Power converter and refrigeration cycle system

Abstract

The objective is to reduce carrier ripple current and to reduce the outflow of carrier ripple current to the power supply. [Solution] The power converter 50 includes a rectifier circuit 2 that converts the three-phase AC input voltage (phase-to-phase voltage Vac) input from AC input terminals 55r, 55s, and 55t into a DC voltage; a converter 31 that outputs an output voltage Vo set to a set voltage value from the DC voltage output from the rectifier circuit 2; a smoothing capacitor 6 connected between the positive converter output terminal (DC output terminal 64p) and the negative converter output terminal (DC output terminal 64n) of the converter 31 that outputs the output voltage Vo; an LC filter 30 having a filter reactor 8 and a filter capacitor 9 arranged between the AC input terminals 55r, 55s, and 55t and the converter 31; and a controller 10 that controls the converter 31.

Description

Technical Field

[0001] The present disclosure relates to a power conversion device and a refrigeration cycle device.

Background Art

[0002] Patent Document 1 discloses a step-down chopper device that takes three-phase alternating current as an input and steps down the voltage converted to direct current via a rectifier by switching a semiconductor switch. The step-down chopper device includes a smoothing capacitor on the output side. Since a current with a carrier ripple current superimposed thereon is generated due to the influence of the switching of the semiconductor switch, if the carrier ripple current is allowed to flow out as it is, there is a risk of damaging peripheral devices.

[0003] Therefore, the step-down chopper device of Patent Document 1 arranges a capacitor (filter capacitor) for removing carrier ripple between a step-down converter composed of a semiconductor switch, a diode, and a reactor and a rectifier. By absorbing the carrier ripple current generated in the step-down converter by the capacitor arranged on the input side of the step-down converter, the outflow of the carrier ripple current to the peripheral devices of the step-down chopper device is reduced.

[0004] Furthermore, the step-down chopper device of Patent Document 1 controls the semiconductor switch with a PWM (Pulse Width Modulation) signal S5 generated by comparing a modulated triangular wave S4 generated based on the voltage Vi of the filter capacitor and an output signal S1 based on the output voltage Vo which is the voltage of the smoothing capacitor. That is, the step-down chopper device of Patent Document 1 performs feedback control of the output voltage Vo based on the output voltage Vo which is the voltage of the smoothing capacitor and the voltage Vi of the filter capacitor. The step-down chopper device of Patent Document 1 can also reduce the capacitance of the filter capacitor on the input side of the step-down converter by reducing the ripple of the output voltage Vo.

Prior Art Documents

Patent Documents

[0005] [Patent Document 1] Japanese Patent Publication No. 2000-312478 [Patent Document 2] International Publication No. WO2023 / 073870 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] Patent Document 2 discloses that if the capacitance of a filter capacitor, which is a capacitor placed between a rectifier and a power conversion unit that converts DC power to AC power, is made too large, the input current to the filter capacitor and the charging and discharging current of the filter capacitor will take on a shape resembling "rabbit ears," i.e., a spike shape. This spike-shaped current flows out from the rectifier to the power supply, causing the power supply current to take on a spike shape. In other words, the power supply current becomes greatly distorted, and the power supply harmonics worsen.

[0007] This disclosure aims to reduce carrier ripple current and reduce the outflow of carrier ripple current to the power supply. [Means for solving the problem]

[0008] The power converter according to this disclosure comprises a rectifier circuit that converts a three-phase AC input voltage input from an AC input terminal into a DC voltage, a converter that outputs an output voltage set to a set voltage value from the DC voltage output from the rectifier circuit, a smoothing capacitor connected between the positive converter output terminal and the negative converter output terminal of the converter that outputs the output voltage, an LC filter having a filter reactor and a filter capacitor arranged between the AC input terminal and the converter, and a controller that controls the converter. The filter reactor is located closer to the AC input terminal than the filter capacitor. [Effects of the Invention]

[0009] The power converter of this disclosure has an LC filter having a filter reactor and a filter capacitor placed between the AC input terminal and the converter, and the filter reactor is placed closer to the AC input terminal than the filter capacitor, so that the carrier ripple current can be reduced and the outflow of carrier ripple current to the power supply can be reduced. [Brief explanation of the drawing]

[0010] [Figure 1] This diagram shows the configuration of the power conversion device according to Embodiment 1. [Figure 2] This diagram shows the configuration of the controller according to Embodiment 1. [Figure 3] This is a diagram explaining duty cycle. [Figure 4] This diagram shows the configuration of the rectifier circuit in Figure 2. [Figure 5] This figure shows the operating waveform of the power converter according to Embodiment 1. [Figure 6] This figure shows the operating waveform of the power converter according to Embodiment 1. [Figure 7] This figure shows the operating waveform of the power converter according to Embodiment 1. [Figure 8] This figure shows the operating waveform of the power converter in Comparative Example 1. [Figure 9] This figure shows the operating waveform of the power converter in Comparative Example 1. [Figure 10] This figure shows the operating waveform of the power converter in Comparative Example 1. [Figure 11] This is an enlarged view of a portion of the operating waveform shown in Figure 10. [Figure 12] This figure shows the operating waveform of the power converter in Comparative Example 2. [Figure 13] This figure shows the operating waveform of the power converter in Comparative Example 2. [Figure 14] This figure shows the operating waveform of the power converter in Comparative Example 2. [Figure 15] This figure shows the operating waveform of the power converter in Comparative Example 3. [Figure 16]It is a diagram showing the operation waveform of the power conversion device of Comparative Example 3. [Figure 17] It is a diagram showing the operation waveform of the power conversion device of Comparative Example 3. [Figure 18] It is a diagram showing the configuration of the power conversion device according to Embodiment 2. [Figure 19] It is a diagram showing the configuration of another example of the converter in FIG. 18. [Figure 20] It is a diagram showing the configuration of the first power conversion device according to Embodiment 3. [Figure 21] It is a diagram showing the configuration of the second power conversion device according to Embodiment 3. [Figure 22] It is a diagram showing the configuration of the power conversion device according to Embodiment 4. [Figure 23] It is a diagram showing the configuration of the controller according to Embodiment 4. [Figure 24] It is a diagram showing the configuration of the refrigeration cycle device according to Embodiment 5. [Figure 25] It is a diagram showing the configuration of the refrigerant circuit in FIG. 24. [Figure 26] It is a diagram showing the configuration of the inverter in FIG. 24. [Figure 27] It is a diagram showing an example of a hardware configuration for realizing the functions of the controller by digital calculation. [[ID=​​​​​​​​Figure 1 shows the configuration of the power converter according to Embodiment 1, and Figure 2 shows the configuration of the controller according to Embodiment 1. Figure 3 is a diagram explaining the duty cycle, and Figure 4 shows the configuration of the rectifier circuit in Figure 2. Figures 5 to 7 show the operating waveforms of the power converter according to Embodiment 1, respectively. Figures 8 to 10 show the operating waveforms of the power converter of Comparative Example 1, respectively. Figure 11 is an enlarged view of a part of the operating waveform in Figure 10. Figures 12 to 14 show the operating waveforms of the power converter of Comparative Example 2, respectively. Figures 15 to 17 show the operating waveforms of the power converter of Comparative Example 3, respectively. The power converter 50 of Embodiment 1 converts the three-phase AC input power input from the three-phase AC power source 1 into DC power and supplies the DC power to the load 7.

[0012] The power converter 50 includes a rectifier circuit 2 that converts the input power (input voltage and input current) of the three-phase AC power supply 1 from AC input terminals 55r, 55s, and 55t into DC power (input voltage and input current), a converter 31 that outputs an output voltage Vo set to a set voltage value from the DC voltage output from the rectifier circuit 2, a smoothing capacitor 6 connected between the positive output terminal (positive converter output terminal) 64p and the negative output terminal (negative converter output terminal) 64n of the converter 31 that outputs the output voltage Vo, and a controller 10 that controls the converter 31, and supplies DC power having an output voltage Vo set to a set voltage value to the load 7 from output terminals 57p and 57n.

[0013] The converter 31 includes a switching element 3, a diode 4, and a control reactor 5. In Embodiment 1, a buck converter 31a is described as an example of the converter 31. In Embodiment 2, a boost converter 31b and a buck-boost converter 31c are described as examples of the converter 31. A smoothing capacitor 6 is connected between the positive DC output terminal 64p and the negative DC output terminal 64n of the buck converter 31a, and the smoothing capacitor 6 stabilizes the output voltage Vo. The DC power having the output voltage Vo is supplied to the load 7. The switching element 3 is a power semiconductor element such as an IGBT (Insulated Gate Bipolar Transistor) or a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor). Figure 1 shows an example of an IGBT. The switching element 3 includes a transistor Tr, which is an IGBT, and a diode Di. The diode Di is connected in antiparallel to the transistor Tr, which is an IGBT. When a MOSFET is used as the transistor Tr of the switching element 3, the collector and emitter of the IGBT are read as the drain and source of the MOSFET.

