Power converter

Abstract

This technology provides the ability to individually control the AC component of the power supply shared by the power buffer circuit and the voltage of the DC link. [Solution] The control unit 10 makes the DC component of the discharge power Pc equal to the DC component of the charge power Pl, and sets the AC component of the discharge power Pc to a value obtained by subtracting the distribution ratio k from the adjustment value S and multiplying the AC component Prec^ of the rectified power Prec by minus 1, and sets the buffering power Pbuf to a value obtained by multiplying the AC component Prec^ of the rectified power Prec by minus 1 and the adjustment value S. For a predetermined value km between 0 and 1, if the distribution ratio is less than the predetermined value km, the adjustment value S is set to a value obtained by dividing the distribution ratio by the predetermined value km, or if the distribution ratio k is greater than or equal to the predetermined value km, the adjustment value S is set to 1.

Description

[Technical Field]

[0001] This relates to a power conversion device having a power buffer circuit. [Background technology]

[0002] When rectifying a single-phase AC voltage obtained from a single-phase AC power supply to obtain a DC voltage, for example, in the power conversion device described in Patent Document 1, a voltage source is generated by a buffer capacitor connected to the DC link via a switching element, and control is performed to keep the DC voltage constant. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Patent No. 5626435 [Overview of the project] [Problems that the invention aims to solve]

[0004] Patent Document 1 proposes a technology that controls the DC voltage to a constant level using only the voltage of the power supply, or the voltage of the power supply and the voltage of the power buffer circuit, thereby supplying constant power. This makes it possible to step up or step down the DC voltage. Furthermore, the charging current of the power buffer circuit is determined by the sum of the charging current and the current flowing from the power supply to the inverter, so that the input power factor is 1. Consequently, due to the relationship between the input and output power, the power buffer circuit always bears the entire AC component of the power supply, and the buffering power of the power buffer circuit cannot be varied.

[0005] Therefore, the purpose of this disclosure is to provide a technology that enables individual control of the AC component of the power supply power shared by the power buffer circuit and the voltage of the DC link. [Means for solving the problem]

[0006] The power conversion device according to the first aspect includes a power supply unit, a capacitor, a power conversion circuit, and a control unit. The power supply unit is composed of one or more rectifiers including a first rectifier that full-wave rectifies a single-phase AC voltage and generates rectified power. The capacitor receives charging power from the first rectifier when the power supply unit includes only the first rectifier, or from a second rectifier different from the first rectifier when the power supply unit includes the second rectifier, and outputs discharging power. The power conversion circuit receives a DC link power obtained by adding a buffering power, which is a power difference obtained by subtracting the charging power from the discharging power, to the rectified power. The control unit controls the power flow such that the DC link power is the sum of the direct conversion power obtained by subtracting the charging power from the rectified power multiplied by a distribution ratio between 0 and 1, and the discharging power. The control unit controls such that the amplitude of the buffering power is proportional to an adjustment value set according to the distribution ratio, and when the distribution ratio is smaller than a preset value between 0 and 1, the adjustment value is set to the value obtained by dividing the distribution ratio by the preset value, or when the distribution ratio is greater than or equal to the preset value, the adjustment value is set to 1.

[0007] In this power conversion device, by switching the set value of the adjustment value based on the distribution ratio k and the preset value km, the buffering power of the power buffer circuit can be varied, so that the AC component of the power supply power shared by the power buffer circuit and the voltage of the DC link can be controlled individually.

[0008] The power conversion device according to the second aspect is the power conversion device according to the first aspect, wherein the control unit makes the DC component in the discharging power equal to the DC component in the charging power, and makes the AC component in the discharging power be the value obtained by multiplying the AC component of the rectified power by minus 1 and the value obtained by subtracting the distribution ratio from the adjustment value, and makes the buffering power be the value obtained by multiplying the AC component of the rectified power by minus 1 and the adjustment value.

[0009] The power conversion device from the third perspective is the power conversion device from the first perspective, where the control unit makes the DC component in the discharge power equal to the DC component in the charging power, and sets the AC component in the discharge power as the value obtained by multiplying the AC component of the rectified power by minus 1 and the value obtained by subtracting the adjustment value and the distribution ratio from 1. The buffering power is set as the value obtained by multiplying the AC component of the rectified power by minus 1 and the value obtained by subtracting the adjustment value from 1.

[0010] In this power conversion device, based on the distribution ratio k and the predetermined value km, by switching the set value of the adjustment value, the buffering power of the power buffer circuit can be varied. Therefore, the AC component of the power supply power shared by the power buffer circuit and the voltage of the DC link can be controlled individually.

[0011] The power conversion device from the fourth perspective is the power conversion device from the first or second perspective, where the discharge power is the sum of a DC component and an AC component. The DC component is the value obtained by dividing the product of the peak value of the single-phase AC voltage and the peak value of the single-phase AC current by 2 and multiplying by the distribution ratio. The AC component is the value obtained by dividing the product of the peak value of the single-phase AC voltage and the peak value of the single-phase AC current by 2, multiplying by the cosine value of twice the phase of the single-phase AC voltage, and further multiplying by the value obtained by subtracting the distribution ratio from the adjustment value.

[0012] The power conversion device from the fifth perspective is the power conversion device from the first or third perspective, where the discharge power is the sum of a DC component and an AC component. The DC component is the value obtained by dividing the product of the peak value of the single-phase AC voltage and the peak value of the single-phase AC current by 2 and multiplying by the distribution ratio. The AC component is the value obtained by dividing the product of the peak value of the single-phase AC voltage and the peak value of the single-phase AC current by 2, multiplying by the cosine value of twice the phase of the single-phase AC voltage, and further multiplying by the value obtained by subtracting the adjustment value and the distribution ratio from 1.

[0013] The power conversion device from the sixth perspective is any one of the power conversion devices from the first to the third perspectives, where when the predetermined value is 1, the control unit sets the adjustment value as the value obtained by dividing the distribution ratio by the predetermined value within the range where the distribution ratio is 0 or more and less than 1.

[0014] The power converter of the seventh aspect is a power converter of any one of the first, third, or fourth aspects, wherein the control unit sets the adjustment value to 1 when the predetermined value is 0, within a range of 0 or more and 1 or less for the distribution ratio.

[0015] The power converter in the eighth aspect is a power converter in any one of the first, third, or fourth aspects, where the adjustment value is the value obtained by dividing the distribution ratio by the predetermined value when the distribution ratio is greater than or equal to 0 and less than a predetermined value. When the distribution ratio is greater than or equal to a predetermined value and less than or equal to 1, the adjustment value is set to 1.

[0016] The power converter of the ninth aspect is a power converter of any one of the first, third, or fourth aspects, wherein the control unit sets the adjustment value to 1 when the load magnitude is greater than the first threshold (high load) and the distribution ratio is greater than or equal to a predetermined value. Furthermore, when the load magnitude is less than the second threshold (where the first threshold ≥ the second threshold) and the distribution ratio is less than a predetermined value, the control unit sets the adjustment value to the value obtained by dividing the distribution ratio by a predetermined value.

[0017] In this power converter, in the high-load region, the mechanical fluctuations on the load side can be reduced by buffering the AC component with a capacitor. Conversely, in the low-load region, the power is small and the mechanical fluctuations on the load side are also small, so a portion of the AC component can be handled by the load side.

[0018] The power converter of the tenth perspective is a power converter of any one of the first, third, or fourth perspectives, and in a motor included in the load, when the motor's rotational speed is a high rotational speed greater than the first rotational speed and the distribution ratio is greater than or equal to a predetermined value, the adjustment value is set to 1. Furthermore, the control unit sets the adjustment value to the value obtained by dividing the distribution ratio by a predetermined value when the motor's rotational speed is a low rotational speed less than the second rotational speed (provided that the first rotational speed ≥ the second rotational speed) and the distribution ratio is less than a predetermined value.

[0019] In this power converter, in the high-speed range, the AC component is buffered by a capacitor, thereby reducing torque fluctuations on the load side. Conversely, in the low-speed range, the power is small and the torque on the load side is also small, so a portion of the AC component can be borne by the load side.

[0020] The power converter of the 11th perspective is a power converter of any one of the 1st, 2nd, or 3rd perspectives, in which the control unit is set to a second predetermined value between 0 and 1 (however, the second predetermined value > predetermined value), and in a specific range within the range of possible distribution ratios that is less than or equal to the second predetermined value, the adjustment value is the value obtained by dividing the distribution ratio by the second predetermined value.

[0021] This power converter allows the rate of increase or decrease of buffering power relative to the distribution ratio to be changed only when the distribution ratio is within a specific range. Furthermore, the control unit can change the adjustment value without changing the distribution ratio.

[0022] The power converter of the 12th perspective is a power converter of any one of the 1st, 2nd, or 3rd perspectives, in which the control unit has set first reference values ​​and second reference values ​​(however, the second reference value ≥ the first reference value) which define the upper and lower limits of the range in which control based on predetermined values ​​is restricted within the range in which the distribution ratio can be taken, and the adjustment value is set to 1 when the distribution ratio is greater than or equal to the first reference value and less than or equal to the second reference value.

[0023] This power converter can perform control that forces the adjustment value to 1 within a specific range for the distribution ratio.

[0024] The power converter of the 13th aspect is the power converter of the 11th aspect, in which the control unit has set first reference values ​​and second reference values ​​(however, the second reference value ≥ the first reference value) which define the upper and lower limits of the range in which control based on predetermined values ​​is restricted within the range in which the distribution ratio can be taken, and the adjustment value is set to 1 when the distribution ratio is greater than or equal to the first reference value and less than or equal to the second reference value.

[0025] This power converter can perform control that forces the adjustment value to 1 within a specific range for the distribution ratio.

[0026] The power converter of the 14th aspect is a power converter of any one of the 13th aspect from the 1st, 2nd, 4th, and 6th aspects, further comprising a DC link having a first power line and a second power line. The power supply unit includes at least one rectifier circuit that supplies rectified power to the DC link. The control unit controls the DC voltage applied to the DC link to become a DC voltage command value, which is its command value, by setting the rectified current ratio and the discharge current ratio. The rectified current ratio is the current ratio in which the rectifier circuit directly supplies converted power to the power converter circuit. The discharge current ratio is the current ratio in which the capacitor discharges.

[0027] If the distribution ratio is smaller than a predetermined value, the adjustment value is set to the value obtained by dividing the distribution ratio by the predetermined value. The rectified current ratio is set to the value obtained by dividing the product of the DC voltage command value, the sine value of the phase of the single-phase AC voltage, and the value obtained by subtracting the distribution ratio from 1 and multiplying by 2, by the product of the peak value of the single-phase AC voltage and a first relational value that varies depending on the value obtained by subtracting the adjustment value from 1. The discharge current ratio is set to the value obtained by dividing the product of the DC voltage command value, the second relational value that varies depending on the value obtained by subtracting the distribution ratio from the adjustment value and the distribution ratio, by the product of the voltage across the capacitor and the first relational value.

[0028] When the distribution ratio is greater than or equal to a predetermined value, the adjustment value is set to 1, and the rectified current ratio is set to the value obtained by dividing the product of the DC voltage command value, the sine value of the phase of the single-phase AC voltage, and the value obtained by subtracting the distribution ratio from 1 and multiplying by 2, by the peak value of the single-phase AC voltage. The discharge current ratio is set to the value obtained by dividing the product of the DC voltage command value, the value obtained by subtracting the distribution ratio from 1, and a third relational value that varies depending on the distribution ratio, by the voltage across the capacitor.

[0029] A charging current is input to the capacitor, which is the value obtained by multiplying the first current (the value obtained by dividing the rectified power by the first voltage, which is obtained by full-wave rectifying a single-phase AC voltage) by the distribution ratio.

[0030] The power converter of the 15th aspect is a power converter of any one of the 13th aspect from the 1st, 3rd, and 5th aspects, further comprising a DC link having a first power line and a second power line. The power supply unit includes at least one rectifier circuit that supplies rectified power to the DC link. The control unit controls the DC voltage applied to the DC link to become a DC voltage command value, which is its command value, by setting the rectified current ratio and the discharge current ratio. The rectified current ratio is the current ratio at which the rectifier circuit directly supplies converted power to the power converter circuit. The discharge current ratio is the current ratio at which the capacitor discharges.

[0031] If the distribution ratio is smaller than a predetermined value, the adjustment value is set to the value obtained by dividing the distribution ratio by the predetermined value. The rectified current ratio is set to the value obtained by dividing the product of the DC voltage command value, the sine value of the phase of the single-phase AC voltage, and the value obtained by subtracting the distribution ratio from 1 and multiplying by 2, by the product of the peak value of the single-phase AC voltage and the fourth relational value which varies with the adjustment value. The discharge current ratio is set to the value obtained by dividing the product of the DC voltage command value, the value obtained by subtracting the adjustment value and the distribution ratio from 1, and the fifth relational value which varies with the distribution ratio, by the product of the voltage across the capacitor and the fourth relational value.

