Inverter system, noise filter, and noise reduction method

Abstract

To provide an inverter system, a noise filter, and a noise reduction method that can enhance the effect of reducing conductive noise.SOLUTION: An inverter system 1 includes: an inverter device 9 having a power conversion unit 41 using switching elements; and a noise filter 7 that inputs current based on a common mode voltage generated during switching operations of the switching elements to a primary winding 25p of a common mode transformer 25 having a primary winding 25p and a secondary winding 25s.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The disclosed embodiments relate to an inverter system, a noise filter, and a noise reduction method. [Background technology]

[0002] Patent Document 1 describes a conductive noise filter that includes common-mode voltage detection means that detects a common-mode voltage generated during switching operations of a power semiconductor device via a grounded capacitor connected to a line between an AC power supply and a rectifier, and a cancellation voltage source that generates a cancellation voltage of the same magnitude as the common-mode voltage but of opposite polarity based on the detected common-mode voltage, and superimposes this cancellation voltage between the connection point of the AC power supply and the grounded capacitor on the line to cancel out the common-mode voltage. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5263663 Summary of the Invention [Problem to be solved by the invention]

[0004] In the conductive noise filters of the above-described prior art, when an error occurs between the voltage value superimposed on the line by the cancellation voltage source and the voltage value capable of canceling out the generated common-mode voltage, it is difficult to suppress the common-mode current caused by the generated error voltage, and there is a possibility that the effect of reducing conductive noise will be insufficient.

[0005] The disclosed embodiments have been made in consideration of such problems, and have an object to provide an inverter system, a noise filter, and a noise reduction method that can enhance the effect of reducing conductive noise. [Means for solving the problem]

[0006] In order to solve the above-described problems, according to one aspect of the present invention, an inverter system is provided that includes: an inverter device having a power conversion unit that uses switching elements; and a noise filter that inputs a current based on a common mode voltage that is generated during switching operations of the switching elements to the primary winding of a common mode transformer having a primary winding and a secondary winding.

[0007] According to another aspect of the present invention, there is provided a noise filter included in an inverter system having an inverter device with a power conversion unit using switching elements, the noise filter comprising: a common mode transformer having a primary winding and a secondary winding; and a current based on a common mode voltage generated during switching operations of the switching elements, inputted to the primary winding of the common mode transformer.

[0008] According to another aspect of the present invention, there is provided a noise reduction method for an inverter system including an inverter device having a power conversion unit using switching elements, the noise reduction method comprising: inputting, to a primary winding of a common mode transformer having a primary winding and a secondary winding, a current based on a common mode voltage generated during switching operations of the switching elements. [Effects of the Invention]

[0009] According to the disclosed embodiments, the effect of reducing conductive noise can be improved. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a diagram illustrating an example of an overall configuration of an inverter system according to an embodiment. [Figure 2] FIG. 2 is a diagram illustrating an example of the configuration of a noise filter according to an embodiment. [Figure 3] FIG. 10 is a diagram illustrating an example of a common mode equivalent circuit of an inverter system of a comparative example. [Figure 4] FIG. 4 is a diagram illustrating an example of an equivalent circuit obtained by converting the equivalent circuit of FIG. 3. [Figure 5] FIG. 2 is a diagram illustrating an example of a common mode equivalent circuit of the inverter system according to the embodiment. [Figure 6] FIG. 6 is a diagram illustrating an example of an equivalent circuit obtained by converting the equivalent circuit of FIG. 5. [Figure 7] 10 is a graph showing an example of a simulation result of output impedance characteristics. [Figure 8] FIG. 10 is a diagram illustrating an example of the overall configuration of an inverter system according to a modified example in which a noise filter is connected between a rectifier unit and a power converter unit. [Figure 9] FIG. 10 is a diagram illustrating an example of the overall configuration of an inverter system according to a modified example in which a noise filter is connected between a power conversion unit and a motor. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments will be described with reference to the drawings.

[0012] <1. Overall configuration of inverter system> An example of the overall configuration of an inverter system 1 according to an embodiment will be described with reference to FIG.

[0013] As shown in FIG. 1, the inverter system 1 includes a line impedance stabilization network (LISN) 3, a power cable 5, a noise filter 7, an inverter device 9, a motor cable 11, and a motor 13.

[0014] The LISN 3 is an artificial power supply network provided to measure conductive noise in the power supply line of the inverter system 1.

[0015] The power cable 5 connects the LISN 3 and the noise filter 7. The power cable 5 has power lines 17r, 17s, and 17t corresponding to each phase of the three-phase AC voltage (R phase, S phase, and T phase) input from the AC power supply 15 via the LISN 3, and a ground line 19. One end of the ground line 19 is connected to earth or a conductor with a large capacity via the LISN 3.

