JP2008178284A - Power converter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power converter capable of finely controlling voltage to reduce high frequency and suppress loss due to PWM control. <P>SOLUTION: A first half bridge circuit 17 has a first switching element 12-1 and second switching element 12-2 connected to a first DC power supply 11. A second half bridge circuit 18 has a third switching element 12-3 and fourth switching element 12-4 connected to a second DC power supply 13. The neutral point of the first DC power supply 11 is connected to the neutral point of the second DC power supply 13 by a half bridge circuit connection line 16, so that the first half bridge circuit 17 is connected to the second half bridge circuit 18. Relating to an AC terminal, one end is led out of the connection point between the first switching element and the second switching element, while the other end is led out from the connection point between the third switching element and the fourth switching element. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a power converter that converts direct current into alternating current.

  PWM control is performed to suppress the harmonic distortion voltage of the AC voltage output from the power converter that converts direct current to alternating current. Generally, PWM control is required to suppress the harmonic distortion voltage of the power converter. It is.

  FIG. 16 is a circuit diagram of a conventional single-phase full-bridge inverter. The first DC power supply 11 in the first half-bridge circuit 17 is grounded at a neutral point, and the first switching element 12-1 and the second switching element 12-2 are connected to the first DC power supply 11. Has been. Similarly, the second DC power supply 13 in the second half-bridge circuit 18 is grounded at a neutral point. The second DC power supply 13 includes a third switching element 12-3 and a fourth switching element 12-. 4 are connected, and free-wheeling diodes D1 to D4 are connected in parallel to the first switching element 12-1 to the fourth switching element 12-4, respectively.

  The upper and lower arms of the first switching element 12-1 and the second switching element 12-2 are connected to the upper and lower arms of the third switching element 12-3 and the fourth switching element 12-4 in parallel with the DC positive line. 14 and a DC negative electrode line 15. Then, one end U of the AC terminal is pulled out from the connection point of the first switching element 12-1 and the second switching element 12-2, and the other end U ′ of the AC terminal is connected to the third switching element 12-3 and the second switching element 12-3. 4 is pulled out from the connection point of the switching element 12-4, and power is supplied from the AC terminals U and U 'to the single-phase AC load. Now, it is assumed that the voltages of the first DC power supply 11 and the second DC power supply 13 are each E across the neutral point. That is, the magnitudes of the DC voltages at both ends supplied to the half-bridge circuit of the conventional single-phase full-bridge inverter must match. In this example, both ends are 2E [V].

FIG. 17 is a waveform diagram showing an example of the output voltage of the AC terminals U and U ′ of the single-phase full-bridge inverter circuit shown in FIG. 16, and Table 1 shows the first switching element 12 of the single-phase full-bridge inverter circuit. It is a table | surface which shows the output voltage with respect to on-off of -1 thru | or 4th switching element 12-4. As shown in FIG. 17 and Table 1, the output voltage of the single-phase full-bridge inverter circuit has three levels of 0, 2E, and −2E.

  As shown in Table 1, there are four modes 1 to 4 for turning on and off the first switching element 12-1 to the fourth switching element 12-4 of the single-phase full-bridge inverter circuit.

  In mode 1, the first switching element 12-1 is off, the second switching element 12-2 is on, the terminal voltage of the AC terminal U is -E, and the third switching element 12-3 is off. In this mode, the fourth switching element 12-4 is on and the terminal voltage of the AC terminal U ′ is −E. Therefore, in this mode 1, the terminal voltage between U and U 'is zero.

  In mode 2, the first switching element 12-1 is on, the second switching element 12-2 is off, the terminal voltage at the AC terminal U is E, the third switching element 12-3 is off, 4 in which the switching element 12-4 is ON and the terminal voltage of the AC terminal U ′ is −E. Therefore, in this mode 2, the terminal voltage between U and U 'is 2E.

  In mode 3, the first switching element 12-1 is on, the second switching element 12-2 is off, the terminal voltage at the AC terminal U is E, the third switching element 12-3 is on, 4 in which the switching element 12-4 is OFF and the terminal voltage of the AC terminal U ′ is E. Therefore, in this mode 3, the terminal voltage between U and U 'is zero.

  In mode 4, the first switching element 12-1 is off, the second switching element 12-2 is on, the terminal voltage of the AC terminal U is -E, the third switching element 12-3 is on, In this mode, the fourth switching element 12-4 is OFF and the terminal voltage of the AC terminal U ′ is E. Therefore, in this mode 4, the terminal voltage between U and U 'is -2E.

  Thus, the output voltage of the single-phase full-bridge inverter circuit repeats modes 1 to 4 by switching on and off the first switching element 12-1 to the fourth switching element 12-4. In this case, the magnitude of the output voltage and the harmonic distortion voltage are changed by adjusting the width d of the rectangular wave.

  Next, FIG. 18 is a circuit diagram of a three-level inverter in a conventional NPC (neutral point clamp) system. The first DC power supply 11 in the first NPC half-bridge circuit 17 is grounded at a neutral point, and the first DC power supply 11 includes the first switching element 12-1 to the fourth switching element 12-4. It is connected. Similarly, the second DC power supply 13 in the second NPC half-bridge circuit 18 is grounded at a neutral point, and the second DC power supply 13 includes the fifth switching element 12-5 to the eighth switching element 12. −8 is connected, and free-wheeling diodes D1 to D8 are connected in parallel to the first switching element 12-1 to the eighth switching element 12-8, respectively.

  A diode D9 is connected between the neutral point of the first DC power supply 11 and the connection point between the first switching element 12-1 and the second switching element 12-2, and the neutrality of the first DC power supply 11 is reached. A diode D10 is connected between the point and a connection point between the third switching element 12-3 and the fourth switching element 12-4. Similarly, a diode D11 is connected between the neutral point of the second DC power supply 13 and the connection point between the fifth switching element 12-5 and the sixth switching element 12-6, and the second DC power supply 13 A diode D12 is connected between the neutral point and the connection point between the seventh switching element 12-7 and the eighth switching element 12-8.

  The upper and lower arms of the first switching element 12-1 to the fourth switching element 12-4 are connected to the upper and lower arms of the fifth switching element 12-5 to the eighth switching element 12-8 in parallel with the DC positive line. 14 and a DC negative electrode line 15. Then, one end U of the AC terminal is pulled out from the connection point of the second switching element 12-2 and the third switching element 12-3, and the other end U ′ of the AC terminal is connected to the sixth switching element 12-6 and the third switching element 12-6. 7 is pulled out from the connection point of the switching element 12-7, and power is supplied from the AC terminals U and U 'to the single-phase AC load. Now, it is assumed that the voltages of the first DC power supply 11 and the second DC power supply 13 are each E across the neutral point. That is, the magnitudes of the DC voltages at both ends supplied to the NPC half-bridge circuit of the conventional single-phase NPC full-bridge inverter must match. In this example, both ends are 2E [V].

FIG. 19 is a waveform diagram showing an example of the output voltage of the AC terminals U and U ′ of the NPC type inverter circuit shown in FIG. 18. Table 2 shows the first switching elements 12-1 to 12 of the NPC type inverter circuit. 8 is a table showing output voltages with respect to ON / OFF of 8 switching elements 12-8. As shown in FIG. 19 and Table 2, the output voltage of the NPC type inverter circuit has five levels of 0, E, 2E, −E, and −2E.

