Electric power conversion device

Abstract

Provided is a technique that makes it possible to individually control a voltage of a DC link and an AC component of electric power supply power that is shared by an electric power buffer circuit. A control unit (10) is configured to: equalize the DC component of discharge electric power (Pc) and the DC component of charge electric power (Pl); set the AC component of the discharge electric power (Pc) to a value that is obtained by multiplying a value that is obtained by subtracting a distribution ratio (k) from an adjustment value (S) by the AC component (Prec^) of a rectified electric power (Prec) and minus 1; set a buffering electric power (Pbuf) to a value that is obtained by multiplying the adjustment value (S) by the AC component (Prec^) of the rectified electric power (Prec) and minus 1; and, with respect to a prescribed value (km) of 0–1 that is set in advance, set the adjustment value (S) to a value that is obtained by dividing the distribution ratio by the prescribed value (km) when the distribution ratio is smaller than the prescribed value (km), or set the adjustment value (S) to 1 when the distribution ratio (k) is equal to or greater than the prescribed value (km).

Description

Power converter

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

[0002] When rectifying a single-phase AC voltage obtained from a single-phase AC power source 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.

[0003] Patent No. 5626435

[0004] Patent Document 1 proposes a technology that controls the DC voltage to a constant level using only the voltage on the power supply side, or the voltage on the power supply side 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 side 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.

[0006] The power conversion device in the first aspect comprises a power supply unit, a capacitor, a power conversion circuit, and a control unit. The power supply unit consists of one or more rectifiers, including a first rectifier, which full-wave rectifies a single-phase AC voltage and generates rectified power. The capacitor receives charging power from the first rectifier if the power supply unit includes only the first rectifier, or from the second rectifier if the power supply unit includes a second rectifier different from the first rectifier, and outputs discharge power. The power conversion circuit receives DC link power, which is the rectified power plus buffering power, which is the power difference obtained by subtracting the charging power from the discharge power. The control unit obtains charging power by multiplying the rectified power by a distribution ratio of 0 to 1, and controls the power flow so that the sum of the directly converted power (rectified power minus charging power) and the discharge power is the DC link power. The control unit controls the amplitude of the buffered power so that it is proportional to an adjustment value set according to the distribution ratio. When the distribution ratio is less than a predetermined value between 0 and 1, the adjustment value is set to the value obtained by dividing the distribution ratio by the predetermined value, or when the distribution ratio is equal to or greater than the predetermined value, the adjustment value is set to 1.

[0007] In this power converter, the buffering power of the power buffer circuit can be varied by switching the setting value of the adjustment value 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 and the voltage of the DC link can be controlled individually.

[0008] The power converter in the second aspect is the power converter in the first aspect, wherein the control unit equalizes the DC component of the discharged power with the DC component of the charging power, and sets the AC component of the discharged power to a value obtained by subtracting the distribution ratio from the adjustment value and multiplying the AC component of the rectified power by minus 1, and sets the buffering power to a value obtained by multiplying the AC component of the rectified power by minus 1, the adjustment value.

[0009] The power converter in the third perspective is the power converter in the first perspective, wherein the control unit equalizes the DC component of the discharged power with the DC component of the charging power, and sets the AC component of the discharged power to a value obtained by subtracting the adjustment value and the distribution ratio from 1, multiplying the AC component of the rectified power by minus 1, and sets the buffering power to a value obtained by subtracting the adjustment value from 1, multiplying the AC component of the rectified power by minus 1.

[0010] In this power converter, the buffering power of the power buffer circuit can be varied by switching the setting value of the adjustment value 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 and the voltage of the DC link can be controlled individually.

[0011] The power converter of the fourth perspective is a power converter of the first or second perspective, in which the discharged 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 which is twice the phase of the single-phase AC voltage, and then multiplying by the value obtained by subtracting the distribution ratio from the adjustment value.

[0012] The power converter of the fifth perspective is a power converter of the first or third perspective, in which the discharged 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 which is twice the phase of the single-phase AC voltage, and then multiplying by the value obtained by subtracting the adjustment value and the distribution ratio from 1.

[0013] The power converter of the sixth aspect is a power converter of any one of the first, third, or fourth aspects, wherein the control unit, when a predetermined value is 1, sets the adjustment value to the value obtained by dividing the distribution ratio by the predetermined value, within the range of a distribution ratio of 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 of the eighth perspective is a power converter of any one of the first, third, or fourth perspectives, and in the range where the distribution ratio is 0 or greater and less than a predetermined value, the adjustment value is the value obtained by dividing the distribution ratio by the predetermined value. In the range where the distribution ratio is 1 or greater and 1 or less, the adjustment value is 1.