[0014] Figure 1 shows an example of a DC variable resistor as load 7. Load 7 is not limited to a DC variable resistor; for example, it could be a constant current load or a constant power load. Alternatively, an inverter (see Figure 24) may be used to convert the current back to AC before connecting a motor (see Figure 25). In this case, the inverter and motor combined can be considered as a DC variable resistor.

[0015] An LC filter 30 is placed between the three-phase AC power supply 1 and the DC input terminals 63p and 63n of the converter 31. More specifically, the LC filter 30 is placed between the three-phase AC power supply 1 and the switching element 3 of the converter 31. That is, the power converter 50 is equipped with an LC filter 30 between the AC input terminals 55r, 55s, and 55t and the switching element 3. Here, a filter reactor 8 is placed immediately after the rectifier circuit 2, and a filter capacitor 9 is placed in the subsequent stage. The role of the LC filter 30 is to reduce the carrier ripple current generated in the converter 31, such as the step-down converter 31a, and to reduce the outflow of the carrier ripple current to the power supply. The role of the LC filter 30 can also be expressed as follows: The role of the LC filter 30 is to reduce the distortion of the power supply current Ips caused by the carrier ripple current generated in the converter 31, such as the step-down converter 31a, while reducing the "rabbit ear" shaped, i.e., spike-shaped, current distortion in the power supply current Ips.

[0016] The power converter 50 of Embodiment 1 will be described in detail. The rectifier circuit 2 is a bridge rectifier circuit composed of, for example, six diodes 19a to 19f. Diodes 19a and 19b connected in series are the r-phase arm of the three-phase AC, diodes 19c and 19d connected in series are the s-phase arm of the three-phase AC, and diodes 19e and 19f connected in series are the t-phase arm of the three-phase AC. An AC input terminal 61r is connected to the connection point of diodes 19a and 19b, an AC input terminal 61s is connected to the connection point of diodes 19c and 19d, and an AC input terminal 61t is connected to the connection point of diodes 19e and 19f. The cathodes of diodes 19a, 19c, and 19e are connected to the positive DC output terminal 62p, and the anodes of diodes 19b, 19d, and 19f are connected to the negative DC output terminal 62n. Rectifier circuit 2 outputs a DC output voltage Va from DC output terminals 62p and 62n. Three-phase AC power supply 1 is connected to the AC input terminals 55r, 55s, and 55t of power converter 50 by power lines 71r, 71s, and 71t. The power lines connected to AC input terminals 55r, 55s, and 55t are generally designated as 71, with 71r, 71s, and 71t used to distinguish between them.

[0017] The AC input terminals 61r, 61s, and 61t of the rectifier circuit 2 are connected to the AC input terminals 55r, 55s, and 55t of the power converter 50, respectively. The input power P, i.e., the inter-phase voltage Vac and the power supply current Ips of each phase, is input to the AC input terminals 61r, 61s, and 61t of the rectifier circuit 2 from the three-phase AC power supply 1 via the power line 71 and the AC input terminals 55r, 55s, and 55t. The inter-phase voltage Vac and power supply current Ips are the input voltage and input current, respectively, to the rectifier circuit 2 of the power converter 50. The inter-phase voltage Vac is the voltage between two phases in the three-phase AC input from the AC input terminals 55r, 55s, and 55t. Rectifier circuit 2 converts the input power P, i.e., input voltage (phase-to-phase voltage Vac) and input current (power supply current Ips), input to the three-phase AC power supply 1 from AC input terminals 55r, 55s, and 55t, into DC power, i.e., DC voltage (output voltage Va) and DC current. Figure 1 shows the phase-to-phase voltage Vac between the s phase and the t phase. Phase-to-phase voltage Vac also exists between the r phase and the s phase, and between the r phase and the t phase.

[0018] Downstream of the rectifier circuit 2, an LC filter 30, a converter 31, and a smoothing capacitor 6 are arranged in sequence, and the output voltage Vo of the smoothing capacitor 6 is output to the load 7 from the output terminals 57p and 57n of the power converter 50. The DC output terminal 62p of the rectifier circuit 2 is connected to the output terminal 57p of the power converter 50 by positive wiring 73p, which contains the filter reactor 8 of the LC filter 30, the switching element 3 of the converter 31, and the control reactor 5. The DC output terminal 62n of the rectifier circuit 2 is connected to the output terminal 57n of the power converter 50 by negative wiring 73n.

[0019] The LC filter 30 has a filter reactor 8 and a filter capacitor 9, and is positioned between the AC input terminals 55r, 55s, and 55t of the power converter 50 and the converter 31. Figure 1 shows an example in which the LC filter 30 is positioned downstream of the rectifier circuit 2 connected to the AC input terminals 55r, 55s, and 55t. The filter reactor 8 of the LC filter 30 shown in Figure 1 is positioned closer to the AC input terminals 55r, 55s, and 55t than the filter capacitor 9, and is connected between the DC output terminal 62p, which is the positive rectifier circuit output terminal of the rectifier circuit 2, and the positive capacitor terminal 68p, which is one end of the filter capacitor 9 connected to the DC input terminal 63p, which is the positive converter input terminal of the converter 31. More specifically, one end of the filter reactor 8 is connected to the DC output terminal 62p of the rectifier circuit, and the other end of the filter reactor 8 is connected to the positive capacitor terminal 68p, which is one end of the filter capacitor 9, and to the DC input terminal 63p of the converter 31 by positive wiring 73p. The other end of the filter capacitor 9, the negative capacitor terminal 68n, is connected to the negative wiring 73n.

[0020] The converter 31 is equipped with DC input terminals 63p and 63n, DC output terminals 64p and 64n, and a control terminal 58. In a step-down converter 31a, which is an example of the converter 31, the collector of the switching element 3 is connected to the DC input terminal 63p, and the emitter of the switching element 3 is connected to the cathode of the diode 4 and one end of the control reactor 5. The other end of the control reactor 5 is connected to the DC output terminal 64p. The anode of the diode 4 is connected to the negative wiring 73n, and the negative wiring 73n connects to the DC input terminal 63n and the DC output terminal 64n. The gate of the switching element 3 is connected to the control terminal 58. The control terminal 58 receives a control signal sig1, whose voltage value is changed by the drive circuit 25 based on the gate signal command G* output from the controller 10. The control signal sig1 is a signal that controls the on and off states of the switching element 3, for example, by PWM control.

[0021] The controller 10 controls the control reactor current IL, which is the current of the control reactor 5 of the step-down converter 31a, and the output voltage Vo, as intended. Sensor information from each sensor to be detected by the power converter 50 is input to the controller 10. Here, the output voltage Vo, which is the voltage of the smoothing capacitor 6 detected by the voltage sensor 11, is input to the controller 10 as voltage sensor information sig2, and the control reactor current IL, which is the current of the control reactor 5 detected by the current sensor 12, is input to the controller 10 as current sensor information sig3. The current sensor 12 that detects the control reactor current IL of the control reactor 5 is located on the DC input terminal 63p side of the control reactor 5. More specifically, the current sensor 12 is located between the emitter of the switching element 3 and the cathode of the diode 4 and one end of the DC input terminal 63p side of the control reactor 5. The control reactor current IL is the current flowing through the positive wiring 73p, and is therefore also the positive wiring current Ip.

[0022] The control signal sig1 is an operation signal that causes the switching element 3 to operate in a predetermined state. Generally, the control signal sig1 corresponds to an on / off signal that controls the switching element 3 to an on state or an off state. This signal is input to the switching element 3 via the drive circuit 25 that operates the switching element 3.

[0023] To control the buck converter 31a, voltage information from the smoothing capacitor 6 and current information from the control reactor 5 are required. Here, the voltage and current information required to control the buck converter 31a are defined as the voltage sensor information (sig2) from the smoothing capacitor 6 and the current sensor information (sig3) from the control reactor 5, detected using the voltage sensor 11 and current sensor 12. However, the voltage information from the smoothing capacitor 6 and the current information from the control reactor 5 do not necessarily need to be detected using the voltage sensor 11 and current sensor 12; estimated values ​​may be used instead.

[0024] Figure 2 shows the configuration of the controller 10. The controller 10 determines a voltage command Vdc* to an arbitrary value, which controls the output voltage Vo, which is the voltage across the smoothing capacitor 6.

[0025] The controller 10 uses a subtractor 21 to calculate the voltage deviation ΔV, which is the difference between the voltage command Vdc* of the smoothing capacitor 6 and the detected voltage value Vdc, which is the detected output voltage Vo of the smoothing capacitor 6. The voltage deviation ΔV is input to the voltage feedback control unit 22, which performs voltage feedback control. Voltage feedback control often uses PI control (proportional-integral control). Voltage feedback control may also use PID control (proportional-integral-derivative control), PD control (proportional-derivative control), etc., and other combinations of P control (proportional control), I control (integral control), and D control (derivative control) are also possible. In the diagram, "feedback" in the voltage feedback control unit and current feedback control unit is written as "FB".

