JP2006262662A - Dc power supply device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a DC power supply device for adjusting the unbalanced voltage of a three phase AC power supply and having input power factor improvement effects. <P>SOLUTION: The device is provided with a bridge rectifying circuit 3, a smoothing capacitor 4, a reactor 2 connected to the three phase AC power supply 1, a capacitor 7 connected between AC input terminals and DC output terminals of respective phases in the bridge rectifying circuit 3 via a bidirectional switch 6, a zero-cross detection means 8 detecting the zero point of the voltage in the three phase AC power supply 1, a DC voltage detection means 9 detecting DC voltages at both ends of the smoothing capacitor 4, a phase voltage detection means 11 detecting the voltage values of the respective phases of the three-phase AC power supply 1, a control signal correction means 12 adjusting the control signal, based on the output of the phase voltage detection means 11 and a bidirectional switch control means 10 driving the bidirectional switch 6. The phase voltage detection means 11 detects the voltage value of the three-phase AC power supply 1, the control signal correction means 12 decides the optimum control signal, according to the value, and the unbalance voltage can be adjusted. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a DC power supply device that uses a rectification method using a bridge rectifier circuit and supplies power to a device, a system, or the like with high power factor and low distortion.

  Conventionally, in a DC power supply device that converts the current of a three-phase AC power supply to DC while keeping the current of a three-phase AC power supply in a sine wave shape for the purpose of reducing harmonic current and improving input power factor, switching is performed by driving the switching element from several kHz to several tens kHz A method has been adopted in which the current flowing through the element is controlled at high speed to follow the target reference sine waveform. However, when the switching element is driven at a high frequency in this way, there are problems such as an increase in loss and an increase in noise generation level. For this reason, in recent years, a DC power supply having a capacity of about several kW has been adapted to reduce the harmonic current and improve the input power factor by driving the switching element once or several times in a half cycle of the commercial frequency. It has become to.

  For example, as a conventional DC power supply device, there are three reactors connected to each phase of a three-phase AC power supply, a bridge rectifier circuit composed of six diodes, and a capacitor connected in series on the output side of the bridge rectifier circuit. There is a combination of two equal smoothing capacitors and three bidirectional switches connected between the middle point of the smoothing capacitors and three reactors (see, for example, Patent Document 1).

  A conventional DC power supply device will be described below with reference to FIGS. 9 to 12 with reference to the drawings. FIG. 9 shows a block diagram of a DC power supply device described as an embodiment corresponding to the three-phase AC power supply in Patent Document 1, and FIG. 10 shows waveforms of respective parts of the conventional DC power supply device.

  In FIG. 9, a three-phase AC power source 1 is a commercial AC power source, and is connected to a bridge rectifier circuit 3 composed of six diodes via reactors 2u, 2v, and 2w. On the output side of the bridge rectifier circuit 3 are connected two series-smoothing capacitors 100, 101 having the same capacity, and a bidirectional switch 6u between these midpoints and the reactors 2u, 2v, 2w, 6v and 6w are connected. The control unit 103 detects the phase voltage of the three-phase AC power supply 1 and outputs a control signal to turn on the bidirectional switches 6u, 6v, 6w at a predetermined timing based on the phase voltage zero cross. Next, the operation will be described with reference to the waveforms of the respective parts shown in FIG.

  The power supply voltage of the three-phase AC power supply 1 changes as shown in FIG. Then, the control unit 103 detects a zero cross of each phase voltage and outputs a control signal to turn on the bidirectional switch of the corresponding phase as shown in FIG. Then, as shown in FIG. 10C, the phase voltage at each input terminal of the bridge rectifier circuit 3 becomes zero corresponding to the period when the bidirectional switch is on, and V0 / 2, Change to repeat V0 / 2.

  V0 is a DC voltage. Therefore, the line voltage at each input terminal of the bridge rectifier circuit 3 has amplitudes of five levels of V0, V0 / 2, 0, −V0 / 2, and −V0, as shown in FIG. A waveform with 8 steps per cycle. The voltage at each input terminal of the bridge rectifier circuit 3 with respect to the neutral point of the power supply voltage is 2V0 / 3, V0 / 2, V0 / 3, 0, −V0 / 3 as shown in FIG. , −V0 / 2 and −2V0 / 3 have amplitudes of seven levels and become a waveform of 12 steps in one cycle.

Thus, since the voltage at each input terminal of the bridge rectifier circuit 3 can be made into a voltage waveform of 12 steps, as shown in (f) of FIG. The harmonic current reduction effect more than the phase 12 pulse rectifier circuit system can be achieved.

