Power Conversion Equipment

Abstract

To provide a power conversion device capable of suppressing a current flowing in a filter even in a case where a converter circuit side phase and an inverter circuit side phase are deviated from each other at two-phase modulation, and of improving the power conversion efficiency without increasing a size of the device.SOLUTION: A power conversion device 1 comprises: a converter circuit C connected with a three-phase AC power supply 91 to convert an AC of the three-phase AC power supply 91 into a DC; a smoothing circuit S connected with DC output terminals 42a and 42b of the converter circuit C, consisting of a capacitor; an inverter circuit I connected with DC terminals 61a and 62b of the smoothing circuit S to convert a DC of the smoothing circuit S into an AC and output the AC to an AC load 92; a converter controller 12 that performs PWM control of the converter circuit C by the two-phase modulation system; and an inverter controller 13 that performs PWM control of the inverter circuit I by the two-phase modulation system. The converter controller 12 performs PWM control of the converter circuit C by the two-phase modulation system by using a two-phase modulation signal for two-phase modulation used by the inverter controller 13.SELECTED DRAWING: Figure 1A

Description

[Technical field]

[0001] The present invention relates to a power conversion device. [Background technology]

[0002] A power conversion device that functions as a non-insulated uninterruptible power supply is known from Patent Document 1 and the like. In the power conversion device described in Patent Document 1, AC from a three-phase AC power supply is converted to DC by a converter circuit, and the DC is further converted to AC by an inverter circuit, and the AC power obtained by switching between the AC power and the AC power directly supplied from the three-phase AC power supply, thereby making the power conversion device function as an uninterruptible power supply.

[0003] Furthermore, a two-phase modulation method is known as a modulation method capable of improving power conversion efficiency, as disclosed in Patent Document 2 and the like. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2005-253262 A [Patent Document 2] Japanese Patent Application Publication No. 59-139871 Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, in the power conversion device described in Patent Document 1, in order to generate a sine wave by smoothing the PWM waveform output by the converter, an AC filter is created using a reactor and a capacitor, and the midpoint of this AC filter is connected to the midpoint of the DC section. Therefore, for example, when two-phase modulation is performed in the power conversion device described in Patent Document 1, the waveform of the two-phase modulation is applied as is to the AC filter, so that a large current flows in the reactor and capacitor of the AC filter on both the converter side and the inverter side.

[0006] Therefore, in order to prevent a large voltage waveform from being applied to the AC filter even when two-phase modulation is used, the capacitor in the AC filter of the converter circuit and the capacitor in the AC filter of the inverter circuit are connected, and the smoothing capacitor is not connected to the neutral point of the AC filter capacitor.

[0007] However, in the above configuration, if the input voltage of the converter circuit is out of phase with respect to the output voltage of the inverter circuit, a large current may flow through the reactor and capacitor of the AC filter. Therefore, when performing two-phase modulation in a power conversion device, there is room for improvement in these respects.

[0008] Therefore, the present invention provides a power conversion device that can improve the efficiency of power conversion without increasing the size of the device, even if the phase of the input voltage of the converter circuit is shifted relative to the output voltage of the inverter circuit during two-phase modulation. [Means for solving the problem]

[0009] A power conversion device according to one aspect of the present embodiment includes: a converter circuit connected to a three-phase AC power source and converting AC from the three-phase AC power source into DC; a smoothing circuit including a capacitor connected to a DC output terminal of the converter circuit; an inverter circuit connected to a DC terminal of the smoothing circuit, converting a DC current from the smoothing circuit into an AC current and outputting the AC current to an AC load; A converter control unit that controls the converter circuit by PWM using a two-phase modulation method; an inverter control unit that controls the inverter circuit by PWM using a two-phase modulation method; Equipped with the converter circuit and the inverter circuit are each formed of a three-phase full-bridge circuit made of switching elements, and an input filter capacitor constituting a filter on the converter circuit side and an output filter capacitor constituting a filter on the inverter circuit side are connected to each other; a smoothing capacitor of the smoothing circuit is not connected to the input filter capacitor and the output filter capacitor; The converter control unit performs PWM control of the converter circuit by two-phase modulation using a two-phase modulation signal used in the inverter control unit. Effect of the Invention

[0010] According to the present invention, by performing PWM control of the converter circuit by two-phase modulation using a two-phase modulation signal used in the inverter control unit, even if the phase shift occurs between the converter circuit side and the inverter circuit side during two-phase modulation, it is possible to suppress the current flowing through the input filter reactor, the input filter capacitor, the output filter reactor, and the output filter capacitor. Therefore, it is possible to improve the efficiency of power conversion without increasing the size of the power conversion device. [Brief description of the drawings]