[0016] The noise filter 7 is connected between the AC power supply 15 and the inverter device 9. The noise filter 7 has a common-mode voltage detection circuit 21, a voltage-current conversion circuit 23, and a common-mode transformer 25. The common-mode voltage detection circuit 21 (an example of a common-mode voltage detection unit) detects a common-mode voltage generated during switching operations of switching elements included in the power conversion unit 41 of the inverter device 9. The voltage-current conversion circuit 23 (an example of a voltage-current conversion unit) outputs a current based on the common-mode voltage detected by the common-mode voltage detection circuit 21. The common-mode transformer 25 has a primary winding 25p and a secondary winding 25s. One end of the primary winding 25p is connected to the voltage-current conversion circuit 23 via an external noise protection circuit 29, and the other end is connected to the ground line 19. The secondary winding 25s is connected to the power supply lines 17r, 17s, and 17t, respectively. The current output from the voltage-current conversion circuit 23 is input to the primary winding 25p of the common-mode transformer 25. With the above configuration, the noise filter 7 inputs a current based on the common mode voltage to the primary winding 25p of the common mode transformer 25.

[0017] The noise filter 7 also has an external noise protection circuit 27 connected to the input of the voltage-current conversion circuit 23, and an external noise protection circuit 29 connected to the output of the voltage-current conversion circuit 23. The external noise protection circuits 27, 29 protect the voltage-current conversion circuit 23 and other components from noise (such as impulse noise) applied from the AC power supply 15. The external noise protection circuit may be provided on only one of the input and output of the voltage-current conversion circuit 23. As shown in FIG. 2, in addition to the external noise protection circuit 27, a high-pass filter 31 and a low-pass filter 33 are also connected to the input of the voltage-current conversion circuit 23, although these are not shown in FIG. 1.

[0018] The inverter device 9 has an input terminal 35 , a ground terminal 37 , a rectifier 39 , a power converter 41 , and an output terminal 43 .

[0019] Power lines 17r, 17s, and 17t are each connected to input terminal 35. A three-phase AC voltage input from AC power supply 15 via LISN 3, power cable 5, and noise filter 7 is input to inverter device 9 via input terminal 35. The other end of ground line 19 and one end of ground line 45 are connected to ground terminal 37.

[0020] The rectifier 39 converts the output of the AC power supply 15, that is, the AC voltage input from the input terminal 35, into a DC voltage.

[0021] The power conversion unit 41 converts a DC voltage into an AC voltage using a switching element. The switching element is a semiconductor device such as an IGBT (Insulated Gate Bipolar Transistor), a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor), or a SiC-MOSFET.

[0022] Power supply lines 47u, 47v, and 47w are connected to the output terminal 43. The three-phase AC voltage (U phase, V phase, and W phase) converted by the power conversion unit 41 is output from the inverter device 9 via the output terminal 43.

[0023] The motor cable 11 connects the inverter device 9 and the motor 13. The motor cable 11 has power supply lines 47u, 47v, and 47w corresponding to each phase of the three-phase AC voltage (U phase, V phase, and W phase) output from the output terminal 43 of the inverter device 9, and a ground line 45. One end of the ground line 45 is connected to the ground terminal 37 of the inverter device 9, and the other end of the ground line 45 is connected to the motor 13. The motor 13 is driven by the drive power supplied from the inverter device 9.

[0024] As described above, the inverter system 1 detects the common mode voltage by the common mode voltage detection circuit 21 close to the inverter device 9, and inputs the voltage at the common mode transformer 25 on the LISN 3 side. In other words, it is configured as a feedforward type.

[0025] The rectifier 39 of the inverter device 9 is mounted on a converter board 49, and the power conversion unit 41 of the inverter device 9 is mounted on an inverter board 51 (an example of a first board). The common mode voltage detection circuit 21, voltage-current conversion circuit 23, common mode transformer 25, etc. of the noise filter 7 are mounted on a noise reduction board 53 (an example of a second board). The converter board 49, inverter board 51, and noise reduction board 53 are each configured as different boards and are arranged separately from each other. Note that board configurations other than those described above may be used as long as at least the inverter board 51 and the noise reduction board 53 are configured as different boards. For example, the converter board 49 and the inverter board 51 may be configured on the same board.

[0026] The configuration of the inverter system 1 described above is an example, and is not limited to the above. For example, the LISN 3 does not necessarily have to be provided. Furthermore, while an example in which the noise filter 7 and the inverter device 9 are configured as separate entities is shown in FIG. 1, the noise filter 7 and the inverter device 9 may be integrated (unitized).

[0027] <2. Noise filter configuration> An example of the configuration of the noise filter 7 will be described with reference to FIG.

[0028] As shown in FIG. 2, the noise filter 7 includes a common mode voltage detection circuit 21, a voltage-current conversion circuit 23, a common mode transformer 25, exogenous noise protection circuits 27 and 29, a high-pass filter 31, and a low-pass filter 33.

