JP2004201433A - Dc linkage system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To simplify a circuit configuration and make it inexpensive, and to concurrently use power from a DC power supply and power from a commercial power supply. <P>SOLUTION: A converter 2 that converts AC power to DC power and outputs it is connected to the commercial power supply 1, a power factor improvement circuit 3 is connected to the converter 2, and a load 5 is connected to the output side of the power factor improvement circuit 3 via an inverter 4. A second boosting circuit 12 that boosts a DC voltage is connected to the DC power supply 11 that outputs the DC power, a second rectifying circuit 13 is connected to the second boosting circuit 12, and the output side of the second rectifying circuit 13 is connected to the inverter 4 so that the output side is in parallel with a first rectifying circuit 7. A second voltage set value V<SB>D</SB>of the DC power from the second boosting circuit 12 is set larger than a first voltage set value V<SB>C</SB>of the DC power from the power factor improvement circuit 3, and power from the DC power supply 11 is fed to the load 5 prior to power from the commercial power supply 1. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a DC link system in which electric power from an AC power supply or a DC power supply for in-house power generation and electric power from a commercial power supply are linked to be used at the same time.
[0002]
[Prior art]
This type of system includes a converter section that converts AC power into DC power on the DC side of an inverter section that converts DC power into AC power, and a reverse blocking type that converts AC power into DC power and prevents backflow. The converter unit is connected in parallel, the AC side of the converter unit is connected to the synchronous generator linked to the rotary prime mover, and the commercial power source is connected to the AC side of the reverse blocking converter unit. Control so that the DC side terminal voltage is higher than the DC side terminal voltage of the reverse blocking converter section, and supply the power generated by the synchronous generator preferentially to the load, and supply the commercial power when it runs short. (See Patent Document 1).
[0003]
[Patent Document 1]
JP-A-11-187698
[Problems to be solved by the invention]
Normally, the converter is switched so that a current corresponding to the voltage required by the load, that is, the output voltage of the AC section from the inverter flows to the AC power obtained by the synchronous generator.
[0005]
However, when the voltage required by the load is close to the voltage of the commercial power supply, the current flows through the converter by switching only near the peak of the power supply voltage waveform of the synchronous generator, so that the output current waveform is distorted. However, there is a disadvantage that the harmonic components increase and the power quality deteriorates.
[0006]
When a DC power supply such as a solar cell can be used at the same time as the commercial power supply, since the voltage from the DC power supply is low, the DC power is converted into AC power by an inverter before being linked to the commercial power supply. However, in such a case, a circuit such as a system interconnection protection device for preventing reverse power flow is required, and there is a disadvantage that the circuit becomes expensive.
[0007]
The present invention has been made in view of such circumstances, and a DC linking system according to the first aspect of the present invention has a simple circuit configuration and a low cost, and can reduce power from a DC power supply and power from a commercial power supply. It is an object of the present invention to provide a DC link system according to the second aspect of the present invention, in which power from an AC power supply and power from a commercial power supply can be used at the same time without lowering power quality. The DC link system according to the third aspect of the present invention is capable of simultaneously using the power from the AC power supply and the power from the commercial power supply without deteriorating the power quality, and has a simple configuration, It is an object of the present invention to cope with an instantaneous power failure of a power supply, and a DC link system according to a fourth aspect of the present invention to cope with a long-term power failure of a commercial power supply.
[0008]
[Means for Solving the Problems]
The DC link system according to the first aspect of the present invention has the following features.
A commercial power supply is connected to a converter that converts and outputs AC power to DC power, a power factor improving circuit is connected to the converter, and a DC power supply that outputs DC power is connected to a booster circuit that boosts a DC voltage. A load is connected to an output side of the power factor correction circuit via an inverter, an output side of the booster circuit is connected to the inverter in parallel with the power factor correction circuit, and DC power output from the booster circuit is The voltage set value is configured to be different from the voltage set value of the DC power output from the power factor correction circuit.
[0009]
(Action / Effect)
According to the configuration of the DC link system of the invention according to claim 1, the AC power from the commercial power supply is converted into the DC power, and the power factor improvement circuit allows the DC current of the set voltage to flow without distortion, The DC power from the DC power supply is raised to the set voltage by the booster circuit, the DC current of the set voltage flows, and is combined with the DC current from the commercial power supply, and converted into AC power by the inverter. Further, the voltage set value of the DC power from the power factor improving circuit can be made different from the voltage set value of the DC power from the booster circuit, and the DC power having the higher voltage set value can be preferentially output.