  As shown in Table 2, there are nine modes 1 to 9 for turning on / off the first switching element 12-1 to the eighth switching element 12-8 of the NPC type inverter circuit.

  For example, in mode 1, as shown in Table 2, the first switching element 12-1 is off, the second switching element 12-2 is on, the third switching element 12-3 is on, and the fourth switching The element 12-4 is off, the terminal voltage of the AC terminal U is 0, the fifth switching element 12-5 is off, the sixth switching element 12-6 is on, and the seventh switching element 12-7 is off In this mode, the eighth switching element 12-8 is off and the terminal voltage of the AC terminal U ′ is zero. Therefore, in this mode 1, the terminal voltage between U and U 'is zero.

  Similarly, in mode 2, the terminal voltage between U and U 'is E, in mode 3, the terminal voltage between U and U' is 2E, in mode 4, the terminal voltage between U and U 'is E, and in mode. 5 is U-U 'terminal voltage is 0, mode 6 is U-U' terminal voltage is -E, mode 7 is U-U 'terminal voltage is -2E, and mode 8 is , The terminal voltage between U and U 'is -E, and when in mode 9, the terminal voltage between U and U' is zero.

  Thus, the output voltage of the NPC type inverter circuit switches the first switching element 12-1 to the eighth switching element 12-8 on and off. In this case, the magnitude of the output voltage and the harmonic distortion voltage change by adjusting the widths d and d 'of the rectangular wave.

As described above, single-phase full-bridge inverters and NPC inverters contribute to the development of industry as a known technique (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 10-337045

  However, in the thing of patent document 1, since the positive electrode and negative electrode of a half bridge circuit are mutually connected, the peak value of an output waveform cannot change the two half bridge circuits which comprise a full bridge circuit. For this reason, there is a limit to harmonic reduction. Further, if the modulation frequency by PWM control is increased in order to suppress the harmonic distortion voltage of the power converter, the loss increases. For this reason, it is necessary to enlarge a radiation fin, and when it does so, the enlargement and cost of an apparatus will increase. On the other hand, there is a method of multiplexing rectangular wave inverters, but there is a limit to the reduction of harmonics in the rectangular wave inverter.

  An object of the present invention is to provide a power converter capable of performing fine voltage control, reducing harmonics and suppressing loss due to PWM control.

  According to a first aspect of the present invention, there is provided a power converter comprising: a first half-bridge circuit having a first switching element and a second switching element connected to a first DC power supply; and the first DC power supply. A second half-bridge circuit having a third switching element and a fourth switching element connected to a second DC power supply having a voltage different from the voltage; a neutral point of the first DC power supply; A half-bridge circuit connection line for connecting the first half-bridge circuit and the second half-bridge circuit by connecting between neutral points of the DC power supply, and one end of the first switching element and the second switching element The other end is drawn out from the connection point of the third switching element and the fourth switching element, and an AC terminal for connecting a single-phase AC load is provided.

  According to a second aspect of the present invention, there is provided a power converter comprising: a first half-bridge circuit having a first switching element and a second switching element connected to a first DC power supply; and the first DC power supply. A second half-bridge circuit having a third switching element and a fourth switching element connected to a second DC power supply having a voltage different from the voltage; a neutral point of the first DC power supply; A half-bridge circuit connection line for connecting the first half-bridge circuit and the second half-bridge circuit by connecting between the neutral points of the DC power supply, and connection of the first switching element and the second switching element Interphase reactor connected between the point and the connection point of the third switching element and the fourth switching element, one end is drawn from the intermediate point of the interphase reactor, and the other end is connected to the half bridge circuit Characterized in that a AC terminal for connecting the single-phase AC load drawn from the line.

  According to a third aspect of the present invention, there is provided a power converter comprising: a first half-bridge circuit having a first switching element and a second switching element connected to a first DC power supply; and the first DC power supply. A second half-bridge circuit having a third switching element and a fourth switching element connected to a second DC power supply having a voltage different from the voltage; a neutral point of the first DC power supply; A half-bridge circuit connection line for connecting the first half-bridge circuit and the second half-bridge circuit by connecting between the neutral points of the DC power supply, and connection of the first switching element and the second switching element For connecting to a single-phase AC load via another transformer winding magnetically coupled to the AC winding connected between the point and the connection point of the third switching element and the fourth switching element AC terminal Characterized by comprising and.

  A power converter according to a fourth aspect of the invention includes a first NPC half-bridge circuit having four or more switching elements connected to a first DC power source and four pieces connected to a second DC power source. A second NPC half-bridge circuit having the above switching elements, an NPC half-bridge circuit connecting line connecting between the neutral point of the first DC power source and the neutral point of the second DC power source, An AC terminal for wiring a single-phase AC load is provided between connection points between a plurality of switching elements of one NPC half-bridge circuit and the second NPC half-bridge circuit.

  A power converter according to a fifth aspect of the invention includes a first NPC half-bridge circuit having four or more switching elements connected to a first DC power source and four pieces connected to a second DC power source. A second NPC half-bridge circuit having the above switching elements, an NPC half-bridge circuit connecting line connecting between the neutral point of the first DC power source and the neutral point of the second DC power source, An interphase reactor connected between connection points between a plurality of switching elements of the first NPC half bridge circuit and the second NPC half bridge circuit, and one end drawn from an intermediate point of the interphase reactor and the other end connected to the half bridge circuit And an AC terminal for connecting a single-phase AC load drawn from the line.

  A power converter according to a sixth aspect of the invention includes a first NPC half-bridge circuit having four or more switching elements connected to a first DC power source and four pieces connected to a second DC power source. A second NPC half-bridge circuit having the above switching elements, an NPC half-bridge circuit connecting line connecting between the neutral point of the first DC power source and the neutral point of the second DC power source, Single-phase AC via the other transformer winding magnetically coupled to the AC winding connected between the connection points between the switching elements of one NPC half-bridge circuit and the second NPC half-bridge circuit An AC terminal for connecting to a load is provided.

  A power converter according to a seventh aspect of the invention is the power converter according to any one of the first to sixth aspects, wherein the voltages of the first DC power supply sandwiching the neutral point are E1, E2, and the neutral point are sandwiched. When the voltage of the second DC power source is E3 and E4, the first DC power source and the second DC power source satisfying E1 + E4 = E2 + E3 are connected.

  A power converter according to an eighth aspect of the invention is characterized in that a plurality of power converters according to any one of the first to seventh aspects are combined to be multiphase or multiplexed.

  According to the present invention, the voltage pulse waveform supplied from the first DC power supply in the first half-bridge circuit and the voltage pulse waveform supplied from the second DC power supply in the second half-bridge circuit are superimposed. Since a voltage waveform can be obtained, fine voltage control can be performed without increasing the number of components and without increasing the modulation frequency. As a result, the harmonics can be reduced, and when the PWM control is applied to this method, the carrier frequency can be suppressed as compared with the case where the PWM control is applied to the conventional method, so that the loss can be suppressed.

