noise canceller according to the first embodiment is a current detection / current output type active noise cancellation circuit.

[0052] The common-mode noise current Ic (common-mode current) is an example of common-mode noise generated by multiple power conversion circuits 31 and 32. The compensation current Io is an example of a cancellation signal generated based on the detected level of common-mode noise.

[0053] In the active noise canceller according to the first embodiment, the detection unit 50 detects the common-mode noise current Ic flowing through the power line 70 as common-mode noise generated by the multiple power conversion circuits 31 and 32. The detection unit 50 detects the noise current Ic on the power supply 10 side of the branching point 80. By detecting the noise current Ic flowing through the power line 70 between the power supply 10 and the branching point 80, the detection unit 50 collectively detects the common-mode noise generated by the multiple power conversion circuits 31 and 32. For example, the detection unit 50 detects the noise current Ic flowing through the power line 70 between the power supply 10 and the branching point 80 using a transformer.

[0054] In the active noise canceller according to the first embodiment, the generation unit 60 generates a compensation current Io to be output to the power line 70 or the ground line 91 based on the level of the noise current Ic detected by the detection unit 50. The generation unit 60 outputs the compensation current Io to the power line 70 on the power conversion circuit 31 side of the location of the detection unit 50. Alternatively, the generation unit 60 is connected to the power line 70 on the power conversion circuit 31 side of the location of the detection unit 50 and outputs the compensation current Io to the ground line 91. For example, the generation unit 60 injects the compensation current Io to the power line 70 or the ground line 91 to reduce the common-mode noise flowing to the power supply 10 based on the detected noise current Ic. For example, the generation unit 60 injects the compensation current Io to the power line 70 or the ground line 91 via a capacitor.

[0055] According to the active noise canceller of the first embodiment, common-mode noise generated by power conversion circuits 31 and 32 mounted on multiple substrates 41 and 42 is collectively detected as a noise current Ic by the detection unit 50. Because it is detected collectively, a generation unit 60, which is fewer than the number of substrates 41 and 42, can generate a compensation current Io, which is a cancellation signal that reduces the common-mode noise generated by the power conversion circuits 31 and 32 mounted on each of the substrates 41 and 42. Since the generation unit 60 is fewer than the number of substrates 41 and 42, the power conversion system 1A can be miniaturized. Furthermore, if at least one of the power conversion circuits 31 and 32 includes a circuit for driving a motor, the common-mode noise generated by the circuit for driving the motor can be reduced.

[0056] In the first embodiment, the active noise canceller detects common-mode noise generated by the power conversion circuits 31 and 32 together using a common detection unit 50. Therefore, compared to a configuration in which common-mode noise generated by power conversion circuit 31 and common-mode noise generated by power conversion circuit 32 are detected by separate detection units, the power conversion system according to the first embodiment can be miniaturized.

[0057] Figure 2 is a block diagram showing a second configuration example of the power conversion system according to the first embodiment. In the second configuration example, the explanation of the parts common to the first configuration example described above will be omitted. The power conversion system 1B shown in Figure 2 differs from the power conversion system 1A shown in Figure 1 in that it includes a circuit board 40 on which a plurality of power conversion circuits (in this example, power conversion circuits 31, 32) are electrically connected to the AC power line 70 at a branching point 80.

[0058] The board 40 is a circuit board such as a printed circuit board. The board 40 may further be equipped with one or more power conversion circuits that convert AC power input via one or more branch lines further branching from branch line 71 or branch line 72 into DC power or AC power.

[0059] According to the active noise canceller of the first embodiment, common-mode noise generated by each of the power conversion circuits 31 and 32 mounted on the substrate 40 is collectively detected as a noise current Ic by the detection unit 50. By detecting them collectively, it becomes possible to generate a compensation current Io, which is a cancellation signal that reduces the common-mode noise generated by each of the power conversion circuits 31 and 32 mounted on the substrate 40, using a generation unit 60 that is smaller than the number of power conversion circuits 31 and 32. Since the generation unit 60 is smaller than the number of power conversion circuits 31 and 32, the power conversion system 1B can be miniaturized. Furthermore, if at least one of the power conversion circuits 31 and 32 includes a circuit for driving a motor, the common-mode noise generated by the circuit for driving the motor can be reduced.

[0060] Figure 3 is a block diagram showing a third configuration example of the power conversion system according to the first embodiment. In this third configuration example, the explanation of parts common to the above-described configuration examples will be omitted. The power conversion system 1C shown in Figure 3 differs from the power conversion system 1A shown in Figure 1 in that the generation unit 60 is mounted on the substrate 41.

