Active filter device, power conversion device, refrigeration cycle device, and method for controlling active filter device

Abstract

An active filter device (3) including a converter (34) that generates a compensation current for suppressing a harmonic current generated from a rectifier circuit (21) that converts power from a three-phase AC power source (4) into DC, and a control device (36) that controls the converter (34). The control device (36) includes a current command calculation unit (110) that calculates a compensation current command for suppressing the harmonic current, a first control amount calculation unit (115) that calculates a first control amount (VrPI*) based on a deviation between the compensation current command and a detected compensation current, and a damping control unit (120) that calculates a pulsating component (ΔiL) of a three-phase input current (iL) and calculates a second control amount (Vr') based on the calculated pulsating component (ΔiL).

Description

[Technical field]

[0001] The present disclosure relates to an active filter device, a power conversion device, a refrigeration cycle device, and a control method for an active filter device. [Background technology]

[0002] A load driving device for inputting power from an AC power source to a load includes a rectifier, such as a diode bridge, and an inverter. Distortion of the power source current generated in the diode bridge causes a decrease in the power factor and an increase in harmonics in the power source current. To improve this, an active filter device is placed in parallel with the load driving device, and the active filter device operates to cancel the power source current distortion generated in the diode bridge, thereby making the power source current sinusoidal.

[0003] It is sufficient if the smoothing capacitor of the inverter has a sufficiently large capacity, but if the smoothing capacitor is made small in capacity in order to miniaturize the device, etc., interference will occur between the load driving device and the active filter device, causing pulsation and making it difficult to make the power supply current a smooth sine wave.

[0004] To address this issue, the interference phenomenon can be mitigated by differentiating the detected power supply voltage, multiplying it by a gain, and then subtracting the resulting value to correct the voltage (see, for example, Patent Document 1). This makes it possible to reduce the capacity of the smoothing capacitor. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2016-116330 A Summary of the Invention [Problem to be solved by the invention]

[0006] In the conventional active filter device described above, it is sometimes necessary to detect the power supply voltage at two or more points in an analog manner, which increases the number of parts. Furthermore, since the power supply voltage is differentiated to correct the voltage, a differentiator with low noise resistance must be used, and there are concerns about the accuracy of correction depending on the noise conditions.

[0007] The present application discloses technology for solving the above problems, and aims to provide an active filter device, a power conversion device, a refrigeration cycle device, and a control method for an active filter device that can effectively mitigate interference between the active filter device and a load driving device with a small number of parts. [Means for solving the problem]

[0008] The active filter device according to the present disclosure comprises: Supplementary A converter that generates a compensation current and a control device that controls the converter. and suppresses harmonic currents generated by rectifier circuits that convert power from three-phase AC power sources to DC. An active filter device, comprising: The control device teeth, Supplementary a current command calculation unit for calculating a compensation current command; a first control amount calculation unit that calculates a first control amount based on a deviation between the compensation current command and the detected compensation current; a damping control unit that calculates a pulsating component of a three-phase input current input to the rectifier circuit and calculates a second control amount based on the calculated pulsating component; a drive signal generator that drives the converter based on the calculated first control amount and the calculated second control amount, The damping control unit calculates the second control amount so as to reduce the output voltage of the three-phase AC power supply in accordance with the magnitude of the calculated pulsating component. Effect of the Invention

[0009] According to the present disclosure, it is possible to effectively cancel harmonic currents generated from a rectifier circuit while reducing the number of parts, and to suppress pulsation of a three-phase input current. [Brief description of the drawings]

[0010] [Figure 1] 1 is a schematic diagram showing a configuration of a power conversion device according to a first embodiment. [Diagram 2] 1 is a diagram showing a configuration of a converter included in the active filter device according to the first embodiment. [Diagram 3] 1 is a block diagram showing a configuration of a control device included in the active filter device according to the first embodiment. [Figure 4] 4 is a flowchart showing an operation of the active filter device. [Diagram 5] 5 is a flowchart showing the operation of a damping control unit included in the control device of the active filter device. [Figure 6A] FIG. 13 is a diagram showing a power supply current waveform in Comparative Example 1. [Figure 6B] FIG. 11 is a diagram showing a power supply current waveform in Comparative Example 2. [Figure 6C] 5 is a diagram showing a power supply current waveform when the active filter device according to the first embodiment is used. FIG. [Figure 7] FIG. 11 is a schematic diagram showing a configuration of a power conversion device according to a second embodiment. [Figure 8] FIG. 11 is a block diagram showing a configuration of a control device included in an active filter device according to a second embodiment. [Figure 9] FIG. 11 is a block diagram showing a configuration of a control device included in an active filter device according to a third embodiment. [Figure 10] FIG. 11 is a block diagram showing a configuration of a control device included in an active filter device according to a fourth embodiment. [Figure 11] FIG. 13 is a block diagram showing a configuration of a control device included in an active filter device according to a fifth embodiment. [Figure 12] FIG. 2 is a block diagram showing a configuration of a repetitive controller. [Figure 13] FIG. 13 is a block diagram showing another example of the configuration of the control device included in the active filter device according to the fifth embodiment. [Figure 14] FIG. 13 is a block diagram showing yet another example configuration of the control device included in the active filter device according to the fifth embodiment. [Figure 15] FIG. 13 is a schematic diagram showing a configuration of a refrigeration cycle device according to a sixth embodiment. [Figure 16] FIG. 2 is a hardware configuration diagram showing an example of a control device included in the active filter device according to the first to sixth embodiments. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, the present embodiment will be described with reference to the drawings. In the drawings, the same reference numerals indicate the same or corresponding parts.

[0012] Embodiment 1 Hereinafter, an active filter device according to a first embodiment and a power conversion device including the same will be described with reference to the drawings. Fig. 1 is a schematic diagram showing the configuration of a power conversion device 1 according to a first embodiment. In Fig. 1, the power conversion device 1 includes a load driving device 2 that converts the power of a three-phase AC power source 4 into a preset power and supplies it to a load, for example, a motor 25, and an active filter device 3 that is connected in parallel to the load driving device 2 and cancels harmonics of a power supply current iP generated by the load driving device 2. The active filter current iAF generated by the active filter device 3 is superimposed on the power supply current iP to make the power supply current iP into a smooth sine wave. The active filter current iAF is a general term for the active filter currents iAFr, iAFt, and iAFs, and the load current iL is a general term for the load currents iLr, iLt, and iLs. The load currents iLr, iLt, and iLs each correspond to the three-phase input currents. Similarly, the power supply current iP is a general term for the power supply currents of each phase.