  Although the zero cross detection means for detecting the zero cross point of the phase voltage is omitted in the block diagram 9 of the conventional example, the phase voltage is normally stepped down by the three-phase transformer 104 as shown in FIG. The phase voltage zero cross of each phase is detected by three zero cross comparators 105u, 105v, 105w. Further, in order to reduce the size and weight, the zero cross point of the phase voltage of any one of the three phases is detected, and the zero cross point of the other two phase voltages is obtained by calculation. The zero cross as shown in FIG. A detection circuit has also been devised. Hereinafter, a method of detecting the phase voltage zero cross of each phase will be described with reference to FIG.

The one-phase voltage zero-cross detection means 106 is connected to the voltage dividing resistors 107u, 107v, and 107w for obtaining a virtual neutral point from each line of the three-phase AC power supply 1, and the voltage dividing resistor 107u on the primary side in series. A photocoupler 108 that generates a zero-cross pulse centered on the zero-cross point of the u-phase voltage by turning on the secondary-side transistor when a current greater than or equal to a predetermined current flows through the voltage resistor 107u; a pull-up resistor 109; The delay circuit 110 includes a delay circuit 110 that delays a predetermined time so that the timing of the voltage rise change of the zero cross pulse coincides with the zero cross point. Then, the two-phase voltage zero-cross calculating means 111 calculates the frequency of the three-phase AC power source 1 from the period of the u-phase zero-cross point detected by the one-phase voltage zero-cross detecting means 106, and from this, a time corresponding to a phase angle of 120 ° Δts1 is calculated. Then, the rising edge of the pulse delayed by Δts1 from the zero-cross point of the u-phase voltage is set as the v-phase zero-crossing point, and the rising edge of the pulse delayed by Δts1 is output as the w-phase zero-crossing point. The one-phase voltage zero-cross detection means 106 shown in FIG. 12 is for making the input format correspond to a three-phase three-wire system, and in the case of a three-phase four-wire system having a neutral point, a direct phase voltage can be detected directly. Therefore, the voltage dividing resistors 107v and 107w are not necessary.
Japanese Patent Laid-Open No. 10-174442

  However, in the conventional DC power supply device as described above, even if the three-phase AC power supply becomes an unbalanced voltage due to some factor, the operation is continued by driving the switch according to the output detected by the DC voltage detection circuit. . That is, the three-phase AC power supply has a problem that it cannot continue to operate without being unbalanced and cannot be adjusted.

  The DC power supply device of the present invention solves the conventional problems as described above, and provides a DC power supply device having an input power factor improvement effect that enables adjustment of an unbalanced voltage of a three-phase AC power supply. The purpose is to do.

  In order to solve the above-mentioned conventional problems, a DC power supply device of the present invention includes a bridge rectifier circuit composed of six diodes, three reactors connected for each phase, three bidirectional switches, Three capacitors each connected to the directional switch, zero cross detection means, DC voltage detection means, phase voltage detection means, and control signal correction means. When the three-phase AC power supply becomes an unbalanced voltage, The unbalanced voltage of the three-phase AC power supply is adjusted by detecting the voltage and determining the optimum control signal according to the value by the control signal correcting means.

Since the DC power supply device of the present invention can determine the optimum control signal according to the detected value by detecting the phase voltage of the three-phase AC power supply, the unbalanced voltage of the three-phase AC power supply can be determined. It becomes possible to adjust.

  According to a first aspect of the present invention, there is provided a three-phase AC power source, a bridge rectifier circuit formed by six diodes for full-wave rectification of the AC from the three-phase AC power source, and a smoothing capacitor for smoothing the output of the bridge rectifier circuit. A bi-directional switch between a reactor connected between the three-phase AC power source and an AC input terminal of each phase of the bridge rectifier circuit; and an AC input terminal and a DC output terminal of each phase of the bridge rectifier circuit Each of each of the three-phase AC power supply, a capacitor connected via a zero-cross detection means for detecting a zero point of the voltage of the three-phase AC power supply, a DC voltage detection means for detecting the voltage across the smoothing capacitor, and Phase voltage detecting means for detecting a phase voltage value, control signal correcting means for adjusting a control signal based on an output of the phase voltage detecting means, an output of the zero-cross detecting means, and the DC voltage detecting means And bi-directional switch control means for driving the bi-directional switch based on the output of the control signal correction means, thereby detecting the phase voltage of the three-phase AC power source and performing optimal control according to the value By determining the signal, the unbalanced voltage of the three-phase AC power supply can be adjusted.