[0016] The power conversion device from the ninth perspective is any one of the power conversion devices from the first to the third perspectives. When the load magnitude is a high load greater than the first threshold and the distribution ratio is greater than or equal to a predetermined value, the control unit sets the adjustment value to 1. Also, when the load magnitude is a low load less than the second threshold (where the first threshold ≥ the second threshold) and the distribution ratio is less than the predetermined value, the control unit sets the adjustment value to the value obtained by dividing the distribution ratio by the predetermined value.

[0017] In this power conversion device, in the high load region, mechanical fluctuations on the load side can be reduced by buffering the AC component with a capacitor. Conversely, in the low load region, since the power is small and the mechanical fluctuations on the load side are also small, a part of the AC component can be borne by the load side.

[0018] The power conversion device from the tenth perspective is any one of the power conversion devices from the first to the third perspectives. In the motor included in the load, when the rotational speed of the motor 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 control unit sets the adjustment value to 1. Also, when the rotational speed of the motor is a low rotational speed less than the second rotational speed (where the first rotational speed ≥ the second rotational speed) and the distribution ratio is less than the predetermined value, the control unit sets the adjustment value to the value obtained by dividing the distribution ratio by the predetermined value.

[0019] In this power conversion device, in the region where the rotational speed is high, torque fluctuations on the load side can be reduced by buffering the AC component with a capacitor. Conversely, in the region where the rotational speed is low, since the power is small and the torque on the load side is also small, a part of the AC component can be borne by the load side.

[0020] The power conversion device from the eleventh perspective is any one of the power conversion devices from the first to the third perspectives. When a second predetermined value that is 0 or more and 1 or less and different from the predetermined value (where the second predetermined value > the predetermined value) is set, in a specific range within the range that the distribution ratio can take and that is less than or equal to the second predetermined value, the control unit sets the adjustment value to the value obtained by dividing the distribution ratio by the second predetermined value.

[0021] In this power conversion device, the rate of increase or decrease of the buffering power with respect to the distribution ratio can be changed only when the distribution ratio is within a specific range. Also, the control unit can change the adjustment value without changing the distribution ratio.

[0022] The power conversion device according to the 12th aspect is any one of the power conversion devices according to the 1st to 3rd aspects, and when a first reference value and a second reference value (where the second reference value ≥ the first reference value) that define the upper and lower limits of the range in which control based on a predetermined value is restricted within the range that the distribution ratio can take are preset in the control unit, when the distribution ratio is greater than or equal to the first reference value and less than or equal to the second reference value, the adjustment value is set to 1.

[0023] In this power conversion device, control for forcibly setting the adjustment value to 1 can be executed when the distribution ratio is within a specific range.

[0024] The power conversion device according to the 13th aspect is the power conversion device according to the 11th aspect, and when a first reference value and a second reference value (where the second reference value ≥ the first reference value) that define the upper and lower limits of the range in which control based on a predetermined value is restricted within the range that the distribution ratio can take are preset in the control unit, when the distribution ratio is greater than or equal to the first reference value and less than or equal to the second reference value, the adjustment value is set to 1.

[0025] In this power conversion device, control for forcibly setting the adjustment value to 1 can be executed when the distribution ratio is within a specific range.

[0026] The power conversion device according to the 14th aspect is any one of the power conversion devices according to the 1st, 2nd, 4th, and 6th to 13th aspects, and further includes 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 so that the DC voltage applied to the DC link becomes the DC voltage command value, which is its command value, by setting a rectification current ratio and a discharge current ratio. The rectification current ratio is the current ratio at which the rectifier circuit directly supplies converted power to the power conversion circuit. The discharge current ratio is the current ratio at 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 a rectified current ratio and a 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.

[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 depending on 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 depending on 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.

