JP5045622B2 - Power converter - Google Patents

Description

  The present invention relates to a power conversion apparatus that is used in various electric appliances for business use, general household use, and business use and that uses a motor (electric motor) or the like as a load.

  Conventionally, this type of power conversion device connects six bidirectional switching elements between a single-phase AC power source and a three-phase load, and converts power from single-phase AC directly to three-phase AC. (For example, refer to Patent Document 1).

  FIG. 13 shows a circuit diagram of a conventional power conversion device described in Patent Document 1. In FIG.

  As shown in FIG. 13, an AC power source 1, a matrix converter circuit 2 connected to the AC power source 1, a matrix converter circuit 2 connected to a three-phase motor 3 serving as a load, and the operation of the matrix converter circuit 2 The control part 4 which controls is provided.

The matrix converter circuit 2 includes a bidirectional switch 10 using two transistors 5 and 6 and diodes 7 and 8, and bidirectional switches 11, 12, 13, 14, 15 assembled in the same configuration as the bidirectional switch 10. As a result of controlling the on / off of a total of 12 transistors in the matrix converter circuit 2 by the control unit 4, a three-phase AC voltage is supplied to the motor 3 and driven. .
JP 2005-45912 A

  However, in the above-described conventional configuration, when a single-phase AC power supply 1 having a commonly used sinusoidal voltage waveform is connected, before and after the timing at which the instantaneous voltage value becomes zero (zero voltage point) In this low voltage period, the electric power supply to the motor 3 of the load is extremely reduced, but the ratio occupied by the low voltage period is considerably high, so that a large fluctuation occurs in the output torque of the motor 3. It had the subject of doing.

  An object of the present invention is to solve the above-described problems and to supply electric power to a load as much as possible even during a low voltage period before and after the zero voltage point of an AC power supply to reduce fluctuations in supply power to the load.

In order to solve the above problems, the power conversion device of the present invention receives an input from a single-phase AC power supply, has a crest factor lower than that of the single-phase AC power supply , and an instantaneous value of the voltage of the single-phase AC power supply is A first power conversion circuit that outputs a single-phase AC voltage that is shorter than the single-phase AC power source and has a low voltage period that is present before and after the timing of zero and that is 1/3 or less of the maximum value; A second power conversion circuit that receives the output of the first power conversion circuit and outputs a three-phase AC voltage to the load , and both the first power conversion circuit and the second power conversion circuit are both Direction switching elements.

  Accordingly, the present invention solves the above-mentioned problem, and the first power conversion circuit equalizes the input voltage to the second power conversion circuit, and in a low voltage period around the zero voltage point of the AC power supply. However, since electric power can be supplied to the load as much as possible, fluctuations in the power supplied to the load can be reduced.

  The present invention shortens the output power drop period that occurs in the low voltage period before and after the timing when the instantaneous value of the voltage of the single-phase AC power supply becomes zero (zero voltage point), and the power supplied to the load is small. A conversion device can be realized.

1st invention receives input from a single phase alternating current power supply, it is a crest factor lower than the single phase alternating current power supply , and exists before and after the timing when the instantaneous value of the voltage of the single phase alternating current power supply becomes zero, In response to the first power conversion circuit that outputs a single-phase AC voltage shorter than the single-phase AC power source during a low voltage period of 1/3 or less of the maximum value, and the output of the first power conversion circuit And a second power conversion circuit that outputs a three-phase AC voltage to a load, and both the first power conversion circuit and the second power conversion circuit are provided with a bidirectional switching element, thereby providing a first The power conversion circuit can level the input voltage to the second power conversion circuit, and it is possible to supply electric power to the load as much as possible even in a low voltage period around the zero voltage point of the AC power supply. From the power supply to the load. It becomes capable of reducing the dynamic.

  In the second invention, in particular, the first power conversion circuit of the first invention outputs a voltage having an effective value lower than that of the input single-phase AC power supply, thereby operating as a step-down chopper. The voltage in which the fluctuation is suppressed is output to the second power converter, and the fluctuation in the power supplied to the load can be reduced.

  In the third aspect of the invention, in particular, the first power conversion circuit of the first aspect of the invention outputs a voltage having an effective value higher than that of the input single-phase AC power supply, thereby operating as a step-up chopper. The voltage in which the fluctuation is suppressed is output to the second power converter, and the fluctuation in the power supplied to the load can be reduced.