[0061] Figure 4 is a block diagram showing a fourth configuration example of the power conversion system according to the first embodiment. In this fourth configuration example, the explanation of parts common to the above-described configuration examples will be omitted. The power conversion system 1D shown in Figure 4 differs from the power conversion system 1A shown in Figure 1 in that the branching point 80 is mounted on the circuit board 41. The circuit board 41 may mount the branching point 80 and the generation unit 60. When the power conversion system 1D is mounted in an air conditioning system, the circuit board 41 may be an inverter circuit board mounted on the outdoor unit, and the circuit board 42 may be an inverter circuit board mounted on the indoor unit.

[0062] Figure 5 is a block diagram showing a fifth configuration example of the power conversion system according to the first embodiment. In this fifth configuration example, the explanation of parts common to the above-described configuration examples will be omitted. The power conversion system 1E shown in Figure 5 differs from the power conversion system 1A shown in Figure 1 in that the detection unit 50 is mounted on the substrate 41. The substrate 41 may be equipped with the detection unit 50, the branching point 80, and the generation unit 60.

[0063] In power conversion systems 1C, 1D, and 1E, the substrates 41 and 42 may be integrated, as with the substrate 40 of power conversion system 1B.

[0064] Figure 6 is a diagram showing a first detailed configuration example of an active noise canceller (detection unit 50 and generation unit 60) according to the first embodiment. The configuration of the power conversion system 1Aa shown in Figure 6 is applicable to any of the power conversion systems 1A to 1E described above. Figure 6 illustrates a configuration in which the generation unit 60 injects a compensation current Io into an injection point 60a on the ground wire 91.

[0065] The detection unit 50 includes an annular magnetic core 51 through which the power line 70 passes on the power supply 10 side of the branching point 80, and an auxiliary winding 52 wound around the magnetic core 51. The detection unit 50 outputs a voltage Vc from the auxiliary winding 52 corresponding to the level of common-mode noise generated by the multiple power conversion circuits 31, 32. The detection unit 50 detects the magnitude of the common-mode noise current Ic (common-mode current) flowing through the power line 70 passing through the magnetic core 51 as a voltage Vc corresponding to the level of common-mode noise. The generation unit 60 generates a compensation current Io, which is a cancellation signal that reduces common-mode noise, based on the voltage Vc corresponding to the level of common-mode noise.

[0066] The generation unit 60 is connected to the power line 70 on the power conversion circuit 31 side of the magnetic core 51 and outputs a compensation current Io to the ground wire 91. As a result, the noise current Ic generated by the power conversion circuits 31 and 32 can be reduced by the compensation current Io output to the ground wire 91.

[0067] The noise current Ic includes a common-mode noise current I1 generated by the power conversion circuit 31 and a common-mode noise current I2 generated by the power conversion circuit 32. Based on the detected noise current Ic, the generation unit 60 injects a compensation current Io into the power line 70 or the ground line 91 to reduce the common-mode noise flowing to the power supply 10.

[0068] Figure 7 shows a second detailed configuration example of the active noise canceller (detection unit 50 and generation unit 60) according to the first embodiment. The configuration of the power conversion system 1Ab shown in Figure 7 is applicable to any of the power conversion systems 1A to 1E described above. Figure 7 illustrates a configuration in which the generation unit 60 injects the compensation current Io to an injection point 60a on the power line 70 on the power conversion circuit 31 side rather than at the position of the magnetic core 51.

[0069] The generation unit 60 reduces the noise current Ic generated by the power conversion circuits 31 and 32 by outputting a compensation current Io to the power line 70 on the power conversion circuit 31 side of the magnetic core 51. The generation unit 60 injects the compensation current Io to the injection point 60a on the branch line 71 between the branch point 80 and the power conversion circuit 31. Based on the detected noise current Ic, the generation unit 60 injects the compensation current Io to the branch line 71 to reduce the common-mode noise flowing to the power supply 10.

[0070] Figure 8 shows a third detailed configuration example of the active noise canceller (detection unit 50 and generation unit 60) according to the first embodiment. The configuration of the power conversion system 1Ac shown in Figure 8 is applicable to any of the power conversion systems 1A to 1E described above. Figure 8 illustrates a configuration in which the generation unit 60 injects a compensation current Io to an injection point 60a on the power line 70 on the power conversion circuit 31 side of the position of the magnetic core 51.

[0071] The generation unit 60 reduces the noise current Ic generated by the power conversion circuits 31 and 32 by outputting a compensation current Io to the power line 70 on the power conversion circuit 31 side of the magnetic core 51. The generation unit 60 injects the compensation current Io to the injection point 60a on the power line 70 between the magnetic core 51 and the branch point 80. Based on the detected noise current Ic, the generation unit 60 injects the compensation current Io to the power line 70 between the magnetic core 51 and the branch point 80 to reduce the common-mode noise flowing to the power supply 10.