[0034] This is a block diagram showing the configuration of the power converter according to the first embodiment. This is a block diagram showing the configuration of the power converter when the rectifier circuit in Figure 1 is composed of two rectifier circuits. This is the equivalent circuit of the power converter shown in Figures 1 and 2. This is a graph showing the relationship between the distribution ratio, buffering power, and DC voltage in the first control. This is a graph showing the relationship between the distribution ratio, buffering power, and DC voltage in the second control. This is a graph showing the relationship between the distribution ratio, buffering power, and DC voltage in the third control. This is a graph showing the operation of the power converter according to the first embodiment. This is a flowchart showing the process of setting adjustment values ​​according to the load. This is a flowchart showing the process of setting adjustment values ​​according to the rotational speed. This is a graph showing the relationship between the distribution ratio and buffering power in the third control of the power converter circuit according to the first modified example. This is a graph showing the relationship between the distribution ratio and buffering power in the third control of the power converter according to the second modified example. This is a graph showing the relationship between the distribution ratio and buffering power in the third control of the power converter according to the third modified example. This is a graph showing the relationship between the distribution ratio, buffering power, and DC voltage in the first control of the second embodiment. This graph shows the relationship between the distribution ratio, buffering power, and DC voltage in the second control of the second embodiment. This graph shows the relationship between the distribution ratio, buffering power, and DC voltage in the third control of the second embodiment. This graph shows the operation of the power converter according to the second embodiment. This graph shows the relationship between the distribution ratio and buffering power in the third control of the power converter circuit according to the first modified example of the second embodiment. This graph shows the relationship between the distribution ratio and buffering power in the third control of the power converter according to the second modified example of the second embodiment. This graph shows the relationship between the distribution ratio and buffering power in the third control of the power converter according to the third modified example of the second embodiment.

[0035] <First Embodiment> (1) Configuration of the power converter 100 Figure 1 is a block diagram showing the configuration of the 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 line 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] The transistor Sc and diode D42 can be considered together as a single switching element (first switch). When the first switch conducts, the capacitor C4 discharges and supplies power to the 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 flowing 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 The 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. The 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 showing that it is an inductive load. Specifically, a reactor Lu and a resistor Ru are connected in series with each other, 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 diagram 2 is a block diagram showing the configuration of the 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 the switch Srec when it is conducting. 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 the actual circuit and the equivalent circuit is 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 ≤ 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 of the currents 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 hereinafter referred to as the rectified current ratio drec. Furthermore, the current ratio dc is the current ratio at which the capacitor C4 discharges, and will therefore be hereinafter referred to as the discharge current ratio dc. 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. Details on setting the rectified current ratio drec and the discharge current ratio dc will be described in section (4) Setting the Current Ratios.

[0068] (3) The control rectifier circuit 3 receives a single-phase AC voltage Vin as input and outputs a rectified power Prec represented by equation [1], with an input power factor of 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 of 0 to 1, and the power buffer circuit 4 outputs discharge power Pc 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] The inverter 5 receives the DC link power Pdc (= Prec + Pc - Pl), which is the sum of the rectified power Prec and the discharge power Pc minus the charging power Pl, from the 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 Pbuf is controlled to equal (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 the 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 buffering 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 expressed by equation [4]. Pc = (k / 2)・Vm・Im + {(S-k) / 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 equation [3] above, 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 in 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 km, the control unit 10 sets the adjustment value S to 1 so that the buffered 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) When km = 1, the first control unit 10 sets S = k / 1 = k in accordance with setting condition A, since the range in which the distribution ratio k is smaller than a predetermined value km is 0 ≤ k < 1, and controls the discharge power Pc such that the buffering power Pbuf = (k / 2)・Vm・Im・cos(2ωt).

[0085] Furthermore, in the range of distribution ratio k = km = 1, S is set to 1 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 C4 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) When km = 0, the second control unit 10 sets S = 1 in accordance with setting condition B, since there is no range in which the distribution ratio k is smaller than the predetermined value km, and km ≤ k, 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 as described above is called the "second control".

[0089] Figure 4B 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 with Vm・Im・cos(2ωt) = 1. Similarly, the value of DC voltage Vdc is not the actual value, but a normalized value with Vdc / Vm. Furthermore, the voltage across capacitor C4 Vc is also normalized with Vc / Vm, and the relationship between DC voltage Vdc and the voltage across it Vc is also shown.

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

[0091] (3-3) The third control + second control control unit 10 sets S to k / km in accordance with setting condition A when the predetermined value km is neither 0 nor 1 but 0 ≤ k < km, and controls the discharge power Pc such that the buffering power Pbuf = {(k / km) / 2}Vm・Im・cos(2ωt). In this embodiment, the control based on the predetermined value km being neither 0 nor 1 but 0 ≤ k < km as described above is called the "third control".

