Power conversion apparatus and heat pump device

Abstract

The present invention comprises: a rectification circuit (3) that rectifies an AC voltage supplied from an AC power supply (1); a first capacitor (13) connected on the DC side of the rectification circuit; a first power converter (5) that is connected in parallel to the first capacitor and has respective phase output terminals connected to one-side ends of respective phase windings of a motor (10), the respective phase windings being independent of one another; a second power converter (9) having respective phase output terminals connected to the other-side ends of the respective windings of the motor; a second capacitor (8) connected on the DC side of the second power converter; a reactor (6) connected by branching from wiring that connects the AC power supply and the rectification circuit; a third power converter (7) that is connected between the reactor and the second capacitor and suppresses harmonic waves; a relay (16) inserted between the AC power supply and the third power converter; and a control unit that charges the second capacitor by driving first and second inverters before starting the motor, and that turns on the relay after the charging. The capacitance of the second capacitor is set to be larger than the capacitance of the first capacitor.

Description

Description: Title of the invention: Power conversion device and heat pump device Technical field:

[0001] - An embodiment of the present invention relates to a power conversion device that drives a motor having an open winding structure, and a heat pump device including the power conversion device.

[0002] Patent Document 1 discloses a single-phase input power converter equipped with a small-capacity film capacitor as a power converter for driving a motor, and describes that it can reduce harmonics in the input current and improve the power factor. However, in a three-phase input power converter, current flows only from the maximum phase to the minimum phase of the three-phase AC current, so that the input current cannot be controlled to a sine wave only by switching in the power converter circuit for driving the motor.

[0003] On the other hand, in order to realize a larger capacity device and a faster motor, a dual inverter system is known in which an open winding motor with independent windings for each phase is driven by two inverters. Even with this dual inverter system, a small capacity capacitor can be used in the DC section, but when connected to a multi-phase AC such as a three-phase AC, the input current of the device cannot be controlled to a sine wave.

[0004] In response to this, Patent Document 2 discloses a system in which a matrix converter is applied to the primary inverter. [. 0 0 5 ] Patent Document 1: Patent No. 4 3 9 1 7 6 8 Patent Document 2: Patent No. 5 5 3 1 2 3 8 Summary of the invention Problem to be solved by the invention Incorporation by reference (Rule 20•6)

[006] In the configuration of Patent Document 2, the three-phase input current can be controlled to a sine wave, but the semiconductor device for the matrix converter, the choke coil used in the AC filter, and other components must be selected with a rating equal to or higher than the rated capacity of the power conversion device, which results in problems such as an increase in the size of the entire power conversion device and an increase in costs.

[0007] Therefore, the present invention provides a power conversion device that can suppress an increase in the overall size and cost even in a dual inverter system, and a heat pump device equipped with the power conversion device.

[0008] A power conversion device according to an embodiment includes: a rectifier circuit which rectifies an AC voltage supplied from an AC power supply; a first storage element connected to a DC side of the rectifier circuit; a first power converter which is configured of a diode and a semiconductor switch connected in parallel to the first storage element, and in which one end of a winding of a first motor having an independent phase winding is connected to each phase output terminal; a second power converter which is configured of a diode and a semiconductor switch and in which the other end of the winding of the first motor is connected to each phase output terminal; a second storage element connected to the DC side of the second power converter; a reactor which is branched off and connected from a wiring which connects the AC power supply and the rectifier circuit; and a third power converter which is configured of a diode and a semiconductor switch connected between the reactor and the second storage element, and in which harmonics are suppressed.

[0009] A heat pump device according to an embodiment includes the power conversion device according to the embodiment and the first motor, and the first motor drives a compressor. [ 0 0 1 0 ] FIG. 1 is a diagram showing a configuration of a power conversion device according to a first embodiment. [Figure 2] Diagram showing the configuration of an air conditioner FIG. 3 is a diagram showing a configuration of a power conversion device according to a second embodiment. [Figure 4] A flowchart showing the processing of the power regeneration absorption operation in the third embodiment. [Figure 5] A diagram showing the switching state of each inverter when performing the power regeneration absorption operation. [Figure 6] Timing chart showing current and voltage waveforms corresponding to the processing contents shown in Figure 5. FIG. 7 is a diagram showing the switching state of each inverter when performing a power regeneration and absorption operation according to a fourth embodiment. FIG. 8 is a diagram showing a configuration of a power conversion device according to a fifth embodiment. FIG. 9 is a diagram showing a configuration of a power conversion device according to a sixth embodiment. FIG. 10 is a diagram showing the configuration of a power conversion device according to a seventh embodiment. FIG. 11 is a diagram showing the configuration of a power conversion device according to the eighth embodiment. [Figure 12] A diagram showing a configuration example of a noise filter circuit. [0 0 1 1 ] First embodiment As shown in FIG. 1, the power conversion device of this embodiment drives a first motor 10. The first motor 10 may be a three-phase permanent magnet synchronous motor or an induction machine, but in this embodiment, it is a permanent magnet synchronous motor. The first motor 10 is a so-called open winding motor, and its three-phase windings are not connected to each other, with both terminals being in an open state. In other words, the first motor 10 has six winding terminals Ua, Va, Wa, Ub, Vb, and Wb.

[0012] The first motor 10 is driven by a dual inverter system using a first inverter 5 and a second inverter 9. The first inverter 5 and the second inverter 9 are three-phase inverters having the same circuit configuration and three sets of two series-connected switching elements, with the intermediate connection points of each series-connected switching element serving as three output terminals. The phase output terminals of the first inverter 5 are connected to the winding terminals Ua, Va, and Wa of the first motor 10, respectively, and the phase output terminals of the second inverter 9 are connected to the winding terminals Ub, Vb, and Wb of the first motor 10, respectively. [0 0 1 3] A rectifier circuit 3 is connected to a three-phase AC power source 1 via a three-phase reactor 2. The rectifier circuit 3 is composed of six diodes connected in a three-phase bridge configuration. Output of the rectifier circuit 3 Supplementation by reference (Rule 20.6) The first capacitor 4, which is an electrolytic capacitor, and the first inverter 5 are connected to the terminals.

[0014] The second inverter 9 is connected in parallel to both ends of the DC side of the second capacitor 8, which is, for example, an electrolytic capacitor, and the power converter 7. Each of the second capacitor 8 and the first capacitor 4 may be a chargeable and dischargeable storage element having a certain capacity, and the element may be replaced with a storage battery or a battery. In other words, the first capacitor 4 corresponds to the first storage element, and the second capacitor 8 corresponds to the second storage element. The high-voltage side terminal and the low-voltage side terminal of the first inverter 5, i.e., both ends of the first capacitor 4, are not connected to the second inverter 9, and the second inverter 9 is independent. In other words, the output terminals of the first inverter 5 and the second inverter 9 are connected only through the windings of the first motor 10, each of which has an independent phase.

[0015] The power converter 7, whose DC section is connected to the second capacitor 8, has the same circuit configuration as the first inverter 5 and the second inverter 9, and has three sets of two switching elements connected in series, and is a three-phase inverter in which the intermediate connection points of each of the series-connected switching elements become three output terminals. Each phase output terminal of the power converter 7 is connected to a three-phase AC power source 1 through a three-phase reactor 6. A flywheel diode is connected in parallel to each of the switching elements constituting the first inverter 5, the second inverter 9, and the power converter 7. Each of these is configured by connecting semiconductor switching elements such as IGBTs in a three-phase bridge, and corresponds to the first to third power converters, respectively. [0 0 1 6 ] Current sensors 11u and 11v are arranged in the U and V phases of the power line connecting the three-phase AC power source 1 and the three-phase reactor 2. The w-phase current is calculated from the u- and v-phase currents detected by these current sensors ! 1u and 11v. Current sensors ! 2U and 1 2V are arranged in the U and V phases of the power line connecting the three-phase AC power source 1 and the three-phase reactor 6. The W-phase current flowing through the three-phase reactor 6 is calculated from the U- and V-phase currents flowing through the three-phase reactor 6 detected by these current sensors ! 2U and 1 2V. [0 0 1 7] Incorporation by reference (Rule 20.6) Voltage sensors 13, 14 detect the terminal voltages of the first capacitor 4 and the second capacitor 8, respectively. Current sensors 15U, 15V, 15W are arranged between each phase output terminal of the first inverter 5 and the winding terminals Ua, VaWa of the first motor 10 to detect the currents flowing through each motor winding of the first motor 10.