  Further, when the voltages of the first DC power supply across the neutral point are E1 and E2, and the voltages of the second DC power supply across the neutral point are E3 and E4, E1 + E4 = E2 + E3 should be satisfied. The output voltage is a sine wave, and the voltages E1 to E4 may have different voltage values. When applied to three phases, each of the three phases can be formed by a half bridge circuit. The number of parts in the configuration can be reduced.

(First embodiment)
FIG. 1 is a circuit diagram of an example of a power converter according to the first embodiment of the present invention. This first embodiment is different from the conventional example shown in FIG. 16 in that the DC positive electrode line 14 and the DC negative electrode line 15 are removed, and the neutral point of the first DC power source 11 and the second DC power source 13 are A neutral bridge is connected by a half-bridge circuit connection line 16.

  In FIG. 1, the first half-bridge circuit 17 includes a first switching element 12-1 and a second switching element 12-2 connected to a first DC power supply 11, and the first switching element 12. -1, a freewheeling diode D1 is connected in parallel, and a freewheeling diode D2 is connected in parallel to the second switching element 12-2. In addition, an AC terminal U is drawn from a connection point between the first switching element 12-1 and the second switching element 12-2.

  The second half-bridge circuit 18 includes a third switching element 12-3 and a fourth switching element 12-4 connected to the second DC power supply 13, and the third switching element 12-3 includes A free-wheeling diode D3 is connected in parallel, and a free-wheeling diode D4 is connected in parallel to the fourth switching element 12-4. In addition, an AC terminal U ′ is drawn from a connection point between the third switching element 12-3 and the fourth switching element 12-4.

  The neutral point of the first DC power supply 11 and the neutral point of the second DC power supply 13 are connected by a half-bridge circuit connection line 16, whereby the first half-bridge circuit 17 and the second DC power supply 13 are connected to each other. Are connected to the half-bridge circuit 18.

  The first switching element 12-1 and the second switching element 12-2 of the first half-bridge circuit 17, and the third switching element 12-3 and the fourth switching element 12 of the second half-bridge circuit 18. -4 is individually controlled. That is, an output voltage command to an example of the power converter according to the first embodiment of the present invention is input to the pulse train determination means 19. The pulse train determination means 19 outputs a pulse train to the gate control circuits 20a and 20b so that the output voltage of the power converter matches the output voltage command. The gate control circuit 20a performs on / off control of the first switching element 12-1 and the second switching element 12-2 by the gate drive circuit 21a based on the pulse train from the pulse train determining means 19. Similarly, the gate control circuit 20b performs on / off control of the third switching element 12-3 and the fourth switching element 12-4 by the gate drive circuit 21b based on the pulse train from the pulse train determining means 19.

  Now, it is assumed that the voltage of the first DC power supply 11 is E across the neutral point, and the voltage of the second DC power supply 13 is E ′ (E ′> E) across the neutral point. To do.

FIG. 2 shows on / off signals of the first switching element 12-1 to the fourth switching element 12-4 as an example of the power converter according to the first embodiment and the waveform of the output voltage between the AC terminals U and U ′. FIG. 3 is a table showing output voltages with respect to ON / OFF of the first switching element 12-1 to the fourth switching element 12-4 as an example of the power converter according to the first embodiment. As shown in FIG. 2 and Table 3, the output voltage of an example of the power converter according to the first embodiment has four levels of −E + E ′, E + E ′, EE ′, and −EE ′. Become.

  As shown in Table 3, the first switching element 12-1 to the fourth switching element 12-4 of the example of the power converter according to the first embodiment have six modes 1 to 6 for on / off.

  In mode 1, the first switching element 12-1 is off, the second switching element 12-2 is on, the terminal voltage of the AC terminal U is -E, and the third switching element 12-3 is off. This is a mode in which the fourth switching element 12-4 is on and the terminal voltage of the AC terminal U ′ is −E ′. Accordingly, in this mode 1, the terminal voltage between U and U 'is -E + E', which is between time points t1 and t2 in FIG.

  In mode 2, the first switching element 12-1 is on, the second switching element 12-2 is off, the terminal voltage at the AC terminal U is E, the third switching element 12-3 is off, 4 in which the switching element 12-4 is ON and the terminal voltage of the AC terminal U ′ is −E ′. Accordingly, in this mode 2, the terminal voltage between U and U 'is E + E', and is between the time points t2 and t3 in FIG.

  In mode 3, the first switching element 12-1 is off, the second switching element 12-2 is on, the terminal voltage of the AC terminal U is -E, and the third switching element 12-3 is off. This is a mode in which the fourth switching element 12-4 is on and the terminal voltage of the AC terminal U ′ is −E ′. Therefore, in this mode 3, the terminal voltage between U and U 'is -E + E', which is between time points t3 and t4 in FIG.

  In mode 4, the first switching element 12-1 is on, the second switching element 12-2 is off, the terminal voltage at the AC terminal U is E, the third switching element 12-3 is on, 4 in which the switching element 12-4 is OFF and the terminal voltage of the AC terminal U ′ is E ′. Accordingly, in this mode 4, the terminal voltage between U and U 'is E-E', and is between time points t4 and t5 in FIG.

  In mode 5, the first switching element 12-1 is off, the second switching element 12-2 is on, the terminal voltage of the AC terminal U is -E, the third switching element 12-3 is on, In this mode, the fourth switching element 12-4 is OFF and the terminal voltage of the AC terminal U ′ is E ′. Therefore, in this mode 5, the terminal voltage between U and U 'is -E-E', which is between time points t5 and t6 in FIG.

  In mode 6, the first switching element 12-1 is on, the second switching element 12-2 is off, the terminal voltage of the AC terminal U is E, the third switching element 12-3 is on, 4 in which the switching element 12-4 is OFF and the terminal voltage of the AC terminal U ′ is E ′. Accordingly, in this mode 6, the terminal voltage between U and U 'is E-E', and is between time points t6 and t7 in FIG.

  As described above, the output voltage of an example of the power converter according to the first embodiment switches on and off the first switching element 12-1 to the fourth switching element 12-4. As a result, the output voltage becomes a two-stage rectangular wave. The absolute value of the height of the first-stage rectangular wave serving as the base is | −E + E ′ |, and the absolute value of the height of the second-stage rectangular wave is | E + E ′ |. In this case, the magnitude of the output voltage and the harmonic distortion voltage change by adjusting the width w of the rectangular wave at the second stage. The width w of the second-stage rectangular wave is changed by adjusting the on / off widths of the first switching element 12-1 and the second switching element 12-2.

  That is, at the time t1 to t4, the fourth switching element 12-4 of the second half-bridge circuit 18 is on, and therefore the first switching element 12-1 of the first half-bridge circuit 17 is turned on. Increasing the on-time and shortening the on-time of the second switching element 12-2 increases the width w of the second-stage rectangular wave, and conversely shortens the on-time of the first switching element 12-1. If the ON time of the second switching element 12-2 is lengthened, the width w of the second-stage rectangular wave is reduced.