[0013] <Configuration of the load driving device 2> Next, the configuration of the load driving device 2 will be described. The load driving device 2 includes a rectifier 21 consisting of a diode bridge, a DC reactor 22, a smoothing capacitor 23, and an inverter 24. The rectifier 21, the DC reactor 22, and the smoothing capacitor 23 convert AC from the three-phase AC power source 4 to DC, and the inverter 24 converts the DC back to AC to drive a motor 25, which is a load, at an arbitrary rotation speed. The motor 25 is assumed to be, for example, a motor for an air conditioning compressor, but is not limited to this type and use of the motor.

[0014] <Configuration of active filter device 3> Next, the configuration of the active filter device 3 will be described. The active filter device 3 is connected in parallel to the rectifier 21, i.e., in parallel to the load driving device 2, to the three-phase AC power source 4, and includes a converter 34 made up of a filter reactor 31, a filter capacitor 32, a control reactor 33, and a power module, which are arranged in each phase of the three-phase AC power source 4. The filter reactor 31 and the filter capacitor 32 form an LC filter, which prevents carrier ripple from flowing out to the three-phase AC power source 4 side.

[0015] Fig. 2 shows a configuration example of a converter 34 included in the active filter device 3. As shown in Fig. 2, the converter 34 may employ a power module using six semiconductor switch elements similar to a typical three-phase inverter. In addition, a smoothing capacitor 35 is connected between the PN outputs of the converter .

[0016] The active filter device 3 detects harmonic currents generated in the rectifier 21 of the load driving device 2 and performs current control to cancel them, thereby operating to offset the harmonic currents generated in the rectifier 21. To perform this control, the active filter device 3 includes a control device 36 that receives various sensor information and outputs a drive signal for the converter 34.

[0017] The load currents iLr, iLt detected by the current sensors 37a, 37b and the active filter currents iAFr, iAFt detected by the current sensors 37c, 37d are input to the control device 36. As shown in Fig. 1, two current sensors are provided for each of the load current and active filter current to detect two of the three phases, and the remaining phase can be omitted because it can be calculated from Kirchhoff's law. These are sensor information necessary to make the power supply current iP sinusoidal.

[0018] Further, the control device 36 receives the interphase voltage Vrs between the R phase and the S phase detected by the voltage sensor 38a, and the voltage Vdc of the smoothing capacitor 35 detected by the voltage sensor 38b. The interphase voltage Vrs is used to calculate the magnitude and phase of the output voltage of each phase, and the output voltages Vr, Vs, and Vt of each phase are calculated. The voltage Vdc of the smoothing capacitor 35 is used to perform voltage control, which will be described later. Note that the output voltage may be detected by detecting the interphase voltage between other phases.

[0019] When the capacity of the smoothing capacitor 23 in the load driving device 2 is large, the load driving device 2 and the active filter device 3 do not interfere with each other, and the harmonic current can be cancelled out by the compensation of the active filter device 3 to make the power supply current iP sinusoidal. However, when the capacity of the smoothing capacitor 23 decreases and the LC resonance frequency increases, the interference phenomenon becomes prominent, making it difficult to perform continuous operation, let alone compensate to cancel out the harmonic current. Therefore, it becomes necessary to change the active filter device 3 or the control device 36 of the active filter device 3 accordingly.

[0020] <Configuration and Operation of the Control Device 36 of the Active Filter Device 3> Fig. 3 is a control block diagram showing the configuration of the control device 36 provided in the active filter device 3. Fig. 4 is a flowchart explaining the operation of the active filter device 3. The control device 36 includes an R-phase control unit 100, a T-phase control unit 140, a subtractor 141, and a drive signal generator 150. Note that the R-phase control unit 100 and the T-phase control unit 140 have equivalent control blocks and perform similar operations, so the R-phase control unit 100 will be described as an example and a description of the T-phase control unit 140 will be omitted.

[0021] First, the control device 36 extracts the harmonic components of the load current iLr and generates a command to cancel them (step ST01). A band pass filter (BPF) 101 extracts a fundamental wave component from an R-phase load current iLr input to a current command calculation unit 110 of the control device 36. A subtractor 102 subtracts the detected load current iLr from the extracted fundamental wave component to calculate a pre-compensation current command iAFr*.

[0022] Next, the portion relating to voltage control will be described. A subtractor 103 calculates the deviation between the voltage command Vdc* of the smoothing capacitor 35 and the detected voltage Vdc, and a PI controller 104 performs PI control (Proportional Integral Control) based on this deviation, and a multiplier 105 multiplies the output control amount by the sine of the power supply voltage, sin θ. An adder 106 adds the multiplication result of the multiplier 105 to the pre-compensation current command iAFr*, which is the output of the subtractor 102, to calculate an active filter current command iAFr*'. By realizing the active filter current command iAFr*', it is possible to suppress harmonic components and make the power supply current sinusoidal.

[0023] Next, the part related to current control will be described. The subtractor 107 calculates the deviation between the active filter current command iAFr*' and the active filter current iAFr detected by the current sensor 37c, and the calculated deviation is input to the PI controller 108 and feedback controlled by PI control, so that the deviation becomes almost zero, and the active filter current command iAFr*' and the active filter current iAFr can be made almost the same. The PI controller 108 outputs a first control amount VrPI*. The first control amount VrPI* corresponds to a voltage command that cancels out the harmonic components of the power supply current iP (R-phase component is iPr). Here, the subtractor 107 and the PI controller 108 correspond to a first control amount calculation unit 115.

[0024] In order to further improve the control performance, a PID controller may be used instead of the PI controller 108 to perform PID control (Proportional Integral Derivative Control). Also, repetitive control may be added, or repetitive control and feedback control may be used together. P control or PD control may be performed without integral control (I control).

[0025] Next, the control device 36 extracts the pulsating components of the three-phase load currents iLr, iLs, and iLt, and generates a command to cancel them (step ST02). This process is mainly performed by the damping control unit 120. Fig. 5 is a flowchart showing the main processing operations in the damping control unit 120. The operation of the damping control unit 120 will be described with reference to Figs. 3 and 5.