[0018] Since the DC parts of the first inverter 5 and the second inverter 9 are both connected to the same three-phase AC power supply 1, when the first motor 10 is driven by the dual inverter method using both the first inverter 5 and the second inverter 9, a zero-phase current flows in the same direction at a predetermined period in each phase winding. For this reason, current sensors 15U, 15V, and 15W are provided corresponding to each phase winding so that the zero-phase current and the current flowing in each motor winding can be detected separately.

[0019] The detection signals output by each of the above sensors 11-15 are input to a control unit 20. The control unit 20 is composed of a microcomputer or the like, and controls the switching of each IGBT constituting the first inverter 5, the second inverter 9 and the power converter 7 based on the detection signals of each of the sensors 11-15. In the above configuration, everything except the first motor 10 constitutes the power conversion device 41. [. 0 2 0] Figure 2 shows the configuration of an air conditioner, which is a heat pump device to which the power conversion device 41 is applied. In addition to air conditioners, heat pump devices to which the power conversion device 41 is applied include hot water generating devices such as hot water heaters and cold and hot water generating devices such as chillers. The air conditioner 21 is composed of refrigerant piping and signal communication lines that connect the indoor unit 24 and the outdoor unit 35 to each other. The indoor unit 24, which is installed indoors, houses the indoor heat exchanger 27 and the indoor fan 30 inside. On the other hand, the outdoor unit 35 is placed outdoors and houses devices such as the control unit 20, the compressor 22, the outdoor heat exchanger 29, the four-way valve 26, the pressure reducer 28, the outdoor fan 31, and the outdoor fan motor 53.

[0021] The compressor 22 is configured by accommodating the compression section 23 and the first motor 10 in the same iron sealed container 25, and the rotor shaft of the first motor 10 is connected to the compression section 23. The compressor 22, the four-way valve 26, the indoor heat exchanger 27, the pressure reducing device 28, and the outdoor heat exchanger 29 are connected to form a closed loop by pipes that serve as refrigerant passages. The compressor 22 is supplemented by a refrigerant supply (Rules 20.6). For example, a single cylinder rotary compressor is used, but this is not limited to this, and multi-cylinder rotary compressors, scroll compressors, and reciprocating compressors can also be used.

[0022] During heating, the four-way valve 26 is in the state shown by the solid line, and the high-temperature refrigerant compressed in the compression section 23 of the compressor 22 is supplied from the four-way valve 26 to the indoor heat exchanger 27, where it condenses and releases heat to the room, heating the room. The refrigerant is then reduced in pressure by the pressure reducing device 28, becomes cold, and flows to the outdoor heat exchanger 29, where it absorbs heat from the outside air and evaporates, returning to the compressor 22. [. 0 2 3] On the other hand, during cooling, the four-way valve 26 is switched to the state shown by the broken line. Therefore, the high-temperature refrigerant compressed in the compression section 23 of the compressor 22 is supplied from the four-way valve 26 to the outdoor heat exchanger 29, where it radiates heat to the outdoors and condenses. It is then decompressed by the pressure reducing device 28, becomes low temperature, and flows to the indoor heat exchanger 27, where it absorbs heat from the indoor air and evaporates, cooling the room and returning to the compressor 22. Then, the indoor and outdoor heat exchangers 27 and 29 are blown by the indoor fan 30 and the outdoor fan 31, respectively, and the blown air is configured to efficiently exchange heat between the indoor air and the outdoor air and the respective heat exchangers 27 and 29. [. 024] Next, the operation of this embodiment will be described. The control unit 20. operates / stops the compressor 22, i.e., the first motor 10, based on an instruction from an indoor control unit (not shown) on the indoor unit 24 side, for example. During the operation of the compressor 22, the control unit 20 performs vector calculation using the current values ​​detected by the current sensors 15U, 15V, and 15W, and the terminal voltages of the first capacitor 4 and the second capacitor 8 detected by the voltage sensors 13 and 14. Based on the calculation results, the control unit 20 operates the switching elements of the first inverter 5 and the second inverter 9 in a coordinated manner, and a desired current flows through each winding of the first motor 10 to drive the first motor 10 at a variable speed.

[0025] Furthermore, while the first motor 10 is in operation, the control unit 20 simultaneously operates the power converter 7 as an active filter circuit to suppress and reduce harmonics flowing through the power line. Specifically, the control unit 20 extracts harmonic currents from the currents flowing through each phase of the reactor 2 detected by the current sensors 11U and 11IV, and calculates a compensation current by taking into account the terminal voltage of the second capacitor 8 so that the reactor currents of each phase detected by the current sensors 12U and 12V cancel out the harmonic currents flowing through the U, V, and W phases (Rule 20.6). The operation of each switching element of the power converter 7 is controlled so that the current is equal to the current I2C. The second capacitor 8, which is the second storage element, has a certain amount of capacity because it is used as a power source for the correction current output by the active filter circuit. [. 026] By configuring the power conversion device 41 as described above, the controllability of the motor using a dual inverter consisting of the first inverter 5 and the second inverter 9 and the first motor 10 having an open winding configuration is improved. In other words, since voltage is applied to the windings of the first motor 10 by the two inverters 5 and 9, the operating range of the first motor 10 can be expanded. In addition, since the voltage applied to the windings of the first motor 10 is multi-level, the iron loss generated in the first motor 10 can be reduced. [. 0 2 7] Furthermore, by devising a driving method for the two inverters 5 and 9 by the control unit 20, the power applied to the first motor 10 can be controlled to a constant value, and the operating range in the high-speed region can be expanded by injecting reactive power. In addition, by connecting the negative side of the DC part of the power converter 7 and the negative side of the DC part of the second inverter 9, the reference voltage of these circuits becomes common. This makes it possible to reduce the number of insulating parts of the driving power source, and to prevent the circuit size from increasing and the cost from increasing. In addition, by operating the power converter 7 as an active filter circuit that performs switching control so as to cancel the harmonic current flowing out from the rectifier circuit 3 to the three-phase AC power source 1 side during the operation of the L-th motor 10, the power source harmonics can be suppressed, and the input current from the three-phase AC power source 1 to the power conversion device 41 can be made closer to a sine wave. [ 0 0 2 8 ] (Second embodiment) In the following, the same parts as in the first embodiment are given the same reference numerals and their explanation is omitted, and only the different parts are explained. In the power conversion device 42 of the second embodiment shown in FIG. 3, a small-capacity first capacitor 43 is used instead of the first capacitor 4 of the power conversion device 41. As a result, the capacitance of the second capacitor 8 is set to be larger than the capacitance of the first capacitor 43. Note that in the drawings of the power conversion device of each embodiment shown below, the sensors 11 to 15 and the control unit 20 are omitted. Also, the operation control of each part by the control unit 20 in the power conversion device of each embodiment is the same as in the first embodiment. Incorporation by reference (Rules 20.6)

[0029] Here, a film capacitor is used for the first capacitor 43, and an electrolytic capacitor is used for the second capacitor 8 with a large capacity. This allows the number of electrolytic capacitors to be reduced. By using a film capacitor for the first capacitor 43, which is less susceptible to deterioration over time as an individual element, the life of the power conversion device 42 can be extended. The first capacitor 43 has a capacity that can cut high-frequency components generated by switching between the first inverter 5 and the second inverter 9, and the current that charges the first capacitor 43 when the power is turned on does not exceed the capacity of the diode that constitutes the rectifier circuit 3. This capacity is generally about several 10 nF. This allows the three-phase reactor 2 to be made smaller.

[0030] On the other hand, the capacity of the second capacitor 8 may be determined based on the compensation capacity of the power converter 7, the output power of the second inverter 9, the ripple current flowing into the second capacitor 8, etc. This capacity is generally about several 1000 / 2 F. Note that the first capacitor 43 and the second capacitor 8 may be storage elements that can be charged and discharged, and storage batteries or batteries may be used instead of electrolytic capacitors.

[0031] If the first capacitor 43 and the second capacitor 8 are considered as storage elements including a storage battery, the maximum amount of energy that can be stored in the second capacitor 8, which is the second storage element, is set to be greater than the maximum amount of energy that can be stored in the first capacitor 43, which is the first storage element. Note that when capacitors are used for the first and second storage elements, the maximum amount of energy of each element corresponds to the electrostatic capacitance. [ 0 0 3 2 ] (Third embodiment) In the third embodiment, a small-capacity first capacitor 43 such as a film capacitor is used in the power conversion device 42 as in the second embodiment. This is an example equipped with a power regenerative absorption operation to prevent overvoltage failure of the first capacitor 43, the first inverter 5, and the rectifier circuit 3 due to regenerative power generated in the first motor 10. FIG. 4 shows an operation flow during such regenerative absorption, and in order to simplify the drawing, the first capacitor 43 is abbreviated as C1 and the second capacitor 8 is abbreviated as C2. FIG. 5 shows the supplementary flow (Rule 20.6) of the first inverter 5 and the second inverter 9 when performing regenerative absorption operation. Only elements that are energized in the circuit are shown.