[0011] [Figure 1A] FIG. 1A is a diagram showing a circuit configuration of a power conversion device according to this embodiment. [Figure 1B] FIG. 1B is a diagram showing a circuit configuration of a converter control unit and an inverter control unit according to the present embodiment. [Figure 2A] FIG. 2A is a diagram showing a circuit configuration of a power conversion device according to a conventional embodiment. [Figure 2B] FIG. 2B is a diagram showing a circuit configuration of a converter control unit and an inverter control unit according to a conventional embodiment. [Figure 3A] FIG. 3A shows the waveform of the u-phase output voltage of the inverter circuit when the three-phase AC voltage input from the three-phase AC power supply in FIG. 2A is in phase with the output voltage of the inverter circuit, and the dashed line shows the voltage waveform with the switching frequency included therein removed. [Figure 3B] FIG. 3B shows the r-phase input voltage waveform of the converter circuit when the above-mentioned phases are in phase, and the dashed line shows the voltage waveform with the switching frequency contained therein removed. [Figure 3C]FIG. 3C shows the r-phase input voltage waveform of the converter circuit when the phase is shifted by 5 degrees, and the dashed line shows the voltage waveform with the switching frequency included therein removed. [Figure 3D] FIG. 3D shows the r-phase input voltage waveform of the converter circuit when the phase is shifted by 15 degrees, and the dashed line shows the voltage waveform with the switching frequency included therein removed. [Figure 3E] FIG. 3E shows a comparison result between the r-phase input voltage waveform of the converter circuit of FIG. 3D and the waveform of the converter modulation command signal, which is the waveform before two-phase modulation is performed. [Figure 4A] FIG. 4A is a waveform showing the potential difference between the u-phase output voltage of the inverter circuit in FIG. 3A and the r-phase input voltage of the converter circuit in FIG. 3B when the three-phase AC voltage input from the three-phase AC power supply in FIG. 2A and the output voltage of the inverter circuit are in phase, and the dashed line is a voltage waveform with the switching frequency included therein removed. [Figure 4B] FIG. 4B is a waveform showing the above-mentioned potential difference when the phase is shifted by 5 degrees, and the dashed line is a voltage waveform with the switching frequency included therein removed. [Figure 4C] FIG. 4C is a waveform showing the above-mentioned potential difference when the phase is shifted by 15 degrees, and the dashed line is a voltage waveform with the switching frequency included therein removed. [Figure 5A] FIG. 5A shows a waveform of a current flowing through a u-phase output filter capacitor of the inverter circuit when the three-phase AC voltage input from the three-phase AC power supply in FIG. 2A is in phase with the output voltage of the inverter circuit. [Figure 5B] FIG. 5B shows a waveform of a current flowing through the u-phase output filter when the phase is shifted by 5 degrees in FIG. 2A. [Figure 5C] FIG. 5C shows a waveform of the current flowing through the u-phase output filter capacitor when the phase is shifted by 15 degrees. [Figure 5D] FIG. 5D shows the value of the ripple current flowing through the output filter capacitor versus the phase difference. [Figure 6A]FIG. 6A shows the output voltage waveform of the u-phase of the inverter circuit when the three-phase AC voltage input from the three-phase AC power supply in FIG. 1A is in phase with the output voltage of the inverter circuit, and the dashed line shows the voltage waveform with the switching frequency included therein removed. [Figure 6B] FIG. 6B shows the r-phase input voltage waveform of the converter circuit when the phases are in phase, and the dashed line shows the voltage waveform with the switching frequency included therein removed. [Figure 6C] FIG. 6C shows the r-phase input voltage waveform of the converter circuit when the phase is shifted by 5 degrees, and the dashed line shows the voltage waveform with the switching frequency included therein removed. [Figure 6D] FIG. 6D shows the r-phase input voltage waveform of the converter circuit when the phase is shifted by 15 degrees, and the dashed line shows the voltage waveform with the switching frequency included therein removed. [Figure 6E] FIG. 6E shows a comparison result between FIG. 6D and the waveform of the converter modulation command signal, which is the waveform before two-phase modulation is performed. [Figure 7A] FIG. 7A is a waveform showing the potential difference between the u-phase output voltage of the inverter circuit in FIG. 6A and the r-phase input voltage of the converter circuit in FIG. 6B when the three-phase AC voltage input from the three-phase AC power supply in FIG. 1A and the output voltage of the inverter circuit are in phase, and the dashed line is a voltage waveform with the switching frequency included therein removed. [Figure 7B] FIG. 7B is a waveform showing the above-mentioned potential difference when the phase is shifted by 5 degrees, and the dashed line is a voltage waveform from which the switching frequency contained therein has been removed. [Figure 7C] FIG. 7C is a waveform showing the above-mentioned potential difference when the phase is shifted by 15 degrees, and the dashed line is a voltage waveform from which the switching frequency contained therein has been removed. [Figure 8A] FIG. 8A shows a waveform of a current flowing through a u-phase output filter capacitor of the inverter circuit when the three-phase AC voltage input from the three-phase AC power supply in FIG. 1A is in phase with the output voltage of the inverter circuit. [Figure 8B]FIG. 8B shows a waveform of the current flowing through the u-phase output filter capacitor when the phase is shifted by 5 degrees. [Figure 8C] FIG. 8C shows a waveform of the current flowing through the u-phase output filter capacitor when the phase is shifted by 15 degrees. [Figure 8D] FIG. 8D shows the value of the ripple current flowing through the output filter capacitor versus the phase difference. [Figure 9] FIG. 9 is a diagram illustrating an example of an uninterruptible power supply according to the present embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, the present embodiment will be described with reference to the drawings. For the sake of convenience, the description of the members having the same reference numbers as those already described in the description of the embodiment will be omitted. Also, for the sake of convenience, the dimensions of each member shown in the drawings may differ from the actual dimensions of each member.