  A second invention is a direct current power supply device according to the first invention, in which the control signal correction means adjusts the phase of the drive pulse of the bidirectional switch according to the voltage value detected by the phase voltage detection means. Yes, it is possible to adjust the unbalanced voltage of the three-phase AC power supply.

  In a third aspect of the present invention, in particular, in the first aspect, the control signal correction unit is configured to adjust the pulse width and phase of the drive pulse of the bidirectional switch according to the voltage value detected by the phase voltage detection unit. It is a power supply device, and it is possible to adjust the unbalanced voltage of the three-phase AC power supply.

  According to a fourth aspect of the invention, in particular, in the invention according to any one of the first to third aspects, the correction value is determined in accordance with a difference in voltage value of each phase detected from the phase voltage detecting means when the three-phase AC power supply is turned on. The DC power supply device configured as described above can adjust the unbalanced voltage of the three-phase AC power supply.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 is a block diagram of a DC power supply device according to a first embodiment of the present invention. In FIG. 1, each phase of u, v, and w of the three-phase AC power supply 1 is input to a bridge rectifier circuit 3 configured by diodes 3u, 3v, 3w, 3x, 3y, and 3z via reactors 2u, 2v, and 2w. Connected to the terminal. The electrolytic capacitor 4 is connected between the positive electrode output and the negative electrode output of the bridge rectifier circuit 3, and the load 5 is connected in parallel to the electrolytic capacitor 4. The bidirectional switches 6u, 6v, 6w are connected together at one end to the negative output of the bridge rectifier circuit 3, and the other terminals are connected to capacitors 7u, 7v, 7w, respectively.

  The other terminals of these capacitors 7 u, 7 v, 7 w are connected to the AC input terminals of the bridge rectifier circuit 3. The zero-cross detection means 8 detects the zero-cross point of the u-phase voltage of the three-phase AC power source 1 and calculates the zero-cross point of the v-phase and the w-phase from the u-phase zero-cross point. The means 10 is for driving and controlling the bidirectional switches 6u, 6v, 6w in accordance with the zero cross point of each phase. The DC voltage detecting means 10 detects the voltage across the smoothing capacitor 4, the phase voltage detecting means 11 detects the u, v, and w phase voltages, and the control signal correcting means 12 This is for determining an optimum control signal according to the voltage value detected by the phase voltage detecting means 11.

  In the above configuration, first, the operation of the entire normal DC power supply apparatus will be described with reference to FIGS. For ease of explanation, the capacitors 7u, 7v, 7w are repeatedly charged and discharged from zero volts to a predetermined voltage Vdc1, the initial voltage value of the capacitors 7u, 7v is zero volts, and the initial voltage value of the capacitor 7w is Vdc1. The initial phase of the three-phase AC power supply 1 will be described focusing on the u-phase current as the phase of the u-phase voltage zero cross.

  First, a zero-cross point of the u-phase voltage of the three-phase AC power supply 1 is detected by the zero-cross detection means 8, and the bidirectional switch control means 9 responds only during the drive time command Δt from this u-phase voltage zero-cross point. The directional switch 6u is driven. At this time, as indicated by an arrow in FIG. 2, the flow of the charging current of the capacitor 7u passes from the u phase of the three-phase AC power source 1 through the reactor 2u, charges the capacitor 7u, and then passes through the diode 3y and the reactor 2v to thereby change the three-phase AC. It will return to the v phase of the power supply 1. Next, when the capacitor 7u is charged up to Vdc1 after the drive time command Δt and the bidirectional switch 6u is turned off, the current flowing through the reactors 2u and 2v tends to be continuous, and is shown by the arrow in FIG. Thus, after charging the electrolytic capacitor 4 from the u phase through the reactor 2u and the diode 3u, the phase returns to the v phase through the diode 3y and the reactor 2v.

  Thereafter, the zero-cross detection means 8 calculates the w-phase voltage zero-cross point, and the bidirectional switch control means 9 drives the corresponding bidirectional switch 6w from the w-phase voltage zero-cross point only during the drive time command Δt. . At this time, the current flowing in the u-phase in FIG. 4 is discharged from the capacitor 7w charged to Vdc1 through the reactor 2w to the electrolytic capacitor 4 through the reactor 2u and the diode 3u from the u-phase of the three-phase AC power source 1 as indicated by the arrow. The discharge current to be added is added, and the current flowing through the u phase during this period continues to increase.