Therefore, since the commercial power supply and the DC power supply are linked by DC, a control configuration in which the DC power from the DC power supply is converted into AC power and synchronized for phase matching as in the case of linking with the AC power from the commercial power supply In addition, a system interconnection protection device for protecting a commercial power system using a commercial power supply can be omitted, the circuit configuration is simple and inexpensive, and the power from the DC power supply and the power from the commercial power supply can be used simultaneously.
Moreover, since the DC power from the DC power supply is increased by the booster circuit, even a DC power supply having a low power supply voltage, such as a solar cell, can be applied to various uses, such as being used in preference to a commercial power supply. Extremely useful.
[0010]
Further, the DC link system of the invention according to claim 2 achieves the above object by
A first converter that converts AC power to DC power and outputs the AC power is connected to a commercial power supply, a first power factor correction circuit is connected to the first converter, and an AC power supply that outputs AC power is connected to an AC power supply that outputs AC power. A second converter that converts power into DC power and outputs the DC power, and connects a second power factor correction circuit that boosts a DC voltage to the second converter; A load is connected to an output side via an inverter, an output side of the second power factor correction circuit is connected to an inverter in parallel with the first power factor correction circuit, and the first power factor correction circuit is connected to the output side. The voltage set value of the DC power output from the second power factor correction circuit is configured to be different from the voltage set value of the DC power output from the second power factor correction circuit.
[0011]
(Action / Effect)
According to the configuration of the DC link system according to the second aspect of the present invention, the AC power from the commercial power supply is converted into the DC power, and the DC power of the set voltage is supplied by the first power factor correction circuit without distortion. On the other hand, the AC power from the AC power supply is increased to the set voltage by the second power factor correction circuit, and a DC current of the set voltage is supplied in a state where there is no distortion to be combined with the DC current from the commercial power supply. Convert to AC power. The voltage set value of the DC power from the first power factor correction circuit is made different from the voltage set value of the DC power from the second power factor correction circuit, and the DC power with the higher voltage set value is preferentially output. be able to.
Therefore, the commercial power supply and the AC power supply are linked by DC, and the circuit configuration is simple and inexpensive, but the current can flow by switching over a wide range of the AC power supply voltage, and the harmonic components can be reduced. Therefore, the power from the AC power supply and the power from the commercial power supply can be used simultaneously without deteriorating the power quality.
Moreover, regardless of the difference between the magnitude of the AC power from the commercial power supply and the magnitude of the AC power from the AC power supply, the output from the predetermined power supply can be used preferentially, and the AC power supply is used in preference to the commercial power supply. It can be applied to various uses, such as using an AC power supply when a commercial power supply fails, and is extremely useful.
[0012]
In addition, the invention according to claim 3 achieves the above object by:
The DC link system according to claim 2,
A DC power supply that outputs DC power, a boosting circuit that boosts a DC voltage is connected, an output side of the boosting circuit is connected to an inverter in parallel with first and second power factor correction circuits, and the boosting circuit is Is set lower than the voltage set value of the DC power output from the first and second power factor correction circuits, and the suppliable power amount of the DC power is The power consumption is set so as to prevent the occurrence of a load abnormality at the time of power failure.
[0013]
(Action / Effect)
According to the configuration of the DC link system according to the third aspect of the present invention, the DC power from the DC power supply is increased to the set voltage by the booster circuit, and the voltage set value is increased by the first and second power factor improvement circuits. The DC power from each of them is set to be smaller than the voltage set value.In the event of a commercial power failure, the power from the AC power supply is insufficient and the load from the DC power supply may cause a load abnormality. Can be paid for.
Therefore, the DC power from the DC power supply is increased by the booster circuit, and the DC power is linked to the commercial power supply and the AC power supply. This eliminates the need for a grid protection device to protect the power grid, and the amount of power sufficient to prevent the occurrence of load abnormalities during a commercial power outage, even with a DC power supply such as a solar battery with a low power supply voltage. With a simple configuration, it is possible to cope with an instantaneous power failure of the commercial power supply while simultaneously using the power from the AC power supply and the power from the commercial power supply without deteriorating the power quality.
[0014]
Further, the invention according to claim 4 achieves the above object by:
The DC link system according to claim 3,
A load is connected between the AC power supply and the second converter or / and at the output side of the inverter, and when the electric power of the DC power supply can be supplied when the commercial power supply fails, the AC power supply of the total load is supplied. It is configured to cut off the part exceeding the rating of.