[0092] Figure 4C is a graph showing the relationship between the distribution ratio k, buffering power Pbuf, and DC voltage Vdc in the third control (0 ≤ k < km). For example, km = 0.5 is used. Furthermore, 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 also not the actual value, but a normalized value using Vdc / Vm. In addition, 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.

[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, the control unit 10 sets S to 1 in accordance with setting condition B in the range km = 0.5 ≤ k ≤ 1, 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) The current ratio setting control unit 10 controls the DC voltage Vdc applied to the DC link 7 to the command value, which is the DC voltage command value Vdc*, by setting the straight 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) In the setting formula for the rectified current ratio drec [1], the input current Iin is expressed as Im・sin(ωt) and is assumed to exhibit 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 rectified 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] we get (1 / 2)・Vm・Im - {(1-S) / 2}・Vm・Im・cos(2ωt) = Vdc・Idc, which leads to the following equation

[10] : 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 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 the 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, so from equation [4], Pc = (k / 2)・Vm・Im + {(S-k) / 2}Vm・Im・cos(2ωt) = Vc・ic, and equation

[14] is derived. ic = (Vm・Im / 2Vc)・{k + (S-k)・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 + (S - k)・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 + (S - k) * 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 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 DC Voltage The DC voltage is determined by the voltage of the power supply, the rectified current ratio drec, and the voltage of the power buffer circuit, and the discharge current ratio dc. The DC voltage is expressed by the following equation: Vdc = drec・Vrec + dc・Vc ...

[19]

[0111] Furthermore, both equation

[11] , which represents the rectified current ratio drec, and equation

[16] , which represents the discharge current ratio dc, are functions of the DC voltage command value (Vdc*). 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 illustrating the operation of the power converter 100 according to this embodiment. Here, the waveform for the first control at Vc = 1.59 and k = 0.75 is shown, and the DC voltage is selected such that the current ratio dz, obtained by subtracting drec and dc from 1, is positive across 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 section "(3-1) First Control", when km = 1, the control unit 10 sets S = k / 1 = k in accordance with setting condition A, since the range in which the distribution ratio k is smaller than the predetermined value km is 0 ≤ k < 1, the equation

[12] representing the rectified flow ratio is given by equation

[20] , and the equation

[17] representing the discharge flow ratio is given by equation

[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, cos(2ωt) = 1 - 2sin ２ Since (ωt), equation

[22] can be derived from equation

[20] , and equation

[23] can be derived from equation

[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 \(dz = 1 - d_{erc} - d_c\), the following equation

[24] is derived from equations

[22] and

[23] . \(dz = 1 - 2(1 - k)\cdot V_{dc}^*\cdot|\sin(\omega t)| / [V_m\{2(1 - k)\sin ２ (\omega t)+k\}] - [k\cdot V_{dc}^* / [V_c\{2(1 - k)\sin ２ (\omega t)+k\}]...

[24]

[0118] Differentiating equation

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

[25] is obtained. \(dz'=-2V_{dc}^*\cdot(1 - k)\cdot\cos(\omega t) / [V_m\{2(1 - k)\sin ２ (\omega t)+k\}] + [8V_{dc}^*\cdot(1 - k) ２ \cos(\omega t)\sin ２ (\omega t) / [V_m\{2(1 - k)\sin ２ (\omega t)+k\} ２ + [4V_{dc}^*\cdot(1 - k)k\cdot\cos(\omega t)\sin(\omega t) / [V_c\{2(1 - k)\sin ２ (\omega t)+k\} ２ ...

[25]

[0119] \(\omega t\) for which \(dz' = 0\) is expressed by the following equation

[26] . \(\omega t=-\arcsin[\{(V_m ２ k ２ - 2V ２ k ２ + 2V_c ２ k) １／２ / (2V_c\cdot k - 2V_c)\}-\{V_m\cdot k / (2V_c\cdot k - 2V_c)\}]...

