JP5044939B2 - DC power supply - Google Patents

Description

  The present invention relates to a DC power supply device that converts a three-phase AC power source into DC and reduces harmonic current flowing through the three-phase AC power source to improve an input power factor.

Conventionally, in a DC power supply that converts the direct current three-phase alternating current for the purpose of improving input power factor and harmonic current reduction is shall not using switching elements, only three reactors and delta connection or a star on the ac side A method of providing a combination of connected capacitors has been widely used. This operating principle is to reduce the harmonic current by suppressing the steep change of the current flowing into the electrolytic capacitor on the DC output side by the reactor, and cancel the current phase delay due to this reactor by the action of the current phase advance of the capacitor. Is to improve.

  However, in such a circuit system (hereinafter referred to as a capacitor AC side arrangement circuit system), the DC output voltage at the time of heavy load is drastically reduced, and in order to prevent this, it is necessary to increase the capacitance of the capacitor. Then, in order to maintain the power factor improvement effect, the inductance of the reactor must be increased, and there is a problem that the entire apparatus is increased in size.

  On the other hand, a circuit system (hereinafter referred to as a capacitor DC side arrangement circuit system) in which a capacitor is arranged on the DC side and the DC voltage drop width under heavy load is reduced even with the same capacitor capacity has been devised (for example, a capacitor DC side arrangement circuit system). , See Patent Document 1).

As such a DC power supply device, as shown in FIG. 15, reactors 2u , 2v , 2w connected to each phase of the three-phase AC power supply 1 , and six diodes 3u , 3v , 3w , 3x , 3y , 3z in a bridge rectifier circuit 3 to be formed, the capacitor 7u provided between the positive terminal of the direct current output and the AC input ends of the bridge rectifier circuit 3, 7v, 7w and, DC reactor 1 3 connected to the DC output ends If, there is constituted an electrolytic capacitor 4 or al.

  However, in the configuration of the conventional capacitor AC side arrangement circuit type DC power supply device, the DC output voltage drop at the time of heavy load becomes a problem. On the other hand, in the configuration of the capacitor DC side arrangement circuit type DC power supply device, at the time of heavy load Although effective in reducing the DC output voltage, it has problems such as an increase in DC output voltage at light loads and a deterioration in power factor.

  The present invention solves the above-described conventional problems, and an object thereof is to provide a DC power supply apparatus that can reduce harmonic current, reduce DC output voltage fluctuation, and reduce input power factor fluctuation. .

In order to solve the above-described conventional problems, a DC power supply device according to the present invention includes a three-phase AC power supply, a bridge rectifier circuit formed of six diodes, and an electrolytic capacitor connected to a DC output terminal of the bridge rectifier circuit. And a reactor connected between the three-phase AC power supply and the AC input terminal of each phase of the bridge rectifier circuit, and between the AC input terminal of each phase of the bridge rectifier circuit and the DC output terminal of the bridge rectifier circuit And a bidirectional switch connected between the capacitor and a DC output terminal of the bridge rectifier circuit, the AC input terminal and the capacitor of each phase of the bridge rectifier circuit Between the two, a second bidirectional switch is provided .

By turning on the bidirectional switch at heavy loads and turning off the bidirectional switch at light loads, this increases DC voltage at light loads while improving the input power factor and reducing harmonic current. The power factor can be prevented from decreasing , and when the load becomes lighter and close to no load, the DC output voltage rises by turning off the second bidirectional switch that was always on. Can be prevented.

  The present invention can provide a DC power supply apparatus that can reduce harmonic current, reduce DC output voltage fluctuations, and reduce input power factor fluctuations.

A DC power supply device according to a first invention includes a three-phase AC power source, a bridge rectifier circuit formed of six diodes, an electrolytic capacitor connected to a DC output terminal of the bridge rectifier circuit, a three-phase AC power source and a bridge A reactor connected between an AC input terminal of each phase of the rectifier circuit, a capacitor connected between an AC input terminal of each phase of the bridge rectifier circuit and a DC output terminal of the bridge rectifier circuit, and the capacitor A DC power supply device including a bidirectional switch connected between a DC output terminal of the bridge rectifier circuit, wherein a second power supply device is connected between the AC input terminal of each phase of the bridge rectifier circuit and a capacitor. by having a bidirectional switch, as well as a possible to reduce harmonic current and improve an input power factor, and on the bidirectional switch at heavy loads, by turning off at light loads, the DC output voltage It is possible to reduce the variation ranges of the input power factor.