[0033] During normal operation (S1), as described above, the control unit 20 drives the first motor 10 using the first inverter 5 and the second inverter 9, and the power converter 7 operates as an active filter circuit. During this normal operation, if the first motor 10 suddenly decelerates or the first inverter 5 and the second inverter 9 stop outputting, regenerative power is generated from the windings of the first motor 10, and this regenerative current flows into the first capacitor 43. This causes the voltage across the first capacitor 43 to rise abnormally.

[0034] Therefore, the control unit 20 detects the voltage rise of the first capacitor 43 by the voltage sensor 13. Then, when the voltage across the first capacitor 43 exceeds a predetermined threshold (S2; YES), it determines that power regeneration by the first motor 10 has occurred, and performs a regenerative absorption operation using the second capacitor 8 shown in FIG. 5 (S3). This prevents the regenerative current that would conventionally flow into the first capacitor 43 from flowing to the second capacitor 8, causing the voltage across the first capacitor 43 to exceed the rated value of each element, resulting in an abnormal rise and damage. [.035] At this time, the control unit 20 controls the switching of the power converter 7 to control the voltage across the second capacitor 8 (C2) (S4). That is, the control unit 20 controls the switching operation of the power converter 7 in a direction to reduce the voltage across the second capacitor 8, and regenerates power to the three-phase AC power source 1. Then, while the voltage across the second capacitor 8 does not fall below the cutoff value for a set time or more (S5: NO), the process returns to step S3 and continues the regenerative absorption operation described above. After that, when the voltage across the second capacitor 8 falls below the cutoff value for a set time or more (S5: YES), the regenerative absorption operation and the switching control of the power converter 7 are stopped (S6).

[0036] In addition, if the voltage across the second capacitor 8, which rises due to the regenerative absorption operation to the second capacitor 8 in step S1, is within the rated voltage range of the second capacitor 8, the second inverter 9 and the power converter 7, the voltage suppression operation of the second capacitor 8 by the power converter 7 in step S4 may be omitted. In this case, the switching control in the power converter 7 is stopped, that is, all switching elements are turned off. Supplement by reference (Rule 20.6)

[0037] In the regenerative absorption operation in step S3, all IGBTs on the upper arm side of the first inverter 5 are turned on, and all IGBTs on the lower arm side are turned off to form a neutral point of the first motor 10. At this time, no power flows from the first motor 10 to the first capacitor 4. Meanwhile, for the second inverter 9, all IGBTs are turned off to make it equivalent to the configuration of the rectifier circuit 3. As a result, regenerative current flows from the first motor 10 to the second capacitor 8. In this way, by performing the regenerative absorption operation during power regeneration by the first motor 10, regenerative power is absorbed only by the second capacitor 8, which has a relatively large capacity, and an abnormal voltage rise in the first capacitor 43 can be prevented. Furthermore, by setting the capacitance of second capacitor 8 to approximately several thousand Farad, it is possible to prevent second capacitor 8 from reaching an overvoltage even during power regeneration.

[0038] Figure 6 shows the current and voltage waveforms of each part when the flow shown in Figure 4 is executed. Although the current waveforms are three-phase, they are not shown separately because there is no need to distinguish between the three phases here. The "load current" in the figure is the current that passes through the three-phase reactor 2, and the "input current" is the current input from the three-phase AC power source 1 to the three-phase reactors 2 and 6. The "power converter current" is the current flowing through the three-phase reactor 6. The "capacitor voltage" is the voltage across the second capacitor 8, and the "switching voltage" is the collector-emitter voltage of the IGBT that constitutes the power converter 7.

[0039] Until the regenerative operation starts, a certain load current flows by driving the first motor 10. At the same time, the power converter 7 operates as an active filter circuit and switches to make the input current sinusoidal. Then, when it is determined in step S2 that regenerative power has been generated, the first inverter 5 and the second inverter 9 perform regenerative absorption operation. At that time, the drive of the first motor 10 stops, so the load current decreases. At the same time, as a regenerative absorption operation, the power converter 7 switches in a direction that reduces the voltage across the second capacitor 8 instead of operating as an active filter circuit, and flows a sinusoidal current instead of a compensation current. As a result, the input current becomes only a sinusoidal current due to the operation of the power converter 7. [0 4 0] When the answer to step S5 becomes "YES", the regenerative power absorption operation ends, and thereafter, supplementation by the reference of the first step (Rule 20.6) All switching operations of the first inverter 5, the second inverter 9 and the power converter 7 stop, and all of the load current, the active filter current and the input current are "0". The voltage of the second capacitor 8 is stabilized at the DC voltage Vdc, which is the voltage obtained by full-wave rectifying the AC power supply. And, the switching voltage in Fig. 6 becomes the DC voltage Vdc, which is the voltage of the second capacitor 8, because the switching element of the power converter 7, i.e., the IGBT, is turned off. [. 0 4 1] In addition, in step S5, if the voltage of the second capacitor 8 shown in FIG. 6 becomes stable, the answer is determined as "YES". Therefore, the threshold value in step S5 does not necessarily have to be set to the same value as the threshold value in step S2. Since the first motor 10 is used to drive the compressor 22, which requires a large torque to drive, the period during which regenerative power is generated is extremely short. For this reason, instead of step S5, it may be determined that the duration from the start of the regenerative absorption operation has exceeded a predetermined time, and the process may proceed to step S6, which ends the regenerative absorption operation.

[0042] In step S2, the generation of regenerative power is determined by the voltage rise of the first capacitor 43. Instead of this, various cases in which the generation of regenerative power is expected, such as when the first motor 10 is suddenly stopped from a high rotation speed, may be incorporated as conditions in advance, and the regenerative absorption operation of steps S3 and S4 may be started when such an event occurs. In addition, by performing the voltage suppression operation of the second capacitor 8 by the power converter 7 in step S4, the capacity of the second capacitor 8 can be made smaller than the above-mentioned value to make the device smaller. In this case, it is possible to use a film capacitor for the second capacitor 8 as well. [ 0 0 4 3 ] (Fourth embodiment) The fourth embodiment also shows an example of power regeneration and absorption operation in the power conversion device 42. In this embodiment, only the operation of the elements of the first inverter 5 in the power regeneration and absorption operation in step S3 of the third embodiment is different, and the rest is the same as the third embodiment. As in FIG. 5, FIG. 7 shows only the elements that are energized in the first inverter 5 and the second inverter 9 when performing the regeneration and absorption operation. The fourth embodiment differs from the third embodiment in that, in the first inverter 5, all the IGBTs on the upper arm side are turned off and all the IGBTs on the lower arm side are turned on. In this case, since the IGBT on the lower arm is turned on for a long time, it is effective to configure the drive power supply for all switching elements on the lower arm of the second inverter 9 with a single bootstrap circuit. [ 0 0 4 4 ] (Fifth embodiment) The power converter 45 of the fifth embodiment shown in Fig. 8 has a configuration in which the three-phase reactor 2 is removed from the power converter 41, 42 of the first or second embodiment, and a reactor 46 is inserted between the rectifier circuit 3 and the first capacitor 8 on the positive side. By inserting the reactor 46 in the DC section in this way, the number of reactors used can be reduced compared to the case where the reactor is inserted in the AC section. Note that, instead of the positive side reactor 46, a reactor may be inserted only on the negative side between the rectifier circuit 3 and the first capacitor 8. [ 0 0 4 5 ] (Sixth embodiment) The power converter 47 of the sixth embodiment shown in Fig. 9 has a configuration in which, in addition to the configuration of the power converter 45, a reactor 48 is also inserted on the negative side between the rectifier circuit 3 and the first capacitor 8. By inserting the reactors 46 and 48 on both the positive and negative sides in this way, it is possible to reduce the zero-phase current generated when the first motor 10 having an open winding configuration is driven by the first inverter 5 and the second inverter 9. In this circuit, the inductance values ​​of the reactors 46 and 48 can be reduced to approximately half compared to the fifth embodiment. [. 0 4 6 ] (Seventh embodiment) The power converter 51 of the seventh embodiment shown in FIG. 10 has a configuration in which a fourth inverter 52 corresponding to the fourth power converter is connected in parallel to the second inverter 9 in the power converter 42 of the second embodiment shown in FIG. 3. That is, the fourth inverter 52 is connected in parallel to the second inverter 9 with respect to the second capacitor 8. This fourth inverter also has the same circuit configuration as the first and second inverters 5, 9 and the power converter 7, and is a three-phase inverter having three sets of two series-connected switching elements, with the intermediate connection points of each series-connected switching element being three output terminals, and each switching element is provided with a flywheel diode connected in inverse parallel. The fourth inverter 52 is a three-phase inverter having a DC brushless three-phase motor, as supplemented by the first citation (Rule 20.6) The second motor 53 is the driving target. For example, the second motor 53 is a fan motor that drives the fan 31 of the outdoor unit 35 in the air conditioner 21 shown in FIG. 2.