[0032] When the distribution ratio is greater than or equal to a predetermined value, the adjustment value is set to 1, and the rectified current ratio is set to the value obtained by dividing the product of the DC voltage command value, the sine value of the phase of the single-phase AC voltage, and the value obtained by subtracting the distribution ratio from 1 and multiplying it by 2, by the product of the peak value of the single-phase AC voltage and the value obtained by subtracting the cosine value of twice the phase of the single-phase AC voltage from 1. The discharge current ratio is set to the value obtained by dividing the product of the DC voltage command value and the distribution ratio by the voltage across the capacitor (Vc).

[0033] A charging current is input to the capacitor, which is the value obtained by multiplying the first current (the value obtained by dividing the rectified power by the first voltage, which is obtained by full-wave rectifying a single-phase AC voltage) by the distribution ratio. [Brief explanation of the drawing]

[0034] [Figure 1] This is a block diagram showing the configuration of a power conversion device according to the first embodiment. [Figure 2]This block diagram shows the configuration of a power converter when the rectifier circuit in Figure 1 is composed of two rectifier circuits. [Figure 3] Figures 1 and 2 show the equivalent circuit of the power converter. [Figure 4A] This graph shows the relationship between the distribution ratio, buffered power, and DC voltage in the first control system. [Figure 4B] This graph shows the relationship between the distribution ratio, buffered power, and DC voltage in the second control system. [Figure 4C] This graph shows the relationship between the distribution ratio, buffered power, and DC voltage in the third control system. [Figure 5] This is a graph showing the operation of the power converter according to the first embodiment. [Figure 6A] This flowchart shows the process of setting adjustment values ​​according to the load. [Figure 6B] This flowchart shows the process of setting adjustment values ​​according to the rotation speed. [Figure 7A] This graph shows the relationship between the distribution ratio and buffered power in the third control of the power conversion circuit according to the first modified example. [Figure 7B] This graph shows the relationship between the distribution ratio and buffered power in the third control of the power converter according to the second modified example. [Figure 7C] This graph shows the relationship between the distribution ratio and buffered power in the third control of the power converter according to the third modified example. [Figure 8A] This graph shows the relationship between the distribution ratio, buffered power, and DC voltage in the first control of the second embodiment. [Figure 8B] This graph shows the relationship between the distribution ratio, buffered power, and DC voltage in the second control of the second embodiment. [Figure 8C] This graph shows the relationship between the distribution ratio, buffered power, and DC voltage in the third control of the second embodiment. [Figure 9] This is a graph showing the operation of the power converter according to the second embodiment. [Figure 10A] This graph shows the relationship between the distribution ratio and buffered power in the third control of the power conversion circuit according to the first modified example of the second embodiment. [Figure 10B] This graph shows the relationship between the distribution ratio and buffered power in the third control of a power converter according to a second modified example of the second embodiment. [Figure 10C] This graph shows the relationship between the distribution ratio and buffered power in the third control of a power converter according to a third modified example of the second embodiment. [Modes for carrying out the invention]

[0035] <First Embodiment> (1) Configuration of power converter 100 Figure 1 is a block diagram showing the configuration of a power converter 100 according to the first embodiment. The power converter 100 includes a rectifier circuit 3 which is a power supply unit, a power buffer circuit 4, an inverter 5 which is a power conversion circuit, and a DC link 7.

[0036] (1-1) Rectifier circuit 3 The rectifier circuit 3 is connected to the single-phase AC power supply 1. The rectifier circuit 3 employs, for example, a diode bridge and is equipped with diodes D31a to D31d.

[0037] Diodes D31a to D31d form a bridge circuit, which rectifies the single-phase AC voltage Vin, which is the input voltage from the single-phase AC power supply 1, into a single-phase full-wave rectified voltage Vrec, which is output between the first power supply LH and the second power supply LL, which are the DC power lines of the DC link 7.

[0038] A higher potential is applied to the first power line LH than to the second power line LL. An input current Iin flows into the rectifier circuit 3 from the single-phase AC power supply 1.

[0039] (1-2) Power buffer circuit 4 The power buffer circuit 4 has a discharge circuit 4a, a charging circuit 4b, and a current blocking unit 4c, and exchanges power with the DC link 7. The discharge circuit 4a includes a capacitor C4, and the charging circuit 4b charges the capacitor C4 by boosting the rectified voltage Vrec.

[0040] The discharge circuit 4a further includes a transistor Sc connected in antiparallel to the diode D42. In this embodiment, the transistor Sc is an insulated-gate bipolar transistor, and will be hereinafter abbreviated as "IGBT".

[0041] Transistor Sc is connected in series with capacitor C4 on the first power line LH side, between the first power line LH and the second power line LL. Antiparallel connection refers to a connection where the forward directions are opposite to each other.

[0042] Specifically, the forward direction of transistor Sc is from the second power line LL to the first power line LH, and the forward direction of diode D42 is from the first power line LH to the second power line LL.

[0043] Transistor Sc and diode D42 can be considered together as a single switching element (first switch). The conduction of the first switch causes capacitor C4 to discharge, transferring power to DC link 7.

[0044] The charging circuit 4b includes, for example, a diode D40, a reactor L4, and a transistor Sl. In this embodiment, the transistor Sl is an IGBT.

[0045] Diode D40 comprises a cathode and an anode, the cathode of which is connected between the first switch and capacitor C4. This configuration is known as a so-called boost chopper.

[0046] Reactor L4 is connected between the first power line LH and the anode of diode D40. Transistor Sl is connected between the second power line LL and the anode of diode D40. Diode D41 is connected in antiparallel to transistor Sl, and the two can be considered together as a single switching element (second switch).

[0047] Specifically, the forward direction of transistor Sl is from the first power line LH to the second power line LL, and the forward direction of diode D40 is from the second power line LL to the first power line LH.

[0048] Capacitor C4 is charged by the charging circuit 4b, generating a voltage Vc across its terminals that is higher than the rectified voltage Vrec. Specifically, energy is stored in reactor L4 by passing current from the first power line LH through the second switch to the second power line LL, and then this energy is stored in capacitor C4 via diode D40 when the second switch is turned off.

[0049] Since the voltage Vc across the diode is higher than the rectified voltage Vrec, basically no current flows through diode D42. Therefore, the conduction / non-conductivity of the first switch depends solely on the conduction / non-conductivity of transistor Sc. For this reason, below, not only transistor Sc but also the first switch, which includes both transistor Sc and diode D42, may be referred to as switch Sc.

[0050] Furthermore, since the potential of the first power line LH is higher than that of the second power line LL, basically no current flows through diode D41. Therefore, the conduction / non-conductivity of the second switch depends solely on the conduction / non-conductivity of transistor Sl. For this reason, below, not only transistor Sl but also the second switch, which includes both transistor Sl and diode D41, may be referred to as switch Sl.

[0051] (1-3) Inverter 5 Inverter 5 converts the DC voltage between the first power line LH and the second power line LL into an AC voltage and outputs it to the output terminals Pu, Pv, and Pw. Inverter 5 includes six switching elements Sup, Svp, Swp, Sun, Svn, and Swn.

[0052] Switching elements Sup, Svp, and Swp are connected between their output terminals Pu, Pv, and Pw and the first power line LH, respectively, while switching elements Sun, Svn, and Swn are connected between their output terminals Pu, Pv, and Pw and the second power line LL, respectively.

[0053] Inverter 5 constitutes a so-called voltage-type inverter and includes six diodes Dup, Dvp, Dwp, Dun, Dvn, and Dwn.

[0054] Diodes Dup, Dvp, Dwp, Dun, Dvn, and Dwn are all positioned with their cathodes facing the first power line LH and their anodes facing the second power line LL. Diode Dup is connected in parallel with the switching element Sup between the output terminal Pu and the first power line LH.

[0055] Similarly, diodes Dvp, Dwp, Dun, Dvn, and Dwn are connected in parallel with switching elements Svp, Swp, Sun, Svn, and Swn, respectively. AC currents Iu, Iv, and Iw are output from the output terminals Pu, Pv, and Pw, respectively, and these constitute a three-phase AC current. For example, IGBTs are used for the switching elements Sup, Svp, Swp, Sun, Svn, and Swn.

[0056] (1-4) Inductive load 6 The inductive load 6 is, for example, a motor, and is illustrated in an equivalent circuit diagram demonstrating that it is an inductive load. Specifically, a reactor Lu and a resistor Ru are connected in series, and one end of this series connection is connected to the output terminal Pu. The same applies to reactors Lv, Lw and resistors Rv, Rw. The other ends of these series connections are also connected to each other.

[0057] (2) Equivalent Circuit Figure 2 is a block diagram showing the configuration of a power converter when the rectifier circuit 3 in Figure 1 is composed of two rectifier circuits.

[0058] Compared to the configuration shown in Figure 1, the rectifier circuit 3 differs in that it includes a first rectifier circuit 31 and a second rectifier circuit 32. Therefore, the discharge circuit 4a is connected in series between the first power line LH and the power line on the negative electrode output side of the second rectifier circuit 32, and the charging circuit 4b is connected to the output side of the second rectifier circuit 32. However, since they can be treated equivalently in the equivalent circuits, the control method is the same.

[0059] Figure 3 is the equivalent circuit of the circuits shown in Figures 1 and 2. In Figure 3, the current ire c1 is equivalently represented as the current irec1 that passes through switch Srec when it is conducting. Note that in Figures 1 and 2, Srec and Sz do not exist as actual elements, but Sz conducts equivalently due to the control on the inverter side, and Sc conducts due to the control of the power buffer circuit. Therefore, during the remaining Srec period, the current blocking section 4c in Figure 1 and the first rectifier circuit 31 corresponding to the current blocking section 4c in Figure 1 in Figure 2 are passively conducting. The comparison between actual circuits and equivalent circuits is publicly known, for example, in Japanese Patent Publication No. 5629885, so the details are omitted here.

[0060] Similarly, the discharge current ic is equivalently represented as the current ic that flows through the switch Sc when it is conducting.

[0061] Furthermore, when the output terminals Pu, Pv, and Pw of the inverter 5 are connected in common to either the first power line LH or the second power line LL, the current flowing through the inverter 5 to the inductive load 6 is also equivalently represented as the zero-sequence current iz that flows through the switch Sz when it is conducting.

[0062] Figure 3 also shows the reactor L4, diode D40, and switch Sl that constitute the charging circuit 4b, with the current il flowing through the reactor L4 indicated.

[0063] In this equivalent circuit, the current ratios drec, dc, and dz, which are the conduction ratios of switches Srec, Sc, and Sz, respectively, and the DC current Idc input to inverter 5 are introduced.

[0064] Here, the DC current Idc is expressed as the input current of the power conversion circuit because the inverter 5 and inductive load 6 are three-phase, and the sum of the three-phase AC power is constant, as is generally known, and the DC voltage is constant. Therefore, the inverter 5, which corresponds to the inverter and inductive load, may be a single-phase inverter or a DC / DC converter, or it may be a DC load such as a resistive load or an inductive load.

[0065] Since the currents irec1, ic, and iz are obtained by multiplying the DC current Idc by the current ratios drec, dc, and dz, respectively, these are the average values ​​over the switching period of switches Srec, Sc, and Sz.

[0066] Furthermore, the DC current Idc is the sum of the currents irec1, ic, and iz that conduct through switches Srec, Sc, and Sz respectively, so drec + dc + dz = 1. However, 0 ≤ drec ≤ c ≤ 1, 0 ≤ dc ≤ 1, and 0 ≤ dz ≤ 1.

[0067] The current ratios drec, dc, and dz can be seen as the current distribution ratio of the DC current I dc to each current irec1, ic, and iz. Furthermore, the current ratio drec is the current ratio that sets the period during which the rectifier circuit 3 is connected to the DC link 7 and current can flow to the inverter 5, and will therefore be referred to as the rectified current ratio drec below. Furthermore, the current ratio dc is the current ratio at which the capacitor C4 discharges, and will therefore be referred to as the discharge current ratio dc below. Furthermore, the current ratio dz is the current ratio at which a zero-sequence current iz always flows in the inverter 5 regardless of the output voltage, and will therefore be referred to as the zero current ratio dz. The settings of the rectified current ratio drec and the discharge current ratio dc will be described in detail in section (4) Setting the Current Ratios.

[0068] (3) Control The rectifier circuit 3 receives a single-phase AC voltage Vin as input, sets the input power factor to 1, and outputs a rectified power Prec represented by equation [1]. Prec = Vm·Im·sin 2 (ωt) =(1 / 2)Vm·Im-(1 / 2)Vm·Im·cos(2ωt)···[1]

[0069] However, the peak value Vm of the single-phase AC voltage Vin, the power supply angular frequency ω, the peak value Im of the input current Iin, and time t were introduced. ωt, which is the product of the power supply angular frequency ω and time t, represents the phase of the single-phase AC voltage Vin. The AC waveform is the product of the sine value of the phase ωt of the AC waveform and its peak value.

