JP4512117B2 - Multiple power conversion device and multiple transformer - Google Patents

Description

  The present invention relates to a multiple power conversion device in which a plurality of single-phase cell inverters are connected in series, and a multiple transformer used therefor.

  In variable speed operation of a high-voltage (for example, 3 kV or more) motor, a multiple power conversion device in which single-phase cell inverters are connected in series is used to increase the capacity of the inverter and improve the output waveform. This multiplex power converter uses a multiplex transformer that outputs a plurality of three-phase AC voltages having different phases from a three-phase AC power supply. For example, Patent Document 1 discloses one of two U, V, and W phases. A method has been proposed in which the secondary windings are shifted by 20 degrees and the phases of the six secondary windings are shifted by 10 degrees, each of the remaining two phases. As a result, power supply harmonics are reduced by a combination of 18-pulse rectification and 36-pulse rectification.

A single-phase AC signal obtained by multiplex connection of these outputs is input to the motor. This device is characterized in that a high voltage can be directly applied to the motor without using an output transformer by increasing the number of single-phase cell inverters or increasing the DC voltage of the smoothing capacitor unit. For this reason, power loss due to the output transformer can be ignored, and highly efficient power conversion can be realized. At this time, in order to reduce power supply harmonics, by adjusting the phase of the secondary winding of the multiple transformer, the input phase to each of the n single-phase cell inverters for each output phase (n is a natural number) Similarly for the output phase, shift by 60 / n degrees. Thereby, the 6n pulse rectification can reduce harmonics of orders lower than the (6n-1) and (6n + 1) orders. These are generally known, and a multiplex power conversion device using this is described in Patent Document 2.
Japanese Patent Laid-Open No. 10-337042 US Pat. No. 5,625,545

  However, in the technology of each patent document, when the phase is shifted by 60 / n degrees in common for each phase, the harmonic order that cannot be reduced becomes 11th order, 13th order or more when n = 2 and the number of stages is small. , There is a problem that lower-order harmonic currents remain compared to when n = 3 or 4. Further, when some windings of each phase are combined as in Patent Document 1, harmonic currents other than (6k + 1), (6k-1) (k is a positive integer) may be generated. There is also.

  Then, this invention makes it a subject to provide the multiplex power converter which can reduce a lower harmonic current, and the multiplex transformer used for this.

In order to solve the above-described problem, the multiple power conversion device of the present invention is configured such that when n and m are natural numbers, m-phase AC power input to the primary winding is supplied to (m × n) secondary windings. A multiple transformer for distribution and m sets of multiple power converters, wherein the multiple power converter converts AC power distributed to each secondary winding into AC power of variable voltage or variable frequency. In a multiplex power conversion apparatus configured by connecting n-stage single-phase cell inverters in series, the secondary winding of the multiplex transformer is 60 / n between the n single-phase cell inverters corresponding to the in-phase output. has a phase difference of each degree, the phase difference between the m × n single-phase cell inverters corresponding to m phase is characterized in that there by 60 / (m × n) degrees.

The secondary current of the multiplex transformer includes a harmonic current generated by the single-phase cell inverter, and this harmonic current has a component due to voltage ripple and a component independent of voltage ripple.
Since the phase difference between m × n single-phase cell inverters corresponding to all m phases is 60 / (m × n) degrees, it is a component that does not depend on voltage ripple, and (6n−1), ( 6n + 1) Harmonic current lower than the order is reduced. Also, by adjusting the capacitance of the smoothing capacitor provided in the single-phase cell inverter or the impedance of the multiple transformer, the voltage ripple of the smoothing capacitor is reduced, thereby reducing the voltage ripple, and the harmonic current due to the voltage ripple. Ingredients are reduced. Further, the output of the multiple power conversion device is set to three phases U, V, and W, and the phase difference of the input signal from the secondary winding of the multiple transformer to the single-phase cell inverter is (U, V, W). ), (W, U, V) or (V, W, U) in the order of 20 / n degrees or advanced.