[0072] Figure 9 is a block diagram showing a first configuration example of a power conversion system according to the second embodiment. In the second embodiment, the description of the same configuration, operation, and effects as in the first embodiment described above will be omitted by referring to the above description.

[0073] The power conversion system 2A according to the second embodiment includes a detection unit 50 and a generation unit 60 as an active noise canceller according to the second embodiment. The active noise canceller according to the second embodiment detects a common-mode noise current Ic (common-mode current) and outputs a compensation voltage Vo generated based on the level of the detected common-mode current to the power line 70. The active noise canceller according to the second embodiment is a current detection / voltage output type active noise cancellation circuit.

[0074] The compensation voltage Vo is an example of a cancellation signal generated based on the level of common-mode noise detected.

[0075] In the active noise canceller according to the second embodiment, the generation unit 60 generates a compensation voltage Vo to be output to the power line 70 based on the level of the noise current Ic detected by the detection unit 50. The generation unit 60 outputs the compensation voltage Vo to the power line 70 on the power conversion circuit 31 side of the location of the detection unit 50. For example, the generation unit 60 measures the common-mode voltage generated in the power line 70 based on the level of the noise current Ic, and reduces the noise current Ic by applying a compensation voltage Vo with the opposite polarity to the common-mode voltage to the power line 70. For example, the generation unit 60 applies the compensation voltage Vo to the power line 70 via a transformer.

[0076] According to the active noise canceller of the second embodiment, common-mode noise generated by power conversion circuits 31 and 32 mounted on multiple substrates 41 and 42 is collectively detected as a noise current Ic by the detection unit 50. Because it is detected collectively, a generation unit 60, which is fewer than the number of substrates 41 and 42, can generate a compensation voltage Vo, which is a cancellation signal that reduces the common-mode noise generated by the power conversion circuits 31 and 32 mounted on the substrates 41 and 42. Since the generation unit 60 is fewer than the number of substrates 41 and 42, the power conversion system 2A can be miniaturized. Furthermore, if at least one of the power conversion circuits 31 and 32 includes a circuit for driving a motor, the common-mode noise generated by the circuit for driving the motor can be reduced.

[0077] The circuit boards 41 and 42 of power conversion system 2A may be integrated, as with circuit board 40 of power conversion system 1B. The mounting area of ​​circuit board 41 of power conversion system 2A may be extended, as with circuit boards 41 of power conversion systems 1C to 1E.

[0078] Figure 10 is a diagram showing a first detailed configuration example of an active noise canceller (detection unit 50 and generation unit 60) according to the second embodiment. The power conversion system 2Aa shown in Figure 10 is applicable to the power conversion system 2A described above. Figure 10 illustrates a configuration in which the generation unit 60 outputs a compensation voltage Vo to the power line 70 between the branching point 80 and the power conversion circuit 31.

[0079] The detection unit 50 detects the magnitude of the common-mode noise current Ic (common-mode current) flowing through the power line 70 that penetrates the magnetic core 51 as a voltage Vc corresponding to the level of common-mode noise. The generation unit 60 generates a compensation voltage Vo, which is a cancellation signal that reduces common-mode noise, based on the voltage Vc corresponding to the level of common-mode noise.

[0080] The generation unit 60 reduces the noise current Ic generated by the power conversion circuits 31 and 32 by outputting a compensation voltage Vo to the power line 70 on the power conversion circuit 31 side of the magnetic core 51. The generation unit 60 outputs a compensation voltage Vo to the branch line 71 between the branch point 80 and the power conversion circuit 31. The generation unit 60 applies a voltage Vp corresponding to voltage Vc to the primary winding of the transformer 62. As a result, a compensation voltage Vo with the opposite polarity to the common-mode voltage generated in the power line 70 is applied to the branch line 71 by the secondary winding of the transformer 62, so that the noise current Ic flowing out to the power supply 10 is reduced to almost zero.

[0081] Figure 11 is a diagram showing a second detailed configuration example of an active noise canceller (detection unit 50 and generation unit 60) according to the second embodiment. The power conversion system 2Ab shown in Figure 11 is applicable to the power conversion system 2A described above. Figure 11 illustrates a configuration in which the generation unit 60 outputs a compensation voltage Vo to the power line 70 between the branching point 80 and the detection unit 50.

[0082] The generation unit 60 reduces the noise current Ic generated by the power conversion circuits 31 and 32 by outputting a compensation voltage Vo to the power line 70 on the power conversion circuit 31 side of the magnetic core 51. The generation unit 60 outputs a compensation voltage Vo to the power line 70 between the branching point 80 and the magnetic core 51. The generation unit 60 applies a voltage Vp corresponding to voltage Vc to the primary winding of the transformer 62. As a result, a compensation voltage Vo with the opposite polarity to the common-mode voltage generated in the power line 70 is applied to the power line 70 by the secondary winding of the transformer 62, so that the noise current Ic flowing out to the power supply 10 is reduced to almost zero.