[0013] 1A is a diagram showing a circuit configuration of a power conversion device 1 according to this embodiment. As shown in FIG 1A, the power conversion device 1 includes an input filter F1, a converter circuit C, a smoothing circuit S, an inverter circuit I, an output filter F2, a converter control unit 12, and an inverter control unit 13.

[0014] The input filter F1 has input filter capacitors 2a-2c and input filter reactors 3a-3c. One terminal of each of the input filter reactors 3a-3c is connected to device input terminals 31a-31c of the power conversion device 1, respectively. The other terminal of each of the input filter reactors 3a-3c is connected to three-phase (r-phase, s-phase, t-phase) converter input terminals 41a-41c of the converter circuit C, respectively. A three-phase AC power supply 91 is connected to the device input terminals 31a-31c of the power conversion device 1.

[0015] One terminal of each of the input filter capacitors 2a to 2c is connected to the terminal of the input filter reactors 3a to 3c on the device input terminals 31a to 31c side, respectively. The other terminal of each of the input filter capacitors 2a to 2c is connected to the neutral line nl. The input filter F1 passes three-phase AC power from the three-phase AC power supply 91 to the converter circuit C, and prevents a signal of a carrier frequency (a frequency that determines a pulse width modulation period in a PWM control method) generated by the converter circuit C from passing to the three-phase AC power supply 91.

[0016] The converter circuit C has six semiconductor switching elements 4a to 4f connected in a three-phase bridge. The semiconductor switching elements 4a to 4f are composed of, for example, IGBTs (insulated gate bipolar transistors) and anti-parallel free wheel diodes. The converter circuit C is composed of a three-phase (r-phase, s-phase, t-phase) full bridge circuit. The converter circuit C converts an AC voltage from a three-phase AC power source 91 into a DC voltage.

[0017] The smoothing circuit S has a smoothing capacitor 5. In the example shown in the figure, the smoothing capacitor 5 is configured as a single capacitor. The smoothing capacitor 5 is a capacitor that smoothes the output of the converter circuit C, and is, for example, an electrolytic capacitor. The smoothing capacitor 5 is connected to converter output terminals 42a and 42b of the converter circuit C.

[0018] The inverter circuit I has six semiconductor switching elements 6a to 6f connected in a three-phase bridge. The semiconductor switching elements 6a to 6f are, for example, configured with IGBTs and free wheel diodes connected in anti-parallel. The inverter circuit I is configured with a three-phase (u-phase, v-phase, w-phase) full bridge circuit. The inverter circuit I has inverter input terminals 61a and 61b connected to both pole terminals of the smoothing capacitor 5, respectively. The inverter circuit I converts the DC voltage from the smoothing circuit S (the DC voltage output by the converter circuit C) into an AC voltage by the switching operation of the semiconductor switching elements 6a to 6f.

[0019] The output filter F2 has output filter reactors 7a-7c and output filter capacitors 8a-8c. One terminal of each of the output filter reactors 7a-7c is connected to inverter output terminals 62a-62c of a three-phase (u-phase, v-phase, w-phase) inverter circuit I. The other terminal of each of the output filter reactors 7a-7c is connected to device output terminals 71a-71c of the power conversion device 1. An AC load 92 to which the three-phase AC power output from the inverter circuit I is supplied is connected to the device output terminals 71a-71c of the power conversion device 1.

[0020] One terminal of each of the output filter capacitors 8a to 8c is connected to the terminal of the output filter reactors 7a to 7c on the device output terminals 71a to 71c side, respectively. The other terminal of each of the output filter capacitors 8a to 8c is connected to the neutral line nl. The output filter F2 passes the AC power output from the inverter circuit I to the AC load 92, and prevents a signal of the carrier frequency generated by the inverter circuit I from passing to the AC load 92.