[26]

[0120] Using equation

[26] , the phase \(\omega t\) that takes the minimum value is calculated from \(k\) and \(V_c\), and by setting \(dz = 0\) in equation

[24] and transforming it into the following equation

[27] , the maximum output voltage \(V_{dc}^* / V_m\) is obtained. \(V_{dc}^* / V_m = 1 / [[2(1 - k)\cdot\sin(\omega t) / \{2(1 - k)\sin ２ (\omega t)+k\}] + [k / (V_c / V_m)\{2(1 - k)\sin ２ (\omega t)+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 the section "(3-2) Second Control", when km = 0, the control unit 10 does not have a range in which 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 straight 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, equation

[28] is rearranged in terms of Vdc* / Vm to 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 Third Control + Second Control As described in the section "(3-3) First Control + Second Control", when the predetermined value km is neither 0 nor 1 but 0 ≤ k < km, the control unit 10 is set to S = k / km in accordance with setting condition A. In Figure 4C, in the range of 0 ≤ k < 0.5, S is set to k / 0.5, and the formula for the straight flow ratio

[12] and the formula for the discharge flow ratio

[17] are expressed by the following formulas

[31] and

[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, cos(2ωt) = 1 - 2sin ２ Since (ωt), equation

[33] can be derived from equation

[31] , and equation

[34] can be derived from equation

[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] Furthermore, since dz = 1 - derc - dc, from equations

[33] and

[34] , the following equation

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

[35] , transform it into the following 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 the adjustment value S (5-1) Setting the adjustment value S according to the load When the AC component Prec^ is input to the 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 the 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 referred to here is 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 th1 and the distribution rate k is greater than or equal to a predetermined value km. If the control unit 10 determines that "the load L is greater than the first threshold th1 and the distribution rate k is greater than or equal to a 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. The control unit 10 determines that the load L is high because it is greater than the first threshold th1.

[0141] Since the distribution ratio k is greater than the predetermined value km, the control assumes km = 1 in the first control explained in Figure 4A, km = 0 in the second control explained in Figure 4B, and k ≥ km in the second control explained in Figure 4C.

[0142] (Step S4) In step S4, the control unit 10 determines whether the load L is less than the second threshold th2 (provided that th1 ≥ th2) and whether the distribution rate k is less than a predetermined value km. If the control unit 10 determines that "the load L is less than the second threshold th2 and the distribution rate k is less than a 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. The control unit 10 determines that the load L is low load or medium load because it is less than the second threshold th2.

[0144] Since the distribution ratio k is smaller than the predetermined value km, the control assumes k < km in the first control described in Figure 4A and k < km in the third control described in Figure 4C.

[0145] (5-2) Setting the adjustment value S according to the motor rotation speed Here, we will explain assuming that the inductive load 6 in Figure 1 is the motor of the compressor installed in the air conditioning system.

[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 rotational 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 rotation speed N in step S11. Alternatively, the operating frequency may be detected instead of the rotation 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 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 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 greater than the first rotational speed N1, and therefore it is rotating at high speed.

[0153] Since the distribution ratio k is greater than the predetermined value km, the control assumes km = 1 in the first control explained in Figure 4A, km = 0 in the second control explained in Figure 4B, and k ≥ km in the second control explained in Figure 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 (provided that N1 ≥ N2) and whether the distribution ratio k is less than a 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 a 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. The control unit 10 determines that the rotational speed N is low speed or medium speed because it is less than the second rotational speed N2.

[0156] Since the distribution ratio k is smaller than the predetermined value km, the control assumes k < km in the first control described in Figure 4A and k < km in the third control described in Figure 4C.

[0157] (6) Modified Version (6-1) First Modified Version In Figure 4C, a third control is performed 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 a second control is performed in which S = 1 when the distribution ratio k is in the range of km ≤ k ≤ 1, with a predetermined value km being the switching point between the third control and the second control.

[0158] However, such switching points are not limited to one, and there may be multiple switching points. For example, if, in addition to a predetermined value km, a second predetermined value kn is provided that is greater than the predetermined value km and between 0 and 1, the control unit 10 can arbitrarily switch the adjustment value S to either k / km or k / kn within the range where the distribution ratio k is 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 modified example 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 instead of a predetermined value km for control, 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] On the other hand, the control unit 10 sets the adjustment value S to S=1 in the range kn = 0.8 ≤ k ≤ 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) In the second modified example, Figure 4C, 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 a 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, with a predetermined value km being 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 while the distribution ratio k is in the range of 0 ≤ k < km. Therefore, a control system is needed that allows switching to the second control midway through the third control.

[0168] In the second 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 control based on a predetermined value km is restricted within the range in which the distribution rate k can take. The first reference value km1 is smaller than the second reference value km2.

[0169] Figure 7B 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 7B, the graph is shown using a predetermined value km = 0.5, a first reference value km1 = 0.3, and a second reference value km2 = 1 as examples.