[0083] Figure 12 is a block diagram showing a first configuration example of a power conversion system according to the third embodiment. In the third embodiment, descriptions of the same configuration, operation, and effects as those of the embodiments described above will be omitted by referring to the above descriptions.

[0084] The power conversion system 3A according to the third embodiment includes a detection unit 50 and a generation unit 60 as an active noise canceller according to the third embodiment. The active noise canceller according to the third embodiment detects a common-mode noise current Ic (common-mode current) and outputs a compensation current Io, which is generated based on the level of the detected common-mode current, to the power line 70 or the ground line 91. The active noise canceller according to the third embodiment is a current detection / current output type active noise cancellation circuit.

[0085] In the active noise canceller according to the third embodiment, the detection unit 50 detects the common-mode noise current Ic flowing through the power line 70 as common-mode noise generated by the multiple power conversion circuits 31 and 32. The detection unit 50 detects the noise current Ic on the power conversion circuits 31 and 32 side of the branching point 80. The detection unit 50 detects the common-mode noise generated by the multiple power conversion circuits 31 and 32 together by detecting the combined noise current Ic of the noise current flowing through branch line 71 and the noise current flowing through branch line 72. For example, the detection unit 50 detects the noise current Ic flowing through branch lines 71 and 72 using a transformer.

[0086] In the active noise canceller according to the third embodiment, the generation unit 60 generates a compensation current Io to be output to the power line 70 or the ground line 91 based on the level of the noise current Ic detected by the detection unit 50. The generation unit 60 outputs the compensation current Io to the power line 70 on the power supply 10 side of the branching point 80. Alternatively, the generation unit 60 is connected to the power line 70 on the power supply 10 side of the branching point 80 and outputs the compensation current Io to the ground line 91. For example, the generation unit 60 injects the compensation current Io to the power line 70 or the ground line 91 to reduce the common-mode noise flowing to the power supply 10 based on the detected noise current Ic. For example, the generation unit 60 injects the compensation current Io to the power line 70 or the ground line 91 via a capacitor.

[0087] Figure 13 is a block diagram showing a second configuration example of a power conversion system according to the third embodiment. In the second configuration example, the explanation of the parts common to the first configuration example described above will be omitted. In the power conversion system 3B shown in Figure 13, the generation unit 60 outputs a compensation current Io to the power line 70 on the power conversion circuit 31 side of the location of the branching point 80 and the detection unit 50. Alternatively, the generation unit 60 is connected to the power line 70 on the power conversion circuit 31 side of the location of the branching point 80 and the detection unit 50, and outputs a compensation current Io to the ground wire 91.

[0088] The circuit boards 41 and 42 of power conversion systems 3A and 3B may be integrated, as with the circuit board 40 of power conversion system 1B. The mounting area of ​​the circuit board 41 of power conversion systems 3A and 3B may be extended, as with the circuit board 41 of power conversion systems 1C to 1E.

[0089] Figure 14 is a diagram showing a first detailed configuration example of an active noise canceller (detection unit 50 and generation unit 60) according to the third embodiment. The configuration of the power conversion system 3Ba shown in Figure 14 is applicable to the power conversion system 3B described above. Figure 14 illustrates a configuration in which the generation unit 60 injects a compensation current Io into an injection point 60a on the ground wire 91.

[0090] The detection unit 50 includes an annular magnetic core 51 through which multiple branch lines 71 and 72 pass, on the side of the power conversion circuits 31 and 32 beyond the branching point 80, and an auxiliary winding 52 wound around the magnetic core 51. The detection unit 50 outputs a voltage Vc from the auxiliary winding 52 corresponding to the level of common-mode noise generated by the multiple power conversion circuits 31 and 32. The detection unit 50 detects the magnitude of the common-mode noise current Ic (common-mode current) flowing through the multiple branch lines 71 and 72 passing through the magnetic core 51 as a voltage Vc corresponding to the level of common-mode noise. The generation unit 60 generates a compensation current Io, which is a cancellation signal that reduces common-mode noise, based on the voltage Vc corresponding to the level of common-mode noise.

[0091] The generation unit 60 is connected to the power line 70 on the power conversion circuit 31 side of the magnetic core 51 and outputs a compensation current Io to the ground wire 91. As a result, the noise current Ic generated by the power conversion circuits 31 and 32 can be reduced by the compensation current Io output to the ground wire 91.

[0092] Figure 15 is a block diagram showing a first configuration example of a power conversion system according to the fourth embodiment. In the fourth embodiment, descriptions of the same configuration, operation, and effects as those of the embodiments described above will be omitted by referring to the above descriptions.