[0070] The AC component (-1 / 2)·Vm·Im·cos(2ωt) shown in the second term on the right-hand side of equation [1] is called the "AC component Prec^".

[0071] As shown in Figure 1, a portion of the rectified power Prec output from the rectifier circuit 3 is distributed from the DC link 7 to the power buffer circuit 4 as charging power Pl with a distribution ratio k between 0 and 1, and the discharge power Pc is output from the power buffer circuit 4 to the DC link 7.

[0072] Therefore, the charging power Pl is expressed by equation [2]. Pl=k·Vm·Im·sin 2 (ωt) =(k / 2)·Vm·Im-(k / 2)Vm·Im·cos(2ωt)···[2]

[0073] Inverter 5 receives DC link power Pdc (=Prec+Pc-Pl), which is the sum of rectified power Prec and discharge power Pc minus charging power Pl, from DC link 7, and outputs AC currents Iu, Iv, and Iw.

[0074] The power exchanged between the power buffer circuit 4 and the DC link 7 is equal to the power difference (Pc-Pl) obtained by subtracting the charging power Pl from the discharge power Pc, and is called the "buffering power Pbuf". Therefore, the DC link power Pdc = Prec + Pbuf.

[0075] For example, if the discharge power Pc is controlled so that the buffering power Pbuf is equal to the absolute value of the AC component Prec^, specifically if it is controlled so that Pbuf = (1 / 2)·Vm·Im·cos(2ωt), the AC component Prec^ of the rectified power Prec is absorbed, and the DC link power Pdc input to inverter 5 will consist only of the DC component (1 / 2)Vm·Im.

[0076] Here, if the ratio of the AC component Prec^ to the AC component of Prec^ that is to be absorbed by the power buffer circuit 4 is the adjustment value S, then the buffered power Pbuf is expressed by equation [3]. Pbuf=(S / 2)·Vm·Im·cos(2ωt)···[3]

[0077] Since Pbuf = Pc - Pl, from equations [2] and [3], the discharge power Pc is given by equation [4]. Pc=(k / 2)·Vm·Im+{(Sk) / 2}Vm·Im·cos(2ωt)···[4]

[0078] Furthermore, the direct conversion power Prec1, which is the power flowing from the rectifier circuit 3 to the inverter 5, is equal to Prec-Pl. Therefore, the DC link power Pdc = Prec1 + Pc holds true.

[0079] Therefore, the direct conversion power Prec1 and the DC link power Pdc are expressed by the following equations [5] and [6]. Prec1 = Prec - Pl = (1-k)·Vm·Im·sin 2 (ωt) ={(1-k) / 2}·Vm·Im-{(1-k) / 2}·Vm·Im·cos(2ωt)···[5] Pdc = Prec1 + Pc =(1 / 2)·Vm·Im-{(1-S) / 2}·Vm·Im·cos(2ωt)···[6]

[0080] As described above, in this embodiment, the control unit 10 obtains charging power Pl by multiplying the rectified power Prec by a distribution ratio k of 0 to 1, and controls the power flow such that the sum of the directly converted power Prec1 (obtained by subtracting the charging power Pl from the rectified power Prec) and the discharge power Pc is the DC link power Pdc.

[0081] In the above equation [3], controlling the discharge power Pc so that the buffering power Pbuf is equal to the absolute value of the AC component Prec^ means setting the adjustment value S to 1.

[0082] In this embodiment, the control unit 10 sets the adjustment value S to k / km when the distribution ratio k is within a range smaller than a predetermined value km (where 0 ≤ km ≤ 1) (hereinafter referred to as setting condition A).

[0083] Furthermore, when the distribution ratio k is greater than or equal to a predetermined value of km, the control unit 10 sets the adjustment value S to 1 so that the buffering power Pbuf becomes equal to the absolute value of the AC component Prec^ (hereinafter referred to as setting condition B). The specific control will be described below.

[0084] (3-1) First control When km=1, the control unit 10 determines that the distribution ratio k is less than a predetermined value of km in the range of 0≦k<1, and sets S=k / 1=k according to setting condition A, and controls the discharge power Pc so that the buffering power Pbuf=(k / 2)·Vm·Im·cos(2ωt).

[0085] Furthermore, in the range of distribution ratio k=km=1, S=1 is set according to setting condition B, and the discharge power Pc is controlled so that the buffering power Pbuf=(1 / 2)·Vm·Im·cos(2ωt). In this embodiment, the control based on the predetermined value km=1 as described above is called the "first control".

[0086] Figure 4A is a graph showing the relationship between the distribution ratio k, buffering power Pbuf, and DC voltage Vdc in the first control (km=1). However, the value of buffering power Pbuf on the graph is not the actual value, but a normalized value using Vm·Im·cos(2ωt)=1. Similarly, the value of DC voltage Vdc is not the actual value, but a normalized value using Vdc / Vm. Furthermore, the voltage across capacitor C4 Vc is also normalized using Vc / Vm, and the relationship between DC voltage Vdc and the voltage across capacitor Vc is also shown.

[0087] In Figure 4A, in the range 0 ≤ k < 1, the buffering power Pbuf is controlled to be proportional to the distribution ratio k with a slope of 1 / 2, and when k = km = 1, the buffering power Pbuf is equal to the absolute value of the AC component Prec^.

[0088] (3-2) Second control When km=0, the control unit 10 determines that there is no range in which the distribution ratio k is less than the predetermined value km, and therefore km≦k. It then sets S=1 according to setting condition B and controls the discharge power Pc in the range 0≦k≦1 such that the buffering power Pbuf=(1 / 2)·Vm·Im·cos(2ωt). In this embodiment, the control based on the predetermined value km=0 described above is called the "second control".

[0089] Figure 4B is a graph showing the relationship between the distribution ratio k, the buffering power Pbuf, and the DC voltage Vdc in the second control (km = 0). However, the value of the buffering power Pbuf on the graph is not the actual value but is normalized with Vm·Im·cos(2ωt)=1. Similarly, the value of the DC voltage Vdc is not the actual value but is normalized with Vdc / Vm. Furthermore, the voltage Vc across the capacitor C4 is also normalized with Vc / Vm, and the DC voltage Vdc also shows the relationship with the voltage Vc across the capacitor C4.

[0090] In Figure 4B, the buffering power Pbuf is constant at 1 / 2. This is because in the range of 0≦k≦1, regardless of the distribution ratio k, the buffering power Pbuf is controlled to be equal to the absolute value of the AC component Prec^.

[0091] (3-3) Third control + Second control When the predetermined value km is neither 0 nor 1 and 0≦k<km, the control unit 10 sets S = k / km in accordance with the setting condition A and controls the discharge power Pc so that the buffering power Pbuf={(k / km) / 2}Vm·Im·cos(2ωt). In this embodiment, the control based on the above-mentioned predetermined value km being neither 0 nor 1 and 0≦k<km is called "third control".

[0092] Figure 4C is a graph showing the relationship between the distribution ratio k, the buffering power Pbuf, and the DC voltage Vdc in the third control (0≦k<km). As an example, km = 0.5 is adopted. Also, the value of the buffering power Pbuf on the graph is not the actual value but is normalized with Vm·Im·cos(2ωt)=1. Similarly, the value of the DC voltage Vdc is not the actual value but is normalized with Vdc / Vm. Furthermore, the voltage Vc across the capacitor C4 is also normalized with Vc / Vm, and the DC voltage Vdc also shows the relationship with the voltage Vc across the capacitor C4.

[0093] In Figure 4C, in the range 0 ≤ k < 0.5, S is set to k / 0.5, and Pbuf = k·Vm·Im·cos(2ωt), so in the range 0 ≤ k < 0.5, the buffering power Pbuf is controlled to be proportional to the distribution ratio k with a slope of 1.

[0094] On the other hand, in the range of km = 0.5 ≤ k ≤ 1, the control unit 10 sets S = 1 according to setting condition B and controls the discharge power Pc so that the buffering power Pbuf = (1 / 2)Vm·Im·cos(2ωt). This corresponds to the second control.

[0095] Therefore, in the range of 0.5 ≤ k ≤ 1, the buffering power Pbuf is constant at 1 / 2 regardless of the value of the distribution ratio k, and the buffering power Pbuf is controlled to be equal to the absolute value of the AC component Prec^.

[0096] (4) Setting the flow ratio The control unit 10 controls the DC voltage Vdc applied to the DC link 7 to become the command value, which is the DC voltage command value Vdc*, by setting the straightened current ratio drec and the discharge current ratio dc.

[0097] The rectified current ratio drec is the current ratio at which the rectifier circuit 3 directly supplies converted power Prec1 to the inverter 5. The discharge current ratio dc is the current ratio at which capacitor C4 discharges.

[0098] (4-1) Setting of the straight flow ratio drec In equation [1], the input current Iin is expressed as Im·sin(ωt), and it is assumed that it exhibits a sinusoidal waveform, so the current il satisfies the following equation [7]. il=k·Im·|sin(ωt)|···[7]

[0099] As can be seen from Figure 3, the current irec output by the rectifier circuit 3 is equal to the sum of current irec1 and current il, so current irec1 is expressed by equation [8]. irec1=(1-k)·Im·|sin(ωt)|···[8]

[0100] The straightened current ratio drec is the value obtained by dividing irec1 by the DC current Idc, and is expressed by the following equation [9]. drec={(1-k)·Im / Idc}·|sin(ωt)|···[9]

[0101] Since the DC link power Pdc is also the product of the DC voltage Vdc and the DC current Idc, from equation [6], (1 / 2)·Vm·Im-{(1-S) / 2}·Vm·Im·cos(2ωt)=Vdc·Idc, and the following equation

[10] is derived. Im / Idc=2Vdc / Vm{1-(1-S)cos(2ωt)}...

[10]

[0102] Substituting equation

[10] into equation [9] and expressing it in terms of the DC voltage command value Vdc*, drec is expressed by equation

[11] . drec=2(1-k)·Vdc*|sin(ωt)| / [Vm{1-(1-S)cos(2ωt)}]···

[11]

[0103] However, if the distribution rate k is less than the predetermined value km, the adjustment value S is set to the value obtained by dividing the distribution rate k by the predetermined value km in accordance with setting condition A, so equation

[11] becomes equation

[12] . drec=2(1-k)·Vdc*|sin(ωt)| / [Vm{1-(1-k / km)cos(2ωt)}]···

[12]

[0104] Furthermore, when the distribution ratio k is greater than or equal to a predetermined value of km, the adjustment value S is set to 1 in accordance with setting condition B, so equation

[11] becomes equation

[13] . drec=2(1-k)·Vdc*|sin(ωt)| / Vm···

[13]

[0105] (4-2) Setting of discharge current ratio dc When the discharge current ic that flows from capacitor C4 to inverter 5 is introduced, the discharge power Pc output from power buffer circuit 4 is also the product of the voltage across capacitor C4 Vc and the discharge current ic. From equation [4], we get Pc = (k / 2)·Vm·Im + {(Sk) / 2}Vm·Im·cos(2ωt) = Vc·ic, which leads to equation

[14] . ic=(Vm Im / 2Vc) {k+(Sk) cos(2ωt)}

[14]

[0106] The discharge current ratio dc is the value obtained by dividing the discharge current ic by the DC current Idc, and is expressed by the following equation

[15] . dc=(Vm·Im / 2Vc·Idc)·{k+(Sk)·cos(2ωt)}···

[15]

[0107] Substituting equation

[10] into equation

[15] and expressing it in terms of the DC voltage command value Vdc*, dc is expressed by equation

[16] . dc=Vdc*·{k+(Sk)·cos(2ωt)} / [Vc·{1-(1-S)cos(2ωt)}]···

[16]

[0108] However, if the distribution rate k is less than the predetermined value km, the adjustment value S is set to the value obtained by dividing the distribution rate k by the predetermined value km in accordance with setting condition A, so equation

[16] becomes equation

[17] . dc=Vdc*·{k+(k / km-k)·cos(2ωt)} / [Vc·{1-(1-k / km)cos(2ωt)}]···

[17]

[0109] Furthermore, when the distribution ratio k is greater than or equal to a predetermined value of km, the adjustment value S is set to 1 in accordance with setting condition B, so equation

[16] becomes equation

[18] . dc=Vdc*·{k+(1-k)·cos(2ωt)} / Vc···

[18]

[0110] (4-3) Maximum value of DC voltage The DC voltage is determined by the voltage on the power supply side and the rectified current ratio drec, and the voltage of the power buffer circuit and the discharge current ratio dc, and the DC voltage is expressed by the following equation. Vdc=drec·Vrec+dc·Vc···

[19]

[0111] Furthermore, both equations representing the rectified current ratio drec

[11] and the discharge current ratio dc

[16] are functions of the DC voltage command value (Vdc*), and in order to obtain a high DC voltage, the current ratio should be set to a large value based on the following constraints.