  When the voltage of the capacitor 7W becomes zero volts after the drive command time Δt and the bidirectional switch 6w is turned off, the current flowing through the v phase and the current flowing through the w phase are opposite in polarity to the u phase current, as shown by the arrows in FIG. During the period, the current that had previously flowed through the reactor 2u charged the electrolytic capacitor 4 through the diode 3u, and was divided into the diode 3y and the reactor 2v, the diode 3z and the reactor 2w, and the reactor 2u via the three-phase AC power supply 1 Flowing back to Thereafter, if the v-phase current has the same polarity as the u-phase current, the current flowing through the reactor 2u as shown in FIG. 6 charges the electrolytic capacitor 4 through the diode 3u, passes through the diode 3z and the reactor 2w, The current flows back to the reactor 2u via the three-phase AC power source 1, and continues to decrease monotonically until the current value becomes zero.

  As described above, the operation has been described by focusing on the u-phase current, but the behavior of the currents of the other phases is the same, and the current of each phase starts to flow from the zero-cross point of the voltage of each phase. The voltage of each phase continues to increase until it reaches its peak value, and then decreases with the voltage drop of each phase, so that the current waveform of each phase becomes a sine wave with the same phase as the voltage waveform of each phase, and the input power factor is improved. It becomes possible.

  FIG. 7 shows outputs gu and gv for driving the bidirectional switches 6u, 6v and 6w of the bidirectional switch control means 9 in one cycle from the zero phase of the u-phase voltage of the three-phase AC power supply 1. , Gw generation timing is shown. In the above description, the method for determining the drive time command Δt of the bidirectional switch control means 9 is not mentioned. Usually, the voltage across the electrolytic capacitor 4 is determined to match the DC voltage target value. Load current detection means for detecting the current flowing through the load 5 may be provided to determine the drive time command Δt from the magnitude of the load current, or input current detection means may be provided to determine the drive time command Δt from the magnitude of the input current. May be determined.

  In the present embodiment, one line of the bidirectional switches 6u, 6v, 6w is connected to the negative output of the bridge rectifier circuit 3 in a lump, but the same operation is performed even when connected to the positive output.

  In the present embodiment, the bidirectional switches 6u, 6v, 6w are driven from the zero-cross point of the voltage of each phase. However, when the inductance of the reactors 2u, 2v, 2w is large or when each phase is high, In this case, when the bidirectional switches 6u, 6v, 6w are turned on, there may occur a problem that zero current switching does not occur. The bidirectional switch control means 9 may be configured to drive the bidirectional switches 6u, 6v, 6w with a predetermined time delay from the zero cross point.

  Next, a method of correcting the drive pulse of the control signal correction unit 12 will be described. Considering the fact that some other factors such as other loads are applied and the u-phase receiving end voltage is lowered and the three-phase AC power supply 1 is unbalanced, the u-phase voltage is lowered by 10 V and the three-phase AC power supply 1 is unbalanced. FIG. 8 shows the waveforms of the u-phase input voltage and input current at that time. By reducing only the pulse width of the driving pulse of the bidirectional switch 6u, the area of Vuc is reduced as shown in FIG. Therefore, the charging / discharging voltage of the capacitor 7u is decreased and the u-phase current is decreased, so that the u-phase power receiving end voltage can be increased, so that the balance of the three-phase AC power source 1 can be maintained.

  In the present embodiment, each phase voltage is detected by the phase voltage detection means 11, and based on the detected value, the pulse width of the drive pulse of each phase is corrected by the control signal correction means 12, and the bidirectional switch control means. Is configured to drive the bidirectional switches 6u, 6v, 6w.

  As described above, the unbalanced voltage of the three-phase AC power supply 1 can be adjusted by adjusting the pulse width of the drive pulse of the bidirectional switch.

(Embodiment 2)
The second embodiment is configured to adjust the phase of the drive pulses of the bidirectional switches 6u, 6v, 6w in the first embodiment. As shown in FIG. 8, the size of the area of Vuc can be changed by shifting the phase td of the drive pulse. Therefore, by adjusting the phase of the drive pulse of each phase according to the detection value of the phase voltage detection means 11 , Keep the balance of each phase current, keep the operation and maintain high power factor.

  As described above, by adopting a configuration that adjusts the phase of the driving pulse of the bidirectional switch, the unbalanced voltage of the three-phase AC power supply 1 can be adjusted.