[0026] First, the three-phase load currents iLr, iLs, and iLt are input to the three-phase current effective value calculator 121 (step ST021). As described above, the load currents iLr and iLt are detected by the current sensors 37a and 37b, and the load current iLs is calculated according to Kirchhoff's law.

[0027] In the three-phase current effective value calculator 121, the three-phase current effective value iL is calculated using the input three-phase load currents iLr, iLs, and iLt. The three-phase current effective value iL is calculated by the formula (1) (step ST022).

number

[0028] Next, in order to extract the amount of change in the three-phase current effective value iL, the pulsating component ΔiL is extracted by the high-pass filter (HPF) 122 (step ST023). Here, the cutoff frequency of the high-pass filter 122 may be about 1 / 10 to 1 / 100 of the pulsating frequency band, as long as it can remove the DC component and extract the pulsating component.

[0029] Next, the extracted pulsating component ΔiL is multiplied by a gain preset in the control gain 123 and output as a correction amount D (step ST024, step ST025).

[0030] A subtractor 131 subtracts the correction amount D from 1, and a multiplier 132 multiplies the resultant output by the R-phase output voltage Vr to calculate a second control amount Vr'. Here, the R-phase output voltage Vr is calculated from the detected output voltage Vrs as described above. This second control amount Vr' corresponds to a command to cancel the pulsation component of the power supply current iP (the R-phase component is iPr).

[0031] Finally, the adder 133 adds the first control amount VrPI* which is the output of the PI controller 108 and the second control amount Vr' which is the output of the multiplier 132 to calculate the R-phase voltage command VrAF* (step ST03).

[0032] The T-phase control unit 140 has a similar configuration to the R-phase control unit 100, but since the phases are different, it is necessary to delay the phase of the sine of the power supply voltage, sin θ, which is the input to the multiplier 105, by 240 degrees. The T-phase voltage command VtAF* is output from the T-phase control unit 140 configured in this way.

[0033] In addition, since the sum of the S-phase voltage command VsAF*, the R-phase voltage command VrAF*, and the T-phase voltage command VtAF* is zero, the S-phase voltage command VsAF* can be calculated by subtracting the R-phase voltage command VrAF* and the T-phase voltage command VtAF* using subtractor 141 (step ST03).

[0034] The drive signal generator 150 receives an S-phase voltage command VsAF*, an R-phase voltage command VrAF*, and a T-phase voltage command VtAF*, and calculates the duties Dr, Ds, and Dt of each phase. Furthermore, the drive signal generator 150 compares the calculated duties Dr, Ds, and Dt of each phase with a reference signal (triangular wave) to generate a signal for performing PWM control (Pulse Width Modulation) (step ST04).

[0035] The generated drive signal controls the on / off of six semiconductor switch elements that make up the converter 34, thereby generating active filter currents iAFr, iAFs, and iAFt that can compensate for pulsation in the power supply current (step ST05). The active filter current iAF is superimposed on the power supply current iP, thereby obtaining a sinusoidal power supply current iP in which harmonics and pulsation are suppressed.

[0036] Considering a method not using the damping control unit 120 in the first embodiment as a comparative example, it is equivalent to setting the control gain 123 to zero in Fig. 3, Vr' = Vr, and the pulsation of the power supply current iP cannot be compensated for. In the damping control unit 120, when the three-phase current effective value iL becomes large, that is, when the pulsation component ΔiL is large, Vr' is corrected to be smaller. On the other hand, when the three-phase current effective value iL is small, the pulsation component ΔiL is small, so Vr' is corrected to be larger, that is, closer to Vr. The damping control unit 120 corrects the output voltage Vr of the three-phase AC power supply 4 to be smaller as the pulsation component ΔiL becomes larger.

[0037] Next, the effects of the first embodiment will be described with reference to the power supply current waveforms in FIGS. 6A to 6C. 6A shows a power supply current waveform for a typical power conversion device equipped with a load driving device and an active filter device, where the smoothing capacitor capacity of the load driving device is 3000 μF. This is taken as Comparative Example 1 for the first embodiment. In this case, the load driving device and the active filter device operate normally without interference. It can therefore be seen that the power supply current waveform is a sine wave.

[0038] Fig. 6B shows a power supply current waveform in Comparative Example 2, where the smoothing capacitor of the load driving device in Comparative Example 1 is reduced to 100μF. When the smoothing capacitor of the load driving device is reduced, the load driving device and the active filter device interfere with each other, causing large pulsations as shown in Fig. 6B, and the power supply current waveform is no longer sinusoidal. In this state, not only is it impossible to reduce harmonic components, but it also adversely affects the operation of the load driving device.

[0039] 6C shows a waveform of the power supply current iP in the power conversion device 1 using the active filter device 3 of the present embodiment 1, in which the capacity of the smoothing capacitor 23 of the load driving device 2 is 100 μF, as in Comparative Example 2. Comparing with FIG. 6B, it can be seen that the pulsation is mitigated and the power supply current waveform approaches the sine wave of Comparative Example 1. In this state of the power supply current waveform, the load driving device 2 can be operated normally, and it is also possible to suppress harmonics of the power supply current, which is one of the purposes of the active filter device 3. In this way, the active filter device 3 of the present embodiment 1 can suppress pulsation caused by interference between the load driving device 2 and the active filter device 3, which occurs when the capacity of the smoothing capacitor 23 of the load driving device 2 is small.

[0040] 6C, a spike current remains, which is due to insufficient control performance of the current control described above. Therefore, in the active filter device 3, a PID controller is used instead of the PI controller 108 that performs current control, and PID control is performed, or repetitive control is added, or repetitive control and feedback control are used together, thereby improving the control performance of the current control.

[0041] As described above, the power conversion device according to the first embodiment includes the active filter device 3 in parallel with the load driving device 2, and the active filter device 3 has the control device 36 for generating an active filter current. The control device 36 has each phase control unit 100, 140 for generating a voltage command for each phase, which has a current command calculation unit 110 for suppressing harmonic components, a first control amount calculation unit 115 for calculating a first control amount VrPI* from the deviation between the calculated compensation current command and the detected compensation current, and a damping control unit 120 for performing damping control. The damping control unit 120 extracts a pulsation component ΔiL of the power supply current iP and outputs a second control amount Vr' based on the extracted pulsation component. The control device 36 generates voltage commands VAFs*, VAFr*VAFt* for each phase using the first and second control amounts, and can generate active filter currents iAFr, iAFs, iAFt that can cancel harmonics in the power supply current and suppress pulsation in the power supply current. By superimposing these active filter currents iAFr, iAFs, and iAFt on the power supply current, not only can the harmonics of the power supply current be suppressed but also pulsation can be compensated for.