  According to the fourth aspect of the invention, in particular, the first power conversion circuit of the second aspect of the invention or the third aspect of the invention has an inductance element, so that the voltage with reduced fluctuations can be obtained while operating as a chopper. It is possible to reduce fluctuations in the power supplied to the load.

  According to a fifth aspect of the present invention, in particular, at least one bidirectional switching element according to any one of the first to fourth aspects of the present invention is composed of a SiC semiconductor, thereby enabling a small, low-loss, high-efficiency power conversion device. Will be realized.

  In the sixth aspect of the invention, in particular, by using the load of any one of the first to fifth aspects as a three-phase motor having a permanent magnet, a high-efficiency three-phase motor can be realized. Since a high power factor can be achieved, it is possible to reduce the capacity of the bidirectional switching element of the second power conversion circuit and reduce the capacity.

  According to the seventh aspect of the invention, in particular, the load of any one of the first to fifth aspects is a three-phase motor whose inductance changes depending on the mechanical phase, so that the fluctuation of the power supplied to the load can be achieved with relatively simple control. Can be reduced.

  In the eighth aspect of the invention, in particular, the three-phase electric motor that is the load of any one of the first to seventh aspects of the invention shall be a small and light user-friendly by using a vacuum cleaner with a fan as a load. Will be able to.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 is a circuit diagram of a power conversion device according to the first embodiment of the present invention.

  In FIG. 1, a first power conversion circuit 22 that receives an input from a single-phase AC power source 21 having an effective value voltage of 200 V and 50 Hz and outputs a single-phase AC voltage having a crest factor lower than that of the single-phase AC power source 21, The second power conversion circuit 23 that receives the output of the power conversion circuit 22 outputs a three-phase AC voltage to a load 24 configured by a three-phase motor.

  The first power conversion circuit 22 includes bidirectional switching elements 30 and 31 using an SiC semiconductor, an inductance element 32, and a capacitor 33.

  Here, the capacitor 33 is for the purpose of removing a high-frequency voltage ripple component generated by turning on and off each bidirectional switching element, and a capacitor to which an AC voltage (alternating voltage) can be applied in about 10 microfarads is used. Compared with a conventional electrolytic capacitor of about 1000 microfarads used for an inverter that is once converted into a DC voltage, the shape is small and the weight is small.

  Similarly, the inductance element 32 suppresses high-frequency current components due to the on / off of each bidirectional switching element, and an inductance value of about several hundred microhenries is used. Loss can be used.

  The second power conversion circuit 22 includes bidirectional switching elements 40, 41, 42, 43, 44, and 45 using SiC semiconductors.

  FIG. 2 is an operation waveform diagram of the power conversion device according to the present embodiment, where (A) is a voltage waveform of the single-phase AC power supply 21, (B) is the conductivity of the bidirectional switching element 30, and (C) is the first waveform. 1 shows an output voltage waveform of one power conversion circuit 22.

  The bidirectional switching element 30 is operated to be repeatedly turned on and off by PWM (pulse width modulation) at a carrier frequency of 50 kHz, and when the absolute value of the instantaneous value of the single-phase AC power supply 21 reaches a peak, The conductivity is almost 50%.

  On the other hand, the bidirectional switching element 31 is given a drive signal so that the current can be operated as a flywheel diode through which the inductance element 32 flows while the bidirectional switching element 30 is off.

  By such an operation, in the present embodiment, the first power conversion circuit 22 operates as a step-down chopper circuit, and the first power conversion circuit 22 has an input single-phase alternating current shown in (a). The voltage waveform shown in (c) having an effective voltage lower than the voltage of the power source 21 is output.

  As for the voltage waveform shown in (c), there are continuous periods in which the absolute value is 140 V, and when compared with a sine wave, the waveform is a crushed waveform, and the crest factor, The maximum value / effective value is about 1.1, which is lower than 1.41 in the case of a sine wave.

  The second power conversion circuit 23 receives the voltage waveform (c) and supplies the three-phase AC voltage to the load 24 by the PWM operation of the bidirectional switching elements 40 to 45. When it becomes about 1/3 (= 33%) or less of the maximum value of the input voltage, it becomes a low voltage period in which it is difficult to supply current to the load 24. In the voltage waveform of (c), 140V The period below / 3 = 47V is a period during which driving is difficult.

  In the present embodiment, the length of the period lower than 47 V is approximately 1 ms, which is suppressed to approximately a half period compared to 2 ms in the case of a sine wave.