[0093] The power conversion system 4A according to the fourth embodiment includes a detection unit 50 and a generation unit 60 as an active noise canceller according to the fourth embodiment. The active noise canceller according to the fourth embodiment detects a common-mode noise current Ic (common-mode current) and outputs a compensation voltage Vo generated based on the level of the detected common-mode current to the power line 70. The active noise canceller according to the fourth embodiment is a current detection / voltage output type active noise cancellation circuit.

[0094] In the active noise canceller according to the fourth embodiment, the generation unit 60 outputs a compensation voltage Vo to the power line 70 to reduce common-mode noise flowing through the power supply 10, based on the noise current Ic detected by the detection unit 50. The generation unit 60 outputs the compensation voltage Vo to the power line 70 on the power supply 10 side of the location of the detection unit 50. For example, the generation unit 60 measures the common-mode voltage generated in the power line 70 based on the level of the noise current Ic, and reduces the common-mode noise flowing through the power supply 10 by applying a compensation voltage Vo with the opposite polarity to the common-mode voltage to the power line 70. For example, the generation unit 60 applies the compensation voltage Vo to the power line 70 via a transformer.

[0095] Figure 16 is a block diagram showing a second configuration example of the power conversion system according to the fourth embodiment. In the second configuration example, the explanation of the parts common to the first configuration example described above will be omitted. The power conversion system 4B shown in Figure 16 differs from the power conversion system 4A shown in Figure 15 in that the generation unit 60 outputs a compensation voltage Vo to the branch line 71 on the power conversion circuit 31 side of the detection unit 50.

[0096] The circuit boards 41 and 42 of the power conversion systems 4A and 4B may be integrated, as with the circuit board 40 of the power conversion system 1B. The mounting area of ​​the circuit board 41 of the power conversion systems 4A and 4B may be extended, as with the circuit board 41 of the power conversion systems 1C to 1E.

[0097] Figure 17 is a block diagram showing a first configuration example of a power conversion system according to the fifth embodiment. In the fifth embodiment, descriptions of the same configuration, operation, and effects as those of the embodiments described above will be omitted by referring to the above descriptions.

[0098] The power conversion system 5A according to the fifth embodiment includes a detection unit 50 and a generation unit 60 as an active noise canceller according to the fifth embodiment. The active noise canceller according to the fifth embodiment detects a common-mode noise voltage Vc (common-mode voltage) and outputs a compensation current Io generated based on the level of the detected common-mode voltage to the power line 70 or the ground line 91. The active noise canceller according to the fifth embodiment is a voltage detection / current output type active noise cancellation circuit.

[0099] The common-mode noise voltage Vc (common-mode voltage) is an example of common-mode noise generated by multiple power conversion circuits 31 and 32.

[0100] In the active noise canceller according to the fifth embodiment, the detection unit 50 detects the common-mode noise voltage Vc generated in the power line 70 as common-mode noise generated by the multiple power conversion circuits 31 and 32. Since the power line 70 is at approximately the same potential at all points, the detection unit 50 detects the noise voltage Vc at any point in the power line 70. By detecting the noise voltage Vc at any point in the power line 70, the detection unit 50 collectively detects the common-mode noise generated by the multiple power conversion circuits 31 and 32. For example, the detection unit 50 detects the noise voltage Vc using impedance elements such as capacitors and resistors.

[0101] In the active noise canceller according to the fifth embodiment, the generation unit 60 generates a compensation current Io to be output to the power line 70 or the ground line 91 based on the level of the noise voltage Vc detected by the detection unit 50. The generation unit 60 outputs the compensation current Io to the power line 70 on the power supply 10 side of the location of the detection unit 50. Alternatively, the generation unit 60 is connected to the power line 70 on the power supply 10 side of the location of the detection unit 50 and outputs the compensation current Io to the ground line 91.

[0102] Figure 18 is a block diagram showing a second configuration example of a power conversion system according to the fifth embodiment. In the second configuration example, the explanation of the parts common to the first configuration example described above will be omitted. In the power conversion system 5B shown in Figure 18, the generation unit 60 outputs a compensation current Io to the power line 70 on the power conversion circuit 31 side of the location of the detection unit 50 and the branching point 80. Alternatively, the generation unit 60 is connected to the power line 70 on the power conversion circuit 31 side of the location of the detection unit 50 and the branching point 80, and outputs a compensation current Io to the ground wire 91.

[0103] Figure 19 is a block diagram showing a third configuration example of the power conversion system according to the fifth embodiment. In this third configuration example, the explanation of parts common to the above-described configuration examples will be omitted. The power conversion system 5C shown in Figure 19 differs from the power conversion system 5B shown in Figure 18 in that the detection unit 50 detects the noise voltage Vc on the power conversion circuit 31 side of the branching point 80.