[0170] In Figure 7B, the control unit 10 normally sets the adjustment value S to S = k / 0.5, where the distribution ratio k is in the range of 0 ≤ k < 0.5, since the predetermined value km = 0.5, and controls the discharge power Pc based on equation [3] so that the buffering power Pbuf = k・Vm・Im・cos(2ωt).

[0171] However, when the distribution ratio k is in the range 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 0 ≤ k < 0.3, and the second control is executed when the distribution ratio k is in the range 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) Figure 7C of the third modified example 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 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 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 in which control based on a predetermined value km and a third control based on a second predetermined value kn are restricted within the range in which the distribution rate k can take. 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 it is desired to force the second control to be performed within a specific range of the distribution ratio k.

[0179] (7) Features (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 of 0 or more and 1 or less, 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 when the distribution ratio is 0 or more and 1 or less, 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, by 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, when the predetermined value km is 1, the control unit 10 sets the adjustment value S to the distribution ratio k in the range of 0 or more 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 of 0 or more and 1 or less.

[0185] (7-6) In the power converter 100, when the distribution ratio k is 0 or greater and 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. When the distribution ratio k is 1 or greater and less than or equal to a predetermined value km, 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 magnitude of the load L is greater than the first threshold th1 and the distribution ratio k is greater than or equal to a predetermined value km. Also, when the magnitude of the load L is less than the second threshold th2 and the distribution ratio k is less than a predetermined value km, the control unit 10 sets the adjustment value S to the value obtained by dividing the distribution ratio k by the predetermined value km.

[0187] In this power converter 100, in the high-load region, the AC component Prec^ is buffered by the 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 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 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.

[0189] In this power converter 100, in the high rotational speed range, the AC component Prec^ is buffered by the 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 the control unit 10 has set a second predetermined value kn (where kn > km) which is different from the predetermined value km and is between 0 and 1, the adjustment value S is set to the value obtained by dividing the distribution rate k by the second predetermined value kn within a specific range of the range in which the distribution rate k can take.

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

[0192] (7-10) In a power converter, when 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 among the range in which the distribution ratio k can take, 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 within a specific range of the distribution ratio k.

[0194] (7-11) In the power conversion device 100, the control unit 10 controls the DC voltage applied to the DC link 7 to the command value, which is 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 the 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 + (S - k)cos(2ωt).

[0197] When the distribution ratio k is greater than or equal to a predetermined value 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) The control 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 such 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 expressed 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-S-k) / 2}Vm・Im・cos(2ωt) ...

[40]

[0205] 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.

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

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

[0209] (1-1) When km = 1, the first control unit 10 sets S = k / 1 = k in accordance with setting condition A, since the range in which the distribution ratio k is smaller than a predetermined value km is 0 ≤ k < 1, and controls the discharge power Pc such that the buffering power Pbuf = {(1-k) / 2}・Vm・Im・cos(2ωt).

[0210] Furthermore, in the range of distribution ratio k = km = 1, S is set to 1 according to setting condition B, and the discharge power Pc is controlled so that the buffering power Pbuf = 0. In this embodiment, the control based on the predetermined value km = 1 as described above is called the "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) When km = 0, the second control unit 10 sets S = 1 in accordance with setting condition B, since there is no range in which the distribution ratio k is less than the predetermined value km, and km ≤ k, and controls the discharge power Pc so that the buffering power Pbuf = 0 in the range of 0 ≤ k ≤ 1. In this embodiment, the control based on the predetermined value km = 0 as 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 with Vm・Im・cos(2ωt) = 1. Similarly, the value of DC voltage Vdc is not the actual value, but a normalized value with Vdc / Vm. Furthermore, the voltage across capacitor C4 Vc is also normalized with 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] (1-3) The third control + second control control unit 10 sets S to k / km in accordance with setting condition A when the predetermined value km is neither 0 nor 1 but 0 ≤ k < km, and controls the discharge power Pc such that the buffering power Pbuf = {(1 - k / km) / 2} Vm・Im・cos(2ωt). In this embodiment, the control based on the predetermined value km being neither 0 nor 1 but 0 ≤ k < km as described above is called the "third control".

[0217] Figure 8C is a graph showing the relationship between the distribution ratio k, buffering power Pbuf, and DC voltage Vdc in the third control (0 ≤ k < km). For example, km = 0.5 is used. Furthermore, 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 also not the actual value, but a normalized value using Vdc / Vm. In addition, 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.