[0042] That is, since the pulsation caused by the interference between the load driving device 2 and the active filter device 3 can be compensated for, the capacity of the smoothing capacitor 23 of the load driving device 2 can be reduced, and the power conversion device can be made more compact. Also, since there is no need to provide two or more voltage sensors for detecting the power supply voltage, the number of parts can be reduced, and the power conversion device can be made more compact.

[0043] Embodiment 2 An active filter device according to embodiment 2 and a power conversion device including the same will be described below with reference to the drawings. Fig. 7 is a schematic diagram showing the configuration of the power conversion device according to embodiment 2, and Fig. 8 is a control block diagram showing the configuration of a control device 36 included in the active filter device 3 according to embodiment 2. Since embodiment 2 has a basic configuration similar to embodiment 1, the following description will focus on the differences.

[0044] The difference from the first embodiment is that the second embodiment further includes a current sensor 37e for detecting a current value iL immediately after the rectifier 21 in the load driving device 2 as shown in FIG. 7. The current value iL detected by the current sensor 37e is input to the control device 36. This current value iL is a current in the DC part downstream of the rectifier 21, and therefore the calculation of the three-phase current effective value in the first embodiment is not required. Therefore, the difference between the first embodiment and the first embodiment in FIG. 8 and FIG. 3 is that the damping control unit 170 of the R-phase control unit 100 does not include a three-phase current effective value calculator, and the current value iL detected by the current sensor 37e is input to the high-pass filter 122. The T-phase control unit 140 also does not include a three-phase current effective value calculator. Therefore, in the flowchart in FIG. 5 of the first embodiment, in the second embodiment, the current value iL is input in step ST021, and step ST022 is omitted. Other configurations and operations of the active filter device 3 and the power conversion device 1 are the same as those in the first embodiment.

[0045] 8, a current value iL detected by a current sensor 37e is input to a high-pass filter (HPF) 122 of a damping control section 170, and a pulsating component ΔiL is extracted. Here, the cutoff frequency of the high-pass filter 122 may be about 1 / 10 to 1 / 100 of the pulsating frequency band, as long as it is possible to remove the DC component and extract the pulsating component.

[0046] Next, the extracted pulsating component ΔiL is multiplied by a gain set in advance in the control gain 123 and output as a correction amount D.

[0047] A subtractor 131 subtracts a correction amount D from 1, and a multiplier 132 multiplies the output by the R-phase power supply voltage Vr to calculate a control amount Vr'. This control amount Vr' corresponds to a command to cancel the pulsation component of the power supply current iP (the R-phase component is iPr).

[0048] The procedure for extracting the harmonic components of the power supply current iP in the control device 36 and generating the first control amount VrPI* which is a command to cancel them is the same as in embodiment 1. Finally, the adder 133 adds the first control amount VrPI* which is the output of the PI controller 108 and the second control amount Vr' which is the output of the multiplier 132 to calculate the R-phase voltage command VrAF*.

[0049] As in the first embodiment, a T-phase voltage command VtAF* is output from T-phase control unit 140 and input to drive signal generator 150 together with an S-phase voltage command VsAF* and an R-phase voltage command VrAF* calculated by subtractor 141, to generate a signal for PWM control of converter 34. The active filter current iAF generated by converter 34 is superimposed on power supply current iP, thereby obtaining a sinusoidal power supply current iP with suppressed harmonics and pulsation.

[0050] As described above, the power conversion device according to the second embodiment has the same effects as those of the first embodiment. That is, it is possible to not only suppress harmonics in the power supply current, but also to compensate for pulsation. Therefore, since it is possible to compensate for pulsation caused by interference between the load driving device 2 and the active filter device 3, it is possible to reduce the capacity of the smoothing capacitor 23 of the load driving device 2, and thus to reduce the size of the power conversion device.

[0051] Furthermore, although the number of current sensors is increased by one from the first embodiment, the configuration of the control device 36 included in the active filter device 3 is simplified. The current value iL detected by the current sensor 37e may be input directly to the control device 36 of the active filter device 3 as described above, or may be input to the control device 36 via communication from a control device (not shown) that drives the load driving device 2.

[0052] Embodiment 3 An active filter device according to a third embodiment and a power conversion device including the same will be described below with reference to the drawings. The power conversion device 1 according to the third embodiment differs from the second embodiment in that it does not include a current sensor 37e for detecting a current value iL immediately after the rectifier 21 in the load driving device 2, but has a similar basic configuration to the first embodiment. The configuration of the control device 36 included in the active filter device 3 is different from that of the first embodiment. The following description will focus on the differences. Note that the same configuration as that of the first embodiment is applied to the power conversion device 1.

[0053] 9 is a control block diagram showing the configuration of a control device 36 included in the active filter device 3 according to the third embodiment. In FIG. 9, a damping control section 180 has a different configuration from the damping control section 120 of the first embodiment. As described above, the damping control unit extracts the pulsating components of the three-phase load currents iLr, iLs, and iLt and generates a command to cancel them. In the first embodiment, an example has been described in which a three-phase current effective value is calculated from the three-phase load currents iLr, iLs, and iLt, and the pulsating components of the load current are calculated using the calculated three-phase current value iL. In this embodiment, the damping control unit 180 includes a three-phase current amplitude calculator 181, calculates a three-phase current amplitude value as the three-phase current value iL, and calculates the pulsating components of the load current using the three-phase current amplitude value.

[0054] When the three-phase load currents iLr, iLs, and iLt are input to a three-phase current amplitude value calculator 181, a three-phase current amplitude value iL is calculated by the following equation (2).

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[0055] To precisely calculate the three-phase current amplitude value iL, it would be accurate to divide the entire equation (2) by 3, but this is not provided here because this can be adjusted later by the control gain 123. The other configurations are the same as in the first embodiment, and the operation of generating a command to cancel the pulsating component from the pulsating component is the same as in the first embodiment, so a description thereof will be omitted.