[0026] In Embodiment 1, since the converter 31 is a step-down converter 31a, the voltage command Vdc* must be set to be less than the voltage across the filter capacitor 9 input to the step-down converter 31a. If the voltage command Vdc* is set to be greater than the voltage across the filter capacitor 9, the switching element 3 will remain constantly on, resulting in the same operation as normal rectification. The output voltage of the step-down converter 31a will be the same as the input voltage, and it will not be possible to boost the voltage to the set voltage of the voltage command Vdc*.

[0027] The output of the voltage feedback control unit 22 is output as a current command IL* for the control reactor 5. The current deviation ΔI, which is the difference between the current command IL* for the control reactor 5 and the detected value of the control reactor current IL for the control reactor 5, is calculated by the subtractor 21 downstream of the voltage feedback control unit 22. The current deviation ΔI is input to the current feedback control unit 23, which performs current feedback control. Current feedback control often uses PI control (proportional-integral control). Current feedback control may also use PID control, PD control, etc., similar to voltage feedback control, and other combinations of P control, I control, and D control are also possible. The output of the current feedback control unit 23 is output as an on-duty command D*. The current feedback control unit 23 generates an on-duty command D* that controls the current flowing through the control reactor 5, i.e., the control reactor current IL, to be within a predetermined current setting range RaI (see Figure 6). The power converter 50 of Embodiment 1 can make the power supply current Ips of the three-phase AC power supply 1 rectangular, i.e., rectangular wave current, by controlling the control reactor current IL within the current setting range RaI. The current feedback control by the current feedback control unit 23 needs to be designed to be as responsive as possible in order to make the power supply current Ips rectangular. More precise control is possible by using iterative control for current control.

[0028] The controller 10 inputs the on-duty command D* and the carrier wave 26 to the carrier comparison unit 24. The carrier wave 26 is often a triangular wave between 5kHz and 20kHz. Figure 2 shows an example where the carrier wave 26 is a triangular wave, but it is also possible to use a sawtooth wave for the carrier wave 26.

[0029] The carrier comparison unit 24 compares the on-duty command D* with the carrier wave 26. If the on-duty command D* is greater than the carrier wave 26, it outputs a gate signal command G* to turn on the switching element 3. Conversely, if the on-duty command D* is less than the carrier wave 26, the carrier comparison unit 24 outputs a gate signal command G* to turn off the switching element 3. The gate signal command G* is a command with a duty cycle D as shown in Figure 3. The gate signal command G* is typically generated using the PWM function on the microcontroller, or by an FPGA (Field-Programmable Gate Array), ASIC (Application Specific Integrated Circuit), etc.

[0030] Let's explain the duty cycle D. Figure 3 shows the pulse of the gate signal command G* of a digital signal. The duty cycle D is obtained by dividing the high period Th, which is the period during which the gate signal command G* is at a high voltage (digital value of 1), by the switching period Tsw of the gate signal command G*. In other words, the duty cycle D is expressed as Th / Tsw. Similarly, the duty cycle D of the control signal sig1 of the digital signal whose voltage value has been changed is also expressed as Th / Tsw. The switching period Tsw is the period of the carrier wave 26.

[0031] By driving the switching element 3 with the control signal sig1 based on the gate signal command G* output from the controller 10, the step-down converter 31a can be controlled to output any desired voltage value.

[0032] The control block diagram of the controller 10 shown in Figure 2 is an example of a control method for controlling the converter 31. This control method is not necessarily required, and the voltage control system, i.e., the voltage feedback control unit 22, or the current control system, i.e., the current feedback control unit 23, may be omitted. However, to control the output voltage Vo, which is the voltage of the smoothing capacitor 6, with high precision, it is desirable to include the voltage control system, i.e., the voltage feedback control unit 22. Also, to make the power supply current Ips of the three-phase AC power supply 1 a rectangular wave, it is desirable to include the current control system, i.e., the current feedback control unit 23.

[0033] Next, the operating waveform of the power converter 50 of Embodiment 1 will be described in comparison with Comparative Examples 1 to 3. Figures 5 to 7 show the operating waveform of the power converter 50 of Embodiment 1. Figures 8 to 11 show the operating waveform of the power converter of Comparative Example 1. Figures 12 to 4 show the operating waveform of the power converter of Comparative Example 2, and Figures 15 to 17 show the operating waveform of the power converter of Comparative Example 3. Where appropriate, the operating waveform of the power converter 50 of Embodiment 1 will be referred to as the operating waveform of Embodiment 1. The power converters of Comparative Examples 1 to 3 differ from the power converter 50 of Embodiment 1 in that the filter inductance Lf of the filter reactor 8 and the filter capacitance Cf of the filter capacitor 9 in the LC filter 30 are different. The common conditions for Embodiment 1 and Comparative Examples 1 to 3 are as follows: As AC output conditions for the three-phase AC power supply 1, the phase voltage Vac is 600V and the AC power supply frequency Fps is 60Hz. The carrier frequency Fca of the carrier wave 26 is 20kHz. The command value of the voltage command Vdc* is 600V. The filter inductance Lf and filter capacitance Cf for Example 1 and Comparative Examples 1 to 3 are as follows: For Example 1, the filter inductance Lf and filter capacitance Cf are 200μH and 10μF. For Comparative Example 1, the filter inductance Lf and filter capacitance Cf are 0μH and 10μF. For Comparative Example 2, the filter inductance Lf and filter capacitance Cf are 4000μH and 10μF. For Comparative Example 3, the filter inductance Lf and filter capacitance Cf are 10μH and 200μF.

[0034] First, the operating waveform of Comparative Example 1 shown in Figures 8 to 11 will be explained. The operating waveform of Comparative Example 1 is the operating waveform when the filter inductance Lf is 0 μH and there is no filter reactor 8. Figure 8 shows the voltage characteristic 80b of the output voltage Vo. Figures 9 and 10 show the current characteristic 81b of the control reactor current IL and the current characteristic 82b of the power supply current Ips, respectively. The power supply current Ips is the current of one phase of a three-phase AC. Figure 11 shows the current characteristic 83, which is an enlarged waveform of the power supply current Ips around time 2.985 [s] in Figure 10. In Figures 8 to 11, the horizontal axis is time [s]. The vertical axis in Figure 8 is the output voltage Vo [V], the vertical axis in Figure 9 is the control reactor current IL [A], and the vertical axis in Figure 10 is the power supply current Ips [A].

[0035] The voltage characteristic 80b of the output voltage Vo in Comparative Example 1 is constant at 600V, as per the command value of the voltage command Vdc*. The current characteristic 81b of the control reactor current IL of the control reactor 5 is controlled to a roughly constant value, and this is also controlled without problems. However, the current characteristic 82b of the power supply current Ips is band-shaped. As shown in Figure 11, the current characteristic 83 of the band-shaped power supply current Ips repeatedly oscillates between 0A (zero level) and 40A-50A, indicating a large fluctuation. This state indicates that the filter capacitor 9 is not sufficiently removing the carrier ripple current generated by the step-down converter 31a, that is, the filter capacitor 9 is not sufficiently absorbing the carrier ripple current. When equipment with a capacitive component, such as a capacitor, is connected to the input side of the power converter in Comparative Example 1 under such conditions, carrier ripple current may flow in and cause damage to the equipment.

[0036] Next, the operating waveform of Comparative Example 2, shown in Figures 12 to 14, will be explained. The operating waveform of Comparative Example 2 is the operating waveform when a filter reactor 8 with a filter inductance Lf of 4000 μH is present. Figure 12 shows the voltage characteristic 80c of the output voltage Vo. Figures 13 and 14 show the current characteristic 81c of the control reactor current IL and the current characteristic 82c of the power supply current Ips, respectively. The power supply current Ips is the current of one phase of a three-phase AC. In Figures 12 to 14, the horizontal axis is time [s]. The vertical axis in Figure 12 is the output voltage Vo [V], the vertical axis in Figure 13 is the control reactor current IL [A], and the vertical axis in Figure 14 is the power supply current Ips [A]. In the case of Comparative Example 2, the control reactor current IL and power supply current Ips of the control reactor 5 fluctuate greatly, and a current resembling "rabbit ears" flows in the power supply current Ips. Furthermore, the voltage characteristic 80c of the output voltage Vo is different from the voltage characteristic 80b of the output voltage Vo in Comparative Example 1. This is undesirable because an excessive current flows through the power converter in Comparative Example 2. To prevent damage to the power converter in Comparative Example 2, it will be necessary to increase the current ratings of the components in the rectifier circuit and the step-down converter.