[0112] Constraints: drec + dc + dz = 1, where 0 ≤ drec ≤ 1, 0 ≤ dc ≤ 1, and 0 ≤ dz ≤ 1.

[0113] Figure 5 shows the waveforms of the power converter 100 according to this embodiment. Here, the waveform of the first control at Vc=1.59 and k=0.75 is shown, and the DC voltage is selected so that the current ratio dz, obtained by subtracting drec and dc from 1, is positive at all phase angles.

[0114] More specifically, as shown in the following sections, we focus on the characteristic that dz has a minimum value, and determine the current ratio from Vc and k at the phase angle ωt where dz(ωt)=0, and find the command value Vdc* at which the DC voltage is at its maximum value. In this case, since ωt=5π / 12, Vdc*=1.21.

[0115] (4-3-1) Flow ratio in the first control As described in the section of "(3-1) First Control", when km = 1, since the range where the distribution ratio k is smaller than the predetermined value km is 0 ≦ k < 1, according to the setting condition A, S is set to k / 1 = k, the expression

[12] representing the rectification current ratio is represented by expression

[20] , and the expression

[17] representing the discharge current ratio is represented by expression

[21] . drec = 2(1 - k)·Vdc*·|sin(ωt)| / [Vm{1 - (1 - k)cos(2ωt)}] ···

[20] dc = k·Vdc* / [Vc·{1 - (1 - k)cos(2ωt)}] ···

[21]

[0116] Here, since cos(2ωt) = 1 - 2sin 2 (ωt), expression

[22] is derived from expression

[20] , and expression

[23] is derived from expression

[21] . drec = 2(1 - k)·Vdc*·|sin(ωt)| / [Vm{2(1 - k)sin 2 (ωt) + k}] ···

[22] dc = k·Vdc* / [Vc·{2(1 - k)sin 2 (ωt) + k}] ···

[23]

[0117] Also, since dz = 1 - drec - dc, the following expression

[24] is derived from expressions

[22] and

[23] . dz = 1 - 2(1 - k)·Vdc*·|sin(ωt)| / [Vm{2(1 - k)sin 2 (ωt) + k}] - [k·Vdc* / [Vc{2(1 - k)sin 2 (ωt) + k}]] ···

[24]

[0118] Differentiating expression

[24] with respect to the phase angle, the following expression

[25] is obtained. dz´ = -2Vdc*·(1 - k)·cos(ωt) / [Vm{2(1 - k)sin 2 (ωt) + k}] +[8Vdc*·(1-k)] 2 cos(ωt)sin 2 (ωt) / [Vm{2(1-k)sin 2 (ωt)+k} 2 ]] +[4Vdc*(1-k)k cos(ωt)sin(ωt) / [Vc{2(1-k)sin 2 (ωt)+k} 2 ]]···[twenty five]

[0119] The value of ωt for which dz'=0 is given by the following equation

[26] . ωt=-arcsin[{(Vm 2 k 2 -2V 2 k 2 +2Vc 2 k) 1 / 2 / (2Vc·k-2Vc)}-{Vm·k / (2Vc·k-2Vc)}]···

[26]

[0120] Using equation

[26] , we calculate the phase ωt at which the minimum value is obtained depending on k and Vc, and by setting dz=0 in equation

[24] , we transform it into equation

[27] to find the maximum output voltage Vdc* / Vm. Vdc* / Vm=1 / [[2(1-k)·sin(ωt) / {2(1-k)sin 2 (ωt)+k}]+[k / (Vc / Vm){2(1-k)sin 2 (ωt)+k}]]···

[27]

[0121] From equation

[27] , the normalized DC voltage (Vdc* / Vm) for Vc and k is obtained, and in Figure 4A, under constant voltage Vc across capacitor C4, the DC voltage Vdc is controlled to increase with increasing distribution ratio k. Also, under constant distribution ratio k, the DC voltage Vdc is controlled to increase with increasing voltage Vc across capacitor C4.

[0122] (4-3-2) Flow ratio in the second control As described in section (3-2) Second Control, when km=0, the control unit 10 does not have a range where the distribution ratio k is less than the predetermined value km, and since km≦k, S is set to 1 in accordance with setting condition B, and in the range of 0≦k≦1, the straightened flow ratio is expressed by equation

[13] and the discharge flow ratio is expressed by equation

[18] .

[0123] Here, we find the condition for 0 ≤ dz. Since dz = 1 - derc - dc, from equations

[13] and

[18] we derive the following equation

[28] . dz=1-2(1-k)·Vdc*·sin(ωt) / Vm-Vdc*{k+(1-k)·cos(2ωt)} / Vc···

[28]

[0124] Since dz has a local minimum, we differentiate the above equation with respect to the phase angle to obtain equation

[29] . dz´=2(1-k)Vdc*·cos(ωt){2sin(ωt) / Vc-1 / Vm}···

[29]

[0125] From equation

[29] , dz is minimized at the phase angle sin(ωt) = Vc / 2Vm. Setting dz=0 at this phase angle and rearranging equation

[28] in terms of Vdc* / Vm, we obtain equation

[30] . Vdc* / Vm=4(Vc / Vm) / {2(1-k)(Vc / Vm) 2 +4}···

[30]

[0126] From the above equation, when we find the normalized DC voltage (Vdc* / Vm) for Vc and k, in Figure 4B, under the condition that the voltage Vc across capacitor C4 is constant, the DC voltage Vdc is controlled to increase with increasing distribution ratio k. Also, under the condition that the distribution ratio k is constant, the DC voltage Vdc is controlled to increase with increasing voltage Vc across capacitor C4.

[0127] (4-3-3) Flow ratio in the third control + second control As described in the section of "(3-3) First control + Second control", when the predetermined value km is neither 0 nor 1 and 0 ≦ k < km, the control unit 10 sets S = k / km in accordance with the setting condition A. In FIG. 4C, in the range of 0 ≦ k < 0.5, S is set to k / 0.5, and the rectifying current ratio formula

[12] and the discharging current ratio formula

[17] are represented by the following formula

[31] and formula

[32] . drec = 2(1 - k)·Vdc*·|sin(ωt)| / [Vm{1 - (1 - 2k)·cos(2ωt)}]···

[31] dc = Vdc*·{k + k·cos(2ωt)} / [Vc·{1 - (1 - 2k)·cos(2ωt)}]···

[32]

[0128] Here, since cos(2ωt) = 1 - 2sin 2 (ωt), formula

[33] is derived from formula

[31] , and formula

[34] is derived from formula

[32] . drec = 2Vdc*·(1 - k)|sin(ωt)| / [Vm{2(1 - 2k)·sin 2 (ωt)}]···

[33] dc = Vdc*·{-2ksin 2 (ωt) + 2k} / [Vc·{2(1 - 2k)·sin 2 (ωt) + 2k}]···

[34]

[0129] Also, since dz = 1 - drec - dc, the following formula

[35] is derived from formula

[33] and formula

[34] . dz = 1 - 2Vdc*·(1 - k)|sin(ωt)| / [Vm{2(1 - 2k)·sin 2 (ωt) + 2k}] - [Vdc*·{-2ksin 2 (ωt) + 2k} / [Vc·{2(1 - 2k)·sin 2 (ωt) + 2k}]]···

[35]

[0130] Differentiating equation

[35] with respect to the phase angle, we obtain equation

[36] . dz´=4Vdc*·k·cos(ωt)sin(ωt) / [Vc{2(1-2k)sin 2 (ωt)+2k}] -2Vdc*·(1-k)·cos(ωt) / [Vm{2(1-2k)sin 2 (ωt)+2k}] +[8Vdc*·(1-2k)(1-k)cos(ωt)sin 2 (ωt) / [Vm{2(1-2k)sin 2 (ωt)+2k} 2 ]] +[4Vdc*·(1-2k)·cos(ωt)sin(ωt)(2k-2ksin 2 (ωt) / [Vc{2(1-2k)sin 2 (ωt)+2k} 2 ]]···

[36]

[0131] The value of ωt for which dz=0 is given by the following equation

[37] . ωt=-arcsin[{(Vm 2 k 2 -2V 2 k 2 +Vc 2 k) 1 / 2 / (2Vc·k-Vc)}-{Vm·k / (2Vc·k-Vc)}]····

[37]

[0132] Using equation

[37] , we calculate the phase ωt at which the minimum value is obtained depending on k and Vc, and by setting dz=0 in equation

[35] , we transform it into equation

[38] to find the maximum output voltage Vdc* / Vm. Vdc* / Vm=1 / [[(1-k)·sin(ωt) / {(1-2k)sin 2 (ωt)+k}]+[{-ksin 2 (ωt)+k} / (Vc / Vm){(1-2k)sin 2 (ωt)+k}]]···

[38]

[0133] From equation

[38] , the normalized DC voltage (Vdc* / Vm) for Vc and k is obtained, and in Figure 4C, under constant voltage Vc across capacitor C4, the DC voltage Vdc is controlled to increase with increasing distribution ratio k. Also, under constant distribution ratio k, the DC voltage Vdc is controlled to increase with increasing voltage Vc across capacitor C4.

[0134] On the other hand, in the range of km = 0.5 ≤ k ≤ 1, the control unit 10 sets S = 1 in accordance with setting condition B, which corresponds to the second control.

[0135] (5) Setting of adjustment value S (5-1) Setting the adjustment value S according to the load When the AC component Prec^ is input to inverter 5, the power is large in the high-load region, and the mechanical fluctuations on the load side become large. Therefore, in the high-load region, the mechanical fluctuations on the load side can be reduced by buffering the AC component Prec^ with capacitor C4.

[0136] Conversely, in the low-load region, the power is small and the mechanical fluctuations on the load side are also small, so a portion of the AC component Prec^ can be borne by the load side.

[0137] Figure 6A is a flowchart showing the process of setting the adjustment value S according to the load.

[0138] (Step S1) In Figure 6A, the control unit 10 detects the load L in step S1. The load here refers to the power supplied to the inductive load 6 in Figure 1, and may be a substitute value such as temperature, humidity, or flow rate that is proportional to the power.

[0139] (Step S2) In step S2, the control unit 10 determines whether the load L is greater than the first threshold value th1 and the distribution ratio k is equal to or greater than a predetermined value km. If the control unit 10 determines that "the load L is greater than the first threshold value th1 and the distribution ratio k is equal to or greater than the predetermined value km", it proceeds to step S3; otherwise, it proceeds to step S4.

[0140] (Step S3) In step S3, the control unit 10 sets the adjustment value S to 1. Since the load L is greater than the first threshold value th1, the control unit 10 determines that it is a high load.

[0141] Since the distribution ratio k is greater than the predetermined value km, the control is assumed to be the control in which km = 1 in the first control described in FIG. 4A, km = 0 in the second control described in FIG. 4B, and k ≧ km in the second control described in FIG. 4C.

[0142] (Step S4) In step S4, the control unit 10 determines whether the load L is less than the second threshold value th2 (where th1 ≧ th2) and the distribution ratio k is less than the predetermined value km. If the control unit 10 determines that "the load L is less than the second threshold value th2 and the distribution ratio k is less than the predetermined value km", it proceeds to step S5; otherwise, it returns to step S1.

[0143] (Step S5) In step S5, the control unit 10 sets the adjustment value S to k / km. Since the load L is less than the second threshold value th2, the control unit 10 determines that it is a low load or a medium load.

[0144] Since the distribution ratio k is less than the predetermined value km, the control is assumed to be the control in which k < km in the first control described in FIG. 4A and k < km in the third control described in FIG. 4C.

[0145] (5-2) Setting of the adjustment value S according to the rotational speed of the motor Here, as the inductive load 6 in FIG. 1, the motor of the compressor mounted on the air conditioner will be assumed and described.

[0146] When the AC component Prec^ is input to inverter 5, power fluctuations become large in the region where the motor speed of the compressor, which is a low torque load, is high, so a configuration is needed to suppress vibrations in the mechanical system.

[0147] Therefore, in the high-speed region, the torque fluctuation on the load side can be reduced by buffering the AC component Prec^ with capacitor C4.

[0148] Conversely, in the low-speed region (low-voltage region), the power is small and the torque on the load side is also small, so a portion of the AC component Prec^ can be borne by the load side.

[0149] Figure 6B is a flowchart showing the process of setting the adjustment value S according to the rotational speed.

[0150] (Step S11) In Figure 6B, the control unit 10 detects the motor's rotational speed N in step S11. Alternatively, the operating frequency may be detected instead of the rotational speed.

[0151] (Step S12) In step S12, the control unit 10 determines whether the rotational speed N is greater than the first rotational speed N1 and the distribution ratio k is greater than or equal to a predetermined value of km. If the control unit 10 determines that "the rotational speed N is greater than the first rotational speed N1 and the distribution ratio k is greater than or equal to a predetermined value of km", it proceeds to step S13; otherwise, it proceeds to step S14.