[0056] In the first embodiment, an example is shown in which a three-phase current effective value is calculated from the three-phase load currents iLr, iLs, and iLt and used as the three-phase current value, and in the third embodiment, an example is shown in which a three-phase current amplitude value is calculated and used as the three-phase current value, but the present invention is not limited to this. For example, it is also possible to use the average value of the three-phase load currents iLr, iLs, and iLt to extract the pulsating components of the three-phase load currents iLr, iLs, and iLt and generate a command to cancel them.

[0057] As described above, the power conversion device according to the third embodiment has the same effects as those of the first embodiment. That is, it is possible to not only suppress harmonics in the power supply current, but also to compensate for pulsation. Therefore, since it is possible to compensate for pulsation caused by interference between the load driving device 2 and the active filter device 3, it is possible to reduce the capacity of the smoothing capacitor 23 of the load driving device 2, and thus to reduce the size of the power conversion device.

[0058] Embodiment 4 An active filter device according to embodiment 4 and a power conversion device including the same will be described below with reference to the drawings. The power conversion device 1 according to embodiment 4 has a basic configuration similar to that of embodiment 1 shown in FIG. 1, but differs in the configuration of the control device 36 included in the active filter device 3. The following description will focus on the differences.

[0059] Fig. 10 is a control block diagram showing a configuration of the control device 36 included in the active filter device 3 according to the third embodiment. In Fig. 10, the control device 36 includes a three-phase / two-phase converter 400 for converting three-phase load currents iLr, iLs, and iLt into two-phase load currents iLd and iLq in the DQ-axis coordinate system, a D-axis control unit 200, a Q-axis control unit 300, and a drive signal generator 150. In the first embodiment, the three-phase load currents iLr, iLs, and iLt are input to the control device 36, but in the third embodiment, the three-phase / two-phase converter 400 converts the three-phase load currents iLr, iLs, and iLt into the DQ-axis coordinate system to obtain load currents iLd and iLq, which are then input and used for control. In addition, the active filter current converted into the DQ-axis coordinate system is also used.

[0060] Since the D-axis control unit 200 and the Q-axis control unit 300 have the same configuration and perform the same operation, the operation of the D-axis control unit 200 will be explained below. The D-axis control unit 200 includes a current command calculation unit 210, a first control amount calculation unit 215, and a damping control unit 220.

[0061] First, the control device 36 extracts the harmonic components of the power supply current iP and generates a command to cancel them. A band-pass filter 201 extracts a fundamental wave component from the D-axis load current iLd input to the control device 36. A subtractor 202 subtracts the load current iLd from the extracted fundamental wave component to calculate a pre-compensation current command iAFd*.

[0062] Next, the portion relating to voltage control will be described. A subtractor 203 calculates the deviation between the voltage command Vdc* of the smoothing capacitor 35 and the detected voltage Vdc, and a PI controller 204 performs PI control based on this deviation, and an adder 206 adds the output control amount and the pre-compensation current command iAFd*, which is the output of the subtractor 202, to calculate an active filter current command iAFd*'. By realizing this active filter current command iAFd*', it is possible to suppress harmonic components and make the power supply current sinusoidal.

[0063] Next, the portion relating to current control will be described. A subtractor 207 calculates the deviation between the active filter current command iAFd*' and the active filter current iAFd, and the calculated deviation is input to a PI controller 208 and feedback-controlled by PI control, so that the deviation becomes almost zero, and the active filter current command iAFd*' and the active filter current iAFr can be made almost the same. The PI controller 208 outputs a first control amount VdPI*. The first control amount VdPI* corresponds to a voltage command that cancels out the harmonic components of the power supply current iP. As described above, the active filter current iAFd is obtained by converting the three-phase active filter currents detected by the current sensors 37c, 37d into the DQ axis coordinate system.

[0064] Here, in order to further improve the control performance, a PID controller may be used instead of a PI controller to perform PID control. Also, repetitive control may be added, or repetitive control and feedback control may be used together. Instead of integral control (I control), P control or PD control may be performed.

[0065] Next, the control device 36 extracts the pulsating component of the power supply current iP and generates a command to cancel it. This processing is mainly performed by the damping control unit 220. The processing operation in the damping control unit 220 is also similar to that in the flowchart shown in FIG. 5, except that a current converted into the DQ axis coordinate system is used.

[0066] First, the load currents iLd and iLq of the DQ axes are input to a three-phase current effective value calculator 221, which calculates the three-phase current effective value iL. The three-phase current effective value iL is calculated by the following equation (3).

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[0067] Next, in order to extract the amount of change in the three-phase current effective value iL, the pulsating component ΔiL is extracted by the high-pass filter 222. Here, similarly to the first embodiment, the cutoff frequency of the high-pass filter 222 may be about 1 / 10 to 1 / 100 of the pulsating frequency band, as long as it is possible to remove the DC component and extract the pulsating component.

[0068] Next, the extracted pulsating component ΔiL is multiplied by a preset gain in the control gain 223 and output as a correction amount D (D=Kd×ΔiL).

[0069] A subtractor 231 subtracts the correction amount D from 1, and a multiplier 232 multiplies the output by the power supply voltage Vd of the D axis to calculate a second control amount Vd'. Here, the power supply voltage Vd of the D axis is obtained by converting the three-phase power supply voltages calculated from the detected power supply voltage Vrs into the DQ axis coordinate system. This second control amount Vd' corresponds to a command to cancel the pulsation component of the power supply current iP.

[0070] Finally, an adder 233 adds the first control amount VdPI* which is the output of the PI controller 208 and the second control amount Vd' which is the output of the multiplier 232, thereby calculating a voltage command VdAF* for the D axis.

[0071] Similarly, the Q-axis voltage command VqAF* can be calculated by the Q-axis control unit 300. However, since the Q-axis is a component equivalent to reactive power, it is not necessary to use the output of the voltage control. Therefore, unlike the D-axis control unit 200, the Q-axis control unit 300 does not include components equivalent to the subtractor 203 and PI controller 204.

[0072] The control gain 323 of the damping control section 320 of the Q-axis control section 300 may be the same as the control gain 223 of the damping control section 220 of the D-axis control section 200, or may be different.