  According to the present invention, lower harmonic currents can be reduced.

(First embodiment)
The multiple power conversion apparatus of this embodiment employs a two-stage multiplexing system with n = 2.
In FIG. 1, a multiplex power conversion apparatus 100 includes a multiplex transformer 20 connected to a three-phase commercial power source 1 with m = 3, and six single-phase cell inverters 3a, 3b, 3c, 3d, 3e, and 3f, and two single-phase cell inverters 3a and 3b, 3c and 3d, and 3e and 3f, whose outputs are connected in series, are connected to the motor 4 in a three-phase connection. The two-stage single-phase cell inverters 3a and 3b whose outputs are connected in series constitute a multi-power converter, and the single-phase cell inverters 3c and 3d and the single-phase cell inverters 3e and 3f are similarly multi-power converters. Configure. That is, the multiplex power conversion apparatus 100 includes a multiplex transformer 20 and three sets of multiplex power converters whose outputs are connected in three phases. In FIG. 1, the multiple power conversion apparatus 100 is provided with a neutral point P and connected to the motor 4 by a three-phase Y connection, but may be connected by a Δ connection.

  The multiple transformer 20 includes a Y-connected primary winding and six three-phase secondary windings, and distributes the three-phase power to the six secondary windings. In addition, the secondary winding maintains a phase difference of 60 / n = 30 degrees between single-phase cell inverters (3a and 3b, 3c and 3d, 3e and 3f) in the U, V, and W phases, Multiple power converters in the same stage of the phase maintain a phase difference of 60/6 = 10 degrees. That is, a phase difference of 60/6 = 10 degrees is maintained between a total of 6 (= 3 phases × n) single-phase cell inverters corresponding to all phases. For example, the phases of the secondary windings of the multiple transformer 20 are 0 degree (U phase 3a), -30 degrees (U phase 3b), 10 degrees (V phase 3c), and -20 degrees (V phase 3d), respectively. , 20 degrees (W phase 3e) and -10 degrees (W phase 3f). In this case, the phase advances by 10 degrees in the order of U → V → W (0 degrees → 10 degrees → 20 degrees and −30 degrees → −20 degrees → −10 degrees).

  Here, in the secondary winding, the single-phase cell inverters of the same phase are insulated from each other, and each phase has a phase angle using a star staggered connection or a delta staggered connection. Here, the staggered connection is a connection in which a plurality of windings are provided in each phase and the windings are crossed over the windings of the other phases. In FIG. 1, the star zigzag connection or the delta zigzag connection is shown. However, when the predetermined phase is shifted, the result is the same regardless of whether the star zigzag connection or the delta zigzag connection is possible. For example, when the delay is 10 degrees, the star staggered connection may be used to delay 10 degrees from the star connection, and the delta staggered connection may be used to advance 20 degrees from the delta connection.

  The n (= 2) AC outputs of each phase of the multiplex transformer 20 are the single-phase cell inverters 3a, 3b (for U-phase output), 3c, 3d (for V-phase output), 3e, 3f (for W-phase output) Is input. The single-phase cell inverters 3a, 3b, 3c, 3d, 3e, and 3f each include a diode rectifying unit 301a, a smoothing capacitor unit 302a, and an inverter unit 303a using a switching element. Convert to phase AC power. That is, in the single-phase cell inverters 3a, 3b, 3c, 3d, 3e, and 3f, the diode rectification unit 301a configured by a three-phase bridge converts three-phase AC power into DC power, and the DC power is converted into a smoothing capacitor unit 302a. And is input to the inverter unit 303a. Note that the ripple voltage of the smoothing capacitor unit 302 a has a frequency twice that of the commercial power supply 1.

