JP2002058176A - Power conversion apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To substantially reduce power consumption in an ordinary operation and to continue the operation without discharging the energy of a DC power supply even if an AC power supply fluctuates significantly. SOLUTION: If the voltage of an AC power supply 1 is within a set value, the output of the AC power supply 1 is used as the output of this power conversion apparatus. If the voltage of the AC power supply 1 is out of the set value, the output of an inverter 4 is used as the output of the apparatus. If, further the voltage of the AC power supply 1 is out of another set value, the operation of an converter 2 is stopped. A state decision circuit 8 and an operation command generating circuit 9 which generate commands corresponding to these states are provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power conversion device such as a UPS (Uninterruptible Power Supply) that inputs an AC power supply and outputs a stable AC power supply.

[0002]

2. Description of the Related Art FIG. 9 is a circuit diagram showing a conventional UPS described in, for example, "Uninterruptible Power Supply (UPS) Introductory Battle Guide p45-50" published in 1989.
Is an AC power supply, 32 is a converter to which the AC power supply 31 is input and converts it into DC power, 33 is a DC power supply connected to the output of the converter 32, and 34 is an inverter which converts the output of the converter 32 into AC power and converts it into AC power , 35 are switches connected between the AC power supply 31 and the load side, 36 is a switch connected between the output of the inverter 34 and the load side, and the switch 35 and the switch 36 are connected on the device load side; It is configured to supply power to the load from the connection terminal.

Next, the operation will be described. AC power supply 31
Is normal, the power is supplied to the load from the AC power supply 31 via the converter 32 and the inverter 34, and via the switch 36 (normal power supply path in the figure). When the AC power supply 31 becomes abnormal, the power of the DC power supply 33 is converted into AC by the inverter 34 and the power is supplied to the load via the switch 36 (the power supply path at the time of a power failure in the figure). In the unlikely event that the converter 32 or the inverter 34 fails, the power of the AC power supply 31 is supplied to the load via the switch 35 (the power supply path at the time of failure of the power converter in the figure).
Works like that.

FIG. 10 shows another conventional example.
Published in July, “Electric Joint Research Vol. 46, No. 3, p.
6] is a circuit diagram showing a conventional UPS described in [6]. In the figure, 31 is an AC power supply, 33 is a DC power supply, 34 is an inverter whose input is connected to the DC power supply 33 and converts DC to AC, and 37 is an AC power supply 31 or an output of the inverter 34, and is connected to a load. Switch.

Next, the operation will be described. AC power supply 31
Is normal, the AC power supply 31 is selected and connected to the load so that the selection switch 37 supplies power from the AC power supply 31 to the load. When the AC power supply 31 deviates from the voltage allowable by the load, the selection switch 37
Of the DC power supply 3
3 to supply AC power to the load.

[0006]

The conventional power converter is constructed as described above. However, in the configuration shown first, even when the AC power supply 31 is normal, the power conversion of the converter 32 and the inverter 34 is performed. Since the power is supplied via the circuit, the power conversion device consumes power by itself, and there is a problem that the device power is larger than the load power and the running cost of the electricity bill increases. For example, 100k
Assuming that the VA device has a total efficiency of 90% at the rated load,
This means that 11 kW of power is always consumed. Also,
In the second configuration, when the AC power supply 31 deviates from the allowable voltage range of the load, power is released from the DC power supply 33, and when the energy of the DC power supply 33 runs out, power supply is stopped. was there.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and greatly reduces the power consumption of the device during normal operation. It is an object of the present invention to provide a power conversion device capable of continuing operation without emitting any gas.

[0008]

According to a first aspect of the present invention, a power converter includes a converter connected to an output of an AC power source, an inverter connected to an output of the converter, and an inverter connected to the inverter. A DC power supply, a switch connected between the AC power supply and the load side, and a switch connected between the inverter and the load side, wherein the voltage fluctuation ranges α and β (α <β ), Means for supplying AC power to the load if the voltage fluctuation range of the AC power supply is within ± α, and means for operating the converter if the voltage fluctuation range exceeds ± α and is within ± β. And means for stopping the operation of the converter when the voltage fluctuation range exceeds ± β.