[0104] The circuit boards 41 and 42 of the power conversion systems 5A, 5B, and 5C may be integrated, as with the circuit board 40 of the power conversion system 1B. The mounting area of ​​the circuit board 41 of the power conversion systems 5A, 5B, and 5C may be extended, as with the circuit board 41 of the power conversion systems 1C to 1E.

[0105] Figure 20 is a block diagram showing a first configuration example of a power conversion system according to the sixth embodiment. In the sixth embodiment, descriptions of the same configuration, operation, and effects as those of the above-described embodiments are omitted by referring to the above-described explanations.

[0106] The power conversion system 6A according to the sixth embodiment includes a detection unit 50 and a generation unit 60 as an active noise canceller according to the sixth embodiment. The active noise canceller according to the sixth embodiment detects a common-mode noise voltage Vc (common-mode voltage) and outputs a compensation voltage Vo generated based on the level of the detected common-mode voltage to the power line 70. The active noise canceller according to the sixth embodiment is a voltage detection / voltage output type active noise cancellation circuit.

[0107] In the active noise canceller according to the sixth embodiment, the generation unit 60 generates a compensation voltage Vo to be output to the power line 70 based on the level of the noise voltage Vc detected by the detection unit 50. The generation unit 60 outputs the compensation voltage Vo to the power line 70 on the power supply 10 side of the location of the detection unit 50.

[0108] Figure 21 is a block diagram showing a second configuration example of a power conversion system according to the sixth embodiment. In this second configuration example, the explanation of the parts common to the first configuration example described above will be omitted. The power conversion system 6B shown in Figure 21 differs from the power conversion system 6A shown in Figure 20 in that the generation unit 60 outputs a compensation voltage Vo to the branch line 71 on the power conversion circuit 31 side of the detection unit 50.

[0109] Figure 22 is a block diagram showing a third configuration example of the power conversion system according to the sixth embodiment. In this third configuration example, the explanation of parts common to the above-described configuration examples will be omitted. The power conversion system 6C shown in Figure 22 differs from the power conversion system 6B shown in Figure 21 in that the generation unit 60 outputs a compensation voltage Vo to the branch line 71 on the power conversion circuit 31 side of the detection unit 50.

[0110] The substrates 41 and 42 of the power conversion systems 6A, 6B, and 6C may be integrated, as with the substrate 40 of the power conversion system 1B. The substrate 41 of the power conversion systems 6A, 6B, and 6C may have an extended mounting area, as with the substrate 41 of the power conversion systems 1C to 1E.

[0111] Figure 23 is a diagram showing a first detailed configuration example of an active noise canceller (detection unit 50 and generation unit 60) according to the sixth embodiment. The configuration of the power conversion system 6Ba shown in Figure 23 is applicable to the power conversion system 6B described above. Figure 23 illustrates a configuration in which the generation unit 60 applies a compensation voltage Vo to the branch line 71 between the branch point 80 and the power conversion circuit 31.

[0112] The detection unit 50 includes a plurality of impedance elements 53, 54 connected in series between the power line 70 and the ground line 91. The impedance elements 53, 54 are capacitors. The detection unit 50 outputs a voltage Vc from the impedance elements 54 corresponding to the level of common-mode noise generated by the plurality of power conversion circuits 31, 32 through voltage division by the impedance elements 53, 54. The detection unit 50 detects the magnitude of the common-mode noise voltage Vc (common-mode voltage) generated in the impedance elements 54 as a voltage Vc corresponding to the level of common-mode noise. The generation unit 60 then generates a compensation voltage Vo, which is a cancellation signal that reduces common-mode noise, based on the voltage Vc corresponding to the level of common-mode noise.

[0113] The generation unit 60 outputs a compensation voltage Vo to the power line 70 on the power conversion circuit 31 side of the detection unit 50. As a result, the noise voltage Vc generated by the power conversion circuits 31 and 32 can be reduced by the compensation voltage Vo output to the power line 70.

[0114] Figure 24 is a diagram showing a second detailed configuration example of an active noise canceller (detection unit 50 and generation unit 60) according to the sixth embodiment. The configuration of the power conversion system 6Ca shown in Figure 24 is applicable to the power conversion system 6C described above. Figure 24 illustrates a configuration in which the generation unit 60 applies a compensation voltage Vo to the branch line 71 between the detection unit 50 and the power conversion circuit 31.

[0115] The generation unit 60 outputs a compensation voltage Vo to the power line 70 on the power conversion circuit 31 side of the detection unit 50. As a result, the noise voltage Vc generated by the power conversion circuits 31 and 32 can be reduced by the compensation voltage Vo output to the power line 70.