[0152] (Step S13) In step S13, the control unit 10 sets the adjustment value S to 1. The control unit 10 determines that the rotational speed N is high speed rotation because it is greater than the first rotational speed N1.

[0153] Since the distribution ratio k is greater than the predetermined value km, it becomes the control assuming km = 1 in the first control described in FIG. 4A, km = 0 in the second control described in FIG. 4B, and k ≧ km in the second control described in FIG. 4C.

[0154] (Step S14) In step S14, the control unit 10 determines whether the rotational speed N is less than the second rotational speed N2 (however, N1 ≧ N2) and whether the distribution ratio k is less than the predetermined value km. If the control unit 10 determines that "the rotational speed N is less than the second rotational speed N2 and the distribution ratio k is less than the predetermined value km", it proceeds to step S15; otherwise, it returns to step S11.

[0155] (Step S15) In step S15, the control unit 10 sets the adjustment value S to k / km. Since the rotational speed N is less than the second rotational speed N2, the control unit 10 determines that it is a low-speed rotation or a medium-speed rotation.

[0156] Since the distribution ratio k is less than the predetermined value km, it becomes the control assuming k < km in the first control described in FIG. 4A and k < km in the third control described in FIG. 4C.

[0157] (6) Modified Example (6-1) First Modified Example In FIG. 4C, when the distribution ratio k is in the range of 0 ≦ k < km, the third control in which the adjustment value S is set to S = k / km is executed. When the distribution ratio k is in the range of km ≦ k ≦ 1, the second control in which S = 1 is set is executed. The predetermined value km is the switching point between the third control and the second control.

[0158] However, such a switching point is not limited to one, and there may be a plurality of switching points. For example, in addition to the predetermined value km, if a second predetermined value kn greater than the predetermined value km and between 0 and 1 is provided, the control unit 10 can arbitrarily switch the adjustment value S to either k / km or k / kn when the distribution ratio k is in the range of 0 ≦ k < kn.

[0159] Figure 7A is a graph showing the relationship between the distribution ratio k and the buffering power Pbuf in the third control of the power converter 100 according to the first modified example. In Figure 7A, the predetermined value km = 0.5 and the second predetermined value kn = 0.8 are shown as examples.

[0160] In Figure 7A, when the distribution ratio k is in the range of 0 ≤ k < 0.2 and 0.3 ≤ k ≤ 0.5, the control unit 10 adopts a predetermined value km = 0.5 and sets the adjustment value S to S = k / 0.5, and controls the discharge power Pc so that the buffering power Pbuf = k·Vm·Im·cos(2ωt) based on equation [3].

[0161] Furthermore, when the distribution ratio k is in the range of 0.2 ≤ k < 0.3 and 0.5 ≤ k < 0.8, the control unit 10 adopts a second predetermined value kn = 0.8 and sets the adjustment value S to S = k / 0.8, and controls the discharge power Pc so that the buffering power Pbuf = (k / 1.6) · Vm · Im · cos(2ωt) based on equation [3].

[0162] Therefore, the first modification is useful when you want to change the rate of increase or decrease of the buffering power Pbuf with respect to the distribution ratio k only when the distribution ratio k is within a specific range.

[0163] Furthermore, the first modification has the advantage that the control unit 10 can change the adjustment value S without changing the distribution ratio k. Specifically, while keeping the distribution ratio k fixed at k=0.3, it is possible to change Pbuf=0.3 when the predetermined value km=0.5 to Pbuf=0.188 when the second predetermined value kn=0.8.

[0164] When using a second predetermined value kn for control instead of a predetermined value km, the range of the distribution ratio k is arbitrarily changed by the control unit 10 according to the load applied to the inductive load 6.

[0165] Meanwhile, in the range kn=0.8≦k≦1, the control unit 10 sets the adjustment value S to S=1 and executes the second control, controlling the discharge power Pc so that the buffering power Pbuf=(1 / 2)Vm·Im·cos(2ωt).

[0166] (6-2) Second Modified Example In FIG. 4C, third control is executed in which the adjustment value S is set to S = k / km when the distribution ratio k is in the range of 0 ≦ k < km, and second control is executed in which the adjustment value S is set to S = 1 when the distribution ratio k is in the range of km ≦ k ≦ 1, and a predetermined value km is the switching point between the third control and the second control.

[0167] In such a case, it is not possible to switch from the third control to the second control in the middle of the range where the distribution ratio k is 0 ≦ k < km. Therefore, a control that can be switched to the second control in the middle of the third control is required.

[0168] In the second modified example, a first reference value km1 and a second reference value km2 that define the upper and lower limits of the range in which the control based on the predetermined value km is restricted are set in advance within the range of possible values of the distribution ratio k. The first reference value km1 is smaller than the second reference value km2.

[0169] FIG. 7B is a graph showing the relationship between the distribution ratio k and the buffering power Pbuf in the third control of the power conversion device 100 according to the second modified example. In FIG. 7B, the graph is described by taking as an example a predetermined value km = 0.5, a first reference value km1 = 0.3, and a second reference value km2 = 1.

[0170] In FIG. 7B, originally, since the control unit 10 has a predetermined value km = 0.5, in the range where the distribution ratio k is 0 ≦ k < 0.5, the adjustment value S is set to S = k / 0.5, and the discharge power Pc is controlled so that the buffering power Pbuf = k·Vm·Im·cos(2ωt) based on Equation [3].

[0171] However, in the range where the distribution ratio k is km1 ≦ k ≦ km2, the third control based on the predetermined value km = 0.5 is restricted, and the second control is executed in this range. Actually, the third control based on the predetermined value km = 0.5 is executed only in the range where the distribution ratio k is 0 ≦ k < 0.3, and the second control is executed in the range where the distribution ratio k is 0.3 ≦ k ≦ 1.

[0172] Therefore, the second modification is useful when you want to force the second control to be performed within a specific range of the distribution ratio k.

[0173] (6-3) Third Variation Figure 7C is a graph showing the relationship between the distribution ratio k and the buffering power Pbuf in the third control of the power converter 100 according to the third modified example. Figure 7C shows the second modified example applied to the third control based on the predetermined value km and the second predetermined value kn explained in Figure 7A.

[0174] In the third modified example, a first reference value km1 and a second reference value km2 are predetermined, defining the upper and lower limits of the range within which the distribution rate k can take, and the range in which the control based on a predetermined value km and the third control based on a second predetermined value kn are restricted. The first reference value km1 is smaller than the second reference value km2.

[0175] In Figure 7C, the graph is illustrated using the following examples: predetermined value km=0.5, second predetermined value kn=0.8, first reference value km1=0.3, and second reference value km2=1.

[0176] In Figure 7C, the control unit 10 would normally set the adjustment value S to k / 0.5 when the distribution ratio k is in the range of 0 ≤ k < 0.2 and 0.3 ≤ k ≤ 0.5, and control the discharge power Pc so that the buffering power Pbuf = k·Vm·Im·cos(2ωt). Furthermore, when the distribution ratio k is in the range of 0.2 ≤ k < 0.3 and 0.5 ≤ k < 0.8, the adjustment value S is set to S = k / 0.8, and control the discharge power Pc so that the buffering power Pbuf = (k / 1.6)·Vm·Im·cos(2ωt).

[0177] However, in the range where the distribution rate k is 0.3 ≤ k ≤ 1, control based on the predetermined value km = 0.5 and the second predetermined value kn = 0.8 is restricted, and the second control is executed in that range. In practice, the third control based on the predetermined value km = 0.5 is executed only in the range where the distribution rate k is 0 ≤ k < 0.2, and the third control based on the second predetermined value kn = 0.8 is executed only in the range where the distribution rate k is 0.2 ≤ k < 0.3.

[0178] Therefore, the third modification, like the second modification, is useful when we want to force the second control to be performed within a specific range of the distribution ratio k.

[0179] (7) Characteristics (7-1) In the power converter 100, the control unit 10 obtains charging power Pl by multiplying the rectified power Prec by a distribution ratio k between 0 and 1, and controls the power flow such that the sum of the directly converted power Prec1 (obtained by subtracting the charging power Pl from the rectified power Prec) and the discharge power Pc is the DC link power Pdc. The control unit 10 controls the amplitude of the buffering power Pbuf so that it is proportional to an adjustment value S set according to the distribution ratio k, and sets the adjustment value S to the value obtained by dividing the distribution ratio by the predetermined value km when the distribution ratio is less than the predetermined value km, or sets the adjustment value to 1 when the distribution ratio k is greater than or equal to the predetermined value km.

[0180] In this power converter 100, the buffering power of the power buffer circuit 4 can be varied by switching the setting value of the adjustment value S based on the distribution ratio k and a predetermined value km. Therefore, the AC component of the power supply power shared by the power buffer circuit 4 and the voltage of the DC link 7 can be controlled individually.

[0181] (7-2) The control unit 10 makes the DC component of the discharge power Pc equal to the DC component of the charge power Pl, and sets the AC component of the discharge power Pc to a value obtained by subtracting the distribution ratio k from the adjustment value S and multiplying the AC component Prec^ of the rectified power Prec by minus 1, and sets the buffering power Pbuf to a value obtained by multiplying the AC component Prec^ of the rectified power Prec by minus 1, and the adjustment value S.

[0182] (7-3) In the power converter 100, the discharge power Pc is the sum of the DC component and the AC component. The DC component is the value obtained by dividing the product of the peak value Vm of the single-phase AC voltage and the peak value Im of the single-phase AC current by 2 and multiplying by the distribution ratio k. The AC component is the value obtained by dividing the product of the peak value Vm of the single-phase AC voltage and the peak value Im of the single-phase AC current by 2, multiplying by the cosine value which is twice the phase ωt of the single-phase AC voltage, and then multiplying by the value obtained by subtracting the distribution ratio k from the adjustment value S.

[0183] (7-4) In the power converter 100, the control unit 10 sets the adjustment value S to the distribution ratio k when the predetermined value km is 1, within the range of the distribution ratio being 0 or greater and less than 1.

[0184] (7-5) In the power converter 100, the control unit 10 sets the adjustment value S to 1 when the predetermined value km is 0, within the range of distribution ratio between 0 and 1.

[0185] (7-6) In the power converter 100, when the distribution ratio k is greater than or equal to 0 and less than a predetermined value of km, the adjustment value S is set to the value obtained by dividing the distribution ratio k by the predetermined value of km. When the distribution ratio k is greater than or equal to a predetermined value of km and less than or equal to 1, the adjustment value S is set to 1.

[0186] (7-7) In the power converter 100, the control unit 10 sets the adjustment value S to 1 when the load L is greater than a first threshold th1 (high load) and the distribution ratio k is greater than or equal to a predetermined value of km. Furthermore, when the load L is less than a second threshold th2 (low load) and the distribution ratio k is less than a predetermined value of km, the control unit 10 sets the adjustment value S to the value obtained by dividing the distribution ratio k by the predetermined value of km.

[0187] In this power converter 100, in the high-load region, the AC component Prec^ is buffered by capacitor C4, thereby reducing mechanical fluctuations on the load side. Conversely, in the low-load region, the power is small and the mechanical fluctuations on the load side are also small, so a portion of the AC component Prec^ can be borne by the load side.

[0188] (7-8) In the power converter 100, when the motor speed N of the motor included in the load L is a high-speed rotation speed greater than the first rotation speed N1 and the distribution ratio k is greater than or equal to a predetermined value of km, the adjustment value S is set to 1. When the motor speed N is a low-speed rotation speed less than the second rotation speed N2 and the distribution ratio k is less than the predetermined value of km, the adjustment value S is set to the value obtained by dividing the distribution ratio k by the predetermined value of km.

[0189] In this power converter 100, in the high rotational speed range, the AC component Prec^ is buffered by capacitor C4, thereby reducing torque fluctuations on the load side. Conversely, in the low rotational speed range, the power is small and the torque on the load side is also small, so a portion of the AC component Prec^ can be borne by the load side.

[0190] (7-9) In the power converter 100, when a second predetermined value kn (where kn > km) different from the predetermined value km is set in the control unit 10, in a specific range within the range of possible distribution rates k that is less than or equal to the second predetermined value kn, the adjustment value S is set to the value obtained by dividing the distribution rate k by the second predetermined value kn.

[0191] In this power converter 100, the rate of increase or decrease of buffering power Pbuf relative to the distribution ratio k can be changed only when the distribution ratio k is within a specific range. In addition, the control unit 10 can change the adjustment value S without changing the distribution ratio k.

[0192] (7-10) In a power converter, the control unit 10 has set a first reference value km1 and a second reference value km2 (where kn ≥ km) which define the upper and lower limits of the range in which control based on a predetermined value km is restricted within the range in which the distribution ratio k can take, and the adjustment value S is set to 1 when the distribution ratio k is greater than or equal to the first reference value km1 and less than or equal to the second reference value km2.

[0193] In this power converter 100, the second control can be forcibly executed when the distribution ratio k is within a specific range.