According to a second aspect of the present invention, there is provided a power converter, comprising: a converter connected to an output section of an AC power supply; an inverter connected to an output section of the converter; a DC power supply input to the inverter; Means for setting a voltage fluctuation range and a maximum allowable current value, comprising: a switch connected between the power supply and the load side; and a switch connected between the inverter and the load side; Means for supplying AC power to the load if is within the voltage fluctuation range; means for operating the converter if the current flowing through the converter is within the maximum allowable current value while exceeding the voltage fluctuation range; and In this case, a means for stopping the operation of the converter is provided.

According to a third aspect of the present invention, there is provided a power conversion device including means for supplying an AC power supply to a load only when the frequency of the AC power supply is within an allowable range.

According to a fourth aspect of the present invention, there is provided a power converter, wherein a plurality of circuits each including an AC power supply, a converter, an inverter, a DC power supply, and a switch are provided in parallel.
It comprises a current sensor for detecting a load current, and means for dividing a load current value by a rated current value that can be supplied per unit to determine a required number of operating points of the circuit.

A power converter according to a fifth aspect of the present invention is provided with means for adding one to the required number of operations.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a circuit diagram showing a power converter according to Embodiment 1 of the present invention. In the figure, reference numeral 1 denotes an AC power supply, 2 denotes an AC power supply 1,
A converter for converting to DC power, 3 is a DC power supply connected to the output side of the converter 2, 4 is an inverter for converting the output of the converter 2 to human power, and converting to AC power, 5 is between the AC power supply 1 and the load side. The connected switch 6 is a switch connected between the output of the inverter 4 and the load side, 7
Is a voltage sensor that detects the voltage of the AC power supply 1, 8 is a state determination circuit that determines an operation state from conditions, and 9 is an operation command creation circuit that creates operation commands for the converter 2, the inverter 4, the switch 5, and the switch 6. .

FIG. 2 is a detailed circuit diagram showing the state judging circuit 8 and the operation command generating circuit 9. In the figure, reference numeral 10 denotes a comparator which receives an output of the voltage sensor 7 and judges a relationship with an allowable load condition. , 11 are comparators which receive the output of the voltage sensor 7 and determine the relationship with the operating conditions of the converter 2. The comparator 10 is a circuit that determines the state of the voltage of the voltage sensor 7 based on a voltage variation range α that can be tolerated by the load as a reference. For example, if the AC power supply 1 is within ± α of the rated voltage, For example, the AC power supply 1 can be supplied to the load, and the output of the comparator 10 is set to the H level.

Further, when the value deviates from ± α, the AC power supply 1 cannot be supplied to the load, and the output of the comparator 10 is set to L level. The comparator 11 uses the voltage fluctuation range β in which the converter 2 can operate as a comparison reference, and determines the state of the voltage of the voltage sensor 7 by a determination circuit. For example, if the AC power supply 1 is within ± β of the rated voltage, The converter 2 is set in the operable state, and the output of the comparator 11 is set to the H level. Also, ±
When it deviates from β, the converter 2 is set in a state where it cannot be operated, and the output of the comparator 11 is set to L level.

The output signals of the two comparators 10 and 11 are input to the operation command generation circuit 9, and the output of the comparator 10 is output as an on / off command of the switch 5. The switch 5 operates to turn on when this command is H, and to turn off when this command is L. Reference numeral 12 denotes an inverter.
, The signal of the comparator 10 is output to the switch 6, so that the operation of the switch 6 is inverted from the on / off operation of the switch 5. A signal from the comparator 11 is output as an operation signal of the converter 2, and the converter 2 operates so as to operate when the output is H and to stop when the output is L. In addition, the inverter 4 outputs a command such that the inverter 4 always operates.