[0218] In Figure 8C, in the range 0 ≤ k < 0.5, S is set to k / 0.5, and Pbuf = {(1 / 2) - k}・Vm・Im・cos(2ωt), and 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.

[0219] On the other hand, in the range 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 = 0. This corresponds to the second 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 the flow ratio (2-1) Setting the straight flow ratio drec As described above, the second embodiment is the same as the first embodiment, but with the adjustment value "S" replaced by "1-S".

[0222] Therefore, the rectified flow ratio drec in the second embodiment is expressed by equation

[42] , which replaces the adjustment value "S" in equation

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

[42]

[0223] 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

[42] becomes equation

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

[43]

[0224] Furthermore, when the distribution ratio k is greater than or equal to a predetermined value km, the adjustment value S is set to 1 in accordance with setting condition B, so equation

[42] becomes equation

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

[44]

[0225] (2-2) Setting the discharge flow ratio dc Similarly to the setting of the discharge flow ratio dc in the second embodiment, the discharge flow ratio dc in the second embodiment is expressed by equation

[45] , which replaces the adjustment value "S" in equation

[16] in the first embodiment with "1-S". dc = Vdc * {k + (1-S-k) * cos(2ωt)} / [Vc * {1-Scos(2ωt)}] ...

[45]

[0226] 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

[45] becomes equation

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

[46]

[0227] Furthermore, when the distribution ratio k is greater than or equal to a predetermined value 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 DC Voltage The DC voltage is determined by the voltage on the power supply side and the rectification 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

[19] described in the first embodiment): Vdc = drec・Vrec + dc・Vc

[0229] Furthermore, both equation

[42] , which represents the rectified current ratio drec, and equation

[45] , which represents the discharge current ratio dc, are functions of the DC voltage command value (Vdc*). To obtain a high DC voltage, the current ratio should be set to a large value based on the following constraints.

[0230] Constraints: drec + dc + dz = 1, where 0 ≤ drec ≤ 1, 0 ≤ dc ≤ 1, and 0 ≤ dz ≤ 1.

[0231] 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.

[0232] 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.

[0233] (3) Modified Version (3-1) First Modified Version In Figure 8C, a third control is performed 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 a second control is performed in which S = 1 when the distribution ratio k is in the range of km ≤ k ≤ 1, with a predetermined value km being the switching point between the third control and the second control.

[0234] However, such switching points are not limited to one, and there may be multiple switching points. For example, if, in addition to a predetermined value km, a second predetermined value kn is provided that is greater than the predetermined value km and between 0 and 1, the control unit 10 can arbitrarily switch the adjustment value S to either k / km or k / kn within the range where the distribution ratio k is 0 ≤ k < kn.

[0235] Figure 10A 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 10A, a predetermined value km = 0.5 and a second predetermined value kn = 0.8 are used as examples.

[0236] In Figure 10A, when the distribution ratio k is in the range of 0 ≤ k < 0.3 and 0.4 ≤ 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 = (1 / 2 - k)・Vm・Im・cos(2ωt) based on equation

[39] .

[0237] Furthermore, when the distribution ratio k is in the range of 0.3 ≤ k < 0.4 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 = (1 / 2 - k / 1.6)・Vm・Im・cos(2ωt) based on equation

[39] .

[0238] 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.

[0239] Furthermore, the first modified example 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 = 0.2 when the predetermined value km = 0.5 to Pbuf = 0.312 when the second predetermined value kn = 0.8.

[0240] When using a second predetermined value kn instead of a predetermined value km for control, 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.

[0241] On the other hand, 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 = 0.

[0242] (3-2) In the second modified example, Figure 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 a 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, with a predetermined value km being the switching point between the third control and the second control.

[0243] In such a case, it is not possible to switch from the third control to the second control while the distribution ratio k is in the range of 0 ≤ k < km. Therefore, a control system is needed that allows switching to the second control midway through the third control.

[0244] In the second 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 control based on a predetermined value km is restricted within the range in which the distribution rate k can take. The first reference value km1 is smaller than the second reference value km2.

[0245] 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 km = 0.5, a first reference value km1 = 0.4, and a second reference value km2 = 1 as examples.

[0246] In Figure 10B, the control unit 10 normally sets the adjustment value S to S = k / 0.5, where the distribution ratio k is in the range of 0 ≤ k < 0.5, since the predetermined value km = 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).