(Embodiment 3)
The third embodiment is configured to adjust the pulse width and phase of the drive pulses of the bidirectional switches 6u, 6v, 6w in the first embodiment. By simultaneously adjusting the pulse width and phase, the controllability of the control signal correction means 12 is improved, and the unbalanced voltage of the three-phase AC power source 1 can be adjusted.

(Embodiment 4)
In the fourth embodiment, the drive pulses of the bidirectional switches 6u, 6v, 6w in the first embodiment are changed according to the voltage value difference of each phase detected from the phase voltage detecting means 11 when the three-phase AC power supply 1 is turned on. The driving pulse correction value is determined. The voltage difference of each phase voltage of the three-phase AC power supply 1 is set finely in units of 1 V or less, and a data table of correction values for each phase corresponding to the set value is determined in the control signal correction means 12. A correction value corresponding to the detection value of the phase voltage detection means 11 when the three-phase AC power supply 1 is turned on is read from the data table and reflected in the bidirectional switch control means 10 to drive the bidirectional switches 6u, 6v, 6w. Is configured to do.

  As described above, the data table of the correction value of the driving pulse of the bidirectional switch is prepared, and the correction is performed according to the difference in the voltage value of each phase detected from the phase voltage detecting means when the three-phase AC power supply 1 is turned on. By determining the value, the unbalanced voltage of the three-phase AC power source 1 can be adjusted.

  As described above, the DC power supply device according to the present invention can adjust the unbalance of the three-phase AC power supply in the DC power supply device that can improve the input power factor. It can be used as an input stage circuit for inverter devices such as rectifiers, air conditioners and refrigerators.

1 is a block diagram of a DC power supply device according to Embodiment 1 of the present invention. Explanatory drawing at the start of capacitor 7u charging according to Embodiment 1 of the present invention Explanatory drawing after completion of capacitor 7u charging in Embodiment 1 of the present invention Explanatory drawing when capacitor 7w discharge starts according to Embodiment 1 of the present invention Explanatory drawing of capacitor 7w discharge completion according to the first embodiment of the present invention Explanatory drawing at the time of v-phase current commutation after completion of capacitor 7w discharge of Embodiment 1 of the present invention Timing diagram of each phase voltage and bidirectional switch driving of embodiment 1 of the present invention U-phase voltage and u-phase current waveform diagram when the three-phase AC power supply of Embodiment 1 of the present invention is unbalanced Block diagram of a conventional DC power supply Waveform diagram of each part of conventional DC power supply Configuration diagram of zero-cross detection means using a three-phase transformer Configuration diagram of zero-cross detection means using one-phase voltage zero-cross detection means

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Three-phase alternating current power supply 2u, 2v, 2w Reactor 3 Bridge rectifier circuit 3u, 3v, 3w, 3x, 3y, 3z Diode 4 Electrolytic capacitor 5 Load 6u, 6v, 6w Bidirectional switch 7u, 7v, 7w Capacitor 8 Zero cross detection Means 9 DC voltage detection means 10 Bidirectional switch control means 11 Phase voltage detection means 12 Control signal correction means

Claims (4)

A three-phase AC power source, a bridge rectifier circuit formed by six diodes for full-wave rectification of the AC from the three-phase AC power source, a smoothing capacitor for smoothing the output of the bridge rectifier circuit, and the three-phase AC power source And a reactor connected between the AC input terminal of each phase of the bridge rectifier circuit, and an AC input terminal and a DC output terminal of each phase of the bridge rectifier circuit connected via a bidirectional switch A capacitor, a zero cross detecting means for detecting a zero point of the voltage of the three-phase AC power supply, a DC voltage detecting means for detecting a voltage at both ends of the smoothing capacitor, and detecting a voltage value of each phase of the three-phase AC power supply Phase voltage detection means, control signal correction means for adjusting a control signal based on the output of the phase voltage detection means, output of the zero cross detection means, the DC voltage detection means, and the control DC power supply device being characterized in that a bidirectional switch control means for driving the bidirectional switch based on the output of the No. correction means. 2. The DC power supply device according to claim 1, wherein the control signal correction means adjusts the phase of the drive pulse of the bidirectional switch. 2. The DC power supply device according to claim 1, wherein the control signal correcting means adjusts a pulse width and a phase of a driving pulse of the bidirectional switch. 2. The control signal correcting unit is configured to determine a correction value according to a difference in voltage value of each phase detected from the phase voltage detecting unit when a three-phase AC power supply is turned on. 4. The DC power supply device according to any one of items 1 to 3.

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