Next, the operation will be described. The comparator 10 determines whether the voltage of the AC power supply 1 is in a normal state in which the voltage can be supplied to the load. If the voltage is normal ('H' state), the switch 5 is turned on, and the power of the AC power supply 1 is directly supplied to the load. (The power supply path when the AC power supply 1 is normal in the figure). AC power supply 1
Deviates from the load allowable voltage range α, the output of the comparator 10 becomes L level, the switch 5 is turned off instantaneously,
The switch 6 turns on. With this operation, power is supplied from the inverter 4.

Here, if the operable voltage range β of the converter 2 can be set to a value larger than α, for example, if the voltage drop of the AC power supply 1 is within the range of α or more and within β, the converter 2 can be operated continuously. Therefore, the power supply to the load can be continued by the power supply path when the AC power supply 1 is lowered in the drawing.

Thus, in normal operation, power is supplied to the load via the switch 5, so that the power consumption of the device can be reduced.
Even if the AC power supply 1 fluctuates greatly, the operable voltage range β of the converter 2 is designed to be wide regardless of the allowable voltage range α of the load, so that the DC power supply 3 Power can be continuously supplied from the inverter 4. Although the operable voltage range of converter 2 has been described with the same upper limit value and lower limit value, the same effect can be obtained even if the range is set differently according to the purpose.

Embodiment 2 In the first embodiment, by setting the operable voltage range of converter 2 wide,
Although the description has been given of the case where the converter 2 can be operated even when the AC power supply 1 is lowered, since the operation of the converter 2 is limited by the supplied current, the lower limit value of the operable voltage of the converter 2 is as follows. A voltage value (rated power value / maximum permissible current value = minimum voltage value) is set so that the maximum permissible current that the converter 2 can flow at the time of a rated load (when supplying rated power). If the operation is limited by this set value, when the load is light, that is, when the current flowing through the converter 2 is small, the converter 2 stops even though the converter 2 can be continuously operated even at the voltage set under the above conditions. It will be. The present embodiment has been made to solve such a problem.

FIG. 3 is a circuit diagram showing a power converter according to a second embodiment of the present invention. In the figure, reference numeral 13 denotes a current sensor for detecting an input current, and the other components are the same as those in the first embodiment. It is. FIG. 4 is a detailed circuit diagram of the state determination circuit 8 and the operation command creation circuit 9 of the present embodiment.
Is a comparator that compares the maximum allowable current value that the converter 2 can supply with the output signal of the current sensor 13 and outputs an H level if the current is equal to or less than the maximum allowable current, otherwise outputs an L level. Otherwise, the configuration is the same as that of the first embodiment.

By using the comparator 14 to compare the energizing current of the converter 2 with the maximum allowable current, the operation is continued when the converter 2 is equal to or less than the maximum allowable current. The operation can be continued until the current exceeds the maximum current, which is the limit of converter 2, and when the load is below the rating, the operating voltage range of converter 2 is wider than in the first embodiment.

Embodiment 3 FIG. In the first embodiment, the voltage range is set as the load allowable condition. However, the load has a frequency allowable range, and the method of the first embodiment cannot cope with such a load. The present embodiment has been made to solve such a problem.

FIG. 5 is a detailed circuit diagram of the state determination circuit 8 and the operation command creation circuit 9 according to the present embodiment.
15 is a frequency measurement circuit for measuring the frequency of the AC power supply 1,
A comparator 16 compares the frequency range γ that can be tolerated by the load with the frequency of the AC power supply 1 and outputs an H level if it is in an allowable range, and outputs an L level otherwise.
The AND circuit outputs an H level when both the output of the comparator 10 for comparing the voltage value and the output signal of the comparator 16 for comparing the frequency value are at the H level. Reference numeral 18 indicates that the power supply frequency deviates from the allowable load value and the comparator 1
6 is a fixed frequency command generation circuit that outputs a command to switch the operating frequency of the inverter 4 to a predetermined fixed frequency when the output of the inverter 6 becomes L level.