[0021] 1B is a diagram showing the circuit configuration of the converter control unit 12 and the inverter control unit 13 according to this embodiment. The converter control unit 12 has a converter modulation command generating unit 121, a first two-phase modulation control unit 122, and a first PWM signal generating unit 123, and performs switching control of the semiconductor switching elements 4a to 4f of the converter circuit C to a desired state. The converter modulation command generating unit 121 receives a three-phase AC voltage from a three-phase AC power supply 91, generates converter modulation command signals Vr, Vs, and Vt consisting of a three-phase AC sine wave, and outputs them to the first two-phase modulation control unit 122. The first two-phase modulation control unit 122 receives the converter modulation command signal from the converter modulation command generating unit 121 and the inverter two-phase modulation signals AI1 to AI6 from the two-phase modulation signal generating unit 134 of the inverter control unit 13, generates converter two-phase modulation command signals Vr', Vs', and Vt', and outputs them to the first PWM signal generating unit 123. Here, the inverter two-phase modulation signals AI1 to AI6 are signals that specify the phase periods shown in Table 1 of the ideal sine wave generated by the inverter sine wave reference generation unit 135. The first two-phase modulation control unit 122 receives the converter modulation command signals Vr, Vs, and Vt from the converter modulation command generation unit 121 and the inverter two-phase modulation signals AI1 to AI6 from the two-phase modulation signal generation unit 134 of the inverter control unit 13, and generates the converter two-phase modulation command signals Vr', Vs', and Vt' shown in Table 1. Here, the voltage between two phases of the converter two-phase modulation command signals Vr', Vs', and Vt' is, for example, Vr'-Vs'=(Vr-Vs-1)-(-1)=Vr-Vs when AI1=1, and does not change before and after the two-phase modulation, and is not affected by the two-phase modulation.

[0022] The first PWM signal generating unit 123 has a comparator 123a and a carrier signal generating unit 123b. The comparator 123a receives the two-phase modulation command signals Vr', Vs', Vt' and a carrier signal Vc such as a triangular wave generated by the carrier signal generating unit 123b, compares them, and outputs PWM drive signals Vgr, Vgs, Vgt. The PWM drive signal Vgr and its inverted signal / Vgr, the PWM drive signal Vgs and its inverted signal / Vgs, and the PWM drive signal Vgt and its inverted signal / Vgt are input to the gates of the semiconductor switching elements 4a to 4f of the converter circuit C, respectively. In other words, the PWM drive signals Vgr, Vgs, Vgt have waveforms that turn on the upper semiconductor switching elements 4a, 4c, 4e and turn off the lower semiconductor switching elements 4b, 4d, 4f when the two-phase modulation command signals Vr', Vs', Vt' are greater than the carrier signal Vc, and when the two-phase modulation command signals Vr', Vs', Vt' are smaller than the carrier signal Vc, the lower semiconductor switching elements 4b, 4d, 4f are turned on and the upper semiconductor switching elements 4a, 4c, 4e are turned off. [Table 1]

[0023] The inverter control unit 13 has an inverter modulation command generating unit 131, a second two-phase modulation control unit 132, a second PWM signal generating unit 133, a two-phase modulation signal generating unit 134, and an inverter sine wave reference generating unit 135, and controls the switching of the semiconductor switching elements 6a to 6f of the inverter circuit I to a desired state. The inverter modulation command generating unit 131 receives an ideal sine wave generated by the inverter sine wave reference generating unit 135, generates inverter modulation command signals Vu, Vv, and Vw consisting of three-phase AC sine waves, and outputs them to the second two-phase modulation control unit 132. The two-phase modulation signal generating unit 134 receives an ideal sine wave, generates inverter two-phase modulation signals AI1 to AI6, and outputs them to the second two-phase modulation control unit 132 and the first two-phase modulation control unit 122 of the converter control unit 12. The second two-phase modulation control unit 132 receives the inverter modulation command signals Vu, Vv, Vw from the inverter modulation command generation unit 131 and the inverter two-phase modulation signals AI1 to AI6 from the two-phase modulation signal generation unit 134, generates two-phase modulation command signals Vu', Vv', Vw', and outputs them to the second PWM signal generation unit 133. The relationship between the inverter modulation command signals Vu, Vv, Vw and the two-phase modulation command signals Vu', Vv', Vw' is obtained by replacing Vr, Vs, Vt in Table 1 with Vu, Vv, Vw, and replacing Vr', Vs', Vt' with Vu', Vv', Vw'. The configuration of the second PWM signal generation unit 133 is the same as that of the first PWM signal generation unit 123 of the converter control unit 12, and therefore a description thereof will be omitted.