[0047] If the energy generated when the first motor regenerates power is large, the DC voltage applied to the inverter 5 increases, which may cause overvoltage breakdown of the first capacitor 43. Therefore, a brake circuit using a semiconductor switch and a large power resistor, or a series circuit of a diode and a large-capacity capacitor is generally connected in parallel to the DC section. In this case, the increase in size and cost due to these additional parts is unavoidable.

[0048] On the other hand, if the first capacitor 43 is made small as in the second embodiment, the DC voltage fluctuates greatly due to the AC voltage fluctuation of the three-phase AC power supply 1. If the AC power supply is single-phase, the voltage becomes zero once every half cycle of the AC power supply. Even in the three-phase AC power supply 1, the voltage pulsates at a frequency six times the AC power supply frequency, and drops to 3 / 2 times the peak voltage every six cycles of the AC power supply. When an inverter circuit using such a pulsating DC voltage is driven, the output power of the inverter and the output power of the motor pulsate, which causes vibration and noise deterioration. In the case of the first motor 10 that drives the compression section 23, this first motor 10 is housed in a heavy iron sealed container 25, and since the compression section 23 itself also generates rotational vibration, measures have been taken to reduce vibration and noise, so this is not a big problem. However, in applications where the motor is used, such as a light-load fan motor, it may have a serious effect and must be avoided.

[0049] Therefore, the second motor 53, to which it is desirable to apply a stable DC voltage, is driven by the fourth inverter 52 using the second capacitor 8 as a DC power source. The capacity of the second capacitor 8 does not affect the harmonics flowing out to the three-phase AC power source 1, so there is no drawback in increasing it. Therefore, by increasing the capacity of the second capacitor 8, a stable DC voltage can be obtained, making it possible to drive the second motor 53, which is sensitive to vibration and noise as described above. In addition, by setting the capacity of the second capacitor 8 to an appropriate capacity that can absorb both the regenerative energy of the first motor 10 and the regenerative energy of the second motor 53, it is not necessary to add a new circuit to absorb the regenerative power as described above. Incorporation by reference (Rule 20.6)

[050] According to the seventh embodiment configured as above, the capacity of the first capacitor 43 is reduced and the reactor 2 is made smaller, and the capacity and high-speed driving of the first motor L0 are increased, while the regenerative energy can be absorbed by the second capacitor 8. And the second motor 53 can be driven by the second capacitor 8 from which a stable DC voltage can be obtained. [ 0 0 5 1 ] (Eighth embodiment) The power conversion device 54 of the eighth embodiment shown in FIG. 11 has a configuration in which a first noise filter circuit 55 is inserted between the three-phase AC power supply 1 and the rectifier circuit 2 in the power conversion device 51 shown in FIG. 10, and a second noise filter circuit 56 is inserted between the three-phase AC power supply 1 and the power converter. In general, when an open-winding motor is driven by a dual inverter system, it is known that common mode noise flows to the ground from both the first inverter 5 and the second inverter 9. On the other hand, in an isolated dual inverter system, the second inverter is not directly connected to the AC power supply, so that the common mode noise flowing to the AC power supply tends to be low.

[0052] However, when the power converter 7 is connected to the second capacitor 8 as in the power conversion device 54, a path is formed through which the common mode noise from the second inverter 9 propagates to the three-phase AC power source 1. Furthermore, since the common mode noise from the fourth inverter 52 connected to the second capacitor 8 propagates through the power converter, the common mode noise flowing from the power converter 7 side to the three-phase AC power source 1 increases more than that from the rectifier circuit 2 side. Therefore, by setting the noise attenuation rate of the second noise filter circuit 56 on the power converter 7 side higher than that of the first noise filter circuit 55 on the rectifier circuit 2 side, the common mode noise of the entire system can be effectively suppressed. [.053] Figure 12 shows an example of the configuration of the first and second noise filter circuits 55, 56. The noise filter circuit for reducing common mode noise is composed of a common mode choke coil 57 inserted in all AC phases and a Y capacitor 58 inserted from all AC phases to ground. To increase the noise attenuation rate, the component constants such as the inductance of the common mode choke coil 57 and the capacitance of the Y capacitor 58 can be increased, or multiple noise filter circuits can be used for supplementation (Rule 20.6). This requires the use of a series connection, which increases the size and cost of the entire power conversion device. L 0 0 5 4 ] In contrast, in the eighth embodiment, the power converter 7 is operated as an active filter circuit, and the power for driving the second motor 53 is supplied via the second motor 10. In this way, the current flowing through the power converter 7 is controlled only to compensate for the harmonics on the rectifier circuit 2 side, so that even if the noise attenuation rate of the second noise filter circuit 56 is increased, the rated current of the components can be kept small, and the increase in the size and cost of the entire power conversion device 54 can be mitigated. Therefore, the rated current of the second noise filter circuit 56 is set smaller than the rated current of the first noise filter circuit 55.

[0055] Furthermore, according to the eighth embodiment, the power conversion device 54 controls the first motor 10 that drives the compressor 22, and also controls the second motor 53 that drives the fan 31 of the outdoor unit 35. Therefore, the two motors 10 and 53 that constitute the air conditioner 21 can be driven by a single power conversion device 54.

[0056] Furthermore, when the power converter 7 is operated as a PWM rectifier that controls the voltage across the second capacitor 8, the current flowing through the reactor 6 increases, so components with a large rated capacity must be selected. On the other hand, by operating the power converter 7 as an active filter circuit, it is possible to minimize the rated capacity of the semiconductor switch and the reactor 6 used in the power converter 7 by supplying the minimum necessary power. [ 0 0 5 7 ] (Other embodiments) The semiconductor switch is not limited to an IGBT, and may be, for example, a power MOSFET. The AC power supply may be single-phase. When setting the magnitude relationship between the capacitances C1 and C2 of the first and second capacitors C1 and C2 to (C1CC2), it is not necessary to use a film capacitor for the first capacitor 4 and an electrolytic capacitor for the second capacitor 8. The voltage across the second capacitor 8 may be boosted by the first inverter 5 and the second inverter 9. (Rule 20.6) The configuration of the noise filter circuit is not limited to that shown in FIG. 12. The heat pump device is not limited to an air conditioner. The power conversion device may be applied to devices other than heat pump devices.

[0058] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the gist of the invention. These embodiments and modifications are included within the scope and gist of the invention, and are included in the scope of the invention and its equivalents described in the claims. Explanation of symbols

[0059] In the drawing, 1 is a three-phase AC power source, 2 is a three-phase reactor, 3 is a rectifier circuit, 4 and 43 are a first capacitor (first storage element), 5 is a first inverter (first power converter), 6 is a three-phase reactor, 7 is a power converter (third power converter), 8 is a second capacitor (second storage element), 9 is a second inverter (second power converter), 10 is a first motor, 20 is a control unit, 21 is an air conditioner, 22 is a compressor, 31 is a fan, 41, 42, 45, 47, 51 and 54 are power conversion devices, 46, 48 are reactors, 52 is a fourth inverter (third power converter). 4 Power converter) 5 3 indicates the second motor, 5 5 indicates the first noise filter circuit, and 5 6 indicates the second noise filter circuit. Incorporation by reference (Rule 20.6) Description of invention: Power conversion device and heat pump equipment Technical field

[0001] An embodiment of the present invention relates to a power conversion device for driving a motor having an open winding structure, and a heat pump device including the power conversion device.

[0002] Conventionally, power conversion devices are known in which a large-capacity capacitor for smoothing DC current is replaced with a small-capacity capacitor for the purpose of miniaturizing passive components and extending the life of the device. For example, Patent Document 1 discloses a configuration in which a regenerative absorption circuit in which a diode, a resistor, and a capacitor are connected in series is connected in parallel to a small-capacity smoothing capacitor in which the maximum value of the pulsating voltage is more than twice the minimum value in the DC section of a power conversion device connected to a single-phase AC power source. In this configuration, the capacity of the capacitor in the DC section can be reduced, but the capacity of the capacitor for absorbing regenerative energy needs to be increased to a certain extent in order to absorb regenerative energy. If the capacitor capacity is increased, the components may be damaged by the inrush current when the power is turned on, so it is necessary to provide a separate inrush prevention circuit, which has been a problem in miniaturizing and reducing the cost of the system.