  Further, in the inverter unit 303a, switching elements S1 and S2 connected in series and switching elements S3 and S4 are connected in parallel, the switching elements S1 and S4 are turned on, and the switching elements S2 and S3 are turned off. The polarity of the output voltage is inverted between the first state in which the switching elements S2 and S3 are turned on and the second state in which the switching elements S1 and S4 are turned off. Further, in the inverter unit 303a, all of the switching elements S1, S2, S3, and S4 may be turned off, the conduction angle of the motor current flowing through the motor 4 is controlled, and the average voltage applied to the motor 4 is Change. Moreover, the rotational speed of the electric motor 4 changes by changing the switching frequency.

Further, the switching elements S1, S2, S3, and S4 of the single-phase cell inverter 3a connected in series and the switching elements S1, S2, S3, and S4 of the single-phase cell inverter 3b are simultaneously ON-OFF controlled and smoothed. A voltage that is twice the DC voltage charged in the capacitor 302a is output. That is, the three multiple power converters drive the motor 4 with a voltage twice as high as the output voltage of the multiple transformer 20 when the outputs are three-phase Y-connected. Note that a commutation diode is connected to each of the switching elements S 1, S 2, S 3, and S 4 to commutate the counter electromotive force due to the internal inductance of the motor 4. In FIG. 1, the switching elements S1, S2, S3, and S4 use IGBTs. However, FETs may be used, and an inverter can be easily configured by combining a pch-FET and an nch-FET. Can do.

  Next, in order to show the effect of this embodiment, an example in which there is no phase shift between the phases of the output voltage of the multiple transformer will be described. FIG. 2 is a block diagram of a comparative example of two-stage multiplex. In this comparative example, the secondary windings of the multiplex transformer 2 are connected by star connection and delta connection for U, V and W phases, and a single-phase cell inverter 3a. Phase to 3f are 0 degree, -30 degree (U phase), 0 degree, -30 degree (V phase), 0 degree, -30 degree (W phase), and there is a phase difference between the phases do not do. In addition, it shows that it is a advance phase, so that a positive numerical value is large. Similarly, when n = 3, each phase is composed of three single-phase cell inverters, and the phase of the secondary winding of the multiple transformer is common to the U, V, and W phases, for example, 0 degrees, −20 degrees, It is shifted by -40 degrees. When n = 4, each phase is composed of four single-phase cell inverters, and the phase of the secondary winding of the multiple transformer is common to U, V, and W phases, for example, 0 degrees, −15 degrees, It is shifted by -30 degrees and -45 degrees.

  Next, the harmonic reduction effect will be described by comparing the present embodiment with a comparative example. The capacitor voltage Vdc of the smoothing capacitor 302a includes a ripple component, and this capacitor voltage Vdc is divided into a DC voltage VDC and a Vdc ripple (twice the inverter output frequency). Further, the secondary current of the multiplex transformer 2 includes a harmonic current component due to switching of the inverter unit 303a. In other words, a harmonic current due to the DC voltage VDC, that is, a harmonic current that does not depend on the Vdc ripple flows, and a harmonic current that depends on the Vdc ripple flows.

  First, in the case where there is no phase shift between the phases as in the comparative example, the secondary current of the multiple transformer 2 is a current component that does not depend on the ripple of the capacitor voltage Vdc of the smoothing capacitor unit 302a and a current that depends on the Vdc ripple. It is divided into components, and each component is approximated as the sum of U, V, and W phases as shown in equations (1) and (2). The Vdc direct current component is modeled by dividing the contributions of the U, V, and W phases into the same phase components.

X-order current component not dependent on Vdc ripple (comparative example): ωx≡x-order frequency Ixs · {sin (ωx · t) + sin (ωx · t) + sin (ωx · t)} = 3 · Ixs · sin (ωx · t) (1)
X-order current component due to Vdc ripple (comparative example): ωc≡Vdc ripple frequency = 2 × inverter output frequency Ixr · {sin (ωc · t) · sin (ωx · t) + sin (ωc · t−2 · 120 ° ) ・ Sin (ωx ・ t) + sin (ωc ・ t + 2 ・ 120 °) ・ sin (ωx ・ t)} = 0 (2)
That is, in the comparative example, the harmonic current component that does not depend on the Vdc ripple mainly remains, and the harmonic current component that depends on the Vdc ripple is completely canceled.