[0116] Figure 25 is a block diagram showing a first modified example of the power conversion system. In this first modified example, the explanation of the same configuration, operation, and effect as in the above-described embodiments will be omitted by referring to the above-described explanation. In the power conversion systems according to the above-described embodiments, the number of detection units 50 and generation units 60 are the same. However, as in the power conversion system 7A shown in Figure 25, the number of detection units 50 may be less than the number of generation units 60.

[0117] The power conversion system 7A comprises a plurality of substrates 41, 42, 43, a detection unit 50, and generation units 60A, 60B.

[0118] The circuit board 43 is equipped with a power conversion circuit 33 that is electrically connected to the AC power line 70 at a branching point 80. The power conversion circuit 33 is electrically connected to the power supply 10 via the power line 70. The power line 70 includes a branch line 73 that branches off from the branching point 80 to the power conversion circuit 33. The branch line 73 electrically connects the branching point 80 and the power conversion circuit 33. The power conversion circuit 33 is a circuit that forward-converts or frequency-converts the AC input via the power line 70 and supplies the converted power to the load 23. The circuit board 43 may further be equipped with one or more power conversion circuits that convert the AC input via one or more branch lines further branching from the branch line 73 into DC or AC.

[0119] Common-mode noise generated by the power conversion circuit 33 is transmitted through the ground wire 93 and branch wire 73 via stray capacitance between the load 23 or the power conversion circuit 33 and the ground wire 93. The common-mode noise generated by the power conversion circuit 33 is generated, for example, in conjunction with the switching operation of the switching elements of the power conversion circuit 33. The ground wire 93 is grounded (connected) to the ground 90 to which the power supply 10 is grounded (connected).

[0120] The detection unit 50 according to the first modified example detects the common-mode noise current Ic flowing through the power line 70 as common-mode noise generated by the multiple power conversion circuits 31, 32, and 33. The detection unit 50 detects the noise current Ic on the power conversion circuits 31, 32, and 33 side of the branching point 80. The detection unit 50 detects the common-mode noise generated by the multiple power conversion circuits 31, 32, and 33 together by detecting the noise current Ic which is the sum of the noise currents flowing through branch line 71, branch line 72, and branch line 73. For example, the detection unit 50 detects the noise currents Ic flowing through branch lines 71, 72, and 73 using a transformer.

[0121] Figure 26 shows an example of the configuration of a detection unit according to a first modified example of a power conversion system. The detection unit 50 includes an annular magnetic core 51 through which branch lines 71, 72, and 73 pass, and a plurality of auxiliary windings 52a, 52b wound around the magnetic core 51. The detection unit 50a outputs the voltage generated by the auxiliary winding 52a to the generation unit 60A. The detection unit 50b outputs the voltage generated by the auxiliary winding 52b to the generation unit 60B.

[0122] In Figure 25, the generation unit 60A generates a compensation current Io that reduces common-mode noise generated by the multiple power conversion circuits 31, 32, and 33 based on the voltage generated by the auxiliary winding 52a of the detection unit 50. The generation unit 60A injects the generated compensation current Io into the branch line 71 or the ground line 91. The generation unit 60B generates a compensation current Io that reduces common-mode noise generated by the multiple power conversion circuits 31, 32, and 33 based on the voltage generated by the auxiliary winding 52b of the detection unit 50. The generation unit 60B injects the generated compensation current Io into the branch line 72 or the ground line 92.

[0123] Figure 27 is a block diagram showing a second modified example of the power conversion system. In the second modified example, explanations of the same configuration, operation, and effects as in the above-described embodiments will be omitted by referring to the above-described explanations. In the power conversion systems according to the above-described embodiments, the detection unit 50 detects common-mode noise generated by all power conversion circuits electrically connected to the branching point 80. However, as shown in the power conversion system 7B in Figure 27, the detection unit 50 may detect common-mode noise generated by some of the power conversion circuits among all power conversion circuits electrically connected to the branching point 80.

[0124] In Figure 27, the detection unit 50 detects common-mode noise generated by some of the power conversion circuits 31, 32, and 33, which are electrically connected to the branch point 80, all at once. The power conversion system 7B is equipped with a noise filter 11 (for example, a common-mode choke coil) on the branch line 73, and the noise filter 11 reduces the common-mode noise generated by the power conversion circuit 33.

[0125] Figure 28 is a block diagram showing a third modified example of the power conversion system. In this third modified example, the explanation of the same configuration, operation, and effects as in the above-described embodiments will be omitted by referring to the above-described explanation. In the power conversion systems according to the above-described embodiments, there is one branching point of the power line 70. However, as in the power conversion system 7C shown in Figure 28, there may be multiple branching points of the power line 70.