[0194] (7-11) In the power converter 100, the control unit 10 controls the DC voltage applied to the DC link 7 to its command value, the DC voltage command value Vdc*, by setting the rectified current ratio drec and the discharge current ratio dc. The rectified current ratio drec is the current ratio at which the rectifier circuit 3 directly supplies converted power Prec1 to the inverter 5. The discharge current ratio dc is the current ratio at which the capacitor discharges.

[0195] When the distribution ratio k is less than a predetermined value km, the adjustment value S is set to the value obtained by dividing the distribution ratio k by the predetermined value km, and the rectified current ratio drec is set to the value obtained by dividing the product of the DC voltage command value Vdc*, the sine value of the phase ωt of the single-phase AC voltage, and the value obtained by subtracting the distribution ratio k from 1 and multiplying by 2, by the product of the peak value Vm of the single-phase AC voltage and the first relational value U which varies depending on the value obtained by subtracting the adjustment value S from 1. Specifically, the first relational value U is expressed as 1-(1-S)cos(2ωt).

[0196] The discharge current ratio dc is set to the value obtained by dividing the product of the DC voltage command value Vdc* and the second relational value V, which varies depending on the value obtained by subtracting the distribution ratio k from the adjustment value S and the distribution ratio k, by the product of the voltage across capacitor C4 Vc and the first relational value U. Specifically, the second relational value V is expressed as k + (Sk)cos(2ωt).

[0197] When the distribution ratio k is greater than or equal to a predetermined value of km, the adjustment value S is set to 1, and the rectified current ratio drec is set to the value obtained by dividing the product of the DC voltage command value Vdc*, the sine value of the phase ωt of the single-phase AC voltage, and the value obtained by subtracting the distribution ratio k from 1 and multiplying by 2, by the peak value Vm of the single-phase AC voltage. The discharge current ratio dc is set to the value obtained by dividing the product of the DC voltage command value Vdc*, the value obtained by subtracting the distribution ratio k from 1, and a third relational value W that varies depending on the distribution ratio k, by the voltage across capacitor C4 Vc. Specifically, the third relational value W is expressed as k + (1-k)cos(2ωt).

[0198] A charging current is input to capacitor C4, which is the value obtained by multiplying the first current (the value obtained by dividing the rectified power Prec by the first voltage obtained by full-wave rectification of the single-phase AC voltage) by the distribution ratio k.

[0199] <Second Embodiment> In the second embodiment, the circuit configuration of the power converter 100 is the same as in the first embodiment, but the control is different. Here, the control in the second embodiment will be described.

[0200] (1) Control The rectifier circuit 3 receives a single-phase AC voltage Vin as input and outputs a rectified power Prec represented by equation [1] described in the first embodiment, with an input power factor of 1.

[0201] In the first embodiment, the control unit 10 uses an adjustment value (S), which is the ratio of the AC component Prec^ to the AC component of Prec^ that is absorbed by the power buffer circuit 4, to control the discharge power Pc so that the buffering power Pbuf is equal to the absolute value of the AC component Prec^.

[0202] On the other hand, in the second embodiment, the control unit 10 uses an adjustment value (1-S), which is the ratio of the AC component Prec^ to the AC component of Prec^ that is not absorbed by the power buffer circuit 4, to control the discharge power Pc so that the buffering power Pbuf becomes 0.

[0203] Therefore, the buffering power Pbuf is given by equation

[39] . Pbuf={(1-S) / 2}·Vm·Im·cos(2ωt)···

[39]

[0204] Since Pbuf = Pc - Pl, the discharge power Pc can be expressed by equation

[40] from equation [2] described in the first embodiment and equation

[39] above. Pc=(k / 2)·Vm·Im+{(1-Sk) / 2}Vm·Im·cos(2ωt)···

[40]

[0205] Also, the direct conversion power Prec1, which is the power from the rectifier circuit 3 to the inverter 5, is equal to Prec - Pl. Therefore, the DC link power Pdc = Prec1 + Pc holds.

[0206] Therefore, the DC link power Pdc is expressed by the following equation

[41] . Pdc = Prec1 + Pc =(1 / 2)·Vm·Im - (S / 2)·Vm·Im·cos(2ωt) ···

[41]

[0207] In the second embodiment, similar to the first embodiment, when the distribution ratio k is in a range smaller than a predetermined value km (where 0 ≤ km ≤ 1) set in advance, the control unit 10 sets the adjustment value S to k / km (hereinafter referred to as setting condition A).

[0208] Also, when the distribution ratio k is greater than or equal to the predetermined value km, the control unit 10 sets the adjustment value S to 1 so that the buffering power Pbuf becomes 0 (hereinafter referred to as setting condition B). Hereinafter, specific control will be described.

[0209] (1 - 1) First control When km = 1, since the range where the distribution ratio k is smaller than the predetermined value km is 0 ≤ k < 1, according to setting condition A, the control unit 10 sets S = k / 1 = k, and controls the discharge power Pc so that the buffering power Pbuf = {(1 - k) / 2}·Vm·Im·cos(2ωt).

[0210] Also, in the range where the distribution ratio k = km = 1, according to setting condition B, the control unit 10 sets S = 1, and controls the discharge power Pc so that the buffering power Pbuf = 0. In this embodiment, the control based on the above - mentioned predetermined value km = 1 is referred to as "first control".

[0211] Figure 8A is a graph showing the relationship between the distribution ratio k, buffering power Pbuf, and DC voltage Vdc in the first control (km=1). However, the value of buffering power Pbuf on the graph is not the actual value, but a normalized value using Vm·Im·cos(2ωt)=1. Similarly, the value of DC voltage Vdc is not the actual value, but a normalized value using Vdc / Vm. Furthermore, the voltage across capacitor C4 Vc is also normalized using Vc / Vm, and the relationship between DC voltage Vdc and the voltage across capacitor C4 is also shown.

[0212] In Figure 8A, in the range 0 ≤ k < 1, the buffering power Pbuf is controlled to be proportional to the distribution ratio k with a slope of -1 / 2, and when k = km = 1, the buffering power Pbuf becomes 0.

[0213] (1-2) Second control When km=0, the control unit 10 determines that there is no range in which the distribution ratio k is less than the predetermined value km, and therefore km≦k. It then sets S=1 according to setting condition B and controls the discharge power Pc so that the buffering power Pbuf=0 in the range 0≦k≦1. In this embodiment, the control based on the predetermined value km=0 described above is called the "second control".

[0214] Figure 8B is a graph showing the relationship between the distribution ratio k, buffering power Pbuf, and DC voltage Vdc in the second control (km=0). However, the value of buffering power Pbuf on the graph is not the actual value, but a normalized value using Vm·Im·cos(2ωt)=1. Similarly, the value of DC voltage Vdc is not the actual value, but a normalized value using Vdc / Vm. Furthermore, the voltage across capacitor C4 Vc is also normalized using Vc / Vm, and the relationship between DC voltage Vdc and the voltage across capacitor C4 is also shown.

[0215] In Figure 8B, the buffering power Pbuf is constant at 0. This means that, within the range of 0 ≤ k ≤ 1, the buffering power Pbuf is controlled to be 0 regardless of the distribution ratio k.

[0216] The 3rd control + the 2nd control (1-3) When the predetermined value km is neither 0 nor 1 and 0 ≤ k < km, the control unit 10 sets S = k / km in accordance with the setting condition A, and controls the discharge power Pc so that the buffering power Pbuf = {(1 - k / km) / 2}Vm·Im·cos(2ωt). In the present embodiment, the control based on the above-described predetermined value km being neither 0 nor 1 and 0 ≤ k < km is referred to as "the 3rd control".

[0217] FIG. 8C is a graph showing the relationship between the distribution ratio k, the buffering power Pbuf, and the DC voltage Vdc in the 3rd control (0 ≤ k < km). However, as an example, km = 0.5 is adopted. Also, the value of the buffering power Pbuf on the graph is not the actual value but is normalized assuming Vm·Im·cos(2ωt) = 1. Similarly, the value of the DC voltage Vdc is not the actual value but is normalized by Vdc / Vm. Further, the voltage Vc across the capacitor C4 is also normalized by Vc / Vm, and the DC voltage Vdc also shows the relationship with the voltage Vc across the capacitor C4 together.

[0218] In FIG. 8C, in the range of 0 ≤ k < 0.5, S is set to k / 0.5, and Pbuf = {(1 / 2) - k}·Vm·Im·cos(2ωt). In the range of 0 ≤ k < 0.5, the buffering power Pbuf is controlled to be proportional to the distribution ratio k with a slope of -1.

[0219] On the other hand, when km = 0.5 ≤ k ≤ 1, the control unit 10 sets S = 1 in accordance with the setting condition B, and controls the discharge power Pc so that the buffering power Pbuf = 0. This corresponds to the 2nd control.

[0220] Therefore, in the range of 0.5 ≤ k ≤ 1, the buffering power Pbuf is controlled to be 0 regardless of the value of the distribution ratio k.

[0221] (2) Setting of the current passing ratio (2-1) Setting of the rectification current passing ratio drec As described above, the second embodiment is obtained by replacing "S" of the adjustment value in the first embodiment with "1 - S".

[0222] Therefore, the rectification current ratio drec in the second embodiment is expressed by Equation

[42] obtained by replacing "S" of the adjustment value in Equation

[11] in the first embodiment with "1 - S". drec = 2(1 - k)·Vdc*·|sin(ωt)| / [Vm{1 - Scos(2ωt)}] ···

[42]

[0223] [[ID=​​​​​​​​​​​​​​​​​​​​​​​​​​​ dc=Vdc*·{k+(1-k / km-k)·cos(2ωt)} / [Vc·{1-(k / km)cos(2ωt)}]···

[46]

[0227] Furthermore, when the distribution rate k is greater than or equal to a predetermined value of km, the adjustment value S is set to 1 in accordance with setting condition B, so equation

[45] becomes equation

[47] . dc=Vdc*·{k-kcos(2ωt)} / Vc{1-cos(2ωt)}···

[47]

[0228] (2-3) Maximum value of DC voltage The DC voltage is determined by the voltage on the power supply side and the rectified current ratio drec, and the voltage of the power buffer circuit and the discharge current ratio dc, and the DC voltage is expressed by the following equation (equation described in the first embodiment

[19] ). Vdc = drec·Vrec + dc·Vc

[0229] Furthermore, both equations representing the rectified current ratio drec

[42] and the discharge current ratio dc

[45] are functions of the DC voltage command value (Vdc*), and in order to obtain a high DC voltage, the current ratio should be set to a large value based on the following constraints. Constraints: drec + dc + dz = 1, where 0 ≤ drec ≤ 1, 0 ≤ dc ≤ 1, and 0 ≤ dz ≤ 1.

[0230] Figure 9 shows the waveforms of the power converter 100 according to this embodiment. Here, the waveform of the first control at Vc=1.59 and k=0.75 is shown, and the DC voltage is selected so that the current ratio dz, obtained by subtracting drec and dc from 1, is positive at all phase angles.

[0231] More specifically, focusing on the characteristic where dz has a minimum value, we determine the current ratio from Vc and k at the phase angle ωt where dz(ωt)=0, and find the command value Vdc* at which the DC voltage is at its maximum value. In this case, Vdc*=1.058.

[0232] (3) Variation (3-1) First Variation In FIG. 8C, when the distribution ratio k is in the range of 0 ≦ k < km, the third control in which the adjustment value S is set to S = k / km is executed, and when the distribution ratio k is in the range of km ≦ k ≦ 1, the second control in which S = 1 is set is executed, and a predetermined value km is the switching point between the third control and the second control.

[0233] However, such a switching point is not limited to one, and there may be a plurality of switching points. For example, in addition to the predetermined value km, when a second predetermined value kn greater than the predetermined value km and between 0 and 1 is provided, the control unit 10 can arbitrarily switch the adjustment value S to either k / km or k / kn when the distribution ratio k is in the range of 0 ≦ k < kn.

[0234] FIG. 10A is a graph showing the relationship between the distribution ratio k and the buffering power Pbuf in the third control of the power conversion device 100 according to the first variation. In FIG. 10A, the predetermined value km = 0.5 and the second predetermined value kn = 0.8 are described as examples.

[0235] In FIG. 10A, when the distribution ratio k is in the ranges of 0 ≦ k < 0.3 and 0.4 ≦ k ≦ 0.5, the control unit 10 adopts the predetermined value km = 0.5, sets the adjustment value S to S = k / 0.5, and controls the discharge power Pc based on Equation

[39] so that the buffering power Pbuf = (1 / 2 - k)·Vm·Im·cos(2ωt).

[0236] Also, when the distribution ratio k is in the ranges of 0.3 ≦ k < 0.4 and 0.5 ≦ k < 0.8, the control unit 10 adopts the second predetermined value kn = 0.8, sets the adjustment value S to S = k / 0.8, and controls the discharge power Pc based on Equation

[39] so that the buffering power Pbuf = (1 / 2 - k / 1.6)·Vm·Im·cos(2ωt).