[0029] The common-mode voltage detection circuit 21 detects a common-mode voltage generated during switching operations of switching elements included in the power conversion unit 41 of the inverter device 9. The common-mode voltage detection circuit 21 has a detection capacitor. In the example shown in FIG. 2, the common-mode voltage detection circuit 21 has three X capacitors 55 (an example of a detection capacitor) and one Y capacitor 57 (an example of a detection capacitor). The X capacitors 55 are connected between the power supply lines 17r, 17s, and 17t, respectively. The Y capacitor 57 is connected between the power supply lines 17r, 17s, and 17t and the ground line 19 (an example of ground). A damping resistor 59 is connected in parallel to the Y capacitor 57.

[0030] Voltage-current conversion circuit 23 outputs a current based on the common mode voltage detected by common mode voltage detection circuit 21. At that time, voltage-current conversion circuit 23 determines the current so that the voltage induced in secondary winding 25s of common mode transformer 25 approximately matches the common mode voltage detected by common mode voltage detection circuit 21. Specifically, as shown in FIG. 2 , voltage-current conversion circuit 23 has a load simulator 61, an operational amplifier 63, and a plurality of resistors 65, 67, 69, and 71.

[0031] The load simulation unit 61 is a circuit that simulates the excitation impedance of the primary winding 25p of the common mode transformer 25. Although not shown, the load simulation unit 61 is configured by combining passive components such as a coil, a capacitor, and a resistor. The resistor 65 is connected between the input unit 23i of the voltage-current conversion circuit 23 and the non-inverting input terminal of the operational amplifier 63. The resistor 67 is connected between the output terminal and the inverting input terminal of the operational amplifier 63. The resistor 69 is connected between the inverting input terminal of the operational amplifier 63 and the ground line 19. The resistor 71 is connected between the output terminal of the load simulation unit 61 and the non-inverting input terminal of the operational amplifier 63. With the above configuration, the voltage-current conversion circuit 23 applies the common mode voltage detected by the common mode voltage detection circuit 21 to both ends of the load simulation unit 61 and outputs the current generated in the load simulation unit 61 to the primary winding 25p of the common mode transformer 25. Voltage-current conversion circuit 23 may have a circuit configuration other than that described above, as long as it is possible to output a current generated by applying a common mode voltage across load simulation unit 61 to primary winding 25p of common mode transformer 25.

[0032] A high-pass filter 31, a low-pass filter 33, and an external noise protection circuit 27 are connected between the common-mode voltage detection circuit 21 and the input section 23i of the voltage-current conversion circuit 23. The high-pass filter 31 suppresses low-frequency common-mode voltages generated due to three-phase imbalances in the power supply lines 17r, 17s, and 17t, and extracts high-frequency common-mode voltages. The low-pass filter 33 suppresses high-frequency voltages generated when noise (such as impulse noise) is applied from the AC power supply 15. The external noise protection circuit 27 reduces noise currents (such as impulse noise currents) generated when noise is applied from the AC power supply 15 and bypasses them within the protection circuit, protecting the voltage-current conversion circuit 23 and other components. The high-pass filter 31, the low-pass filter 33, and the external noise protection circuit 27 are examples of an external noise protection section.

[0033] An external noise protection circuit 29 is connected between the output section 23o of the voltage-current conversion circuit 23 and the primary winding 25p of the common mode transformer 25. When noise (impulse noise, etc.) is applied from the AC power supply 15, the external noise protection circuit 29 reduces the noise current (impulse noise current, etc.) generated via the common mode transformer 25 and bypasses it into the protection circuit, thereby protecting the voltage-current conversion circuit 23 and other components. Although not shown in the figure, the external noise protection circuit 29 is configured by combining passive components such as resistors and semiconductor components such as diodes. The external noise protection circuit 29 is an example of an external noise protection section.

[0034] The configuration of the noise filter 7 described above is an example and is not limited to the above. For example, one or two of the high-pass filter 31, low-pass filter 33, and exogenous noise protection circuit 27 may be connected to the input section 23i of the voltage-current conversion circuit 23. Furthermore, a band-pass filter may be connected instead of or in addition to any one of the high-pass filter 31, low-pass filter 33, and exogenous noise protection circuit 27. The band-pass filter removes voltage in the frequency band suppressed by the high-pass filter 31 or low-pass filter 33.

[0035] <3. Principles for improving the effectiveness of conductive noise reduction> According to the inverter system 1 configured as above, it is possible to enhance the effect of reducing conductive noise. The principle behind this will be described with reference to FIGS.

[0036] As a comparative example for comparison with inverter system 1 according to this embodiment, an inverter system is assumed in which a common-mode voltage is detected in a noise filter, the detected common-mode voltage is amplified by a voltage-type signal source such as an operational amplifier or transistor at a predetermined magnification, and the amplified voltage is input to a power supply line using a common-mode transformer, thereby canceling out the common-mode voltage. Figure 3 shows an example of a common-mode equivalent circuit of the inverter system of this comparative example.