[0015]
(Action / Effect)
According to the configuration of the DC link system according to the fourth aspect of the present invention, when a commercial power supply fails, while the power from the AC power supply is supplied to the load, a portion exceeding the rating for the total load is supplied from the DC power supply. While consuming the power from the DC power supply, the load exceeding the rating can be cut off, and the power from the DC power supply can be made unnecessary. Therefore, power can be continuously supplied to a load smaller than the rating of the AC power supply irrespective of the power failure of the commercial power supply, so that a long-term power failure of the commercial power supply can be satisfactorily dealt with.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, embodiments of the present invention will be described in detail with reference to the drawings.
[0017]
FIG. 1 is a schematic configuration diagram showing a first embodiment (an embodiment of the invention according to claim 1) of a DC link system according to the present invention. The commercial power supply 1 converts AC power into DC power and outputs the converted DC power. The power factor improving circuit 3 is connected to the converter 2, and the output 5 of the power factor improving circuit 3 is connected to the load 5 via the inverter 4.
[0018]
The power factor improvement circuit 3 includes a first booster circuit 6 such as a chopper circuit, a first rectifier circuit 7, a first voltmeter 8 that measures a DC output voltage from the first rectifier circuit 7, It comprises a control circuit 9 and a first switch circuit 10.
[0019]
In the first control circuit 9, the voltage of the DC output from the first rectifier circuit 7, i.e., the first voltage V _C given as the target value of the voltage of the DC output from the first boosting circuit 6 is set Comparing the voltage value measured by the first voltmeter 8 with the first voltage set value V _C , and when the measured voltage value is smaller than the first voltage set value V _C , the first booster circuit 6 On the other hand, when the measured voltage value is larger than the first voltage set value V _C , the first booster circuit 6 is instructed to decrease the number of switching times. outputs a signal, measured voltage value is so controlled to be the first voltage setting value V _C.
[0020]
A DC power supply 11 such as a solar cell or a fuel cell that outputs DC power is connected to a second booster circuit 12 that boosts a DC voltage, and a second rectifier circuit 13 is connected to the second booster circuit 12. The output side of the second rectifier circuit 13 is connected to the inverter 4 so as to be in parallel with the first rectifier circuit 7.
[0021]
A second voltmeter 14 for measuring the voltage of the DC output from the second rectifier circuit 13 is attached to an output portion of the second rectifier circuit 13, and the second voltmeter 14 has a second control circuit 15. And a second switch circuit 16 for switching the second booster circuit 12 is connected to the second control circuit 15.
[0022]
In the second control circuit 15, the voltage of the DC output from the second rectifier circuit 13, i.e., a predetermined second voltage V _D as a target value of the voltage of the DC output from the second boosting circuit 12 is set The voltage value measured by the second voltmeter 14 is compared with the second voltage set value V _{D. When} the measured voltage value is smaller than the second voltage set value V _D , the second booster circuit 12 increasing the switching times for the other hand, when the measured voltage value is greater than the second voltage setting value V _D is instruction to the second switch circuit 16 so as to reduce the number of switching to the second step-up circuit 12 outputs a signal, measured voltage value is so controlled to be a second voltage setting value V _D.
[0023]
The second voltage set value V _D is set larger than the first voltage set value V _C so that the power from the DC power supply 11 can be supplied to the load 5 in preference to the power from the commercial power supply 1. It is configured.
[0024]
In the first embodiment, the first and second control circuits 9 and 15 are constituted by one control circuit, and the first and second switch circuits 10 and 16 are constituted by one switch circuit. And the second voltmeters 8 and 14 are connected to a control circuit, and a switch circuit is connected to the control circuit. In one control circuit, the voltage measured by the first and second voltmeters 8 and 14 and the first Alternatively, a configuration may be adopted in which predetermined switching is performed by comparing each of the values with the second voltage set values V _C and V _D.
[0025]
FIG. 2 is a schematic configuration diagram showing a second embodiment (an embodiment of the invention according to claim 2) of the DC link system according to the present invention. The difference from the first embodiment is as follows.
[0026]
That is, instead of the DC power supply 11 of the first embodiment, an AC generator 21 as an AC power supply is used, and the AC converter 21 has a second converter 22 that converts AC power into DC power and outputs the DC power. At the same time, the second power factor correction circuit 23 is connected to the second converter 22, and the output side of the second power factor correction circuit 23 is connected to the first power factor correction circuit 3 (of the first embodiment). The power factor improving circuit 3) is connected to the inverter 4 in parallel. In FIG. 2, the converter 2 that converts AC power from the commercial power supply 1 to DC power is referred to as a first converter 2.