[0237] Therefore, the first variation is useful when it is desired to change the rate of increase and decrease of the buffering power Pbuf with respect to the distribution ratio k only when the distribution ratio k is in a specific range.

[0238] In addition, the first modification example has the advantage that the control unit 10 can change the adjustment value S without changing the distribution ratio k. As a specific example, while fixing the distribution ratio k at k = 0.3, it is possible to change from Pbuf = 0.2 when the predetermined value km = 0.5 to Pbuf = 0.312 when the second predetermined value kn = 0.8.

[0239] When adopting the control by the second predetermined value kn instead of the predetermined value km, the range of the distribution ratio k is arbitrarily changed by the control unit 10 according to the load applied to the inductive load 6.

[0240] On the other hand, when 0.8 ≦ k ≦ 1, the control unit 10 executes the second control by setting the adjustment value S to S = 1, and controls the discharge power Pc so that the buffering power Pbuf = 0.

[0241] (3-2) Second modification example In FIG. 8C, a third control is executed in which the adjustment value S is set to S = k / km when the distribution ratio k is in the range of 0 ≦ k < km, and the second control is executed when the adjustment value S is set to S = 1 when the distribution ratio k is in the range of km ≦ k ≦ 1, and the predetermined value km is the switching point between the third control and the second control.

[0242] In such a case, it is not possible to switch from the third control to the second control in the middle of the range where 0 ≦ k < km. Therefore, a control that can be switched to the second control in the middle of the third control is required.

[0243] In the second modification example, a first reference value km1 and a second reference value km2 that define the upper and lower limits of the range in which the control based on the predetermined value km is limited among the ranges that the distribution ratio k can take are set in advance. The first reference value km1 is smaller than the second reference value km2.

[0244] Figure 10B is a graph showing the relationship between the distribution ratio k and the buffering power Pbuf in the third control of the power converter 100 according to the second modified example. In Figure 10B, the graph is shown using a predetermined value of km=0.5, a first reference value of km1=0.4, and a second reference value of km2=1 as examples.

[0245] In Figure 10B, the control unit 10 is supposed to have a predetermined value of km = 0.5, so it sets the adjustment value S to S = k / 0.5 within the range of the distribution ratio k = 0 ≤ k < 0.5, and controls the discharge power Pc so that the buffering power Pbuf = (1 / 2-k)·Vm·Im·cos(2ωt) based on equation

[39] .

[0246] However, when the distribution ratio k is in the range of km1 ≤ k ≤ km2, the third control based on the predetermined value km = 0.5 is restricted, and the second control is executed in that range. In practice, the third control based on the predetermined value km = 0.5 is executed only when the distribution ratio k is in the range of 0 ≤ k < 0.4, and the second control is executed when the distribution ratio k is in the range of 0.4 ≤ k ≤ 1.

[0247] Therefore, the second modification is useful when you want to force the second control to be performed within a specific range of the distribution ratio k.

[0248] (3-3) Third Variation Figure 10C is a graph showing the relationship between the distribution ratio k and the buffering power Pbuf in the third control of the power converter 100 according to the third modified example. Figure 10C is an application of the second modified example to the third control based on the predetermined value km and the second predetermined value kn explained in Figure 10A.

[0249] In the third modified example, a first reference value km1 and a second reference value km2 are predetermined, defining the upper and lower limits of the range within which the distribution rate k can take, and the range in which the control based on a predetermined value km and the third control based on a second predetermined value kn are restricted. The first reference value km1 is smaller than the second reference value km2.

[0250] In Figure 10C, the graph is illustrated using the following examples: predetermined value km=0.5, second predetermined value kn=0.8, first reference value km1=0.4, and second reference value km2=1.

[0251] In Figure 10C, the control unit 10 would normally set the adjustment value S to k / 0.5 when the distribution ratio k is in the range of 0≦k<0.3 and 0.4≦k≦0.5, as shown in Figure 10A, and control the discharge power Pc so that the buffering power Pbuf = (1 / 2-k)·Vm·Im·cos(2ωt). Furthermore, when the distribution ratio k is in the range of 0.3≦k<0.4 and 0.5≦k<0.8, set the adjustment value S to S=k / 0.8, and control the discharge power Pc so that the buffering power Pbuf = (1 / 2-k / 1.6)·Vm·Im·cos(2ωt).

[0252] However, in the range where the distribution ratio k is 0.4 ≤ k ≤ 1, control based on the predetermined value km = 0.5 and the second predetermined value kn = 0.8 is restricted, and the second control is executed in that range. In practice, the third control based on the predetermined value km = 0.5 is executed only in the range where the distribution ratio k is 0 ≤ k < 0.3, and the third control based on the second predetermined value kn = 0.8 is executed only in the range where the distribution ratio k is 0.3 ≤ k < 0.4.

[0253] Therefore, the third modification, like the second modification, is useful when we want to force the second control to be performed within a specific range of the distribution ratio k.

[0254] (4) Features (4-1) In the power converter 100, the control unit 10 obtains charging power Pl by multiplying the rectified power Prec by a distribution ratio k between 0 and 1, and controls the power flow such that the sum of the directly converted power Prec1 (obtained by subtracting the charging power Pl from the rectified power Prec) and the discharge power Pc is the DC link power Pdc. The control unit 10 controls the amplitude of the buffering power Pbuf so that it is proportional to an adjustment value S set according to the distribution ratio k, and sets the adjustment value S to the value obtained by dividing the distribution ratio k by the predetermined value km when the distribution ratio is less than the predetermined value km, or sets the adjustment value to 1 when the distribution ratio k is greater than or equal to the predetermined value km.

[0255] In this power converter 100, the buffering power of the power buffer circuit 4 can be varied by switching the setting value of the adjustment value S based on the distribution ratio k and a predetermined value km. Therefore, the AC component of the power supply power shared by the power buffer circuit 4 and the voltage of the DC link 7 can be controlled individually.

[0256] (4-2) The control unit 10 makes the DC component of the discharge power Pc equal to the DC component of the charge power Pl, and sets the AC component of the discharge power Pc to a value obtained by subtracting the adjustment value S and the distribution ratio k from 1, and multiplying the AC component Prec^ of the rectified power Prec by minus 1, and sets the buffering power Pbuf to a value obtained by subtracting the adjustment value S from 1, and multiplying the AC component Prec^ of the rectified power Prec by minus 1.

[0257] (4-3) In the power converter 100, the discharge power Pc is the sum of the DC component and the AC component. The DC component is the value obtained by dividing the product of the peak value Vm of the single-phase AC voltage and the peak value Im of the single-phase AC current by 2 and multiplying by the distribution ratio k. The AC component is the value obtained by dividing the product of the peak value Vm of the single-phase AC voltage and the peak value Im of the single-phase AC current by 2, multiplying by the cosine value which is twice the phase ωt of the single-phase AC voltage, and then multiplying by the value obtained by subtracting the adjustment value S and the distribution ratio k from 1.

[0258] (4-4) In the power converter 100, the control unit 10 sets the adjustment value S to the distribution ratio k when the predetermined value km is 1, within the range of the distribution ratio being 0 or greater and less than 1.

[0259] (4-5) In the power converter 100, the control unit 10 sets the adjustment value S to 1 when the predetermined value km is 0, within the range of distribution ratio between 0 and 1.

[0260] (4-6) In the power converter 100, when the distribution ratio k is greater than or equal to 0 and less than a predetermined value of km, the adjustment value S is set to the value obtained by dividing the distribution ratio k by the predetermined value of km. When the distribution ratio k is greater than or equal to a predetermined value of km and less than or equal to 1, the adjustment value S is set to 1.

[0261] (4-7) In the power converter 100, the control unit 10 sets the adjustment value S to 1 when the load L is greater than a first threshold th1 (high load) and the distribution ratio k is greater than or equal to a predetermined value of km. Furthermore, when the load L is less than a second threshold th2 (low load) and the distribution ratio k is less than a predetermined value of km, the control unit 10 sets the adjustment value S to the value obtained by dividing the distribution ratio k by the predetermined value of km.

[0262] In this power converter 100, in the high-load region, the capacitance of capacitor C4 can be reduced by having the AC component Prec^ carried by the load side. Conversely, in the low-load region, since the power is small and the mechanical fluctuations on the load side are also small, a portion of the AC component Prec^ can be carried by capacitor C4.

[0263] (4-8) In the power converter 100, when the motor speed N of the motor included in the load L is a high-speed rotation speed greater than the first rotation speed N1 and the distribution ratio k is greater than or equal to a predetermined value of km, the adjustment value S is set to 1. When the motor speed N is a low-speed rotation speed less than the second rotation speed N2 and the distribution ratio k is less than the predetermined value of km, the adjustment value S is set to the value obtained by dividing the distribution ratio k by the predetermined value of km.

[0264] In this power converter 100, in the high rotational speed range, the capacitance of capacitor C4 can be reduced by shifting the AC component Prec^ to the load side. Conversely, in the low rotational speed range, since the power is small and the torque on the load side is also small, a portion of the AC component Prec^ can be shifted to capacitor C4.

[0265] (4-9) In the power converter 100, when a second predetermined value kn (where kn > km) different from the predetermined value km is set in the control unit 10, in a specific range within the range of possible distribution rates k that is less than or equal to the second predetermined value kn, the adjustment value S is set to the value obtained by dividing the distribution rate k by the second predetermined value kn.

[0266] In this power converter 100, the rate of increase or decrease of buffering power Pbuf relative to the distribution ratio k can be changed only when the distribution ratio k is within a specific range. In addition, the control unit 10 can change the adjustment value S without changing the distribution ratio k.

[0267] (4-10) In a power converter, the control unit 10 has set a first reference value km1 and a second reference value km2 (where kn ≥ km) which define the upper and lower limits of the range in which control based on a predetermined value km is restricted within the range in which the distribution ratio k can take, and the adjustment value S is set to 1 when the distribution ratio k is greater than or equal to the first reference value km1 and less than or equal to the second reference value km2.

[0268] In this power converter 100, the second control can be forcibly executed when the distribution ratio k is within a specific range.

[0269] (4-11) In the power converter 100, the control unit 10 controls the DC voltage applied to the DC link 7 to its command value, the DC voltage command value Vdc*, by setting the rectified current ratio drec and the discharge current ratio dc. The rectified current ratio drec is the current ratio at which the rectifier circuit 3 directly supplies converted power Prec1 to the inverter 5. The discharge current ratio dc is the current ratio at which the capacitor discharges.

[0270] When the distribution ratio k is less than a predetermined value km, the adjustment value S is set to the value obtained by dividing the distribution ratio k by the predetermined value km, and the rectified current ratio drec is set to the value obtained by dividing the product of the DC voltage command value Vdc*, the sine value of the phase ωt of the single-phase AC voltage, and the value obtained by subtracting the distribution ratio k from 1 and multiplying by 2, by the product of the peak value Vm of the single-phase AC voltage and the fourth relational value X which varies with the adjustment value S. Specifically, the fourth relational value X is expressed as 1-Scos(2ωt).

[0271] The discharge current ratio dc is set to the value obtained by dividing the product of the DC voltage command value Vdc* and the fifth relation value Y, which varies depending on the value obtained by subtracting the adjustment value S and the distribution ratio k from 1 and the distribution ratio k, by the product of the voltage across capacitor C4 Vc and the fourth relation value X. Specifically, the fifth relation value Y is expressed as k + (1 - (S + k))cos(2ωt).

[0272] When the distribution ratio k is greater than or equal to a predetermined value of km, with the adjustment value S set to 1, the rectified current ratio drec is set to the value obtained by dividing the product of the DC voltage command value Vdc*, the sine value of the phase ωt of the single-phase AC voltage, and the value obtained by subtracting the distribution ratio k from 1 and multiplying by 2, by the product of the peak value Vm of the single-phase AC voltage and the cosine value obtained by subtracting twice the phase (ωt) of the single-phase AC voltage from 1. The discharge current ratio dc is set to the value obtained by dividing the product of the DC voltage command value Vdc* and the distribution ratio k by the voltage across capacitor C4, Vc.

[0273] A charging current is input to capacitor C4, which is the value obtained by multiplying the first current (the value obtained by dividing the rectified power Prec by the first voltage obtained by full-wave rectification of the single-phase AC voltage) by the distribution ratio k.