[0037] As shown in FIG. 3, the common mode equivalent circuit of the comparative example has a voltage source Vamp of an operational amplifier 73 and an output impedance Zoamp of the operational amplifier 73. The voltage source Vamp and the output impedance Zoamp are connected in series to form a closed circuit on the primary side of a common mode transformer 75. The common mode equivalent circuit of the comparative example also has an impedance Zlisn of the LISN, an impedance Zpc of the power cable, an excitation impedance Zcmt of the common mode transformer 75, an impedance Zxyc of the X capacitor 55 and the Y capacitor 57 that form the common mode voltage detection circuit, a common mode voltage source Vcom of the inverter device, and an impedance Zmc of the motor cable. The common mode voltage source Vcom and the impedances Zlisn, Zpc, Zcmt, and Zmc are connected in series, and the impedance Zxyc is connected in parallel with the impedance Zmc to form a closed circuit on the secondary side of the common mode transformer 75.

[0038] Figure 4 shows an example of an equivalent circuit obtained by modeling the common mode transformer 75 of the equivalent circuit of Figure 3 as a T-type circuit and converting the common mode voltage source Vcom and impedances Zmc and Zxyc, as well as the voltage source Vamp and impedances Zoamp and Zcmt, using Thévenin's theorem. As shown in Figure 4, the equivalent circuit after conversion has impedance Zlisn, impedance Zpc, composite impedance Z1, composite voltage V1 of the operational amplifier, composite voltage V2 of the inverter device, and composite impedance Z2. These impedances Zlisn and Zpc, composite impedances Z1 and Z2, and composite voltages V1 and V2 are connected in series to form a closed circuit.

[0039] The composite impedance Z1 is expressed by Equation 1. Z1=(Zcmt×Z'oamp) / (Zcmt+Z'oamp)...Equation 1 The composite voltage V1 is expressed by equation 2. V1={Zcmt / (Zcmt+Z'oamp)}×V'amp...Equation 2 The composite voltage V2 is expressed by Equation 3. V2={Zxyc / (Zxyc+Zmc)}×Vcom...Equation 3 The composite impedance Z2 is expressed by Equation 4. Z2=(Zxyc×Zmc) / (Zxyc+Zmc)...Equation 4 The voltage V'amp and impedance Z'oamp are obtained by converting the voltage Vamp and impedance Zoamp of the operational amplifier 73 to the secondary side of the common mode transformer 75. For example, if the turns ratio of the common mode transformer 75 is a, then V'amp is Vamp×a, and Z'oamp is Zoamp×a. 2 This becomes:

[0040] In FIG. 4, the voltage V'amp required to completely cancel out the common mode voltage Vcom and suppress noise is expressed by equation 5, since V1=V2. {Zcmt / (Zcmt+Z'oamp)}×V'amp={Zxyc / (Zxyc+Zmc)}×Vcom V'amp={(Zcmt+Z'oamp) / Zcmt}×{Zxyc / (Zxyc+Zmc)}×Vcom...Equation 5

[0041] If the common mode voltage detected by the common mode voltage detection circuit is Vcomdet, the common mode voltage Vcomdet is expressed by Equation 6. Vcomdet={Zxyc / (Zxyc+Zmc)}×Vcom-{(Zxyc×Zmc) / (Zxyc+Zmc)×Icom}...Equation 6 Note that Icom is the common mode current that flows through the closed circuit in Figure 4 due to the common mode voltage.

[0042] Transforming equation 6 yields equation 7. {Zxyc / (Zxyc+Zmc)}×Vcom=Vcomdet+{(Zxyc×Zmc) / (Zxyc+Zmc)×Icom}...Equation 7 Substituting Equation 7 into Equation 5 gives Equation 8. V'amp={(Zcmt+Z'oamp) / Zcmt}×[Vcomdet+{(Zxyc×Zmc) / (Zxyc+Zmc)×Icom}]...Equation 8 Equation 8 gives the voltage V'amp required to completely cancel out the common-mode voltage Vcom and suppress noise.

[0043] However, the motor cable impedance Zmc included in the term {(Zxyc × Zmc) / (Zxyc + Zmc) × Icom} in Equation 8 is the impedance between the UVW power lines and the ground line in the motor cable, and is difficult to grasp. Furthermore, the common-mode current Icom is difficult to detect because it is minute and high-frequency. For this reason, in the inverter system of the comparative example, it is conceivable to omit this term and use Equation 9 for the voltage V'amp. V'amp={(Zcmt+Z'oamp) / Zcmt}×Vcomdet...Equation 9 In this case, due to the difference between Equation 8 and Equation 9, in the inverter system of the comparative example, an error occurs between the voltage value capable of canceling out the common mode voltage and the voltage value input to the power line using the common mode transformer.