  On the other hand, from time t4 to t7, the third switching element 12-3 of the second half-bridge circuit 18 is on, and therefore the second switching element 12-2 of the first half-bridge circuit 17 is turned on. Increasing the on-time and shortening the on-time of the first switching element 12-1 increases the width w of the second-stage rectangular wave, and conversely shortens the on-time of the second switching element 12-2. If the on-time of the first switching element 12-1 is increased, the width w of the second-stage rectangular wave is decreased.

  Here, as can be seen from FIG. 2, the output voltage of the power converter has four levels of −E + E ′, E + E ′, EE ′, and −EE ′, and does not take a value of 0, but is particularly problematic. Not. For example, a sine wave can be created without a zero level. Also, a grid-connected inverter for NAS (sodium sulfur) battery or the like is based on active power control, and there is no problem if the output voltage follows the steady change of the grid voltage. Also in the case of reactive power control devices, it is rare to reduce the voltage output to zero.

FIG. 3 is a characteristic diagram showing the relationship between the fundamental wave effective value and the distortion wave index. Here, as an index indicating a distorted wave, calculation was made using the distorted wave index shown below for convenience. The distortion wave index K is assumed to be represented by the following equation (1).

Conventional examples 1 and 2 having characteristics shown in Table 4 were prepared as conventional power converters.

  In Conventional Example 1, the amplitude 2E of the rectangular wave of the output voltage shown in FIG. 17 is 1 p.u., and the pulse width d of the rectangular wave is the fundamental wave effective value 0.6, 0.7, 0.8, 0.9. , 1.0 p.u. corresponding to 4.1, 5.0, 6.0, 7.2 ms, and the conventional example 2 has the amplitude of the rectangular wave of the output voltage shown in FIG. 2E is 1.2 p.u., and the pulse width d of the rectangular wave corresponds to the fundamental wave effective values of 0.6, 0.7, 0.8, 0.9, and 1.0 p.u. It was changed to 7, 4.5, 5.3, 6.3, and 7.6 ms. In FIG. 3, K1 is a characteristic curve of Conventional Example 1, and K2 is a characteristic curve of Conventional Example 2.

Next, Examples 1, 2, and 3 having the characteristics shown in Table 5 were prepared as an example of the power converter according to the first embodiment of the present invention.

  In Example 1, the height (−E + E ′) of the first stage rectangular wave of the output voltage shown in FIG. 2 is 0.55 p.u., and the height of the second stage rectangular wave of the output voltage is 0.65 p. u., the pulse width w of the second-stage rectangular wave is 1.1, 2 corresponding to the fundamental effective values 0.6, 0.7, 0.8, 0.9, 1.0 p.u. .3, 3.5, 4.9, and 6.7 ms. In Example 2, the height (−E + E ′) of the first-stage rectangular wave of the output voltage shown in FIG. 2 is 0.5 p.u., and the height of the second-stage rectangular wave of the output voltage is 0.7 p. u., and the pulse width w of the second-stage rectangular wave is 1.5, 2 corresponding to the fundamental wave effective values of 0.6, 0.7, 0.8, 0.9, 1.0 p.u. .6, 3.8, 5.1, and 6.8 ms. In Example 3, the height (−E + E ′) of the first-stage rectangular wave of the output voltage shown in FIG. 2 is 0.4 p.u., and the height of the second-stage rectangular wave of the output voltage is 0.8 p. u. The pulse width w of the second-stage rectangular wave is 2.2, 3 corresponding to the fundamental effective values 0.6, 0.7, 0.8, 0.9, 1.0 p.u. .2, 4.2, 6.3, and 7.0 ms. 3, K3 is the characteristic curve of the first embodiment, K4 is the characteristic curve of the second embodiment, and K5 is the characteristic curve of the third embodiment.

As can be seen from FIG. 3, in Examples 1, 2, and 3 (characteristic curves K3, K4, and K5), the distortion wave index is reduced compared to Conventional Examples 1 and 2 (characteristic curves K1 and K2). I understand that. This is considered because the output voltage is approximated to a sine wave as a convex shape in which the second-stage rectangular wave is superimposed on the first-stage rectangular wave as shown in FIG.
It is desirable to adjust the voltage levels of the first stage and the second stage according to the target fluctuation range of the fundamental effective value. In addition, it is necessary to design so that the pulse width of the second stage is zero according to the voltage adjustment range, and the target fundamental wave effective value is secured only by the first stage pulse.

  In FIG. 2, the first switching element 12-1 and the second switching element of the first half-bridge circuit 17 are arranged so that the second-stage rectangular wave of the output voltage is positioned approximately at the center of the first-stage rectangular wave. Although the on / off control of 12-2 is performed, as shown in FIG. 4, it is possible to have a characteristic in which the second-stage rectangular wave of the output voltage is biased to one side of the first-stage rectangular wave. FIG. 4 shows a case where the second-stage rectangular wave is biased to the right in the figure. As a result, an unbalanced voltage for compensation can be generated when the unbalanced voltage is compensated by the power converter.

  In the above description, the AC output voltage is taken out between the AC terminal U from the first half-bridge circuit 17 and the AC terminal U ′ from the second half-bridge circuit 18. As shown, the interphase reactor 22 is connected between the AC terminal U from the first half-bridge circuit 17 and the AC terminal U ′ from the second half-bridge circuit 18, and from the midpoint of the interphase reactor 22. The terminal UN may be taken out, the terminal N may be taken out from the half-bridge circuit connection line 16, and an AC output voltage may be taken out between the terminal UN and the terminal N.

  In this case, the sum of the voltage of the AC terminal U from the first half bridge circuit 17 and the voltage of the AC terminal U ′ from the second half bridge circuit 18 is output as an output voltage between the AC terminals UN and N. Is done.

  FIG. 6 shows on / off signals and AC terminals UN, N of the first switching element 12-1 to the fourth switching element 12-4 as another example of the power converter according to the first embodiment shown in FIG. It is a wave form diagram of the output voltage between. As shown in FIG. 6, the on / off states of the third switching element 12-3 and the fourth switching element 12-4 of the second half bridge circuit 18 are reversed with respect to the waveform diagram shown in FIG. Yes.

  Further, as shown in FIG. 7, the connection point between the first switching element 12-1 and the second switching element 12-2 and the connection point between the third switching element 12-3 and the fourth switching element 12-4. The AC winding 23 is connected to the AC winding 23, and AC terminals UT and UT ′ for connecting to a single-phase AC load are taken out via the other transformer winding 24 magnetically coupled to the AC winding 23. You may do it.

  According to the first embodiment, the neutral point of the first DC power source 11 in the first half-bridge circuit 17 of the power converter and the neutral point of the second DC power source 13 in the second half-bridge circuit 18. Since the two switching elements of the first half-bridge circuit 17 and the two switching elements of the second half-bridge circuit 18 are on / off controlled by connecting only between the points, the first DC power supply 11 supplies The voltage waveform obtained by superimposing the voltage pulse waveform to be supplied and the voltage pulse waveform supplied from the second DC power supply 13 in two stages can be obtained. Therefore, fine voltage control can be performed without increasing the number of parts and without increasing the modulation frequency. As a result, a voltage waveform approximate to an AC waveform can be obtained, and harmonics can be reduced. Further, when PWM control is applied to this method, the carrier frequency can be suppressed compared to the case where PWM control is applied to the conventional method, so that loss can be suppressed.