Next, when the phase is shifted as in the first embodiment, equations (1) and (2) are rewritten as equations (3) and (4). Of the ± in the equation, the sign + indicates the case where the phase is advanced by 10 degrees in the order of U → V → W, and the sign − indicates the case where the phase is delayed by 10 degrees.
X-order current component independent of Vdc ripple:
Ixs · {sin (ωx · t) + sin (ωx · t ± x · 10 °) + sin (ωx · t ± x · 20 °)} (3)
X-order current component due to Vdc ripple:
Ixr · {sin (ωc · t) · sin (ωx · t) + sin (ωc · t-2 · 120 °) · sin (ωx · t ± x · 10 °) + sin (ωc · t + 2 · 120 °) · sin (ωx · t ± x · 20 °)} (4)

Note that the first to third terms of the equation (4) are rewritten as the equations (5) to (7), respectively.
sin (ωc ・ t) ・ sin (ωx ・ t) = 1/2 ・ {cos (ωx−ωc) ・ t−cos (ωx + ωc) ・ t} (5)
sin (ωc · t−2 · 120 °) · sin (ωx · t ± x · 10 °) = 1/2 · [cos {(ωx-ωc) · t ± x · 10 ° + 240 °} −cos {( ωx + ωc) ・ t ± x ・ 10 ° -240 °}] (6)
sin (ωc ・ t + 2 ・ 120 °) ・ sin (ωx ・ t ± x ・ 20 °) = 1/2 ・ [cos {(ωx-ωc) ・ t ± x ・ 20 ° −240 °} −cos { (ωx + ωc) ・ t ± x ・ 20 ° + 240 °}] (7)
From the above, it can be seen that by shifting the phase of each phase, the x-order harmonic due to the Vdc ripple becomes (shifts) the beat component (ωn ± ωc) due to the Vdc ripple frequency ωc and the harmonic ωx.

  Further, as a specific value of the first embodiment, the inverter output frequency is 50 Hz which is the same as the power supply frequency (that is, ωc = 2π × 100 Hz), and the magnitude of the x (= 9, 11, 13, 15) order harmonic component. Are obtained as shown in equations (8) to (13). It is assumed that the phase is advanced by 10 degrees in the order of U → V → W.

○ 9th harmonic Vdc ripple component; x (= 11th order) -Vdc ripple (secondary):
1/2 ・ I11r ・ {cos (ω9 ・ t) + cos (ω9 ・ t + 110 ° + 240 °) + cos (ω9 ・ t + 220 ° −240 °)}
= 1/2 ・ I11r ・ {2.92 ・ cos (ω9 ・ t) ＋0.51 ・ sin (ω9 ・ t)}
= 1.48 ・ I11r ・ sin (ω9 ・ t ＋ 80.1 °) (8)
Vdc DC component; x = 9th order: None

○ 11th harmonic Vdc ripple component; x (= 13th order) -Vdc ripple (secondary):
1/2 ・ I13r ・ {cos (ω11 ・ t) + cos (ω11 ・ t + 130 ° + 240 °) + cos (ω11 ・ t + 260 ° −240 °)}
= 1/2 · I13r · {2.92 · cos (ω11 · t) + 0.51 · sin (ω11 · t)}
= 1.48 ・ I13r ・ sin (ω11 ・ t ＋ 80.1 °) (9)
Vdc DC component; x = 11th order:
I11s · {sin (ω11 · t) + sin (ω11 · t + 110 °) + sin (ω11 · t + 220 °)}
＝ I11s ・ {0.3 ・ cos （ω11 ・ t) −0.11 ・ sin （ω11 ・ t)}
＝ 0.32 ・ I11s ・ sin （ω11 ・ t−69.9 °） (10)