[0044] On the other hand, in the common-mode equivalent circuit of the comparative example, impedance Zpc is small because it is a cable. Furthermore, the combined impedance Z2 is also small because it is rate-determined by the impedances of the X and Y capacitors at high frequencies. Note that impedance Zlisn is used to measure conducted noise and does not play a role in reducing the common-mode current Icom, so it is not considered here. Furthermore, because the output impedance Zoamp of the operational amplifier is small, the combined impedance Z1 expressed in Equation 1 is also small, making it impossible to effectively utilize the excitation impedance Zcmt of the common-mode transformer 75. As a result, it is difficult to suppress the common-mode current Icom caused by the generated error voltage, which may result in insufficient conducted noise reduction.

[0045] Fig. 5 shows an example of a common mode equivalent circuit of the inverter system 1 according to this embodiment. As shown in Fig. 5, the common mode equivalent circuit of the inverter system 1 has a current source Iamp of the voltage-current conversion circuit 23 and an output impedance Zoamp of the voltage-current conversion circuit 23. The current source Iamp and the output impedance Zoamp are connected in parallel to form a closed circuit on the primary side of the common mode transformer 25. Note that the closed circuit on the secondary side of the common mode transformer 25 is the same as that shown in Fig. 3, and therefore a description thereof will be omitted.

[0046] Figure 6 shows an example of an equivalent circuit obtained by modeling the common mode transformer 25 of the equivalent circuit of Figure 5 as a T-type circuit and converting the common mode voltage source Vcom and impedances Zmc and Zxyc, and the current source Iamp and impedances Zoamp and Zcmt using Thévenin's theorem. As shown in Figure 6, the equivalent circuit after conversion has impedance Zlisn, impedance Zpc, composite impedance Z3, composite voltage V3 of the operational amplifier, composite voltage V4 of the inverter device, and composite impedance Z4. These impedances Zlisn and Zpc, composite impedances Z3 and Z4, and composite voltages V3 and V4 are connected in series to form a closed circuit.

[0047] The composite impedance Z3 is expressed by the above-mentioned equation 1. The composite voltage V3 is expressed by equation 10. V3={Zcmt / (Zcmt+Z'oamp)}×Z'oamp×I'amp...Equation 10 The composite voltage V4 is expressed by the above-mentioned equation 3. The composite impedance Z4 is expressed by the above-mentioned equation 4. The current I'amp and impedance Z'oamp are obtained by converting the current Iamp and impedance Zoamp of the voltage-current conversion circuit 23 into the secondary side of the common mode transformer 25. For example, if the turns ratio of the common mode transformer 25 is a, I'amp is Iamp / a, and Z'oamp is Zoamp×a 2 This becomes:

[0048] In FIG. 6, the current I'amp required to completely cancel out the common mode voltage Vcom and suppress noise is expressed by equation 11, since V3=V4. {Zcmt / (Zcmt+Z'oamp)}×Z'oamp×I'amp={Zxyc / (Zxyc+Zmc)}×Vcom I'amp={(Zcmt+Z'oamp) / (Zcmt×Z'oamp)}×{Zxyc / (Zxyc+Zmc)}×Vcom...Equation 11

[0049] Substituting the above-mentioned formula 7 into formula 11 gives formula 12. I'amp={(Zcmt+Z'oamp) / (Zcmt×Z'oamp)}×[Vcomdet+{(Zxyc×Zmc) / (Zxyc+Zmc)×Icom}]...Equation 12 Equation 12 gives the current I'amp required to completely cancel out the common-mode voltage Vcom and suppress noise.

[0050] For the same reason as above, when the term {(Zxyc×Zmc) / (Zxyc+Zmc)×Icom} in equation 12 is omitted, the current I′amp is given by equation 13. I'amp={(Zcmt+Z'oamp) / (Zcmt×Z'oamp)}×Vcomdet={(Zcmt / Z'oamp+1) / Zcmt}×Vcomdet...Equation 13 5 and 6, the output impedance Z'oamp of voltage-current conversion circuit 23 is sufficiently larger than the excitation impedance Zcmt of common mode transformer 25. Therefore, Equation 13 can be approximated as Equation 14. I'amp≒Vcomdet / Zcmt...Equation 14 In this way, in the inverter system 1, the current I'amp defined by equation 14 can cancel out most of the common-mode voltage.

[0051] Note that, due to the difference between Equation 12 and Equation 14, it is conceivable that an error voltage will occur in the inverter system 1 according to this embodiment, as in the comparative example described above. However, as shown in the equivalent circuits in FIGS. 5 and 6, the use of current source Iamp results in a very large output impedance Zoamp (Z'oamp converted to the secondary side) of voltage-current conversion circuit 23. This allows the combined impedance Z1 expressed by Equation 1 to be increased, and the excitation impedance Zcmt of common mode transformer 75 to be effectively utilized. As a result, it becomes possible to suppress the common mode current Icom due to the generated error voltage, thereby enhancing the effect of reducing conductive noise.