[0126] The power conversion system 7C comprises a plurality of circuit boards 41, 42, 43, 44, a detection unit 50, and a generation unit 60. The descriptions of the circuit board 44, power conversion circuit 34, load 24, branch line 74, and ground wire 94 are omitted by referring to the above description. The plurality of circuit boards 41, 42, 43, 44 are equipped with power conversion circuits 31, 32, 33, 34 which are electrically connected to the AC power line 70 at branch point 81. The plurality of circuit boards 41, 42 are equipped with power conversion circuits 31, 32 which are electrically connected to the AC power line 70 at branch point 80. The plurality of circuit boards 43, 44 are equipped with power conversion circuits 33, 34 which are electrically connected to the AC power line 70 at branch point 82.

[0127] As described above, embodiments have been explained, but these embodiments are presented as examples only, and the present invention is not limited by these embodiments. The above embodiments can be implemented in various other forms, and various combinations, omissions, substitutions, and modifications are possible without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents.

[0128] This international application claims priority based on Japanese Patent Application No. 2024-169853, filed on 30 September 2024, and the entire contents of Japanese Patent Application No. 2024-169853 are incorporated herein by reference.

[0129] 1A, 1B, 1C, 1D, 1E, 2A, 3A, 3B, 4A, 4B, 5A, 5B, 5C, 6A, 6B, 6C, 7A, 7B, 7C Power Conversion System 10 Power Supply 11 Noise Filter 21, 22, 23, 24 Load 30, 31, 32, 33, 34 Power Conversion Circuit 40, 41, 42, 43, 44 Substrate 50 Detection Unit 51 Magnetic Core 52 Auxiliary Winding 53, 54 Impedance Element 60 Generation Unit 60a Injection Point 61 Generation Circuit 62 Transformer 70 Power Line 71, 72, 73, 74 Branch Line 80, 81, 82 Branch Point 90 Ground 91, 92, 93, 94 Ground Wire 200 Refrigeration System

Claims

1. A power conversion system comprising: a plurality of circuit boards (41, 42, 43, 44) on which power conversion circuits (31, 32, 33, 34) are electrically connected to an AC power line (70) at a branching point (80); a detection unit (50) that collectively detects common-mode noise generated by the plurality of power conversion circuits; and a generation unit (60) that generates a cancellation signal to be output to the power line or ground line (91) based on the level of the common-mode noise detected by the detection unit, wherein the number of generation units is less than the number of circuit boards.

2. The power conversion system according to claim 1, wherein the power conversion circuit includes a circuit for driving a motor.

3. A power conversion system comprising a circuit board (40) on which a plurality of power conversion circuits (31, 32) are mounted, which are electrically connected to an AC power line (70) at a branching point (80), wherein the power conversion circuits include circuits for driving motors, and the system comprises a detection unit (50) for collectively detecting common-mode noise generated by the plurality of power conversion circuits, and a generation unit (60) for generating a cancellation signal to be output to the power line or ground line based on the level of the common-mode noise detected by the detection unit, wherein the number of generation units is less than the number of power conversion circuits.

4. The power conversion system according to any one of claims 1 to 3, wherein the detection unit includes an annular magnetic core (51) through which the power line passes on the power supply side of the branching point, and an auxiliary winding (52) wound around the magnetic core, and outputs a voltage corresponding to the level from the auxiliary winding.

5. The power conversion system according to claim 4, wherein the generation unit outputs the cancellation signal to the power line on the power conversion circuit side of the position of the magnetic core.

6. The power conversion system according to claim 4, wherein the generating unit is connected to the power line on the power conversion circuit side of the position of the magnetic core, and outputs the cancellation signal to the ground wire.

7. The power line includes a plurality of branch lines (71, 72) that branch from the branching point to a plurality of power conversion circuits, and the detection unit includes an annular magnetic core (51) through which the plurality of branch lines pass, on the power conversion circuit side of the branching point, and an auxiliary winding (52) wound around the magnetic core, and outputs a voltage corresponding to the level from the auxiliary winding, the power conversion system according to any one of claims 1 to 3.

8. The power conversion system according to claim 7, wherein the generation unit outputs the cancellation signal to the branch line on the power conversion circuit side of the position of the magnetic core.

9. The power conversion system according to claim 7, wherein the generating unit is connected to the branch line on the power conversion circuit side of the magnetic core and outputs the cancellation signal to the ground wire.

10. The power conversion system according to any one of claims 1 to 3, wherein the detection unit includes impedance elements (53, 54) connected between the power line and the ground line, and outputs a voltage corresponding to the level by voltage division by the impedance elements.

11. The power conversion system according to claim 10, wherein the generation unit outputs the cancellation signal to the power line on the power conversion circuit side of the detection unit.

12. An air conditioning system comprising the power conversion system according to any one of claims 1 to 11.

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