The output of the comparator 10 and the output of the comparator 16 are ORed by the AND circuit 17, so that when either the power supply voltage value or the frequency deviates from the allowable load condition, the power supply is switched to the inverter 4. In particular, when the frequency deviates from the allowable value, the output frequency of the inverter 4 is fixed to a predetermined frequency by the fixed frequency command generation circuit 18, and a stable electric power in consideration of the frequency can be supplied to the load.

Embodiment 4 In the first embodiment, the power conversion circuit having the physique of the rated power is operated even under a light load, and the conversion efficiency is poor. In addition, since the converter is kept on standby while the power is supplied by the switch 5, there is no load loss of the converter. Therefore, the present embodiment is made to reduce such no-load loss and improve the conversion efficiency of the device.

FIG. 6 is a circuit diagram showing a power converter according to a fourth embodiment of the present invention. In FIG. 6, reference numeral 19a denotes a converter 2 which receives an AC power supply 1 and converts it into DC power.
And an inverter 4 that receives the output of the converter 2 as an input and converts it into AC power, and a switch 6 that is connected between the output of the inverter 4 and the load side. It has the same configuration as the conversion circuit 19a. Each of the power conversion circuits 19a to 19d has an input side connected to the AC power supply 1, an input of the inverter 4 connected to the DC power supply 3, and an output side connected to the switch 5 respectively.
Are respectively connected, and power is supplied to the load from the connection portion. Reference numeral 20 denotes a current sensor for detecting a load current, and its output is input to the operation command generation circuit 9 of the present embodiment.

FIG. 7 is a detailed circuit diagram of the state determining circuit 8 and the operation command creating circuit 9 of the present embodiment.
Is the comparator 1 of the first embodiment.
It is the same as 0. Reference numeral 21 denotes an operation control circuit to which an output of the current sensor 20 is input and which generates an operation command for a plurality of power conversion circuits 19a to 19d. 22 divides the output value of the current sensor 20 by the rated current value that can be supplied per unit,
An operation number determination circuit 23 for determining the required operation number by rounding up a fraction is an operation instruction generation circuit that outputs an operation instruction to each of the power conversion circuits 19a to 19d according to the output of the operation number determination circuit 22.

Next, the operation will be described. The required number of operating units is determined by the operating number determining circuit 22 so that the rated current per unit × the number of operating units> the load current, and the operation command generating circuit 23 operates only the required number of operating units, so that it always matches the load capacity. Operation with the reduced capacity becomes possible. This allows
Useless losses can be reduced.

Embodiment 5 In the fourth embodiment, 1
Since the required number of operating units was determined so that the rated current per unit × the number of operating units> the load current, in the unlikely event that one of the power conversion circuits operating in parallel fails, the remaining power conversion circuits become overloaded, Power supply cannot be continued. Therefore, in the present embodiment, power supply can be continued even if one of the units operating in parallel fails.

FIG. 8 is a circuit diagram showing an operation control circuit 21 according to a fifth embodiment of the present invention.
The adder 24 for adding 1 is added to the output side of the operating number determination circuit 22 of FIG. With this adder 24,
One extra unit is always operated, and even if a failure occurs, power supply can be continued.

[0032]

According to the power converter according to the first aspect of the present invention, the converter connected to the output of the AC power supply, the inverter connected to the output of the converter, and the DC input to the inverter. A power supply, a switch connected between the AC power supply and the load side, and a switch connected between the inverter and the load side,
Means for setting voltage fluctuation ranges α and β (α <β), means for supplying AC power to the load if the voltage fluctuation range of the AC power supply is within ± α, and voltage fluctuation range exceeding ± α and ± β If it is within the range, a means for operating the converter and a means for stopping the operation of the converter when the voltage fluctuation range exceeds ± β are provided, so that the power consumption of the device can be reduced.