[0052] FIG. 7 shows an example of the simulation results of the output impedance characteristics. The graph in FIG. 7 is a double logarithmic graph with the horizontal axis representing frequency and the vertical axis representing impedance magnitude, with both the horizontal and vertical axes on a logarithmic scale. The graph shows the output impedance (Zoamp) of voltage-current conversion circuit 23 alone, the excitation impedance on the primary side of common mode transformer 25, and the composite impedance of these two impedances. As shown in FIG. 7, in the frequency range of 1 MHz or less, the output impedance of voltage-current conversion circuit 23 alone is more than 10 times larger than the excitation impedance on the primary side of common mode transformer 25, and the composite impedance is approximately equal to the excitation impedance on the primary side of common mode transformer 25. Therefore, it can be confirmed that the composite impedance Z3 (FIG. 6) expressed by the above-mentioned equation 1 also becomes large. Note that the characteristics shown in FIG. 7 are the output impedance on the primary side of common mode transformer 25. When converted to the secondary side, if the turns ratio of common mode transformer 25 is a, the impedance becomes a. 2 This increases the effect of suppressing the common mode current Icom.

[0053] <4. Effects of the embodiment> As described above, in the inverter system 1 of this embodiment, a current is input to the primary winding 25p of the common mode transformer 25 based on the common mode voltage generated during switching operations of the switching elements provided in the power conversion unit 41 of the inverter device 9. This allows the common mode voltage to be reduced by the voltage induced in the secondary winding 25s of the common mode transformer 25. In this case, by configuring the inverter system 1 so that a current is input to the primary winding 25p of the common mode transformer 25, the combined impedance Z3 in the common mode equivalent closed circuit of the inverter system 1 can be increased. This allows the common mode current Icom due to the generated error voltage to be suppressed even if an error occurs between the voltage value induced in the secondary winding 25s of the common mode transformer 25 by the noise filter 7 and a voltage value capable of canceling out the generated common mode voltage. This enhances the effect of reducing conductive noise.

[0054] Furthermore, in this embodiment, the current input from voltage-current conversion circuit 23 to primary winding 25p of common mode transformer 25 may be determined so that the voltage induced in secondary winding 25s of common mode transformer 25 approximately matches the common mode voltage detected by common mode voltage detection circuit 21. In this case, most of the common mode voltage generated during the switching operation of the switching elements can be offset by the voltage induced in secondary winding 25s of common mode transformer 25.

[0055] Furthermore, in this embodiment, the inverter board 51 on which the power conversion unit 41 of the inverter device 9 is mounted and the noise reduction board 53 on which the voltage-current conversion circuit 23 of the noise filter 7 is mounted may be different boards. In this case, by separating the inverter board 51 and the noise reduction board 53, it is possible to prevent a noise source on the inverter board 51 from affecting the noise filtering function of the noise reduction board 53, thereby preventing a decrease in the noise reduction function. Furthermore, by making the noise reduction board 53 on which the voltage-current conversion circuit 23 is mounted detachable, it becomes possible to change or add noise filtering functions.

[0056] Furthermore, in this embodiment, voltage-current conversion circuit 23 may include a load simulation unit 61 that simulates the excitation impedance of primary winding 25p of common mode transformer 25. In this case, by using load simulation unit 61, it is possible to determine a current value at which the voltage induced in secondary winding 25s of common mode transformer 25 substantially coincides with the common mode voltage detected by common mode voltage detection circuit 21.

[0057] Furthermore, in this embodiment, voltage-current conversion circuit 23 may apply the common mode voltage detected by common mode voltage detection circuit 21 to both ends of load simulation unit 61, and output the current generated in load simulation unit 61 to primary winding 25p of common mode transformer 25. In this case, the voltage induced in secondary winding 25s of common mode transformer 25 can be made to match the common mode voltage detected by common mode voltage detection circuit 21 with high accuracy.

[0058] In this embodiment, the load simulation unit 61 may be configured using passive components. In this case, the excitation impedance characteristics of the primary winding 25p of the common mode transformer 25 can be reproduced with high accuracy.

[0059] Furthermore, in this embodiment, the common mode voltage detection circuit 21 may be configured with a detection capacitor. In this case, most of the common mode current flowing from the power conversion unit 41 through the ground line 45 is bypassed by the detection capacitors (X capacitor 55, Y capacitor 57) of the common mode voltage detection circuit 21, making it possible to accurately detect the common mode voltage while suppressing the common mode current flowing to the LISN 3 side.

[0060] Furthermore, in this embodiment, the common mode voltage detection circuit 21 may be configured to include at least the Y capacitor 57. This allows most of the common mode current flowing from the power conversion unit 41 to the ground line 45 to be bypassed by at least the Y capacitor 57 of the common mode voltage detection circuit 21, making it possible to accurately detect the common mode voltage while suppressing the common mode current flowing to the LISN 3 side.

[0061] If the noise filter 7 includes an LC circuit consisting of a coil and a capacitor, resonance may occur in a specific frequency band, resulting in an increase in noise. Therefore, in this embodiment, a damping resistor 59 may be connected in parallel to the Y capacitor 57. In this case, the resonance in the LC circuit can be damped, preventing an increase in noise.