  Therefore, it is possible to shorten the output power decrease period that occurs in the low voltage period before and after the timing (zero voltage point) at which the instantaneous value of the voltage of the single-phase AC power supply 21 becomes zero. A power conversion device that suppresses fluctuations in supply power is realized.

  Since the load 24 is composed of a three-phase motor (motor), the fluctuation of the generated torque is suppressed, the power performance is high, and the occurrence of vibration due to the torque fluctuation is also generated. It can be reduced as much as possible.

  FIG. 3 shows a cross-sectional view of the bidirectional switching elements 30, 31, 40 to 45.

  In the present embodiment, SiC semiconductor 50 realized by crystallizing silicon carbide is obtained by forming a P + layer and an N + layer on an N− layer, and SD1, SD2 terminals from both ends as terminals, Further, G1 and G2 are drawn out as gates (control terminals).

  If a control voltage is applied to the G1 terminal with respect to the SD1 terminal and a control voltage (gate voltage) is applied to the G2 terminal with respect to the SD2 terminal, the control voltage (gate voltage) is applied as in the case of a general MOSFET. When there is no (zero voltage, etc.), the two MOSFETs connected in reverse polarity are equivalently connected in series, so that the bidirectional switching elements, that is, SD1 and SD2 With respect to both the positive and negative voltages, it is possible to control whether or not current flows using the G1 terminal and the G2 terminal, and the ON voltage generated in series between the two MOSFET elements in the ON state. The chip area is improved because of the low Ron characteristics, which are the characteristics of SiC semiconductors, and high reliability under high temperature conditions. To the silicon in equivalent or less as compared to the conventional unidirectional switching element using the (MOSFET, etc.), has become a possible configuration of a practical bidirectional switching element.

  FIG. 4 shows a configuration diagram of the load 24 in the present embodiment.

  A load 24 configured as a three-phase motor is a rotation provided by attaching four permanent magnets 60, 61, 62, and 63 to the surface of an iron core 64 formed by laminating silicon steel plates, and rotating around an output shaft 65. The stator 66 has a stator 67 provided on the outside of the rotor 66, and the stator 67 is composed of an iron core 68 and windings 70 to 75 that are also formed by laminating silicon steel plates.

  FIG. 5 shows a connection diagram of the windings 70 to 75.

  The windings 70 to 75 are mechanically arranged at 180 degrees and are connected in series, and when current flows, the same polarity is generated at a location facing the rotor 66. .

  FIG. 6 shows the voltage generated between the terminals of the three-phase terminals U, V, W (for example, between U and V) when the load 24 of the present embodiment is driven from the outside, that is, the induced electromotive force of no load. As shown, since the permanent magnets 60 to 63 have a four-pole configuration, the voltage is generated with positive / negative polarity with a mechanical phase (mechanical angle) of 180 degrees as a cycle. Yes.

  As a driving method of each of the bidirectional switching elements 40 to 45 which are constituent elements of the second power conversion device 23, for example, using a Hall IC, which has been generally used for driving a DC brushless motor, for example. , While detecting the position of the rotor 66, driving a rectangular wave (square wave) that conducts electricity at an electrical angle of 120 degrees, PWM method so that the voltage / current waveform is close to a sine wave, and position For example, a sensorless method may be used in which detection is performed from the detected value of the current value of each phase without using a Hall IC, and the current vector is divided into a d-axis component and a q-axis component and controlled. Various control configurations such as what is called vector control are possible.

  Thus, since the three-phase motor of the load 24 is configured using permanent magnets, a high-efficiency three-phase motor can be realized, and the three-phase motor can have a high power factor. For this reason, it is possible to reduce the capacity (product of withstand voltage and current capacity) of the bidirectional switching elements 40 to 45 that are components of the second power conversion circuit 23 in particular and at a low cost.

  When a three-phase motor using permanent magnets is used as the load 24, the magnitude of the generated voltage is proportional to the speed of rotation, so that a high induced electromotive force is generated between the lines, especially at high speeds. If the low voltage period near the zero point of the single-phase AC power supply 21 becomes longer, the current supply tends to be difficult.

  In this regard, in the present embodiment, since the low voltage period is shortened, the period during which the power supplied to the load 24 is reduced can be shortened, so that good power performance can be ensured.

(Embodiment 2)
FIG. 7 is a circuit diagram of the power conversion device according to the second embodiment of the present invention.