[0037] Next, the operating waveforms of Example 1 shown in Figures 5 to 7 will be explained. The operating waveforms of Example 1 are those when a filter reactor 8 with a filter inductance Lf of 200 μH is present. Figure 5 shows the voltage characteristics 80a of the output voltage Vo. Figures 6 and 7 show the current characteristics 81a of the control reactor current IL and the current characteristics 82a of the power supply current Ips, respectively. The power supply current Ips is the current of one phase of a three-phase AC. In Figures 5 to 7, the horizontal axis is time [s]. The vertical axis in Figure 5 is the output voltage Vo [V], the vertical axis in Figure 6 is the control reactor current IL [A], and the vertical axis in Figure 7 is the power supply current Ips [A]. In Example 1, the pulsation of the control reactor current IL of the control reactor 5 is smaller than in Comparative Example 2, and it can be seen that the carrier ripple current of the power supply current Ips is also removed. The results of Example 1 are more desirable than those of Comparative Examples 1 to 3, and the operating waveform of Example 1 indicates that appropriate parameters have been set for the filter inductance Lf of the filter reactor 8 and the filter capacitance Cf of the filter capacitor 9.

[0038] Finally, the operating waveform of Comparative Example 3, shown in Figures 15 to 17, will be explained. The operating waveform of Comparative Example 3 is the operating waveform when the balance between the filter inductance Lf and the filter capacitance Cf is disrupted compared to Example 1. The filter inductance Lf and filter capacitance Cf of Comparative Example 3 are 10 μH and 200 μF. The resonant frequency Fre of the LC filter in Comparative Example 3 is the same as the resonant frequency Fre of the LC filter 30 in Example 1. The resonant frequency Fre [Hz] can be expressed by equation (1). Fre=1 / (2π×√(Lf×Cf)) ···(1)

[0039] Figure 15 shows the voltage characteristics 80d of the output voltage Vo. Figures 16 and 17 show the current characteristics 81d of the control reactor current IL and 82d of the power supply current Ips, respectively. The power supply current Ips is the current of one phase of a three-phase AC. In Figures 15 to 17, the horizontal axis is time [s]. The vertical axis in Figure 15 is the output voltage Vo [V], the vertical axis in Figure 16 is the control reactor current IL [A], and the vertical axis in Figure 17 is the power supply current Ips [A]. In Comparative Example 3, the output voltage Vo fluctuates compared to Example 1. Also, the current characteristics 82d of the power supply current Ips show greater waveform distortion compared to the current characteristics 82a of the power supply current Ips in Example 1, similar to Comparative Example 2.

[0040] This section describes how to set the parameters of the LC filter 30, namely the filter inductance Lf and filter capacitance Cf. First, considering the removal of carrier ripple current, the LC filter 30, which has a filter reactor 8 and a filter capacitor 9, is operated as a low-pass filter to remove the carrier ripple current generated in the step-down converter 31a. The resonant frequency Fre of the LC filter 30 should be set lower than the carrier frequency Fca, so that attenuation is effective in the bandwidth of the carrier frequency Fca. For example, if the resonant frequency Fre is set to less than half of the carrier frequency Fca, the bandwidth of the carrier frequency Fca can be attenuated in the current passing through the LC filter 30. Therefore, in order to remove carrier ripple current, the upper limit of the resonant frequency Fre of the LC filter 30 should be half of the carrier frequency Fca.

[0041] Next, let's consider a method to reduce the distortion of the power supply current Ips. When converting to DC using the rectifier circuit 2, if the resonant frequency Fre of the LC filter 30 is low, the power supply current Ips will have a spike shape containing harmonics resembling "rabbit ears". To counteract this, increasing the filter inductance Lf of the filter reactor 8 will smooth out the power supply current Ips into a square wave shape. However, if the power supply current Ips is made into a square wave shape by only adjusting the filter inductance Lf, the filter inductance Lf becomes too large, which increases the size and price of the LC filter 30.

[0042] Therefore, another method to reduce the distortion of the power supply current Ips is to increase the resonant frequency Fre of the LC filter 30. While a higher resonant frequency Fre is preferable to the power supply frequency Fps, if it is approximately 18 times or more the power supply frequency Fps, the power supply current Ips can be considered a square wave current. When the resonant frequency Fre is 18 times or more the power supply frequency Fps, unlike the current characteristic 82c of the power supply current Ips in Comparative Example 2, multiple current rises can be eliminated within one period of the power supply current Ips for each phase, even with some fluctuations. Therefore, to reduce the distortion of the power supply current Ips and make it a square wave current, the lower limit of the resonant frequency Fre of the LC filter 30 should be 18 times the power supply frequency Fps. If the filter capacitance Cf of the filter capacitor 9 is too large, the power supply current Ips will not be a square wave current, as in the current characteristic 82d of the power supply current Ips in Comparative Example 3. For this reason, it is preferable to use a film capacitor with a small filter capacitance Cf and a large current rating for the filter capacitor 9.

[0043] The resonant frequency Fre of the LC filter 30 only needs to satisfy both conditions: it must be less than or equal to half of the carrier frequency Fca and at least 18 times the power supply frequency Fps. For example, the parameters of the LC filter 30 in the power converter 50 of Embodiment 1, namely the filter inductance Lf and filter capacitance Cf, are Lf = 200 μH and Cf = 10 μF. The resonant frequency Fre can be calculated from equation (1). In this case, the resonant frequency Fre is approximately 3600 Hz, which is about one-quarter of the carrier frequency Fca and 60 times the power supply frequency Fps. The output voltage Vo, control reactor current IL, and power supply current Ips in the power converter 50 of Embodiment 1 can be the characteristics shown in Figures 5, 6, and 7.

[0044] The output of the rectifier circuit 2 generates pulsations that include components that are multiples of 6 of the power supply frequency Fps (6th, 12th, 18th, etc.). However, to improve the characteristics of the rectifier circuit 2, it is desirable for the resonant frequency Fre of the LC filter 30 to be higher. By increasing the resonant frequency Fre of the LC filter 30 from 6th of the power supply frequency Fps to 3 times that, i.e., 18 times the power supply frequency Fps, the output of the rectifier circuit 2 can obtain good characteristics.

[0045] The LC filter 30 will exhibit good characteristics if the filter capacitance Cf [F] of the filter capacitor 9 is designed within the range where equation (2) holds true, using the phase-to-phase voltage Vac [V] and input power P [W] of the three-phase AC power supply 1. The input power P can be either the rated power or the maximum power. Cf≦P / Vac 2 ×0.001 ···(2)

[0046] The LC filter 30 exhibits good characteristics when the filter capacitance Cf of the filter capacitor 9 is proportional to the input power, inversely proportional to the square of the power supply voltage, and less than 1 / 1000th of that capacitance. The reason for making it proportional to the power and inversely proportional to the square of the power supply voltage is to keep the waveform shape of the power supply current Ips itself the same even when the power and power supply voltage change.

[0047] The lower limit of the filter capacitance Cfmin, which is the lower limit of the filter capacitance Cf of the filter capacitor 9, can be calculated from equation (1) and half of the carrier frequency Fca, which is the upper limit of the resonant frequency Fre. The lower limit of the filter capacitance Cfmin is 1 / (Lf × π 2 ×Fca 2 Therefore, the filter capacitance Cf[F] of the filter capacitor 9 should be set within the range that satisfies equations (2) and (3). Cf≧1 / (Lf×π 2 ×Fca 2 ) ···(3)

[0048] The power converter 50 of Embodiment 1 includes a converter 31 that is PWM controlled by a control signal sig1 generated based on a carrier wave 26 and an on-duty command D*, and the resonant frequency Fre of the LC filter 30 is set to be greater than or equal to a predetermined lower limit frequency Fremin, and less than or equal to half the carrier frequency Fca of the carrier wave 26. The lower limit frequency Fremin of the resonant frequency Fre is 18 times the frequency of the three-phase AC, i.e., the power supply frequency Fps. In other words, the setting conditions for the LC filter 30 of Embodiment 1, using the resonant frequency Fre, are that the resonant frequency Fre is greater than or equal to the lower limit frequency Fremin, and less than or equal to half the carrier frequency Fca of the carrier wave 26. Furthermore, the setting conditions for the filter capacitance Cf of the filter capacitor 9 in the LC filter 30 of Embodiment 1 are within the range that satisfies equations (2) and (3).

[0049] The power converter 50 of Embodiment 1 can prevent damage to peripheral equipment by reducing the outflow of carrier ripple current. Furthermore, by reducing the distortion of the power supply current Ips, component losses can be reduced, making it possible to use components with lower current ratings.

[0050] The functional blocks of the controller 10, namely the subtractor 21, voltage feedback control unit 22, current feedback control unit 23, and carrier comparison unit 24, may be implemented by the processor 98 and memory 99 shown in Figure 27. Figure 27 shows an example of a hardware configuration in which the controller's functions are implemented by digital calculations. In this case, the subtractor 21, voltage feedback control unit 22, current feedback control unit 23, and carrier comparison unit 24 are implemented by the processor 98 executing a program stored in the memory 99. Alternatively, multiple processors 98 and multiple memory 99 may work together to execute each function.