[0062] In this embodiment, the noise filter 7 may have external noise protection circuits 27, 29 on at least one of the input section 23i and the output section 23o of the voltage-current conversion circuit 23. In this case, the voltage-current conversion circuit 23 can be protected from noise (impulse noise) applied from the AC power supply 15.

[0063] In this embodiment, at least one of a high-pass filter 31, a low-pass filter 33, and a band-pass filter may be connected to the input section 23i of the voltage-current conversion circuit 23. In this case, it is possible to suppress or remove voltage in a specific frequency band, thereby preventing breakdown of the voltage-current conversion circuit 23 and accurately detecting the common-mode voltage.

[0064] In this embodiment, the external noise protection circuit 29 connected to the output section 23o of the voltage-current conversion circuit 23 may include semiconductor components such as passive components and diodes. In this case, when noise (impulse noise) is applied from the AC power supply 15, the impulse noise current generated via the common mode transformer 25 can be suppressed. This makes it possible to prevent breakdown of the voltage-current conversion circuit 23 due to the impulse noise current.

[0065] In this embodiment, the noise filter 7 may be connected between the AC power supply 15 and the power conversion unit 41 of the inverter device 9. In this case, a feedforward inverter system 1 can be realized by detecting the common mode voltage using a common mode voltage detection circuit 21 close to the inverter device 9 and inputting the voltage through a common mode transformer 25 on the LISN 3 side. This suppresses oscillations caused by a design that increases the amplification factor of the amplifier circuit (high-gain design), thereby improving stability. It also suppresses an increase in conducted noise due to overshooting of the voltage injected into the power lines 17r, 17s, and 17t, and a reduction in the conducted noise suppression effect due to a phase delay in the amplifier circuit.

[0066] <5. Variations> The disclosed embodiments are not limited to those described above, and various modifications are possible within the scope of the spirit and technical concept of the present invention. Such modifications will be described below.

[0067] (5-1. When connecting a noise filter between the rectifier and power converter) In the above embodiment, the inverter system 1 is configured so that the noise filter 7 is connected between the AC power supply 15 and the power conversion unit 41 of the inverter device 9, but the connection position of the noise filter 7 may be other than the above. For example, as in an inverter system 1A shown in Fig. 8, the noise filter 7A may be connected between the rectification unit 39 and the power conversion unit 41 of the inverter device 9.

[0068] In the noise filter 7A, the common-mode voltage detection circuit 21 has two X capacitors 55 (an example of a detection capacitor) and one Y capacitor 57 (an example of a detection capacitor). The X capacitors 55 are connected between the power supply lines 77p, 77n provided between the rectifier unit 39 and the power converter 41, respectively. The Y capacitor 57 is connected between the power supply lines 77p, 77n and the ground line 45 (an example of ground). Although not shown in the figure, a damping resistor 59 is connected in parallel to the Y capacitor 57. The other configuration of the noise filter 7A is the same as that of the noise filter 7 of the embodiment, and therefore description thereof will be omitted. In this modification, the inverter device 9 and the noise filter 7A are configured integrally. Note that the inverter device 9 and the noise filter 7A may be configured as separate bodies. Furthermore, the converter board 49, the inverter board 51, and the noise reduction board 53 may be configured as a single board or two boards.

[0069] According to this modification, similar to the above embodiment, it is possible to realize an inverter system 1A that can enhance the effect of reducing conductive noise. Furthermore, since the inverter device 9 and the noise filter 7A can be integrated, the system configuration can be simplified.

[0070] (5-2. Connecting a noise filter between the power converter and the motor) In the above embodiment, the inverter system 1 is configured such that the noise filter 7 is connected between the AC power supply 15 and the power conversion unit 41 of the inverter device 9, but the connection position of the noise filter 7 may be other than the above. For example, as in the inverter system 1B shown in FIG. 9 , the noise filter 7B may be connected between the power conversion unit 41 of the inverter device 9 and the motor 13.

[0071] The configuration of the noise filter 7B is the same as that of the noise filter 7 of the embodiment. In the noise filter 7B, the three X capacitors 55 constituting the common mode voltage detection circuit 21 are connected between the power supply lines 47u, 47v, and 47w, respectively. Furthermore, one Y capacitor 57 is connected between the power supply lines 47u, 47v, and 47w and the ground line 45 (an example of ground). Although not shown, a damping resistor 59 is connected in parallel to the Y capacitor 57.

[0072] According to this modification, similar to the above embodiment, it is possible to realize an inverter system 1B that can enhance the effect of reducing conductive noise.

[0073] In addition to the above, the methods according to the above-described embodiments and modifications may be combined as appropriate. Although not specifically illustrated, the above-described embodiments and modifications may be implemented with various modifications within the spirit and scope of the invention.