[0073] As in the first embodiment, the D-axis voltage command VdAF* and the Q-axis voltage command VqAF* are input to the drive signal generator 150, which generates a signal for driving the converter 34 by PWM control. This makes it possible to generate active filter currents iAFr, iAFs, and iAFt capable of compensating for the pulsation of the power supply current, and to obtain a sinusoidal power supply current iP in which harmonics and pulsation are suppressed.

[0074] As described above, the power conversion device according to the fourth embodiment has the same effects as those of the first embodiment. That is, it is possible to not only suppress harmonic components of the power supply current, but also to compensate for pulsation. Therefore, since it is possible to compensate for pulsation caused by interference between the load driving device 2 and the active filter device 3, it is possible to reduce the capacity of the smoothing capacitor 23 of the load driving device 2, and thus to reduce the size of the power conversion device.

[0075] Embodiment 5. An active filter device according to embodiment 5 and a power conversion device including the same will be described below with reference to the drawings. The power conversion device 1 according to embodiment 5 has a basic configuration similar to that of embodiment 1 shown in FIG. 1, but differs in the configuration of the control device 36 included in the active filter device 3. The following description will focus on the differences.

[0076] 11 is a control block diagram showing the configuration of a control device 36 included in the active filter device 3 according to embodiment 5. The difference from embodiment 1 is that after a current pulsation component ΔiL is calculated, the current pulsation component ΔiL and the sine of the power supply voltage sin θ are multiplied by a multiplier 191, and a voltage command value is corrected via a repetitive controller 192.

[0077] Repetitive control is an effective control method when similar characteristics occur repeatedly, such as in AC power supplies. By using multiple integrators corresponding to the AC power supply voltage, the deviation can be reduced little by little for each power supply cycle, allowing the voltage to approach the target value.

[0078] 12 is a block diagram showing the configuration of the repetitive controller 192. The repetitive controller 192 includes a deviation accumulating means 920, an input selecting means 921, and an output selecting means 922. The deviation accumulation means 920 has a total of N integrators m corresponding to the power supply phase angle θ. That is, a total of N integrators, integrators m0, m1, ..., mN-1, are provided for each power supply phase angle. For example, when the control frequency is 18000 Hz and the power supply frequency of the three-phase AC power supply 4 is 60 Hz, one cycle of the AC power supply is divided into N = 300 power supply phase angle ranges, and N = 300 integrators m0, m1, ..., m299 are provided. In this case, the divided power supply phase angle width is 1.2 deg (π / N = 360 deg / 300), and one integrator m calculates the deviation for every 1.2 deg of the power supply phase angle.

[0079] The input selection means 921 selects an integrator corresponding to the power supply phase angle θ from among the integrators m0, m1, . . . , mN-1, and accumulates the current deviation.

[0080] The output selection means 922 selects an integrator corresponding to the power supply phase angle θ advanced by the set delay phase from among the integrators m0, m1, . . . , mN-1, and causes the integrator to output a control amount. The set delay phase must take into consideration two types of delay: (A) caused by each computing unit constituting the control device 36, and (B) a delay of the reactor current in the active filter device 3.

[0081] (A) Delay due to each computing unit The delay caused by the calculator is due to a calculation time delay of the calculator such as a microcomputer constituting the control device 36, and generally corresponds to one control period. One control period is the above-mentioned power supply phase angle width.

[0082] (B) Reactor current delay In the active filter device 3, a drive signal generator 150 generates a signal for PWM controlling a converter 34 based on voltage commands VsAF*, VtAF*, VrAF* for each phase calculated by a control device 36. A current flows to the converter 34 via a control reactor 33. At this time, the relationship between the reactor current IL and the reactor voltage VL is expressed by the following voltage equation (4), where the inductance of the control reactor 33 is L.

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[0083] As shown in equation (4), since the reactor current IL is expressed as the integral of the reactor voltage VL, even if the converter 34 outputs the reactor voltage VL, it takes a certain amount of time until it is reflected as a current value. This reactor current delay corresponds to one control cycle, and it is necessary to take into account this delay of one control cycle.

[0084] As described above, the sum of the delays due to the two types of factors is two control periods, so the timing at which the output selection means 922 selects an output is set to be two control periods ahead of the timing at which the input selection means 921 selects an input. For example, as shown in FIG. 12, when the input selection means 921 selects the integrator m0 in response to the power supply phase angle θ, the output selection means 922 selects the integrator m2, which has an advanced phase angle of two, and the current deviation accumulated in the integrator m2 is output. The power supply phase angle θ may be input to the repetitive controller 192, or may be input based on the sine of the power supply voltage sin θ input to the multiplier 191 at the previous stage.

[0085] A value that takes into account the current deviation in the current pulsation component ΔiL is the output of the repetitive controller 192, and this output is input to a subtractor 193, which subtracts it from the R-phase power supply voltage Vr to calculate a controlled variable Vr'. The procedure for extracting the harmonic components of the power supply current iP in the control device 36 and generating the first control amount VrPI* which is a command to cancel them is the same as in embodiment 1. Finally, the adder 133 adds the first control amount VrPI* which is the output of the PI controller 108 and the second control amount Vr' which is the output of the damping control unit 190 to calculate the R-phase voltage command VrAF*.

[0086] Next, another configuration of the control device 36 to which repetitive control is applied will be described. Fig. 13 is a control block diagram showing another configuration of the control device 36 included in the active filter device 3 according to the embodiment 5. The difference from Fig. 11 is that in Fig. 13, a repetitive controller 109 is provided in parallel with the PI controller 108 of the first controlled variable calculation unit 116.

[0087] Fig. 14 is a control block diagram showing yet another configuration of the control device 36 included in the active filter device 3 according to the fifth embodiment. In Fig. 14, the two repetitive controllers 192 and 109 in Fig. 13 are integrated into one. The product of the pulsating component ΔiL of the current calculated by the multiplier 191 and the sine sinθ of the power supply voltage is subtracted by a subtractor 194 from the output of the subtractor 107, and the result is input to a repetitive controller 195 to calculate a current deviation for each power supply period. The control amount VrPI*, which is the output of the PI controller 108, and the output of the repetitive controller 195 are added by an adder 134, and the result is added by an adder 133 to the power supply voltage Vr of the R phase, thereby calculating a voltage command VrAF* of the R phase.