○ 13th harmonic Vdc ripple component; x (= 11th order) + Vdc ripple (secondary):
1/2 ・ I11r ・ {−cos (ω13 ・ t) −cos (ω13 ・ t + 110 ° −240 °) −cos (ω13 ・ t + 220 ° + 240 °)}
= 1/2 ・ I11r ・ {−0.19 ・ cos (ω13 ・ t) +0.21 ・ sin (ω13 ・ t)}
＝ 0.14 ・ I11r ・ sin (ω13 ・ t−42.1 °) (11)
Vdc DC component; x = 13th order:
I13s · {sin (ω13 · t) + sin (ω13 · t + 130 °) + sin (ω13 · t + 260 °)}
＝ I13s ・ {−0.21 ・ cos （ω13 ・ t) ＋0.19 ・ sin （ω13 ・ t)}
＝ 0.28 ・ I13s ・ sin （ω13 ・ t−47.9 °） (12)

○ 15th harmonic Vdc ripple component; x (= 13th order) + Vdc ripple (secondary):
1/2 ・ I13r ・ {−cos (ω15 ・ t) −cos (ω15 ・ t + 130 ° −240 °) −cos (ω15 ・ t + 260 ° + 240 °)}
= 1/2 ・ I13r ・ {0.11 ・ cos (ω15 ・ t) −0.3 ・ sin (ω15 ・ t)}
＝ 0.16 ・ I13r ・ sin (ω15 ・ t−20.1 °) (13)
Vdc DC component; x = 15th order: None

From the above calculation, the 11th and 13th harmonic amplitudes by the DC voltage VDC of the comparative example are 3I11s and 3I13s, whereas the 11th and 13th harmonic amplitudes of this embodiment are about 0.3I11s and 0.3I13s. The harmonic amplitude drops to about 1/10. Instead, the 9th and 11th harmonic amplitudes increase due to the Vdc ripple component. However, they can reduce the harmonic amplitude due to the Vdc ripple by increasing the smoothing capacitor capacity of the single-phase cell inverter. It is also possible to reduce harmonic components by increasing the impedance of the multiple transformer. In the comparative example, the harmonic current component due to the DC voltage VDC was mainly used. Therefore, even if the Vdc ripple was reduced by adjusting the smoothing capacitor capacity, the harmonics could not be sufficiently reduced.
That is, according to the present embodiment, by shifting the phase of the secondary winding of the multiple transformer 2 by the same magnitude, higher order than the comparative example that reduces the harmonics smaller than (6n ± 1). Even harmonics can be reduced. Thereby, even in the multiplex power conversion apparatus 100 with a small number of stages, it is possible to sufficiently reduce the harmonic current.

  3 and 4 show the simulation results. FIG. 3 shows the current waveform of the power source current (A) and the FFT (Fast Fourier Transform) analysis result as simulation results in the comparative example shown in FIG. 2 and the present embodiment (n = 2) shown in FIG. FIG. 3A shows the current waveform of the comparative example, and FIG. 3C shows the current waveform of the present embodiment. This embodiment has less waveform distortion. FIG. 3B shows the FFT analysis result of the comparative example, and FIG. 3D shows the FFT analysis result of the present embodiment. In contrast to the fundamental wave of 50 Hz, in the comparative example, many 11th-order, 13th-order harmonics and (6n ± 1) -order harmonics equivalent to those of the 12-pulse diode / thyristor rectifier are generated. On the other hand, in the present embodiment, the ninth and eleventh harmonics are generated, but can be reduced more greatly than in the comparative example.

  Moreover, FIG. 4 shows the ratio (%) of each of those harmonic components. A white bar indicates a comparative example, and a hatched bar indicates the first embodiment. Note that the ninth and eleventh harmonic amplitudes can also be reduced by increasing the capacitor capacity of the smoothing capacitor unit 302a and the impedance of the multiple transformer 20.