[0003] Also, Patent Document 1 describes that a single-phase input power converter equipped with a small-capacity film capacitor can reduce harmonics in the input current and improve the power factor. However, in a three-phase input power converter, current flows only from the maximum phase to the minimum phase of the three-phase AC, so the input current cannot be controlled to a sine wave only by switching in the power conversion circuit for driving the motor.

[0004] On the other hand, in order to realize a larger capacity of the device and a faster motor, a dual inverter system is known in which an open winding motor with independent windings for each phase is driven by two inverters, as shown in Patent Document 2, for example. Even in this dual inverter system, a small capacity capacitor is used in the DC section. However, in the end, it is necessary to provide a separate inrush protection circuit for the regenerative energy absorption capacitor, which requires a certain amount of capacity. Furthermore, when connected to a polyphase AC such as a three-phase AC, the input current of the device cannot be controlled to a sine wave. [0005I] In response to this, Patent Document 3 discloses a system in which a matrix converter is applied to the primary inverter.

[0006] Patent Document 1: Patent No. 4391768 Patent Document 2: Patent No. 7218131 Patent Document 3: Patent No. 5531238 Overview of the invention Problems that the invention aims to solve

[0007] The configuration of Patent Document 3 makes it possible to control the three-phase input current to a sine wave, but the semiconductor devices for the matrix converter, the choke coils used in the AC filter, and other components must be selected with a rating equal to or greater than the rated capacity of the power conversion device, which creates issues such as an increase in the size of the entire power conversion device and increased costs.

[0008] Therefore, the present invention provides a power conversion device that does not require a separate inrush current prevention circuit in a dual inverter system, is highly efficient, and can suppress the increase in size and cost of the entire device, and a heat pump device equipped with the power conversion device.

[0009] The power conversion device of the embodiment includes a rectifier circuit that rectifies an AC voltage supplied from an AC power source, a first capacitor that is connected to the DC side of the rectifier circuit, and a diode and a semiconductor switch that are connected in parallel to the first capacitor. The first power converter has a first output terminal to which one end of a winding of a motor having independent phase windings is connected. Incorrect submission (Rule 20.5-2) the other end of the motor winding is connected to each phase output terminal; a second power converter comprising a diode and a semiconductor switch; a second capacitor connected to a DC side of the second power converter; a reactor connected by branching off from a wiring connecting the AC power supply and the rectifier circuit; a third power converter comprising a diode and a semiconductor switch connected between the reactor and the second capacitor and suppressing harmonics; a relay inserted between the AC power supply and the third power converter; and a control unit which drives the first and second inverters to charge the second capacitor before starting the motor and turns on the relay after charging, wherein the capacitance of the second capacitor is set to be larger than the capacitance of the first capacitor. [0010I] Also, a heat pump device according to an embodiment includes the power conversion device according to the embodiment and the motor, and the motor drives a compressor.

[0011] [Fig. 1] Fig. 1 is a diagram showing a configuration of a power conversion device in a first embodiment. [Fig. 2] Fig. 2 is a diagram showing a configuration of an air conditioner. [Figure 3] Figure 3 is a flow chart showing the processing from turning on the power to starting the motor. [Figure 4] Figure 4 is a timing chart showing current and voltage waveforms corresponding to the processing contents shown in Figure 3. [Figure 5] Figure 5 is a diagram showing the configuration of a power conversion device in a second embodiment. [Fig. 6] Fig. 6 is a flow chart showing the processing contents of the regenerative absorbing operation in the third embodiment. [Figure 7] Figure 7 shows the switching state of each inverter when performing regenerative absorption operation. [Figure 8] Figure 8 is a timing chart showing current and voltage waveforms corresponding to the processing contents shown in Figure 6. [Fig. 9] Fig. 9 is a diagram showing the switching state of each inverter when performing regenerative absorption operation in the fourth embodiment. FIG. 10 is a diagram showing a configuration of a power conversion device in a fifth embodiment.

[0012] (First embodiment) As shown in Fig. 1, the power conversion device 41 of this embodiment drives a motor 10. The motor 10 is assumed to be a three-phase permanent magnet synchronous motor or an induction machine, but in this embodiment, it is a permanent magnet synchronous motor. The motor 10 is a so-called open winding motor, and the three-phase windings are not connected to each other and both terminals are in an open state. In other words, the motor 10 has six winding terminals Ua, Va, Wa, Ub, Vb, and Wb.

[0013] The motor 10 is driven by a dual inverter system using a first inverter 5 and a second inverter 9. The first inverter 5 and the second inverter 9 have the same circuit configuration, and are three-phase inverters having three sets of two series-connected switching elements, with the intermediate connection points of each series-connected switching element serving as three output terminals. The output terminals of each phase of the first inverter 5 are connected to the winding terminals Ua, Va, and Wa of the motor 10, respectively, and the output terminals of each phase of the second inverter 9 are connected to the winding terminals Ub, Vb, and Wb of the motor 10, respectively.

[0014] A three-phase AC power source 1, which is the power source of the power conversion device 41, is connected to a rectifier circuit 3 via a three-phase reactor 2 of the power conversion device 41. The rectifier circuit 3 is configured by connecting six diodes in a three-phase bridge configuration. A first capacitor 4, which is a small-capacity film capacitor, and a first inverter 5 are connected to the output terminals of the rectifier circuit 3.

[0015] The second inverter 9 is connected in parallel to the second capacitor 8, which is, for example, an electrolytic capacitor, and both ends of the DC side of the power converter 7. The high-voltage side terminal and the low-voltage side terminal of the first inverter 5, i.e., both ends of the first capacitor 4, are not connected to the second inverter 9, and the second inverter 9 is independent. In other words, the first inverter 5 and the second inverter 9 are not connected to each other even if their output terminals are different from each other (Rule 20.5-2). Each phase of Motor 1 〇 is connected only through an independent winding. [0016I] Each phase output terminal of the power converter 7 is connected to the three-phase AC power source 1 through a three-phase reactor 6 and a relay 16. The first inverter 5, the second inverter 9, and the power converter 7 are each configured by connecting semiconductor switching elements such as GBTs, etc., in a three-phase bridge configuration with flywheel diodes connected in parallel, and correspond to the first to third power converters, respectively. The connection position of the relay 16 may be between the three-phase AC power source 1 and the three-phase reactor 6, or between the three-phase reactor 6 and the power converter 7. The relay 16 is a single three-phase relay that simultaneously opens and closes each of the power lines of the U, V, and W phases without a current suppressing element or the like being provided in parallel. On the other hand, no relay or inrush current prevention circuit is provided between the three-phase power source 1 and the rectifier circuit 3. That is, the relay 16 is inserted in the power supply line of the section from the three-phase AC power supply 1 to the three-phase reactor 6 between the rectifier circuit 2 and the three-phase AC power supply 1 and leading to the power converter 7. [0017I] Current sensors 11U, 11V are arranged on the U and V phases of the power line connecting the three-phase AC power supply 1 and the three-phase reactor 2. Current sensors 12U, 12V are arranged on the U and V phases of the power line connecting the three-phase AC power supply 1 and the three-phase reactor 6. Voltage sensors 13, 14 detect the terminal voltages of the first capacitor 4 and the second capacitor 8, respectively. Current sensors 15U, 15V, 15W are arranged between each phase output terminal of the first inverter 5 and the winding terminals Ua, Va, Wa of the motor 10.

[0018] The detection signals output by the above sensors 11-15 are input to a control unit 20. The control unit 20 is composed of a microcomputer or the like, and controls the switching of the first inverter 5, the second inverter 9, and each IGBT constituting the power converter 7 based on the detection signals of the sensors 11-15. The control unit 20 also controls the opening and closing of the relay 16. In the above configuration, the components excluding the motor 10 constitute the power conversion device 41.

[0019] In addition, the capacitance of the second capacitor 8 is set to be larger than that of the first capacitor 4. Furthermore, a film capacitor was mistakenly submitted as the first capacitor 4 (Rule 20.5-2). In the above embodiment, an electrolytic capacitor is used for the second capacitor 8, but this is not limiting and any other capacitor may be used as long as it satisfies the above-mentioned capacitance requirements. For example, both capacitors may be electrolytic capacitors or film capacitors. [0020I] The first capacitor 4 has a capacity sufficient to cut high frequency components generated by switching between the first inverter 5 and the second inverter 9, and a capacity sufficient to ensure that the current that charges the first capacitor 4 when the power is turned on does not exceed the withstand voltage of the rectifier circuit 3, more specifically, the withstand voltage of the diode that constitutes the rectifier circuit 3. This capacity is generally on the order of several 10A AC F. This allows the three-phase reactor 2 to be made smaller.