[0024] FIG. 2A is a diagram showing an example of a circuit configuration of a conventional power conversion device 200. FIG. 2B is a diagram showing circuit configurations of a converter control unit 12 and an inverter control unit 13 according to a conventional embodiment. As shown in FIG. 2B, in the power conversion device 200, the converter control unit 12 and the inverter control unit 13 have two-phase modulation signal generating units 124 and 134, respectively. The converter control unit 12 is configured to use converter two-phase modulation signals AC1 to AC6 output from the two-phase modulation signal generating unit 124, and the inverter control unit 13 is configured to use inverter two-phase modulation signals AI1 to AI6 output from the two-phase modulation signal generating unit 134. On the other hand, the power conversion device 1 according to the present embodiment shown in FIGS. 1A and 1B is different in that only the inverter control unit 13 has the two-phase modulation signal generating unit 134, and the converter control unit 12 and the inverter control unit 13 commonly use the inverter two-phase modulation signals AI1 to AI6 output from the two-phase modulation signal generating unit 134.

[0025] 3A is a waveform of the output voltage Eu of the u-phase of the inverter circuit I when the three-phase AC voltage input from the three-phase AC source 91 in FIG. 2A and the output voltage of the inverter circuit I are in phase, and the dashed line is a voltage waveform with the switching frequency included therein removed. FIG. 3B is an input voltage waveform of the r-phase of the converter circuit C when the phases are in phase, and the dashed line is a voltage waveform with the switching frequency included therein removed. FIG. 3C is an input voltage waveform of the r-phase of the converter circuit C when the phases are shifted by 5 degrees, and the dashed line is a voltage waveform with the switching frequency included therein removed. FIG. 3D is an input voltage waveform of the r-phase of the converter circuit C when the phases are shifted by 15 degrees, and the dashed line is a voltage waveform with the switching frequency included therein removed. FIG. 3E shows a comparison result between FIG. 3D and the waveform of the converter modulation command signal, which is a waveform before two-phase modulation.

[0026] Fig. 4A is a waveform showing a potential difference between the output voltage Eu of the u phase of the inverter circuit I in Fig. 3A and the input voltage Er of the r phase of the converter circuit C in Fig. 3B when the three-phase AC voltage input from the three-phase AC source 91 in Fig. 2A and the output voltage of the inverter circuit I are in phase, and the dashed line is a voltage waveform with the switching frequency included therein removed. Fig. 4B is a waveform showing the potential difference when the phase is shifted by 5 degrees, and the dashed line is a voltage waveform with the switching frequency included therein removed. Fig. 4C is a waveform showing the potential difference when the phase is shifted by 15 degrees, and the dashed line is a voltage waveform with the switching frequency included therein removed. It can be seen that the voltage value of the pulse-like voltage increases as the phase increases.

[0027] Fig. 5A shows the waveform of the current flowing through u-phase output filter capacitor 8a of inverter circuit I when the three-phase AC voltage input from three-phase AC source 91 and the output voltage of inverter circuit I are in phase in Fig. 2A. Fig. 5B shows the waveform of the current flowing through u-phase output filter capacitor 8a when the phase is shifted by 5 degrees in Fig. 2A. Fig. 5C shows the waveform of the current flowing through u-phase output filter capacitor 8a when the phase is shifted by 15 degrees. It can be seen that the value of the current flowing through u-phase output filter capacitor 8a increases as the phase increases.

[0028] Figure 5D shows the value of the ripple current flowing through the output filter capacitor 8a versus the phase difference. As shown in Figure 5D, the ripple current flowing through the output filter capacitor 8a increases from when the phase is in phase until it is shifted by 5 degrees, and when the phase is shifted by 5 degrees, a ripple current of 120 mAp-p flows. This is because a large pulse-like voltage is generated between the output filter reactor 7a-output filter capacitor 8a-input filter capacitor 2a-input filter reactor 3a due to the phase shift between the input voltage Er and the output voltage Eu. Therefore, the components used as the output filter reactor 7a, output filter capacitor 8a, input filter capacitor 2a, and input filter reactor 3a must be made larger.

[0029] 5A to 5D show the current flowing through the u-phase output filter reactor 7a and output filter capacitor 8a in the inverter circuit I, but the currents flowing through the v-phase and w-phase output filter reactors 7b and 7c and output filter capacitors 8b and 8c are also the same. The currents flowing through the r-phase, s-phase, and t-phase input filter capacitors 2a to 2c and input filter reactors 3a to 3c in the converter circuit C are also the same (the same applies in the following explanation).