[0051] The switching element 3 may be a silicon semiconductor element formed using silicon, or a wide-bandgap semiconductor element formed using a wide-bandgap semiconductor material with a larger bandgap than silicon. Examples of wide-bandgap semiconductor materials include silicon carbide (SiC), gallium nitride (GaN)-based materials, or diamond. The semiconductor material for the diode 4 can also be silicon or a wide-bandgap semiconductor material, similar to the switching element 3. When the switching element 3 and diode 4 are semiconductor elements formed from wide-bandgap semiconductor materials, i.e., wide-bandgap semiconductor elements, they have faster switching speeds and operating speeds, and lower losses such as switching losses, compared to silicon semiconductor elements. Furthermore, wide-bandgap semiconductor elements have higher voltage resistance and heat resistance than silicon semiconductor elements. Therefore, when the switching element 3 and diode 4 are wide-bandgap semiconductor elements, the heat sinks and other coolers for the switching element 3 and diode 4 can be made smaller, and in some cases, heat sinks and other coolers may not even be necessary.

[0052] As described above, the power converter 50 of Embodiment 1 includes a rectifier circuit 2 that converts the three-phase AC input voltage (phase-to-phase voltage Vac) input from AC input terminals 55r, 55s, and 55t into a DC voltage; a converter 31 that outputs an output voltage Vo set to a set voltage value from the DC voltage output from the rectifier circuit 2; a smoothing capacitor 6 connected between the positive converter output terminal (DC output terminal 64p) and the negative converter output terminal (DC output terminal 64n) of the converter 31 that outputs the output voltage Vo; an LC filter 30 having a filter reactor 8 and a filter capacitor 9 arranged between the AC input terminals 55r, 55s, and 55t and the converter 31; and a controller 10 that controls the converter 31. The filter reactor 8 is located closer to the AC input terminals 55r, 55s, and 55t than the filter capacitor 9. In the power converter 50 of Embodiment 1, with this configuration, an LC filter 30 having a filter reactor 8 and a filter capacitor 9 is arranged between the AC input terminals 55r, 55s, and 55t and the converter 31. Since the filter reactor 8 is positioned closer to the AC input terminals 55r, 55s, and 55t than the filter capacitor 9, it is possible to reduce the carrier ripple current and reduce the outflow of carrier ripple current to the power supply.

[0053] Embodiment 2. Figure 18 shows the configuration of a power converter according to Embodiment 2, and Figure 19 shows the configuration of another example of the converter in Figure 18. The power converter 50 of Embodiment 2 differs from the power converter 50 of Embodiment 1 in that the converter 31 is either a boost converter 31b or a buck-boost converter 31c. The differences from the power converter 50 of Embodiment 1 will be mainly described.

[0054] Figure 18 shows an example where converter 31 is a boost converter 31b. Figure 19 shows an example where converter 31 is a buck-boost converter 31c. In the boost converter 31b, which is an example of converter 31, one end of the control reactor 5 is connected to the positive DC input terminal 63p, and the other end of the control reactor 5 is connected to the collector of the switching element 3 and the anode of the diode 4. The cathode of the diode 4 is connected to the positive DC output terminal 64p. The control reactor 5 and diode 4 are inserted into the positive wiring 73p. The emitter of the switching element 3 is connected to the negative wiring 73n, and the negative wiring 73n connects to the DC input terminal 63n and the DC output terminal 64n. The gate of the switching element 3 is connected to the control terminal 58. A control signal sig1, whose voltage value is changed by the drive circuit 25 based on the gate signal command G* output from the controller 10, is input to the control terminal 58. The control signal sig1 is a signal that controls the on and off states of the switching element 3, for example, by PWM control. The current sensor 12, which detects the control reactor current IL, which is the current of the control reactor 5, is located between the DC input terminal 63p and one end of the control reactor 5.

[0055] The role of the LC filter 30 is to reduce the carrier ripple current generated in the converter 31, such as the boost converter 31b, and to reduce the outflow of the carrier ripple current to the power supply. The role of the LC filter 30 can also be expressed as follows: The role of the LC filter 30 is to reduce the distortion of the power supply current Ips caused by the carrier ripple current generated in the converter 31, such as the boost converter 31b, while reducing the "rabbit ear" shaped, or spike-shaped, current distortion in the power supply current Ips.

[0056] The configuration of the controller 10 is the same as in Embodiment 1. Since the same control configuration as in Embodiment 1 can be used, a detailed explanation will be omitted, but the voltage command Vdc* that controls the output voltage Vo, which is the voltage of the smoothing capacitor 6, is determined to an arbitrary value. Since the converter 31 is a boost converter 31b, the voltage command Vdc* must be set to be greater than the voltage of the filter capacitor 9 input to the boost converter 31b.

[0057] In the boost converter 31b, the input side is the control reactor 5, and a waveform like a triangular wave becomes the input to the boost converter 31b, so the carrier ripple current generated is less than that of the buck converter 31a. However, the LC filter 30 and the parameter selection method for the LC filter 30 described in Embodiment 1 are effective in reducing the carrier ripple current and reducing the outflow of the carrier ripple current to the power supply.

[0058] In Figure 18, the boost converter 31b is shown as an example of a two-level configuration, but it goes without saying that it is also possible to increase the number of switching elements 3 to create a three-level configuration, etc., by connecting multiple switching elements 3 in series. Similarly, the buck converter 31a described in Embodiment 1 may also be made into a three-level configuration. The converter 31 can also be a buck-boost converter 31c that combines the functions of the boost converter 31b and the buck converter 31a.

[0059] The buck-boost converter 31c shown in Figure 19 comprises two switching elements 3a and 3b, a control reactor 5, and two diodes 4a and 4b. The configuration consisting of the switching element 3a, diode 4a, and control reactor 5 is the same as that of the buck converter 31a shown in Embodiment 1. The configuration consisting of the control reactor 5, switching element 3b, and diode 4b is the same as that of the boost converter 31b shown in Figure 18. In the buck-boost converter 31c, the collector of the switching element 3a is connected to the DC input terminal 63p, and the emitter of the switching element 3a is connected to the cathode of the diode 4a and one end of the control reactor 5. The other end of the control reactor 5 is connected to the collector of the switching element 3b and the anode of the diode 4b. The cathode of the diode 4b is connected to the DC output terminal 64p. The anode of diode 4a and the emitter of switching element 3b are connected to the negative wiring 73n, which in turn connects to the DC input terminal 63n and the DC output terminal 64n. The switching element 3a, control reactor 5, and diode 4b are inserted into the positive wiring 73p. The gate of switching element 3a is connected to control terminal 58a, and the gate of switching element 3b is connected to control terminal 58b.

[0060] Control terminals 58a and 58b receive control signal sig1, whose voltage value is modified by the drive circuit 25 based on a gate signal command G* output from the controller 10. More specifically, control terminal 58a receives control signal s1a, whose voltage value is modified by the drive circuit 25 based on a gate signal command G1* output from the controller 10. Control terminal 58b receives control signal s1b, whose voltage value is modified by the drive circuit 25 based on a gate signal command G2* output from the controller 10. The code for the control signals input to control terminals 58a and 58b is generally sig1, with s1a and s1b used to distinguish between them. The code for the gate signal command output from the controller 10 is generally G*, with G1* and G2* used to distinguish between them. The current sensor 12, which detects the control reactor current IL, which is the current of the control reactor 5, is positioned between the emitter of the switching element 3a, the cathode of the diode 4a, and one end of the control reactor 5. The control reactor current IL detected by this current sensor 12 is also the positive wiring current Ip, as it flows through the positive wiring 73p, similar to the control reactor current IL shown in Figures 1 and 18. The control signal sig1 is a signal that controls the on and off states of switching elements 3a and 3b, for example, by PWM control. When the buck-boost converter 31c functions as a buck converter, switching element 3b is set to the off state, and switching element 3a is controlled to the on and off states. When the buck-boost converter 31c functions as a boost converter, switching element 3a is set to the on state, and switching element 3b is controlled to the on and off states. In Figure 19, an example of a 2-level configuration of the buck-boost converter 31c is shown, but it goes without saying that it is also possible to increase the number of switching elements 3 to create a 3-level configuration, etc., by connecting multiple switching elements 3 in series.

[0061] The power converter 50 of Embodiment 2, like the power converter 50 of Embodiment 1, can prevent damage to peripheral equipment by reducing the outflow of carrier ripple current. Furthermore, by reducing the distortion of the power supply current Ips, component losses can be reduced, making it possible to use components with lower current ratings. In the power converter 50 of Embodiment 2, an LC filter 30 having a filter reactor 8 and a filter capacitor 9 is arranged between the AC input terminals 55r, 55s, 55t and the converter 31, and since the filter reactor 8 is positioned closer to the AC input terminals 55r, 55s, 55t than the filter capacitor 9, the carrier ripple current can be reduced and the outflow of carrier ripple current to the power supply can be reduced.