  Further, the secondary winding of the multiple transformer 20 is adjusted, for example, the input phases to the single-phase cell inverters 3a to 3f of each of the two phases for the U, V, and W phases are set to 0 degrees and −30, respectively. Degree (U phase), 10 degrees, -20 degrees (V phase), -10 degrees, -40 degrees (W phase), W (U phase), 10 (= 30 / n) degrees in order of V Or V, W, U in order of 0 degree, -30 degree (U phase), -20 degree, -50 degree (V phase), -10 degree, -40 degree (W phase) The same effect can be obtained by advancing the phase by 10 (= 30 / n) degrees.

  In addition, the multiple power conversion device of the present embodiment shifts the input phase difference to the in-phase single-phase cell inverters (3a and 3b, 3c and 3d, 3e and 3f) by 60 / n = 30 degrees, and supports all phases. A total of 6 (= 3 phases × n) single-phase cell inverters need only hold relative phase differences of 60 / 3n = 10 degrees, and is irrelevant to the absolute value of the phase. For example, the phase of each single-phase cell inverter (3a and 3b, 3c and 3d, 3e and 3f) is 15 degrees, -15 degrees (U phase), 25 degrees, -5 degrees (V phase), 5 degrees, The same effect is obtained even at −25 degrees (W phase).

  Further, the diode rectifier 301a shown in FIG. 1 can be configured by using a semiconductor switching element such as a thyristor instead of a diode bridge and replacing it with a converter. This replacement is performed for all the diode rectifiers of the single-phase inverters 3a to 3f. As mentioned above, in this embodiment, a power supply harmonic can be reduced significantly rather than a comparative example.

(Second Embodiment)
Next, a difference between the second embodiment of the present invention and the first embodiment will be described. In the first embodiment, the phase advances by 10 degrees in the order of the U, V, and W phases, whereas in the second embodiment, the phase is delayed by 10 degrees. Thereby, although the calculation formula is not shown, the 11th and 13th harmonic components due to the DC voltage VDC are reduced as in the first embodiment, and the harmonic components due to the Vdc ripple are reduced in the second embodiment. 13th and 15th order components are generated.

  The multiple power converter 110 of FIG. 5 adjusts the secondary winding phase of the multiple transformer 21, and in-phase single-phase cell inverters (3a and 3b, 3c and 3d, 3e and 3f) in the U, V, and W phases. 60 / n = 30 degrees between them, and a total of 6 (= 3 phases × n) single-phase cell inverters corresponding to all phases has a phase difference of 60 / 3n = 10 degrees. This is the same as the embodiment. However, the secondary windings of the multiple transformer 21 are 0 degrees (U phase 3a), -30 degrees (U phase 3b), -10 degrees (V phase 3c), -40 degrees (V phase 3d), -20 The second embodiment is different from the first embodiment in that the phase is delayed so as to be degrees (W phase 3e) and −50 degrees (W phase 3f). As in the first embodiment, the harmonic amplitude is reduced by reducing the Vdc ripple by increasing the smoothing capacitor capacity.

Further, separately from FIG. 5, the secondary winding of the multiple transformer 21 is adjusted so that, for example, the input phases to the two single-phase cell inverters 3a to 3f for the U, V, and W phases are 0 degrees each. , -30 degrees (U phase), -10 degrees, -40 degrees (V phase), 10 degrees, and -20 degrees (W phase), the phase is delayed by 10 degrees in the order of W, U, V. Or 10 degrees in the order of V, W, U, such as 0 degree, −30 degrees (U phase), 20 degrees, −10 degrees (V phase), 10 degrees, −20 degrees (W phase). The same effect as in the case of FIG. 5 can also be obtained by delaying by degrees. Further, as in the first embodiment, the input phase differences to the single-phase cell inverters (3a and 3b, 3c and 3d, 3e and 3f) of the same phase are shifted by 60 / n = 30 degrees, corresponding to all phases. A total of 6 (= 3 phases × n) single-phase cell inverters only need to hold a phase difference of 60 / 3n = 10 degrees, and is independent of the absolute value of the phase. Similarly to the description of the first embodiment, any one of the delta zigzag and the star zigzag is equivalent if the predetermined phase can be shifted.
From the above, in this embodiment, the multiple power conversion device using multiple transformers has the effect of significantly reducing power supply harmonics compared to the comparative example.