[0030] As described above, when the phase of the three-phase AC voltage input from the three-phase AC source 91 and the ideal sine wave voltage generated by the inverter sine wave reference generating unit 135 is shifted by 5 degrees, the voltage fluctuation at the change point of the applied voltage Eu-Er applied to the output filter reactor 7a, the output filter capacitor 8a, the input filter capacitor 2a, and the input filter reactor 3a becomes large, so that the output filter reactor 7a and the output filter capacitor 8a are likely to oscillate. Therefore, the current flowing through the output filter reactor 7a and the output filter capacitor 8a may become a ripple current of about 120 mAp-p as shown in FIG. 5D.

[0031] In response to this, the inventors have investigated a circuit configuration for synchronizing the phase of the input voltage Er of the converter circuit C and the output voltage Eu of the inverter circuit I.

[0032] 6A shows the waveform of the output voltage Eu of the u-phase of the inverter circuit I when the three-phase AC voltage input from the three-phase AC source 91 in FIG. 1A and the output voltage of the inverter circuit I are in phase, and the dashed line shows the voltage waveform with the switching frequency included therein removed. FIG. 6B shows the input voltage waveform of the r-phase of the converter circuit C when the phases are in phase, and the dashed line shows the voltage waveform with the switching frequency included therein removed. FIG. 6C shows the input voltage waveform of the r-phase of the converter circuit C when the phases are shifted by 5 degrees, and the dashed line shows the voltage waveform with the switching frequency included therein removed. FIG. 6D shows the input voltage waveform of the r-phase of the converter circuit C when the phases are shifted by 15 degrees, and the dashed line shows the voltage waveform with the switching frequency included therein removed. FIG. 6E shows a comparison result between FIG. 6D and the waveform of the converter modulation command signal, which is the waveform before two-phase modulation.

[0033] 7A is a waveform showing a potential difference between the output voltage Eu of the u phase of the inverter circuit I in FIG. 6A and the input voltage Er of the r phase of the converter circuit C in FIG. 6B when the three-phase AC voltage input from the three-phase AC source 91 in FIG. 1A is in phase with the output voltage of the inverter circuit I, and the dashed line is a voltage waveform with the switching frequency included therein removed. FIG. 7B is a waveform showing the potential difference when the phase is shifted by 5 degrees, and the dashed line is a voltage waveform with the switching frequency included therein removed. FIG. 7C is a waveform showing the potential difference when the phase is shifted by 15 degrees, and the dashed line is a voltage waveform with the switching frequency included therein removed. It can be seen that even when the phase is large, no pulse-like voltage is generated, as in the case when the phase is in phase.

[0034] Fig. 8A shows a waveform of a current flowing through u-phase output filter capacitor 8a of inverter circuit I when the three-phase AC voltage input from three-phase AC source 91 and the output voltage of inverter circuit I are in phase in Fig. 1A. Fig. 8B shows a waveform of a current flowing through u-phase output filter capacitor 8a when the above-mentioned phase is shifted by 5 degrees in Fig. 1A. Fig. 8C shows a waveform of a current flowing through u-phase output filter capacitor 8a when the above-mentioned phase is shifted by 15 degrees.

[0035] FIG. 8D shows the ripple current value flowing through the output filter capacitor 8a with respect to the phase difference. As shown in FIG. 8D, the ripple current flowing through the output filter capacitor 8a hardly changes from when the phase is in phase to when it is shifted by 15 degrees, and even when the phase is shifted by 15 degrees, the ripple current is suppressed to 30 mAp-p. This is because, in the power conversion device 1 according to this embodiment, the converter control unit 12 and the inverter control unit 13 are configured to commonly use the inverter two-phase modulation signals AI1 to AI6 output from the two-phase modulation signal generation unit 134, so that even when the phase of the input voltage Er and the output voltage Eu is shifted, no pulse-shaped voltage is generated between the output filter reactor 7a-output filter capacitor 8a-input filter capacitor 2a-input filter reactor 3a. Therefore, it is possible to maintain a long two-phase modulation period without increasing the size of the components used as the output filter reactor 7a, the output filter capacitor 8a, the input filter capacitor 2a, and the input filter reactor 3a, and the efficiency of the power conversion can be improved.

[0036] As shown in FIG. 9, the power conversion device 1 may be provided with a bypass circuit 301 configured to be able to connect the r-phase device input terminal 31a and the u-phase device output terminal 71a, the s-phase device input terminal 31b and the v-phase device output terminal 71b, and the t-phase device input terminal 31c and the w-phase device output terminal 71c, respectively, and a storage battery 9 connected in parallel with the smoothing capacitor 5 to the converter output terminals 42a and 42b of the converter circuit C. In the case of a configuration in which the bypass circuit 301 is provided, a power supply route can be formed in which AC power is directly supplied from the three-phase AC power source 91 to the AC load 92 through the bypass circuit 301. This allows power to be continuously supplied to the AC load 92 even when maintenance of the power conversion device 1 is performed. In the case of a configuration in which the storage battery 9 is provided, a power supply route can be formed in which the power stored in the storage battery 9 is supplied to the AC load 92 through the inverter circuit I. As a result, even when the three-phase AC power supply 91 experiences a power outage, the power stored in the storage battery 9 can be continuously supplied to the AC load 92 via the inverter circuit I, and the power conversion device 1 can be used as an uninterruptible power supply 300.