  For example, when the DC power supplies 11 and 13 are DC power supplies such as fuel cells and NAS batteries, even if an imbalance occurs in the DC power supplies 11 and 13 due to deterioration over time, the multilevel inverter is based on the unbalanced state. Can be realized. Therefore, effective use of a fuel cell, a NAS battery, etc. can be performed. In addition, since the distance from the fuel cell or NAS battery as the DC power sources 11 and 13 to the first switching element 12-1 to the fourth switching element 12-4 can be made equal, the wiring inductance compensation design is easy. Become.

(Second Embodiment)
FIG. 8 is a circuit diagram of an example of a power converter according to the second embodiment of the present invention. This second embodiment is different from the conventional example shown in FIG. 18 in that the DC positive electrode line 14 and the DC negative electrode line 15 are removed, and the neutral point of the first DC power source 11 and the second DC power source 13 are A neutral point is connected by an NPC half bridge circuit connection line 16. The same elements as those in the conventional example shown in FIG.

  In FIG. 8, the neutral point of the first DC power supply 11 and the neutral point of the second DC power supply 13 are connected by an NPC half bridge circuit connection line 16, whereby the first NPC half bridge circuit is connected. 17 and the second NPC half bridge circuit 18 are connected. The first switching element 12-1 to the fourth switching element 12-4 of the first NPC half-bridge circuit 17 and the fifth switching element 12-5 to the eighth switching of the second NPC half-bridge circuit 18 The elements 12-8 are individually controlled. In FIG. 8, illustration of a control device for controlling the first switching element 12-1 to the eighth switching element 12-8 is omitted.

  Now, it is assumed that the voltage of the first DC power supply 11 is E across the neutral point, and the voltage of the second DC power supply 13 is E ′ across the neutral point. Further, it is assumed that E ′> 2E.

  FIG. 9 shows on / off signals of the first switching element 12-1 to the eighth switching element 12-8 as an example of the power converter according to the second embodiment and the waveform of the output voltage between the AC terminals U and U ′. FIG. 6 and Table 6 are tables showing output voltages with respect to ON / OFF of the first switching element 12-1 to the eighth switching element 12-8 as an example of the power converter according to the second embodiment.

As shown in FIG. 9 and Table 6, the output voltage of an example of the power converter according to the second embodiment is 0, E, −E + E ′, E ′, E + E ′, −E, EE ′, There are nine levels -E 'and -EE'. Here, since the voltage E ′ of the second DC power supply 13 satisfies E ′> 2E, the relationship of E ′> − E + E ′>E>0> EE ′ holds, and the AC terminals U, U The waveform of the output voltage between 'is as shown in FIG. When the voltage E ′ of the second DC power supply 13 is E <E ′ <2E, the relationship E ′>E> −E + E ′>0> EE−E ′ holds, and when 2E ′ <E, > E−E ′> E ′>0> −E + E ′, and if E ′ <E <2E ′, the relationship E> E ′>EE−>0> −E + E ′ is satisfied. Thus, the output voltage of 9 levels, 0, E, -E + E ', E', E + E ', -E, EE', -E ', depending on the magnitude of the voltage E' of the second DC power supply 13. , −EE ′ changes in magnitude.

  As shown in Table 6, there are 16 modes 1 to 16 for turning on and off the second switching element 12-1 to the eighth switching element 12-8 as an example of the power converter according to the second embodiment.

  For example, in mode 1, as shown in Table 6, the first switching element 12-1 is off, the second switching element 12-2 is on, the third switching element 12-3 is on, and the fourth switching The element 12-4 is off, the terminal voltage of the AC terminal U is 0, the fifth switching element 12-5 is off, the sixth switching element 12-6 is on, and the seventh switching element 12-7 is off In this mode, the eighth switching element 12-8 is off and the terminal voltage of the AC terminal U ′ is zero. Therefore, in this mode 1, the terminal voltage between U and U 'is zero.

  Similarly, the terminal voltage between U and U 'is E in mode 2, the terminal voltage between U and U' is -E + E 'in mode 3, and the terminal voltage between U and U' is E in mode 4. In the mode 5, the terminal voltage between U−U ′ is E + E ′, in the mode 6, the terminal voltage between U−U ′ is E ′, and in the mode 7, the terminal voltage between U−U ′ is −E + E ′. In mode 8, the terminal voltage between U and U 'is E, in mode 9, the terminal voltage between U and U' is 0, and in mode 10, the terminal voltage between U and U 'is -E. The terminal voltage between U and U 'is EE', the terminal voltage between U and U 'is -E' when in mode 12, and the terminal voltage between U and U 'is -EE' when in mode 13. In mode 14, the terminal voltage between U and U 'is -E', in mode 15, the terminal voltage between U and U 'is EE', and in mode 16, UU '. The terminal voltage is -E.

  As described above, the output voltage of an example of the power converter according to the second embodiment switches the first switching element 12-1 to the eighth switching element 12-8 on and off. As a result, the output voltage becomes a four-stage rectangular wave. The absolute value of the height of the first-stage rectangular wave serving as the base is | E |, and the absolute value of the height of the second-stage rectangular wave is | −E + E ′ | The absolute value of | E ′ | is the absolute value of the height of the rectangular wave in the fourth stage is | E + E ′ |. In this case, the magnitude of the output voltage and the harmonic distortion voltage change by adjusting the width of the rectangular wave in the second to fourth stages. In order to change the width of the rectangular wave in the second to fourth stages, the on / off width of the first switching element 12-1 to the fourth switching element 12-4 is adjusted. Further, a value of 0 can be taken as the output voltage.

  In this embodiment, the voltage pulse is generated under the condition of 2E <E ′. On the other hand, when a voltage pulse is generated under the condition of 2E> E ′, the absolute value of the height of the first-stage rectangular wave is | −E + E ′ |, and the absolute value of the height of the second-stage rectangular wave is | In this case, a stepped rectangular wave voltage can be generated.

  FIG. 10 is a circuit diagram of another example of the power converter according to the second embodiment of the present invention. This is obtained by replacing the 3-level inverter shown in FIG. 8 with a 5-level inverter. The first DC power supply 11 in the first NPC half bridge circuit 17 has four power supplies, and each voltage is E. Similarly, the second DC power supply 13 in the second NPC half-bridge circuit 18 has four power supplies, and each voltage is E ′.

  The first DC power supply 11 in the first NPC half-bridge circuit 17 is grounded at a neutral point. The first DC power supply 11 includes the first switching element 12-1 to the eighth switching element 12-. 8 is connected. Similarly, the second DC power source 13 in the second NPC half-bridge circuit 18 is grounded at a neutral point, and the ninth DC switching element 12-9 to the sixteenth switching element 12 are connected to the second DC power source 13. −16 is connected, and free-wheeling diodes D1 to D16 are connected in parallel to the first switching element 12-1 to the sixteenth switching element 12-16, respectively.