[0062] Embodiment 3. Figure 20 shows the configuration of the first power converter according to Embodiment 3, and Figure 21 shows the configuration of the second power converter according to Embodiment 3. In Embodiments 1 and 2, an example was shown in which the filter reactor 8 of the LC filter 30 was placed between the rectifier circuit 2 connected to the AC input terminals 55r, 55s, and 55t and the converter 31, but the filter reactor 8 may also be placed between the AC input terminals 55r, 55s, and 55t and the rectifier circuit 2. The power converter 50 of Embodiment 3 differs from the power converter 50 of Embodiments 1 and 2 in that the filter reactor 8 is placed between the AC input terminals 55r, 55s, and 55t and the rectifier circuit 2. The differences from the power converter 50 of Embodiments 1 and 2 will be mainly described.

[0063] In the first power converter 50 of Embodiment 3 shown in Figure 20, a first filter reactor 8 is connected between the AC input terminal 55r and the AC input terminal 61r, which is the rectifier circuit input terminal of the rectifier circuit 2. Similarly, a second filter reactor 8 is connected between the AC input terminal 55s and the AC input terminal 61s, which is the rectifier circuit input terminal of the rectifier circuit 2, and a third filter reactor 8 is connected between the AC input terminal 55t and the AC input terminal 61t, which is the rectifier circuit input terminal of the rectifier circuit 2. The LC filter 30 of Embodiment 3 has three filter reactors 8 and a filter capacitor 9 flanking the rectifier circuit 2. The three filter reactors 8 shown in Figure 20 are on the AC side (alternating current side), so they can also be called AC reactors.

[0064] Since the AC side receives a three-phase AC input, a total of three filter reactors 8 are required. However, even with this configuration, the LC filter 30 can be operated effectively. It should be noted, however, that the filter inductance Lf of filter reactor 8 is doubled because the signal passes through filter reactor 8 twice in the round trip.

[0065] Alternatively, the second power converter 50 of Embodiment 3, as shown in Figure 21, may be configured. It is also possible to reuse the reactor of the common mode choke coil 42, which is installed for noise reduction, as the filter reactor 8. In the second power converter 50 of Embodiment 3, the filter reactor 8 is connected between the AC input terminals 55r, 55s, and 55t and the AC input terminals 61r, 61s, and 61t, which are the input terminals of the rectifier circuit 2, and the three filter reactors 8 corresponding to each phase of the three-phase AC constitute the common mode choke coil 42. The common mode choke coil 42 is normally effective in common mode, but it can also be used in normal mode because it has some inductance.

[0066] The power converter 50 of Embodiment 3, like the power converters 50 of Embodiments 1 and 2, can prevent damage to peripheral equipment by reducing the outflow of carrier ripple current. Furthermore, by reducing the distortion of the power supply current Ips, component losses can be reduced, making it possible to use components with low current ratings. In the power converter 50 of Embodiment 3, an LC filter 30 having three filter reactors 8 and filter capacitors 9 is arranged between the AC input terminals 55r, 55s, and 55t and the converter 31. Since the three filter reactors 8 are positioned on the AC input terminals 55r, 55s, and 55t side of the filter capacitors 9 that are sandwiched between the rectifier circuit 2, the carrier ripple current can be reduced, and the outflow of carrier ripple current to the power supply can be reduced.

[0067] Embodiment 4. Figure 22 shows the configuration of the power converter according to Embodiment 4, and Figure 23 shows the configuration of the controller according to Embodiment 4. In the power converter 50 of Embodiments 1 and 2, an example was shown in which the current sensor 12 detects the control reactor current IL as the positive wiring current Ip flowing through the positive wiring 73p. However, the current sensor 12 may also detect the rectifier circuit current Irc, which is the current flowing through the filter reactor 8 and is the output current of the rectifier circuit 2, as the positive wiring current Ip flowing through the positive wiring 73p. The power converter 50 of Embodiment 4 differs from the power converter 50 of Embodiments 1 and 2 in that it uses the rectifier circuit current Irc as the positive wiring current Ip. The differences from the power converter 50 of Embodiments 1 and 2 will be mainly described.

[0068] Figure 23 shows the configuration of the controller 10 of Embodiment 4. This differs from the controller 10 shown in Figure 2 in that the rectifier circuit current Irc is input to the negative input (minus side input) of the subtractor 21 between the voltage feedback control unit 22 and the current feedback control unit 23. The subtractor 21, located downstream of the voltage feedback control unit 22, calculates the current deviation ΔI, which is the difference between the current command IL* of the control reactor 5 and the detected value of the rectifier circuit current Irc output from the rectifier circuit 2 and flowing through the filter reactor 8. The current deviation ΔI is input to the current feedback control unit 23, which performs current feedback control. Although the detected value of the rectifier circuit current Irc does not perfectly match the detected value of the control reactor current IL of the control reactor 5, since both the rectifier circuit current Irc and the control reactor current IL are positive side wiring currents Ip, the rectifier circuit current Irc may be used as a substitute for the control reactor current IL.

[0069] The power converter 50 of Embodiment 4, like the power converters 50 of Embodiments 1 and 2, can prevent damage to peripheral equipment by reducing the outflow of carrier ripple current. Furthermore, by reducing the distortion of the power supply current Ips, component losses can be reduced, making it possible to use components with lower current ratings. In the power converter 50 of Embodiment 4, an LC filter 30 having a filter reactor 8 and a filter capacitor 9 is arranged between the AC input terminals 55r, 55s, and 55t and the converter 31. Since the filter reactor 8 is positioned closer to the AC input terminals 55r, 55s, and 55t than the filter capacitor 9, the carrier ripple current can be reduced, and the outflow of carrier ripple current to the power supply can also be reduced.

[0070] Furthermore, since the power converter 50 of Embodiment 4 observes the power supply side more closely than the LC filter 30, it can make the power supply current Ips of the three-phase AC power supply 1 a rectangular wave, i.e., a rectangular wave current. Since the three-phase AC power supply 1 outputs three-phase AC current, the power supply current Ips of each phase is shifted by 120 degrees. Therefore, the power converter 50 of Embodiment 4 can make the power supply current Ips closer to a rectangular wave current with 120 degrees of energization than the power converter 50 of Embodiments 1 and 2. In the power converter 50 of Embodiment 4, the converter 31 is controlled based on the output voltage Vo and the rectifier circuit current Irc, so unless special measures are taken, the current of the control reactor 5, i.e., the control reactor current IL, will be distorted. However, by appropriately setting the parameters of the LC filter 30, i.e., the filter inductance Lf of the filter reactor 8 and the filter capacitance Cf of the filter capacitor 9, the waveform distortion of the current of the control reactor 5, i.e., the control reactor current IL, can be reduced.

[0071] Embodiment 5. Figure 24 is a diagram showing the configuration of a refrigeration cycle device according to Embodiment 5. Figure 25 is a diagram showing the configuration of the refrigerant circuit in Figure 24, and Figure 26 is a diagram showing the configuration of the inverter in Figure 24. Embodiment 5 describes a refrigeration cycle device 120 equipped with a power conversion device 50 including the converter 31, LC filter 30, and controller 10 of Embodiments 1 to 4.

[0072] The refrigeration cycle device 120 has a refrigerant circuit 110 that constitutes a refrigeration cycle in which the refrigerant circulates while repeatedly undergoing the processes of "compression," "condensation," "expansion," and "evaporation." Examples of the refrigeration cycle device 120 include air conditioners and refrigeration systems. In the following explanation, an air conditioner will be used as an example of the refrigeration cycle device 120.

[0073] The power converter 50 of Embodiment 5 shown in Figure 24 is a power converter in which an inverter 32 is added to the power converter 50 of Embodiments 1 to 4. In the power converter 50 of Embodiment 5 shown in Figure 24, the DC output terminal 64p of the converter 31 and the DC input terminal 65p of the inverter 32 are connected by a positive power line 74p, and the DC output terminal 64n of the converter 31 and the DC input terminal 65n of the inverter 32 are connected by a negative power line 74n. In Figure 24, the smoothing capacitor 6 connected between the positive power line 74p and the negative power line 74n and the voltage sensor 11 that detects the output voltage Vo, which is the voltage of the smoothing capacitor 6 are omitted. Also in Figure 24, the LC filter 30 having a filter reactor 8 and a filter capacitor 9, which is placed between the AC input terminals 55r, 55s, 55t and the converter 31 are omitted. The power converter 50 of Embodiment 5 shown in Figure 24 is an example of supplying three-phase AC power to a motor 51, which is an AC motor.

[0074] The inverter 32 is a bridge inverter circuit composed of, for example, six switching elements 3a to 3f. Switching elements 3a and 3b connected in series are the u-phase arms of the three-phase AC, switching elements 3c and 3d connected in series are the v-phase arms of the three-phase AC, and switching elements 3e and 3f connected in series are the w-phase arms of the three-phase AC. AC output terminal 66u is connected to the connection point of switching elements 3a and 3b, AC output terminal 66v is connected to the connection point of switching elements 3c and 3d, and AC output terminal 66w is connected to the connection point of switching elements 3e and 3f. The collectors of switching elements 3a, 3c, and 3e are connected to the positive DC input terminal 65p, and the emitters of switching elements 3b, 3d, and 3f are connected to the negative DC input terminal 65n. The inverter 32 outputs three-phase AC power from its AC output terminals 66u, 66v, and 66w via the output terminals 56a, 56b, and 56c of the power converter 50. The input terminals 67a, 67b, and 67c of the refrigerant circuit 110 are connected to the output terminals 56a, 56b, and 56c of the power converter 50 by power lines 72u, 72v, and 72w. The power lines connecting the AC output terminals 66u, 66v, and 66w of the inverter 32 to the output terminals 56a, 56b, and 56c of the power converter 50 are also denoted as 72u, 72v, and 72w. The power lines connected to the input terminals 67a, 67b, and 67c of the refrigerant circuit 110 are generally denoted as 72, with 72u, 72v, and 72w used for distinction.