[0037] As described above, the power conversion device 1 according to the present embodiment includes a converter circuit C connected to a three-phase AC power source 91 and converting AC from the three-phase AC power source 91 into DC, a smoothing circuit S connected to DC output terminals 42a and 42b of the converter circuit C and made of a capacitor, an inverter circuit I connected to DC terminals 61a and 62b of the smoothing circuit S and converting DC from the smoothing circuit S into AC and outputting it to an AC load 92, a converter control unit 12 that PWM controls the converter circuit C by a two-phase modulation method, and an inverter control unit 13 that PWM controls the inverter circuit I by a two-phase modulation method. The converter circuit C and the inverter circuit I are three-phase full bridge circuits made of switching elements 4a to 4f and 6a to 6f, and an input filter capacitor 2a constituting a filter on the converter circuit side and an output filter capacitor 8a constituting a filter on the inverter circuit side are connected to the converter control unit 12. The converter control unit 12 performs PWM control of the converter circuit C by a two-phase modulation method using an inverter two-phase modulation signal for two-phase modulation used in the inverter control unit 13.

[0038] According to this configuration, by performing PWM control by the two-phase modulation method of the converter circuit C using the inverter two-phase modulation signal for two-phase modulation used in the inverter control unit 13, even if the input voltage Er and the output voltage Eu are out of phase during two-phase modulation, no pulse-like voltage is generated between the output filter reactor 7a-output filter capacitor 8a-input filter capacitor 2a-input filter reactor 3a, and the ripple current flowing therethrough can be suppressed. Therefore, it is possible to maintain a long two-phase modulation period without increasing the size of the power conversion device, and the efficiency of power conversion can be improved.

[0039] Furthermore, according to the power conversion device 1 of this embodiment, the inverter control unit 13 may have an inverter sine wave reference generation unit 135 and a two-phase modulation signal generation unit 134. The inverter sine wave reference generation unit 135 may generate an ideal sine wave and output it to the two-phase modulation signal generation unit 134, and the two-phase modulation signal generation unit 134 may receive the ideal sine wave, generate an inverter two-phase modulation signal, and output it to the converter control unit 12.

[0040] According to this configuration, both the inverter control unit 13 and the converter control unit 12 are configured to perform PWM control by the two-phase modulation method using an ideal sine wave as an inverter two-phase modulation signal for two-phase modulation. Even if the input voltage Er and the output voltage Eu are out of phase during two-phase modulation, no pulse-like voltage is generated between the output filter reactor 7a-output filter capacitor 8a-input filter capacitor 2a-input filter reactor 3a, and the ripple current flowing therethrough can be further suppressed. Therefore, it is possible to maintain a long two-phase modulation period without increasing the size of the power conversion device 1, and the efficiency of power conversion can be improved.

[0041] Moreover, according to the power conversion device 1 of this embodiment, the converter control unit 12 may have a converter modulation command generating unit 121, a first two-phase modulation control unit 122, and a first PWM signal generating unit 123. The converter modulation command generating unit 121 may receive a three-phase AC voltage from the three-phase AC power supply 91, generate a converter modulation command signal consisting of a three-phase AC sine wave, and output the converter modulation command signal to the first two-phase modulation control unit 122. The first two-phase modulation control unit 122 may receive the converter modulation command signal from the converter modulation command generating unit 121 and the inverter two-phase modulation signals AI1 to AI6 from the two-phase modulation signal generating unit 134 of the inverter control unit 13, generate two-phase modulation command signals Vr', Vs', Vt', and output the two-phase modulation command signals Vr', Vs', Vt' to the first PWM signal generating unit 123.

[0042] Moreover, according to the power conversion device 1 of this embodiment, the inverter control unit 13 may further include an inverter modulation command generating unit 131, a second two-phase modulation control unit 132, and a second PWM signal generating unit 133. The inverter modulation command generating unit 131 may receive an ideal sine wave generated by the inverter sine wave reference generating unit 135, generate an inverter modulation command signal consisting of a three-phase AC sine wave, and output it to the second two-phase modulation control unit 132. The second two-phase modulation control unit 132 may receive the inverter modulation command signal from the inverter modulation command generating unit 131 and the inverter two-phase modulation signals AI1 to AI6 from the two-phase modulation signal generating unit 134, generate inverter modulation command signals Vu, Vv, and Vw, and output them to the second PWM signal generating unit 133.