  A diode D17 is connected between the connection point of the first switching element 12-1 and the second switching element 12-2 and the connection point of the first power supply E and the second power supply E of the first DC power supply 11. The diode D18 is connected between the connection point of the first power supply E and the second power supply E of the first DC power supply 11 and the connection point of the fifth switching element 12-5 and the sixth switching element 12-6. Is done. A diode D19 is connected between the connection point of the second switching element 12-2 and the third switching element 12-3 and the connection point of the second power supply E and the third power supply E of the first DC power supply 11, A diode D20 is connected between a connection point between the second power supply E and the third power supply E of the first DC power supply 11 and a connection point between the sixth switching element 12-6 and the seventh switching element 12-7, Furthermore, a diode D21 is connected between the connection point of the third switching element 12-3 and the fourth switching element 12-4 and the connection point of the third power supply E and the fourth power supply E of the first DC power supply 11. The diode D22 is connected between the connection point of the third power supply E and the fourth power supply E of the first DC power supply 11 and the connection point of the seventh switching element 12-7 and the eighth switching element 12-8. Is done.

  Similarly, a diode is connected between the connection point of the ninth switching element 12-9 and the tenth switching element 12-10 and the connection point of the first power supply E ′ and the second power supply E ′ of the second DC power supply 13. D23 is connected, between the connection point of the first power supply E ′ and the second power supply E ′ of the second DC power supply 13 and the connection point of the thirteenth switching element 12-13 and the fourteenth switching element 12-14. Is connected to the diode D24. A diode D25 is connected between the connection point of the tenth switching element 12-10 and the eleventh switching element 12-11 and the connection point of the second power supply E ′ and the third power supply E ′ of the second DC power supply 13. The diode D26 is connected between the connection point of the second power supply E ′ and the third power supply E ′ of the second DC power supply 13 and the connection point of the fourteenth switching element 12-14 and the fifteenth switching element 12-15. Are connected, and the connection point between the eleventh switching element 12-11 and the twelfth switching element 12-12 and the connection point between the third power supply E ′ and the fourth power supply E ′ of the second DC power supply 13 A diode D27 is connected between them, and the connection point between the third power supply E ′ and the fourth power supply E ′ of the second DC power supply 13 and the fifteenth switching element 12-15 and the sixteenth switching element 12-16. Diode D28 is connected between the points.

  The neutral point of the first DC power supply 11 and the neutral point of the second DC power supply 13 are connected by an NPC half bridge circuit connection line 16, and one end U of the AC terminal is connected to the fourth switching element 12. -4 and the fifth switching element 12-5, and the other end U ′ of the AC terminal is drawn from the connection point of the twelfth switching element 12-12 and the thirteenth switching element 12-13. Yes. As shown in another example circuit in the second embodiment, the distorted wave can be further reduced by increasing the number of levels.

  In the above description, the AC output voltage is extracted from between the AC terminal U from the first half-bridge circuit 17 and the AC terminal U ′ from the second half-bridge circuit 18. 5, the interphase reactor 22 is connected between the AC terminal U from the first half-bridge circuit 17 and the AC terminal U ′ from the second half-bridge circuit 18, and the interphase The terminal UN may be taken out from the intermediate point of the reactor 22, the terminal N may be taken out from the half bridge circuit connection line 16, and an AC output voltage may be taken out between the terminals UN and N.

  Further, the NPC half-bridge circuit 17 is controlled to be turned on and off so that the 1 + n-stage rectangular wave of the output voltage is positioned approximately at the center of the n-stage rectangular wave. FIG. 4 shows the first embodiment. As shown, the 1 + n-stage rectangular wave of the output voltage can be biased to one of the n-stage rectangular waves. As a result, an unbalanced voltage for compensation can be generated when the unbalanced voltage is compensated by the power converter.

  Further, as shown in FIG. 7 of the first embodiment, the connection point of the first switching element 12-1 and the second switching element 12-2 and the third switching element 12-3 and the fourth switching element. An AC winding 23 is connected to the connection point of the element 12-4, and the AC winding 23 is connected to a single-phase AC load via the other transformer winding 24 magnetically coupled to the AC winding 23. The terminals UT and UT ′ may be taken out.

  According to the second embodiment, in addition to the effects of the first embodiment, the four switching elements of the first NPC half-bridge circuit 17 and the four switching elements of the second NPC half-bridge circuit 18 Since the voltage pulse waveform supplied from the first DC power supply 11 and the voltage pulse waveform supplied from the second DC power supply 13 are superimposed in four stages, a voltage waveform can be obtained. Can be secured, so finer voltage control is possible.

(Third embodiment)
FIG. 11 is a circuit diagram of an example of a power converter according to the third embodiment of the present invention. This third embodiment is different from the first embodiment shown in FIG. 1 in that the voltages of the first DC power supply 11 across the neutral point are E1, E2, and the second across the neutral point. The voltage of the DC power source 13 is set to E3 and E4 so that E1 + E4 = E2 + E3 is satisfied.

FIG. 12 shows the waveforms of the ON / OFF signals of the first switching element 12-1 to the fourth switching element 12-4 and the output voltage between the AC terminals U and U ′ as an example of the power converter according to the third embodiment. FIG. 7 is a table showing output voltages with respect to on / off of the first switching element 12-1 to the fourth switching element 12-4 as an example of the power converter according to the third embodiment. As shown in FIG. 12 and Table 7, the output voltage of an example of the power converter according to the third embodiment has four levels of E1−E3, E1 + E4, −E2 + E4, and −E2−E3.

  As shown in Table 7, there are six modes 1 to 6 for turning on and off the first switching element 12-1 to the fourth switching element 12-4 as an example of the power converter according to the third embodiment.

  In mode 1, the first switching element 12-1 is on, the second switching element 12-2 is off, the terminal voltage at the AC terminal U is E1, the third switching element 12-3 is on, 4 in which the switching element 12-4 is OFF and the terminal voltage of the AC terminal U ′ is E3. Therefore, in this mode 1, the terminal voltage between U and U 'is E1-E3, which is between time points t1 and t2 in FIG.

  In mode 2, the first switching element 12-1 is on, the second switching element 12-2 is off, the terminal voltage at the AC terminal U is E1, the third switching element 12-3 is off, No. 4 switching element 12-4 is on, and the terminal voltage of the AC terminal U ′ is −E4. Accordingly, in this mode 2, the terminal voltage between U and U 'is E1 + E4, which is between time points t2 and t3 in FIG.

  In mode 3, the first switching element 12-1 is on, the second switching element 12-2 is off, the terminal voltage of the AC terminal U is E1, the third switching element 12-3 is on, 4 in which the switching element 12-4 is OFF and the terminal voltage of the AC terminal U ′ is E3. Therefore, in this mode 3, the terminal voltage between U and U 'is E1-E3, and is between time points t3 and t4 in FIG.

  In mode 4, the first switching element 12-1 is off, the second switching element 12-2 is on, the terminal voltage of the AC terminal U is -E2, and the third switching element 12-3 is off. In this mode, the fourth switching element 12-4 is on and the terminal voltage of the AC terminal U ′ is −E4. Therefore, in this mode 4, the terminal voltage between U and U 'is -E2 + E4, which is between time points t4 and t5 in FIG.