[0274] While embodiments of this disclosure have been described above, it should be understood that various modifications to the form and details are possible without departing from the spirit and scope of this disclosure as described in the claims. [Explanation of Symbols]

[0275] 3 Rectifier circuit (power supply section) 5. Inverter (Power Conversion Circuit) 7 DC Link 10 Control Unit 31 1st rectifier circuit (1st rectifier) 32 Second rectifier circuit (second rectifier) 100 Power converter C4 Capacitor drec rectifier current ratio dc discharge current ratio k distribution ratio km Predetermined value km1 First reference value km2 Second Reference Value kn Second predetermined value LH 1st power line LL 2nd power line Im Single-phase AC current peak value PC discharge power Pbuf Buffering Power Pdc (Direct Current Link Power) Pl charging power Prec rectified power Prec1 Direct Conversion Power Vm is the peak value of single-phase AC voltage. Vdc DC voltage Vdc* DC voltage command value

Claims

1. A power supply unit (3) consisting of one or more rectifiers, including a first rectifier (31) that full-wave rectifies a single-phase AC voltage and generates rectified power (Prec), If the power supply unit (3) includes only the first rectifier (31), charging power (Pl) is input from the first rectifier (31), or if it includes a second rectifier (32) different from the first rectifier (31), charging power (Pl) is input from the second rectifier (32), and a capacitor (C4) outputs discharge power (Pc), A power conversion circuit (5) receives a DC link power (Pdc) which is the sum of the rectified power (Prec) and a buffering power (Pbuf), which is the power difference obtained by subtracting the charging power (Pl) from the discharge power (Pc). A control unit (10) controls the power flow, which obtains the charging power (Pl) by multiplying the rectified power (Prec) by a distribution ratio (k) of 0 or more and 1 or less, and the sum of the direct conversion power (Prec1), obtained by subtracting the charging power (Pl) from the rectified power (Prec), and the discharge power (Pc), and the DC link power (Pdc). Equipped with, The control unit (10) controls the amplitude of the buffered power (Pbuf) so that it is proportional to an adjustment value (S) set according to the distribution ratio (k). For a predetermined value (km) between 0 and 1, When the distribution ratio (k) is smaller than the predetermined value (km), The adjustment value (S) is the value obtained by dividing the distribution ratio (k) by the predetermined value (km). When the distribution ratio (k) is equal to or greater than the predetermined value (km), The adjustment value (S) is set to 1. Power converter (100).

2. The control unit (10) The DC component in the discharge power (Pc) and the DC component in the charging power (Pl) are made equal, and the AC component in the discharge power (Pc) is set to the value obtained by subtracting the distribution ratio (k) from the adjustment value (S) and multiplying the AC component of the rectified power (Prec) by minus 1. The buffering power (Pbuf) is the value obtained by multiplying the adjustment value (S) by the AC component of the rectified power (Prec) and minus 1. The power conversion device (100) according to claim 1.

3. The control unit (10) The DC component in the discharge power (Pc) and the DC component in the charging power (Pl) are made equal, and the AC component in the discharge power (Pc) is set to a value obtained by subtracting the adjustment value (S) and the distribution ratio (k) from 1, and then multiplying the AC component of the rectified power (Prec) by minus 1. The buffering power (Pbuf) is defined as the value obtained by subtracting the adjustment value (S) from 1, multiplied by the AC component of the rectified power (Prec) and minus 1. The power conversion device according to claim 1.

4. The aforementioned discharge power (Pc) is, The DC component is obtained by dividing the product of the peak value (Vm) of the single-phase AC voltage and the peak value (Im) of the single-phase AC current by 2 and multiplying by the distribution ratio (k), The AC component is obtained by dividing the product of the peak value (Vm) of the single-phase AC voltage and the peak value (Im) of the single-phase AC current by 2, multiplying by the cosine value (cos(2ωt)) which is twice the phase (ωt) of the single-phase AC voltage, and further multiplying by the value obtained by subtracting the distribution ratio (k) from the adjustment value (S), It is the sum of, A power conversion device (100) according to claim 1 or claim 2.

5. The aforementioned discharge power (Pc) is, The DC component is obtained by dividing the product of the peak value (Vm) of the single-phase AC voltage and the peak value (Im) of the single-phase AC current by 2 and multiplying by the distribution ratio (k), The AC component is obtained by dividing the product of the peak value (Vm) of the single-phase AC voltage and the peak value (Im) of the single-phase AC current by 2, multiplying by the cosine value (cos(2ωt)) which is twice the phase (ωt) of the single-phase AC voltage, and then multiplying by the value obtained by subtracting the adjustment value (S) and the distribution ratio (k) from 1, It is the sum of, A power conversion device (100) according to claim 1 or claim 3.

6. The control unit (10) When the predetermined value (km) is 1, In the range of 0 or greater and less than 1, The adjustment value (S) is the value obtained by dividing the distribution ratio (k) by the predetermined value (km). A power conversion device (100) according to any one of claims 1 to 3.

7. The control unit (10) When the predetermined value (km) is 0, Within the range of 0 or more and 1 or less, The adjustment value (S) is set to 1. A power conversion device (100) according to any one of claims 1 to 3.

8. The control unit (10) In the range where the distribution ratio (k) is 0 or greater and less than the predetermined value (km), The adjustment value (S) is the value obtained by dividing the distribution ratio (k) by the predetermined value (km). In a range where the distribution ratio (k) is greater than or equal to the predetermined value (km) and less than or equal to 1, The adjustment value (S) is set to 1. A power conversion device (100) according to any one of claims 1 to 3.

9. The control unit (10) When the load is high and greater than the first threshold (th1), and the distribution ratio (k) is greater than or equal to the predetermined value (km), the adjustment value (S) is set to 1. When the magnitude of the load is low, less than the second threshold (th2, where th1 ≥ th2), and the distribution ratio (k) is less than the predetermined value (km), the adjustment value (S) is set to the value obtained by dividing the distribution ratio (k) by the predetermined value (km). A power conversion device (100) according to any one of claims 1 to 3.

10. In a motor included in the load, When the rotational speed of the motor is a high-speed rotational speed greater than the first rotational speed (N1) and the distribution ratio (k) is equal to or greater than the predetermined value (km), the adjustment value (S) is set to 1. When the rotational speed of the motor is a low rotational speed less than the second rotational speed (N2, where N1 ≥ N2) and the distribution ratio (k) is less than the predetermined value (km), the adjustment value (S) is set to the value obtained by dividing the distribution ratio (k) by the predetermined value (km). A power conversion device (100) according to any one of claims 1 to 3.

11. The control unit (10) When a second predetermined value (kn, where kn > km) different from the aforementioned predetermined value (km) is set to be between 0 and 1, In the range of possible distribution rates (k), within a specific range less than or equal to the second predetermined value (kn), The adjustment value (S) is the value obtained by dividing the distribution ratio (k) by the second predetermined value (kn). A power conversion device (100) according to any one of claims 1 to 3.

12. The control unit (10) In cases where a first reference value (km1) and a second reference value (km2, however km2 ≥ km1) are set in advance to define the upper and lower limits of the range in which control based on the predetermined value (km) is restricted, among the range in which the distribution ratio (k) can take, When the distribution ratio (k) is greater than or equal to the first reference value (km1) and less than or equal to the second reference value (km2), the adjustment value (S) is set to 1. A power conversion device (100) according to any one of claims 1 to 3.

13. The control unit (10) In cases where a first reference value (km1) and a second reference value (km2, however km2 ≥ km1) are set in advance to define the upper and lower limits of the range in which control based on the predetermined value (km) is restricted, among the range in which the distribution ratio (k) can take, When the distribution ratio (k) is greater than or equal to the first reference value (km1) and less than or equal to the second reference value (km2), the adjustment value (S) is set to 1. The power conversion device (100) according to claim 11.

14. The system further comprises a DC link (7) having a first power line (LH) and a second power line (LL), The power supply unit (3) includes at least one rectifier circuit that supplies the rectified power (Prec) to the DC link (7), The control unit (10) The rectifier-to-current ratio (drec) is the current ratio at which the rectifier circuit supplies the directly converted power (Prec1) to the power conversion circuit, The discharge current ratio (dc), which is the current ratio at which the capacitor (C4) discharges, By setting this, the DC voltage (Vdc) applied to the DC link (7) is controlled to become the DC voltage command value (Vdc*), which is the command value of the DC voltage (Vdc). If the distribution ratio (k) is less than the predetermined value (km), The adjustment value (S) is defined as the value obtained by dividing the distribution ratio (k) by the predetermined value (km). The aforementioned rectified flow ratio (drec) is, The DC voltage command value (Vdc*) and, The sinusoidal value (|sin(ωt)|) of the phase (ωt) of the aforementioned single-phase AC voltage, The value obtained by subtracting the distribution ratio (k) from 1 and multiplying by 2 (2(1-k)) and The product of It is set to a value obtained by dividing the peak value (Vm) of the single-phase AC voltage by the product of a first relational value (U) that varies by a value obtained by subtracting the adjustment value (S) from 1 (1-k / km), The aforementioned discharge flow ratio (dc) is, The DC voltage command value (Vdc*) and, The value obtained by subtracting the distribution rate (k) from the adjustment value (S) (k / km-k) and the second relational value (V) which varies depending on the distribution rate (k) The product of The value is set to the value obtained by dividing the voltage across the capacitor (C4) (Vc) by the product of the first relational value (U), When the distribution ratio (k) is equal to or greater than the predetermined value (km), With the adjustment value (S) set to 1, The aforementioned rectified flow ratio (drec) is, The DC voltage command value (Vdc*) and, The sinusoidal value (|sin(ωt)|) of the phase (ωt) of the aforementioned single-phase AC voltage, The value obtained by subtracting the distribution ratio (k) from 1 and multiplying by 2 (2(1-k)) and The product of It is set to a value obtained by dividing the aforementioned single-phase AC voltage by its peak value (Vm), The aforementioned discharge flow ratio (dc) is, The DC voltage command value (Vdc*) and, The value obtained by subtracting the distribution rate (k) from 1 (1-k) and the third relational value (W) which varies depending on the distribution rate (k) The product of It is set to a value obtained by dividing by the voltage (Vc) across the capacitor (C4), To the aforementioned capacitor (C4), The first voltage (Vm・|sin(ωt)|) obtained by full-wave rectifying the aforementioned single-phase AC voltage is The first current (Im・|sin(ωt)|) is the value obtained by dividing the rectified power (Prec) by the above. A charging current (k・Im・|sin(ωt)|) obtained by multiplying the aforementioned distribution ratio (k) is input. A power conversion device (100) according to claim 1 or claim 2.

15. The system further comprises a DC link (7) having a first power line (LH) and a second power line (LL), The power supply unit (3) includes at least one rectifier circuit that supplies the rectified power (Prec) to the DC link (7), The control unit (10) The rectifier-to-current ratio (drec) is the current ratio at which the rectifier circuit supplies the directly converted power (Prec1) to the power conversion circuit, The discharge current ratio (dc), which is the current ratio at which the capacitor (C4) discharges, By setting this, the DC voltage (Vdc) applied to the DC link (7) is controlled to become the DC voltage command value (Vdc*), which is the command value of the DC voltage (Vdc). If the distribution ratio (k) is less than the predetermined value (km), The adjustment value (S) is defined as the value obtained by dividing the distribution ratio (k) by the predetermined value (km). The aforementioned rectified flow ratio (drec) is, The DC voltage command value (Vdc*) and, The sinusoidal value (|sin(ωt)|) of the phase (ωt) of the aforementioned single-phase AC voltage, The value obtained by subtracting the distribution ratio (k) from 1 and multiplying by 2 (2(1-k)) and The product of It is set to a value obtained by dividing the peak value (Vm) of the single-phase AC voltage by the product of the fourth relational value (X) which varies according to the adjustment value (S). The aforementioned discharge flow ratio (dc) is, The DC voltage command value (Vdc*) and, The value obtained by subtracting the adjustment value (S) and the distribution rate (k) from 1 (1 - (k / km + k)) and the fifth relational value (Y) which varies depending on the distribution rate (k) and The product of The value is set to the value obtained by dividing the voltage across the capacitor (C4) (Vc) by the product of the fourth relational value (X), When the distribution ratio (k) is equal to or greater than the predetermined value (km), With the adjustment value (S) set to 1, The aforementioned rectified flow ratio (drec) is, The DC voltage command value (Vdc*) and, The sinusoidal value (|sin(ωt)|) of the phase (ωt) of the aforementioned single-phase AC voltage, The value obtained by subtracting the distribution ratio (k) from 1 and multiplying by 2 (2(1-k)) and The product of The value is set to the product of the peak value (Vm) of the single-phase AC voltage and the value obtained by subtracting twice the phase (ωt) of the single-phase AC voltage's cosine value (1 - cos(2ωt)) from 1. The aforementioned discharge flow ratio (dc) is, The DC voltage command value (Vdc*) and the distribution ratio The product of It is set to a value obtained by dividing by the voltage (Vc) across the capacitor (C4), To the aforementioned capacitor (C4), The first voltage (Vm・|sin(ωt)|) obtained by full-wave rectifying the aforementioned single-phase AC voltage is The first current (Im・|sin(ωt)|) is the value obtained by dividing the rectified power (Prec) by the above. A charging current (k・Im・|sin(ωt)|) obtained by multiplying the aforementioned distribution ratio (k) is input. A power conversion device (100) according to claim 1 or claim 3.

Images