  In FIG. 7, a first power conversion circuit 80 that receives an input from a single-phase AC power supply 21 having an effective value voltage of 200 V and 50 Hz and outputs a single-phase AC voltage having a lower crest factor than the single-phase AC power supply 21, The second power conversion circuit 81 that receives the output of the power conversion circuit 80 outputs a three-phase AC voltage to a load 82 configured by a three-phase motor.

  The first power conversion circuit 80 includes bidirectional switching elements 85 and 86 using an SiC semiconductor, an inductance element 87, and a capacitor 88.

  The second power conversion circuit 81 includes bidirectional switching elements 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, and 101 using SiC semiconductors.

  FIG. 8 is an operation waveform diagram of the power conversion device according to the present embodiment. (A) is the voltage waveform of the single-phase AC power supply 21, (B) is the conductivity of the bidirectional switching element 86, and (C) is the first. 1 shows an output voltage waveform of one power conversion circuit 80.

  The bidirectional switching element 85 is an operation that repeats on / off by PWM (pulse width modulation) at a carrier frequency of 50 kHz, and at the time when the absolute value of the instantaneous value of the single-phase AC power supply 21 peaks. The conductivity is almost 0%.

  On the other hand, the bidirectional switching element 86 is given a drive signal so that the current can be operated as a flywheel diode in which the inductance element 87 flows while the bidirectional switching element 85 is off.

With this operation, the first power conversion circuit 80 operates as a step-up chopper circuit in the present embodiment, and the first power conversion circuit 80 has an input single-phase alternating current shown in FIG. The voltage waveform shown in (c) having an effective voltage higher than the voltage of the power source 21 is output.

  Regarding the voltage waveform shown in (c), there are continuous periods in which the absolute value is 280 V, and when compared with a sine wave, the waveform is a crushed head, and the crest factor, The maximum value / effective value is about 1.1, which is lower than 1.41 in the case of a sine wave.

  The second power conversion circuit 81 is supplied with the voltage waveform (c), and the three-phase AC voltage is supplied to the load 82 by the switching operation of the bidirectional switching elements 90 to 101. When it becomes about 1/3 (= 33%) or less of the maximum value of the input voltage, it becomes a low voltage period in which it is difficult to supply current to the load 82. In the voltage waveform of (c), 280V The period below / 3 = 93V is a period during which driving is difficult.

  In the present embodiment, the length of the period below 93V is approximately 1 ms, which is suppressed to approximately a half period compared to 2 ms in the case of a sine wave.

  Therefore, it is possible to shorten the output power reduction period that occurs in the low voltage period before and after the timing (zero voltage point) at which the instantaneous value of the voltage of the single-phase AC power supply 21 becomes zero. A power conversion device that suppresses fluctuations in supply power is realized.

  Since the load 82 is composed of a three-phase electric motor (motor), fluctuations in the generated torque are suppressed, the power performance is high, and vibrations caused by torque fluctuations are also generated. It can be reduced as much as possible.

  The bidirectional switching elements 85, 86, 90 to 101 have the same cross-sectional view as that of FIG. 3 described in the previous embodiment.

  FIG. 9 shows a configuration diagram of the load 82 in the present embodiment.

  A load 82 configured as a three-phase motor has a rotor 112 in which an iron core 110 configured by laminating silicon steel plates is rotatably provided around an output shaft 111, and a stator 117 provided outside the rotor 112. The stator 117 is composed of an iron core 118 and windings 120 to 125 that are also formed by laminating silicon steel plates.

  FIG. 10 shows a connection diagram of the windings 120 to 125.

  The windings 120 to 125 are mechanically arranged at 180 degrees and are connected in series, and when current flows, a different polarity is generated at a location facing the rotor 112. When a current is supplied from the X terminal to the X terminal, a magnetic flux due to the current is generated so as to penetrate the shaft 111.

  FIG. 11 shows the inductance value (self-inductance value) between the UX terminals, which is one of the three phases when the load 82 of the present embodiment is driven from the outside. (Mechanical angle) With a period of 90 degrees, the inductance changes, and a maximum value Lmax and a minimum value Lmin are generated.

Each bidirectional switching element 90-101 which is a component of the second power conversion device 81 is switched according to the relative positional relationship (phase) between the rotor 112 and the stator 117, and the inductance becomes (from Lmin). In the period of increase (to Lmax), reluctance torque is generated by supplying current, and electric power is supplied from the second power converter 81 to the load 82, and at the same time, the electric power in the load 82 is supplied. Conversion from power to mechanical power is also performed.