[0075] The control signal s1a is input to the gate of switching element 3a via control terminal 59a, and the control signal s1b is input to the gate of switching element 3b via control terminal 59b. Similarly, the control signal s1c is input to the gate of switching element 3c via control terminal 59c, and the control signal s1d is input to the gate of switching element 3d via control terminal 59d. The control signal s1e is input to the gate of switching element 3e via control terminal 59e, and the control signal s1f is input to the gate of switching element 3f via control terminal 59f. The code for the control terminals of the inverter 32 is generally 59, and 59a to 59f are used to distinguish between them. The code for the control signals input to the inverter 32 is generally sig1b, and s1a to s1f are used to distinguish between them.

[0076] The control terminal 58 of the converter 31 receives the control signal sig1a output by the drive circuit 25a based on the gate signal command G* output from the controller 10. The control terminal 59 of the inverter 32 receives the control signal sig1b output by the drive circuit 25b based on the gate signal command Gi* output from the controller 10. The drive circuit 25a and control signal sig1a are the drive circuit 25 and control signal sig1 of the power conversion device 50 in Embodiments 1 to 4. The control signal sig1b is a signal that controls the on and off states of the switching elements 3a to 3f by, for example, PWM control. The drive circuit 25b outputs a control signal sig1b with a changed voltage value based on the gate signal command Gi* output from the controller 10. The gate signal command Gi* is generated for each switching element 3a to 3f. The gate signal command Gi* can be a gate signal command that performs normal PWM control.

[0077] An example of a refrigeration cycle device 120, an air conditioner, is configured as a refrigeration cycle, or refrigerant circuit 110, with the compressor 101, four-way valve 102, outdoor heat exchanger 103, expansion device 104, indoor heat exchanger 105, four-way valve 102, and compressor 101 connected in that order by refrigerant piping 108. Specifically, the refrigerant circuit 110 consists of the compressor 101, condenser (outdoor heat exchanger 103 or indoor heat exchanger 105), expansion device 104, and evaporator (indoor heat exchanger 105 or indoor heat exchanger 105) connected in a ring shape by refrigerant piping. In the refrigerant circuit 110, the indoor heat exchanger 105 is the indoor part 107, while the compressor 101, four-way valve 102, outdoor heat exchanger 103, and expansion device 104 are the outdoor part 106. The indoor unit of the air conditioner is equipped with the indoor heat exchanger 105 in the indoor part 107. The outdoor unit of the air conditioner includes a power converter 50 and an outdoor unit 106 containing a compressor 101, a four-way valve 102, an outdoor heat exchanger 103, and an expansion device 104. The compressor 101 includes a motor 51 and a compression element 101a. The motor 51 is powered by the power converter 50 and rotated. The power converter 50 supplies power to the motor 51 to rotate it. The motor 51 is connected to the compression element 101a, and the motor 51 and the compression element 101a constitute the compressor 101 that compresses the refrigerant.

[0078] Next, the operation of the air conditioner will be explained using the cooling operation as an example. It should be assumed that, when performing the cooling operation, the four-way valve 102 has already switched the flow path so that the refrigerant discharged from the compressor 101 goes towards the outdoor heat exchanger 103, and the refrigerant flowing out from the indoor heat exchanger 105 goes towards the compressor 101.

[0079] The motor 51 of the compressor 101 is rotated by the power converter 50, causing the compression element 101a of the compressor 101, which is connected to the motor 51, to compress the refrigerant, and the compressor 101 discharges high-temperature, high-pressure refrigerant. The high-temperature, high-pressure refrigerant discharged from the compressor 101 flows into the outdoor heat exchanger 103 via the four-way valve 102, where it exchanges heat with the outside air and dissipates heat. The refrigerant that flows out of the outdoor heat exchanger 103 is expanded and depressurized by the expansion device 104, becoming a low-temperature, low-pressure two-phase gas-liquid refrigerant, which flows into the indoor heat exchanger 105. The refrigerant that flows into the indoor heat exchanger 105 exchanges heat with the air in the air-conditioned space, evaporates, and becomes a low-temperature, low-pressure gaseous refrigerant, which flows out of the indoor heat exchanger 105. The gaseous refrigerant that flows out of the indoor heat exchanger 105 is drawn into the compressor 101 via the four-way valve 102 and compressed again. The above operations are repeated. When the air conditioner is in cooling operation, the outdoor heat exchanger 103 acts as a condenser and the indoor heat exchanger 105 acts as an evaporator. When the air conditioner is in heating operation, the operation is reversed, with the outdoor heat exchanger 103 acting as an evaporator and the indoor heat exchanger 105 acting as a condenser.

[0080] In Figure 24, an example is shown in which a power converter 50, which is an inverter 32 added to the power converter 50 of Embodiments 1 to 4, is applied to the power converter that supplies power to the compressor 101 of an air conditioner, which is an example of a refrigeration cycle device 120. However, the invention is not limited to this. Needless to say, the refrigeration cycle device 120 can be applied not only to air conditioners but also to heat pump devices, refrigeration devices, and other refrigeration cycle devices in general.

[0081] As described above, the refrigeration cycle device 120 of Embodiment 5 includes a refrigerant circuit 110 in which a compressor 101, a condenser (outdoor heat exchanger 103 or indoor heat exchanger 105), an expansion device 104, and an evaporator (indoor heat exchanger 105 or indoor heat exchanger 105) are connected in a ring shape by refrigerant piping 108, and a power converter 50 that supplies power to the compressor 101 and drives it. The power converter 50 includes a rectifier circuit 2 that converts the three-phase AC input voltage (phase-to-phase voltage Vac) input from AC input terminals 55r, 55s, and 55t into a DC voltage; a converter 31 that outputs an output voltage Vo set to a set voltage value from the DC voltage output from the rectifier circuit 2; a smoothing capacitor 6 connected between the positive converter output terminal (DC output terminal 64p) and the negative converter output terminal (DC output terminal 64n) of the converter 31 that outputs the output voltage Vo; an LC filter 30 having a filter reactor 8 and a filter capacitor 9, positioned between the AC input terminals 55r, 55s, and 55t and the converter 31; and a controller 10 that controls the converter 31. Furthermore, the power converter 50 includes an inverter 32 that converts the DC output voltage Vo output from the converter 31 into an AC voltage and is controlled by the controller 10. The filter reactor 8 is positioned closer to the AC input terminals 55r, 55s, and 55t than the filter capacitor 9. In the refrigeration cycle device 120 of Embodiment 5, with this configuration, the LC filter 30 having a filter reactor 8 and a filter capacitor 9 is arranged between the AC input terminals 55r, 55s, and 55t and the converter 31 in the power converter 50, and since the filter reactor 8 is positioned closer to the AC input terminals 55r, 55s, and 55t than the filter capacitor 9, the carrier ripple current can be reduced and the outflow of carrier ripple current to the power supply can be reduced.

[0082] While this disclosure describes various exemplary embodiments and examples, the various features, aspects, and functions described in one or more embodiments are not limited to the application of a particular embodiment, but are applicable individually or in various combinations to the embodiments. Accordingly, countless variations not illustrated are conceivable within the scope of the art disclosed in this specification. For example, these include modifying, adding, or omitting at least one component, or extracting at least one component and combining it with a component from another embodiment.

[0083] Although preferred embodiments have been described in detail above, the invention is not limited to the embodiments described above, and various modifications and substitutions can be made to the embodiments described above without departing from the scope of the claims.

[0084] The various aspects of this disclosure are summarized below as an appendix.