[0021] By setting the first capacitor 4 to such a small capacity, the inrush current to the first capacitor 4 generated when the power is turned on to the power conversion device 41 becomes an acceptable level, and an inrush current prevention circuit is not required. In general, an inrush current prevention circuit is composed of a three-phase relay or single-phase relay for large currents inserted in series in the power line, and a PTC thermistor connected in parallel to the relay. Before turning on the power, the relay is opened, and after turning on the power, only a limited current flows through the PTC thermistor to gradually charge the capacitor, and when the voltage of the capacitor rises and the large inrush current stops flowing, the relay is closed. As a result, excessive inrush current does not flow into the rectifier circuit, etc., and the device can be protected.

[0022] On the other hand, the capacity of the second capacitor 8 may be determined based on the compensation capacity of the power converter 7, the output power of the second inverter 9, the ripple current flowing into the second capacitor 8, etc. This capacity is generally about several 1000 to several 1000 MF. Since the second capacitor 8 has a certain degree of large capacity, there is a possibility that an inrush current will flow through the rectifier circuit part of the power converter 7 when the power is turned on. Therefore, the generation of such an inrush current is prevented by the circuit and control described later, and an inrush current prevention circuit is not required for the second capacitor 8 either. As a result, an inrush current prevention circuit is not required for the power conversion device 41 as a whole.

[0023] Figure 2 shows the incorrect submission of an air conditioner, which is a heat pump device to which the power converter 4.1 applies (Rule 20.5.2) The configuration is shown in FIG. 1. In addition to air conditioners, heat pump equipment to which the power conversion device 41 is applied includes hot water generating equipment that serves as a hot water heater, and hot and cold water generating equipment such as chillers. The air conditioner 21 is composed of refrigerant piping and signal communication lines that connect the indoor unit 24 and the outdoor unit 35 to each other. The indoor unit 24 installed indoors houses the indoor heat exchanger 27 and the indoor fan 30 inside. On the other hand, the outdoor unit 35 is placed outdoors and houses devices such as the control unit 20j, compressor 22, outdoor heat exchanger 29i, four-way valve 26, pressure reducing device 28, outdoor fan 31, and outdoor fan motor 53. [0024I] The compressor 22 is configured by housing the compression section 23 and the motor 10 in the same iron sealed container 25, and the rotor shaft of the motor 10 is connected to the compression section 23. The compressor 22, the four-way valve 26, the indoor heat exchanger 27, the pressure reducing device 28, and the outdoor heat exchanger 29 are connected to form a closed loop by a pipe that serves as a refrigerant passage. The compressor 22 is, for example, a one-cylinder rotary compressor, but is not limited to this, and a multi-cylinder rotary compressor, scroll compressor, or reciprocating compressor can also be used. [0025I] During heating, the four-way valve 26 is in the state shown by the solid line, and the high-temperature refrigerant compressed in the compression section 23 of the compressor 22 is supplied from the four-way valve 26 to the indoor heat exchanger 27, where it condenses and releases heat to the room, heating the room. The refrigerant is then reduced in pressure in the pressure reducing device 28, becomes cold, and flows to the outdoor heat exchanger 29, where it absorbs heat from the outside air, evaporates, and returns to the compressor 22.

[0026] On the other hand, during cooling, the four-way valve 26 is switched to the state shown by the broken line. Therefore, the high-temperature refrigerant compressed in the compression section 23 of the compressor 22 is supplied from the four-way valve 26 to the outdoor heat exchanger 29, where it radiates heat to the outdoors and condenses. The refrigerant is then decompressed by the pressure reducing device 28, becomes low temperature, and flows to the indoor heat exchanger 27, where the refrigerant evaporates by absorbing heat from the indoor air, cools the room, and returns to the compressor 22. The indoor and outdoor heat exchangers 27 and 29 are then blown by the indoor fan 30 and the outdoor fan 31, respectively, and the configuration is such that the heat exchange between the indoor air and the outdoor air is efficiently performed by the blown air. Incorrect submission (Rule 20.5-2) It has been done. [0027I] Next, the operation of this embodiment will be described. The control unit 20 controls the entire power conversion device 41. The control unit 20 operates / stops the compressor 22, i.e., the first motor 10, based on an instruction from an indoor control unit (not shown) on the indoor unit 24 side. During the operation of the compressor 22, the control unit 20 performs vector calculation using the current value detected by the current sensors 15U, 15V, and 15W, and the terminal voltages of the first capacitor 4 and the second capacitor 8 detected by the voltage sensors 13 and 14. Based on the calculation result, the control unit 20 operates each switching element of the first inverter 5 and the second inverter 9 in cooperation with each other, and a desired current flows through each winding of the first motor 10 to drive the first motor 10 at a variable speed. [0028I] Furthermore, the control unit 20 operates the power converter 7 as an active filter circuit to suppress and reduce harmonics flowing through the power line while the motor 10 is in operation. The control unit 20 extracts harmonic currents from the currents flowing through each phase of the reactor 2 detected by the current sensors 11U and 11V, and controls the operation of each switching element of the power converter 7 so that the reactor currents of each phase detected by the current sensors 12U and 12V become correction currents that cancel out the harmonic currents flowing through the U, v, and w phases, taking into account the terminal voltage of the second capacitor 8. This active filter circuit operation of the power converter 7 suppresses power supply harmonics and makes the current flowing from the rectifier circuit 3 to the AC power supply 1 closer to a sine wave.

[0029] The second capacitor 8 has a certain capacity because it is used as a power source for a correction current when the power converter 7 functions as an active filter circuit. When the power converter 7 is operated as an active filter circuit, a power source with a high voltage that can compensate for harmonics is required. For this reason, it is desirable to keep the terminal voltage of the second capacitor 8, which serves as a power source when the active filter circuit is operating, at a predetermined value or higher. Therefore, the control unit 20 may control the on / off of the switching element of the power converter 7 so as to keep the terminal voltage of the second capacitor 8 at a constant value or higher in parallel with the operation of the active filter circuit. In addition, when the motor 1 〇 is in a low load state, etc., the generation of harmonic currents is prevented. Incorrect submission (Rules 20.5-2) If the amount becomes very small, the control unit 20 can detect this and stop the power converter 7, stop the active filter circuit operation, and reduce the switching loss of the switching elements of the power converter 7. [0030I] By configuring the power conversion device 41 as described above, the controllability of the motor using the dual inverter consisting of the first inverter 5 and the second inverter 9 and the motor 10 having an open winding configuration is improved. The power converter 7 is switched and controlled so that the current flowing from the rectifier circuit 3 to the AC power supply 1 side approaches a sine wave, and is operated as an active filter circuit, so that the power supply harmonics can be suppressed. In other words, since the voltage is applied to the winding of the motor 10 by the two inverters 5 and 9, the operating range of the motor 10 can be expanded. In addition, since the voltage applied to the winding of the motor 10 is multi-level, the iron loss generated in the motor 10 can be reduced. [0031 I] Furthermore, by devising a method of driving the two inverters 5 and 9 by the control unit 20, it is possible to control the power applied to the motor 10 at a constant level and expand the operating range in the high-speed region by injecting reactive power. Also, by connecting the negative side of the DC section of the power converter 7 and the negative side of the DC section of the second inverter 9, the reference voltage of these circuits becomes common. This makes it possible to reduce the number of insulating points in the drive power supply, and to prevent the circuit size from increasing and the cost from increasing. Here, control that eliminates the need for an inrush current prevention circuit when the power conversion device 41 is turned on will be described with reference to Figs. 3 and 4. The power conversion device 41 may be turned on when wiring is connected during installation, when a breaker (not shown) provided between the three-phase AC power source 1 and the power conversion device 41 is opened and then turned on, or when the three-phase AC power source 1 is restored from a power outage. In the initial state of the power conversion device 41, when the three-phase AC power source 1 is not connected, i.e., when the power is not turned on, the relay 16 is off. [0033I] When AC power is supplied from the three-phase AC power source 1 to the power conversion device 41, the first capacitor 4 is charged through the rectifier circuit 3 (S1). When the terminal voltage of the first capacitor 4 exceeds the threshold value (YES in S2), the control unit 20 performs the first and second erroneous input (Rule 20.5-2). Switching of the inverters 5 and 9 is started (S3). Here, the switching pattern is set to DC excitation of the motor 10. DC excitation is generally used for rotor positioning before starting the motor 10, and is a current that does not create a rotating magnetic field by passing current only through a specific phase of the motor winding 10. With this DC excitation current pattern, the motor 10 does not rotate. In this DC excitation switching pattern, the PWM duty is adjusted in advance so that a large current does not flow into the second capacitor 8. As a result, the second capacitor 8 is gradually charged through the first and second inverters 5 and 9 (S4), and no temporary excessive current flows through the rectifier circuit 3. [0034I] Next, when the terminal voltage of second capacitor 8 exceeds the threshold value (YES in S5), control unit 20 turns on relay 16 (S6). At this point, the voltage across second capacitor 8 has already risen to a sufficiently high voltage, so even if relay 16 is turned on, a large current does not flow through the rectifier section of power converter 7. Then, drive control of motor 10 is started (S7).