According to the power converter according to claim 2 of the present invention, a converter connected to the output of the AC power supply;
An inverter connected to the output of the converter, a DC power supply input to the inverter, a switch connected between the AC power supply and the load side, and a switch connected between the inverter and the load side. Means for setting a voltage fluctuation range and a maximum allowable current value; means for supplying an AC power supply to a load when the AC power supply is within the voltage fluctuation range; Means for operating the converter if is within the maximum allowable current value, and means for stopping the operation of the converter when the current value exceeds the maximum allowable current value, so that the operating range of the converter can be widened.

According to the power converter of the third aspect of the present invention, the means for supplying the AC power to the load is provided only when the frequency of the AC power is within the allowable range. Can be supplied to the load.

According to the power converter of the fourth aspect of the present invention, a plurality of circuits each including an AC power supply, a converter, an inverter, a DC power supply, and a switch are provided in parallel, a current sensor for detecting a load current, and a load sensor. Current value is 1
Means for determining the required number of operating points of the circuit by dividing by the rated current value that can supply power per unit is provided, so that useless loss can be reduced.

According to the power converter according to claim 5 of the present invention, since means for adding 1 to the required number of operations is provided,
Even if one of the units operating in parallel fails, power supply can be continued.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a power converter according to a first embodiment of the present invention.

FIG. 2 is a detailed circuit diagram of the power conversion device according to the first embodiment of the present invention.

FIG. 3 is a circuit diagram showing a power converter according to Embodiment 2 of the present invention.

FIG. 4 is a detailed circuit diagram of a power conversion circuit device according to a second embodiment of the present invention.

FIG. 5 is a circuit diagram showing a power converter according to Embodiment 3 of the present invention.

FIG. 6 is a circuit diagram showing a power converter according to a fourth embodiment of the present invention.

FIG. 7 is a detailed circuit diagram of a power converter according to a fourth embodiment of the present invention.

FIG. 8 is a circuit diagram showing a power conversion device according to a fifth embodiment of the present invention.

FIG. 9 is a circuit diagram showing a conventional uninterruptible power supply.

FIG. 10 is a circuit diagram showing a conventional uninterruptible power supply.

[Explanation of symbols]

1 AC power supply, 2 converters, 3 DC power supplies, 4 inverters, 5 and 6 switches.

Claims (5)

[Claims] 1. A converter connected to an output of an AC power supply, an inverter connected to an output of the converter,
A power converter having a DC power supply input to the inverter, a switch connected between the AC power supply and the load side, and a switch connected between the inverter and the load side, Means for setting the fluctuation range α, β (α <β); means for supplying the AC power to the load if the voltage fluctuation range of the AC power supply is within ± α; A power converter, comprising: means for operating the converter if β or less, and means for stopping operation of the converter when the voltage fluctuation range exceeds ± β. 2. A converter connected to the output of the AC power supply, an inverter connected to the output of the converter,
A power converter having a DC power supply input to the inverter, a switch connected between the AC power supply and the load side, and a switch connected between the inverter and the load side, Means for setting a fluctuation range and a maximum allowable current value; means for supplying the AC power supply to a load if the AC power supply is within the voltage fluctuation range; and A power converter, comprising: means for operating the converter when the current is within the maximum allowable current value; and means for stopping operation of the converter when the current exceeds the maximum allowable current value. 3. The power converter according to claim 1, further comprising means for supplying the AC power to a load only when the frequency of the AC power is within an allowable range. 4. A circuit comprising an AC power supply, a converter, an inverter, a DC power supply, and a switch, wherein a plurality of circuits are provided in parallel, a current sensor for detecting a load current, and a rated current value capable of supplying a load current value per unit. The power converter according to any one of claims 1 to 3, further comprising: means for dividing the number of required points of the circuit. 5. The power converter according to claim 4, further comprising means for adding one to the required number of operations.