[0027]
The second power factor correction circuit 23 includes a third booster circuit 24 such as a chopper circuit, a third rectifier circuit 25, a third voltmeter 26 for measuring a DC output voltage from the third rectifier circuit 25, It comprises a third control circuit 27 and a third switch circuit 28.
[0028]
In the third control circuit 27, a predetermined third voltage V _D1 is set as a target value of the DC output voltage from the third rectifier circuit 25, that is, the DC output voltage from the third booster circuit 24. The voltage value measured by the third voltmeter 26 is compared with the third voltage set value V _D1 , and when the measured voltage value is smaller than the third voltage set value V _D1 , On the other hand, when the measured voltage value is larger than the third voltage set value V _D1 , the third switch circuit 28 is instructed to decrease the number of switching times. A signal is output, and control is performed so that the measured voltage value becomes the third voltage set value V _D1 .
[0029]
Third voltage set value V _D1 is set to be larger than first voltage set value V _C , and power generated from AC generator 21 can be supplied to load 5 prior to power from commercial power supply 1. It is configured as follows. The other configuration is the same as that of the first embodiment, and the description thereof will be omitted by retaining the same reference numerals.
[0030]
FIG. 3 is a schematic configuration diagram showing a third embodiment (an embodiment of the invention according to claims 3 and 4) of the DC link system according to the present invention. The difference from the second embodiment is as follows. .
[0031]
That is, the following configuration is added to the configuration of the first embodiment.
A fourth booster circuit 32 for boosting a DC voltage is connected to a DC power supply 31 such as a solar cell that outputs DC power, and a fourth rectifier circuit 33 is connected to the fourth booster circuit 32. Of the rectifier circuit 33 is connected to the inverter 4 in parallel with the first and third rectifier circuits 7 and 15.
[0032]
A fourth voltmeter 34 for measuring the voltage of the DC output from the fourth rectifier circuit 33 is attached to an output portion of the fourth rectifier circuit 33, and the fourth voltmeter 34 has a fourth control circuit 35. Is connected, and a fourth switch circuit 36 for switching the fourth booster circuit 32 is connected to the fourth control circuit 35.
[0033]
In the fourth control circuit 35, a predetermined fourth voltage V _H is set as a target value of the DC output voltage from the fourth rectifier circuit 33, that is, the DC output voltage from the fourth booster circuit 32. The voltage value measured by the fourth voltmeter 34 is compared with the fourth voltage set value V _{H. When} the measured voltage value is smaller than the fourth voltage set value V _H , the fourth booster circuit 32 On the other hand, when the measured voltage value is larger than the fourth voltage set value V _H , the third switch circuit 36 is instructed to decrease the number of times of switching. outputs a signal, measured voltage value is so controlled to be the fourth voltage setting value V _H.
[0034]
A load 38 is connected between the AC generator 21 and the second converter 2 and on the output side of the inverter 4 via a circuit breaker 37. The load 5 is configured by itself so as not to exceed the rating of the alternator 21, and the loads 38, 38 are configured to exceed the rating of the alternator 21 in a state where the loads 5 are combined with the load 5.
[0035]
The fourth voltage set value V _H is set to a value lower than the first and third voltage set values V _C and V _D1 , and the amount of power that can be supplied by the DC power supply 31 is a power failure of the commercial power supply 1. Sometimes, even when power is supplied to all of the loads 5, 38, and 38, power is supplied to a portion exceeding the rating of the AC generator 21 for a predetermined time (time for turning off the breaker 37 described later). Therefore, the power amount is set to an amount of power sufficient to prevent the occurrence of abnormalities in the loads 38, 38.
[0036]
A power failure detector 39 for detecting a power failure of the commercial power source 1 and outputting a power failure signal is attached to the output side of the commercial power source 1. The power failure detector 39 is connected to the fifth control circuit 40 and the The circuit breakers 37, 37 are connected to the control circuit 40 of FIG.
[0037]
The fifth control circuit 40 outputs a shutoff signal to the circuit breakers 37, 37 in response to the power failure signal from the power failure detector 39, and supplies the DC power from the DC power supply 31 to the loads 38, 38 until the load is completely supplied. The circuit breakers 37, 37 are configured to be shut off. The other configuration is the same as that of the second embodiment, and the description thereof will be omitted by retaining the same reference numerals.
[0038]
According to the configuration of the third embodiment, it is possible to continuously supply power from the AC generator 21 to the load 5 that does not exceed the rating of the AC generator 21 even when the commercial power supply 1 experiences a power failure for a long time.