[0085] (Note 1) A rectifier circuit that converts the three-phase AC input voltage received from the AC input terminal into a DC voltage, A converter that outputs an output voltage set to a set voltage value from the DC voltage output from the rectifier circuit, A smoothing capacitor connected between the positive converter output terminal and the negative converter output terminal of the converter from which the output voltage is output, An LC filter having a filter reactor and a filter capacitor is disposed between the AC input terminal and the converter. The system includes a controller for controlling the converter, The filter reactor is positioned closer to the AC input terminal than the filter capacitor. Power converter. (Note 2) The filter reactor is connected between one end of the filter capacitor, which is connected to the positive rectifier circuit output terminal of the rectifier circuit and the positive converter input terminal of the converter. The power conversion device described in Appendix 1. (Note 3) The filter reactor is connected between the AC input terminal and the rectifier circuit input terminal of the rectifier circuit. The power conversion device described in Appendix 1. (Note 4) The aforementioned filter reactor constitutes a common mode choke coil. The power conversion device described in Appendix 3. (Note 5) Let Vac be the voltage between two phases of the three-phase AC input from the AC input terminal, and let P be the power of the three-phase AC input from the AC input terminal. The capacitance Cf of the filter capacitor, with F as the unit, Cf≦P / Vac 2 ×0.001 It satisfies the following conditions and is above the lower limit capacitance, A power conversion device as described in Appendix 1 or 2. (Note 6) Let Vac be the voltage between two phases of the three-phase AC input from the AC input terminal, and let P be the power of the three-phase AC input from the AC input terminal. The capacitance Cf of the filter capacitor, with F as the unit, Cf≦P / Vac 2 ×0.001 It satisfies the following conditions and is above the lower limit capacitance, A power conversion device as described in Appendix 3 or 4. (Note 7) The converter includes a switching element that is PWM controlled by a control signal generated based on a carrier wave and an on-duty command. The resonant frequency of the LC filter is set to be above a predetermined lower limit frequency and below half the frequency of the carrier wave. A power conversion device as described in any one of the following appendices: 1, 2, or 5. (Note 8) The converter includes a switching element that is PWM controlled by a control signal generated based on a carrier wave and an on-duty command. The resonant frequency of the LC filter is set to be above a predetermined lower limit frequency and below half the frequency of the carrier wave. A power conversion device as described in any one of the appendices 3, 4, or 6. (Note 9) The aforementioned lower limit frequency is 18 times the frequency of the three-phase AC. The power conversion device described in Appendix 7. (Note 10) The aforementioned lower limit frequency is 18 times the frequency of the three-phase AC. The power conversion device described in Appendix 8. (Note 11) The controller includes a current feedback control unit that generates an on-duty command to control the current flowing through the filter reactor to be within a predetermined current setting range. A power converter as described in Appendix 7 or 9. (Note 12) The converter is equipped with a control reactor, The controller includes a current feedback control unit that generates an on-duty command to control the current flowing through the control reactor to be within a predetermined current setting range. A power conversion device as described in any one of the appendices 7 to 10. (Note 13) The current setting range is set so that the input current of the three-phase AC becomes a rectangular wave current. A power conversion device as described in Appendix 11 or 12. (Note 14) The converter is one of the following: a buck converter, a boost converter, or a buck-boost converter. A power conversion device as described in any one of the appendices 1 to 13. (Note 15) The system includes an inverter that converts the DC output voltage output from the converter into an AC voltage. The controller controls the inverter. A power conversion device as described in any one of the appendices 1 to 14. (Note 16) A refrigerant circuit in which a compressor, condenser, expansion device, and evaporator are connected in a ring shape by refrigerant piping, The power converter described in Appendix 15, which supplies power to the compressor and drives it. A refrigeration cycle system equipped with a device. [Explanation of Symbols]

[0086] 2...Rectifier circuit, 3...Switching element, 3a, 3b, 3c, 3d, 3e, 3f...Switching element, 5...Control reactor, 6...Smoothing capacitor, 8...Filter reactor, 9...Filter capacitor, 10...Controller, 23...Current feedback control unit, 26...Carrier wave, 30...LC filter, 31...Converter, 31a...Step-down converter, 31b...Step-up converter, 31c...Step-up / step-down converter, 32...Inverter, 42...Common mode choke coil, 50...Power converter, 55r, 55s, 55t...AC input terminal, 61r, 61s, 61t...AC input terminal, 62p...DC output terminal (positive side rectifier circuit output terminal), 63p...DC input terminal (positive side converter input terminal), 64p...DC output terminal ( 64n…DC output terminal (negative converter output terminal), 68p…Positive capacitor terminal, 101…Compressor, 103…Outdoor heat exchanger (condenser or evaporator), 104…Expansion device, 105…Indoor heat exchanger (evaporator or condenser), 108…Refrigerant piping, 110…Refrigerant circuit, 120…Refrigeration cycle device, Cf…Filter capacity, Cfmin…Lower limit filter capacity, D*…On duty command, Fca…Carrier frequency, Fps…Power supply frequency, Fre…Resonant frequency, Fremin…Lower limit frequency, IL…Control reactor current, Irc…Rectifier circuit current, P…Input power, RaI…Current setting range, sig1, sig1a, sig1b…Control signals, Va…Output voltage, Vac…Phase voltage, Vo…Output voltage

Claims

1. A rectifier circuit that converts the three-phase AC input voltage received from the AC input terminal into a DC voltage, A converter that outputs an output voltage set to a set voltage value from the DC voltage output from the rectifier circuit, A smoothing capacitor connected between the positive converter output terminal and the negative converter output terminal of the converter from which the output voltage is output, An LC filter having a filter reactor and a filter capacitor is disposed between the AC input terminal and the converter. The system includes a controller for controlling the converter, The filter reactor is positioned closer to the AC input terminal than the filter capacitor. Power converter.

2. The filter reactor is connected between one end of the filter capacitor, which is connected to the positive rectifier circuit output terminal of the rectifier circuit and the positive converter input terminal of the converter. The power conversion device according to claim 1.

3. The filter reactor is connected between the AC input terminal and the rectifier circuit input terminal of the rectifier circuit. The power conversion device according to claim 1.

4. The aforementioned filter reactor constitutes a common mode choke coil. The power conversion device according to claim 3.

5. Let Vac be the voltage between two phases of the three-phase AC input from the AC input terminal, and let P be the power of the three-phase AC input from the AC input terminal. The capacitance Cf of the filter capacitor, with F as the unit, Cf≦P / Vac 2 ×0.001 It satisfies the following conditions and is above the lower limit capacitance, The power conversion device according to claim 1.

6. Let Vac be the voltage between two phases of the three-phase AC input from the AC input terminal, and let P be the power of the three-phase AC input from the AC input terminal. The capacitance Cf of the filter capacitor, with F as the unit, Cf≦P / Vac 2 ×0.001 It satisfies the following conditions and is above the lower limit capacitance, The power conversion device according to claim 2.

7. Let Vac be the voltage between two phases of the three-phase AC input from the AC input terminal, and let P be the power of the three-phase AC input from the AC input terminal. The capacitance Cf of the filter capacitor, with F as the unit, Cf≦P / Vac 2 ×0.001 It satisfies the following conditions and is above the lower limit capacitance, The power conversion device according to claim 3.

8. Let Vac be the voltage between two phases of the three-phase AC input from the AC input terminal, and let P be the power of the three-phase AC input from the AC input terminal. The capacitance Cf of the filter capacitor, with F as the unit, Cf≦P / Vac 2 ×0.001 It satisfies the following conditions and is above the lower limit capacitance, The power conversion device according to claim 4.

9. The converter includes a switching element that is PWM controlled by a control signal generated based on a carrier wave and an on-duty command. The resonant frequency of the LC filter is set to be above a predetermined lower limit frequency and below half the frequency of the carrier wave. A power conversion device according to any one of claims 1, 2, 5, or 6.

10. The converter includes a switching element that is PWM controlled by a control signal generated based on a carrier wave and an on-duty command. The resonant frequency of the LC filter is set to be above a predetermined lower limit frequency and below half the frequency of the carrier wave. A power conversion device according to any one of claims 3, 4, 7, or 8.

11. The aforementioned lower frequency limit is 18 times the frequency of the three-phase AC. The power conversion device according to claim 9.

12. The aforementioned lower frequency limit is 18 times the frequency of the three-phase AC. The power conversion device according to claim 10.

13. The controller includes a current feedback control unit that generates an on-duty command to control the current flowing through the filter reactor to be within a predetermined current setting range. The power conversion device according to claim 9.

14. The converter is equipped with a control reactor, The controller includes a current feedback control unit that generates an on-duty command to control the current flowing through the control reactor to be within a predetermined current setting range. The power conversion device according to claim 9.

15. The converter is equipped with a control reactor, The controller includes a current feedback control unit that generates an on-duty command to control the current flowing through the control reactor to be within a predetermined current setting range. The power conversion device according to claim 10.

16. The current setting range is set so that the input current of the three-phase AC becomes a rectangular wave current. The power conversion device according to claim 13.

17. The current setting range is set so that the input current of the three-phase AC becomes a rectangular wave current. The power conversion device according to claim 14.

18. The current setting range is set so that the input current of the three-phase AC becomes a rectangular wave current. The power conversion device according to claim 15.

19. The converter is one of the following: a buck converter, a boost converter, or a buck-boost converter. A power conversion device according to any one of claims 1 to 8.

20. The system includes an inverter that converts the DC output voltage output from the converter into an AC voltage. The controller controls the inverter. A power conversion device according to any one of claims 1 to 8.

21. A refrigerant circuit in which a compressor, condenser, expansion device, and evaporator are connected in a ring shape by refrigerant piping, The power converter according to claim 20, which supplies power to the compressor and drives it. A refrigeration cycle system equipped with a device.

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