  In the present embodiment, the reluctance torque generated by the current flowing through each of the windings 120 to 125 is positive regardless of the polarity of the current, and a positive torque is generated as long as the inductance increases. The on / off control of the bidirectional switching elements 90 to 101 supplies the electric power to the load 82 equally regardless of whether a positive or negative current is supplied depending on the polarity of the output voltage of the first power conversion circuit 80. Then, the load 82 is a three-phase motor, and an operation of outputting mechanical power from electric power is performed, so that control can be realized relatively easily.

  Compared with a load using a permanent magnet as in the second embodiment, there is no voltage of the nature of induced electromotive force that is generated in proportion to the speed, and thus a low voltage period around the zero voltage of the single-phase AC power supply 21 However, in this embodiment, the load is reduced by the amount of the low voltage period shortened by the action of the first power conversion circuit 80 in the present embodiment. Since the period during which the power supplied to 82 is reduced is short, good power performance can be ensured.

(Embodiment 3)
FIG. 12 is a cross-sectional view of the power conversion device according to the third embodiment of the present invention.

  12, the power conversion device 130 having the configuration described in the first embodiment, the load 131, and the fan 132 that is attached to the load 131 and rotates are housed in a casing 134 together with the paper pack 133, and the hose 140 and the nozzle 141 is connected from the paper pack.

  Further, a front wheel 142 and a rear wheel 143 for making the floor surface movable are rotatably attached to the housing 134, and a power plug 151 for connecting the single-phase AC power source 150 to the power conversion phase 130, and a power cord 152 is connected to form a vacuum type vacuum cleaner.

  In the above configuration, the fan 132 is rotationally driven at several tens of thousands of revolutions per minute, and dust is collected from the nozzle 141 through the hose 140 into the paper pack 133, and can be cleaned.

  Here, as described in the first embodiment, the power conversion device 130 can be configured with a small, lightweight capacitor, inductance element, and the like. It can be lightweight and very convenient to use.

  As described above, the power conversion device according to the present invention can provide a power conversion device with improved current supply to the load in a low voltage period near the zero point of the single-phase AC power supply and small fluctuations in supply power. Become.

Circuit diagram of power conversion apparatus according to Embodiment 1 of the present invention Operation waveform diagram of the power converter Sectional view of bidirectional switching element of power converter Same as above, sectional view of load of power converter Same as above, load diagram of power converter Same as above, induced electromotive force waveform diagram of load of power converter Circuit diagram of power conversion device according to Embodiment 2 of the present invention Operation waveform diagram of the power converter Same as above, sectional view of load of power converter Same as above, load diagram of power converter Same as above, inductance diagram of load of power converter Sectional drawing of the vacuum cleaner in Embodiment 3 of this invention Circuit diagram of power converter in prior art

Explanation of symbols

21, 150 Single-phase AC power supply 22, 80 First power conversion circuit 23, 81 Second power conversion circuit 24, 82, 131 Load (three-phase motor)
30, 31, 40, 41, 42, 43, 44, 45, 85, 86, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101 Bidirectional switching element 32, 87 Inductance element 50 SiC semiconductor 60, 61, 62, 63 Permanent magnet 132 Fan

Claims (8)

Receiving input from a single-phase AC power supply, the crest factor is lower than that of the single-phase AC power supply , and exists before and after the timing when the instantaneous value of the voltage of the single-phase AC power supply becomes zero. The first power conversion circuit that outputs a single-phase AC voltage whose low voltage period is less than or equal to / 3 is shorter than the single-phase AC power supply, and receives the output of the first power conversion circuit to generate a three-phase AC voltage. A power conversion device including a second power conversion circuit that outputs to a load, wherein each of the first power conversion circuit and the second power conversion circuit includes a bidirectional switching element. The power conversion device according to claim 1, wherein the first power conversion circuit outputs a voltage having an effective value lower than that of the input single-phase AC power supply. The power conversion device according to claim 1, wherein the first power conversion circuit outputs a voltage having an effective value higher than that of the input single-phase AC power supply. The power converter according to claim 2 or 3, wherein the first power conversion circuit includes an inductance element. The power conversion device according to any one of claims 1 to 4, wherein at least one bidirectional switching element is formed of a SiC semiconductor. The power converter according to any one of claims 1 to 5, wherein the load is a three-phase motor having a permanent magnet. The power converter according to any one of claims 1 to 5, wherein the load is a three-phase motor whose inductance varies depending on a mechanical phase. The power converter according to any one of claims 1 to 7, wherein the three-phase electric motor as a load is a vacuum cleaner using a fan as a load.

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