[0088] 13 and 14, as in the first embodiment, a T-phase voltage command VtAF* is output from a T-phase control unit 140 and input to a drive signal generator 150 together with an S-phase voltage command VsAF* and an R-phase voltage command VrAF* calculated by a subtractor 141, to generate a signal for PWM controlling the converter 34. The active filter current iAF generated by the converter 34 is superimposed on the power supply current iP, making it possible to obtain a sinusoidal power supply current iP in which harmonics are suppressed and pulsation is suppressed.

[0089] As described above, the power conversion device according to the fifth embodiment has the same effects as those of the first embodiment. That is, it is possible to not only suppress harmonics in the power supply current, but also to compensate for pulsation. Therefore, since it is possible to compensate for pulsation caused by interference between the load driving device 2 and the active filter device 3, it is possible to reduce the capacity of the smoothing capacitor 23 of the load driving device 2, and thus to miniaturize the power conversion device. Furthermore, by taking the current deviation into account in the pulsation component, it is possible to further suppress the pulsation component.

[0090] 13 shows an example of a configuration in which the repetitive controller 109 is provided in parallel with the PI controller 108 of the first control amount calculation unit 116 in comparison with FIG. 11, but the present invention is not limited to this. As explained in the above-mentioned embodiments, a repetitive controller may be provided in parallel with the PI controller 108 in FIG. 3 of the first embodiment, and a repetitive controller may be provided in parallel with the PI controller 108 in FIG. 9 of the third embodiment. It goes without saying that the present invention can also be applied to the second and fourth embodiments.

[0091] Embodiment 6 Hereinafter, a refrigeration cycle apparatus according to the sixth embodiment will be described with reference to the drawings. Fig. 15 is a schematic diagram showing the configuration of a refrigeration cycle apparatus according to the sixth embodiment. The refrigeration cycle apparatus includes a power conversion device 1 that converts power from a three-phase AC power source 4 into predetermined power, and an air conditioner 500 having a motor 25 to which power from the power conversion device 1 is input. Here, the power conversion device 1 described in the first to fifth embodiments is applied to the refrigeration cycle apparatus.

[0092] 15, an air conditioner 500 includes a compressor 501, a four-way valve 502, an outdoor heat exchanger 503, and an expander 504 as an outdoor unit 506, and an indoor heat exchanger 505 as an indoor unit 507. The compressor 501 includes a motor 25 that is driven by power supplied from the power conversion device 1, and a compression element 501a that is connected to the motor 25 and compresses the refrigerant. In the air conditioner 500, the compressor 501, the four-way valve 502, the outdoor heat exchanger 503, the expander 504, the indoor heat exchanger 505, the four-way valve 502, and the compressor 501 are connected in this order by refrigerant piping to form a refrigerant circuit.

[0093] Next, the operation of the air conditioner 500 will be described using cooling operation as an example. It is assumed that, when performing cooling operation, the four-way valve 502 has switched the flow path in advance so that the refrigerant discharged from the compressor 501 flows toward the outdoor heat exchanger 503, and the refrigerant flowing out of the indoor heat exchanger 505 flows toward the compressor 501.

[0094] When the motor 25 of the compressor 501 is driven to rotate by the power conversion device 1, the compression element 501a of the compressor 501 connected to the motor 25 compresses the refrigerant, and the compressor 501 discharges a high-temperature, high-pressure refrigerant. The high-temperature, high-pressure refrigerant discharged from the compressor 501 flows into the outdoor heat exchanger 503 via the four-way valve 502, where it exchanges heat with the outside air and dissipates heat. The refrigerant flowing out from the outdoor heat exchanger 503 is expanded and decompressed by the expander 504, becoming a low-temperature, low-pressure two-phase gas-liquid refrigerant, which flows into the indoor heat exchanger 505. The flowed-in low-temperature, low-pressure two-phase gas-liquid refrigerant exchanges heat with the air in the space to be air-conditioned in the indoor heat exchanger 505 and evaporates, becoming a low-temperature, low-pressure gas refrigerant, which flows out from the indoor heat exchanger 505. The gas refrigerant flowing out from indoor heat exchanger 505 passes through four-way valve 502, is sucked into compressor 501, and is compressed again. The above operation is repeated. Here, outdoor heat exchanger 503 corresponds to a condenser, and indoor heat exchanger 505 corresponds to an evaporator. In other words, this is an example of an air conditioner 500 equipped with a refrigerant circuit configured by connecting a compressor, a condenser, an expander, and an evaporator in a ring shape with refrigerant piping.

[0095] As described above, according to the refrigeration cycle apparatus of embodiment 6, the refrigeration cycle apparatus includes a power conversion device 1 and an air conditioner 500, and the power conversion device 1 of embodiments 1 to 3 is applied to drive the motor 25 of the compressor 501 of the air conditioner 500. Therefore, the smoothing capacitor 23 of the load driving device 2 of the power conversion device 1 can be made smaller in capacity and downsized, and it is possible to supply power with suppressed harmonics and pulsations to the motor 25, making it possible to operate the air conditioner 500 stably.

[0096] Note that, in FIG. 15, an example is shown in which the power conversion device 1 according to embodiments 1 to 5 is applied to drive the motor 25 of the compressor 501 of an air conditioner 500. However, this is not limited to this, and it goes without saying that the power conversion device can be applied to not only air conditioners, but also heat pump devices, refrigeration devices, and other refrigeration cycle devices in general.

[0097] An example of a hardware configuration of the control device 36 of the active filter device 3 constituting the power conversion device 1 in any of the above-mentioned first to sixth embodiments is shown in Fig. 16. As shown in Fig. 16, the control device 36 includes, for example, a processor 1000 and a storage device 1100 as a processing circuit. The processor 1000 may include a CPU (Central Processing Unit), an ASIC (Application Specific Integrated Circuit), an IC (Integrated Circuit), an FPGA (Field Programmable Gate Array), various logic circuits, various signal processing circuits, etc. Also, the processor 1000 may include a plurality of processors of the same type or different types, and each process may be shared and executed. The storage device 1100 may include a RAM (Random Access Memory) configured to be able to read and write data from the processor 1000, and a ROM (Read Only Memory) configured to be able to read data from the processor 1000, etc. The processor 1000 executes a program input from the storage device 1100 such as a ROM.