  In mode 5, the first switching element 12-1 is off, the second switching element 12-2 is on, the terminal voltage of the AC terminal U is -E2, and the third switching element 12-3 is on. In this mode, the fourth switching element 12-4 is OFF and the terminal voltage of the AC terminal U ′ is E3. Therefore, in this mode 5, the terminal voltage between U and U 'is -E2-E3, which is between time points t5 and t6 in FIG.

  In mode 6, the first switching element 12-1 is off, the second switching element 12-2 is on, the terminal voltage of the AC terminal U is -E2, and the third switching element 12-3 is off. In this mode, the fourth switching element 12-4 is on and the terminal voltage of the AC terminal U ′ is −E4. Therefore, in this mode 6, the terminal voltage between U and U 'is -E2 + E4, which is between time points t6 and t7 in FIG.

  As described above, the output voltage of an example of the power converter according to the third embodiment is switched between modes 1 to 6 by switching on and off the first switching element 12-1 to the fourth switching element 12-4. repeat. As a result, the output voltage becomes a two-stage rectangular wave. The absolute value of the height of the first-stage rectangular wave is | -E2 + E4 |, | E1-E3 |, and the absolute value of the height of the second-stage rectangular wave is | E1 + E4 |, | -E2- E3 |.

  Here, | −E2 + E4 | = | E1−E3 | and | E1 + E4 | = | −E2−E3 |. Therefore, E1 + E4 = E2 + E3. As a result, the absolute values of the positive and negative waveforms are equal, and an AC sine wave is obtained. As in the case of the first embodiment, the magnitude of the output voltage and the harmonic distortion voltage can be adjusted by changing the width w of the rectangular wave at the second stage.

    Further, even if the output of any of the voltages E1 to E4 of the DC power supplies 11 and 13 becomes 0, an AC sine wave can be obtained as long as E1 + E4 = E2 + E3 is satisfied.

  In the above description, the AC output voltage is extracted from between the AC terminal U from the first half-bridge circuit 17 and the AC terminal U ′ from the second half-bridge circuit 18. 5, the interphase reactor 22 is connected between the AC terminal U from the first half-bridge circuit 17 and the AC terminal U ′ from the second half-bridge circuit 18, and the interphase The terminal UN may be taken out from the intermediate point of the reactor 22, the terminal N may be taken out from the half bridge circuit connection line 16, and an AC output voltage may be taken out between the terminals UN and N.

  In the present embodiment as well, a compensation unbalance voltage can be generated when the power converter compensates the unbalance voltage.

  Further, as shown in FIG. 7 of the first embodiment, the connection point of the first switching element 12-1 and the second switching element 12-2 and the third switching element 12-3 and the fourth switching element. An AC winding 23 is connected to the connection point of the element 12-4, and the AC winding 23 is connected to a single-phase AC load via the other transformer winding 24 magnetically coupled to the AC winding 23. The terminals UT and UT ′ may be taken out.

  Next, it is also possible to combine a plurality of power converters of the first embodiment, the second embodiment, and the third embodiment to constitute a multiphase power converter. FIG. 13 is a circuit diagram showing an example of a three-phase power converter configured by combining three power converters according to the third embodiment of the present invention, and FIG. 14 is a circuit diagram of FIG. It is a wave form diagram of the output voltage between the on-off signal of the switching element of a phase power converter, and the alternating current terminal of three phases.

  The first half bridge circuits 17U, 17V, 17W and the second half bridge circuits 18U, 18V, 18W are provided for the three-phase U phase, V phase, and W phase. A first DC power supply 11 is connected in parallel to the first half-bridge circuits 17U, 17V, and 17W, and a second DC power supply 13 is connected in parallel to the second half-bridge circuits 18U, 18V, and 18W. The neutral point of the first DC power supply 11 and the neutral point of the second DC power supply 13 are connected by a half bridge circuit connection line 16, whereby the first half bridge circuits 17 U, 17 V, 17W and the second half bridge circuits 18U, 18V, 18W are connected.

  The U-phase first half-bridge circuit 17U has switching elements S1 and S2, and free-wheeling diodes D1 and D2 are connected in parallel to the switching elements S1 and S2, respectively. U is pulled out. The V-phase first half-bridge circuit 17V includes switching elements S3 and S4, and free-wheeling diodes D3 and D4 are connected in parallel to the switching elements S3 and S4, respectively, from the connection point of the switching elements S3 and S4. The AC terminal V is pulled out. Further, the W-phase first half-bridge circuit 17W includes switching elements S5 and S6, and free-wheeling diodes D5 and D6 are connected in parallel to the switching elements S5 and S6, respectively, from the connection point of the switching elements S5 and S6. The AC terminal W is drawn out.

  Similarly, for the second half-bridge circuits 18U, 18V, and 18W, the U-phase second half-bridge circuit 18U includes switching elements S7 and S8, and the switching elements S7 and S8 include free-wheeling diodes D7 and D8, respectively. Are connected in parallel, and the AC terminal U ′ is drawn from the connection point of the switching elements S7 and S8. Further, the V-phase second half-bridge circuit 18V has switching elements S9 and S10, and free-wheeling diodes D9 and D10 are connected in parallel to the switching elements S9 and S10, respectively, from the connection point of the switching elements S9 and S10. The AC terminal V ′ is drawn out. Further, the W-phase second half-bridge circuit 18W includes switching elements S11 and S12, and free-wheeling diodes D11 and D12 are connected in parallel to the switching elements S11 and S12, respectively, from the connection point of the switching elements S11 and S12. The AC terminal W ′ is drawn out.

  As shown in FIG. 14, the output voltage of the three-phase power converter has four levels E1-E3, E1 + E4, -E2 + E4, and -E2-E3, as in FIG.

In addition, there are six modes 1 to 6 for turning on and off the twelve switching elements S1 to S12.

  In mode 1, the switching elements S2, S4, S6, S8, S9, S12 are on, the switching elements S1, S3, S5, S7, S10, S11 are off, the terminal voltage of the AC terminal U is E1, and the AC terminal U ′ The terminal voltage of the AC terminal V is −E2, the terminal voltage of the AC terminal V ′ is E3, the terminal voltage of the AC terminal W is E1, and the terminal voltage of the AC terminal W ′ is E3. Therefore, in this mode 1, the terminal voltage between U and U 'is E1-E3, the terminal voltage between V and V' is -E2-E3, and the terminal voltage between WW 'is E1 and E3. Between time t1 and t2.

  Similarly, by switching on and off the switching elements S1 to S12, the mode changes to modes 2 to 6, and the mode is repeated. As a result, the output voltage of the terminal voltage between U and U ', the terminal voltage between V and V', and the terminal voltage between W and W 'becomes a two-stage rectangular wave as in FIG. Next, a plurality of power converters of the first embodiment, the second embodiment, and the third embodiment are combined with a transformer or an interphase reactor to form a multiphase or multiplexed power converter. It is also possible to do. FIG. 15 is a configuration diagram of a multiphase power converter according to an embodiment of the present invention, and FIG. 15A is a configuration diagram of a multiphase power converter in which a three-phase power converter is configured by transformer coupling. FIG. 15B is a configuration diagram of a multiphase power converter in which a three-phase power converter is configured by interphase reactor coupling.