A DC power supply device according to a second aspect of the present invention comprises the DC voltage detection means for detecting the DC output voltage of the bridge rectifier circuit and the bidirectional switch control means, particularly in the first invention, wherein the DC voltage detection means By controlling the bidirectional switch or the bidirectional switch and the second bidirectional switch by the bidirectional switch control means based on the detected value, the bidirectional switch or the bidirectional switch And the operation of the second bidirectional switch can be automatically controlled.

According to a third aspect of the present invention, there is provided a DC power supply apparatus according to the first aspect of the invention, comprising a load current detecting means for detecting a load current and a bidirectional switch control means, based on a detection value of the load current detecting means. By controlling the bidirectional switch or the bidirectional switch and the second bidirectional switch by the bidirectional switch control means, the bidirectional switch or both of the bidirectional switch and the second switch are controlled. Operation of the directional switch can be automatically controlled.

According to a fourth aspect of the present invention, there is provided a direct current power supply apparatus according to the first aspect of the invention, comprising input current detection means for detecting an input current from a three-phase AC power supply, and bidirectional switch control means. By controlling the bidirectional switch or the bidirectional switch and the second bidirectional switch by the bidirectional switch control means based on the detected value of the means, the bidirectional switch or the bidirectional switch The operation of the switch and the second bidirectional switch can be automatically controlled.

  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 circuit diagram of a DC power supply device according to a first embodiment of the present invention. In FIG. 1, each phase of u, v, w of the three-phase AC power source 1 is input to a bridge circuit 3 composed of diodes 3u, 3v, 3w, 3x, 3y, 3z via reactors 2u, 2v, 2w. Connected to the terminal. Here, the AC input terminal corresponding to the u phase of the bridge rectifier circuit 3 is defined as Du, the AC input terminal corresponding to the v phase is defined as Dv, and the AC input terminal corresponding to the w phase is defined as Dw. 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. Capacitors 7u, 7v, and 7w are connected as star connections in which one end is connected to Du, Dv, and Dw of bridge rectifier circuit 3, respectively. The bidirectional switch 6 is connected between the other end of the capacitors 7u, 7v and 7w connected as a star connection and the negative output of the bridge rectifier circuit.

  In the above configuration, the operation and action will be described below with reference to FIGS. First, regarding the operation and effect of improving the input power factor and reducing the harmonic current, in FIG. 1, the state in which the bidirectional switch 6 is OFF is equivalent in circuit to a DC power supply device of the conventional capacitor AC side arrangement type. The operation of the reactors 2u, 2v, and 2w to reduce the harmonic current and increase the power factor by using the capacitors 7u, 7v, and 7w is a well-known conventional technique. Omit. In addition, the bidirectional switch 6 is in an on state in which the DC power supply device of the conventional capacitor DC side arrangement type and a circuit in which the connection point of the capacitors 7u, 7v, 7w is changed from the positive output of the bridge rectifier circuit to the negative output Therefore, the operations and effects of the harmonic current reduction and the input power factor improvement are the same, and thus detailed description thereof is omitted.

  Next, suppression of fluctuations in the DC output voltage and fluctuations in the input power factor in the present embodiment will be described. Therefore, the characteristics of the conventional DC power supply device will be described first. FIG. 2A is a graph showing the results of simulations for the characteristics of input power and DC output voltage, and input power and input power factor in a conventional DC power supply of the capacitor AC side arrangement type. Similarly, FIG. 2B is a simulation result graph in the DC power supply device of the capacitor DC side arrangement type. The simulation conditions at this time are input three-phase 400v, 50 Hz, reactors 2u, 2v, 2w, inductance 30mH, capacitors 7u, 7v, 7w, capacitance 20uF.

  As can be seen by comparing FIG. 2 (a) and FIG. 2 (b), in the DC power supply device of the capacitor AC side arrangement type, the DC output voltage rise at the time of light load is small, specifically, when the input power is 100W. The DC output voltage is 570V. On the other hand, the input power factor decreases greatly under heavy load, specifically 88.1% when the input power is less than 10 kW.