(Third embodiment)
Although 1st Embodiment demonstrated the case where n = 2 which connected two single phase cell inverters in series about each phase, it can connect four single phase cell inverters in series about each phase. In FIG. 6, the multiple power conversion device 120 according to the third embodiment of the present invention has n = 4 single-phase cell inverters 31a to 31L connected to each of U, V, and W phases. In the multi-transformer 22, the input phase to each single-phase inverter is 0 degree, -15 degree, -30 degree, -45 degree (U phase), -5 degree, -20 degree, -35 degree,- The secondary winding phase is adjusted to 50 degrees (V phase), -10 degrees, -25 degrees, -40 degrees, and -55 degrees (W phase).

  In addition, even if it is other than FIG. 6, the phase difference whether the input to the four single-phase cell inverters (31a to 31d, 31e to 31h, 31i to 31L) of each phase is delayed or advanced by 60 / n = 15 degrees respectively. In a total of 12 (= 3 phases × n) single-phase cell inverters corresponding to all phases, it is only necessary to maintain a phase difference of 60 / 3n = 5 degrees. As a result, as in the first embodiment, the 23rd and 25th harmonic amplitudes, which were comparative examples and could not be reduced by the configuration corresponding to 24 pulse rectification, can be reduced.

  Although not shown, the same applies to n = 3. In the case of n stages for each phase and m phase output, the input phases between n single-phase cell inverters for each phase are 60 / n degrees each. By maintaining a phase difference of 60 / (m × n) degrees between a total of n × m single-phase cell inverters corresponding to the phases, higher harmonics can be reduced than in the comparative example. Moreover, a high voltage | pressure motor can be driven by making the output voltage of a multiplex power converter device into 3 kV or more by a line voltage.

(Fourth embodiment)
Next, differences of the fourth embodiment of the present invention from the first embodiment to the third embodiment will be described. In this embodiment, n single-phase cell inverters for each phase are multiple-connected in a three-phase output power converter. When one phase is a U phase, a phase whose output is delayed by 120 degrees relative to the U phase is a V phase, and a phase advanced by 120 degrees is a W phase, from the primary winding to the secondary winding of the multiple transformer Phase difference of (U, V, W), (W, U, V), or (V, W, U) in the order of 20 / n degrees or delayed, and then further secondary to V phase The secondary phase of the multi-transformer is adjusted so that the winding phase is delayed by 120 degrees and the secondary winding phase with respect to the W phase is a phase advanced by 120 degrees. For example, when n = 2, 0 degrees, −30 degrees (U phase), −110 (= 10−120) degrees, −140 (= −20−120) degrees (V phase), 140 (= 20 + 120) degrees , 110 (= −10 + 120) degrees (W phase). In the present embodiment, the phase of the Vdc ripple is adjusted by adjusting the secondary phase of the multiple transformer in consideration of the phase difference (120 degrees) of each phase. The fourth embodiment has an effect of reducing the harmonic amplitude due to the DC voltage VDC, as in the first embodiment.

It is a block diagram of the multiplex power converter of 1st Embodiment of this invention. It is a block diagram of the multiple power converter device which is a comparative example. It is the figure which compared 1st Embodiment and the comparative example about the power supply current by simulation, and its FFT analysis result. It is the figure which compared 1st Embodiment and the comparative example about the harmonic component of the power supply current by simulation. It is a block diagram of the multiple power converter device of 2nd Embodiment of this invention. It is a block diagram of the multiple power converter device of 3rd Embodiment of this invention.