[0098] <Other embodiments> (1) In Fig. 3, the six semiconductor switch elements constituting converter 34 are IGBTs (Insulated Gate Bipolar Transistors) with diodes connected in anti-parallel, but MOSFETs (Metal Oxide Semiconductor Field Effect Transistors) may also be used. In addition, the semiconductor switch elements are not limited to those made of Si (silicon) semiconductors, and wide band gap semiconductors such as SiC (silicon carbide) and GaN (gallium nitride) may also be used.

[0099] (2) Although an example in which one inverter 24 and one motor 25 are provided has been shown, a plurality of each may be provided. Also, the inverter 24 may be a DC / DC converter, and the motor 25 may be changed to a general DC load so as to be driven by DC.

[0100] Although the present disclosure describes various exemplary embodiments and examples, the various features, aspects, and functions described in one or more embodiments are not limited to application to a particular embodiment, but may be applied to the embodiments alone or in various combinations. Therefore, countless modifications not exemplified are assumed within the scope of the technology disclosed in the present specification, including, for example, modifying, adding, or omitting at least one component, and further, extracting at least one component and combining it with a component of another embodiment. [Explanation of symbols]

[0101] 1: power conversion device, 2: load driving device, 3: active filter device, 4: three-phase AC power supply, 21: rectifier, 22: DC reactor, 23: smoothing capacitor, 24: inverter, 25: motor, 31: filter reactor, 32: filter capacitor, 33: control reactor, 34: converter, 35: smoothing capacitor, 36: control device, 37a, 37b, 37c, 37d, 37e: current sensor, 38a, 38b: voltage sensor, 100: R-phase control unit, 101, 201: band pass filter (BPF), 102, 103, 107, 131, 141, 193, 194, 202, 203, 207, 231, 302, 307, 331: subtractor, 104, 108, 204, 208, 308: PI controller, 105, 132, 191, 232, 332: multiplier, 106, 133, 134, 206, 233, 333: adder, 110, 210, 310: current command calculation unit, 115, 116, 215, 315: first control amount calculation unit, 120, 170, 180, 190, 220, 320: damping control unit, 121, 221, 321: three-phase current effective value calculator, 122, 222, 322: high-pass filter (HPF), 123, 223, 323: control gain, 140: T-phase control unit, 150: drive signal generator, 181: three-phase current amplitude value calculator, 109, 192, 195: repetitive controller, 200: D-axis control section, 300: Q-axis control section, 500: air conditioner, 501: compressor, 501a: compression element, 502: four-way valve, 503: outdoor heat exchanger, 504: expansion device, 505: indoor heat exchanger, 506: outdoor unit, 507: indoor unit, 920: deviation accumulation means, 921: input selection means, 922: output selection means, 1000: processor, 1100: storage device, m, m0, m1, m2, mN-1: integrators.

Claims

1. An active filter device comprising: a converter that generates a compensation current; and a control device that controls the converter, the active filter device suppressing harmonic currents generated from a rectifier circuit that converts power from a three-phase AC power source into DC power, The control device includes: a current command calculation unit that calculates a compensation current command; a first control amount calculation unit that calculates a first control amount based on a deviation between the compensation current command and the detected compensation current; a damping control unit that calculates a pulsating component of a three-phase input current input to the rectifier circuit and calculates a second control amount based on the calculated pulsating component; a drive signal generator that drives the converter based on the calculated first control amount and the calculated second control amount, The damping control unit calculates the second control amount so as to reduce the output voltage of the three-phase AC power supply in accordance with the calculated magnitude of the pulsating component.

2. 2. The active filter device according to claim 1, wherein the damping control unit calculates a pulsating component based on any one of an effective value of the three-phase input current input to the rectifier circuit, an amplitude value of the three-phase input current input to the rectifier circuit, and an average value of the three-phase input current input to the rectifier circuit, and calculates a second control amount based on the calculated pulsating component.

3. 2. The active filter device according to claim 1, wherein the damping control unit calculates a pulsating component of a three-phase input current input to the rectifier circuit based on an output current of the rectifier circuit, and calculates a second control amount based on the calculated pulsating component.

4. the control device includes a three-phase to two-phase converter that converts three-phase power of the three-phase AC power supply into two-phase power in a DQ-axis coordinate system; The first control amount calculation unit calculates the first control amount corresponding to two phases; 2. The active filter device according to claim 1, wherein the damping control section calculates the second controlled variable corresponding to two phases.

5. the damping control unit includes a repetitive controller having deviation accumulation means including a plurality of integrators corresponding to different power supply phase angles of the three-phase AC power supply, The repetitive controller includes: the deviation accumulating means accumulates the current deviation of the pulsating component calculated for each of the power supply phase angles in the integrator; 5. The active filter device according to claim 1, wherein the current deviation is output from the integrator corresponding to the selected power supply phase angle.

6. 6. The active filter device according to claim 5, wherein the deviation accumulating means uses a power supply phase angle width calculated from a frequency of the three-phase AC power supply and a control frequency, and includes a plurality of integrators provided corresponding to the power supply phase angles that differ for each of the power supply phase angle widths.

7. The repetitive controller includes: the deviation accumulating means selects the integrator corresponding to the power supply phase angle that is two power supply phase angle widths ahead of the power supply phase angle for accumulating the current deviation, and outputs the current deviation; 7. The active filter device according to claim 6, wherein the damping control section calculates the second controlled variable by using the current deviation output from the repetitive controller.

8. 5. A power conversion device comprising: a load driving device that includes the rectifier circuit that converts power from the three-phase AC power supply into DC, and that converts the output power of the rectifier circuit into a predetermined power and supplies it to a load; and the active filter device according to claim 1.

9. 9. A refrigeration cycle apparatus comprising: a refrigerant circuit in which a compressor, a condenser, an expander, and an evaporator are connected in a ring shape by refrigerant piping; and the power conversion device according to claim 8, which supplies a predetermined electric power to the compressor.

10. A control method for an active filter device for suppressing harmonic currents generated from a rectifier circuit that converts power from a three-phase AC power source into DC by generating a compensation current, comprising the steps of: calculating a compensation current command, and calculating a first control amount based on a deviation between the calculated compensation current command and a detected compensation current; calculating a pulsating component of a three-phase input current input to the rectifier circuit, and calculating a second control amount based on the calculated pulsating component; generating the compensation current based on the calculated first control amount and the calculated second control amount; a second control amount calculating step of calculating the second control amount so as to reduce an output voltage of the three-phase AC power supply in accordance with a magnitude of the calculated pulsating component.

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