  On the other hand, in the DC power supply device of the capacitor DC side arrangement method, the DC output voltage rises greatly at light load and rises to DC output voltage 650V at input power 100W, but the input power factor decrease at heavy load is small. The input power is less than 10 kW, which is 95.6%.

  As described above, since the DC power supply device has contradictory characteristics depending on the arrangement of the capacitors, in the DC power supply device according to the present embodiment, the DC output voltage and the input power factor are set by turning the bidirectional switch 6 on and off. It is intended to improve the characteristics. In other words, when the load is light, the bidirectional switch 6 is turned off to prevent an increase in the DC output voltage, and the reduction of the input power factor is improved. In addition to preventing a decrease in voltage, it also prevents a decrease in input power factor.

FIG. 3 is a diagram simulating the characteristics of the input power, the DC output voltage, and the input power factor of the DC power supply device according to the present embodiment. FIG. 3 is a graph when the bidirectional switch 6 is turned on at an input power of 4 kW or more. From the graph, in the DC power supply device according to the present embodiment, it is possible to suppress the fluctuation of the DC output voltage within the range of 570 V to 507 V between 100 W and 10 kW. As for the input power factor, an input power factor of 80% or more can be secured at an input power of 2 kW or more, and 95% or more can be secured even at an input power of 10 kW. FIG. 4 is a graph showing the characteristics of the harmonic current with respect to the input power of the DC power supply device in the present embodiment. In FIG. 4, the regulation value of the IEC harmonic current regulation is set to 100%, and the ratio to that is shown only for the highest fifth harmonic. However, for other harmonics, a margin can be secured. Yes.

  Thus, in the DC power supply device according to the present embodiment, it is possible to suppress fluctuations in the DC output voltage and fluctuations in the input power factor while improving the input power factor and reducing the harmonic current. In addition, since the operation of the bidirectional switch 6 is a simple changeover switch, it is possible to take advantage of the low noise and high efficiency features of a DC power supply device using only conventional passive elements. . Thus, since the bidirectional switch 6 is only a switching operation, it may be composed of a mechanical contact such as a relay instead of a semiconductor element.

  In the present embodiment, the bidirectional switch 6 is connected to the negative output of the bridge rectifier circuit 3, but may be connected to the positive output.

  FIG. 5 is a circuit diagram for performing switch control with a DC voltage in the present embodiment. In FIG. 5, a DC voltage detection means 8 for detecting the DC output voltage of the bridge rectifier circuit 3 and a bidirectional switch control means 9 are provided to control ON / OFF of the bidirectional switch 6 and bidirectional. The bidirectional switch control means 9 turns off the bidirectional switch 6 and turns off the bidirectional switch 6 when the DC output voltage exceeds a predetermined value when the bidirectional switch 6 is on. In some cases, the bidirectional switch 6 may be turned on when the direct-current output voltage becomes a predetermined value or less. With such a configuration, it is possible to automatically control on / off of the bidirectional switch 6 for obtaining the effect of suppressing the fluctuation of the DC output voltage and the fluctuation of the input power factor as described above.

  FIG. 6 is a circuit diagram for performing switch control by load current in the present embodiment. In FIG. 6, the on / off determination of the bidirectional switch 6 may be performed based on the load current. In this case, instead of the DC voltage detecting means 8, the load current detecting means 10 for detecting the load current is used. To control.

  FIG. 7 is a circuit diagram for performing switch control by an input current in the present embodiment. In FIG. 7, the on / off determination of the bidirectional switch 6 may be performed based on the input current. In this case, the input current detection means 11 for detecting the input current instead of the DC voltage detection means 8. The bidirectional switch control means 9 controls on / off of the bidirectional switch 6 according to the input current.

(Embodiment 2)
FIG. 8 is a circuit diagram of a DC power supply device according to the second embodiment of the present invention. In FIG. 8, capacitors 7u, 7v, 7w connected to the AC input terminals Du, Dv, Dw of the respective phases are compared with FIG. 1, which is a circuit diagram of the DC power supply device according to the first embodiment of the present invention. A second bidirectional switch 12 having a three-pole configuration is provided between the two.