[0074] The problems and effects that the above-described embodiments and modifications are intended to solve are not limited to those described above. The embodiments and modifications may solve problems or achieve effects that are not described above, or may solve only some of the problems or achieve only some of the effects that are described. [Explanation of symbols]

[0075] 1. Inverter system 1A inverter system 1B Inverter System 5 Power cable 7 Noise Filter 7A noise filter 7B Noise Filter 9. Inverter device 11 Motor cable 13 Motor 15 AC power supply 17r power line 17s power line 17t power line 19 Ground wire 21 Common mode voltage detection circuit 23 Voltage-current conversion circuit 23i Input section 23o Output section 25 Common mode transformer 25p primary winding 25s secondary winding 27 External noise protection circuit 29 External noise protection circuit 31 High-pass filter 33 Low-pass filter 39 Rectifier 41 Power conversion section 45 Ground wire 47u power wire 47v power line 47w power line 49 Converter Board 51 Inverter board 53 Noise reduction board 55 x Capacitors 57 Y capacitor 59 Damping Resistor 61 Load simulation section 63 Operational Amplifier 77n power line 77p power line

Claims

1. an inverter device having a power conversion unit using switching elements; a noise filter that inputs a current based on a common mode voltage generated during a switching operation of the switching element to the primary winding of a common mode transformer having a primary winding and a secondary winding; An inverter system equipped with

2. The noise filter comprises: a common mode voltage detection unit that detects the common mode voltage; a voltage-current converter that outputs a current based on the common mode voltage detected by the common mode voltage detector; the common mode transformer, to which the current output from the voltage-current conversion unit is input, The voltage-current converter includes: determining the current so that the voltage induced in the secondary winding of the common mode transformer substantially coincides with the common mode voltage detected by the common mode voltage detection unit; The inverter system according to claim 1 .

3. a first substrate on which the power conversion unit is mounted; a second substrate on which the voltage-current converter is mounted and which is a substrate different from at least the first substrate; The inverter system according to claim 2 .

4. The voltage-current converter includes: a load simulation unit that simulates the excitation impedance of the primary winding of the common mode transformer; The inverter system according to claim 2 .

5. The voltage-current converter includes: the common mode voltage detected by the common mode voltage detection unit is applied to both ends of the load simulation unit, and a current generated in the load simulation unit is output to the primary winding of the common mode transformer; The inverter system according to claim 4 .

6. The load simulation unit having passive components, The inverter system according to claim 4 or 5.

7. The common mode voltage detection unit having a detection capacitor; The inverter system according to claim 2 .

8. The detection capacitor is A Y capacitor connected between a power supply line and ground, or an X capacitor and the Y capacitor connected between the power supply lines, The inverter system according to claim 7 .

9. The common mode voltage detection unit a damping resistor connected in parallel to the Y capacitor; The inverter system according to claim 8 .

10. The noise filter comprises: an external noise protection unit for protecting the voltage-current conversion unit from noise applied from an AC power supply, at least one of an input unit and an output unit of the voltage-current conversion unit; The inverter system according to claim 2 .

11. The external noise protection unit connected to the input unit includes: having at least one of a high-pass filter, a low-pass filter, and a band-pass filter; The inverter system according to claim 10.

12. The external noise protection unit connected to the output unit includes: The semiconductor device has at least one of a passive component and a semiconductor component. The inverter system according to claim 10 or 11.

13. The noise filter comprises: connected between an AC power supply and the power conversion unit; The inverter system according to claim 1 .

14. The inverter device is a rectifier unit that converts the output of the AC power supply into a DC voltage; the power conversion unit that converts the DC voltage into an AC voltage; and The noise filter comprises: connected between the rectification unit and the power conversion unit; The inverter system according to claim 1 .

15. The inverter system includes: The inverter device further includes a motor that is driven by the driving power supplied from the inverter device. The noise filter comprises: connected between the power conversion unit and the motor; The inverter system according to claim 1 .

16. A noise filter provided in an inverter system including an inverter device having a power conversion unit using a switching element, a current based on a common mode voltage generated during a switching operation of the switching element is input to the primary winding of a common mode transformer having a primary winding and a secondary winding; Noise filter.

17. a common mode voltage detection unit that detects the common mode voltage; a voltage-current converter that outputs a current based on the common mode voltage detected by the common mode voltage detector; the common mode transformer, to which the current output from the voltage-current conversion unit is input, The voltage-current converter includes: determining the current so that the voltage induced in the secondary winding of the common mode transformer substantially coincides with the common mode voltage detected by the common mode voltage detection unit; 17. The noise filter according to claim 16.

18. A noise reduction method for an inverter system including an inverter device having a power conversion unit using switching elements, comprising: a current based on a common mode voltage generated during a switching operation of the switching element is input to the primary winding of a common mode transformer having a primary winding and a secondary winding; A noise reduction method comprising:

19. inputting a current based on the common mode voltage, detecting the common mode voltage; determining the current so that a voltage induced in the secondary winding of the common mode transformer substantially matches the detected common mode voltage; inputting the determined current into the primary winding of the common mode transformer; 20. The noise reduction method of claim 18, comprising:

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