[0035] The threshold value of the terminal voltage of the second capacitor 8 in step S5 may be set to a value roughly equivalent to the rectified value of the AC power supply voltage, but may also be set after confirming in advance by experiment or the like a threshold level at which an excessively large inrush current does not flow into the second capacitor 8 even when the power supply is turned on. Note that the charging of the capacitor in steps S1 and S4 is carried out naturally and is not actively controlled by the control unit 20, but is described in the flow chart to make the operation easier to understand.

[0036] As described above, if the relay 16 is turned off when the power is turned on, only the first capacitor 4, which has a relatively small capacity, is charged. Since the capacity of this first capacitor 4 is small, the inrush current generated during charging does not exceed the capacity of the elements constituting the rectifier circuit 3 and does not become a large current that may destroy the elements. When the first capacitor 4 is charged to a certain extent, the second capacitor 8 is gradually charged through the open winding motor 10 and the first capacitor 4 by the DC excitation drive of the first and second inverters 5 and 9. At this time, the first and second inverters 10 and 11 are connected to each other. The switching patterns of V5 and V9 control the charging current of the second capacitor 8 so that it does not become excessive. [0037I] After that, by turning on the relay 16 at the timing when the voltage across the second capacitor 8 becomes approximately equal to the value obtained by rectifying the AC power supply voltage, the second capacitor 8 having a relatively large capacity can be shifted to a steady state operation without causing an excessively large charging current to flow from the power converter 7 side. Therefore, according to this embodiment, it is possible to safely shift from power-on to a steady state operation without providing a protection circuit such as an inrush current prevention circuit. 〇

[0038] In addition, since the relay 16 is provided in the middle of the wiring that supplies power only to the third power converter 7 and the second capacitor 8 that operate as an active filter circuit, only a small current flows through it compared to the current that flows through the reactor 2 for driving the motor with the first and second inverters 5 and 9. Therefore, a small relay with a low rated current can be used, which contributes to the miniaturization of the device.

[0039] (Second embodiment) In the following, the same parts as those in the first embodiment are denoted by the same reference numerals and the description thereof is omitted, and the different parts are described. In the drawings of the power conversion device of each embodiment shown below, the sensors 11 to 15 and the control unit 20 are omitted. In the power conversion device 42 of the second embodiment shown in FIG. 5, a third capacitor 17 is connected to the DC section of a power converter 7 operated as an active filter circuit. The negative terminal of the second capacitor 8 and the negative terminal of the third capacitor 17 are commonly connected. The anode of the diode 18 is connected to the positive terminal of the second capacitor 8, and the cathode is connected between the positive terminals of the third capacitor 17.

[0040] According to the second embodiment configured as above, by connecting the negative side of the DC section of the power converter 7 and the negative side of the DC section of the second inverter 9 and inserting a diode 18 between the positive terminals of the second capacitor 8 and the third capacitor 17, it becomes possible to absorb the regenerative energy generated when the motor 10 is stopped by the third capacitor 17 as well. Therefore, the erroneous submission of the first and second capacitors 4 and 8 (Rule 20.5-2) The capacity can be reduced.

[0041] (Third embodiment) The third embodiment shows an example of a regenerative absorption operation in the power conversion device 41 or 42. Fig. 6 shows an operation flow during regenerative absorption, and Fig. 7 shows only elements that are energized in the first inverter 5 and the second inverter 9 when performing the regenerative absorption operation. During normal operation (S11), when the voltage across the first capacitor 4 etc. exceeds a predetermined threshold value (YES in S12), the control unit 20 determines that regeneration by the motor 10 has occurred, and performs the regenerative absorption operation shown in Fig. 5 (S13).

[0042] Also at this time, the power converter 7 is switched and controlled to control the voltage across C2, the second capacitor 8 (S14). That is, the power converter 7 is operated as a power regeneration PWM rectifier. That is, the power converter 7 is switched and controlled to return the regenerative power to the three-phase AC power supply 1 side so that the voltage across the second capacitor 8 that absorbs the regenerative power of the motor 10 becomes a predetermined voltage lower than the rated voltage value of the element. During the regenerative absorption operation, since the first and second inverters 5 and 9 are not driving the motor 10, no harmonics are generated. For this reason, the power converter 7 does not need to perform a harmonic suppression operation, and there is no problem even if the power converter 7 stops the active filter circuit operation and instead operates as a power regeneration PWM rectifier. And while the voltage across the both ends does not fall below the threshold value for more than the set time (NO in S15), it returns to step S13 and continues the regenerative absorption operation. When the voltage across the both ends falls below the threshold value for more than the set time (YES), the regenerative absorption operation and the switching control of the power converter 7 are stopped (S16).

[0043] In the regenerative absorption operation in step S13, all the IGBTs on the upper arm side of the first inverter 5 are turned on and all the IGBTs on the lower arm side are turned off to form the neutral point of the motor 10. At this time, no power flows from the motor 10 to the first capacitor 4. On the other hand, for the second inverter 9, all the IGBTs are turned off to make it equivalent to the configuration of the rectifier circuit 3. As a result, power flows from the motor 10 to the second capacitor 8. In this way, by performing the regenerative absorption operation during regeneration by the motor 10, the regenerative power can be absorbed only by the second capacitor 8 having a relatively large capacitance. By setting the capacitance of the second capacitor 8 to about several 100 to several 1000 μF, overvoltage can be prevented even during regeneration. By performing the regenerative absorption operation during regeneration by the motor 10, the regenerative power can be absorbed only by the second capacitor 8 having a relatively large capacitance. By setting the capacitance of the second capacitor 8 to about several 100 to several 1000 μF, overvoltage can be prevented even during regeneration. [0044I] Fig. 8 shows the current and voltage waveforms of each part when the flow shown in Fig. 6 is executed. Although the current waveforms are three-phase, they are not shown separately because there is no need to distinguish between the three phases here. In the figure, the "load current" is the current flowing through the three-phase reactor 2, and the "input current" is the current input from the three-phase AC power source 1 to the three-phase reactors 2 and 6. The "power converter current" is the current flowing through the power converter 7, that is, the current flowing through the three-phase reactor 6. The "second capacitor voltage" is the terminal voltage of the second capacitor 8, and the "switching voltage" is the collector-emitter voltage of the IGBT that constitutes the power converter 7. In FIG. 8, regeneration of the motor 10 occurs, and when the voltage of the first capacitor 4 (not shown) rises to a threshold value, the regeneration absorption operation starts. When the regeneration absorption operation starts, the voltage across the second capacitor 8 rises once, but in parallel, the power converter 7 operates as a power regeneration PWM rectifier, so the regenerative current flowing into the second capacitor 8 is regenerated to the three-phase AC power source 1 and does not rise extremely large. After that, when the regeneration of the motor 10 ends, the voltage across the second capacitor 8 drops due to the power regeneration PWM rectifier operation of the power converter 7. Then, when the time when the voltage across the second capacitor 8 falls below the threshold value becomes equal to or longer than the set time, the switching of the power converter 7 stops, and the regeneration absorption and power regeneration operation ends. As a result, the switching voltage is fixed to Vdc, which is a full-wave rectified smoothed DC voltage of the three-phase AC power supply 1, and the load current, input current, and power converter current all become "0", and the regenerative absorption operation ends. Note that while the power converter 7 is operating as a power regenerative PWM rectifier, a sine wave current synchronized with the voltage of the three-phase AC power supply 1 flows in the input current. [0046I] In addition, in the step S15, the end of the regenerative absorption operation is judged as follows: If the voltage of the capacitor 8 becomes stable, the answer may be "YES". In addition, since the actual generation time of the regenerative power is short, the end of the regenerative absorbing operation may be determined based on the elapsed time from the start of the regenerative absorbing operation. The threshold value in step S15 does not necessarily have to be set to the same value as the threshold value in step S13.