In the present embodiment, the point similar to the case shown in the first embodiment is the same in that the bidirectional switch 6 is turned on / off to suppress the fluctuation of the DC output voltage and the fluctuation of the input power factor. The difference is that the second bidirectional switch 12 is turned on / off at a lighter load than the load condition for turning the directional switch 6 on / off. This is because the input power factor with respect to the input power of the first embodiment shown in FIG. 3 is improved compared to the conventional capacitor DC side arrangement type DC power supply device, but the input power is less than 2 kW. The purpose is to improve the sudden drop in light load.

  In other words, in a DC power supply device in which a light load state of less than several tens of percent with respect to the rated power exists or frequently enters such a state, turning off the second bidirectional switch 12 This prevents the input power factor from deteriorating at light loads.

  In FIG. 8, when the second bidirectional switch 12 is turned off, it becomes a DC power supply device that merely improves the power factor by the reactors 2u, 2v, and 2w. However, only such reactors 2u, 2v, and 2w are used. FIG. 9 shows the relationship between the DC output voltage and the input power factor with respect to the input power of the DC power supply device using the. In this case as well, the calculation result by simulation is shown, and the conditions are the same as those in the graph of FIG. 3 with respect to the fact that the input voltage 3 phase 400V is 50 Hz and the reactors 2u, 2v and 2w have an inductance of 30 mH. FIG. 9 is a graph of the input power, the DC output voltage, and the input power factor of a DC power supply device that improves the input power factor using only the reactor. As can be seen from FIG. 9, when the harmonic current is reduced and the input power factor is improved only with the reactors 2u, 2v, and 2w on the AC side, the DC output voltage rapidly decreases as the load becomes heavier. As a power supply device, the output characteristics are very poor.

  However, focusing on the light load area, the input power factor of 90% or more can be secured even in the range of input power from 500 W to 2.4 kW, which is very effective for improving the input power factor in the light load area. I understand. In the present embodiment, taking advantage of the improvement of the input power factor by only the reactors 2u, 2v, and 2w in such a light load region, the second bidirectional operation is performed in a light load region that greatly reduces the input power factor. The characteristics can be improved by turning off the switch 12.

  FIG. 10 shows the relationship between the DC output voltage and the input power factor with respect to the input power when the bidirectional switch 6 is turned off when the input power is 4 kW or less and the second bidirectional switch 12 is turned off when the input power is 2.4 kW or less. Indicates. As a matter of course, the calculation result by simulation is also shown in this case. The input voltage three-phase 400V is 50 Hz, the reactors 2u, 2v and 2w have an inductance of 30 mH, and the capacitors 7u, 7v and 7w have a capacitance of 20 uF. This is the same as the characteristic graph of FIG.

  As can be seen from FIG. 10, in the DC power supply device according to the present embodiment, the input power factor can secure 90% or more in the entire region of the input power from 500 W to 10 kW, and the fluctuation of the DC output voltage also starts from 100 W. It is possible to keep the voltage within the range of 564V to 507V between 10kW. Also in this embodiment, the IEC harmonic current regulation can be sufficiently cleared. FIG. 11 is a graph showing the characteristics of the fifth harmonic current with respect to the input power of the DC power supply device in the present embodiment.

  Thus, in the DC power supply device according to the present embodiment, it is possible to improve the input power factor and reduce the harmonic current even in a light load state of 10% or less. In addition, since the operations of the bidirectional switch 6 and the second bidirectional switch 12 are merely switching operations, the low noise and high efficiency, which are the features of a conventional DC power supply device using only passive elements, are known. The characteristics can be utilized as in the first embodiment.

  In FIG. 8, the second bidirectional switch 12 has a three-pole configuration. However, when the second bidirectional switch 12 is turned on / off only when the bidirectional switch 6 is off, the capacitor 7u is used. , 7v, 7w, any two capacitors may be separated, so that a two-pole configuration is possible.

  Further, a DC voltage detecting means 8 for detecting the DC output voltage of the bridge rectifier circuit 3 and a bidirectional switch control means 9 for controlling on / off of the bidirectional switch 6 and the bidirectional switch 12 are provided. The bidirectional switch control means 9 provides the bidirectional switch 6 when the DC output voltage exceeds a predetermined value when the bidirectional switch 6 and the second bidirectional switch 12 are on. The second bidirectional switch 12 may be turned off when the DC output voltage becomes a predetermined value or more with the bidirectional switch 6 turned off. When both the bidirectional switch 6 and the bidirectional switch 12 are off, the second bidirectional switch 12 is first turned on and then the bidirectional switch 6 as the DC output voltage decreases. You can do this to turn on.