[0039]
In the second and third embodiments, the first and third control circuits 15 and 27 use the electric energy required by the load 5 as shown in the graph of the correlation between the set voltage and the total output current in FIG. That is, as the total output current from the commercial power supply 1 and the AC generator 21 increases, the third voltage set value V _D1 from the AC generator 21 decreases little by little until near the rated value a of the commercial power supply 1 In the vicinity of the rated value a, the first voltage set value V _C from the commercial power supply 1 is almost equal to the first voltage set value V _C from the commercial power supply 1. After exceeding the rated value a, the first voltage set value V _C from the commercial power supply 1 is gradually increased. It is designed to decrease. Thus, while the AC generator 21 is operated with the rated generated power, the power from the commercial power supply 1 can be smoothly supplied in a manner that compensates for the power shortage as the power shortage occurs.
[0040]
【The invention's effect】
As is apparent from the above description, according to the DC link system of the first aspect of the present invention, the AC power from the commercial power supply is converted into the DC power, and the power factor improving circuit adjusts the set voltage without distortion. A DC current is passed, while the DC power from the DC power supply is raised to the set voltage by the booster circuit, the DC current of the set voltage is passed, the DC current from the commercial power supply is combined, and the inverter is converted to AC power by the inverter. Since the power supply and the DC power supply are linked by DC, a control configuration that converts DC power from the DC power supply into AC power and synchronizes them for phase matching as in the case of linking with AC power from the commercial power supply, or a commercial configuration This eliminates the need for a system interconnection protection device for protecting the commercial power system using the power supply, and allows the circuit configuration to be simple and inexpensive, and the power from the DC power supply and the power from the commercial power supply to be used simultaneously.
In addition, the DC power from the DC power supply is increased by the booster circuit, and the voltage set value of the DC power from the power factor correction circuit is made different from the voltage set value of the DC power from the booster circuit. Since the power can be output preferentially, even a DC power supply such as a solar cell having a low power supply voltage can be applied to various uses, such as being used preferentially over a commercial power supply. Useful.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing a first embodiment of a DC link system according to the present invention.
FIG. 2 is a schematic configuration diagram showing a second embodiment of the DC link system according to the present invention.
FIG. 3 is a schematic configuration diagram showing a third embodiment of the DC link system according to the present invention.
FIG. 4 is a graph showing a correlation between a set voltage and a total output current.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Commercial power supply 2 ... Converter, 1st converter 3 ... Power factor improvement circuit, 1st power factor improvement circuit 4 ... Inverter 5 ... Load 11 ... DC power supply 12 ... First booster circuit (boost circuit)
21. AC generator (AC power supply)
22 second converter 23 second power factor improving circuit 31 DC power supply 32 fourth booster circuit (boost circuit)
38… Load

Claims (4)

A commercial power supply is connected to a converter that converts and outputs AC power to DC power, a power factor improving circuit is connected to the converter, and a DC power supply that outputs DC power is connected to a booster circuit that boosts a DC voltage. A load is connected to an output side of the power factor correction circuit via an inverter, an output side of the booster circuit is connected to the inverter in parallel with the power factor correction circuit, and DC power output from the booster circuit is A DC link system, wherein a voltage set value is made different from a voltage set value of DC power output from the power factor correction circuit. A first converter that converts AC power to DC power and outputs the AC power is connected to a commercial power supply, a first power factor correction circuit is connected to the first converter, and an AC power supply that outputs AC power is connected to an AC power supply that outputs AC power. A second converter that converts power into DC power and outputs the DC power, and connects a second power factor correction circuit that boosts a DC voltage to the second converter; A load is connected to an output side via an inverter, an output side of the second power factor correction circuit is connected to an inverter in parallel with the first power factor correction circuit, and the first power factor correction circuit is connected to the output side. A DC set voltage of the DC power output from the second power factor correction circuit is different from a voltage set value of the DC power output from the second power factor correction circuit. The DC link system according to claim 2,
A DC power supply that outputs DC power, a boosting circuit that boosts a DC voltage is connected, an output side of the boosting circuit is connected to an inverter in parallel with first and second power factor correction circuits, and the boosting circuit is Is set lower than the voltage set value of the DC power output from the first and second power factor correction circuits, and the suppliable power amount of the DC power is A DC link system set to an amount of power sufficient to prevent abnormalities in the load during a power outage. The DC link system according to claim 3,
A load is connected between the AC power supply and the second converter or / and at the output side of the inverter, and when the electric power of the DC power supply can be supplied when the commercial power supply fails, the AC power supply of the total load is supplied. DC link system that cuts off parts that exceed the rating.

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