[0043] Moreover, the power conversion device 1 further includes a bypass circuit 301 in parallel with the converter circuit C and the inverter circuit I, and the converter control unit 12 and the inverter control unit 13 can switch between a route for supplying the power stored in the storage battery 9 from the inverter circuit I to the AC load 92 and a route for supplying the power from the bypass circuit 301 to the AC load 92 according to a predetermined condition (for example, during a power outage or maintenance). In this way, the power conversion device 1 can also function as a non-insulated uninterruptible power supply.

[0044] Although the present embodiment has been described above, it goes without saying that the technical scope of the present embodiment should not be interpreted as being limited by the description of the present embodiment. The present embodiment is merely an example, and it is understood by those skilled in the art that various modifications of the embodiment are possible within the scope of the invention described in the claims. The technical scope of the present embodiment should be determined based on the scope of the invention described in the claims and its equivalents. [Explanation of symbols]

[0045] 1,200 Power conversion equipment 2a~2c Input filter capacitors 3a~3c Input filter reactor 4a~4f Semiconductor switching elements 5 Smoothing capacitor 6a~6f Semiconductor switching elements 7a~7c Output filter reactor 8a~8c Output filter capacitors 9. Storage battery 12 Converter control section 13 Inverter control unit 121 Converter modulation command generator 131 Inverter modulation command generator 122 First two-phase modulation control section 132 Second two-phase modulation control section 123 1st PWM signal generation section 133 2nd PWM signal generation section 123a,133a Comparator 123b, 133b Carrier signal generator 124,134 Two-phase modulation signal generator 135 Inverter sine wave reference generator 31a~31c Device input terminals 41a~41c Converter input terminals 91 Three-phase AC power supply 92 AC load 300 Uninterruptible Power Supply 301 Bypass circuit C converter circuit EU Output Voltage Er Input voltage F1 Input Filter F2 Output Filter I Inverter circuit nl neutral line S smoothing circuit

Claims

1. a converter circuit connected to a three-phase AC power source and converting AC from the three-phase AC power source into DC; a smoothing circuit including a capacitor connected to a DC output terminal of the converter circuit; an inverter circuit connected to a DC terminal of the smoothing circuit, converting a DC current from the smoothing circuit into an AC current and outputting the AC current to an AC load; A converter control unit that controls the converter circuit by PWM using a two-phase modulation method; an inverter control unit that controls the inverter circuit by PWM using a two-phase modulation method; Equipped with the converter circuit and the inverter circuit are each formed of a three-phase full-bridge circuit made of switching elements, and an input filter capacitor constituting a filter on the converter circuit side and an output filter capacitor constituting a filter on the inverter circuit side are connected to each other; The converter control unit performs PWM control of the converter circuit by a two-phase modulation method using a two-phase modulation signal for two-phase modulation used in the inverter control unit. Power conversion equipment.

2. The inverter control unit has an inverter sine wave reference generation unit and a two-phase modulation signal generation unit, the inverter sine wave reference generating unit generates an ideal sine wave and outputs it to the two-phase modulation signal generating unit; the two-phase modulation signal generating unit receives the ideal sine wave, generates a two-phase modulation signal, and outputs the two-phase modulation signal to the converter control unit; The power conversion device according to claim 1 .

3. the converter control unit includes a converter modulation command generating unit, a first two-phase modulation control unit, and a first PWM signal generating unit; the converter modulation command generation unit receives the three-phase AC voltage of the three-phase AC power supply, generates a converter modulation command signal consisting of a three-phase AC sine wave, and outputs the generated signal to the first two-phase modulation control unit; the first two-phase modulation control unit receives the converter modulation command signal from the converter modulation command generation unit and the two-phase modulation signal from the two-phase modulation signal generation unit of the inverter control unit, generates a two-phase modulation command signal, and outputs the two-phase modulation command signal to the first PWM signal generation unit; The power conversion device according to claim 2 .

4. The inverter control unit further includes an inverter modulation command generating unit, a second two-phase modulation control unit, and a second PWM signal generating unit, the inverter modulation command generating unit receives the ideal sine wave generated by the inverter sine wave reference generating unit, generates an inverter modulation command signal consisting of a three-phase AC sine wave, and outputs the inverter modulation command signal to the second two-phase modulation control unit; the second two-phase modulation control unit receives an inverter modulation command signal from the inverter modulation command generation unit and a two-phase modulation signal from the two-phase modulation signal generation unit, generates a two-phase modulation command signal, and outputs the two-phase modulation command signal to a second PWM signal generation unit; The power conversion device according to claim 3 .

5. a bypass circuit in parallel with the converter circuit and the inverter circuit; the converter control unit and the inverter control unit switch between power supply from the inverter circuit to the AC load and power supply from the bypass circuit to the AC load according to a predetermined condition. The power conversion device according to claim 1 .

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