[0247] However, when the distribution ratio k is in the range 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 0 ≤ k < 0.4, and the second control is executed when the distribution ratio k is in the range 0.4 ≤ k ≤ 1.

[0248] 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.

[0249] (3-3) Figure 10C of the third modified example 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.

[0250] 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 in which control based on a predetermined value km and a third control based on a second predetermined value kn are restricted within the range in which the distribution rate k can take. The first reference value km1 is smaller than the second reference value km2.

[0251] 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.

[0252] 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).

[0253] 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.

[0254] Therefore, the third modification, like the second modification, is useful when it is desired to force the second control to be performed within a specific range of the distribution ratio k.

[0255] (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 of 0 or more and 1 or less, 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 when the distribution ratio is less than or equal to the predetermined value km when the distribution ratio k is greater than or equal to the predetermined value km.

[0256] 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.

[0257] (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.

[0258] (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.

[0259] (4-4) In the power converter 100, when the predetermined value km is 1, the control unit 10 sets the adjustment value S to the distribution ratio k in the range of 0 or more and less than 1.

[0260] (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 of 0 or more and 1 or less.

[0261] (4-6) In the power converter 100, when the distribution ratio k is 0 or greater and 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. When the distribution ratio k is 1 or greater and less than or equal to a predetermined value km, the adjustment value S is set to 1.

[0262] (4-7) In the power converter 100, the control unit 10 sets the adjustment value S to 1 when the magnitude of the load L is greater than the first threshold th1 and the distribution ratio k is greater than or equal to a predetermined value km. Also, when the magnitude of the load L is less than the second threshold th2 and the distribution ratio k is less than a predetermined value km, the control unit 10 sets the adjustment value S to the value obtained by dividing the distribution ratio k by the predetermined value km.

[0263] In this power converter 100, in the high-load region, the capacitance of capacitor C4 can be reduced by shifting the AC component Prec^ to 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 shifted to capacitor C4.

[0264] (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 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 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.

[0265] 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.

[0266] (4-9) In the power converter 100, when the control unit 10 has set a second predetermined value kn (where kn > km) which is different from the predetermined value km and is between 0 and 1, the adjustment value S is set to the value obtained by dividing the distribution rate k by the second predetermined value kn within a specific range of the range in which the distribution rate k can take.

[0267] In this power converter 100, the rate of increase or decrease of the buffering power Pbuf relative to the distribution ratio k can be changed only when the distribution ratio k is within a specific range. Furthermore, the control unit 10 can change the adjustment value S without changing the distribution ratio k.

[0268] (4-10) In a power converter, when 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 among the range in which the distribution ratio k can take, 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.

[0269] In this power converter 100, the second control can be forcibly executed within a specific range of the distribution ratio k.

[0270] (4-11) In the power conversion device 100, the control unit 10 controls the DC voltage applied to the DC link 7 to the command value, which is 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 the converted power Prec1 to the inverter 5. The discharge current ratio dc is the current ratio at which the capacitor discharges.

[0271] 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).

[0272] 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 relational 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 relational value X. Specifically, the fifth relational value Y is expressed as k + (1 - (S + k))cos(2ωt).

[0273] When the distribution ratio k is greater than or equal to a predetermined value 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 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.

[0274] 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.

[0275] 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.

[0276] 3 Rectifier circuit (power supply unit) 5 Inverter (power conversion circuit) 7 DC link 10 Control unit 31 First rectifier circuit (first rectifier) ​​32 Second rectifier circuit (second rectifier) ​​100 Power conversion device C4 Capacitor drec Rectified 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 First power line LL Second power line Im Peak value of single-phase AC current Pc Discharge power Pbuf Buffering power Pdc DC link power Pl Charging power Prec Rectified power Prec1 Direct conversion power Vm Peak value of single-phase AC voltage Vdc DC voltage Vdc* DC voltage command value

Claims

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). or 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). 　 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. 　 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. 　 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. 　 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. 　 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. 　 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. 　 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. 　 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. 　 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. 　 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. 　 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. 　 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. 　 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)) 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)) 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 across the capacitor (C4) (Vc), 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 converter (100) according to any one of claims 1, 2, 4, 6 to 13. 　 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)) 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)) 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 across the capacitor (C4) (Vc), 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 converter (100) according to any one of claims 1, 3, 5 to 13.

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