  As shown in FIG. 15 (a), a three-phase power converter is configured by connecting two half-bridge circuits 10 in series with a transformer coupling for each of the three phases U, V, and W. Yes. Further, as shown in FIG. 15B, a three-phase power converter is configured by connecting two half-bridge circuits 10 in series with interphase reactors for each of the three U-phases, V-phases, and W-phases. is doing. Thereby, the multiphase power converter which has the effect of 1st Embodiment and the effect of 2nd Embodiment can be provided. By multiplexing these converters, harmonics can be further reduced and the capacity can be increased.

1 is a circuit diagram of an example of a power converter according to a first embodiment of the present invention. FIG. 6 is a waveform diagram of an on / off signal of the first to fourth switching elements and an output voltage between the AC terminals U and U ′ in the example of the power converter according to the first embodiment of the present invention. The characteristic view which shows the relationship between a fundamental wave effective value and a distortion wave index | exponent. FIG. 6 is a waveform diagram of another example of the on / off signal of the first to fourth switching elements and the output voltage between the AC terminals U and U ′ in the example of the power converter according to the first embodiment of the present invention. The circuit diagram of the other example of the power converter concerning the 1st Embodiment of this invention. The wave form diagram of the output voltage between the on-off signal of the 1st switching element of the other examples of the power converter concerning the 1st Embodiment of this invention thru | or the 4th switching element, and AC terminal U, U '. The circuit diagram of another example of the power converter concerning the 1st Embodiment of this invention. The circuit diagram of an example of the power converter concerning the 2nd Embodiment of this invention. FIG. 10 is a waveform diagram of an on / off signal of first to eighth switching elements and an output voltage between AC terminals U and U ′ of an example of a power converter according to a second embodiment of the present invention. The circuit diagram of another example of the power converter concerning the 2nd Embodiment of this invention. The circuit diagram of an example of the power converter concerning the 3rd Embodiment of this invention. The wave form diagram of the output voltage between the on-off signal and alternating current terminal U and U 'of the 1st switching element of the example of the power converter concerning the 3rd Embodiment of this invention thru | or a 4th switching element. The circuit diagram which shows an example of the three-phase power converter comprised combining the three power converters concerning the 3rd Embodiment of this invention. FIG. 14 is a waveform diagram of an on / off signal of a switching element of the three-phase power converter shown in FIG. 13 and an output voltage between three-phase AC terminals. The block diagram of the polyphase power converter concerning embodiment of this invention. The circuit diagram of the conventional single phase full bridge inverter. FIG. 17 is a waveform diagram showing an example of output voltages of AC terminals U and U ′ of the single-phase full-bridge inverter circuit shown in FIG. 16. The circuit diagram of the conventional NPC type inverter. The wave form diagram which shows an example of the output voltage of alternating current terminal U of the NPC type inverter circuit shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... 1st DC power supply, 12 ... Switching element, 13 ... 2nd DC power supply, 14 ... DC positive line, 15 ... DC negative line, 16 ... Half bridge circuit connection line, 17 ... 1st half bridge circuit, DESCRIPTION OF SYMBOLS 18 ... 2nd half bridge circuit, 19 ... Pulse train determination means, 20 ... Gate control circuit, 21 ... Gate drive circuit, 22 ... Interphase reactor, 23 ... AC winding, 24 ... Transformer winding

Claims (8)

  A first half-bridge circuit having a first switching element and a second switching element connected to a first DC power supply, and a second DC power supply having a voltage different from the voltage of the first DC power supply. The second half-bridge circuit having the connected third switching element and fourth switching element is connected to the neutral point of the first DC power supply and the neutral point of the second DC power supply. A half-bridge circuit connection line connecting the first half-bridge circuit and the second half-bridge circuit, one end being drawn from the connection point of the first switching element and the second switching element, and the other end being the third A power converter comprising: an AC terminal that is drawn from a connection point of the switching element and the fourth switching element and connects a single-phase AC load.   A first half-bridge circuit having a first switching element and a second switching element connected to a first DC power supply, and a second DC power supply having a voltage different from the voltage of the first DC power supply. The second half-bridge circuit having the connected third switching element and fourth switching element is connected to the neutral point of the first DC power supply and the neutral point of the second DC power supply. A half-bridge circuit connection line for connecting the first half-bridge circuit and the second half-bridge circuit, a connection point between the first switching element and the second switching element, a third switching element and a fourth switching The interphase reactor connected between the connection points of the elements and one end pulled out from the midpoint of the interphase reactor and the other end pulled out from the half-bridge circuit connection line to connect a single-phase AC load Power converter characterized by comprising a order AC terminals of.   A first half-bridge circuit having a first switching element and a second switching element connected to a first DC power supply, and a second DC power supply having a voltage different from the voltage of the first DC power supply. The second half-bridge circuit having the connected third switching element and fourth switching element is connected to the neutral point of the first DC power supply and the neutral point of the second DC power supply. A half-bridge circuit connection line for connecting the first half-bridge circuit and the second half-bridge circuit, a connection point between the first switching element and the second switching element, a third switching element and a fourth switching An electric power comprising an AC winding connected between the connection points of the elements and an AC terminal for connecting to a single-phase AC load via another transformer winding magnetically coupled conversion .   A first NPC half-bridge circuit having four or more switching elements connected to the first DC power source and a second NPC half bridge having four or more switching elements connected to the second DC power source A bridge circuit, an NPC half bridge circuit connection line connecting between a neutral point of the first DC power source and a neutral point of the second DC power source, a first NPC half bridge circuit, and a second NPC half A power converter comprising: an AC terminal for wiring a single-phase AC load between connection points between a plurality of switching elements of a bridge circuit.   A first NPC half-bridge circuit having four or more switching elements connected to the first DC power source and a second NPC half bridge having four or more switching elements connected to the second DC power source A bridge circuit, an NPC half bridge circuit connection line connecting between a neutral point of the first DC power source and a neutral point of the second DC power source, a first NPC half bridge circuit, and a second NPC half Interphase reactor connected between connection points between multiple switching elements of the bridge circuit, and one end is drawn from the middle point of the interphase reactor and the other end is drawn from the half bridge circuit connection line to connect a single-phase AC load A power converter comprising: an AC terminal.   A first NPC half-bridge circuit having four or more switching elements connected to the first DC power source and a second NPC half bridge having four or more switching elements connected to the second DC power source A bridge circuit, an NPC half bridge circuit connection line connecting between a neutral point of the first DC power source and a neutral point of the second DC power source, a first NPC half bridge circuit, and a second NPC half An AC winding connected between connection points between a plurality of switching elements of the bridge circuit and an AC terminal for connecting to a single-phase AC load via the other magnetically coupled transformer winding A power converter characterized by that.   The first DC power supply satisfying E1 + E4 = E2 + E3, where E1 and E2 are the voltages of the first DC power supply sandwiching the neutral point, and E3 and E4 are the voltages of the second DC power supply sandwiching the neutral point The power converter according to any one of claims 1 to 6, wherein a second DC power supply is connected.   A power converter characterized in that a plurality of power converters according to any one of claims 1 to 7 are combined and multiphased or multiplexed.

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