[0047] (Fourth embodiment) The fourth embodiment also shows an example of a regenerative absorption operation in the power conversion device 41 or 42. Like FIG. 6, FIG. 9 shows only the elements that are energized in the first inverter 5 and the second inverter 9 when performing a regenerative absorption operation. The difference from the third embodiment is that in the first inverter 5, all the IGBTs on the upper arm side are turned off and all the IGBTs on the lower arm side are turned on. In this case, since the IGBTs on the lower arm side are turned on for a long period of time, it is effective when the driving power supply of the second inverter 9 is configured with a bootstrap circuit.

[0048] (Fifth embodiment) The power converter 43 of the fifth embodiment shown in FIG. 1 O has a configuration in which the three-phase reactor 2 is removed from the power converter 41, and a reactor 44 is inserted on the positive side between the rectifier circuit 3 and the first capacitor 8. By inserting the reactor 44 in the DC section in this way, the number of reactors used can be reduced compared to when it is inserted in the AC section. The reactor to be inserted in the DC section may be only the high-potential side line as shown in FIG. 1 O, or may be distributed at both ends of the high-potential side line and the low-potential side line. In this distributed arrangement, the inductance of each reactor can be approximately half that of when only one reactor is inserted.

[0049] (Other embodiments) The semiconductor switch is not limited to a GBT, and may be, for example, a power MOSFET. The AC power supply may be single-phase. When setting the magnitude relationship of the capacitances C1 and C2 of the first and second capacitors to (C1VC2), it is not necessary to use a film capacitor for the first capacitor 4 and an electrolytic capacitor for the second capacitor 8. The second capacitor may be a capacitor such as a storage battery. (Rule 20.5-2) In step S3 of FIG. 3, before the relay 16 is turned on, the first and second inverters 5 and 9 output a switching pattern for DC excitation of the motor 10 to charge the second capacitor 8, but the current pattern at this time is not limited to the DC excitation switching pattern, and may be any switching pattern that can gradually charge the second capacitor 8 without rotating the motor 10 using the first and second inverters 5 and 9. [0050I] Heat pump equipment is not limited to air conditioners. Furthermore, the power conversion device may be applied to equipment other than heat pump equipment. Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the gist of the invention. These embodiments and their variations are within the scope and gist of the invention, and are also within the scope of the invention and its equivalents set forth in the claims. Explanation of symbols [0051 I In the drawings, 1 is a three-phase AC power source, 2 is a three-phase reactor, 3 is a rectifier circuit, 4 is a first capacitor, 5 is a first inverter (first power converter), 6 is a three-phase reactor, 7 is a power converter (third power converter), 8 is a second capacitor, 9 is a second inverter (second power converter), 10 is a motor, 16 is a relay, 20 is a control unit, 21 is an air conditioner, 22 is a compressor, 31 is a fan, 41-43 are power converters, and 44 is a reactor. Incorrect submission (Rule 20.5-2)

Claims

32 Claims

1. A power conversion device comprising: a rectifier circuit which rectifies an AC voltage supplied from an AC power supply; a first storage element connected to a DC side of the rectifier circuit; a first power converter comprising a diode and a semiconductor switch connected in parallel to the first storage element, the first power converter having one end of a winding of a first motor having an independent phase winding connected to each phase output terminal; a second power converter comprising a diode and a semiconductor switch and having the other end of the winding of the first motor connected to each phase output terminal; a second storage element connected to the DC side of the second power converter; a reactor branched off and connected from a wiring connecting the AC power supply and the rectifier circuit; and a third power converter which suppresses harmonics and comprises a diode and a semiconductor switch connected between the reactor and the second storage element.

2. The power conversion device according to claim 1, wherein a voltage across the second storage element is controlled by at least one of the first power converter and the second power converter, or the third power converter.

3. The power conversion device according to claim 1, wherein a maximum amount of energy stored in the second storage element is set to be greater than a maximum amount of energy stored in the first storage element.

4. The first storage element is a film capacitor, and the second storage element is an electrolytic capacitor. 2 The power conversion device according to claim 1,

5. The power conversion device according to claim 3, further comprising a control unit that performs a power absorbing operation when power is regenerated by the first motor by turning off all semiconductor switches of the second power converter and turning on or off semiconductor switches of the first power converter to short-circuit one of the winding ends of the motor and cause the second storage element to absorb the regenerative power.

6. The power conversion device according to claim 5, wherein the control unit performs the power absorption operation when it detects that the voltage across the first storage element has exceeded a predetermined threshold value. 33

7. The power conversion device according to claim 6, wherein the control unit causes the third power converter to perform a switching operation during the power absorption operation, and stops the switching operation of the third power converter when it detects that the voltage across the second storage element has fallen below a predetermined threshold value.

8. The power conversion device according to claim 1, further comprising reactors inserted on both the positive and negative sides between the rectifier circuit and the first power converter.

9. The power conversion device according to claim 1, further comprising a fourth power converter connected in parallel to the second storage element, comprising a diode and a semiconductor switch, and driving a second motor with an AC output from the fourth power converter.

10. The power conversion device according to claim 9, comprising: a first noise filter circuit inserted between the AC power supply and the rectifier circuit; and a second noise filter circuit inserted between the AC power supply and the fourth power converter, the second noise filter circuit having a noise attenuation rate set to be larger than that of the first noise filter circuit.

11. The power conversion device according to claim 1, wherein the rated current of the second noise filter is set to be smaller than the rated current of the first noise filter.

12. A heat pump device comprising: a power conversion device according to any one of claims 1 to 11; and a first motor, wherein the first motor drives a compressor. [Claim] 3] A heat pump device comprising: the power conversion device according to any one of claims 9 to 1; the first motor; and the second motor, wherein the first motor drives a compressor and the second motor drives a blower. Supplement by reference (Rule 20.6) Scope of the claim

1. A first power converter, comprising: a rectifier circuit for rectifying an AC voltage supplied from an AC power source; a first capacitor connected to a DC side of the rectifier circuit; a diode and a semiconductor switch connected in parallel to the first capacitor, the first power converter having one end of a winding of a motor having independent phase windings connected to each phase output terminal; a second power converter, comprising a diode and a semiconductor switch, the other end of the winding of the motor connected to each phase output terminal; a second capacitor connected to the DC side of the second power converter; a reactor branched off from a wiring connecting the AC power source and the rectifier circuit and connected; and wherein the capacitance of the second capacitor is set to be larger than the capacitance of the first capacitor.

2. The power conversion device according to claim 1, wherein the first capacitor is a film capacitor, and the second capacitor is an electrolytic capacitor.

3. The power conversion device according to claim 1, wherein the first capacitor has a capacity sufficient to cut high frequency components generated by switching between the first power converter and the second power converter, and a capacity sufficient to ensure that a current for charging the first capacitor when power is turned on does not exceed a capacity of the rectifier circuit 3.

4. The power conversion device according to claim 1, wherein the control unit causes the third power converter to operate as an active filter circuit. Incorrect submission (Rule 20.5bis)

5. The power conversion device according to claim 1, further comprising a diode having a third capacitor connected to a DC section of the third power converter, a negative terminal of the second capacitor and a negative terminal of the third capacitor commonly connected, an anode connected to a positive terminal side of the second capacitor, and a cathode connected to a positive terminal side of the third capacitor.

6. The power conversion device according to claim 1, wherein the control unit, when power is regenerated by the motor, performs a regenerative absorption operation of turning off all semiconductor switches of the second power converter and turning on or off semiconductor switches of the first power converter to short-circuit one of the winding ends of the motor and cause the second capacitor to absorb the regenerative power.

7. The power conversion device according to claim 6, wherein the control unit performs the regenerative absorption operation when it detects that the voltage across the first capacitor has exceeded a predetermined threshold value.

8. The power conversion device according to claim 6, wherein the control unit, when performing the regenerative absorption operation, causes the third power converter to operate as a power regenerative PWM rectifier that regenerates power to the AC power supply.

9. The power conversion device according to claim 1, further comprising a reactor inserted between the AC power supply and the rectifier circuit.

10. The power conversion device according to claim 1, further comprising a reactor inserted between the rectifier circuit and the first power converter.

11. A heat pump device comprising: a power conversion device according to any one of claims 1 to 10; and a motor, wherein the motor drives a compressor. Incorrect submission (Rule 20.5bis)

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