Explanation of symbols

1 Commercial power supply 2, 20, 21, 22, 23 Multiple transformers,
3a, 3b, 3c, 3d, 3e, 3f, 31a, 31b, 31c, 31d, 31e, 31f, 31g, 31h, 31i, 31j, 31k, 31L Single-phase cell inverter 4 Electric motor 100, 105, 110, 120 Multiple power Conversion device 301a Diode rectifier unit 302a Smoothing capacitor unit 303a Inverter unit P Neutral point

Claims (6)

When n and m are natural numbers, a multiple transformer that distributes m-phase AC power input to the primary winding to (m × n) secondary windings and m sets of multiple power converters The multiplex power converter includes a plurality of n-phase cell inverters that are connected in series to convert AC power distributed to the secondary windings into variable voltage or variable frequency AC power. In the power converter,
The secondary winding of the multiple transformer has a phase difference of 60 / n degrees between the n-stage single-phase cell inverters corresponding to the common-phase output, and (m × n) single-phase cells corresponding to the m-phase. A multiple power conversion device characterized in that a phase difference between phase cell inverters is 60 / (m × n) degrees. When n and m are natural numbers, a multiple transformer that distributes m-phase AC power input to the primary winding to (m × n) secondary windings and m sets of multiple power converters The multiplex power converter includes a plurality of n-phase cell inverters that are connected in series to convert AC power distributed to the secondary windings into variable voltage or variable frequency AC power. In the power converter,
The secondary winding of the multiple transformer has a phase difference of 60 / n degrees between the n-stage single-phase cell inverters corresponding to the common-phase output, and the phase between the phases of the single-phase cell inverter corresponding to the same stage. A multiple power conversion device, wherein the phase difference is 60 / (m × n) degrees. When m = 3 and the output of the multiple power converter is a three-phase output of U, V, and W,
The phase difference of the secondary winding of the multiple transformer is delayed or advanced by 20 / n degrees in the order of (U, V, W), (W, U, V), or (V, W, U). The multiple power conversion device according to claim 1 or 2, wherein A multiple transformer that distributes three-phase AC power input to the primary winding to six secondary windings, and three sets of multiple power converters, the multiple power converter including the secondary windings; In a multiple power conversion apparatus configured by connecting two single-phase cell inverters in series to convert AC power distributed to a line into variable voltage or AC power of variable frequency,
The secondary winding of the multiple transformer maintains a phase difference of 30 degrees between the two single-phase cell inverters corresponding to the in-phase output, and the phase difference between the six single-phase cell inverters corresponding to the three phases. Is a multiple power conversion device characterized by 10 degrees. When n is a natural number, it includes a multiple transformer that distributes three-phase AC power input to the primary winding to 3 × n secondary windings, and three sets of multiple power converters, The power converter is composed of n single-phase cell inverters that are connected in series to convert AC power distributed to the secondary windings into variable voltage or variable frequency AC power. In the multiple power conversion device that drives the three-phase load device with an output phase difference,
The secondary winding of the multiple transformer has a phase difference of 60 / n degrees between the n single-phase cell inverters corresponding to the common-phase output,
In the three-phase load device, the first phase is the U phase, the phase whose output is delayed by 120 degrees with respect to the U phase is the V phase, and the phase advanced by 120 degrees with respect to the U phase is the W phase. And
The multiple transformer has a phase difference from the primary winding to the secondary winding of 20 / n degrees in the order of (U, V, W), (W, U, V) or (V, W, U). A multiple power conversion device characterized in that it advances or delays step by step, the secondary winding phase with respect to the V phase is delayed by 120 degrees, and the secondary winding phase with respect to the W phase is advanced by 120 degrees. The multiplex power converter according to any one of claims 1 to 5 , wherein an output voltage of the multiplex power converter is a line voltage of 3 kV or more.

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