  With the configuration described above, the bidirectional switch 6 and the second bidirectional switch 12 are turned on / off to obtain the effect of suppressing the fluctuation of the DC output voltage and the fluctuation of the input power factor as described above. Can be automatically controlled. A circuit diagram in this case is shown in FIG.

  On the other hand, on / off determination of the bidirectional switch 6 and the second bidirectional switch 12 may be performed based on the load current. In this case, the load current is detected instead of the DC voltage detection means 8. Load current detecting means 10 is provided, and bidirectional switch control means 9 controls on / off of bidirectional switch 6 and second bidirectional switch 12 in accordance with the load current. A circuit diagram in this case is shown in FIG.

  Further, the bidirectional switch 6 and the bidirectional switch 12 may be turned on / off based on the input current. In this case, the input current for detecting the input current instead of the DC voltage detecting means 8 is used. The detecting means 11 is provided, and the bidirectional switch control means 9 controls on / off of the bidirectional switch 6 and the second bidirectional switch 12 according to the input current. A circuit diagram in this case is shown in FIG.

  The DC power supply device according to the present invention can reduce the harmonic current of the three-phase AC power supply and improve the input power factor, so that it can be used to supply power to the inverter circuit. It can be used as an input stage circuit of a compressor driving device.

Circuit diagram of DC power supply apparatus according to Embodiment 1 of the present invention Relationship diagram of input power, DC output voltage, and input power factor in a conventional DC power supply Relationship diagram of input power, DC output voltage, and input power factor in Embodiment 1 of the present invention Relationship diagram between input power and harmonic current regulation value ratio in Embodiment 1 of the present invention Circuit diagram in case of control of switch of embodiment 1 of the present invention by DC voltage Circuit diagram in the case of controlling the switch according to the first embodiment of the present invention by load current Circuit diagram in the case of controlling the switch according to the first embodiment of the present invention by an input current Circuit diagram of DC power supply apparatus according to Embodiment 2 of the present invention Relationship diagram of input power, DC output voltage, and input power factor of a DC power supply unit that improves input power factor only with a reactor Relationship diagram of input power, DC output voltage, and input power factor in Embodiment 2 of the present invention Relationship diagram between input power and harmonic current regulation value ratio in Embodiment 2 of the present invention Circuit diagram in case of control of switch of embodiment 2 of the present invention by DC voltage Circuit diagram in case of controlling switch of embodiment 2 of the present invention by load current Circuit diagram in the case of control of switch of embodiment 2 of the present invention by input current Circuit diagram of conventional DC power supply

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 6 Bidirectional switch 7u, 7v, 7w Capacitor 8 DC voltage detection means 9 Both Directional switch control means 10 Load current detection means 11 Input current detection means 12 Second bidirectional switch

Claims (4)

A three-phase AC power source, a bridge rectifier circuit formed of six diodes, an electrolytic capacitor connected to a DC output terminal of the bridge rectifier circuit, an AC input terminal of each phase of the three-phase AC power source and the bridge rectifier circuit, A reactor connected between the capacitor, a capacitor connected between the AC input terminal of each phase of the bridge rectifier circuit and the DC output terminal of the bridge rectifier circuit, and the DC output terminal of the capacitor and the bridge rectifier circuit A direct-current power supply device including a bidirectional switch connected in between, wherein a second bidirectional switch is provided between the AC input terminal of each phase of the bridge rectifier circuit and the capacitor. DC power supply . DC voltage detection means for detecting the DC output voltage of the bridge rectifier circuit, and bidirectional switch control means, both based on the detection value of the DC voltage detection means, the bidirectional switch control means, 2. The DC power supply device according to claim 1, wherein the directional switch or the second bidirectional switch is controlled. A load current detecting means for detecting a load current; and a bidirectional switch control means. Based on a detection value of the load current detecting means, the bidirectional switch control means includes a bidirectional switch or a second switch. 2. The DC power supply device according to claim 1, wherein two bidirectional switches are controlled. Input current detection means for detecting an input current from a three-phase AC power supply, and bidirectional switch control means, based on the detection value of the input current detection means, the bidirectional switch control means, 2. The DC power supply device according to claim 1, wherein the bidirectional switch or the second bidirectional switch is controlled.

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